Transverse and sagittal angulations of proximal segment after sagittal split and vertical ramus osteotomies and their influence on the stability of distal segment.

BACKGROUND/PURPOSE: This study aimed at comparing the transverse and sagittal angulations of proximal segment after sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO), and examining their influences on the stability of distal segment. METHODS: Patients who received SSRO (n = 21) or IVRO (n = 11) for mandibular setback were included. Lateral and posteroanterior cephalograms taken within 1 month before surgery (T1), within 1 week after surgery (T2), and at least 6 months after surgery (T3) were analyzed. The angulation of each proximal segment relative to the upper orbital margin line was measured on posteroanterior cephalogram and the sum of both angles (total ramus angle, TRA) was obtained. On lateral radiograph, ramus inclination angle (RIA) relative to a horizontal reference line 7° to the sella-nasion was assessed and B-point position was measured. RESULTS: From T1 to T2, more increases in TRA and RIA were noted after IVRO than after SSRO. From T2 to T3, TRA and RIA significantly decreased in IVRO group but remained relatively stable in SSRO group. ΔTRA(T1-T2) positively related to upward rotation of distal segment for SSRO and downward rotation for IVRO from T2 to T3. For SSRO only, ΔRIA(T1-T2) significantly related to forward movement of distal segment during remodeling. CONCLUSION: TRA and RIA increase significantly after IVRO and then regress, whereas they increase mildly after SSRO and remain stable. Increase in TRA significantly relates to distal segment rotation during remodeling for both surgeries, but increase in RIA relates to forward relapse of the distal segment only for SSRO. The reasons underlying the correlations are not certain and deserve future investigations.

A pilot study applying digital radiography for estimating ratio of supported single-root surface area.

BACKGROUND: The prognosis of a tooth with periodontitis is affected by the amount of supporting bone. A key factor in retaining a tooth is the ratio of supported root surface. Currently, root surfaces cannot be accurately measured using conventional dental radiographs, which only measure the length of bone support on proximal surfaces. METHODS: Eight extracted, single-rooted teeth were 3-dimensionally digitized using a contact technique for true surface area measurements. Root length, projection area, and pixel values were then measured on digital radiographs. The accuracy of the ratio estimation of supported surface area from linear, area, and pixel values was calculated and compared. RESULTS: The mean error from linear estimation was 7.9%; the mean error from area estimation was 1.0%; and the mean error from pixel value estimation was 1.3%. One-way analysis of variance (ANOVA) showed significant differences in all estimations while Scheffé's analysis further revealed significant differences only in the linear estimation. CONCLUSIONS: A three-dimensional digitizing device could be used as a non-destructive method of measuring root surface area. The ratio of supported single-root surface area could be estimated with high accuracy from the projected area data acquired on the digital dental radiographs. The thickness data as reflected from the pixel values in the digital images did not improve the estimation accuracy. Estimations using only length data yielded significantly less accuracy. Digital dental x-ray images provide the potential for estimating the ratio of supported root surface efficiently.

Accuracy of supported root ratio estimation from projected length and area using digital radiographs.

BACKGROUND: The purpose of this study was to evaluate the accuracy of supported single-root surface ratio estimated from the length and projected area of the tooth, using digital dental radiographs. METHODS: Eight extracted, single-root teeth were three-dimensionally digitized using a contact technique for surface area measurement. The data were then processed using engineering application software and length, projection area, and true surface area of the root at a designated length were obtained. Based on these three measurements, the accuracy of the supported surface area ratio measurement at different lengths of the root was evaluated. RESULTS: The largest mean errors from linear and area estimation were 9.58% and -1.16%, respectively. The 95% confidence intervals were all positive, indicating that linear measurements overestimated supported ratio. T tests showed that linear estimations resulted in significant differences in all eight teeth and area estimations in five teeth. When analyzing the supported ratio of the alveolar bone receding from the cemento-enamel junction (CEJ) toward the apex of the root at each mm, linear estimation showed significant differences down to 8 mm, while area estimation showed significant differences only up to 2 mm. CONCLUSIONS: The results of this study indicate that a reliable estimate of the ratio of root surface area supported by alveolar bone cannot be determined from linear or area data. However, when the marginal bone destruction exceeds 2 mm from the CEJ, area estimation does not show a significant difference in the supported region. As demonstrated in this study, root surface ratio estimation function could be an advantage of digital dental x-ray systems in which projected root area is readily observed.