Journal of Mashhad Dental School
Year:2008 | Volume:32 | Issue:3 (66)|Papers Count:12

Introduction: One of the most common methods for reconstruction of endodontic teeth is post core crown. There are many factors affecting the fracture resistance of the teeth; such as, ferrule and the type of cement used as the luting agent. The purpose of this in vitro study was to investigate if the resin cement used was able to improve the fracture resistance of teeth restored with cast post core crowns.Materials & Methods: In this experimental in vitro study, 40 intact second mandibular premolars were endodontically treated after their crowns were removed so that the remained root parts were 15mm. The teeth were divided into four groups of ten teeth each. Groups 1 and 2 had ferrule while groups 3 and 4 were non-ferrule groups. The posts of groups 1 and 2 were cemented with Glass Ionomer cement, while the posts of other groups were cemented with resin cement. Then the crowns were made in the same shape in which we could apply the compressive load with 1mm/min speed at an angle of 45 degrees on the buccal cusp tip to induce fracture. ANOVA and t test were used for statistical analyses. Results: In ferrule group cemented with Glass-Ionomer, the mean fracture strength was greater than non-ferruled group cemented with Glass-Ionomer. There was no statistical difference between the ferrule group cemented with resin cement, compared with and non ferruled groups.Conclusion: In teeth post cemented with resin, cervical ferrule does not increase the fracture strength of the teeth significantly.

Introduction: The correlation between psychiatric and anxiety states and occurrence of periodontal disease has been reported. The aim of this study was to evaluate periodontal diseases in patients with depression compared with the control group.Materials & Methods: In this cross-sectional study, a case group consisted of 30 patients with depression in Mashhad Ebnesina hospital whose severity was assessed by Beck depression inventory, were selected. A group of 30 individuals, who had been referred to oral medicine department of Mashhad dental school, were considered as the control group. The two groups matched in sex with the age range of 20-40 years. The patients were undergone periodontal examinations using mirror and Williams’s periodontal probe. Other personal information including age, sex, education level and occupation were also recorded. The data were analyzed using SPSS soft ware (t-test, ANOVA and Duncan test).Results: Moderate depression was the most common type and severe depression was the least common. In this study we didn’t find any significant relationship between depression and periodontal disease, but there was a significant relationship between case and control group in Plaque index and bleeding on probing (P=0.03). There were not any significant differences in probing depth, clinical attachment level and gingival index between the two groups (P>0.05).Conclusion: No Significant relationship was found between depression and periodontal diseases. Plaque index and bleeding on probing were different in the two groups although other indices Such as pocket depth and attachment loss were not significantly different in the two groups.

Introduction: Lichen planus is a chronic mucocutaneos disease and relatively frequent in adult, which involves 0.2-2% of population. There are limited studies on frequency and clinical pattern of oral lichen planus in Iran. This study was designed in order to evaluate clinical and epidemiological features of Oral lichen planus (OLP) patients referred to oral Medicine Department of Mashhad dental school during 2000-2005 compared with other populations.Materials & Methods: In this descriptive study, the patients’ data were collected from files of 420 OLP patients who had been referred to oral medicine department of Mashhad dental school and included age, sex, chief compliment, skin involvment, location, type & form of lesions. Data were analysed with SPSS 11.5 statistical software.Results: The mean age of these OLP patients was 41.16 years. 64.9% of cases were female and 35.1% were male. Buccal mucosa was most frequently involved (85.2%). The most prevalent clinical type was reticular form (76.9%). 15.5% of patients had skin involvement.Conclusion: Based on the results of this study, the importance of proper history and clinical examination is of great importance to achieve the best diagnosis and treatment plan for OLP. Considering the variety of epidemiologic findings, we need more extensive epidemiological study of this kind to be more familiar with our OLP patients and to schedule clinical research and treatment plan in our society.

Introduction: Elastomeric chains are used for space closure in orthodontics. In this study the effect of sodium fluoride (NaF) mouth rinse on the elastic properties of chains was evaluated.Materials & Methods: In this in vitro study, 6-linked sections of transparent open chains of American Orthodontics and Dentaurum companies were tested in two groups. In the first group, chains were only stored in artificial saliva. Chains of the second group were daily immersed in 0.05% NaF rinse for 1 minute, then in a mixture solution of saliva and NaF for 30 minutes, and then were stored in saliva. At time intervals of initial, 1,24 hours, 1,2,3 weeks, displacement of each specimen to obtain forces of 150g and 300g was determined with Zwick machine in the tensile test. Also at the same intervals, after the specimens were stretched to 100% of their original length in the degradation test, the applied force was measured. Results: Specimens required more displacement to achieve forces of 150g and 300g in the mixture solution than saliva, but the difference was only significant for the 300g force (P=0.020). Force degradation of chains was not statistically different between the two solutions. American Orthodontics chains showed more force degradation than Dentaurum (P<0.001).Conclusion: Daily use of NaF mouth rinse did not cause considerable increase in the displacement of chains to achieve conventional orthodontic forces (150g) and did not affect the force degradation of selected chains. Because of their higher force degradation, American Orthodontics chains should be changed at shorter intervals than Dentaurum ones.

Introduction: Dental Implants used noticeably for treatment of edentulous patients, are foreign bodies installed in direct contact with bone. Therefore, their characteristics should not be harmful for surrounding tissues. Surface characteristics are one of the implant characteristics. This study was performed to evaluate the effect of two types of implant surface characteristics (TPS and SLA) on bone loss, pocket depth and bleeding on probing. Materials & Methods: This prospective study was approved by ethical committee of Mashhad University of Medical sciences and performed on 56 TPS (Titanium Plasma Spray) and 39 SLA (Sandblasted, Large grit, Acid-etched) implants in Mashhad dental school in 2006. Bleeding on probing, pocket depth and bone loss were evaluated one year after insertion. The data were collected and analyzed using Mann Whitney U test. Results: Mean bone loss and pocket depth were significantly different between SLA and TPS groups (P=0.003, P<0.001). They were lower in SLA group but no significant differences were found with respect to bleeding on probing (P=0.510). Conclusion: Based on these findings, it is better to make use of implants with SLA surface coating.

Introduction: Color Research has shown that shade guides do not always match the color of natural teeth. Moreover, Visual evaluation of dental colors has been found to be inconsistent and unreliable. In Fact it has always been important when using different shade guides. Our purpose was to evaluate effects of two shade guides, Vita-Classic & 3DMaster and shade selection repeatability with two groups of dentistry students and supplying them with a useful training in principles of color and shade selection techniques.Materials & Methods: In this analytical-descriptive study, ten male and ten female senior dentistry students with a little clinical experience in working with shade guides were chosen. Each Student used Vita-Classic & 3DMaster shade guides to determine the shade of the maxillary right canines of twenty patients. Shade selection was randomly repeated two weeks later by the same practitioners, same patients and the same protocol. t-test for comparing repeatability among means was used for statistical analysis (a=0.05).Result: There was no significant difference with use of different shade guide systems (P=0.31). Use of 3DMaster had no significant effect in increasing the repeatability in male and female groups (P=0.23). Shade selection repeatability was lightly greater in male group compared with female group in use of both two shade guides. Conclusion: Eventually training level and learning of color principles and shade selection methods seems to be the most important factor in practitioner’s ability. Vita-Classic and 3DMaster and sex had few effects on shade selection repeatability enhancement.

Introduction: Maximus dental implants are used when there are limitations like inadequate mesiodistal space. This study was carried out to clinically and radiographically investigate Maximus implants which were installed in the regions of maxillary lateral and mandibular incisors using immediate nonfunctional loading.Materials & Methods: In this clinical trial study, approved by ethical committee of Mashhad University of Medical Sciences, 21 implants for 12 patients (2 male and 10 female) between 18 and 42 years old were inserted. Clinical and radiographic measurements were recorded in recall sessions and analyzed statistically using t.test and ANOVA. Results: After one year of examination, none of the implants failed and the mean bone resorption was 1.06±0.90. The means for pocket depth and plaque index were 1.62±0.3 and 14.57±2.56, respectively. The mean of gingival index after 6 months was 0.21±0.36 and it reached 0 after one year. The mean of bleeding index after 6 month was 0.03±0.085 and after one year it was equal to 0.Conclusion: Considering the very high success rate and low bone resorption around Maximus implants with immediate nonefunctional loading during one year of examination, it appears that using low diameter implants for edentulous regions of small bone width or mesiodistal space is a suitable treatment.

Introduction: Ceramic inserts are claimed to reduce polymerization shrinkage and microleakage in posterior tooth-colored restorations. The purpose of this study was to evaluate the gingival microleakage in tooth colored restorations with ceramic-inserts (Cerana) in primary pulpotomized molar teeth.Materials & Methods: In this experimental in vitro study forty extracted human primary second molars were prepared with standardized MOD cavities so that the gingival margin was located on the dentin in mesial box and on the enamel in distal box. The teeth were randomly divided into 4 groups with 10 teeth in each and restored as follows: Group 1: light-cure glass ionomer, Group 2: light-cure glass ionomer with cerana, Group 3: composite resin, Group 4: composite resin with cerana. The high intensity program (HIP) was used for light-curing. After thermocycling (1000 cycles, 5-55oc) and load cycling (250000 cycles), micro leakage was evaluated by “dye penetration” technique. Data were statistically analyzed by Ordinal regression and Wilcoxon at significance level of 95%.Results: No statistically significant differences were found between the groups with and without cerana. Microleakage at the dentin margin was greater than that of the enamel margin significantly.Conclusion: Use of cerana with HIP does not reduce microleakage at gingival margin in class II restorations. However, the effectiveness of cerana with other restorative techniques and light curing methods needs to be assessed in further studies.

Introduction: Prefabricated endodontic post is one of the most effective factors to increase retention in severely destroyed teeth restorations. The retention is related to the post and cement. The aim of this study was to compare the retentive capacity of two prefabricated endodontic posts comented with two different luting cements.Materials & Methods: In this parallel experimental in vitro study, 32 intact similar single root premolars were divided into two equal groups. The teeth were cut at CEJ and received endodontic treatment. The post spaces were prepared with pisoreamer drills. In the first group, Dentatus posts were cemented with zinc phosphate in eight teeth and the remainder was cemented with glass ionomer. In the other group para posts were cemented in two subgroups the same as Dentatus posts. After mounting all specimens in acrylic resin blocks the retention of each post was measured with Instron testing machine and the data were analyzed with student t-test (¥=0.05).Results: The mean retention value of the para post group was higher than the other one (P<0.001). But there was no significant difference between two cements (P=0.11). The retention values for zinc phosphate cement was higher in para post group (P<0.001) but in Dentatus group there was no difference between subgroups (P=0.64).Conclusion: The retention capacity was higher with para post in comparison with Dentatus. Zinc phosphate showed higher retention with para post but there was no difference between zinc phosphate and glass ionomer cement in retention of Dentatust post.

Introduction: Oral habits are patterns of muscle contractions, which are of a complicated nature and inflict unnatural forces on teeth, jaws, muscle and temporomandibular joints. The aim of this study was to determine the association between some of parafunctional habits with signs and symptoms of temporomandibular disorders in high school girls.Materials & Methods: In this study, a group of 630 girls, aged 15-17 years, randomly selected from seven high schools in Yazd, completed a questionnaire and were examined clinically with regard to various signs of tempomandibular disorders. Clinical examination included the followings: 1. Mastication muscle (temporalis and masseter) tenderness on palpation. 2. TMJ tenderness during opening and closing. 3. Clicking of TMJ. 4. Maximum extent of vertical mouth opening. The data were analyzed by ANOVA and Chi-square test. Results: The prevalence of parafunctional habits was 87.9%. The highest prevalence of parafunctional habit was hand leaning, following by gum chewing. The mean gum chewing time was 2.02h/day±1.37. The lowest prevalence of parafunctional habit was jaw play. A total of 50.7% of girls had at least one sign of TMD. There was a significant relationship between hand leaning and tenderness of TMJ (P=0.004) and mastication muscle (P=0.025). There was a significant relationship between gum chewing and tenderness of TMJ (P=0.003), clicking (P=0.031) and limited mouth opening (P=0.003). The most prevalent symptom of TMD was TMJ noises. The most prevalent sign of TMD was limitation of vertical mouth opening.Conclusion: In our study, there was a significant correlation between parafunctional habits and TMJ disorders.

Introduction: Displacement of tooth or root fragments into adjacent anatomical spaces is an uncommon complication of the removal of teeth. In this paper with presenting two cases, inwhich during extracting mandibular third molar, the tooth was displaced into pterygomandibular space, principles of prevention and management have been discussed. Results: First case was a 23 year old man with mesioangular third molar. His dentist had tried to extract it by close technique and the teeth entered the pterigomandibular space. Second case was a 35 year old man with a horizontal third molar. His dentist used flap approach to extract it, but the teeth was pushed into pterigomandibular space. Conclusion: Following the principles of prevention, patient selection, appropriate technique of tooth extraction and also choosing proper instruments especially for the third molars with the highest prevalence of displacement into the pterygomandibulars space during extraction, is necessary which has the most incidences meanwhile.