Discussion - References.
A number of studies have evaluated the long-term results after periradicular surgery, using diverse clinical and radiographic parameters (Harty et al. 1970, Rud et al. 1972,Mikkonenn et al.1983, Friedman et al.1990, Pecora et al. 1995). In some studies, success rates under 50% were reported (Friedman et al. 1990), whilst others had success rates of 90% (Harty et al. 1970) or even 100% (Pecora et al. 1995). This wide variation in the results is a reflection of the multiplicity of surgical concepts, materials and methods used; differences in the criteria over which the healing parameters are based on, the observation periods, age groups studied, differences between patients, teeth and selection criteria. Of the three surgical variants in the current study, some difference in the results after a year of evaluation was observed. The results reported in the classic radiographic study of Rud et al. (1972) present 35.83%with unsatisfactory healing, 23.33% uncertain healing, 23.33% incomplete healing and 17.5% complete healing with a conventional technique in120 cases. The results in this study showed a better radiographic response, particularly in group C, which may have been a result of the use of OsteoGen and the nonbioabsorbable membrane GoreTex.
The statistical analysis established a significant difference between the final values of the sizes of the radiographic periapical lesions in groups A and C, from which it can be deduced that C is better than A. The size of the lesion may be a critical factor because the distance between hard and soft tissues could determine the type of tissue that will grow during healing. If fibrous tissue establishes itself first, it will probably act as a barrier to prevent bone formation (Pecora et al.1995). Tay et al. (1978), established that when the pathological area in creases in size the rate of success of periradicular surgery decreases, but lesions of more than12 mm showed a tendency to have complete repair similar to small lesions. In the current study, when regeneration techniques were used, with or without synthetic filling material, the lesions of larger size had healed completely in12 months. When the conventional technique was used, there were persistent small radiolucent areas in those larger lesions. Pecora et al. (1995) evaluated the healing of periapical lesions of more than10 mm, and showed clinical and radiographic evidence of complete bone regeneration, when the membrane technique was used asa barrier. In the current study, the histological analysis demonstrated that when Gore- Tex1membraneswereused, there was bone regeneration inmost of the cases in groups B and C, whilst in group A, bone regeneration was observed in only some cases. How ever, it could be that group A require more time for healing to be completed.
The results obtained in the histological evaluations were similar to the studies reported by Dahlin et al. (1988) and Nyman (1991) in experimental studies in animals. The better results obtained in group C are possibly related to the simultaneous use of a synthetic filling material (bioabsorbable hydroxylapatite), which has been recommended as necessary to keep the existing space in the bone defects under the barrier (Rankow & Krasner 1996), achieving better results than with the membrane alone. Thus, the simultaneous use of regeneration techniques and filling materials, allows a more predictable healing response by the action of a double mechanism: firstly, the membrane allows the re-population of the defect with regenerative cells derived from the periodontal ligament and the endosteum; and secondly, the filling material acts as reservoir and matrix for the deposition of new bone.
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