Evaluation of the degree of taper and convergence angle of full ceramo-metal crown preparations by different specialists centers at Assir region, Saudi Arabia

Background: Ceramo-metal crowns are commonly indicated for restoration of extensively damaged posterior teeth. Prosthodontists have ability to prepare teeth for retention, resistance, and longevity of the restorations

Objectives: The aim was to measure the degrees of the taper and convergence angle [CA] of dies prepared by different prosthodontists at Assir region, and the effect of the tooth position on the taper and CAs degrees

Materials and Methods: Eighty stone dies were obtained from specialist dental clinics, College of Dentistry at King Khalid University [KKU], Muhayil, Kamis-Mushayat and Assir Dental Centers. All the dies were mounted with the occlusal plane of the prepared teeth parallel to the floor. Photographs of buccal and proximal aspects were taken for each die. The photographs were transferred into a personal computer, AutoCAD software program was used to measure the mesio-distal [MD] and bucco-lingual [BL] taper and CA of each preparation. Analysis of variance [ANOVA] was used to test the level of significance difference, which was set at 5%

Results: The highest values were observed with Kamis-Mushayat Center for BL [31.89] taper and Assir Center for MD [38.21] and overall CA degrees [34.38]. The mean values for KKU specialist dental clinics were the lowest for all parameters of CA degrees [22.91]. ANOVA showed statistically significant [P < 0.05] differences with the mean CAs between all the four dental centers. The MD, BL taper and overall CA for all the premolar teeth was significantly lower than molar teeth. No statistical difference in the overall CA between maxillary and the mandibular arch [P > 0.05]

Conclusions: The values of MD, BL taper and CA degrees carried-out by specialist at College of Dentistry, KKU are the lowest values of the prepared teeth compared with other dental centers at Assir region. There was no significant difference between maxillary and mandibular arch, while taper and CA are lower at premolars comparing to molars. The recommended taper and CAs are difficult to be achieved clinically

Comparison of immediate complete denture, tooth and implant-supported overdenture on vertical dimension and muscle activity

PURPOSE: To compare the changes in the occlusal vertical dimension, activity of masseter muscles and biting force after insertion of immediate denture constructed with conventional, tooth-supported and Implant-supported immediate mandibular complete denture. MATERIALS AND METHODS: Patients were selected and treatment was carried out with all the three different concepts i.e, immediate denture constructed with conventional (Group A), tooth-supported (Group B) and Implant-supported (Group C) immediate mandibular complete dentures. Parameters of evaluation and comparison were occlusal vertical dimension measured by radiograph (at three different time intervals), Masseter muscle electromyographic (EMG) measurement by EMG analysis (at three different positions of jaws) and bite force measured by force transducer (at two different time intervals). The obtained data were statistically analyzed by using ANOVA-F test at 5% level of significance. If the F test was significant, Least Significant Difference test was performed to test further significant differences between variables. RESULTS: Comparison between mean differences in occlusal vertical dimension for tested groups showed that it was only statistically significant at 1 year after immediate dentures insertion. Comparison between mean differences in wavelet packet coefficients of the electromyographic signals of masseter muscles for tested groups was not significant at rest position, but significant at initial contact position and maximum voluntary clench position. Comparison between mean differences in maximum biting force for tested groups was not statistically significant at 5% level of significance. CONCLUSION: Immediate complete overdentures whether tooth or implant supported prosthesis is recommended than totally mucosal supported prosthesis.

The effect of thermocycling on the bonding of different restorative materials to access opening through porcelain fused to metal restorations

PURPOSE: Porcelain fused to metal (PFM) crowns provide the best treatment option for teeth that have a large or defective restoration. More than 20% of teeth with PFM crowns or bridges require non-surgical root canal treatment (NSRCT). This may be due to the effect of restorative procedures and the possible leakage of bacteria and or their by-products, which leads to the demise of the tooth pulp. Thus, this study was planned to compare the ability of the restorative materials to seal perforated PFM specimens. MATERIALS AND METHODS: The study evaluates the ability of amalgam, composite or compomer restorative materials to close perforated PFM specimen's in-vitro. Ninety PFM specimens were constructed using Ni-Cr alloys and feldspathic porcelain, and then they were divided into 3 groups: amalgam (A), composite + Exite adhesive bond (B) and compomer + Syntac adhesive bond (C). All the PFM samples were embedded in an acrylic block to provide complete sealing of the hole from the bottom side. After the aging period, each group was further divided into 3 equal subgroups according to the thermocycling period (one week for 70 cycles, one month for 300 cycles and three months for 900 cycles). Each subgroup was put into containers containing dye (Pelikan INK), one maintained at 5degrees C and the other at 55degrees C, each cycle for 30 sec time. The data obtained was analyzed by SPSS, 2006 using one way ANOVA test and student t-test and significant difference level at (P<.01). RESULTS: The depth of dye penetration was measured at the interfaces of PFM and filling materials using Co-ordinate Vernier Microscope. The lowest levels of the dye penetration for the three groups, as well as subgroups were during the first week. The values of dye leakage had significantly increased by time intervals in subgroups A and C. CONCLUSION: It was seen that amalgam showed higher leakage than composite while compomer showed the lowest level of leakage.