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Journal of Oral Science & Rehabilitation Volume 2 | Issue 1/2016 49 F a c t o r s a f f e c t i n g p r i m a r y s t a b i l i t y o f t a p e r e d i m p l a n t s w i t h d i f f e r e n t t h r e a d d e s i g n Introduction Dental implant stability is important for achiev- ing osseointegration. The implant body design and the thread geometry are significant for im- provement of the mechanical implant stability. Tapered implants appearto have bettermechan- ical stability than do parallel-walled implants.1 A study comparing the insertion torque of ta- pered and ofcylindricalimplants has shownthat tapered implants are associated with higher primary stability than are cylindrical implants.2 In an experimental study on dogs, Kim et al. compared the mechanical properties oftapered and parallel-walled implants interms ofsuccess rates.3 Maximum insertiontorque and maximum removal torque were assessed. The results showed significantlyhighervalues of maximum insertion torque and maximum removal torque for tapered implants than for parallel-walled implants. In addition, use of cylindrical non- threaded implants has been associated with a higher implant failure rate compared with threaded implants.4 Moreover, it has been pos- tulated that tapered implants have a better load distribution to surrounding bone by mimicking the natural root form.5 The implant bodydesign andthethread geo- metryhavebeencomparedinamulticenterclini cal study with immediate loading protocols. Different implant designs, such as tapered im- plants with a symmetric thread design (Nobel- ReplaceTapered Groovy),tapered implantswith a progressive thread design (NobelActive inter- nal connection), and cylindrical implants with the same thread profile as the NobelActive in- ternal connection but with a narrow neck (NobelActive external connection), presented a similarcumulative survivalrate afterthreeyears of loading.6 In addition, the bone condensation technique in cancellous bone and other surgical techniques may influence implant stability.7 The quality ofthe osteotomy might be influ- enced by the clinician’s surgical experience1, 8 and therefore the primary stability could be affected.Thereisalackofstudiesintheliterature evaluating primary stability and its relation to surgical experience. Therefore, the aim of this studywastoevaluatetheprimarystabilityoftwo implantdesignswithdifferentthreadgeometries placed by two clinicians with different levels of clinicalexperienceinimplantsurgicalprocedures and placed into two different bone qualities. Materials & methods Two surgeonswith different levels ofexperience performed the drilling: expert (GR, 25 years’ ex- perience in implant dentistry, had placed more than 10,000 implants) and intermediate (RD, 15 years’experienceinimplantdentistry,hadplaced fewer than 5,000 implants). The implant bed on synthetic bone blocks was prepared for two dif- ferent implant designs: Replace Select Tapered regular platform (Nobel Biocare, Gothenburg, Sweden), a tapered implant with a symmetric thread design (TST) and conical connection; and Figs. 1a & b a b Mechanical properties Block ofType II density Block ofType IV density Compressive yield strength 31.0 MPa 2.30 MPa Compressive modulus 0.759 GPa 0.032 GPa Table 1 Mechanical properties of the synthetic blocks used in the experiment. Figs. 1a & b Synthetic bone blocks used in the experiment. (a) Type II dense bone. (b) Type IV soft bone. Table 1 Volume 2 | Issue 1/201649