Development and validation of a short-term clinical model for assessing calculus inhibitory agents

The purpose of this project was to develop and validate an efficient, short-term clinical model for assessing topically-applied anticalculus agents. In this model, calculus development occurred within 14 days on both labial and lingual surfaces of the mandibular anterior teeth. Because of documented long-term clinical efficacy, pyrophosphate dentifrices were used to investigate the validity of the short-term calculus model for evaluating anticalculus agents. This paper provides the results of the final 3 studies conducted during the development of this model. For each study, the design consisted of two 14-day phases, i.e., a control phase and a treatment phase, separated by a 7-day washout phase. At the start of each phase, a prophylaxis was performed on the mandibular anterior teeth to remove all plaque and calculus. At the end of each phase, supragingival calculus formation on the labial and lingual surfaces of these same teeth was measured using the VMI scoring method. Twice a day during the control phase, subjects applied a control dentifrice undiluted to the test teeth with a custom-fitted toothshield and brushed only the exposed teeth with the same dentifrice. For the treatment phase, subjects were randomly assigned to groups balanced on the basis of control-phase calculus scores and then delivered the dentifrices using the toothshield as in the first phase. After 14 days, calculus formation occurred in all groups. However, the pyrophosphate dentifrice groups had significantly less calculus (16-30%) than the control dentifrice group. These studies demonstrated that this methodology permitted rapid formation of dental calculus, and by substantiating with anticalculus systems documented to have activity in long-term human trials, it is concluded that this short-term clinical model is valid for assessing anticalculus agents.