This investigation describes the long-term benefits of guided tissue regeneration with barrier membranes in a population of 175 patients with severe intrabony defects and treated in a periodontal private practice. These data describe the long-term outcomes of a patient cohort who had been attending a periodontal maintenance program with various levels of compliance. In the analyses three definitions of failures were utilized: 1) tooth loss; 2) CAL loss with respect to the level observed at initial presentation before regenerative therapy; and 3) CAL loss from the level observed 1 year after periodontal regeneration.

The data indicated that tooth retention was greater than 96% over a more than 10-year period. This is remarkable, since at baseline presentation these teeth were severely compromised by an average CAL loss of 10.7 ± 2.4 mm, Table 5. probing depths of 8.7 ± 2.3 mm, and the presence of deep intrabony defects with an average depth 6.6 ± 2.1 mm.

In terms of preservation of the original attachment, more than 92% of the treated teeth presented up to 15 years after regeneration with CAL in a position equal or more coronal than at baseline, when the infection control phase of periodontal therapy was completed, while approximately a third of the teeth lost >1 mm of regenerated attachment during the 15-year follow up. In other words, the large amounts of clinical attachment gained with regenerative therapy were preserved over time in most of the sites and contributed to overall long-term stability of periodontal support in severely involved teeth.

Within the limits of the retrospective design of this investigation, these data clearly indicate that GTR treated teeth gain long-term benefits following application of this treatment modality. The observed 96% survival 10 years after treatment of severely compromised teeth compares favorably with reports of the possible alternatives, including extraction and replacement of these teeth with implants. Such comparison is particularly relevant since, on many occasions, given the severe loss of alveolar bone support, the implant alternative would have required some bone augmentation. Furthermore, available survival data of implants do not specifically include patients diagnosed with severe periodontitis or sites compromised by severe resorption of the marginal alveolar bone as a result of periodontitis.

The results of the Cox proportional hazard models indicate that the significant factors affecting the survival functions were stable for the three definitions of failures that were utilized. Cigarette smoking increased the odds of failure, while participation in a periodontal recall program decreased this probability. These observations confirm previous data that have indicated that cigarette smoking is an important predictor of the long-term outcomes of periodontal therapy. Smokers have been shown to have higher odds of losing teeth during periodontal maintenance care. In previous investigations on different clinical material, the authors have shown that cigarette smokers had inferior clinical outcomes following periodontal regeneration and that smokers were more likely to experience loss of clinical attachment at regenerated sites.

The data also indicate the importance of patient’s participation in a carefully planned periodontal care program. Subjects who failed to fully comply with this program or who attended a community-based preventive program in a general practice experienced significantly more disease progression and tooth loss. Previous prospective investigations from our group have indicated that patients who fail to comply with a periodontal maintenance program in a specialist environment have higher chances of showing recurrence of periodontitis at the regenerated site, as well as at other sites.

The Cox proportional hazard models (Table 4) indicated the presence of significant differences in the long-term performance of different GTR treatment modalities. Over the years this group of patients has been treated with three different approaches in terms of regenerative materials: non-resorbable ePTFE membranes, polylactic acid-based absorbable membranes, and a combination of absorbable membranes and filler materials. An initial assessment of the data (not shown) indicates that the observed differences in survival seem to be associated with a lower incidence of events following treatment with absorbable membranes and possibly higher and earlier rates of events following the use of combination treatment. At this stage, however, further analyses and investigations are required before reaching any conclusion regarding the effects of different materials.

In this study, no significant differences were observed in terms of disease progression in patients positive for specific IL-1 polymorphisms. The data are not in agreement with a previous report, where authors observed significantly more attachment loss in carriers of the rare alleles at two sites of the interleukin-1 gene complex. The observed differences can be attributed to a variety of factors, including the presence of insufficient power to correctly assess the role of the genetic polymorphisms as well as differences in the efficacy of the periodontal care program. The latter observation may be indirectly supported by the high rate of recurrence observed in the cited study over a relatively short period.

Of interest was the observation that the conditional probability of observing an event (tooth loss or CAL loss) remained relatively constant over the observation period. In turn, this indicates that the chronological distribution of failures is relatively constant and that Figure 3. there are no indications that the regenerated attachment may show early signs of senescence.

In conclusion, data presented in this study suggest that regenerative periodontal treatment represents an important alternative for the management of severely compromised teeth since clinical improvements following GTR treatment of intrabony defects can be maintained over time in the great majority of cases and long-term tooth retention was observed in more than 96% of cases.