الفهرس 
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Abstract
The present work had been performed to answer the question of whether the PRF and topical ozone application can enhance the regeneration of three-wall periodontal defect and which one is the superior. For this study, a sample of forty Wistar albino rats, weighting about 300–360 g. and aged between 3-4 months old, was assigned into three groups as follows: A. group I (control group, n=20): was subdivided into two subgroups: • Subgroup A (Negative control group, n=10): this group was SHAM operated; i.e. a mucoperiosteal flap was incised, reflected and reclosed with no defect induction or any applied treatment. • Subgroup B (Positive control group, n=10): the three-wall alveolar bone defect was created followed by closure of the mucoperiosteal flap without treatment. B. group II (Ozone treated group, n=10): in this group, the created defect was filled with ozone gel followed by closure of the mucoperiosteal flap. C. group III (PRF treated group, n=10): in this group, the created defect was treated with PRF followed by closure of the mucoperiosteal flap. • 2 weeks after surgery, five rats per each group were euthanized using an anesthetic overdose. The residual rats were euthanized 4 weeks postsurgery. The tissue specimens were tested histologically under LM using H & E and MT staining to assess the intensity of inflammation and the degree of new bone and PDL formation. Also, anti-PCNA immunohistochemical staining was done to evaluate and compare the cellular proliferation and rate of regeneration of different groups. Another added assessment tool was SEM for analyzing the ultra structure of alveolar defect area and the newly formed bone. Statistical analyses were done for the histomorphometric measurements of the new bone height and new bone surface area and the anti-PCNA counting of group I subgroup B, group II and group III. Collectively, in group I subgroup A, both LM and SEM examinations revealed a normal histological structure of the periodontal tissues. In group I subgroup B, both LM and SEM analyses showed persistence of the periodontal defect accompanied with severe inflammatory cell infiltration in both 2 and 4 weeks periods. Mild new bone formation was observed yet surrounded by numerous osteoclastic activity with no incidence of regeneration of functioning PDL fibers. In group II, in 2 weeks period, partial regeneration of the periodontium was seen with moderate new bone formation of woven structure. New functionally oriented PDL fibers were also seen in some specimens. In 4 weeks period, almost complete restoration of the normal architecture of periodontium was reached with regeneration of the mesial alveolar bone wall. The PDL space was occupied with functionally oriented PDL bundles. In group III, in 2 weeks period, all specimens showed almost complete obliteration of the defect area with new periodontal tissues. Moderate bone regeneration and identification of regenerated alveolar crest, horizontal and oblique groups of PDL were recorded. In 4 weeks period, the alveolar bone defect was almost completely regenerated to a level almost reaching that of the interradicular septum. The normal architecture of PDL was restored with identification of its principal fiber bundles. The statistical analysis of the new alveolar bone height revealed a significant difference between group I subgroup B and group II and between group I subgroup B and group III in 2 weeks follow up period. This difference was highly significant in 4 weeks follow up period between the above mentioned groups. No significant difference was found between group II and III in both time intervals. When comparing different intervals within the same group, a non significant difference was found between 2 and 4 weeks follow up periods of group I subgroup B while a significant difference was found between 2 and 4 weeks periods of both group II and III. The statistical analysis of the new bone surface area displayed a significant difference between group I subgroup B and group II and between group I subgroup B and group III in 2 weeks follow up period. In 4 weeks follow up period, the difference between group I subgroup B and group II was significant while it was highly significant between group I subgroup B and group III. The difference between group II and group III was non significant in 2 weeks and significant in 4 weeks follow up periods with group III being superior. When comparing the values of the different intervals in the same group, a non significant difference was found between 2 and 4 weeks follow up periods of group I subgroup B while the difference was significant between 2 and 4 weeks periods of both group II and III. Finally, in anti-PCNA immunohistochemical statistical analysis, a non significant difference was detected between the numbers of anti-PCNA positive nuclei of the three groups in both time intervals. However, the anti- PCNA counting was highest in group III followed by group II and lowest in group I subgroup B. when comparing between different time intervals, a non significant difference was found between the number of anti-PCNA positive nuclei in the 2 and 4 weeks periods of the three groups with anti-PCNA counting being highest in 2 weeks period than 4 weeks period in the three groups. 2. Conclusion: The outcomes of the current study demonstrate that: a) The surgically created three-wall periodontal defects are not self-healing defects. b) Topical ozone administration has a tendency to enhance and accelerate the healing process of induced periodontal defect in an animal model. c) PRF is a beneficial way to avoid possible complications and to have a better chance for both soft and hard tissue healing in periodontitis. d) Both ozone and PRF could promote periodontal regeneration in rats, within 4 weeks, with similar improvements in soft tissue and hard tissue parameters. However, the efficacy of PRF is more pronounced than ozone.