Transmission of radiant light energy through the sides of fiber posts.

OBJECTIVES: Resin cements are light polymerized, but the light may not reach all areas of root canals. The purpose of this study was to determine the best predictor of transmitted light radiant exposure (TLRE) from posts' sides. MATERIALS AND METHODS: Fiber posts were placed in a custom-made apparatus and advanced by 1-mm increments. The LED curing probe tip was activated for 40 s on the coronal end of the post. The TLRE was measured with an LED radiometer detector positioned on the side of the post exposed by an opening in the apparatus. Hierarchical multiple linear regression analysis was performed. RESULTS: Post system explained an additional 23.62% of the variation in TRLE. Adding actual post diameter explained an additional 62.64% of the variation in TRLE. While adding post length explained an additional 0.67%. Changing post system from FiberKleer to Postec Plus will decrease the mean value of TRLE by 4.90 units on average. Also, a one-unit increase of actual post diameter and length will decrease the value of TRLE by 44.96 and 0.44 units respectively. The TLRE ranged from 46 to 290 mJ/cm2 , which was between 0.73% and 6.63% of the original emanating light. CONCLUSIONS: The changes in post system, posts' diameter and length can be used to predict the unit changes in TLRE on the side of a translucent fiber post. Emanating radiant exposure from the side of the post was lower than 6.63% of the exposure entering the post. CLINICAL RELEVANCE: Fiber post diameter and length and post system can influence light radiant exposure transmitted from posts' sides, transmitting minimal radiant exposure, which can be increased by increasing curing duration.

Degree of conversion of resin cement with varying methacrylate compositions used to cement fiber dowels: A Raman spectroscopy study.

STATEMENT OF PROBLEM: Studies on the degree of conversion of dental cement in relation to the number of methacrylate components are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the degree of conversion of single- and multicomponent methacrylate-containing dental cements around opaque and translucent fiber dowels at varying depths. MATERIAL AND METHODS: Teeth were prepared for standard endodontic therapy, and a dowel space was created. Opaque and translucent fiber dowels consisting of Aestheti-Plus (AP) and FiberKleer were cemented with 4 methacrylate (MA)-containing cements, including RelyX U100 (R), which contains TEGDMA; Duolink (D), which contains TEGDMA and BisGMA; and Variolink N LC (V) and Breeze (B), which contain TEGDMA, BisGMA, and UDMA. Light-emitting diode polymerization was performed for 60 seconds. The specimens were immediately cut into halves and measured within the first hour at depths of 1, 3, and 5 mm using Raman spectroscopy, and the degree of conversion (DC) of resin cement was calculated. Data were analyzed using 3-way ANOVA and the Tukey multiple comparison test (α=.05). RESULTS: The measured dowel regions were not significantly different at various depths (P=.10). The dowel and cement types significantly influenced the degree of conversion of the cement (P<.05). The V and B cements exhibited a higher DC than D and R cements. With AP dowels, the DC of cement D was lower than that of the V, B, and R cements. CONCLUSIONS: Within the limitations of this in vitro study, the degrees of conversion of the tested resin cements were not affected by the tested dowel depths. Higher DC was found in cement with more than 2 types of flexible MA. Opaque dowels produced a lower DC than translucent dowels.

Frequency of undercuts and favorable path of insertion in abutments prepared for fixed dental prostheses by preclinical dental students.

STATEMENT OF PROBLEM: Existing publications are lacking regarding guidelines to measure the path of insertion (POI) or placement of multiple abutments for fixed prostheses in terms of angle evaluation other than by the visual judgment of the operator. PURPOSE: The purpose of this preclinical study was to evaluate the incidence of undercuts and favorable path of insertion for prepared typodont abutments for 3-unit fixed dental prostheses by comparing different angles within and between both abutments of 3-dimensional (3D) scanned and digitized preparations and measured with computer-aided design (CAD) software. MATERIAL AND METHODS: Sixty-six maxillary first premolar and maxillary first molar prepared typodont abutments were 3D-scanned and digitized using the Prep-Assist optical 3D scanner and exported as stereolithography (STL) files. These files were imported into CAD software, and 18 different angles were measured within and between the 2 abutments to determine the incidence of undercuts and the frequency of obtaining a favorable path of insertion. RESULTS: Twenty-seven (40.9%) preparations had no clearly visible undercut when viewed virtually. Moreover, a minimum of 12 (44.4%) to a maximum of 26 (96.3%) of the 27 preparations had a favorable POI. CONCLUSIONS: Fewer than half of the fixed dental prosthesis preparations did not have a clearly visible undercut when viewed virtually. A favorable POI was found in 44.4% to 96.3% of the preparations. Favorable POIs were found to occur more frequently in the faciopalatal dimension than in the mesiodistal dimension.

Convergence angles of metal ceramic crowns prepared by dental students.

STATEMENT OF PROBLEM: Convergence angles of crown preparations achieved by dental students vary from the recommended angles and depend on many variables and factors. Sex of operators and examination conditions in which preparations were made have not been reported in the literature. PURPOSE: The purpose of this study was to determine the mean convergence angles produced by fifth-year dental students at King Abdulaziz University. MATERIAL AND METHODS: Maxillary first premolar abutment preparations for metal ceramic restoration were made by fifth-year dental students on typodonts under preclinical examination conditions. A total of 68 preparations, made by 38 male and 30 female students, were randomly selected for evaluation of the buccolingual and mesiodistal convergence angles of each abutment tooth with an optical preparation scanner and digitizer to produce 3-dimensional digital objects. Two-sided t tests were performed to compare the buccolingual and mesiodistal angles between the sexes. RESULTS: The mean mesiodistal angle of all preparations was 11.11 ±4.79 degrees, and the mean buccolingual angle was 10.49 ±3.95 degrees. The mean buccolingual angle in preparations by male students was 10.16 ±3.90 degrees, compared with 11.46 ±5.06 degrees in preparations by female students. The mean mesiodistal angle was 10.92 ±4.03 degrees in preparations by male students, compared to 10.66 ±4.45 degrees in preparations by female students. No statistical difference was observed between the sexes for either angle (buccolingual, P=.435; mesiodistal, P=.497). The smallest and largest angles observed were 2.59 and 24.64 degrees. Approximately 12% of male students and 10% of female students made preparations with less than a 6-degree (ideal convergence angle) buccolingual or mesiodistal angle. CONCLUSIONS: The average convergence angles produced were between 10.16 and 11.46 degrees. Several students were able to achieve ideal convergence angles. Male and female students achieved similar buccolingual and mesiodistal convergence angles.