Title:
[Dual insertion paths design characteristics and short-term clinical observation of rotational path removable partial dentures].

Abstract:
To investigate design methods of dual insertion paths and observe a short-term clinic overview of rotational path removable partial  dentures (RPDs).
In the study, 40 patients with partial edentulous arches were included and divided into two groups. The patients in group one  were restored with rotational path RPDs (10 Kennedy class III and 10 Kennedy class IV respectively). The patients in group two (20 patients), whose  edentulous area was matched with the patients' in group one, were restored with the linear path RPDs. After surveying and simulative preparation on  diagnostic casts, the basic laws of designing rotational path RPDs were summarized. The oral preparation was accurately performed under the guidance  of indices made on diagnostic casts after simulative preparation. The 40 dentures were recalled two weeks and one year after the insertion. The  evaluations of the clinic outcome, including retention, stability, mastication function, esthetics and wearing convenience, were marked out as good,  acceptable, and poor. The comparison of the evaluation results was performed between the two groups.
In the rotational path design for  Kennedy class III or IV RPDs, the angles (α) of dual insertion paths should be designed within a scope, approximate 10°-15°.When the angle (α) became  larger, the denture retention turned to be better, but accordingly the posterior abutments needed more preparation. In the clinical application, the first  insertions of the 40 dentures were all favorably accomplished. When the rotational path RPDs were compared to linear path RPDs, the time consuming on  first insertion had no statistical difference[(32±8) min and (33±8) min respectively, P>0.05]. Recalled two weeks and one year after the insertion, in the  esthetics evaluation, 20 rotational path RPDs were all evaluated as "A", but only 7(two weeks after) and 6 (one year after) linear path RPDs were evaluated  as "A"(P<0.05). There was no significant difference in other evaluation results.
Rotational path incorporated an initial straight path of  placement, which gained access to undercut areas by rigid guide plate, followed by a final curved path of placement. Without showing clasps in the  anterior part of the mouth, esthetics could be improved remarkably. The results of this preliminary study suggest that rotational path RPDs can get the  similar retention, stability and mastication function as linear path RPDs. Meanwhile, simulative preparation on diagnostic casts, oral preparation under the  guidance of indices and precise fabrication of framework are indispensable procedures.