Association of characteristics of delivery and medical conditions during the first month of life with developmental defects of enamel.

BACKGROUND: Developmental defects of enamel (DDE) may be influenced by health problems and illness in children. The aim of the study was to identify the main characteristics of birth (delivery) and adverse medical conditions during the first month of life that may be related to DDE in permanent teeth. METHODS: 1000 schoolchildren between the ages of 9 and 11 years were selected for this cross-sectional study by multistage randomization from four educational zones in Shiraz in 2013. Intraoral examination was used to diagnose DDE according to World Health Organization screening guidelines and the Modified DDE Index. The data on seven birth factors as well as health and nutritional conditions during the first month of life were collected by a questionnaire completed by the parents, and were analyzed with the chi-squared test, Spearman's correlation and binary logistic regression. RESULTS: 469 (48.2%) out of 974 schoolchildren had at least one permanent tooth with DDE. The defects were significantly related with Apgar score at birth <7 (p = 0.003) and illness during the first month (p = 0.035). The frequency of DDE was significantly lower in the third child in families compared to the first and second child (p = 0.005). However, DDE showed no significant relationship with gestational age, delivery type, birth weight, gender or type of feeding during early infancy. CONCLUSIONS: Three associated factors were identified (birth Apgar score, illness during the first month of life, birth order) for DDE in permanent teeth. No specific illness was found to be significantly associated with DDE

Effect of EDTA Conditioning on Microleakage of Four Adhesive Systems in Composite Restorations

Objective: Evaluating the effect of dentin conditioning with EDTA on microleakage of composite resin restorations, using two etch and rinse and two self-etch adhesives.Materials and Methods: One hundred and sixty extracted molars received class V cavity preparations right under the CEJ and were randomly divided into eight groups of 20, usingfour different adhesive systems. These adhesives included Adper Scotchbond Multi-purpose (SBMP), Adper Single Bond (SB), Clearfil SE Bond (CSEB), and Adper Prompt L-Pop (PLP). In the SBMP and SB experimental groups, EDTA was applied instead of phosphoric acid. In the CSEB and PLP experimental groups, EDTA conditioning was added to the bonding process. After thermocycling, the amount of dye penetration was evaluated using stereomicroscope. The data were analyzed using the Kruskal-Wallis and Dunn tests.Results: Two etch and rinse adhesives (SBMP, SB) showed a significantly lower micro-leakage than the two self-etch adhesives, CSEB and PLP, (P<0.05). No significant differ-ence was observed among the experimental groups. PLP and CSEB showed significantly less microleakage using EDTA conditioning (P<0.05). There was no significant difference for SBMP and SB when applying either phosphoric acid or EDTA.Conclusion: In the cases of SBMP and SB, EDTA conditioning is as effective as phos-phoric acid in preventing microleakage. In cases of CSEB and PLP, EDTA conditioning can significantly improve the sealing ability

Dentin Bond Strength of Two One-Bottle Adhesives after Delayed Activation of Light-Cured Resin Composites

Objective: Adverse surface interactions between one-bottle adhesives and chemical-cured composites may occur with delayed light activation of light-cured composites. The purpose of this study was to assess the Effects of delayed activation of light-cured compositeson shear bond strength of two one-bottle adhesives with different acidity to bovine dentin.Materials and Methods: Flat dentin surface was prepared on sixty-six bovine incisors using 600 grit carbide papers. Prime&Bond NT, and One-Step adhesives and resin composite were applied in six groups: 1) immediate curing of the composite, 2) the composite was left 2.5 minutes over the cured adhesive before light activation, 3) prior to delayed activation of the composite, the cured adhesive was covered with a layer of nonacidic hydrophobic porcelain bonding resin (Choice 2) and cured immediately. After thermocycling,shear bond strength (SBS) test was performed using a universal testing machine at 1 mm/min crosshead speed. Data were analyzed with Friedmans two-way Non-parametric ANOVA.Results: The SBS of delayed activation of Prime&Bond was significantly lower than immediate activated (P<0.05). Decrease in the SBS of One-Step was not statistically significant after delayed activation. The SBS of delayed activation of Prime&Bond and One-Step with an additional resin layer was significantly higher than delayed activation (P<0.001).Conclusion: The bond strength of Prime&Bond might be compromised by the higher acidity of this adhesive during the 2.5 minutes delayed activation of light-cured composite.Addition of a layer of hydrophobic resin compensated the effect of delayed activation andimproved the bond strength

Effect of Repeated Container Lid Opening on Dentin Shear Bond Strength of Two Dentin Adhesive Systems

Objective: Comparing the effect of repeated opening of the container lid of two dentin adhesive systems, Prime&Bond NT (P&B NT) and iBond (iB), on shear bond strength.Materials and Methods: Intact bovine lower incisors (n=60), fixed in acrylic were ran-domly divided into six groups (n=10). Groups I and II were set as control groups. P&B NT and iB were applied on the samples after five days a week, three times a day for two weeks of use in groups III and VI; and after four weeks of use in groups V and VI. The samples were evaluated by a universal testing-machine (Instron, cross-head speed 1mm/min) and stereomicroscope.Results: There was no significant difference between the bond strengths in any of the three P&B NT. The mean amount of the shear bond strength for iB after 60 times of use (15.31 MPa) was significantly lowerthan that at the baseline (23.51 MPa). There was no significant difference between iB at the baseline and after 30 times of use (19.26 Mpa), and also between iB after 30 times of use and after 60 times of use. All P&B NT groups showed significantly highershear bond strengths when compared with their similar iB groups in iB.Conclusion: Repeated use (60 times) of the all-in-one adhesive container seems to reduce dentin shear bond strength. Therefore, containers with a lower content of the same adhe-sive or a single-dose of the adhesive are preferred

Assessing the Relationship between Dental Caries and Anthropometric Indices in 9-11-Year-old Primary School Children of Shiraz

Abstract Background and aim: Dental caries is the most prevalent chronic childhood disease that has a profound impact on the health of both the individual and community health. On the other, the overweight and underweight in children is a major public health concern influenced by common factors with dental caries. The aim of the present study was to assess the relationship between DMFT (Decay-Missing-Filled-permanent teeth) and anthropometry indices in 9-11 year old primary school children of the city of Shiraz, Iran-2012. Methods: The present cross-sectional study was conducted on primary school children, aged 9 to 11 years, selected by cluster random sampling in four areas of Shiraz city, in 2012. The prevalence of children with dental caries was calculated by measuring the number of teeth decayed, missing or filled duo to caries (DMFT) indices using the WHO screening standards. Weight, height, and sitting height were measured and body mass index (BMI) and leg height were calculated. The association between Anthropometry and DMFT were examined using bivariate correlation and linear regression tests by the SPSS software. The difference mean DMFT index between five groups of BMI was evaluated by ANOVA and post hoc Tukey tests. Results: A total of 974 pupils were studied. Mean DMFT was 0.94±1.46. There were significant association between DMFT and BMI (r=-0/91 p=0/005). Mean DMFT was significantly reduced from underweight children to obese children (p=0/027). Conclusion: Underweight children have a higher risk of developing caries in their permanent teeth. Key words: Body Mass Index, Anthropometry, DMF Inde

Unerupted Primary Molar Teeth Positioned Inferior to the Permanent Premolar: A Case Report

Primary tooth impaction is a rare finding during the development of primary dentition. Several factors contribute to the impaction of a deciduous tooth. This report describes the diagnosis and treatment of a 10-year-old boy who presented an impacted second primary mandibular molar. This tooth, located inferior to the second premolar together with an odontoma, was positioned superior to the premolar teeth. Treatment consisted of surgical removal of the impacted deciduoustooth and odontoma and placement of a passive lower lingual holdingarch. Periodic examination was indicated for follow- up. Early intervention was recommended to manage orofacial disfigurement and to avoid consequent problems

A practicable and reliable test for metal powder spreadability : development of test and analysis technique

A crucial step in the powder bed metal additive manufacturing process is the formation of a thin layer of powder on top of the existing material. The propensity of the powder to form thin layers under the conditions used in additive manufacturing is critically important, but no test method has yet been established to measure this characteristic, which is sometimes referred to as spreadability. The current work spreads a single layer of powder using commercial equipment from the paint and food industries and derives the density of a layer of powder, which is of a similar thickness to that in additive manufacturing. Twenty-four powders from eight suppliers have been tested and the density of the layers has been measured as a function of various parameters. Twenty-two of the powders successfully form thin layers, with a density of at least 40% of each powder’s apparent density. Hall flow time did not correlate with the spread layer density, although the two powders that did not spread did not pass through the Hall funnel. The roughness of the plate onto which the powder was spread, the recoater speed, the layer thickness, particle size and aspect ratio all affect the measured layer density. Results of the new test are repeatable and reproducible. These findings can be used to develop a test for spreadability for metal powders that can be used for additive manufacturing, which will help to improve the quality of printed components. QC 20230524</p