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Responsibility of the dentist in complete dentures
COMPLETE
DENTURES
RESPON9IBILITY
OF THE
DENTIST
JUDSON C. HICKEY, D.D.S., MSc.,”
IN COMPLETE
DENTURES
CARL0. BOUCHER, D.D.S.,**
AND JULIAN B. WOELFEL, D.D.S.” The Ohio State University,
CoUege of Dentistry,
Columbus,
Ohio
have been asked to pass laws that would permit commercial dental laboratories to construct dentures directly for edentulous patients. Much of the cause of this problem results from dentists who are unwilling to assume their rightful responsibilities in complete denture construction. This article will discuss those phases of complete dentures that the dentist is obligated by his profession to perform himself, EVERAL STATE LEGISLATURES
S
MOUTH
PREPARATION
The dentist must be certain that all tissues of the mouth are in a healthy condition before impressions are made. This procedure may include nutritional therapy, treatment relining of the old dentures, occlusal corrections, corrections by surgical operation, and removal of the old dentures from the mouth for varying periods of time. Even under ideal conditions, the old dentures must be left out of the mouth a minimum of 24 hours to permit tissue recovery before final impressions are made. Hyperplastic tissue that develops under dentures, often under the labial flange of the upper denture, is usually caused by excess pressures from occlusion. The treatment includes (1) keeping the old dentures out of the mouth until the inflammation recedes and (2) removal of the hyperplastic tissue surgically or removal of the tissue surgically, with an immediate relining of the oId denture with zinc oxide-eugenol impression paste (Fig. 1). The inflamed, pebbly tissue that sometimes develops in the palate under upper dentures is called papillomatosis (Fig, 2). This tissue can be a precancerous lesion and must be treated accordingly. If the condition has not improved appreciably after the dentures have been kept out for 7 to 10 days, a biopsy of the tissue Supported in part by grant D-543X-3 from the National Institutes of Health, U. S. Public Health Service. Presented before the Wisconsin State Dental Meetlng in Milwaukee, Wis. This article is being published simultaneously in THE JOURNAL OF PROSTHETIC DENTISTRY and The Wbconsin Dental Journal by special arrangement between the editors. *Associate Professor, Division of Prosthodontics. **Professor and Chairman, Division of Prosthodontics. 637
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should be made. A biopsy report of pseudoepitheliomatous hyperplasia indicates that the involved tissue should be stripped away from the bone. The old denture is relined at the time of operation with zinc oxide-eugenol impression paste to reduce pain and aid in the granulation process. New dentures can be constructed in 2 to 3 weeks after the healing is complete. Papillomatosis is thought to be caused by malocclusion, ill-fitting or poorly contoured dentures, or excessive relief areas with sharp edges. Loose fibrous bands of tissue on the lower ridge and soft movable tissue over tuberosities should be removed. Even though the residual ridge is small, a firm bearing surface is a better foundation than one that is movable. The fibrous connective tissue on the tuberosities reduces the space between the upper jaw and the retromolar pads and may prevent proper extension of the dentures. An inadequate nutritional intake must be corrected for some patients before beginning denture construction. A diet that is high in protein content and rich in vitamins and minerals, particularly vitamins B and C and calcium, will usually restore such individuals to nutritional health. However, most patients in this category should be referred to a physician for treatment. IMPRESSIONS
Each mouth must be studied carefully to determine anatomic structures and landmarks and the consistency of the soft tissue. The tray that carries the final impression material into place must be in harmony with these attachments and must provide space for the final impression material. Adequate tissue coverage and control of the tissue are more important than the materials used for the tray or the final impression, assuming these materials are stable, accurate, and correctly used. The thickness of the labial flange of the tray is determined by esthetic factors and the available space between the lip and the ridge. A thick impression pulls the tissue away from the labial surface of the bone at the reflection, and when the thickness of the labial flange of the completed denture is reduced, the tissue drops back and a space develops between the soft tissue and the lingual surface of the labial flange of the denture near the border. A thin edge of a flange of a tray will not sufficiently support the final impression material to allow it to fill the available space.
Fig.
1.--A,
Hyperplastic tissue dentures are made.
B,
must be eliminated or made firm before The hyperplastic tissue has been removed
impressions surgically.
for
new
Etx:r:”
Fig.
RESPONSIBILITY
2.-Papillomatosis
OF THE
may
DENTIST
be a precancerous
IN
lesion
COMPLETE
and must
639
DENTURES
be treated
accordingly.
The buccal notch of the impression is almost always shorter and thinner than other borders of the tray because of the action of the buccal frenum (Fig. 3). Adequate space must be provided so the tissues in this region can move without displacing the denture. The buccal vestibule or space should be filled but not overfilled. Inadequate bulk of material in this space lessens the area of tissue contact with the denture base and reduces retention and stability. The posterior end of the upper denture must pass through the hamular notches on each side and extend at least as far back as the vibrating line. The border of the impression should follow around the tuberosity into the notch, so this part of the tray should extend slightly posteriorly to the vibrating line. If the ham&r notches are not included in the impression, the seal will not be adequate in this region when pressure is applied on the cuspid on the opposite side of the mouth. Areolar tissue is present in the hamular notch, and glandular tissue is found in the region of the vibrating line. These tissues are displaceable, which allows the addition of a posterior palatal seal on the denture. The posterior palatal seal is developed in the impression, and then a small narrow bead is placed on the finished denture. The bead extends through the hamular notches and about 2 mm. in front of the vibrating line at the end of the denture. The labial and buccal borders of the lower tray are developed in a manner similar to that for the upper tray (Fig. 3). The posterior part of the lower impression includes the retromolar pad. No additional seal is placed on the pad, since its contents should not be displaced. The lingual border of the lower tray is developed by a series of tongue movements, as described by Boucher. l In the anterior part, from bicuspid to bicuspid, the border is limited by the sublingual folds, the lingual frenum, and the submaxillary caruncles. In the molar region, the tray extends below the level of the mylohyoid ridge and slopes toward the tongue to allow freedom of movement of the mylohyoid muscle. Posteriorly, the tray turns laterally and fills the retromylohyoid space to complete the border seal and guide the tongue onto the top of the lingual flange.
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HICKEY,
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AND
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D.
E.
F.
Fig. 3.-Impressions and D, A modified impression material. A
IMPRESSION
for the same patient are made in different final impression materials. plaster. B and E, A zinc oxide-eugenol paste. C and F, A rubber-base
MATERImALS
Several different final impression materials produce good results if the tray is correctly formed (Fig. 3). However, the working properties and consistencies must be understood by the dentist. Plaster of Paris absorbs saliva, thus it gives a more accurate tissue reproduction of the posterior one-third of the palate (over the palatal glands) than other materials. However, plaster has a short critical working period, fractures easily, and sometimes is so thick that overextended borders may result. Zinc oxide-eugenol impression paste flows readily, gives good detail, and is of such a nature that one impression can be made inside another after proper relief.
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This is a good material for lower final impressions when it is desirable to place more of the occlusal stress on the tissue of the buccal shelf (the area between the crest of the residual ridge and the external oblique line) than on the ridge crest. Rubber-base impression material records good detail. However, because of its make-up, many pressure spots that are obvious with other materials may go unnoticed. JAW
RELATION
RECORDS
An articulator is used in complete denture construction for convenience and because of the lack of a solid base in the patient’s mouth. For the articulator to simulate jaw movements, at least four jaw relations must be transferred from the patient to the instrument : (1) the relation of the jaws to the opening axis, (2) the vertical separation of the jaws, (3) the horizontal relation of the lower to the upper jaw in centric relation, and (4) the relation of the lower jaw to the upper jaw when the mandible is protruded so that the incisor teeth are edge to edge. All of these records must be made by the dentist. There are no short cuts or average values that will work. RELATION
OF
THE
JAWS
TO
OPENING
AXES
The relationship of the maxillae to the opening axis of the mandible is transferred to the articulator by means of the face-bow. The lower cast is then related to the opening axes by an interocclusal centric relation record. An arbitrary face-bow mounting seems to be adequate for most edentulous patients. A mark on each side of the face, 12 mm. forward from the foot of the tragus on a line from the tragus to the outer canthus of the eye, is used as the location of the arbitrary axis. These points locate the mandibular axis close to its true position in many patients. A wax or plaster interocclusal record can be made between the occlusion rims while the face-bow is in position, thus allowing both casts to be mounted on the articulator at the same time. The convenience in mounting the casts in this manner makes the use of the face-bow worth while. VERTICAL
RELATION
OF
THE
JAWS
The vertical separation of the jaws that is established in the mouth and mounted on the articulator is the vertical relation of occlusion. This is the space between the jaws when the teeth are in contact. The vertical relation of rest position is constant enough, at least over short periods of time, to serve as a guide in establishing the vertical relation of occlusion. The space between the teeth when the jaw is at rest position is the interocclusal distance, which varies with different patients. Several methods of determining the vertical relation of occlusion are in common usage. The vertical position of the mandible at which the maximal force can be applied is thought to correspond to the vertical relation of rest position. This position may be determined by a Boos Bimeter (Fig. 4). Actually, pain and
J. Pros. Den. July-August, 1962
Fig. 4A.-The Fig. 4B.-The lower resin base. Fig. 4C.-The
central central Bimeter
bearing bearing is in place
plate is mounted on the upper screw and pressure indicating
acrylic resin denture base. gauge are mounted on the
in the mouth.
fatigue limit the amount of force with which an edentulous patient can close the mouth. Thus, the most force can be applied when the ridges are parallel, because the denture bases tend to move the least in this position. Ridge parallelism, rather than the vertical relation of rest position, is what is most often determined by the power test. One physiologic method entails swallowing as a means for determining the vertical relation of occlusion. An upper occlusion rim is developed, and three cones of soft wax are placed on a lower resin trial denture base. The patient performs a series of swallows which shorten the wax cones according to the closure of the mandible (Fig. 5). We have not found consistency in the final position by this method. Measurements can be made between a point on the nose and one on the chin when the jaw is at rest position with nothing in the mouth. A Coble balancer is mounted between an upper contoured occlusion rim and a lower resin trial denture base. The occlusion rims are placed in the mouth, and the central bearing pin is adjusted so that the previously measured points are 3 to 5 mm. closer together (Fig. 6). This distance on the face indicates 2 to 3 mm. of interocclusal distance between the occlusion rims in the bicuspid region. We find that the vertical di-
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12
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DENTURES
643
mension of occlusion is often closed too far for some patients when it is determined by this method. When correctly formed, the occlusion rim should equal the height of the extracted tooth plus the amount of tissue resorption that has occurred. With this in mind, wax occlusion rims can be developed for proper lip support and to the height of the vertical relation of occlusion (Fig. 7). This can be determined by the dentist only with the patient present. The procedure entails developing the upper occlusion rim so that the in&al plane is parallel with the interpupillary line and at a height that allows for the length of the natural tooth plus the amount of tissue resorption that has occurred. The length of the upper lip can be a guide if it is of average length. The occlusal plane, posteriorly, is made to parallel the ala-tragus line (Fig. 8) on the basis of the position of most natural occlusal planes. Then, the lower occlusion rim is adjusted to meet evenly with the upper rim and reduced until an adequate interocclusal distance is obtained. Some of the tests that aid in establishing the correct vertical relation of occlusion with the occlusion rims are ( 1) over-all facial support, (2) visual observation of a space between the rims when the jaws are at rest, (3) pronunciation of words containing sibilants (s, sh, c, ch, j, and Z) , which should cause the rims to come close together but not to contact, (4) measurements between dots on the face, (5) determination of whether the lower rim is level with the lower lip at the corner of the mouth, and (6) parallelism of the upper and lower ridges after the casts are mounted on the articulator. This method is logical in that the occlusion rims represent teeth that were known at one time to be in the mouth, it allows for several different tests, it is fairly easy, and it is not time consuming.
A.
Fig. 5.-A, Cones of soft wax are attached to the lower resin base and occlusion rim. B, The cones have been shortened, by contacts made during height that indicates the vertical dimension of occlusion.
contact the swallowing,
Upper to a
644
HICKEY,
HORIZONTAL
RELATIONS
OF
BOUCHER,
AND
J. Pros. Den. July-August, I.962
WOELFEL
JAWS
There are a multitude of horizontal positions that the mandible can assume in relation to the maxillae in the normal range of function. However, the only relation that the edentulous patient can repeat with regularity is centric relation. Centric relation is the most posterior relation of the mandible to the maxillae at the established vertical dimension. Centric relation must be recorded from the patient’s mouth and transferred to the articulator. It is a mandibular position that the patient may use many times during mastication and many times during the rest of the day in swallowing or whenever the teeth may come together. If the denture bases are to remain stable on the residual ridges with no inclined plane interference, the teeth must meet evenly in this posterior position as well as in all lateral and protrusive positions within the range of normal function. If the teeth are to meet evenly in centric relation, it must be correctly recorded in the mouth and reproduced on the articulator. Some of the methods used to indicate and record centric relation are extraoral and intraoral needle point tracings with central bearing devices, functional chew-in procedures, and direct interocclusal records (Fig. 9).
Fig. Fig. Fig.
6A.-The BB.-The GC.-The
Coble balancer is mounted on the trial denture mandible is at rest position. balancer is adjusted to allow for an adequate
bases. interocclusal
distance.
%%E‘4”
Fig.
7.-The
RESPONSIBILITY
occlusion
I +ms
OF THE
are
DENTIST
IN
COMPLETE
contoured for correct lip suppo vertical dimension of occlusion.
645
DENTURES
Ia-t
md
t.o the
height
of 1:he
The needle point tracings give a graphic indication of the horizontal position of the mandible in relation to the maxillae. The extraoral tracing is easier to observe than the intraoral. The hole often used on the tracing plate of the intraoral device allows the patient a place to put pressure on the trial bases that may not be detected. Whenever central bearing devices are used, as in the needle point tracings, errors are introduced when movable tissue is present on the ridges or when jaw size or position prevents proper centering of the tracing devices in both the upper and lower jaws. Chew-in records may be made with an abrasive material between the occlusion rims or with sharp cutting studs attached to one of the rims. The patient moves the jaw from side to side and either develops the shape of the occlusal plane or cuts pathways with the studs. The pathways are used to mount the casts on the articulator in centric relation and then to adjust the condylar guidances of the instrument. Functional records have the disadvantage of movement of the denture bases on the residual ridges as the mandible is moved. Also, the resistance of the abrasive material usually prevents the record from being developed in the most posterior mandibular position. Direct interocclusal centric relation records are made between the occlusion rims after the vertical dimension of occlusion has been established. Soft plaster or wax is ordinarily used as the recording medium. Sufficient trial centric relation closures should be practiced by the patient under the guidance of the dentist until both the patient and the dentist have learned to recognize the position. Then the recording medium is placed between the occlusion rims in the regions of the bicuspid and molar teeth only. The patient retrudes the mandible to the horizontal position of centric relation and closes the mouth to the vertical level of the established vertical relation, but he must stop the closure before the recording medium is penetrated. If the hard wax of an occlusion rim contacts the opposing rim,
HICKEY,
646
BOUCHER,
AND
J. Pros. July-August,
WOELFEL
Den. 1.962
the denture bases move on the supporting tissue or soft tissue is displaced. In either instance, the record will be incorrect. The record is made as close to the selected vertical dimension of occlusion as possible. This method is adequate for most patients and does not possess some of the inherent errors of the other procedures. PROTRUSIVE
RELATION
RECORD
A record of the jaw relation when the incisor teeth are in an edge to edge position is necessary to adjust the condylar guidances of the articulator. This record is made in soft wax or plaster of Paris, and usually is made after the anterior teeth have been placed in the final positions in the occlusion rims. SELECTION
OF
TEETH
Tooth selection is one phase of denture construction that the dentist must perform himself. Many guides are available to him for making his selection. Diagnostic casts and photographs are the best guides when they are available. Roentgenograms made when natural teeth were present give some clues, and some patients can produce teeth that had been removed previously. In many instances, the size and shape of the face and residual ridge provide insight as to the size and shape of the tooth, A large face or ridge usually indicates that the natural teeth had been large, and the outline form of the tooth is usually in harmony with the shape of the face and ridge. Measurements can be made that work on an average basis. A measurement of the greatest width of the face in the region of the zygomatic arches divided by 16 gives an average width of the upper central incisor, while the same width divided by 3.3 gives the average over-all width of the upper six anterior teeth (flat plane).2 A measurement around a correctly contoured occlusion rim between marks made at the corners of the mouth gives an indication of the over-all width of the upper six anterior teeth (Fig. 10). The six anterior teeth selected from the mold guide can be quickly arranged On the occlusion rim or on a tooth selector and tried in the mouth (Fig. 11). This procedure eliminates many improper tooth selections.
Fig.
&.-A,
The
incisal
plane B, The
of the occlusal
upper plane
occlusion is parallel
rim is parallel to the ala-trams
to the line.
interpupillary
line.
ygge*
‘4”
RESPONSIBILITY
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DENTIST
IN
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DENTURES
647
Fig. Q.-A, The extraoral tracing devices are mounted on the occlusion rims. B, The extraoral needle point tracing devices are ln the patient’s mouth. C, The intraoral tracing device is mounted on the denture bases and is in the patients mouth. D, Cutting studs are mounted on modeling compound occlusion rims. E, Pathways indicating jaw movement have been cut into the occlusal surface of the lower modeling compound occlusion rim. F, A direct interocclusal record is made in soft plaster of Paris. Note the hand and finger positions.
Posterior teeth are selected on the basis of the size of the ridges and the interarch space. Long posterior teeth (from the occlusal surface to the cervical end) are usually better looking than short teeth when space permits their use. Anatomic teeth can be made to harmonize with the guiding factors of mandibular movement more easily than other tooth forms. No data have shown that anatomic teeth cause more soreness or ridge resorption than other posterior tooth forms. The color of the teeth must be in harmony with the coloring of the face. The least conspicuous color is the objective. Older individuals usually require darker colors of teeth, but this is not a hard and fast rule. The color of the tooth is checked in three places : (1) alongside the face, (2) under the upper lip, and (3)
648
HICKEY,
Fig.
lOA.-A
mark
that
corresponds
BOUCHER,
AND
to the corner
J. Pros. July-August,
WOELFEL
of the mouth
is made
Den. 1962
on the occlusion
rim. the
Fig. lOB.-A measurement around mouth indicates the approximate
the width
occlusion rim between the marks at the of the six anterior teeth when set up.
in the mouth with the upper lip raised as in smiling. checked in both artificial and natural light.
corners
of
The color of teeth should be
TRY-IN
The contoured occlusion rims are used as a guide for the placement of the anterior teeth (Fig. 12). The dental laboratory technician should be instructed to arrange the anterior teeth so that the labial surfaces are flush with the labial surface of the occlusion rim. In this manner, the teeth on the trial denture base will support the face in the same manner as the occlusion rim. The first phase of the try-in is the verification of the jaw relation records. The vertical dimension of occlusion is tested by the same procedures that were used for its establishment. Centric relation is tested by having the patient retrude the mandible and close on the back teeth until the first contact is made. If the teeth touch and then slide on each other, the record is incorrect. If all teeth meet the same at the first contact as they do on the articulator and if the position cannot be proved to be wrong, it may be assumed to be correct. No matter how small the error, the lower cast must be remounted with a new interocclusal centric relation record.
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RESPONSIBILITY
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DENTURES
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The hand position when making or verifying centric relation records is important. It should be such that both trial denture bases will be correctly positioned with a minimum of interference from the dentist’s hands. The controlling hand is inverted (thumb down and palm toward the patient’s face). Then, with the ball of the thumb and the index finger of the same hand of the dentist placed between the occlusal surfaces of the teeth and with the inverted hand extending up over the patient’s eyes, the patient is instructed to pull the jaw back and close until a tooth touches. This is the best method for testing centric relation we have used (Fig. 9). The dentist is responsible for modifying the arrangement of the anterior teeth to complete the esthetic appearance. The preliminary arrangement of the anterior teeth always needs alteration when it is seen in the mouth. The labiolingual placement of the teeth and the contour of the labial surface of the denture-base material determine the support of the lips. When incorrectly supported, either labiolingually or vertically, the lips cannot function naturally because the musculature forming the modiolus is not held at its correct length, and when it contracts, nothing happens, or too much happens. There are some guides that are helpful in labiolingual positioning of the anterior teeth : (1) the labial surface of the teeth should be as far forward as the labial flange (Fig. 13), (2) the labial surface of the central incisors should be 8 to 10 mm. in front of the middle of the incisive papilla (Fig. 14)) (3) the imaginary root of the artificial tooth should be in front of the residual ridge by the amount of the resorption of the ridge, (4) the sibilant sounds should necessitate the upper and lower anterior teeth to move approximately edge to edge, and (5) the texture of the skin of the lips should be similar to that of other areas of the face. The arch form of the teeth should follow the arch form of the ridge, but with allowance made for surgical accidents that may have occurred (a broken labial plate, etc.). Many variations can be incorporated in the anterior tooth arrangement to produce naturalness (Fig. 15). Full use should be made of diagnostic casts and photographs. The midline of the central incisors usually looks best in the middle of the face, with the long axis of the central incisors in harmony with the long axis of the face. The incisal edges should follow the lower lip when the patient smiles and should be ground to assimilate wear according to age. Irregularities that are not the same on both sides of the dental arch and spaces between some of
Fig,
Il.--A, A possible tooth selection viewed in the mouth to observe
is arranged on a preformed their size and form in relation
selector. B, The teeth to that of the face.
are
HICKEY,
650
BOUCHER,
AND
WOELFEL
J. Pros. Den. July-August, 1962
A.
B.
Fig. toured try-in.
12.-A,
occlusion
The occlusion rims are improperly rims serve as a goo(l guide for
contoured positioning
for the
lip support. B, Properly anterior teeth for their
confirst
the teeth are effective. The effect of sex, personality, and age of each patient on individual tooth form and position should be considered in the final arrangement of the teeth.s POSTERIOR
TOOTH
ARRANGEMENT
The dentist is responsible for the final arrangement of posterior teeth. If written instructions to the dental laboratory are not adequate for meeting certain situations, the dentist should observe the arch form, occlusal plane, and occlusion of the teeth before the dentures are processed and cured.
Fig.
13.-A, The anterior teeth have been set too far lingually in B, The anterior teeth are in their correct positions in relation
relation to the labial to the labial flange.
flange.
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RESPONSIBILITY
OF THE
DENTIST
IN
COMPLETE
DENTURES
6.51
The posterior tooth arrangement must be such that it preserves the correct form of the dental arch. This means that, in some instances, the upper teeth may be in a buccal version or in a “cross-bite” relationship. The height of the acclusal plane is located between the incisal edge of the lower cuspid and the height of the posterior one-third of the retromolar pad. The posterior teeth are positioned buccolingually so that a perpendicular line through the buccal turning point of the crest of the ridge bisects the buccal cusps of the lower first molar. No part of any posterior tooth should be lingual to the mylohyoid ridge. The posterior teeth should never extend further posteriorly than the beginning of the retromolar pad. Likewise, they should not extend onto ridge inclines that tend to produce unseating or skidding forces on the denture bases during mastication. If the ridge inclines upward toward the retromolar pad, a tooth or teeth should be omitted or teeth with a smaller mesiodistal dimension should be used. When smaller teeth are used, the next size longer tooth (vertically) should be selected to avoid an unsightly exposure of denture-base material. COMPLETION
OF DENTURES
After the dentures are cured, the face-bow mounting is preserved by remounting the upper denture on the articulator with a remounting record jig. Processing
Fig. 14.-The labial surfaces of the central incisors should be from 8 to 10 mm. in front of the middle of the incisive papilla. Note the relation of the labial surface of the tooth to the labial surface of the cast.
changes are not corrected on the articulator since a new interocclusal centric relation record is made from the patient’s mouth on the day the dentures are inserted. Immediately after the dentures are placed in the mouth, the patient is instructed to hold them tightly together. Then an interocclusal protrusive record is made in plaster of Paris. These records are laid aside for the adjustment of the articulator, later.
652
HICKEY,
Fig. 15.-A, The tooth arrangement the patient. B, The tooth arrangement, appearance of the patient.
BOUCHER,
AND
WOELFEL
is in harmony with the age, although not totally displeasing,
J. Pros. Den. July-August, 1.962
sex, and personality does not enhance
of the
Then an interocclusal centric relation record is made in soft, quick-setting plaster of Paris with the opposing teeth just out of contact. The lower denture is mounted on the articulator and the condylar guidances on the articulator are adjusted. The teeth are ground first into centric occlusion as indicated by articulating paper marks. Then the occlusion is corrected for the eccentric positions. The method of grinding ensures that the teeth contact uniformly in centric relation and in all other positions within the normal range of function. Central bearing devices, wax over the teeth, and articulating paper in the mouth have been used as means for correcting the occlusion. These methods have the disadvantage of denture movement on the supporting tissues. Even though the articulator does not duplicate jaw movements perfectly, for most patients, it does a better job than can be accomplished working directly in the mouth. The poorest procedure is the use of abrasive paste on the teeth in the patient’s mouth because it provides no control over the places where the teeth are modified. Grinding the teeth on the articulator allows the dentist to select the part of the tooth he wishes to modify and to work on a dry surface. The dentist must be certain that the patient is educated in the use and care of the dentures and informed that routine yearly dental examinations are necessary. Written instructions on these phases are helpful. ADJUSTMENTS
All complete denture patients should be given 24 and 48 hour appointments for denture adjustments. The dentist is responsible for adjustments until the dentures are comfortable. The nature and location of soreness caused by dentures are often a guide to the cause of the difficulty. Some of the common locations, causes of soreness, and complaints are (1) soreness at the reflection because of overextended denture borders, (2) soreness on the slope or crest of the ridge from malocclusion or pressure spots in the impression, (3) soreness during swallowing from pressure on the mylohyoid ridge or overextension of the distal end of the lingual flange, (4) soreness of frenula because of insufficient notch size or sharpness, (5) burning or a sensation of numbness from pressure on the incisive papillae or mental fora-
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RESPONSIBILITY
OF THE
DENTIST
IN
COMPLETE
DENTURES
65.1
men, (6) generalized soreness from malocclusion, excessive vertical dimension of occlusion, avitaminosis, or unhygienic dentures, and (7) cheek-biting lesions resulting from insufficient horizontal overlap of the upper over the lower teeth. Complaints about loosening of the upper denture may result from (1) excessive thickness of the distobuccal corner of a buccal flange which causes displacement of the upper denture during yawning or wide open or lateral jaw movements, (2) excessive thickness or height in the buccal notch region which displaces the denture during smiling, (3) malocclusion which may cause a loosening after the dentures have been worn several hours, (4) lack of proper distal extension or an inadequate posterior palatal seal which causes tipping of the denture when biting on the front teeth, and (5) tissue displaced during the making of the impression. Complaints about loosening of the lower denture may result from (1) in-lproper tooth placement, either too far buccally or too far lingually, (2) improper border form or length, (3) failure to fill the retromylohyoid space, (4) insufficient space for action of mylohyoid muscle, (5) insufficient size or incorrect shape of the buccal notches, (6) incorrect form of the polished surface of the denture so that the cheeks and tongue tend to raise the denture rather than help to hold it down, (7) bad tongue habits of the patient, and (8) errors in occlusion. SUMMARY
The dentist is obligated to perform certain essential phases of complete denture construction. These include making a comprehensive diagnosis, making certain that the oral tissues are healthy before work is started, making the impressions, producing jaw relation records, selecting the teeth, correcting the jaw relation records, rearranging the anterior teeth for esthetic appearance, correcting the occlusion at the time of the first insertion of the dentures, and making whatever denture adjustments may be necessary. If the dental profession is to maintain its high standard of denture service, the dentist must not delegate to someone else any phase of denture construction he should complete himself. REFERENCES
1. Boucher, C. 0. : Impressions for Complete Dentures, J.A.D.A. 30:14-Z, 1943. 2. House, M. M., and Loop, J. L: Form and Color Harmony in the Dental Art, Monograph. Whittier, Calif., 1939, M. M. House. : Its Practical Application, J. PROS. DEU. 3. Frush, J. P., and Fisher, R. D.: Dentogenics 9:914-921, 1959. THE OHIO STATE UNIVERSITY COLLEGE OF DENTISTRY 305 WEST TWELFTH AVE. COLUMBUS 10, OHIO
DENTURES
RESPON9IBILITY
OF THE
DENTIST
JUDSON C. HICKEY, D.D.S., MSc.,”
IN COMPLETE
DENTURES
CARL0. BOUCHER, D.D.S.,**
AND JULIAN B. WOELFEL, D.D.S.” The Ohio State University,
CoUege of Dentistry,
Columbus,
Ohio
have been asked to pass laws that would permit commercial dental laboratories to construct dentures directly for edentulous patients. Much of the cause of this problem results from dentists who are unwilling to assume their rightful responsibilities in complete denture construction. This article will discuss those phases of complete dentures that the dentist is obligated by his profession to perform himself, EVERAL STATE LEGISLATURES
S
MOUTH
PREPARATION
The dentist must be certain that all tissues of the mouth are in a healthy condition before impressions are made. This procedure may include nutritional therapy, treatment relining of the old dentures, occlusal corrections, corrections by surgical operation, and removal of the old dentures from the mouth for varying periods of time. Even under ideal conditions, the old dentures must be left out of the mouth a minimum of 24 hours to permit tissue recovery before final impressions are made. Hyperplastic tissue that develops under dentures, often under the labial flange of the upper denture, is usually caused by excess pressures from occlusion. The treatment includes (1) keeping the old dentures out of the mouth until the inflammation recedes and (2) removal of the hyperplastic tissue surgically or removal of the tissue surgically, with an immediate relining of the oId denture with zinc oxide-eugenol impression paste (Fig. 1). The inflamed, pebbly tissue that sometimes develops in the palate under upper dentures is called papillomatosis (Fig, 2). This tissue can be a precancerous lesion and must be treated accordingly. If the condition has not improved appreciably after the dentures have been kept out for 7 to 10 days, a biopsy of the tissue Supported in part by grant D-543X-3 from the National Institutes of Health, U. S. Public Health Service. Presented before the Wisconsin State Dental Meetlng in Milwaukee, Wis. This article is being published simultaneously in THE JOURNAL OF PROSTHETIC DENTISTRY and The Wbconsin Dental Journal by special arrangement between the editors. *Associate Professor, Division of Prosthodontics. **Professor and Chairman, Division of Prosthodontics. 637
HICKEY,
638
BOUCHER,
AND
WOELFEL
J. Pros. Den. July-August, 1.962
should be made. A biopsy report of pseudoepitheliomatous hyperplasia indicates that the involved tissue should be stripped away from the bone. The old denture is relined at the time of operation with zinc oxide-eugenol impression paste to reduce pain and aid in the granulation process. New dentures can be constructed in 2 to 3 weeks after the healing is complete. Papillomatosis is thought to be caused by malocclusion, ill-fitting or poorly contoured dentures, or excessive relief areas with sharp edges. Loose fibrous bands of tissue on the lower ridge and soft movable tissue over tuberosities should be removed. Even though the residual ridge is small, a firm bearing surface is a better foundation than one that is movable. The fibrous connective tissue on the tuberosities reduces the space between the upper jaw and the retromolar pads and may prevent proper extension of the dentures. An inadequate nutritional intake must be corrected for some patients before beginning denture construction. A diet that is high in protein content and rich in vitamins and minerals, particularly vitamins B and C and calcium, will usually restore such individuals to nutritional health. However, most patients in this category should be referred to a physician for treatment. IMPRESSIONS
Each mouth must be studied carefully to determine anatomic structures and landmarks and the consistency of the soft tissue. The tray that carries the final impression material into place must be in harmony with these attachments and must provide space for the final impression material. Adequate tissue coverage and control of the tissue are more important than the materials used for the tray or the final impression, assuming these materials are stable, accurate, and correctly used. The thickness of the labial flange of the tray is determined by esthetic factors and the available space between the lip and the ridge. A thick impression pulls the tissue away from the labial surface of the bone at the reflection, and when the thickness of the labial flange of the completed denture is reduced, the tissue drops back and a space develops between the soft tissue and the lingual surface of the labial flange of the denture near the border. A thin edge of a flange of a tray will not sufficiently support the final impression material to allow it to fill the available space.
Fig.
1.--A,
Hyperplastic tissue dentures are made.
B,
must be eliminated or made firm before The hyperplastic tissue has been removed
impressions surgically.
for
new
Etx:r:”
Fig.
RESPONSIBILITY
2.-Papillomatosis
OF THE
may
DENTIST
be a precancerous
IN
lesion
COMPLETE
and must
639
DENTURES
be treated
accordingly.
The buccal notch of the impression is almost always shorter and thinner than other borders of the tray because of the action of the buccal frenum (Fig. 3). Adequate space must be provided so the tissues in this region can move without displacing the denture. The buccal vestibule or space should be filled but not overfilled. Inadequate bulk of material in this space lessens the area of tissue contact with the denture base and reduces retention and stability. The posterior end of the upper denture must pass through the hamular notches on each side and extend at least as far back as the vibrating line. The border of the impression should follow around the tuberosity into the notch, so this part of the tray should extend slightly posteriorly to the vibrating line. If the ham&r notches are not included in the impression, the seal will not be adequate in this region when pressure is applied on the cuspid on the opposite side of the mouth. Areolar tissue is present in the hamular notch, and glandular tissue is found in the region of the vibrating line. These tissues are displaceable, which allows the addition of a posterior palatal seal on the denture. The posterior palatal seal is developed in the impression, and then a small narrow bead is placed on the finished denture. The bead extends through the hamular notches and about 2 mm. in front of the vibrating line at the end of the denture. The labial and buccal borders of the lower tray are developed in a manner similar to that for the upper tray (Fig. 3). The posterior part of the lower impression includes the retromolar pad. No additional seal is placed on the pad, since its contents should not be displaced. The lingual border of the lower tray is developed by a series of tongue movements, as described by Boucher. l In the anterior part, from bicuspid to bicuspid, the border is limited by the sublingual folds, the lingual frenum, and the submaxillary caruncles. In the molar region, the tray extends below the level of the mylohyoid ridge and slopes toward the tongue to allow freedom of movement of the mylohyoid muscle. Posteriorly, the tray turns laterally and fills the retromylohyoid space to complete the border seal and guide the tongue onto the top of the lingual flange.
640
HICKEY,
BOUCHER,
AND
WOELFEL
J. Pros. Den. July-August, 1.962
D.
E.
F.
Fig. 3.-Impressions and D, A modified impression material. A
IMPRESSION
for the same patient are made in different final impression materials. plaster. B and E, A zinc oxide-eugenol paste. C and F, A rubber-base
MATERImALS
Several different final impression materials produce good results if the tray is correctly formed (Fig. 3). However, the working properties and consistencies must be understood by the dentist. Plaster of Paris absorbs saliva, thus it gives a more accurate tissue reproduction of the posterior one-third of the palate (over the palatal glands) than other materials. However, plaster has a short critical working period, fractures easily, and sometimes is so thick that overextended borders may result. Zinc oxide-eugenol impression paste flows readily, gives good detail, and is of such a nature that one impression can be made inside another after proper relief.
2izi2‘4”
RESPONSIBILITY
OF THE
DENTIST
IN
COMPLETE
DENTURES
641
This is a good material for lower final impressions when it is desirable to place more of the occlusal stress on the tissue of the buccal shelf (the area between the crest of the residual ridge and the external oblique line) than on the ridge crest. Rubber-base impression material records good detail. However, because of its make-up, many pressure spots that are obvious with other materials may go unnoticed. JAW
RELATION
RECORDS
An articulator is used in complete denture construction for convenience and because of the lack of a solid base in the patient’s mouth. For the articulator to simulate jaw movements, at least four jaw relations must be transferred from the patient to the instrument : (1) the relation of the jaws to the opening axis, (2) the vertical separation of the jaws, (3) the horizontal relation of the lower to the upper jaw in centric relation, and (4) the relation of the lower jaw to the upper jaw when the mandible is protruded so that the incisor teeth are edge to edge. All of these records must be made by the dentist. There are no short cuts or average values that will work. RELATION
OF
THE
JAWS
TO
OPENING
AXES
The relationship of the maxillae to the opening axis of the mandible is transferred to the articulator by means of the face-bow. The lower cast is then related to the opening axes by an interocclusal centric relation record. An arbitrary face-bow mounting seems to be adequate for most edentulous patients. A mark on each side of the face, 12 mm. forward from the foot of the tragus on a line from the tragus to the outer canthus of the eye, is used as the location of the arbitrary axis. These points locate the mandibular axis close to its true position in many patients. A wax or plaster interocclusal record can be made between the occlusion rims while the face-bow is in position, thus allowing both casts to be mounted on the articulator at the same time. The convenience in mounting the casts in this manner makes the use of the face-bow worth while. VERTICAL
RELATION
OF
THE
JAWS
The vertical separation of the jaws that is established in the mouth and mounted on the articulator is the vertical relation of occlusion. This is the space between the jaws when the teeth are in contact. The vertical relation of rest position is constant enough, at least over short periods of time, to serve as a guide in establishing the vertical relation of occlusion. The space between the teeth when the jaw is at rest position is the interocclusal distance, which varies with different patients. Several methods of determining the vertical relation of occlusion are in common usage. The vertical position of the mandible at which the maximal force can be applied is thought to correspond to the vertical relation of rest position. This position may be determined by a Boos Bimeter (Fig. 4). Actually, pain and
J. Pros. Den. July-August, 1962
Fig. 4A.-The Fig. 4B.-The lower resin base. Fig. 4C.-The
central central Bimeter
bearing bearing is in place
plate is mounted on the upper screw and pressure indicating
acrylic resin denture base. gauge are mounted on the
in the mouth.
fatigue limit the amount of force with which an edentulous patient can close the mouth. Thus, the most force can be applied when the ridges are parallel, because the denture bases tend to move the least in this position. Ridge parallelism, rather than the vertical relation of rest position, is what is most often determined by the power test. One physiologic method entails swallowing as a means for determining the vertical relation of occlusion. An upper occlusion rim is developed, and three cones of soft wax are placed on a lower resin trial denture base. The patient performs a series of swallows which shorten the wax cones according to the closure of the mandible (Fig. 5). We have not found consistency in the final position by this method. Measurements can be made between a point on the nose and one on the chin when the jaw is at rest position with nothing in the mouth. A Coble balancer is mounted between an upper contoured occlusion rim and a lower resin trial denture base. The occlusion rims are placed in the mouth, and the central bearing pin is adjusted so that the previously measured points are 3 to 5 mm. closer together (Fig. 6). This distance on the face indicates 2 to 3 mm. of interocclusal distance between the occlusion rims in the bicuspid region. We find that the vertical di-
Volume
Number
12
4
RESPONSIBILITY
OF THE
DENTIST
IN
COMPLETE
DENTURES
643
mension of occlusion is often closed too far for some patients when it is determined by this method. When correctly formed, the occlusion rim should equal the height of the extracted tooth plus the amount of tissue resorption that has occurred. With this in mind, wax occlusion rims can be developed for proper lip support and to the height of the vertical relation of occlusion (Fig. 7). This can be determined by the dentist only with the patient present. The procedure entails developing the upper occlusion rim so that the in&al plane is parallel with the interpupillary line and at a height that allows for the length of the natural tooth plus the amount of tissue resorption that has occurred. The length of the upper lip can be a guide if it is of average length. The occlusal plane, posteriorly, is made to parallel the ala-tragus line (Fig. 8) on the basis of the position of most natural occlusal planes. Then, the lower occlusion rim is adjusted to meet evenly with the upper rim and reduced until an adequate interocclusal distance is obtained. Some of the tests that aid in establishing the correct vertical relation of occlusion with the occlusion rims are ( 1) over-all facial support, (2) visual observation of a space between the rims when the jaws are at rest, (3) pronunciation of words containing sibilants (s, sh, c, ch, j, and Z) , which should cause the rims to come close together but not to contact, (4) measurements between dots on the face, (5) determination of whether the lower rim is level with the lower lip at the corner of the mouth, and (6) parallelism of the upper and lower ridges after the casts are mounted on the articulator. This method is logical in that the occlusion rims represent teeth that were known at one time to be in the mouth, it allows for several different tests, it is fairly easy, and it is not time consuming.
A.
Fig. 5.-A, Cones of soft wax are attached to the lower resin base and occlusion rim. B, The cones have been shortened, by contacts made during height that indicates the vertical dimension of occlusion.
contact the swallowing,
Upper to a
644
HICKEY,
HORIZONTAL
RELATIONS
OF
BOUCHER,
AND
J. Pros. Den. July-August, I.962
WOELFEL
JAWS
There are a multitude of horizontal positions that the mandible can assume in relation to the maxillae in the normal range of function. However, the only relation that the edentulous patient can repeat with regularity is centric relation. Centric relation is the most posterior relation of the mandible to the maxillae at the established vertical dimension. Centric relation must be recorded from the patient’s mouth and transferred to the articulator. It is a mandibular position that the patient may use many times during mastication and many times during the rest of the day in swallowing or whenever the teeth may come together. If the denture bases are to remain stable on the residual ridges with no inclined plane interference, the teeth must meet evenly in this posterior position as well as in all lateral and protrusive positions within the range of normal function. If the teeth are to meet evenly in centric relation, it must be correctly recorded in the mouth and reproduced on the articulator. Some of the methods used to indicate and record centric relation are extraoral and intraoral needle point tracings with central bearing devices, functional chew-in procedures, and direct interocclusal records (Fig. 9).
Fig. Fig. Fig.
6A.-The BB.-The GC.-The
Coble balancer is mounted on the trial denture mandible is at rest position. balancer is adjusted to allow for an adequate
bases. interocclusal
distance.
%%E‘4”
Fig.
7.-The
RESPONSIBILITY
occlusion
I +ms
OF THE
are
DENTIST
IN
COMPLETE
contoured for correct lip suppo vertical dimension of occlusion.
645
DENTURES
Ia-t
md
t.o the
height
of 1:he
The needle point tracings give a graphic indication of the horizontal position of the mandible in relation to the maxillae. The extraoral tracing is easier to observe than the intraoral. The hole often used on the tracing plate of the intraoral device allows the patient a place to put pressure on the trial bases that may not be detected. Whenever central bearing devices are used, as in the needle point tracings, errors are introduced when movable tissue is present on the ridges or when jaw size or position prevents proper centering of the tracing devices in both the upper and lower jaws. Chew-in records may be made with an abrasive material between the occlusion rims or with sharp cutting studs attached to one of the rims. The patient moves the jaw from side to side and either develops the shape of the occlusal plane or cuts pathways with the studs. The pathways are used to mount the casts on the articulator in centric relation and then to adjust the condylar guidances of the instrument. Functional records have the disadvantage of movement of the denture bases on the residual ridges as the mandible is moved. Also, the resistance of the abrasive material usually prevents the record from being developed in the most posterior mandibular position. Direct interocclusal centric relation records are made between the occlusion rims after the vertical dimension of occlusion has been established. Soft plaster or wax is ordinarily used as the recording medium. Sufficient trial centric relation closures should be practiced by the patient under the guidance of the dentist until both the patient and the dentist have learned to recognize the position. Then the recording medium is placed between the occlusion rims in the regions of the bicuspid and molar teeth only. The patient retrudes the mandible to the horizontal position of centric relation and closes the mouth to the vertical level of the established vertical relation, but he must stop the closure before the recording medium is penetrated. If the hard wax of an occlusion rim contacts the opposing rim,
HICKEY,
646
BOUCHER,
AND
J. Pros. July-August,
WOELFEL
Den. 1.962
the denture bases move on the supporting tissue or soft tissue is displaced. In either instance, the record will be incorrect. The record is made as close to the selected vertical dimension of occlusion as possible. This method is adequate for most patients and does not possess some of the inherent errors of the other procedures. PROTRUSIVE
RELATION
RECORD
A record of the jaw relation when the incisor teeth are in an edge to edge position is necessary to adjust the condylar guidances of the articulator. This record is made in soft wax or plaster of Paris, and usually is made after the anterior teeth have been placed in the final positions in the occlusion rims. SELECTION
OF
TEETH
Tooth selection is one phase of denture construction that the dentist must perform himself. Many guides are available to him for making his selection. Diagnostic casts and photographs are the best guides when they are available. Roentgenograms made when natural teeth were present give some clues, and some patients can produce teeth that had been removed previously. In many instances, the size and shape of the face and residual ridge provide insight as to the size and shape of the tooth, A large face or ridge usually indicates that the natural teeth had been large, and the outline form of the tooth is usually in harmony with the shape of the face and ridge. Measurements can be made that work on an average basis. A measurement of the greatest width of the face in the region of the zygomatic arches divided by 16 gives an average width of the upper central incisor, while the same width divided by 3.3 gives the average over-all width of the upper six anterior teeth (flat plane).2 A measurement around a correctly contoured occlusion rim between marks made at the corners of the mouth gives an indication of the over-all width of the upper six anterior teeth (Fig. 10). The six anterior teeth selected from the mold guide can be quickly arranged On the occlusion rim or on a tooth selector and tried in the mouth (Fig. 11). This procedure eliminates many improper tooth selections.
Fig.
&.-A,
The
incisal
plane B, The
of the occlusal
upper plane
occlusion is parallel
rim is parallel to the ala-trams
to the line.
interpupillary
line.
ygge*
‘4”
RESPONSIBILITY
OF THE
DENTIST
IN
COMPLETE
DENTURES
647
Fig. Q.-A, The extraoral tracing devices are mounted on the occlusion rims. B, The extraoral needle point tracing devices are ln the patient’s mouth. C, The intraoral tracing device is mounted on the denture bases and is in the patients mouth. D, Cutting studs are mounted on modeling compound occlusion rims. E, Pathways indicating jaw movement have been cut into the occlusal surface of the lower modeling compound occlusion rim. F, A direct interocclusal record is made in soft plaster of Paris. Note the hand and finger positions.
Posterior teeth are selected on the basis of the size of the ridges and the interarch space. Long posterior teeth (from the occlusal surface to the cervical end) are usually better looking than short teeth when space permits their use. Anatomic teeth can be made to harmonize with the guiding factors of mandibular movement more easily than other tooth forms. No data have shown that anatomic teeth cause more soreness or ridge resorption than other posterior tooth forms. The color of the teeth must be in harmony with the coloring of the face. The least conspicuous color is the objective. Older individuals usually require darker colors of teeth, but this is not a hard and fast rule. The color of the tooth is checked in three places : (1) alongside the face, (2) under the upper lip, and (3)
648
HICKEY,
Fig.
lOA.-A
mark
that
corresponds
BOUCHER,
AND
to the corner
J. Pros. July-August,
WOELFEL
of the mouth
is made
Den. 1962
on the occlusion
rim. the
Fig. lOB.-A measurement around mouth indicates the approximate
the width
occlusion rim between the marks at the of the six anterior teeth when set up.
in the mouth with the upper lip raised as in smiling. checked in both artificial and natural light.
corners
of
The color of teeth should be
TRY-IN
The contoured occlusion rims are used as a guide for the placement of the anterior teeth (Fig. 12). The dental laboratory technician should be instructed to arrange the anterior teeth so that the labial surfaces are flush with the labial surface of the occlusion rim. In this manner, the teeth on the trial denture base will support the face in the same manner as the occlusion rim. The first phase of the try-in is the verification of the jaw relation records. The vertical dimension of occlusion is tested by the same procedures that were used for its establishment. Centric relation is tested by having the patient retrude the mandible and close on the back teeth until the first contact is made. If the teeth touch and then slide on each other, the record is incorrect. If all teeth meet the same at the first contact as they do on the articulator and if the position cannot be proved to be wrong, it may be assumed to be correct. No matter how small the error, the lower cast must be remounted with a new interocclusal centric relation record.
i%c%-L“ ‘4”
RESPONSIBILITY
OF THE
DENTIST
IN
COMPLETE
DENTURES
649
The hand position when making or verifying centric relation records is important. It should be such that both trial denture bases will be correctly positioned with a minimum of interference from the dentist’s hands. The controlling hand is inverted (thumb down and palm toward the patient’s face). Then, with the ball of the thumb and the index finger of the same hand of the dentist placed between the occlusal surfaces of the teeth and with the inverted hand extending up over the patient’s eyes, the patient is instructed to pull the jaw back and close until a tooth touches. This is the best method for testing centric relation we have used (Fig. 9). The dentist is responsible for modifying the arrangement of the anterior teeth to complete the esthetic appearance. The preliminary arrangement of the anterior teeth always needs alteration when it is seen in the mouth. The labiolingual placement of the teeth and the contour of the labial surface of the denture-base material determine the support of the lips. When incorrectly supported, either labiolingually or vertically, the lips cannot function naturally because the musculature forming the modiolus is not held at its correct length, and when it contracts, nothing happens, or too much happens. There are some guides that are helpful in labiolingual positioning of the anterior teeth : (1) the labial surface of the teeth should be as far forward as the labial flange (Fig. 13), (2) the labial surface of the central incisors should be 8 to 10 mm. in front of the middle of the incisive papilla (Fig. 14)) (3) the imaginary root of the artificial tooth should be in front of the residual ridge by the amount of the resorption of the ridge, (4) the sibilant sounds should necessitate the upper and lower anterior teeth to move approximately edge to edge, and (5) the texture of the skin of the lips should be similar to that of other areas of the face. The arch form of the teeth should follow the arch form of the ridge, but with allowance made for surgical accidents that may have occurred (a broken labial plate, etc.). Many variations can be incorporated in the anterior tooth arrangement to produce naturalness (Fig. 15). Full use should be made of diagnostic casts and photographs. The midline of the central incisors usually looks best in the middle of the face, with the long axis of the central incisors in harmony with the long axis of the face. The incisal edges should follow the lower lip when the patient smiles and should be ground to assimilate wear according to age. Irregularities that are not the same on both sides of the dental arch and spaces between some of
Fig,
Il.--A, A possible tooth selection viewed in the mouth to observe
is arranged on a preformed their size and form in relation
selector. B, The teeth to that of the face.
are
HICKEY,
650
BOUCHER,
AND
WOELFEL
J. Pros. Den. July-August, 1962
A.
B.
Fig. toured try-in.
12.-A,
occlusion
The occlusion rims are improperly rims serve as a goo(l guide for
contoured positioning
for the
lip support. B, Properly anterior teeth for their
confirst
the teeth are effective. The effect of sex, personality, and age of each patient on individual tooth form and position should be considered in the final arrangement of the teeth.s POSTERIOR
TOOTH
ARRANGEMENT
The dentist is responsible for the final arrangement of posterior teeth. If written instructions to the dental laboratory are not adequate for meeting certain situations, the dentist should observe the arch form, occlusal plane, and occlusion of the teeth before the dentures are processed and cured.
Fig.
13.-A, The anterior teeth have been set too far lingually in B, The anterior teeth are in their correct positions in relation
relation to the labial to the labial flange.
flange.
~2llml&
RESPONSIBILITY
OF THE
DENTIST
IN
COMPLETE
DENTURES
6.51
The posterior tooth arrangement must be such that it preserves the correct form of the dental arch. This means that, in some instances, the upper teeth may be in a buccal version or in a “cross-bite” relationship. The height of the acclusal plane is located between the incisal edge of the lower cuspid and the height of the posterior one-third of the retromolar pad. The posterior teeth are positioned buccolingually so that a perpendicular line through the buccal turning point of the crest of the ridge bisects the buccal cusps of the lower first molar. No part of any posterior tooth should be lingual to the mylohyoid ridge. The posterior teeth should never extend further posteriorly than the beginning of the retromolar pad. Likewise, they should not extend onto ridge inclines that tend to produce unseating or skidding forces on the denture bases during mastication. If the ridge inclines upward toward the retromolar pad, a tooth or teeth should be omitted or teeth with a smaller mesiodistal dimension should be used. When smaller teeth are used, the next size longer tooth (vertically) should be selected to avoid an unsightly exposure of denture-base material. COMPLETION
OF DENTURES
After the dentures are cured, the face-bow mounting is preserved by remounting the upper denture on the articulator with a remounting record jig. Processing
Fig. 14.-The labial surfaces of the central incisors should be from 8 to 10 mm. in front of the middle of the incisive papilla. Note the relation of the labial surface of the tooth to the labial surface of the cast.
changes are not corrected on the articulator since a new interocclusal centric relation record is made from the patient’s mouth on the day the dentures are inserted. Immediately after the dentures are placed in the mouth, the patient is instructed to hold them tightly together. Then an interocclusal protrusive record is made in plaster of Paris. These records are laid aside for the adjustment of the articulator, later.
652
HICKEY,
Fig. 15.-A, The tooth arrangement the patient. B, The tooth arrangement, appearance of the patient.
BOUCHER,
AND
WOELFEL
is in harmony with the age, although not totally displeasing,
J. Pros. Den. July-August, 1.962
sex, and personality does not enhance
of the
Then an interocclusal centric relation record is made in soft, quick-setting plaster of Paris with the opposing teeth just out of contact. The lower denture is mounted on the articulator and the condylar guidances on the articulator are adjusted. The teeth are ground first into centric occlusion as indicated by articulating paper marks. Then the occlusion is corrected for the eccentric positions. The method of grinding ensures that the teeth contact uniformly in centric relation and in all other positions within the normal range of function. Central bearing devices, wax over the teeth, and articulating paper in the mouth have been used as means for correcting the occlusion. These methods have the disadvantage of denture movement on the supporting tissues. Even though the articulator does not duplicate jaw movements perfectly, for most patients, it does a better job than can be accomplished working directly in the mouth. The poorest procedure is the use of abrasive paste on the teeth in the patient’s mouth because it provides no control over the places where the teeth are modified. Grinding the teeth on the articulator allows the dentist to select the part of the tooth he wishes to modify and to work on a dry surface. The dentist must be certain that the patient is educated in the use and care of the dentures and informed that routine yearly dental examinations are necessary. Written instructions on these phases are helpful. ADJUSTMENTS
All complete denture patients should be given 24 and 48 hour appointments for denture adjustments. The dentist is responsible for adjustments until the dentures are comfortable. The nature and location of soreness caused by dentures are often a guide to the cause of the difficulty. Some of the common locations, causes of soreness, and complaints are (1) soreness at the reflection because of overextended denture borders, (2) soreness on the slope or crest of the ridge from malocclusion or pressure spots in the impression, (3) soreness during swallowing from pressure on the mylohyoid ridge or overextension of the distal end of the lingual flange, (4) soreness of frenula because of insufficient notch size or sharpness, (5) burning or a sensation of numbness from pressure on the incisive papillae or mental fora-
Volume 12 Number 4
RESPONSIBILITY
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DENTIST
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COMPLETE
DENTURES
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men, (6) generalized soreness from malocclusion, excessive vertical dimension of occlusion, avitaminosis, or unhygienic dentures, and (7) cheek-biting lesions resulting from insufficient horizontal overlap of the upper over the lower teeth. Complaints about loosening of the upper denture may result from (1) excessive thickness of the distobuccal corner of a buccal flange which causes displacement of the upper denture during yawning or wide open or lateral jaw movements, (2) excessive thickness or height in the buccal notch region which displaces the denture during smiling, (3) malocclusion which may cause a loosening after the dentures have been worn several hours, (4) lack of proper distal extension or an inadequate posterior palatal seal which causes tipping of the denture when biting on the front teeth, and (5) tissue displaced during the making of the impression. Complaints about loosening of the lower denture may result from (1) in-lproper tooth placement, either too far buccally or too far lingually, (2) improper border form or length, (3) failure to fill the retromylohyoid space, (4) insufficient space for action of mylohyoid muscle, (5) insufficient size or incorrect shape of the buccal notches, (6) incorrect form of the polished surface of the denture so that the cheeks and tongue tend to raise the denture rather than help to hold it down, (7) bad tongue habits of the patient, and (8) errors in occlusion. SUMMARY
The dentist is obligated to perform certain essential phases of complete denture construction. These include making a comprehensive diagnosis, making certain that the oral tissues are healthy before work is started, making the impressions, producing jaw relation records, selecting the teeth, correcting the jaw relation records, rearranging the anterior teeth for esthetic appearance, correcting the occlusion at the time of the first insertion of the dentures, and making whatever denture adjustments may be necessary. If the dental profession is to maintain its high standard of denture service, the dentist must not delegate to someone else any phase of denture construction he should complete himself. REFERENCES
1. Boucher, C. 0. : Impressions for Complete Dentures, J.A.D.A. 30:14-Z, 1943. 2. House, M. M., and Loop, J. L: Form and Color Harmony in the Dental Art, Monograph. Whittier, Calif., 1939, M. M. House. : Its Practical Application, J. PROS. DEU. 3. Frush, J. P., and Fisher, R. D.: Dentogenics 9:914-921, 1959. THE OHIO STATE UNIVERSITY COLLEGE OF DENTISTRY 305 WEST TWELFTH AVE. COLUMBUS 10, OHIO