Journal of Dentistry, Shiraz University of Medical Sciences
Volume:11 Issue: 3, 2010

Statement of Problem: Polymerization shrinkage is one of the major problems of the current dental composites and it can cause marginal gap and post-operative sensitivity.

The purpose of this study was to investigate the effect of nanoporous fillers on the polymerization shrinkage and degree of conversion of an experimental dental composite in three different curing modes and also comparing the its results of it with another experimental composite containing conventional fillers.Methods and Material: In this study, the experimental composite was prepared by mixing the silane treated fillers with monomers. The monomers consisted of 70% Bis-GMA and 30% TEG DMA by weight. The experimental composite was divided into two groups according to their filler type, i.e. conventional micro-hybrid and nanoporous. In order to make nanoporous fillers, the fillers were sintered in 1300°c and grinded Camphorquinon and DMA EMA were used as initiator-accelerator systems. Polymerization shrinkage was measured using bonded disc method in three curing modes (High Intensity, Ramp, Standard). The degree of convention was measured using FTIR spectroscopy.

The results showed that the nanoporous fillers have a positive effect on the reduction of polymerization shrinkage strain. No significant difference was found in polymerization shrinkage of the three curing modes. Neither the type of the fillers nor the mode of cure had an effect on the degree of conversion.

Lower polymerization shrinkage strain can be achieved by using nanoporous fillers. The mode of cure does not affect the polymerization shrinkage.

Statement of Problem: Ameloblastomas are locally aggressive tumors with which the researchers have been mostly concerned to understand their biological behavior. Overexpression of minichromosome maintenance 3 (MCM3, a recently introduced marker) has been reported in different cancers. There is no study about MCM3 expression in ameloblastoma. This study aims at the evaluation of MCM3, Ki-67 and p27 in ameloblastoma.Methods and Material: In this analytical study, 18 ameloblastomas were selected. Clinicohistopathological data were recorded and immuohistochemical staining was done on the newly cut sections for Ki-67 antigen, p27 kip1 and MCM3. The immunostained cells were counted on 10 HPF (Labeling Index) and then classified into negative (LI5), low (550) levels. Statistical analysis was done performed in SPSS, version 13, using ordinal regression and Freidman tests. P value less than 0.05 was considered significant.

Results

Among the lesions, 5 (27.8%) and 13 (72.2%) were negative and weak for Ki-67, respectively. Also, 5 (27.8%), 11(61.1%) and 2 (11.1%) lesions were negative, weak and moderate, respectively for p27. Ki-67 and p27 staining were seen more frequently in the ameloblast layer and stellate reticulum, respectively. None of the samples was stained by MCM3. There were significant differences among Ki-67, p27 and MCM3 expression in ameloblastomas but no differences were found between sex, age and tumor size and expression of these markers.

Conclusion

Most of the ameloblastomas expressed low levels of Ki-67 and p27 (72.2% and 61.1%, respectively). It could not be concluded exactly how these tumors will behave in the future, because low expression of p27 is in favor of cell proliferation (in contrast to low expression of Ki-67). To find out how biological behavior of these tumors will be in the future, other markers should be evaluated and all the patients should be followed up. Regarding the negative expression of MCM3 in all lesions, it seems that MCM3 is not involved in the pathogenesis of ameloblastoma.

Statement of Problem: Contamination during the procedure is the main reason for failure of fissure sealant therapy. In clinical conditions with difficult isolation such as with semi-erupted tooth or poor cooperation of the patient, the contamination is probable. There are is a limited number of clinical studies regarding the effect of adhesive on the success rates of fissure sealant The present study was conducted to compare the effects of two adhesives on the success rate of fissure sealant in the contaminated enamel. Methods and Material: In this clinical trial study, 35 school children (6-8 years of age) with healthy and newly-erupted upper molar teeth participated. Sixty molar teeth were selected and divided into two groups. PQ1 adhesive was used for one group and PROMPT-L-POP for the other. As the teeth were newly erupted and the distopalatal area was in contact with the gingival sulcus and therefore it was impossible to isolate, the distal area was considered as contaminated and the mesial area, capable of adequate isolation, was assumed as isolated. In each group, after etching in one side, the teeth were treated only with sealant and on the other side before treatment with sealant, firstly the bonding agent was applied. So, two control groups were formed for each bonding agent. After 3, 6 and 12 -month intervals, the results of the treatment were studied in terms of the success and failure and then analyzed using Wilcoxon, Mann Whitney and Chi-square tests. The success rate of the sealant treatment increased significantly, by using adhesives (p <0.001). The use of the two adhesives significantly increased the success rate of the fissure sealant on the contaminated teeth, even more than when the teeth had been isolated properly and treated only with fissure sealant (p <0.001). The result of using PQ1 was better than that of Prompt-l-pop although the difference was not statistically significant. The results of the study showed that the contaminated enamel influenced the success of treatment after etching and before sealant application. So, the use of the adhesives in the treatment of fissure sealants is recommended in both the isolated and contaminated conditions.

Statement of Problem: There is a probability of interaction between impression materials especially Polyether with the external surface of the adhesive layer of the immediately sealed dentin in the presence of oxygen inhibited layer. The aim of the present study was to evaluate the effect of three different surface cleaning methods on the shear bond strength of porcelain to the immediately sealed dentin.Methods and Material: In this in-vitro study, the facial surfaces of 60 extracted premolars were immediately sealed, using single-bond adhesive. Then, the immediately sealed dentin surfaces were buried in the polyether impression material while setting. After the impression materials were removed, the samples were randomly divided into 4 groups. In group 1, porcelain samples were bonded to the teeth surfaces using resin cement without any surface cleaning. In groups 2, 3 and 4, surface cleaning using acid etche, air abrasion and pumice with rubber cup prophylaxis were applied respectively for each group before bonding the porcelain samples. Shear bond strength test was performed at the strain rate of 0.5 mm/min. The data were analyzed using One-way ANOVA and Tukey post-hoc tests. There were significant differences between the shear bond strength of the control group and the three surface cleaning method groups (p <0.001). The mean of the shear bond strength in the acid etch group was greater than that of the two other experimental groups; however, there were no significant differences between the three surface cleaning methods (p = 0.5). Surface cleaning of immediately sealed dentin using acid etche, air abrasion and prophylaxis, after impression with polyether, significantly improves the strength of the bond.

Statement of Problem: Bitewing radiography is a suitable clinical technique for the diagnosis of interproximal caries. Many researches performed in this field have shown that direct digital radiography and conventional radiography films in dentistry are similar in detecting inter- proximal caries. To compare the effects of image processing mode of colorize on the efficacy of the detection of interproximal carious lesions viewed in direct digital radiography.Methods and Material: A total of 102 proximal surfaces of the extracted human premolar teeth on direct digital images with and without application of pseudocolor filter were evaluated by three observers. The teeth were sectioned and viewed microscopically to determine the gold standard. The kappa value agreement ratio was calculated. Sensitivity and specificity values in normal digital images were found to be 66.7% and 60% and for colorized images 80.5% and 50%, respectively. However, there was no statistically significant difference between the two types of images (p = 0.12). In this study, application of pseudocolor software failed to result in statistically significant differences between normal and colorized digital images.

Statement of Problem: Dental age estimation methods are used in the treatment plan and the identification of the age of unknown corps and skulls. One of the methods of age estimation is Foti method which is based on regression analysis of dental variables (number of tooth germs and erupted tooth) for which four models have been proposed. The aim of the present study was to compare the dental age derived from these four methods with the Demirjian method on the basis of chronological age.Methods and Material: In this cross-sectional descriptive study, 150 panoramic radiographs of 90 girls and 60 boys aged 6-20 years were studied. The variables required for regression analysis were derived from clinical examinations and panoramic radiographs. Demirjian age was determined using panoramic radiographs. The mean chronological age was 10.74±3.02, Demirjian age 11.16, ± 2.76, model one 11.57±1.61, two 11.44±2.35, three 11.53± 2.49 and four was 11.24±1.85 years. The comparison between chronological age, Demirjian age and regression models showed a statistically significant difference. The obtained ages from Demirjian methods and regression models were showed shown to be overestimated. A positive association was found between the real ages and age estimates derived from these four models. The equations allow age estimation in specific situations (such as when only either the maxillae or mandible is available or when the radiography is not available).

Statement of Problem: Bacteria are possibly left in the cavity after its preparation and can multiply after restoration. Thus, cavity disinfection prior to restoration can be effective if it does not interfere with adhesive resin adaptation. To evaluate the effect of the application of chlorhexidine 2% on the microleakage of composite restorations using four adhesives.Methods and Material: In this experimental study, standard class V cavities were prepared in the buccal surfaces of 88 human premolars at the CEJ. The teeth were randomly divided into 8 groups, each containing 11 teeth. Four adhesives of Scotchbond Multi-Purpose (SBMP), Excite (Ex), Clearfi SE Bond (CSEB) and iBond (iB) were used according to their manuafacturer's instructions in the four control groups. In the four experimental groups, the same adhesives were used, but in the SBMP and EX groups, 2% chlorhexidine solution for 40 seconds was applied after the etching. In the CSEB and iB groups, chlorhexidine was applied before the adhesive application. The cavities were filled using Z250. The samples were immersed in 0.2% methylene blue after finishing the restorations and thermocycling. Dye penetration was evaluated using stereomicroscope after sectioning. Kruskal-Wallis and Dunn tests, were used for statistical analysis. There wereas no significant differences among the microleakage of the control groups at the incisal and gingival margins (p >0.05). Chlorhexidine did not affect the microleakage of the four adhesives. The results indicated that 2% chlorhexidine solution may not interfere with the sealing ability of the tested adhesives.

Statement of Problem: Retention of dental posts is an important factor for the longevity of final restorations in endodontically treated teeth. It can be influenced by such factors as the type of post, type of cement, the bond between the cement and dentin, and also cement with post surface.

The purpose of this study was to investigate the effect of a metal primer on the retention of casting posts luted with resin cement.Methods and Material: The crowns of 30 intact canine teeth were removed at CEJ with a disc. After root canal treatment, the post space was prepared in each specimen to a depth of 12mm. The posts were casted of non-precious alloy and sandblasted. The teeth were randomly divided into two groups (n=15). For both groups, casting posts were cemented into post spaces using panavia F2 according to the manufacturer’s instruction. The posts in group 1 were additionally pre-treated with Alloy Primer. The specimens were thermocycled and then debonded on an instron machine with a crosshead speed of 1 mm/min. The force required for dislodgement of the posts from the prepared spaces was recorded and the results were analyzed using t-test. Stereomicroscope was used to study the fracture interface in both groups.

The mean retention forces were 112.45±28.37 N for group 1 and 59.5±7.19 N for group 2. A statistically significant improvement in retention was found in the specimens in group 1 as compared with group 2 (p <0.05). Stereomicroscopy showed that failure at cement-post interface was 20% in group 1 and 60% in group 2

Under the conditions of this study, casting posts pre-treated with metal primer provided a significantly greater retention.Key words:

Statement of Problem: Previous studies have reported possible counteraction between chlorhexidine (CHX) and sodium lauryl sulfate (SLS) in dentifrice. For the same reason, different times application of CHX have has been advocated. The aim of this study was to compare four different measures of CHX application along with tooth brushing on the plaque control.Methods and Material: The study was a single blinded, randomized 4cell, cross- over design. It used a four day plaque accumulation model to compare four different oral hygiene regimens with a wash out period of 7 days. Forty healthy volunteers were enrolled in the study and received thorough dental prophylaxis at the beginning of each 4 day of the test period. The regimens included the use of CHX mouth rinse before (Regimen A), immediately after (Regimen B), and 30 minutes after tooth brushing (Regimen C). Regimen D included only brushing with SLS-containing dentifrice. At the end of each 4 day of the testing period, the plaque was scored with Turesky index. No other oral hygiene measures were allowed. The difference between the groups was analyzed using repeated measure ANOVA. The overall indices of regimens A, B, C, and D were 0.90, 0.87, 0.83, and 0.96, respectively. There was no significant difference in plaque accumulation among the four regimens. Within the limitations of the present study, it can be concluded that the anti-plaque efficacy of 0.2% CHX rinse was not reduced in combination of tooth brushing with SLS-containing dentifrice, and there was no significant difference between the four regimens.

Statement of Problem: Impaction of the third molar teeth is common. Due to the probable complications resulting from tooth impaction and the effects of the impaction pattern on treatment plan, the evaluation of this pattern is important. This study aims at evaluation of the impaction pattern of the third molar teeth and its relation with the depth of impaction.Methods and Material: In this descriptive study, panoramic radiographs of 409 patients aged 20-40 years old who referred to Dental Clinic of Guilan University in a two-year period were chosen. The depth of impaction was evaluated according to the relationship between the Ccementoenamel junction Junction (CEJ) of the third molar tooth with the alveolar crest. Winter classification was used for detection of the angulations of the impacted teeth. Pearson Chi square test was applied for data analysis. There were 44.7% males and 55.3% females in this study. Evaluation of the impaction depth showed that, the most frequent impaction level was level C in in the maxilla, and it was level B in the mandible it was level B. In the maxilla, 47.5% and in the mandible, 41.2% of the impacted teeth were found in the male patients. The maximum and minimum frequency of different kinds of impaction angulations was vertical (67%) and horizontal (0%) in the maxilla. In the mandible, it was mesioangular (57.3%), distoangular (1.1%), respectively. In the evaluation of different impaction angulations based on the impaction depth, most of the vertical and mesoangular patterns of the impacted teeth were accompanied with level C and level B, respectively. There was no difference between female and male patients for frequency of the impacted teeth in the maxilla and mandible. Distribution of the angular pattern of impaction was different in the maxilla and mandible. There was no significant difference between the frequency of impaction angulations in different impaction levels.

Statement of Problem: General practitioners and pediatricians are in an ideal position to advice advise families about the prevention of oral diseases in their children because of their frequent contacts with families for routine preventive visits in the child’s first few years of life. The aim of this study was to determine the knowledge, attitude and practice regarding the prevention of oral diseases among an Iranian group of physicians and pediatricians.Methods and Material: This cross-sectional study was conducted on 296 physicians and pediatricians in Isfahan. A self-administered questionnaire was used to determine the socio-demographic information, knowledge on risk factors, attitude and practice about the prevention of oral diseases. The collected data were analyzed using t-test and Chi-square statistical tests. The mean scores of knowledge, attitude and practice on the prevention of oral diseases among physicians and pediatricians were 62± 14, 94± 8 and 38± 17, respectively. No significant differences were detected between physicians and pediatricians in their scores (p >0.05). Knowledge and also their practice showed a correlation with their attitude. Physicians who worked at governmental centers had better oral health practice. Based on the findings of this study, the present educational courses about oral health in medical school both in undergraduate and postgraduate curricula are insufficient. The good level of knowledge and attitude but weakness in oral health practice revealed that the increased level of knowledge and attitude does not necessarily lead to good practice in prevention of oral diseases. Therefore, practical education on oral health and training for referring the cases to dentists during medical students’ education can improve their practice in oral health preventive measures.

Central giant cell granuloma (CGCG) is a non-neoplastic proliferative intra-osseous lesion which occurs almost exclusively in the jaws, anterior to the molars and more commonly in the mandible. This article presents an unusual case of CGCG in a 56-year old edentulous woman with the chief complaint of a rapidly growing lesion in the anterior part of her maxilla. Based on the clinical findings and radiographic pattern of its huge calcification (in the panoramic view and CT scan), the lesion was misdiagnosed as destructive fibro-osseous or malignant lesion, but it was histopathologically diagnosed as CGCG. This case report is presented to highlight the importance of histopathology in the diagnosis of this enigmatic lesion.