Skip to main content

Table 1 Study type according to evidence level

From: Clinical reliability of zirconium abutment in implant restorations in the English and Korean literature

Grade Study type
1 (high) Systematic literature review targeting RCTs (systematic review with/without meta-analysis)
2 Randomized controlled trial, systematic literature review targeting category 3
3 Quasi-RCT, cohort study, case-control study, observational/analytic study
4 (low) Cross-sectional study, case series, before/after study, case report, non-analytic study
  1. Source: Health Insurance Review and Assessment Service. Republic of Korea, 2013a