A Digital Chairside Technique for an Accurate Evaluation of the Taper of the Prepared Teeth for the Restoration of Crowns and Fixed Partial Dentures.

AIM: The aim of the article was to provide a digital chairside method for the objective evaluation of the taper of prepared abutment teeth retaining a fixed partial denture (FPD). BACKGROUND: According to research, the taper of the abutment teeth supporting an FPD has a direct effect on both retention and stress transmission to the abutment teeth. However, no approaches have been documented in the literature that objectively quantify the taper of the prepared teeth chairside, in a simple and cost-effective manner. TECHNIQUE: The proposed technique utilized an intraoral camera with an on-the-go (OTG) connection, and a silicone dental bite block. The images of the prepared teeth were captured using this camera from the facial aspect. An indigenous program was developed using the MATLAB (Matrix Laboratory 2013) software for the analysis of the images and the taper of each abutment tooth was calculated in degrees using the software. CONCLUSION: The novel, chairside, digital technique utilizes an intraoral camera and a computer-generated software package to quantify and evaluate the taper of abutment teeth efficiently. This, in turn, can help minimize the errors in the treatment of FPD and improve the retention of the prosthesis. CLINICAL SIGNIFICANCE: The current technique enables the clinician to avoid over-preparation of the abutment teeth by assessing its taper chairside. This digital technique can be a beneficial alternative to the existing procedures for an accurate assessment of taper, especially for the inexperienced operator. Hence, the quality of retention, and thereby the long-term success of the crowns and FPDs, can be enhanced. This article was presented as a postgraduate paper titled "Scan and Plan" on March 6, 2020, at 22nd IPS (Indian Prosthodontic Society) PG Convention, Kochi, India.

A Novel Functional Swallow Method to Establish the Posterior Palatal Seal during the Maxillary Edentulous Final Impression: A Case Report.

AIM AND OBJECTIVE: To propose an alternate, r eliable, and easy-to-use functional swallow method for establishing the posterior palatal seal. BACKGROUND: Accurate r egistration of the posterior palatal seal is crucial to the success of the maxillary complete denture. The conventionally used functional "Ah" technique may not be r eliable at times to record the posterior palatal seal, hence compromising the retention of the maxillary complete denture. Case description and technique: A 70-year-old female patient requiring complete dentures presented with an unusually tense soft palate during the phase of posterior palatal seal development. The soft palate did not relax and remained in a superior position when the "Ah" functional method was used to record the seal. The posterior palatal seal area could not be compressed sufficiently during border molding, preventing the formation of an adequate seal. Hence, a new functional technique was devised to relax and displace the soft palate for developing an effective seal. This case report describes a novel and reliable method of displacing the posterior palatal seal area with a low-fusing compound by utilizing the patient's functional swallow position. CONCLUSION: The functional swallow method can be used effectively as an alternative and reliable method to obtain a consistent posterior palatal seal. CLINICAL SIGNIFICANCE: The functional swallow method of developing the posterior palatal seal is simple, less demanding on the clinician, and can save chairside time. It also helps in an easy transfer of the demarcated posterior palatal seal area to the custom tray. The method lets the dentist be in charge of developing the seal rather than relying on the arbitrary cast scrapping by the technician. Also, the seal can be achieved by employing commonly used materials.

Comparison of Shear Bond Strengths of Conventional Resin Cement and Self-adhesive Resin Cement bonded to Lithium Disilicate: An in vitro Study.

AIM: The aim of this study is to compare the shear bond strengths of conventional resin cement and self-adhesive resin cement bonded to lithium disilicate. MATERIALS AND METHODS: A total of 40 extracted human molar teeth were mounted in self-cure acrylic resin. Teeth were prepared to obtain flat occlusal surface. About 40 lithium disilicate specimens of dimension-10 mm in diameter and thickness of 2 mm-were fabricated using lost wax technique. The samples were divided into four groups: Groups I, II, III, and IV (n = 10). The specimens were surface treated with Monobond S silane coupling agent. Self-etching primer and bonding agent were applied on the bonding surface of the teeth in groups I and III. The specimens were bonded to the primed teeth with the Multilink N resin cement and subjected to the universal testing machine. The specimens were light-cured. Specimens in groups II and IV were luted to teeth using self-adhesive cement RelyX U100. The same force was applied over the specimen as mentioned above. Excess cement was removed, and light curing was done. The specimens in groups III and IV were subjected to thermocycling for 10,000 cycles at temperatures altering between 5°C and 55°C. RESULTS: The shear bond strengths of conventional resin cement and self-adhesive resin cement with lithium disilicate were tested before and after thermocycling. Results indicated that thermocycling has no significant effect on the bond strengths of conventional or self-adhesive resin cement. However, from the study, it is seen that conventional resin cement had a higher shear bond strength value than the self-adhesive resin cement. CONCLUSION: There was a significant difference between the average shear bond strength values of conventional resin cement (Multilink N) and self-adhesive resin cement (RelyX U100) when bonded to lithium disilicate disks, and thermocycling had no significant effect on the bond strength of conventional or self-adhesive resin cements. CLINICAL SIGNIFICANCE: Among all-ceramic systems available, lithium disilicate materials have emerged as an excellent esthetic material for fabrication of anterior and posterior crowns and three-unit anterior fixed partial dentures because of their high translucency and improved optical properties. For successful clinical outcomes, the luting agent should have high bond strength not only to the ceramic surface, but also to the tooth surface.

Effect of microwave postpolymerization treatment on residual monomer content and the flexural strength of autopolymerizing reline resin.

BACKGROUND: Microwave postpolymerization has been suggested as a method to improve the flexural strength of an autopolymerizing denture reline resin. However, the effect of microwave postpolymerization on the residual monomer content and its influence on flexural strength have not been investigated. OBJECTIVES: This study analyzed the effect of microwave postpolymerization on the residual monomer content and its influence on the flexural strength of an autopolymerizing reline resin (Denture Liner). MATERIALS AND METHODS: A total of 70 specimens (64 Chi 10 Chi 3.3 mm) were polymerized according to the manufacturer's instructions and divided into 7 groups (n = 10). Control group specimens were not subjected to any further processing. Before testing, the specimens were subjected to postpolymerization in a microwave oven using different power (550 and 650 W) and time (3, 4, and 5 min) settings. Two specimens of each group were then manually ground into fine powder and samples extracted from the specimens using reflux method. The samples were then subjected to gas chromatography for residual monomer determination in area%. Eight specimens were subjected to a three-point bending device with a span of 50 mm and crosshead speed of 5 mm/min, and the flexural strength was determined in MPa. Data analyses included Student's t-test and one-way analysis of variance. RESULTS: For the Denture Liner reline resin, the residual monomer content decreased and the flexural strength increased significantly with the application of microwave irradiation using different time/power combinations. The specimens with the lowest residual monomer content were the similar specimens which presented with the highest flexural strength. CONCLUSION: Microwave postpolymerization irradiation can be an effective method for increasing the flexural strength of denture liner (at 650 W for 5 min) by reducing the residual monomer content by further polymerization at free radical sites.