Abstract
ObjectivesThe wear of telescopic crowns is a common problem often reducing the patient's satisfaction with the denture and resulting in a renewal of the denture. The study aims to compare the wear behavior of conical crowns using electroplated copings (group E) with standard telescopic crowns with cast female parts (group C). Material and Methods10 conical crowns were milled for each group of a cast gold alloy. The specimen of group E had a conicity of 2º. The cast secondary crowns of group C had a 0º design. The electroplated coping was established by direct electroforming. An apparatus accomplishing 10,000 wear cycles performed the wear test. The retentive forces and the correlating distance during insertion and separation were measured. The wear test was separated in a start phase, an initial wear phase and the long term wear period. The retention force value and the force-distance integral of the first 0.33 mm of each cycle were calculated. ResultsThe retentive forces were significantly higher for group E and the integrals were significantly lower for this group except the integral at cycle 10,000. The changes of retention force and integral did not differ significantly between both groups in all phases. The change of the integrals as well as the integral at the particular cycles showed higher interquartile distances for group C. ConclusionsWithin the limitations of this study the tested conical crowns showed clinically acceptable retentive properties. The values reached a range comparable to retentive elements tested in recent literature. The values of group C showed higher ranges. The force measured for group E was significantly higher than for group C but the integrals showed an opposite tendency. The results indicate that an exclusive analysis of the force is not sufficient as the integral is not equivalent to the force although it describes the retentive property of the system in a better way than the force over a distance is described. Both systems seem to be suitable for clinical practice.
Highlights
There is a wide choice of different retentive elements that can be used for denture retention[1-5,8,13]
The initial retention force of the group E specimens reached a median value of 6.54 N and an interquartile range of 2.25 N (Table[1], Figure 4)
Within the limitations of this study it can be stated that the two double crown systems tested reach sufficient retention forces
Summary
There is a wide choice of different retentive elements that can be used for denture retention[1-5,8,13]. Almost all of these systems consist of two main parts used to connect teeth or implants to removable dentures. The change is caused by tribological processes affecting the surface structures of the male and female parts[6,8,9]. The four most relevant tribological factors are tribochemical reaction, abrasion, adhesion and surface disruption. They can appear separately or can overlap each other[10]. The influence, appearance and combination of these factors are affected by the material and construction of the retentive element
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