Geert Boering

RESORBABLE POLY(L-LACTIDE) PLATES AND SCREWS FOR THE FIXATION OF ZYGOMATIC FRACTURES

Ten patients with unstable zygomatic fractures were treated with resorbable poly(L-lactide) (PLLA) plates and screws. The results show that this method of fixation gives good stability over a sufficiently long period to enable undisturbed fracture healing.

Resorbable materials of poly(l-lactide). VI. Plates and screws for internal fracture fixation

Poly(L-lactide) (PLLA) with an extremely high molecular weight (Mv up to 1 X 10(6)) was synthesized at a low catalyst concentration (0.015 wt%) and temperatures between 100-110 degrees C. Besides good mechanical properties the as-polymerized PLLA exhibited a microporous structure. Plates and screws of this material were used for the treatment of mandibular fractures, both in dogs and in sheep. Bone healing was uneventful and proceeded without callus formation or signs of inflammation. Fracture healing was accompanied by a progressive degradation of the microporous implants of PLLA.

Resorbable materials of poly(l-lactide): VII. In vivo and in vitro degradation

In vivo and in vitro degradation of high molecular weight poly(L-lactide) used for internal bone fixation has been investigated. Within 3 months as-polymerized, microporous PLLA (Mv = 6.8-9.5 X 10(5] exhibited a massive strength-loss (sigma b = 68-75 MPa to sigma b = 4 MPa) and decrease of Mv (90-95%). At week 39, the first signs of resorption were evident (mass-loss 5 wt%). Except for dynamically loaded bone plates no differences between in vivo and in vitro degradation of PLLA were observed. The increase of crystallinity of PLLA upon degradation (up to 83%) is likely to be attributed to recrystallization of tie-chain segments. A more ductile PLLA exhibiting a lower rate of degradation was prepared by extraction of low molecular weight compounds with ethyl acetate.

DEGRADATION OF AND TISSUE REACTION TO BIODEGRADABLE POLY(L-LACTIDE) FOR USE AS INTERNAL-FIXATION OF FRACTURES - A STUDY IN RATS

Samples of high-molecular-weight poly(L-lactide) (PLLA) (Mv = 9.0 x 10(5), a biomaterial developed for plates and screws used in internal fixation of jaw fractures, were implanted subcutaneously in the backs of rats to study tissue reaction to PLLA and to follow the degradation process. The PLLA seemed to follow the degradation pattern typical of biodegradable polyesters. After pure hydrolysis up to about 104 wk, phagocytic activity of macrophages was found at about 143 wk. Full resorption of PLLA was not demonstrated in this study. Except for the early and final parts of the implant period, no acute or chronic inflammatory reaction was observed. No implant was rejected. It is estimated that more than 3 yr will be required for total resorption of PLLA. For bone-healing this long period is of no practical importance. There is no need for removal of PLLA after fracture healing as is the case with metal fixation devices. Thus, PLLA has potential application in internal fixation of fractures and osteotomies in the maxillofacial region and other fractures that are not too heavily loaded in the human body.

TISSUE RESPONSES TO DEGENERATIVE CHANGES IN THE TEMPOROMANDIBULAR-JOINT - A REVIEW

The articular cartilage covering of the mandibular condyle and the articular eminence, as well as the tissue of the articular disc, may be affected by degenerative changes associated with osteoarthrosis. Degenerative changes of cartilage alter its physical properties and, as a result, affect its ability to withstand compressive and shearing stresses. Increased friction between the articular surfaces may impair joint movement and may elicit compensatory or pathologic responses of the cartilage and the adjacent tissues, such as capsule and ligaments, synovial membrane, subchondral bone, and associated musculature. In this review, these structural changes are described and related to common signs and symptoms of craniomandibular dysfunction, such as clicking, locking and instability, pain and tenderness, restricted ranges of mandibular motion, crepitation, deformity, muscle wasting, and changes of occlusion.

OSTEOARTHROSIS AS THE CAUSE OF CRANIOMANDIBULAR PAIN AND DYSFUNCTION - A UNIFYING CONCEPT

It has been demonstrated that osteoarthrotic changes in the temporomandibular joint (TMJ) and in other synovial joints show a similar course, both clinically and (ultra)microscopically. Initially, cartilage changes and possibly also changes in the synovial membrane set up a vicious cycle of cartilage breakdown accompanied by attempts at repair. When the degradative process exceeds the response of repair, the osteoarthrotic disorder progresses into clinically detectable stages. Frequently, the gliding capacity of the articular disc is also impaired, giving rise to an internal derangement. In this article, a concept is presented in which it is suggested that in many cases of craniomandibular pain and dysfunction TMJ osteoarthrosis is the basic disorder.

Osteoarthritis and internal derangemen of the temporomandibular joint: A light microscopic study

To describe osteoarthritic changes of the temporomandibular joint (TMJ) and their relation to internal derangements, 22 randomly selected TMJ autopsy specimens were dissected and studied by light microscopy. Normal disc position was seen in eight joints, partial anterior displacement of the discs in eight joints, and complete anterior displacement of the discs in five joints; one joint had a perforated disc. Degenerative changes, such as horizontal splitting, clustering of chondrocytes, bone marrow fibrosis, sclerosis, erosion, cyst formation, and reduction in TMJ size, were found in 11 of the 14 joints with displacement or perforation of the disc and in four of the eight joints with normal disc position. Internal derangement appeared to be associated with osteoarthritis. The relations between remodeling, aging, internal derangement, and osteoarthritis are discussed.

The structure, biochemistry, and metabolism of osteoarthritic cartilage: A review of the literature

PURPOSE To understand the possible significance of the presence of proteases, cytokines, growth factors, and arachidonic acid metabolites in the osteoarthritic temporomandibular joint (TMJ), the pathogenesis of TMJ osteoarthritis (OA) is discussed, based on knowledge of structure, biochemistry and metabolism of osteoarthritic cartilage in general, and a classification of TMJ OA is presented.

Morbidity from iliac crest bone harvesting

PURPOSE The iliac crest is the most common donor site for autogenous bone grafting in maxillofacial surgery. The aim of this study was to evaluate retrospectively the morbidity of bone harvesting from the inner table of the anterior iliac crest. PATIENTS AND METHODS Sixty-five patients were recalled 1 to 4 years after iliac crest bone harvesting. The morbidity as well as the patients satisfaction were evaluated by a survey of the medical record, a mail-in questionnaire, and a standardized physical examination. RESULTS There was good acceptance of this bone harvesting procedure, and the morbidity was low. CONCLUSION Bone harvesting from the inner table of the anterior iliac crest is a good option for reconstructing bone defects.

Maxillary Sinus Function After Sinus Lifts for the Insertion of Dental Implants

PURPOSE The influence of bone augmentation of the floor of the maxillary sinus for the insertion of dental implants on sinus function has not been well investigated. In this study, the influence of the sinus lift on the development of maxillary sinus pathology was evaluated using generally accepted diagnostic criteria. MATERIAL AND METHODS A group of 45 patients in whom a sinus lift procedure had been performed were evaluated for sinus pathology 12 to 60 months after bone transplantation and implant insertion, using a questionnaire, conventional radiographic examination, and nasoendoscopy. RESULTS Postoperative maxillary sinusitis was detected in two of five patients with a predisposition for sinusitis, but in none of the other 40 patients. The occurrence of iatrogenic sinus membrane perforations during surgery was not related to the development of postoperative sinusitis in patients with healthy sinuses. CONCLUSION The occurrence of postoperative chronic sinusitis appears to be limited to patients with a predisposition for this condition. These predisposing factors need to be considered when evaluating patients for sinus lift procedures.