Periodontal repair in dogs: gingival tissue occlusion, a critical requirement for GTR?

BACKGROUND

Design criteria for guided tissue regeneration (GTR) devices include biocompatibility, cell occlusion, space maintenance, tissue integration, and ease of use. Previous studies have established the importance of wound stabilization and space provision during the early healing sequel for successful GTR outcomes as well as evaluated biocompatibility, tissue integration, and clinical manageability of various biomaterials. The importance of cell or tissue occlusion has yet to be established. The objective of this study was to evaluate the role of tissue occlusion as a critical determinant for GTR outcomes.

METHODS

Routine, critical size, 5-6 mm, supra-alveolar, periodontal defects were created around the mandibular premolar teeth in six young adult Beagle dogs. Space-providing expanded polytetrafluoroethylene (ePTFE) membranes, with (macroporous) or without (occlusive) 300- microm laser-drilled pores, 0.8 mm apart, were implanted to provide for GTR. Treatments were randomly assigned to left and right jaw quadrants in subsequent animals. The gingival flaps were advanced to cover the membranes and sutured. The animals were euthanized at 8 weeks postsurgery for histologic and histometric analysis.

RESULTS

Three animals experienced wound failure within 2-3 weeks postsurgery resulting in exposure and removal of the occlusive ePTFE membranes. All defect sites, irrespective of membrane configuration or history of membrane exposure and removal, exhibited substantial evidence of periodontal regeneration including a functionally oriented periodontal ligament. To evaluate the biologic potential of GTR devices, only animals without wound failure and membrane removal were included. Alveolar bone regeneration for animals receiving occlusive and macroporous ePTFE membranes averaged (+/-sd) 3.2+/-1.1 versus 2.0+/-0.4 mm (p=0.3113). Cementum regeneration was enhanced in defect sites receiving the occlusive ePTFE membrane compared to the macroporous membrane (4.7+/-0.4 versus 2.3+/-0.2 mm; p=0.0167). Ankylosis was observed in one animal. Limited root resorption was observed in a second animal.

CONCLUSION

Tissue occlusion does not appear to be a critical determinant for GTR. However, tissue occlusion may be a requirement for optimal GTR. Moreover, macroporous space-providing devices may increase the predictability of clinical GTR therapy.

Effect of recombinant human bone morphogenetic protein-2 in dehiscence defects with non-submerged immediate implants: an experimental study in Cynomolgus monkeys

BACKGROUND

Alveolar ridge aberrations commonly compromise optimal dental implant installation. To offset any variance between an aberrant alveolar ridge and prosthetic designs, bone augmentation procedures become necessary. The objective of this study was to evaluate bone formation and osseointegration at alveolar dehiscence defects following augmentation of the defect site with recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) at dental implant installation including transmucosal positioning of the dental implant.

METHODS

Four adult male Cynomolgus monkeys received dental implants in contralateral extraction socket sites with surgically created 6 x 4 mm buccal dehiscence defects following elevation of mucoperiosteal flaps. Contralateral sites received rhBMP-2/ACS (rhBMP-2 at 1.5 mg/ml; 0.1 mg/defect) or served as sham-surgery controls. The flaps were adapted and sutured around the healing abutments leaving the implants in a transmucosal position. The animals were sacrificed at 16 weeks postsurgery and block sections of the implant sites were harvested and prepared for histometric analysis.

RESULTS

One dental implant from each treatment group failed to osseointegrate. Another 3 dental implants (sham-surgery controls) failed to osseointegrate with newly-formed bone in the defect area. Thus, 7 of 8 defect sites (4/4 animals) receiving rhBMP-2/ACS compared to 4 of 8 sites (2/4 animals) receiving sham-surgery exhibited evidence of osseointegration with newly formed bone in the defect area. Mean +/- SD defect height amounted to 5.3 +/- 0.2 and 5.4 +/- 0.1 mm for the rhBMP-2/ACS and sham-surgery sites, respectively. Vertical bone gain in rhBMP-2/ACS treated defects (3.9 +/- 0.3 mm) did not differ significantly from that in the sham-surgery control (3.7 +/- 0.4 mm; P > 0.05; paired t-test, N = 4). There were also no significant differences noted for coronal bone-implant contact (3.0 +/- 0.6 versus 3.6 +/- 0.5 mm), and bone-implant contact within the defect site (28.5% +/- 15.1% versus 27.4% +/- 31.7%) and within resident bone (46.9% +/- 26.8% versus 47.8% +/- 39.4%) for the rhBMP-2/ACS and control sites, respectively.

CONCLUSIONS

The observations in this study point to a substantial native osteogenic potential of the alveolar process that has previously not been explored and show that surgical reentry observations of new bone formation may not necessarily indicate that osseointegration has occurred. Bone formation in control defects was substantially greater than predicted, limiting the value of adding an osteoinductive biologic construct.

Periodontal repair in dogs: evaluation of a bioabsorbable space-providing macroporous membrane with recombinant human bone morphogenetic protein-2

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) technologies have been shown to significantly support alveolar bone formation. Biomaterial limitations, however, have restricted the biologic potential for onlay indications. The objective of this study was to evaluate regeneration of alveolar bone and periodontal attachment, and biomaterials reaction following surgical implantation of a space-providing, bioabsorbable, macroporous, polyglycolic acid-trimethylene carbonate (PGA-TMC) membrane combined with a rhBMP-2 construct in a discriminating onlay defect model.

METHODS

Routine supraalveolar periodontal defects were created at the mandibular premolar teeth in 9 beagle dogs. Contralateral jaw quadrants in subsequent animals were randomly assigned to receive the dome-shaped PGA-TMC (100 to 120 microm pores) membrane with rhBMP-2 (0.2 mg/mL) in a bioresorbable hyaluronan (Hy) carrier or the PGA-TMC membrane with Hy alone (control). The gingival flaps were advanced to submerge the membranes and teeth and sutured. Animals were euthanized at 8 and 24 weeks postsurgery for histologic observations.

RESULTS

Jaw quadrants receiving the PGA-TMC membrane alone experienced exposures at various time points throughout the study. Jaw quadrants receiving the PGA-TMC/rhBMP-2 combination remained intact, although one site experienced a late minor exposure. Newly formed alveolar bone approached and became incorporated into the macroporous PGA-TMC membrane in sites receiving rhBMP-2. The PGA-TMC biomaterial was occasionally associated with a limited inflammatory reaction. Residual PGA-TMC could not be observed at 24 weeks postsurgery. Residual Hy could not be observed at any time interval. Regeneration of alveolar bone height (means +/- SD) was significantly increased in sites receiving the PGA-TMC/rhBMP 2 combination compared to control (3.8 +/- 1.3 versus 0.7 +/- 0.5 mm at 8 weeks and 4.6 +/- 0.8 versus 2.1 +/- 0.4 mm at 24 weeks; P < 0.05). Limited cementum regeneration was observed for PGA-TMC/rhBMP-2 and PGA-TMC control sites. Ankylosis compromised regeneration in sites receiving PGA-TMC/rhBMP-2.

CONCLUSIONS

The bioabsorbable, space-providing, macroporous PGA-TMC membrane appears to be a compatible biomaterial for bone augmentation procedures. rhBMP-2 significantly enhances alveolar bone augmentation and soft tissue healing when combined with the PGA-TMC membrane.

RhBMP-2/alphaBSM induces significant vertical alveolar ridge augmentation and dental implant osseointegration

BACKGROUND

Recombinant human bone morphogenetic protein 2 (rhBMP-2) in a carrier has been shown to induce significant bone formation. Several candidate carriers, however, lack structural integrity to offset compressive forces that may compromise rhBMP-2 bone induction, in particular, for challenging onlay indications such as alveolar ridge augmentation.

PURPOSE

The objective of this study was to evaluate rhBMP-2 in a calcium-phosphate cement carrier, alphaBSM, for vertical alveolar ridge augmentation and immediate dental implant osseointegration.

MATERIALS AND METHODS

Six adult Hound Labrador mongrels with 5 mm critical size supra-alveolar peri-implant defects were used. Three animals received rhBMP-2/alphaBSM (rhBMP-2 at 0.40 and 0.75 mg/mL) in contralateral jaw quadrants (total implant volume/defect approximately 1.5 mL). Three animals received alphaBSM without rhBMP-2 (control group). The animals were euthanized at 16 weeks post surgery, and block biopsies were processed for histologic and histometric analysis.

RESULTS

rhBMP-2/alphaBSM induced substantial augmentation of the alveolar ridge. Control sites exhibited limited new bone formation. Vertical bone augmentation averaged (+/- SD) 4.9 +/- 1.0 mm (rhBMP-2 at 0.40 mg/mL), 5.3 +/- 0.3 mm (rhBMP-2 at 0.75 mg/mL), and 0.4 +/- 0.4 mm (control); new bone area 8.5 +/- 4.2 mm2, 9.0 +/- 1.9 mm2, and 0.5 +/- 0.4 mm2; new bone density 55.1 +/- 6.4%, 61.1 +/- 6.0%, and 67.7 +/- 9.5%; and new bone-implant contact 26.9 +/- 17.5%, 28.5 +/- 1.4%, and 24.6 +/- 16.1%, respectively. Residual alphaBSM comprised < 1% of the new bone. Bone density for the contiguous resident bone ranged from 65 to 71%, and bone-implant contact ranged from 49 to 64%.

CONCLUSIONS

Surgical implantation of rhBMP-2/alphaBSM appears an effective protocol for vertical alveolar ridge augmentation procedures and immediate dental implant osseointegration and for onlay indications of lesser complexity.

Effect of surgical implantation of recombinant human bone morphogenetic protein-2 in a bioabsorbable collagen sponge or calcium phosphate putty carrier in intrabony periodontal defects in the baboon

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) in a proper carrier has been shown to induce clinically relevant bone formation for several oral/maxillofacial and periodontal indications and to stimulate regeneration of the periodontal attachment. The objective of this study is to evaluate regeneration of alveolar bone, cementum, periodontal ligament, and associated root resorption and ankylosis following surgical implantation of rhBMP-2 in an absorbable collagen sponge (ACS) or a calcium phosphate putty (alphaBSM) carrier in 3-wall intrabony periodontal defects in the baboon.

METHODS

rhBMP-2/ACS and rhBMP-2/alphaBSM were implanted in surgically produced, maxillary and mandibular, large size, 3-wall intrabony defects in 4 baboons. Contralateral jaw quadrants were implanted with buffer/ACS, buffer/ alphaBSM, or served as sham-operated surgical controls. Treatments were allocated to left and right, maxillary and mandibular, jaw quadrants following a randomization schedule. Four months following implantation, block biopsies of defect sites were obtained, processed, and subjected to histologic and histometric analysis.

RESULTS

Defect sites receiving rhBMP-2/ACS and rhBMP-2/alphaBSM demonstrated significantly greater regeneration than controls. No significant differences were observed between defect sites receiving rhBMP-2/ACS or rhBMP-2/alphaBSM regarding epithelial migration and connective tissue attachment and new bone formation. However, rhBMP-2/ACS supported significantly greater new cementum formation. Ankylosis or root resorption were not observed.

CONCLUSIONS

The results of this study support the use of rhBMP-2 to enhance periodontal regeneration of intrabony periodontal defects. While this novel technology holds promise, refinement in carrier systems may provide the key to enhancement of the regenerative potential.

Bone repair following recombinant human bone morphogenetic protein-2 stimulated periodontal regeneration

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable sponge (ACS) carrier is currently being evaluated as candidate therapy for periodontal regeneration. The objective of this study was to characterize, in some detail, tissue reactions following surgical implantation of rhBMP-2/ACS into periodontal defects.

METHODS

Four young adult, male beagle dogs with surgically induced, bilateral, critical size, supra-alveolar, mandibular premolar defects sequentially received rhBMP-2/ACS (rhBMP-2 at 0.2 mg/ml) in right and left jaw quadrants. After 4 or 8 weeks of healing, experimental teeth with surrounding tissues were harvested and processed for light and transmission electron microscopy.

RESULTS

Surgical implantation of rhBMP-2/ACS into large supra-alveolar periodontal defects resulted in a variable tissue response without marked difference between 4- and 8-week observations. New bone, exceeding the volume of the normal alveolar process, had formed within 4 weeks. The regenerated bone tissue consisted of finely trabeculated woven bone. Marrow spaces exhibited a continuous lining of osteoblasts, osteoclasts, and resting cells. The marrow spaces contained numerous large, thin-walled vessels but were almost devoid of collagen fibrils or fibroblasts. Large voids (seromas) encountered in the newly formed bone were free of structured elements except for occasional aggregates of effete erythrocytes. A variety of tissue reactions were observed along the root surface including areas of resorption, areas of hard tissue deposition, and areas without resorptive or appositional activity. Ankylosis was a frequent observation, although areas showing characteristics of a periodontal ligament with a fine layer of acellular fiber cementum and occasional inserting Sharpey's fibers were also observed. Osteoblasts facing the root surface often appeared to be in a highly active state judged by their cuboidal shape, well-developed endoplasmic reticulum and numerous mitochondria, and the presence of an adjacent layer of preosteoblasts. Conspicuous bundles of wide collagen fibrils near the dentin surface as well as within the marrow spaces were considered to represent remnants of the ACS. These fibrils were associated with areas of mineralization as verified by examination of undecalcified specimens.

CONCLUSIONS

rhBMP-2/ACS elicits a rapid osteoinductive process throughout the implant as well as along and onto the instrumented adjacent root surface. Lamellated trabecular bone was the predominant regenerated tissue. A typical cementum-periodontal ligament-alveolar bone relationship was a rare observation. The great variability in histological tissue response along the instrumented root surface indicates that the stimulus to hard tissue formation resided primarily in the rhBMP-2/ACS implant rather than in the root surface.

Healing patterns in calvarial bone defects following guided bone regeneration in rats. A micro-CT scan analysis

OBJECTIVE

The objective of this study was to evaluate healing patterns of critical-size calvarial bone defects treated according to principles of guided bone regeneration using micro-CT scan analysis. Specifically, the contribution of bone, periosteum and dura mater to the amount and mineralization of newly formed bone was evaluated.

MATERIAL AND METHODS

Surgically induced, critical-size calvarial bone defects in 48 adult male Wistar rats received the following: an occlusive expanded polytetrafluoroethylene (ePTFE) membrane at the exo- and endocranial aspect (OO; n = 12); an occlusive membrane at the exocranial and a perforated membrane at the endocranial aspect (OP; n = 12); a perforated membrane at the exocranial and an occlusive membrane at the endocranial aspect (PO; n = 12); and a perforated membrane at the exo- and endocranial aspect (PP; n = 12). The animals were euthanized at 4 weeks for quantitative analysis of bone volume fraction and mineralization in the region of interest (ROI) as well as in the external, middle and central area of the defect using micro-CT.

RESULTS

Bone volume fraction ranged from 31.4% (OP) to 24.5% (PP). No differences were found among the groups. Bone volume fraction and mineralization in the middle area were significantly greater in group OP than in group PP, and in the central area in group OO and PO than in group PP.

CONCLUSIONS

The results of this study suggest that use of occlusive ePTFE membranes enhances bone formation and maturation in the calvarial skeleton. When occlusion of endo- and exocranial tissues was compromised by membrane perforation, impaired bone formation and mineralization were observed.

Prevalence and severity of periodontal disease at mandibular molar teeth in smokers with regular oral hygiene habits

BACKGROUND

Smoking appears to be detrimental to health because it has been associated with several diseases including cancer and cardiovascular diseases. Smoking also appears to be a major environmental factor associated with periodontal disease progression. The objective of this study was to evaluate the prevalence and severity of periodontal destruction as influenced by smoking in a Thai population.

METHODS

Gingival health and periodontal conditions at mandibular molar furcation sites in 120 Thai dental patients (60 smokers and 60 never-smokers, age range 31 to 60 years) with generally high oral hygiene standards and regular dental care habits were evaluated.

RESULTS

Smokers exhibited more frequent and severe mandibular molar periodontal destruction than never-smokers. The prevalence and severity of gingival recession, periodontal pocket formation, clinical attachment loss, furcation involvement, and tooth mobility were significantly increased in smokers compared to never-smokers. Seventy-three percent of the smokers exhibited furcation involvement in contrast to only 20% of the never-smokers.

CONCLUSIONS

The results of this study suggest that smoking appears to be a major environmental factor associated with accelerated periodontal destruction in adult smokers with generally high oral hygiene standards and regular dental care habits in a Thai population.

Peri-implant bone regeneration using recombinant human bone morphogenetic protein-2 in a canine model: a dose-response study

The objective of this study was to evaluate the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) dose on alveolar ridge augmentation and dental implant osseointegration. Bilateral, 5 mm supraalveolar, peri-implant defects were surgically created in 6 beagle dogs. rhBMP-2 (0.05, 0.1 or 0.2 mg/ml) in an absorbable collagen sponge (ACS) carrier was molded around the fixtures and wounds were closed. Treatment variations were alternated between animals (incomplete block design). Animals were sacrificed at week 8 postsurgery. Nine of twelve jaw quadrants healed uneventfully. Two jaw quadrants exhibited wound failure by week 4 and one by week 8 postsurgery. Radiographic bone regeneration was observed in defects without wound failure from week 4 postsurgery. Radiolucent voids of variable size and shape were observed and regressed over time. In weeks 6 through 8, there was an apparent increase in bone density and trabecular structure, while bone height and volume decreased. Histometric analysis revealed limited differences in bone regeneration between experimental conditions. Bone regeneration area averaged (+/- SD) 1.0 +/- 0.5, 3.5 +/- 1.4 and 2.3 +/- 0.4 mm2 for the 0.05, 0.1 and 0.2 mg/ml dose, respectively. There were no significant differences in osseointegration. Osseointegration in newly formed bone averaged 19 +/- 4%, 18 +/- 10% and 21 +/- 6% for the 0.05, 0.1 and 0.2 mg/ml rhBMP-2 sites, respectively. Collectively, the data suggest that there are no dramatic differences in bone induction and osseointegration within the selected dose and observation interval.

Effect of recombinant human bone morphogenetic protein-2/absorbable collagen sponge (rhBMP-2/ACS) on healing in 3-wall intrabony defects in dogs

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge (ACS) carrier is being evaluated as a candidate therapy for periodontal regeneration. The objective of this study was to evaluate regeneration of alveolar bone and cementum, and associated root resorption and ankylosis following surgical implantation of rhBMP-2/ACS in a canine clinical model.

METHODS

Bilateral 3-wall intrabony periodontal defects were surgically induced in the premolar region in the maxilla and mandible in 8 young adult Korean mongrel dogs. The defects in each animal received rhBMP-2/ACS (rhBMP-2 at 0.2 mg/ml, total implant volume/defect approximately 0.1 ml) or buffer/ACS, or served as sham-operated controls. Surgeries were sequenced for each animal to provide postmortem observations following 8- and 24-week healing intervals. Treatment outcomes were evaluated using clinical, radiographic, and histometric parameters.

RESULTS

Surgical implantation of rhBMP-2/ACS resulted in accelerated enhanced bone formation in the 3-wall intrabony periodontal defects but in no apparent enhancement of cementum regeneration. rhBMP-2/ACS did not appear to be associated with aberrant healing events such as root resorption and ankylosis under these simulated clinical conditions.

CONCLUSIONS

Surgical implantation of rhBMP-2/ACS may be used safely to support regeneration of alveolar bone in intrabony periodontal defects in dogs without aberrant events such as root resorption or ankylosis complicating the regenerative procedure. rhBMP-2/ACS does not appear to have a significant effect on cementum regeneration and formation of a functional periodontal ligament in this model.