الفهرس 
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Abstract
The aim of the present study was to assess radiographically and histopathologically the regenerative potential of necrotic immature teeth in a dog model following treatment with either: Propolis, TAP or without intracanal medication.
Six dogs aged - months were selected for this study. Double rooted premolars in each quadrant were included in the study summing up a total number of teeth ( teeth/dog). All previously infected teeth were re-entered and the root canals of all experimental teeth ( ) were irrigated with mL of NaOCl per tooth and dried with sterile paper points. No mechanical instrumentation was performed in any of the canals. The teeth were then divided equally into three groups according to the treatment modalility as follows: group (I): root canals medicated with TAP, group (II): root canals medicated with a paste of pure propolis and group (III): Root canals didn’t receive intracanal medication and were sealed with temporary filling. After weeks, all root canals were irrigated with mL of NaOCl and mL of sterile saline, then bleeding were induced to
Summary
fill the canal spaces. The teeth received double coronal seal with MTA and Ketac molar (glass ionomer filling material).
Teeth were further subdivided into three equal groups according to the post-treatment evaluation period after which the dogs were sacrified for histopathological evaluation of the teeth at: two week, four weeks and eight weeks.
Radiographic evaluation included the following parameters: the change in root length, the change in root thickness and the change in the width of the apical diameter.
Histopathological evaluation included quantative analysis (presence or absence of new hard tissue on the internal root canal walls, presence or absence of vital tissue within the canal space, and presence or absence of apical closure) and qualitative analysis for identification of newly formed hard and soft tissue structures.
Radiographic evaluation:
Results showed that through all evaluation period there was no statistically significant difference between TAP and Propolis groups; both showed the statistically significantly highest mean percentage change in root length and dentin thickness while irrigation group showed the statistically significantly lowest mean percentage change. Regarding the change in apical diameter After weeks as well as weeks; there was no statistically significant
Summary
difference between TAP and Propolis groups; both showed the statistically the highest mean change in apical diameter. Irrigation group showed the statistically significantly lowest mean change in apical diameter. While after weeks, Propolis group statistically showed the highest mean change in apical diameter. TAP group showed statistically lower mean value. Irrigation group statistically showed the lowest mean change in apical diameter.
Histopathological evaluation:
Quantative analysis: Through all evaluation periods; there was no statistically significant difference between TAP and Propolis groups; both showed statistically the highest mean new hard tissue score as well as vital tissue score. Irrigation group showed statistically the lowest mean new hard tissue score and vital tissue score. Regarding apical closure after week as well as after week ; there was no statistically significant difference between the presence of apical closure in the three groups.
While after week ; there was no statistically significant difference between TAP and Propolis groups; both showed the highest mean presence of apical closure. Irrigation group showed statistically the lowest presence of apical closure.
Qualitative analysis: Histopathological evaluation revealed that samples medicated with TAP and propolis showed that cementum like tissue was demonstrated along the inner surface of root dentin resulting in increase in root thickness. Most of the samples
Summary
showed closure of the apical terminus of the root again with cementum like tissue. Regarding the inward growth of soft tissue, samples showed the presence of pulp like fibrous tissue devoid of odontoblastic layer with calcified islands of osteoid tissue. However, some samples from the propolis group showedthe presence of pulp like tissue with odontoblastic layer