فهرست مطالب fatemeh maleknejad

Reconstruction of hard dental tissue after endodontic treatment is a difficult and important duty of the dentist. According to the general opinion, endodontically treated teeth are inferior in quality, more brittle, predisposed to fractures and crackings. The aim of the present study was to compare the fracture resistance of endodontically treated maxillary premolars including MOD cavities with different restoration methods Ninety intact extracted human maxillary premolars were assigned to six different restoration methods. After endodontic treatment, MOD cavities with 2/3 inter cuspal distance was prepared and restoration was carried out by one of the following Group I: Buccal and palatal cusps were reduced 2mm and were restored with indirect composite onlay. Group II: The cavity preparation was same as group I, and then were restored with porcelain onlay. Group III: Reduction of palatal cusp was done as much as 2mm. One semihorizontal threaded pin was placed in buccal cusp and then was restored with amalgam. Group IV: The cavities were prepared same as group III and were restored with posterior resin composite.Group V: The MOD cavities were restored with amalgam. Group VI: The cavities were restored with posterior composite. The teeth in all groups were subjected to thermocycling and mechanical loading. Then all specimens were loaded to failure with static force in a universal testing machine at 0.5 mm/min. The mode of fracture was determined using a stereomicroscope and classified according to 3 categories, cohesive failure of tooth, and cohesive failure of restoration and mixed. Data were analyzed with ANOVA and Tukey test (=0.05). ANOVA showed significant differences among groups (P<0.001) Tukey test found that the highest fracture resistance were in groups I, II IV. The most unfavorable fracture site was occurred in group 1. Endodontically treated maxillary premolars with wide MOD cavities could be successfully restored by indirect composite and porcelain onlay and semihorizontal threaded pin plus composite.

Background and aims. Adhesive permeability is hindered byapplication of an additional layer of hydrophobic resin, which increases its concentration within the hydrophilic layer, reduces its affinity to water, and enhances its physical prop-erties. The aim of the present study was to evaluate the effect of a hydrophobic layer on the microleakage of class V com-posite restorations using different adhesives.Materials and methods. The adhesives including total-etch Scotchbond MP and Single Bond, and the self-etch Clearfil SE Bond and Clearfil S3 Bond were applied to 80 class V cavities in vitro on the buccal surface in CEJ and then were fol-lowed by hydrophobic resin (Margin Bond) in half of the cavities in each group (n=10). After restoration with microhybrid composite, Z100 and immersion in fuchsine, the degree of microleakage was assessed. Data were analyzed using the Kruskal-Wallis, Man-Whitney, and Wilcoxon tests.Results. The hydrophobic layer significantly reduced the microleakage of Clearfil SE Bond and Clearfil S3Bond only in dentin (p<0.05). There was no significant difference between enamel and dentinal margins in Clearfil S3 Bond, Clearfil SE Bond plus Margin Bond, and Clearfil S3 Bond plus Margin Bond (p>0.05).Conclusion. Within the limitation of this study, only Clearfil S3 Bond could demonstrate the identical values of micro-leakage in enamel and dentinal margins.

Theoretical and clinical teachings in dentistry are not always according to the dentistry curriculum requirements، but they serve as the basis upon which Dentistry graduates start their own practice. The aim of this study was to find the resemblance between dentistry curriculum requirements with clinical experiences in restorative clinics of Mashhad Dental School in the two academic years of 2007 & 2008. Recorded data related to the teachings devoted to posterior Amalgam and Composite restorations were gathered from the archive of Restorative Department of Mashhad Dental School. Teaching volume was determined by considering the number of lecturers and sessions of preclinical exercises in the operative simulation laboratory during the General Dentistry program. Data available for direct posterior restorations placed by fourth، fifth and sixth year students were gathered from the students'' report papers. The collected data were coded and categorized according to the surface number of posterior amalgam fillings (AFS1، AFS2، AFS3) and posterior composite fillings (CFS1، CFS2، CFS3). These finding were placed on spreadsheets of Excel program and the related bar graphs were constructed for comparison of the devoted teaching volume and practice with the Dentistry curriculum requirements and the number of posterior amalgam and composite restorations. Theoretical and practical teachings of amalgam and composite restorations have been in favor of amalgam with the ratio of 2 to 1. Clinically، practiced posterior composite restorations were 3 times more than the curriculum requirement. For the placement of three surface posterior restorations، amalgam favored over composite. Shift to the placement of posterior composite restorations needs to be addressed within dentistry curriculum، so the newly graduated dentists are prepared to place composite restorations properly.

The adhesives type and placement application technique may be important in long term stability and function of composite veneers. This study was conducted to evaluate the influence of dentin adhesive application techniques (pre-curing vs. non-curing) on micro leakage and marginal adaptation of indirect composite veneer restorations. A total etch bonding system, Excite/Variolink II (EXV), and a self-etching primer system, Panavia F 2.0 (PF2) were used in this in-vitro investigation. Forty-eight human central incisors were prepared for composite veneer restoration. These teeth were then divided into two groups (n=24). Pre-cure adhesive (PC) with light cure technique as well as no pre-cure (NPC) prior to resin cement insertion in half of specimens in each group. By using these methods, we worked with four experimental subgroups (PC+EXV, NPC+EXV, PC+PF2, NPC+PF2). Composite veneers (Tetric Ceram resin) were cemented using a dual-cured resin luting agents. All specimens were then stored in distilled water at 37oC for 24 hours before checking for marginal leakage. By random sampling, two specimens were selected from each group for SEM observations and evaluation of marginal adaptation at 1050 time magnifications. Data was analyzed by ordinal regression and link function of probit type at α ≤0.05. The highest and lowest micro leakage values were observed in dentinal margins of NPC+EXV and PC+EXV subgroups respectively. A significant difference was observed between dentinal and enamel margins on micro leakage values of PC and NPC groups (P<0.05), meaning that, pre-cure adhesive was more effective than resin cements alone. No adhesive layer was observed in non pre-cured adhesive specimens. The effect of pre-curing adhesive was not material specific. The pre-cured adhesives showed the best resistance to dye penetration, although the film thickness of luting agent was slightly increased.

The aim of this study was to compare a one-year clinical performance of two composites (Ariston PHC with Tetric) in class II cavity preparations. Ninety-six class I and II modified cavity preparations in identical patients were prepared. Metallic matrix was used for restoration of class II preparations. Ariston PHC and Tetric were used for restorations. The clinical criteria consisted of post-operative sensitivity, marginal discoloration, recurrent caries and marginal adaptation that were evaluated after one year. The Fisher’s exact test, t-test and Chi-square Pearson were used for analysis of data (P≤0.05). There was no significant difference between the two composites regarding post-operative sensitivity and marginal adaptation. Marginal discoloration by Ariston PHC was significantly less than Tetric. Most of this marginal discoloration was observed in proximal margins of class II restorations. There were only two recurrent caries (5.1%) in cervical margins of Tetric restorations.The maxilla and mandible did not have a significant effect on clinical criteria. There was no significant difference in post-operative sensitivity between the two composites. Marginal discoloration using Ariston PHC was significantly less than that of Tetric. No significant failure was observed when using any of the composites.

Restoration of endodontically-treated anterior teeth with weakened roots requires special attention. The purpose of this investigation was to compare the fracture resistance of experimentally weakened anterior roots reinforced with three different methods using tooth-colored materials. Forty human sound maxillary central incisors were used in this in vitro study. The crowns of 30 teeth were removed 2mm above the CEJ. After root-canal therapy, flared canals were simulated. The teeth were filled with D.T. light-post plus resin composite (Clearfil DC Core Automix) in group 1, D.T. light-post plus two accessory posts (Reforpin+Panavia F 2.0) in group 2 and D.T. light-post plus Panavia F 2.0 in group 3. Access cavities in the fourth (control) group were restored after ideal root-canal therapy. Following cementation of the posts and restoration of the crowns with Clearfil Photo-Core composite, the roots were embedded in acrylic resin blocks, 1 mm below the CEJ. After 24h storage, the samples were loaded in an Instron testing machine with a crosshead speed of 0.5 mm/min at a 45° angle to the long axis of the tooth on the palatal surfaces until failure. The data were analyzed using ANOVA and Tukey test (P=0.05). The lowest (300.17 N) and highest (585.11 N) mean fracture resistance values were observed in the third and fourth groups, respectively (P<0.05). These values were not significantly different between the first, second and third groups. The results showed that Reforpin could be used as an alternative to resin composite for internal reinforcement of weakened roots.

Although light cured composites are easily accessible, self/dual-cure cements and composite resins also have broad clinical applications. The aim of this study was to evaluate the incompatibility between new adhesives and different types of cement and composite resin restorations and their effects on interface bond strength. All articles and theses on adhesives and cement/composite resin restorations up to June 2005, available at Mashhad dental school library, medline and other internet information banks were collected and evaluated. Some two–step-total-etch and one–step-self–etch adhesives were incompatible with self/dual–cured cements and composite resins. This is due to the large concentration of acidic, ionic and hydrophilic resin monomers that result in adverse chemical interactions and increased permeability of these adhesives. In order to prevent the adverse acid-base chemical interactions between simplified adhesives, light cured cements or composites or dual cured adhesives containing catalysts should be used. For neutralizing the permeability effect of simplified adhesives, light cured composites or a single layer of unfilled resin bonding or flowable composites should be applied over the adhesive layer to induce rapid curing.

This invitro study evaluated the effect of ultrasonic cleanser after casting surface treatment on bond strength of alloy to enamel. Therefore, the aim of this study was to evaluate the effect of ultrasonic on bond strength of etched base metal. 80 sound canines were selected. After cleaning and mounting in cold cured acryle, rectangular Ni-Cr-Br plates with 9 mm2 surface area and 0.5 mm thickness were made that adapted with lingual surfaces. One process was created in mid part of each plate. Fitting surface of all samples were sandblasted. They were divided into two groups of 40,based on the type of treatment: A)surface treatment with acidic M3 gel. B) surface treatment with 150-200µ alumina sandblast. Finally each group was divided into two subgroups of 20, based on using the ultrasonic or without using it. Then samples were adhered to lingual surfaces with Scotch Bond Mulit Purpose (3M – Co). and Duo Cement (Coltene). After 1000 thermal cycling, shear test was established by cross head speed of 2mm/min. Data analysis was done by two variables ANOVA with 95% significance level. 1. Mean bond strength was significantly greater in subgroup without ultrasonic use (60-74 kg) than the other subgroups (45-62kg). 2. The group using just M3 acidic gel without ultrasonic had the greatest bond strength (74.52 kg). 3. Comparing two factors (Sandblast- Acid), bond strength was greater after using acid. 4. Increase in bond strength was observed in all groups without ultrasonic use. Use of M3 acidic gel without ultrasonic use increases the bond strength of Ni-Cr-Br alloy to enamel significantly.