JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2006 | Volume:18 | Issue:2 (59)|Papers Count:18

Background and Aim: Bonding systems have been traditionally used on normal dentin, even though caries-affected and sclerotic dentin is often the clinically relevant bonding substrates. A self-etching primer adhesive system (Clearfil SE Bond) was evaluated for its ability to bond to caries-affected and normal dentin.Materials and Methods: In this experimental study, twelve extracted human primary molars with occlusal caries were selected. The enamel and superficial dentin were ground with a diamond disk and stained with a caries detector solution (propylen glycol and 1% acid red). The red-stained soft dentin which was classified as infected dentin was excavated and the affected dentin and surrounding normal dentin were polished with a 600 grit silicon carbide paper under running water to achieve a flat surface. The entire flat surface was bonded with Clearfil SE Bond (Kuraray) according to the manufacturer's instructions and covered with composite resin Clearfil AP-X (Kuraray) to form a composite crown, approximately 4.5 mm high. The teeth were stored in distilled water at room temperature for 24 hours and were then sectioned with a diamond saw under running water in both X and Y directions, perpendicular to the bonded surface with dimensions of approximately 0.8-1 mm, so that the bonded areas of the affected or normal dentin were isolated. The obtained rods were divided into two groups: Affected and sound dentin. After measuring the cross-sectional areas at the interface, the specimens were mounted in a microtensile tester machine and pulled under tension to failure. The mode of failure was evaluated using a stereomicroscope and the data were analyzed by t-test.Results: Statistical analysis indicated that the microtensile bond strength in affected dentin (21.53±6.52MPa) was significantly lower (p<0.05) than normal dentin (26.98±7.31MPa).Conclusion: The studied self-etch system, attained lower microtensile bond strength in affected dentin as compared to normal dentin.

Background and Aim: 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. Materials and Methods: 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.Conclusion: 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.

Background and Aim: Condensation silicons are more commonly used in fixed Prosthodontics than other elastomers. The aim of this study was to compare the accuracy and dimensional stability of two condensation silicons: Speedex and Irasil.Materials and Methods: A metal master model containing two abutments representing two prepared teeth with definite dimensions was prepared and a metal tray was made. 40 impressions were taken (20 of each impression material) and 10 of them were poured with die stone (Prevest) after 30 minutes and the other 10 were poured after 120 minutes, according to the manufacturer's instructions.Using a stereomicroscope M6c-10 and Digital camera moticam-480 the following dimensions were measured three times on the metal and stone models: (1) x = distance between the center of the abutments (2) y1 = height of the abutment with an undercut (3) y2 = height of the abutment without an undercut (4) z1= width of the abutment with an undercut, and (5) z2 = width of the abutment without an undercut. The difference between the dimensions of the main and stone models was assessed.Results: Multivariance and T-tests were used for statistical analysis. There was no significant difference in dimensional stability between groups 1 and 4 (Speedex, 30' and Speedex, 120') and between groups 2 and 3 (Irasil, 30'-120'). A significant difference was observed between Speedex and Irasil in both time periods (30 and 120 minutes). The difference between the die stone and the master model was significant in mesiodistal (x) and buccolingual (z1) dimensions for both materials. A significant difference was also found between Irasil and the main model in occlusogingival (y1) and buccolingual (z2) dimensions in both time periods, but Speedex failed to show a significant difference in the same dimensions and time periods. In the y2 dimension in contrast to Irasil, Speedex demonstrated a significant decrease of dimensional stability.Conclusion: Timing did not affect the dimensions of the two impression materials. The mesiodistal dimensions (x) of both Speedex and Irasil increased on the casts. A significant difference was found in dimensional stability between Speedex and Irasil impression materials.

Background and Aim: Considering the cost and quantity of tooth loss in the process of cavity preparation, repairing composite restorations instead of replacing them would be much more efficient. The aim of this study was to evaluate and compare the effectiveness of different mechanical surface treatment methods on the shear bond strength (SBS) between old and new composites.Materials and Methods: In this experimental in vitro study, 80 cylindrical specimens were fabricated from Tetric Ceram Composite (A1, vivadent) and were preserved in 37°c distilled water. They were divided into 4 groups according to the surface treatment method: control (no treatment), roughening by a diamond bur, polishing with Sof- Lex disks and air-abrasion. All specimens were thermocycled (0.5-55°c, 500 cycles) prior to testing for SBS. An Instron Universal Testing Machine (5mm/min Cross head imm) was used to evaluate the SBS of the specimens. Data were analysed by one-way ANOVA and Duncan tests.Results: The highest to lowest shear bond strengths were seen in the Sof-Lex disk, air abrasion, diamond bur and control groups, respectively. A significant difference was observed between all three experimental groups (air abrasion, diamond bur, Sof-Lex disk) and the control group. There were no significant differences between the air abrasion and diamond bur groups, but the other groups revealed a significant difference when compared as pairs.Adequate wetting and induction of a microretentive surface, may explain the high SBS observed in the Sof-Lex group.Conclusion: The results of this study emphasize the importance of mechanical surface conditioning prior to composite restoration repair.

Background and Aim: Ameloblastoma is one of the most common odontogenic tumors, occasionally with unusual features. In this study an uncommon odontogenic tumor, histologically similar to ameloblastoma and adenomatoid odontogenic tumor with hard tissue formation is reported.Case Report: A 19-year old female presented with a unilocular lesion on the right side of the maxilla, extending from the canine to the first molar. The tumor tissue was unicystic overall and typical plexiform ameloblastoma was observed in some areas. Dentinoid formation and tubular dentin was observed in the tumor stroma, whereas enamel matrix was not seen.Conclusion: Very few cases of this variant of ameloblastoma have been reported and the name "adenoid ameloblastoma with dentinoid" is suggested for these lesions.

Background and Aim: The use of silk suturing materials and cyanoacrylate tissue glue are common in wound closure after periodontal surgeries, gingival grafts, tumor removal, etc. The aim of this study was to compare the use of silk sutures and cyanoacrylate tissue glue (EPIGLU) in wound closure after periodontal flaps in patients with moderate periodontitis.Materials and Methods: This experimental study was conducted on fifteen patients (10 female, 5 male) aged 25-55 years with moderate periodontitis in need of flap surgery on both sides. After a Widman modified surgical flap, the incision lines were randomly closed with silk sutures on one side (control group) and EPIGLU on the other side (study group). The patients were followed for 2 weeks post surgery and the two groups were compared in terms of pain, bleeding, wound healing, sensitivity and tissue compatibility. Sign and Friedman tests were used to compare the results.Results: The use of EPIGLU showed no significant differences with silk sutures in most cases but the differences became more prevalent with time.Conclusion: Considering the favorable properties of EPIGLU such as improved wound healing, less bleeding, superior clinical performance, minimal chair time and patient acceptability, it is suggested as a replacement for silk sutures.

Background and Aim: Diet is the most important etiologic factor in dental erosion. Erosion of dietary origin in children is frequently related to carbonated drinks and acidic foods. The aim of this study was to evaluate the effects of some acidic soft drinks on enamel micro-hardness of primary teeth.Materials and Methods: This interventional in vitro study was performed on 40 healthy deciduous teeth. Enamel blocks were prepared and were polished on their external surfaces using water and sand paper. The baseline hardness was measured using Vickers microhardness measuring apparatus. The enamel blocks were then immersed in 20cc Coca Cola, Zam Zam, Pepsi and Ab-Ali yoghurt-drink for 5 minutes and their microhardness was assessed. The data were analyzed using co-variance and paired sample t-tests.Results: The baseline hardness in primary teeth, was 378.4±31.65 (kg/mm2) for Coca Cola, 373.57±30.31 (kg/mm2) for Zam Zam, 378.38±21.92 (kg/mm2) for Pepsi and 385.43±34.79(kg/mm2) for Ab-Ali yoghurt-drink, before being placed in the experimental soft drinks. After immersion (second hardness), these values decreased to 333.02±32.15 (kg/mm2), 339.65±20.91 (kg/mm2), 342.27±28.01 (kg/mm2) and 341.46±32.34 (kg/mm2) for Coca Cola, Zam Zam, Pepsi and Ab-Ali yoghurt soft drinks, respectively. The reduction in microhardness was statistically significant for each of the tested soft drinks but a statistically significant difference was not observed between the study groups.Conclusion: The intake of soft drinks such as Coca Cola, Zam Zam, Pepsi and Ab-Ali yoghurt-drink can reduce enamel microhardness in primary teeth.

Background and Aim: Studies concerning the effects of post-core design on fracture resistance of endodontically treated teeth remain controversial. The aim of this in vitro study was to compare the effect of two post-core designs on the fracture resistance of endodontically treated teeth.Materials and Methods: Sixty extracted human maxillary central and canine incisors with similar root dimensions were selected for this study. The crowns were sectioned from 4mm above the buccal CEI line. All crowns were prepared with 1 mm reduction and a chamfer finish line. After mounting and endodontic therapy, the teeth were randomly divided into 3 groups: Group 1 (control): restored with self-cured composite (no posts); Group 2: restored with cast post-cores and a shoulder preparation; Group 3: restored with cast post-cores and a contra bevel preparation. Each specimen was subjected to load (N) on the lingual surface at a 135° angle to the long axis with an Instron material testing machine until fracture at a crosshead speed of 2 mm/min. One way analysis of variance and t-test were used to compare the results.Results: The mean fracture resistance for groups 1, 2 and 3 was 534.62 N, 709.38 Nand 1395.94 N, respectively.The fractures in group 1 were restorable in 61.5% of the specimens, and in group 2 and 3 in 12.5% of the cases. There were no statistically significant differences between the three groups. Conclusion: Within the limitations of this study neither of the two tested post-core designs, improved the strength of the endodontically treated anterior teeth.

Background and Aim: Ditching plaster dieJis a very important part in fabricating fixed prosthetics. Some clinicians humidify the plaster die to simplify the procedure. The objective of this investigation was to assess the effect of humidity on the surface hardness of plaster die.Materials and Methods: In this experimental study, American-made type 4 gypsum was used according to the manufacturer's instructions. 70 dies were prepared and were divided into seven groups of 10, 24 hours after pouring the gypsum. The hardness of the control group (first group) was immediately examined. The second, third and forth groups were dipped into water for 10 seconds and the fifth, sixth and seventh groups for 10 minutes. The hardness of the second and fifth groups was assessed immediately, the third and sixth groups after 5 hours and the fourth and seventh groups after 24 hours of being removed from water. Statistical analysis was performed using one-way ANOVA, Duncan and t-tests.Results: The duration of humidification and dehydration affected the surface hardness of plaster dies. Maximum hardness was observed in the control group (no humidification) (P< 0.001). Surface hardness after humidification for 10 seconds without dehydration revealed the second highest values, after the control group (p< 0.001). Hardness was minimal when the humidifying time was 10 minutes without dehydration (P< 0.001).Conclusion: Humidification of plaster dies can decrease the surface hardness which is irreversible.

Background and Aim: In orthodontic therapy, different materials are used and subjected to a damp oral environment, which can modify their properties. The purpose of this study was to evaluate the biocompatibility of eight metallic and non metallic orthodontic materials in human oral fibroblast culture.Materials and Methods: The specimens consisted of eight clinically used materials, including two coil springs, two glass ionomer cements, two a-rings and two orthodontic acrylic resins. Teflon was used as a negative control.After a release period of each material in the culture medium for 20 days, the viability of oral cultivated fibroblasts was compared to the negative control by MTT assay. Biocompatibility was also assessed using the direct method in which cell viability was evaluated by an invert phase contrast microscope, after direct exposure to the tested materials.Results: MTT assay showed stainless steel (P.V=0.665) and Bayer acrylic resin (P.V=0.179) to be biocompatible with gingival fibroblasts. Significant differences were observed between the biocompatibility of all study groups [Nickel titanium (PV=0.037), Acropars acrylic resin (PV=0.014) and both studied a-rings (PV=0.001), (PV=0.016)] and the control group.According to the direct method, stainless steel and Nickel titanium showed grade 1, glass ionomer cements grade 4 and other materials revealed grade 0 cytotoxicity. Conclusion: The two studied glass ionomer cements were highly cytotoxic. Bayer acrylic resm was more biocompatible than Acropars acrylic resin.

Background and Aim: Autopolymerized and heat polymerized acrylic resins are widely used in dentistry for various purposes. Despite the polymerization method, the conversion of monomer into polymer is not complete and varying amounts of free or unreacted monomer (residual monomer) remain in the polymerized resin. The aim of this study was to determine the residual monomeric methyl metacrylate content in the saliva of patients using acrylic dentures, at different time intervals.Materials and Methods: Informed consents were obtained from 25 patients with complete dentures, ranging in age from 35 to 65 years. 1 mL samples of whole saliva were collected upon insertion of the dentures and 1 day, 1 week and 1 month after wearing them. Methyl methacrylate (MMA) levels were measured by use of gas chromatography. Data were analyzed by repeated measurement ANOVA and paired sample T-tests.Results: The maximum concentration of monomer released into saliva was detected one day after insertion of the dentures. The Mean (SD) MMA content in saliva was 0.4±12 (ng/ml) upon insertion, and 0.7±0.16 (ng/ml), 0.5±0.13 (ng/ml), and 0.38±0.1 (ng/ml) on the 1st day, 1st week and 1st month post-insertion, respectively. Conclusion: The maximum amount of monomer released by heat-polymerized poly-MMA was observed on the first day after insertion, which, while not a toxic or primary irritant dose, could sensitize patients or elicit an allergic reaction. For minimization of the adverse effects, patients could be advised not to wear their dentures overnight, 24 hours after delivery.

Background and Aim: Xerostomia and burning mouth syndrome are two relatively common complaints mostly encountered during adult age. They may have a great impact on the quality of life and become a serious health problem for patients. This study was designed to determine the frequency of subjective dry mouth and burning mouth syndrome (BMS) in elder residents of sanitariums in Tehran.Materials and Methods: In this cross-sectional investigation, the study group consisted of elderly adults (65 years and over), residing in twenty seven of the 36 sanitariums in Tehran. 499 volunteers (308 women and 191 men) underwent medical examination. Diagnosis was based on the patients' complaints of both subjective dry mouth (SDM) and BMS. No obvious oral lesion was detected in the BMS cases.Results: 124 (24.8%) individuals were classified as having subjective oral dryness and BMS. SDM and BMS were seen in 121 (24.2%) and 39 (7.8%) of the 499 cases, respectively. A statistically significant difference was observed between women (27.9%) and men (18.3%) with SDM (P=0.026), but not BMS (9.1% female, 5.8 male). Conclusion: Subjective dry mouth and burning mouth syndrome are relatively frequent problems in elderly residents of sanitariums in Tehran. A higher percentage of females are involved as compared to males.

Background and Aim: It has been stated that hydrocolloid impression materials (Alginate) should be poured immediately to gain maximum dimensional stability. With modem formulations of these materials, it is possible to store the impression at 100% humidity for varying periods. The purpose of this study was to evaluate the effect of storage time on dimensional stability of casts poured from two types of alginate impression materials.Materials and Methods: A metal model (CK steel) composed of two metal plates, one holding the impression tray and the other holding two dies, was used to make the impressions. Five impressions were taken with the Iranian (Golchai) and foreign (Alginoplast) alginates for each tested time interval. The impressions were stored in 100% humidity for 0, 15, 30, 60 and 180 minutes and then poured with type III dental stone. The stone casts were measured with a digital caliper and the results were compared between the groups using two-way ANOVA and Tukey tests.Results: A statistically significant difference was encountered between the dimensions of the casts poured from the two alginates at the tested time intervals (p=0.027). No significant difference was observed between the experimental casts' dimensions and the master model at the different storage times (p=0.0230). A 0.06 mm and 0.01 mm difference was found between the master model and the mean height of dye no.2 in the Iranian and foreign groups, respectively.Conclusion: The results of this study show that the studied hydrocolloid materials can be stored in a humid environment for 3 hours, without undergoing significant changes.

Background and Aim: One of the materials used for repairing root-end fillings is mineral trioxide aggregate (MTA).MTA has been reported to remain soft when placed in perforations with a high degree of inflammation. The purpose of this study was to evaluate the effect of environmental pH on the setting and micro structure of MTA.Materials and Methods: In this interventional study, tooth-colored MTA (Pro Root, Dentsply, USA) was mixed according to the manufacture's instructions. The mixture was placed into cylindrical polycarbonate tubes. The specimens were randomly divided in to four groups of 9 and were subjected to a pressure of 3.22 MPa~ 6kg applied for 1 minute in a custom-made condenser device. Each of the 9 specimens were then stored at room temperature and saturated humidity in four plastic plates containing buffer solutions of butyric and propyonic acid with a pH of 4.4, 5.4, 6.4 and 7.4, for 4 days. The Vickers hardness test was performed on each specimen. The microstructures of the specimens were analyzed using a scanning electron microscope after sectioning the specimens with a scalpel. Data were subjected to one-way ANOVA.Results: The lowest and highest PH values were 4.4 and 7.4, respectively. A statistically significant difference was observed between all four groups (p<0.05). Unrelated MTA particles scattered in a non uniform matrix were seen in specimens stored in pH 4.4 solutions whereas cases kept in a pH 7.4 environments had distinctive crystalline structures embedded in a more uniform matrix.Conclusion: The results indicate that the acidic pH of inflamed tissues can adversely affect the setting of MTA.

Background and Aim: The aim of this study was to assess the relationship between corresponding upper buccal cusp distance (IBD) with Gothic arch width, inter-condylar width (ICW) and inter-upper canine distance (ICD) in an Iranian population.Materials and Methods: In this cross sectional investigation, subjects consisted of 42 adults with intact dentitions and class I occlusion, with no history of orthodontic treatment and TMJ disorders. Study casts were made from alginate impressions taken from maxillary teeth. Gothic arch tracing was performed and arbitrary hinge axes were determined on both sides. The distance between these points was recorded as the inter-condylar width (ICW) using a facebow. The Gothic arch width, ICW, IBD and ICD were measured by a vernier caliper. Pearson correlation test was used for statistical analysis (P≤0.05).Results: A significant correlation was not observed between the Gothic arch width and IBD. The correlation between IBD, ICW and ICD was highly significant (P<0.01).Conclusion: Based on the results of the present study, the position of the maxillary teeth can be determined by measuring ICW or ICD.