الفهرس 
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Abstract
RPI and I-bar clasps are currently used in bilateral free-end saddle cases due to their stress releasing effect. The clasp arm disengages the tooth by applying a class II lever effect. However, this is not the case in asymmetric bases because the fulcrum line shifts distally towards the short saddle area and places the retentive tips mesial to the fulcrum axis. This applies a class I lever effect and places torque on the abutment. Thus, it seemed valuable to asses the effect of RPL clasp with a retentive tip placed more distally and farther from the fulcrum axes, on the abutment and the residual ridge.
Fifteen patients exhibiting lower asymmetric free-end saddles were selected and rehabilitated with removable partial dentures. Patients were divided into three equal groups according to the type of clasp placed on abutments on the short edentulous side. RPI, RPL and I-bar clasps were used respectively for groups I, II and III. Whereas the abutment on the long edentulous side received RPI clasp in the three groups.
Data required for this study were collected before denture insertion, three, six and nine months after denture insertion.
Pocket depth measurement using William’s graduated periodontal probe revealed a slight increase in pocket depth for all abutments of short and long saddle areas. Abutment bearing I-bar clasps showed significant difference in increase of pocket depth compared to those bearing RPL and RPI clasps.
Radiographic assessment of changes in bone height and density, around the abutments and at specially marked points on the residual alveolar ridge, was carried out by RVG system following long cone paralleling technique.
Marginal bone loss was significant at the end of the study period for all abutments of short saddle area. No statistical significant difference in loss of bone height between groups receiving RPI and I-bar clasps. However, significantly less amount of marginal bone loss was detected for abutment receiving RPL clasps.
Crestal bone loss was evident for all groups at the short and long saddle areas, but no significant difference was detected among the three groups on both short and long saddle areas.
Increase in bone density was evident at the end of the study period around abutments of both short and long saddle areas for the three groups. Patients receiving RPL clasps showed the least increase in bone density, while there was no difference between the other two groups.
Effect of RPI clasp retainer on the increase in pocket, reduction of marginal and crestal bone height and increase in bone density on the long saddle area was the same among the three groups.