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Results for “Maxillofacial Prosthesis”

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At least 631 records · Page 35Linked to original sources
PubMed1999

Effects of processing parameters on physical properties of the silicone maxillofacial prosthetic materials.

OBJECTIVES: Maxillofacial prostheses are commonly fabricated using dental stone molds. However, for evaluating physical properties, maxillofacial materials are most often cured in metal molds. A-2186 is a silicone-based maxillofacial prosthetic material. Because its cure may be inhibited by traces of impurities, its physical properties may be different when it contains additives and is cured in dental stone molds, compared to when it is cured in metal molds without additives. This study's purpose is to determine and compare the physical properties of A-2186 cured in stainless steel molds and stone molds. The effects of additives and cure conditions on the physical properties were also studied. METHODS: Hardness, tensile strength, ultimate elongation, and tear strength of A-2186 cured in dental stone molds, stainless steel molds, and with and without additives were determined. The bonding strength of A-2186 to four adhesives was determined by the peel test. All comparisons were made using analysis of variance (ANOVA). RESULTS: Hardness, tensile strength and ultimate elongation of A-2186 cured in stainless steel molds are significantly higher than those cured in stone molds. Adding a small amount of a pigment, a kaolin and a fiber reduces hardness, tensile strength, ultimate elongation and tear strength. Except for Hydrobond, the bond strength of the adhesives to A-2186 was not significantly affected by the cure conditions and additives. SIGNIFICANCE: Physical properties of A-2186 are affected by the additives commonly used in fabricating maxillofacial prostheses, and use of stone molds for curing degrades A-2186's mechanical properties. In fabricating clinical prostheses, special attention should be exercised to avoid contamination of A-2186 with impurities that could inhibit curing and produce inferior prostheses.

Adhesiveness↗
PubMed2003

Element release from titanium devices used in oral and maxillofacial surgery.

Optical microscopy, scanning electron microscopy and X-ray microanalysis (EDS system) were used on c.p. titanium devices (21 grids and 10 plates) removed from 28 patients without signs of inflammation 6-24 months after surgery. Plates, grids and surrounding tissue were investigated to evaluate the titanium release and accumulation. Titanium was only present in the interfacial bone, probably due to fretting, and in all fibrous tissue surrounding the devices. Titanium content followed a decreasing gradient extending from the device surface and was not detected at a distance greater than 1mm. High titanium levels were found in blood cells in the connective tissue. In conclusion, titanium release from the devices stops only after bone is laid down on the titanium surfaces. Titanium release does not seem to interfere with the osteogenic process but perhaps may interact with it.

Bone Plates↗
PubMed2003

An elastomeric material for facial prostheses: synthesis, experimental and numerical testing aspects.

Current materials used for maxillofacial prostheses are far from ideal and there is a need for new improved materials which better simulate the tissues they are replacing. This study was based on a mixed experimental/analytical/numerical approach. A new polymeric material was developed to provide a better alternative to the materials currently used in maxillofacial prosthetics. A series of experimental tensile tests were performed in order to characterise the tensile properties of the material. A Mooney-Rivlin type hyperelastic formulation was chosen to describe the constitutive behaviour of the polymer which operates at the finite strain regime. The material parameters (two) of the constitutive law were identified with the experimental data. The Mooney-Rivlin material was found to be suitable to represent accurately the mechanical behaviour of the polymer up to 50% strain as shown by the excellent agreement between analytical and experimental results. An FE model reproducing all the characteristics of the experimental tensile tests was built and a series of three FE analyses were conducted and has proven the proper finite element implementation of the material model. This preliminary study will serve as a basis to introduce more complex features such as viscoelasticity and wrinkling of the soft polymeric structure in order to optimise the performances of the final prosthetic material.

Biocompatible Materials↗
PubMed1999

Incorporation of particulated bone implants in the facial skeleton.

The purpose of this study was to compare the regenerative response of autogenous cortical and cancellous bone chips and a natural particulate resorbable bone mineral (RBM) (Bio-Oss, Geistlich-Pharma, Wolhusen, Switzerland) in standardized bony defects relating paranasal sinuses to one another and to bone blocks. On 13 skeletally mature female goats four standardized critical-sized full thickness bone defects were made in the frontal bone overlying the frontal sinus. These defects were filled at random with cortical bone chips, cancellous bone chips, spongiosa granules of a RBM or left empty. Fluorochrome bone markers were injected subcutaneously 1 and 5 weeks after transplantation, and one week before the animals were killed. The animals were killed at 3, 6, 12 and 24 weeks after surgery. Autogenous cancellous bone chips is the material of choice for bridging a bony defect in the maxillofacial area where there is no need for mechanical strength. They heal in the same way as cancellous bone blocks do. Cortical bone chips are not reliable enough to be used as a solitary bone-grafting material under these conditions. A cortical block as a solitary implant gives better results. RBM granules as solitary implant in a critical-sized defect do not stimulate osteoconduction but give rise to an extensive osteoclastic activity stimulated by the mutual loose relation. A solid block of RBM is in a similar case more reliable.

Absorbable Implants↗
PubMed2000

A follow-up study of orbital prostheses supported by dental implants.

PURPOSE: This study reports on the use of osseointegrated dental implants for anchorage of orbital prostheses. PATIENTS AND METHODS: Nine patients were treated with 25 implants inserted in the periorbital area after exenteration of the globe. Implants of 9, 11, and 13 mm length, with a diameter of 3.5 mm, were used. RESULTS: All implants were stable at the stage 2 operation and could be connected with abutments. In 7 cases (19 implants), orbital prostheses were fabricated and have been worn for an average of 3 years. One of the 19 implants was lost after 3 years because of load stress. During the mean observation period, there were only slight skin reactions around the transcutaneous abutments. CONCLUSION: These results suggest that normal dental implants can be used to anchor craniofacial prostheses without altering their design or the surgical method.

Adult↗
PubMed2003

Analysis of the properties of silicone rubber maxillofacial prosthetic materials.

OBJECTIVES: Maxillofacial prosthetic materials are used to replace facial parts lost through disease or trauma. Silicone rubbers are the materials of choice, however it is widely accepted that these materials do not possess ideal properties. The objective of this study was to assess the properties of a range of commercially available silicone rubber maxillofacial materials and make recommendations for improvements. METHODS: Specimens of five commonly used maxillofacial materials were prepared in dental flasks according manufacturers instructions. Tear strength, tensile strength, percentage elongation, hardness, water absorption and water contact angles were determined for each material. RESULTS: The tear strength of Factor II, Cosmesil HC and Nusil were all comparable and significantly higher than Cosmesil St and Prestige (p<0.001). Nusil had a significantly higher tensile strength and elongation in comparison to the other materials (p<0.001) and Cosmesil St and Cosmesil HC were significantly harder (p<0.001). Factor II was significantly less wetted and Prestige and Cosmsesil St had a significantly higher water absorption in comparison to the other materials. CONCLUSIONS: None of the commercially available silicone rubber materials possessed ideal properties for use as a maxillofacial prosthetic material. Factor II, however, showed more favourable properties due to it's high tear strength, softness and ease of manipulation.

Absorption↗
PubMed2003

Surface modification of an experimental silicone rubber maxillofacial material to improve wettability.

OBJECTIVES: Good wettability of maxillofacial prosthetic materials is important so that a lubricating layer is formed with supporting tissues thus reducing patient discomfort. The purpose of the study was to surface modify an experimental silicone rubber material in order to improve wettability. METHODS: Samples of experimental silicone rubber were surface modified by first argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes. These were compared with the same silicone rubber which had ethyleneoxy functional surfactants incorporated into the polymer matrix. In all cases contact angles, tear strength and water uptake were measured. RESULTS: Surface modified materials had comparable contact angles to surfactant modified silicone rubber all being significantly lower than the unmodified material. Surface modified materials, however, had a significantly higher tear strength and lower water uptake in comparison to surfactant modified materials. CONCLUSIONS: Argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes proved an effective way of improving the wettability of an experimental silicone rubber maxillofacial prosthetic material without altering bulk properties.

Materials Testing↗
PubMed1995

CAD by processing of computed tomography data and CAM of individually designed prostheses.

In the past an economic fabrication of individual prostheses used in reconstructive cranio-maxillo-facial surgery was not possible due to technical deficiencies. Now, through the consistent use of the most modern computer-based techniques developed in the field of industrial engineering, these costs can be reduced to an economic level. Mathematical freeform surfaces models are first created from helical computed tomography data. These serve as the basis for an efficient and idealized construction of prostheses geometries, and provide control-data for a computerized numerical control-fabrication. In 4 clinical cases this new processing technique has successfully been utilized in the fabrication of individually designed prostheses for the reconstruction of skull defects. The range of opportunities offered is reflected not only in the great variety of possible geometric details, but also in the fact that the prostheses may be manufactured--partly using indirect impression-taking techniques--from 3 different biocompatible materials so far and other applications are likely to turn up.

Computer Simulation↗
PubMed2004

Histological analysis of bone/heteroplastic implant interfaces in dog tibia.

This work presents histological analysis of interfaces between bone and heteroplastic implants in dog tibias. The study was performed in four tibias (of four mongrel dogs) into which cylindrical implants were inserted. One ceramic (titania) implant and three grit-blasted titanium implants (with sandblasted and acid-corroded surfaces) were chosen for histological analysis of the implant surface/bone tissue interface. The implants remained in the tibias for eight months and none were loaded during this period. The animals were subsequently sacrificed and the samples were processed for analysis. Light microscope analysis revealed a large amount of osteoid tissue and proximity of osteoblasts and osteocytes to the implant surfaces. In addition, little or no fibrous tissue was observed between the bone and implant surfaces. The titanium implants presented better osseointegration than did the ceramic implant.

Animals↗
PubMed1983

Chondrosarcoma arising in the nasal septum.

A case is presented of a chondrosarcoma arising in the nasal septum and extending into the maxillary sinuses. This tumour is unusual in the head and neck and rarely arises in the nasal septum. Diagnostic difficulties are discussed. The treatment was radical surgery with removal of a major portion of the upper jaw, necessitating reconstruction with a maxillo-facial prothesis.

Aged↗
PubMed1992

The prosthetic care of Sigmund Freud.

An account is given of Sigmund Freud's illness and care following the diagnosis of oral cancer in 1923. The key figure in the clinical management was Professor Hans Pichler of Vienna, who undertook the maxillectomy and most of the subsequent prosthetic care. Other contributors included Doctors Schroeder and Weinmann and Professor Kazanjian. Two of Freud's obturators are in the collection of the Freud Museum, London. An examination of these, together with reference to a copy of Pichler's clinical notes, also in the Museum's collection, has allowed the position of these prostheses, within the overall scheme of Freud's care, to be identified.

Austria↗