Comparative evaluation of implant designs: influence of diameter, length, and taper on strains in the alveolar crest. A three-dimensional finite-element analysis.
OBJECTIVE
Our aim was to analyze and compare systematically the relative and interactive effects of implant diameter, length, and taper on calculated crestal bone strains.


METHODS
Three-dimensional finite-element models were created of a 20-mm premolar section of the mandible with a single endosseous implant embedded in high- or low-density cancellous bone. Oblique (200-N vertical and 40-N horizontal) occlusal loading was applied. Cortical and cancellous bone were modeled as transversely isotropic and linearly elastic. Perfect bonding was assumed at all interfaces. A two-level factorial statistical design was used to determine the main and interactive effects of four implant design variables on maximum shear strains in the crestal alveolar bone: diameter, length of tapered segment, length of untapered segment, and taper. Implant diameter ranged from 3.5 to 6 mm, total implant length from 5.75 to 23.5 mm, and taper from 0 to 14 degrees , resulting in 16 implant designs.


RESULTS
Increasing implant diameter resulted in as much as a 3.5-fold reduction in crestal strain, increasing length caused as much as a 1.65-fold reduction, whereas taper increased crestal strain, especially in narrow and short implants, where it increased 1.65-fold. Diameter, length, and taper have to be considered together because of their interactive effects on crestal bone strain.


CONCLUSIONS
If the objective is to minimize peri-implant strain in the crestal alveolar bone, a wide and relatively long, untapered implant appears to be the most favorable choice. Narrow, short implants with taper in the crestal region should be avoided, especially in low-density bone.
Petrie
Cynthia S
CS
Department of Restorative Dentistry, School of Dentistry, University of Missouri-Kansas City, Kansas City, MO 64108, USA. petriec@umkc.edu
Williams
John L
JL
D000539:Alveolar Process / Q000473:pathology / Q000503:physiopathology*; D001641:Bicuspid; D015519:Bone Density / Q000502:physiology; D015921:Dental Implants; D017267:Dental Prosthesis Design; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible / Q000473:pathology / Q000503:physiopathology; D008954:Models, Biological; D016348:Osseointegration / Q000502:physiology; D013314:Stress, Mechanical
D015921:Dental Implants