JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2011 | Volume:23 | Issue:1 (78)|Papers Count:12

Background and Aim: In the past few years an alarming rise in the occurence of oral and oropharyngeal squamous cell carcinoma which now comprises 3% of all cancers in men and 2% of all cancers in women has been seen. Tobacco smoking is a single most well-known and important risk factor for squamous cell carcinoma in oral cavity. However, the pathogenesis, especially the initial changes brought about by smoking is not fully understood.The aim of this study is to compare cytological findings of apparently normal buccal mucosa among smokers and nonsmokers based on samples obtained by brush biopsy.Materials and Methods: Thirty-eight smokers and 42 nonsmokers, who did not show any conspicuous oral lesions were evaluated in a cross-sectional study. The specimens were taken from healthy and apparently normal buccal mucosa by a commercial cytobrush. Cytologic evaluation of biopsy specimens in terms of frequency of dysplasia/neoplasia, granular cells, binuclear cells, coarse chromatin, clear nucleus, apoptotic cells, pleomorphism in nuclear and cytoplasmic morphology was performed. Chi square test was used for comparison and analysis.Results: Studied samples included 80 men (mean age, 40 years) in both groups. There was no dysplastic or neoplastic changes in any of the groups. Cytologic studies demonstrated that clear nucleus, coarse chromatin and the frequency of nuclear pleomorphism showed statistically significant differences between the two groups (P<01, P<001 and P<01 respectively).Conclusion: Buccal mucosa of smokers showed some differences compared to samples from nonsmokers. However, the clinical significance of these changes is uncertain.

Background and Aim: In the recent years, the demand for esthetic restoration led to developement of tooth colored post. The establishment of reliable retention between post and root canal is an important factor. Current prefabricated tooth-colored posts are fiber and zirconia posts. Loss of fitness in these posts reduces the post retention; therefore, there is a need for fabricating a tooth colored post that may be fitted in the root canal. The aim of this study was to compare the bond strength of fiber posts and custom made zirconia posts with two cement types (resin cement and zinc phosphate) to root dentin.Materials and Methods: Thirty-two single root extracted teeth were prepared and endodontically treated. They were divided into two groups (fiber post, zirconia post); in each group two cement subgroups (zincphosphate and panavia F2) were used for cementation. Bond strength was measured with the push-out method. Failure modes were observed under a stereomicroscope (20x). Data were analyzed with the two way ANOVA test.Results: In both post groups, bond strengths of panavia F2 were higher than zinc phosphate. The least bond strength was for fiber post/zinc phosphate group (4.60MPa) and the highest bond strength was for zirconia/Panavia F2(14.92 MPa). Most of the failures were at the post-cement interface.Conclusion: Higher bond strength may be achieved with custom made zirconia post and resin cement than fiber posts. So, fitness is a critical factor in post retention and we should not rely only on the bonding ability of resin cement for post retention.

Background and Aim: Bonding agents with acceptable mechanical properties are required for a persistent bond between dental composites and tooth substrate. The purpose of this study was to investigate the effects of formulation of the resin on the mechanical properties and bond strength to the enamel.Materials and Methods: Experimental resins containing Bis-GMA and TEGDMA at the ratios (w/w) of 60/40, 50/50, 40/60 were prepared. Specimens (n=10) were prepared and tested after 24 h exposure to 37° C water for flexural strength (FS), micro-tensile strength (MTS) and micro-shear bond strength (MSBS) to the enamel. A proprietary bonding agent (Heliobond, Ivoclar Vivadent) was used as control. Data were analyzed by one-way ANOVA and Tukey HSD tests (a=0. 05).Results: The results showed that there were significant statistical differences between flexural strength of the adhesives (p<0.05). The adhesive which contained 60% BisGMA showed the highest flexural strength (57.42 Mpa), while the adhesive containing 40% BisGMA showed the lowest flexural strength (31.82 Mpa). MTS and MSBS did not differ significantly (p>0.05).Conclusion: Based on the results of this study, although the content of BisGMA did not affect the microtensile strength and microshear bond strength to the enamel, the flexural strength tended to increase by the increase in BisGMA content.

Background and Aim: Reinforcement with fiber is one of effective methods for improvement in flexural properties of indirect composite resin restorations. The composition of the overlying veneering composite plays a critical role in the flexural properties of the final fiber reinforced restoration. The aim of this in-vitro study was to evaluate the effect of fiber reinforcement on the flexural strength of three laboratory-processed fiber-reinforced composite resins.Materials and Methods: In this experimental-laboratory study, 72 bar type specimens (3×2×25 mm) were constructed by using three types of fiber-reinforced composite resins (Gradia, Signom, Bellglass) and one Plexiglas mold. In each type of composite resin, two groups (one with fiber and one without fiber) were constructed. These specimens were tested by the three-point bending method to measure flexural strength. Data were statistically analyzed with two way ANOVA, Tukey and T-test at 0.05 significance level.Results: The mean flexural strength of Gradia with fiber was higher than the other groups (150.14 MPa) and the mean flexural strength of Signom without fiber was the least (60.53 MPa). There was a significant difference between the mean primary fracture force in the three groups (P<0.001).Conclusion: Within the limitations of this study, it may be concluded that reinforcement with fiber considerably increases the fracture resistance of composite specimens and the overlying veneering composite may play an important role in the transverse strength of fiber reinforced composite specimens.

Background and Aim: The establishment of reliable bonds at root-post-core interfaces is critical for the clinical success of post retained restorations. Severe stress concentration at post-cement interface increases the probability of post debonding from the root. The aim of this study was to investigate the effects of different surface treatments on bond strengths of a non-metallic post in the root.Materials and Methods: Fifty extracted human canines or premolars that had just one root canal were endodontically treated. D.T Light Posts (RTD/France) recieved surface treatments in five categories:1) Application of silane2) Sandblast with Alumina particles3) Sandblast with Alumina particles + application of silane4) Etching with hydrofluoric acid + application of silaneThe posts were cemented in roots using panavia F 2.0 resin cement. A push-out test was performed on three different sections of each root to measure bond strengths.Data were analyzed with ANOVA and Post hoc tests at P<0.05.Failure modes were observed under a stereomicroscope (10 ×).Results: Surface treatments used in this study (silane application, sandblast, sandblast + silane, HF etching + silane) did not increase the push-out bond strengths of fiber post used in this study. (P>0.05)The most failures in different groups of surface treatments occurred at the cement material-post interface.Conclusion: The use of silane, sandblast method and etching with HF did not increase the push-out bond strength of fiber post used in this study.

Background and Aim: Many protective materials such as varnishes as well as specially designed agents are used to protect glass ionomer cements against hydration and dehydration. The use of enamel bonding agents is also purposed. This study was conducted to evaluate the efficacy of an enamel bonding agent. Vickers microhardness was used as the criteria for judgment.Materials and Methods: Forty five discs (2×6 mm) were made from each of the two glass ionomer cements using Fuji II and Fuji IX. They were divided equally into three subgroups, which were protected with either finishing gloss/3M, Margin bond/Coltene or without protection (control). Microhardness of the specimens was evaluated at 24 hours, one week and one month after preparation. Data were analyzed by 3-way ANOVA and Tukey post-hoc test.Results: The highest Vickers hardness number (VHN) for Fuji IX and Fuji II was recorded when protected with Margin bond at 1 month (110.54 ± 6.52 and 106.43 ± 8.30, respectively), whereas the lowest VHN was observed for the control group at 1 day (80.29 ± 6.78 and 62.18 ± 7.46, respectively). There was no significant difference between Fuji II and Fuji IX coated specimens at all time intervals. Protecting the glass ionomer cements with either of the two agents exhibited similar results. Microhardness of the tested glass ionomers increased during the test period; however, the only differences detected were between one day and one month specimens.Conclusion: The performance of enamel bonding agent in protecting the glass ionomers was similar to that of especially designed coating material.

Introduction: One of the significant aspects in the treatment of extensive pathological bone lesions is the reconstruction of the created defect due to lesion resection. This article is a report of the defect reconstruction which was created in the mandible due to resection of an ameloblastoma using a two-stage procedure which was carried out at first by freezing the mandibular bone segment in liquid nitrogen followed by reimplantation of the mandibular body in its bed.Case report: This case is a 18-year-old man with mandibular ameloblastoma which was treated by hemimandibulectomy. The segment was immersed in liquid nitrogen and freezed for 4 months before reimplantment in the defect place in order to freeze and kill the residual tumor cells and as the framework after being filled with the patient’s autogenous bone and bone marrow was consequently fixed in its place with miniplate.The grafts conformed to the receiving site thoroughly and there was minimum asymmetry in the face. The use of autogenous bone from the same region for reconstruction had a positive effect on the patient psychologically. The bone constructed with the best quantity and quality where the implants were inserted.Conclusion: This technique may be used as an alternative method for reconstruction of bone defects due to resection of mandibular pathological lesions together with other methods such as the free iliac crest graft or the fibula graft and also other methods.

Background and Aim: Parodontax dentifrice is a plant-based dentifrice which is supposed to have specific effect in preventing and treating gingivitis. The purpose of the present study was to compare clinical effectiveness of Parodontax and Crest complete toothpaste in controlling gingival inflammation and microbial plaque.Materials and Methods: This double-blind clinical trial was performed on 40 patients with gingivitis that had been referred to the periodontal department of Shahed Dental School. The subjects were randomly allocated into either the test group (n=20, Parodontax) or the control group (n=20, 7 Crest Complete). Turesky`s Plaque Index and Loe`s and Silness`s Gingival Index were used to evaluate plaque and gingivitis at baseline and one month after dentifrices' application. Plaque and Gingival index changes were evaluated by Wilcoxon test in each group and Mann-Whitney test between the test and control group.Results: After one month, in the Crest group, PI reduced from 2.58 to 2.46 and in the Parodontax group PI reduced from 2.68 to 2.48. There was a significant reduction in plaque levels in both test and control groups. However, there was no significant difference between the two groups. Gingival index, decreased from 1.43 to 1.22 in the control group and from 1.36 to 1.15 in the test group. A significant reduction in gingivitis was observed in each group, although there was no significant difference between the two groups.Conclusion: Both dentifrices had similar effects on PI and GI. Parodontax dentifrice does not cause significant reduction in gingival inflammation and microbial plaque accumulation.