Written by Kenley Hunt, DDS, and Mitchell Turk, DDS Wednesday, 20 June 2012 09:01
This is the last article in a 4-part series which discuss the Bioesthetic principles of restorative treatment, from preliminary diagnosis through case delivery. The case presented to illustrate the principles and procedures involves a patient with an uncomfortable bite, wear of the maxillary anterior dentition, and wear on the mandibular canines.
The first article of the series discussed the principles of Bioesthetic Dentistry and the preliminary diagnosis based on those principles. The preliminary occlusal diagnosis was made on models mounted in a centric related position of the condyles (not stabilized), evaluating the form and function in the patient’s gnathic system.
The second article discussed the importance of adhering to natural genetic form in restoring the chewing system, since Bioesthetic Dentistry accepts natural form as the basis for comprehensive diagnosis and rehabilitation.
The theme of the third article was a final diagnosis, using a maxillary anterior guided orthosis (MAGO) appliance. The procedure allows healing of the joint and muscles, thereby enabling the positioning of the condyles into a healthy, stable, and repeatable position from which to diagnose and treat the patient. The third article also discussed the procedures and considerations of coronaplasty involved on the final patient models mounted on the articulator in stable condylar position. These 3 articles may be accessed through the Dentistry Today Web site at the Web address dentistrytoday.com.
This last article will present the actual development of the treatment plan on the patient models and the techniques of transferring the subtractive and additive elements of the treatment plan to the patient, with consideration of the entire mastication/chewing system.
Performing the Adjustments on the Casts
Knowing how the teeth will be shaped, and where the subtractive coronaplasty stops and the additive coronaplasty begins, places the operator in control of the end result. As discussed in part 3,1 the test positions of positions one to 4 demonstrate the existing problems, necessitating that the practitioner evaluate how much of the posterior teeth must be reshaped before adding wax to the anterior tooth length to develop proprioceptive anterior guidance that protects the posterior teeth during function.
Once the operator has the end result in mind, the actual adjustments to the models can begin, starting with the centrically-related position (see part 3;1 position 4). The articulator is locked in the position, and the models are closed together until the first point of contact. The incisal pin is dropped and locked where it touches the incisal table. Dropping the incisal pin creates a stable position to accurately mark the models with the Mylar ribbon (Accufilm II [Parkell]). After an adjustment is made on the posterior teeth, the models are closed again, the pin is dropped, and another marking is made of the point of contact. This process is continued until the desired end point is reached.
When the posterior teeth contact and the anterior teeth do not couple, as in a centric relation (CR) occlusion, the clinician must understand what will occur to the position of the condyle in the fossa as the interferences to closure are eliminated from the teeth on the model. If the mandible fulcrums around the molars, the condyles will move upward and forward into the fossa, while the mandibular incisal contact remains near its original centric occlusion (CO) position. However, if the contact of the molars causes the condyle to slide forward along the path of the fossa eminence, then the condyle will return up the path of the eminence, causing the mandibular incisal edges to also go upward and backward. This situation may result in a mandibular incisal edge impingement on the tissue of the anterior palatal papilla.
Place a strip of black Mylar articulating ribbon in an articulating ribbon holder. Place the ribbon (one side at a time) between the posterior teeth, and then gently tap the stone model of the teeth together 2 to 3 times. The marks will usually show on the mesial inclines of the maxillary teeth and the distal inclines of the mandibular teeth; or, in the case of a buccal-lingual discrepancy, on the lingual inclines of the maxillary cusp triangular ridges and buccal inclines of the mandibular. Use a No. 699 high-speed bur to reduce the casts where the marks were produced. When removing the marks, think about recontouring the occlusal surface to a natural, unworn form. Push the point of the bur down into the fossae to deepen them concurrently with the removal of stone on the inclines of the teeth. After removing all the marks in all 4 quadrants by carving the stone, repeat the marking and carving procedure again, and again. Be aware of the remaining thickness of enamel on the patient’s teeth; reducing beyond this depth in stone would represent dentinal exposure in the mouth.
Adjusting the posterior teeth in this manner allows the clinician to “warp” the maxillary cusps distally and the mandibular cusps mesially. When the cusp tips contact marginal or transverse ridges, use the point of the bur to carve grooves. These procedures reduce the interfering cuspal inclines, but they may not allow complete closure of the teeth before markings begin to appear on distal inclines of maxillary teeth and mesial inclines of mandibular teeth. At this stage, one must begin deepening grooves and fossae as premature contacts are removed from the stone, creating developmental and supplementary grooves on cusp inclines and marginal ridges. Do not reduce cusps, except as in rule No. 3 in part 3.1 Before marking the cast again, slightly reduce all marks in all 4 quadrants. Proceeding in this manner will result in an even amount of tooth reduction in all 4 quadrants. Each time, close the models into contact and drop the incisal pin to the incisal table for stability.
As soon as all the posterior teeth are adjusted into even contact on both sides, and the condyles are in a centrically related position, one must determine how much more reshaping must take place to bring the anterior teeth into contact. If the space between the anterior teeth is between 0.5 mm and 1.0 mm (depending on the age of the patient and clinical judgment), the operator should add wax to the lingual side of the maxillary anterior teeth in order to create the CR contacts. The wax represents the form of the material that will eventually be placed intraorally as the final restoration for the patient.
|Figures 1 and 2. Coronaplasty completed on maxillary and mandibular hinge axis mounted models. There should be at least one small point of contact on each cusp tip where the convexity of the cusp tip touches the opposing convexity of the marginal ridge (Class I occlusion) or fosse (Class II occlusion).|
|Figures 3 and 4. Diagnostic wax-up showing anterior guidance. Note posterior clearance.|
If the space between the anterior teeth is 0.5 mm or less when the posteriors are in an even contact, the decision can be made to continue the CR adjustment to reduce the occlusal vertical dimension and close the space between the anterior teeth. Continue to remove all marks on all teeth in each quadrant by marking them and adjusting them again and again. Do not reduce cusps, except as in rule No. 3, presented in part 3.1 When the anterior teeth begin to mark the ribbon, the CR adjustment is complete.
If any anterior teeth cannot be brought into CR contact, or if the clinician elects to leave space between the anterior teeth to prevent over reduction of the posterior teeth, wax must be added (simulating a restorative material) to complete the contact. Total CR contacts will range from 8 to 10 per side, not including contacts on the anterior teeth. Try to create (as much as possible) centric contacts on convex surfaces of cusp tips, fossae, and marginal ridges, as long as the natural-like crown morphology is preserved (Figures 1 and 2).
After the CR adjustments are completed (adjustment position 4), the incisive/surtrusion movements are adjusted (adjustment position 5). First, the necessary lengths of the incisors must be determined. The amount of posterior tooth clearance, created by the incisive edge-to-edge position of the maxillary and mandibular incisors, is dependent on the lengths of these incisors. Second, if there is a lack of coupling of the anterior teeth, the operator must add wax to the incisal edges of the mandibular incisors and/or to the lingual surfaces of the maxillary incisors. After these determinations are made, release the articulator latch, place red Mylar ribbon between the anterior teeth, and move the articulator along the incisive/surtrusion movement. Adjust the maxillary lingual concavities with the discoid end of a wax carver for smooth, even contact of the incisal edges of the mandibular central incisors against the mesial marginal ridges of the maxillary central incisors in the incisive/surtrusion movement. Remember, when the incisal edges are positioned against each other, there should be an even contact of the maxillary central incisors against the incisal edges of the mandibular central incisors and the mesial incisal corners of the mandibular lateral incisors.
With the incisive/surtrusion adjustments completed, adjustments are made at the 6 and 7 positions; the right and left lateral border movements. Unlock the articulator and place the red marking ribbon between the posterior teeth on both sides. Move the articulator in border movements along the curved Bennett path of the articulator to mark any chewing or nonchewing (working and balancing) side interferences. If marks are created, a decision must be made whether to remove the interferences, or if wax can be added to the lingual surface of the contralateral canine to overcome the interference. For conservation of tooth structure, it is usually better to tighten the overlap of the canines rather than reduce the buccal and lingual cusps of the posterior tooth morphology. The distal surfaces of the maxillary teeth and the mesial surfaces of the mandibular teeth (distal of uppers, mesial of lowers [DUML]) are adjusted to remove marks that do not occur on marginal ridges or in fossae. To recreate the natural anatomy of the teeth, cut grooves in the triangular ridges for cusps in the opposing arch. While adjusting lateral movements, do not remove any black CR holding contacts.
Once the interferences in the lateral border movements are removed completely, all remaining interferences in the intermediate lateral movements are eliminated (adjustment points 8 and 9). These will usually show up on the slopes of the cusps.
It is important to realize that in a human being, the act of closure is a surtrusion and/or medial surtrusion guided movement, not a protrusive or lateral protrusive movement that we apply in the use of an articulator. However, in utilizing the articulator, if the coronaplasty has been completed properly, the following criteria will have been met:
1. Centric contacts of the anterior teeth and posterior teeth will hold 8-µm Mylar film.
2. When the casts are moved in the incisive/surtrusive direction, maintaining constant contact with the incisors, an immediate posterior release of the film will occur.
3. When the articulator is moved from CR in lateral border paths along the curved Bennett paths, while maintaining contact with the maxillary and mandibular canines, there will be an immediate release of the film on both—the chewing (working) and nonchewing (balancing)—sides.
Upon the completion of the model coronaplasty, the anterior wax-up is created to verify that the anterior-posterior relationship is functionally correct (Figures 3 and 4). At this time, the smile and facial esthetic considerations need to be taken into account. Do the anterior teeth fit into these frameworks? If not, then the morphologic considerations need to be worked out on the diagnostic models.
INTRAORAL SUBTRACTIVE CORONAPLASTY
To control postoperative pain and salivary flow, the patient was given orally administered hydrocodone 5 mg (Vicodin) and Saltropine 0.4 mg one hour prior to the dental appointment. The patient arrived with the MAGO appliance in the mouth. He was positioned in the chair at a 45°-angle. No anesthesia was used. The MAGO was removed, and the Dawson bilateral technique (Figure 5) was used to occlude the dentition, holding the condyles in the superior/anterior medial position. The assistant held an 8-µm black Mylar ribbon (Accufilm II) on both posterior sides, as the clinician controlled the closure to mark the first point of contact. In this case, the first point of contact occurred on the buccal incline of the mandibular left second molar. Using a diamond bur (No. 8274-016 [Brasseler USA]), the occlusal contact points on the maxillary and mandibular second molars were removed, except for the small area closest to the proposed CR position (Figure 6). A subsequent marking then displayed a contact on the mandibular right second molar and on the mandibular left second and first molar.
Continued recording and adjusting of CR contacts on the maxillary and mandibular posterior teeth created contacts of equal intensity on all posterior and anterior teeth. The contacts were confirmed by holding 8-µm of Mylar film (Figure 7). The natural anatomies of the teeth were recreated by deepening the central and marginal ridge grooves and developing “sluiceways.” Care was taken to avoid reduction of cusp tip CR contacts.
|Figure 5. The maxillary anterior guided orthotic is removed, and using the Dawson technique, both posterior quadrants are marked.||Figure 6. First point of contact on left side is the same as the premature contact removed from centric relation (CR) mounted models.|
|Figure 7. Equal intensity contacts are developed on all teeth.|
|Figures 8 and 9. Even contacts on all teeth.|
The refinement of the coronaplasty takes place with an additional procedure. The coronaplasty was “challenged” with the use of several 0.003 tin foil shims, placed on the lingual and incisal edges of the maxillary central incisors. At full closure, the shims separated the mandibular posterior teeth from the maxillary posterior teeth, recreating a Class III lever. The shims were removed, one at a time, each time marking the posterior area with Mylar ribbon (Accufilm II) until a contact point was observed. This procedure was demonstrated in part 31 challenging the MAGO. The premature occlusal contacts were adjusted away, using fine carbide burs and Cratex (Cratex Manufacturing) wheels until even contacts were developed on the posterior and anterior teeth. Upon completion, the teeth were polished (EP System [Brasseler USA]) (Figures 8 and 9).
After completion of the subtractive coronaplasty, a new set of maxillary and mandibular study models were taken and mounted on the articulator, using a hinge axis transfer of the maxillary model and an open-bite CR registration. These models were used to confirm the accuracy of the subtractive coronaplasty procedure and to wax up the form of the proposed veneers on the maxillary 8 anterior teeth and the mandibular canines. At this point, the existing vertical dimension of occlusion was determined to be appropriate and the incisive and lateral excursions were developed. This wax-up becomes the template for the final porcelain restorations.
Intraoral Additive Coronaplasty
After all CR contacts were developed, an anterior guiding system still needed to be designed to create optimum function. By restoring the natural lengths of the maxillary 8 anterior teeth and the 2 mandibular canines, the anterior guidance could be re-established, its longevity improved by the re-establishment of the proprioceptive relationship of the entire chewing system. A preparation guide was fabricated from the wax-up by the dental laboratory (Haupt Dental Laboratory in Brea, Calif) to facilitate the amount of tooth reduction during the preparation phase of the treatment (Figure 10). The maxillary veneers were prepared by removing the necessary thickness of enamel on the facial surfaces. The preparation guide assisted in determining the appropriate amount of tooth structure to be reduced.
|Figure 10. Preparation guide is prefabrication from the wax-up.||Figure 11. Tooth reduction of the maxillary teeth.|
|Figure 12. Preparation models mounted in CR with stable joint.|
The wax-up determined that only a minimal amount of tooth structure needed to be removed from the incisors. Most of the added wax represented additional porcelain to the labial surfaces and lengths of the maxillary anterior teeth to provide proper lip support (Figure 11). The preparation of the mandibular canines involved reducing only the functioning areas of the incisal one third of these canines. Final impressions were taken of the preparations and poured, using an accurate water/stone ratio to ensure accurate models. Again, a hinge axis transfer was performed to relate the maxillary model to the axis of rotation of the patient and a new open bite CR record was taken to mount the mandibular model. These models were used to fabricate the final restorations, create the anterior guidance, and to restore form and esthetics to the smile (Figure 12).
The placement of functional and esthetic provisional restorations was as critical as the final restorations, due to the care needed to protect the stable and healthy status of the temporomandibular joint. Provisionals were planned at the wax-up stage by creating a clear matrix (RSVP [Cosmedent]) that could later be filled with a bisacryl provisional resin (Protemp Plus [3M ESPE]) then placed over the preparations (Figure 13). After the provisional material set, the provisional was removed from the preparations. Carefully, the excess material was trimmed away, and the gingival interproximal embrasures were opened to prevent gingival impingement by the resin. The resulting provisional was contoured, polished, and then cemented in place (Figure 14).
|Figure 13. RSVP (Cosmedent) matrix of wax-up for transferring provisionals to the mouth.||Figure 14. Final anterior provisionals.|
|Figure 15. Provisionals adjusted into CR and anterior guidance developed.||Figure 16. Two maxillary centrals bonded and the same time as well checking Occlusion with Mylar ribbon.|
|Figure 17. The right maxillary lateral is placed and occlusion checked and then the left maxillary lateral is placed and occlusion checked.||Figure 18. Always check to make sure natural tooth stop is holding after adjusting occlusion (Figures 17).|
Final occlusal adjustments included making CR contacts coincidental with stable condylar position (CR = CO), then harmonizing functional mandibular movements by adjusting lingual surfaces of the maxillary anterior provisionals to provide incisive/surtrusion guidance and the mesiolingual of the maxillary canines to provide right and left medial/surtrusion guidance, creating continuous posterior cusp clearance all the way to closure, and final polish (Figure 15).
After cementation of the provisional crowns, the Bennett movement was checked by supporting the chewing side of the head with one hand, then applying inward and upward pressure at the angle of the mandible on the nonchewing side, as the patient went into a chewing side movement. Any marks on slopes of cusps were removed.
These provisionals were worn for 4 weeks to evaluate esthetics, comfort, and function. After that time, consent was signed for approval for the final restorations to be fabricated, duplicating the provisionals. As an option, the patient could have chosen to fully etch the teeth and use composite as the final restorative material. In cases with financial constraints, or a young age of a patient, this option would provide a viable choice.
To place the final restorations, the teeth were initially pumiced and etched with 30% phosphoric acid. The teeth were then rinsed and a desensitizer was applied (GLUMA [Heraeus Kulzer]). A resin-bonding agent (All Bond 2 [Bisco Dental Products]) was applied to the conditioned surfaces, then a translucent composite resin cement (Insure [Cosmedent]) was applied to the internal aspects of the restorations. Initially, the 2 maxillary central incisors were placed at the same time to avoid misalignment (Figure 16). The contacts of the mandibular incisal edges against the lingual surfaces of the maxillary incisors were checked, as well as the incisive/surtrusion guidance. Then, one by one, the other maxillary veneers including the premolars (Figure 17) were placed, checking the appropriate incisal and posterior contacts after placing each one (Figure 18). The 2 mandibular canine veneers were placed last. One at a time, the occlusal contacts were checked, and then the chewing and nonchewing excursions were evaluated.
The incisive/surtrusion guidance was developed by having the patient perform an incisive movement of the mandibular incisors on the lingual surfaces of the maxillary incisors against Mylar marking ribbon. These adjustments were made until a continuous smooth path was developed against the mesiolingual marginal ridges of the 2 maxillary incisors.
The canine guidance was developed with a smooth medial surtrusion pathway recorded on the lingual surfaces of the maxillary canine teeth, being careful to eliminate any CR contacts on the lingual of the maxillary canines that might cause the mandible to deviate right or left, causing the condyles to come out of CR (Figures 19 and 20).
|Figures 19 and 20. Completed case with posterior contacts and anterior guidance.|
|Figures 21 and 22. A Vinyl Occlusal Test Evaluation was taken to verify that there were no distal of uppers or mesial of lowers interferences. (21) Perforation on distal marginal ridge indicates premature contact. (22) Premature interferences have been removed from the first and second molars Note lack of perforations.|
Once all of the restorations had been placed and all CR contacts on the restorations were adjusted to contact with the same intensity as the posterior teeth, the coronaplasty was “challenged.” As previously discussed in part 3,1 the coronaplasty was challenged with the use of several 0.003 tin foil shims, placed on the maxillary central incisors. The shims were removed, one at a time, marking the posterior area with Mylar articulating ribbon until a contact point was observed. The premature occlusal contacts were adjusted away, using fine carbide burs and Cratex wheels until even CR contacts were developed on the posterior and anterior teeth.
At this point, a procedure termed Vinyl Occlusal Test Evaluation (VOTE) was performed. The VOTE is an assessment tool to locate elusive occlusal interferences and to calm down sensitive teeth and muscles. This technique can be accomplished only after the anterior guidance has been established. The rule for eliminating incisive interferences is the DUML (Figures 21 and 22). This coronaplasty technique was previously discussed in part 3.1
|Figures 23 and 24. Incisive/surtrusion position improvement with clearance of the second molars.|
|Figures 25 and 26. Right chewing test position creating adequate posterior cleance on the chewing and nonchewing sides.|
|Figures 27 and 28. Proper anterior guidance results in optimum esthetics and function.|
|Figures 29 and 30. The form of the teeth affects the smile and the face.|
When maxillary distal inclines are “too close” to the mesial mandibular inclines, avoidance patterns may occur while engaged in the dynamics of mastication. When those surfaces are slightly modified, creating a space of 0.3 mm to 0.4 mm, patients report a greater comfort and confidence in their occlusion. Performing the VOTE will help the stability of their vertical chewing pattern.
The maxillary anterior teeth were then checked for any fremitis by placing the tip of the operator’s finger on the facial surface and then guiding the patient into a tapping motion in the CR position. If done correctly, the sound of the teeth coming together should resemble a sharp ring, like the impact of glass. A dull sound should alarm the practitioner to check for defective contacts. After placement, all teeth were polished, using a Cosmedent Polishing Kit (Cosmedent).
The final case satisfies the 3 principles required for longevity, comfort, and beauty, ie, an occlusion that has natural genetic form with equal intensity contacts—A proprioceptive anterior guidance that:
- Relegates incisive/surtrusion guidance to the incisors,
- Provides/enures right and left medial surtrusion guidance to the canines, creating clearance of the posterior teeth to avoid noxious stimuli to the central nervous system, and,
- During the act of closure, smoothly guides the condyles back to an orthopedically stable, physiologic position (Figures 23 to 30).
After completion of the coronaplasty, a prophylaxis was performed with the application of topical fluoride. The patient was instructed to use a prescription fluoride dentifrice (Prevident 5000 [Colgate]) at least once daily. The necessity to follow up on the adjustments according to postoperative protocol was discussed, with a thorough review of what was accomplished. The patient was seen during hygiene appointments every 6 months.
Upon clinical examination at 5 years postoperatively, there were no signs of breakage or opposing wear and no recurrent symptoms of discomfort.
The noble goal of giving to our patients, either young or older, attractive and functional dentitions can be achieved by following the principles of Bioesthetic Dentistry, outlined in this series of articles. One must realize though, that while the techniques, procedures, and materials may vary, the 3 principles we have discussed cannot be compromised. The excellence of esthetics, of course, is of paramount importance.
The privilege, responsibility, and opportunity to apply these principles in conservative treatment of the young pristine dentitions to avoid functional wear and minimize occlusal overloads, lie with the restorative dentist. Adherence to these sound principles ensures the clinicians the ability to achieve the highest level of dental health for their patients. In this fashion, the clinicians not only enhance the appearance of the patient, but improve a person’s personality, self esteem, and systemic and dental health for a lifetime.
- Hunt K, Turk M. Bioesthetic dentistry, part 3. Dent Today. 2012;31(4):132-137.
Disclosure: Dr. Hunt reports no disclosures.
Disclosure: Dr. Turk reports no disclosures.
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