Prosthodontic treatment

Forty-nine days (range: 27–113 days) after placement of the healing abutment, the abutment was removed and the implant position was registered by an impression coping on the implant.

The final implant-supported restoration was fabricated by using an individually designed angulated screw channel (ASC) zirconium abutment (Nobel Biocare®, Zürich, Switzerland) and veneering porcelain. The metal adaptor (Nobel Biocare®, Zürich, Switzerland), ASC abutment (Nobel Biocare®, Zürich, Switzerland) and porcelain crown were screw-retained with a torque of 35 Ncm. All materials and clinical procedures were handled according to the manufacturer’s instructions.

Follow-up regimen

All patients were recalled after a mean follow-up period of 24 months from crown placement (range: 14–32 months) by JH.

Outcome measures

• Implant survival: Implant failure was defined as implant mobility or removal of a stable implant due to progressive peri-implant marginal bone loss or infection.

• Implant crown survival: Failure of the implant crown was defined as a loss of a mounted crown irrespective of the cause.

• Clinical parameters (probing depth, bleeding on probing, presence of plaque, keratinised peri-implant tissue, recession of peri-implant soft tissue)

• Radiographic peri-implant marginal bone change

• Radiographic marginal bone change of the adjacent tooth surfaces

• Biological and technical complication

• Patient-related outcome measures (PROMs)

Probing depth (PD) and bleeding on probing (BOP) were measured using a light probing force (approximately 25 g) to the nearest millimeter with a conventional periodontal probe at six sites per implant (mesiobuccal, buccal, distobuccal, distooral, lingual and mesiooral). Plaque was registered using a plaque control record (PCR; presence of plaque yes/no) [34]. Recession of peri-implant tissue (REC; six sites) and the width of the keratinised peri-implant tissue (KT; 1 buccal aspect of the implant) were measured to the nearest millimeter with the above-mentioned periodontal probe.