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.

BIO-OSS--a resorbable bone substitute?

BIO-OSS is an allergen-free bone substitute material of bovine origin, used to fill bone defects or to reconstruct ridge configurations. Seventy one patients (39 female, 32 male) received 126 BIO-OSS implantations. Some health parameters or habits were documented to eliminate possible risk factors of influence. The diameter of jaw defects filled with BIO-OSS was measured. There was a significant influence of the defect size on the healing result. In X-ray controls, BIO-OSS served to identify the surrounding native bone. The density of the BIO-OSS areas was higher than in control sites. These radiological results were supported by bone biopsies. Histologically, the permanency of the BIO-OSS was still recognizable after 6 years and longer. The ingrowth of newly formed bone in the BIO-OSS scaffold explained the increased density of the implanted regions. There were no clinical signs of BIO-OSS resorption. Therefore, we can assume that form corrections achieved by BIO-OSS insertions will last.

Histological findings in guided bone regeneration (GBR) around titanium dental implants with autogenous bone chips using a new resorbable membrane

The aim of this study was to test the value of the new polydioxanone-membrane (PDS, Ethicon, Norderstedt, Germany) in combination with autogenous bone as a spacer for guided bone regeneration of denuded implant surfaces compared to simple augmentation. Forty implants were selected for 20 test cases (with membrane) and 20 control cases (without membrane) and were distributed randomly in 19 patients who were treated according to a standard protocol and examined. The defects were filled with autogenous bone chips, harvested interforaminally or locally, and were covered by the PDS membrane within the test group (control group: periosteum). The membranes were fixed with Memfix screws and cover screws. Seven membranes became exposed and were removed before reentry. Within the control group, three augments were sequestered. After 6 months, reentry was performed, the healing results were observed clinically, and biopsies were taken. The test group, including the seven cases with early removal of the membrane, showed that bone had filled in the defects in 95% of test cases, compared with 60% for the control group. The results of this study show that single augmentation of defects exceeding 9 mm2 is not sufficient. The membrane used in this investigation may be helpful for guided bone regeneration (GBR) at denuded screw thread sites in implant dentistry.

Preclinical and clinical studies of a collagen membrane (Bio-Gide)

Membranes are used to guide the repopulation of defects by preferred cells and to achieve a specific healing effect. The collagen membrane studied, Bio-Gide, was developed particularly for periodontal, peri-implant applications or to improve the ossification of bone defects of any origin. Bio-Gide is a bilayer membrane; one compact and smooth layer is covered by a particularly dense film, designed to prevent the invasion of soft tissue in a membrane-protected bone defect. The other, rough side of Bio-Gide must be placed towards the bone defect in order to make bone ingrowth possible. As a prerequisite for its therapeutic use in humans, the collagen matrix must be devoid of major immunogenicity. The immunological response to the membrane material was analysed in rabbits. Later, a clinical prospective study provided information about the bone regeneration effect under the Bio-Gide membrane inserted in six patients selected at random. The immune response to the collagen membrane Bio-Gide and the bone healing was tested in these patients when undergoing oral surgery.