Effect of Long-term Immersion in Water and Artificial Saliva on the Flexural Strength of Two Heat Cure Denture Base Resins.

AIM: The aim of the present study was to compare and evaluate the flexural strength of heat-polymerized Lucitone 199 and SR Ivocap denture base resin materials which uses polymerization techniques of compression molding and injection molding respectively and effect of artificial saliva and distilled water on long-term. MATERIALS AND METHODS: Ninety specimens each from both the materials measuring 65 × 10 × 3 mm were prepared. After the polymerization, flexural strength was calculated after 24 hours (control group) without immersing in the liquid medium. The test group specimens immersed in saliva and distilled water at 37°C was calculated for the flexural strength at 2 weeks, 1 month, 2 months and 4 months. The flexural strength was measured using a universal testing machine. One-way analysis of variance (ANOVA) method was used to analyze the data, pairwise comparisons were done using Bonferroni post hoc test with a probability of less than 0.05 were considered to be statistically significant. RESULTS: The evaluation showed that, despite the duration of immersion and type of acrylic resin, high flexural strength was seen with specimens immersed in saliva than specimens under distilled water. The higher flexural strength was seen in SR Ivocap compared to that of Lucitone199 with the p value less than 0.05 which showed significant statistically. CONCLUSION: From the results, we can conclude that the higher flexural strength was shown in specimens of SR Ivocap fabricated through injection molding technique compared to specimens of Lucitone 199 fabricated through compression molding technique after immersion in artificial saliva and distilled water for long term. CLINICAL SIGNIFICANCE: The homogeneous copolymer beads, the difference in the water sorption and powder to liquid ratios also affect the mechanical properties of the resins other than the type of resin used in the dentures base.

The Effect of Different Abutment Designs and Materials on Stress Distribution in Implants and Peripheral Bones: A Three-Dimensional Finite Element Analysis.

AIMS: To evaluate and compare the distribution of stress patterns around a single implant-supported crown with various abutment designs using different abutment materials. SETTING AND DESIGN: This is an in vitro study to evaluate and compare stress distribution patterns. METHODS: The three-dimensional (3D) finite element models included four stock and four customized abutments made of Titanium, Zirconia, Fibre-Reinforced Composite, and Poly Ether-Ether Ketone (PEEK) attached to an end-osseous root form implant. The models were subjected to a 300 N vertical load at the central fossa and a 150 N oblique load at the centre of the lingual inclines of the buccal cusps of the mandibular molar crown designed on the model. STATISTICAL ANALYSIS USED:  The stress distribution within the implant and the surrounding supporting structures was evaluated using finite element analysis. RESULTS: In all the models, stresses on the implants were observed to be concentrated in the neck of the implants in the first few threads. Irrespective of the abutment design, PEEK abutment transferred greater stresses to implants and Zirconia abutment transferred lesser stresses to implants. In the implants, the customized abutment showed lesser stress values than the stock abutment during oblique loading. CONCLUSIONS: Stresses on implants and cortical bone can be reduced by using Zirconia as an abutment material compared to Titanium, Fibre-Reinforced Composite, and Poly Ether-Ether Ketone material. Customized abutments improve the load transfer between the prosthesis and the implant and the surrounding bone, lessen the micro-movement of the abutments, and distribute the stress more evenly across the implant's component parts.

Optimizing Root Canal Therapy: An In Vitro Comparative Study of Innovative File Systems on Mandibular Premolar Fracture Resistance.

INTRODUCTION AND AIM:  Root canal therapy is a vital procedure for saving teeth by removing infection and cleaning the complex root canal system. However, a delicate balance exists between thorough cleaning and preserving tooth strength. The study aims to evaluate the instrumentation effect of three innovative file systems, XP-endo® shaper, Reciproc®, and Self-adjusting file (SAF) on fracture resistance of mandibular premolars. MATERIALS AND METHODS: Thirty single-rooted mandibular premolars were collected; a standard access cavity was prepared and the working length was established 1 mm short of the apex. The teeth were randomly divided into three groups(n=10). In Group 1, the shaping of the specimens was achieved using XP-endo® shaper; in Group 2, it was instrumented using Reciproc® file; and in Group 3, it was instrumented using SAF. All samples were decoronated and the roots were mounted vertically in acrylic resin and subjected to fracture resistance under a universal testing machine. RESULTS: Intergroup analysis was done by one-way ANOVA followed by Bonferroni post hoc test, which did not report a statistically significant difference (p>0.05). CONCLUSION: All three tested file systems were similar in fracture resistance. XP-endo® shaper exhibited better fracture resistance on root canal instrumentation when compared to Reciproc® and SAF although they are not statistically significant.