Effect of triangular mesh resolution on the geometrical trueness of segmented CBCT maxillofacial data into STL format.

OBJECTIVES: To determine the optimal level of mesh reduction that would maintain acceptable levels of geometrical trueness while also minimizing the impact on other parameters such as file size and processing time. METHODS: Intraoral and extraoral maxillofacial defects were created on 8 cadaver heads and scanned by using a CBCT scanner (NewTom 3D Imaging, Verona). DICOM data were segmented to produce head (n=8) and skull models (n=8) saved as standard tessellation language (STL) files. A further processing of head models was preformed to produce face (n=8) and ear models (n=8). A mesh reduction process was performed for each STL model (reference, R0) by generating 50% (R1), 75% (R2), and 90% (R3) reductions. The 3 datasets were compared to the R0 file using 3D evaluation software (GOM Inspect) using a global best-fit algorithm, to calculate the root mean square (RMS) deviations. Statistical analyses were performed at a level of significance of α=0.05. RESULTS: There was no 3D deviation after the 50% triangular mesh reduction in the 4 datasets. Minor 3D deviations were observed after 75% reduction, in all groups. After 90% reduction, higher 3D deviations were observed, and especially in head and skull. Statistically significant increase in 3D deviations was observed with higher degrees of mesh reduction (p < 0.001). CONCLUSION: The resolution of CBCT-based maxillofacial defect models can be reduced up to 50%, with neglectable concern to inaccuracy. CLINICAL SIGNIFICANCE: Accurate maxillofacial models can be obtained from CBCT DICOM files after segmentation and export as STL files, even when the mesh resolution is reduced up to 50%. This information can be valuable for practitioners and researchers working with 3D models of maxillofacial defects.

Evaluation of the Osseodensification Technique in Implant Primary Stability: Study on Cadavers.

PURPOSE: The objective of this study was to compare the osseodensification drilling technique used with Densah implant drills (Versah) to standard drilling by evaluating their contribution to primary implant stability. MATERIALS AND METHODS: A total of 21 mandibles dissected from cadavers were selected. Axiom drills (Anthogyr) were used for 29 standard drilling (SD) protocols in the control group. In the test group, the Densah profile drills were used to perform 29 osteotomies (OD). Implant placement was performed for 58 of these procedures. The insertion torque (IT) and implant stability quotient (ISQ) were recorded. High-resolution CBCT allowed for a postoperative analysis of the peri-drilling bone tissue. For 16 osteotomies without implant placement, Mann-Whitney U test was used for comparison of IT and ISQ values between groups. Spearman rank correlation coefficient was used between IT and ISQ values. The significance level was α = .05. RESULTS: The IT values for OD and SD were, respectively, 34.9 Ncm ± 19.1 and 23.6 Ncm ± 9.8. The IT was significantly higher in the OD group compared to the SD group (P = .036). A moderate positive correlation (ρ = 0.527) between IT and ISQ was observed, as well as a significant increase (P = .026) in bone density. CONCLUSION: There was a significant increase in IT and bone density following an osseodensification procedure compared to standard drilling.

An Atypical Path of the Lingual Nerve in the Retromolar Region: Incidence in Oral Surgery.

The Lingual nerve is frequently anesthetized during oral, maxillofacial, or otorhinolaryngology surgery. It originates below the oval hole in the infratemporal region, follows its path down and forward, and moves away from the medial surface of the ramus. From there, it goes just above the mylohyoid line. It approaches the lateral margin of the tongue and crosses the Wharton's canal, and divides into numerous branches. Some cases of temporomandibular joint syndrome or myofascial pain syndrome could be a result of its anatomical variations. Also, the jurisprudence has always condemned the practitioner if for not demonstrating that the path of the injured nerve presents an anomaly which makes his involvement inevitable. The purpose is to present one of the multiple atypical paths of the lingual nerve not described in the retromandibular trigone, demonstrating that its damage constitutes a risk that cannot be controlled.

Biomechanical analysis of skull trauma and opportunity in neuroradiology interpretation to explain the post-concussion syndrome: literature review and case studies presentation.

Traumatic head injuries are one of the leading causes of emergency worldwide due to their frequency and associated morbidity. The circumstances of their onset are often sports activities or road accidents. Numerous studies analysed post-concussion syndrome from a psychiatric and metabolic point of view after a mild head trauma. The aim was to help understand how the skull can suffer a mechanical deformation during a mild cranial trauma, and if it can explain the occurrence of some post-concussion symptoms. A multi-step electronic search was performed, using the following keywords: biomechanics properties of the skull, three-dimensional computed tomography of head injuries, statistics on skull injuries, and normative studies of the skull base. We analysed studies related to the observation of the skull after mild head trauma. The analysis of 23 studies showed that the cranial sutures could be deformed even during a mild head trauma. The skull base is a major site of bone shuffle. Three-dimensional computed tomography can help to understand some post-concussion symptoms. Four case studies showed stenosis of jugular foramen and petrous bone asymmetries who can correlate with concussion symptomatology. In conclusion, the skull is a heterogeneous structure that can be deformed even during a mild head trauma.

Augmented Reality for Interactive Visualization of 3D Maxillofacial Prosthetic Data.

PURPOSE: To introduce an augmented reality (AR) application for students, patients, and practitioners to use to visualize a maxillectomy defect, the associated obturator prosthesis, and the eventual effects on the patient's facial appearance. MATERIALS AND METHODS: Various 3D virtual models related to maxillectomy defects and their prosthetic rehabilitations were used to illustrate the handheld AR application. The AR "scene" was created using Vuforia and Unity3D software. Within this scene, 3D virtual models were linked to the target image by detecting a symbol track marker. The final file was saved as an installable application and exported for Android smart devices. RESULTS: The target image containing the maxillectomy defect and the prosthetic rehabilitation were successfully visualized interactively in 3D mode using the handheld AR maxillofacial prosthetic application. CONCLUSION: An AR application for visualizing maxillofacial prosthetic data could interestingly be developed as a pedagogic tool to explain prosthetic treatments.

Technical Protocol for Presenting Maxillofacial Prosthetics Concepts to Dental Students using Interactive 3D Virtual Models within a Portable Document Format.

An appropriate presentation of maxillofacial defects and their prosthetic rehabilitation concepts using traditional two-dimensional educational materials is challenging for dental students and prosthodontics residents. This technique article introduces a simple approach to visualize and communicate three-dimensional (3D) virtual models embedded into a portable document format (PDF) file for presenting maxillofacial prosthetics concepts and enhancing students' spatial ability when learning maxillofacial prosthetics. MeVisLab software was used to combine various maxillofacial models and save them as a single 3D model. Adobe Acrobat Pro DC software was used to import the 3D model and create interactive visualization PDF documents. Adobe reader software was then used to visualize the content of the PDF documents. This approach allows educators to develop PDF files with multiple 3D models for teaching maxillofacial prosthetics concepts and communicate them with their students. Students can simply open the PDF file, activate the 3D mode, and interactively manipulate the 3D models to enhance their spatial ability for learning maxillofacial prosthetics.

Bruxism in Movement Disorders: A Comprehensive Review.

Bruxism is an abnormal repetitive movement disorder characterized by jaw clenching and tooth gnashing or grinding. It is classified into two overlapping types: awake bruxism (AB) and sleep bruxism (SB). Theories on factors causing bruxism are a matter of controversy, but a line of evidence suggests that it may to some extent be linked to basal ganglia dysfunction although so far, this topic has received little attention. The purpose of this article was to review cases of bruxism reported in various movement disorders. The biomedical literature was searched for publications reporting the association of bruxism with various types of movement disorders. As a whole, very few series were found, and most papers corresponded to clinical reports. In Parkinsonian syndromes, AB was rarely reported, but seems to be exacerbated by medical treatment, whereas SB is mainly observed during non-REM sleep, as in restless leg syndrome. AB is occasionally reported in Huntington's disease, primary dystonia, and secondary dystonia; however, its highest incidence and severity is reported in syndromes combining stereotypies and cognitive impairment, such as Rett's syndrome (97%), Down syndrome (42%), and autistic spectrum disorders (32%). Taken as a whole, AB seems to be more frequent in hyperkinetic movement disorders, notably those with stereotypies, and is influenced by anxiety, suggesting an involvement of the limbic part of the basal ganglia in its pathophysiology.

Prevalence of Bruxism in Hemifacial-Spasm Patients.

PURPOSE: A previous study reported an increased prevalence of bruxism (25%) in patients with cranio-cervical dystonia (CCD) compared to normal controls (13%). CCD can affect the muscles of the head and neck. Besides the CCD affecting these muscles, hemifacial spasm (HFS) is a form of peripheral myoclonus due to a neurovascular conflict affecting the muscles of the face. The fact that they affect the same muscle regions could lead to other links in clinical manifestations such as bruxism, which is more common in patients with CCD than in the normal population. The aim was to study the prevalence of bruxism in patients with HFS. MATERIALS AND METHODS: Patients with HFS were enrolled in the department of clinical neurophysiology (Bordeaux University Hospital) over a 6-month period. They were paired regarding age, the absence of neurological pathology or neuroleptics intake. To be included in the study, patients needed to have had unilateral involuntary facial muscle contractions affecting one hemiface. A hetero-questionnaire and a clinicial study were performed. The diagnostic criteria of bruxism included parafunction items such as grinding and clenching and at least one of the following clinical signs: abnormal tooth wear, temporomandibular joint (TMJ) pain, TMJ clicking, muscle hypertonia (masseter or temporal muscles). Additional epidemiological data were collected including age, sex, disease duration, stress, and sleep disorders. Stress symptoms inventory included symptoms like depression, strong heartbeat, dry mouth, anger, inability to concentrate, weakness, fatigability, insomnia, headache, and excessive sweating. The sleep disorder diagnosis included at least two of the symptoms described in the ICSD-3. All these criteria were recorded as either present (scored "1") or absent (scored "0"). RESULTS: The prevalence of bruxism in the two groups (normal and HFS) was not significantly different (p = 0.37). The rate was not significantly different between sleep and awake bruxism (p = 0.15) in both groups. Stress influenced the occurrence of bruxism in these two groups (p < 0.001). CONCLUSION: The results of this study indicated that clenching behaviors were higher in the HFS group, and that factors such as stress affected this group. The prevalence of bruxism was not higher in this population than in the normal control.

Bruxism in craniocervical dystonia: a prospective study.

AIMS: Bruxism pathophysiology remains unclear, and its occurrence has been poorly investigated in movement disorders. The aim of this study was to compare the frequency of bruxism in patients with craniocervical dystonia vs. normal controls and to determine its associated clinical features. METHOD: This is a prospective-control study. A total of 114 dystonic subjects (45 facial dystonia, 69 cervical dystonia) and 182 controls were included. Bruxism was diagnosed using a hetero-questionnaire and a clinical examination performed by trained dentists. Occurrence of bruxism was compared between the different study populations. A binomial logistic regression analysis was used to determine which clinical features influenced bruxism occurrence in each population. RESULTS: The frequency of bruxism was significantly higher in the dystonic group than in normal controls but there was no difference between facial and cervical dystonia. It was also higher in women than in men. Bruxism features were similar between normal controls and dystonic patients except for a higher score of temporomandibular jaw pain in the dystonic group. DISCUSSION: The higher frequency of bruxism in dystonic patients suggests that bruxism is increased in patients with basal ganglia dysfunction but that its nature does not differ from that seen in bruxers from the normal population.

Bilateral absence of mental foramen in a living human subject.

The mental foramen, through which the mental nerve emerges, is an important anatomic landmark in odonto-stomatology. Knowing its anatomic variations, according to the ethnic group or age, is essential when performing local anesthesia or implant and orthognathic surgeries. Besides the presence of a supernumerary foramen and variations in its location, numerous topographies have been described such as unilateral or bilateral triple foramina, hypoplasia or agenesis. The case reported here is extremely rare because it has been observed in a living and asymptomatic patient whose scan shows a bilateral absence of mental foramen.

Comparison of Conventional Transcrestal Sinus Lift and Ultrasound-Enhanced Transcrestal Hydrodynamic Cavitational Sinus Lift for the Filling of Subantral Space: A Human Cadaver Study.

The implant-supported prosthetic rehabilitation of the posterior maxilla may require sinus-grafting procedures due to poor quality and low volume of bone. This can be accomplished using a "lateral window" sinus augmentation or with an osteotome sinus floor elevation (OSFE). The hydrodynamic ultrasonic cavitational sinus lift (HUCSL) (Intralift) is derived from the osteotome technique and allows the reduction of some of the traumatic effects of the osteotome technique. The aim of this study was to compare OSFE and the HUCSL procedures on fresh human cadaver heads. Primary outcomes were the height and width of the grafting area in the sinus floor area. Eighty-four maxillary sinuses were selected. On each fresh cadaver head, 2 sinus lifts were done using OSFE and HUCSL in the maxillary sinuses. Computerized tomography scans were performed on each head before and after the surgeries. Measurements were done on radiologic pictures using dedicated software, and the integrity of the sinus membrane was observed after dissecting the maxillae. The use of HUCSL resulted in a significantly higher sinus floor augmentation in the mesio-distal and bucco-palatal direction compared with the osteotome technique (P < .001). There was no correlation between mesio-distal and bucco-palatal diameters of sinus floor augmentation when only the osteotome protocol was considered (r = 0.27 and P = .08). In contrast, the mesio-distal and bucco-palatal diameters of floor augmentation were correlated when the HUCSL protocol was considered (r = 0.79, P < .001). HUCSL represents a good alternative method for sinus floor elevation.

Transverse cervical and great auricular nerve distribution in the mandibular area: a study in human cadavers.

The angle of the jaw is innervated by the auricular branch of the superficial cervical plexus (SCP). Cervical cutaneous nerves of the CP carry the sensation from the antero-lateral cervical skin. It is clinically relevant to identify the cervical cutaneous nerve distribution and the nerve point using superficial landmarks but published studies describing the emerging patterns and cervical cutaneous nerve branch distributions in the mandible are rare. The overlap between the cervical and trigeminal and facial nerve distributions and anastomoses is highly variable. The objective of this study was to characterize the distribution of the SCP nerves in the different parts of the mandible. Two hundred and fifty fresh and formalin-fixed human cadaver heads were microdissected to observe the distribution of the transverse cervical (TCN) and great auricular (GAN) nerves. Two main groups (G1 and G2) based on the emergence of the TCN and GAN behind the posterior edge of the sternocleidomastoid muscle and three types (T1, T2, and T3) based on their distribution in the different mandibular parts were observed. Statistical analysis showed that parameters related to the mandibular side (P = 0.307), gender (P = 0.218), and group (P = 0.111) did not influence the facial distribution of these nerves. The only parameter influencing the distribution was the type of nerve (GAN and TCN) (P < 0.001). In the face, the SCP reached the mandible in 97% of cases, its distribution and extent were subject-dependent. These results confirmed that the SCP could supply accessory innervation to the mandible through the TCN.

Assessment of the correlation between implant stability and bone density by computed tomography and resonance frequency analysis in fresh cadavers.

PURPOSE: Because of the immediate loading implant process, clinicians must consider implant primary stability issues before initiating surgery. The aim of this study was to assess the correlation between the bone density assessed by computed tomography (CT) images and the primary stability of two implant designs, as determined by resonance frequency analysis (RFA). MATERIALS AND METHODS: Sixty implants (30 NobelActive, 30 NobelSpeedy [Nobel Biocare]) were placed in five totally edentulous fresh cadaver maxillae. Before surgery, CT images were analyzed and bone densities measured. Implant primary stabilities (measured in implant stability quotient [ISQ] units) were determined along the buccolingual and mesiodistal axes by RFA. Correlations were assessed using the Pearson correlation test. RESULTS: Bone densities were similar near NobelActive and NobelSpeedy implants: 434.67 (± 220.53) versus 479.87 (± 209.05) Hounsfield Units (HU). Bone densities and NobelActive primary stabilities were highly correlated with ρ = 0.74 (P = .000) and ρ = 0.78 (P = .000) for the buccolingual and mesiodistal axes, respectively. An association was found between the 350 HU and 50 ISQ values, confirming good primary stabilities. For NobelSpeedy implants, no correlation was found regardless of the axis, with ρ = -0.07 (P = .72) (buccolingual) and ρ = -0.10 (P = .59) (mesiodistal). However, poor and good stabilities were observed in the anterior and posterior areas, respectively. CONCLUSION: This study revealed variations in primary stabilities depending on the implant design. The primary stability of conical implants with a double-lead thread design (NobelActive) seemed bone density-dependent regardless of the area of the maxilla, whereas the primary stability of nearly parallel-wall implants with a classical thread design (NobelSpeedy) seemed dependent on anatomical morphology. These results raise questions about the specific roles of the implant shape and thread design depending on the bone density and alveolar morphology.

Comparison of 2 crestal sinus floor lift techniques performed on human cadavers.

PURPOSE: To compare the effectiveness of 2 different techniques to lift the maxillary sinus floor through a crestal approach on fresh human cadaver heads: the Intralift technique using Piezosurgery and the Summers technique using osteotomy. MATERIALS AND METHODS: Two different protocols were simulated on 11 fresh human cadaver heads or 22 maxillary sinuses. Inclusion criteria were: bilateral edentulous maxilla with a residual ridge height between 3 and 9 mm. CT scans were performed before and after surgery on all fresh cadaver heads. Both Intralift and Summers techniques were performed on the same maxilla on the 2 sinuses. The surgical procedure was performed by 2 independent operators, 1 experienced and 1 novice to compare the 2 results. The parameters assessed were the procedure duration and the sinus membrane preservation. RESULTS: The procedure duration was shorter when the operator was more experienced (P = 0.03). There was a correlation between the operator dexterity and the time required for surgery. The Intralift technique seemed safer for sinus membrane preservation. CONCLUSION: The Intralift technique is an interesting alternative to the Summers technique.

Surgical anatomy of the preauricular anteroparotid approach for mandibular condyle surgery.

PURPOSE: The different surgical approaches used to treat mandibular condyle fractures are carried out in the periparotid skin area and can lead to facial nerve injury. We conducted a preauricular and anteroparotid surgical approach. Our main aim was to show the anatomical relationship between this approach site and the facial nerve branches, and to define cutaneous landmarks to locate the extraparotid facial nerve branches. METHOD: A 2-step dissection of 13 fresh human cadaver semi-heads was performed: a preauricular approach followed by a superficial parotidectomy to visualize the facial nerve. Its course and ramifications were studied and compared to cutaneous landmarks. The proximity of the facial nerve branches with the surgical approach site was observed. RESULTS: The approach allowed systematically visualising the zygomatic and/or buccal branches. No facial nerve branches were sectioned. In three cases (23 %), a nerve branch was visualized during the approach. The buccal and zygomatic branches were ramified in 77 % of cases. CONCLUSIONS: During our preauricular anteroparotid approach, the buccal and zygomatic branches were visualized but none was sectioned. Most often the approach was carried out between these two branches (46 % of cases). Cutaneous landmarks used were reliable to define a safe and nerve-free area for dissection. The buccal and zygomatic branches are very interesting because their high number of ramifications and anastomoses could serve as nerve relays in case of surgical lesion.

Mandibular ridge expansion using a horizontal bone-splitting technique and synthetic bone substitute: an alternative to bone block grafting?

PURPOSE: Inadequate bone width in atrophic edentulous jaws is a challenge for successful oral rehabilitation with endosseous dental implants. The aim of this clinical study was to evaluate the effectiveness of a new method for ridge expansion with sagittal splitting using a new surgical device (Crest-Control Bone Splitting System, Meisinger) and to determine whether it is necessary to fill the expansion area with bone substitute to maintain the expanded bone volume. MATERIALS AND METHODS: During a 3-year period, a prospective study was performed in 32 patients (59% women, 41% men). All participants needed implants in the horizontally atrophied edentulous mandible and were treated in a private practice and a hospital. The only inclusion criteria were a mandibular ridge width between 3 and 4 mm and ridge height of at least 11 mm. Expansion with horizontal splitting of the ridge was performed simultaneously with implant placement. In 17 of the 32 arches, selected alternately, the expanded ridges were filled with a biphasic calcium phosphate (hydroxyapatite 60% and beta-tricalcium phosphate 40%) synthetic bone substitute (SBS 60/40). The other 15 expanded arches were left unfilled. All areas were covered with a resorbable collagen membrane (Bio-Gide, Geistlich). Results were analyzed with the Mann-Whitney and Kruskal-Wallis tests (α=.05). RESULTS: There was a significant difference (α=.02) between the patients who received SBS 60/40 (17 cases) and those who did not (15 cases). The ridges that received SBS 60/40 after expansion showed no bone resorption. CONCLUSION: Horizontal expansion of the ridge is easily reproducible. In this study, in very narrow ridges, a lack of bone substitute resulted in significant resorption of 3- to 4-mm-wide crests (5%), even after expansion. A bone substitute should be placed to maintain the alveolar bone walls after expansion.

Arteriovenous malformation (AVM) of the maxilla complicated by a local pathogen infection.

Arteriovenous malformations (AVM) are usually observed on the skin, but they can also rarely affect the visceral organs and the maxillofacial area. In the maxillofacial area, these lesions can spread and they are potentially dangerous, as a biopsy or even a simple tooth extraction can lead to a catastrophic haemorrhage that may eventually cause death. There are several indications for the treatment, including age, size and type of vascular malformation. The purpose of this report is to describe an AVM on the maxilla, first diagnosed as an epulis, which has been treated for several years as a chronic local periodontitis. The lesion was finally stabilised after an antibiotic therapy. Improved knowledge of the development of these lesions and collaboration between dentists, radiologists and surgeons are necessary to improve the diagnosis and treatment of vascular malformations.

Results of oral implant-supported prostheses after mandibular vertical alveolar ridge distraction: a propos of 54 sites.

OBJECTIVE: The aim of this study was to present retrospective long-term results of oral implant-supported prostheses after mandibular vertical alveolar ridge distraction. STUDY DESIGN: Patients who had alveolar mandibular distraction before oral rehabilitation from 1999 to 2009 were retrospectively reviewed. RESULTS: Fifty-four distractions were performed in 25 women and 12 men with a mean age of 51.7 years. Seventeen patients had bilateral distraction. Most of the distracted sites were posterior. Global major complications were major misdirection (3.7%), fracture (3.7%), and permanent alveolar nerve paresthesia (1 patient). All of the patients experienced osseous improvement. Mean height of the distraction was 11.7 mm. A total of 127 implants were inserted with survival and success rates, respectively, of 100% and 96.2% (mean follow-up of 62 months). All of the patients had satisfactory oral rehabilitation. CONCLUSIONS: Mandibular alveolar vertical distraction could be a reliable and effective procedure with precise indications. A less complicated implant distractor may simplify the procedure.

A 4-year follow-up of two complete mandibular implant-supported removable prostheses in a patient with severe rheumatoid polyarthritis: case report.

Rheumatoid polyarthritis is a systemic autoimmune disease characterized by chronic synovitis and bone damage associated with significant functional disability and morbidity. This case report describes a 4-year follow-up of a 56-year-old female receiving polymedication for severe rheumatoid polyarthritis and osteoporosis with a fully edentulous maxilla treated with two osseointegrated implants supporting a removable mandibular prosthesis. No practitioner wanted to use implants to stabilize her mandibular prosthesis because of the health risks involved. This report encourages the dental practitioner to be familiar with the symptoms and oral manifestations of rheumatoid polyarthritis in order to help manage this disease when patients lose all of their teeth.

Orthodontic reduction of a displaced alveolar fracture: a case study.

A 42-year-old woman had sustained a severe dental trauma with an alveolar fracture after an epileptic attack. A tooth block 31, 32, 33 and 34 was dislocated about 7 mm in buccal direction. Panoramic X-rays and CT-scan disclosed the alveolar fracture without total disjunction of the fragment. An orthodontic appliance was used to reduce the fracture with gentle forces during a 5-month period. Normal function was established and the teeth remained vital.