- Email: [email protected]
Development of a new endosseous dental implant. Part I: Animal studies
MAXILLOFACIAL PROSTHETICS TEMPOROMANDIBULAR JOINT SECTION
l
DENTAL IMPLANTS
EDITORS
I. KENNETH
RONALD
ADISMAN
I’. DESJARDINS
Development of a new endosseous dental implant. Part I: Animal studies M. B. Weiss, D.D.S.,* Rush-Presbyterian
and W. Rostoker, Ph.D. **
St. Luke’s
Medical
Center,
and University
T
he need to replace missing teeth by artificial means has been the mission of dentists since early Egyptian times. The development of an effective endosseous dental implant to act as a tooth substitute was the primary goal of this research. Such an achievement would make available to the dentist an replacement. alternate mode of prosthodontic Another goal of the study was to develop a system of implantation that would allow the general practitioner to treat the patient with an implant in his office.
BACKGROUND The literature on dental implants is extensive. In Europe, Formiggini’. y used metallic pins in the form of a tripod to serve as a fixed partial denture abutment. Chercheve’-’ used a metal spiral as an implant. In the United States, Linkow”-‘” advocated driving a metallic blade into the bone to serve as an anchor for a prosthesis. At the request of the American Dental Association (ADA) Council on Dental Materials and Devices, Natiella et al.“’ reviewed 274 articles that were mostly clinical reports showing a complete lack of standardized clinical experiments. As a result, the ADA Council on Dental Materials and Devices stated that there was insufficient information available to warrant the use of implants as a routine procedure.*‘1 A symposium on implant dentistry was cosponsored by the ADA Council on Dental Materials and Devices and by the National Institutes of Health. A statement published by the Council on Dental Mate-
Presented at the American Prosthodontic Society, Chicago, Ill. *Associate Professor, Department of General Surgery, Rush University; Associate Attending, Presbyterian-St. Luke’s Hospital; Professor Emeritus of Dentistry, University of Illinois. **Professor of Metallurgy and Bioengineering, University of Illinois.
646
DECEMBER
1981
VOLUME
46
NUMBER
6
of Illinois,
Chicago,
Ill.
rials and Devices and the Council on Dental Research declared that endosseous dental implants should be considered in the new technique phase and that more studies were needed.” The Council on Dental Materials and Devices reaffirmed its position on dental endosseous implants in March 1975, stating that implants should still be considered in the new technique stage of development.” In view of this lack of conclusive scientific data, the National Institute of Dental Ressearch granted funds in 1978 to support a conference on the benefits and risks of dental implants. Experts in implant research and those experienced in clinical implant dentistry gathered to reach a consensus on dental implants. Following this Harvard consensus conference, the Council on Dental Materials and Devices stated in 1979 that dental implants should be evaluated on a benefit-risks basis to the patient and promised an updated position paper when more data became available.‘” Thus, although endosseous implants have been used extensively, the field of dental implantology lacks scientifically conducted animal and human studies.
MATERIALS AND DESIGN OF FIBER-METAL ENDOSSEOUS DENTAL IMPLANTS Studies of both long bone and alveolar bone have established that healthy and stable calcified tissue will grow into a porous material, provided that the material itself is inert in its environment and that the pores or channels are large enough. The porous material may be ceramic, a polymer, or created from a metal alloy, as long as biocompatibility exists. Although other metals have been used for human implants, titanium has proven to offer the biocompatibility, strength, and malleability needed for a fiber-metal endosseous dental implant.‘:-” The term “fiber-metal” describes the porous surface of the implant. The surface, which is attached to OOZ-3913/81/120646
+ 06$00.60/00
1981 The C. V. Mosby Co.
NEW ENDOSSEOUS
DENTAL
Fig. 1. Fig. 2. root. Fig. 3. power). Fig. 4. power). Fig. 5. Fig. 6. Fig. 7.
IMPLANT
Porous fiber-metal endosseous dental implant. Root socket experimental implant for dog. Implant Undecalcified
histological
section of normal
bone ingrowth
is same diameter as around wires
{low
Undecalcified cross-section of normal bone with fibrous tissue interface (higher II, fibrous tissue interface. Implant and crown in baboon. Implant site in baboon. Crown on implant in baboon.
a solid center post, is fabricated from unalloyed titanium. The solid center post is made from an alloy of titanium that contains aluminum and vanadium. These materials are extremely corrosion resistant and are noble metals in the electromotive series. THE JOURNAL
cylinder
OF PROSTHETIC
DENTISTRY
Their use in combination will not result in galvanic corrosion, which is common with many other metallit combinations. The porous meshwork is manufactured from fine wires shaped in an interlocking configuration of 647
WEISS AND
ROSTOKER
considered a failure when it exfoliated and was lost or wheti suppuration and inflammation indicated its removal. There were 11 failures among the 78 implants. Following sacrifice of the animals, histological evaluation was made of the specimens. The sections in the dog study showed bony ingrowth into the wire meshwork after 3 weeks (Fig. 3). There was a normal distribution of osteocytes and haversian systems, the fibrous tissue was normal with varying layers of fibrocytes, and the vascular elements were in normal distribution (Fig. 4). Electron probe studies confirmed that there was always an interface of fibrous tissue 5 to 50 p thick between the bone and the metal.
Baboon studies
Fig. 8. Radiograph and crown.
of mandibular
molar tooth implant
metal and continuous voids with a quite precise overall shape. The meshwork-post combination is heated to a high temperature in a high vacuum. This process, called sintering, generates strong metallurgical bonds at all points of contact. The fiber-metal dental implant (Fig. 1) has the following attributes: (1) a pore volume of at least 50%, (2) completely interconnecting pore channels, almost all of which are sufficiently large to allow bony ingrowth, and (3) mechanical properties that include acceptable strength, elastic compliance comparable to that of the host bone, and great resistance to cracking and fracture.
Dog studies In 1969, the fiber-metal dental implant was first used as a tooth replacement in mongrel dogs. Fibermetal implants were inserted in the root wound sockets of the extracted molar teeth of these dogs (Fig. 2). Seventy-eight implants were studied for periods from 1 week to 1 year. An implant was
648
The next phase of the research subjected the implant to the forces of mastication. The female baboon was selected as the experim’ental animal because the dentition and masticatory movements resemble those of humans. Thirty animals were used in the experiment, with an average of eight implants placed in each animal. All implants had a root portion embedded in bone and a crown portion extending into the oral cavity. The crown was fabricated of acrylic resin that reproduced the normal morphology of the baboon tooth (Fig. 5). Each crown affixed to the implant was put in functional occlusion with the opposing natural tooth. None of the functioning implants was attached to an adjacent tooth. The teeth were extracted, and the edentulous region was allowed to heal for at least 4 weeks. Following the healing period, the animal was anesthetized intravenously with sodium thiamylal, and normal saline was administered intravenously during surgery. Sodium thiamylal was admded through the saline as needed. The edentulous region chosen for implantation was entered with a scalpel, and an incision was made along the crest of the residual alveolar ridge. The mucosa and the periosteum were reflected, exposing the bone. A calibrated, tapered bone drill in a low-speed handpiece was used to bore the initial opening to the necessary depth (Fig. 6). Normal saline solution was sprayed on the bur during the drilling procedure. A specially made four-fluted end mill fitted to the low-speed dental handpiece was used to create an opening of appropriate size to accept the implant. A hand reamer was used to size the opening more
DECEMBER
1981
VOLUME
46
NUMBER
6
NEW ENDOSSEOUS
DENTAL
IMPLANT
Fig. 9. A to C. Vertical undecalcified histological section of baboon implant. a, gingival crest; b, normal bone; C, normal connective tissue; d, center post of implant; and e, capillaries. (Magnification, x 50.)
THE JOURNAL
OF PROSTHETIC
DENTISTRY
649
WElSS AND
ROSTOKER
Fig. 10. Vertical section of undecalcified bone from baboon. A, implant; and B, bone. (Magnification, X 75.) (Transmitted light.) Fig. 11. Same specimen as in Fig. 10 under ultraviolet light. A, implant; B, bone; and C, fluorescing calcifying bone tagged with tetracycline. (Magnification, x 75.) exactly and allow the implant to be in intimate contact with the bone for its entire length. Normal saline was used to cool the drill and lavage the opening in the bone. The implant was placed in a seating instrument and inserted into the prepared opening by hand pressure or by a light tap of a mallet. The implant was placed with the fiber-metal meshwork 0.5 mm below the crest of the alveolar bone. The animal was placed on a regimen of penicillin and a soft diet for 6 days. The successful implant was fully stabilized after 4 weeks, at which time impressions were made for the construction of acrylic resin crowns. The crowns were adjusted to harmonize with the occlusion of the animal. The implants were radiographed and photo
DISCUSSION The baboon study showed results similar to those of the dog study with regard to the response of the host bone and soft tissue to the presence of the implant. Because the baboon specimens had longer survival times, most specimens showed bony ingrowth through the entire meshwork up to the
650
solid metal core. A fibrous interface of varying widths was always present between the bone and the metal. The characteristics of the bone and fibrous tissue were normal and could not be distinguished from the adjacent surrounding tissues. The bone surrounding the implant wires in the baboon specimens exhibited normal haversian systems and osteocytes distributed in the normal pattern of the jaw bones (Fig. 9). Animals administered tetracycline prior to sacrifice produced histological sections demonstrating that the investing bone in and around the implant was viable, living, and normal. The calcifying bone was tagged with the tetracycline and fluoresced when the histological section was viewed under ultraviolet light (Figs. 10 and 11). Histological analysis of failing implants revealed that bone was being replaced with inflammatory cells by the resorption process. When the process was rapid (due to influences such as traumatic occlusion), hemorrhage, purulent exudate, and resultant infection occurred. The investing bone of the slowly failing implant was replaced by connective tissue, and the implant remained immobile when only one-third of it was still invested in bone. Experience from other types of failing implants has shown that the most vulnerable site is where the implant penetrates through the oral mucosa into the oral cavity. The interface between the soft tissue and the metal is a pathway for bacteria and loxins of the oral cavity to reach the supporting bone and cause resorption of the bone, with resultant mobility and possible loss of the implant.
DECEMBER
1981
VOLUME
46
NUMBER
6
NEW ENDOSSEOUS
DENTAL
IMPLANT
By contrast, this implant has open fiber-metal meshwork on the superior surface in proximity to the bone. This fiber meshwork allows ingrowth of normal connective tissue or, in some cases, bone (Fig. 9, B). As a result, the superior implant surface is sealed and provides a normal physiological base for the gingival tissue that is closely adherent to the highly polished biocompatible implant post. This combination of sealants resists the penetration of destructive elements from the oral cavity. In this study, 182 implants were placed in baboons. Over an experimental period of 26 months, 69 implants were lost. Eighty-two crowns were placed into occlusion.
Chercheve,. R.: Report of the 18th session on implant dentures. Miami Inform Dent 44:4355, 1962. 5. Chercheve, R.: Les Implants Endo-osseux. Paris, 1962, Libraire Maloine, pp 127-138. 6. Linkow, L. I.: Clinical evaluation of the various designed endosseous implants. .J Oral Implant Tranrplant Surg 12:35, 1966. 7. Linkow. I,. 1.: Reevaluation of mandibular unilateral subperiosteal implants. A 12.year report. ,J PROSTHET DENT 4.
17:509,
8. 9. 10.
BIOCOMPATIBILITY
Il.
To determine if the implant metal exerted a toxic effect on the host calcified tissues, electron microprobe analysis was performed. The purpose was to evaluate the possibility of ion migration from the titanium implant to the surrounding bone and soft tissue. The investigation was conducted in cooperation with the ADA Health Foundation Research Institute. Baboons were killed at 3, 5, and 12 months postimplantation. Blocks of bone containing the implant were prepared for microprobe evaluation. The microprobe employed was a Cambridge Microscan V (Cambridge Instruments, Ltd., Cambridge, England) operating at 10 kV and using a beam diameter of 0.5 to 1 p. Specimens were analyzed in 0.5 p steps for 20 seconds per step. Each line was scanned twice at distances ranging from 30 to 90 p at four different sites in each specimen. The scan alternated between titanium and bone. Some encapsulating connective tissue, 4 to 10 p thick and separating the implant from trabecular bone, was included in all pathways as the electron beam traversed the titanium-bone surface. Th e presence of titanium could not be detected in either the connective tissue or the adjacent remodeling bone. This suggests that corrosion had not occurred as late as 12 months postimplantation.22. 2)
12. 13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
REFERENCES 1. Formiggini, M.: Otto anni di proctica co1 mio metodo d’infibulazione mettalica endomascellare, risultati e considerazioni. Riv Ital Stomatol 10:39, 1955. 2. Formiggini, M.: Implanti alloplastici endomascellari con viti metallich cave. Atti Simp Implanti Alloplastic 3:10, 1955. 3. Chercheve, R.: Report on implants into bone. Rev Fr Odontostomatol 9:621, 1962.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
1967.
Linkow, L. I.: Prefabricated mandibular prosthesis for intraosseous implants. J PROWHET DENT :!0:367, 1968. Linkow, L. I.: The endosseous blade implant and its use in orthodontics. Int J Orthod l&149, 1969. Linkow, L. I.: Endosseous oral implantology: A 7-year progress report. Dent Clin North Am 14: 185, 1970. Linkow, L. I.: Prefabricated maxillary endosteal implant prosthesis. J PROSTHET DENT 23:441, 1970. Linkow, I,. I.: Endosseous blade-vent implants: A two-year report. J PROSTHET DENT 23:441, 1970. Natiella, J. R., Armitage, J. E., Greene, Jr., George W., and Meenaghan, M. A.: Current evaluation ofdental implants. ,J Am Dent Assoc 84:1358, 1972. Council on Dental Materials and Devices and Council on Dental Research: Current evaluation of’ dental endosseous implants. J Am Dent Assoc 88:394, 1974. Council on Dental Materials and Devices: Council reaffirms position on dental endosseous implants J Am Dent Assoc 90:670, 1975. Council on Dental Materials and Devices: Harvard consensus conference: A comment. ,J Am Dent Assoc 98:373, 1979. Lueck, R. A., Galante, J., Rostoker, W., and Ray, R. D.: Development of an open pore metallic implant to permit attachment to bone. Surg Forum 20:53A, 101, 1971. Lembert, E., Galante, J,, and Rostoker, W.: Fixation of skeletal replacement by fiber metal composites. Clin Orthop 87:303, 1972. Galante, J., and Rostoker, W.: Fiber metal composites in the fixation of skeletal prosthesis. J Biomed Mater Res 4:43. 1973. Rostoker, W., Galante, J., and Shen, G.: Some mechanical properties of sintered fiber metal composites. J Test Eva1 2:107, 1974. Anderson, G. B. J., Gaechter, A., Galante, J., and Rostoker, W.: Segmental replacement of long bor.es in baboons using a fiber titanium implant. J Bone Joint Surg [AM] 60:31,1978. Weiss, M. B., Lyons, H. W., Rostoker, W., Galante, J., and Lenke, J.: Electron probe analysis of osseous sites containing fiber implants. J Dent Res Abstract Ko. 390, p 145, IADR Abstracts, March 1972. Weiss, M. B., and Ronen, E.: New device to quantitate alveolar bone loss. Oral Surg 44:322. 1977.
Reprint requeststo: DR. MARVIN B. WEISS RUSH UNIVERSITY
600 S. PAULINA, RM. 433-A.A.F. CHICAGO, IL 60612
651
l
DENTAL IMPLANTS
EDITORS
I. KENNETH
RONALD
ADISMAN
I’. DESJARDINS
Development of a new endosseous dental implant. Part I: Animal studies M. B. Weiss, D.D.S.,* Rush-Presbyterian
and W. Rostoker, Ph.D. **
St. Luke’s
Medical
Center,
and University
T
he need to replace missing teeth by artificial means has been the mission of dentists since early Egyptian times. The development of an effective endosseous dental implant to act as a tooth substitute was the primary goal of this research. Such an achievement would make available to the dentist an replacement. alternate mode of prosthodontic Another goal of the study was to develop a system of implantation that would allow the general practitioner to treat the patient with an implant in his office.
BACKGROUND The literature on dental implants is extensive. In Europe, Formiggini’. y used metallic pins in the form of a tripod to serve as a fixed partial denture abutment. Chercheve’-’ used a metal spiral as an implant. In the United States, Linkow”-‘” advocated driving a metallic blade into the bone to serve as an anchor for a prosthesis. At the request of the American Dental Association (ADA) Council on Dental Materials and Devices, Natiella et al.“’ reviewed 274 articles that were mostly clinical reports showing a complete lack of standardized clinical experiments. As a result, the ADA Council on Dental Materials and Devices stated that there was insufficient information available to warrant the use of implants as a routine procedure.*‘1 A symposium on implant dentistry was cosponsored by the ADA Council on Dental Materials and Devices and by the National Institutes of Health. A statement published by the Council on Dental Mate-
Presented at the American Prosthodontic Society, Chicago, Ill. *Associate Professor, Department of General Surgery, Rush University; Associate Attending, Presbyterian-St. Luke’s Hospital; Professor Emeritus of Dentistry, University of Illinois. **Professor of Metallurgy and Bioengineering, University of Illinois.
646
DECEMBER
1981
VOLUME
46
NUMBER
6
of Illinois,
Chicago,
Ill.
rials and Devices and the Council on Dental Research declared that endosseous dental implants should be considered in the new technique phase and that more studies were needed.” The Council on Dental Materials and Devices reaffirmed its position on dental endosseous implants in March 1975, stating that implants should still be considered in the new technique stage of development.” In view of this lack of conclusive scientific data, the National Institute of Dental Ressearch granted funds in 1978 to support a conference on the benefits and risks of dental implants. Experts in implant research and those experienced in clinical implant dentistry gathered to reach a consensus on dental implants. Following this Harvard consensus conference, the Council on Dental Materials and Devices stated in 1979 that dental implants should be evaluated on a benefit-risks basis to the patient and promised an updated position paper when more data became available.‘” Thus, although endosseous implants have been used extensively, the field of dental implantology lacks scientifically conducted animal and human studies.
MATERIALS AND DESIGN OF FIBER-METAL ENDOSSEOUS DENTAL IMPLANTS Studies of both long bone and alveolar bone have established that healthy and stable calcified tissue will grow into a porous material, provided that the material itself is inert in its environment and that the pores or channels are large enough. The porous material may be ceramic, a polymer, or created from a metal alloy, as long as biocompatibility exists. Although other metals have been used for human implants, titanium has proven to offer the biocompatibility, strength, and malleability needed for a fiber-metal endosseous dental implant.‘:-” The term “fiber-metal” describes the porous surface of the implant. The surface, which is attached to OOZ-3913/81/120646
+ 06$00.60/00
1981 The C. V. Mosby Co.
NEW ENDOSSEOUS
DENTAL
Fig. 1. Fig. 2. root. Fig. 3. power). Fig. 4. power). Fig. 5. Fig. 6. Fig. 7.
IMPLANT
Porous fiber-metal endosseous dental implant. Root socket experimental implant for dog. Implant Undecalcified
histological
section of normal
bone ingrowth
is same diameter as around wires
{low
Undecalcified cross-section of normal bone with fibrous tissue interface (higher II, fibrous tissue interface. Implant and crown in baboon. Implant site in baboon. Crown on implant in baboon.
a solid center post, is fabricated from unalloyed titanium. The solid center post is made from an alloy of titanium that contains aluminum and vanadium. These materials are extremely corrosion resistant and are noble metals in the electromotive series. THE JOURNAL
cylinder
OF PROSTHETIC
DENTISTRY
Their use in combination will not result in galvanic corrosion, which is common with many other metallit combinations. The porous meshwork is manufactured from fine wires shaped in an interlocking configuration of 647
WEISS AND
ROSTOKER
considered a failure when it exfoliated and was lost or wheti suppuration and inflammation indicated its removal. There were 11 failures among the 78 implants. Following sacrifice of the animals, histological evaluation was made of the specimens. The sections in the dog study showed bony ingrowth into the wire meshwork after 3 weeks (Fig. 3). There was a normal distribution of osteocytes and haversian systems, the fibrous tissue was normal with varying layers of fibrocytes, and the vascular elements were in normal distribution (Fig. 4). Electron probe studies confirmed that there was always an interface of fibrous tissue 5 to 50 p thick between the bone and the metal.
Baboon studies
Fig. 8. Radiograph and crown.
of mandibular
molar tooth implant
metal and continuous voids with a quite precise overall shape. The meshwork-post combination is heated to a high temperature in a high vacuum. This process, called sintering, generates strong metallurgical bonds at all points of contact. The fiber-metal dental implant (Fig. 1) has the following attributes: (1) a pore volume of at least 50%, (2) completely interconnecting pore channels, almost all of which are sufficiently large to allow bony ingrowth, and (3) mechanical properties that include acceptable strength, elastic compliance comparable to that of the host bone, and great resistance to cracking and fracture.
Dog studies In 1969, the fiber-metal dental implant was first used as a tooth replacement in mongrel dogs. Fibermetal implants were inserted in the root wound sockets of the extracted molar teeth of these dogs (Fig. 2). Seventy-eight implants were studied for periods from 1 week to 1 year. An implant was
648
The next phase of the research subjected the implant to the forces of mastication. The female baboon was selected as the experim’ental animal because the dentition and masticatory movements resemble those of humans. Thirty animals were used in the experiment, with an average of eight implants placed in each animal. All implants had a root portion embedded in bone and a crown portion extending into the oral cavity. The crown was fabricated of acrylic resin that reproduced the normal morphology of the baboon tooth (Fig. 5). Each crown affixed to the implant was put in functional occlusion with the opposing natural tooth. None of the functioning implants was attached to an adjacent tooth. The teeth were extracted, and the edentulous region was allowed to heal for at least 4 weeks. Following the healing period, the animal was anesthetized intravenously with sodium thiamylal, and normal saline was administered intravenously during surgery. Sodium thiamylal was admded through the saline as needed. The edentulous region chosen for implantation was entered with a scalpel, and an incision was made along the crest of the residual alveolar ridge. The mucosa and the periosteum were reflected, exposing the bone. A calibrated, tapered bone drill in a low-speed handpiece was used to bore the initial opening to the necessary depth (Fig. 6). Normal saline solution was sprayed on the bur during the drilling procedure. A specially made four-fluted end mill fitted to the low-speed dental handpiece was used to create an opening of appropriate size to accept the implant. A hand reamer was used to size the opening more
DECEMBER
1981
VOLUME
46
NUMBER
6
NEW ENDOSSEOUS
DENTAL
IMPLANT
Fig. 9. A to C. Vertical undecalcified histological section of baboon implant. a, gingival crest; b, normal bone; C, normal connective tissue; d, center post of implant; and e, capillaries. (Magnification, x 50.)
THE JOURNAL
OF PROSTHETIC
DENTISTRY
649
WElSS AND
ROSTOKER
Fig. 10. Vertical section of undecalcified bone from baboon. A, implant; and B, bone. (Magnification, X 75.) (Transmitted light.) Fig. 11. Same specimen as in Fig. 10 under ultraviolet light. A, implant; B, bone; and C, fluorescing calcifying bone tagged with tetracycline. (Magnification, x 75.) exactly and allow the implant to be in intimate contact with the bone for its entire length. Normal saline was used to cool the drill and lavage the opening in the bone. The implant was placed in a seating instrument and inserted into the prepared opening by hand pressure or by a light tap of a mallet. The implant was placed with the fiber-metal meshwork 0.5 mm below the crest of the alveolar bone. The animal was placed on a regimen of penicillin and a soft diet for 6 days. The successful implant was fully stabilized after 4 weeks, at which time impressions were made for the construction of acrylic resin crowns. The crowns were adjusted to harmonize with the occlusion of the animal. The implants were radiographed and photo
DISCUSSION The baboon study showed results similar to those of the dog study with regard to the response of the host bone and soft tissue to the presence of the implant. Because the baboon specimens had longer survival times, most specimens showed bony ingrowth through the entire meshwork up to the
650
solid metal core. A fibrous interface of varying widths was always present between the bone and the metal. The characteristics of the bone and fibrous tissue were normal and could not be distinguished from the adjacent surrounding tissues. The bone surrounding the implant wires in the baboon specimens exhibited normal haversian systems and osteocytes distributed in the normal pattern of the jaw bones (Fig. 9). Animals administered tetracycline prior to sacrifice produced histological sections demonstrating that the investing bone in and around the implant was viable, living, and normal. The calcifying bone was tagged with the tetracycline and fluoresced when the histological section was viewed under ultraviolet light (Figs. 10 and 11). Histological analysis of failing implants revealed that bone was being replaced with inflammatory cells by the resorption process. When the process was rapid (due to influences such as traumatic occlusion), hemorrhage, purulent exudate, and resultant infection occurred. The investing bone of the slowly failing implant was replaced by connective tissue, and the implant remained immobile when only one-third of it was still invested in bone. Experience from other types of failing implants has shown that the most vulnerable site is where the implant penetrates through the oral mucosa into the oral cavity. The interface between the soft tissue and the metal is a pathway for bacteria and loxins of the oral cavity to reach the supporting bone and cause resorption of the bone, with resultant mobility and possible loss of the implant.
DECEMBER
1981
VOLUME
46
NUMBER
6
NEW ENDOSSEOUS
DENTAL
IMPLANT
By contrast, this implant has open fiber-metal meshwork on the superior surface in proximity to the bone. This fiber meshwork allows ingrowth of normal connective tissue or, in some cases, bone (Fig. 9, B). As a result, the superior implant surface is sealed and provides a normal physiological base for the gingival tissue that is closely adherent to the highly polished biocompatible implant post. This combination of sealants resists the penetration of destructive elements from the oral cavity. In this study, 182 implants were placed in baboons. Over an experimental period of 26 months, 69 implants were lost. Eighty-two crowns were placed into occlusion.
Chercheve,. R.: Report of the 18th session on implant dentures. Miami Inform Dent 44:4355, 1962. 5. Chercheve, R.: Les Implants Endo-osseux. Paris, 1962, Libraire Maloine, pp 127-138. 6. Linkow, L. I.: Clinical evaluation of the various designed endosseous implants. .J Oral Implant Tranrplant Surg 12:35, 1966. 7. Linkow. I,. 1.: Reevaluation of mandibular unilateral subperiosteal implants. A 12.year report. ,J PROSTHET DENT 4.
17:509,
8. 9. 10.
BIOCOMPATIBILITY
Il.
To determine if the implant metal exerted a toxic effect on the host calcified tissues, electron microprobe analysis was performed. The purpose was to evaluate the possibility of ion migration from the titanium implant to the surrounding bone and soft tissue. The investigation was conducted in cooperation with the ADA Health Foundation Research Institute. Baboons were killed at 3, 5, and 12 months postimplantation. Blocks of bone containing the implant were prepared for microprobe evaluation. The microprobe employed was a Cambridge Microscan V (Cambridge Instruments, Ltd., Cambridge, England) operating at 10 kV and using a beam diameter of 0.5 to 1 p. Specimens were analyzed in 0.5 p steps for 20 seconds per step. Each line was scanned twice at distances ranging from 30 to 90 p at four different sites in each specimen. The scan alternated between titanium and bone. Some encapsulating connective tissue, 4 to 10 p thick and separating the implant from trabecular bone, was included in all pathways as the electron beam traversed the titanium-bone surface. Th e presence of titanium could not be detected in either the connective tissue or the adjacent remodeling bone. This suggests that corrosion had not occurred as late as 12 months postimplantation.22. 2)
12. 13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
REFERENCES 1. Formiggini, M.: Otto anni di proctica co1 mio metodo d’infibulazione mettalica endomascellare, risultati e considerazioni. Riv Ital Stomatol 10:39, 1955. 2. Formiggini, M.: Implanti alloplastici endomascellari con viti metallich cave. Atti Simp Implanti Alloplastic 3:10, 1955. 3. Chercheve, R.: Report on implants into bone. Rev Fr Odontostomatol 9:621, 1962.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
1967.
Linkow, L. I.: Prefabricated mandibular prosthesis for intraosseous implants. J PROWHET DENT :!0:367, 1968. Linkow, L. I.: The endosseous blade implant and its use in orthodontics. Int J Orthod l&149, 1969. Linkow, L. I.: Endosseous oral implantology: A 7-year progress report. Dent Clin North Am 14: 185, 1970. Linkow, L. I.: Prefabricated maxillary endosteal implant prosthesis. J PROSTHET DENT 23:441, 1970. Linkow, I,. I.: Endosseous blade-vent implants: A two-year report. J PROSTHET DENT 23:441, 1970. Natiella, J. R., Armitage, J. E., Greene, Jr., George W., and Meenaghan, M. A.: Current evaluation ofdental implants. ,J Am Dent Assoc 84:1358, 1972. Council on Dental Materials and Devices and Council on Dental Research: Current evaluation of’ dental endosseous implants. J Am Dent Assoc 88:394, 1974. Council on Dental Materials and Devices: Council reaffirms position on dental endosseous implants J Am Dent Assoc 90:670, 1975. Council on Dental Materials and Devices: Harvard consensus conference: A comment. ,J Am Dent Assoc 98:373, 1979. Lueck, R. A., Galante, J., Rostoker, W., and Ray, R. D.: Development of an open pore metallic implant to permit attachment to bone. Surg Forum 20:53A, 101, 1971. Lembert, E., Galante, J,, and Rostoker, W.: Fixation of skeletal replacement by fiber metal composites. Clin Orthop 87:303, 1972. Galante, J., and Rostoker, W.: Fiber metal composites in the fixation of skeletal prosthesis. J Biomed Mater Res 4:43. 1973. Rostoker, W., Galante, J., and Shen, G.: Some mechanical properties of sintered fiber metal composites. J Test Eva1 2:107, 1974. Anderson, G. B. J., Gaechter, A., Galante, J., and Rostoker, W.: Segmental replacement of long bor.es in baboons using a fiber titanium implant. J Bone Joint Surg [AM] 60:31,1978. Weiss, M. B., Lyons, H. W., Rostoker, W., Galante, J., and Lenke, J.: Electron probe analysis of osseous sites containing fiber implants. J Dent Res Abstract Ko. 390, p 145, IADR Abstracts, March 1972. Weiss, M. B., and Ronen, E.: New device to quantitate alveolar bone loss. Oral Surg 44:322. 1977.
Reprint requeststo: DR. MARVIN B. WEISS RUSH UNIVERSITY
600 S. PAULINA, RM. 433-A.A.F. CHICAGO, IL 60612
651