Alternative Metal-free Conical Crowns Overdentures in Mandibular Immediate Loading

Objectives: Overdentures retained by conical crowns (ORCC) for the edentulous mandible is an entirely implant-supported overdenture, exactly like the Toronto Bridge, but removable. ORCC was first presented in 2001 by May and Romanos, using a pre-built metal-bar reinforced prosthetic system (ORCCm). We revised this technique by preparation of a metal free, fiber-reinforced ORCC (ORCCf). ORCCf is designed as a Toronto Bridge, with hygienically maintainable spaces between the implants and is lighter than ORCCm.

In this study we preliminarily compare ORCCf with ORCCm.

Methods: We prepared ORCCf fixed in place directly on surgery day, connecting it to four  fixtures inserted into the intraforaminal region of the edentulous jaw, through four conical crowns. We developed a metal-free and methylmetacrylate-free denture in which a thick layer of polyethylene fibres is mixed with composite-resin into which composite-teeth are inserted. The fibre-reinforced denture was completed on surgery day. ORCCm was built with standard methyl-metacrylate resins and resin-teeth.

In total, ORCCf group included 40 fixtures inserted in 10 patients. ORCCm group included 36 fixtures inserted in 9 patients. We compared number of fixtures lost and of major and minor breakages over a 12-month follow-up (Fisher's exact test). In both groups, standard surgical procedures for immediate loading were adopted.

Results:

	Fixture lost	Major breakages	Minor breakages
ORCCf Group	0	0	1
ORCCm Group	1	2	3

 No statistical differences were observed.

Conclusions: These preliminary results seem to suggest that ORCCf may be at least as durable as ORCCm in terms of number of fixtures lost and breakages. It should be considered that ORCCF is lighter than ORCCm and it could also be considered that a chairside reparation is always feasible, since ORCCf is composed of composite-resin. Therefore, ORCCf might potentially be a good alternative to standard ORCCm.