Robert B Kerstein

Bio: Robert B Kerstein is an academic researcher from Tufts University. The author has contributed to research in topics: Dental occlusion & Occlusal Adjustment. The author has an hindex of 21, co-authored 31 publications receiving 1283 citations.

Determining a relationship between applied occlusal load and articulating paper mark area.

Abstract: 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.

Electromyographic and computer analyses of patients suffering from chronic myofascial pain-dysfunction syndrome: before and after treatment with immediate complete anterior guidance development.

Abstract: Seven women patients at Tufts University School of Dental Medicine were evaluated for the subjective symptoms of a myofascial pain dysfunction. Each patient was evaluated by an occlusal analysis of the T-Scan computer to determine posterior disclusion time during excursive movements, and EMG analysis of the masseter and temporalis muscles. Each patient was then treated occlusally by developing immediate complete anterior guidance. This adjustment process involved the removal of all lateral and protrusive interferences prior to habitual closure adjustments. No attempt was made to retrude the mandible in centric relation, and splints were not used to deprogram the musculature before adjustment. In this study, protrusive movements and interferences were not examined, and there was no control group. Posttreatment EMG and T-Scan computer analyses revealed that by shortening disclusion times to less than 0.5 second in any lateral excursions, muscle function returned to normal in all seven patients in approximately 1 month's time. A direct correlation seemed to exist between contractile muscle activity and disclusion time. Lengthy disclusion time leads to excessive muscle activity that introduces spasm and fatigue of the masseter and temporal muscles. These results indicated that a partial explanation of the etiology of MPDS may be the time the molars and nonworking premolars remain in contact during excursive movements--a phenomenon termed "disclusion time."

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.

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

Abstract: 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 (r(2) = 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.

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.

Cement-retained versus screw-retained implant restorations: a critical review

Abstract: This article presents a comparison of screw-retained and cement-retained implant prostheses based on the literature. The advantages, disadvantages, and limitations of the 2 different types of restorations are discussed, because it is important to understand the influence of the attachment mechanism on many clinical aspects of implant dentistry. Several factors essential to the long-term success of any implant prosthesis were reviewed with regard to both methods of fixation. These factors include: (1) ease of fabrication and cost, (2) passivity of the framework, (3) retention, (4) occlusion, (5) esthetics, (6) delivery, and (7) retrievability. (More than 50 references).

A systematic review of the performance of ceramic and metal implant abutments supporting fixed implant reconstructions.

Abstract: OBJECTIVES: The objective of this systematic review was to assess the 5-year survival rates and incidences of complications associated with ceramic abutments and to compare them with those of metal abutments. METHODS: An electronic Medline search complemented by manual searching was conducted to identify randomized-controlled clinical trials, and prospective and retrospective studies providing information on ceramic and metal abutments with a mean follow-up time of at least 3 years. Patients had to have been examined clinically at the follow-up visit. Assessment of the identified studies and data abstraction was performed independently by three reviewers. Failure rates were analyzed using standard and random-effects Poisson regression models to obtain summary estimates of 5-year survival proportions. RESULTS: Twenty-nine clinical and 22 laboratory studies were selected from an initial yield of 7136 titles and data were extracted. The estimated 5-year survival rate of ceramic abutments was 99.1% [95% confidence interval (CI): 93.8-99.9%] and 97.4% (95% CI: 96-98.3%) for metal abutments. The estimated cumulative incidence of technical complications after 5 years was 6.9% (95% CI: 3.5-13.4%) for ceramic abutments and 15.9% (95% CI: 11.6-21.5%) for metal abutments. Abutment screw loosening was the most frequent technical problem, occurring at an estimated cumulative incidence after 5 years of 5.1% (95% CI: 3.3-7.7%). All-ceramic crowns supported by ceramic abutments exhibited similar annual fracture rates as metal-ceramic crowns supported by metal abutments. The cumulative incidence of biological complications after 5 years was estimated at 5.2% (95% CI: 0.4-52%) for ceramic and 7.7% (95% CI: 4.7-12.5%) for metal abutments. Esthetic complications tended to be more frequent at metal abutments. A meta-analysis of the laboratory data was impossible due to the non-standardized test methods of the studies included. CONCLUSION: The 5-year survival rates estimated from annual failure rates appeared to be similar for ceramic and metal abutments. The information included in this review did not provide evidence for differences of the technical and biological outcomes of ceramic and metal abutments. However, the information for ceramic abutments was limited in the number of studies and abutments analyzed as well as the accrued follow-up time. Standardized methods for the analysis of abutment strength are needed.

Zirconia as a dental implant abutment material: a systematic review.

Abstract: Purpose The focus of this systematic review was to assess the published data concerning zirconia dental implant abutments from various aspects. Materials and methods To identify suitable literature, an electronic search was performed using PubMed. The keywords "zirconia," "zirconium," "ceramic," "dental abutments," "dental implants," "plaque," and "bacteria" were included. Titles and abstracts were screened, and literature that fulfilled the inclusion criteria was selected for a full-text reading. Articles were divided into four groups: (1) studies on the mechanical properties of zirconia abutments, (2) studies on the peri-implant soft tissues around zirconia abutments, (3) studies on plaque accumulation on zirconia, and (4) clinical studies on the survival of zirconia abutments. Results The initial literature search resulted in 380 articles. For groups 1 to 4, 11, 4, 7, and 3 articles satisfied the inclusion and exclusion criteria, respectively. Only 1 randomized clinical study was identified. Review of the selected articles showed that zirconia abutments were reliable in the anterior region from both biologic and mechanical points of view. Furthermore, zirconia abutments may represent a material surface less attractive for early plaque retention compared to titanium. Three clinical follow-up studies indicated that zirconia abutments could function without fracture and peri-implant lesions. Conclusions Based on the reviewed literature, zirconia has the potential to be used as a dental abutment material, although some issues have to be studied further.

Topical review: sleep bruxism and the role of peripheral sensory influences.

Abstract: Sleep bruxism (SB) is an unusual orofacial movement described as a parafunction in dentistry and as a parasomnia in sleep medicine. Since several peripheral influences could be involved in sleep-wake regulation and the genesis of rhythmic jaw movements, the authors have reviewed the relevant literature to facilitate understanding of mechanisms possibly involved in SB genesis. Various animal and human studies indicate that during either wakefulness or anesthesia, orofacial sensory inputs (eg, from periodontium, mucosa, and muscle) could influence jaw muscle activity. However, the role of these sensory inputs in jaw motor activity during sleep is unclear. Interestingly, during sleep, the jaw is usually open due to motor suppression; tooth contact most likely occurs in association with sleep arousal. Recent physiologic evidence supports an association between sleep arousal and SB; a sequential change from autonomic (cardiac) and brain cortical activities precede SB-related jaw motor activity. This suggests that the central and/or autonomic nervous systems, rather than peripheral sensory factors, have a dominant role in SB genesis. However, some peripheral sensory factors may exert an influence on SB through their interaction with sleep-wake mechanisms. The intent of this review is to integrate various physiologic concepts in order to better understand the mechanisms underlying the genesis of SB.

Occlusal adjustment for treating and preventing temporomandibular joint disorders.

Abstract: Background There has been a long history of using occlusal adjustment in the management of temporomandibular disorders (TMD). It is not clear if occlusal adjustment is effective in treating TMD. Objectives To assess the effectiveness of occlusal adjustment for treating TMD in adults and preventing TMD. Search methods We searched the Cochrane Oral Health Group's Trials Register (April 2002); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2002, Issue 2); MEDLINE (1966 to 8th April 2002); EMBASE (1980 to 8th April 2002) and handsearched journals of particular importance to this review. Additional reports were identified from the reference lists of retrieved reports and from review articles of treating TMD. There were no language restrictions. Unpublished reports or abstracts were considered from the SIGLE database. Selection criteria All randomised or quasi-randomised controlled trials (RCTs) comparing occlusal adjustment to placebo, reassurance or no treatment in adults with TMD. The outcomes were global measures of symptoms, pain, headache and limitation of movement. Data collection and analysis Data were independently extracted, in duplicate, by two review authors (Holy Koh (HK) and Peter G Robinson (PR)). Authors were contacted for details of randomisation and withdrawals and a quality assessment was carried out. The Cochrane Collaboration's statistical guidelines were followed and risk ratios calculated using random-effects models where significant heterogeneity was detected (P < 0.1). Main results Over 660 trials were identified by the initial search. Six of these trials, which reported results from a total of 392 patients, were suitable for inclusion in the review. From the data provided in the published reports, symptom-based outcomes were extracted from trials on treatment. Data on incidence of symptoms were extracted from trials on prevention. Neither showed any difference between occlusal adjustment and control groups. Authors' conclusions There is an absence of evidence, from RCTs, that occlusal adjustment treats or prevents TMD. Occlusal adjustment cannot be recommended for the management or prevention of TMD. Future trials should use standardised diagnostic criteria and outcome measures when evaluating TMD.