Evaluation of Effect of Zirconia Surface Treatment with CO2 and Nd:YAG Lasers on Shear Bond Strength between Zirconia Frameworks and Porcelain Veneers.

AIM: The purpose of this study was to evaluate the effect of zirconia surface treatment with CO2 and Nd:YAG laser on shear bond strength (SBS) between the zirconia framework and porcelain veneering. MATERIALS AND METHODS: In this in vitro study, zirconia blocks were converted to 50 cubes and were divided randomly into 5 groups. After sintering (S), porcelain was applied in the control group. The surface treatment of the second to fifth groups included CO2 laser + (S), (S + CO2), Nd:YAG laser + (S), and (S + Nd), respectively. The SBS test was done, and data were analyzed by SPSS16 software. One sample was randomly chosen from each group and the type of failure was examined under scanning electron microscope (SEM). To compare the pairs of means, the least significant difference test was used and the determined significance level was 5% (p < 0.05). RESULTS: The SBS of S + Nd group was significantly higher than the other ones, except for S + CO2 group. The least amount of SBS belonged to CO2 + S and the highest to S + Nd group. There were no significant differences between the other groups. CONCLUSION: The bond strength of veneering porcelain to zirconia can be altered by surface treatments. It can also be affected by the type and sequence of laser and sintering application. The effect of Nd:YAG laser on the surface of zirconia, in order to create roughness to increase SBS, is better than that of CO2 laser. CLINICAL SIGNIFICANCE: Surface treatment of zirconia by certain types of lasers reduces the chipping of the ceramic veneer and increases the success rate of all-ceramic restorations.

Evaluation of the gray level of restorative materials using cone-beam computed tomography: A cross-sectional study.

BACKGROUND: Densitometry plays an important role in the diagnosis and treatment planning. Due to diversity in density, equal amounts of different materials absorb various amounts of X-rays and yield different radiographic views. OBJECTIVES: The aim of this study was to evaluate the gray scales of 5 commercially available restorative materials, including amalgam, composite resin, flowable composite resin, glass-ionomer, and Dycal. MATERIAL AND METHODS: Samples of the 5 test materials from various manufacturers were prepared, each 5-millimeter-thick. There were 7 glass-ionomer samples and 10 of each of the other materials, making a total of 47 samples in the study. The test materials were scanned using a Kodak cone-beam computed tomography (CBCT) unit. Subsequently, the gray scales were determined and evaluated by a radiologist using OnDemand3DTM Dental software and analyzed with SPSS v. 22 software. RESULTS: Amalgam had a higher gray scale than the other groups of restorative materials. In some cases, it was the same as that of composite resin; however, it was significantly different from gray scales of flowable composite resin, glass-ionomer and Dycal. It was concluded that composite resin and amalgam were high in gray scale, while flowable composite resin, glass-ionomer and Dycal exhibited low gray scales. CONCLUSIONS: Amalgam and composite resin had high gray scales, and glass-ionomer and Dycal exhibited the lowest gray scale values. The findings show that CBCT can be helpful in differentiating amalgam and composite resin from other materials.

Cone Beam Computed Tomography Findings of Desmoplastic Ameloblastoma of Maxilla.

Desmoplastic ameloblastoma (DA) is one of 6 subtypes and also a rare variant of ameloblastoma. It is not recognized perfectly up to now. Although most of the conventional ameloblastomas can be diagnosed in posterior of the mandible, DA more transpires in anterior of the jaws. Our patient was a 57-year-old man with swelling in the right side of the anterior maxilla. In the medical examination bone expansion was detected with a normal covering mucosa and no discoloration. This paper provides more information about cone beam computed tomography image features of DA.

Effect of Field of View on Detection of Condyle Bone Defects Using Cone Beam Computed Tomography.

In maxillofacial imaging, cone beam computed tomography (CBCT) is currently the modality of choice for assessment of bony structures of the temporomandibular joint (TMJ). Factors affecting the quality of CBCT images can change its diagnostic accuracy. This study aimed to assess the effect of field of view (FOV) and defect size on the accuracy of CBCT scans for detection of bone defects of the TMJs. This study was conducted on 12 sound TMJs of 6 human dry skulls. Erosions and osteophytes were artificially induced in 0.5, 1, and 1.5-mm sizes on the anterior-superior part of the condyle; CBCT scans were obtained with 6, 9, and 12-inch FOVs by NewTom 3G CBCT system. Two maxillofacial radiologists evaluated the presence/absence and type of defects on CBCT scans. The Cohen kappa was calculated to assess intra- and interobserver reliability. The Mann-Whitney U test was applied to compare the diagnostic accuracy of different FOVs.In comparison of 6- and 12-inch, 9- and 12-inch FOVs in detection of different sizes of erosive lesions, difference was significant (P <0.05), whereas difference between 6- and 9 inch just in 0.5-mm erosive lesion was significant (P = 0.04). In comparison of 6- and 12-inch FOVs in detection of different sizes of osteophyte lesion, difference was significant (P < 0.05), whereas between 6- and 9-inch FOVs statistically significant difference was not observed (P > 0.05). The highest and the lowest diagnostic accuracy of CBCT scans for condyle defects were obtained with 6-inch and 12-inch FOVs, respectively. Diagnostic accuracy of CBCT scans increased with an increase in size of bone defects.