Abstract
The aim of this study was to evaluate the effect of varying the diameter, connection type and loading on stress distribution in the cortical bone for implants with a high crown-implant ratio. Six 3D models were simulated with the InVesalius, Rhinoceros 3D 4.0 and SolidWorks 2011 software programs. Models were composed of bone from the posterior mandibular region; they included an implant of 8.5 mm length, diameter Ø 3.75 mm or Ø 5.00 mm and connection types such as external hexagon (EH), internal hexagon (IH) and Morse taper (MT). Models were processed using the Femap 11.2 and NeiNastran 11.0 programs and by using an axial force of 200 N and oblique force of 100 N. Results were recorded in terms of the maximum principal stress. Oblique loading showed high stress in the cortical bone compared to that shown by axial loading. The results showed that implants with a wide diameter showed more favorable stress distribution in the cortical bone region than regular diameter, regardless of the connection type. Morse taper implants showed better stress distribution compared to other connection types, especially in the oblique loading. Thus, oblique loading showed higher stress concentration in cortical bone tissue when compared with axial loading. Wide diameter implant was favorable for improved stress distribution in the cortical bone region, while Morse taper implants showed lower stress concentration than other connections.
Highlights
The placement of implants in the posterior mandible with reduced bone availability is a challenge for dental implantology
Due to the small number of studies that have investigated the effect of diameter and connection type, the aim of this study was to evaluate the effect of varying the diameter and connection type on stress distribution in the cortical bone tissue for implants with a high crown-implant ratio
Oblique loading showed higher tensile compared to axial loading, external hexagon (EH) and internal hexagon (IH) implants showed a higher tensile stress than Morse taper (MT) implants, regardless of the implant diameter (Fig. 4B)
Summary
The placement of implants in the posterior mandible with reduced bone availability is a challenge for dental implantology. The options that can facilitate placement of conventional implants include use of bone graft and/ or lateralization of the inferior alveolar nerve; this modality of treatment is associated with high costs and morbidity. The use of short implants may be an alternative, viable and effective treatment option [1]. Short implants with wide diameter may increase survival rates [2]; it is more acceptable than surgical placement of bone grafts in the posterior jaw [3]. There is concern regarding the longevity of these implants from a biomechanical perspective [4]. The incidence of oblique loads at short implants can impact longevity [5], mainly owing to the increase in crown-implant ratio [6], which increases stress concentration in the bone tissue around the implant [7]
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