Clinical investigation of the On1 two‐piece abutment concept‐ preliminary results

Abstract

Background: Conventional implant restoration procedures use one‐piece healing abutments that are secured at implant surgery and replaced with a final restoration after healing. Disconnection of the temporary abutment disrupts the initial soft tissue attachment and may compromise the peri‐implant mucosal barrier. Thus, a two‐piece abutment (On1, Nobel Biocare AB, Gothenburg, Sweden), consisting of tissue‐level base placed at the time of surgery and interchangeable prosthetic components, was developed. Aim/Hypothesis: This multi‐center investigation evaluated the clinical performance of the On1 concept after 1 year of function. The primary outcome was marginal bone level change. Secondary outcomes included soft tissue parameters, ease of use, patient and clinician satisfaction. Material and Methods: Patients requiring at least one single tooth replacement or 3‐unit bridge in canine or posterior sites were included. Anodized variable thread tapered implants (NobelActive, Nobel Biocare AB, Gothenburg, Sweden) were placed in healed sites and an On1 base (height 1.75 mm (_I_n _i_=_I_ _i_79), 2.5 mm (_I_n _i_=_I_ _i_29)) was immediately attached to the implant with an On1 healing cap. Digital impressions were taken 2 weeks after surgery and final prosthesis was placed after a 12‐week healing period. Clinical follow‐ups were performed at 3‐, 6‐ and 12‐months after prosthetic delivery. Intraoral radiographs were taken at implant insertion, prosthetic delivery, and at 6‐ and 12‐month follow‐ups. Soft tissue evaluation included quantification of buccal keratinized mucosa, gingival index (GI), modified sulcus bleeding index (mBI), and modified plaque index (mPI). Clinician reported ease of use and confidence were scored on a scale of 0–10. Data analysis was performed with SPSS v24 (IBM, Armonk, USA). Results: 74 patients (32 female, 42 male, age 53.1 ± 12.6y) received 108 implants. As of March 2018, 33 patients (40 implants) completed the 6‐month follow‐up. Implant survival was 98.1% with 2 implant failures in 2 patients. Mean marginal bone levels were −0.37 ± 1.0 mm (_I_n _i_=_I_ _i_101) and −1.1 ± 1.0 mm (_I_n _i_=_I_ _i_81) at implant insertion and prosthetic delivery, respectively. Buccal keratinized mucosa was present at all sites with a mean height of 3.4 ± 1.1 mm (_I_n _i_=_I_ _i_108) at implant surgery and 3.2 ± 1.5 mm (_I_n _i_=_I_ _i_40) at 6 months. mPI was 0.35 ± 0.54 and 0.63 ± 0.63, mBI was 0.28 ± 0.45 and 0.23 ± 0.42, GI was 0.2 ± 0.44 and 0.3 ± 0.52 at 3 (_I_n _i_=_I_ _i_69) and 6 (_I_n _i_=_I_ _i_40) months, respectively. Ease of use scores regarding base placement, tactile feeling at the connection, prosthetic delivery and impression taking were 7.2 ± 2.4, 7.0 ± 2.3, 5.7 ± 3.1 and 8.5 ± 1.7, respectively. Clinician confidence was 8.0 ± 1.5 (_I_n _i_=_I_ _i_56) and 8.4 ± 1.1 (_I_n _i_=_I_ _i_33) at 3 and 6 months, respectively. Conclusions and Clinical Implications: The On1 two‐piece abutment concept eliminates the need to disrupt the soft tissue barrier during the prosthetic workflow from start to finish. The presence of stable keratinized mucosa at all sites and slight improvements in gingival and bleeding indices after 6 months indicates that the On1 concept performs well in terms of soft tissue health. Together with good early survival rates, we conclude that the On1 concept is safe and effective for single tooth or 3‐unit bridge restorations. [ABSTRACT FROM AUTHOR]