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BACKGROUND: Dental shade guides are used before restorative and prosthodontic procedures for the evaluation of tooth color. The spectral coverage of the specific shaded guide and a clinician's experience in shade matching are the two most important factors for a clinically viable shade match of the restoration to the given tooth. Repeated disinfection of the shade guide with disinfectant lead to a clinically significant difference of the shade to be matched, finally resulting in a clinically unacceptable prosthesis. The purpose of this study is to evaluate the effects of disinfection on various shade tabs of VITA 3D Master Shade guide after being subjected to 2 years of simulated disinfection with 70% isopropyl alcohol. METHODOLOGY: Two sets of VITA 3-D Master Shade Guides were used. One set of each shade guide was assessed after simulated use and surface disinfection with 70% isopropyl alcohol (test group), while the other full set was subjected to cleansing with distilled water (control group). Spectrophotometer was used to measure each of the shade tabs. Readings were recorded at regular intervals of 120, 240, 360, 480, 600, 720, 840, and 960 disinfection cycles. The ΔE values obtained were used to examine the color difference. RESULTS: There was a significant difference in terms of ΔE between the shade tabs of control and test groups of VITA 3D Master shade guides after 960 cycles of disinfection. The change in mean ΔE was more in the test specimens in the shade tabs of VITA 3D Master Shade Guide tabs than the control specimens. These results are of statistical significance, but they might not be of any clinical significance. CONCLUSION: There was a statistically significant but clinically nonsignificant color change in the shade tabs of VITA 3D Master shade guides after 2 years of simulated use and disinfection with 70% isopropyl alcohol.
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INTRODUCTION: Dental caries remains the most important dental health problem in developing countries. Application of varnish on tooth surfaces is shown to promote the uptake of firmly bound fluoride by enamel, which is considered important. Along with the incorporation of fluoride into the crystalline lattice, there is formation of calcium fluoride compounds on enamel. METHODOLOGY: Seventy deciduous canines were covered with nail polish. A window measuring 4 mm × 4 mm was left on their buccal surface, These were randomly assigned to seven groups (n = 6): S: sound enamel not subjected to any regimen or treatment; N: negative control, subjected to the pH-cycling regimen without any treatment; D1 and D2: subjected to the pH-cycling regimen and treated two times daily with 1100 and 500 ppm F dentifrice, respectively; VF: fluoride varnish (subjected to F-varnish before and in the middle of the pH-cycling regimen); and VF + D1 and VF + D2. After a period of 10 days, sectioning of teeth was done, and enamel demineralization was measured. RESULTS: The combination of dentifrice and varnish (groups VF + D1 and VF + D2) significantly reduced demineralization compared with the N group at all distances evaluated (P < 0.05), but the combination did not differ from the dentifrice groups at most distances from the surface (P > 0.05). CONCLUSION: The results of this study suggest that the combination of F-varnish with dentifrices containing 500 or 1100 ppm F is not more effective in reducing demineralization in primary teeth than the isolated effect of dentifrice containing 1100 ppm.
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BACKGROUND: The thermal expansion of the investment can be restricted by the metal casting ring because the thermal expansion of the ring is less than that of the investment. The ringless casting procedure is in use in clinical dentistry, though there is little scientific data to support its use in fixed partial dentures. In this study, marginal discrepancy of castings produced with the ringless casting technique and the conventional technique using the metal rings were compared. MATERIALS AND METHODS: A total of 30 wax patterns were fabricated directly on a metal die. Optical stereomicroscope was used to measure the marginal discrepancy between the metal die and wax patterns. A total of 15 castings were invested using Bellavest T phosphate-bonded investment with the ringless technique and 15 were invested with the same investment with a metal ring; 30 castings were produced using a nickel-chromium ceramo-metal alloy. The internal surface of the castings was not modified and seated with finger pressure. The vertical marginal discrepancy was measured using an optical stereomicroscope at a magnification of 100x. The data obtained were statistically analyzed using students t-test (paired t-test and unpaired t-test). RESULTS: The castings of the ringless technique provided less vertical marginal discrepancy (240.56 ± 45.81 µ) than the castings produced with the conventional metal ring technique (281.98± 53.05 µ). The difference was statistically significant. CONCLUSION: The ringless casting technique had produced better marginal accuracy compared with conventional casting technique. Ringless casting system can be used routinely for clinical purpose.
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Revestimento para Fundição Odontológica , Técnica de Fundição OdontológicaRESUMO
BACKGROUND: The fracture of acrylic resin denture is rather common occurrence and causes inconvenience to the patients. This study was carried out to evaluate and compare the impact strength and fracture morphology of four different heat cure acrylic materials. MATERIALS AND METHODS: Acrylic resin specimens were prepared using preformed metal die of dimension 65 × 10 × 3 mm. The specimens were finished, polished and subjected to impact strength evaluation using impact testing machine. The loads at which the specimens fracture are recorded and subjected to statistical analysis. Fracture surface analysis was done. Macroscopic analysis was performed by visual inspection of the fractured surfaces using a stereoscopic microscope. About 5 mm sections of all the fragments were subjected to scanning electron microscopy for microscopic analysis to verify fracture morphology. RESULTS: Mean values of the impact strength were compared by statistical methods. The impact strength data were subjected to variance homogeneity tests. Fracture surface analysis data was analyzed by statistical methods. The mean impact strength of Lucitone 199 was higher than Acrylyn-H, DPI Heat cure & Trevalon. CONCLUSION: Within the limitations of this study, it was concluded that the impact strength of the acrylic resins is affected by the reinforcement of fibers. Increased intermediate fractures increased impact strength. Brittle fractures morphology showed fewer undercuts and clearer surface. Intermediate fractures morphology showed more undercuts than clear surfaces.
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INTRODUCTION: Ever since the introduction of the minimal preparation fixed partial dentures, the major concern of the clinicians has been its longevity. AIMS AND OBJECTIVE: The objective of the present study was to compare the clinical performance of resin bonded cantilever bridges with conventional cantilever bridges for a period of 1 year and to evaluate the periodontal changes of abutment teeth using radio visio graphy. MATERIALS AND METHODS: Fourteen patients with missing first or second premolar were selected for the study. The patients were divided into 2 groups, conventional cantilever group and resin bonded cantilever group. RESULTS: The results were analyzed using Student's t test and Mann-Whitney U test. The clinical success rate for both the groups was 100%. The amount of bone loss at 6 months for conventional group was 0.11 mm and for resin bonded bridge group was 0.10 mm. The amount of bone loss at 1 year for conventional cantilever group was 0.14 mm and for resin bonded fixed partial denture group was 0.16 mm. There was no statistical difference between both the groups. The results showed that the resin bonded cantilever bridges can be used for the treatment of missing posterior tooth.
