Effect of interocclusal appliance on masticatory performance of patients with bruxism

This study was designed to evaluate masticatory performance in bruxist patients. The experimental group was composed of 16 dentate volunteers presenting with bruxism and treated by interocclusal appliances and a control group, consisting of 16 dentate volunteers with no symptoms of bruxism. To evaluate masticatory performance, the volunteers chewed .03 grams of peanuts contained in polyvinyl wrapper for four and twelve masticatory cycles. The number of chewed particles was counted using an optical scanning method by Image-Pro Plus 1.4 software (Media Cybernetics, Inc., Silverspring, MD). The score was expressed as the mean of the number of chewed particles for each wrapper. Masticatory performance evaluations were carried out in a single period for the control group and for the experimental group, before interocclusal appliance insertion, and after seven, 15, 30, and 60 days. Comparison between groups, as well as between before and after interocclusal appliance insertion, showed no significant differences (P>.05), irrespective of the number of masticatory cycles.23426426

Impact strength and fracture morphology of denture acrylic resins

Statement of problem. Microwave-polymerization cycles may affect the impact strength and fracture morphology of denture base acrylic resin, and the microstructural effects of these processes have not been fully determined. Purpose. This study evaluated the impact strength and fracture morphology of denture base acrylic resins processed by microwave energy and hot water bath. Material and methods. Twenty specimens measuring 65 x 10 x 2.5 mm were fabricated from each of 4 acrylic resins processed according to the manufacturers' recommendations: Lucitone 550 (control; 9 hours at 74 degrees C); Onda Cryl (3 minutes at 360 W + 4 minutes pause + 3 minutes at 810 W); Acron MC (3 minutes at 500 W); and Vipi Wave (20 minutes at 180 W + 5 minutes at 540 W). The impact strength was evaluated in an impact testing machine using the Charpy method with a load (impact action) of 3.95 J. Mean values Of impact strength were compared by Tukey honestly significant difference test (alpha = .05). Fractures were classified as brittle or intermediate. Fractographic analysis was performed for all fragments by angle analyses of crack propagation, and the microstructural morphology characterization was accomplished with scanning electron microscopy (SEM). Data from the fractography analysis were submitted to the Kruskal-Wallis test for angles and radius (alpha = .05). Results. Significant differences (P < .001) were found in the impact strength for Vipi Wave and Acron MC acrylic resins, which demonstrated the lowest values (0.19 +/- 0.04 and 0.21 +/- 0.02, respectively). Most fractures were classified as brittle (Lucitone 55%; Onda Cryl 75%; Acron MC 90%; Vipi Wave 65%). Fractographic angle analysis of brittle fractures showed no differences among acrylic resins studied; however, angle values of intermediate fractures for Onda Cryl were lower in comparison with those from Lucitone 550 and Vipi Wave (P = .03). The SEM observations revealed that brittle fractures showed defined and organized crystallographic planes, whereas the intermediate fractures had a disorganized appearance. Conclusion. Within the limitations of this study, it was observed that impact strength in microwave-polymerized acrylic resins varies according to the period of irradiation. Acrylic resins exhibited a high number of brittle fractures, irrespective of the processing technique.96536737

Occlusal force, electromyographic activity of masticatory muscles and mandibular flexure of subjects with different facial types

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Objective: The aim of this study was to evaluate whether vertical facial patterns influence maximal occlusal force (MOF), masticatory muscle electromyographic (EMG) activity, and medial mandibular flexure (MMF). Material and Methods: Seventy-eight dentate subjects were divided into 3 groups by Ricketts's analysis: brachyfacial, nnesofacial and dolychofacial. Maximum occlusal force in the molar region was bilaterally measured with a force transducer. The electromyographic activities of the masseter and anterior temporal muscles were recorded during maximal voluntary clenching. Medial mandibular flexure was calculated by subtracting the intermolar distance of maximum opening or protrusion from the distance in the rest position. The data were analyzed using ANOVA followed by Tukey's HSD test. The significance level was set at 5%. Results: Data on maximum occlusal force showed that shorter faces had higher occlusal forces (P<0.0001). Brachyfacial subjects presented higher levels of masseter electromyographic activity and medial mandibular flexure, followed by the mesofacial and dolychofacial groups. Additionally, dolychofacial subjects showed significantly lower electronnyographic temporalis activities (P<0.05). Conclusion: Within the limitations of the study, it may be concluded that maximum occlusal force, masticatory muscle activity and medial mandibular flexure were influenced by the vertical facial pattern.194343349Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [476385/2004-0

Chewing side, bite force symmetry, and occlusal contact area of subjects with different facial vertical patterns

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Craniofacial dimensions influence oral functions; however, it is not known whether they are associated with function asymmetry. The objective of this study was to evaluate chewing side preference and lateral asymmetry of occlusal contact area and bite force of individuals with different craniofacial patterns. Seventy-eight dentate subjects were divided into 3 groups according to the VERT index as follows: (1) mesofacial, (2) brachyfacial and (3) dolichofacial. Chewing side preference was evaluated using jaw tracking equipment, occlusal contact area was measured by silicon registration of posterior teeth, and bite force was measured unilaterally on molar regions using 2.25 mm-thick sensors. Statistical analysis was performed using ANOVA on Ranks, Student's t-test, and Mann-Whitney tests at a 5% significance level. Mesofacial, brachyfacial, and dolichofacial subjects presented more occlusal contact area on the left side. Only dolichofacial subjects showed lateral asymmetry for bite force, presenting higher force on the left side. No statistically significant differences were found for chewing side preference among all groups. Within the limitations of this study, it can be concluded that craniofacial dimensions play a role in asymmetry of bite force. ClinicalTrials.gov ID: NCT01286363.255446452Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [476385/2004-0, 140204/2009-1

Micro-CT analysis of the rodent jaw bone micro-architecture: A systematic review

Introduction: Knowledge about macro- and micro-structural characteristics may improve in vivo estimation of the quality and quantity of regenerated bone tissue. For this reason, micro-CT imaging has been applied to evaluate alveolar bone remodelling, alterations of periodontal ligament thickness and cortical and trabecular bone changes in rodent jaw bones. In this paper, we provide a systematic review on the available micro-CT literature on jaw bone micro-architecture. Methodology: A detailed search through the PubMed database was performed. Articles published up to December 2013 and related to maxilla, mandible and condyle with quantitatively analysed bone micro-architectural parameters were considered eligible for inclusion. Two reviewers assessed the search results according to inclusion criteria designed to identify animal studies quantifying the bone micro-architecture of the jaw rodent bones in physiological or drug-induced disease status, or in response to interventions such as mechanical loading, hormonal treatment and other metabolic alterations. Finally, the reporting quality of the included publications was evaluated using the tailored ARRIVE guidelines outlined by Vignoletti and Abrahamsson (2012). Results: Database search, additional manual searching and assessment of the inclusion and exclusion criteria retrieved 127 potentially relevant articles. Eventually, 14 maxilla, 20 mandible and 12 condyle articles with focus on bone healing were retained, and were analysed together with 3 methodological papers. Each study was described systematically in terms of subject, experimental intervention, follow-up period, selected region of interest used in the micro-CT analysis, parameters quantified, micro-CT scanner device and software. The evidence level evaluated by the ARRIVE guidelines showed high mean scores (between 18 and 25; range: 0–25), indicating that most of the selected studies are well-reported. The major obstacles identified were related to sample size calculation, absence of adverse event descriptions, randomization or blinding procedures. Conclusions: The evaluated studies are highly heterogeneous in terms of research topic and the different regions of interest. These results illustrate the need for a standardized methodology in micro-CT analysis. While the analysed studies do well according to the ARRIVE guidelines, the micro-CT procedure is often insufficiently described. Therefore we recommend to extend the ARRIVE guidelines for micro-CT studies

Strength of Denture Base Resins Repaired with Auto- and Visible Light-Polymerized Materials

Purpose: Clinicians are still confused about the choice of repair method, which depends on factors such as the length of time required for processing, the mechanical strength of the repaired material, and the effect of stress concentration in the acrylic resins before the repair. The aim was to determine the impact and flexural strength characteristics, such as stress at yield, Young's modulus, and displacement at yield of denture base resins fractured and repaired by three methods using heat-, auto-, and visible light-polymerized acrylic resins. Material and Methods: For impact and flexural strength tests, 18 rectangular specimens measuring 50 x 6 x 4 mm(3) and 64 x 10 x 3.3 mm(3), respectively, were processed using Impact 2000, Lucitone 550, Impact 1500, and QC-20 acrylic resins. Fracture tests were performed according to ISO1567:1999. Afterward, all fractured specimens were stored in distilled water at 37 degrees C for 7 days, and then repaired with (1) the same acrylic resin used for specimen fabrication (n = 6), (2) an autopolymerized acrylic resin (TruRepair, n = 6), and (3) a visible light acrylic resin (Versyo. com, n = 6). The repaired specimens were again submitted to the same fracture tests, and the failures were classified as adhesive or cohesive. Data from all mechanical tests after repair by the different methods were submitted to two-way ANOVA, and mean values were compared by the Tukey test. Results: All acrylic resins showed adhesive fractures after impact and flexural strength tests. Differences (p < 0.05) were found among repair methods for all acrylic resins studied, with the exception of displacement at yield, which showed similar values for repairs with auto-and visible light-polymerized acrylic resins. The highest values for impact strength, stress, and displacement at yield were obtained when the repair was made with the same resin the specimen was made of. Conclusion: Denture base acrylic resins repaired with the same resin they were made of showed greater fracture strength.18649650