Robert B. Kerstein

Combining technologies: a computerized occlusal analysis system synchronized with a computerized electromyography system.

Abstract Current advances in computer technologies have afforded dentists precision ways to examine occlusal contacts and muscle function. Recently, two separate computer technologies have been synchronized together, so that an operator can record their separate diagnostic data simultaneously. The two systems are: the T Scan II Occlusal Analysis System and the Biopak Electromyography Recording System. The simultaneous recording and playback capacity of these two computer systems allows the operator to analyze and correlate specific occlusal moments to specific electromyographic changes that result from these occlusal moments. This synchronization provides unparalleled evidence of the effect occlusal contact arrangement has on muscle function. Therefore, the occlusal condition of an inserted dental prosthesis or the occlusal scheme of the natural teeth (before and after corrective occlusal adjustments) can be readily evaluated, documented, and quantified for both, quality of occlusal parameters and muscle activity and the responses to the quality of the occlusal condition. This article describes their synchronization and illustrates their use in performing precision occlusal adjustment procedures on two patients: one who demonstrates occlusal disharmony while exhibiting the signs and symptoms of chronic myofascial pain dysfunction syndrome, and the other who had extensive restorative work accomplished but exhibits occlusal discomfort post-operatively.

Determining a Relationship Between Applied Occlusal Load and Articulating Paper Mark Area

Articulating paper mark size has been widely accepted in the dental community to be descriptive of occlusal load. The objective of this study is to determine if any direct relationship exists between articulating paper mark area and applied occlusal load. A uniaxial testing machine repeatedly applied a compressive load, beginning at 25N and incrementally continuing up to 450N, to a pair of epoxy dental casts with articulating paper interposed. The resultant paper markings (n = 600) were photographed, and analyzed the mark area using a photographic image analysis and sketching program. A two-tailed Student’s t-test for unequal variances compared the measured size of the mark area between twelve different teeth (p < 0.05). Graphical interpretation of the data indicated that the mark area increased non-linearly with increasing load. When the data was grouped to compare consistency of the mark area between teeth, a high variability of mark area was observed between different teeth at the same applied load. The Student’s t-test found significant differences in the size of the mark area approximately 80% of the time. No direct relationship between paper mark area and applied load could be found, although the trend showed increasing mark area with elevating load. When selecting teeth to adjust, an operator should not assume the size of paper markings, accurately describing the markings’ occlusal contact force content.

A Force Reproduction Analysis of Two Recording Sensors of a Computerized Occlusal Analysis System

Abstract The purpose of this study was to measure the performance of a new design of occlusal sensor, the high definition (HD) sensor, and directly compare this sensor to the previous design. This new HD sensor design has increased active recording area by 33%, and decreased inactive recording area by 50% as compared to the previous design (G3). This was accomplished by determining the force reproduction variability for repeated occlusal closures on the same sensor for a sampling of sensors from both designs. Thirty (30) G3 and 30 HD sensors were consistently positioned and loaded 24 times between articulated epoxy casts by a Pneumatic Occlusal Force Simulator. Their force reproduction consistency was measured as an electronic voltage drop across six occlusal contacts that were consistently located on all sensors. The force variability of the two sensor designs was determined by comparing the consistency of the voltage drops across the six occlusal contacts. An analysis of variance was employed to determine the variability of force reproduction over multiple closures across six occlusal contact regions. For five of the six contacts, the G3 sensor mean variances, were significantly larger (p<0.05) than those of the HD sensor. The within sensor variability of the HD sensor was significantly less than that of the G3 sensor. Within the limitations of this study, the HD sensor exhibited less variable force reproduction than the G3 sensor for at least 20 in-laboratory loading cycles.

Relationship between articulation paper mark size and percentage of force measured with computerized occlusal analysis

PURPOSE Articulation paper mark size is widely accepted as an indicator of forceful tooth contacts. However, mark size is indicative of contact location and surface area only, and does not quantify occlusal force. The purpose of this study is to determine if a relationship exists between the size of paper marks and the percentage of force applied to the same tooth. MATERIALS AND METHODS Thirty dentate female subjects intercuspated into articulation paper strips to mark occlusal contacts on their maxillary posterior teeth, followed by taking photographs. Then each subject made a multi-bite digital occlusal force percentage recording. The surface area of the largest and darkest articulation paper mark (n = 240 marks) in each quadrant (n = 60 quadrants) was calculated in photographic pixels, and compared with the force percentage present on the same tooth. RESULTS Regression analysis shows a bi-variant fit of force % on tooth (P<.05). The correlation coefficient between the mark area and the percentage of force indicated a low positive correlation. The coefficient of determination showed a low causative relationship between mark area and force (r2 = 0.067). The largest paper mark in each quadrant was matched with the most forceful tooth in that same quadrant only 38.3% of time. Only 6 2/3% of mark surface area could be explained by applied occlusal force, while most of the mark area results from other factors unrelated to the applied occlusal force. CONCLUSION The findings of this study indicate that size of articulation paper mark is an unreliable indicator of applied occlusal force, to guide treatment occlusal adjustments.

The Effect of Disclusion Time Reduction on Maximal Clench Muscle Activity Levels

Abstract Simultaneous recording of excursive function and muscle activity on 62 MPDS patients demonstrated that reducing prolonged disclusion time (1.4 seconds per excursion) to short disclusion time (0.41 seconds per excursion) created a therapeutic effect such that within one month’s time following treatment, there was an observed increase in the maximal clenching capacity of the masseter and temporalis muscles. This clinical treatment effect appears to be the result of decreased ischemia in these same muscles resultant from minimizing the time posterior teeth compress their periodontal ligament mechanoreceptors as these teeth are engaged and disengaged during excursive function.

A Comparison of ICAGD (Immediate Complete Anterior Guidance Development) to Mock ICAGD for Symptom Reductions in Chronic Myofascial Pain Dysfunction Patients

The purpose of this study is to assess what impact shortening disclusion time to less than .5 seconds during right and left mandibular excursions has on myofascial pain(s) symptoms present in a dental student population. Twenty-five dental students, who exhibited symptomatology consistent with myofascial pains patient, were divided into a treatment, control, and an untreated group. They participated in an occlusal adjustment study which measured changes in disclusion time, as well as, myofascial pains muscular symptom remissions resultant from treatment. The treated group of ten subjects received ICAGD occlusal adjustments to shorten their disclusion time to less than .5 seconds per mandibular excursion. The goal of this therapy was to totally disclude the posterior teeth in a measurable time frame of .5 seconds or less. The control group of eight subjects received mock ICAGD with tooth polishing. The goal of this therapy was to simulate ICAGD adjustments for possible placebo effect on symptom remissions. The untreated group had their disclusion times measured but received no treatment to adjust, or to simulate adjustment to their occlusion. The goal of analyzing an untreated group was to attempt to show that mock treatment (performed on the control subjects), or no treatment (performed on the untreated subjects), resulted in no measurable change in the disclusion time in either of these two subject groups. Each subject was recalled for disclusion time measurement four to five times in a one-year period of observation, at which time, they were required to report their myofascial pains symptom status by answering an ordinal scale questionnaire. The results suggest that shortening disclusion time to less than .5 seconds per mandibular excursion can induce remissions of many muscular myofascial pains symptoms. Additionally, mock ICAGD occlusal adjustments did not appear to be a factor in the control subjects treatment response, as this group showed no statistically significant symptom remissions.

Disclusion time measurement studies: Stability of disclusion time—A 1-year follow-up

Six of seven women were recalled after 1 year to remeasure their right- and left-side working disclusion times. Before the occlusal adjustment technique known as immediate complete anterior guidance development (ICAGD), these patients presented lengthy mean disclusion times (> 1.0 second) and multiple chronic myofascial pain dysfunction syndrome (MPDS) symptoms. After ICAGD, these patients presented with short mean disclusion times (< 0.7 second) and no chronic MPDS symptoms were observed. At 1-year follow-up, there was no statistical difference between present measurements of disclusion time and those of 1 year earlier. In addition, all six posttreatment patients demonstrated no observed chronic MPDS symptoms. However, the symptom of nocturnal bruxism appeared to recur with some chronic regularity. These results suggest that, for this population, disclusion time was stable over the 1-year period of observation, and the short disclusion time appears to allow normal daily muscle function with significantly lessened appearance of chronic myofacial pain dysfunction symptoms.

Treatment of Myofascial Pain Dysfunction Syndrome with Occlusal Therapy to Reduce Lengthy Disclusion Time—A Recall Evaluation

A recall study of 102 myofascial pain dysfunction syndrome-temporomandibular disorder (MPDS-TMD) patients, treated with disclusion time reduction therapy from 1983 to 1991, was undertaken to determine the long-term results of this treatment on symptom reductions. The patients were asked to fill out a symptom questionnaire which used ordinal number scales to determine their disease status (frequency and intensity of muscular, joint and dysfunctional symptoms; frequency of medication and appliance use) before and after they were treated with disclusion time reduction. The statistical results indicate that discluson time reduction therapy is a highly effective treatment regimen for MPDS and that it has lasting effects on symptom reduction. In addition, the results of this recall study indicate that occlusion, and more specifically, lengthy pretreatment disclusion time, does play a primary role in the symptomatology, and most probably, in the etiology of MPDS and TMD.

Disclusion time measurement studies: A comparison of disclusion time between chronic myofascial pain dyfunction patients and nonpatients: A population analysis

From a pool of 89 patients, 49 patients were classified as having chronic myofascial pain dysfunction syndrome (MPDS), and 40 were classified as asymptomatic or non-MPDS patients designated as the control group for the study. To achieve balanced sample size in both groups, 40 patients were arbitrarily selected from the MPDS group. All patients from each of the two primary groups were then categorized and assigned to one or more subgroups according to the following criteria: (1) jaw classification, (2) open occlusion, (3) previous orthodontic therapy, or (4) no previous orthodontic therapy. A fifth subgroup composed of only MPDS patients and equally divided into those who had or had not experienced orthodontic therapy was established to determine whether mean disclusion time differences occur between orthodontic and nonorthodontic MPDS patients. All 80 patients were evaluated for disclusion time of their right and left mandibular excursions to determine statistical population comparisons. Statistical assessment of right and left disclusion times for women and men in the MPDS and non-MPDS groups was performed separately for each of the five subgroups. Analysis of the comparisons revealed that in all except two of the subgroups, mean disclusion time was significantly longer in the MPDS patient group than in the non-MPDS group. The two subgroups in which this was not apparent were those with open occlusion and orthodontic patients compared with nonorthodontic patients. These findings suggest that lengthy posterior disclusion time may be of diagnostic importance when the differing etiologic factors of chronic MPDS patients are evaluated.

Clinician accuracy when subjectively interpreting articulating paper markings

Abstract Aims: The aim of this study was to determine whether Subjective Interpretation of paper markings is a reliable method for identifying the relative occlusal force content of tooth contacts. Methodology: 295 clinicians selected the “Most Forceful” and “Least Forceful” occlusal contacts in six occlusal-view photographs of articulating paper marks that were later compared against computerized occlusal analysis relative occlusal force measurements of the same tooth contacts. Means and standard deviations were calculated by years in clinical practice and by number of occlusion courses taken. A Chi-square analysis was also performed. Results: The mean correct for 295 participant dentists was 1·53 (±1·234). There were no significant differences found for years in practice (P>0·16) or number of occlusion courses taken (P>0·75). The Chi-square analysis showed a sensitivity of 12·6%, a specificity of 12·4%, a positive predictive value of 12·58%, and a negative predictive value of 12·42%. Chance was calculated at 12·5% correct. Conclusions: Subjective Interpretation is an ineffective clinical method for determining the relative occlusal force content of tooth contacts. The reported low scores obtained from a large group of participant dentists suggest clinicians are unable to reliably differentiate high and low occlusal force from looking at articulating paper marks. This longstanding method of visually observing articulating paper marks for occlusal contact force content should be replaced with a measurement-based, objective method.