Shear bond strength of a ceromer to noble and base metal alloys

Background and Aim: The improvement of the physical and chemical properties of resins as well as great advances achieved in the field of chemical bonding of resin to metal has changed the trend of restorative treatments. Today the second generation of laboratory resins have an important role in the restoration of teeth. The clinical bond strength should be reliable in order to gain successful results. In this study the shear bond strength (SBS) between targis (a ceromer) and two alloys (noble and base metal) was studied and the effect of thermocycling on the bond investigated. Materials and Methods: In this experimental study, alloys samples were prepared according to the manufacturer. After sandblasting of bonding surfaces with 50µ AI2o3 Targis was bonded to the alloy using Targis I link. All of the samples were placed in 37°C water for a period of 24 hours. Then half of the samples were subjected to 1000 cycles of thermocycling at temperatures of 5°C and 55°C. Planear shear test was used to test the bond strength in the Instron machine with the speed rate of 0.5mm/min. Data were analyzed by SPSS software. Two-way analysis of variance was used to compare the bond strength among the groups. T test was used to compare the alloys. The influence of thermocycling and alloy type on bond strength was studied using Mann Whitney test. P<0.05 was considered as the limit of significance. Result: The studied alloys did not differ significantly, when the samples were not thermocycled (P=0.136) but after thermocycling a significant difference was observed in SBS of resin to different alloys (P=000.1). Thermal stress and alloy type had significant interaction, with regard to shear bond strength (P=0.003). There was a significant difference in SBS before and after thermocycling in noble alloys (P=0.009), but this was not true in base metals (P=0.29). Maximum SBS (19.09 Mpa) belonged to Degubond 4, before thermocycling. Minimum SBS (8.21 Mpa) was seen in Degubond 4 after thermocycling. Conclusion: The effect of thermocycling in reducing bond strength of resin to metal depends on the type of alloy. The noble metal studied is significantly affected by thermal tensions

Evaluation of patients' satisfaction from dental care services: TUMS, school of dentistry, 1385-86

"nBackground and Aims: Association between patient satisfaction and success of the treatment determines the quality of health care. Measuring the level of satisfaction is an important factor for improving the quality of services provided by a system, so it is necessary to determine the expectations of patients. The aim of this study was to evaluate the patient satisfaction from services provided by the dental faculty of Tehran University of Medical Sciences."nMaterials and Methods: In this descriptive and cross-sectional study, 385 patients were randomly selected from different departments of dental faculty including prosthodontics, endodontics, periodontics, operative dentistry, radiology and oral medicine. A two-part questionnaire including demographic characteristics of patients and satisfaction from reception process, infection control, student and personnel behavior, and the outcome of treatment was filled out by patients. Data were analyzed using SPSS software."nResults: The most dissatisfying factor was the time wasted in paying the cost and the most satisfying factor was student behavior. General satisfaction form the process was evaluated (complete satisfaction 51.9%, partial satisfaction 38.4% and dissatisfaction 9.6%), and 62.9% of patients were completely agree with introducing dental faculty to others."nConclusion: The most satisfying item was student behavior which indicates that this factor is of great importance in increasing the quality of treatment. The deficiencies determined by patient can provide reliable data for determination and regulation of health care policies

The Convergence Angle of Full-coverage Crown Preparations Made by Dental Students

Objective: A clinically feasible convergence angle in full-coverage crown preparations, meeting the requirements for proper retention and resistance forms, has always been a matter of interest for laboratory and clinical researches. This study aims to evaluate the angle in teeth prepared by both under- and post-graduate students at Tehran University of Medical Sciences, Faculty of dentistry, Department of Prosthodontics.Materials and Methods: Samples consisted of 196 prepared teeth for full-coverage crown restoration by third year postgraduate and fifth year undergraduate students in the Department of Prosthodontics. Two images were obtained from each die by a scanner and both bucco-lingual and mesio-distal convergence angles were measured, by two different assessors, via Auto CAD 14 software. The data were analyzed using analysis of variance.Results: There were statistically significant differences between the teeth prepared by un-der- and post-graduate students in mesio-distal convergence angles of all maxillary teeth, except for canines. Significant differences were found between bucco-lingual convergence angles of the maxillary canines and molars.Conclusion: The recently recommended convergence angles are more clinically feasible compared to the classic 4 to 10 degrees that was previously suggested for all teeth. It also seems that clinical experience does not necessarily lead to a decrease in convergence an-gles during preparation

colorimetric evaluation of Cercon zirconia and metal ceramic restorations in two thicknesses of veneering porcelain

"nBackground and Aims: The aim of this study was to evaluate the effect of zirconia and base metal cores on the color of restorations. Furthermore, the effect of different backings on the color of cercon zirconia was evaluated."nMaterials and Methods: The specimens were Cercon zirconia and metal ceramic discs with "high Au" and "base metal" alloys. Cercon zirconia discs were veneered with veneering shade of A2 and two thickness of porcelain"n(0.7 mm, 1.2 mm). There were 3 discs in each group. Metal ceramic discs were made of "nickel-chromium" alloy (Verobond) and "high Au" alloy (World 89) and two shades (A2, A3.5) and two thicknesses of veneering porcelain. 3 types of backing (high Au, nickel-chromium and A3 shade composite) were made for Cercon zirconia discs. Spectrophotometric evaluation of zirconia discs (on 3 backings) and metal ceramic discs was done. One-way ANOVA and Tukey tests were used for data analysis."nResults: There were no significant differences between the amounts of L*, a*, b* for Cercon zirconia on different backings (P>0.05). In comparison between different core groups, a* was significantly higher in metal ceramic groups compared with that of zirconia groups (P<0.05)."nConclusion: Cercon zirconia can completely mask the underlying backing