Written by John Cranham, DDS Wednesday, 30 April 2003 19:00
In parts 1 and 2 of this series, we looked at the diagnostic and treatment phases of optimum dentistry. The first goal is to identify any factor that can contribute to the breakdown of the dentition, combined with all elective aesthetic objectives. Optimum dentistry is the integration of state-of-the-art aesthetic dentistry with traditional comprehensive care.1
The treatment phase is driven by the objectives uncovered in the diagnostic phase. Once all pathology and aesthetic objectives are visualized, a wax-up is completed that will be used to fabricate temporaries. Phase 1 treatment will involve the elimination of infection, caries, and periodontal disease. Phase 2 (if it is a restorative case) will involve the preparation of the teeth and the placement of provisional restorations. The provisionals allow the restorative team to test the aesthetic and functional parameters to see if they meet the satisfaction of both the doctor and the patient. Once this has been accomplished, impressions of the properly contoured temporaries can be mounted interchangeably with the master casts to ensure a properly contoured final restoration. This time-tested approach is both a predictable and efficient way to practice restorative dentistry.2
It is interesting that a tremendous emphasis has been placed on developing technology for the diagnosis and treatment phases of treatment. Imaging methods now exist that allow us to see anywhere inside the body. From an interproximal lesion seen on a bitewing x-ray to an anteriorly displaced disc seen on an MRI, almost anything can be imaged. Additionally, the restorative team has a variety of ways to transfer the gnathological movements of the patient. Depending on the level of communication, a dentist can choose a simple face-bow transfer to a fixed path articulator or a hinge axis recording, and panographic tracing that can be utilized to transfer to a fully adjustable instrument. The dental team has tremendous choice, as it should, in these phases of treatment.
With all these technological advances, instruments to aid in case finishing have not been as prevalent. This is interesting when we consider that the success of the case hinges on how well it is adjusted and fits within the physiologic parameters of the patient. This article looks at some state-of-the-art instrumentation that will open a previously closed physiologic window and provide better data when finishing restorative procedures.
|Figure 1. Preoperative retracted view.|
A 40-year-old male presented to the office with the desire to make an aesthetic change (Figure 1). He had seen a dentist regularly, and was aware that his teeth were getting progressively shorter. He admitted to clenching and grinding his teeth for most of his adult life. He had heard of porcelain veneers and was seeking our help to give him a larger, fuller smile and close all spaces. It was also important to him that whatever he did, it would last him a long time.
Records were taken at this appointment to completely evaluate the patient. A panorex film as well as a full-mouth series of x-rays were taken utilizing the DenOptix Digital Imaging System (DENTSPLY Gendex). Twelve digital photographs were taken with the Fuji S1 Pro (seen in part 1 of this article), 4 of which were printed and shared with the patient. A full periodontal examination was performed as well as a tooth-by-tooth clinical evaluation.
The TMJ was evaluated with joint vibration analysis (JVA) (BioPak-BioResearch), range of motion (ROM), load testing, and Doppler auscultation. The muscles of mastication were examined using muscle palpation as well as EMG functional muscle testing during clenching, protrusion, and right and left lateral mandibular movements. The occlusion was evaluated by checking each tooth for mobility, migration, and signs of wear. Alginate impressions were made of the teeth, and a Delar wax centric jaw relation record was made using bimanual manipulation.3 A face-bow transfer was made so that the casts could be mounted on a SAM III articulator (Great Lakes Prosthodontics).
The clinical findings revealed a periodontally healthy patient. There was no primary caries, but secondary caries was found around some of the larger amalgam restorations in the posterior sextants. The photographs helped the patient visualize the extent of the damage caused by his bruxing problem. A minimum of 3 mm of tooth structure had been lost on the maxillary and mandibular incisors because of the wear process. The models were also used to verify that he had heavy working and balancing interferences, and it was explained how these can contribute to increased muscle activity, further increasing the damage.4,5
JVA, ROM, load testing, and Doppler auscultation indicated a very healthy TMJ. No signs of tension, tenderness, or any kind of noise were heard in any excursive movement or during load testing. The panorex also indicated normal condylar size and shape.
|Figure 2a. EMG recording of a right working movement. The patient is instructed to clench for 4 seconds, then slide into a right working movement. Note the elevated muscle activity during the excursion.||Figure 2b. EMG recording of the protrusive movement. The patient is instructed to clench for 4 seconds, then slide forward. Note the elevated muscle activity during the excursion.|
|Figure 2c. EMG recording of a left working movement. The patient is instructed to clench for 4 seconds, then slide into a left working movement. Note the elevated muscle activity during the excursion.|
The muscles of mastication were slightly sore to the touch, particularly in the temporal area. Electromyography (EMG) (BioPak-BioResearch) testing showed hyperactivity in protrusive, right, and excursive movements (Figures 2a, 2b, and 2c). During the functional EMG analysis, the patient was asked to squeeze his teeth together for 2 to 4 seconds and then move into the prescribed movement (either protrusive, right, or left lateral movements). A properly adjusted occlusion should show immediate shutdown of the muscles. Note how the muscles stay hyperactive for several seconds during the excursive movement.4,5
The clinical photographs, combined with several before-and-after photos, were utilized to find the look the patient wanted. It was clear that he desired longer teeth that were in the bleaching range of colors. The patient, with the guidance of the clinical team, chose an 040 shade on the chromoscopic shade guide.
The case was worked up and presented to the patient. Because of the occlusal problems and extensive wear, and because of the patient’s desire for optimum aesthetics, Eris (Ivoclar Vivadent) was the material chosen to restore the patient.6 Teeth Nos. 5 through 12 and Nos. 21 through 28 would require full-coverage crowns, while teeth Nos. 2 through 4 and 13 through 15 would be restored with onlay-veneer restorations. The maxillary posterior teeth were prepared to eliminate the secondary caries and also open the vertical dimension of occlusion 2 mm. This open vertical allowed the restorative team to lengthen the maxillary teeth without deepening the overbite of the patient, which can be detrimental to a bruxer.4 This plan was presented to the patient, helping him understand that this would provide the aesthetic result he was looking for as well as correct and control the occlusal problems that had broken down his own dentition. The patient understood and scheduled for treatment.
The patient was brought in for 2 successive morning appointments. The first day, the upper arch was prepared, tissues were retracted, a final impression was made with Take One (Kerr Corp), and a processed acrylic temporary was fabricated using Alike (GC America). The temporary was cemented with Tempbond (Kerr Corp).
The following morning, the mandibular teeth (Nos. 21 through 28) were prepared for Eris crowns, and the posterior amalgams were removed and replaced using Optibond Solo Plus (self-etching) (Kerr Corp) and Point 4 composite resin (Kerr Corp). The tissues were retracted, a final impression was made with Take One, and an Alike processed acrylic temporary was fabricated and cemented into place with Tempbond.
|Figure 3. Properly adjusted provisional restorations. Equal intensity contacts around the arch, with immediate posterior disclusion.|
The temporaries were adjusted to satisfy the patient’s aesthetic expectations and to fulfill the requirements of an ideal occlusal scheme. The provisionals provided equal intensity contacts in centric relation with an anterior guidance in harmony with the envelope of function (Figure 3). A face-bow transfer was made, and impressions of the provisional restorations were taken as well as a series of jaw relation records so that the provisional models could be mounted interchangeably with master die models. The casts, with all photos of the preoperative state, preparations, and temporaries, were sent to the laboratory with a detailed laboratory prescription.
|Figure 4. Post-op view of smile. Note size and shape of anterior teeth exhibiting correct width-to-length ratio and golden proportion.||Figure 5. Post-op retracted view. Eris crowns 5 through 12 and 21 through 28, with Eris Onlay veneers on 2 through 4 and 12 through 15.|
Three weeks later, the patient returned to the office for delivery. The provisional restorations were removed and tried in with Nexus II clear try-in paste (Kerr Corp). The patient approved the aesthetics, and permission was given for delivery. The restorations were bonded into place in 3 phases: teeth Nos. 5 through 12 were bonded in one batch; teeth Nos. 21 through 28 in another batch; and teeth Nos. 2 through 4 and 13 through 15 in the last batch. The teeth were etched with phosphoric acid for 10 to 15 seconds, rinsed, and left moist. Optibond Solo Plus (Kerr Corp) was painted on the teeth in multiple coats and thinned with a gentle stream of dry air. The Nexus II dual-cure cement was mixed, placed in a Centrix syringe, and injected into the previously silaned Eris restorations. Upon placement, the restorations were spot-cured in place using a 2-mm tip on a Demetron LED light (Kerr Corp). The cement was cleaned up, and each restoration was cured for 40 seconds from the facial, lingual, and incisal directions (Figures 4 and 5).
|Figure 6. “Finished” restorations using articulating paper and patient input, appearing to provide equal intensity contact.||Figure 7. “Finished” restorations using articulating paper and patient input, appearing to provide immediate posterior disclusion.|
Ultrathin red paper (Accufilm 1-Parkell) and blue paper (Accufilm 2-Parkell) were utilized to adjust the teeth to simultaneous contact in centric relation and to eliminate all posterior interferences in lateral movements (Figures 6 and 7). The margins were finished and polished with ET Brasseler finishing carbides, and the interproximals were finished with Brasseler diamond finishing strips.
Opening the Physiologic Window
While a great deal of time and effort goes into finishing any restorative case, the traditional approach has always relied on the marks the articulating paper left on the teeth and feedback from the patient. While both of these methods remain an important part of the finishing process, technological advances now allow us to take the final occlusal adjustments to another level.
Equal Intensity Contacts
|Figure 8. T-Scan II 2-D view of the “finished occlusion” in maximum intercuspation. Contact is primarily on the anterior teeth with the center of force too far forward. More work needs to be done.||Figure 9. T-Scan II 3-D view of the “finished occlusion” in maximum intercuspation. The bar graphs help illustrate the most intense markings. Tooth 15 as well as the anterior region are striking too hard.|
|Figures 10a and 10b. Illustrating the occlusion with just 10 minutes more adjusting. Note a more balanced, harmonious bite in centric occlusion.|
The T-Scan II (Tekscan) is a U-shaped device with an ultrathin sensor designed to measure tooth contact.7,8 It is connected to a personal computer and includes sophisticated software that allows occlusal analysis from a variety of perspectives. Figures 8 and 9 show 2-dimensional and 3-dimensional graphs illustrating the force concentration zones. The red and yellow-green colors show the location and intensity of the actual tooth contacts (red being the most intense). Note on the 3-dimensional depiction, the red elicits the tallest bar. The blue and blue-green colors illustrate compression of the sensor and are not significant. The graphs seen in Figures 8 and 9 were taken immediately after we had gone as far as we possibly could with articulating paper. Note that while the articulating paper marks seem adequate, most of the force is in the anterior part of the mouth, far from a balanced bite. Additionally, the T-Scan II will measure the degree in which the bite is balanced anterior-posteriorly and left to right. This can be seen by looking at the position of the red- and white-checkered square that moves over the 2-dimensional graph. The goal is to center it in the white oval in the center of the arch. Note its anterior displacement. It was clear we had more work to do. Figures 10a and 10b illustrate an additional 10 minutes of adjustment, resulting in more harmonious, equal intensity contacts.
|Figure 11a. T-Scan II: Force versus time graph of the finished left lateral movement. The gray line is total force that stays high and drops sharply at the A line (where disclusion starts) and drops to nearly zero at the B line (where disclusion ends). Total time for disclusion is less then a half second, which is ideal. The red line is the force on the right side of the mouth; the green line is the force on the left side of the mouth. They are balanced until disclusion begins. The red line drops at the A line (where disclusion begins) as the green line increases. This graph is indicative of a good lateral movement.||Figures 11b, 11c, and 11d This illustrates a 3-D graphical depiction of tooth contact at the beginning (a), middle (b), and end (c) of a left lateral movement. Again, indicating a harmonious anterior guidance.|
Functional movements can be obtained to measure force concentrations over time.9 This is extremely helpful in testing to see if the goal of providing posterior disclusion has been accomplished. Kerstein has shown that immediate posterior disclusion is in fact not possible,10 and the goal is to get the posterior teeth to disclude in less than a half second. Figure 11a is a graph that depicts force over time in a left lateral movement. The gray line depicts the total force, the red line is the percentage of force on the right side of the mouth, and the green line is the percentage of force on the left side of the mouth. This graph shows our finished equilibration. The patient clenches from 1.2 to 2.5 seconds. Notice the green and red lines are together, showing a balanced bite. Lines A and B illustrate the time it takes for the posterior teeth to disclude; less than a half second, which is ideal. Notice how the gray line (total force) drops from 100% to 0% during this time. Figures 11b, 11c, and 11d are snapshots at the beginning, middle, and end of the 0.4-second sequence in 3-dimension, showing a properly adjusted anterior guidance.
Documented Muscle Shutdown
|Figure 12a. Post-op EMG recording. Patient was instructed to clench for 4 seconds, then slide into a right working movement. Note the rapid decrease of electrical activity of the masseter and temporalis muscles.||Figure 12b. Post-op EMG recording. Patient was instructed to clench for 4 seconds, then slide into protrusion. Note the rapid muscular shut down.|
|Figure 12c. Post-op EMG recording. Patient was instructed to clench for 4 seconds, then slide into a left lateral movement, once again documenting muscular shut down.|
A final EMG is obtained by measuring the muscle activity in protrusion and right and left excursive movements. Figures 12a, 12b, and 12c illustrate proper shutdown of the muscles during
a right lateral, protrusive, and left lateral movement, respectively. The patient is instructed to clench from 2 to 4 seconds and then move in the prescribed fashion. Note the almost immediate shutdown of the muscles of mastication at 4 seconds, when the excursive movement is initiated. This exhibits a gnathostomatic system that is in harmony.11 This is an extremely important physiologic measurement. It gives the dentist and the patient tremendous confidence that not only the aesthetic goals have been reached, but the functional goals as well.
THE FUTURE IS NOW
The addition of personal computers to the operatory has produced a myriad of technologies allowing us to take better care of our patients. While many of these instruments have been developed for the diagnostic and treatment phases of treatment, this article has reviewed certain instruments that will provide important information when finishing a restorative case.
Dr. Cranham would like to thank Rich Shafer from Bayview Dental Lab in Norfolk, Va, for the fabrication of the beautiful restorations in this case.
1. Cranham J. Optimum dental care, part one. Dent Today. 2003;22(3):56-61.
2. Cranham J. Optimum dental care, part two. Dent Today. 2003;22(4):76-82.
3. Dawson PE. Evaluation, Diagnosis, and Treatment of Occlusal Problems. 2nd ed. St Louis, Mo: Mosby; 1989:41-51.
4. Williamson EH, Lundquist DO. Anterior guidance: its effect on electromyographic activity of the temporal and masseter muscles. J Prosthet Dent. 1983;49:816-823.
5. Manns A, Rocabado M, Cadenasso P, et al. The immediate effect of the variation of anterioposterior laterotrusive contacts on the elevator EMG activity. Cranio. 1993;11:184-191.
6. Seghi RR, Sorensen JA. Relative flexural strength of six new ceramic materials. Int J Prosthodont. 1995;8:239-246.
7. Reza Moini M, Neff PA. Reproducibility of occlusal contacts utilizing a computerized instrument. Quintessence Int. 1991;22:357-360.
8. Harvey WL, Hatch RA, Osborne JW. Computerized occlusal analysis: an evaluation of the sensors. J Prosthet Dent. 1991;65:89-92.
9. Kerstein RB. Disclusion time measurement studies: stability of disclusion time- a 1-year follow-up. J Prosthet Dent. 1994;72:164-168.
10. Kerstein RB. Disclusion time measurement studies: a comparison of disclusion time between chronic myofascial pain dysfunction patients and nonpatients: a population analysis. J Prosthet Dent. 1994;72:473-480.
11. Kerstein RB, Wright NR. Electromyographic and computer analyses of patients suffering from chronic myofascial pain-dysfunction syndrome: before and after treatment with immediate complete anterior guidance development. J Prosthet Dent. 1991;66:677-686.
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