الفهرس 
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Abstract
The aim of our study was to assess the regenerative potential of young permanent immature teeth with necrotic pulp following different treatment protocols, via either revascularization protocol as a well-established protocol in the literature compared to regeneration with the use of a nano scaffold with or without growth factor (BMP-2).
This study was an animal study which was performed for histopathologic and radiographic evaluation of the treatment outcomes over 3 months of follow up.
The total number of roots (96) 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 48 roots and was further subdivided into 36 experimental roots and 12 control roots. The experimental samples were also subdivided into 3 subgroups according to the treatment protocol: Subgroup (A): Revascularization (12 roots), Subgroup (B): Mesoporous silica Scaffold (12 roots), Subgroup (C): Mesoporous silica Scaffold impregnated with BMP-2 (12 roots) and two control subgroups; subgroup (D) Positive control (6 roots) and subgroup (E) Negative control (6 roots). Each individual root was taken as the unit of measure. Each subgroup was both histopathologically and radiographically evaluated.
Induction of infection was done followed by canal disinfection using calcium hydroxide. Treatment protocols were performed according to the previous classification and samples were left for follow up according to the evaluation 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 taken using digital sensor then 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 scores were counted and data were statistically analyzed.
Histological evaluation:
Histological evaluation included 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, statistically significant difference was shown between different subgroups where subgroup C show the highest mean increase in length, except for subgroup (C) “positive controls” which recorded the lowest mean percent increase in root length.
While regarding increase in dentine thickness, after one as well as three months; there was a statistically significant difference between groups. Comparisons between groups revealed that negative control group showed the statistically significantly highest mean percentage increase in root thickness. Mesoporous silica + BMP-2 group showed statistically significantly lower mean value than negative control group followed by blood clot group. Positive control group showed the statistically significantly lowest mean percentage increase in root thickness.
Regarding the decrease in apical diameter, at one month there was a statistically significant difference between groups. Comparisons between groups revealed that negative control group showed the highest mean percentage increase in apical closure with non-statistically significant difference from Mesoporous silica + BMP-2 group but a statistically significant difference from all other groups. There was no statistically significant difference between Mesoporous silica + BMP-2; Mesoporous silica and blood clot groups; all showed lower mean percentage increase in apical closure values. Positive control group showed the statistically significantly lowest mean percentage increase in apical closure.
After three months, there was a statistically significant difference between groups. comparisons between groups revealed that negative control group showed the statistically significantly highest mean percentage increase in apical closure. Mesoporous silica + BMP-2 showed statistically significantly lower mean percentage increase in apical closure followed by Mesoporous then blood clot group. Positive control group showed the statistically significantly lowest mean percentage increase in apical closure.
Histological evaluation of inflammation was done using inflammatory cell count. The evaluation method showed that at one month and three months, positive control group showed the statistically significantly highest mean count. While negative control subgroup showed the statistically significantly lowest mean inflammatory cell counts. After one and three months, there was a statistically significant difference between groups. There was no statistically significant difference between Mesoporous silica and blood clot groups; both showed statistically significantly lower median inflammatory cell counts. Mesoporous silica + BMP-2 showed statistically significantly lower median counts. Negative control group showed the statistically significantly lowest median inflammatory cell counts.
Regarding bone resorption, Positive control group showed the highest prevalence of resorption and Negative control group showed no resorption in both evaluation periods.
After one month, there was a statistically significant difference between groups. Blood clot group showed lower prevalence of resorption. Mesoporous silica and Mesoporous silica + BMP-2 groups showed lower prevalence of resorption.
After three months, there was a statistically significant difference between groups (P-value <0.001, Effect size = 0.684). Positive control group showed the highest prevalence of resorption. Blood clot group showed lower prevalence of resorption followed by Mesoporous silica then Mesoporous silica + BMP-2 group. Negative control group showed no 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 & C, 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.
In blood clot as well as negative control groups; there was no statistically significant change in vital tissues inside the pulp scores between the evaluation periods.
As regards Mesoporous silica, Mesoporous silica + BMP-2 as well as positive control groups, there was a statistically significant increase in vital tissues inside the pulp scores after three months.
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 & C, 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, after one as well as three months; there was a statistically significant difference between groups. Negative control group showed the highest prevalence of apical closure. Mesoporous silica + BMP-2 group showed lower prevalence of apical closure followed by Mesoporous silica then blood clot groups. Positive control group showed no apical closure.