Frontiers in Dentistry
Volume:2 Issue: 1, Winter 2005

Statement of Problem: Ceramics as in ceramo-metallic and all ceramic tooth restorations have grown popular owing to their high tissue compatibility and esthetic advantages. Such restorations have the capability to deliver valuable services over a long period of time; however, failures under intraoral conditions are not unanticipated. The purpose of this in-vitro study was to investigate the shear bond strength of composite resin to porcelain using different bonding system materials. In this experimental study forty porcelain blocks were prepared and randomly divided into four equal groups. The porcelain surfaces were then etched with HF for 2 minutes, washed with water for 2 minutes and treated with a silane layer. The silane treated porcelain surfaces were left for one minute and then the specimens were bonded to composite resin as follow: Group 1 (control group), hybrid composite Z100 was applied and light cured from four directions for 20 seconds. Group 2, flowable composite was applied and light cured for 20 seconds. Group 3, unfilled resin was used and photo cured for 20 seconds. Group 4, (Dentin bonding agent) adhesive resin was used followed by 20 seconds photo curing. Hybrid composite resin Z100 was subsequently applied on all porcelain surfaces of groups 2, 3 and 4, and light cured for 20 seconds from four directions. Specimens were then subjected to thermocycling 1000 times. Shear bond strength was determined by a Universal testing machine. The data obtained was subjected to a one-way ANOVA test. The results indicate that there is a statistically significant difference between adhesive group and the other three groups of hybrid, flowable and unfilled resin (P<0.05). The results from this study showed that the shear bond strength of composite resin to porcelain was significantly higher for porcelain bonded surfaces using a dentin bonding agent than that of other materials tested.

Statement of Problem: Various factors are involved in causing inflammation following root canal treatment. Controlling these factors may relieve the related pain. One of these factors is extrusion of debris beyond the apex. Although debris extrusion happens in all instrumentation techniques, researchers have declared that in coronal flaring technique, there is minimum debris extrusion. The purpose of this study was to evaluate and compare the inflammation of periapical area following root canal therapy, using conventional and profile rotary instrumentation in cats'' teeth, from a histopathological point of view. This experimental study conducted on thirty Persian one year old cats. Three groups of samples were chosen and treated with different methods. First group were prepared by step-back instrumentation technique using stainless steel K-type files. Second group were prepared by crown down technique using Ni-Ti files. Third group were prepared using profile GT rotary system at 150-rpm speed. Animals were subjected to vital perfusion at 8, 24 & 48 hour intervals after instrumentation. The canine teeth were separated from the jaw along with some of the supporting structures. Then decalcification and laboratory processing were carried out and samples were evaluated histologically. Collected data were analyzed using Kruskal-Wallis test. The results showed that in vital teeth with no evidence of periapical pathosis, the inflammation following various instrumentation methods was not statistically different. In vital teeth, the periapical inflammation following various methods of instrumentation is not statistically different.

Statement of Problem: Due to the growing popularity of vital bleaching by Carbamide Peroxide it is imperative to understand the effect of such agents on enamel and dentine. The purpose of this study was to evaluate the effect of a 16% carbamide peroxide bleaching gel; Vivastyle on enamel staining susceptibility. Thirty bovine specimens were selected and randomly divided into two groups of fifteen. The experimental group was subjected to Vivastyle gel and then was immersed in coffee, for half an hour daily for three weeks. The control group was only immersed in coffee. The teeth were evaluated by colorimeter readings to measure L*, a*, b* of each tooth. Total color differences between two colors (ΔE) were calculated using the following formula: ΔE= [(ΔL*) 2 + (Δa*) 2+ (Δb*) 2]. ΔE1 represent color difference after bleaching; ΔE2: bleached and immersed in coffee, and ΔE3 immersed in coffee. Mean color difference were: 9.478, 13.808, and 7.230 for ΔE1, ΔE2, and ΔE3 respectively. Paired comparison by Duncan test showed that there was a significant difference between ΔE1 and ΔE2 (P0.000). t-test showed that there was no significant difference between ΔE3 and ΔE1. (P=0.08), however, ΔE3 had significant difference with ΔE2 (P0.000). After vital bleaching, the enamel staining susceptibility is significantly increased.

Statement of Problem: Assessing oral hygiene in children plays an important role in determining the health status of communities and evaluating national health promotion programs. In 1997 in Geneva, international organizations agreed on the global goal of achieving a minimum of 90% caries free teeth in 5 year old children. This study was aimed to assess the oral health status in Iranian children. Among kindergarten children residing in the capital of Iran, Tehran, 400 children between the ages of three and five years were randomly selected and participated in this study. Their deciduous teeth were examined and the health index of dmft was determined for each child. The collected data were analyzed using the one-way ANOVA (with Tukey–Kramer multiple comparisons test for Post Hoc test), t test, and chi square test. In this age group, only 48.3% of the children had no tooth decay. This information shows how far we are from accomplishing the aforementioned goal. A significant increase in tooth decay in these children was correlated with neglecting oral and dental hygiene, and also failing to brush the teeth regularly and wash the mouth after consuming sweets (P<0.001). Unfortunately, visits to dentists for regular check-ups are not frequent enough, and dental caries was seen more in children who did not have regular visits than those who did (P<0.001). More accurate planning seems necessary to achieve 90% caries free teeth in 5 year old children. More emphasis must be placed on prevention programs and educating public to observe dental hygiene by brushing the teeth regularly, washing the mouth after consuming sweets, and paying their dentists regular visits.

Statement of the problem: In the evolution of orthodontics, the changes in soft tissue, especially smile line attracts considerable attention. The present study was carried out to evaluate the correlation of the smile line with the vertical parameters of anterior part of face. Forty-six Iranian adults, aged between 18-25 years were selected. Five quantitative and three qualitative variables of smile analysis were recorded for each subject. Cephalometric analysis was carried out using angular and linear parameters. The correlations between smile line variables and cephalometric parameters were calculated using Spearman and Pearson’s correlation analyses. The result of this study showed that the cephalometric parameters of N-Me, Pn-Line, N-B, N-Pg had significant correlations with quantitative variable of tooth-lower lip position. The P-values were P=0.003, P=0.027, P=0.006, P=0.002 respectively. N-Me, N-B, N-Pg represented significant correlations with interlabial gap on smile (P= 0.006, P=0.036, P=0.002 respectively). There was a significant correlation between N-Pg and quantitative factor of tooth-upper lip position (P=0.034). Upper incisor to palatal plane showed a significant correlation with qualitative variable of tooth-upper lip position (P=0.019), interlabial gap on smile (P=0.004), and tooth-upper lip position (P=0.006). Upper incisor to FH represented a reverse relation with incisal edge to lower lip (P=0.028).This parameter also showed significant correlations with quantitative factors of tooth-lower lip position (P=0.040) and crown height (P=0.002). According to the results of this study, it can be concluded that, linear skeletal and dental vertical factors affect the vertical features of smile. Angular vertical parameters, except gonial angle, influence the vertical position of smile.

Statement of problem: Digital measurement of RVG may improve diagnostic interpretation of radiographs in terms of accuracy, although it has been shown that validity of linear measurements of interproximal bone loss could not be improved by basic digital manipulations. The aim of this study was to evaluate the accuracy of RadioVisioGraphy (RVG) in the linear measurement of interproximal bone loss in intrabony defects. Thirty two radiographs of 56 periodontally diseased teeth exhibiting interproximal intrabony defects were obtained by a standardized RVG technique and Intrabony defect depths were determined by linear measurement analysis of RVG. The following four distances were assessed intrasurgically: the cemento enamel junction (CEJ) to the alveolar crest, the CEJ to the deepest extention of the bony defect (BD), the occlusal plane to the BD and the OP to the AC. Comparison between RVG measures and intrasurgical estimates were performed using paired t-test. The radiographic measurements overestimated interproximal bone loss as compared to the intrasurgical measurements: CEJ-BD measurement by RVG was 6.8033.589 mm and intra-surgically was 6.4923.492 (P<0.000). No statistically significant difference was seen between CEJ and occlusal references in RVG measurements (P<0.729). Radiographic assessment by either the CEJ or occlusal references overestimated bone loss as compared to the intrasurgical gold standard.

Fusion is a developmental anomaly defined as the union of two normally separated tooth buds or the partial splitting of one tooth bud into two buds. Depending on the stage of development, fusion may be either complete or incomplete. The significance of this particular case was that this fusion occurred in a posterior permanent mandibular tooth, while such a manifestation is more reported in maxillary anterior teeth; either in the primary (0.5%) or permanent (0.1%) dentition. The genetic basis for this anomaly is probably autosomal dominant with reduced penetrance. In addition, the essential findings for differential diagnosis include number of teeth, radiography and clinical features.

Bonding brackets to the enamel surface has gained much popularity today. New adhesive systems have been introduced and marketed and a considerable increase in research regarding bond strength has been published. A considerable amount of these studies deal with shear bond strength of adhesives designed for orthodontic purpose. Previous studies have used variety of test designs. This diversity in test design is due to the fact that there is no standard method for evaluating shear bond strength in orthodontics. Therefore comparison of data obtained from different study is almost impossible. This article tries to briefly discuss the developments occurred in the process of shear bond strength measurement of orthodontic adhesives with an emphasis on the type of test set up and load application. Although the test designs for measuring shear bond strength in orthodontics are still far from ideal, attempts must be made to standardize these tests especially in order to make comparison of different data easier. It is recommended that test designs be set up in such a manner that better matches with the purpose of the study.