الفهرس 
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Abstract
The present study was conducted to evaluate and compare the histological and
radiographical outcomes of revascularization procedures in necrotic mature permanent teeth
with apical periodontitis in dogs using three different scaffolds: BC alone, BC combined with
HA, and HA scaffold alone.
Thirty-nine mature permanent incisors from four male mongrel dogs were selected for
this study. Under general anesthesia, pulp necrosis and apical periodontitis were
experimentally induced by extirpating the pulpal tissue and leaving the access opened for
three weeks. REPs were applied in two visits. At the first visit, mechanical preparation of root
canals was accomplished using ProTaper Next rotary system up to size X3 (#30). Canals were
irrigated with 1.5% NaOCI, and calcium hydroxide was applied as an intracanal medicament
for two weeks. At the second visit, the apical foramen was enlarged to size #30 in all
experimental teeth. The teeth were then assigned into three groups according to the scaffold
applied. In group I (n = 13), REPs were carried out using BC as a scaffold alone. In group II
(n = 13), REPs were carried out using combined HA and BC as a scaffold. In group III (n =
13), REPs were carried out using HA as a scaffold alone.
After three months, the dogs were euthanized. The bone blocks containing teeth and
periapical tissues were processed and stained with Hematoxylin and Eosin for regular
histological examination, Masson’s trichrome stain for detection of collagen fibers, and Gram
stain for detection of any residual bacteria. Intracanal and periapical tissues were assessed and
scored based on histological parameters including the presence or absence and extent of new
vital tissues in the pulp space, intracanal vascularity, intracanal mineralization, bacterial
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contamination, intracanal and apical inflammation intensity and cell counts, apical bone
resorptions, and apical cementum resorptions. Additionally, the periapical healing was
assessed radiographically using the periapical index score (PAI) before and after REPs for all
experimental groups.