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PubMedDate not supplied

Dynamic mechanical properties of silicone maxillofacial prosthetic materials and the influence of frequency and temperature on their properties.

PURPOSE: This study evaluated the dynamic mechanical properties of silicone elastomers for maxillofacial applications and the influence of frequency and temperature on their properties. MATERIALS AND METHODS: Seven currently used silicone maxillofacial prosthetic materials were used. Storage modulus, loss modulus, and loss tangent were determined over the frequency range from 0.01 to 100 Hz at both 23 and 37 degrees C using a dynamic viscoelastometer. Contribution ratios of type of material, temperature, and frequency for each rheologic parameter were also determined. RESULTS: Storage modulus, loss modulus, and loss tangent of all materials were greater at higher frequencies. Loss tangent and loss modulus were especially affected; the contribution ratios of frequency were 72% and 48%, respectively. These three rheologic parameters were insensitive to changes in temperature over the range tested; contribution ratios of temperature were less than 3%. There were significant differences in dynamic mechanical properties among the materials. Elasto Synsil showed higher storage modulus and loss modulus than the other materials (Cosmesil T001, Elastosil M3500, Episil, Ideal, Premium, Silskin 2000) at all frequencies and temperatures tested. Loss tangent values ranged from 0.02 to 0.20. Silicone maxillofacial prosthetic materials had almost no viscous component and exhibited elastic behavior. However, a wide range of ability in energy absorption was found among the materials. CONCLUSION: The results suggest that a maxillofacial prosthesis should have a laminate or hybrid structure consisting of both the material with a greater cushioning effect and that with a higher elastic recovery.

Analysis of Variance↗
PubMed1999

Color stability and colorant effect on maxillofacial elastomers. Part II: weathering effect on physical properties.

STATEMENT OF PROBLEM: The clinical life of a maxillofacial prosthesis averages about 6 months, before it needs to be refabricated. Degradation of the color and physical properties of the prosthesis are the principle reasons for replacement. PURPOSE: This second part of a 3-part in vitro investigation evaluated the change in physical properties of popular colorant-elastomer combinations as a result of weather exposure. MATERIAL AND METHODS: Fifteen dumbbell-shaped and 15 trouser-shaped specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorant combinations (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants) for a total of 540 specimens. The 15 dumbbell-shaped and trouser-shaped specimens of each elastomer colorant combination were separated into 5 of each shape among 3 test condition groups (control, time passage, and natural weathering). Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural-weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Evaluations of hardness and tear strength were made on trouser-shaped specimens, and evaluations of the ultimate tensile strength and percentage elongation on dumbbell-shaped specimens. Physical property data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among the test conditions. When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. RESULTS: Exposure to weathering and time changes of the physical properties of many colorant-elastomer combinations indicated that properties of a clinical prosthesis can change with time. CONCLUSION: The addition of colorants to the silicones altered the effects of weathering. In addition, the silicones were not as stable as previously assumed.

Analysis of Variance↗
PubMed2001

[From the concept of permanent percutaneous connections to that of permanent percutaneous electrical connections].

Percutaneous abutment of an extra-oral implant provides two main functions: support of bone anchored hearing aid (BAHA) and fixing maxillofacial prosthesis (MFP). Further developing this concept, and using available surgical strategies and materials, leads to a new application in extra-oral implantology. We analyzed the evolution of concepts in the field of permanent percutaneous connection (PPC) to the new concept of PPEC (permanent percutaneous electric connection), presenting a clinical case.

Biocompatible Materials↗
PubMed1988

Force-displacement properties of a modified cross-linked silicone compared with facial tissues.

A dimethyl siloxane triacetoxy terminated silane, Type A adhesive, was modified with the base component of a medium grade polydimethyl siloxane with vinyl groups, MDX 4-4210, to produce a more pliable maxillofacial prosthesis. Force-displacement curves of various ratios of Type A adhesive/MDX 4-4210 were determined and compared with force-displacement curves obtained from human subjects. Within the force range of 0.4 to 1.2 N, the force-displacement slopes obtained on human subjects compared favourably with some of the Type A adhesive/MDX 4-4210 test specimens. The force-displacement slopes for the elastomers and humans were not in agreement for forces below 0.4 N.

Biocompatible Materials↗
PubMedDate not supplied

Midface volume replacement with a transmaxillary implant.

BACKGROUND: Volume replacement is an essential component of midface rejuvenation. Previously designed alloplastic implants augment bony prominences. The Maxout implant was configured to add height to the lowest surface, the canine fossa. METHODS: A random series of patients, from an office-based practice requested midface augmentation. Three of these patients were human immunodeficiency virus (HIV) positive. With the patient under local anesthetic, bilateral Maxout implants were inserted through either an intraoral or an intranasal incision. RESULTS: All the implants produced a satisfactory aesthetic improvement. In one HIV-positive patient, one implant placed intraorally became infected and required removal. It was replaced 3 months later through the transnasal approach. All the patients had retained their implants 1 year later. CONCLUSIONS: The Maxout implant is easy to insert and remove, aesthetically effective, secured by bone structures, and located in a neutral position. The risk of infection must be considered, especially for HIV-positive patients.

Adult↗
PubMed1998

Osseointegrated implants and orbital defects: U.C.L.A. experience.

PURPOSE: A clinical study of 23 craniofacial implants placed in 8 irradiated and nonirradiated orbital detects was conducted over a 7-year period. MATERIAL AND METHODS: Implant-retained orbital prostheses were fabricated, implant success rate was determined, and the soft tissue responses were recorded at 6-month intervals. As a result of patient death, no data were gathered on three implants. A five-point scale was used to record the health of the peri-implant soft tissues and the patients were followed from 9 to 72 months. The unit of measure was a visit/site that was assigned for each instance an implant site was evaluated. Evaluations were conducted at 6-month intervals, and for the study period, there were 80 visit/sites. RESULTS: The study revealed that 42.5% (34/80) of the visit/sites demonstrated an absence of inflammation; 23.7% (19/80) of visit/sites demonstrated slight redness; 13.8% (11/80) demonstrated peri-implant red and moist tissues; 6.2% (5/80) demonstrated granulation tissue associated with the implants; and 13.8% (11/80) infection of the peri-implant soft tissues was noted. Implant success rate was 35% (7/20); implant success rate in the nonradiated patients was 37.5% (3/8) and the success rate for radiated patients was 33.3% (4/12). Implants placed in the orbital region demonstrated a high failure rate. Most implant failures occurred late as opposed to early in the study period. CONCLUSION: Orbital implants should be placed in patients who understand that long-term success rates may be low and require meticulous hygiene maintenance.

Adult↗
PubMed1998

Simultaneous malaroplasty with porous polyethylene implants and orthognathic surgery for correction of malar deficiency.

PURPOSE: Patients with skeletal malrelationships caused by maxillary anteroposterior defect and midface hypoplasia may present with an alteration of cheekbone contour. High osteotomies, segmental osteotomies of the zygomatic complex, and malar expansion with alloplastic materials can be performed to improve facial aesthetics. This article describes the restoration of cheekbone-nasal base-lip contour by performing a malaroplasty using an alloplastic implant in addition to orthognathic surgery. PATIENTS AND METHODS: From 1995 to 1996, 17 patients with maxillomandibular malrelationships and deficient cheekbone contour were tested by malar augmentation with porous high-density polyethylene in association with maxillary advancement and mandibular setback. The diagnosis of cheekbone contour alteration was made after observing the patient from a lateral, frontal, and oblique point of view. The position of the implant was determined by using Mladick's point, with lateral or medial extension in relation to the depressed area. RESULTS: By the restoration of normal cheekbone-nasal base-upper lip contour produced excellent aesthetic results in all patients. CONCLUSIONS: Malaroplasty in association with bimaxillary orthognathic surgery seems to be an effective procedure for treating midface skeletal deficiencies.

Biocompatible Materials↗
PubMed1997

Lactosorb panel and screws for repair of large orbital floor defects.

In a series of five patients with extensive fractures of the orbital floor, we used a biodegradable sheet for bridging of the bony defects. To achieve optimal support of the orbital contents in their anatomically correct position, we fixed the sheet with at least two resorbable screws to the infraorbital rim. This new technique appears to be superior to conventional methods because it offers reproducible results without the need for secondary interventions.

Adolescent↗
PubMed1998

Maxillofacial prosthodontics and reconstruction: a Canadian view.

A craniofacial osseointegration and maxillofacial prosthetic rehabilitation unit in Edmonton, Canada was visited by the author as part of a higher specialist training programme. The unit has an international reputation as a centre of excellence for the treatment of patients with head and neck abnormalities. The report examines the activities of the unit and how it achieves its 'patient centred' approach to care.

Canada↗
PubMed2000

Exposure of high-density porous polyethylene (Medpor) used for contour restoration and treatment.

Porous high-density polyethylene (Medpor) is a biocompatible large-pore, high-density polyethylene implant. It is well tolerated by surrounding tissue, and its porous structure is rapidly infiltrated by host tissue. It is a highly stable and somewhat flexible porous alloplast that has rapid tissue ingrowth into its pores. However, when the implant is placed under a thin cover of skin, there is a risk of exposure. A total of 52 Medpor implants were placed in 31 patients over a four-year period. The implants were used for the chin, malar area, nasal reconstruction, ear reconstruction, orbital reconstruction, and the correction of mandibular contour deformities. Many of these implants were placed in areas considered problematic, such as those with thin or atrophic soft-tissue coverage and extensive scarring. There were nine complications, including three patients in whom the implant was exposed; these are presented here.

Adult↗
PubMed1999

Stereoscopic lithography: customized titanium implants in orofacial reconstruction. A new surgical technique without flap cover.

Head and neck surgery may involve complex methods of composite reconstruction that do not replicate the volume and contour of the normal anatomy. 'Functional' reconstruction implies replication of the normal volume and contour of both hard and soft tissues to produce normal form and function of the face, mouth and jaws. Techniques such as stereoscopic lithography and computer-assisted design, and-manufacture (CAD-CAM) have been successfully used with computer-numerized control (CNC) milling to manufacture customized titanium implants for single-stage reconstruction of the maxilla, hemimandible and dentition without the use of composite flap cover after the removal of tumours. Reduction in theatre time and personnel, less need for intensive care, and earlier discharge from hospital, indicate possible savings of Pound Sterling 17,000-Pound Sterling 19,000 per patient. There are implications for surgery in general, and further research and development is advocated.

Adult↗
PubMed2003

Extra-oral craniofacial endosseous implants and radiotherapy.

This paper discusses the use of extra-oral endosseous craniofacial implant (EOECI) therapy in irradiated bone. The survival rate of EOECIs in irradiated bone is reviewed and the controversy over the optimal time prior to place implants is described. The advantages and disadvantages of pre- and post-implant radiotherapy are addressed. The EOECI rehabilitation and osteoradionecrosis and the evidence of the potential role of hyperbaric oxygen are reviewed. Strategies for improving the clinical outcome of EOECIs are suggested.

Animals↗
PubMed2002

Preshaped hydroxyapatite tricalcium-phosphate implant using three-dimensional computed tomography in the reconstruction of bone deformities of craniomaxillofacial region.

We prepared solid life-sized models and templates of implants based on three-dimensional computed tomography data in six cases with a bone deformity of the craniomaxillofacial region. After simulation surgery using these models and templates, the preshaped hydroxyapatite-tricalcium phosphate (HAP-TCP) implants were prepared to fill in the facial bone defects, and implantation was performed. Consequently, implants fitted the individual bone defects, and satisfactory facial contouring was obtained in five cases. In one case with severe cutaneous scarring in the grafted site, it was necessary to reduce the volume of the preshaped HAP-TCP implant during surgery. In conclusion, the three-dimensional, solid, life-sized model and template are useful for preoperative detailed simulation, and the use of preshaped HAP-TCP implants based on the template probably contributes to successful reconstruction of complex facial bone deformities and to the reduction of surgical invasion, resulting in achievement of better results.

Adult↗
PubMed2003

Maxillofacial reconstruction with prefabricated osseous free flaps: a 3-year experience with 24 patients.

Between January of 1998 and May of 2002, 25 prefabricated osseous free flaps (23 fibula and two iliac crest flaps) were transferred in 24 patients to repair maxillary (six flaps) or mandibular (eight flaps) defects after tumor resection, severe maxillary (four flaps) or mandibular (one flap) atrophy (Cawood VI), maxillary (one flap) or mandibular (three flaps) defects after gunshot injury, and maxillary (two flaps) defects after traffic accidents. Prefabrication included insertion of dental implants, positioned with a drilling template in a preplanned position, and split-thickness grafting. Drilling template construction was based on the prosthetic planning. The template determined the position of the implants and the site and angulation of osteotomies, if necessary. The mean delay between prefabrication and flap transfer was 6 weeks (range, 4 to 8 weeks). While the flap was harvested, a bar construction with overdentures was mounted onto the implants. The overdentures were used as an occlusal key for exact three-dimensional positioning of the graft within the defect. The bar construction also helped to stabilize the horseshoe shape of the graft. The follow-up period ranged from 2 months to 4 years (mean, 21 months), during which time two total and three partial flap losses occurred. One total loss was due to thrombosis of the flap veins during the delay period, whereas the other total loss was caused by spasm of the peroneal artery. Two partial losses were due to oversegmentation of the flaps with necrosis of the distal fragment, whereas one partial loss was caused by disruption of the vessel from the distal part. Of the 90 implants that were inserted into the prefabricated flaps during the study period, 10 were lost in conjunction with flap failure; of the remaining 80 implants, four were lost during the observation period, for a success rate of 95 percent. Flap prefabrication based on prosthetic planning offers a powerful tool for various reconstructive problems in the maxillofacial area. Although it involves a two-stage procedure, the time for complete rehabilitation is shorter than with conventional procedures.

Accidents, Traffic↗
PubMed2006

Maxillary and mandibular osteosyntheses with PLGA and P(L/DL)LA implants: a 5-year inpatient biocompatibility and degradation experience.

BACKGROUND: This study consists of a 5-year experience with 413 maxillary and mandibular resorbable plate osteosyntheses focusing on clinically apparent foreign body reaction (i.e., swelling, osteolyses, and fistulation), indirect implant degradation (i.e., palpability and radiographic reossification), and direct implant degradation (i.e., molecular weight and crystallinity of explants). METHODS: Eighty fracture and reconstruction cases (32 female and 48 male patients, aged 1 to 83 years) were osteofixated with poly(L-lactide-co-glycolide) (PLGA) copolymer (n = 20) (139 PLGA osteosyntheses) or poly(L-lactide-co-DL-lactide) [P(L/DL)LA] (n = 60) [274 P(L/DL)LA osteosyntheses]. Local revisions (n = 30) were performed during secondary operations at 3, 6, 12, 18, or 24 months. Average clinical and radiographic follow-up lasted 29 months (range, 6 to 63 months). RESULTS: Five patients (6 percent) had apparent foreign body reactions, whereas 75 (94 percent) did not. One P(L/DL)LA mild reaction was effectively treated with cold packs and analgesics, one PLGA and three P(L/DL)LA medium severe reactions were treated with curettage, and one local osteolysis disappeared at 6 months. Implant palpability lasted 12 (PLGA) or 24 months [P(L/DL)LA]. The difference was significant (p < 0.000001). Burr holes reossified at 24 (PLGA) and 36 months [P(L/DL)LA] (p < 0.05). The 85:15 PLGA explants' initial 44,600 molecular weight decreased to 11,000 at 6 months; and scarce powdering granular residuals, too small for molecular weight assessment, were encountered at 12 months. The 70:30 P(L/DL)LA initial molecular weight of 45,000 decreased to 25,000 at 6 months and 8,000 at 18 months and to similar granules at 24 months (p < 0.02). Histology showed macrophages, giant cells, lymphocyte infiltration, little granulocytic infiltration, and minimal bleeding residuals. CONCLUSIONS: Both copolymers showed reliable biocompatibility and disintegration. Overall, 6 percent clinically apparent foreign body reactions were controlled conservatively and by local curettage; 85:15 PLGA degraded within 12 months and 70:30 P(L/DL)LA within 24 months, leaving powdering residual granules. Burr holes reossified 12 months later.

Absorbable Implants↗