The purpose was to aid in determining termination of instrumentation and obturation. A meta-analysis was conducted as to success/failure of different obturation lengths. Inclusion criteria were (a) minimum follow-up of 2 yr, (b) data on obturation length, (c) definition of success/failure, (d) available data on success/failure, (e) radiographic evaluation. Correlations were made as to success/failure as related to length of obturation from the apex. When comparing group A (obturated 0 -1 mm from apex) versus group C (obturated past apex) using the DerSimonian and Laird estimates, group A showed a marginally better (p Ͻ 0.10) success rate than group C by 28.8%. Group A had better success than group B (obturated Ͼ1 mm short); the difference was insignificant. The results were similar after controlling for study quality using a single random effects regression model. In conclusion, the meta-analysis indicated that a better success rate is achieved when treatment includes obturation short of the apex. here has been disagreement where to terminate instrumentation and obturation (1). Kuttler (2) believed termination should be to the apical constriction, when the apical constriction exists. Seltzer et al. (3) found that the reaction to tissues were milder when instrumenting short of the apex as compared to instrumenting beyond the apex. In a subsequent study, Seltzer et al. (4) concluded that optimum tissue repair was found when canals were instrumented and filled short of the apex; material that was forced into the periapical tissues caused a chronic inflammatory response. Green (5, 6) Weine, (7) Frank (8), and Stein (9) advocated obturating short of the radiographic apex (0.5-2.0 mm). They based their arguments on Kuttler's microscopic analysis (2) or on their own studies. Walton and Torabinejad (10) and Weine (5) also agree with obturating short of the radiographic apex, with the additional consideration that, in the presence of root and/or bone resorption, preparation and obturation should be to even shorter lengths. Alternatively, Schilder (11, 12) advocated debridement and obturation to the radiographic apex, which often results in material being extruded into periradicular tissues.Given the varying opinions on where to terminate, a meta-analysis of the literature may clarify this issue. Meta-analysis is a statistical procedure that combines the results of independent studies that are determined to be "combinable" (13). Assessment of the validity and quality of the independent studies is essential (14). Through a meta-analysis, information is maximized when obtained from the available data; this would not be possible from any single study. The goals of a meta-analysis include: (a) increasing statistical power for comparing end-points and subgroups, (b) resolving uncertainty when reports disagree, (c) encouraging improvements in the quality of primary research, and (d) helping to plan for future research (15).The process of conducting a meta-analysis is similar to other research plans: first, formulate t...