Journal of Dental Medicine

In this investigation, the position of hyoid bone was compared in three skeletal groups of class I, II and III. The study was based on evaluating 77 lateral cephalometric radiographs, 40 girls and 37 boys, which were divided into 3 groups. Group 1, 2, and 3 consist of 26, 25, and 26 radiographs. 19 cephalometric landmarks and 10 planes were used in order to tracing the radiographs. In all patients, 9 skeletal and 4 cervical vertebrae parameters were measured to determine the hyoid bone. These parameters were compared between three skeletal groups regardless of sex and then, in another statistical analysis, parameters were compared based on patients sex. Statistical analysis showed that in class III patients, the hyoid bone was positioned more anteriorly than two other groups. Also in this group, the hyoid bone had less inclination and it was more horizontal in relation to mandibular plane. In skeletal class II patients this bone was positioned more superiorly than two other groups. Due to these findings it can be concluded that perimandibular muscles and bones could affect the growth of mandible. In addition, comparison of the parameters between two sexes revealed that the hyoid bone was positioned more anteriorly and inferiorly in boys. Also it was shown that in the girls, the position of hyoid bone was closer to the position of this bone in skeletal class I patients.

Background and Aim: Chlorhexidine is a mouthwash with known antibacterial effect but its antifungal effect is not clear. The aim of this study was to compare the antimicrobial effects of nystatin and chlorhexidine mouthwashes (one Iranian product and the other, commercial) on Candida albicans under in vitro condition. Materials and Methods: In this experimental study, the strains of Candida albicans used consisted of one standard strain (PTCC 5027) and ten local isolates. The latter were obtained from patients referred to different dental clinics in Kerman city. The specimens were taken from the gum and palate area by sterile swabs and dipped into Stewards transport medium, transferred to the laboratory within one hour, and cultured on Sabauraud dextrose Agar. Colonies showing the characteristic appearance of Candida were further cultured and routine differential tests including germ tube formation were performed to confirm the diagnosis of

C.albicans. These were used to prepare a microbial cell suspension of 0.5 Mc Farland concentration. Each cell suspension was inoculated over duplicate plates of SDA and 4 wells of 5 mm diameter were made using sterile cork borers. Each previously coded mouthwash was placed in corresponding well and incubated for 24-48 hours and the diameter of inhibition zone was measured with ruler. The minimum inhibitory concentration (MIC) of each mouthwash for each isolate of Candida albicans was determined using dilution tube technique. Data were analyzed by SPSS package using proper statistical tests with P<0.05 as the limit of significance.

Results: There was a significant difference between the antimicrobial effects of the four tested mouthwashes. The results indicated that Iranian nystatin mouthwash had the greatest effect and the average inhibition zone from the highest to the lowest was associated with Iranian nystatin, foreign nystatin, Iranian chlorhexidine and foreign chlorhexidine respectively. The MIC determination revealed that generally nystatin was more effective than chlorhexidine. No statistical difference was seen between the Iranian and foreign samples.

Conclusions: Despite the antifungal effects of chlorhexidine, more investigations on different strains of C.albicans is required before recommending its cilinical application.

Background and Aim: Contaminated dental handpieces have the potential to transfer infection to patients. New generation of autoclavable turbines have to some extent overcome the problem however, in clinic sometimes it is necessary to use chemical to disinfect handpieces. The aim of this study was to determine the antimicrobial effect of some routinely used disinfectant solutions on dental contaminated handpieces.

Materials and Methods: In this experimental study 35 turbines were sterilized. The turbines' heads were inserted into microbial suspension containing staphylococcus, pseudomonas and candida and then exposed to the disinfectant solutions. Inoculations into culture medium were made at different intervals. All medium was incubated for 24 hours at 37^oC followed by spectrophotometer inspection for detection of microbial growth. Serial dilutions of disinfectant agents were used to determine the highest dilution in which there was no microbial growth. Kruskal wallis test was used for statistical analysis and p<0.05 was considered as the level significance.

Results: Ethanol had antimicrobial effect on all of the tested microorganisms at dilution of 1:4. Betadine at dilution of 1:64 caused inhibition of all of the microbes except pseudomonas. Micro 10 had antimicrobial effect up to dilution of 1:256 but could not inhibit microbial growth at higher dilution. Sodium hypochlorite inhibited growth of the three microoganisms up to dilution of 1:1024.

Conclusion: Based of on the results of this study sodium hypochlorite was found to be the most effective antimicrobial agent among those used in this study, inhibiting microbial growth at the highest dilution.

Background and Aim: A key factor in restoring the endodontically treated teeth is ferrule preparation. When the ferrule is absent, occlusal loads may cause the post or root to fracture. The purpose of this in vitro study was to evaluate the effect of ferrule preparation on fatigue resistance of teeth restored with quartz-fiber posts.

Materials and Methods: Twenty single-rooted lower premolars having similar dimentions were randomly devided into two groups of 10. In control group the teeth were prepared with 3-mm of remaining coronal tooth structure and in test group teeth were prepared with 1-mm of remaining coronal tooth structure. The teeth were endodontically treated. 9-mm long Post holes were prepared, and D.T. light quartz-fiber(RTD,France) posts were cemented with Panavia F2(Kuraray,Japan).Then the core build up was done with Bisco core build up composite(Bisco,USA) and full metal crowns were cemented with Zinc phosphate(Harvard cement, Germany). All specimens were mounted in acrylic resin blocks and intermittently loaded (180 N) at an angulation of 45- degree to the long axis of the teeth at a frequency of 4 loads per second, until failure occurred.

Results: There was significant difference between the loads cycles of two groups studied. (p<0.0001).

Conclusion: The results of this study showed that an increased amount of coronal dentin significantly increases the fracture resistance of teeth restored with quartz-fiber posts.