Journal of Dental School
Volume:32 Issue: 1, 2014

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 FRC post restorations to dental students in Department of Restorative Dentistry. 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, student's perspectives were sought via a questionnaire. Data were analyzed using SPSS, Student’s t-test and Chi-square test. 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. Watching the educational film yielded greater test scores than the clinical demonstration.

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. 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. 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. The degree of marginal microleakage in soft-start (SS) polymerization was not significantly different from that in conventional and pulse polymerizations of class V composite restorations.

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, CenoBone has been recently produced by HamanandSazBaft 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. 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, CenoBone was fixed by titanium screws, covered with CenoMembrane (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. 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 CenoBone 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±38.74μ. The percentage of new bone formation was 58.43±26.42% and the percentage of remnant particles was 4.07±2.44%. 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.

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

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. 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. 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 now effect on the average surface microhardness of the materials under review(P>0/05). All three materials were resistant to the destructive effects of APF gel and it did not make a significant microhardness changes.