Purpose : Prosthodontic complications related to implant assisted maxillary overdentures are reported more often. This in vitro study examined the influence of implant number and palatal coverage on retention, cyclic fatigue and denture base deformation of maxillary overdentures supported by five versus seven unsplinted mini implants.
Materials and methods: An edentulous model of maxillary arch with mini diameter implant dummies was fabricated. The implants were inserted into the anterior, premolar, and molar areas. Maxillary experimental dentures with complete and partial palatal coverage were fabricated. Cyclic dislodging forces were applied to assess cyclic fatigue and the resulting change in denture retention. Strain gauges were used to assess the deformation induced into the dentures when cyclic fatigue test was carried out on overdentures assisted by seven implants and five implants after excluding the posterior implants.
Results: Cyclic fatigue and denture base deformation induced in overdentures with partial palatal coverage assisted by five mini implants were significantly higher than overdentures with complete palatal coverage whether assisted by seven or five implants (P < .05). Overdentures with partial palatal coverage assisted by seven mini implants exhibited non-significant changes in retention, cyclic fatigue and base deformation when compared to overdentures with complete palatal coverage assisted by five mini implants.
Conclusion: Maxillary five mini implant assisted overdentures with partial palatal coverage revealed much higher cyclic fatigue and induced denture base deformation than overdentures with complete palatal coverage regardless of the mini implant number. With respect to retention, fatigue failure and denture deformation, maxillary seven mini implant assisted overdentures with partial palatal coverage exhibited no significant difference comparable to five mini implant assisted maxillary overdenture with complete palatal coverage.