Influence of diameter and length on primary stability in various implant site densities-An in vitro study in polyurethane blocks.

BACKGROUND: The influence of dental implant length and diameter on primary stability in various bone densities is not well understood. AIM: To in vitro study the effect of length and diameter on resonance frequency analysis (RFA), insertion torque (IT) and displacement (DP) measurements of dental implants in different implant site densities. MATERIALS AND METHODS: Dental implants of four different diameters (O 3.5, 4.0, 4.5 and 5.0 mm) and three different lengths (7, 11 and 15 mm) (Neoss Ltd, Harrogate, UK) were placed in polyurethane blocks of three different densities (Sawbones Europe AB, Malmo, Sweden). The primary stability was assessed by RFA (ISQ) (Osstell, Osstell AB, Gothenburg, Sweden) and insertion torque measurements (IT(max) in N cm) (iChiropo, Bien-Air Dental SA, Bienne, Switzerland). In addition, the blocks were mounted in a rig and a lateral force of 25 N cm was applied to the implants and the DP was measured in mum with a micrometer gauge placed on the opposite side of the load transducer. Statistical analyses using linear and quadratic models were applied. RESULTS: Implant length, diameter and block density were found to be significant independent predictors of RFA, IT(max), and DP measurements. Implant length had a strong effect, while the effect of diameter in general was subtle, particularly in the softest block. CONCLUSIONS: Implant length affects primary stability more than implant diameter in polyurethane blocks of uniform density along the whole length of the tested implants.