الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 204 |  |  |
| | | from | 204 | | |
Abstract
This study was conducted to compare and evaluate both histologically and radiographically the outcome of REPs in necrotic mature permanent teeth, with apical periodontitis, in dogs using three different scaffold materials namely induced BC alone, BC combined with PRF scaffold and PRF scaffold alone.
Thirty-six mature permanent incisors from 4 male mongrel dogs were used in this study. Pulpal necrosis and apical periodontitis were experimentally induced by removing the pulpal tissue and leaving the access opened for three weeks. REPs were carried out in two visits. During the first visit, mechanical root canal preparation was performed using ProTaper Next rotary system up to size X3. Canals were irrigated constantly with 1.5% NaOCl and calcium hydroxide was used as an intracanal medicament for a period of two weeks. At the second visit, apical foramen enlargement was performed in the experimental teeth till size 30. Various scaffolds were induced or placed inside root canals according to the experimental group. In group I, (n=12), REPs were performed using BC as a scaffold alone. In group II, (n=12), REPs were performed using PRF and BC together as a scaffold. In group III (n=12), REPs were performed using PRF as a scaffold alone.
Three months later, dogs were sacrificed and bone blocks containing incisors were processed and stained with Hematoxylin & Eosin for general histological examination, Masson’s trichrome stain for detection of collagen fibres, and Gram stain for detection of any residual bacteria. The intracanal and periapical tissues were analyzed and scored according to histological parameters including presence or absence and extent of vital tissues inside the pulp space, intracanal vascularity, inflammatory extent, intracanal mineralization, residual bacteria, apical bone resorptions and apical cementum resorptions. In addition, periapical index score
154
(PAI) was used to evaluate and compare the health status of the periapical area radiographically before and after REPs among the different experimental groups.
Histological observations revealed statistically significant greater number of samples in group II showing intracanal tissues reaching the cervical third. group I showed statistically significant higher number of samples with intracanal tissues reaching the middle third, when compared with group III. group III showed statistically greater number of samples with tissues occupying the apical third when compared with group II. group I and II showed statistically greater number of samples with high vascularity compared to group III. Mild to moderate inflammatory cell infiltrates were observed in most specimens in different groups with no statistically significant differences. Cementum-like tissue was found to be deposited on the internal canal walls in samples of different groups with no significant differences. Islands of bone-like tissue were found in statistically greater number of samples in group I, compared to group III. No residual bacteria were detected in any of the samples. Apical bone and cementum resorptions were found to be statistically higher in samples in group I.
Radiographically, there were no significant differences regarding the PAI scores among the experimental groups following REPs. Statistically significant differences were found in all experimental groups when comparing PAI scores at time of disinfection to those three months postoperatively, in each experimental group.