Journal of Dental School, Shahid Beheshti University of Medical Sciences

Objective: Different educational tools are now commonly used in universities worldwide such as illustrations, audio and videotapes, etc. This study aimed to compare the efficacy of educational film and clinical demonstration for instruction of Fiber-Reinforced Composite (FRC) post restorations to dental students in Department of Restorative Dentistry.

Methods: This interventional study was conducted on 70 fifth year dental students in Mashhad University. Students were divided into two groups. Group 1 students watched live demonstration of a treatment procedure (FRC post restoration) while group 2 watched the educational film of the same procedure. Both groups participated in a post-test. Also, students' perspectives were sought via a questionnaire. Data were analyzed using SPSS, Student’s t-test and Chi-square test.

Results: The mean post-test score of group 2 students (educational film) was greater than that of group 1 students (clinical demonstration) and the difference in this respect between the two groups was statistically significant (p=0.008). Considering the score of 7 as an acceptable score, 44 students gained scores 7 or higher; out of which, 16 were in group 1 (clinical demonstration) and 28 were in group 2 (educational film). The difference in this regard between the two groups was statistically significant (p=0.003). Most students preferred watching the educational film to the crowded clinical demonstration sessions.

Conclusion: Watching the educational film yielded greater test scores than the clinical demonstration.

Objective: Different methods have been suggested to overcome the polymerization shrinkage of composite restorations. Changing the light curing protocol to improve polymerization by using new light curing units is among these methods. The new devices are more efficient, portable and durable and produce less heat. This study aimed to assess the marginal microleakage of class V composite restorations subjected to three different light curing protocols and mechanical cycles.

Methods: This was an in-vitro experimental study. Class V cavities measuring 2x3x1.5 mm were prepared on the buccal and lingual surfaces of 90 extracted human premolar teeth 1.5 mm above and below the cement enamel junction (CEJ). The samples were selected using convenience sampling and divided into 9 experimental groups of 10 each by using the Table of Random Numbers to  control for the bias. The cavities were restored with packable composite resin along with Tetric-N- Bond and cured using three light curing protocols of conventional (680 mW/cm2 for 30s), soft-start (380 mW/cm2 for 10s followed by 680 mW/cm2 for 20s) and pulse (680 mW/cm2 for 30s,1s interval and 1s of lighting). The teeth were then subjected to mechanical cycles of 0, 500,000 and 1,000,000 and immersed in 2% Fuchsin for 24h. The teeth were then sectioned in half from the middle of the restoration buccolingually and the degree of microleakage was evaluated under a stereomicroscope (Zeiss, Germany) with 40X magnification. Data were analyzed using the Kruskal Wallis and the Mann-Whitney tests.

Results: Despite the structural differences between the enamel and dentin margins, no significant difference was found in the degree of microleakage between the enamel (occlusal wall, p>0.05) and dentin (gingival wall, p>0.05) margins among the understudy groups.

Objective: Alveolar ridge preservation in patients with inadequate bone volume is one treatment option for successful implant placement and can be done by using bone graft materials. On the other hand, Ceno Bone has been recently produced by Hamanand Saz Baft Kish Co. as a bone bioimplant of allograft origin. This study aimed to assess the clinical, histologic and histomorphometric results of Bone Strip Allograft (CenoBone) for horizontal alveolar ridge augmentation.

Methods: In this semi-experimental clinical trial, 7 areas requiring horizontal ridge augmentation  and subsequent implant placement in the maxilla were selected using non-randomized consecutive sampling. Surgeries were mostly performed via the buccal cortical plate of the edentulous ridge. The buccal bone was decorticated, Ceno Bone was fixed by titanium screws, covered with Ceno Membrane (resorbable) and sutured. Buccolingual width of the ridge was measured in stage-one surgery and six months later in stage-two surgery for implant placement. A core biopsy was also taken to assess the trabecular thickness, percentage of new bone formation, percentage of remnant particles, degree of inflammation, foreign body reaction, vitality, bone-biomaterial contact and number of blood vessels by microscopic, histologic and histomorphometric analyses of the slides. The clinical ridge width values in the first- and second-stage surgeries were analyzed using  Wilcoxon Signed Rank test.

Results: The mean clinical ridge width at 2mm distance from the ridge crest was 2.49 (0.72) mm in the first-stage and 4.79 (0.75) mm in the second-stage surgery. The mean clinical ridge width at  5mm distance from the ridge crest was 3.6 (0.57) mm in the first-stage and 6.3 (1.13) mm in the second-stage surgery. At both sites, application of Ceno Bone significantly increased the clinical ridge width in the second-stage surgery (both ps<0.05). Also, inflammation in most specimens (85.7%) was grade I and no case of foreign body reaction was seen. Bone was vital in all patients. The  mean  trabecular  thickness was  87.96  (38.74)μ.  The percentage  of new  bone  formation was

58.43 (26.42%) and the percentage of remnant particles was 4.07% (2.44%).

Conclusion: The results of this preliminary study revealed that application of CenoBone stimulates osteogenesis and significantly increases the clinical ridge width at 2 and 5mm distances from the ridge crest for implant placement.

Objective: Since orthodontic and orthognathic treatment planning in each ethnic group must be done according to the soft tissue facial characteristics regarded as beauty, they thus vary from country to country. The main purpose of this articlewas to determine the mean range of the middle third of soft tissue facial profile and anteroposterior lip positioning using 3angular and 2 linear measurements in adult male and female Iranians to compare with European standards.

Methods: After clinical examination of 180 dental students, 70 Iranian adults who had normal occlusion aged between 21 to 29 years (mean:24.5 years) were selected(35 males and 35females). After obtaining consent form, lateral cephalograms were taken in natural head position (NHP) (as seen in a mirror) and analyzed according to the Rickets(E-Line),Tweed-Merrifield(Z-angle) and Holdaway (H-angle).For comparison of data with standards, the One-Sample-t-test and for comparison of measurements between groups, Independent Sample-t-test was used.

Results: Radiographic evaluation revealed that all Iranian samples had significant differences with European standards with no differences between males and females. In the Rickets (E-Line)  analysis, both upper (p<0.001)and lower(p<0.01) lips were behind the E-line. In the Tweed- Merrifield (Z-angle) analysis this angle in the Iranian sample was smaller (p<0.001) and in the Holdaway (H-angle) analysis our sample had smaller H-angle as well (p<0.001).

Conclusion: Iranian adults have retruded upper and lower lip position in both sexes  and  more convex profile than European standards; thismay be due to a more retruded position of the chin and lips or more prominence of the nose in Iranian samples.

Objective: Repair of an indirect restoration is usually preferred over its replacement. This study aimed to evaluate the effect of silane in different surface preparation techniques on the bond strength of direct to indirect composite resin.

Methods: For this in vitro experimental study, 48 indirect composite cubes were fabricated, divided into 4 groups of 12 and subjected to the following preparation techniques: Group 1. Sandblasting with 50μaluminum oxide particles (SB), Group 2. Sandblasting+ silanization (SB+Sil), Group 3. Etching with 9.5% hydrofluoric (HF) acid, Group 4. Etching with 9.5% HF acid+ silanization (HF+Sil). Before the restoration process, specimens were subjected to 500 thermal cycles and received surface preparations. Single Bond adhesive was applied to the surface in all groups. Specimens were restored with direct composite resin and stored in an incubator at 37°C for 24h. Fracture was induced in the specimens by an Instron machine and the shear bond strength was measured. Data were converted to mega Pascal and analyzed using two-way ANOVA and Tukey’s post hoc.

Results: The highest shear bond strength was 13.85 (2.75) MPa and belonged to group 1; while the lowest bond strength was 8.43 (1.35) MPa and observed in group 2.

Conclusion: Based on the obtained results, composite surface preparation by sandblasting yields more favorable results than HF acid etching and application of silane can also increase the bond strength.

Objective: Probable effect of fluoride containing materials like APF on sealants is very important. The purpose of this study is to assess the effect of frequent application of APF (1.23%) on the surface microhardness of two fissure sealants and one flowable composite.

Methods: In this experimental study, 81 specimens of two fissure sealants and one flowable composite were prepared, using special polymer mold in three groups of 27 including unfilled resin sealant (Fissurite F, Voco), filled resin sealant (Fissurit FX, Voco) and one flowable composite (Arabesk Flow, Voco). Then, these three groups were divided into three sub groups of 9 as follows: Group 1, 4, 7 (control): No treatment- Group 2, 8, 5: Single application using APF- Group 3, 6, 9: Six times application using APF. The APF was applied on the experimental specimens every time  for 4 minutes. Then, the samples were stored in the distilled water. Finally, the surface microhardness of the sealants was measured using Vickers test. The statistical analysis was performed by 2-way ANOVA & One-way ANOVA tests.

Results: Type of materials (without filler, containing filler and flowable composite) was effective on the surface microhardness and the difference between three types of materials was statically significant (p<0.001).Unfilled fissure sealants, showed minimum surface microhardness and flow able composite showed maximum surface microhardness. Also, the frequency of gel use (once or many times), had no effect on the average surface microhardness of the materials under review (p>0.05).

Conclusion: All three materials were resistant to the destructive effects of APF gel and it did not make a significant microhardness changes.

Objective: Microbial plaque is among the main etiologies of periodontal disease, and tooth brushing with toothpaste is the most commonly used method of plaque control. This study aimed to compare the efficacy of tooth brushing with and without three different dentifrices.

Methods: Thirty dental students were randomly selected to participate in this clinical trial and were asked to refrain from any plaque control measure for 24 hours. Candidates were then randomly assigned to one of the three groups of tooth brushing with Pooneh whitening toothpaste, Crest 3D White, Sensodyne Original and tooth brushing without toothpaste. Subjects were asked to brush their teeth for two minutes using the Bass technique. Plaque index was calculated before and after the intervention. This process was repeated until all subjects experienced all the understudy interventional protocols (tooth brushing with three different toothpastes and without toothpaste). Data were analyzed by repeated measures ANOVA and paired t-test.

Results: No statistically significant difference was noted in the efficacy of plaque control by tooth brushing with Crest 3D White and Sensodyne Original and tooth brushing without toothpaste; however, significant differences were noted in this respect between Pooneh toothpaste and the remaining three tooth brushing protocols (p≤0.001).

Conclusion: Tooth brushing without toothpaste may have a plaque control efficacy equal or even higher than that of tooth brushing with toothpaste.

Objective: Oral non- Hodgkin’s lymphoma (NHL) is a relatively rare neoplasm that may develop in the soft tissues or jaw bones, with or without node or marrow involvement. Oral lymphomas  are often difficult to diagnose as there are no characteristic clinical features and usually appear as non- tender swellings.

Case: We describe clinical, radiographic, histopathological and immunohistochemical findings of three cases of multifocal NHLs presenting in the oral cavity.

Conclusion: If the oral lesion is multifocal, extra nodal lymphoma must be considered in the differential diagnosis.