Journal of Mashhad Dental School
Year:2009 | Volume:33 | Issue:1 (68)|Papers Count:16

Introduction: Today, much of the researches and innovations in dental materials are focused on simplification of the bonding procedures. The aim of this study was to assess the shear bond strength (SBS) of a new self-adhesive flowable composite (Class V Embrace Wetbond, Pulpdent, Watertown, USA) to dentin.Materials & Methods: In this in vitro experimental study, 40 intact human third molars were selected and randomly divided into 4 groups of 10 teeth. Group I (Control group): After etching and application of Excite Bond (Ex), Tetric Flow (TF) composite was injected into the plastic ring over the prepared dentin surface and light cured (Etch/Ex/TF).Group II: After etching and application of Ex, Embrace Wet bond (EW) composite was injected into the plastic ring and light cured (Etch/Ex/EW).Group III: After etching, EW was injected into the plastic ring and light cured (Etch/EW). Group IV: EW was injected into the plastic ring and light cured according to manufacturer's instruction (EW).The data were analysed by ANOVA and Scheffe tests.Results: The mean SBS and Standard deviations for groups I, II, III, IV were 13.38±0.82, 9.99±1.30, 2.42±0.58 and 3.08±0.85 MPa respectively. Statistical analysis revealed that:1. The mean SBS of EW composite in groups II, III, IV was significantly lower than groups I (P<0.05).2. The mean SBS of EW composite in group III and IV was significantly lower than group II (P<0.05).3. The mean SBS of groups III, IV were not significantly different (P>0.05).Conclusion: Bond strength of EW composite without application of bonding agents was much lower than TF composite combined with Ex bond. Applications of EW composite over the total etch adhesive improved SBS. Application of EW composite over the etched dentin did not improve SBS.

Introduction: The surface roughness of orthodontic arch wires is an important factor as it influences corrosion, friction, tooth movement, biocompatibility, aesthetics and hygiene. The purpose of this study was to evaluate the surface roughness of seven groups of orthodontic arch wires from different manufacturers.Materials & Methods: A cross sectional study was carried out on two arch wires manufactured by different companies (four Niti and three stainless steel) from different manufacturers. Surface profilometry was performed using a profilometer. Data were analyzed using Mann Whitney and Kruskal-Wallis tests.Results: The average surface roughness of Niti wires manufactured by Smart, American Orthodontics, OrthoTechnology and Allstar were: 1289±915 A°, 1378±372 A°, 2444±369 A° and 5242±2832 A° respectively. The average surface roughness of stainless steel wires manufactured by Allstar, Orthotechnology and American Orthodontics were: 710±210 A°, 1831±1156 A° and 4018±2214 A°. Stainless steel arch wire made by American orthodontics and nickel titanium arch wire made by Allstar showed the highest roughness significantly (P<0.006).Conclusion: Stainless steel arch wire made by American Orthodontics and nickel titanium arch wires manufactured by Allstar showed the highest surface roughness among the studied arch wires. Use of arch wires with least surface roughness is recommended.

Introduction: One of the characteristics of brackets is resistance to corrosion. Corrosion could disturb dental movement through increasing, the friction between arch wire and slot. It could also cause dental discoloration. The aim of this study was to compare corrosion rate as well as corrosion site of five commonly used brackets in Iran.Materials & Methods: In this in vitro experimental study, 80 lower central stainless steel brackets (18- slot) from different companies (Mira, Dentaurum, Forte, Joli and 3M) were selected. At first, the brackets were mounted in Rapid impression material and the photographs were taken from six different views for assessing slots, bases, and wings using stereomicroscope device with X50 magnification. Then, each 8 brackets were put into a capped glass containing artificial saliva with PH=7.2 and they were incubated in 37±1°c temperature. The amount of released Nickel ion was measured by Atomic absorption technique after 6 weeks and for each bracket, photographs were taken again from previous views. Statistical analysis was done using Chi-square, Cochrane and Kruskal-Wallis and McNimar tests.Results: The minimum Nickel ion release belonged to 3M brackets (0.86±0.1 PPB) and the maximum release was for Forte brackets (17.49±0.01 PPB). Furthermore, corrosion was seen more in bracket bases (mesh surfaces) and it was less observed in their faces.Conclusion: The order of the Nickel ion release was: 3M<Dentaurum< Joli< Mira<Forte. Corrosion was the highest in the base of the brackets.

Introduction: In posterior mandibular region, the most important anatomic landmark related to implant place is mandibular canal which precise determination of its distance to alveolar crest as well as its buccolingual position is of great importance. One of the imaging techniques for implant treatment especially in the case of limited number of implants is conventional tomography which provides cross-sectional images as well as lower rate of radiation compared to CT scan. In this article, the accuracy of conventional tomography in determination of mandibular canal position was evaluated.Materials & Methods: This study was a kind of diagnostic test validity 24 sites on 4 dry human mandibles were selected and conventional linear tomography was provided (promax apparetus. On tomograms, distance of superior border of canal to alveolar crest and distance of mandibular canal to buccal & lingual cortex were measured by a caliper with the accuracy of 0.1 mm. Then mandibules were sectioned in certain sites by osteotome and mentioned distances were directly measured on these sections. Obtained measures from tomograms and mandibular sections were analyzed by student paired t-test.Results: Statistical difference was merely found in distance of canal to buccal cortex. Except for one case, differences in results were in the range of ±1 mm.Conclusion: Regarding the acceptable accuracy especially on placement of limited number of teeth, use of conventional tomography is recommended.

Introduction: The denture cleansers used daily by patients can damage soft denture liners. The goal of this study was to determine the surface roughness and hardness of a silicone soft liner, Gc-Reline, after immersion in calgon+sodium hypochlorite or in 1% sodium hypochlorite solutions.Materials & Methods: In this in vitro experimental study, 63 ring shaped specimens of silicone soft liner (14mm in diameter and 2mm thickness) for hardness test and 63 specimens (31mm in diameter and 10mm thickness) for surface roughness test were prepared. The specimens were divided into 3 equal groups (no=21) for each test. Then each group was subdivided into 3 subgroups according to time of immersion in cleansers (no=7). Each subgroup was soaked 8 hours per day in distilled water (W), calgonsodium hypochlorite (C) or in 1% Sodium hypochlorite (H) solutions for 1, 30 and 60 days. Roughness was measured in micrometer by a profilometer and hardness was assessed using Shore A test apparatus. The data were analyzed using Two-Way ANOVA test.Results: No change was observed in surface roughness ( mm) and hardness of silicone samples after 1, 30 and 60 days immersion in water (W) but in comparison to control group, surface roughness of samples in both cleansers was increased significantly in all time period of the study (P<0.05). Hardness of silicone specimens after 1, 30 and 60 days immersion in C group did not change but after 60 days soaking of samples in H solution, hardness was enhanced significantly (P<0.05).Conclusion: Both solutions of calgon+hypochlorite sodium and 1% hypochlorite sodium increased surface roughness of silicone liners. This increase was higher in 1% hypochlorite sodium solution. The 1% hypochlorite solution increased hardness of silicone soft liners after 60 days. No change in hardness was observed in other time period of this study.

Introduction: The success rate of implantation in augmented ridges depends on the quality of regenerated bone. Histologic studies are needed to stablish bone formation in these techniques. This study was performed to compare histologic features of regenerated bone in Distraction osteogenesis and autogenous bone graft in ridge augmentation.Materials & Methods: This pilot study was done in mandiubular dental pads of sheep. Distraction osteogenesis was performed on one side and the other side was augmented using autogenous bone graft. Posterior pad in each side was used as control. After 8 weeks, reentries were performed and sheep were sacrificed. Bone tissue samples of each area were prepared for histologic evaluation and comparison.Results: In control area, only normal bone tissue was observed and there was no evidence of fibrous or cartilage tissue. Bone trabecules in lamellar form were accompained with resting zones with less inactive fibrous tissue. There was moderate to severe chronic inflammation. In distraction zone, mature woven and lamellar bone was observed in some vascular and cellular stroma containing collagen fibers and blood vessels. There was less inflammation. In some area there was some cartilage.Conclusion: In spite of some advantages for autogeuous bone graft, Due to its complications, technical difficulties, bone resorption and unfavourable histologic features compared with distraction, distraction osteogenesis technique could be used for ridge augmentation.

Introduction: Diabetes mellitus is a complex disease that results in severe metabolic disorders. Recently; great advances about diagnostic criteria of diabetes have occurred. The aim of the present study was cytomorphometric and microscopic analysis of buccal epithelium in diabetic patients in order to find a new procedure for diagnosis.Materials & Methods: In this cohort study, buccal epithelial smear of 12 patients with type I diabetes, 12 patients with type II diabetes, and 24 normal subjects as a control were taken. Papaniculao technique was used for staining the samples and the nuclear and Cytoplasmic area were measured by counting point method. Cytoplasmic / nuclear ratio was calculated. t-test was used for statistical analysis through SPSS13.Results: The epithelial cells of diabetic patients showed binucleation and karyorrhexis. The nuclear and cytoplasmic area as well as cytoplasmic/ nuclear ratio were significantly lower in diabetic patients compared to healthy controls (P<0.05).Conclusion: Diabetes mellitus can produce some alterations in oral epithelial cells. Although these changes are not specific in diabetes, they can be used in diagnosis of this disease.

Introduction: Dental clinic is an environment where infectious disease transmission occurs easily. Therefore prevention of cross infection in the dental clinic is a crucial aspect of dental practice. Infectious disease can pose significant problems in the dental office. The purpose of this study was evaluation of Mashhad Dental students' rate of awareness and behavior on infection control.Materials & Methods: In this cross-sectional analytical study, 149 dental students (3rd, 4th, 5th and 6th grade) from Mashhad dental school participated. The self-administered questionnaire was composed of 2 parts (awareness and behavior). Data were collected and analyzed using Kruskal-Wallis, Mann-Whitney and X2 (Exact) to detect the differences among groups.Results: There was a significant difference in use of eye protection, gown and shield among grades of students (P<0.001) but there was no significant difference in awareness about the use of mask and gloves among different grades (P>0.05). Results showed that students' awareness was poor on infection control. 27.5% of students showed poor behavior, 60.4% moderate and 12.1% showed good behavior on infection control.Conclusion: Mashhad Dental students' awareness towards infection control was poor and they showed different behaviors. A need for better education forward infection control is anticipated.

Introduction: Pyogenic Granuloma is a tumorlike lesion of oral cavity that is considered to be non-neoplastic in nature and arises in response to local irritation. Most studies show that this lesion is more common in women than men, possibly because of the vascular effects of female hormones. The purpose of this study was to evaluate the expression of estrogen and progesterone receptors in pyogenic granuloma in pregnant, non-pregnant women and men compared with normal mucosa by immunohistochemistry.Materials & Methods: In this study, cross-sectional analytical 36 paraffin blocks of pyogenic granuloma samples (12 samples of pregnant women, 12 samples of non-pregnant women, 12 samples of men and 9 samples of normal mucosa) were obtained from O.M.F pathology department of Mashhad Dental School. 4 micron sections were prepared and stained by immunohistochemistry staining (Based on Dako factory instruction). After immunostaining, estrogen and progesterone receptors expression in three areas including epithelium, inflammatory and mesenchymal cells were evaluated. The data were analyzed by fisher's exact test.Results: After comparing the expression of estrogen receptors in epithelium (P=0.1), inflammatory cells (P=0.184), mesenchymal cells (P=0.316) in studied groups, no statistically differences were found. Expression of progesterone receptors was not seen in epithelium of any samples and it’s expression in inflammatory and mesenchymal cells was poor (P=0.19,P=0.547).Conclusion: Although estrogen and progesterone receptor expression was observed in pyogenic granulomas of oral mucosa in pregnant, non pregnant women, men and normal mucosa, it did not seem to play an important role in pathogenesis of this lesion or these hormones may have put on effect by other mechanisms other than binding to specific receptors.

Introduction: The most common failure of tooth color posts is retention failure of posts. The aim of this study was to evaluate the effect of different surface treatments on the bond strength of quartz fibere posts.Materials & Methods: In this experimental in vitro study, 70 mandibular single root canal premolar teeth that had no decay or crack, were selected and then endodontically treated. Post space preparation was made 9 mm long. 70 quartz fiber reinforced composite (FRC) posts were randomly divided into five groups for applying different surface treatments: Air abrasion, 24% Hydrogen peroxide, 21% sodium ethoxide, Potassium permanganate 20%, no treatment (control). Then, a single layer of silane was applied to post surface of half of the specimens in each group. Next, the specimens were submitted to the pull out test. The failure mode was determined by stereomicroscope and SEM. The statistical analysis was performed using Two-Way ANOVA and Tukey’s test (α=0.05).Results: Only bond strength of Potassium permanganate group was significantly greater than those obtained with other groups (P<0.05). Use of silane decreased the bond strength significantly (P<0.05). Assessment of failure mode showed as the bond strength increased, the mixed failure mode increased. SEM evaluation revealed that application of air abrasion and potassium permanganate damaged the quartz fibers.Conclusion: Application of Potassium permanganate increased the bond strength and application of silane decreased bond strength significantly. Application of potassium permanganate and air abrasion damaged quartz fibers.

Introduction: One of the most important factors in myofascial pain dysfunction syndrome is mental disorder which increases muscle tonicity and causes myolgia. The purpose of this study was to determine the frequency of psychiatric disorders in patients with Myofascial Pain Dysfunction Syndrome (MPDS).Materials & Methods: In this descriptive cross sectional study, all patients with MPDS referred to oral medicine department of Mashhad dental school (from September 2003 to October 2004) were examined by a psychiatrist and according to the criteria set by DSM-IV-IR, the presence and type of psychiatric disorders were evaluated. The data were analysed by chi-square test and One Way ANOVA.Results: Among 57 patient examined, 100% subjects were diagnosed with at least one psychiatric disorder.93.1% of subjects were categorized as anxiety disorders.Conclusion: According to existence of psychiatric disorders in 100% of patients with MPDS, improvement of their mental condition should be considered in the therapy provided.

Introduction: Relatively high prevalence of facial deficiencies caused by trauma and the need for ablative surgeries in maxillofacial cancers, cause aesthetic and functional problems for patients which can be rehabilitated with surgery, prosthesis or both of them. Prosthetic reconstruction for these patients has many advantages such as controlling wound healing, aesthetic, easy  and non expensive treatment. In this article the process for nose prosthesis fabrication with silicon materials has been presented step by step.Results: A 49 year-old female patient with past medical history of diabetes mellitus that had rhino-cerebral mucormycosis following by diabetic coma and had under gone ablative surgery in hospital. The resected regions in this surgery included nasal septum, superior, Middle and inferior conchea, anterior wall of ethmoid sinus, middle wall of maxillary sinus and anterior wall of sphenoid sinus, in addition to parts of hardpalate (maxillary anterior alveolar segment). She said that after the surgery, she rarely showed up in the public and always covered the defect with a guaze. Her speech was completely hypernasal and she had difficulty in swallowing. For satisfying her functional and aesthetic needs, a nasal silicon prosthesis attached to obturator prosthesis in maxilla with magnet retention was fabricated.Conclusion: Reconstruction of Midface deficiencies according to defect region, its extension and patient's age can be accompolished with surgery, prosthesis or a combination of both approaches. In this patient, a nasal prosthesis and maxillary obturator was fabricated. In this article nasal prosthesis fabrication step by step was explained.