Dental Pulp/Dentin Regeneration by Blood? – Meta Analysis of Apical Revascularization

Objectives: Each year ~5.4 million children and adolescents in the U.S. suffer from dental infections, leading to arrested tooth-root development and tooth loss. Apical revascularization (AR), adopted by the American Dental Association for its perceived ability to enable tooth-root growth, is being accepted worldwide.
Methods: PubMed, Scopus and Google-Scholar searches were performed up to July 31, 2016. A total of 36 AR cases were selected using PRISMA and pre-defined inclusion and exclusion criteria. We quantified tooth-root development digitally on pre- and post-operative radiographs: root lengths as ratios of the treated and adjacent reference teeth, root-dentin geometry by subtracting root-canal area from tooth-root area, and apical closure as the ratio of crown and apical opening widths. A linear mixed effects model with nested random effects was adopted for statistical analyses.
Results: Following AR with 6- to 66-month recalls, root apices remained open in 13.9% cases (types I), whereas apical calcification bridge formed in 47.2% cases (type II). Apical closure (type III) occurred in 38.9% cases. Tooth-root lengths lacked significant postoperative gain among all subjects (p=0.3472) or in any of type I, II or III subgroups. Root-dentin area showed significant increases in type III cases, but not in types I or II patients. Root-dentin area ratios differentiated subtypes: Type I <0.58, type II between 0.58 and 0.79, and type III >0.79. Root apices narrowed significantly in types II and III, but not in type I patients. Author-graded apical closure status was substantiated by quantitative apical-width measurements.
Conclusions: Contrary to the commonly held clinical perception, AR does not increase root length in the majority of qualified clinical cases, and further lacks consistency in promoting root widening or apical closure. Whether circulating blood is sufficient for tissue-specific regeneration warrants experimental and clinical investigations.