Prosthodontic Book Chapter 18: The Try-in Appointment

CHAPTER 18 The Try-in Appointment Charles L. Bolender SECTION I: PERFECTION AND VERIFICATION OF JAW RELATION RECORDS The vertical dimension and centric relation (CR) of edentulous jaws are tentatively established with the occlusion rims, as described in Chapter 16. After the preliminary arrangeme...

CHAPTER 18 The Try-in Appointment Charles L. Bolender SECTION I: PERFECTION AND VERIFICATION OF JAW RELATION RECORDS The vertical dimension and centric relation (CR) of edentulous jaws are tentatively established with the occlusion rims, as described in Chapter 16. After the preliminary arrangement of the artificial teeth on the occlusion rims, it is essential that the accuracy of the jaw relation records made with the occlusion rims be tested, perfected if incorrect, and then verified to be correct. The dentist must assume that the preliminary jaw relation records were incorrect until they can be proven correct. This mental attitude of the dentist—attempting to prove that the jaw relation records are wrong—is essential in perfecting and verifying jaw relation records. Patients should be advised to leave existing dentures out of the mouth for a minimum of 24 hours before the jaw relation records are perfected and verified at the time of the try-in appointment. Unfortunately, most patients will find this to be an unreasonable request. An acceptable alternative is to have the existing dentures relined with a soft temporary material. Whichever approach is taken, the soft tissues of the basal seat will be rested and in the same form as they were when the final impressions were made. If this procedure is not followed, the distorted condition of the soft tissue can prevent the registration of accurate interocclusal records. It is almost impossible to overemphasize the importance of perfection and verification of jaw relation records. The appearance and comfort of the patient, occlusion of the teeth, and health of the supporting tissues are all directly related to the accuracy of jaw relation records. VERIFYING THE VERTICAL DIMENSION The maxillary and mandibular trial dentures are placed in the patient’s mouth. The patient is instructed to close lightly so the maxillary labial frenum can be checked to see that it is absolutely free. This is necessary before the relation of the lip to the teeth can be observed. If the denture border causes binding of the frenum, the labial notch should be deepened. Next, a tentative observation of the centric occlusion (CO) is made. The mandible is guided into CR by a thumb placed directly on the anteroinferior portion of the chin with patient instructions to “open and close until you feel the first feather touch of your back teeth.” At first contact, the patient opens and repeats this closure, only this time stopping the instant a tooth touch is felt and then closing tight. The procedure will reveal errors in CR by the touch and slide of teeth on each other. Errors in CR can interfere with tests for vertical relations. The vertical dimensions of occlusion and of rest must now be given careful consideration because the final positions of the anterior and posterior teeth will depend to a great extent on the amount of space that is available vertically. Unfortunately, there is no precise scientific method of determining the correct occlusal vertical dimension. The acceptability of the dentures’ vertical relations depends on the experience and judgment of the dentist. Nevertheless, the factors that govern final determination of this relation can be said to hang on careful consideration of the following: 1. Preextraction records 2. The amount of interocclusal distance to which the patient was accustomed, either before the loss of natural teeth or with old dentures 329 330 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures 3. Phonetics and esthetics 4. The amount of interocclusal distance between the teeth when the mandible is in its rest position 5. A study of facial dimensions and facial expression 6. Lip length in relation to the teeth 7. The interarch distance and parallelism of the ridges as observed from the mounted casts 8. The condition and amount of shrinkage of the ridges A combination of these factors and considerations may be used to aid in determining an acceptable vertical dimension. VERIFYING CENTRIC RELATION After the vertical dimension has been determined, CR is verified. This can be done by intraoral observation of intercuspation or by an extraoral method on the articulator. A Intraoral Observation of Intercuspation The test for accuracy of the preliminary CR record involves the observation of intercuspation when the mandible is pulled back by the patient as far as it will go and closure is stopped at the first tooth contact. The patient is guided into CR by a thumb placed on the anteroinferior portion of the chin and the index fingers bilaterally on the buccal flanges of the lower trial denture (Figure 18-1). With the index fingers, the dentist checks that the lower trial denture is seated in an inferoanterior direction. The patient pulls his lower jaw back as far as it will go and closes just until the back teeth make a “feather touch.” As tooth contact approaches, the dentist’s index fingers should rise off the buccal flanges. Pressure on the buccal flanges, or stretching the lip with the index fingers, will create the risk of posteriorly displacing the lower trial denture. Then the patient closes tightly. Any error in CR will be apparent when the teeth slide over each other, especially if anatomical teeth are used (Figure 18-2). A second closure made with the same instructions B Figure 18-1 A, Hand and finger positions for checking the accuracy of centric relation records. B, As tooth contact approaches, the index fingers are raised off the buccal flanges to avoid displacement of the lower denture. Chapter 18 The Try-in Appointment Figure 18-2 An error in centric occlusion (CO) that is due to an error in centric relation mounting will produce contact of the inclined planes of the cusps (B). Further closure will allow the teeth to slide into CO (A). The path of closure is an arc (C) about the posterior terminal hinge axis. and a stop at first tooth contact will permit visual observation of any error. Errors in the mounting may prevent intercuspation of some teeth when the first contact is made. If the patient stops the closure at the instant the first teeth touch, an error will be indicated by the space between the lower tooth or teeth and the teeth they were supposed to touch. The amount of error observed in this manner will be magnified by the effect of the inclined plane contacts. All the teeth that occluded uniformly on the articulator must have equally uniform contacts in the mouth; if they do not, the touch and slide observation will prove the mounting incorrect. Once it is determined that the mounting is incorrect, a preliminary observation of esthetics is made. If the anterior teeth are not placed to support the lip properly, their positions are corrected. Then vertical overlap of the anterior teeth is carefully noted. This is important because the amount of vertical overlap will be a guide to the amount of closure permitted when the next interocclusal record is made. Because complete dentures rest on movable soft tissues, it is difficult to detect anything other than gross occlusal errors by visual observation of the occlusion. As a result, one should not rely on visualization for the final determination of cast mounting accuracy. The posterior teeth are removed from the lower occlusion rim, and both occlusion rims are placed in the mouth. Impression plaster (or an interocclusal registration paste), is mixed, and with the hands in the same position as for testing the previ- 331 ous record, the selected recording medium is placed on both sides of the lower occlusion rim in the molar and premolar regions. This may be done with a narrow plaster or cement spatula. Then the patient is instructed to pull the lower jaw back and close slowly until requested to stop and hold that position. The closure is stopped when the anterior teeth have the same vertical overlap as they had before the posterior teeth were removed. Thus the vertical relation of the two jaws will not have changed. When the plaster or registration paste is set, the new record is removed with the two occlusion rims, and the lower cast is remounted on the articulator. In an alternate technique an abbreviated beeswax occlusion rim is used to replace the removed posterior teeth. (The rim may replace all the posterior teeth, or else a “tripod” of beeswax stops can be used [Figure 18-3].) The patient is Figure 18-3 A modified beeswax interocclusal record of centric relation (CR) is made to correct an error in the preliminary mounting of casts. The lower posterior teeth are removed so there will be no contact between upper and lower trial dentures. The vertical overlap of anterior teeth is a guide to the vertical dimension at which CR will be recorded. Arrows indicate the beeswax tripod of stops. 332 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures guided into the most retruded mandibular position at the selected vertical dimension when the upper posterior teeth will indent the softened opposing wax rims. The lower cast is remounted on the articulator, and the lower posterior teeth are reset in CO. The occlusion rims, with the teeth in good tight CO, are returned to the mouth, and the same tests are made as before. If the teeth occlude perfectly and uniformly when the lower jaw is drawn back as far as it will go, the CR mounting may be assumed to be correct. There should be uniform simultaneous contact on both sides of the mouth, in the front and back and without any detectable touch and slide. It is essential with this procedure that the dentist tries to find an error in the previous record. The record must be assumed to be incorrect unless no touch and slide can be detected. The entire procedure is repeated until all doubt as to the correctness of the relationship of the casts is gone. Figure 18-4 Artificial teeth positioned on a Dentatus ARH articulator. Extraoral Articulator Method CR can be checked or verified by an extraoral method in which observations are made on the articulator rather than in the mouth. The technique is easy and thus attractive, but its use depends on taking one or two liberties. A CR registration in soft wax is placed between the opposing teeth. The teeth do not contact through the wax; thus the record is made at a slightly increased vertical dimension. Although clinical experience endorses this technique, a purist might argue that such verification is likely to work correctly only if a kinematic hinge axis, rather than an arbitrary face bow recording, is used originally. Because conclusive research to support such an argument is absent and because extensive clinical application of the technique has led to predictable and reproducible results, it deserves description. Remember: The purpose of the extraoral method is to determine whether the position of the teeth on the articulator (Figure 18-4) is the same as that in the patient’s mouth (Figure 18-5). As mentioned previously, it is difficult to detect occlusal errors by clinical observation, so wax, plaster, or a bite registration paste must Figure 18-5 The same trial dentures as shown in Figure 18-4 being evaluated for proper occlusion. Clinical observation of tooth contacts is not as accurate as the extraoral method. Chapter 18 The Try-in Appointment be used as the recording medium in this technique. Impression material (e.g., two pieces of Aluwax) is placed over the posterior mandibular teeth (Figure 18-6). A thickness is chosen that will eliminate the danger of making contact with the opposing teeth when biting pressure is exerted. No wax is placed on the anterior teeth because anterior tooth contact tends to cause the patient to protrude his lower jaw. The teeth must be completely dry and the wax pressed firmly on the teeth to elimi- 333 Figure 18-6 A second layer of warmed Aluwax is applied to the first layer, which has been carefully adapted to the posterior teeth. nate voids between it and the teeth. The two thicknesses of wax are sealed with a warm spatula (Figure 18-7). The chilled upper trial denture is placed in the patient’s mouth. Next, just the wax portion is immersed in a water bath of 130° F (54° C) for 30 seconds (Figure 18-8). Both the temperature and the time are critical in achieving a uniformly softened wax. (Aluwax retains heat longer than baseplate wax, which provides more working time for the next step.) The mandibular trial denture is seated with the index fingers bilaterally positioned on the buccal flanges. The mandible is guided into CR by a thumb on the anteroinferior portion of the chin to direct some guidance toward the condyles. The thumb must be on the point of the chin, not under it; the patient is guided in a hinge movement, closing lightly into the wax (Figure 18-9). As contact with the wax approaches, the index fingers are raised from the buccal flanges. The patient then closes into the wax until a good index is made (Figure 18-10). Care must be taken that the patient does not penetrate the wax and make tooth contact. If one method of suggested retrusion does not work, another may. In any case, a minimum amount of occlusal pressure should be exerted on the wax. The lower trial denture is then carefully removed from the mouth and placed in ice water to chill the wax thoroughly (Figure 18-11). Next, the trial dentures are removed from the ice water and Figure 18-7 The two layers of Aluwax are sealed with a warm spatula. Figure 18-8 Only the Aluwax is immersed in 130° F (54° C) water for 30 seconds. 334 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures Figure 18-9 The mandible is guided into centric relation with the thumb on the anteroinferior portion of the chin and the index fingers seating the lower trial denture in a downward and forward direction. Figure 18-10 The patient is instructed to close lightly into the softened wax. The index fingers should be slightly raised from the buccal flanges at this point. dried. It is important that the imprint of the opposing teeth be crisp and about 1 mm deep, with no penetration of the wax by a maxillary tooth (Figure 18-12). If penetration occurs, it will likely deflect the occlusal contact as well as shift the bases or change the maxillomandibular relation horizontally and vertically. The chilled dentures are returned to the patient’s mouth, and the patient is guided into CR. The record is acceptable if there is no tilting or torquing of the trial dentures from initial contact to Figure 18-11 The lower trial denture and attached Aluwax are chilled in ice water for several minutes. Figure 18-12 The occlusal record should be approximately 1-mm deep and free of any penetration by the underlying teeth. complete closure (Figure 18-13). Underlying soft tissue displacement may cause a slight movement of the bases and must be taken into account when evaluating the contact. If the record is unacceptable, the procedure must be repeated. After the wax has been chilled, the trial dentures are placed on their casts, and the locked articulator is closed in CR; the opposing teeth should fit into the indentations in every way (anteriorly, posteriorly, laterally, and vertically) (Figure 18-14). When the original CR interocclusal record and the check are both correct, these teeth will fit into the indentations surprisingly well. Chapter 18 The Try-in Appointment Figure 18-13 A C Checking the accuracy of the interocclusal wax record clinically. B D Figure 18-14 With the condylar mechanisms locked in a centric position (A and B), the upper teeth should fit accurately into the wax index (C and D). When this occurs, it means that the original recording was correct. 335 336 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures Figure 18-15 A plaster interocclusal centric relation (CR) record is used to test the accuracy of preliminary mounting on the articulator. The location of the condylar sphere in contact with the posterior, lateral, and superior elements of the condylar housing indicates that the preliminary record and test record are clinically identical. Thus the casts on the articulator are assumed to be in CR. If the opposing teeth do not fit exactly into the indentations in the new record, it means that the original mounting was incorrect or that the patient did not bite cleanly into the interocclusal wax. To evaluate this, the dentist must return the chilled trial dentures and wax record to the mouth and reevaluate their accuracy, as previously described. If the record still appears to be correct in the patient’s mouth, then the original CR registration, mounting, or both were incorrect. In these cases, the mandibular cast must be separated from the mounting ring and the cast remounted by means of the last interocclusal wax record. The new mounting is again checked to prove or disprove its correctness. If the initial registration (preliminary CR record) was made in plaster or a bite registration paste, the same recording medium should be used to verify the accuracy of the mounting on the articulator. Likewise, if wax was used, wax should be the verifying medium. However, it is easier to distort wax when the record is removed from the mouth and tested on the articulator (Figure 18-15). SECTION II: ECCENTRIC JAW RELATION RECORDS, ARTICULATOR AND CAST ADJUSTMENT, ESTABLISHMENT OF THE POSTERIOR PALATAL SEAL When the final occlusion is developed and corrected on the articulator, it is essential that the movements of the articulator simulate mandibular positions or movements of the patient within the range of normal functional contacts of teeth. Thus the condylar elements of the articulator must be adjusted so that they approximate the condylarguiding factors within the temporomandibular joints (TMJs). These adjustments of the condylar elements of the articulator are made by means of interocclusal eccentric records. PROTRUSIVE AND LATERAL RELATIONS There seems to be confusion in the minds of many dentists as to what a protrusive registration is intended to attain. The idea that the angle and lines Chapter 18 The Try-in Appointment of the bony fossa completely govern the path of the condyle is erroneous. A study of the anatomy and function of the joint reveals that the condylar path is governed partly in its shape and function by the meniscus. The meniscus is attached in part to the lateral pterygoid and moves forward during opening and lateral mandibular movements. The path is controlled further by the shape of the fossa, the attachments of the ligaments, the biting load during movement (muscular influence), and the amount of protrusion. Variation in registrations can be caused by several factors. The registration may vary according to the biting pressure exerted after the mandible has been protruded. The condyle, not being locked on a path, is subject to change in its path with a variation of pressure. Undoubtedly, there is some leeway for adaptability to conform to the changing conditions of the teeth. Many parts of the body are phenomenal in their ability to adapt to unusual conditions, and the TMJ is one of them. Not many complete dentures could be worn if this were not true. However, registration of a normal comfortable movement of the condyle in its path, with subsequent harmonious eccentric occlusion and CO to conform to this, greatly augments lasting function of dentures. Therefore there does not seem to be much excuse for failure to register this path because it is not difficult or time-consuming in proportion to the results obtained. CONTROLLING FACTORS OF MOVEMENT Edentulous patients bring only one controlling factor to the movement of the mandible, a fact that seems to be misunderstood generally. The misconception exists because many dentists think the condyle paths control the movement of the mandible entirely. In the laws of articulation, the incisal guidance provided by the anterior teeth is an important part of the control. This guidance is always decided by the dentist, consciously or not. With semiadjustable articulators like the Dentatus, Hanau, and Whip Mix, incisal guidance is controlled by the inclination of the incisal guidance mechanism, which is determined by the horizontal and vertical overlap of the anterior teeth. The incisal guidance is more influential in controlling movements of the mandible than the condylar paths are because the 337 condylar paths are farther away from the cusp inclines, which both the incisal angle and the condyle angle influence. ECCENTRIC RELATION RECORDS A previous chapter underscored the fact that eccentric relation records are rarely used in the fabrication of complete dentures. They are referred to in this chapter mainly for historical purposes. Their consideration also provides interesting insights into the complexity of mechanical simulation of jaw movement. Skipping over this section is certainly an option for the reader. The path of the condyle in protrusive and lateral movements is not on a straight line. The shape of the mandibular fossa is an ogee curve as viewed in the sagittal plane. This double curve will cause the apparent path of the condyle to be different with varying amounts of mandibular protrusion. The ideal amount of protrusion for making the record is the exact equivalent of the amount of protrusion necessary to bring the anterior teeth end to end. However, the mechanical limitations of most articulators require a protrusive movement of at least 6 mm so the condylar guidance mechanisms can be adjusted. Methods of registering the condyle path may be classified as intraoral and extraoral. Extraoral methods are generally exemplified by the Gysi and McCollum techniques. The intraoral methods may be listed as (1) plaster and carborundum grind-in, (2) chew-in by teeth opposing wax, (3) chew-in modified by a central bearing point, (4) Needles’s styluses cutting a compound rim, (5) Needles’s technique modified by a Messerman tracer, (6) protrusive registration in softened compound, (7) protrusive registration in plaster, and (8) protrusive registration in softened wax. Lateral and protrusive condylar inclinations may be registered when straight protrusive movements are made. Many dentists consider these shortrange lateral movements sufficiently indicative for practical purposes. However, for a complete registration, lateral records are necessary to indicate the limit of the range of movement, as shown by the Gothic arch (needle point) tracings. Wax interocclusal records may be made on the occlusion rims before the teeth are set up or on 338 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures the posterior teeth at the try-in appointment. Records made on occlusion rims must be considered tentative because the vertical and horizontal overlaps of the anterior teeth have not as yet been determined and the exact amount of protrusion and the level at which the anterior teeth are to contact are still unknown. These preliminary records permit tentative adjustment of the condylar guidances on the articulator. Plaster interocclusal records are made after the anterior teeth have been arranged for esthetics and after both CR and the vertical dimension have been verified. If the horizontal overlap is sufficient to obtain enough protrusive movement of the lower jaw that the articulator can be adjusted, this record will be adequate. It also will be an accurate record of the relation of the jaws during incision. If the horizontal overlap of the incisors is too small to permit sufficient mandibular movement for adjustment of the condylar guidance, the patient must be instructed to protrude the jaw farther when the record is made. The minimum amount of protrusion for condylar guidance adjustment is 6 mm. This limitation is necessary because of mechanical deficiencies of most articulating instruments. Lateral interocclusal records can be made to set the condylar inclination and the mandibular lateral translation on the articulator. However, with complete dentures, it is more difficult to secure accurate and reproducible lateral records than protrusive records, in part because of the displaceability of the ridge mucosa. In addition, most semiadjustable articulators are not able to accept many lateral eccentric records. It is therefore generally accepted that making lateral interocclusal records for patients with complete dentures is not practical and probably not warranted. Eccentric interocclusal records may be made with the guidance of extraoral tracings. While the tracing device is still attached to the occlusion rims, the amount of protrusive movement is determined by observation of the distance between the apex of the tracing and the needle point. The amount and direction of the lateral movement can be determined by observing the distance of the needle point from the apex of the tracing while the needle is on one of the arcs of the tracing. When the needle point is 6 mm from the apex, the mandible in the first molar region will be approxi- mately 3 mm lateral to its position in CR. The molar tooth will have moved laterally 3 mm because it is approximately midway between the tracing and the working-side condyle. Protrusive Interocclusal Records for the Whip Mix Articulator (Arcon Type) After try-in, the trial dentures are placed on the articulator. The lateral condylar guidances are set at 0 degrees so the articulator will be moved in a straight protrusive direction. The horizontal condylar guidances are set at 25 degrees to give an indication of the space that will exist between the posterior teeth when the mandible is protruded. The lower member of the articulator is moved forward approximately 6 mm, with the teeth out of contact and then closed, until the incisal edges of the lower anterior teeth reach the vertical level of the incisal edges of the upper anterior teeth. The 6 mm of forward movement that is necessary to permit proper adjustment of the horizontal condylar path of the articulator may bring the lower anterior teeth several millimeters in front of the upper anterior teeth. The horizontal relation of the lower to the upper anterior teeth and the relationship of the midlines of the upper and lower anterior teeth are observed carefully because they will be the guides to the dentist that the patient has closed in approximately the proper position when the protrusive record is made in the mouth (Figure 18-16, A). Interfering opposing posterior teeth that contact before the lower anterior teeth reach the desired vertical relation should be removed from the wax occlusion rim. When the dentist has become familiar with the relation of the lower to the upper anterior teeth in the protrusive position, the trial dentures are removed from the articulator and placed in the patient’s mouth. The trial dentures are held in position by the dentist in the same way as for making the interocclusal CR record. The patient is instructed to move his jaw straightforward and then to bite lightly on his front teeth. The dentist determines the amount and nature of the forward protrusion by the previous observation of the relationship of the anterior teeth on the articulator. The patient practices closing in Chapter 18 The Try-in Appointment A 339 B Figure 18-16 A, The articulator (Whip Mix) in a protrusive position to show the amount of forward movement necessary to adjust the condylar elements. This relationship will guide the dentist when a protrusive record is made in the patient’s mouth. B, The patient rehearses closing in protrusive position, and the dentist observes the anteroposterior relation of the opposing anterior teeth and their alignment (between the upper and lower central incisors); this will be used as a guide for the amount and direction of protrusive movement. The movement should be similar to that observed on the articulator. the protrusive position under the guidance of the dentist until both become familiar with the procedure (Figure 18-16, B). A small amount of recording material that does not distort easily when set (impression plaster) is placed on the occlusal surfaces of the lower posterior teeth. Then, as in the practice sessions, the patient protrudes his mandible and closes into the recording material. The patient is instructed to stop the closure before the opposing teeth make contact and to hold the jaw lightly and steadily in the desired position until the recording material sets. The relationship of the lower to the upper anterior teeth in the patient’s mouth should closely approximate the relationship observed on the articulator and during the rehearsal sessions. The trial dentures and interocclusal record are removed from the mouth. The lateral condylar guidances on the upper member of the articulator are set at 20 degrees so they will not interfere if the mandible has not moved forward in straight protrusion and the horizontal condylar guidances are set at 0 degrees. Then the trial dentures and interocclusal protrusive record are returned to the articulator (Figure 18-17, A). The horizontal condylar housings are rotated individually until the guidance plates contact the condylar spheres (Figure 18-17, B and C) and the angulation of the protrusive movement for both sides is recorded. The advantages of the protrusive registration made in plaster, or a recording material of similar consistency, are that the resistance to the biting force is minimal and uniform and there is nothing that guides the patient’s mandible except the memory patterns of mandibular protrusion and the instructions by the dentist. Also, the recording material will not be distorted during adjustment of the articulator. The disadvantage of plaster is related to the difficulty many patients experience in holding their mandibles in a steady protrusive position long enough for the material to set. Protrusive Interocclusal Record for the Dentatus Articulator (Non-Arcon Type) Three thicknesses of Aluwax are placed over the occlusal surfaces of the mandibular posterior teeth, rather than the two described for CR verification. The edges of the wax are sealed on both the buccal and the lingual sides with a warm spatula (Figure 18-18). The chilled upper trial denture should be placed in position on the upper cast mounted in the articulator. Next, only the Aluwax portion of the lower trial denture is immersed in a water bath of 130° F (54° C) 340 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures B A C Figure 18-17 Trial denture bases positioned by an interocclusal protrusive record (impression plaster) are returned to the Whip Mix articulator. A, The horizontal condylar guidance mechanism is not in contact with the condylar sphere (arrow). B, The condylar mechanism is rotated into contact with the condylar sphere (arrow), thus establishing horizontal condylar guidance on the articulator. C, An interocclusal protrusive record has been made in wax, with the articulator adjusted as in B. Figure 18-18 warm spatula. Three layers of Aluwax sealed with a Figure 18-19 Only the Aluwax portion is immersed in 130° F (54° C) water for 30 seconds. Chapter 18 The Try-in Appointment 341 for 30 seconds (Figure 18-19). The lower trial denture is placed on the lower cast, and the articulator is set a quarter of an inch (6 mm) in protrusion with the condyle paths, registering 25 degrees. At this position, the upper member of the articulator is pressed into the warm wax to approximately a third of its depth. The mandibular trial denture is removed from the cast, and the wax record is chilled thoroughly. Both trial dentures are now placed in the patient’s mouth, and the patient is taught how to protrude into these indentations. The patient rehearses this protrusive action to prepare for making such a protrusive movement later when the wax is softened. The mandibular trial denture is now removed from the mouth and the wax record is resoftened in hot water. Care is taken not to destroy the indentations. The trial denture is reinserted into the mouth, and the patient is told to feel carefully and move into these markings in the manner rehearsed previously (Figure 18-20). (Instructions have already been given not to exert occlusal pressure into these indentations until told to do so.) The position of the teeth relative to the indentations is carefully observed, and when the teeth coincide with these markings, the patient is instructed to bite, but not to bite through the wax. As an alternative the patient can be instructed to relax his jaw muscles while the dentist elevates the mandible with the index finger placed beneath the inferior portion of the chin. With either approach, the anterior teeth should remain slightly out of contact to avoid any tooth interference. The wax record is chilled in the mouth, removed, and examined for any contact between the teeth. The trial dentures are replaced on the articulator, and the articulator is protruded so the maxillary teeth will fit partially into the indentations. The locknuts for the condylar guidance slot adjustments are loosened. While pressure is exerted on the upper articulator member with one hand and the condylar guidance slot is worked back and forth with the other hand, a condylar path inclination is found that permits the teeth to stay in contact with the wax throughout (Figure 18-21). This adjustment is repeated for the opposite side. It will readily be seen that too steep a path prevents contact in the posterior part of the arch, and too horizontal a path prevents contact in the anterior part of the arch. As stated earlier, the correct degree of condylar path incline can be attained by tooth contact of the wax throughout the arch; the condylar guidance slot is locked in the position thus obtained. A protrusive record is first made on the articulator so the correct amount of protrusive distance (which is also centered) will guide the patient’s Figure 18-20 The mandible is guided into the index previously made on the articulator. Figure 18-21 Pressure on the Dentatus articulator with one hand and back and forth movement of the condylar guidance slot with the other permit a condylar path inclination to be found that gives uniform contact of the wax index and opposing teeth. 342 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures mandible to the desired protrusive position. Unless the patient has a guide and has rehearsed, it will be extremely difficult to keep the mandible from closing too far or not far enough in protrusive occlusion, to the right or left in lateral occlusion, or in a combination of protrusion and lateral occlusion. Such a record will give an unsatisfactory setting to the articulator. The record is made with a protrusive distance a quarter of an inch (6 mm) because it is thought that with a shorter distance the condyle will not move down its path sufficiently to be recorded on the instrument. A protrusive movement of more than a quarter of an inch is usually beyond the range of the patient, and registration of a greater distance is not necessary. An alternative procedure involves the use of impression plaster for making the protrusive interocclusal record, as described for the Whip Mix articulator. ESTABLISHMENT OF THE POSTERIOR PALATAL SEAL The posterior palatal seal is completed before the final arrangement of the posterior teeth because this final arrangement is a laboratory procedure and is done in the absence of the patient. The posterior border of the denture is determined in the mouth, and its location is transferred onto the cast. A T burnisher, or mouth mirror, is pressed along the posterior, angle of the tuberosity until it drops into the pterygomaxillary (hamular) notch (Figure 18-22). The locations of the right and left pterygomaxillary notches are marked with an indelible pencil. On the median line of the anterior part of the soft palate are two indentations formed by the coalescence of ducts known as the foveae palatinae. The shape of these depressions varies from round or oval to oblong. The dentist can make them more readily discernible by having the patient hold his nose and attempt to blow through it (Valsalva maneuver). This will accentuate the foveae palatinae and vibrating line. The vibrating line of the soft palate, normally used as a guide to the ideal posterior border of the denture, usually is located slightly anterior to the foveae palatinae. However, it may be on or slightly posterior to the foveae palatinae. The slight devia- Figure 18-22 The pterygomaxillary (hamular) notch (arrow) in the mouth often is deceiving. To be certain of its location, the dentist can palpate it with a mouth mirror placed posterior to the tuberosity (arrow). tion from these markings is estimated by having the patient say “ah” and thus vibrate the soft palate. The dentist observes closely and marks the vibrating line with an indelible pencil (Figures 18-23 and 18-24). The two pterygomaxillary notch markings are joined to the median line mark. The trial denture base is now inserted so the indelible pencil line will x Figure 18-23 The vibrating line has been traced on the palatal tissues with indelible pencil. The X with arrows marks where it passes through the hamular notch on both sides slightly anterior to the foveae palatinae. Chapter 18 The Try-in Appointment 343 Figure 18-24 The vibrating line and width of the posterior palatal seal depend on the soft palate form (A, B, or C). Form C allows only a narrow posterior palatal seal; A allows the widest seal. be transferred from the soft palate to the trial denture base, and the excess baseplate is reduced to this line (Figure 18-25). The trial denture base is placed on the cast, and a knife or pencil is used to mark a line following the posterior limits of the baseplate (Figure 18-26). This line should extend laterally 3 mm beyond the crest of the hamular notch. The anterior line that indicates the location of the posterior palatal seal is drawn on the cast in A front of the line indicating the end of the denture (Figure 18-27). The width of the posterior palatal seal itself is limited to a bead on the denture that is 1- to 1.5-mm high and 1.5-mm broad at its base (Figure 18-28). A greater width creates an area of tissue placement that will have a tendency to push the denture downward gradually and to defeat the purpose of the posterior palatal seal. In other words, the posterior palatal seal should not be made B Figure 18-25 A, The indelible pencil line across the palate in Figure 18-23 has been transferred to the denture base and can be seen rather indistinctly (1), anterior to the solid line marking the end of the denture (2). B, The trial denture base is shortened posteriorly with an acrylic bur as far as this line. Continued 344 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures C Figure 18-25 cont’d C, The trial denture base shows the anticipated length of the completed denture. X denotes the location of the vibrating line that was transferred from the patient’s mouth. Figure 18-26 Posterior extent of the trial denture base traced on the cast. too wide. Placement of tissue should be such that when the dentures move in function, as they always do, the placed tissue will move with the dentures and not break the seal. A V-shaped groove 1- to 1.5-mm deep is carved into the cast at the location of the bead. A large, sharp scraper is used to carve it, passing through the hamular notches and across the palate of the Figure 18-27 The posterior line (A) indicates the end of the denture posteriorly across the palate. The anterior line (B) marks the location of the posterior palatal seal that will be carved into the cast and transferred as a bead onto the denture. cast (Figures 18-29 and 18-30). The groove will form a bead on the denture that provides the posterior palatal seal (Figure 18-31). The bead will be 1to 1.5-mm high, 1.5-mm wide at its base, and sharp at its apex. The depth of the groove in the cast will be determined by the thickness of the soft tissue Chapter 18 The Try-in Appointment 345 Figure 18-28 Sagittal diagrammatic view of denture in place in the mouth. A bead on the posterior extent (A) is 1 to 1.5-mm high and 1.5-mm broad at the base, and 2-mm anterior to the end of the denture (B). C, Movable soft palate. D, Muscles of the soft palate. Figure 18-29 A groove is carved into the cast (arrows) with a large, sharp scraper to form the posterior palatal seal. against which it is placed and will establish the height of the bead. The narrow and sharp bead will sink easily into the soft tissue to provide a seal against air being forced under the denture. If the bead has been made too high, the sharpness will make this apparent within 24 hours of the insertion of the dentures, and it can be easily relieved. The narrowness of the bead makes the seal with minimal downward pressure on the denture. Figure 18-30 The groove in the cast (arrows) forms a bead on the finished denture (Figure 18-28). Figure 18-31 The denture ends on the cast at A. The bead (B), located 2 mm in front of the vibrating line, is extended laterally through the center of the hamular notches. 346 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures SECTION III: CREATING FACIAL AND FUNCTIONAL HARMONY WITH ANTERIOR TEETH The anatomical structures that collectively form the face normally develop concurrently and are interdependent during function throughout life. Disruptive events in this homeostatic complex can range from relatively minor changes, such as a deflective occlusal contact to major alterations in bodily form, such as removal of the natural teeth, which drastically affects the form and function of the remaining living parts. In this context of homeostasis, creating facial and functional harmony with anterior teeth becomes a biological challenge of utmost significance. Not only must the teeth be of proper form, size, and color to harmonize with the face, but they also must become a functioning component in a living environment that depends on their proper position for its normal physiological activity. This proper position allows patients to preserve their facial identities as they existed when natural teeth were present. The ability of patients to maintain their normal facial expressions will likely be the most important psychological factor in acceptance of the dentures. ANATOMY OF NATURAL APPEARANCE AND FACIAL EXPRESSION The dentist who is treating a patient with complete dentures has as much to do with the beauty of the face as has any other medical specialist. The B A C Figure 18-32 A, The lower part of this face lacks proper contour because of inadequate support for the orbicularis oris muscle and muscles related to it. B, Facial contours have been properly restored. The improvement in appearance is directly related to the position of the artificial teeth and the form of the suporting base material of the complete dentures (C). Chapter 18 The Try-in Appointment appearance of the entire lower half of the face depends on the dentures. It is usually not difficult on casual meeting to detect the person who is wearing poorly constructed dentures (Figure 18-32). The characteristic thin, drooping upper lip that appears lengthened and has a reduced vermilion border is typical of malpositioned anterior teeth and probably a reduced vertical dimension of occlusion. Tense, wrinkled lips often reveal the patient’s efforts to hold the denture in place. The drooping corners of the mouth tell the story of the misshapen and misplaced dental arch form of the anterior teeth, the thin denture borders, and often the reduced occlusal vertical dimension. The appearance of premature aging may be caused not by age itself but by the lack of support for the lips and cheeks due to the loss or improper replacement of teeth. The apparent extra fullness of the lower lip may be the result of too broad a mandibular dental arch or the elimination or reduction of the mentolabial sulcus. This may indicate that the lower anterior teeth have been placed too far lingually or that the labial flange of the lower denture base is overextended or too thick. 347 Normal Facial Landmarks One must study normal facial landmarks before attempting to achieve the goal of a natural and pleasing facial expression with complete dentures. The facial landmarks of the lower third of the face have a direct relationship to the presence of the natural teeth (Figure 18-33). The contours of the lips depend on their intrinsic structure and the support for them provided by the teeth and the soft tissues or denture bases behind them. When the natural teeth are lost, these landmarks and surrounding facial tissues become distorted. To reestablish normal appearance and function, the dentist must replace the artificial teeth in the same position as the natural teeth that were lost. The lips vary in length, thickness, shape, and mobility in different patients. Such variance accounts for the degree of visibility of the upper and lower anterior teeth during speech and other facial expressions. When the mandible is in the resting position, the lips usually contact each other and turn slightly outward, exposing the vermilion border. The vertical groove in the middle of the Figure 18-33 Facial landmarks. A, Nares; B, rima oris; C, lower lip; D, mentum; E, mentolabial sulcus; F, angulus oris; G, upper lip; H, philtrum; I, nasolabial sulcus; J, ala nasi. 348 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures upper lip is called the philtrum, and the horizontal depression midway between the lower vermilion border and the bottom of the chin is called the mentolabial sulcus, or groove (see Figure 18-33). Incorrect positioning of the anterior teeth or supporting base material of complete dentures will alter the normal appearance of the vermilion border, the philtrum, and the mentolabial sulcus in edentulous patients. The nasolabial sulcus, or groove, is a depression in the skin on each side of the face, which runs angularly outward from the ala of the nose to approximately just outside the corners of the mouth (anguli oris) (see Figure 18-33). The zygomaticus muscle originates on the zygomatic bone and angles downward and forward to insert at the corner of the mouth into the orbicularis oris muscle. The action of the two zygomatici muscles in elevating the corners of the mouth for smiling produces the nasolabial sulcus (Figure 18-34). Many older patients want to have the nasolabial sulcus obliterated because it becomes a wrinkle as the skin loses resilience. Removal of the nasolabial fold has been attempted by thickening the denture base under the fold, but the extra bulk in this location causes a very unnatural appearance. The sulcus is normal and should not be eliminated. The proper treatment is to bring the entire upper dental arch forward to its original position when the natural teeth were present and to maintain the original arch form of the natural teeth and their supporting structures. Thus the prominence of the nasolabial sulcus will be restored to its original contour. In many patients, the corners of the lip line (rima oris) will be as high as the center portion, but the lip line will not necessarily be straight all the way across. The upper lip rests on the labial surfaces of the upper anterior teeth, and the lower lip on the labial surfaces of the lower anterior teeth and incisal edges of the upper teeth. For this reason, the edge of the lower lip should extend outward and upward from the mentolabial sulcus. A reproduction of the horizontal overlap of the natural anterior teeth in the denture is essential to maintaining proper contour of the lips (Figure 18-35). A study of the inclination of the osseous structure supporting the lower anterior teeth indicates that in most patients the clinical crowns of the lower teeth are labial to the bone that supports them. Likewise, a study of the inclination of osseous structure and the inclination of maxillary anterior teeth reveals that the upper lip functions on an incline (Figure 18-36). Neglect of these factors in the replacement of natural teeth often will cause the lip to be ill formed and, in time, lead to the formation of vertical lines in the lip. Maintaining Facial Support and Neuromuscular Balance The orbicularis oris muscle and its attaching muscles are important in denture construction inasmuch as the various contributing muscles have bony origins and their insertions are into the modioli and orbicularis oris muscle at the corners of the mouth (Figure 18-37). Thus the functioning length of all these muscles depends on the function of the orbicularis oris. The muscles that merge into the orbicularis oris are the zygomaticus, the quadratus labii superioris, the caninus (levator anguli oris), the mentalis, the quadratus labii inferioris, the triangularis (depressor anguli oris), the buccinator, and the risorius. The orbicularis oris is the muscle of the lips. It is sphincterlike, attaching to the maxillae along a median line under the nose by means of a band of fibrous connective tissue known as the maxillary labial frenum and to the mandible on a median line by means of the mandibular labial frenum. The buccinator is a broad band of muscle forming the entire wall of the cheek from the corner of the mouth and passing along the outer surface of the maxilla and mandible until it reaches the ramus, where it passes to the lingual surface to join the superior constrictor of the pharynx at the pterygomandibular raphe (see Figure 18-37, B). The two buccinators and the orbicularis form a functional unit that depends on the position of the dental arches and the labial contours of the mucosa or the denture base for effective action. With the loss of teeth, the function of the orbicularis, buccinator, and attaching muscles is impaired. Because these muscles of expression are no longer supported at their physiological length, contraction of the unsupported fibers does not produce normal facial expression because the lips and face no longer move naturally or maybe even at all. Contraction simply takes up the droop in the fibers. However, Chapter 18 The Try-in Appointment Surface Markings Muscles of Expression Pr OOc N DoN ah AN DN ih QLS ApN zh NS DSN Z Ph MxL Tu OOr Rz R BN OOr RO AO MnL QLI MS T P A Me B Figure 18-34 The polyfunctional pyramid. A, Underlying superficial musculature. Ah, Angular head; DN, dilator naris; DSN, depressor septi nasi; ih, infraorbital head; N, nasalis; OOC, orbicularis oculi; OOR, orbicularis oris; P, platysma; Pr, procerus; QLI, quadratus labii inferioris; QLS, quadratus labii superioris; R, risorius; T, triangularis; Z, zygomaticus; ZH, zygomatic head. B, Surface anatomy. AN, Ala nasi; AO, angulus oris; ApN, apex nasi; BN, basis nasi; DoN, Dorsum nasi; Me, mentum; MnL, mandibular lip; MS, mentolabial sulcus; MxL, maxillary lip; NS, nasolabial sulcus; Ph, philtrum; RO, rima oris; RZ, red zone or vermilion border; Tu, tubercle. (From Martone AL, Edwards : J Prosthet Dent 11:1009-1018, 1961.) 349 350 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures A B Figure 18-35 A, Reproduction of a patient’s former horizontal overlap with the correct facial contour. B, Horizontal overlap changed so the maxillary anterior teeth contact the mandibular teeth, with resultant damage to the upper lip. when these muscles are correctly supported by complete dentures, impulses coming to them from the central nervous system cause a shortening of the fibers that allows the face to move in a normal Figure 18-36 The incisal edges and labial surfaces of the lower anterior teeth are labial to the bone supporting them. The inclination of the labial plate of bone and the labial surfaces of the upper anterior teeth causes the upper lip to function on an incline. It is easy to observe the lack of support of the lip that will result when artificial anterior teeth are positioned over the crest of the residual ridge. Resorption of the alveolar process in the mandibular anterior region after removal of the anterior teeth will move the residual bony ridge lingually at first and then labially as resorption continues. manner. Thus the memory patterns of facial expression developed within the neuromuscular system when the patient had natural teeth are continued or reinforced so the patient’s original appearance is maintained (Figure 18-38). Three factors affect the face in repositioning the orbicularis oris with complete dentures: (1) the Chapter 18 The Try-in Appointment thickness of the labial flanges of both dentures, (2) the anteroposterior position of the anterior teeth, and (3) the amount of separation between the mandible and the maxillae (Figure 18-39). If the jaws are closed too far, and the dental arch is located too far posteriorly, the upward and backward positioning of the orbicularis oris complex will move the insertions of these muscles closer to their origins. This will cause the muscles to sag 351 when at rest and to be less effective when contracting. Such positions automatically drop the corners of the mouth, with a resultant senile edentulous expression, and may lead to atrophy of the muscle fibers. The correct width of the maxillary denture borders plays a great part in supporting these muscles and lengthening the distance that they must extend to reach their insertion. If the mouth has Zygomaticus major Quadratus labii Caninus Risorius Platysma Triangularis Quadratus labii inferioris A Figure 18-37 A, Muscles that maintain facial support. When artificial teeth and the denture base material restore the lips to their correct contour, the facial muscles will be at their physiological length, and contraction will create the normal facial expression of the patient. Continued B Figure 18-37 cont’d B, Functional unit of the buccinator. This muscle (1) and the orbicularis oris muscle (2) depend on the position of the upper denture for their proper action. (3) is the pterygomandibular raphe, and (4) is the superior constrictor of the pharynx. A B Figure 18-38 A, These lips are incorrectly contoured and are not moving naturally during speech. The lack of facial expression results from inadequate support of the lips by the anterior teeth, improper thickness of the labial flanges, and an inadequate vertical dimension of occlusion. B, The lips have been restored to correct contour with new dentures. Chapter 18 The Try-in Appointment 353 Figure 18-39 Notice the activity of the lips during speech when they are properly supported by new dentures. Compare this with the lack of activity in the same patient (Figure 18-38, A). been edentulous a long time, with considerable resorption of the residual ridges, the borders need to be thick to restore the position of the muscles (Figure 18-40). Repositioning anterior teeth that are protruding or slightly protruding to reduce their horizontal overlap and improve the appearance of the A patient is a serious mistake. The muscles, teeth, and all associated structures grew simultaneously; therefore the physiological length of the muscles was determined early. In fact, the muscles of the face, cheeks, tongue, and lips helped align the natural teeth in the dental arches. To move teeth back in dentures is to invite a loss of B Figure 18-40 A and B, The labial flange is thick at the borders. This thickness harmonizes with the available space in the patient’s mouth because of resorption of the upper residual ridge. Continued 354 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures The guides that are considered in developing facial and functional harmony include the following: 1. 2. 3. 4. 5. The preliminary selection of artificial teeth The horizontal orientation of anterior teeth The vertical orientation of anterior teeth. The inclination of anterior teeth Harmony in the general composition of anterior teeth 6. Refinement of individual tooth positions 7. The concept of harmony with sex, personality, and age of the patient 8. The correlation of esthetics and incisal guidance C Figure 18-40 cont’d C, The bulk is needed for correct support of the upper lip. facial expression that may be more damaging to the appearance of the patient than the slightly protruding teeth. Individual pronounced irregularities may be improved, as long as the position of the dental arch in its support of the orbicularis oris muscle and attaching muscles is not perceptibly altered. Thus normal facial expression and proper tone of the skin of the face depend on the position and function of the facial muscles. These muscles can function physiologically only when the dentist has positioned and shaped the dental arches correctly and has given the mandible a favorable vertical position. In addition, the dentures themselves must have a pleasing and natural appearance in the patient’s mouth, a condition that is dependent on arranging the artificial teeth in a plan that simulates nature. This, then, is the challenge of creating facial and functional harmony with anterior teeth. BASIC GUIDES TO DEVELOPING FACIAL AND FUNCTIONAL HARMONY After an acceptable vertical dimension of occlusion has been determined and the horizontal relation of the casts on the articulator has been verified for CR, the appearance of the patient is studied and modifications are made in the arrangement of the teeth to obtain a harmonious effect with the patient’s face. Although these factors are discussed individually, for simplicity they are interrelated in the actual clinical situation. Preliminary Selection of the Artificial Teeth The preliminary selection of teeth must be critically evaluated for size, form, and color as they have been arranged in the trial denture. The six upper anterior teeth, when properly supporting the upper lip, should be of sufficient overall width to extend in the dental arch to approximately the position of the corners of the mouth and still allow for individual irregularities of rotation, overlapping, and spacing. The canines should extend distally so they can be the turning point in the dental arch. The form of the teeth should be harmonious with the face but not necessarily identical with the outline form of the face. The color of the teeth should blend with the face so the teeth do not become the main focal point of the face. The anterior teeth are the principal ones to be considered in esthetics, although the posterior teeth, involving height of plane and width of arch, play their part also. Any records used in the initial selection of teeth should be consulted at this time to ensure that the desired result has been achieved (Plate 18-1). The dentist must make changes in the selection of teeth if such changes will improve the appearance of the dentures. Horizontal Orientation of the Anterior Teeth The position and expression of the lips and the lower part of the face are the best guides for deter- Chapter 18 The Try-in Appointment mining the proper anteroposterior orientation of anterior teeth. The other guides or measurements are secondary and must be ultimately related to the appearance of the patient. The greatest harm done in esthetics is setting the maxillary anterior teeth back to or under the ridge, regardless of the amount of resorption that has taken place. A study of the anterior alveolar process will disclose that its direction is upward and backward from the labial surface of the maxillary i