The Temporomandibular Joint Implant Controversy: A Review of Autogenous Alloplastic Materials and Their Complications
Deborah N. Baird, MD, FAAP, Rowlett, TX, USA
William J. Rea, MD, FACS, FAAEM, Environmental Health Center-Dallas, Dallas, TX, USA
Since the late 1970s, the treatment of temporomandibular joint (TMJ) abnormalities has proliferated. Seminars on the treatment of TMJ disorders became popular and rendered the dentist an authority on the disease. As a consequence of this new-found knowledge, aggressive surgical intervention for disc derangements also increased. It was believed that joint pathology was the cause of the patient’s symptomatology. It was also suspected that proper disc repositioning or replacement with either autogenous or alloplastic materials would prevent future joint changes. Although early reports appeared promising, over just a few years, more and more failures occurred with reports of incapacitating pain and further joint destruction. More surgery ensued (as few as two or as many as 20), all to rectify these disastrous outcomes. This presentation is an overview of the basic joint structure/pathology and treatment modalities applied, as well as an introduction to the different alloplastic materials used and their complications. A future paper will discuss the involvement of a systemic disease process distant to the localized area of the TMJ. TMJ implants have not only become a modern medical nightmare but a legal and political minefield as well.
Keywords: Temporomandibular joint, myofacial pain syndrome, polytetrafluoroethylene: proplast, foreign body giant cell reaction, autogenous/alloplastic disc replacements, costochrondral rib grafts, silastic sheeting, condylar osteoarthritis, titanium total joint prostheses.
Source: Journal of Nutritional & Environmental Medicine (1998) 8:289-300.
Temporomandibular joint disorder (TMJ) is estimated to affect 30 million Americans with approximately 1 million new patients diagnosed yearly . The vast majority of these patients can be treated with conservative, non-invasive therapies. Only about 8% of patients require surgical intervention . Of TMJ patients, 80% are female . In the past decade, at least 100,000 patients have received alloplastic material in their joints with another 300,000 patients having received autogenous tissue including costochondral rib grafts . It was speculated that these iterpositional implants (IPI) would take the place of the patient’s own damaged disc. These implants have become a disaster that is indeed worse than the breast implant disaster because the failure rate is approaching 80% . Two major alloplastic materials have been used. The first, Silastic sheeting (Dow Corning, Midland, MI, USA), has been used since the 1960s for joint replacements of the small bones of the hands and feet and the first reported use in the temporomandibular joint (TMJ) was in 1969 . Silastic sheeting for TMJ became popular during the 1970s and was voluntarily withdrawn in 1993 . The second, and the more severe in its damage, was Proplast I and II (Vitek, Houston, TX, USA). Proplast, or polytetrafluoroethylene (PTFE), was used in the late 1970s but not made into precut discs until 1983 . Oral surgeons rapidly accepted its supposed advantages and placed it in an estimated 25,000–30,000 patients ,
STRUCTURE AND PATHOLOGY
The TMJ is unique in that it does not function independently but in tandem with its contralateral joint. Therefore, diseases that affect one joint and its surrounding structures can in turn affect the other joint, as well as muscles and (fascial) structures. Mobility is accomplished by an initial hinge motion (straight vertical opening) as well as gliding forward (increasing vertical opening) and side to side . Vertical movement is about 50 mm with 10 mm protrusion and 10 mm lateral movement . The TMJ can deliver in chewing forces 7 Kgf to 23 Kgf for cheese and as high as 35 Kgf for peanuts . This is an important concept to understand in the utilization of surgical techniques and implants that will withstand these stress factors.
The condyles articulate with the glenoid fossa which is part of the floor of the middle cranial fossa. An avascular cartilaginous, non-innervated disc is positioned between the condyle and fossa to cushion the movement. The disc is attached to the lateral pterygoid muscle anteriorly, which in spasm may pull the disc forward causing dislocation. With anterior dislocation the condylar head comes in contact with the highly innervated retromeniscal tissue causing severe pain . Joint movements are accomplished by the muscles of mastication: masseters, temporalis and lateral and medial pterygoids. Therefore, when pathology is noted in the TMJ, it can affect any of these muscles bilaterally with pain and spasm and, like a domino effect, it may involve adjacent structures such as the sternocleidomastoid muscles, trapezius, scalenii muscles, paraspinal and the back and shoulders. If the pain is long term and recalcitrant to palliative therapy, specific trigger points in these areas become evident as well as the presence of autonomic nervous system dysfunction, which in turn perpetuates the patient's chronic pain (reflex sympathetic dystrophy). The symptomatology progresses further than just the TMJ and becomes the broader descriptive of myofascial pain syndrome (MPD).
Farrar , in 1979, refuted two popular and diverse etiological theories of MPD. The first was based on emotional stress (i.e., bruxism) and the second on dental malocclusion. The syndrome itself was defined by Farrar as consisting of the four symptoms of pain, muscular tenderness, limitation of jaw movements and clicking. However, TMJ symptomatology is markedly diverse. We now also include joint crepitus, tinnitus, vertigo, sleep disturbances and depression. Etiology was divided into developmental abnormalities, diseases, dysfunction and injuries. The most important of these are the developmental abnormalities and intracapsular diseases. It has always been hard to separate muscle and joint disorders as they usually coexist. This increased awareness and knowledge led to an aggressive approach to TMJ treatment in the 1980s.
The most common cause of internal derangement is the anterior displacement of the disc with reduction upon opening, or a more advanced stage of anterior displacement without reduction . The joint can adapt to these mechanical disturbances, but if adaptation can no longer occur degenerative changes and inflammation ensue . Non-invasive treatment consisting of teeth equilibration, interincisal splints to try to recapture the disc, orthodontics, physical therapy, i.e., heat/cold, spray and stretch, transcutaneous electrical nerve stimulation (TENS), biofeedback, hypnosis, diet restrictions and other stress reduction modalities have all been tried. Pain medication including non-steroidal anti-inflammatory drugs (NSAIDs), benzodiazepams, antidepressants and narcotics have been utilized as an adjunct to the above treatment modalities.
Indications for TMJ surgery consist of internal derangement, degenerative joint disease, condylar fractures, neoplastic diseases, growth deformities, fibrous/bony ankylosis, rheumatoid or non-rheumatoid arthritis and hypomobility disorders . The recommended primary surgical procedure for hypomobility, internal derangement, synovitis and degenerative joint diseases is now arthroscopic surgery, but this was not the vogue in the 1980s . Early reports of simple lysis and lavage were met with skepticism and it was not until 1988 that the American Academy of Oral Maxillofacial Surgery (AAOMS) published its position and indications for arthroscopic surgery .
Open surgical reduction and repair of the disc was the procedure of choice during the 1980s. But if this was not feasible, the option of simple discectomy versus replacement with autogenous or alloplastic material was considered. Discectomy is the oldest and most commonly performed operation for TMJ pain with internal derangement . The remainder of the joint is left in situ and rehabilitation consists of early mobilization and decreased joint stress for the first 6 months. Condylar changes seem to stabilize radiologically by 6 months post-operatively. The outcome in 80-90% of patients is relief of pain . Eriksson  published a retrospective study showing that 15 patients who had menisectomies performed with a mean follow-up of 29 years were all pain-free with all joints showing radiographic changes of flattening of the condyle and the presence of osteophytes. Two-thirds of the operated joints exhibited crepitus. However, surgery during the 1980s involved the use of a replacement disc material, either autogenous or alloplastic.
In 1909, metatarsal bone was used in the first condylar reconstruction, and the first costochondral graft was utilized in 1920 . The use of costochondral junction grafts from actively growing samples was recommended by Sarat and Robinson in 1956 . It was the growth potential and the capacity for remodeling that made rib grafts efficacious for children and for congenital deformities [13, 14]. However, intrinsic growth potential presented a problem with excessive growth during pregnancy [13, 14]. The contralateral 6th or 7th rib was resected with a minimum of a 2 cm bony rib and a cartilagenous portion not to exceed 0.5–1 cm as more than this carried a risk of fracture at the costochondral junction. Intermaxillary fixation was maintained for 2–6 weeks and then active therapy of the jaw began [13, 14]. Reoccurrence of ankylosis after graft replacement is rare . Reconstruction of the TMJ disc has also been done with dermis, auricular cartilage, freeze-dried dura and temporalis muscle and fascia. A temporalis muscle flap was first described in 1898 by Golovine for reconstruction of orbital exenteration . Subsequently it has become a popular replacement for the TMJ disc . This muscle-pericranial flap does not cause the problem of toxicity of alloplastic disc replacement, has a low degree of friction, and has positional stability . It is easy with only 1 surgical site to harvest and rotate the muscle fascia to the proper site and anchor it in place. However, long-term success is still a problem .
Autogenous bony tissues other than costochondral grafts that have been used were metatarsal, iliac crest, fibula, tibia, cranial bone and sternoclavicular grafts (SCG). Initially, the SCG was harvested with a pedicle flap of sternocleidomastoid muscle and rotated to reconstruct the mandible using a whole-joint graft and thus leaving a defect . Wolford et al.  were the first to report the use of a free partial thickness SCG which was replaced in their different groups of patients. The first group consisted of prior Proplast/Teflon implants with a failure rate of 71%. The second group consisted of patients with inflammatory joint pathology with a failure rate of 50%. Group three consisted of congenital abnormalities and one tumor with a success rate of 93%. Morbidity consisted of clavicular fractures in 10% of their patients. This has shown some promise in group three pathoses but not in patients with prior alloplastic implantation or inflammatory disorders (i.e., arthritis) . Also, in young children the SCG is too thin and fractures easily . The continued search for an optimal joint replacement, with optimal function and relief of pain and good cosmetic outcome, led to synthetic or alloplastic materials.
In 1963, Robert Christensen  first described a molded vitallium (cobalt-chromium) prosthesis which covered the glenoid fossa. This was secured to the skull with two to three screws, and the meniscus was allowed to remain in situ which he felt helped to prevent adhesions and lubricated and lessened joint trauma. At times the disc was unsalvageable and was removed. This process was also used with a condylar component. Christensen devised about 50 different sizes from cadaver skulls for a custom-fit in individual patients. Statistics showed a favorable outcome.
Morgan [18, 19] in 1971 first described a vitallium articular eminence implant of an acrylic condylar head and vitallium shank being utilized to replace an absent condyle. His total TMJ joint replacement was reported in 1976. This consisted of a vitallium and silastic implant attached to the glenoid fossa with an acrylic head and vitallium ramus as the shank portion. He stressed the necessity of an implant on the glenoid fossa to prevent a metallic condylar prosthesis from penetrating the floor of the cranial vault when significantly impacted. A 10-year follow-up of his total joints reported none being removed. Significant improvement of TMJ symptoms was found in 85% of patients. A retrospective study of an articular eminence performed by House, Morgan et al.  consisting of 103 patients from the years 1965 through 1977 gave a 41.7% excellent, 28.8% good, 14.1% fair and 15.3% poor response. Only 14 patients out of a total of 100 respondents had to undergo more surgical procedures.
Proplast has been used since 1960 as a filler in non-stress bearing areas of the body because of its porous surface, and its consequential in-growth of fibrous tissue . In 1970, Charnley had to replace all his hip joints made of Teflon (PTFE) owing to reported material failure . Foreign body giant cell reaction was of significant consequence. He found that high density polyethylene was 300 times better than Teflon [21, 22]. In spite of these early results, Homsy introduced his Proplast/Teflon IPI in 1976 . Early PTFE was bonded with carbon (Proplast I). In 1983, precut discs of PTFE bonded to aluminum oxide were manufactured by Homsy (Vitek). In a letter of application to the Food and Drug Administration (FDA), Bureau of Medical Devices, 23 November 1982, Vitek stated that their IPI was substantially equivalent to other materials that were in commercial distribution prior to 28 May 1976 . The further stated purpose was "intended to restore height and contour of the articular eminence, act as a disc replacement and generally separate articular surfaces to reduce pain and improve function." The suggested indications for usage of PTFE IPI implants were: (1) internal derangement–as a scaffold for disc repair and (2) degenerative joint disease as a limited restoration of condylar height following a condylar shave with an intact and functional disc . Contraindications consisted of debilitated patients, patients unable to co-operate with post-operative instructions, systemic diseases such as uncontrolled diabetes, collagen vascular disease and cardiovascular disease which may lead to poor wound healing, allergic diseases, osteomyelitis, insufficient bone or tissue to support the implant, open draining cavities, active infection and patients receiving a metallic condyle . A survey of 322 surgeons reported a 91% satisfactory result with surgical placement of the IPI in 5,070 procedures . Both Homsy and Kent reported that the most common reason for failure was infection, occurring only in 4% of patients . A retrospective study of 301 TMJ, IPI placements by Estabrooks et al. . comparing interincisal opening, occlusion, joint sounds, joint degeneration and patient satisfaction in a 6-year study from 1981 to 1987 reported an overall success rate of 88.7%. The average follow-up period was 33 months and 90% of the patients were female. Radiologically there was an increase in condylar degenerative changes and a positive bone scan. In 1982 a reported study of 12 patients by Gallagher and Wolford  utilizing either silastic or Proplast implants reported the superiority of the Proplast over silicone over a 4-year period with no Proplast patients needing reoperation.
The opposite consensus by Wagner et al.  reported a 74% failure rate of severe pain, malocclusion, restricted opening and radiological degenerative changes of the condyles (100%) and fossa (68%). Implants had to be removed as early as 2 months to 3.5 years after placement. Histologically, a foreign body giant cell (FBGC) reaction was seen in each specimen. These reactions of a severe degree have been noted by many different authors [24, 25-30]. Fragmentation of the Teflon occurred as it could not withstand the joint stresses. As a consequence, macrophages formed around these fragments in an effort to ingest them . As a result of the formation of FBGC reaction, lysosomal enzymes and hydrolases are released which in turn cause further osseous and non-osseous tissue damage and mediate the migration of more macrophages into the area and more and more destruction occurs in the joint as well as the surrounding tissue and bone. Light and electron microscopy of the fibrous connective tissue has shown that the implant material is responsible for the foreign body reaction by the successive micro fragmentation of the implant material. The stimulation of the osteoclasts by the Proplast material is responsible for the bony changes . This destructive reaction can be associated with pain, hypomobility and malocclusion. But in many patients, however, all these lesions can be silent . Westlund  further felt that owing to the silent nature of failures, early statistics may have reported them as successes. The extensive damage to the joint and surrounding tissues continues even after the IPI is removed , and Chuong et al.  recommended the use of an operating microscope to debride all tissues of fragmented Teflon particles so FBGCR reoccurence would be minimized. Replacement of joints with autologous tissue after IPI removal resulted in a continuation of the FBGC reaction and the ultimate destruction of the implanted tissue . Five years after IPI removal, FBGC reaction was confirmed on histopathologic examination after reoperation .
One of the most extensive studies was done by Henry and Wolford , evaluating 107 patients (163 joints) treated with PTFE. Only 12% of joints showed no significant osseous changes radiographically. Ankylosis was the common reason for failure. Temporalis fascia and muscle graft had a 13% success rate, and grafts with split ramus osteotomies 31%. Dermal grafts had a success rate of 8%, conchal cartilage 25%, costochondral grafts 12% and sternoclavicular grafts 21%. If the number of surgeries prior to reconstruction were greater than two, the success rate approached zero. An improved rate of success was achieved only with a total joint prosthesis (Techmedica). A study by Fontenot and Kent  had shown the in vitro life of Proplast/Teflon IPIs to be approximately 3 years.
A paucity of animal models in IPI placement of either PTFE-A12O3 or silicone was the problem when first manufactured. In 1986 Timmis et al.  reported a sham discectomy in New Zealand adult rabbits. One TMJ was used as the control and in the other TMJ either silicone or PTFE was used. At 2, 4, 8 and 20 weeks the animals were sacrificed and examined histologically. PTFE showed increased severity of the articular surface destruction and increasing FBGC reaction which was maximal at 20 weeks, as well as a 46.2% tearing of the implants in all joints. The silicone faired somewhat better, with the severity of the FBGC reaction less than the PTFE group with return to a more normal articular surface in one half of the cases at 20 weeks. Though less stable than the PTFE, the silicone fractured in only one half of the specimens. This study corroborated findings being seen in patients and the need for further evaluation of materials used in IPI implantation.
More than 60% of PTFE treated joints have shown severe destructive osseous changes in comparison to none who had a simple discoplasty . Tomography as well as coronal CAT scan and MRI have readily shown the destruction of the joint, its tissue and the adjacent osseous condyle and glenoid fossa [32, 33, 34]. The most severe and dangerous destructive lesions have been the erosion of the PTFE implant into the middle cranial fossa. Smith et al.  removed Teflon/Proplast implants from 31 patients with six having perforation into the middle cranial fossa, and in some instances exposure of the dura was seen on operation . The perforation can progress to a cerebrospinal fluid (CSF) leak with a needed illiac bone graft for closure . Bony defects with CSF leak can be closed with fat, muscle, cartilage, bone or a combination of tissues.
Lymphadenopathy may occur following the placement of PTFE disc replacements as a result of the migration of Teflon into the adjacent lymphatics, resulting in an FBGC reaction that initially is hard to distinguish from an acute infection. Again, this response is a direct result of the inability of the IPI to withstand the stresses of mastication . Infection can be a problem in the joint itself necessitating the removal, debridement and aggressive antibiotic treatment. Haug et al.  reported such a case of a pseudomonas infected IPI removal with subsequent continued infection in the total joint prosthetic replacement.
There is still no exact mechanism in the literature that explains the reason for the severe FBGC reaction and its mobilization of macrophages. What is evident in the literature is the need to remove the PTFE implants because of the severe joint destruction .
In 1962, Swanson introduced a silicone small joint prosthesis for the hand . It was only a matter of time before it was used in the TMJ. Its use escalated in the late 1970s, and it was recommended initially as a permanent and then as a temporary disc replacement because of its ability to form a fibrous capsule around the silicone [30, 40, 41, 43]. Kalamchi  in 1987 presented a retrospective study of 68 patients in whom silicone disc replacement was used between 1970 and 1985 for osteoarthritis and limited incisal opening. Sixty-three patients had good results with the longest time interval of 14 years 7 months. He also emphasized the need for good physiotherapy and compliance by these patients. Wilkes in 1982 proposed the use of temporary silicone replacement to help avoid post-operative adhesions and its subsequent removal in 2–4 months . This was recommended to circumvent some of the longer complications of the wearing and thinning of the silicone with eventual fractures [40, 44].
Tucker et al.  (1989) using Macaca fascicularis monkeys underwent placement of temporary silastic material as a disc replacement bilaterally. The one side was removed at 3–4 months and the contralateral side continued to have the silicone in place. The animals were sacrificed at 3, 4, 5 and 6 months post-removal and the sides compared. Irregularities of the articular bony surfaces were noted on the control side but, as the animals approached 5-6 months, the side with silicone which was still in situ displayed a thick fibrous capsule, minimal FBGC reaction and minimal articular surface bony irregularities. The author concluded that using silastic implants only as a temporary replacement was recommended. Long-term use potentially caused tearing, localized inflammation and the deposition of silicone particles in regional lymph nodes.
Foreign body giant cell reaction with the occasional spread to the lymph nodes was well known in any silicone implanted joint of the body. Nalbandian et al.  in 1983 sought to prove its benign nature utilizing dog autopsies upon natural death (> 10 years) as well as a 14-year follow-up of a human with multiple silicone joint replacements. Their statistics sought to prove that FBGC synovitis occurred in <1% of operated cases and lymphadenopathy was observed in 0.01% of cases. The mild, benign nature of the reaction did not negate cessation of its use as implant material.
Dolwick and Aufdemorte  in 1985 were the first to point out the severity of the FBGC reaction with deposition of silicone in nodal tissues as well as a rheumatoid synovitis in sites adjacent to the silicone material. Furthermore, this reaction should be considered in all patients who have joint swelling and pain post-operatively at any interval. Without a doubt, silicone does indeed play a significant role in causing FBGC reactions and bony resorption and destruction. A comparison of TMJ discectomies with and without silicone replacement by Westesson et al.  clearly shows the destructive nature of silicone implants in comparison to a very acceptable and benign course of the joint with disc removed and no alloplastic material placed. Eriksson et al.  also showed the benign course of discectomy versus discectomy with silicone implantation and suggested that its use should be seriously questioned. Electronmicroscopy corroborates this as well as an energy dispersive X-ray microanalysis (EDX) in the study by Hartman [47, 48]. The morphologic findings surrounding the long-term silicone implants included "a foreign body reaction, synovitis, dystrophic calcification, fibrocartilaginous metaplasia, and hyalinization scarring of the particulate silicone debris inducing a pathologic response in the tissues and migrating to nodes" .
Silicone has a high coefficient of friction and poor wear characteristics, and will thus be worn easily, fragmented and dispersed into the surrounding tissues . "An inflammatory reaction (FBGCR) and bony resorption/destruction ensues. The indigestible silicone continues the macrophage responses-the exact pathologic mechanism still not being known, and more and more destruction ensues" . Destructive lesions of the mandible were seen in one third of patients by Westesson .
TOTAL JOINT PROSTHESIS
From 1971 to 1975 Kent's  first condylar prostheses were individually made with a standard head, neck and shank. Kent coated his shank with Proplast I (PTFE-Carbon) material. In 1975 he modified his prosthesis to form a box-like shank which was reported as having increased stability. In 1982, Kent's shank was bonded with Proplast II material (PTFE-A12O3). The Vitek/Kent partial or total TMJ prosthesis was manufactured from 1982 to 1990  (VK I in 1982–1986; VK II in 1986–1990). The VK I fossa prosthesis had a superior surface of Proplast and an inferior surface of Teflon. It was used as a partial joint with a normal condyle or as a total joint with a metallic condyle. The VK II fossa had a superior surface of Proplast and an inferior surface of ultra-high molecular weight polyethylene (UHMWPE). The head of the VK II condyle was displaced more laterally as well. The success rates of VK I partial and total joint prothesis were 42.4% and 57.9% respectively after a 5–6 year follow-up. The VK I was discontinued because of the poor wear of the Teflon . On the other hand, the VK II partial and total joint prosthesis success rate was 100% and 89% with a follow-up of less than 3 years. Kent felt that the increased success of the VK II was directly related to the discontinuance of Teflon and the utilization of UHMWPE. Again, the cumulative success rate decreased with a history of prior surgeries before placement of his total joint. The VK II was removed from the market when the FDA intervened.
The most custom fit of all joint prosthesis was the Techmedica CAD/CAM [52, 53] custom computer-assisted design/computer-assisted make-up (Camarillo, CA, USA). Though devised in 1988, it too, like the rest of its predecessors, was removed from the market by the FDA in 1993 in spite of multiple letters written by both surgeons and patients requesting that it remain available (author's personal communication). The fossa component was composed of a commercially pure titanium sheet welded to titanium mesh for bone and soft tissue in-growth and in turn bonded to UHMWPE as its articulating surface. The mandibular component was composed of a head of chrome-cobalt-molybdenum attached to a titanium shank. Each component was screwed in place with 4–5 titanium screws. Each patient required a CAT scan done with their teeth in occlusion, a model of the skull was made, and then a perfect fit was fashioned from the model by the individual surgeon. Only after the customized adjustments were done was the system sent back to the manufacturer for final construction [52, 53]. The surgical time was diminished owing to this perfect fit. Removal of most of the condylar head and neck was especially necessary in those patients with previous silastic or PTFE, IPIs because of the material remaining embedded in the surrounding tissue that could continue an FBGC reaction .
A retrospective study of the Techmedica by Mercuri et al.  was done on 215 patients consisting of 363 joints (13 males and 202 females). There were 296 patients with joints bilaterally and 67 unilaterally. The average age at the time of implantation was 40 years and the duration was 0–4 years. Favorable results for pain improvement in 58%, increased incisal opening in 51% and improvement of diet in 55% were noted at 1 and 2 years post-operatively. Those parameters measured on patients in the 0 to 4 surgery and 5 to 9 surgery groups faired much better than the multiple surgery group of 10 or more procedures prior to the placement of the Techmedica prosthesis. A total of 19 patients (8.8%) had failure of the prosthesis; either design (9), biologic failures (3), and 1 both biologic and design, 1 material failure, and 5 requested to have the prosthesis removed because of increased pain. Extrapolating the design/patient failures to 4 years, a success rate of 92% was realized. Of interest is the number of patients who had either Vitek IPI or Vitek/Kent joint prosthesis (17.21%) prior to placement of the Techmedica. Thirty-three percent of those patients were located in the 10 or more surgery group.
One more type of total TMJ prothesis that merits mention is the use of a polyoxymethylene (Delrin) condylar head which was affixed to a titanium mesh shank . Delrin had been reported as being used successfully in elbow replacement surgeries. The titanium mesh could be molded to the mandible with the potential of early appositional bone growth with little evidence of bony resorption.
Implants gave oral surgeons many options in the 1970s and 1980s, but unfortunately they have left many patients with mutilated and unsalvagable joints who are destined to develop other systemic problems. These problems have become more complex than can be handled by just one surgical/medical discipline. An environmental evaluation is a recommended procedure before any decision is made to place a joint prosthesis. In our experience, a prosthesis is usually not needed but, if necessary, an autogenous material is far preferable to an alloplastic joint replacement. Further historical controversies and clinical case histories will be discussed in a future article.
The authors wish to thank Dean White, DDSS Oral Maxillofacial Surgeon (Bedford, TX, USA) for photographic contributions.
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