| Summary: | The purpose of this investigation was to observe the connecting rigidity of various precision attachments and to compare their connecting rigidities with the conical crown retained telescope (CCT). The connecting rigidity of a retainer was assessed using the flexibility test to measure the mesial and distal end displacements. Four precision attachments were analyzed: the dovetail slide attachment beyeler, cylindrical slide attachment, Spang Stabilex and Mini SG. The CCT was used as the control. Although there were many statistically significant differences between the displacements with the various attachments, displacements when vertically loaded were very small: all mesial end displacements were within 3 μm and distal end displacements were 21.4 μm. The largest of the mesial end displacements when horizontally loaded was as large as 44.5 μm (dovetail slide beyeler), while the others were all below 16.5 μm. The same phenomena occurred with the distal end displacements when horizontally loaded: the largest was seen with the dovetail slide beyeler, followed sequentially by the Spang Stabilex, CCT, cylindrical slide, and the Mini SG. The distal displacement with the dovetail slide beyeler was as large as 75.2 μm; those with the others were all below 31.2 μm, with numerous statistically significant differences between the displacements with the various attachments. Thus, connecting rigidities of rigid precision attachments are very similar to CCT, and only the dovetail slide beyeler attachment is too weak to resist horizontal displacement force.
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