Accuracy of Manual and Virtual Predictive Tracings in Patients Submitted to Orthognathic Surgery.

Cephalometric tracing done manually was considered gold standard for the cephalometric analysis in the last decades. The digital radiographs began to be commonly used in order to make that in a digital way. The objective was to define the accuracy of the predictive and final cephalometric tracings performed manually and virtually. The authors selected 20 patients submitted to bimaxillary orthognathic surgery. The data were collected from lateral cephalometric radiographs, in the preoperative and postoperative periods. The interest were: points, angles (Sella-Nasion to A point angle; Sella-Nasion to B point angle; Frankfurt plane to Mandibular plane angle; Frankfurt plane to occlusal plane angle; Upper and lower central incisors long axes angle; Incisor to Mandibular plane angle; Upper incisor axis to Sella-Nasion plane angle) distances (Co-A; Co-Gn). Data were submitted to the Shapiro-Wilk, analysis of variance, and Kruskal-Wallis tests. The measurement differences were compared using a t test. Descriptive statistics were performed in Excel 2013 and SPSS software, P <0.05 being considered significant. No statistically significant difference was found between the mean values predictive and postoperative of the angles and distances within the manual and digital groups. When comparing the means of the differences between the predictive values and the final values, only the 1:1 angle presented a statistically significant difference, indicating a greater accuracy of the digital predictive tracing for this measure. In conclusion, both methods for obtaining predictive tracings are accurate, which shows that clinical results can be successfully simulated by the most accessible technique.

Guided versus non-guided chin repositioning: a retrospective study on accuracy.

Genioplasty is a widely used surgical approach to address chin deformities by performing an osteotomy on the inferior border of the mandible to allow for comprehensive repositioning of the chin. This study aimed to compare the accuracy of freehand chin repositioning with a guided technique that employed specialised surgical guides. For this retrospective study, data from 30 adult patients who underwent orthognathic surgery to correct dentofacial deformities were analysed. All patients underwent virtual planning before surgery, with half of them treated using freehand chin repositioning and the other half using the guided technique. The surgical outcomes were measured and compared with the virtual plan to assess the positional and rotational accuracy of the techniques. In terms of translational assessment, noteworthy values that exceeded clinically acceptable limits were observed only in sagittal movement in the freehand group (0.97 mm, interquartile range (IQR) 0.73-2.29 mm). Regarding rotational accuracy, both groups exhibited an IQR that surpassed acceptable limits for pitch (3.26°, IQR 2.06-5.20 for the guided group and 2.57°, IQR 1.63-4.24° for the freehand group). The Mann-Whitney test indicated no statistical differences between the groups in any translational or rotational assessment. In conclusion, although there was no statistical difference, the guided technique proved effective in achieving clinically acceptable accuracy in all positions and almost all rotations, displaying superior results in sagittal positioning compared with the freehand technique. To fully harness the advantages of guides and to guarantee accuracy in all rotations, we recommend further research involving guides made of more rigid materials, and customised implants.

Nasal Septal Deviation After Surgically Assisted Rapid Maxillary Expansion.

Background and Aim: Surgically assisted rapid maxillary expansion (SARME) is a surgical technique widely used to correct deficiency of the transverse maxillary dimension. Although some studies investigated the effect of SARME on nasal and facial alterations, there is no evidence that correlates nasal septal deviation (NSD) to SARME as a possible postoperative sequel. The aim of this study is to address and quantify possible variations in the position of the nasal bony septum after SARME and identify any NSD as a postoperative outcome of this surgical technique. Patients and Methods: This is a retrospective study, conducted at the Department of Oral and Maxillofacial Surgery of the University Hospital of Araraquara (Unesp, faculty of dentistry), SP, Brazil. Twenty-nine patients who underwent SARME were studied; every patient was evaluated by cone-beam computerized tomography (CBCT) before (T0) and six months after surgery (T1), and we collected the variation of nasal septal position by measuring the distance between the bony septum and the nasal lateral wall. Our measurements were carried out at the level of the head, midpoint and tail of the inferior turbinate. Results: A mean NSD ranging from 0.4 to 1.2 mm was measured, and it is more pronounced at the anterior part of the bony septum. Twenty-seven patients (93.1%) presented minor changes in bony septum position; in 2 cases (6.8%), a significant NSD was found (p < 0.05). Conclusion: A variation of bony nasal septum position can be expected in any direction after SARME, and it is more pronounced at anterior portion.

Bone formation after surgically assisted rapid maxillary expansion: comparison of 2 distraction osteogenesis protocols.

OBJECTIVE: The aim of this study was to compare bone formation between 2 distraction osteogenesis protocols by analyzing cone beam computed tomography (CBCT) scan data. STUDY DESIGN: In this retrospective study, the efficacy of 2 different surgically assisted rapid maxillary expansion protocols (group 1 [G1], 3 × 0.25 mm/d; group 2 [G2], 1 mm start followed by 2 × 0.25 mm/d) was analyzed using CBCT scans obtained at 3 time points: preoperatively (T0), immediately after surgery (T1), and 6 months after surgery (T2). Bone formation at T0, T1, and T2 was analyzed using the Dolphin Imaging 11 program. RESULTS: At T1, both groups had significantly higher bone volume than at T0 (G1, 135.6 vs 124.65 mm3, respectively; G2, 153.49 vs 118.9 mm3, respectively), with no significant difference between groups (P = .6). Moreover, bone density measured in the region of interest was similar between groups at all 3 time points; however, in both groups, bone density was significantly lower at T1 and T2 than at T0 (P < .01), with no difference between T1 and T2. CONCLUSIONS: Bone density between the incisors decreased with progressive distraction (i.e., increasing volume), regardless of the distraction protocol used; thus, both protocols can be used safely in clinical practice. Nevertheless, our results indicate that stress should not be applied to the incisors within 6 months of surgery, regardless of the protocol used. Surgeons and orthodontists should therefore consider immature bone formation and avoid using excessive force to close a diastema.

In vitro mechanical test of grid plates for mandibular angle fractures.

This study evaluated, by mechanical testing, the strength of four-hole grid plates used for mandibular angle fracture fixation. Much has been discussed about the treatment of mandibular fractures with straight or curved plates. However, there are few studies about the use of grid plates. The geometry of such plates provides three-dimensional stability, resistance against torque associated with a low profile. Ninety polyurethane hemimandibles were used as substratum. The hemimandibles were divided into nine groups and fixation of the fractures was performed varying the type and position of plate and type of screw. An intact hemimandible group was used as control. It was possible to observe that plates positioned at the tension zone present the highest load values, both for dislocations of 3 and 5 mm. There was no statistical difference when plates with or without an intermediate bar were tested. The locking screws were more efficient than the non-locking screws when the plates were positioned at the neutral zone. Results allowed us to conclude that grid plates installed at the tension zone presented greater mechanical efficiency. If grid plates are positioned at the neutral zone, they should have an intermediate bar and be fixed with locking screws.