Abstract
The purpose of this study was to evaluate different retention systems (cement- or screw-retained) and crown designs (non-splinted or splinted) of fixed implant-supported restorations, in terms of stress distributions in implants/components and bone tissue, by 3-dimensional (3D) finite element analysis. Four 3D models were simulated with the InVesalius, Rhinoceros 3D, and SolidWorks programs. Models were made of type III bone from the posterior maxillary area. Models included three 4.0-mm-diameter Morse taper (MT) implants with different lengths, which supported metal-ceramic crowns. Models were processed by the Femap and NeiNastran programs, using an axial force of 400 N and oblique force of 200 N. Results were visualized as the von Mises stress and maximum principal stress (σmax). Under axial loading, there was no difference in the distribution of stress in implants/components between retention systems and splinted crowns; however, in oblique loading, cemented prostheses showed better stress distribution than screwed prostheses, whereas splinted crowns tended to reduce stress in the implant of the first molar. In the bone tissue cemented prostheses showed better stress distribution in bone tissue than screwed prostheses under axial and oblique loading. The splinted design only had an effect in the screwed prosthesis, with no influence in the cemented prosthesis. Cemented prostheses on MT implants showed more favorable stress distributions in implants/components and bone tissue. Splinting was favorable for stress distribution only for screwed prostheses under oblique loading.
Highlights
Rehabilitation with implant-supported fixed prostheses is a predictable modality to restore lost function and esthetics in partially or totally edentulous patients
No difference was found for the splinted crown design for both retention systems (Figs. 3 and 4)
The cement may be better at filling discrepancies, absorbing and equalizing the stress of deformations caused by contact between the abutment and implant in the prosthesis structure [16]
Summary
Rehabilitation with implant-supported fixed prostheses is a predictable modality to restore lost function and esthetics in partially or totally edentulous patients. Morse taper (MT) implants have shown high success rates with good bone preservation in implantsupported restorations [1]. This clinical performance can be explained by the reduced incidence of microgap and bacterial contamination [2]. The maxillary posterior area after tooth loss often can limits the use of the longer implants. In these situations, short implants may be recommended with the aim of avoiding auxiliary surgical procedures [5]. Short implants may present greater risks when compared to implants with conventional lengths, especially when placed in the posterior region [6]. The splinted crowns of short implants can be indicated in atrophic maxilla because transmit more uniform stress in structures with higher reduction of stress in the periimplant region [4]
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