Effect of carbamide peroxide bleaching agent on the surface roughness and gloss of a pressable ceramic.

OBJECTIVE: This study evaluated the influence of carbamide peroxide, 10% and 16%, on the surface roughness and gloss of a pressable ceramic. MATERIALS AND METHODS: Carbamide peroxide (10% or 16%) was applied for 4 hours or 3 hours per day for 14 days, respectively, in pressable ceramic discs (14 mm × 2 mm). Specimens were stored in distilled water at 37°C. Surface roughness and gloss were determined before carbamide peroxide application (T0 ), 7 days (T7 ) and 14 days (T14 ) after the initial treatment. ANOVA was used with repeated measures and multiple comparisons with a Bonferroni adjustment (P < 0.005). RESULTS: Significant increase in surface roughness was observed over time (P < 0.001), with T0 < T7 < T14 . When the gloss was analyzed, significant differences were found (P < 0.001), control group showed a higher gloss than those of the 10% and 16% groups. Significant decrease in gloss was observed over time (P < 0.001), with T0 > T7 > T14 . CONCLUSIONS: The surface roughness of pressable ceramics increased, while their gloss significantly decreased when 10% or 16% carbamide peroxide was applied. The specimens treated with 16% carbamide peroxide exhibited higher surface roughness and less gloss than the specimens treated with 10% carbamide peroxide. CLINICAL SIGNIFICANCE: This study found that carbamide peroxide gels commonly used in at-home procedures influenced the surface roughness and gloss of a pressable ceramic that is often used for rehabilitation esthetics.

Evaluation of Marginal Misfit of Metal Frameworks Welded by Gas-Torch, Laser, and Tungsten Inert Gas Methods.

PURPOSE: The objective of this study was to evaluate the marginal fit and the flexural resistance of nickel-chromium frameworks welded by different techniques, gas-torch, laser, and tungsten inert gas (TIG), compared with that of frameworks made via one-piece casting. METHODS: To evaluate the marginal fit, a master model was fabricated simulating four implants. Transfers and replicas were used to transfer the positions of the implants to the model, using a silicone matrix. The bars were waxed up and casted. Three assessments of misfit were performed for each implant using a stereomicroscope before and after welding in two predetermined regions, totaling six readings for each implant. To evaluate the flexural resistance, one group was made casting the specimens in one piece. Other 3 groups using gas-torch, laser, and TIG welding techniques were made after sectioned transversally. The data showed normal distribution and two-way ANOVA for marginal fit and one-way ANOVA for flexural resistance, and Tukey's posttest (α=0.05) was performed. RESULTS: For the marginal fit, the three welding methods presented similar results and were different from one-piece casting. For the flexural resistance, significant differences were observed among the studied groups (p < 0.001), and the one-piece group presented higher resistance compared to the three welding techniques. CONCLUSIONS: Within the limits of this study, the three welding techniques yielded similar misfit results, and the laser and TIG techniques presented similar flexural resistance but lower than gas-torch and one-piece casting.

Removal of Implant and New Rehabilitation for Better Esthetics.

Tooth loss can result in loss of facial esthetics, in addition to its effect on mastication, swallowing, and speech. Adequate planning is required in order for the prosthetic treatment of the teeth and implants to be successful. Here, we present a clinical case demonstrating that improper positioning of an implant can make prosthetic rehabilitation unfeasible, necessitating new surgical and rehabilitation planning to achieve the desired esthetics. The patient had a missing right lateral incisor and cuspid, and a buccally directed implant. The preferred treatment regimen involved the removal of this implant and placement of another one more properly positioned distally and three dimensionally. The repositioning of the implant made rehabilitation treatment with a mesial cantilever possible. Due to esthetic considerations, gingival conditioning in the cantilever region was performed in the temporary prosthesis phase. The changes adopted in planning the surgery and rehabilitation resulted in good esthetics as well as functional outcomes.

Photoelastic stress analysis of different designs of cement-retained fixed partial dentures on Morse taper oral implants.

There is no consensus in literature regarding the best plan for prosthetic rehabilitation with partial multiple adjacent implants to minimize stress generated in the bone-implant interface. The aim of this study was to evaluate the biomechanical behavior of cemented fixed partial dentures, splinted and nonsplinted, on Morse taper implants and with different types of coating material (ceramic and resin), using photoelastic stress analysis. A photoelastic model of an interposed edentulous space, missing a second premolar and a first molar, and rehabilitated with 4 different types of cemented crowns and supported by 2 adjacent implants was used. Groups were as follows: UC, splinted ceramic crowns; IC, nonsplinted ceramic crowns; UR, splinted resin crowns; and IR, nonsplinted resin crowns. Different vertical static loading conditions were performed: balanced occlusal load, 10 kgf; simultaneous punctiform load on the implanted premolar and molar, 10 kgf; and alternate punctiform load on the implanted premolar and molar, 5 kgf. Changes in stress distribution were analyzed in a polariscope, and digital photographs were taken of each condition to allow comparison of stress pattern distribution around the implants. Cementation of the fixed partial dentures generated stresses between implants. Splinted restorations distributed the stresses more evenly between the implants than nonsplinted when force was applied. Ceramic restorations presented better distribution of stresses than resin restorations. Based on the results obtained, it was concluded that splinted ceramic restorations promote better stress distribution around osseointegrated implants when compared with nonsplinted crowns; metal-ceramic restorations present less stress concentration and magnitude than metal-plastic restorations.

Tensile bond strength of cast commercially pure titanium dowel and cores cemented with three luting agents.

PURPOSE: The purpose of this study was to compare the tensile strength of commercially pure titanium dowels and cores cemented with zinc phosphate or resin cements. METHODS: Twenty-one extracted human canines were endodontically treated. The root preparations were accomplished using Largo reamers (10mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the dowel and cores were made, and specimens were cast in commercially pure titanium (n=7) and divided in three groups: TZ-CP Ti dowels luted with zinc phosphate luting agent, TP-CP Ti dowels luted with Panavia F and TR-CP Ti dowels luted with RelyX U100. Tensile strengths were measured in a universal testing machine at a crosshead speed of 0.5mm/min. The results (N) were statistically analyzed by ANOVA and Tukey tests (α=0.01). RESULTS: The ANOVA indicated that there were significant differences among the groups tested. A Tukey multiple comparison procedure was performed and revealed statistically significant higher retention values for the dowel luted with RelyX U100 when compared with zinc phosphate or Panavia F. CONCLUSION: Cast commercially pure titanium dowels and cores fixed with RelyX U100 cement presented superior bond strength retention when compared to zinc phosphate and Panavia F.