Radiographic Evaluation of Narrow Diameter Implants after 5 years of clinical function: a Retrospective Study. 
Abstract The use of regular sized dental implants is generally recommended to ensure adequate bone to implant contact.  However when the width of the edentulous crest is insufficient for the placement of a regular sized implant, the use of a narrow diameter implant (NDI) should be considered to prevent the use of invasive reconstruction techniques such as grafting procedures.  The aim of the present study was to evaluate the survival and marginal bone levels of NDIs five years after prosthetic loading.  One hundred and fifty-nine NDIs belonging to four brands (Straumann, Astra Tech, Biolok, Xive) in 71 patients were evaluated.  Clinical and radiographic evaluations using digital panoramic radiography were carried out.  Two implants failed and no progressive bone loss or periapical lesions were detected in the remaining 157 implants which brings an overall success rate of 98.74%.  The mean marginal bone loss (MBL) was found as 1 mm on mesial and 0.98 mm on distal side of the implants.  No statistically significant relationship was detected between patient age, gender, implant location, implant length, type of the prosthesis and MBL (P > 0.05).  Among the 4 brands used, the MBL around Biolok implants were detected as the highest; but significantly higher than the MBL around only the Astra Tech implants (P < 0.05).  The results of the present study indicated that NDIs can be a good solution for specific clinical situations where regular sized implants are not suitable.