Journal of Islamic Dental Association of IRAN
Volume:30 Issue: 4, Autumn 2018

  Restoration of endodontically treated teeth is one of the most important and challenging topics in restorative dentistry. Longevity of such restorations is an essential factor in treatment planning. Amalgam build-up is a conservative method for restoration of endodontically treated teeth. Therefore, this study aimed to assess the longevity of this type of restoration in endodontically treated molar teeth. In this retrospective study, 110 endodontically treated molar teeth of 98 patients that had received amalgam build-up restorations with at least one cusp coverage with 3-10 years of longevity were evaluated. The restorations included mesio-occluso-distal (MOD;40%), disto-occlusal (DO;23%), mesio-occlusal (MO;17%) and complex amalgam restorations (20%). Binary logistic regression and Kaplan-Meier tests were used for statistical analysis. Of all restorations, cracks were observed in 22.7% of restorative materials and 10.9% of teeth. Secondary caries was found in 29% of the teeth. Based on binary lo-gistic regression, MOD restorations had significantly higher rate of marginal fracture and recurrent caries (P<0.05). Teeth with one or four built-up cusps were significantly more resistant to fracture compared to other groups. Patients, who regularly used dental floss had significantly lower rate of secondary caries and restoration fracture (P=0.032). The average longevity of amalgam build-up restorations was 8.45 years, which is comparable to minimum longevity of casting restorations. Thus, amalgam restorations seem to be an acceptable conservative method for restoration of endodontically treated teeth

Marginal adaptation has a significant role in the success and longevity of indirect restorations. This experimental study compared the effect of intraoral and extraoral scanning on the marginal adaptation of the crowns which was made using the CEREC AC system. A Typodont maxillary first molar was prepared and served as the master die for an all-ceramic restoration. In the first group, the model was scanned ten times directly by the intraoral scanner. In the second group, ten conventional impressions were made from Typodont, and the extraoral scanner scanned the resulting gypsum casts. The data was used to design and build crowns from IPS e.max CAD blocks. The crowns were placed on the prepared tooth, and the marginal gap was measured at 16 points by a stereomicroscope at ×35 magnification. Collected data were analyzed using t-test. The mean marginal gap for intraoral and extraoral groups were 74.83 ± 10.07 μm and 102.56 ± 6.89 μm respectively. The gap was significantly less in the intraoral group (P-value = 0.001). Marginal adaptation was clinically acceptable in both groups, although the results of intraoral scanning showed significantly lower gap than extraoral scanning.
Keywords: Computer aided design/computer aided manufacturing, all-ceramic crowns, intraoral scanners, extraoral scanners, Dental Marginal Adaptatio

The aim of this study was to compare the knowledge and skill performance obtained by dental students exposed to two different instructional modalities for periodontal flap surgery: a Computer-Assisted Learning (CAL) multimedia software program and traditional lecture. In this experimental study, fifty volunteer fourth-year dental students with similar grade point average (GPA) scores, with the age range of 22 to 27 years, were divided into two groups (n=25). They all completed a pretest. The test group used a multimedia software, while the control group attended a lecture with the same educational content. Immediately after the lecture and after the students of the soft-ware group have finished watching the program, they completed a test consisting of 14 questions. Then, they were all assigned to perform some skills of periodontal flap surgery on an animal model. The performance of each student was assessed using a questionnaire of 13 items. Data were analyzed using independent samples t-test, Fisher's exact test, and Pearson's chi-squared test. There were no differences in prior knowledge between the two groups at the baseline. The software group had a final average exam score of 12.8+1.50, and the lecture group had an average score of 10.24+1.36; the difference was statistically significant (P<0.001). The CAL group had superior performance in some skills related to periodontal flap surgery (9.98+4.63 and 4.26+4.07, respectively; P<0.000). The multimedia software program can be used as an adjunct to traditional education or as a means of self-instruction in teaching periodontal flap surgery techniques.

  Carbonated diet soda is the most common etiologic factor for dental erosion, and fluoride products have been proposed as an option for the preven-tion of that problem. This study evaluated the effect of Remin Pro and neutral sodium fluoride on the prevention of dental enamel erosion using profilometry. This study was conducted using an experimental-laboratory method on 20 extracted premolars with no corrosion, abrasion, crack or hypocalcification. For a proper evaluation, the buccal aspect of each specimen was polished using 800- to 1200- and 2500-grit silicon carbide papers. Enamel was analyzed by surface profilometry. Samples were randomly allocated into two groups of Remin Pro and neutral sodium fluoride for pretreatment. After pretreatment, the surface rough-ness of enamel was measured. In the third stage, the samples were exposed to cola, rinsed with deionized water, and stored in artificial saliva, and surface loss and rough-ness were measured. Independent samples t-test and repeated measures analysis of var-iance (ANOVA) were used to analyze the data. According to the results of this study, neutral sodium fluoride foam and Remin Pro reduced enamel erosion. The mean surface roughness after pretreatments with Remin Pro and neutral sodium fluoride foam was less than that after polishing (P=0.004) and exposure to acid (P=0.026). Neutral sodium fluoride foam and Remin Pro have the same effect on preventing dental erosion.

  Bonding of zirconia to resin cement is challenging, and the zirconia surface requires surface treatment to yield an acceptable bond strength. This study aimed to evaluate the effect of different surface treatments on the bond strength of zirconia to a resin cement. In this in-vitro experimental study, 60 zirconia discs measuring 12 mm in diameter and 2 mm in thickness were randomly divided in to six groups of 10: (I) No treatment, (II) sandblasting plus neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1 W), (III) sandblasting plus Nd:YAG laser (2 W), (IV) Nd:YAG laser alone (1 W), (V) Nd:YAG laser alone (2 W), and (VI) sandblasting. Using a custom-made punch, a V-shaped bonding area with a 4-mm diameter and 90° angle was created in a Teflon tape. Composite cylinders (Filtek Z250) were then fabricated and bonded to conditioned zirconia ceramic using Clearfil self-adhesive lut-ing cement. Specimens were stored in distilled water at 37°C for 24 hours. Then, the specimens were tested for bond strength using a universal testing machine. Data were analyzed using two-way analysis of variance (ANOVA) followed by t-test. One-way ANOVA and Tukey's HSD (honestly significant difference) test were applied for evaluating the effect of the laser. Sandblasting caused a significantly higher bond strength compared to other methods (P=0.00). Among the laser-irradiated groups, Nd:YAG laser (2 W) yielded a higher bond strength (P<0.05). Sandblasting of high-strength zirconia ceramic can significantly increase its bond strength, but no significant difference in bond strength was noted in the laser-irradiated groups

  Permanent first molars (PFMs) are highly susceptible to caries due to their special anatomical form, early eruption, lack of awareness about their eruption and misidentifying them from the primary teeth. Parental awareness about the existence of PFMs in their children’s mouth could lead to caries prevention. This study aimed to determine the level of parental awareness about the presence of PFMs and its relation to DMFT index in 7-9-year-old children in Rasht. This analytical cross-sectional study was conducted on 553 elementary school students in Rasht. Cluster random sampling was done. A checklist was filled out by the parents after obtaining their informed consent. Intraoral examination was performed by one specialist using a dental mirror, an explorer and a head light. Children’s DMFT index of PFMs (DMFT6) was recorded. Data were entered into SPSS software version 21. Chi- square test, Cochran’s test, sign test and logistic regression model were used for statistical analysis. In this study, only 151 parents (27.3%) knew about the PFMs’ eruption time. DMFT6 was 0.48±0.84 in 7-9-year-olds. There was a significant correlation between DMFT6 and the frequency of consumption of sugary snacks (P=0.025) and toothbrushing (P=0.016). But the correlation between DMFT6 and parental knowledge (P=0.918), gender (P=0.44), father’s educational level (P=0.103) and mother’s educational level (P=0.145) was not significant. Considering the low level of awareness of parents, attention to early education, prevention and treatment is necessary.