Analysis of Primary Stability of Dental Implants Inserted in Different Substrates Using the Pullout Test and Insertion Torque

The aim of the study was to evaluate mechanical behavior of implants inserted in three substrates, by measuring the pullout strength and the relative stiffness. 32 implants (Master Porous-Conexao, cylindrical, external hexagon, and surface treatment) were divided into 4 groups ( ): pig rib bone, polyurethane Synbone, polyurethane Nacional 40 PCF, and pinus wood. Implants were installed with the exact distance of 5？mm of another implant. The insertion torque (N·cm) was quantified using the digital Kratos torque meter and the pullout test (N) was performed by an axial traction force toward the long axis of the implant (2？min/mm) through mount implant devices attached to a piece adapted to a load cell of 200？Kg of a universal testing machine (Emic DL10000). Data of insertion torque and maximum pullout force were submitted to one-way ANOVA and Bonferroni tests ( ). Polyurethane Nacional 40 PCF and pinus wood showed the highest values of insertion torque and pullout force, with significant statistical difference ( ) with other groups. The analysis showed stiffness materials with the highest values for primary stability. 1. Introduction Over the last few years, dental implants have shown satisfactory success rates in several clinical situations [1]. For favorable prognosis, some requirements are needed such as the absence of mobility of the implant during surgical procedure, which is defined as primary stability. This property is essential for the maintenance of the peri-implant hard and soft tissues [2–4] and, for this reason, it is a determining factor for complete osseointegration [5–7]. Good primary stability allows balanced distribution of masticatory effort and functional occlusal loads [8] soon after the implant is inserted. This stability may decrease over time due to peri-implant bone remodeling [9]. For long-term success in Implant Dentistry, the following factors related to the patient must be taken into consideration: bone quality and volume, peri-implant clinical parameters, implant stability [6, 9], factors related to the surgical technique, and the selection of implants. These previously assessed factors provide predictable osseointegration and if load can be applied or not. Some methods for assessing primary stability have already been proposed, as insertion torque and resonance frequency, but no methods show completely precise results. Medical orthopedics proposes a method to simulate this analysis, the pullout test, which despite the need for specific devices for each type of implant, it is established in this medical specialty [10–17].