Long-term evaluation of hollow screw and hollow cylinder dental implants: Clinical and radiographic results after 10 years

Background: In 1988, an implant manufacturer offered a new dental implant system, with a wide choice of hollow cylinder (HC) and hollow screw (HS) implants. The purpose of this retrospective study of HS and HC implants was to evaluate clinical and radiographic parameters of peri-implant tissue and to analyze surgical and prosthetic aftercare. Methods: A total of 89 HS and 26 HC implants in 38 edentulous patients were available for complete evaluation. The patients were treated with overdentures stabilized by two or four implants. The follow-up period was 10 years. Results: The results of the clinical evaluation showed a mean sulcus probing depth of 3.3 +/- 1.3 mm (range = 2 to 10 mm). The mean radiographic bone loss was 2.2 +/- 2.1 mm (range = 0. 1 to 12.2 mm). One implant (HS) was removed during the osseointegration period. Three other implants (two HS and one HC) in three patients had to be removed after 10 years. The survival rate of the HS implant (96.6%) was comparable to the HC implant (96.1%). The success rate of the HS implant (93.3%) was slightly more favorable compared to the HC implant (88.5%). The HS and HC implants met the Albrektsson criteria of success. Conclusions: HS and HC implants provide a stable base for long-term support of a mandibular overdenture. Furthermore, it is important to monitor peri-implant bone level by taking annual radiographs and measuring probing depth, especially after prolonged service