Clinical comparison of masticatory performance and electromyographic activity of patients with complete dentures, overdentures, and natural teeth.

In this study, which is the first of its kind, it has been shown that overdenture patients, when compared to complete denture patients, while chewing a test food for a constant number of strokes, expended an equivalent amount of muscle effort, chewed more slowly and efficiently, and evidenced significantly better masticatory performance by producing an increased volume of fine test food particles. These findings provide a sound justification for the extra effort required to retain some natural teeth to provide overdenture services to patients. The fact that patients can masticate food more efficiently with overdentures than with complete dentures justifies the increased cost and time involved in their construction. The longitudinal effects that overdentures have on the basic physiopathologic processed involved in the progression of ridge resorption and the advantages of maintaining periodontal proprioception also should be studied.

Four variables affecting magnitude of dentrifice abrasiveness.

A five-factor study was done on human dentin abrasion that involved two abrasives, either alone or in dentifrice form, two brush brands, two brush hardnesses, two concentrations, and two temperatures of testing. The hard brushes caused 3.6 times as much wear as the soft brushes, a greater influence than the abrasives compared. A brush X hardness interaction indicated that there is a wide variation among the stiffness gradings of toothbrushes. Tests run at 37 C were 28% less abrasive than those at room temperature, suggesting a softening of bristles because of the warmer temperature. A highly significant abrasive X concentration interaction showed that dentifrices became more than twice as abrasive on dilution form 100 to 50%, but that abrasives alone did not show such changes on dilution. The second study included two hardnesses, two abrasives, three diluents, four concentrations, and two replicates. An interaction was found between abrasive and diluent, showing that glycerine inhibited abrasion by 88% in comparison with saliva and CMC. A hardness X concentration interaction showed that wear varied widely with concentration for the hard brush but scarcely at all for the soft brush. These findings suggest that abrasiveness of dentifrices depends strongly on testing conditions and that no single set of conditions is suitable for evaluating dentifrice abrasiveness.

Effect of toothbrush variables on wear of dentin produced by four abrasives.

A study was conducted to explore the effect of brush brand, brush hardness, and the concentration of abrasive on the wear of human dentin by four dentifrice abrasives. The two hard brushes produced similar and high levels of abrasion, whereas the two medium brushes of the same brands gave dissimilar and lower levels of abrasion. Dilution changed the ranking of two of the four abrasives.