Population-Based Design of Mandibular Fixation Plates with Bone Quality and Morphology Considerations

In this paper we present a new population-based implant design methodology, which advances the state-of-the-art approaches by combining shape and bone quality information into the design strategy. The method may enhance the mechanical stability of the fixation and reduces the intra-operative in-plane bending which might impede the functionality of the locking mechanism. The computational method is presented for the case of mandibular locking fixation plates, where the mandibular angle and the bone quality at screw locations are taken into account. The method automatically derives the mandibular angle and the bone thickness and intensity values at the path of every screw from a set of computed tomography images. An optimization strategy is then used to optimize the two parameters of plate angle and screw position. The method was applied to two populations of different genders. Results for the new design are presented along with a comparison with a commercially available mandibular locking fixation plate (MODUS® TriLock® 2.0/2.3/2.5, Medartis AG, Basel, Switzerland). The proposed designs resulted in a statistically significant improvement in the available bone thickness when compared to the standard plate. There is a higher probability that the proposed implants cover areas of thicker cortical bone without compromising the bone mineral density around the screws. The obtained results allowed us to conclude that an angle and screw separation of 129° and 9mm for females and 121° and 10mm for males are more suitable designs than the commercially available 120° and 9m

Design optimisation of patient-specific implants and total joint replacements in oral & maxillofacial surgery

This thesis focuses on the development, implementation, evaluation, and optimization of 3D-virtual surgical planning (VSP) workflows and patient specific implants (PSI) for oral and maxillofacial surgery (OMFS). The studied fields are: head and neck reconstructive surgery (Section I) and temporomandibular joint (TMJ) replacement surgery (Section II). Section III of this thesis focuses on optimisation and validation workflows and intertwines with both aforementioned fields. Current conventional osteosynthesis reconstruction plates (RPs) and PSIs are accompanied by complications, such as, mechanical instability, screw loosening, plate fracture and inaccurate positioning. In TMJ total joint replacement (TMJ-TJR) surgery, correct positioning of TMJ-TJR prostheses and their movement behaviour are focus areas. The general aim of the research described in this thesis was to solve these complications and focus areas by means of mechanical reconsiderations, developing patient-specific (PS) solutions to be used in guided surgery and optimising current workflows in order to enhance the current generation of PS-RPs and TMJ-TJR prostheses by increasing their level of patient-specificity, making them more specific to the patient than currently is the case.Improvements were made by developing patient specific alternatives, which were experimentally and clinically validated. Furthermore, by presenting workflows that allow for improvements in the development of patient specific implants and temporomandibular joint total joint replacements, and by presenting enhanced mechanical testing methodologies, the research presented in this thesis will come together in a next, even more patient specific generation of patient specific implants and temporomandibular joint total joint replacements

Reliability of Digital Dental Cast Measures as Compared to Cone-Beam Computed Tomography for Analyzing the Transverse Dimension

The purpose of this study was to assess the consistency in diagnosing the transverse dimension on cone-beam computed tomography (CBCT) images as compared to digital dental models. The study consisted of 11 patients with posterior crossbite at the level of the first molar and 17 patients with no crossbite at the level of the first molar. 13 patients were male and 15 patients were female with an overall mean age of 13.6 years. Eight linear measurements and two angular measurements were made on CBCT images of the patients and six linear measurements were made on the corresponding digital dental casts. CBCT and model measurements were compared using One-Way Analysis of Variance (ANOVA) and Pearson correlation tests were used to seek relationships between the dental and skeletal measurements on CBCT. All ratios between maxillary and corresponding mandibular measurements were larger in non-crossbite patients than in crossbite patients. The central fossa (CF) was found to be the most representative and reliable tooth measurement in judging dental and skeletal transverse dimensions. A normative CF-CF ratio was determined to be equal to or greater than 1.10 for non-crossbite patients. High correlations were found between dental and skeletal measurements for non-crossbite patients with a CF-CF ratio equal to or greater than 1.10, but were not found for crossbite patients with a CF-CF ratio less than 1.10. In conclusion, CBCT scans may not provide additional diagnostic information as compared to dental models for non-crossbite patients. However, CBCT scans may be diagnostically beneficial for crossbite patients. Further studies with a larger sample size are needed to determine the validity of this study

Biodegradable versus titanium osteosynthesis in maxillofacial traumatology:A systematic review with meta-analysis and trial sequential analysis

Titanium osteosynthesis is currently the fixation system of choice in maxillofacial traumatology. Biodegradable osteosynthesis systems have the ability to degrade in the human body. The aim of this study was to conduct a systematic review, with meta- and trial sequential analyses, to assess the efficacy and morbidity of biodegradable versus titanium osteosynthesis after maxillofacial trauma. MEDLINE, Embase, and CENTRAL were searched for randomized controlled trials and prospective and retrospective controlled studies. Five time periods were studied: perioperative, short-term (0-4 weeks), intermediate (6-12 weeks), long-term (>12 weeks), and overall follow-up. After screening 3542 records, 24 were included. All had a high risk of performance and detection bias due to the nature of the interventions. Meta-analysis showed no differences in efficacy or morbidity between biodegradable and titanium osteosynthesis. The risk of perioperative screw breakage was significantly higher (risk ratio 17.13, 95% confidence interval 2.19-34.18) and the symptomatic plate removal rate lower in the biodegradable group (risk ratio 0.11, 95% confidence interval 0.02-0.57), which was confirmed by the trial sequential analysis. The quality of evidence ranged from very low to moderate. Based on the narrative review and meta-analyses, current evidence shows that biodegradable osteosynthesis is a viable alternative to titanium osteosynthesis when applied in the treatment of maxillofacial trauma, with similar efficacy but significantly lower symptomatic plate removal rates. Perioperative screw breakage occurred significantly more often in the biodegradable group compared to the titanium group

PRELIMINARY FINDINGS OF A POTENZIATED PIEZOSURGERGICAL DEVICE AT THE RABBIT SKULL

The number of available ultrasonic osteotomes has remarkably increased. In vitro and in vivo studies have revealed differences between conventional osteotomes, such as rotating or sawing devices, and ultrasound-supported osteotomes (Piezosurgery®) regarding the micromorphology and roughness values of osteotomized bone surfaces. Objective: the present study compares the micro-morphologies and roughness values of osteotomized bone surfaces after the application of rotating and sawing devices, Piezosurgery Medical® and Piezosurgery Medical New Generation Powerful Handpiece. Methods: Fresh, standard-sized bony samples were taken from a rabbit skull using the following osteotomes: rotating and sawing devices, Piezosurgery Medical® and a Piezosurgery Medical New Generation Powerful Handpiece. The required duration of time for each osteotomy was recorded. Micromorphologies and roughness values to characterize the bone surfaces following the different osteotomy methods were described. The prepared surfaces were examined via light microscopy, environmental surface electron microscopy (ESEM), transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM) and atomic force microscopy. The selective cutting of mineralized tissues while preserving adjacent soft tissue (dura mater and nervous tissue) was studied. Bone necrosis of the osteotomy sites and the vitality of the osteocytes near the sectional plane were investigated, as well as the proportion of apoptosis or cell degeneration. Results and Conclusions: The potential positive effects on bone healing and reossification associated with different devices were evaluated and the comparative analysis among the different devices used was performed, in order to determine the best osteotomes to be employed during cranio-facial surgery

A radiographic analysis of Mandibular Symphysis dimension in black South African adult patients with differing skeletal patterns

Orthodontic treatment often involves planned tooth movement within the confined spaces of the alveolar bone trough. Tooth movement within the alveolar trough may be limited by thin labial and lingual cortical plates. Moving lower incisors beyond the mandibular symphysis dimensions may result in damage to roots and alveolar bone.4 Aim and objective The aim of the study was to evaluate limitation of treatment in different skeletal patterns due to mandibular symphysis dimension in order to evaluate limitations of tooth movement within the confines of the mandibular alveolar trough.The objective was to determine the mandibular symphysis dimensions in subjects with differing skeletal patterns Design The design was a retrospective, cross-sectional study. Methods A sample of 180 pre-treatment lateral cephalometric radiographs of black South African subjects were stratified into three groups based on their skeletal classification. Each Class was further divided into equal numbers of males and females. Descriptive statistics, Student’s t-test, ANOVA test and Pearson correlation coefficient were used to analyse the data and p-values of <0.05 were considered statistically significant. Results Subjects with skeletal Class I pattern had a greater LA compared to subjects with skeletal Class II pattern. Subjects with skeletal Class I pattern had a greater LH and LA in females than in males. Subjects with skeletal Class III pattern had greater LH in males than in females

CBCT location of the fusion between the buccal and lingual cortical in the mandibular ramus : importance to sagittal split osteotomy

Mandibular Sagittal Split Osteotomy (MSSO) is a popular technique in orthognathic surgery used both to advance and to retreat the mandible. However, MSSO may incur in important complications, such as bad splits and sensorineural injuries. Knowing the location of the fusion between the buccal and lingual cortical (FBLC) in the mandibular ramus and the bone thickness in the region where osteotomies will be performed is determinant in MSSO planning to avoid complications. The aim of this study was to document and evaluate possible differences between sexes regarding the location of the FBLC in relation to the superior cortical of mandibular foramen (MF) and bone thickness in the region of interest for MSSO in a Brazilian population. Eighty five cone-beam Computed Tomography (CBCT) scans were used to perform linear measurements to determine the location of the FBLC. Bone thickness from the mandibular canal (MC) to the cortical external surfaces and the diameter of the MC were measured at three different points: mandibular ramus (A), mandibular angle (B) and mesial of the second molar (C). The FBLC was located at a mean distance of 8.3 mm from the superior cortical of the MF in males and 8.1 mm in females. There was no difference between males and females regarding the mean bone thickness from the MC to the buccal external surface at all the points investigated (p >>0.05). Bone thickness from the lingual external surface to the MC was bigger among females than males in regions B and C (p<0.05). The diameter of the MC was bigger among males in regions B and C. Sexual dimorphism regarding mandibular bone thickness but not regarding the location of FBLC was present. This fundamental knowledge may assist to the panning of MSSO