الفهرس 
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Abstract
The present study was conducted to assess the antibacterial efficiency of Propolis during preparation of infected root canal and its ability to promote regeneration for the treatment of immature non-vital dogs’ teeth.
A total of six mongrel dogs aged approximately 4-6 months were selected for this study. The four premolars in each quadrant were included in the study summing up the total number of teeth to 96 (16 teeth/dog). 72 samples were used as an experimental group and 24 samples were used as a control group. The 72 samples were classified into two main equal groups according to the type of intrcanal medication used: group (I): root canals medicated with pure paste of Propolis, group (II): root canals medicated with TAP, each group was further subdivided into two subgroups according to the type of regenerative material used: subgroup (A): Propolis paste as root canal orifice plug subgroup (B): MTA as root canal orifice plug, each subgroups was further subdivided into three subdivisions according to the post treatment evaluation period (2 dogs were scarified for histological evaluation in each period) , Subdivision (1): after 2 weeks, Subdivision (2): after one month, Subdivision (3): after 2 months. While the 24 samples were classified into Positive and Negative Control Groups as follows: Positive control group (12 samples - 4 premolars for each period of evaluation): with induced periapical infections without any treatment modalities and left open, Negative control group (12 samples - 4 premolars for each period of evaluation): sound teeth left for normal maturation.
Anti-microbial effectiveness for all samples of group (I) and group (II) were assessed; pre exposure to intracanal medicaments bacteriologic sampling was done, propolis and TAP were introduced to all canals and post exposure to intracanal medicaments bacteriologic sampling was done. Antibacterial effectiveness of the different intracanal medicaments were assessed by determining the percentage of reduction in colony counts (%RCC) before and after placement of the intracanal medicaments. Data were collected, tabulated and statistically analyzed.
Histological evaluation included quantitative 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 structure. Data were collected, tabulated and statistically analyzed.
Radiographic evaluation included measuring increase in length, thickness and occurrence of apical closure. Radiographs were standardized using Image-J software with Turbo Reg plug-in. Increase in length and thickness were measured in each subgroup, data were collected and statistically analyzed. Apical closure score were counted and data were statistically analyzed.
Phase I (Antimicrobial Effectiveness):
Results showed that at base line and after three weeks there was no statistically significant difference between TAP and Propolis groups; both showed statistically significantly lower mean values.
Phase II (Regeneration):
Radiographic evaluation:
Results showed that through all periods of evaluation there was no statistically significant difference between Propolis and MTA subgroups; all showed statistically significant high mean percentage change in root length, dentin thickness and apical closure. The negative control group showed the highest mean percentage change and the positive control showed the lowest mean change in root length, dentin thickness and apical diameter.
Histologic evaluation:
Quantitative analysis: Through all evaluation periods; there was no statistically significant difference between Propolis and MTA subgroups they showed statistically higher mean new hard tissue score, vital tissue score as well as apical closure score. Negative control group showed statistically the highest mean scores while positive control group showed statistically the lowest mean hard and vital tissues scores.
Qualitative analysis: Histopathological evaluation revealed that of Propolis and MTA subgroups showed that cementum like tissue was demonstrated along the inner surface of the root dentin resulting in increase in root thickness. Most of the Propolis and MTA subgroups sample’s showed closure of the apical terminus of the root again with cementum like tissue. Regarding the inward growth of soft tissue, most of the samples showed the presence of pulp like fibrous tissue devoid of odontoblastic layer with calcified islands of osteoid tissue. However , some samples from the MTA subgroup showed the presence of pulp like tissue with odontoblastic layer.
Conclusions:
Based on the results of the present study, it could be concluded that:
1. Propolis as a natural substance can be comparable with TAP as a disinfection treatment option in regeneration process.
2. Using the experimental materials (Propolis and MTA) as root canal orifice plug were effective in inducing hard tissue deposition and soft tissue ingrowth in root canal space.
3. Regarding the nature of soft tissue ingrowth, it resembled periodontal connective tissue and pulp like fibrous tissue.