BackgroundHyoid bone plays a significant role in physiological functions of craniofacial region and it’s position adapts to changes of the head. The purpose of this study was to determine the position of the hyoid bone among subjects with class I, class II and class III skeletal patterns and evaluate the gender differences.Material and MethodsOne hundred and ten lateral cephalograms (59 females and 51 males) from different skeletal patterns (class I, II and III) were selected. The skeletal patterns were determined according to ANB angle. Using MicroDicom software, different linear and angular measurements (6 variables) was carried out to determine the position of hyoid bone. Intraclass correlation coefficient was used to verify reliability. Descriptive statistics of the variables were calculated and analyzed using two-way ANOVA and Bonferroni statistical methods.ResultsThe mean distance from the hyoid bone (H) to mandibular plane (MP), to palatal plane (PP), as well as to a third cervical vertebra (C3) was more in males than females (p=0.023, p<0.001, p<0.001 respectively). The mean H to PP distance was significantly more in skeletal class I compared to class III (P=0.01). The mean H to C3 distance was significantly more in skeletal class I compared to class II (P=0.008). The mean angle between H-MP and H-PP did not show any statistical difference among three skeletal classes (p=0.102, P=0.213) and among male and female groups (P=0.172, P=0.904).ConclusionsThe hyoid bone is positioned more superior and posterior in females than males and its location differs among different skeletal classes. It is placed more posterior in skeletal class II patterns and more inferior and anterior in skeletal class I patterns. Key words:Hyoid bone, Lateral cephalometry, Class III, Class II, skeletal pattern, Orthodontics.

Background In patients with fixed orthodontics, the presence of orthodontic appliances causes dental plaque accumulation and hygiene problems. The purpose of this study was to evaluate the effect of Propolis and chlorhexidine mouthwashes on plaque and gingival indices in patients who are undergoing orthodontic treatment. Material and Methods In this triple blind study, in total, 37 patients aged from 15 to 35 years those who have been undergoing fixed orthodontic treatment were studied. After that, one of the mouthwashes that containing either Propolis or Chlorhexidine was randomly prescribed to patients. The patients were asked to use mouthwashes twice a day after brushing their teeth for three weeks consecutively. Indicators of plaque, gingival and periodontal status (PI, GI, CPI) were determined on Ramford teeth at the beginning and at the end of three weeks for each patient. Then the results were analyzed statistically. Results The difference between the values of plaque index ( P <0.001), gingival index ( P =0.006) and periodontal index ( P = 0.005) before and after administration of Propolis were statistically significant. The difference was also statistically significant for all three indexes of plaque ( P <0.001), gingival ( P =0.001) and periodontal ( P =0.003) before and after chlorhexidine mouthwash usage. The indices after using mouthwashes were not statistically significant different between two mouthwash groups. Conclusions It seems that Propolis mouthwash can be used as a suitable alternative in patients with fixed orthodontic treatment without the side effects of chlorhexidine mouthwash. Key words: Mouthwash, antimicrobial, Oral hygiene, Propolis, Dental plaque.

Dental practitioners are susceptible to Musculoskeletal Disorders (MSDs). The symptoms may begin from education courses. The aim of this study was to assess prevalence of musculoskeletal pain reports and correlated factors among the Mashhad Dental School students, Iran. A total of 177 undergraduate and postgraduate dental students, who were involved in educational clinical training, completed a questionnaire focusing on pain reports of different body anatomical regions. Variables such as gender, academic grade, academic year, clinical working hour, regular exercise times and also pain characteristics including pain duration intensity and frequency were evaluated. As results 82% of undergraduate students and 90% of postgraduate students reported body pain in at least one region. The most prevalent pain locations were: chest/shoulder (46.9%), head/neck (41.8%), middle back (33.9%) and right hand (25.4%). Severity of reported pain was increased due to performing dental work, increased working stress and working fatigue. Regular exercise was associated with alleviated some pain characteristics. As conclusions musculoskeletal pain reports were highly prevalent among dental students. Attention to prevention of musculoskeletal disorders should be considered as priority in dental schools. For dental students exercise training courses for strengthening muscles of shoulder/chest, neck and back are necessary.

Background Orthodontic appliances impede good dental plaque control by brushing. Antimicrobial mouth rinses were suggested to improve this performance. We therefore aimed to investigate the effects of combined mouthrinse containing chlorhexidine (CHX) and sodium fluoride (NaF) on clinical oral hygiene parameters,and plaque bacterial level. Material and Methods In this double-blind clinical study, 60 fixed orthodontic patients aged 14-25 years were randomly assigned to one of four mouthrinses groups: 1- combined CHX /NaF 2- CHX 0.06% 3- NaF0.05% 4-placebo. Following baseline examination patients were instructed to use the assigned mouthrinse twice daily for 21 days. Bleeding index (BI), modified gingival index (MGI) and plaque index (PI) were determined at the baselineand after three weeks of rinsing. Samples from supragingival plaque were obtained for the assessment of total bacterial, Streptococcus mutans and Lactobacilli colony counts. Data were analyzed by Wilcoxon, Kruskal-Wallis, and Mann-Whitney tests. Results Clinical parameters; All three active mouth rinses induced significant improvements of BI, MGI, and PI (P<0.05). Results of CHX/NaF were slightly, but not significantly, better than CHX. CHX/NaF and CHX induced significantly more changes than NaF and placebo. Microbiological measurements; Except placebo, other mouthrinses reduced total bacterial, Streptococcus mutans, and Lactobacilli counts significantly (P<0.05). CHX/NaF acted against Lactobacilli significantly more than others. Conclusions Adding CHX0.06%/NaF0.05% combined mouth rinse to daily oral hygiene regimen of orthodontic patients significantly improved oral hygiene status. Effect of this combined mouth rinse on dental plaque Lactobacilli was remarkable. However, large controlled trials could provide more definitive evidence. Key words:Mouthrinse, fluoride, chlorhexidine, plaque.

Dental students did not have favorable working postures. They were at an intermediate to high risk for developing MSDs which calls for a change in their working postures. Therefore students should be trained with ergonomic principles and to achieve the best results, ergonomic lessons should be accompanied by practice and periodical evaluations.