A 6-Year Prospective Study of 620 Stress-Diversion Surface (SDS) Dental Implants
A 6-year prospective study was conducted to assess the clinical success rates and crestal bone response of a dental implant system with a stress-diversion design. Mathematical modeling, digital radiography with applied isodensity, and finite element analysis were used to highlight the effect of the stress distribution design. A total of 386 hydroxyapatite-coated prototypes and 234 commercial grit-blasted external hex implants were placed in virgin bone as well as various grafted maxillary regions, with 36% of the posterior implants being immediately loaded. Prototypes achieved 96.6% survival over a 3-year period. The grit-blasted implant, placed from 2000 to 2003, showed a 95% survival rate. There were no significant changes in crestal bone levels after the first 12 months of prosthetic loading. Engineering evaluations suggested that undesirable stresses were distributed from the crest of the ridge down through the center of the implant body.Abstract
The study implant: (A) standard external hex, (B) polished 0.7-mm titanium collar, (C) 6.5-mm with stress-diversion thread, (D) tapered self-tapping implant body, (E) cutout in the driving thread
Isodensity marking on bone around the (A) study implant configuration at the crest of the ridge and other regions of equal density, (B) at the study implant thread portion of the implant, (C) at the crest of the ridge of a standard screw implant, and (D) the remainder of the standard implant body
Number of failures in the 6-year implant study
Finite element analyses of the study implant and standard screw-type implants showing von Mises stresses. In both pairs of schematics, the study implant is on the left and the standard screw implant is on the right. (A) Depicts on-axis compressive loading of 50 pounds of force (average occlusal load) with equal parameters in both models. Note the reduction in crestal stress, depicted by the smaller red band (maximum von Mises stress) around the study implant at the crest of the ridge versus the standard design. (B) Depicts these same implants under off-axis transverse cantilever loading of 4.535 inch-pounds. Again, the study implant shows a decrease in the crestal stress (red) band and the dispersion of these stresses toward the center of the implant
Contributor Notes
Gary R. O'Brien, DDS, is in general practice in Los Angeles. Address correspondence to Dr O'Brien, 411 North Central, Suite 225, Glendale, CA 91203 (drobrien@scidentistry.com)
Aron Gonshor, PhD, DDS, is in private practice and is a lecturer at McGill University, Oral and Maxillofacial Surgery, Montreal, Quebec, Canada
Alan Balfour, BSBE, is an independent biomedical engineering consultant who assisted in the design of the SDS Dental Implant, and is located in Petaluma, California