Skeletal stability following mandibular advancement: is it influenced by the magnitude of advancement or changes of the mandibular plane angle?

OBJECTIVES: The aim of this study was to investigate the effects of advancement magnitude and changes in mandibular plane angle on the stability of mandibular advancement. MATERIALS AND METHODS: This retrospective cohort study evaluated the postoperative stability of mandibular advancement in class II skeletal subjects who underwent bilateral sagittal split osteotomy. Radiographs taken preoperatively, immediately postoperatively and 1 year postoperatively were traced and analyzed using linear and angular measurements. To determine horizontal and vertical relapse, an X-Y coordinate system was established in which the X-axis was constructed by rotating S-N downward by 7° (approximation of the Frankfort horizontal plane) and the Y-axis was defined as a line perpendicular to the X-axis and passing through the point Sella. For certain reference points including point A, point B, pogonion and menton, the perpendicular distance between each point and both axes was determined and cephalometric variables were recorded as X and Y coordinates. RESULTS: Twenty-five subjects were studied. A significant correlation between the amount of mandibular advancement and relapse in the B point (vertical and horizontal) and the pogonion point was observed (vertical and horizontal, P<0.001). Evaluation of data demonstrated a positive correlation between the mandibular plane angle (SN/ML) change and vertical relapse in the B point (P<0.05). A simple regression model demonstrated that 74% of horizontal relapse and 42.3% of vertical relapse in the B point was related to the amount of mandibular advancement. The receiver operating characteristic test showed that 8.5 mm mandibular advancement is related to a relapse rate of 1 mm or more in the pogonion, vertically or horizontally. CONCLUSION: The magnitude of mandibular advancement is a stronger surgical predictor for horizontal rather than vertical relapse at the B point. Changes in mandibular plane angle (SN/ML) during surgery affect vertical, but not horizontal relapse at the B point.

[Study of reasons for extraction of permanent teeth in Shiraz 2012-2013]

Introduction and Aims: tooth extraction done for any reasons has negative effect on humans psychological aspect .more ever extraction cause disorder in mastication, atheistic and speaking. The aim of this research is to study the relation frequency of extracting permanent with the reasons of it in dental clinics and Shiraz dental school in 1392 in Shiraz

Methods: this cross-sectional study has targeted 800 patients whose 2110 teeth were removed using simple sampling method among those referred to dental clinics in Shiraz. Information such as gender, age, educational level, the main cause of the tooth removal [Tooth decay, periodontal disease, prostheses, orthodontics, and also patient's desire to do so] and type of tooth were collected. Data analysis was performed using SPSS18 software and used chi-square test and logistic regression

Results: caries [25%], a combination of decay and periodontal problems [19.8 %], Patient's request [11.2%] were the most common causes of tooth removal. Chi-square test showed no significant correlation between the tooth and Gender [p=0.358?2=11.72 ]. Chi-square test showed a statically significant correlation between patients' level of education and the tooth extraction

Conclusion: based on the results, most of the teeth were extracted due to decay and a combination of decay and periodontal problems or patients' request considering the fact that they could be preserved which shows the need for increasing preventive programs and further periodic examination