Ulf M. E. Wikesjo

Periodontal Repair in Dogs: Evaluation of a Bioabsorbable Space-Providing Macro- Porous Membrane with Recombinant Human Bone Morphogenetic Protein-2

BACKGROUNDnRecombinant 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 spaceproviding, bioabsorbable, macroporous, polyglycolic acid-trimethylene carbonate (PGA-TMC) membrane combined with a rhBMP-2 construct in a discriminating onlay defect model.nnnMETHODSnRoutine 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 domeshaped PGA-TMC (100 to 120 μm 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.nnnRESULTSnJaw 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.nnnCONCLUSIONSnThe bioabsorbable, space-providing, macroporous PGA-TMC membrane appears to be compatible biomaterial for bone augmentation procedures. rhBMP-2 significantly enhances alveolar bone augmentation and soft tissue healing when combined with the PGA-TMC membrane. J Periodontol 2003; 74:635-647.

CEMENTAL TEAR RELATED TO RAPID PERIODONTAL BREAKDOWN : A CASE REPORT

Cemental tears have been described both in exposed and unexposed cementum. The phenomenon is believed to be elicited by overloading or acute trauma from occlusion. In this case report a patient, with a history of periodontal health, presented with an acute periodontal lesion on the distal aspect of a bridge abutment tooth. Periapical radiographs demonstrated an extensive vertical intrabony defect adjacent to the vital abutment tooth containing a radiopaque foreign body. Histological examination of the surgically removed foreign body revealed a piece of dental cementum with some attached soft tissue. The lesion responded well to a surgical approach. Healing was uneventful and periodontal health was restored. This case illustrates that cemental tear should be considered as a differential diagnostic entity in isolated sites with rapid periodontal breakdown. J Periodontol 1992;63:220-224.

PERIODONTAL REGENERATION AROUND NATURAL TEETH

1. Evidence is conclusive (Table 2) that periodontal regeneration in humans is possible following the use of bone grafts, guided tissue regeneration procedures, both without and in combination with bone grafts, and root demineralization procedures. 2. Clinically guided tissue regeneration procedures have demonstrated significant positive clinical change beyond that achieved with debridement alone in treating mandibular and maxillary (buccal only) Class II furcations. Similar data exist for intraosseous defects. Evidence suggests that the use of bone grafts or GTR procedures produce equal clinical benefit in treating intraosseous defects. Further research is necessary to evaluate GTR procedures compared to, or combined with, bone grafts in treating intraosseous defects. 3. Although there are some data suggesting hopeful results in Class II furcations, the clinical advantage of procedures combining present regenerative techniques remains to be demonstrated. Additional randomized controlled trials with sufficient power are needed to demonstrate the potential usefulness of these techniques. 4. Outcomes following regenerative attempts remain somewhat variable with differences in results between studies and individual subjects. Some of this variability is likely patient related in terms of compliance with plaque control and maintenance procedures, as well as personal habits; e.g., smoking. Variations in the defects selected for study may also affect predictability of outcomes along with other factors. 5. There is evidence to suggest that present regenerative techniques lead to significant amounts of regeneration at localized sites on specific teeth. However, if complete regeneration is to become a reality, additional stimuli to enhance the regenerative process are likely needed. Perhaps this will be accomplished in the future, with combined procedures that include appropriate polypeptide growth factors or tissue factors to provide additional stimulus.

Effects of cyclosporin A on the mandibular condylar cartilage in rats

Twenty, 5-week-old, male, Sprague-Dawley rats were divided into a control and a cyclosporin A (CSA) group for evaluating effects of the drug on condylar cartilage. Animals in the treatment group daily received CSA (15 mg/kg body wt) in mineral oil by gastric feeding over a 4-week observation interval. Control animals received mineral oil only. Five animals from each group were killed at weeks 2 and 4 of study. After histological processing, five tissue sections from the mid-region of the condyle were selected and examined. Three compositional zones (articular fibrous, proliferative, and hypertrophic) of the superior, posteriosuperior and posterior regions of the condylar cartilage were evaluated by light microscopy. At week 2, total condylar cartilage thickness was similar in the CSA and control groups, but the thickness of each zone was altered in CSA-treated animals, including a decrease of the fibrous and proliferative zones and an increase in hypertrophic zone compared to control (P<0.05). At week 4, CSA-treated animals exhibited overall decreased cartilage thickness, including decreased thickness of each zone compared to control (P<0.05). The results suggest that CSA has an inhibitory effect on the maturation of the mandibular condyle in rats.