Dental implants are now a widely accepted treatment option for the replacement of missing teeth. The therapeutic goal of dental implants is to support restorations that replace single or multiple missing teeth so as to provide patient comfort, function, and esthetics as well as assist in the ongoing maintenance of remaining intraoral and perioral structures. However, anatomic limitations such as the maxillary sinus may limit the amount of bone available to place traditional length implants (>10 mm). To avoid invasive sinus elevation procedures, manufacturers have developed shorter implants (<10 mm). Multiple studies have proven that short implants are equally successful to longer implants [1,2,3,4,5,6,7,8,9]. Tapered implant design further enhances primary implant stability, especially in the posterior maxilla where bone quality is usually poor [10,11,12].

The purpose of this study was to evaluate the initial stability of the OsseoSpeed TX™^{Footnote 1} tapered implant (OSPTX) and to compare it to the standard OsseoSpeed™¹ parallel walled implant (OSP) as well as to compare the soft bone and standard surgical protocols. Both implants included in this study are manufactured from high-grade commercially pure titanium with surface roughness produced via a fluoride treatment process. The OSPTX and OSP implants are self-tapping implants. The implants used in this study were all of 4.0 mm in diameter and 8 mm in length. Microthreads™ characterize the coronal aspect of both implants. The OSPTX implant has the same features as OSP except the apex of the implant is tapered (Fig. 1).

Successful integration of dental implants is largely dependent on their primary stability [13]. Implants placed in the maxilla present more challenges due to the poor bone quality usually found in these areas. Another anatomic challenge in the posterior maxilla is the pneumatization of the maxillary sinus which can limit the length of implant that can be placed. To avoid invasive sinus augmentation procedures, implants have been designed in shorter lengths such as 8 mm. To further enhance short implant primary stability, a tapered design has been developed which has been proven to provide greater initial stability [10,11,12, 14]. Implant stability can be evaluated by different measures such as torque at the time of implant placement, resistance to reverse torque, and resonance frequency analysis (RFA). Multiple studies have established feasibility for validating implant stability in lab and animal models to justify using resonance frequency analysis in clinical trials [15, 16]. Limited literature exists on the OSPTX implant design, and to our knowledge, no clinical studies exist that compare OSP to OSPTX. A recent ex vivo comparison of two different designs of OSPTX implants in porcine mandibles demonstrated that a conical neck design presented higher primary stability (insertion torque and implant stability quotient (ISQ)) than a cylindrical neck design [17]. In our study, both the torque value and ISQ value were recorded at the time of placement. ISQ values were also recorded at implant uncovery at 6 weeks and also at 6 and 12 months when the final restoration was placed.