ABSTRACT
Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures
Objectives: The purpose of this study was to compare the shear bond strength [SBS] of porcelain in the porcelain fused to metal and all-ceramic crowns with Zirconia core
Materials and Methods: Two groups were selected: porcelain fused to metal [PFM] and porcelain fused to Zirconia [PFZ] [n = 30].In the PFM group, a wax model [10 × 10 × 10mm]was used to cast metal base [Ni_Cr alloy]. In the PFZ group, an acrylic cubic model [10 × 10 × 10mm] was made as Zirconia model for scanning.15 cubic Zirconia samples were milled by CAD-CAM. The procedure of porcelain veneering was conducted by the conventional layering technique up to 2 mm thickness [2.5 × 2.5 × 2 mm]. All specimens were stored in water for 48 hrs. Thermal cycling was conducted for 20000 cycles between 55[degree sign]C and 5[degree sign]C alternatively for 30s.All samples were mounted in acrylic resin and the SBS test was performed, using a universal testing machine. The analysis of data was performed at a significance level of 0.05 using Kolmogorov-Smirnov and Mann-Whitney U-test
Results: Mean of SBS in PFM and PFZ was 24.57 and 20.88, respectively. The results of Mann-Whitney test showed that there was no statistically significant difference between the two groups of porcelain fused to metal and Zirconia in item shear bond strength [p = 0.455]
Conclusions: There was no significant difference between the two groups of PFM and PFZ in the item SBS
ABSTRACT
Diagnosis of periapical pathology is of paramount importance in enabling the clinician to provide immediate and appropriate dental treatment. Both intraoral digital radiography and film radiography are used to detect periapical pathology. The purpose of this study was to compare the accuracy of digital radiographic imaging with conventional radiography in detecting chemically created lesions. For conducting this experimental study one cow cadaver mandibular Jaw was used. After building four 1x1cm[2] pools at first molar areas, 35% Hydrochloric acid solution used to create chemically lesions. The designed time for chemically lesions was 4, 12, 24 and 36 hrs following acid exposure. Then, 1 digital and 1 conventional image with E-Speed film was taken from each half-jaw and images evaluated by five examiners. Wilcoxon signed Ranks test used for statistical analysis. The results of this study showed that diagnosis were more precise in detecting lesions with RVG than conventional radiography. This difference was statistically significant [p<0.05]. Regarding the acceptable quality of digital radiographs comparing to conventional radiographs we suggest using this method for detecting bone lesions
ABSTRACT
Anthropometric measurements can be correlated to cephalometric values and have a complementary role to facilitate diagnosis. This Study aimed to determine the correlation between lateral cephalometric and anthropometric indices in the Iranian population. A cross-sectional study using Anthropometric-Cephalometric indices was carried out on 26 subjects with normal occlusion and harmonious facial ratios. Fiberglass meter, wooden ruler and millimetric Anthropometer [Aesculap Inc.] was used as well as hand-made instruments to measure the palm length and angles of the hand. General measurements including height and weight were also taken. For cephalometric measurements, radiographs were taken by an oral and maxillofacial radiologist. Data were subjected to SPSS 9 software. To determine the normal distribution Kolmogorov-Smirnov test was used and P<0.05 was considered significant. Also Spearman and Pearson coefficient correlation was calculated and t-test was performed. In 12 of the 26 cases the correlation coefficient regarding the bizygomatic width [FW] with lower face height [LFH], SE, S-Gn; facial height [FH] with Pog to NB, Nasion-Menton; upper lip vermilion with SE, weight with ANB, Ar-Go; LFH with Ar-Go, forearm length with angle of facial convexity, height with Na-ANS were significant at p<0.01. There was correlation between LFH and FW and Facial Depth that infers three-dimensional proportional facial growth. The forearm length and the facial convexity angle [non-craniofacial anthropometric indices] have a negative co-efficient of correlation. This means that the longer the forearm the straighter the profile. Though there are numerous statistically significant relations between anthropometric and cephalometric indices, in this study these relations were not so clinically momentous in most of the cases
Subject(s)
Humans , Cross-Sectional Studies , Biometry , OrthodonticsABSTRACT
The effect of smear layer on dentinal tubules is remarkable in endodontic treatments. The aim of this study was measuring the range of dye penetration in dentinal tubules with and without smear layer. Thirty extracted human teeth used in this study. At first, segments e prepared with 5 mm length from each tooth's root and then their canals widened by a 1/4 mm diameter bur, so that the smear layer appeared. The external, superior and inferior surfaces of the segments covered by 2 layers of nail varnish. The segments divided to 2 groups of 15 samples. The first group samples immersed in 17% EDTA for 2 minutes and then in 5.25% NaOCl for 20 minutes to remove the smear layer. After that the samples immersed in 2% basic fushin for 24 hours, the second group samples immersed in 2% basic fushin without removing the smear layer. After water rinse, all samples sectioned horizontally from middle of the root and photographs was taken of each samples surfaces. After transmitting the photographs to a computer, the percentage of the dye penetration into dentinal tubules of each sample calculated by Photoshop software. Due to results, the range of dye penetration in dentine tubules of the teeth with and without smear layer had no statistically significant difference [P-Value=0.120]. According to the result, smear layer removal have no effect on dentin permeability to dye penetration and dentin sclerosis is an important factor in this subject. Performing studies on the teeth with certain age and using other methods such as microbial permeability evaluation are needed