Validity of the M-L scale and Vivadent scale in clinical wear study

Shu-cheng Chang, DDS, MS,(a) Shiro Suzuki, DDS, PhD,(b) and Yu-Hwa Pan, DDS, MS(c)

(a)Mackay Memorial Hospital, Taipei, Taiwan, (b)Clinical Research and Department of Prosthodontics, University of Alabama at Birmingham, Birmingham, USA, and (c)Dental Department, Chang-Gung Memorial Hospital, Keelung, Taiwan

Purpose: The purpose of this study was to evaluate the validity of two commonly used visual inspection methods, the M-L scale and the Vivadent scale, in a clinical wear study.
Materials and Methods: Sixty study casts were evaluated using both the Micro-Vu metrology system and visual inspection methods. Values obtained by using the visual inspection methods were correlated to those measured by the Micro-Vu metrology system. The same principles were applied to prepare specimens to test the precision of the proposed technique.
Results: This new impression technique in conjunction the Micro-Vu system was proved to be precise. The mean of the differences between repeat measurements was 1.26 μm with a standard deviation of 0.8 μm. When comparing the validity of the two scales, the M-L scale was found to be better than the Vivadent scale. Values obtained by using visual inspection methods were larger than values obtained by using the Micro-Vu metrology system. Overall values obtained by using the M-L scale were smaller than those obtained by the Vivadent scale. The effect of evaluators and the interactions between influencing factors were prominent as to significantly reverse the effect of some evaluators.
Conclusion: Based upon the results of this study, it was concluded that the validity of the currently used visual inspection methods was considerably influenced by many factors, the desirability of continuing these types of measurements for definitive wear assessment should be reconsidered. (Int Chin J Dent 2005; 5: 22-32.)

Key Words: Baldwin illusion, mental average procedure, M-L scale, validity, Vivadent scale.