Influence of the Altered-Cast Impression Technique on Distal-Extension Alveolar Ridge Morphology and Restorative Result / 天津医药

ABSTRACT

Objective To investigate the impact of the modified cast impression technique on distal-extension alve-olar ridge morphology of partially edentulous casts and the restoration outcome of removable partial dentures (PRDs). Meth-ods Fifty-four patients with mandibular free-end dentition defect were selected. Impressions were taken from each patient using both modified cast technique and conventional technique. Coronary cross-sections of the casts were scanned from dis-tal to mesial extension;the images were compared to reveal morphological differences. And the relationship between these differences and location of the cross-sections were analyzed. After the patients were evenly divided into two groups per paired design, the impressions were taken using the respective modified cast and conventional impression techniques to pre-pare RPDs. The subsequent comparisons between the two groups included frequency of adjustments during the adaptive phase, masticatory efficiency of the denture at ending of the adaptive phase and visible movement of the extension base dur-ing mastication. SPSS 16.0 software was used for statistical analysis. Results The number of pixels in the same cross-sec-tion was less in the impression taken with modified cast technique than that with conventional technique. And their differ-ence is of statistical significance (P ＜ 0.01). The difference in the number of pixels (D) was negatively correlated with the number of cutting and grinding, and N (location of the cross-sections). In addition, there were statistically significant differ-ences in frequency of adjustments during the adaptive phase (times1.12 ± 0.77 vs 3.41 ± 0.82), masticatory efficiency of the denture (0 vs 18.5%) and visible movement of the extension base during mastication (96.3%vs 74.1%) between the modified cast group and conventional group. Conclusion Morphology of distal-extension alveolar ridge of the casts differs signifi-cantly between the impressions obtained with modified cast technique and the impressions obtained with the conventional technique;the difference increases with greater distance to the distal surface of the terminal abutments. The restoration out-come of RPDs is significantly better with the modified cast impression technique than with the conventional impression tech-nique.