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Progress in implant dentistry—An evaluation
P ro g ress in im p lan t d e n tis try — A n evalu a tio n
Isaih Lew, D.D.S., New York
The history of implant dentures is pre sented, and the present two-stage technic of implanting the lower complete denture is described. Criticisms of implant den tures are discussed. Patients with difficult ridges, who have been fitted with im planted lower .complete dentures, have received a measure of comfort and func tion far exceeding that obtained with conventional dentures, for periods rang ing up to ten years. Improvements in upper complete denture implant technics promise to yield a perfected technic in the near future. Indications also are promising for implanted partial dentures. There is still room for improved implant materials and designs. Much more re search is required before all the potentials of implant dentures are to be realized.
J. P. Weinmann,1 addressing the Amer ican Academy for Implant Dentures in its scientific session on the nature of bone and its relationship to implants in den tistry, likened the dentists’ persistence in developing a feasible implant technic to the story of the bumblebee. The bumble bee has a large body and tiny wings. Ac cording to the laws of Isaac Newton and authorities on the subject of aero dynamics, the bumblebee should not be
able to fly. It has also been said that, fortunately, the bumblebee does not know anything about the laws of aerodynamics. Similarly, the implant dentist, in spite of physiological, anatomical, and surgi cal axioms to the contrary, persisted doggedly in the attempt to develop the implant technic, with gradual but cer tain recognition by his peers. D E V E L O P M E N T O F T H E IM P L A N T
Twelve years of refinement and perfec tion have lifted at least one form of im plant dentures, the full lower implant, out of the realm of experimentation into a field of valued and tried adjuncts to prosthetic service. This achievement has created a recognizable impact in dentalmedical circles throughout the world. It has enhanced the stature of the American dental profession and opened the way for further growth in leadership to the American dentist. In May 1957, the Prosthetic Research Board of the National Academy of Sciences called a conference2 on skeletal attachments. Represented were the lead ers of orthopedic research centers, as well as engineers, ophthalmologists and other scientists—all trying to find a solution for a skeletal fixation for improved amputee prostheses, eye prostheses and other pros thetic appliances. Goldberg,, Gershkoff
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and Lew, representing the implant den tists, were pleasantly surprised to learn that they had achieved some of the few clinically positive results which helped solve problems presented by represent atives of other disciplines. It was almost inevitable that the im plant should be developed by the dentist, because his discipline combines knowl edge of anatomy, physiology, histopathology, the dynamics of function, pres sure, stress and strain, with understand ing of metallurgy. For thousands of years men have at tempted to replace lost oral function with various substitutes; Petronious attempted to repair cleft palates with gold in the 16th century. Steel, iron, copper, silver, aluminum, magnesium, glass, lead, por celain, bone, shell and self-polymerizing resins have been tried. The various at tempts in implant development can be classified in three categories: the intraosseous, the transosseous and the sub periosteal. Most of the early work was concerned with intraosseous implants. Maggiolo3 of Paris, 1809; Edwards4 of New York, 1889; Schnoel, 1905; and Greenfield,5 1913, attempted to replace a lost tooth by placing a foreign body in the open socket. In the early nineteen twenties, Brill6 in Germany, and Skinner7 in the United States, attempted to tunnel through the tuberosity with a tube of metal, intending to affix a conventional prosthesis to the implanted tubule. It was not until the now classic research on the electropassive nature of metals suitable for implant work was reported by Venable and Stuck8 in 1936 and later efforts by Bernier and Canby9 in 1943, that the final impetus to the evolution of the modern full denture implant occurred. McCall,10 Weinberg11 and Strock12 at tempted to apply this knowledge to single and to unilateral implants. Dahl,13 in 1943 proposed a crude alveolar type subperiosteal implant, but met with great discouragement. Finally, in 1948, Gold berg and Gershkoff14 breached the sea of
skepticism and reported the first success ful lower implant (Fig. 1,A). A pro fusion of reports from other pioneers fol lowed. Ogus15 in 1951 suggested a novel idea for an implant with removable abut ments, which did not prove clinically feasible. Lew16 in 1952 reported a simple technic for an immediate upper pros thesis, and a more modified technic for a direct bone impression lower implant (Fig. 1,C). Loechler and Mueller,17 Berman,18 Bodine19 and Killebrew20 fol lowed along with their own variations of new ideas in regard to placement and configurations of abutments, the number and thickness of struts, the application to cleft palate, and a one-stage technic20 of Killebrew’s similar to the early template method of Goldberg and Gershkoff. Prog ress and changes in implant design and technic occurred rapidly and added to the confusion of the concepts in early years of the implant. In 1952 I addressed21 the newly formed American Academy for Implant Den tures, in St. Louis, on problems and de sign of the implant. This meeting was one of the early attempts to evaluate dif ferent implant technics and to evolve a standard implant design (Fig. 1, 2). It helped to bring about implants with im proved abutments, elimination of pares thesia, the perfection of impressions, and the two-stage technic which is commonly employed today. Along about this time men in Europe and South America, many of whom had studied or read some of the early work on this subject, attempted to put into use other ideas for implants. Marziani22 at tempted to use a swaged tantalum mesh implant with claims of success. His tech nic in the early stages included fixing the implant in position with intraosseous or transosseous wires. Professor Pejrone23 of Turino attempted to place an implant by using direct impression with a rapid cast technic while the patient was kept in a semi-anesthetized state for six to eight hours. Schroeder24 suggests the use of a
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Fig. I • Evolution of mandibular implant design. A: Crude, bulky frame, thick struts, flat abutments, screws in crest of ridge over bicuspid canal region, resulting in injury to nerve, paresthesia, and so forth. B: Example of effort to extend design to buccal-external oblique region. C: Attempt to relieve region of the mental foramen. Direct impression technic was used, and there are fewer struts over crest of ridge in region of incision. First such implants were weak, too mobile and bent easily. D: Design to overcome faults in C. More secondary struts, screw hole in region of accessibility and bone density, (external oblique ridge and mentolabial region), and away from canal. E: Current design giving maximum strength and minimum bulk, with open areas over alveolar bone allowing for possible resorption. Note simple tapered abutments. Stress of function is spread over widest cortical bone area (external oblique ridqe, lingual bony plate and mentolabial region) similar method, using gold mesh with im mediate fabrication. Formiggini25 used hollow endomaxillary screws. Marziani and Pejrone have used the one-stage tantalum-swaged method, attempting to keep the patient anesthetized while the impression is taken, the implants swaged, and the entire assembly placed in the mouth. This procedure is extremely long and extremely traumatic to the tissues and presents other problems too nu merous to mention. Kress’s work20 on the relief of strain and stress on the superstructure by the utilization of plastic sleeves under the superstructure is an other improvement in implant design which attempts to minimize some of the functional stress. In the annals of the pro ceedings of the European Academy on Implants, convening in Pavia, Italy, ref
erence is made repeatedly to the works of Goldberg and Gershkoff, Killebrew, Bodine, Kosch, Loechler, Jermyn, Herschfus, Lew, and others. Constant reference is made to the work of Americans, par ticularly by Marcel Parant, Roccia,27 Borghesio, Rattenberg,28 Marziani, and others who have observed the work of the American implant dentists over the past 12 years and have compared their results with those of men in South America, Italy, France and Germany. The predominant conclusion is that the method followed in America has proved most durable and most reliable in the greatest number of instances. Other technics are currently used to improve denture stability and to replace lost oral anatomy. Among these are the magnetic implant,29 the graft of auto
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genous bone30 to restore lost tissue, the use of Vitallium or other chrome cobalt alloys to restore bone lost in osteosar coma,31 the transplant of tooth germ,32 the use of acrylic implants and, finally, the use of magnets in conventional den tures for the purpose of effecting greater stability. It is easy to understand why, to the general practitioner and many sur geons and prosthodontists throughout the country, the implant picture is a maze of confusion. These various approaches to the improvement of oral rehabilitation or reconstruction are mentioned so that the reader can know that specific reference is made to the denture implant as the sub
periosteal technic to differentiate from all others. In the past half century, much has appeared in prosthetic periodicals on the understanding of centric relation, or hinge axis, in the development of stable bases, vertical dimension, maximum func tion and esthetics. And yet an increasing number of patients have atrophied maxil lae and mandibles which defy the best prosthetic efforts (Fig. 3 ). These patients have prevailed on the dentist to attempt more radical implant procedures. All too often they have been dismissed as neu rotic or uncooperative. Seldom did a prosthodontist roentgenographically ex
Fig. 2 • Evolution of maxillary implant design. Below and center: Implant design (1950) attempting to achieve stability by distributing stress over palatal bone avoiding incisal canal and postpalatine foramen. Occlusal stress caused anterior-posterior dislocation and mobility. Above right: Frame design (1952) covering more of palate, to overcome objection of early design. Above left: Current design extending to malar process and base of nasal spine, creating tripod effect for greater stability in all phases of mastication. Screw holes are used for early fixation in midline where cortical bone can receive screw safely. Use of surgical prosthetic splint and accurate impression material eliminates use of screws in many instances
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Fig. 3 • Left: Typical condition in patient suitable for implant: low ridge: genial tubercle attachments higher than alveolar ridge: sharp crest with mylohyoid undercuts: no vestibule with high muscle attach ments. Right: Lateral plate of typical edentulous patient suitable for implant amine the mandible to ascertain the possibility of factors such as high mental foramen, dehiscent canal, high muscle attachments, absence of vestibule, inoper able spiny ridges, and so forth, as a cause of failure of conventional dentures (Fig. 4 ). In the process of making a bone impression for an implant operation, implant dentists have observed that atrophied mandibles have, with great fre quency, a large mental foramen with a sensitive artery, vein, and mental nerve, not only on the crest of the ridge but often in the molar region directly under the point of the greatest stress (Fig. 4, above, right and below ). Frequently, the alveolar bone has atrophied and the roof o f the canal has disappeared, to produce a dehiscency not tolerant to a denture base. The mandible, when vertical di mension is lost, turns lingually, forming a sharp angular border from molar to molar. This creates insurmountable func tional problems. Some prosthodontists and surgeons, in desperation, may sug gest radical alveolectomy or a Kazanjian operation to deepen the vestible, or some more radical surgery to relieve the mylo hyoid ridge and to create a more tolerant osseous structure beneath the mucosa. Though the implant technic may ap pear to be a radical procedure, implant dentists, paradoxically, have developed a
great respect for conserving remaining osseous structure. They have observed that with the removal of the outer thin layer of cortical bone, a procedure com mon to such operations, rapid absorption of cancellous bone occurs for a year or so until a new layer of cortical bone is formed. In the meantime, the resulting atrophy creates greater problems with the diminished bone than were present at the onset. In recent years, Landa,35 Brochere,36 Dolder,37 Collet and Briggs38 have de scribed the concomitant psychological symptoms of toothless men, and the vital function and importance of stable den tures to the sensibility of people who are edentulous. They have been concerned with factors that create inferiority com plexes, gagging symptoms, emotional de pression, and other psychological reac tions to loss of oral integrity, and there is little that can be added to their admirable work in this field. However, it has been suggested by psychologists that hysteria accompanying the loss of a tooth or any bodily tissue is a response to fear of cas tration or loss of potency. Emotional stress associated with the prospect of be coming edentulous, especially in active, middle-aged patients, can often reach such proportions as to cause the patient to resist oral rehabilitation. T o many of
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these patients, the only oral restorations that will be acceptable are those that are necessary to their own security and stability. These people’s problems are as real and as deserving of recognition as any serious disturbance and can no longer be dismissed to a general file of neurotics. Increased longevity has resulted in a larger number of people with dwindling osseous structures and associated denture problems. Recent efforts toward objectivity in de termining effectiveness of prosthetic serv ice have effected revaluation of denture effectiveness. Manly and Vinton39 showed that 500 “ ideal” dentures have an aver age efficiency of only 23 per cent in masti cation. Knowlton,40 using a Boos pressure indicator, suggests that an implant den ture has 50 per cent more pressure toler
ance than a tissue-borne base. The work of Yurkstas and Curby41 and, more re cently, of Frechette42 and Stromberg,43 is leading to more realistic and more scientific methods for determining effi ciency of artificial teeth and of forces under the dentures. Their findings ulti mately will foreshadow future successful dentures. Space limits a discussion of the de velopment of the implant from the early, uncertain template methods to more ac curate two-stage technics. Problems of trauma, stability, paresthesia, bone loss, type of tooth material, early fixation and periods of being without teeth all have been overcome and are more fully covered in other reports.21’ 44'48 It is diffi cult to discuss implants, however, with out describing some of the technic. It
Fig. 4 • Above left: Model of mandible illustrating evolution of atrophy of mandible justifying im plant procedure. Cut-away surface shows loss of alveolar bone with mental foramen and contents resting on crest of ridge under greatest stress of denture. Above right: Model of denuded mandible, showing that what appeared on clinical examination as good ridge for a denture actually had mental foramen and contents open on crest of ridge or in periphery of denture base. Below: Model of bone, illustrating sharp alveolar ridge and lingual undercuts making difficult denture problems. Alveolectomy of such a ridge would increase severity of problem
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has been the lack of understanding of the method and all of its ramifications that has resulted in failures, and not the tech nic itself. TECHNIC
The primary step is in the selection of the patient for the implant. The patient must be able to understand the complexity of the procedure and be fully cooperative. Thorough examination of physiologic and psychologic conditions may save untold difficulties. After the patient’s suitability for the implant procedure has been established, accurate impressions are made, employ ing the bite and wax set-up as in the conventional denture procedure. Roent genograms, including lateral and occlusal
views, and thorough intraoral examina tion, help to locate points important in designing the framework, impression trays, position of screws, and other types of fixation used. The implant dentist may develop within his own mind a threedimensional image of the mandible or maxilla of the patient as a result of these thorough examinations. The patient is now ready for the pri mary impression operation. Tissues are incised along the crest of the ridge and retracted radically, and a careful impres sion is taken in accurate materials, using compound, zinc oxide, rubber base mate rial, or the new sili-gel impression mate rial (Fig. 5, above left). Tissues are care fully debrided and coapted. The old denture may be lined with a suitable material and placed over the incision to
Fig. 5 • Above left: Alveolar bone denuded, tissues retracted, ready for impression. Above right: Stone model with waxed implant framework, abutment surveyed parallel and screw hole countersunk, ready for casting. Below: Cast implant frame and superstructure articulated against upper waxed denture
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improve the patient’s comfort during the ance, function and esthetics, are attained. healing period. In this most critical phase, Again, failure to use good judgment in novices often perpetrate a series of errors the selection of tooth material, the trau which can culminate only in failure. They matic effect, of natural opposing teeth, may fail to open tissues adequately, and and failure to avoid ischemic effects of impressions may show lack of detail in the superstructure pressing orf the mu extension to the vital dense bone; also, cosa over implant framework are some often they traumatize bone excessively in of the factors contributing to complica dissecting the mental nerve and sub tions in the implant. The obligation of both the surgeon and lingual tissues. The use of preoperative antibiotics, antihistamines, postoperative the prosthodontist does not end after they sedation, and warm saline packs during have inserted a successful implant. Their surgery, materially diminishes the gross responsibilities, if they are to maintain a ness of postoperative sequelae. healthy implant, continue for the life of Models are now duplicated, and the the appliance. Periodic surveillance with implant and superstructure are carefully roentgenograms and clinical checks must designed and fabricated (Fig. 5, above be arranged to avoid loose screws, hyper right, below). Roentgenograms are made trophied tissue, and excessive wear and to preclude faulty castings of the implant. closure, conditions which can result from Each implant denture must be designed increased function allowed by the im carefully by the doctor and not the tech plant (Fig. 6,7). All must be promptly nician. Failures result when untrained attended to in order to maintain the im dental personnel assume responsibility for plant and the health of the patient. Care the fabrication of a highly technical ap ful oral hygiene must be demanded, just pliance; lack of adequate coverage or as of any patient under periodontal treat strength, lack of proper thickness of ment. struts, improper position of the abut When one considers the many problems ments and, especially, lack of parallelism confronted, it is surprising to find the of the superstructure in consequent oc percentage of failures so low. During the clusal restoration are failures which can evolution of the implant procedure, many result. evaluations made by prominent prostho The second surgical procedure should dontists and oral surgeons tended to con not be attempted until complete healing fuse many practitioners. Nichols48 made a has occurred. Premature entry for the lengthy report on his original research on insertion may cause failure of tissue dogs in which the validity of the denture closure and ensuing discomfort. To be implant was questioned. This article is cautioned against are carelessly fitted beautifully written, well illustrated, and screws, failure to remove early granula is an impressive effort. Nichols concluded tion tissue before the implant is fitted, with the observation that complete den and indifferent use of coapting technics. ture implants are not feasible; to the The patient is discharged with a pros average reader, he probably made an ex thetic surgical splint (a denturehke plat cellent and convincing case. However, if form with anterior teeth, developed to the article is read carefully, it will be seen ease postoperative problems for the pa that the original statement is that the im tient while he awaits the fabrication of plants were placed in the dental arch of the final superstructure).47 a dog, using the methods of Goldberg Within four to six weeks the final and Gershkoff. No one experienced in superstructure is fabricated. Here all con implant dentistry would attempt to insert summate skill must be applied so that an implant in an alveolar bone in which centric relation, dimension, vertical bal recent extractions had been made, nor
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*
-
4 ^
9
Fig. 6 • Top two rows: Direct impression implant placed in 1950. It is well fitting, properly designed. Bottom two rows: Same region, seven years later; no appreciable bone loss, good function, healthy on clinical examination would he expect a unilateral implant un supported in the arch of a dog to remain for any time, because animals cannot be told to leave the surgery unmolested. But what is most important, an understanding of the implant procedure would show the absence of any similarity of this tech nic used by Nichols on the dogs, with the early efforts of Goldberg and Gershkoff. Nichols’ thesis proves merely that the Nichols implant does not work on dogs —and nothing else! Bleicher49 sparsely reviewed implant
progress, using some of the afore-mentioned research as a basis for pessimism, but admits that some implants may be successful. Behrman,29 who debated with the author at great length before the Academy of Dental Medicine, has now inserted several successful lower implants, to modify his early skepticism. There are many instances of repeated efforts at laboratory animal experimentation, no tably those of Bernier and Canby,9 Bodine,19 Herschfus,80 and my own more recent unpublished report of work on
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m
m
f- SmÊÊ « « 1 Rq. 7 • Early^template Implant which never fit accurately. Top two rows: Space between implant and bone at time of insertion ( 1950). Bottom two rows: Noticeable setting of implant three years later, with reqion of rarefaction and absorption of bone. Mobility of frame, poor extension to cortical bone, lack of close approximation con tributed to failure monkeys where I placed implants in edentulous regions of the jaws of monkeys, and secured the implants with fixed bridges so the monkey could not remove them. There is still a problem of debris around the implant. Nevertheless, I was sufficiently impressed with the results to feel that further research in that field should be encouraged. I was convinced that various materials which were used in this implant (such as teflon and kel-F and a combination of these plastics with Vitallium castings) might bring about improvements in the fabrication of im plants. Laboratory animal experimenta tion is valuable only to test the tolerance and physiological reaction of tissue to material buried in the tissue. A labora tory animal cannot act and react as hu mans do, and any experiment expecting them to do so is bound to be invalid. Approximately 95 per cent of lower implant dentures have given patients with difficult lower ridges comfort and function far exceeding that obtained with conventional dentures, for a period ranging up to nine or ten years. This reality cannot be ignored, despite the failure of the technic on dogs. As far as the complete lower implant is concerned,
it is needless to have recourse to labora tory animals when there are several thousand human implants available for examination and evaluation. Men of stature in the surgical and prosthetic fields, such as Marcel Parant,51 Franz Hildebrand of Sweden and many other leaders of the dental societies of Mexico, South America and remote corners of the world came to review and see actual im plants which have functioned for the past ten years. Their reaction is best sum marized in the statement made by Pro fessor Isauma Nakasoma,52 professor of prosthetic dentistry in the Tokyo Medical and Dental University. He said, As far as m odern prosthetics is concerned . . . one o f the most significant . . . advances in the past fifty years has been the full denture im plant as perform ed by the leading im plantodontists in the United States.
It is difficult to understand how any one should attempt the implant pro cedure without availing himself of all the facts and that, having fallen into diffi culties, he will condemn the implant tech nic as unfeasible. Bodecker,03 editorial izing in the New York Dental Journal, stresses the blessings of the implant to the edentulous patient who cannot be fitted for conventional dentures. He must be commended for his advice of caution in the selective application of the implant procedure. But here again the implant is chastised for the reckless abuse of the technic by those who are not qualified to attempt the implant. The American Academy of Denture Implants was founded in 1950 for the sole purpose of preventing exploitation and abuse and to provide a forum for the exchange of news of progress and de velopment in implants. Strict selective judgment is exercised in determining a patient’s need for an implant; it should be noted that of every 12 patients who ask for a lower implant, only one or two qualify. In an attempt to evaluate the technic, design and effectiveness of implant pro-
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Table • Evaluation of impianf procedures performed
Dentist Number of reporting procedures 1948-1951 A B
C
D
20 IL 3 II 1 DL 2 DU 3 DPL
Number of procedures 1951-1957
Total
72 DL 16 DU
108
19 DL 3 DU Il DPU&L
42
1 incomplete 28 DL 1 DU 4 DPL
34
1 IL 21 DL
22
IL
' DL
Failures IL DL 6 DU IL 2 DL 3 DU 3 DPL incomplete DL DU IL DU
DPU&L
Percentage of success (combines206 procedures) 68% 95% 50% 80% IL= Indirect lower (template-X-ray method). DL = Direct lower bone Impression technic. DU= Direct upper bone impression technic. DPU = Direct partial upper bone impression technic. DPL = Direct partial lower bone impression technic. DPU & L= Direct partial upper and direct partial lower bone impression technic. cedures, I have compiled observations of implants which have been placed by my self and those of my colleagues with whom I have been able to effect a scien tific and mutual exchange of information for a period of seven to nine years. Some members of the Academy were picked at random, such as Bodine, Gershkoff and Goldberg, Jermyn and Meibauer. All have performed a sufficient number of implants during the past ten years to provide an adequate number for evalua tion and analysis. It must be stressed that at best these are clinical observations embodying a critical review of shortcom ings. These evaluations are to be found in the table. The criteria for judging a successful implant were: complete coverage; ab sence of pain and pathologic condition over several years; patient comfort and function; negative roentgenographic find ings; stability. All implants evaluated in
the table employed Vitallium special sur gical alloy. It is interesting to note that most failures in all technics occurred in the first three years of implant develop ment. Success in the lower direct implant technic would be closer to 98 per cent if notation were made of the fact that the failures reported by Gershkoff, Goldberg and Lew occurred in the early change from template or indirect technic to di rect bone impression. Design of implants was constantly altered, and each failure suggested an improvement such as elimi nation of alveolar mesh or strut, change of abutment, position of screws, avoidance of mental foramen and consequent par esthesia, atid so forth (Fig. 1). Surgical technics were refined and ultimate stand ardization of design was evolved. Thus, almost 98 per cent of direct lower im plants from 1952 through 1957 were suc cessful. It was also observed that the percent-
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age of success was greatest with patients of long edentulous experience who had greatest atrophy of the mandible and showed a great need for the implant. In most instances, patients selected for the implant procedure had a history of multiple denture failures. In many pa tients, extreme deformities resulting from accident, surgery, neoplasm, and senile atrophy defied conventional procedures but responded favorably to implant treat ment. Patients with prognathism,54 ortho pedic failures,47 dehiscent canals,14 as well as chronically disabled spastic and muscular atrophy patients, were helped by implant dentures (Fig. 8). The history of most upper implants is similar to that of lower implants. The early upper implants either covered alveolar bone or were connected by nar row palatal struts. Most of these were failures. Those upper implants made with complete palatal coverage and ex tending toward nasal spine and malar processes have had a much higher per centage of success (Fig. 2). Improve ments appear every year and there ap pears good promise of perfected technic in the near future. With the eventual evaluation of the work of Kanitz and Goncalves,55 Marziani,22 Lew, Meibauer,56 Nordgren, Bello,57 and others, perhaps the success of the upper implant will equal that of the lower implant.
Partial implants are still too few in number and too recent to evaluate properly, but indications are promising. Partial upper implants have so far been more successful than lower partial im plants. In the latter, the friability of lingual tissue often leads to penetration. I attempt to avoid lingual struts in lower partial implants where possible. The unilateral or free-end saddle im plant has been a challenging type of oral implant and has created peculiar prob lems. I have placed numerous successful restorations of this type. The results have not been consistently perfect, nor have the implants been in the mouth long enough for adequate evaluation. I have reported48 on my technic, discussing some successful implants that have been in place for five years (Fig. 9). Trainin58 has reported a novel modification of the unilateral implant. Marziani, Pejrone, Hammer58 and others of the European Implant Society report several unique adaptations, with possible success for the unilateral implant. C O N C L U S IO N S
There are still many problems concerning the optimum selection of materials for implants and the possibility of improved design. But the fact remains that im plants have remained in good function,
Fig. 8 • Left: Postoperative view of oral mucosa around implant five years after insertion. Right: Anterior-posterior view of upper and lower implant. Upper implant, an early design, showed mobility and was later removed. Lower implant is still in position eight years after insertion
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Fig. 9 • Above: Patient with upper natural den tition opposing lower anterior teeth and left moiar. Because patient refused to wear removable appliances, anterior teeth were prepared for abutments and an implant inserted. Center: Com pleted superstructure cemented in position. Be low: Implant with gold frame joined to anterior abutments
free of infection and with relatively stable qualities for as long as nine years. Authorities on bones, pathology, and his tology, such as Weinmann, Elfenbaum80 and Walter,81 have noted the absence of so-called foreign body responses, excessive bone loss or other insidious sequelae. The mouth with a successful implant remains firm and pink, free of any discharge around the abutment. The abutment be haves the same as any normal tooth, even to the accumulation of calculus and materia alba, and must be treated periodontally similarly to a natural tooth. Roentgenographic examination shows little bone change, and a normal and even rate of resorption common to the age and physiological condition of the patient. If the screws are in normal posi tion, there should be healthy bone adap tation (Fig. 6, 8 left). The condition around the strut is similar to the gingi val crevice; the mucosa forms a protec tive sheath around the strut, similar to a tight rubber sleeve. The sheath appears resistant to instruments, is extremely dense, glossy and tolerant of the implant. Examination of an upper implant that had been in position for four years and was finally removed because the patient had experienced slight tenderness, showed several things (Fig. 10). Careful micro scopic examination of this tissue disclosed that it takes the pink eosin stain, shows a homogenous matrix with compressed fibrocytes with slight evidence of any in flammatory process, and no evidence of a foreign body reaction. The sheath around the implant is called a peri-implant sheath. Examination with a high power microscope shows that these fibro cytes are more compressed and form a denser collagenous lining around the im plant strut. Marziani28 describes the im plant as, . . . a condition which tends to m odify the b io logical exigencies of its surrounding within physiological limits in order to restore a func tion from a state o f injury. It should not be considered as a foreign body. In fact, a cor-
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Fig. 10 • Above: Upper implant removed after five years, with tissue attached to deep struts (implant was of very early design). Below left: Magnification of tissue around struts showing normal fibrous tissue and no foreign body reaction. Below right: Section near post showing normal oral epithelium (A) changing to typical peri-implant tissue around struts (B,C) rectly perform ed im plant creates a ‘c o existence’ between the organism and the im plant material.
Marziani, however, believes that a per forated tantalum plate is an ideal mate rial. Bjorn1*2 of Sweden, analyzing im plant tissue, compares the similarity and difficulties around implants to problems of periodontal situations; that is, pocket formation, accumulation of pathologic conditions in these pockets, similar to those sometimes found in periodontal tissue. Pessimistic conjectures of osteo myelitis and various carcinogenic factors of the so-called foreign bodies are the least of the problems in implants, and certainly such conjectures never have been voiced by any implant dentist. De
spite the vast progress already made in implant dentistry, there are still endless areas of investigation and research open. There is work to be done if all the po tentials of implant dentistry are to come to maximum fruition. 200 Central Park South
1. Weinmann, J. P. Biological factors influencing im plant denture success. J. Implant Den. 2:12 May 1956. 2. Proceedings, Conference on attachment of semi buried foreign bodies. Prosthetic Research Board, Na tional Academy of Sciences, May 18-19, 1957. 3. Jourdan et Maggiolo. Le manuel de l'art du dentiste. Nancy, 1807. 4. Edwards, J. W. Implantation of metallic capsules. Den. Off. & Lab., 4th series 3:84, 1889. 5. Greenfield, E. J. Implantation of artificial crown and bridge abutments. D. Cosmos 55:364 April 1913.
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6. Brill, N. Forudsaetninger for og fremgangsmâder ved anvendelse af specielle ankre for affagelige proteser. Tandlaegebl. 58:379 Aug. 1954. 7. Skinner, P. R. Intraosseous metal implants for denture stabilization. D. Digest 52:427 Aug. 1946. 8. Venable, C. S.; Stuck, W. G., and Beach, A. Effects on bone of the presence of metals; based upon electrolysis. Ann. Surg. 105:917 June 1937. 9. Bernier, J. L., and Canby, C. P. Histologic studies on the reaction of alveolar bone to vîtallîum implants. J.A.D.A. 30:188 Feb. 1943. 10. McCall, J. O. Vitalliumimplant as a bridge abutment. D. Items of Interest 68:15 Jan. 1946. 11. Weinberg, B. D. Subperiosteal implantation of vitallium (cobalt-chromium alloy) artificial abutment. J.A.D.A. 40:549 May 1950., 12. Strock, A. E. Experimental work on a method for the replacement of missing teeth by direct implanta tion of a metal support into the alveolus. Am. J. Orthodont. & Oral Surg. 25:467 May 1939. 13. Dahl, G. S. A. Om môilîgheten for implantation i de kâken an metallskelett som bas eller retention for fosta eller aotaglosa proteser. Odont. Tskr. 51:440, I9'43. 14. Goldberg, N. I., and Gershkoff, A. Implant lower denture. D. Digest 55:490 Nov. 1949. 15. Ogus, W. I. Research report on implantation of metals. D. Digest 57:58 Feb. 1951. 16. Lew, L Implant denture—a simplified upper tech nique using immediate prosthesis. D. Digest 58:10 Jan. 1952. 17. Loechler, P. S., and Mueller, M. W. Successful implant dentures. North-West Den. 31:134 July 1952. 18. Berman, N. An implant technique for full lower dentures. D. Digest 57:438 Oct. 1951. 19. Bodine, R. L., Jr., and Kotch, R. L. Experimental subperiosteal dental implants. U.S. Armed Forces M. J. 4:441 March 1953. 20. Killebrew, R. H. Mandibular implant denture. J. Pros. Den. 2:618 Sept. 1952. 21. Lew, !. Problems and design of the implant. Report to the American Academy of Implant Dentures, St. Louis, 1952. 22. Marziani, L. Degll Impiantî dentari intraossei e Soffoperiostali. Riv. ital. Stomat. 8:998 July 1953. 23. Peirone, G. Considerazioni suglî Impionti sottoperiostei. Riv. ital. Stomat. 10:20 Jan. 1955. 24. Schroeder^ A. Die subperiostale Goldnetzlmplantatlon in einer Sitzung. Schweiz. Mschr. Zahnhk. 67:23 Jan. 1957. 25. Formîggînî, M. S. Impiantî alloplastici endomascellarl con viti metallîche cave. Associazîone Europea Odonto-Stomatologica per qli Impiantî. Attî del simposîo deglî impiantî alloplastici, March 19-20, 1955, p. 195. 26. Personal communication to author. 27. Roccia, B. Oral surgery. Internat. D. J. 7:96 March 1957. 28. Rottenberg^ A. Nouvelles considerations sur les implantes d’acrylîque. Assocîazione Eurooea OdontoStomatologîca per glî Impîantî. Attî del sîmposîo degli impiantî alloplastici, March 19-20, 1955, p. 179. 29. Behrman, S. J. Implantation: principles, prac tices and predictions. J. D. Med. 10:116 July 1955. 30. Cohen, B. M. Antibiotics and întraoral bone grafts. J. Oral Surg. 13:34 Jan. 1955. 31. Conley, J. J. Use of vitallium prostheses and implants în reconstruction of mandibular arch. Plast. & Reconstr. Surg. 8:150 Aug. 1951. 32. Hahn, W. E. Capacity of developina teeth germ elements for self-differentiation when transplanted. J. D. Res. 20:5 Feb. 1941. 33. Flohr, W. L'Imolantation de résine au nîveau de la face et des maxillaires: résultats cliniques et histologiques. Rev. Stomat. 54:113 Feb.-March 1953.
34. Sarojet, A., and Broulgirard, J. Magnetic pros thesis. Rev. Odont.-Stomat. 12:11, 1952. 35. Landa, J. S. Dynamics of psychosomatic dentistry. Brooklyn, Dental Items of Interest, 1953. 36. Brochere, F. incidences psychologiques de I'appareillage en prosthese totale. Odontologie 73:652 Dec. 1952. 37. Dolder, E. Zur Psychologie des Zahn-Verlustes und des Zahn-Ersatzes. Deut. zahnarztl. Zschr. 8:469 April 15, 1956. 38. Collet, H. A., and Briggs, D. L. Some psychologic aspects of denture-stimulated gagging. J. Pros. Den. 3:665 Sept. 1953. 39. Manly, R. S., and Vinton, P. Prosthodontist's prob lem patients. New York D. J. 18:113 March 1952. 40. Knowlton, J. P. Masticatory pressures exerted with implant dentures as compared with soft-tissueborne dentures. J. Pros. Den. 3:721 Sept. 1953. 41. Yurkstas, A., and Curby, W. A. Force analysis of prosthetic appliances during function. J. Pros. Den. 3:82 Jan. 1953. 42. Frechette, A. R. Masticatory forces associated with the use of various types of artificial teeth. J. Pros. Den. 5:252 March 1955. 43. Stromberg, W. R. Method of measuring forces of denture bases against supporting tissues. J. Pros. Den. 5:268 March 1955. 44. Lew, I. Progress report on full implant dentures. J. Pros. Den. 3:571 July 1953. 45. Lew, I. Implant concepts from abroad. J. Implant Den. 2:16 May 1956. 46. Lew, I. Free-end saddle prosthesis: part two. D. Digest 63:456 Oct. 1957. 47. Lew, I. Upper and lower Implant dentures—fixa tion with surgical prosthetic splint. J. Implant Den. 1:36 May 1955. 48. Nichols, F. C. Semiburied denture implants: re view of literature and experimental study. J. Oral Surg. 12:217 July 1954. 49. Bleicher, S. H. Lower implant denture: a review of the literature. J.A.D.A. 53:310 Sept. 1956. 50. Herschfus, L. Histopathologic findings on vital lium implants in dogs. J. Pros. Den. 4:413 May 1954. 51. Parant, M. Utilisation des implants metalllques dits sous-periostés aux Etats-Unis. Associazione Europea Odonto-Stomatologica per gli Implanti. Atti del sim posio degli impianti alloplastici, March 19-20, 1955, p. 63. 52. Conversation with the author. 53. Bodecker, C. F. Implantation—its use and abuse. Editorial. New York State D. J. 21:150 March 1955. 54. Jermyn, A. C. Personal communication with author, 1957. 55. Kanitz, W., and Goncalves, W. O. Upper implants —a modified technique. D. Digest 61:353 Aug. 1955. 56. Meibauer, W. Personal communication to author, 1957. 57. Bello, B. V., and Areal, P. G. E. Dentaduras im plantadas; Implant dentures. Rio de Janeiro, 1956. 58. Trainin, B. Fixed-removable implant bridge. J. Implant Den. 3:26 May 1957. 59. Hammer, H. Zum Problem der operativen Verbesserung ungünstiger Prosthesenlager im Unterkieferbereich, im besonderen durch subperiostale Gerüstimplantationen. Deut. zahnarztl. Zschr. 10:416 March I, 1955. 60. Elfenbaum, A. Roentgenographic evaluation in denture construction. J. Implant Den. 3:12 May 1957. 61. Walter, J. Personal communications to author, (956. 62. Bjorn, H. Experimental prosthetic implants. Asso ciazione Europea Odonto-Stomatologica per gli ,Im pianti. Atti del simposio degli impianti alloplastici. March 19-20, 1955, p. 103.
Isaih Lew, D.D.S., New York
The history of implant dentures is pre sented, and the present two-stage technic of implanting the lower complete denture is described. Criticisms of implant den tures are discussed. Patients with difficult ridges, who have been fitted with im planted lower .complete dentures, have received a measure of comfort and func tion far exceeding that obtained with conventional dentures, for periods rang ing up to ten years. Improvements in upper complete denture implant technics promise to yield a perfected technic in the near future. Indications also are promising for implanted partial dentures. There is still room for improved implant materials and designs. Much more re search is required before all the potentials of implant dentures are to be realized.
J. P. Weinmann,1 addressing the Amer ican Academy for Implant Dentures in its scientific session on the nature of bone and its relationship to implants in den tistry, likened the dentists’ persistence in developing a feasible implant technic to the story of the bumblebee. The bumble bee has a large body and tiny wings. Ac cording to the laws of Isaac Newton and authorities on the subject of aero dynamics, the bumblebee should not be
able to fly. It has also been said that, fortunately, the bumblebee does not know anything about the laws of aerodynamics. Similarly, the implant dentist, in spite of physiological, anatomical, and surgi cal axioms to the contrary, persisted doggedly in the attempt to develop the implant technic, with gradual but cer tain recognition by his peers. D E V E L O P M E N T O F T H E IM P L A N T
Twelve years of refinement and perfec tion have lifted at least one form of im plant dentures, the full lower implant, out of the realm of experimentation into a field of valued and tried adjuncts to prosthetic service. This achievement has created a recognizable impact in dentalmedical circles throughout the world. It has enhanced the stature of the American dental profession and opened the way for further growth in leadership to the American dentist. In May 1957, the Prosthetic Research Board of the National Academy of Sciences called a conference2 on skeletal attachments. Represented were the lead ers of orthopedic research centers, as well as engineers, ophthalmologists and other scientists—all trying to find a solution for a skeletal fixation for improved amputee prostheses, eye prostheses and other pros thetic appliances. Goldberg,, Gershkoff
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and Lew, representing the implant den tists, were pleasantly surprised to learn that they had achieved some of the few clinically positive results which helped solve problems presented by represent atives of other disciplines. It was almost inevitable that the im plant should be developed by the dentist, because his discipline combines knowl edge of anatomy, physiology, histopathology, the dynamics of function, pres sure, stress and strain, with understand ing of metallurgy. For thousands of years men have at tempted to replace lost oral function with various substitutes; Petronious attempted to repair cleft palates with gold in the 16th century. Steel, iron, copper, silver, aluminum, magnesium, glass, lead, por celain, bone, shell and self-polymerizing resins have been tried. The various at tempts in implant development can be classified in three categories: the intraosseous, the transosseous and the sub periosteal. Most of the early work was concerned with intraosseous implants. Maggiolo3 of Paris, 1809; Edwards4 of New York, 1889; Schnoel, 1905; and Greenfield,5 1913, attempted to replace a lost tooth by placing a foreign body in the open socket. In the early nineteen twenties, Brill6 in Germany, and Skinner7 in the United States, attempted to tunnel through the tuberosity with a tube of metal, intending to affix a conventional prosthesis to the implanted tubule. It was not until the now classic research on the electropassive nature of metals suitable for implant work was reported by Venable and Stuck8 in 1936 and later efforts by Bernier and Canby9 in 1943, that the final impetus to the evolution of the modern full denture implant occurred. McCall,10 Weinberg11 and Strock12 at tempted to apply this knowledge to single and to unilateral implants. Dahl,13 in 1943 proposed a crude alveolar type subperiosteal implant, but met with great discouragement. Finally, in 1948, Gold berg and Gershkoff14 breached the sea of
skepticism and reported the first success ful lower implant (Fig. 1,A). A pro fusion of reports from other pioneers fol lowed. Ogus15 in 1951 suggested a novel idea for an implant with removable abut ments, which did not prove clinically feasible. Lew16 in 1952 reported a simple technic for an immediate upper pros thesis, and a more modified technic for a direct bone impression lower implant (Fig. 1,C). Loechler and Mueller,17 Berman,18 Bodine19 and Killebrew20 fol lowed along with their own variations of new ideas in regard to placement and configurations of abutments, the number and thickness of struts, the application to cleft palate, and a one-stage technic20 of Killebrew’s similar to the early template method of Goldberg and Gershkoff. Prog ress and changes in implant design and technic occurred rapidly and added to the confusion of the concepts in early years of the implant. In 1952 I addressed21 the newly formed American Academy for Implant Den tures, in St. Louis, on problems and de sign of the implant. This meeting was one of the early attempts to evaluate dif ferent implant technics and to evolve a standard implant design (Fig. 1, 2). It helped to bring about implants with im proved abutments, elimination of pares thesia, the perfection of impressions, and the two-stage technic which is commonly employed today. Along about this time men in Europe and South America, many of whom had studied or read some of the early work on this subject, attempted to put into use other ideas for implants. Marziani22 at tempted to use a swaged tantalum mesh implant with claims of success. His tech nic in the early stages included fixing the implant in position with intraosseous or transosseous wires. Professor Pejrone23 of Turino attempted to place an implant by using direct impression with a rapid cast technic while the patient was kept in a semi-anesthetized state for six to eight hours. Schroeder24 suggests the use of a
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Fig. I • Evolution of mandibular implant design. A: Crude, bulky frame, thick struts, flat abutments, screws in crest of ridge over bicuspid canal region, resulting in injury to nerve, paresthesia, and so forth. B: Example of effort to extend design to buccal-external oblique region. C: Attempt to relieve region of the mental foramen. Direct impression technic was used, and there are fewer struts over crest of ridge in region of incision. First such implants were weak, too mobile and bent easily. D: Design to overcome faults in C. More secondary struts, screw hole in region of accessibility and bone density, (external oblique ridge and mentolabial region), and away from canal. E: Current design giving maximum strength and minimum bulk, with open areas over alveolar bone allowing for possible resorption. Note simple tapered abutments. Stress of function is spread over widest cortical bone area (external oblique ridqe, lingual bony plate and mentolabial region) similar method, using gold mesh with im mediate fabrication. Formiggini25 used hollow endomaxillary screws. Marziani and Pejrone have used the one-stage tantalum-swaged method, attempting to keep the patient anesthetized while the impression is taken, the implants swaged, and the entire assembly placed in the mouth. This procedure is extremely long and extremely traumatic to the tissues and presents other problems too nu merous to mention. Kress’s work20 on the relief of strain and stress on the superstructure by the utilization of plastic sleeves under the superstructure is an other improvement in implant design which attempts to minimize some of the functional stress. In the annals of the pro ceedings of the European Academy on Implants, convening in Pavia, Italy, ref
erence is made repeatedly to the works of Goldberg and Gershkoff, Killebrew, Bodine, Kosch, Loechler, Jermyn, Herschfus, Lew, and others. Constant reference is made to the work of Americans, par ticularly by Marcel Parant, Roccia,27 Borghesio, Rattenberg,28 Marziani, and others who have observed the work of the American implant dentists over the past 12 years and have compared their results with those of men in South America, Italy, France and Germany. The predominant conclusion is that the method followed in America has proved most durable and most reliable in the greatest number of instances. Other technics are currently used to improve denture stability and to replace lost oral anatomy. Among these are the magnetic implant,29 the graft of auto
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genous bone30 to restore lost tissue, the use of Vitallium or other chrome cobalt alloys to restore bone lost in osteosar coma,31 the transplant of tooth germ,32 the use of acrylic implants and, finally, the use of magnets in conventional den tures for the purpose of effecting greater stability. It is easy to understand why, to the general practitioner and many sur geons and prosthodontists throughout the country, the implant picture is a maze of confusion. These various approaches to the improvement of oral rehabilitation or reconstruction are mentioned so that the reader can know that specific reference is made to the denture implant as the sub
periosteal technic to differentiate from all others. In the past half century, much has appeared in prosthetic periodicals on the understanding of centric relation, or hinge axis, in the development of stable bases, vertical dimension, maximum func tion and esthetics. And yet an increasing number of patients have atrophied maxil lae and mandibles which defy the best prosthetic efforts (Fig. 3 ). These patients have prevailed on the dentist to attempt more radical implant procedures. All too often they have been dismissed as neu rotic or uncooperative. Seldom did a prosthodontist roentgenographically ex
Fig. 2 • Evolution of maxillary implant design. Below and center: Implant design (1950) attempting to achieve stability by distributing stress over palatal bone avoiding incisal canal and postpalatine foramen. Occlusal stress caused anterior-posterior dislocation and mobility. Above right: Frame design (1952) covering more of palate, to overcome objection of early design. Above left: Current design extending to malar process and base of nasal spine, creating tripod effect for greater stability in all phases of mastication. Screw holes are used for early fixation in midline where cortical bone can receive screw safely. Use of surgical prosthetic splint and accurate impression material eliminates use of screws in many instances
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Fig. 3 • Left: Typical condition in patient suitable for implant: low ridge: genial tubercle attachments higher than alveolar ridge: sharp crest with mylohyoid undercuts: no vestibule with high muscle attach ments. Right: Lateral plate of typical edentulous patient suitable for implant amine the mandible to ascertain the possibility of factors such as high mental foramen, dehiscent canal, high muscle attachments, absence of vestibule, inoper able spiny ridges, and so forth, as a cause of failure of conventional dentures (Fig. 4 ). In the process of making a bone impression for an implant operation, implant dentists have observed that atrophied mandibles have, with great fre quency, a large mental foramen with a sensitive artery, vein, and mental nerve, not only on the crest of the ridge but often in the molar region directly under the point of the greatest stress (Fig. 4, above, right and below ). Frequently, the alveolar bone has atrophied and the roof o f the canal has disappeared, to produce a dehiscency not tolerant to a denture base. The mandible, when vertical di mension is lost, turns lingually, forming a sharp angular border from molar to molar. This creates insurmountable func tional problems. Some prosthodontists and surgeons, in desperation, may sug gest radical alveolectomy or a Kazanjian operation to deepen the vestible, or some more radical surgery to relieve the mylo hyoid ridge and to create a more tolerant osseous structure beneath the mucosa. Though the implant technic may ap pear to be a radical procedure, implant dentists, paradoxically, have developed a
great respect for conserving remaining osseous structure. They have observed that with the removal of the outer thin layer of cortical bone, a procedure com mon to such operations, rapid absorption of cancellous bone occurs for a year or so until a new layer of cortical bone is formed. In the meantime, the resulting atrophy creates greater problems with the diminished bone than were present at the onset. In recent years, Landa,35 Brochere,36 Dolder,37 Collet and Briggs38 have de scribed the concomitant psychological symptoms of toothless men, and the vital function and importance of stable den tures to the sensibility of people who are edentulous. They have been concerned with factors that create inferiority com plexes, gagging symptoms, emotional de pression, and other psychological reac tions to loss of oral integrity, and there is little that can be added to their admirable work in this field. However, it has been suggested by psychologists that hysteria accompanying the loss of a tooth or any bodily tissue is a response to fear of cas tration or loss of potency. Emotional stress associated with the prospect of be coming edentulous, especially in active, middle-aged patients, can often reach such proportions as to cause the patient to resist oral rehabilitation. T o many of
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these patients, the only oral restorations that will be acceptable are those that are necessary to their own security and stability. These people’s problems are as real and as deserving of recognition as any serious disturbance and can no longer be dismissed to a general file of neurotics. Increased longevity has resulted in a larger number of people with dwindling osseous structures and associated denture problems. Recent efforts toward objectivity in de termining effectiveness of prosthetic serv ice have effected revaluation of denture effectiveness. Manly and Vinton39 showed that 500 “ ideal” dentures have an aver age efficiency of only 23 per cent in masti cation. Knowlton,40 using a Boos pressure indicator, suggests that an implant den ture has 50 per cent more pressure toler
ance than a tissue-borne base. The work of Yurkstas and Curby41 and, more re cently, of Frechette42 and Stromberg,43 is leading to more realistic and more scientific methods for determining effi ciency of artificial teeth and of forces under the dentures. Their findings ulti mately will foreshadow future successful dentures. Space limits a discussion of the de velopment of the implant from the early, uncertain template methods to more ac curate two-stage technics. Problems of trauma, stability, paresthesia, bone loss, type of tooth material, early fixation and periods of being without teeth all have been overcome and are more fully covered in other reports.21’ 44'48 It is diffi cult to discuss implants, however, with out describing some of the technic. It
Fig. 4 • Above left: Model of mandible illustrating evolution of atrophy of mandible justifying im plant procedure. Cut-away surface shows loss of alveolar bone with mental foramen and contents resting on crest of ridge under greatest stress of denture. Above right: Model of denuded mandible, showing that what appeared on clinical examination as good ridge for a denture actually had mental foramen and contents open on crest of ridge or in periphery of denture base. Below: Model of bone, illustrating sharp alveolar ridge and lingual undercuts making difficult denture problems. Alveolectomy of such a ridge would increase severity of problem
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has been the lack of understanding of the method and all of its ramifications that has resulted in failures, and not the tech nic itself. TECHNIC
The primary step is in the selection of the patient for the implant. The patient must be able to understand the complexity of the procedure and be fully cooperative. Thorough examination of physiologic and psychologic conditions may save untold difficulties. After the patient’s suitability for the implant procedure has been established, accurate impressions are made, employ ing the bite and wax set-up as in the conventional denture procedure. Roent genograms, including lateral and occlusal
views, and thorough intraoral examina tion, help to locate points important in designing the framework, impression trays, position of screws, and other types of fixation used. The implant dentist may develop within his own mind a threedimensional image of the mandible or maxilla of the patient as a result of these thorough examinations. The patient is now ready for the pri mary impression operation. Tissues are incised along the crest of the ridge and retracted radically, and a careful impres sion is taken in accurate materials, using compound, zinc oxide, rubber base mate rial, or the new sili-gel impression mate rial (Fig. 5, above left). Tissues are care fully debrided and coapted. The old denture may be lined with a suitable material and placed over the incision to
Fig. 5 • Above left: Alveolar bone denuded, tissues retracted, ready for impression. Above right: Stone model with waxed implant framework, abutment surveyed parallel and screw hole countersunk, ready for casting. Below: Cast implant frame and superstructure articulated against upper waxed denture
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improve the patient’s comfort during the ance, function and esthetics, are attained. healing period. In this most critical phase, Again, failure to use good judgment in novices often perpetrate a series of errors the selection of tooth material, the trau which can culminate only in failure. They matic effect, of natural opposing teeth, may fail to open tissues adequately, and and failure to avoid ischemic effects of impressions may show lack of detail in the superstructure pressing orf the mu extension to the vital dense bone; also, cosa over implant framework are some often they traumatize bone excessively in of the factors contributing to complica dissecting the mental nerve and sub tions in the implant. The obligation of both the surgeon and lingual tissues. The use of preoperative antibiotics, antihistamines, postoperative the prosthodontist does not end after they sedation, and warm saline packs during have inserted a successful implant. Their surgery, materially diminishes the gross responsibilities, if they are to maintain a ness of postoperative sequelae. healthy implant, continue for the life of Models are now duplicated, and the the appliance. Periodic surveillance with implant and superstructure are carefully roentgenograms and clinical checks must designed and fabricated (Fig. 5, above be arranged to avoid loose screws, hyper right, below). Roentgenograms are made trophied tissue, and excessive wear and to preclude faulty castings of the implant. closure, conditions which can result from Each implant denture must be designed increased function allowed by the im carefully by the doctor and not the tech plant (Fig. 6,7). All must be promptly nician. Failures result when untrained attended to in order to maintain the im dental personnel assume responsibility for plant and the health of the patient. Care the fabrication of a highly technical ap ful oral hygiene must be demanded, just pliance; lack of adequate coverage or as of any patient under periodontal treat strength, lack of proper thickness of ment. struts, improper position of the abut When one considers the many problems ments and, especially, lack of parallelism confronted, it is surprising to find the of the superstructure in consequent oc percentage of failures so low. During the clusal restoration are failures which can evolution of the implant procedure, many result. evaluations made by prominent prostho The second surgical procedure should dontists and oral surgeons tended to con not be attempted until complete healing fuse many practitioners. Nichols48 made a has occurred. Premature entry for the lengthy report on his original research on insertion may cause failure of tissue dogs in which the validity of the denture closure and ensuing discomfort. To be implant was questioned. This article is cautioned against are carelessly fitted beautifully written, well illustrated, and screws, failure to remove early granula is an impressive effort. Nichols concluded tion tissue before the implant is fitted, with the observation that complete den and indifferent use of coapting technics. ture implants are not feasible; to the The patient is discharged with a pros average reader, he probably made an ex thetic surgical splint (a denturehke plat cellent and convincing case. However, if form with anterior teeth, developed to the article is read carefully, it will be seen ease postoperative problems for the pa that the original statement is that the im tient while he awaits the fabrication of plants were placed in the dental arch of the final superstructure).47 a dog, using the methods of Goldberg Within four to six weeks the final and Gershkoff. No one experienced in superstructure is fabricated. Here all con implant dentistry would attempt to insert summate skill must be applied so that an implant in an alveolar bone in which centric relation, dimension, vertical bal recent extractions had been made, nor
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*
-
4 ^
9
Fig. 6 • Top two rows: Direct impression implant placed in 1950. It is well fitting, properly designed. Bottom two rows: Same region, seven years later; no appreciable bone loss, good function, healthy on clinical examination would he expect a unilateral implant un supported in the arch of a dog to remain for any time, because animals cannot be told to leave the surgery unmolested. But what is most important, an understanding of the implant procedure would show the absence of any similarity of this tech nic used by Nichols on the dogs, with the early efforts of Goldberg and Gershkoff. Nichols’ thesis proves merely that the Nichols implant does not work on dogs —and nothing else! Bleicher49 sparsely reviewed implant
progress, using some of the afore-mentioned research as a basis for pessimism, but admits that some implants may be successful. Behrman,29 who debated with the author at great length before the Academy of Dental Medicine, has now inserted several successful lower implants, to modify his early skepticism. There are many instances of repeated efforts at laboratory animal experimentation, no tably those of Bernier and Canby,9 Bodine,19 Herschfus,80 and my own more recent unpublished report of work on
LEW . . . V O L U M E 59, SEPTEMBER 1959 • 487
m
m
f- SmÊÊ « « 1 Rq. 7 • Early^template Implant which never fit accurately. Top two rows: Space between implant and bone at time of insertion ( 1950). Bottom two rows: Noticeable setting of implant three years later, with reqion of rarefaction and absorption of bone. Mobility of frame, poor extension to cortical bone, lack of close approximation con tributed to failure monkeys where I placed implants in edentulous regions of the jaws of monkeys, and secured the implants with fixed bridges so the monkey could not remove them. There is still a problem of debris around the implant. Nevertheless, I was sufficiently impressed with the results to feel that further research in that field should be encouraged. I was convinced that various materials which were used in this implant (such as teflon and kel-F and a combination of these plastics with Vitallium castings) might bring about improvements in the fabrication of im plants. Laboratory animal experimenta tion is valuable only to test the tolerance and physiological reaction of tissue to material buried in the tissue. A labora tory animal cannot act and react as hu mans do, and any experiment expecting them to do so is bound to be invalid. Approximately 95 per cent of lower implant dentures have given patients with difficult lower ridges comfort and function far exceeding that obtained with conventional dentures, for a period ranging up to nine or ten years. This reality cannot be ignored, despite the failure of the technic on dogs. As far as the complete lower implant is concerned,
it is needless to have recourse to labora tory animals when there are several thousand human implants available for examination and evaluation. Men of stature in the surgical and prosthetic fields, such as Marcel Parant,51 Franz Hildebrand of Sweden and many other leaders of the dental societies of Mexico, South America and remote corners of the world came to review and see actual im plants which have functioned for the past ten years. Their reaction is best sum marized in the statement made by Pro fessor Isauma Nakasoma,52 professor of prosthetic dentistry in the Tokyo Medical and Dental University. He said, As far as m odern prosthetics is concerned . . . one o f the most significant . . . advances in the past fifty years has been the full denture im plant as perform ed by the leading im plantodontists in the United States.
It is difficult to understand how any one should attempt the implant pro cedure without availing himself of all the facts and that, having fallen into diffi culties, he will condemn the implant tech nic as unfeasible. Bodecker,03 editorial izing in the New York Dental Journal, stresses the blessings of the implant to the edentulous patient who cannot be fitted for conventional dentures. He must be commended for his advice of caution in the selective application of the implant procedure. But here again the implant is chastised for the reckless abuse of the technic by those who are not qualified to attempt the implant. The American Academy of Denture Implants was founded in 1950 for the sole purpose of preventing exploitation and abuse and to provide a forum for the exchange of news of progress and de velopment in implants. Strict selective judgment is exercised in determining a patient’s need for an implant; it should be noted that of every 12 patients who ask for a lower implant, only one or two qualify. In an attempt to evaluate the technic, design and effectiveness of implant pro-
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Table • Evaluation of impianf procedures performed
Dentist Number of reporting procedures 1948-1951 A B
C
D
20 IL 3 II 1 DL 2 DU 3 DPL
Number of procedures 1951-1957
Total
72 DL 16 DU
108
19 DL 3 DU Il DPU&L
42
1 incomplete 28 DL 1 DU 4 DPL
34
1 IL 21 DL
22
IL
' DL
Failures IL DL 6 DU IL 2 DL 3 DU 3 DPL incomplete DL DU IL DU
DPU&L
Percentage of success (combines206 procedures) 68% 95% 50% 80% IL= Indirect lower (template-X-ray method). DL = Direct lower bone Impression technic. DU= Direct upper bone impression technic. DPU = Direct partial upper bone impression technic. DPL = Direct partial lower bone impression technic. DPU & L= Direct partial upper and direct partial lower bone impression technic. cedures, I have compiled observations of implants which have been placed by my self and those of my colleagues with whom I have been able to effect a scien tific and mutual exchange of information for a period of seven to nine years. Some members of the Academy were picked at random, such as Bodine, Gershkoff and Goldberg, Jermyn and Meibauer. All have performed a sufficient number of implants during the past ten years to provide an adequate number for evalua tion and analysis. It must be stressed that at best these are clinical observations embodying a critical review of shortcom ings. These evaluations are to be found in the table. The criteria for judging a successful implant were: complete coverage; ab sence of pain and pathologic condition over several years; patient comfort and function; negative roentgenographic find ings; stability. All implants evaluated in
the table employed Vitallium special sur gical alloy. It is interesting to note that most failures in all technics occurred in the first three years of implant develop ment. Success in the lower direct implant technic would be closer to 98 per cent if notation were made of the fact that the failures reported by Gershkoff, Goldberg and Lew occurred in the early change from template or indirect technic to di rect bone impression. Design of implants was constantly altered, and each failure suggested an improvement such as elimi nation of alveolar mesh or strut, change of abutment, position of screws, avoidance of mental foramen and consequent par esthesia, atid so forth (Fig. 1). Surgical technics were refined and ultimate stand ardization of design was evolved. Thus, almost 98 per cent of direct lower im plants from 1952 through 1957 were suc cessful. It was also observed that the percent-
LEW . . . V O L U M E 59, SEPTEMBER 1959 • 489
age of success was greatest with patients of long edentulous experience who had greatest atrophy of the mandible and showed a great need for the implant. In most instances, patients selected for the implant procedure had a history of multiple denture failures. In many pa tients, extreme deformities resulting from accident, surgery, neoplasm, and senile atrophy defied conventional procedures but responded favorably to implant treat ment. Patients with prognathism,54 ortho pedic failures,47 dehiscent canals,14 as well as chronically disabled spastic and muscular atrophy patients, were helped by implant dentures (Fig. 8). The history of most upper implants is similar to that of lower implants. The early upper implants either covered alveolar bone or were connected by nar row palatal struts. Most of these were failures. Those upper implants made with complete palatal coverage and ex tending toward nasal spine and malar processes have had a much higher per centage of success (Fig. 2). Improve ments appear every year and there ap pears good promise of perfected technic in the near future. With the eventual evaluation of the work of Kanitz and Goncalves,55 Marziani,22 Lew, Meibauer,56 Nordgren, Bello,57 and others, perhaps the success of the upper implant will equal that of the lower implant.
Partial implants are still too few in number and too recent to evaluate properly, but indications are promising. Partial upper implants have so far been more successful than lower partial im plants. In the latter, the friability of lingual tissue often leads to penetration. I attempt to avoid lingual struts in lower partial implants where possible. The unilateral or free-end saddle im plant has been a challenging type of oral implant and has created peculiar prob lems. I have placed numerous successful restorations of this type. The results have not been consistently perfect, nor have the implants been in the mouth long enough for adequate evaluation. I have reported48 on my technic, discussing some successful implants that have been in place for five years (Fig. 9). Trainin58 has reported a novel modification of the unilateral implant. Marziani, Pejrone, Hammer58 and others of the European Implant Society report several unique adaptations, with possible success for the unilateral implant. C O N C L U S IO N S
There are still many problems concerning the optimum selection of materials for implants and the possibility of improved design. But the fact remains that im plants have remained in good function,
Fig. 8 • Left: Postoperative view of oral mucosa around implant five years after insertion. Right: Anterior-posterior view of upper and lower implant. Upper implant, an early design, showed mobility and was later removed. Lower implant is still in position eight years after insertion
490 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
Fig. 9 • Above: Patient with upper natural den tition opposing lower anterior teeth and left moiar. Because patient refused to wear removable appliances, anterior teeth were prepared for abutments and an implant inserted. Center: Com pleted superstructure cemented in position. Be low: Implant with gold frame joined to anterior abutments
free of infection and with relatively stable qualities for as long as nine years. Authorities on bones, pathology, and his tology, such as Weinmann, Elfenbaum80 and Walter,81 have noted the absence of so-called foreign body responses, excessive bone loss or other insidious sequelae. The mouth with a successful implant remains firm and pink, free of any discharge around the abutment. The abutment be haves the same as any normal tooth, even to the accumulation of calculus and materia alba, and must be treated periodontally similarly to a natural tooth. Roentgenographic examination shows little bone change, and a normal and even rate of resorption common to the age and physiological condition of the patient. If the screws are in normal posi tion, there should be healthy bone adap tation (Fig. 6, 8 left). The condition around the strut is similar to the gingi val crevice; the mucosa forms a protec tive sheath around the strut, similar to a tight rubber sleeve. The sheath appears resistant to instruments, is extremely dense, glossy and tolerant of the implant. Examination of an upper implant that had been in position for four years and was finally removed because the patient had experienced slight tenderness, showed several things (Fig. 10). Careful micro scopic examination of this tissue disclosed that it takes the pink eosin stain, shows a homogenous matrix with compressed fibrocytes with slight evidence of any in flammatory process, and no evidence of a foreign body reaction. The sheath around the implant is called a peri-implant sheath. Examination with a high power microscope shows that these fibro cytes are more compressed and form a denser collagenous lining around the im plant strut. Marziani28 describes the im plant as, . . . a condition which tends to m odify the b io logical exigencies of its surrounding within physiological limits in order to restore a func tion from a state o f injury. It should not be considered as a foreign body. In fact, a cor-
L EW . . . V O L U M E 59, SEPTEMBER 1959 • 491
Fig. 10 • Above: Upper implant removed after five years, with tissue attached to deep struts (implant was of very early design). Below left: Magnification of tissue around struts showing normal fibrous tissue and no foreign body reaction. Below right: Section near post showing normal oral epithelium (A) changing to typical peri-implant tissue around struts (B,C) rectly perform ed im plant creates a ‘c o existence’ between the organism and the im plant material.
Marziani, however, believes that a per forated tantalum plate is an ideal mate rial. Bjorn1*2 of Sweden, analyzing im plant tissue, compares the similarity and difficulties around implants to problems of periodontal situations; that is, pocket formation, accumulation of pathologic conditions in these pockets, similar to those sometimes found in periodontal tissue. Pessimistic conjectures of osteo myelitis and various carcinogenic factors of the so-called foreign bodies are the least of the problems in implants, and certainly such conjectures never have been voiced by any implant dentist. De
spite the vast progress already made in implant dentistry, there are still endless areas of investigation and research open. There is work to be done if all the po tentials of implant dentistry are to come to maximum fruition. 200 Central Park South
1. Weinmann, J. P. Biological factors influencing im plant denture success. J. Implant Den. 2:12 May 1956. 2. Proceedings, Conference on attachment of semi buried foreign bodies. Prosthetic Research Board, Na tional Academy of Sciences, May 18-19, 1957. 3. Jourdan et Maggiolo. Le manuel de l'art du dentiste. Nancy, 1807. 4. Edwards, J. W. Implantation of metallic capsules. Den. Off. & Lab., 4th series 3:84, 1889. 5. Greenfield, E. J. Implantation of artificial crown and bridge abutments. D. Cosmos 55:364 April 1913.
492 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
6. Brill, N. Forudsaetninger for og fremgangsmâder ved anvendelse af specielle ankre for affagelige proteser. Tandlaegebl. 58:379 Aug. 1954. 7. Skinner, P. R. Intraosseous metal implants for denture stabilization. D. Digest 52:427 Aug. 1946. 8. Venable, C. S.; Stuck, W. G., and Beach, A. Effects on bone of the presence of metals; based upon electrolysis. Ann. Surg. 105:917 June 1937. 9. Bernier, J. L., and Canby, C. P. Histologic studies on the reaction of alveolar bone to vîtallîum implants. J.A.D.A. 30:188 Feb. 1943. 10. McCall, J. O. Vitalliumimplant as a bridge abutment. D. Items of Interest 68:15 Jan. 1946. 11. Weinberg, B. D. Subperiosteal implantation of vitallium (cobalt-chromium alloy) artificial abutment. J.A.D.A. 40:549 May 1950., 12. Strock, A. E. Experimental work on a method for the replacement of missing teeth by direct implanta tion of a metal support into the alveolus. Am. J. Orthodont. & Oral Surg. 25:467 May 1939. 13. Dahl, G. S. A. Om môilîgheten for implantation i de kâken an metallskelett som bas eller retention for fosta eller aotaglosa proteser. Odont. Tskr. 51:440, I9'43. 14. Goldberg, N. I., and Gershkoff, A. Implant lower denture. D. Digest 55:490 Nov. 1949. 15. Ogus, W. I. Research report on implantation of metals. D. Digest 57:58 Feb. 1951. 16. Lew, L Implant denture—a simplified upper tech nique using immediate prosthesis. D. Digest 58:10 Jan. 1952. 17. Loechler, P. S., and Mueller, M. W. Successful implant dentures. North-West Den. 31:134 July 1952. 18. Berman, N. An implant technique for full lower dentures. D. Digest 57:438 Oct. 1951. 19. Bodine, R. L., Jr., and Kotch, R. L. Experimental subperiosteal dental implants. U.S. Armed Forces M. J. 4:441 March 1953. 20. Killebrew, R. H. Mandibular implant denture. J. Pros. Den. 2:618 Sept. 1952. 21. Lew, !. Problems and design of the implant. Report to the American Academy of Implant Dentures, St. Louis, 1952. 22. Marziani, L. Degll Impiantî dentari intraossei e Soffoperiostali. Riv. ital. Stomat. 8:998 July 1953. 23. Peirone, G. Considerazioni suglî Impionti sottoperiostei. Riv. ital. Stomat. 10:20 Jan. 1955. 24. Schroeder^ A. Die subperiostale Goldnetzlmplantatlon in einer Sitzung. Schweiz. Mschr. Zahnhk. 67:23 Jan. 1957. 25. Formîggînî, M. S. Impiantî alloplastici endomascellarl con viti metallîche cave. Associazîone Europea Odonto-Stomatologica per qli Impiantî. Attî del simposîo deglî impiantî alloplastici, March 19-20, 1955, p. 195. 26. Personal communication to author. 27. Roccia, B. Oral surgery. Internat. D. J. 7:96 March 1957. 28. Rottenberg^ A. Nouvelles considerations sur les implantes d’acrylîque. Assocîazione Eurooea OdontoStomatologîca per glî Impîantî. Attî del sîmposîo degli impiantî alloplastici, March 19-20, 1955, p. 179. 29. Behrman, S. J. Implantation: principles, prac tices and predictions. J. D. Med. 10:116 July 1955. 30. Cohen, B. M. Antibiotics and întraoral bone grafts. J. Oral Surg. 13:34 Jan. 1955. 31. Conley, J. J. Use of vitallium prostheses and implants în reconstruction of mandibular arch. Plast. & Reconstr. Surg. 8:150 Aug. 1951. 32. Hahn, W. E. Capacity of developina teeth germ elements for self-differentiation when transplanted. J. D. Res. 20:5 Feb. 1941. 33. Flohr, W. L'Imolantation de résine au nîveau de la face et des maxillaires: résultats cliniques et histologiques. Rev. Stomat. 54:113 Feb.-March 1953.
34. Sarojet, A., and Broulgirard, J. Magnetic pros thesis. Rev. Odont.-Stomat. 12:11, 1952. 35. Landa, J. S. Dynamics of psychosomatic dentistry. Brooklyn, Dental Items of Interest, 1953. 36. Brochere, F. incidences psychologiques de I'appareillage en prosthese totale. Odontologie 73:652 Dec. 1952. 37. Dolder, E. Zur Psychologie des Zahn-Verlustes und des Zahn-Ersatzes. Deut. zahnarztl. Zschr. 8:469 April 15, 1956. 38. Collet, H. A., and Briggs, D. L. Some psychologic aspects of denture-stimulated gagging. J. Pros. Den. 3:665 Sept. 1953. 39. Manly, R. S., and Vinton, P. Prosthodontist's prob lem patients. New York D. J. 18:113 March 1952. 40. Knowlton, J. P. Masticatory pressures exerted with implant dentures as compared with soft-tissueborne dentures. J. Pros. Den. 3:721 Sept. 1953. 41. Yurkstas, A., and Curby, W. A. Force analysis of prosthetic appliances during function. J. Pros. Den. 3:82 Jan. 1953. 42. Frechette, A. R. Masticatory forces associated with the use of various types of artificial teeth. J. Pros. Den. 5:252 March 1955. 43. Stromberg, W. R. Method of measuring forces of denture bases against supporting tissues. J. Pros. Den. 5:268 March 1955. 44. Lew, I. Progress report on full implant dentures. J. Pros. Den. 3:571 July 1953. 45. Lew, I. Implant concepts from abroad. J. Implant Den. 2:16 May 1956. 46. Lew, I. Free-end saddle prosthesis: part two. D. Digest 63:456 Oct. 1957. 47. Lew, I. Upper and lower Implant dentures—fixa tion with surgical prosthetic splint. J. Implant Den. 1:36 May 1955. 48. Nichols, F. C. Semiburied denture implants: re view of literature and experimental study. J. Oral Surg. 12:217 July 1954. 49. Bleicher, S. H. Lower implant denture: a review of the literature. J.A.D.A. 53:310 Sept. 1956. 50. Herschfus, L. Histopathologic findings on vital lium implants in dogs. J. Pros. Den. 4:413 May 1954. 51. Parant, M. Utilisation des implants metalllques dits sous-periostés aux Etats-Unis. Associazione Europea Odonto-Stomatologica per gli Implanti. Atti del sim posio degli impianti alloplastici, March 19-20, 1955, p. 63. 52. Conversation with the author. 53. Bodecker, C. F. Implantation—its use and abuse. Editorial. New York State D. J. 21:150 March 1955. 54. Jermyn, A. C. Personal communication with author, 1957. 55. Kanitz, W., and Goncalves, W. O. Upper implants —a modified technique. D. Digest 61:353 Aug. 1955. 56. Meibauer, W. Personal communication to author, 1957. 57. Bello, B. V., and Areal, P. G. E. Dentaduras im plantadas; Implant dentures. Rio de Janeiro, 1956. 58. Trainin, B. Fixed-removable implant bridge. J. Implant Den. 3:26 May 1957. 59. Hammer, H. Zum Problem der operativen Verbesserung ungünstiger Prosthesenlager im Unterkieferbereich, im besonderen durch subperiostale Gerüstimplantationen. Deut. zahnarztl. Zschr. 10:416 March I, 1955. 60. Elfenbaum, A. Roentgenographic evaluation in denture construction. J. Implant Den. 3:12 May 1957. 61. Walter, J. Personal communications to author, (956. 62. Bjorn, H. Experimental prosthetic implants. Asso ciazione Europea Odonto-Stomatologica per gli ,Im pianti. Atti del simposio degli impianti alloplastici. March 19-20, 1955, p. 103.