Re-attachment of periodontal ligament by collagen in experimentally-induced alveolar bone dehiscence in dogs

Polymer-assisted regeneration therapy with Atrisorb barriers in human periodontal intrabony defects

AIM

This study compared clinical results of 40 periodontal osseous defects treated by two types of absorbable barrier materials.

MATERIAL AND METHODS

Thirty patients (23 males and seven females) suffering from moderate to advanced periodontitis (with comparable osseous defects) were randomly assigned to receive either Atrisorb barrier (n = 22; group A) or Resolut XT barrier (n = 18; group B) therapy. Periodontal phase I treatment and oral hygiene instruction were performed before periodontal surgery. Papillary preservation, partial thickness flap, citric acid root conditioning, and decortication procedures were applied during the operation. Bone defects were filled with demineralized freeze-dried bone allograft and minocycline mixture (4:1 ratio). Postoperative care included 0.10% chlorhexidine rinse daily and antibiotic medication for 2 weeks. Clinical assessments including probing depth (PD), clinical attachment level (CAL), gingival recession (GR), plaque index (PII), gingival index (GI), and radiographic examinations were taken at the baseline, preoperatively and at 3 and 6 months after regenerative surgery.

RESULTS

Six months following therapy, both Atrisorb and Resolut XT groups had achieved comparable clinical improvement in pocket reduction (3.9 versus 4.4 mm), attachment tissue gain (clinical attachment gain; 3.5 versus 3.6 mm), and reduction in the GI and in the PII. Within-group comparisons showed significant attachment gain and pocket reduction between baseline data and those at both 3 and 6 months postoperatively (p < 0.01). There were no statistically significant differences in any measured data between groups A and B.

CONCLUSIONS

The results of this study indicate that a comparable and favorable regeneration of periodontal defects can be achieved with both Atrisorb and Resolut XT barriers. Further long-term study and histologic observations of tissue healing are needed to evaluate whether Atrisorb is promising for clinical use.

Bone morphogenetic protein induced repair of compartmentalized segmental diaphyseal defects

In adult rabbits, mid-diaphyseal segments of the radius or ulna were excised to produce defects greater than the critical size for spontaneous bone repair. The defects were enveloped in sleeves composed of nonbiodegradable expanded polyfluoroethylene (ePTFE), pore size 30, 60, 90 microns, and compared with sleeves of three biodegradable materials. Bone morphogenetic protein and associated noncollagenous bone matrix protein (BMP/NCP) or recombinant human morphogenetic protein (rhBMP-2) were implanted inside the sleeves. Albumin was implanted for a control system. Without intracompartmental BMP, only about 10%-15% of the defect was repaired by bone growth extending from the bone ends into the sleeves composed of ePTFE, pore size 30 microns. With sleeves with pore size 60 or 90 microns and intracompartmental BMP/NCP, 54%-96% regeneration occurred within 8 weeks after the operation. Sleeves of biodegradable nonimmunogenic materials such as polyorthoester (POE) and polylactic-polyglycollic acids (PLA/PGA) permitted 86%-98% restoration of bone continuity, but only when BMP was present in the lumen. With puncture holes (0.5 mm in diameter), implants of BMP/NCP in the 30-micron PTFE sleeve produced transmembrane external callus formation and bone regeneration to 147%. Sleeves composed of aorta first calcified, then induced complete intracompartmental bone regeneration. Atelocollagen sleeves incited a low-grade inflammatory cell reaction and did not promote complete regeneration. Under conditions presently undisclosed segments of the ulna bridged with ePTFE, were incompletely paired, even with intracompartmental BMP/NCP. Puncture holes of 0.5 mm admitted ingrowth of capillaries and introduced local conditions favorable for the response to BMP/NCP. BMP/NCP may promote proliferation of nutrient vessels and differentiation of bone marrow stroma cells between the open bone ends. For further investigation, the hypothesis to be examined is that the optimum response to BMP/NCP and rhBMP-2 would emerge in compartments containing first a high concentration gradient and second proliferating perivascular cells.

Implications of cellular and molecular biology advances in periodontal regeneration

BACKGROUND

The mechanisms by which new periodontium is established on root surfaces previously exposed to periodontal disease has been an area of active research interest for the past decade.

METHODS

Recently, histological examination of periodontal regeneration has revealed a complex process orchestrated by temporo-spatial specific cell-matrix interactions.

RESULTS

Advances in cell and molecular biology techniques have provided invaluable tools to begin investigating the cascade of events occurring periodontal regeneration.

CONCLUSION

This report summarizes current understanding of the cellular and molecular aspects of periodontal regeneration and determines the clinical relevance of these findings.

Does root surface conditioning with citric acid delay healing?

Effects of topical citric acid application on tissue maturation was studied in standardized periodontal defects in 6 beagle dogs. Following elevation of facial mucoperiosteal flaps, fenestration defects, 3 mm in diameter, were made through the cortical bone and recessed 0.5 mm into the dentin of maxillary canines. 1 defect in each dog was conditioned with a saturated solution of citric acid for 3 min and then rinsed with saline. Control defects in contralateral teeth were treated with saline only for the same length of time. The defects were covered with an expanded polytetrafluoroethylene membrane and the flaps repositioned and sutured. 14 days postsurgery, healing appeared more advanced along the defect walls and floor than in the center of the defect in all instances. Histometrically, citric acid-conditioned defects exhibited a higher density of collagen fibers along the defect walls and floor and adjacent to the barrier membrane as well as more advanced resolution of the residual blood clot than the surgical controls. Differences in fibroblast density within specimen pairs were non-significant. All control defects but none of the acid-conditioned defects showed an artifactual split between the dentin walls and the granulation tissue. This study failed to support the contention that topical application of citric acid to root surfaces may delay healing following periodontal surgery.

Collagen gel and membrane in guided tissue regeneration in periodontal fenestration defects in dogs

The effect of a collagen gel matrix as a submembranous space-maintaining material was evaluated in guided tissue regeneration procedures. In 4 dogs, contralateral surgical circular fenestration defects, 5 mm in diameter, were produced at the midbuccal aspect of the alveolar bone in 8 maxillary canines. Removal of bone, PDL and cementum was complete. Experimental sites were filled with collagen gel and covered with collagen membranes; control sites were covered with collagen membranes and the underlying space was spontaneously filled with blood. Mucogingival flaps were repositioned. Histological and histomorphometric observations, 6 weeks post-surgery, indicated that defects covered by collagen membranes presented the most impressive regeneration with almost complete coverage of the denuded root by new cementum (98.4%) and new bone (63.2%). In the experimental defects, 83.5% coverage of new cementum with only 21.9% new bone regeneration was observed. These results suggest that collagen gel, interfered with healing by PDL and bone-derived cells in the submembranous space.

Extracellular matrix interactions during the in vivo degradation of collagen membranes in the rat skin: immunohistochemical distribution of collagen types IV, V, and VI

The role of collagen implant material (CIM) in periodontology is of considerable interest to the clinical dentist because of the capacity of connective tissue (CT) regeneration and partial prevention of epithelial cell migration onto the root surface. The aim of this study was to demonstrate alterations of the CT matrix after the use of CIM in subcutaneous pockets in the rat skin. We used 15 rats in this study. After sedation, two subcutaneous pockets (2 cm in length) were surgically made in the animals' backs. Collagen membranes were implanted in one of the two pockets (test site). The other pocket served as control. Then, 4, 7, 14, 21, and 28 days after implantation, the animals were sacrificed and biopsies preserved for histologic and immunohistochemical examination. Incubation with antibodies against CT matrix components (collagen type IV, V, and VI) were used for immunostaining. Histologically, the CIM was migrated by inflammatory cells in the first 7 days. Newly formed fibroblasts and blood vessels (BV) were present 14 days postimplantation. Collagen type IV was localized in the basement membranes of the epithelium, BV, and nerves. An increase in the BV amount was demonstrated around (and later in) the implant material. Collagen type V was found in a filament pattern of distribution and was inserted into the implant after 4 weeks of healing. Collagen type VI showed a microfibrillar pattern of distribution with a delayed formation in the graft mass. The data showed the alterations of the matrix after implantation of collagen type I membranes in the rat skin.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative clinical study: the use of human type I collagen with and without the addition of metronidazole in the GTR method of treatment of periodontal disease

This investigation was undertaken to evaluate cross-linked human type I collagen, with and without added metronidazole, when used as a barrier membrane in the guided tissue regeneration (GTR) principle of treatment for periodontal disease. 16 patients suffering from moderate to severe periodontitis with 78 bilaterally matched periodontal defects underwent similar contralateral surgical flap procedures after preliminary scaling, polishing and oral hygiene instruction. At the experimental sites, which were selected at random, the flap was closed over metronidazole impregnated collagen as a GTR membrane, the contralateral sites receiving a plain collagen barrier as control. The plaque index (PLI), gingival index (GI), bleeding index (BI), probing pocket depth (PPD) and probing attachment level (PAL) were recorded at baseline, 6, 12 and 26 weeks post-operatively. The bony defects were classified and furcation involvement noted. The clinical parameters were recorded by an examiner, other than the surgeon, who had been previously assessed for accurate reproducibility of measurements and was unaware of the experimental sites. PPD and PAL were measured with a constant pressure probe, localised by a soft stent. Post-operative discomfort was evaluated by means of a questionnaire. PLI, GI and BI were significantly improved compared to baseline for both test and control sites at 6, 12 and 26 weeks post surgery (p < 0.001) but there was no significant difference between these sites (p > 0.05). There was a reduction in PPD at 6 weeks which was significant at 12 and 26 weeks post-operatively (p < 0.001) for both test and control sites, but no difference between these sites was evident (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a collagen matrix on healing in periodontal fenestration defects in dogs

Contralateral periodontal fenestration defects in seven beagle dogs were used to evaluate influence of a collagen matrix on periodontal wound healing. The defects (6 x 4 mm) were created through the buccal cortical plates of the maxillary canine teeth following elevation of mucoperiosteal flaps. The collagen was fitted to the defects on one side. Contralateral defects served as controls. Flaps were repositioned and sutured. Dogs were sacrificed 4 weeks after surgery and block sections including teeth and surrounding structures were prepared for histometric analysis. No meaningful differences in cementum and bone regeneration were observed between treatments. There was seemingly more bone regeneration in the apical than in the coronal aspect of the defects and significantly more cementum regeneration. Root resorption was observed in one collagen and one control defect. Ankylosis was not observed. The results suggest that the maxillary canine periodontal fenestration defect can be used as a model to evaluate factors that may enhance cementum and bone regeneration. The collagen matrix neither enhanced nor inhibited periodontal wound healing in this model.

Clinical evaluation of a biodegradable collagen membrane in guided tissue regeneration

A bio-resorbable type I collagen membrane was investigated as a barrier for guided tissue regeneration. Ten human subjects with at least one pair of contralateral periodontal lesions with probing pocket depths of greater than or equal to 5 mm and radiographic evidence of greater than or equal to 40% bone loss were included. Each patient underwent contralateral surgical flap procedures. A collagen barrier was adapted to the tooth in the experimental defect and the flap replaced and sutured. The controls consisted of the same procedure without the placement of the barrier. Standardized measurements of change in probing attachment levels and fill of intrabony defects were obtained at the time of surgery and 1 year later at the time of surgical re-entry. The differences in change of probing attachment levels and amount of bone fill between individual test and control sites were compared utilizing the student's t-test for paired samples. The mean probing attachment gain in the test sites was 0.56 +/- 0.57 mm, and there was a mean probing attachment loss of 0.71 +/- 0.91 mm in the control sites (P less than 0.01). The gain of bone in test lesions was 1.16 +/- 0.95 mm, while no gain was observed in the control lesions (P less than 0.01). The results of this study demonstrated that sites treated with a collagen barrier comprised of cross-linked bovine Type I collagen exhibited significantly better healing as compared to control sites over the 1-year period of the study.

Collagen linkage in periodontal connective tissue reattachment. An ultrastructural study in beagle dogs

Early stages of connective tissue reattachment to surgically denuded cementum and root dentin following citric acid application were studied in fenestration wounds. Block specimens were obtained after seven, 14, and 21 days. Continuity between newly deposited collagen fibrils in the granulation tissue and unmasked dental matrix collagen had been established within seven days by interdigitation of fibrils in an up to 0.5 micron-wide zone at the cementum or dentin surface. Splicing of collagen at the fibrillar level by direct attachment to the severed end of matrix fibrils or by juxtapositioning of new and old fibrils was seen in rare instances only. At 14 and 21 days, distinct bundles of collagen fibrils inserted deeply into the orifice of dentinal tubules. Arrested and reversed surface resorption was encountered at all time points. At these sites as well, new collagen fibrils interdigitated with denuded matrix collagen, while some resorbed surfaces were characterized by absence of collagen continuity. The results lend continued support to the concept of reattachment based on interdigitation of collagen fibrils. However, since attachment is established even in the absence of this feature, a significant role for specific attachment substances not shown can also be postulated.