A. Pahlavan , S. Banava ,
Volume 16, Issue 4 (9 2004)
Abstract
Statement of Problem: Composite reins have recently become popular for posterior teeth restorations. Gap formation and subsequent microleakage are of the complications resulting from such restorations. One of the techniques to overcome polymerization shrinkage of composite resins is sandwich technique (application of glass ionomer as a base beneath the composite resin). Since polymerization patterns in two types of composite resins (light cure and self cure) differ from each other, various effects on the bond strength between glass ionomer and dentin are expected.
Purpose: The aim of this in vitro study was to evaluate the effects of self- cure and light- cure composite resins in sandwich technique on the bond strength of light cure glass ionomer and dentin.
Materials and Methods: 40 extracted human premolars were selected and divided into four groups:Group 1: Light cure glass ionomer of 1mm thickness was placed on dentin.Group 2: 1mm thickness of light cure glass ionomer plus a mass of self cure composite resin of 2mm thickness were placed.Group 3: 1mm thickness of light cure glass ionomer plus light cure composite resin as two separate 1mm layer were placed.Group 4: 1mm thickness of light cure glass ionomer with 37% phosphoric acid etching followed by two separate layers of light cure composite resin of 1 mm thickness were placed.SEM was used to determine gap size ai Gl- dentin and Gi- composite interlaces. The findings were analyzed by ANOVA and t-student tests.
Results: Groups 1 and 2 showed no gap at Gl-dentm interface and also cracks were not observed in all these specimens. In group 3, there was gap between light cure GI and light cure composite resin and cracks were seen in GI, too. Group 4 showed gap at both interfaces and more cracks were seen in GI. Groups I and 2 showed the least gap formation and group 4 showed the most. Statistically significant difference was found between groups 3, 4 and group 1 (control), 2.
Conclusion: Base on this study, the application of self-cure composite resin on light cure GI showed no gap and crack formation on Gl-dentin and Gl-composite interfaces and GI itself. However, light cure composite resins and glass ionomer etching aggregated crack and gap formation.
S. Banava , K. Najibfard , Mh. Ghahremani , Sn. Ostad ,
Volume 20, Issue 1 (4 2007)
Abstract
Background and Aim: An important requirement for a dentin bonding agent is biological compatibility. Since dentin bonding agents are placed in cavity preparations with subgingival extensions, with direct contact to gingival and mucosal tissues, tissue response to these materials must be investigated. The aim of this study was to examine the cytotoxicity of AdheSE, a self etching adhesive, on human gingival fibroblasts.
Materials and Methods: In this experimental in vitro study, primary human gingival fibroblasts were exposed to different dilutions of primer & bond of AdheSE (Vivadent, Liechtenstein). The toxicity of the primer was tested in 30 seconds, 300 seconds and 24 hours. The cytotoxicity of the bond was analyzed in uncured mode after 20 seconds, 5 minutes and 24 hours. In cured mode, tested materials were analyzed after 24 and 48 hours. Cytotoxic effects were evaluated using MTT, cell counting and DNA condensation assays. Data were analyzed by two way repeated measure ANOVA with p<0.05 as the level of significance.
Results: MTT Assay revealed that uncured AdheSE Bond was toxic only in 10-1 dilution and the difference with control group was significant (P<0.05). By increasing the time to 300sec. and 24h, dilutions of 10-2 and 10-4 were the most cytotoxic respectively. Cytotoxicity of uncured primer after 30 sec. and 300 sec. began from 10-2 and after 24h began from 10-2 and reached to 10-1. AdheSE in cured mode showed significant difference with control group in 1:2 (P<0.001),1:4 & 1:6 (P<0.01) dilutions. In cell counting assay only the 1:2 dilution was significantly more toxic than control group. Apoptosis (a morphological and biochemical distinct form of cell death that regulates cell turnover) comprised in less than 5% of total death in both cured and uncured adhesives.
Conclusions: Based on the results of this study, by increasing the exposure time, smaller amounts of bonding could be cytotoxic. Cytotoxicity was related to material, dilution, time of exposure and curing. It would be necessary to identify the toxic ingredients of this adhesive and replace them by more biocompatible components.
E. Jalalian , S. Banava , S. Erfani ,
Volume 20, Issue 3 (4 2007)
Abstract
Background and Aim: Considering flexural strength of fiber-reinforced composites (FRC) and also the role of conservative cavities in protecting sound tissue of abutments, the aim of this study was to evaluate the fracture resistance of these bridges by handmade samples in vitro.
Materials and Methods: In this experimental in vitro study, 44 sound newly extracted teeth were used to make 22 fixed inlay bridges including 11 three unit anterior upper inlay bridges substituting clinical model of upper central and 11 three unit posterior lower inlay bridges substituting clinical model of lower first molar. Specimens were prepared with FRC and mounted with artificial PDL in acryl. Cases were exposed to final load by using Universal Testing Machine (Instron 1195) with the speed of 1 mm/min. Statistical analysis was performed by Kolmogorov- Smirnov, independent sample T and Kaplan-Meier tests with p<0.05 as the level of significance.
Results: Based on the statistical tests, the 95% confidence interval of mean was 450-562 N in anterior and 1473- 1761 N in posterior area. Fracture strength was high in the studied groups. Fractures in both groups occurred on composite facing, and the framework remained intact. The highest percentage of fracture in posterior teeth was in the middle of pontic towards the distal connector and in the anterior teeth in the lateral connector, between central pontic and lateral abutment. Using the independent sample T test a significant statistical difference was observed between two groups (P<0.001). The fracture resistance of anterior samples was lower than the posterior ones.
Conclusion: Based on the results of this study regarding the high fracture resistance in both areas FRC inlay bridges could be recommended for upper anterior and lower posterior teeth in clinical dentistry certainly more studies are needed to ascertain this treatment option.
Sh. Nasermostofi, A. Raghanians, S. Banava, E. Jalalian, A. Abdollah,
Volume 22, Issue 1 (11 2009)
Abstract
Background and Aim: A key factor in restoring the endodontically treated teeth is ferrule preparation. When the ferrule is absent, occlusal loads may cause the post or root to fracture. The purpose of this in vitro study was to evaluate the effect of ferrule preparation on fatigue resistance of teeth restored with quartz-fiber posts.
Materials and Methods: Twenty single-rooted lower premolars having similar dimentions were randomly devided into two groups of 10. In control group the teeth were prepared with 3-mm of remaining coronal tooth structure and in test group teeth were prepared with 1-mm of remaining coronal tooth structure. The teeth were endodontically treated. 9-mm long Post holes were prepared, and D.T. light quartz-fiber(RTD,France) posts were cemented with Panavia F2(Kuraray,Japan).Then the core build up was done with Bisco core build up composite(Bisco,USA) and full metal crowns were cemented with Zinc phosphate(Harvard cement, Germany). All specimens were mounted in acrylic resin blocks and intermittently loaded (180 N) at an angulation of 45- degree to the long axis of the teeth at a frequency of 4 loads per second, until failure occurred.
Results: There was significant difference between the loads cycles of two groups studied. (p<0.0001).
Conclusion: The results of this study showed that an increased amount of coronal dentin significantly increases the fracture resistance of teeth restored with quartz-fiber posts.
