Retention performance of magnetic attachments on dental implants

Introduction: Considering the problem of stabilization of removable prostheses dental mag-netic systems (DMS) offer an alternative to traditional methods. Regarding the technological advantages during the last years DMS have been developed that promise an increase of retentive force by small type of construction. Two physical principles are used: mono-systems with open (MO) and with closed magnetic loops (MC). Furthermore, there are 3 de-signs of keepers for retained roots: prefabricated dowelretained keepers (PK), individual caps of magnetic alloys (IC) and preformed magnets cast on caps of conventional alloys (CC).The aim of this study was to evaluate and to compare the mechanical performance of contemporary DMS used on tooth roots. Methods: 11 different DMS were standardized tested for maximal retentive force and dynamical development during draw off in an adjusted computer-navigated test-machine (v=20mm/s, s=40mm). From IC/CC-systems root-attachments were produced according to the manufacturers' instructions. 5 specimens of each product were investigated. Denture-magnets and the corresponding keepers or caps were fixed in an individual non-magnetic construction. The results were descriptively and statistically analysed (H-/U-Test). The findings were compared with the manufacturers' statements. Results: The maximum retentive force ranged from 6,58N to 1,38N. Compared to the manufacturers' information significantly lower initial retention forces were found in all specimens (p0.05). MC showed the highest and MO the lowest initial retention forces. This relation changed with an increasing gap between root and magnet. Considering the different heights and diameters of the products no significant differences were found among the PK-, IC- and CC-systems. Conclusion: In all products maximum retention forces were found no-table under the manufacturers' information. There were significant differences between the clinically important draw-off forces, whereas no differences between the rootkeeper-designs were found. These results could be useful by individual choice of DMS on retained tooth roots. Keywords: magnets, keeper, retention, overdentures, attachments