Influence of maxillary advancement surgery on skeletal and soft-tissue changes in the nose - a retrospective cone-beam computed tomography study.

OBJECTIVES: Surgical correction of skeletal maxillary retroposition is often associated with changes in the morphology of the nose. Unwanted alar flaring of the nose is observed in many cases. The aim of the present study was therefore to investigate the influence of surgical advancement of the maxilla on changes in the soft-tissue morphology of the nose. Having a coefficient that allows prediction of change in the nasal width in Caucasian patients after surgery would be helpful for treatment planning. MATERIALS AND METHODS: All 33 patients included in this retrospective study were of Caucasian descent and had skeletal Class III with maxillary retrognathia. They were all treated with maxillary advancement using a combination of orthodontic and maxillofacial surgery methods. Two cone-beam computed tomography (CBCT) datasets were available for all of the study's participants (16 female, 17 male; age 24.3 ± 10.4 years): the first CBCT imaging was obtained before the planned procedure (T0) and the second 14.1 ± 6.4 months postoperatively (T1). Morphological changes were recorded three-dimensionally using computer-aided methods (Mimics (Materialise NV, Leuven/Belgium), Geomagic (Geomagics, Morrisville/USA)). Statistical analysis was carried out using SPSS 21 for Mac. RESULTS: The mean sagittal advancement of the maxilla was 5.58 mm. The width of the nose at the alar base (Alb) changed by a mean of + 2.59 mm (±1.26 mm) and at the ala (Al) by a mean of + 3.17 mm (±1.32 mm). Both of these changes were statistically highly significant (P = 0.000). The increase in the width of the nose corresponded to approximately half of the maxillary advancement distance in over 80 % of the patients. The nasolabial angle declined by an average of -6.65° (±7.71°). CONCLUSIONS: Maxillary advancement correlates with a distinct morphological change in nasal width. This should be taken into account in the treatment approach and in the information provided to patients.

Distribution of endosseous bony canals in the mandibular symphysis as detected with cone beam computed tomography.

PURPOSE: The purpose of this article was to investigate the distribution of endosseous bony canals in the anterior mandible using cone beam computed tomography (CBCT) technology. MATERIALS AND METHODS: Two hundred ninety-nine images based on CBCT of the anterior mandible were analyzed for the presence of endosseous canals. The bony canals were observed in relationship to the adjacent anatomical structures, and relationships between their topographic variability and patient age and gender were analyzed. RESULTS: Bony canals were found in the anterior mandible in almost 86% of the examined patients, independent of age and gender. The highest regional frequency was seen in the midline area, followed by the lateral incisor and canine regions. The length of the canals ranged from 5 to 15 mm (mean, 10.55 mm). Multiple (two or three) canals were also observed in approximately 9% of the scans. Varying appearances of these bony canals in the symphysis region were also demonstrated. CONCLUSIONS: Endosseous canals in the mandibular symphysis were found using CBCT scans. CBCT seems to be an important diagnostic technique for evaluation of the exact distribution of bony canals in the symphysis region that may help reduce the risk of surgical complications.

Use of stereolithographic drilling and cutting guides in bilateral mandibular distraction.

Mandibular distraction osteogenesis is used in the treatment of patients with syndromic and nonsyndromic class II mandibular hypoplasia. The three-dimensional distraction of the mandible is extremely complex. Past experience with mandibular distraction has demonstrated the indispensability of solid presurgical planning to achieve predictable results. We report a method for a virtual three-dimensional planning of the bilateral mandibular distraction with intraoperative transfer by stereolithographic guides. Five patients (mean age, 22.8 years) with bilateral mandibular hypoplasia were examined with preoperative and postoperative computed tomographic scans. The direction and dimension of the distraction were planned on the three-dimensional computed tomographic scans. Tooth- and bone-borne stereolithographic guides for transferring the planning were then applied intraoperatively. It was feasible to transfer and perform the surgery as planned by the use of the stereolithographic drilling and cutting guides. The mean distraction width was 11.33 (SD, 8.32) mm. The mean difference of the distraction width between the planning and the achieved final mandibular position was 1.80 (SD, 0.43) mm. The intercondyle distance decreased by 3.28 (SD, 1.01) mm. A parallel distraction within the planned vectors was achieved. Mandibular distraction osteogenesis in the treatment of severe mandibular hypoplasia needs careful presurgical planning. Parallel distraction and fast placement of the distractors are provided by the planning. The method provides a useful tool for both planning and intraoperative transfer of the virtually preplanned distraction vectors.

Changes after surgically-assisted maxillary expansion (SARME) to the dentoalveolar, palatal and nasal structures by using tooth-borne distraction devices.

Different devices are available to aid surgically-assisted maxillary expansion. In this study we have evaluated the changes to the anchoring teeth, the hard palate, and the lower nasal passage made by tooth-borne distraction devices. Thirty-one patients (mean (SD) age 28 (2) years) with deficiencies in the transverse width of the maxilla were examined by computed tomography and cone beam scans before and after operation. The data were analysed with the help of Wilcoxon's signed rank test and Spearman's r correlation. The mean (SD) distraction width was 6.5 (2.3) mm. All anchorage teeth were tilted (p<0.01). The axes changed by a mean (SD) of 4.8 (0.9)° in the first premolar and 3.1 (0.8)° in the first molar. The nasal isthmus increased by a mean (SD) of 2.5 (0.3) mm. The hard palate adjacent to the anchoring teeth increased anteriorly by a mean (SD) of 2.8 (0.4) mm and posteriorly by 2.7 (0.4) mm. The hard palate was lowered by 1.2 (0.8) mm. There was a significant correlation in the distraction width, with changes in the intercoronal and interapical distances of the anchoring premolars (p<0.05) and with the interapical distance of the anchoring molars (p<0.01). There was also a correlation between the distraction width and the overall gain in width of the lower nasal passage (p<0.05). The results suggested that surgically-assisted maxillary expansion with tooth-borne devices has significant effects on the anchoring teeth, the nasal floor, and the hard palate. Both tilting of the teeth and an evenly distributed movement of the segments were seen.

Changes in the mandibular and dento-alveolar structures by the use of tooth borne mandibular symphyseal distraction devices.

PURPOSE: Different devices to perform a mandibular symphyseal distraction osteogenesis (MSDO) are available. This study evaluates how tooth borne distraction devices change to the teeth, the mandible and the condyles. MATERIALS AND METHODS: 19 patients (mean age 27.1) with anterior width deficiencies of the mandible were examined with routine pre- and postoperative CT-scans 1 month before and 4 months after a mean distraction width of 5.68 mm (SD 0.88). The anchorage teeth of the tooth borne device were examined concerning displacement of their axes as well as the movement of the condyles and the mandibular symphysis. The data were evaluated using Wilcoxon signed rank test and Spearman rho correlation. RESULTS: Significant tilting of the anchorage teeth was observed (p<0.01). The axes changed by 3.32° (SD 1.57) in the first premolar and by 2.63° (SD 1.75) in the first molar. A total of 2.67 mm (SD 1.17) of bone was formed on the symphysis. A significant correlation was found between distraction width and intercoronal distance changes of the anchorage teeth (p<0.01). No significant change of the intercondylar distance was found pre- and postoperatively in the Wilcoxon test. CONCLUSION: MSDO with tooth borne devices has strong effects on the anchorage teeth. No severe effects on the condyles were observed. The postoperative width gain is a result of newly generated bone in the symphysis and tooth tilting. Nevertheless stable postoperative bite corrections are achievable.

Long term effects of surgically assisted rapid maxillary expansion without performing osteotomy of the pterygoid plates.

PURPOSE: Surgically assisted rapid maxillary expansions (SARME) are commonly used to widen the maxilla. This study evaluates long term stability of surgically assisted rapid palatal expansion without performing osteotomy of the pterygoid plates and its effects on nasal airway volume. MATERIALS AND METHODS: 13 patients (mean age 31, 23+/-6, 11) with a maxillary transverse deficit of at least 5mm were examined 1 month before and on average 63 months after a mean palatal distraction of 8.29+/-1.68mm by acoustic rhinometry. Profiles of the nasal airway volumes were collected. A cast model analysis was performed. The data were evaluated using Wilcoxon signed rank test. RESULTS: A V-shaped movement of the segments was observed. The gain for total nasal volume was 23.25%. Findings indicate a significant enhancement of nasal volume in all patients (P<0.01) as result of the maxillary expansion. No relapse occurred in the study group. CONCLUSION: SARME provides a long term stable orthodontic bite correction and permanently enhances the nasal airways. A transverse shift of the segments can be achieved over the whole bony palate even when no osteotomy of the pterygo-maxillary suture is performed.