After 7 years (7.3 years [6.7–8]), all patients who completed the original study were invited for a re-examination. After a multitude of recall strategies including telephone and letters, 17 subjects responded and were recalled to the university dental clinic between April and November 2015. After signing the written informed consent, medical and dental history were recorded and a clinical examination and full-mouth radiographs were taken.

In total, 12 subjects completed baseline, 12-month and 7-year examinations and were thus included in this analysis (Fig. 1).

All clinical examinations were performed by the same calibrated, blinded and board-certified periodontist (AMA) who also had done the examinations in the previous study. The same clinical indexes and the same type of instruments as in the original study were used.

Dichotomous plaque scores and PPD were recorded at six sites per treated implant, using a 0.20-N (20-g) defined force periodontal probe (UNC, DB 764 R, AESCULAP, B. Braun). Dichotomous bleeding on probing (BoP) and dichotomous purulent suppuration (PuS) were all registered at six sites (i.e. mesiofacial, facial, distofacial, distolingual, lingual and mesiolingual). The height of the buccal keratinized mucosa was also registered.

One postgraduate student from the prosthodontic department evaluated the supraconstructions related to access for interproximal oral hygiene, misfit of prostheses, prosthetic material, number of implants supporting the fixed dental prostheses, presence of cantilever extensions and presence of abutments.

The occlusion, articulation, interferences, horizontal overbite, vertical overbite and occlusal morphology were examined and recorded.

Evaluation of the supraconstructions considering mechanical complications such as fractures of or material or chipping, abutment screw loosenings, abutment fractures, and implant and framework fractures were performed.

The prosthetic supraconstructions were carefully cleaned and positioned in ultrasound before repositioned on the implants.

Intraoral radiographs were obtained of the included implants and for the full dentition using Digora phosphor plates with a standard Eggen film holder (Eggen X-ray AS). The radiographs were scanned and digitized with the Digora Optime Soredex intraoral digital imaging system. The technique used at baseline and at the 12-month recall appointment, with an occlusal bite index with dental wax (Kerr Dental®) stuck to an Eggen film holder, had dried out and was no longer possible to use at the 7-year re-examination.