Effect of orthodontic extraction of mandibular premolars on third molar angulation after treatment with fixed appliances : A cross-sectional study.

PURPOSE: Orthodontic treatment involving premolar extractions might improve the angulation of lower third molars, which are the teeth most often impacted. This study analyzes the impact of first/second lower premolar extraction during orthodontic therapy on the angulation of mandibular third molars. METHODS: A total of 120 patients treated non-extraction (n = 40), with extraction of first (n = 40), or second lower premolars (n = 40) were included. The mesiodistal angulation of lower third molars relative to the adjacent tooth and their developmental stage were evaluated from posttreatment orthopantomograms. Between-group differences were statistically evaluated at a significance level of 0.05. RESULTS: The orthopantomograms of 120 patients (51% female) with a median age of 15.2 years at the time of debonding were evaluated after a mean treatment duration time of 2.9 years. No difference (P > 0.05) was seen between the average angulation of the lower third molars of the right (mean = 24.4°, standard deviation [SD] 13.6°) and the left side (mean = 23.6°, SD 14.1°). No differences in the angulation of the lower third molar were found between the non-extraction and extraction groups for the right (P = 0.44) or the left side (P = 0.22). Likewise, no differences were found when comparing the first and second premolars for the right (P = 0.26) or the left side (P = 0.10). Premolar extraction was associated with an advanced root development stage of the right third molar (odds ratio 7.1; 95% confidence interval 1.1-48.1; P = 0.04), with no differences between extraction of the first or second premolar (P = 0.10). CONCLUSION: Orthodontic treatment involving premolars extractions might be associated with a small acceleration in root development, but not with the angulation, of lower third molars.

Effect of field of view (FOV) positioning and shielding on radiation dose in paediatric CBCT.

OBJECTIVE: To investigate the effect of two different large field of view (FOV) positions in the vertical dimension and shielding (thyroid collar and eyeglasses) on the effective dose and the local doses of various sites of the craniofacial complex. METHODS: Organ doses and effective doses were calculated based on the measured doses using 27 pairs of thermoluminescent dosemeters in a paediatric tissue-equivalent of a 10-year-old anthropomorphic phantom. The large FOV of the 3D Accuitomo F170 CBCT scanner was used to image parts of the craniofacial complex. Six protocols were performed: (A) cranial position without shielding; (B) cranial position with shielding; (C) caudal position without shielding; (D) caudal position with shielding, (E) similar to C with 3600 rotation and (F) similar to D with 360° rotation. Measurements were obtained in duplicate, and the relative δ value (%) was applied to compare the average doses between the protocols. RESULTS: Changing the FOV position from cranial to caudal without using shielding resulted in an increase of the effective dose of 18.8%. Use of shielding in the caudal position reduced the dose by 31.6%. Local absorbed dose of the thyroid had the most relevant impact on calculation of the effective dose, followed by oesophagus, bone marrow and bone surfaces, especially when comparing the different protocols. CONCLUSIONS: Application of shielding devices for thyroid in combination with a most caudal positioning of FOV led to the lowest local absorbed doses as well as the effective dose in a child phantom model.

Condylar resorption in orthognathic patients after mandibular bilateral sagittal split osteotomy: a systematic review.

Objective: To systematically search the literature and assess the available evidence regarding the incidence and quantification of condylar resorption following bilateral sagittal split osteotomy (BSSO) of the mandible in orthognathic patients. Search methods: Electronic database searches of published and unpublished literature were performed. The reference lists of eligible studies were hand searched for additional studies. Selection criteria: Randomized clinical trials (RCTs), prospective, and retrospective studies with patients of any age that underwent BSSO were included. Data collection and analysis: Study selection, data extraction, and risk of bias assessment were performed individually and in duplicate. Results: One RCT, 3 prospective, and 10 retrospective studies were included in this review. The lack of standardized protocols and the high amount of heterogeneity precluded a valid interpretation of the actual results through pooled estimates. There was a substantial consistency among studies, however, that young, female patients with mandibular deficiency and high mandibular plane angle, submitted to surgical counterclockwise rotation of mandibular segments, were more prone to a higher risk for condylar resorption after BSSO. The level of evidence was found to be low given the high/serious risk of bias in all included studies. Conclusions: Condylar resorption should be taken into account as a potential postsurgical complication after BSSO. However, its incidence and quantification need precautious interpretation owing to the low level of evidence and the high heterogeneity of studies. Additional high-quality prospective research assisted by 3D imaging technology is needed to allow more definitive conclusions. Registration: Study not registered. Conflict of interest: None.

Incidence of anatomical variations and disease of the maxillary sinuses as identified by cone beam computed tomography: a systematic review.

PURPOSE: To analyze available evidence on the incidence of anatomical variations or disease of the maxillary sinuses as identified by cone beam computed tomography (CBCT) in dentistry. MATERIALS AND METHODS: A focused question was developed to search the electronic databases MEDLINE, EMBASE, the Cochrane Oral Health Group Trials Register, and CENTRAL and identify all relevant papers published between 1980 and January 19, 2013. Unpublished literature at ClinicalTrials.gov, in the National Research Register, and in the Pro-Quest Dissertation Abstracts and Thesis database was also included. Studies were included irrespective of language. These results were supplemented by hand and gray literature searches. RESULTS: Twenty-two studies were identified. Twenty were retrospective cohort studies, one was a prospective cohort study, and one was a case control study. The main indication for CBCT was dental implant treatment planning, and the majority of studies used a small field of view for imaging. The most common anatomical variations included increased thickness of the sinus membrane, the presence of sinus septa, and pneumatization. Reported sinus disease frequency varied widely, ranging from 14.3% to 82%. There was a wide range in the reported prevalence of mucosal thickening related to apical pathology, the degree of lumenal opacification, features of sinusitis, and the presence of retention cysts and polyps. More pathologic findings in the maxillary sinus were reported in men than in women, and the medial wall and sinus floor were most frequently affected. CONCLUSION: CBCT is used primarily to evaluate bony anatomy and to screen for overt pathology of the maxillary sinuses prior to dental implant treatment. Differences in the classification of mucosal findings are problematic in the consistent and valid assessment of health and disease of the maxillary sinus.