Journal of Dental School
Volume:25 Issue: 4, 2008

Together with the controversy which exists in the efficacy of new PAC light curing units, this study evaluated the irradiation effect of plasma ARC and halogen light curing units on the microhardness of three resin composites. In this experimental study, two light – curing units including Remecure CL 15 (PAC) (with the output of 1600 mW/cm2) and Arialux (QTH) (with the output of 710 mW/cm2) were used. Six specimens of three type of resin composite were prepared in a steel mold with 2mm thickness. The three composites were CeramX (Dentsply), Heliomolar (Vivadent) and Z100 (3M). Curing time with Remecure was 5 seconds and with Arialux was as the composite manufacturer recommended. After 24 hours, vickers hardness measurements on top and bottom surfaces of each specimen were made and the bottom/top vickers hardness (B/T VHN) was determined. Microhardness of two surfaces in each group was compared by t, 2-way ANOVA and Tukey tests. For CeramX composite two light curing units showed the same microhardness on the top and bottom surfaces. Heliomolar showed significantly lower values of microhardness on both surfaces and B/T VHN with Remecure. In Z100 specimens microhardness (on both surfaces) was lower with Remecure but B/T VHN was the same (P<0.05). Except Heliomolar specimens which were cured by Remecure, B/T VHN was acceptable in all groups (more than 80%). The efficiency of Remecure unit in manufacturer's instruction time was equivalent or lower than conventional halogen light depending on the type of resin composite.

Nowadays various types of dental cements are used in fixed prosthetic treatments with different indications. On the other hand, these indications may be changed over a lot every day and new materials are being produced. The aim of this study was to determine the practice of dentists (included general practitioners and prosthodontists) about applications and manipulations of dental cements in fixed prosthetic treatments. Methods & Materials: The study was designed as a cross-sectional, descriptive method. Samples were 362 general practitioners (GP) and 32 (academic and non-academic staff) specialists worked in Great Tehran in 2004. Sampling was done in a simple random method. The questionnaire consisted of 11 questions. After determining the validity of questionnaire, it's reliability was confirmed by means of a test – retest exam. Zinc phosphate was the most frequent cement in fixed partial denture restorations (FPDs) in non-vital teeth (54.4% of GPs and 51.3% of specialists). In vital teeth, both in preparations near and distant to the pulp, polycarboxylate were used frequently by GPs (50.8% and 56.4%, respectively) and specialists (531% and 34.4%, respectively). The most of dentists in both groups were using zinc oxide with eugenol in temporary restorations near the pulp (55.5% and 62.5%, respectively). Zinc phosphate was frequently used for post and core cases (54.5% and 71.9%, respectively). The choices of general practitioners were relatively similar to specialists.

It is well - known that sex hormones regulate bone metabolism. Sex steroids increase osteoblasts activities and affect growth, remodeling and bone homeostasis. The aim of this study was to examine the effects of sex hormones deficiency on craniofacial growth in rats. Methods & Materials: Fifty, thirty–day–old Wistar rats comprised the sample in this experimental study. 25 male rats were divided into 2 groups: Experimental group, ORX, (n=15) and control group, sham- operation, (n=10) and 25 female rats were divided in the same way: Experimental group, OVX, (n=15) and control group, sham- operation, (n=10). Body length and weight were registered monthly. The rats were sacrificed 6 months after the surgery. Direct millimetric measurements of the skeletodental variables and the tibial length were obtained by using electronic caliper. Serum testosterone, progesterone and estradiol levels were measured by ELISA. One Way ANOVA, Tukey and Student t tests were used to analyze the data. Serum testosterone level significantly decreased in the ORX group as compared with the male sham- operated group. In the ORX group, body length and weight, coronoid height, mandibular length, mandibular arch length, midfacial width, midfacial length, midfacial height, calvarial width, maxillary arch width, premaxillary length, nasal bone height, facial width, basisphenoid bone length and tibia bone length were significantly smaller than in the male control group. Structures showing cartilaginous growth were influenced more than structures showing sutural growth. Estradiol level did not change in OVX group, but despite the significant decrease in progesterone level, no significant differences except weight were found between the OVX group and female control group. In conclusion, it is strongly suggested that the suppression of sex hormones secretion in the growth phase might inhibit craniofacial growth and results in poor craniofacial development and developing malocclusion.

Due to different complications of tongue tie, this study aimed at determining the prevalence of tongue tie in 12 – 14 years olds students of Tehran city in 2003. Methods & Materials: This descriptive study was done on 4900 students randomly selected and studied by questionnaire and clinical examinations. The examinations were done by dental mirror under daylight. The individuals who were unable to point the tongue tip or touch the palate with the tip of the tongue when the mouth was semi opened, were considered to be tongue tied. The data were analyzed by SPSS 11.0, descriptive statistics and chi – square test. Tongue tie prevalence was determined as 2.33% (114 cases). 57 (50%) of them were male and 57 ones (50%) were females. 67.6% of the patients showed crowding of upper anterior teeth, 30.7% crowding of lower anterior teeth, anterior and posterior crossbite was observed in 38.7% and 27% respectively, 6.3% and 17.1% presented anterior and posterior open bite, 17.1% with gingival recession in lower anterior teeth, 19.8% with diastema among lower central teeth. 41.4% had complaint from stiffness at shoulders, 20.7% from speaking disorders, 1.8% from breathing disorders and 28% of food impactions. 46.8%, 15.3% and 37.9% of them showed Cl I, Cl II and Cl III respectively with no normal occlusion being found. The prevalence of tongue tie among Tehran students was higher compared to some studies. As different meanings are mentioned about tongue tie, this difference can be justified.

Regarding to the prevalence of gingival recession, esthetic and sensitivity problems of denuded roots, a variety of surgical techniques have been used to cover recession type defects. This sequential matched randomized double blind clinical trial was designed to compare the clinical outcome following treatment of localized gingival recession by subepithelial connective tissue graft (SeCTG) with and without epithelial collar. Methods & Materials: Nine consecutively patients with bilateral 24 Miller class I gingival recession in non - molar teeth, were participated in this study. The surgical areas were randomly selected as split mouth and were treated by SeCTG with or without epithelial collar. Clinical measurements including recession height (RH), recession width (RW), probing depth (PD), keratinized gingiva (KG), and clinical attachment level (CAL) were measured at baseline and 3 months post operatively by means of Williams probe, caliper and stent. Changes in these clinical parameters were calculated in and between groups and analyzed statistically with paired T test. Both treatments resulted in a significant decrease in RH (1.88± 0.93 mm, P<0.000 in SeCTG with collar epithelium 1.54±1.11 mm, P<0.001 in SeCTG without collar epithelium) and RW (1.62±1.38 mm, P<0.002 in SeCTG with collar epithelium 1.22±1.62 mm, P<0.024 in SeCTG without collar epithelium). The mean changes in RH, RW, KG, CAL in each group to baseline were significant. However, the amount of these variables were not significant between the two groups. The subepithelial connective tissue graft with epithelial collar offers a more convenient approach for handling and suturing as a root coverage procedure and increasing width of keratinized gingiva in Miller class I recession defects specially in fixed and removable partial dentures for abutment teeth.

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder with an incidence of 1/15000, which is sometimes called the adrenogenital syndrome. This disorder which occurs during fetal development is a consequence of inborn errors in cortisol biosynthesis. Compensatory overproduction of ACTH by the fetus to overcome cortisol deficiency produces hyperplastic but inefficient adrenal cortices. More than 90% of cases result from mutations of CYP21 gene, leading to 21- hydroxyllase deficiency, which is essential not only for cortisol biosynthesis but also for aldosterone formation. Deficient or excessive mineralocorticoid production is the other major clinical problem associated with CAH syndrome. The distinctive clinical features of the CAH syndrome result from inappropriate production of both sex steroids and mineralocorticoids. In its classical form, CAH is severe and consists of the virilizing (increase of androgens) and salt wasting (lack of aldosteron) phenotype. When a probond exists, early prenatal diagnosis for CAH can be performed by direct molecular analysis in the first trimester. Case Report: In recently reported case, the patient is a 10 year old young boy whose parent's chief complaint were unerupted maxillary right central incisor. After taking a complete history the patient was diagnosed with CAH. His 18 year old sister was affected too. Up to now, there has been no report regarding the oral and dental status of these patients in the literature. It is probable that delayed eruption and root formation of some teeth can be related to either this congenital disorder or drug consumption.

During infection control process, disinfection of prosthesis is important. But disinfecting method can cause some changes on dentures surface. The aim of this study was to evaluate the effect of disinfectant agents on surface roughness of denture base materials. Methods & Materials: In this study two chemical disinfectants (sodium hypochlorite 0.5%, glutaraldehyde 2%) and two dentures resin materials (Acropars, Meliodent) were used. 40 acrylic resin samples were made. Changes from baseline for surface roughness at four different times (10 minutes, 30 minutes, 24 hours and 7 days) were recorded. ANOVA and Duncan and T-test analysis compared the mean surface roughness of the groups. Mean variation of surface roughness for Acropars resin in sodium hypochlorite and glutaraldehyde at 24 hours and 7 days was significant (P<0.001). This variation for Meliodent resin 7 days after immersion in hypoclorite 0.5% was significant (P<0.001). Mean variation of surface roughness for Meliodent resin in glutaraldehyde was not significant for the time of the study. Mean surface roughness difference among Meliodent and Acropars resin in glutaraldehyde and sodium hypochlorite after 10 minutes and 24 hours was significant (P<0.001). The difference between these two acrylic resin after 7 days in gluteraldehyde was also significant (P<0.001). Result of this study indicated sodium hypochlorite 0.5% and glutaraldehyde 2% can be used on Acropars only up to a period of 30 minutes. Sodium hypochlorite 0.5% can be used on Meliodent for 24 h. However gluteraldehyde 2% can be used for a longer period.

The determination of the tooth size- arch size relationship (space analysis) is an important factor for diagnosis and treatment planning in the mixed dentition. It is essential to use this analysis before eruption of the canines, first and second premolars. This study produced linear regression equations for an Iranian population. Study models of 276 subjects (138 males and 138 females) were selected from pretreatment patients’ records of Orthodontic Department of Dental School and private offices in Shiraz. The greatest mesiodistal diameters of all teeth on each model were obtained except the second and third molar by digital caliper with 0.01mm accuracy. Finally, regression equations (Y=a+bx) were formulated to be used clinically for the estimation of mesiodistal width of permanent unerupted canines and premolars. SPSS software and Wilcoxon Signed Ranks test were used to analyze the date. The coefficients of determination (r2) of the regressions ranged between 0.17 and 0.47 and were higher for females than males, and also mandible than maxilla. It found significant difference between the prediction of this study and Moyers’ prediction. The equations derived in this study were Y=11.71+0.43x and Y=8.22+0.57x for maxilla and mandible respectively. At the other hand, the 85% level was a more accurate determination than the commonly used 75% confidence level likewise. Moyers’ prediction tables were found to under-estimate tooth size summation compared with the present investigation.

Comparing medical universities is a useful tool to identify best practices and situation analysis in educational services and may be used as a benchmark tool for planning and identifying goals and periorities. In this study we designed criteria to compare dental schools structures and performances and identified best practices among them. Methods & Materials: In this experimental study, in the project’s expert panel committee, consisting of dentistry faculty members and medical education experts, a benchmarking tool was devised by using goal analysis and brain storming methods. This tool was used to measure the educational performances of dental schools nationwide. Indicators’ weights were defined through consensus developing methods. Each school was asked to introduce a representative who would complete a questionnaire, which was designed to collect schools’ information. In the next step, all the divisions were visited by project's members. Then, data retrieval was performed and verified at the project’s office. Fifty seven criteria for evaluating educational services in dental schools were classified in 7 subgroups: 1. national university enterance exam (2.1%), 2. faculties (15.7%), 3. equipment & facilities (23.2%), 4. management (31.6%), 5. help & support systems (7.4%), 6. outputs (14.6%) and 7. faculty products (5.4%). Shahid Beheshti Dental School gained the first rank, with the score of 70.12 out of 100. Authorities have used practical strategies and benchmarks of this study for qualitative and quantitative improvement of educational services.

Plaque induced gingivitis is the most prevalent form of periodontal diseases and there are several reports demonstrating low efficiency of mechanical methods to control the dental plaque completely. Chemical method has been found as an adjunct to mechanical plaque control. The purpose of this clinical trial was to evaluate the clinical outcomes of chlorhexidine when used subgingivally with dental floss versus normal flossing alone. Thirty-seven female dental students with gingivitis and at least 2 sites with probing depth of 2mm and bleeding on probing in each quadrant participated in this split mouth clinical trial study. Following the initial evaluation of Plaque Index (PI), Bleeding Index (BI) and Gingival Index (GI), all patient received oral hygiene instruction, polishing and SRP (Scaling & Root Planning) if needed and their quadrants were affected by chlorhexidine impregnated floss in one side and dental floss in another side randomly. The measurements were repeated at 3 & 6 weeks. Then data were analyzed statistically within each group (Paired T Test) and between the groups (T Test) with an α-error level less than 0.05. Both methods presented significant improvement in PI and GI after 3 & 6 weeks and chlorhexidine impregnated floss showed a significantly greater reduction in PI after 3 weeks (1.5±0.7) and GI after 6 weeks (1.2±0.4) as compared to dental floss alone (respectively 1.7±0.65, 1.5±0.35, P<0.05). The results indicated that chlorhexidine impregnated floss provided a more significant improvement of clinical outcomes than dental floss alone and recommends long term studies on various samples to validate these results.