A Review of Laboratory Methods to Determine Toothbrush Safety and Efficacy

Laboratory toothbrush evaluations have focused on three primary areas: hardness, efficacy and end-rounding. There is an accepted ISO standard for toothbrush texture, to categorize products from extra soft to extra firm. New toothbrush designs, with changes in bristle tufting, alignments, and lengths, yield reproducible results in the ISO procedure. New research has focused on a mathematical model that predicts stiffness, which overestimates in the 25-30% range. Efficacy testing has focused on the ability of toothbrush bristles to achieve interproximal penetration or access between and around artificial teeth or simulated tooth models. The majority of methods reviewed use "cleaning" or removal of deposited materials adherent to dentoform teeth. One test procedure uses deposition of ink from toothbrush bristles onto dentoform tooth surfaces. Many different approaches have been used over the years to evaluate efficacy. One method used since 1979 in several laboratories, and 3 methods developed in 1993 and 1994 are compared in detail for similarities and differences in testing performance criteria. Two of these procedures have been predictive of clinical plaque removal efficacy testing. Lack of bristle end-rounding was recognized in the 1930s and was related to gingival tissue damage. A revival of interest in end-rounding has occurred since the mid-80s using SEM and definitions and drawings of acceptable endings. The primary use of the new procedure has been to determine the % of acceptable and/or highest degree of end-roundness for the various toothbrush brands studied. No clinical gingival safety studies have been located related to these new laboratory end-rounded methods.