József Barabás

Finite element analysis of the human mandible at 3 different stages of life

OBJECTIVE This study analyzed detailed models of human mandibles at 3 different stages of life with simulation of supra normal chewing forces at static conditions. METHODS AND MATERIALS Finite element analysis (FEA) was used to generate models from cone-beam computerized tomograms (CBCT) of 3 patients aged 12, 20, and 67 years, using numerically calculated material parameters. Estimated chewing forces were then applied to the simulations. RESULTS The results reflect higher elasticity in younger models in all regions of the mandible. The experimental models show that physiologic load stress and strain distributional changes of the mandible vary according to age. CONCLUSION The CBCT-based model generation used in this study provided high-quality model definition of the 3 individual patients of different ages. FEA has great potential to predict bone responses to paradigms of mechanical activity. Future applications of FEA will include surgical planning, surgical hardware testing, and the design of scaffolds and tissue-engineered constructs.

Differentiation of Primary Human Submandibular Gland Cells Cultured on Basement Membrane Extract

There is no effective treatment for the loss of functional salivary tissue after irradiation for head and neck cancer or the autoimmune disease Sjögrens syndrome. One possible approach is the regeneration of salivary glands from stem cells. The present study aimed to investigate whether small pieces of human submandiblar gland tissue contain elements necessary for the reconstruction of salivary rudiments in vitro via acinar and ductal cell differentiation. Primary submandibular gland (primary total human salivary gland; PTHSG) cells were isolated from human tissue and cultured in vitro using a new method in which single cells form an expanding epithelial monolayer on plastic substrates. Differentiation, morphology, number, and organization of these cells were then followed on basement membrane extract (BME) using RNA quantitation (amylase, claudin-1 (CLN1), CLN3, kallikrein, vimentin), immunohistochemistry (amylase and occludin), viability assay, and videomicroscopy. On the surface of BME, PTHSG cells formed acinotubular structures within 24 h, did not proliferate, and stained for amylase. In cultures derived from half of the donors, the acinar markers amylase and CLN3 were upregulated. The PTHSG culture model suggests that human salivary gland may be capable of regeneration via reorganization and differentiation and that basement membrane components play a crucial role in the morphological and functional differentiation of salivary cells.

Possibilities of preventing osteoradionecrosis during complex therapy of Tumors of the oral cavity

In recent years, there has been a dramatic increase in the number of tumors of the head and neck. Their successful treatment is one of the greatest challenges for physicians dealing with oncotherapy. An organic part of the complex therapy is preoperative or post-operative irradiation. Application of this is accompanied by a lower risk of recurrences, and by a higher proportion of cured patients. Unfortunately, irradiation also has a disadvantage: the development of osteoradionecrosis, a special form of osteomyelitis, in some patients (mainly in those cases where irradiation occurs after bone resection or after partial removal of the periosteum). Once the clinical picture of this irradiation complication has developed, its treatment is very difficult. A significant result or complete freedom from complaints can be attained only rarely. Attention must therefore be focussed primarily on prevention, and the oral surgeon, the oncoradiologist and the patient too can all do much to help prevent the occurrence of osteoradionecrosis. Through coupling of an up-to-date, functional surgical attitude with knowledge relating to modern radiology and radiation physics, the way may be opened to forestall this complication that is so difficult to cure.

Atypical courses of the mandibular canal: Comparative examination of dry mandibles and x-rays

Knowledge of the course of the mandibular canal and its anatomic variations is of great importance in oral surgery, especially in preprosthetic operations and the insertion of endosteal implants and during the planning of removable dentures prepared in cases involving extensively atrophied mandibles. We review the literature on duplicated mandibular canals, which is based exclusively on radiologic findings. Then, we compare this with an examination of dry mandibles and further radiologic studies. The incidence of duplicated mandibular canals observed in macroscopic examinations of mandibles was substantially higher than that revealed by radiographs. One case involving a novel variation, a triple mandibular canal, is reported.

Use of Bioplant HTR Synthetic bone to eliminate major jawbone defects: long-term human histological examinations

This article describes the long-term follow-up of Bioplant HTR Synthetic bone (HTR: hard tissue replacement) in the human organism, as revealed by clinical, radiological and histological examinations and observations over a period of 5 years. Twenty-nine patients with lesions, 9 keratocysts, 16 radicular cysts, 3 traumatic cysts and 1 odontome were followed continuously during this period. All patients selected for follow-up had two criteria in common: the initial intervention had been performed at least 5 years previously; and the largest diameter of the bone defect was at least 2 cm. In all cases, when large bone defects were filled with HTR, the cavity was eventually filled with newly formed and remodelled bone. The process of ossification was relatively slow. In these cases, complete bony regeneration took up to 5 years. Ossification did not continue in the soft parts around the bone cavity. The histological pictures confirmed complete bone healing over the time.

Porous Hydroxyapatite and Aluminium-Oxide Ceramic Orbital Implant Evaluation Using CBCT Scanning: A Method for In Vivo Porous Structure Evaluation and Monitoring

Objective. This study aimed to define CBCT as a technique for postimplantation in vivo examination of porous hydroxyapatite and aluminium-oxide orbital implant shape, volume and density changes. Methods and Materials. CBCT was used to evaluate 30 enucleated patients treated with spherical polyglactin 910 wrapped hydroxyapatite and aluminum-oxide orbital implants. The mean duration of patient followup was 3.2 years or 1338 days with a range of 0.2 to 7.2 years or 79 to 2636 days in a population with an average age of 40.8 years. Results. The resolution of currently clinically used CBCT equipment allowed detailed structural observation of the orbital hydroxyapatite implants with some modifications. Volume and shape estimations were possible while density evaluation was more complicated compared to medical source computed tomography. The mean densities of the orbital implants were followed and a consistent gradual decrease identified from the beginning of implantation which was better defined after the applied correction procedure. Conclusion. CBCT with lower dosages of radiation exposure can be used to follow changes in implanted high-density porous structures. The density evaluation is possible with calibration modifications. Changes in orbital implant densities identified in this study may correspond to healing and maturation of soft tissues surrounding and penetrating the implants.

Titanium implants with oxidized surfaces: the background and long-term results

The purpose of this paper is to give an overview of different implant surface modification technologies?including the presentation of a new technique, involving the formation of a ceramic titanium oxide coating. Three techniques are used to modify metal surfaces: (1) addition of material, (2) removal of material and (3) modification of material already present, e.g. by means of laser or electron-beam thermal treatment. The new technique outlined in this paper relates to the production of a corrosion-resistant, 2000?2500 ? thick, ceramic oxide layer with a consistent crystalline structure on the surface of a titanium implant. The layer is grown electrochemically from the bulk of the metal and modified by heat treatment. Such ceramic oxide-coated implants have advantageous properties compared to implants covered with other coatings: a higher external hardness; a greater force of adhesion between the titanium and the ceramic oxide coating; virtually perfect insulation between an organism and a metal and therefore no possibility of triggering metal allergy. Plates and screws for maxillofacial osteosynthesis and dental root implants with ceramic oxide coatings were subjected to various physical, chemical and electron microscope tests for qualitative characterization, and have been applied in surgical practice over a period of 15 years. The mini-plates removed were examined for the possible surface alterations which may occur during the implantation period. The sites of the removal were inspected for metallosis, which is common when titanium mini-plates are used. The results obtained demonstrate the good properties of the ceramic oxide-coated implants.

False diagnosis caused by Warthin tumor of the parotid gland combined with actinomycosis.

A case is reported in which a unilateral parotid gland cystadenolymphoma was combined with actinomycosis. A 48-year-old woman presented with a mass in the left parotid region and paresis of the lower left palpebra. The computed tomography, echography, and parotid radiographic findings did not exclude a neoplasm of the left parotid gland. The ramus of the mandible was involved in the process. Intraoperative freezing histology, total parotidectomy, and partial mandibulectomy were performed, with sacrifice of the facial nerve followed by nerve reconstruction. The final histological evaluation was Warthin tumor with actinomycosis. Four years after treatment, the patient is free of disease. No similar cases seem to have been reported thus far.

Tophaceous gout of the temporomandibular joint: a report of 2 cases.

its overwhelming functional importance, the exist-ing information in the literature, and our experi-ence with this case, we believe that the manage-ment protocol should be individualized based onthe presentation and course of the disease. Conser-vative management, under watchful eyes, may beattempted in those presenting early with a benigncourse. However, it would be prudent to maintaina low threshold for converting to aggressive surgi-cal management should the disease intensify, withextension and systemic involvement, despite aptmedical management.

Measurement of Orbital Volume after Enucleation and Orbital Implantation

Introduction This article reports experience relating to the measurement of orbital volume by means of cone beam computed tomography (CBCT) and Cranioviewer program software in patients who have undergone enucleation and orbital implantation. Patients and Methods CBCT scans were made in 30 cases, 10 of which were later excluded because of various technical problems. The study group therefore consisted of 20 patients (8 men and 12 women). The longest follow-up time was 7 years, and the shortest was 1 year. In all 20 cases, the orbital volume was measured with Cranioviewer orbital program software. Slices were made in the ventrodorsal direction at 4.8 mm intervals in the frontal plane, in both bony orbits (both that containing the orbital implant and the healthy one). Similar measurements were made in 20 patients with various dental problems. CBCT scans were recorded for the facial region of the skull, containing the orbital region. The Cranioviewer program can colour the area of the slices red, and it automatically measures the area in mm. Results In 5 of the 20 cases, the first 4 or all 5 slices revealed that the volume of the operated orbit was significantly smaller than that of the healthy orbit, in 12 cases only from 1 to 3 of the slices indicated such a significant difference, and in 3 cases no differences were observed between the orbits. In the control group of patients with various dental problems, there was no significant difference between the two healthy orbits. The accuracy of the volume measurements was assessed statistically by means of the paired samples t-test. Summary To date, no appropriate method is avaliable for exact measurement of the bony orbital volume, which would be of particular importance in orbital injury reconstruction. However, the use of CBCT scans and Cranioviewer orbital program software appears to offer a reliable method for the measurement of changes in orbital volume.