[First and second order generalized estimating equations and it's application in analyzing longitudinal microleakage data]

Longitudinal data are frequently obtained in medical studies. When the main aim of a study is marginal modeling of the mean and the correlation structure is considered as a nuisance parameter, the first- order generalized estimating equations [GEE1] is usually an appropriate option. However, when the modeling of correlation structure is considered the aim of a study, the second- order generalized estimating equations [GEE2] may be the first choice for analyzing the available data. The aim of the study was to evaluate application of first- and second-order generalized estimating equations to analyze longitudinal microleakage data. In this study, GEE1 and GEE2 methods were used to analyze data obtained from a study of microleakage in two root- end filling materials [CEM and MTA] in two different thicknesses and two diameters at three different times of measurement [one day, one week and one month after treatment]. The obtained results from these statistical approaches were compared in continuous and binary [presence of absence] microleakage data. The results from the GEE1 and GEE2 methods showed that time of measurement, material type, diameter and thickness of filling material had significant effects on [continuous] microleakage rate. In addition, in binary microleakage data, these methods revealed that only time and material type were the significant factors. The correlations between measurements were not significant in continuous data, while they were significant in binary response microleakage data. Since the correlations between pairs of measurements were not significant in continuous microleakage data and the obtained estimates were similar in both GEE1 and GEE2 methods, so the simpler GEE1 method seems to be adequate for these data. In contrast, in binary microleakage data, significant correlations were found between measurements. Therefore, in this case the GEE2 methodology may be used to estimate the correlation structure more efficiently

Orofacial clefts and risk factors in Tehran, Iran: a case control study

Non-syndromic cleft lip with or without cleft palate [CL/P] or cleft palate only [CPO] are orofacial clefts with multifactorial etiology. These include environmental factors and heterogeneous genetic background. Therefore, studies on different and homogenous populations can be useful in detecting related factors. The aim of the present study was to evaluate the risk factors in patients with non-syndromic cleft in Tehran, Iran. Data from 300 patients and 300 controls were collected between 2005 and 2010. Binary logistic regression analyses were used to calculate relative risk by odds ratio [OR] and%95 confidence interval. Low maternal age [OR=1.06, 95% Cl, 1.011-1.113], low socioeconomic status [OR=0.23, 95% Cl, 0.007-0.074], maternal systemic disease [OR=0.364; 95% Cl, 0.152-0.873] and passive smoking [OR=0.613, 95% Cl, 0.430-0.874] increased the risk for CL/P and CPO. There was a significant difference in iron and folic acid use during pregnancy when the case and control groups were compared. In assessing for orofacial cleft risk, we should consider lack of folic acid supplementation use, maternal age and systemic diseases and passive smoking as risk factors

[Experimental comparison of hygroscopic expansion in three different composite resins]

These days dental composites are very popular because they look good and are similar to human teeth regarding color. Hygroscopic expansion is one of the physical properties of dental composites. A dental composite may lose its efficiency as a restoration material because of water absorption. The objective of this study was to compare the hygroscopic expansion of three dental composites. In this experimental study, to assess the effective factors of hygroscopic expansion, we used three different dental composites [Kalore, P90 and Z250]. The length of these composites in water and saliva were measured eighteen times in a three-month period. We used the marginal modeling technique, in which the correlation between response data can be included for analysis. The results of marginal modeling showed that the type of composite is significantly related to hygroscopic expansion [P<0.05]; demonstrating the highest hygroscopic expansion for P90 and the lowest for Z250. In addition, time as an independent variable had a statistically significant effect on hygroscopic expansion [P<0.05]. However, we found no significant difference between the hygroscopic expansion of saliva and water [P>0.05]. Overall, our findings showed that hygroscopic expansion is significantly related to the type of composite and time. Therefore, we should utilize the composites with lower hygroscopic expansion [such as Z250] for filling the patients' teeth

Evaluation of solid waste management in the chemistry laboratories of Tehran Universities

Particular importance of hazardous wastes is due to having characteristics such as toxicity, flammability, corrosively and reactivity. Some of the chemical wastes due to having hazardous materials must be collected and managed in a proper manner, since they are potentially harmful to the environment. Owing to the fact that educational centers have important roles in developing countries, so the main objective of the present study was to investigate, hazardous waste management in chemistry laboratories of Ministry of Science universities, in Tehran, Iran. Study area of this research includes all chemistry laboratories in Tehran universities which were covered by Ministry of Science. To obtain the number of samples, based on Scientific Principles and identification formula, 64 samples were calculated. In addition, sampling was done by Stratified sampling. Validated checklists were used for data gathering. Data analysis were done by Descriptive statistics [mean, frequency and etc.] and inferential statistics [kruskal-wallis test]. results obtained in this study indicate that Sharif University by obtaining the mean score of 60.5 and Tehran University by obtaining the mean score of 4.5-6 are placed in best and worst rank, respectively. Beheshty, Alzahra and Tarbiat Moallem univesities by acquiring the mean score of 20-28.5 have a same position in ranking table. Results show that most of the studied laboratories do not have any collection program and only 26.5 percent of them have acceptable programs.The separation and storing program observed in about 12.5 percent. Hazardous wastes* management in chemistry laboratory of Tehran Universities was not in good status. And from the standpoint of management, only 12.5 percent of studied cases are in good status, while 75 percent was in undesirable status

[Effect of Bio-Gen [Bioteck]and Bio-Oss with and without alendronate on bone formation by [guided bone regeneration]: [a histomorphometric study in dogs]]

Several different graft materials, e.g. autologous, allografts, alloplasts or xenografts have been used to preserve or reconstruct the ridge anatomy. The purpose of this study was to investigate histologically and histomorphometrically experimental defects that grafted with Bio-Gen and Bio-oss and influence of local delivery of Alendronate with graft materials on bone formation. This experimental study did in 5 dog's tibia, 7 round intrabony defects, 6mm in diameter and approximately 4 mm in depth were made with trephine bur, each defect in each tibia filled randomly with following groups: 1] Bio-Gen [Bio-teck]+BCG membrane, 2] BBM[Bio-Oss]+Bio-gide membrane, 3]Bio-Gen+ alendronate+BCG membrane, 4] Bio-oss+alendronate+Bio-gide membrane, 5] BCG membrane, 6] Bio-gide membrane, 7] Control [empty]. Animals developed euthanized after 3 months. Immediately after euthanasia the tibia bones were dissected out and the proximal part of the tibias containing the defects were removed in blocks and prepared for Histologic and Histomorphometric evaluation. The data were analyzed using the ANOVA and Tukey procedures. P-values were less than 0.05. Newly formed bone was well evident in all of the defects inflammatory cells were less than 10% in all of them. The mean percentage of new bone in these 4 groups [with grafted materials] was higher than the other ones [with membrane and without grafted materials] and control groups [p<0.05]. There is no statistical different between Bio-Oss and Bio-Gen groups [with or without alendronate] in vital bone percentages. Application of single dose alendronate combination with Bio-oss or Bio-Gen granules doesn't improves bone formation. Bio-Gen granules are considered an osteoconductive graft material suitable for regeneration of bone

[Fatigue resistance and failure mode of endodontically restored premolars with indirect composite resin restoration-in vitro]

The present study aimed at determination of the fatigue resistance and failure mode of cusp-replacing onlays in endodontically treated premolars using indirect composite resin restorations. In this experimental study, 84 human premolars were randomly divided into 7 groups of 12. These groups were prepared as follows: Intact teeth used in group1 as control, the second group covers the endodontically treated teeth, restored with indirect onlays using Z-250 composite resin, the next two groups [i.e. 3, 4] were similar to the second group, but subjected to 1 and 2 million fatigue load cycles, respectively. Groups 5, 6, 7 were similar to groups 2, 3, 4, respectively, however, in these groups Tetric Ceram used as the restorative material. All specimens were loaded using a Universal Testing Machine until fracture occurred and the mode of failure observed with naked eye. Kruskal-Wallis and Chi-Square tests were used to analyze the data [alpha=.05]. All specimens withstood the masticating simulation. The mean fracture strength for groups 1 to 7 were: 1276.92, 1269.05, 1217.80, 1188.13, 1228.97, 1127.86, 1105.58, respectively. No statistically significant differences were found between the groups in fracture strength and failure mode. There was no statistically significant difference between two types of resin composite [P=0.203] and load cycles [P=0.298] after zero, 4 and 8 years aging. Within the limitation of this study, restored premolars with indirect composite onlays show fatigue resistance equal to natural tooth up to 8 years after restoration. Furthermore, no statistically significant differences were found between 4 and 8 years of load cycles. Tetric Ceram Z-250 restoration agent showed no effect on the tooth fracture resistance with the most observed fractures to be occur under CEJ with no capability to be restored

[Oral health related quality of life among Iranian children: Part I - Validity, reliability, prevalence and seventy assessment of daily impact factors]

Given the current need for studies evaluating oral health related quality of life among the Iranian children, this study was designed to test the validity and reliability of a Persian version of Child-OIDP index and also evaluate the prevalence and impact of oral disorders on the quality of life of 11-14-year-old Iranian children. In this cross-sectional study, after translation of Child-OIDP instrument into Persian language, the psychometric properties of this index were evaluated in terms of face, content and construct validity. In addition, the internal and test-retest reliability were evaluated. A sample of 384 Iranian children aged 11-14-years old completed the instrument via a face-to-face interview. Each interview was followed by a clinical examination as well as completion of a self-administered questionnaire providing the information on demographic and oral health behaviors. The Persian version of Child-OIDP demonstrated excellent validity and reliability. The index showed significant associations between perceived oral treatment needs and perceived satisfaction regarding their oral cavity [P<0.001]. ICC was 0.784, and Cronbacrf s alpha was 0.59. About 54% of children reported dental disorders over the past 3 months that impacted on daily performances, according to Child-OIDP index. The most prevalent affected activities were eating and oral hygiene performance. The most prevalent oral disorder leading to impact were sensitivity tooth and gingival bleeding. Based on the results of this study, it can be concluded that the Persian version of Child-OIDP index is a valid and reliable instrument for evaluation of oral health-related quality of life as applied to Iranian children. The prevalence of oral impacts was moderate. The pattern of impacts differed according to the type of self-perceived oral problem

[Relationships between smoking and IL-1 beta concentrations in chronic periodontal patients]

Cigarette smoking is a significant risk factor in pathogenesis and progression of periodontal diseases. Smoking could interfere with pro-inflammatory cytokines in inflammatory process. IL-1 beta is a main inflammatory cytokine in gingival crevicular fluid [GCF] which contributes in periodontitis. In fact it is a key molecule in pathogenesis of periodontitis. This study aimed to investigate the correlation between cigarette smoking and concentration of cytokine interleukin [IL]-1 beta in GCF of patients with moderate-to-sever chronic periodontitis. Sixty subjects were entered into this analytical case-control study, divided equally into smokers and non smokers. Two groups were matched in clinical parameters, age and sex. GCF samples were collected in one diseased and one healthy site from each subject. The IL-1 beta concentration in all 120 samples was determined by ELISA kits, specific for IL-1 beta. The observed data were analysed with SPSS 13 software using T, Paired T, Chi-square and Mann-whitney tests. Mean concentration of GCF IL-1 beta in healthy sites of the smokers was significantly more than non smokers [p<0.01]. But in diseased sites no significant differences were shown between the two groups. The differences between concentration of IL-1 beta in smokers and nonsmokers were not significant. Although no significant differences were found in concentration of IL-1 beta between all smokers and all non smokers, there were significant differences between two groups in healthy sites, which require more investigations

[Validity of teeth width measurements on conventional versus 3D models]

For proper diagnosis of orthodontic problems of a patient, different measurements and analysis should be performed on dental cast. In recent years, due to introduction of paperless offices, 3D reconstruction methods and softwares are available in order to build virtual dental casts and measurements on them. The purpose of the present study was to compare the validity of teeth width measurements on conventional versus 3D models. In this diagnosis study, twenty set-ups of upper and lower casts using artificial teeth corresponding to various malocclusions were created. Impressions were taken of them providing 20 plaster models. The plaster models were scanned by laser surface scanner and the crown widths measured by its software. The gold standard was the teeth width measured by caliper before setting up the teeth. The mesiodistal crown width was also measured on casts as conventional method. The crown width was compared between the three methods by F test, ICC and Dahlberg formula. Coefficient of validity between measurements by 3D scanning and gold standard in overall teeth measurements [premolar to premolar] was 0.914. The mean difference between laser scanning method and gold standard was 1.7 mm and between conventional method and gold was 0.34 mm. In most of the measurements, the difference between mesiodistal crown width belonged to canines. The accuracy of laser surface scanning system was clinically acceptable and in the range of similar studies, but these is not enough for research purposes and it should be improved. In reference to advantages of computerized methods in near future, these methods will be the clinical standard for orthodontic diagnosis

[Microscopic assessment of the effects of chemoradiotherapy on normal oral mucosa in patients with head and neck cancer]

There are only few studies about effect of chemoradiotherapy based on cellular level. The aim of this study was to evaluate the effects of such treatment on normal cells of oral mucosa. Seventy patients whose normal oral mucosa was exposed to radiation during the course of chemoradiotherapy were selected. Before starting the treatment, 2 slides from the normal oral mucosa were prepared for each patient, one from keratinized and one from non keratinized mucosa. At the end of treatment 2 other slides were taken from the same area too. After observing the slides under light microscope in blind form, the results of the observation from the first slides were compared with the results of the second one. Statistical analysis was carried out by Mc Nemar, Marginal Homogeneity and Wilcoxon tests. The results revealed changes in nucleus and cytoplasm. and N/C ratio, formation of bizar cells, cellular abnormality, nucleous and cytoplasmic vacuolization in affected cells during treatment. There was statistically significant differences between the groups [p < 0.001]. Keratinization of basal cell mucosa in cytology slide was observed after treatment [P < 0.01] and also there was an increase in number of inflammatory cells [p < 0.001]. Cellular apoptosis, numerous granular cells with large size granules, cells with multiple nucleous and clear nuclei, bacterial colony and candida were observed after treatment. chemoradiotherapy may induce formation of bizar cells, abnormal nocleous and cytoptasm, changes in N/C ratio. Cellular abnormality, and cellular vacuolization

Correlation between periodontal diseases and mouth breathing

Some studies have reported direct relationship between mouth breathing and increased susceptibility of patients to develop periodontal diseases. The present study was designed to evaluate the correlation between periodontal diseases and mouth breathing in Iranian population. This historical cohort study was conducted with 90 participants aged 20-35 years-old, who were referred to Isfahan Dental School and few other private dental clinics in the city of Isfahan in the year 2003. All participants had to be free of relevant systemic conditions. The cases were defined as patients with mouth breathing, having dome-shaped palate and open mouth [lips] when in rest position. Oral examination was conducted using 3 diagnostic criteria. Forty-five patients who were confirmed by all three criteria were included in the study as cases. The control group was composed of subjects who had normal breathing from their nose. The gingival index was determined for posterior and anterior regions of all participants. The statistical analysis was conducted and Mann- Whitney U tests was used in order to determine group differences. The gingival indices in the anterior region of cases were determined. The number of individual with scores 1, 2 and 3 were five [11.1%], 36 [80%] and four [8.9%] respectively. The scores in control group for five subjects [11.1%] was [0] or had no gingival condition, 32 [71.1%] subjects had score one and eight [17.8%] had score 2. The group differences were statistically significant [P < 0.001]. No significant difference was detected in posterior gingival indices [P > 0.05]. Mouth breathing can be a contributing factor in increasing the risk of periodontal diseases

[Fluoride retention in saliva following toothbrushing with two Iranian fluoride dentifrices, Nasim and Crend in comparison with sample dentifrices]

The presence of fluoride in oral fluids, is necessary for prevention of dental caries. The aim of this study was to determine the extent of fluoride retention in saliva after brushing with two Iranian fluoridated toothpastes, Nasim and Crend in comparison with MacLeans and Crest. Ten adults used a nonfluoride dentifrice for 10 days before the experiment and between different stages of the experiment. The dentifrices included Nasim and MacLeans [with sodium monofluorophosphate] and Crend and Crest [with sodium fluoride]. In each procedure, participants brushed their teeth with 1.5 gr of the dentifrices under trial for 1 minute. Saliva samples were collected at baseline, 1, 30, 60; 120 minutes after tooth brushing and fluoride ion were measured by potentiometry technique. The data were analyzed by Repeated Measurements, Paired t, One Way ANOVA and Tukey tests. All dentifrices under this trial, had the highest fluoride concentration in saliva 1 minute after brushing [P<0.005] and after that time fluoride concentration decreased gradually. Crest toothpaste in comparison with Crend had higher fluoride retention in the 60 and 120 minutes [60 minutes: [0.9824 +/- 0.0988, 0.5173 +/- 0.770] [P<0.005]; 120 minutes: [0.8103 +/- 0.0615, 0.3651 +/- 0.0580] [P<0.008]]. The Crest dentifrice showed the most fluoride retention in saliva, MacLeans and Nasim dentifrices had similar values of fluoride retention while the Crend dentifrice showed the least values of fluoride retention

Modified index of orthodontic treatment needs [IOTN] assessment by senior dental students

Rater's reliability is an important issue in index calculation. The purpose of this study was to evaluate the intra-examiner agreement in identification of orthodontic treatment needs using modified IOTN. In this analytical cross-section study, six senior dental students identified IOTN on 42 dental casts by means of a standard DHC ruler with a two-week time lag. The kappa and association models were used to analyze the data. The kappa statistics showed intra-rater agreements between 0.54 and 0.77 [ +/- 0.65], which can be considered as [good]. About 33% of the students had problems in distinguishing the first and second levels of the index, while there were fewer problems in distinguishing between the second and third levels. The category identification with most problems was the distinction between the first and second levels [0.48], and the one with the least problem was that of the second and third levels [0.99]. The distinction of the first and second levels in modified IOTN is hard for the examiners. Therefore, this issue should be considered in calibration training programs when using this index in screening, survey or epidemiological evaluations