Journal of Dental Biomaterials
Volume:1 Issue: 2, 2014

Statement of Problem: One of the factors in dental erosion is consumption of acidic soft drinks. Although the effects of various additives to acidic soft drinks for the prevention of tooth erosion have been assessed, little data have been published on the possibility of preventing the erosion through soft drinks containing calcium-carbonate nanoparticles. To examine the erosive factors of 7up soft drink and to determine the possibilities of decreasing or preventing the erosion phenomenon of the soft drink containing calcium-carbonate nanoparticles. 7up soft drink was assigned as control and a set of solutions containing 0.04, 0.05, and 0.06 vol % of the nano-particles were assigned as the experimental solutions. The pH, titratable acidity (TA), calcium and phosphorus concentrations and degree of saturation with respect to enamel hydroxyapatite (DSEn) were calculated. These parameters refer to assessment of erosive potential of the soft drinks. The erosion potential was evaluated based on the micro-hardness and the structural changes of the tooth surface using scanning electron microscopy (SEM).Data were analyzed using Kruskal-Wallis H test,andBonferroni-adjusted Mann-Whitney U test. An increase in the nano-additive content of the solutions increased pH and DSEn; however, it decreased the TA (P < 0.05). There was a significant difference between the micro hardness in the control and experimental groups (p<0.001). SEM imagesrevealed less surface erosion of the specimens stored in the higher nano-additive concentrations. The modified drink containing 0.06% nano-additive revealed the highest hardness with no evidenceof tooth erosion. Adding calcium carbonate nanoparticles to soft drinks can be considered as a novel method to reduce or prevent tooth erosion.

Statement of Problem: Endodontically treated teeth are more prone to fracture. The post and core are often used to provide the necessary retention for prosthetic rehabilitation. The purpose of this study was to: 1) compare the fracture strength of endodontically treated teeth restored either with Nickel-Chromium (Ni- Cr) post or Non- Precious Gold-color alloy (NPG) post compared to the control group and 2) evaluate the fracture site in each group. In this experimental study, endodontic treatment was carried out for 45 extracted maxillary premolars. The specimens were divided into 3 groups (n=15). Group1: restored with NPG post and core, group2: restored with Ni-Cr post and core, and group 3, no post and core were used after endodontic treatment and the access cavity was filled with amalgam. Failure force was recorded in Newton when root or remaining coronal structure fracture was occurred. Data were analyzed using one-way analysis of variance (ANOVA), Student t-test and Tukey HSD test to compare the three groups. There was a statistically significant difference among all groups (p<0.05). Fracture resistance of the teeth restored by NPG posts was significantly higher than those restored by Ni- Cr (p< 0.001). Results showed that the fracture mainly occurred in the root of the teeth restored with Ni- Cr and NPG post while fractures occurred in the core portion of the teeth restored with amalgam. The findings of the present study indicated that the fracture strength of the teeth without using cast post and core was significantly lower than the teeth restored with cast post and core. Also the teeth restored by NPG post had a significantly higher fracture resistance than Ni-Cr posts.

Statement of Problem: Recognition and determination of facial and dental midline is important in dentistry. Currently, there are no verifiable guidelines that direct the choice of specific anatomic landmarks to determine the midline of the face or mouth. The purpose of this study was to determine which of facial anatomic landmarks is closest to the midline of the face as well as that of the mouth. Frontal full-face digital images of 92 subjects (men and women age range: 20-30 years) in smile were taken under standardized conditions; commonly used anatomic landmarks, nasion, tip of the nose, and tip of the philtrum were digitized on the images of subjects and aesthetic analyzer software used for midline analysis using Esthetic Frame. Deviations from the midlines of the face and mouth were measured for the 3 clinical landmarks; the existing dental midline was considered as the fourth landmark. The entire process of midline analysis was done by a single observer and repeated twice. Reliability analysis and 1-sample t- tests were conducted. The Intra-class correlation coefficients (ICCs) for reliability analysis of RFVand RCV measures made two times revealed that the reliabilities were all acceptable. The results indicated that each of the 4 landmarks deviated uniquely and significantly (P<.001) from the midlines of the face as well as mouth in both males and females. There was a significant difference between the mean ratios of the chosen anatomic landmarks and the midlines of the face and mouth. The hierarchy of anatomic landmarks closest to the midline of the face is: (1) midline of the commissures, (2) nasion, (3) tip of philtrum,(4)dental midline, and (5) tip ofthe nose. The closest anatomic landmarks to the mouth midline are: (1) tip of philtrum, (2) dental midline, (3) tip of nose, and (4) nasion.

Statement of Problem: A general process in implant design is to determine the reason of possible problems and to find the relevant solutions. The success of the implant depends on the control technique of implant biomechanical conditions. The goal of this study was to evaluate the influence of both abutment and framework materials on the stress of the bone around the implant by using three-dimensional finite element analysis. A three-dimensional model of a patient’s premaxillary bone was fabricated using Cone Beam Computed Tomography (CBCT). Then, three types of abutment from gold, nickel-chromium and zirconia and also three types of crown frame from silver-palladium, nickel-chromium and zirconia were designed. Finally, a 178 N force at angles of zero, 30 and 45 degrees was exerted on the implant axis and the maximum stress and strain in the trabecular, cortical bones and cement was calculated. With changes of the materials and mechanical properties of abutment and frame, little difference was observed in the level and distribution pattern of stress. The stress level was increased with the rise in the angle of pressure exertion. The highest stress concentration was related to the force at the angle of 45 degrees. The results of the cement analysis proved an inverse relationship between the rate of elastic modulus of the frame material and that of the maximum stress in the cement. The impact of the angle at which the force was applied was more significant in stress distribution than that of abutment and framework core materials.

Statement of Problem: The effect of porcelain surface on the antagonist acrylic teeth has not been widely studied. This study aimed to investigate the effect of polished porcelain, glazed porcelain, and natural teeth (as the control group) on the acrylic resin teeth. In this experimental-laboratory study, a total of 60 specimens of glazed and polished porcelain, natural teeth, and acrylic resin teeth were prepared; in groups of 15 samples each. The denture teeth specimens were examined in terms of tooth wear against glazed or polished or enamel surfaces. After the abrasion test using the polishing machine, the wear of each sample was measured based on the weight lost by a digital scale. The wear surfaces of acrylic teeth were observed by SEM to evaluate the wear characteristic. The data were analyzed using Independent Sample t-test. The glazed and polished porcelain teeth abraded the denture teeth significantly more than the natural teeth (P=0.001). Although there was not a significant difference between the glazed and polished porcelain (P= 0.059), the polished porcelain caused less tooth wear than the glazed porcelain. According to the results of this study, glazed porcelain caused less tooth wear on denture teeth than both of the polished porcelain and natural teeth.