Frontiers in Dentistry
Volume:3 Issue: 2, Spring 2006

Statement of Problem: Perforations are significant complications that can occur during root canal therapy and may result in the destruction of adjacent periodontal tissues. An ideal material for repairing a perforation should be biocompatible and have a high sealing ability. The aim of this study was to compare histologic tissue responses of experimentally induced pulp chamber perforations in dogs’ teeth repaired with amalgam, light-cured glass ionomer and Mineral Trioxide Aggregate (MTA). Fifty-four lower premolars of 9 dogs were used for this interventional study. Access cavities were prepared and perforations were created on the floors of the pulp chambers. The samples were divided into three experimental groups of 12 teeth and positive and negative control groups consisted of 12 and 6 teeth, respectively. The perforations in the study groups were sealed with amalgam, light-cured glass ionomer and MTA. All access cavities were filled with light-cured glass ionomer. Five dogs were sacrificed after seven days and 4 dogs were put to death after 28 days. The premolars along with the surrounding alveolar bone were cut in block sections and histologically evaluated for inflammation, bone formation and epithelial proliferation. The data were analyzed by Kruskal-Wallis and Mann-Whitney tests. A statistically significant difference was observed in inflammation and bone regeneration, between amalgam and MTA at both time periods. It appears that MTA and GI are more suitable materials for perforation repair, as compared to amalgam

Statement of Problem: Mineral trioxid aggregate (MTA) cement is widely used for root-end filling, pulp capping, perforation repair and other treatments in endodontics. Investigations have shown similar physical and chemical properties for Portland cement (type I), Root MTA and ProRoot MTA. The aim of this in vivo study was to evaluate the reaction of dog canine pulp after pulp capping with Root MTA and Portland cement versus ProRoot MTA. All four canines from fifteen healthy dogs, 12-18 months of age, were mechanically exposed via buccal class V cavities under aseptic conditions. MTA, Portland cement and Root MTA were prepared according to the manufactures’ instructions and placed in the cavities. Tricresol formalin was used in the control group. After 4, 8 and 12 weeks, the animals were sacrificed and the teeth were fixed and processed for light microscopic analysis. The presence and thickness of the dentinal bridge and the degree of inflammation were evaluated. Data were submitted to Mann-Whiteny and Kruskal Wallis tests for statistical analysis. No statistically significant difference was found in the presence and thickness of the dentinal bridge, and the degree of inflammation between Root MTA, Portland cement and ProRoot MTA (P>0.05). Root MTA, Portland cement and ProRoot MTA showed similar comparative results when used as direct pulp capping materials. The results of this study support the idea that Portland cement and Root MTA have the potential to be used in clinical situation similar to those in which ProRoot MTA is being used.

Statement of problem: It is yet unclear whether fiber-reinforced composite posts can enhance the mechanical properties and prevent vertical fractures of teeth under chewing loads. The purpose of this study was to compare the fracture resistance and failure mode of endodontically treated teeth restored with three different post systems. Thirty-six maxillary canines were randomly divided into three groups (n=12). All teeth received endodontic therapy and one of three post systems of cast post-and-core, zirconia fiber post, and quartz fiber post. Cast posts-and-cores were cemented using zinc phosphate cement, fiber posts were luted with dual-cured resin cement, and composite cores were prepared. Compressive load was applied at a 135° angle to the long axis of the tooth at a crosshead speed of 1mm/min until fracture occurred. One-way ANOVA and Tukey-Karmer test were used to determine the difference of the failure loads between the groups (α=0.05). The mean values (SD) for fracture resistance were 1631(803), 513(348) and 789(390) N in the cast post-and-core, zirconia fiber post and quartz fiber post groups, respectively. Teeth restored with cast posts-and-cores exhibited significantly higher resistance to fracture (P<0.01); however, 92% of the fractures occurred in the tooth structure. There was no statistically significant difference in fracture resistance between the zirconia fiber and quartz fiber post groups. Fracture mainly occurred in the composite cores of these groups. This study showed that the fracture resistance of cast post-and-core was significantly higher than zirconia and quartz fiber posts; however, the failure mode was more favorable in teeth restored with fiber posts.

Statement of problem: The guided bone regeneration (GBR) technique does not always produce consistent results. Bone filling within the space provided by the membrane can be incomplete. The aim of this study was to evaluate the effect of a collagen membrane (Bio-Gide) in combination with or without deproteinezed bovine bone mineral (Bio-Oss) on the healing of calvarial defects in rabbits. Twelve New Zealand white rabbits were used in this randomized single-blind experimental study. Four equal defects were created on the calvarium of all animals. Each defect in each rabbit was randomly assigned to one of the following treatment groups: Group 1(control), no treatment; Group 2, covered with Bio-Gide; Group 3, filled with Bio-Oss; Group 4, filled with Bio-Oss and Bio-Gide. The animals were sacrificed for histologic and histomorphometric analysis, 30 and 60 days after treatment. A significant difference was not observed in regenerated bone between the control and Bio-Gide groups (P>0.05), at 1 and 2 months. The amount of regenerated bone was significantly higher (P<0.05) in the Bio-Oss and Bio-Oss+Bio-Gide groups as compared to the control group. The difference in regenerated bone was not significant (P>0.05) between the Bio-Oss and Bio-Oss+Bio-Gide groups. Bone regeneration increased significantly in all treatment groups, between the two study periods (P<0.05). In groups 3 and 4, the presence of a collagen membrane did not affect the amount of new bone regeneration. According to these results, use of a collagen membrane has no additional benefit in the regeneration of intrabony defects.

Statement of Problem: Digital Subtraction Radiography (DSR) needs reproducible alignment between the x-ray source, the object, and the film for obtaining identical projections of the same anatomic region. The aim of this study was to evaluate the effect of bite registrations (placed on individual bite blocks) on the reproducibility of parallel periapical radiographs, obtained every 2 months, in patients undergoing periodontal surgery for furcation involvement. Ninety eight parallel periapical radiographs were used in this study. The radiographs were taken with individual bite-blocks attached to the beam-guiding device. In order to individualize the bite blocks, bite registrations were fabricated using silicon impression material, and were placed on the individual bite blocks. All radiographs in each series were processed under similar conditions and were digitized with the flatbed scanner fitted with a transparency adaptor (hp Scanjet 7400) at 300 dpi resolution. Reproducibility of this method for obtaining similar parallel periapical radiographs was assessed by measuring the horizontal and vertical distances between two selected unchanged reference points on each radiograph and comparing them in each series. Reliability of measurements was analyzed using the one way random model intraclass correlation coefficient for average of raters. For both measurements (Horizontal and Vertical) statistically significant reliability was found between three repeated radiographs with two month intervals in 16 patients, as well as 5 repeated radiographs with two month intervals in 10 patients (P<0.001). The result of this study shows that bite registration on individual bite blocks is enough for obtaining identical parallel periapical radiographs.

Statement of Problem: Assessment of mandibular size and position is essential when planning a treatment strategy for patients with Class II malocclusion. This study was carried out to evaluate the mandibular size and position of 8-13 year-old children with Class II Division 1 malocclusion whom were referred to the Faculty of Dentistry, Shiraz University of Medical Sciences, Iran. 935 lateral cephalograms of children with normal occlusion (425 films) and Class II Division 1 patients (510 films) referred to the Department of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences, during 2002 to 2004 were evaluated. The control and Class II Division 1 subjects were each divided into three groups according to age (8-9, 10-11 and 12-13 years), and were further divided into two subgroups according to gender. The radiographs were converted to computer-readable X and Y coordinate and data obtained from 29 linear and angular measurements in the cranial base, mandible and dentition, were compared. The cranial base angle was significantly larger in Class II Division 1 patients as compared to the control subjects. A smaller mandible along with a protrusive dentition was observed in the test group. The form and position of the mandible was also different in comparison to normal cases. All class II patients showed a vertical growth pattern and an increased facial height. The main factors responsible for class II Division 1 malocclusion in 8-13 year-old children in present study were retropositioning of the lower jaw and a short mandibular length.

A new design for anterior fixed-partial denture (FPD) and crown is described. This article presents its advantages, disadvantages, indications and contraindications. The new design which has been exercised for 8 years provides esthetics and high strength for the restorations and the results have been satisfactory.

A case of maxillary antrolith in a 14-year-old girl is presented. A radiopaque mass, thought to be a supernumerary tooth, was incidentally found on a panoramic radiograph obtained for orthodontic purposes. During surgical exploration the maxillary sinus was penetrated and 6 calcified masses were discovered. Histopathologic analysis revealed a calcium deposition around a necrotic mass.