Table 2.

In vitro studies on the mechanical properties of the implant-abutment connection by the prosthetic index

Reference	Method	Model	Implant and/or abutment	Results or Implications
Zancope et al., 2017 [28]	Bending Test and Fatigue Loading Test	Three-dimensional finite element model	Morse taper implants, with 11.5-degree angulation of the internal conical portion	The presence of the prosthetic index on the Morse tapered implant did not reduce the fracture resistance of the implant
Zhang et al., 2022 [29]	Loading Test	Three-dimensional finite element model	3.5 mm × 11 mm bone level implants with an indexed component, Ankylos, Dentsply Friadent GmbH, Mannheim, Germany	Morse taper connection with platform switching (MT-PS) with indexing could reduce stresses within cancellous bone, but lead to higher stress concentrations in the abutment neck and greater susceptibility to mechanical complications
Perriard et al., 2002 [18]	Loading test and fatigue tests	Resin block model and three-dimensional finite element model	standard 6 degrees taper 7 mm height abutment (Straumann, Waldenburg, Switzerland)	The mechanical resistance of the abutment to bending and torsional forces is equal regardless of whether the prosthetic index is present
Hung et al., 2019 [30]	Torque/detorque test and loading test	Three-dimensional finite element model	5 mm × 11 mm implants with an indexed component, Shinhung MST	Internal hex connection has higher compressive strength than internal hex connection combined with Morse taper design
Villarinho et al., 2017 [11]	Mechanical cycling and Removal torque and tensile removal force tests	Resin block model	3.75 mm × 11 mm Morse taper connection implants (Neodent, Curitiba, Brazil)	Indexed tapered abutments may induce greater biomechanical risk in single-crown restorations when under function
Cerutti-Kopplin et al., 2014 [32]	Reverse torque tests	Stainless-steel block model	4.3 mm × 10 mm implants with Morse taper connections (Alvim CM; Neodent) with an internal hexagona	There was no significant difference in reverse torque between indexed and non-indexed support groups
Martins et al., 2019 [13]	Mechanical fatigue test	Resin block model	3.5 mm × 11.5 mm implants with prosthetic Morse taper connection (Pross Implantes, RibeirãoPreto, SP, Brazil)	Indexed abutment retaining screws were more susceptible to loosening during reverse torque testing than non-indexed abutments
Hyun et al., 2020 [33]	Compressive strength tests	Resin block model	4 mm bone level implants with an indexed component (ComMed, Chang Gung medical technology Co., Ltd, Taiwan)	The increase in contact area resulted in less variation in rotation of Morse tapered abutments containing the positioning index
Yao et al., 2015 [22]	Antirotational tests	Resin block model	5.0 × 10 mm implant with a conical connection (taper angle = 7°) (CowellMedi, Busan, South Korea)	Adding a positioning (octagonal) index to the taper connection provides resistance to rotation but affects the flexural strength of the abutment
De Oliveira et al., 2016 [12]	Removal torque and tensile removal force test after thermomechanical cycling	Resin block model	4 mm × 13 mm implants with an indexed component (Titamax CM Cortical, Instradent AG)	Morse tapered abutments with positioning (hexagon) index have good resistance to rotation
Michelon et al., 2019 [34]	Mechanical cycling and postcycling tensile strength test	Resin block model	Morse taper connection implants, 3.5 × 11.0 mm with 11.5-degree internal angle conical connection	Cyclic loading increased the tensile strength of the Morse tapered implants regardless of the presence of an index. The presence of the index did not significantly change the tensile test values before and after cyclic loading
Nokar et al., 2020 [35]	Torque/detorque test and loading test	Stainless-steel block model	4.5 mm × 10 mm bone level implants (Implantium, Dentium Co, Seoul, South Korea)	Abutments with indexes do not have reduced flexural capacity under static loading compared to abutments without prosthetic indexes