Technovit 4071

Osteoarthritic femoral heads (n = 5) were obtained from patients undergoing routine total hip arthroplasty for clinically diagnosed OA (by X-ray) at the Royal Hallamshire Hospital (Sheffield). The specimens were stored in 70% ethanol at the time of retrieval for at least one month to reduce biological risk [28 (link)]. All research procedures were approved by the ethics committee of the South Yorkshire and North Derbyshire Musculoskeletal Biobank (Reference Number: STH 15691).
On the day prior to testing, specimens were removed from the ethanol solution, placed on absorbent paper for 30 min to remove excess liquid and potted in polymethylmethacrylate (PMMA, Technovit 4071, Kulzer GmbH, Hanau, Germany). The specimens were aligned such that the loading axis was perpendicular to the intraoperative surgical femoral neck cut. The femoral neck portion was potted in a 6 mm thick PMMA baseplate and a 6 mm top-plate was created that conformed to the superior surface of the femoral head (2–4 mm deep) to ensure an even application of the load. Parafilm was placed between the embedding material and the femoral head to ensure that the specimen did not adhere to the top plate whilst the resin set. After potting, specimens were placed in a custom-made loading device (Figure 1).

A block-shaped mold with the negative shape of the occlusal cFDP geometry was planned in the CAD software (Geomagic DesignX Build Ver. 2022.0, 3D Systems). The insertion direction of the cFDPs (identical to the tooth axis directions) was oriented vertically. This mold was 3D-printed (V-Print Model, Voco GmbH, Cuxhaven, Germany) and attached with its planar upper side to a paralleling device. Aluminum blocks received two drillings, each 14 mm in diameter and 8 mm in distance. After provisionally joining metal dies and cFDPs, cFDPs were attached to the paralleling device via the mold, such that the vertical direction was identical to the insertion direction, and the die roots were covered with shrink tubing and lowered into the drillings of the aluminum block and embedded with acrylic resin (Technovit 4071; Kulzer GmbH).

Sixty ti-base abutments (diameter 4.3 mm, GH 2.0 mm, CONELOG, Titanium base Crown, Camlog Biotechnologies AG, Basel, Switzerland) were divided into five groups (n = 12) according to the cleaning protocol after contamination with human saliva (Table 1). The sample size was based on previous studies using a similar methodology [8 (link),9 (link),10 ,31 ,32 (link)].
The design of the lithium disilicate crown (IPS e.maxCAD A3/A 16 (S), Ivoclar Vivadent, Schaan, Liechtenstein) was derived from an upper central incisor of 15 mm in dimensions and was modified by a horizontal ring, as used in previous studies, to provide a standardized pull-off testing procedure [9 (link),10 ,32 (link)].
Sixty implants (diameter 4.3 mm GH 16 mm CONELOG, Camlog Biotechnologies AG, Basel, Switzerland) were fixed in a standardized way in acrylic resin blocks and bonded with self-curing acrylic (Technovit 4071, Kulzer GmbH, Hanau, Germany), according to ISO Norm 14801 (ISO, 2006), with a 3 mm exposed rough implant surface to simulate bone loss.
The ti-base abutments received a standardized airborne-particle abrasion surface treatment with 50 µm aluminum oxide at 2.0 bar of air pressure and were then cleaned in an ultrasonic alcohol bath for 5 min and dried with oil-free air.