Evaluation of Flexural Strength of Thermocycled Interim Resin Materials Used in Prosthetic Rehabilitation- An In-vitro Study.

INTRODUCTION: Provisional restoration is an analytical component of fixed prosthodontics serving as a ground plan for the design of fixed dental prosthesis. Flexural strength is critical in case of long standing fixed dental prosthesis, to appreciate success of full mouth rehabilitation cases and temporomandibular joint dysfunction therapies. AIM: The present study was to evaluate the flexural strength of different provisional restorative resins used for prosthetic rehabilitation. MATERIALS AND METHODS: Forty identical samples (n=10 for each material) measuring 25mm×2mm×2mm according to ADA/ANSI specification no. 27 were fabricated using autopolymerizing Poly Methyl Methacrylate (PMMA) (Group A); heat activated PMMA (Group B); autopolymerizing Bis-GMA composite resin (Group C) and light activated Urethane Dimethacrylate Resin (UDMA) (Group D). For 14 days all these samples were stored in artificial saliva. Ten samples from each material were subjected to thermal cycling for 2500 cycles (5°C to 55°C). Later, a standard three point bending test was conducted on all the specimens with a universal testing machine at a crosshead speed of 0.75mm/min. Statistical analysis used included Kruskal-Wallis and Mann-Whitney U test. RESULTS: The mean flexural strength of specimens confirmed higher flexural strength for Group C (102.98 Mpa) followed by Group B (91.86 Mpa), Group A (79.13 Mpa) and Group D (60.01 Mpa). There were significant differences between any two materials tested (p <0.05). Comparison between mean flexural strength values between four groups revealed significant difference between the interim materials (p <0.05). CONCLUSION: The greatest flexural strength was observed for Bis-GMA composite resins followed by heat cure methacrylate resins, autopolymerizing methacrylate resins and was least for light cure resins. While fabricating provisional restorations, these greater values should be considered for better outcome of the treatment.

Evaluation of the Luting Cement Space for Provisional Restoration by using Various Coats of Die Spacer Materials-An Invitro Study.

AIM: The present study was to evaluate the space provided for the temporary luting cement, after the application of various coats of die spacers, during the fabrication of provisional crowns and bridges. MATERIALS AND METHODS: A total of 50 specimens of dental stone with provisional crowns on all these samples were prepared and were divided into five groups based on the application of various coats of different die spacers. Later these specimens were sectioned buccolingually and were observed using a stereomicroscope under 100X magnification. The images thus obtained were evaluated and noted for the amount of space between the inner surface of the provisional crown and the specimens at five different locations using Image Pro 6.0 Express software and the values were subjected to one-way ANOVA test, and unpaired t-test. RESULTS: There was a significant increase of luting space thickness with various die spacer applications than the specimens of control group. CONCLUSION: Specimens of double coat applications of silver and gold die spacers showed higher luting cement space than the separating media application specimens.

The Comparison of Shear Bond Strength Between Fibre Reinforced Composite Posts with Three Different Composite Core Materials - An In vitro Study.

AIM: The aim of this study is to compare the shear bond strength between fiber reinforced composite post with three different composite core materials. MATERIALS AND METHODS: The materials used for the study were: 30 maxillary central incisors, pre fabricated fiber reinforced composite post (postec plus posts), Multi-core heavy body, Ti-core, Fluoro-core, Etchant gel, Silane coupling agent, Dentin bonding agent, Standardized gutta percha points, Rely-X dual cure composite resin. A total of 30 human maxillary central incisor were selected for this study. They were divided into three groups of 10 specimens each namely A, B and C. RESULTS: The results obtained were analyzed by using one way analysis (ANOVA) and Tukey Honestly Significant Difference and they showed highest mean shear bond strength for group C when compared with group A and group B. There is no significant difference in the shear bond strength values between group A and group B. CONCLUSION: The teeth restored with multicore HB showed highest shear bond strength. The teeth restored with Fluoro core showed lowest shear bond strength. No statistically significant difference exists between the shear bond strength values between Ti-core and Fluoro-core.

Ergonomics and musculoskeletal disorder: as an occupational hazard in dentistry.

OBJECTIVE: Musculoskeletal disorders (MSDs) are commonly experienced in dentistry. The objective of this study is to determine the prevalence of ergonomics and MSDs among dental professionals. MATERIALS AND METHODS: A cross-sectional survey was conducted among 170 dentists of different specialties. The questionnaire gathered information regarding demographic details, MSDs, work duration, working status, awareness of ergonomics, etc. Data was analyzed using SPSS version 15.0. Student's t-test and analysis of variance (ANOVA) test was used for comparison in mean scores. Stepwise multiple linear regression analysis was used to assess the independent variables that significantly influenced the variance in the dependent variable (pain). RESULTS: It was found that 73.9% of the participants reported musculoskeletal pain and most common painful sites were neck and back. More than half of the participants, i.e. 232 (59.3%) were aware of correct ergonomic posture regarding dental. Almost percentage of pain increased significantly with increase in age and working time. Among all specialties, prosthodontics were found to have more prevalence of MSDs. CLINICAL SIGNIFICANCE: The appearance of musculoskeletal symptoms among dental professionals was quite common. It suggested that ergonomics should be covered in the educational system to reduce risks to dental practitioners.