Different substitute biomaterials as potential scaffolds in tissue engineering.

PURPOSE: To find the optimal scaffold for tissue-engineered bone, one approach is to test existing biomaterials on their suitability as scaffolds. In this study, the suitability of different alloplastic and xenogenic biomaterials as scaffolds for ex vivo osteoblast cultivation was investigated. MATERIALS AND METHODS: Normal human osteoblast cells were cultured on the surface of bovine collagenous materials, bovine hydroxyapatite, porcine gelatin, synthetic polymer, and collagen-containing bovine hydroxyapatite, and the investigation of proliferation was performed after 24, 72, and 120 hours. Measurement of the differentiation marker alkaline phosphatase and osteocalcin was made after 20 days of incubation. RESULTS: The obtained data showed significantly higher proliferation and differentiation rates in cells cultivated on collagen-rich biomaterials in comparison to noncollagenous or collagen-poor biomaterials (P < .05). DISCUSSION: In tissue engineering the scaffold should be biocompatible and serve as a proper matrix for the cells to produce the new structural environment of extracellular matrix ex vivo. Collagen supports initial cell attachment and cell proliferation, allowing immature osteogenic cells to differentiate into mature osteoblasts, but collagen may not be the only dominating factor for cell-matrix interaction during ex vivo bone formation. CONCLUSION: These data suggest that a 3-dimensional collagen matrix can provide a more favorable environment for the attachment, proliferation, and differentiation of in vitro osteoblastlike cells, at least until the initial stage of differentiation, than noncollagenous biomaterials.

Analysis of bone resorption after secondary alveolar cleft bone grafts before and after canine eruption in connection with orthodontic gap closure or prosthodontic treatment.

PURPOSE: We sought to analyze the success rate of secondary alveolar cleft bone grafts before and after canine eruption in connection with orthodontic gap closure or gap opening. PATIENTS AND METHODS: Sixty-eight secondary alveolar cleft bone grafts with iliac crest spongiosa were carried out in 57 patients (mean age, 9 years; age range, 8 to 11 years) with 11 bilateral and 46 unilateral clefts of the lip, alveolus, or palate. Gap closures were carried out after 53 bone grafts (78%), and gap openings with subsequent dental implants were carried out with 15 bone grafts (22%). The parameters acquired radiologically (orthopantomograms) at the time of the surgery and the follow-up examination (mean age, 3 years; age range, 7 months to 9 years) were 1) bone resorption in relation to the interdental height of the alveolar process in the vicinity of the cleft and 2) root growth of the teeth in the vicinity of the cleft. The statistically significant differences (P <.05) were monitored with a software program. Resorption grades I and II (>50% of the interalveolar bone height) were considered to be a success. RESULTS: Resorption was grade I in 69%, grade II in 19%, grade III in 10%, and grade IV in 1% of cases. Thus, the overall success rate was 88%. At the time of the osteoplasty, the root growth of the tooth in the immediate vicinity of the cleft was fully completed in 27 teeth (39%), three-quarters completed in 23 teeth (26.5%), and semicompleted in 18 teeth (33.8%). Twelve teeth (18%) in the vicinity of the cleft (lateral incisors/canine) remained unerupted and displaced after the surgery. It was necessary to expose unerupted teeth surgically to reposition them orthodontically. The resorption losses were significantly lower with gap closures than with gap openings (P <.001). However, bone grafts performed before canine eruption were largely carried out with the objective of orthodontic gap closure, in contrast to the bone grafts that were carried out after canine eruption (P <.02). CONCLUSION: Gap closures provide more favorable results than do gap openings in regard to resorption. Controlled dental eruptions or orthodontic gap closures reduce the graft resorption. The exact timing of surgery proved to be only a secondary consideration.