الفهرس 
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Abstract
This study was an animal study which was performed for radiographic and histopathologic evaluation of the treatment outcomes over 3 months of follow up.
The total number of teeth (48), was divided into 2 equal groups according to the post treatment evaluation period; group I and group II for: Evaluation periods of one month and three months respectively. Each group included 24 teeth and was further subdivided into 16 experimental teeth and 8 control teeth. The experimental samples were also subdivided into 2 subgroups according to the treatment protocol: Subgroup (A): Revascularization (8 teeth), Subgroup (B): Scaffold impregnated with BMP-2(Infuse bone graft) and DPSCs (8 teeth) and two control subgroups; subgroup (C) Positive control and subgroup (D) Negative control. Each individual root was taken as the unit of measure. Each subgroup was both radiographically and histopathologically evaluated.
Induction of infection was done followed by canal disinfection using the triple antibiotic paste. Treatment protocols were performed according to the previous classification and samples were left for follow up according to the period for each group.
Radiographic evaluation:
Radiographic evaluation included measuring increase in root length, increase in dentin 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.
Histological evaluation:
Histological evaluationincluded inflammatory cell count,bone resorption, tissue in-growth, hard tissue deposition and apical closure. The variables were quantitatively evaluated using appropriate scoring system. Data were collected, tabulated and statistically analyzed.
Results:
Regarding the increase in root length, at one month as well as three months, no statistically significant difference was shown between different subgroups, except for subgroup (C) “positive controls” which recorded the lowest mean percent increase in root length.While regarding increase in dentine thickness at one month statistical analysis showed that there was no significant difference between subgroups (D) “negative controls” and (B). Slightly significant difference was noticed between the former subgroups and subgroup (A) and very significant difference was recorded towards subgroup (C) “positive controls”. At three months. statistical analysis showed that there was no statistically significant difference between different subgroups, except for subgroup (C) “positive controls” which recorded the lowest mean percent increase in root thickness.
Regarding the decrease in apical diameter, at one month as well as three months, there was no statistically significant difference between different subgroups, except for subgroup (C) “positive controls” which recorded the lowest mean apical closure percent.
Histological evaluation of inflammation was done using inflammatory cell count. The evaluation method showed that at one month and three months, positive control subgroup showed the statistically significantly highest mean count. While negative control subgroup showed the statistically significantly lowest mean inflammatory cell counts. At one month, there was statistically significant difference between subgroup (A) and subgroup (B) both showed significantly lower mean inflammatory cell counts. While at three months, there was no statistically significant difference between subgroup (A) and subgroup (B).
Regarding bone resorption, at one month as well as three months, there was significant difference between the subgroups. Subgroup (C) “positive controls” recorded the highest prevalence of bone resorption. Subgroup (A) and subgroup (B) showed a lower prevalence of bone resorption. Subgroup (D) “negative controls” showed no prevalence of bone resorption.As regards to tissue in-growth, the histopathological analysis for subgroup (A) showed that the nature of this tissue resembled periodontal connective tissue with variable amounts of inflammatory cell infiltration and noticeable angiogenic activity. Regarding subgroup (B), the histopathological analysis showed that the nature of this tissue resembles the pulp tissue with variable amounts of inflammatory cells infiltration and noticeable angiogenic activity. Furthermore, a layer of odontoblast-like cells undergo differentiation could be observed opposite to a predentin layer.
The extent of in-growth was evaluated in terms of scores. At one month and three months, there was statistical significant difference between all the subgroups.
For Hard tissue deposition, subgroup (A) showed apparently layer of apical hard tissue formation resembles cementum–like tissue is covered by a thin layer of cementoid tissue. Regarding subgroup (B), hard tissue formation was observed that resembles osteodentin covered with a layer of prenentin could be detected. Odontoblast-like cells could be observed entrapped inside the mineralized tissue. At one month and three months, there was no statistically significant difference between the experimental subgroups. All showed statistically significant difference with subgroup (C) “positive controls”.
For apical closure at one month, there was a no significant difference between the subgroups. At three months, there was a significant difference between the subgroups. Subgroup (D) and subgroup (B) showed the highest prevalence of apical closure. Followed by Subgroup (A) and subgroup (C)