الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The regeneration procedure involves many steps; canal debridement and intra canal medicament dressing, induction of bleeding from the apical tissue and placement of three to four millimeters of calcium silicate material over the blood clot at the cement–enamel junction, and finally a coronal restoration. Root canal disinfection is essential prior to invoking bleeding. Single visit regenerative endodontic therapy used the irrigation solution as the sole disinfectant. Recently, matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has appeared as a promising approach for microbial identification and strain typing in endodontics.
The aim of the present study was to compare single visit and multiple visits regeneration protocols microbiologically (using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)), clinically and radiographically using cone beam computed tomography (CBCT).
A randomized controlled clinical trial was performed recruiting 35 patients, 8-13 years with traumatized immature permanent teeth showing periapical lesions. They were randomly divided in two groups before induction of bleeding, Biodentine cervical plug application, and sealing. group I (n=5) single-visit and group II (n=11) multiple-visit. Field decontamination and negative control samples were performed before collecting samples using a file. For both groups, the first visit included access-cavity-preparation and first sample collection (A). Minimal instrumentation, irrigation with 20ml 1.5% sodium-hypochlorite, 10ml saline were done for group II or 2.5% and further irrigation with 20ml 17% EDTA, 10ml saline for group I. Then sample (B) was collected, bleeding was induced, and the tooth sealed. For group II calcium hydroxide was placed for 1-2weeks then removed and irrigation was done with 20ml 17% EDTA, 10ml saline, and finally sample (C) was collected before bleeding induction. Collected dentine-debris were placed in thioglycolate-broth, cultured, and examined by MALDI-TOF-MS. Cases were followed for 12months. Microbial reduction, absence of signs and symptoms, resolution of lesions and root development presented successful microbiological, clinical, and radiographic outcomes, respectively. The outcomes of both groups were compared statistically (p < 0.05)
Out of the forty isolates recovered from the 16 traumatized teeth included in the present study, 37 isolates were reliably identified by MALDI-TOF MS. Twelve teeth (62.5%) were polymicrobial. The recovered bacteria belonged to five phyla, 15 genera and 25 species. Firmicutes was the predominant phylum (P < 0.001) over Bacteroidetes, Proteobacteria, Actinobacteria, and Fusobacteria. Gram positive bacteria were significantly more prevalent than Gram negative (p = 0.03). Facultative anaerobes were the most prevalent (P<0.001) compared to strict anaerobes and strict aerobes. The latter was the least prevalent. The clinical trial was prematurely terminated due to the COVID-19 pandemic. The post hoc power was 94.17% regarding decrease in lesion size. No statistically significant difference existed between the two protocols in the clinical and microbial outcomes. Radiographically, group II showed statistically significant decrease in lesion size and volume, increase in lesion bone density and intracanal calcification presence.