JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2016 | Volume:28 | Issue:1|Papers Count:6

Background and Aim: Data regarding the efficacy of universal adhesives are limited. This study aimed to assess the durability of a universal adhesive bond to superficial dentin using etch and rinse and self-etch modes. Materials and Methods: In this in vitro, experimental study, 32 sound molars were randomly divided into two groups of Scotchbond Universal adhesive with two-step etch and rinse mode and Scotchbond Universal adhesive with one one-step self-etch mode as recommended by the manufacturer. Coronal part of teeth was restored with composite. The teeth were mounted in acrylic blocks and prepared according to the trimming protocol. The specimens were then randomly divided into two groups of immediate and 5000 thermal cycles and were then subjected to tensile load at a crosshead speed of 1mm/minute. Data were analyzed using two-way ANOVA. Results: The interaction effect of the two independent variables on microtensile bond strength was not significant (P=0. 957). Bond strength in etch and rinse group was significantly higher than that of self-etch group (P<0. 001). Bond strength in thermocycling subgroups was significantly higher than that of immediate subgroups (P=0. 034). Conclusion: Etch and rinse mode was superior to self-etch mode for use of Scotchbond Universal, and thermocycling increased the bond strength of this adhesive.

Background and Aim: Debonding is the most commonly encountered failure in teeth restored with fiber posts that mainly occurs at the weakest interface (dentin-cement interface). Thus, reinforcement of this interface is mandatory. The aim of this study was to evaluate the effect of different root dentin surface treatments after post space preparation on bond strength of fiber posts cemented with a self-adhesive resin cement. Materials and Methods: Forty extracted sound single-rooted teeth underwent root canal therapy. After post space preparation, the teeth were assigned to four group of 10 teeth according to the type of dentin surface treatment: Group 1: 2% chlorhexidine rinse, group 2: 37% phosphoric acid etching and then irrigating with saline, group 3: rinse with xylene and then irrigation with saline, group 4: rinse with saline (control group). Then, fiber posts were cemented with Total cem cement and the teeth were sectioned horizontally. Specimens were observed under a stereomicroscope at X10 magnification and failure modes of each group were determined. Results were analyzed by one-way ANOVA. Results: There was no significant difference between the mean bond strength of the four groups (P=0. 174). The highest mean bond strength value was found in phosphoric acid group (8. 18± 3. 19 MPa) and the lowest belonged to the control group (6. 21± 1. 81 MPa). Conclusion: Our results showed that dentin surface treatment with phosphoric acid before cementation of fiber posts with a self-adhesive cement improves the bond strength.

Background and Aim: Microleakage is a drawback of composite restorations and it is more noticeable in dentinal walls. Despite advances in dentin bonding agents, no adhesive can completely eliminate microleakage and provide a hermetic seal. This study aimed to compare microleakage of three resin bonding agents namely a universal adhesive, two-step self-etch system and two-step total-etch system. Materials and Methods: This in vitro, experimental study was conducted on 68 human molars. Class V cavities were prepared in the buccal or lingual surfaces of the teeth with occlusal margins in the enamel and gingival margins in dentin. The teeth were then randomly divided into four groups of 17. Group A: Adper Single Bond 2, group B: Clearfil SE Bond, group C: Scotchbond Universal adhesive (self-etch) and group D: Scotchbond Universal adhesive (total-etch). The teeth were then restored using different bonding agents and a microhybrid composite resin. The specimens were then subjected to 1000 thermal cycles between 5-55° C. The entire restoration surface except for 1mm around the margins was coated with nail varnish. The teeth were immersed in 2% methylene blue for 24 hours and sectioned longitudinally in a buccolingual direction and observed under a stereomicroscope to determine microleakage. Microleakage in use of the three bonding agents was compared using the Kruskal Wallis test (P<0. 05). Results: Based on the Kruskal Wallis test, no significant difference was noted in enamel and dentin margins among different adhesives but the enamel margin showed less microleakage than the dentin margin. Conclusion: Different adhesive systems tested in this study showed similar microleakage at the enamel and dentinal margins.

Background and Aim: The use of ceramics has a long history. A new category of these materials was used in medicine in 1960 introduced as bioceramics. Biocompatibility, osteoinductivity and sealing ability are among the most favorable characteristics of endodontic bioceramics. Introduction of mineral trioxide aggregate (MTA) revolutionized endodontics and this new era is progressively growing. Materials and Methods: This article reviews endodontic bioceramic materials in the Iranian market such as different types of MTA (ProRoot, Angelus, Root MTA), calcium enriched mixture (CEM) cement, Endo Sequence, iRoot products and MTA Fill apex sealer. Electronic search was carried out for the existing literature in PubMed, Medline and Google Scholar from July 1995 to January 2016 and more clinically applicable data were collected. Conclusion: Favorable characteristics and promising results of bioceramics make them suitable for use in endodontics and new products of this generation are increasingly introduced to the dental market.

Background and Aim: Different attachment designs have been developed to connect implant to natural teeth in partial dentures; however, adequate studies have not been performed to determine stress distribution patterns in these designs. The present study aimed to assess stress distribution patterns in natural tooth and implant supported removable partial denture with different attachment designs using photoelastic analysis. Materials and Methods: In this in vitro, experimental study, a photoelastic model of a partially edentulous mandible was fabricated and two Ankylosis implants were inserted at the site of first molar teeth bilaterally. Implants and teeth were connected by a partial denture and the acrylic base and implants were connected using ball and telescopic crown attachment types. Two crowns, one with resilient and the other one with rigid attachment were fabricated on the abutment teeth. Separate frameworks were designed and removable partial dentures were fabricated. Next, 100 N load was applied vertically to the area between implant and tooth. The pattern of stress distribution in implant in use of different implant-tooth attachment designs was studied by means of photoelastic method. Results: The lowest stress concentration was noted in use of resilient attachment while rigid attachment showed the highest level of stress concentration. Conclusion: Resilient attachment between implant and tooth created minimum stress concentration in implant; however, removable partial dentures were slightly instable in use of this attachment type. The decision to use different implant-tooth attachment types must be made based on clinical conditions.

Background and Aim: Inappropriate transfer of pressure during final impression making in fabrication of complete denture can result in ridge resorption. This study aimed to assess the effect of vent size and spacer thickness on pressure produced during maxillary edentulous impression making by different impression materials in vitro. Materials and Methods: This experimental study was carried out using a maxillary edentulous model, two types of impression materials (regular body addition silicone and zinc oxide eugenol) and two types of trays with spacer thicknesses of 0 and 1. 5 mm and each thickness with four vent sizes of 0, 0. 5, 1 and 2 mm. Totally eight types of trays for each impression material (80 samples) were used. Impressions were made and transferred pressure in the first molar area of edentulous ridge and mid-palatal raphe was measured (g/mm2) by two load cells. Data were analyzed using two-way ANOVA, post hoc Tukey’ s test and t-test. Results: As the vent size or thickness of spacer increased, the mean pressure on maxillary edentulous ridge decreased from 59. 0± 2. 22 to 36. 8± 2. 50 and 98. 5± 5. 85 to 42. 8± 2. 11 g/mm² in ridge area and 35. 0± 1. 66 to 19. 4± 1. 74 and 52. 1± 3. 80 to 22. 3± 1. 25 g/mm² in mid-palatal raphe for regular body addition silicone and zinc oxide eugenol, respectively. Comparison between groups indicated that there were significant differences in the magnitude of pressure in use of the two materials and areas with different vent sizes and thicknesses of spacer (P< 0. 001). Conclusion: Impression pressure changes significantly by change in tray design or impression material. For making impressions of an edentulous maxilla, using a tray with a 1. 0 mm or larger venthole or 1. 5 mm spacer thickness is recommended.