Journal of Dental School
Year:2011 | Volume:29 | Issue:3 (89)|Papers Count:14

Background and Aim: Recent technologic advances allow models to be digitized, measured with software tools, stored electronically and retrieved with a computer. The purpose of this study is to evaluate the validity of computerized 2-D dolphin, 3-D laser scanning and manual methods of dental cast analysis.Materials & Methods: Twenty setups, simulating various types of malocclusions with different degrees of rotational and inclination of teeth, variety of spacing condition and curve of spee depths, were constructed. The values of tooth size were calculated from isolated artificial teeth out of setups (gold standard). These setups were duplicated using alginate, resulting in 20 corresponding dental stone models. Models were analyzed with digital calipers manually. The digital images were scanned and were analyzed with the Dolphin software. The analyses included mesiodistal dimension of isolated teeth and the measurement of Bolton scale. The results of the two mentioned methods were compared with the results of another study on these models by the means of three dimension scanning with gold standard. Inter Class Correlation were used to evaluate significance of differences. The difference of the varying methods was obtained through the Dolhberg formula.Results: Results showed that there is the highest correlation between gold standard and manual methods, then between the gold standard and the two dimension methods, and finally, between gold standard and 3-D scanning. Statistically, methods had significant differences (P<0.05), which is clinicaly acceptable.Conclusion: In comparison to gold standard, manual method is still the most accurate for cast space analysis, but difference in overall size calculation is only 1.8 mm which seems clinically acceptable.

Background & Aim: Consumption of acidic carbonated beverages is the most important etiologic factor for dental erosion. Studies show that nano hydroxyl apatite can remineralize initial caries lesions. The aim of this study was to determine the effect of that nano hydroxy apatite on the micro hardness of enamel of permanent third molar after exposing to soft beer.Materials & Methods: This in vitro study was done on 18 permanent third molars without caries and crack. After measurement of the micro hardness of the teeth, these teeth were placed in the 40 cc of Delester and secondary micro hardness of them were measured. Then the teeth were divided in to two groups randomly and were exposed to nano hydroy apatite in treatment group and tap water in control group and finally micro hardness of the teeth was determined. Changes in micro hardness were analyzed with paired t test in each group and ANOVA between groups.Results: The results showed that micro hardness of 18 samples after exposing to lemon Delester -Behnoosh- reduced to 92.5% of primary micro hardness and paired t test showed that this is significant statistically (P=0.009). Micro hardness of 9 samples in water group after exposing to water was 99.3% of secondary micro hardness and paired t test showed there is not significant statistically (P=20.6). Micro hardness of 9 samples in nano hydroxy apatite after exposing to nano hydroxy apatite was 98.2% of secondary micro hardness and paired t test showed there is significant statistically (P=0.012).Conclusion: Based on the results of this study nano hydroxyl apatite can remineralize erosive lesion on the enamel of permanent teeth resulting from exposing to lemon Delester.

Background & Aim: The elimination clinical avail of auto grafts make the instance development use of supersede material of bone graft as xenografts and allografts. cytotoxic effect of materials and biomaterials on Lively human cells is the Object that always should attendants to it. In present study had tried to comparison evaluation cytotoxic effete of two bio material -human BMG and coral madrepora -on human peripheral mono nuclear blood cells.Materials & Methods: In present experimental study after to make preparation peripheral blood with fycole method and After preparation and sterilization of human BMG and coral madrepora, Then, human BMG and coral madrepora, aside to gether are divided into 10, 20, 50 mg portions and cultured on 24-well of 100000 mononuclear cells of peripheral blood and they are evaluated after 24, 48 and 72 hours. MTT method was used for evaluation of cytotoxic effect using ELISA reader in 540 nm wave lengths. Light absorption rate depends on MTT uptake by the cells, indicating vital activity of the cells. Result evaluated with variance and whilcoxon-rank sum and mann u whitnney test. Results: All of the human BMG doses that were used weren't toxic and all of them increased number of the human peripheral blood mononuclear cells (P<0.005). But coral madrepora, was decried number of the human peripheral blood mononuclear cells after 24 hour in 50 mg doses and after 48 hours in 10 mg doses and after 72 hours in 20 and 50 mg doses.Conclusion: With increasing of human BMG concentration and passing time, increasing of human peripheral blood mononuclear cells can be observed and it has a statistically significant difference with control group. Therefore, as a conclusion, human BMG is compatible with human blood mononuclear cells. But coral madrepora had toxicity for this blood cells. However for more judgment, need more study with different cells.

Background and Aim: Despite doubts about the necessity of the presence of keratinized gingival tissue around teeth, increasing its width is still of special importance in particular situations. Among currently used procedures, free gingival autograft is more common. The aim of this study was to clinically compare the free gingival graft taken from palate(FGGP) versus free gingival graft taken from attached gingiva (FGGA) following a healing period of one, two and three month that will determine and introduce the superior procedure to be used in practice. Materials & Methods: The present study was a controlled, split mouth clinical trial which 10 pairs of lower anterior and premolar teeth requiring gingival augmentation were exposed to surgery using (FGGP) and (FGGA). Statistical data analysis was done using SPSS software. Chi- square (X2) test was used for comparison of color matching between two groups. Nonparametric Mann- Whitney test was used for comparison of mean keratinized gingival width and dimensional changes of graft between two groups.Results: This study demonstrated that the increased amount of keratinized gingival width three months following the surgery was significant for both groups but there were no statistically significant differences between two groups (P>0.05). With regard to the color matching with adjacent tissue, the results of (FGGA) was superior to (FGGP) (P<0.05). The amount of dimensional changes in the (FGGP) was more than (FGGA) (P<0.05).Conclusion: Both procedures had the ability to increase the keratinized gingival width; however (FGGA) had lower dimensional changes. In addition, (FGGA) had better color matching and esthetic.

Background and Aim: Color matching between natural teeth,shade guides and metal-ceramic restorations is a common clinical problem. Difficulties related to color matching arise from structural differences between metal-ceramic crowns and natural teeth, the limitation of range of available ceramic shades, inadequate shade guides, different type of metal alloys, and varying composition of ceramic materials.The aim of this in vitro study was to investigate the influence of various porcelains on the final color of metal-ceramic restorations.Materials & Methods: Three commercial porcelains for metal-ceramic restorations, Vita VMK95 (Vident, Brea, CA, USA), ceramco2 (Dentsply, Burlington, NJ, USA) and Noritake (Noritake, Tokyo, Japan) and alloy T3 (Ticonium, Division of CMP Indnstries LLC) were combined in metal-ceramic disks with standardized thickness of layeres.10 disk (10 mm) were prepared for each porcelains in A3 shade. the samples were analyzed with a spectrophotometer, and data were obtained in the CLELAB color system. The recorded data were analyzed with One Way Analysis of Variance and Tukey test.Results: The type of porcelains overlying disks had significant effect on color of metal ceramic restoration (P<0.001) in three coordinate dimensions (L, a, b). The Vita porcelain had most similar to the control group (DE=1.58) and the ceramco2 porcelain was least similar to the control group (DE=2.65).Conclusion: The data of this study indicated that type of porcelain had significant effect on metal-ceramic restoration color.

Background and Aim: Bone substitute biomaterials can prevent severe root resorptions during orthodontic treatments by induction of new bone formation leading in more healthy periodontal status after treatment. Furthermore, NanoBoneTM graft offers several advantages to be applied in the surgery defects due to its nanocrystalline hydroxy apatite components and nanosized biomaterial structures. The purpose of this study was to evaluate the tissue reactions in the socket preservation using NanoBoneTM following orthodontic tooth movement.Materials & Methods: In this experimental study, 4 dogs were selected of the mixed race following defects preparations in the mesial aspect of the first premolar in each quadrant of the animals. NanoBoneTM was applied in one side as a case region while the opposite side remained hollow as a control side. The first premolar was moved mesially using orthodontic forces and the orthodontic tooth movement was calculated at different time intervals. When the teeth reached half the way, the animals were sacrificed and the sections were subjected to histopathologic assessments. The orthodontic tooth movement values were analyzed using three-way ANOVA test.Results: The mean overall premolar movement towards canine in the socket filled with NanoBoneTM was 1.076 mm while it was 1.203 mm in the control side. No significant differences were noted regarding the graft material, the time and jaw position. Root resoprtion was evident in the pressure regions of both groups and new bone formation was noted in the defects filled using NanoBoneTM.Conclusion: It was concluded that NanoBoneTM has osteoconductive properties with the decreased root resoprtion due to the limited tooth movements. Therefore, the tooth can be moved into the NanoBoneTM graft material and the graft can be used as a substitution for autogenous bone during orthodontic tooth movements.

Background and Aim: Leukoplakia, is considered as the most common precancerous oral lesion. Numerous researches have shown that the effect of various risk factors in malignancy of leukoplakia differs in different societies. Being so, this study was designed to evaluate the probability rate of malignant transformation of oral leukoplakic lesions in relation to risk factors of age, sex, smoking habit of patients, clinical appearance and site of the oral lesions in Shiraz from 1368 to 1388.Materials & Methods: This retrospective analytical-descriptive research was performed by collecting all leukoplakia from the Shiraz Nemazi and Khalili Hospitals as well as Oral Medicine and Oral Pathology Departments of Shiraz Dental School from 1368 to 1388 were selected according to their files. Patients with malignant transformation considered as the target group and those without such transformation named control group. Risk factors such as age, sex, smoking habit, clinical appearance and site of the lesions, as independent factors were evaluated in relation to their effect in malignant transformation of the oral leukoplakia through recording of necessary data via filling of special questionnaires. Chance rate in both groups was also evaluated. Data were analyzed by Excell, SPSS and Epi statistical software.Results: Malignant transformation rate of oral leukoplakia was 40.8%. This rate showed increase with age increase especially after, forty years. The malignancy rate in females after the age of forty was higher than males. Although smoking will increase the chance of oral leukoplakia, most malignant transformations, were seen in non–smokers. Tongue was the most sites and lips were the least common site for malignant transformation and white and red lesions (erythroplakic lesions) have the highest rate of malignant transformation in both sexes. Conclusion: Data showed that factors such as age, sex, smoking habit, clinical appearance and site of oral lesions were in direct relation to malignant transformation of oral lesions of leukoplakia.

Background and Aim: Dentists can play an important role in the cessation of tobacco use which is known as the leading preventable cause of death in the world. The aim of this study was to assess the barriers that limit the active involvement of Iranian senior dental students in tobacco cessation program.Materials & Methods: In this cross sectional descriptive study, we used stratified cluster random sampling to obtain a representative sample of 335 subjects from 11 dental schools in Iran. They filled out a two page questionnaire which contained questions regarding demographics including age, sex, smoking status and average of their practice activity per week, knowledge and attitude towards tobacco cassation counseling in dental settings and the barriers limiting the application of tobacco cessation counseling methods.Results: Having good knowledge about tobacco cessation programs, positively influences the attitudes of students toward application of these programs in the dental setting (P<0.004). Patients’ resistance to advice, lack of supportive organizations in developing tobacco cessation services and training facilities for tobacco cessation in dental settings and the preference of providing dental treatments rather than tobacco cessation were the most important barriers from the point of view of the participants in this study. Regarding two of the barriers, the point of view of male and female study subjects had statistically significant difference (P<0.05).Conclusion: Considering the positive attitude of Iranian senior dental students toward participation in tobacco counseling cessation programs and shortage of their knowledge regarding tobacco cessation protocols; a good instruction program and removing the perceived barriers in implementing these programs might enhance dentists’ role in helping tobacco users quit.

Background and Aim: Hearing loss (deafness) is a disability that is often over looked because it is not obvious. This study investigates oral health care status and behaviors between two groups of hearing and deaf and hard-of-hearing (D&HH) adolescents in Tehran in 1385. Materials & Methods: A hundred and ninety two (D&HH) students (87 females, 105 males) attending special nonresidential public schools and 193 hearing students (87 females, 106 males) attending regular public schools from all areas of Tehran, ages 12-16 years answered a written questionnaire about frequency of dental visits, reason and time of last dental visit, frequency and time of brushing. Information about DMFT was obtained through oral examination. Chi-square and T tests were used for statistical analysis and p=0.001 was considered significant.Results: Significant differences existed between hearing and D&HH group from different states. The hearing group had more dental visits and frequency of tooth brushing than D&HH group (P=0) and (P=0.002) respectively. Mean DMFT score in hearing and D&HH adolescents was 3.13 (SD=2.852) and 3.37 (SD=3.034) respectively. The MT score in D&HH and hearing adolescents was 0.16 (SD=0.474) and 0.04 (SD=0.273) respectively which was significantly higher than hearing group (P=0.006). There was no significant difference between mean DMFT score of the two groups (P=0.116).Conclusion: Three findings of concern are the higher rate of Extracted teeth, less dental visits and tendency of tooth brushing by D&HH adolescents. The oral health care knowledge and practices of D&HH adolescents will improve through a controlled school-based oral health education program.

Background & Aim: Unicystic ameloblastoma is one type of ameloblastoma with different clinical, radiographic, pathologic and treatment response. The aim of this article is presenting a unicystic ameloblastoma with ameloblastic fibroma in its wall.Case Report: A 16 year old boy with a painless expansion in the left side of mandible came into a maxillofacial surgery office. Radiographic views showed a unilocular lesion with involvement of mandibular border and root resorption. Aspiration was positive. Differential diagnosis consist of follicular cyst, odontogenic keratocyst and unicystic ameloblastoma. The lesion was removed with an exisional biopsy and curettage.Conclusion: This article reports a collision of unicystic ameloblastoma and ameloblastic fibroma. Treatment was based on exisional biopsy and curettage.