Frontiers in Dentistry
Volume:1 Issue: 4, Autumn 2004

Statement of Problem: In some clinical situations, repair of composite restorations is treatment of choice. Improving the bond strength between one new and old composite usually requires increased surface roughness to promote mechanical interlocking since chemical bonding might not be adequate. Similarly, the treatment of a laboratory fabricated resin composite restoration involves the same procedures, and there is a need to create the strongest possible bond of a resin cement to a previously polymerized composite. The aim of this study was to evaluate the effect of various surface treatments on the shear bond strength of repaired to aged composite resin. Eighty four cylindrical specimens of a composite resin were fabricated and stored in distilled water for 100 days prior to surface treatment. Surface treatment of old composite was done in 6 groups as follow: 1- Air abrasion with CoJet sand particles with micoretcher  silane  dentin bonding agent 2- Air abrasion with 50µm Al2O3 particles phosphoric acid silane dentin bonding agent 3- Air abrasion with 50µm Al2O3 particles  phosphoric acid  dentin bonding agent 4- Diamond bur  phosphoric acid  silane  dentin bonding agent 5- Diamond bur  phosphoric acid  dentin bonding agent 6- Diamond bur  phosphoric acid  composite activator  dentin bonding agent Then fresh composite resin was bonded to treated surfaces. Twelve specimens were also fabricated as control group with the same diameter but with the height twice as much as other specimens. All of the specimens were thermocycled prior to testing for shear bond strength. The bond strength data were analyzed statistically using one way ANOVA test, t test and Duncan''s grouping test. One-way ANOVA indicated no significant difference between 7 groups (P=0.059). One-way ANOVA indicated significant difference between the three diamond bur groups (P=0.036). Silane had a significant effect on the repair bond strength of diamond bur/silane group. There was no significant difference in the bond strength diamond bur/composite activator group and diamond bur/no silane group. Silane had no significant effect on the repair bond strength of air abrasion group. The lowest bond strength was for diamond bur/ composite activator group. The best surface treatment for repair of an aged composite restoration could be used of diamond bur with silane, air abrasion with or without silane or ceramic deposition with CoJet Sand system. Silanation is a necessary step in the repair of composite resin with the use of diamond bur but not with the use of air abrasion.

Statement of Problem: Microleakage is the most important factor in composite restorations failure, resulting in marginal degradation, marginal staining, secondary caries and pulp damage. One of the factors that influence microleakage is the method of caries removal. Convention rotary instrumentation generates smear layer on the dental surface, whereas chemo-mechanical caries removal increases surface roughness. The aim of this study was to compare the microleakage of composite restorations following caries removal via conventional versus chemo-mechanical methods. One hundred class V carious human posterior teeth were randomly divided into two equal groups. Caries were completely removed with carbide burs in group one and according to manufacturer''s instruction in chemo-mechanical group (Carisolv group or group two). Then the same composite restorative material, followed by finishing and polishing, filled all the cavities. Subsequently the specimens were thermocycled and then placed in dye solution. The teeth were sectioned through the restorations and evaluated for microleakage scores using a stereomicroscope. The data were analyzed using Mann-Whitney-U test. Prevalence of scores 0 and 1 of microleakage in occlusal margins in group one was 80% and 20%, respectively and in group two 74% and 36%, respectively. Prevalence of scores 0, 1 and 2 of microleakage in gingival margins in group one was 56%, 36% and 8%, respectively and 42%, 42% and 16% in group two, respectively. Scores 3 and 4 of microleakage were not seen in any of the groups. Statistical analysis showed significant difference in microleakage between occlusal and gingival margins in each group (P<0.05) but not between the two methods (P>0.05). The results from this study indicate no significant difference in microleakage between conventional and chemo-mechanical caries removal methods.

Statement of Problem: Recently, it has been proposed that different adhesive materials can be used for direct pulp capping. Previous studies have demonstrated that multi steps dentin adhesives could form reparative dentin similar to calcium hydroxide (CH). The aim of this study was to evaluate the histological pulp response of ninety mechanically exposed cat pulps to two adhesive resins (Scotch Bond MP and Single Bond 3M) were compared with a calcium hydroxide cement (Dycal, Dentsply). Class V facial cavities with similar pulpal exposures were prepared in canines. In the experimental groups phosphoric acid was used to etch the enamel and dentin and pulp exposure, and after it dentin adhesives was applied. The exposure point of the control group was capped with Dycal then the remainder of the cavities was etched and a dentin adhesive (single bond) was applied. All of the cavities were restored with a composite resin (Z 100) in usual manner. The animals were scarified after 7, 30 and 60 days (n=30), and the pulp evaluated histologically, statistical analysis was carried out with Kruskal- Wallis test (α=0.05). The data showed that most of the cases had mild inflammation of pulp tissue. There was no significant difference in inflammatory reaction of pulp by Dycal and two adhesive systems, severe inflammatory reaction of pulp was observed only in most of the 30- day Single Bond group. Soft tissue organization of dentin bridge was less than Scotch Bond and Dycal groups, the differentiation of dentin bridge was less than Scotch Bond group after 7 days. Slight inflammatory cell infiltration was the main reaction of exposed pulp when two commercially available adhesive resins were placed directly on the exposed pulp. There was no significant difference in inflammatory reaction of pulp between Dycal and two adhesive systems after 7 days and 60 days. After 7 days most of the specimens showed an amount of predentin deposition.

Statement of Problem: Many studies have indicated that genetic disturbances are common findings in patients with Oral Squamous Cell Carcinoma (OSCC). Identification of these changes can be helpful in diagnostic procedures of these tumors. The aim of this study was to appraise the chromosomal disorders in blood and tissue patients with OSCC. Methods and Materials: In this descriptive study, the study group consisted of all OSCC patients who were referred to the Faculty of Dentistry, Tehran University of Medical Sciences, Maxillofacial Surgery Clinic of Shariati Hospital, and Amir Aalam Hospital from September 2000 to November 2002. In order to study chromosomal disorders in the peripheral blood lymphocytes, 5 mL of blood was obtained from each patient In patients with the large lesion, a piece of involved tissue were obtained and cultured for 24 hours. This led to 29 blood samples and 16 tissue specimens and any relation between OSCC and age, sex, smoking and alcohol use were evaluated. In this study, OSCC was more common in males than in females (3 to 5). 31% of our patients were smokers, and one had a history of alcoholic consumption. There was an increase in incidence of OSCC with age. In this study, all patients had numerical (aneuploidy, polyploidy) and structural chromosomal disorders (double minute, fragment, breakage and dicentric). There was significant difference between blood and tissue chromosomal disorders (aneuploidy, polyploidy,breakage) in OSCC patients. It can be concluded that chromosomes in patients with OSCC might show some genetic aberration and evaluation of involved tissue might be better way for determining this disorders.

Statement of the Problem: Endodontic surgery if required is considered as an additive therapy after classic endodontic treatments. The most prevalent type of endodontic surgeries are apicoectomy and corrective surgeries. Type of material applied in apicoectomies is of high importance. Root end filling material should not only be biocompatible but also provide appropriate seal. Considering these findings, the subject of this paper was to compare the histologic responses of the periradicular tissues after using Root MTA and Portland cement, as Root end fillings, with Pro Root MTA. The aim of the present study was to introduce a suitable material for root end filling. The canals of sixty maxillary canines of cats, after cutting the crowns and exposing the pulps, were instrumented 1 mm beyond the apex until 25 # file to develop periapical lesion after 28 days. They were then randomly divided into five groups. After apicoectomy, Pro Root MTA, Root MTA and Portland cement were placed, as root end filling materials in three experimental groups whereas the two remaining groups were considered as positive and negative controls. After 3, 6 and 12 weeks the animals were sacrificed and the specimens were stained for histologic evaluation under light microscope. The data were submitted to statistical analyses (Fisher exact test, k2 test and one- way variance analysis). No statistically significant difference was found between these three materials in cementum apposition on roots and implanted materials, fibrous capsule formation and the severity of inflammation, however, bone formation in Root MTA group was significantly less than pro Root MTA and Portland cement groups. The extent of inflammation thickness in Portland cement group was significantly less than Pro Root MTA group. According to these findings if long term investigations with larger sample size confirm the obtained results of the present study, Root MTA and Portland cement which are cost- effective and readily available, can replace Pro Root MTA in endodontic surgeries.

Statement of Problem: Due to the appearance of palatal height difference in orthodontic patients we decided to carry out this study. The purpose of this research was to determine palatal height in persons with normal occlusion and different malocclusions (class I, II Div I and III) and comparing them with each other. In this cross sectional research, 240 subjects were selected. Sixty cases (30 girls and 30 boys) with normal occlusion within 16-18 years old were selected in random cluster sampling from high schools in Mashhad. Examination technique was direct observation, lateral cephalometric radiography, impression and preparing study model for measuring. For every kind of malocclusion 60 young patients, 30 females and 30 males, within the range of 16-20 years old attended orthodontic treatment in private dental offices or Orthodontics Department of Mashhad Dental School. The examination technique was indirect observation, using lateral cephalometry selected of 5395 lateral cephalograms and related study models for measuring. Mean, minimum, maximum. and height of the palate was initially determined and then normal occlusion was compared with every kind of malocclusion using SPSS statistical software. One way analysis of variance (ANOVA), t-test (independent groups) and also Duncan test were used for comparison. The ANOVA test showed that there were no statistically significant differences between females in normal occlusion and different malocclusions (P=0.486). In boys the palatal height was significantly higher in class III males than class II and class I malocclusions and the height of palate for normal boys is significantly higher than class I malocclusion (P<0.05). Comparison of other groups was not significantly different. In each group height of palate was significantly lower in females than males (P<0.001). From this research we concluded that palatal height is different in females and males in normal occlusion and class III. The difference in palatal height between normal occlusion, class I, class II and class III malocclusions with each other in boys (P=0.003) was due to the difference between class I and class III, class II and III class I and normal. In comparison palatal height in the males the difference between normal occlusion and Class I malocclusion, also class III malocclusion were significant.

Statement of Problem: When a tooth is treated endodontically, there are several objectives, which must be met for the root canal therapy to be successful. One of those objectives is the complete obturation of the root canal system. The purpose of this study was to evaluate the apical sealability of the Theramfil endodontic obturation technique and compared it with lateral condensation. Thirty human maxillary permanent anterior teeth were similarly prepared. Following instrumentation, the roots randomly divided into two experimental groups of ten and two control groups (positive and negative) of five each. Ten roots were obturated with Thermafil and ten with lateral condensation. All immersed in Indian ink, then cleared and apical dye penetration was evaluated. Average leakage values were minimum of 1mm to maximum of 2.9mm for lateral condensation and minimum 2mm to maximum 6mm for Thermafil group. There was statistically significant difference between Lateral Condensation and Thermafil obturation techniques (P<0.05). The results of this study indicate that root canals treated by lateral condensation technique leak less than Thermafil ones.

Statement of Problem: Knowledge of internal anatomy of tooth plays an important role in a successful endodontics treatment. For a proper endodontic treatment, it is not only important to know the form of normal anatomy of tooth’s interior but one must also be acquainted with the possible diverse forms. A thorough understanding of the internal anatomy of human mandibular incisors (central and lateral). A total of 205 central and lateral mandibular incisors that had healthy roots were selected and put in 10% formalin solution. After cleaning the samples with the help of brushes and other devices, they were kept in 5% sodium hypochlorite solution. Finally the roots were cleaned and the samples were prepared for next stages. Three methods were used, coloring (fushin1%, radiography (buccolingual and proximal sides), and cross-sectioning (cervical- middle-apical). The result indicated that: - 88%of the teeth had a single canal and one apical foramen; - 8% of the teeth had a single canal and two apical foramena; - 3.5% of the teeth had two canals and one apical foramen; - 0.5% of the teeth had two canals and two apical foramena; A thorough understanding of the pulp morphology is essential for successful treatment of root canal. Therefore, a dentist should always be on the watch for the existence of two canals or a two-branched canal while working on the mandibular incisor teeth. it is essential to have the necessary precision in finding the second canal.