A short-term study in sheep with the Groningen temporomandibular joint prosthesis

Abstract

As part of the pre-clinical testing process of a newly developed temporomandibular joint (TMJ) prosthesis, animal experiments were performed. In 14 sheep, the right TMJ was replaced by the developed TMJ prosthesis. The prosthesis consisted of a skull part, a mandibular part and an intervening polyethylene disc. In the first series (6 sheep), three designs were tested, differing in the applied metal (stainless steel or titanium) and in the fitting method of the skull part (a fitting member or bone cement). The sheep were sacrificed after 8-16 weeks. In the second series (8 sheep), the preferred titanium fitting member design was applied, and the sheep were sacrificed after 2-10 weeks. One sheep was excluded because no correct position of the prosthesis parts could be achieved. At sacrifice, the removal torque of the screws was measured, and the surrounding tissues were harvested for histologic examination. The sheep recovered well and functioned until the end of the scheduled sacrifice date. Encountered problems were two disc dislocations, one fistula formation, and one screw failure. All mandibular parts were clinically stable, as were most skull parts with a fitting member, and one of both skull parts fitted with bone cement. The clinically observed stability was confirmed by the removal torque values, which indicated well-integrated screws. It is concluded that the TMJ prosthesis could remain stable and functional over the initial healing period. The main restriction of the sheep model is the much larger translatory capacity compared with patients, which adversely influences tissue healing.

Biomechanical analysis of a temporomandibular joint condylar prosthesis during various clenching tasks

“…The study results showed that 3 staggered bone screws can provide optimal implant stability and bone stress and strain distributions in a TMJ condylar prosthesis . This finding supported the study findings of by van Loon et al, who performed experiments in sheep and found that a TMJ condylar prosthesis could be firmly fixated using three screws (van Loon et al, 2000a). In this study, the maximum relative micromotion values between the TMJ condylar prosthesis and bone for the six clenching tasks were all less than 28 mm, which is the maximum relative micromotion that can be tolerated for bone ingrowth into the implant surface (Pilliar et al, 1986).…”

Mesenchymal Stem Cells and Platelet Gel Improve Bone Deposition within CAD-CAM Custom-Made Ceramic HA Scaffolds for Condyle Substitution

“…Sheep have bone remodeling patterns similar to those of humans [21], with at least equal chewing forces. The TMJ undergoes adaptive changes even when chewing causes only minor displacement of the condylar head, while articular degenerative changes may develop earlier in adults because of their poor aptitude for subchondral bone remodeling.…”

Surface wear in a custom manufactured temporomandibular joint prosthesis

“…10,11 This lack of testing is a significant shortcoming, as mechanical properties and wear resistance play a pivotal role in determining the long term outcomes of TJR and, therefore, the need for revision or replacement surgery. 2,7 As far as the authors are aware of, Van Loon et al 12,13 are the only group to publish their in vitro TMJ TJR wear results, prior to commercial release of their prosthesis. They designed a wear testing machine, which simulated the articulation of the mandibular head against the ultra-high molecular weight polyethylene (UHMWPE) disc, while the implant was submerged in bovine fetal calf serum, diluted with distilled water.…”