Temperature-responsive size-exclusion chromatography using poly(N-isopropylacrylamide) grafted silica

This article reviews studies presented during the last 20 years on the surgical treatment of intrabony defects. Treatments include open flap debridement alone (OFD); OFD plus demineralized freeze-dried bone allograft (DFDBA), freeze-dried bone allografts (FDBA), or autogenous bone; and guided tissue regeneration (GTR). The review includes only studies that presented baseline and final data on probing depths, intrabony defect depths as measured during surgery, clinical attachment level (CAL) gain, and/or bone fill. Some reports were case studies and some controlled studies comparing different treatments. In order to assess what can be accomplished in terms of pocket reduction, clinical attachment level gain, and bone fill with the various treatment modalities, data from studies of each treatment category were pooled for meta-analysis in which the data from and power of each study were weighted according to the number of defects treated. In addition, where there were data for each individual defect treated, these were used for simple regression analysis evaluating the influence of intrabony defect depth on treatment outcome in terms of CAL gain and bone fill. This was done in an effort to assess some predictability of the outcome of the various treatments. OFD alone resulted in limited pocket reduction, CAL gain averaged 1.5 mm and bone fill 1.1 mm. Bone fill, but not CAL gain, correlated significantly to the depth of the defect (R=0.3; P < 0.001), but the regression coefficient was only 0.25. OFD plus bone graft resulted in limited pocket reduction. CAL gain and bone fill averaged 2.1 mm. Bone fill showed a somewhat stronger correlation to defect depth than following OFD alone (R=0.43; P < 0.001) with a regression coefficient of 0.37. GTR resulted in significant pocket reduction, CAL gain of 4.2 mm, and bone fill averaging 3.2 mm. CAL gain and bone fill correlated significantly (P < 0.001) to defect depth (R=0.52 and 0.53 respectively) with the largest regression coefficients (0.54 and 0.58 respectively) among the three treatment modalities. By comparing outcomes following the various treatments it became obvious that to benefit from GTR procedures, the intrabony defect has to be at least 4 mm deep.     

Guided tissue regeneration update

The ultimate goal of periodontal therapy is to restore periodontal tissues lost through disease or trauma. The most predictable way to accomplish this goal is by guided tissue regeneration (GTR). The principle of GTR is to give preference to certain cells to repopulate the wound area to form a new attachment apparatus. Clinically this is accomplished by placing a barrier over the defect thereby excluding gingival tissues from the wound during early healing. The first generation of GTR barriers were non-resorbable which implies that they have to be removed in a second surgical procedure. Resorbable barriers have recently been introduced, changing GTR into a single-step procedure. Periodontal defects that will predictably benefit from GTR therapy are intrabony, furcation class II and gingival recession defects. This paper reviews the scientific evidence of what can be achieved by GTR procedures for various periodontal defects as well as factors of importance to increase the predictability of a successful treatment outcome.     

Stress and coping behaviors of substance-abusing mothers

BACKGROUND: The guided regeneration of periodontal tissues demonstrated to represent a therapeutical technique with predictable results. It has been observed that different materials, used as regenerative membranes, offer very similar results. Unconventional materials too, like the rubber dam, seem to be useful in the guided tissues regeneration technique. The object of the present study has been to comparatively evaluate the effectiveness of Gore-Tex and rubber dam-made membranes in the therapy of intra-osseous periodontal defects. MATERIALS AND METHODS: Six patients with two similar intra-osseous defects, participated in the study; one defect has been treated using, during the surgical intervention, a Gore-Tex membrane, while the other has received, a fragment of sterile rubber dam membranes. The principal clinical parameters of the periodontal health (probing depth -PD- and attachment loss -AL-) has been evaluated in both the defects before and 6 months after the periodontal surgery. RESULTS AND CONCLUSIONS: The results have showed that there are not statistically significant differences (p > 0.05) in the healing of the intra-osseous defects treated by rubber dam or Gore-Tex. The conclusion is drawn that the rubber dam can represent a valid and cheap alternative to the materials traditionally used in the regenerative surgery of the periodontal tissues.     

Postoperative healing complications associated with Gore-Tex Periodontal Material. Part II. Effect of complications on regeneration

The gain in open probing attachment level as a result of a guided tissue regeneration procedure with Gore-Tex Periodontal Material was measured in 62 sites. The incidence of complications was evaluated. When sites with a complication were compared to those without the complication, there was no statistically different gain or loss of newly regenerated tissue. However, the occurrence of sloughing of the gingival flap decreased the amount of gain in open probing attachment level. Analysis of the data also revealed that the combined use of allografts and a delay in the removal of the Gore-Tex Periodontal Material had a synergistic positive effect on the gain in open probing attachment level. No association between these treatment variables and the incidence of the complications was found.     

Regenerative periodontal therapy in mucogingival surgery for root coverage

This article illustrates the potential benefits of regenerative periodontal therapy in mucogingival surgery and esthetic dental treatment. Cases are described in which the treatment of soft-tissue recessions and root exposures are treated with surgical procedures where both clinical soft-tissue augmentation and the regeneration of periodontal attachment are obtained. Cases are also presented to illustrate the clinical application of guided tissue regeneration. Resorbable and nonresorbable barriers are placed over the root surface and bone and covered by the overlying flap, which allows the selective repopulation of the lesion by progenitor cells and the inhibition of a long junctional epithelium. Emphasis is placed on regenerative procedures in soft-tissue augmentation, particularly with respect to rationales, techniques, and indications.     

Treatment of peri-implantitis using guided bone regeneration and bone grafts, alone or in combination, in beagle dogs. Part 1: Clinical findings and histologic observations

The purpose of this study was to evaluate and compare the treatment of ligature-induced peri-implantitis using guided bone regeneration and two bone grafts alone and in combination. Mandibular premolars and first molars were extracted from four beagle dogs and after 3 months of healing, three Br?nemark implants were placed on each side of the mandibles. Following abutment connection 3 months later, experimental peri-implantitis was induced by tying plaque-retentive ligatures around all abutments. Ligatures and abutments were removed after 3 months, and bony defects measured and treated with either: (1) debridement only; (2) debridement plus resorbable hydroxyapatite; (3) debridement plus canine freeze-dried demineralized bone; (4) debridement plus guided bone regeneration; (5) debridement plus resorbable hydroxyapatite and guided bone regeneration; or (6) debridement plus canine freeze-dried demineralized bone and guided bone regeneration. Pretreatment and 4-month-posttreatment comparison revealed a significant but variable degree of clinically appreciable hard tissue fill with all treatment procedures. Guided bone regeneration procedures resulted in the greatest fill, followed by bone grafts alone and flap debridement. There was no significant difference between guided bone regeneration and both guided bone regeneration/graft combinations; therefore, guided bone regeneration procedures appear to be a predictable treatment for plaque-induced peri-implant defects.     

Comparison of 2 regenerative procedures--guided tissue regeneration and demineralized freeze-dried bone allograft--in the treatment of intrabony defects: a clinical and radiographic study

The purpose of this study was to compare clinically and radiographically the effectiveness of guided tissue regeneration (GTR), using a bioabsorbable polylactic acid softened with citric acid ester barrier and commercially available demineralized freeze-dried bone allograft (DFDBA) in the treatment of 2- and 3-wall intrabony defects. Twelve patients each with one treated defect comprised each group. Conservative treatment was completed 2 to 4 months prior to surgery. Clinical measurements, plaque index, gingival index, probing depths (PD), clinical attachment levels (CAL) and recession (REC), were comparable in both groups at baseline. They were repeated at 12 months. Surgical measurements were also comparable at baseline in both groups. In the GTR group, at baseline the mean distance between the cemento-enamel junction (CEJ) and base of the defect was 12.3 +/- 2.9 mm and in the DFDBA group 11.3 +/- 1.8 mm. The defect depth was 6.3 +/- 2.0 mm and 5.4 +/- 1.3 mm, respectively. Radiographs were taken at baseline and 12 months later and compared using non-standardized digital subtraction radiography. In the GTR group, mean PD decreased from 7.9 +/- 2.5 mm to 3.5 +/- 1.4 mm and mean CAL from 10.8 +/- 2.8 mm to 7.0 +/- 1.6 mm, the differences being statistically significant (P = 0.002), while REC increased from 2.9 +/- 1.2 mm to 3.5 +/- 1.1 mm. In the DFDBA group, mean PD decreased from 7.1 +/- 1.1 mm to 3.5 +/- 1.1 mm and mean CAL from 9.8 +/- 1.5 mm to 6.6 +/- 1.7 mm (P = 0.002), while REC increased from 2.8 +/- 1.0 mm to 3.1 +/- 1.2 mm. No significant differences were found when the clinical results of the 2 groups were compared. Radiographic differences between the baseline and reconstructed images 12 months later were observed in both groups. Mean crestal bone resorption was 15.3 +/- 22.5% in the GTR group and 10.4 +/- 31.8% in the DFDBA group, and mean improvement in the distance between the CEJ and the base of the defect was 22.8 +/- 18.1% in the GTR group and 15.3 +/- 13.6% in the DFDBA group. However, the mean improvement in the intrabony depth was larger in the GTR group (71.9 +/- 29.1%) than in the DFDBA group (35.4 +/- 21.6%) (P = 0.007). In conclusion, within the limits of this study, both regenerative procedures were beneficial in treating intrabony defects. No statistical significant differences were observed between the 2 groups, with the exception of radiographic defect resolution which was significantly greater in the GTR group.     

Periodontal repair in intrabony defects treated with a calcium sulfate implant and calcium sulfate barrier

THIS RANDOMIZED, CONTROLLED, CLINICAL STUDY was designed to evaluate outcome following surgical implantation of an allogeneic, freeze-dried, demineralized bone matrix-calcium sulfate (DBM+CS) composite with a CS barrier in intrabony periodontal defects. Twenty-six patients contributing 26 deep intrabony defects completed the study. Thirteen patients received the DBM+CS implant. Thirteen patients received gingival flap surgery alone (GFS; control). Clinical outcome was assessed at 6 and 12 months postsurgery. At 12 months postsurgery, probing depth (PD) reduction (mean +/-SD) for the DBM+CS and GFS group was to 4.3+/-0.5 and 3.0+/-1.3 mm; clinical attachment gain was to 2.9+/-0.8 and 1.7+/-1.5 mm; and probing bone level gain was to 2.9+/-1.4 and 1.2+/-1.2 mm, respectively. There were no apparent differences between evaluations at 6 and 12 months postsurgery. Clinical improvements were significantly different from presurgery for both groups at both observation intervals (P < 0.01). There were no significant differences between groups in PD reduction and clinical attachment gain. Probing bone level gain was significantly greater in the DBM+CS group compared to controls (P < 0.05). In summary, surgical implantation of DBM+CS with a CS barrier resulted in reduced PD and improved attachment levels comparable to that achieved by gingival flap surgery alone. However, gain in probing bone levels in deep intrabony periodontal pockets assessed by clinical parameters was greater than that observed by gingival flap surgery alone. These changes were noted at both 6 and 12 months after surgery. This regenerative technique needs further biologic evaluation before being generally accepted.     

Clinical comparison of bioabsorbable barriers with non-resorbable barriers in guided tissue regeneration in the treatment of human intrabony defects

The purpose of the study was to compare the effects of guided tissue regeneration (GTR) with expanded polytetrafluoroethylene (ePTFE) non-resorbable barriers and polylactic acid bioabsorbable barriers in humans with intrabony defects due to periodontitis. Ten patients presented with 2 intrabony defects each. Mucoperiosteal flaps were performed. One of the defects was randomly assigned for placement of the ePTFE barrier over the roots and alveolar bone and the other defect with placement of the polylactic acid barrier. A minimum of 9 months after barrier placement, surgical reentry was performed. The data were evaluated by the Wilcoxon matched-pairs signed-ranks test and the Fisher exact test. Treatment with both types of barriers produced significant changes from baseline for all parameters, except in the ePTFE group for the amount of bony crest resorption (P = 0.055) and in the polylactic acid group for increased recession (P = 0.109). The results showed no significant differences between the barriers for any parameters: probing depth reduction (polylactic acid 2.60 +/- 1.90, ePTFE 2.80 +/- 1.40; P = 1.000); attachment gain (polylactic acid 1.40 +/- 1.43, ePTFE 1.90 +/- 1.29; P = 0.336); increased recession (polylactic acid 0.80 +/- 1.40, ePTFE 1.10 +/- 0.99; P = 0.531); amount of vertical bone fill (polylactic acid 1.60 +/- 1.84, ePTFE 2.00 +/- 2.49; P = 0.984); bony crest resorption (polylactic acid -1.30 +/- 1.06, ePTFE -1.30 +/- 1.63; P = 1.000); depth of bony defect reduction (polylactic acid 2.90 +/- 1.20, ePTFE 3.30 +/- 1.70; P = 0.750); width of bony defect reduction (polylactic acid 2.20 +/- 1.23, ePTFE 2.20 +/- 1.23; P = 0.875); or volumetric changes (polylactic acid 33.50 +/- 19.70 microl, ePTFE 34.00 +/- 18.40 microl; P = 0.750).     

The influence of endodontic treatment upon periodontal wound healing

The interrelationship between periodontal and endodontic disease has aroused much speculation, confusion, and controversy. Pulpal and periodontal problems are responsible for more than 50% of tooth mortality today. Diagnosis is often difficult since these diseases have been studied primarily as separate entities. The toxic substances of the pulp may initiate periodontal defects through canal ramifications and patent dentinal tubules, thus impairing wound healing in regenerative procedures. Although no studies exist addressing the direct effect of pulpal infection on the outcome of guided tissue regeneration (GTR) procedures, several studies do indicate that pulpal status may play a significant role toward the end results of GTR. This review article discusses the potential influence of endodontic treatment on the long-term outcomes of GTR. Potential pathways between the pulp and periodontal ligament, which may be responsible for the failure of the regeneration of new periodontal attachment apparatus, are explored. Examination and review of the clinical and research findings in the literature relating to perio-endo lesions are made to demonstrate that a negative influence may exist between GTR outcomes and the status of the pulp.     

Clinical comparison of resorbable and non-resorbable barriers for guided periodontal tissue regeneration

The purpose of this study was to compare the clinical results of guided periodontal tissue regeneration (GPTR) using a resorbable barrier manufactured from a copolymer of polylactic and polyglycolic acids (Resolut Regenerative Material) with those of non-resorbable e-PTFE barrier (Gore-Tex Periodontal Material). 12 subjects participated, 6 with similarly paired class II furcations and 6 with 2 similar 2, 3-wall periodontal lesions. The resorbable and non-resorbable barriers were randomly assigned to 1 defect in each subject. Non-resorbable barriers were removed in six weeks. Plaque index (PlI), gingival index (GI), probing depth (PD), clinical attachment level (CAL) and gingival recession (R) were recorded at baseline, (i.e., immediately prior to surgery) and at 12 months postsurgically. The clinical healing was similar and uneventful in both groups. Intrabony pockets depicted significant changes from baseline (p < 0.05) for probing depth reduction and gain in clinical attachment levels. No differences were found between treatments. Class II furcations showed significant improvements from baseline (p < or = 0.05) for probing depth reduction and clinical attachment gain. No differences were detected between treatments. It is concluded that the resorbable barrier tested is as effective as the nonresorbable e-PTFE barrier for the treatment of class II furcations and intrabony defects.     

Guided tissue regeneration in the esthetic zone

Common cosmetic failures in guided tissue regeneration (GTR) procedures performed in the esthetic zone include an unacceptable postoperative recession of the gingival flap and loss of the papillae. This article describes the dynamics of flap healing that contribute to esthetic failures. Specific technique modifications of GTR procedures that enhance the predictability of successful functional and esthetic outcomes are described.     

Preimplant guided bone regeneration in the anterior maxilla

Guided bone regeneration is a clinical procedure aimed at promoting bone formation at sites where there is severe bone loss. The purpose of this article was to demonstrate reconstruction of deformations of the alveolar process resulting from traumatic injuries to maxillary incisor teeth by guided bone regeneration procedures followed by insertion of dental implants. In both cases, submembranous space-making was stabilized by human demineralized freeze-dried bone. Implant insertion at the sites of bone augmentation resulted in successful restorations. Histologic examination of biopsy samples from the submembranous hard tissue revealed particles of demineralized freeze-dried bone allografts partially surrounded by uninflamed connective tissue and by vital bone adjacent and adhered to the demineralized freeze-dried bone allograft particles.     

Generalizability of the added benefits of guided tissue regeneration in the treatment of deep intrabony defects. Evaluation in a multi-center randomized controlled clinical trial

BACKGROUND: Several studies have shown that GTR therapy of intrabony defects results in significantly better outcomes than access flap alone. Most of the available data, however, have been produced in highly controlled research environments by a small group of investigators. Generalizability of results to different clinicians and different subject populations has not been evaluated so far. METHODS: This parallel group study involved 143 patients recruited in a practice-based research network of 11 offices in 7 countries. It was designed to evaluate: 1) the applicability of the documented added benefits of GTR in the treatment of intrabony defects to different populations, and 2) the generalizability of the expected results to different clinicians. GTR was compared to access flap alone. Defects, one in each patient, were accessed with a previously described papilla preservation flap in both the test and control group. In addition, GTR sites received application of a bioabsorbable poly-D,L-lactide-co-glycolide membrane. A stringent plaque control regimen was enforced in all patients during the 1-year observation period. Outcomes included gains in clinical attachment (CAL) and reductions in probing depth. RESULTS: Observed gains in CAL were 2.18 +/- 1.46 mm for access flap and 3.04 +/- 1.64 mm for the GTR-treated group. The treatment-associated difference was statistically significant (P = 0.03) after correcting for both center effect and defect anatomy. Among the various centers, a 1.73 mm difference in CAL gain was observed. This is a clinically relevant amount, which underlines the significance of center variability in the outcome of periodontal surgical procedures. A frequency distribution analysis of the obtained CAL gains indicated that GTR treatment of deep intrabony defects decreased, with respect to the access flap control, the probability of obtaining only a modest attachment gain at 1 year. Conversely, CAL gains of 4 mm or more were observed in more than 40% of GTR-treated defects and in less than 20% of the controls (P < 0.0001). CONCLUSIONS: These data indicate that GTR therapy of deep intrabony defects performed by different clinicians on various patient populations resulted in both greater amounts and improved predictability of CAL gains than access flap alone.     

Immunosuppression in therapy of glomerulonephritis

This study clinically evaluated a bioabsorbable barrier membrane designed for periodontal regeneration. Ten Class II furcations and 12 interproximal infrabony defects were treated by flap debridement and placement of a bioabsorbable barrier membrane using the principles of guided tissue regeneration. Treatment was evaluated in terms of changes in vertical probing depth, horizontal attachment level, clinical attachment level, and recession. Baseline data were collected on the day of surgery, and outcome measurements were performed at the 1-year appointment. The mean initial probing depth for Class II furcations was 6.5 mm. At 1 year, the mean probing depth was reduced to 2.9 mm, a 3.6 mm change. These differences were clinically and statistically significant (P < 0.01). There was a mean gain of 2.4 mm in clinical attachment level (P < 0.01) and a mean 3.4-mm change in horizontal attachment level (P < 0.01). Recession increased 1.2 mm. For interproximal infrabony defects, there was a mean probing depth reduction of 5.0 mm (P < 0.01), a mean gain of clinical attachment level of 3.8 mm (P < 0.02), and a mean increase of 1.2 mm in recession (P < 0.04). The results indicate that significant improvements occurred after treatment of Class II furcations and interproximal infrabony defects with the use of a bioabsorbable barrier membrane and guided tissue regeneration.     

Guided tissue regeneration. A status report for the American Journal of Dentistry

This report reviews clinical results which have been obtained with guided tissue regeneration (GTR) using non-resorbable and resorbable materials. The report highlights the clinical factors that affect and that should be considered in order to improve the predictability of the results obtained after GTR. The indications for GTR procedures are reviewed and the surgical technique is described. The importance of periodontal maintenance, and the significance of adjunctive therapies in GTR procedures are also discussed. Based upon the vast scientific information and clinical experience with GTR, it can be stated that with the use of either resorbable or non-resorbable materials a new attachment, determined both clinically and histologically, will be promoted providing that the principles of GTR are properly implemented.     

Treatment of deep and shallow intrabony defects. A multicenter randomized controlled clinical trial

This prospective multicenter intra-individual randomized controlled clinical trial was designed to compare the efficacy of guided tissue regeneration (GTR) with bioresorbable barrier membranes versus access flap surgery, in intrabony defects. 2 similar defects were selected in each of 23 patients and randomly assigned to 1 of the 2 treatments. Surgery consisted of an identical procedure except for the omission of the barrier membrane in the flap control sites. At 1-year, probing pocket depth reductions were 4.3+/-2.3 mm in GTR treated sites and 3.0+/-1.5 mm in the flap control sites (p=0.02, paired t-test). Clinical attachment level (CAL) gains were 3.0+/-1.7 mm in the GTR sites and 1.6+/-1.8 mm in the control sites (p=0.009, paired t-test). A subset analysis, performed according to the initial depth of the intrabony component of the defects (INFRA), indicated that in shallow defects (INFRA < or =3 mm) treated with the access flap alone, CAL gains were 1+/-1.5 mm, while in deep ones (INFRA > or =4 mm) they were consistently greater (1.9+/-1.9 mm). The % CAL gains, calculated as the % of the baseline intrabony component depth, however, were almost identical in the 2 subpopulations (45.8+/-64.7% in shallow and 43.8+/-37.6% in deep defects). Similarly, in the GTR sites, linear CAL gains were greater in deep (3.7+/-1.7 mm) than in shallow defects (2.2+/-1.3 mm), but no differences were observed in terms of % CAL gains (76.7+/-27.7% and 75.8+/-45%, respectively). The frequency distribution of CAL changes expressed as %s of the baseline INFRA indicates that most of the sites treated with GTR (73% in shallow and 92% in deep defects) gained 50% or more CAL. Furthermore, many defects (64% of shallow and 33% of deep defects) reached 100% of CAL gain. The present study demonstrated that: (i) GTR with bioresorbable barrier membranes resulted in a significant added benefit in comparison with access flap alone; (ii) the linear amounts of CAL gains were greater in deep than in shallow defects; (iii) CAL gains expressed as %s of the baseline depths of the intrabony component, were similar in shallow and deep defects; (iii) the regenerative procedure tested in the present study resulted in CAL gains equal to the depth of the intrabony component of the defect in some, but not in most of the instances.     

Periodontal surgery of vertical bony defects with or without synthetic bioabsorbable barriers. 12-month results

The aim of the present study was to clinically and radiographically compare guided tissue regeneration (GTR) therapy with bioabsorbable polyglactin 910 barriers and conventional periodontal surgery in intrabony defects. In 26 patients with advanced periodontitis, 29 teeth exhibiting interproximal intrabony defects were treated; 15 by conventional periodontal surgery (control) and 14 by GTR (test). Before and 12 months after surgery, clinical parameters were assessed and standardized radiographs were taken. On the radiographs the distances from the cemento-enamel junction (CEJ) to the alveolar crest (AC), and the CEJ to the most apical extension of the bony defect (BD) were measured using a computer-assisted analyzing device (LMSRT). Twelve months after surgery, 24 patients with 27 lesions were available for examination. For both methods statistically significant (P < 0.001) probing depth (PD) reduction (mean +/- standard deviation) of -4.49 +/- 1.94 mm (n = 13, test) and -3.22 +/- 1.48 mm (n = 14, control), as well as clinical attachment gain (CAL-V) of 3.41 +/- 1.59 mm (test) and 2.07 +/- 1.10 mm (control), was observed. Radiographic changes of the distance CEJ to AC of -0.95 +/- 1.72 mm (n = 9, test), and -0.98 +/- 1.53 mm (n = 11, control) were not significant. A significant bony fill (distance CEJ-BD) of 1.05 +/- 1.22 mm was observed for the test group (P < 0.01); the 0.68 +/- 2.04 mm bony gain for the control group was not statistically significant. The PD reduction (P < 0.05) and attachment gain (P < 0.01) in the test group was statistically significantly more favorable than in the control group. Twelve months after surgery, statistically more favorable PD reduction and attachment gain was observed using polyglactin 910 barriers than compared to conventional flap surgery. Hence, the use of bioabsorbable barriers for therapy of intrabony defects may be recommended.     

Effect of allogeneic, freeze-dried, demineralized bone matrix on guided bone regeneration in supra-alveolar peri-implant defects in dogs

This randomized, split-mouth design study evaluated the adjunctive effect of allogeneic, freeze-dried, demineralized bone matrix on guided bone regeneration in a critical-size, supra-alveolar, peri-implant defect model. Contralateral supra-alveolar peri-implant defects, 5 mm in height, each including two titanium implants, were surgically created in five beagle dogs. Demineralized bone matrix in autologous blood was placed over the implants in one randomly selected mandibular jaw quadrant. A space-making expanded-polytetrafluoroethylene membrane was used to provide guided bone regeneration bilaterally. Following a 16-week healing interval, tissue blocks were harvested and prepared for histometric analysis. Differences between experimental conditions (guided bone regeneration sites with and without demineralized bone) were evaluated using paired t tests (n = 4). Demineralized bone particles were discernible, with limited signs of resorption. The bone matrix particles appeared to be solidified within a dense connective tissue matrix and in close contact with the implants. Limited matrix remineralization was apparent adjacent to the alveolar crest. No statistically significant differences were found between experimental conditions for any parameter examined. Peri-implant defect height averaged 5.0 +/- 0.2 mm and 4.9 +/- 0.4 mm, vertical bone regeneration 1.5 +/- 0.9 mm and 1.1 +/- 0.4 mm, osseointegration within the extent of the defect 10.0 +/- 3.9% and 15.3 +/- 5.3%, osseointegration within the extent of regenerated bone 30.4 +/- 13.7% and 52.1 +/- 17.9%, and osseointegration within the alveolar base 68.8 +/- 13.1% and 74.4 +/- 7.1% for guided bone sites with and without demineralized bone, respectively (P > .05). The results suggest that freeze-dried demineralized bone has no adjunctive effect on guided bone regeneration in supra-alveolar peri-implant defects, that guided bone regeneration has a limited potential to enhance alveolar regeneration in this defect model, and that a 16-week healing interval appears insufficient for turnover and maturation of demineralized bone under provisions for guided bone regeneration.     

Outcome variables for the study of periodontal regeneration

The most reliable outcome variable for assessing periodontal regeneration is human histology; however, the morbidity associated with this technique makes it feasible only in isolated case studies designed to prove that a drug, device, or technique is capable of regenerating the lost periodontium including bone, cementum, and functionally oriented periodontal ligament. In the absence of this genuine variable, other "surrogate" variables must be used. Of these, measurement of new bone is the primary alternative. Direct bone measurements, including linear and volumetric assessment, are by far the best tools; however, the need for a second surgical procedure is a definite drawback of this technique. To overcome this problem, other outcomes have been employed: sounding bone measurements is a less invasive method, albeit it is also less accurate. Another tool that has been tested extensively is radiographic analysis. Conventional radiography is not useful in most regenerative trails where minimal or no crestal changes occur. The use of standardized radiographs and image processing techniques to measure alveolar bone changes has not significantly enhanced the applicability of this method. Digital subtraction radiography (DSR) offers some improvement over previous techniques; however, the correlation between the magnitude of clinical bone changes and changes in the digital image is yet to be substantiated. Other variables have been successfully used in regenerative studies. These include clinical attachment level changes, change in probing depth, and gingival recession. The information derived from these variables, especially attachment level changes, supplement and substantiate the direct bone measurements. Other variables that may be monitored are those associated with plaque formation, periodontal pathogens and gingival inflammation; while not direct measures of regeneration, these variables are likely to affect future prognosis and treatment stability. In summary, direct bone measurements are the most ideal surrogate outcome variable, although clinical attachment level measurements are commonly used in large-scale regenerative clinical trials. Clinical response may be assessed at different time intervals; however, the endpoint measurements for regenerative studies should be taken at least 12-months postoperatively.