Accuracy between virtual surgical planning and actual outcomes in orthognathic surgery by iterative closest point algorithm and color maps: A retrospective cohort study.

BACKGROUND: To evaluate the accuracy between actual outcomes and virtual surgical planning (VSP) in orthognathic surgery regarding the use of three-dimensional (3D) surface models for registration using iterative closest point (ICP) algorithm and generated color maps. MATERIAL AND METHODS: Construction of planning and postoperative 3D models in STL files format (M0 and M1, respectively) from CBCT of 25 subjects who had been submitted to bimaxillary orthognathic surgery was performed. M0 and M1 were sent to Geomagic software in semi-automatic alignment surface mesh order of M0 and M1 for registration using ICP algorithm to calculate mean deviation (MD, MD+, MD-, SD) and root mean square (RMS - 3D Error). Color maps were generated to assess qualitative congruence between M0 and M1. From deviation analysis, 3D Error was defined as accuracy measurement. To assess the reproducibility, the workflow was performed by two evaluators multiple times. t-tests were used to assess whether all means of MD, MD+, MD-, SD and 3D Error values would be ≤ - 2 mm and ≥ 2 mm. RESULTS: High intra and inter evaluators correlation were found, supporting the reproducibility of the workflow. t-tests proved that all MDs and 3D Error values were > - 2 mm and < 2 mm. CONCLUSIONS: 3D error mean was within the standards of clinical success lower than 2 mm. ICP algorithm provided a reproducible method of alignment between 3D models and generated color maps to evaluate 3D congruence but did not answer all methodological parameters regarding the assessment of accuracy in orthognathic surgery.

Chemical and structural analyses of titanium plates retrieved from patients.

The aim of this study was to evaluate the microscopic structure and chemical composition of titanium bone plates and screws retrieved from patients with a clinical indication and to relate the results to the clinical conditions associated with the removal of these devices. Osteosynthesis plates and screws retrieved from 30 patients between January 2010 and September 2013 were studied by metallographic, gas, and energy dispersive X-ray (EDX) analyses and the medical records of these patients were reviewed. Forty-eight plates and 238 screws were retrieved. The time elapsed between plate and screw insertion and removal ranged between 11 days and 10 years. Metallographic analysis revealed that all the plates were manufactured from commercially pure titanium (CP-Ti). The screw samples analyzed consisted of Ti-6Al-4V alloy, except four samples, which consisted of CP-Ti. Titanium plates studied by EDX analysis presented greater than 99.7% titanium by mass. On gas analysis of Ti-6Al-4V screws, three samples were outside the standard values. One CP-Ti screw sample and one plate sample also presented an oxygen analysis value above the standard. The results indicated that the physical properties and chemical compositions of the plates and screws did not correspond with the need to remove these devices or the time of retention.

Comparison of five different fixation techniques of sagittal split ramus osteotomy using three-dimensional finite elements analysis.

The aim of this study was to compare the mechanical stress over hemimandible substrate and hardware after sagittal split ramus osteotomy (SSRO) fixed with five different techniques using three-dimensional (3D) finite element analysis. A 3D finite element model of a hemimandible was created and a 5mm advancement SSRO was simulated on a computer model. The model was fixed with five different techniques: 3 linear 60° screw arrangement; 3 linear 90° screw arrangement; 3 inverted L screw arrangement; 1 conventional miniplate; and 1 locking miniplate with four monocortical screws. Load was applied until 3mm displacement was reached and the results were compared with previous mechanical and photoelastic tests, thus analysing the mechanical stresses developed in the proximity of miniplates and screws and within the fixation system itself. The maximum principal stress values demonstrate a lower mechanical stress rate in bone and in the fixation system with the inverted L arrangement, followed by the linear 90° and linear 60° arrangements. The locking miniplate/screw system presented lower maximum principal stress and better stress distribution compared with the conventional system. Under the conditions tested, the reversed L arrangement provided the most favourable stress dissipation behaviour.

Skeletal stability after inferior maxillary repositioning without interpositional graft.

True vertical maxillary deficiency is a characteristic of short face syndrome. In these patients, inferior repositioning of the maxilla (IRM) is indicated to improve facial aesthetics and function, but this procedure has been described as the most unstable. The aim of this study was to evaluate the long term, post surgical stability of IRM, fixed with four 2.0mm L-shaped miniplates, without any type of graft. A cephalometric study was performed, analysing linear measurements (anterior nasal spine, the A point, top of the incisor, top of the buccal-mesial cusp of the first molar, and posterior nasal spine on an X-Y coordinate system) traced immediately preoperatively, immediately postoperatively and at least 6 months post operatively. Eight young adult patients who underwent IRM were studied. The average results of this study were: surgical movement of 4.65 mm at I point, 5.32 mm at anterior nasal spine (ANS) point, and 4.70 mm at A point and relapses of 1.60 mm (35%), 2.23 mm (43%) and 2.10 mm (46%), respectively. It was concluded, that IRM using this type of internal rigid fixation without graft is unstable.

Mandibular fractures in a group of Brazilian subjects under 18 years of age: A epidemiological analysis.

OBJECTIVE: This study showed a retrospective analysis of the etiology, incidence and treatment of maxillofacial injuries in a pediatric and adolescent population of the State of Sao Paulo. METHODS: We analyzed 2986 medical records of victims of facial trauma under 18 years, treated between 1999 and 2008 by the Department of Oral and Maxillofacial Surgery, Piracicaba Dental School, University of Campinas, Sao Paulo - Brazil. During this period, 757 patients under 18 were victims of maxillofacial trauma, of which, 112 patients had 139 lines of fracture in the mandible. The most affected age group were male adolescents. RESULTS: The bicycle accidents constituted the main etiology (34.82%). The conservative treatment was used in 51% of cases, and 49% received surgical treatment. Only 5 cases of postoperative complications were identified. CONCLUSION: The incidence of trauma and mandible fractures in pediatric and adolescent patients was high in the area of study. Bicycle accidents and falls being the main etiological factors. The group of adolescents was most affected. The conservative and surgical treatment was used almost in the same proportion.