الفهرس 
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Abstract
The important goals in the prosthodontic treatment are mainly conservative, preservative and biologic; hence this study was carried out to assess the biologic effect of telescopic partial denture designs on denture supporting structures. The effect of a commonly used design with double bilateral telescopic crowns as retainers versus a design with single bilateral telescopic crown on abutments and cingulum rests on the adjacent teeth was the goal of this study.
This study was carried out on twenty patients having bilateral distal extension edentulous ridges with first premolars as the last standing abutments. Patients were thoroughly selected and prepared to avoid the effect of systemic and oral factors on the results of the study.
Partial dentures were designed with lingual bar as major connector and telescopic crowns as retainers. Patients were equally divided into two groups, according to the design of the retainers. Group I included patients that were rehabilitated by lower RPDs retained by bilateral TCs on abutment teeth and cingulum rests on the adjacent canine teeth. While group II, included patients that were rehabilitated by lower removable partial dentures retained by bilateral telescopic crowns on first premolars and canines on each side of the dental arch.
The effect of each design on the supporting structures was evaluated by measuring pocket depth, gingival index and marginal bone height of the abutments and the changes in height of the alveolar residual ridge.
Pocket depth was measured by graduated periodontal probe. Gingival index was assessed according to Loe and Silness gingival index score. (103) Bone height proximal to the abutments and the residual ridge 20 mm distal to the abutments were radiographically assessed by periapical radiographs following the long cone paralleling technique and scanned to the image processing software to be interpreted.
Data were collected at time of denture insertion, three, six, nine and twelve months after denture insertion. Data were statistically analyzed.
The results of the present study showed an increase in the means of pocket depth, marginal and crestal bone loss of abutments at the end of the study period for both groups. Comparing the changes occurring in both groups in the pocket depth, gingival index score and in the marginal bone loss was statistically insignificant. However, a statistically significant increase in the means of crestal bone loss was evident in patients rehabilitated by bilateral telescopic crowns and cingulum rests as indirect retainers.