The characterization of the mechanical strength of chewable tablets

The purpose of this research was to identify possible test procedures for the evaluation of the strength of chewable tablets with respect to prevention of damage to teeth or mandibular joints when tablets are consumed. Diametral compression and flexure tests were employed to evaluate the strength of commercial samples from five manufacturers of chewable vitamin C tablets. Weibull analysis was used to assess the brittleness of these tablets. The tablets had a lower tensile strength value when determined by the diametral compression test compared to the flexure test ratio which ranged from 0.27 to 0.4. The value for the Weibull modulus ranged from 5 to 16, indicating an appreciable degree of brittleness of the samples. Relating the values for the mechanical strength to suggested practical values for the prevention of damage to the teeth or the mandibular joints indicated that most tablets exceeded these values. The flexure test reflects the practical situation closest, and a limiting tensile strength value of 2 MPa should not be exceeded for chewable tablets. The tablet batches tested were also characterized by a large batch-to-batch variability, suggesting uncontrolled manufacturing procedures. Commercially distributed chewable vitamin C tablets could provide a possible health hazard to teeth and mandibular joints. This hazard could be limited by a mechanical strength test specification.