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P e r i i m p l a n t s o f t - t i s s u e a n d b o n e l e v e l s w i t h d i f f e r e n t i m p l a n t n e c k d e s i g n s Introduction Bone loss after implant integration and through time of function usually begins at the neck and spreads to the first thread of the body or to the first contact between the bone and the rough surface of the implant,1 and can be divided into 2 different phases depending on the time of occurrence.2–5 The first, early bone loss, is related to re-entry surgery after the healing time or prosthetic connection,6 and the second, late bone loss, emerges during the time of implant and prosthesis function.4, 7, 8 Criteria for evaluation of implant success are generally based on clinical and radiological aspects, such as probing depth, implant mobility and periim- plant bone changes.9 It has been reported that the criteria for successful implant therapy include a median marginal bone loss of < 1–1.5 mm during the first year, followed by an annual rate of vertical bone loss of ≤ 0.2 mm.10 In the last few decades, it has been sug- gested that marginal bone loss is dependent on several factors, such as the implant neck sur- face design1, 4, 11–13 and characteristics.14, 15 It has been proposed that bone retention elements such as microthreads and a rough surface at the implant neck might help stabilize the mar- ginal bone.1, 12, 16, 17 Although the conventional smooth implant neck allows the least accumu- lation of plaque,18, 19 several studies have eval- uated marginal bone loss according to the implant neck involved—machined implant necks and rough necks with microthreads—and have shown more marginal bone loss around these implants compared with implants with a rough surface topography at the implant neck.4, 12, 13, 20 The relatively smooth, machined coronal portion is designed to end slightly above the gingival margin of the periimplant soft tissue, thus making the microgap or inter- face between implant and restoration easily accessible for oral hygiene and resulting in a supragingival location of the crown margin.21 Lang et al. in a consensus report concluded that prospective controlled studies on the effects of different implant designs and surfaces had demonstrated that marginal bone levels were generally well preserved after installation of the dental prosthesis (at least for fixed resto- rations) on a variety of implant types (cumula- tive bone loss: < 0.5 mm after 3 years).11 How- ever, these studies had a 1-year follow-up and there are no clinical studies comparing the long-term influence of different designs and surface treatments of implant necks on periim- plant tissue. The purpose of this study was to assess the effect of the implant neck designs and neck surface treatments on periimplant tissue health and radiographic bone loss after 3 years of functional loading of implants with the same body and prosthetic connection but different neck designs. Materials and methods S t u d y d e s i g n a n d s a m p l e A retrospective cohort study was carried out in the Oral Surgery and Implantology Unit of the University of Valencia, Valencia, Spain, between September 2015 and December 2016. This study complied with the ethical principles for medical research involving human subjects established in the Declaration of Helsinki of 1975, as revised in 2013, of the World Medical Assembly. All of the patients received information about the study and were asked to sign a written informed consent form before taking part. The study design was approved by the ethics board of the University of Valencia (approval number: H1467620442582). Patients who had received single or partial prosthetic rehabilitations on TSA or TSA Advance implants (Phibo, Barcelona, Spain), had a minimum of 3 years of follow-up and who agreed to participate in the study and signed an informed consent were included. Patients who had undergone bone grafting procedures (block bone grafts or guided bone regeneration), had immediate post-extraction implants, had sys- temic diseases, were undergoing drug treat- ments capable of affecting gingival health, or had a history of bisphosphonate use during con- trol visits, as well as pregnant or nursing women and patients with missing information, were excluded. Patients were classified into 2 cohorts according to the implant design: – group A (TSA): patients treated with implants presenting a neck design without micro- threads, with a 1.5 mm machined surface and an internal connection and without platform switching (Fig. 1a); and – group B (TSA Advance): patients treated with implants presenting a neck design with a 0.7 mm machined surface and microthreads with a rough surface and an internal connec- tion and without platform switching (Fig. 1b). Journal of Oral Science & Rehabilitation Volume 3 | Issue 4/2017 17