فهرست مطالب

Journal of Research in Dental and Maxillofacial Sciences
Volume:3 Issue: 2, Spring 2018

  • تاریخ انتشار: 1397/02/07
  • تعداد عناوین: 7
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  • E Jalalian, MR Bagheri *, S Masoumi Pages 1-6
    Background and aim
    Marginal adaptation affects the long-term success of full-coverage restorations. This study aimed to assess the effect of porcelain sintering and zirconia core thickness on the marginal adaptation of all-ceramic restorations.
    Materials and methods
    In this in-vitro experimental study, a standard brass die, 7 mm in length and 5 mm in diameter, was fabricated using a milling machine. A classic chamfer finish line with the depth of 0.8 mm was prepared with 10-degree tapered walls. Copings were fabricated on the die using the computer aided design/computer aided manufacturing (CAD/CAM) system and were divided into three groups (n=10) with 0.3-mm (group 1), 0.5-mm (group 2), and 0.7-mm (group 3) core thicknesses. The copings were placed on the dies and randomly coded. The vertical gap was measured at 10 points on the margin under a scanning electron microscope (SEM). After porcelain sintering, the crowns were placed again on the dies, and the vertical gap was measured again at the same points. Data were analyzed using analysis of variance (ANOVA) and paired t-test.
    Results
    There was a significant difference among the three groups in marginal gap (P<0.05). The comparison of marginal gaps before and after porcelain sintering showed no significant changes with 0.3-mm and 0.5-mm thicknesses (P>0.05) but the difference was statistically significant with 0.7-mm core thickness (P<0.05).
    Conclusion
    It may be concluded that by increasing the zirconia core thickness, the marginal gap of all-ceramic crowns decreases. Regarding 0.3-mm and 0.5-mm core thicknesses, porcelain sintering had no effect on marginal gap but regarding 0.7-mm core thickness, marginal gap increased after sintering.[U1] [U1]5
    Keywords: Zirconia, Marginal Adaptation, Computer Aided Design, Computer Aided Manufacturing, Dental Porcelain
  • N Moezzi ghadim, M Taghibakhsh *, H Godarzi, N Liravinezhad hoseini, S Alirezaei Pages 7-13
    Background and aim
    Reduction of oral pathogens is very important in the healing of oral ulcers and infections. The side effects of chemical drugs have attracted more attention to medicinal plants. The present study assessed the effect of clove, thyme, garlic, and cinnamon ethanolic extracts on the growth of Streptococcus mutans (S. mutans) and Lactobacillus by measuring the inhibition zone diameter.
    Materials and methods
    In this in-vitro experimental study, suspensions of standard strains of S. mutans (PTCC5027) and Lactobacillus (PTCC1608) were inoculated on Müller-Hinton agar using a sterile swab. 10 g of crushed and dried plants was dissolved in 100 ml of ethanol, and an ethanolic extract was obtained after passing through a filter and evaporation. 10 μl of each extract was poured onto blank discs which were placed on plates containing bacteria. A disc containing the control groups, including 0.2% chlorhexidine and a blank disc, was also placed on the plates. The plates were placed in a jar for 24 hours at 37°C and then the inhibition zone diameter around each disc was measured. Ten replicates were performed for each herbal extract. Data were analyzed by analysis of variance (ANOVA) and post hoc tests.
    Results
    All four ethanolic herbal extracts were able to inhibit the growth of S. mutans and Lactobacilli. For both bacteria, the largest inhibition zone was observed with chlorhexidine, followed by clove, thyme, garlic, and cinnamon, respectively. There was a significant difference between the inhibition zone diameters formed by the extracts (P<0.01).
    Conclusion
    Ethanolic extract of clove showed more prominent antibacterial effects than ethanolic extracts of thyme, garlic, and cinnamon.
    Keywords: Clove, Thyme, Garlic, Cinnamon, Chlorhexidine, Streptococcus mutans, Lactobacillus, Microbial Sensitivity Tests
  • S Alirezaei, E Razeghi, M Rezaie, N Moezi Ghadim, L Sabet Ghadam * Pages 14-23
    Background and Aim
    Halitosis, candidiasis, and metallic taste are some of the oral complications in chronic renal failure patients undergoing dialysis. The aim was to evaluate the prevalence of oral manifestations and the related factors in hemodialysis patients at selected hospitals of Tehran in 2016.
    Materials and Methods
    This cross-sectional study was performed through observation, examination, interviewing, reviewing the medical records, and completing the information form. Oral manifestations were examined with indices of halitosis, metallic taste, and candidiasis. The presence of each indicator was considered as oral manifestations, and the measurement was standardized and performed by a student under the supervision of the respective professors. The training required for measurements was provided by the supervisor and the advisor. The reliability was measured in a seven-day pilot study. An organoleptic method was used to measure halitosis. The diagnosis of metallic taste and candidiasis was made through interviewing and observation, respectively.
    Results
    The study was performed on 250 patients (58.8% male and 41.2% female) with the mean age of 59 years (17 to 88 years). The average duration of dialysis was 62 months. Oral manifestations were present in 91.2% of patients. The most common oral manifestation was halitosis (90%), followed by metallic taste (12%), and candidiasis (10.8%). The incidence of candidiasis was higher in older patients and denture wearers (P≥0.05). Halitosis and metallic taste did not relate to the studied factors (P≥0.2 and ≥0.9).
    Conclusion
    The prevalence of oral manifestations in chronic kidney failure patients undergoing hemodialysis is high. Etiologic studies are recommended to understand the causes and to reduce the complications.
    Keywords: Oral Manifestations, Renal Dialysis, Chronic Kidney Failure, Oral Candidiasis, Metallic Taste, Halitosis
  • M Rezai, T Farrokhnia *, M Vatanpour, S Lesan, SH Yazdipour Pages 24-30
    Background and aim
    Lack of proper assessment of students' knowledge regarding theoretical contents leads to disappointment and negligence by weak students. This study assessed multiple-choice questions (MCQs) of oral and maxillofacial medicine courses in the first semester of the academic year 2014-2015.
    Materials and Methods
    In this cross-sectional study, questions of theoretical oral medicine courses 1, 2, and 3 were assessed according to twelve items in Millman's checklist, including clearness of stem, negative option for stem, specific option, contrastive option, positive words in stem and options, writing structure of stem, duplicated option, the spelling of stem and options, vertically of options, positivity of stem and options, and use of "all of the above" and "none of the above" phrases in options. Difficulty and discrimination coefficients of each question and the rate of compliance with Millman's principles were evaluated using Excel 2007 and SPSS 16. Data were analyzed using descriptive statistics, analysis of variance (ANOVA), and Regression analysis.
    Results
    The responses of 219 students to 113 MCQs were evaluated. In theoretical course 1 with 40 MCQs, discrimination coefficient was 0.36±0.2, difficulty coefficient was 73.2±15.02, and correlation coefficient was 0.58. In theoretical course 2 with 35 MCQs, discrimination coefficient was 0.2±0.04, difficulty coefficient was 70.91±25.13, and correlation coefficient was 0.47. In theoretical course 3 with 38 MCQs, discrimination coefficient was 0.3±0.19, difficulty coefficient was 68.73±26.89, and correlation coefficient was 0.5. The percentage of compliance with Millman's principles was 81.88%, 83.58%, and 84.42% in courses 1, 2, and 3, respectively.
    Conclusion
    The weakest discrimination coefficient was noted in theoretical oral medicine 2. The high percentage of simple difficulty coefficient in the three theoretical courses indicates the necessity of training faculty members in designing questions.
    Keywords: Educational Measurement, Educational Test Performances, Learning, Feedback, Oral Medicine
  • GR Esfahani Zadeh *, N Akhavan Saless, M Noor Bakhsh, MH Salari, D Ghalebaaghi Pages 31-36
    Background and Aim
    Due to the importance of the bond strength between zirconia core (ZC) and porcelain veneer (PV) as well as the paradox about the functionality of sandblasting on the solidity between those layers, this research aimed to evaluate the effect of sandblasting on the shear bond strength (SBS) between ZC and PV.
    Materials and Methods
    After preparing 20 zirconia discs (7 mm × 3 mm) in this experimental study, they were randomly divided into two groups of case and control. In the case group, sandblasting with 120-μm aluminum oxide particles (Al2O3) was performed under 3.5-bar pressure at 10 mm distance from the zirconia surface for 15 seconds. Next, all the samples were cleaned with ultrasonic and 96% isopropyl alcohol for 3 minutes as well as steam cleaning for 10 seconds. Then, the samples were veneered with porcelain (3 mm × 5 mm). SBS was assessed using a universal testing machine. After data collection, the mean and standard deviation (SD) were calculated and analyzed using T-test.
    Results
    The SBS between ZC and PV was 62.56±8.35 MPa in the case group (after sandblasting) and 94.62±7.69 MPa in the control group. The SBS showed a significant statistical difference between the two groups (P=0.001).
    Conclusion
    The result of this research indicated that sandblasting reduces the SBS between ZC and PV. Considering the limitations and the methodology of the study, the hypothesis regarding the positive impact of sandblasting on SBS was not proven.
    Keywords: Zirconium oxide, Dental Porcelain, Surface Properties, Dental Bonding, Ceramics
  • S Farhadi, F Shahsavari *, K Alf Pages 37-45
    Background and Aim
    It has been suggested that oral lichen planus (OLP) can be a potential premalignant lesion. Reports are also available on the role of bcl-2 and p53 proteins in malignant transformation of OLP into oral squamous cell carcinoma (OSCC). Due to controversies in these reports, the present study aimed to compare the expression of p53 and bcl-2 markers in OLP and OSCC.
    Materials and Methods
    In this experimental study, immunohistochemical (IHC) staining was performed on erosive OLP and well-differentiated OSCC samples using bcl-2 and p53 antibodies. One-thousand cells per slide were counted, and the results were reported as percentages. The results were scored, and Mann-Whitney U test was used to compare staining grades in the two lesions.
    Results
    Twenty-two OLP and 25 OSCC samples with a mean age of 49.3±15.8 years were evaluated. Bcl-2 expression was reported to be 16.27±8.95% in OLP and 16.4±22.9% in OSCC. Expression of p53 was 30.86±28.26% in OLP and 49.6±29.6% in OSCC. The difference in bcl-2 expression between the two lesions was not significant (P=0.266), whereas this difference was significant for p53 expression (P=0.02). The correlation coefficient between these two markers was reported to be 0.45 in OSCC and 0.1 in OLP.
    Conclusion
    According to the results, there was a significant difference in p53 expression between OLP and OSCC samples, whereas this difference was not significant for bcl-2. There was no significant association between the expressions of these two markers in the samples. Therefore, there does not seem to be a high malignancy potential for the studied OLP samples.
    Keywords: Oral Lichen Planus, Oral Squamous Cell Carcinoma, bcl-2, p53
  • O Hamzezadeh Tofighi *, F Khabir, OR Fazlisalehi Pages 46-49
    Background
    Third molars are the most frequently impacted teeth, and extensive research has been carried out delineating their impaction prevalence, classification, and treatment approaches. We present a rare case of an impacted mandibular third molar which went through unprecedented changes in angulation over an eight-year time span with no particular pathologic, traumatic, or therapeutic interference.
    Case presentation
    A 22-year-old female presented with an asymptomatic mesioangular impacted lower right third molar. Upon the patient’s next visit (eight years later), the newly obtained panoramic radiograph showed that the tooth’s crown has angulated towards the roots of the adjacent tooth, rendering the impaction to be horizontal rather than mesioangular. Given the changing position and angulation, it was decided to surgically extract the tooth.
    Conclusion
    Early extraction of impacted teeth in patients that are candidates for such treatment in terms of age and medical conditions is recommended since changes in the angulation of impacted teeth could make the procedure more difficult.
    Keywords: Impacted Tooth, Mandible, Third Molar, Case Reports