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Journal of Oral Science & Rehabilitation No. 4, 2016

Journal of Oral Science & Rehabilitation Volume 2 | Issue 4/2016 63 E f f e c t s o f i n s e r t i o n t o r q u e o n h a r d a n d s o f t t i s s u e a f t e r t w o y e a r s Introduction The use of dental implants is considered a safe and reliable procedure for replacing missing teeth.Severalfactorsareinvolvedintheachieve- ment of implant primary stability, such as the insertion torque, the implant’s macrogeometry, the surgical technique, and the bone quality and quantity. Primary stability is regarded as one of the main factors for the achievement of osseo- integration, that is, secondary stability.1 It has been observed that micromovements > 50–150 μm have a detrimental effect on bone formation aroundthe implant surface, leadingto the formation of fibrous tissue and consequent- ly implant failure.2 With implant primary stabili- ty being related to the mechanical connection between the implant and the bone, it could be influencedbytheimplant’sdesign,thebonequal- ity and quantity, and the surgical site prepara- tion.3, 4 Inserting an implant in an undersized implant site osteotomy requires considerable force,which is referredto asthe insertiontorque. The bone is an elastictissue before exceedingthe yielding point: It can tolerate a certain level of strain owing to a relaxation effect.5 When the strain exceeds the yielding point, bone microf- ractures can be observed; this could cause an ischemic necrosis6 and, consequently, bone re- sorption. High insertion torque protocols have been suggested to enhance and accelerate im- plant success, considered as being strictly relat- ed to the bone–implant mechanical interlocking and primarystability.7 However,the compressive forces caused by a high insertion torque could delay or compromise the process of osseointe- gration.8 A modified thread design could signifi- cantly help to decrease the strain developed on the bone surface comparedwiththe convention- al thread design.9 Although the scientific litera- ture is not uniform regarding the minimum in- sertion torque required to obtain successful osseointegration, values between 32 N cm and 50 N cm are recommended.10 One factor affect- ing the esthetic outcome of implants is buccal bonethicknessaftertheimplantsitepreparation. In healed ridges, 2 mmthickness is recommend- ed, although there is insufficient scientific evi- denceto establish athresholdforminimum buc- cal bone thickness.11, 12 The primary objective of the present study was to evaluate and compare the clinical out- comes for implants placed with a high insertion torque (50–100 N cm) and a regular insertion torque(within50Ncm)inhealedridges,interms of changes at the marginal bone level. The null hypothesis was that there was no difference in themarginalbonelevelchangesbetweenthetwo groups;thealternativehypothesiswasthatthere was a difference. The secondary objective of this study was to analyze the correlation between the residual thickness ofthe buccalbone afterimplant osteo- tomy preparation and the facial soft-tissue level tiontorqueandfrom50Ncmto100Ncmforhighinsertiontorque.Three implants failed. Two implants showed at the 12-month evaluation a mar- ginal bone loss > 1.5 mm and were thus considered unsuccessful. C o n c l u s i o n Implants inserted with a high insertion torque in healed bone ridges showedmoreperiimplantboneremodelingandfacialsoft-tissuerecession thanimplantsinsertedwithregularinsertiontorqueaftertwoyears,both in the maxilla and in the mandible. The findings suggest that the clinician should pay attention to several factors in implant therapy, such as the thickness of the buccal bone, the corticalization of the surgical site, the implant’s macrogeometry and the potential influence of insertion torque on implant therapy outcomes. K e y w o r d s Insertion torque, dental implants, buccal bone thickness, marginal bone resorption, soft-tissue recession. Volume 2 | Issue 4/201663

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