The retention of implant-supported prostheses is provided by the use of a screw or cement. Recently, it was demonstrated that cement-retained prostheses had a higher rate of technical and biological complications [1], despite a better passive fit than the screw-retained restorations [2]. The CAD/CAM development of the implant-supported prostheses allows a better passively fit with screw-retained prostheses [3], and the development of the mechanics of screws reduced screw-loosening complications [4]. Screw retained prostheses can be retrievable and seem to be an efficient restorative method to prevent peri-implantitis caused by cement excess around the abutment [5, 6]. Nevertheless, these restorations have some disadvantages due to the presence of an access-hole opening that can alter the occlusal morphology and reduce the fracture resistance of the ceramic [7, 8]. It is reported that the integrity of the access-hole filling is in relation with the ceramic fracture resistance [9]. The esthetic outcome of the access hole filling is also influenced by the marginal integrity and the long-term stability of the filling material [10, 11].

An in vitro evaluation of a modified 4-META (4-methacryloxyethyl trimellitate anhydride)/MMA-TBB (methyl methacrylate-tri-n-butyl borane) – based resin (M4M) was conducted to compare the wear behavior to a photo-polymerizing nano-hybrid composite resin (CR), and the results were quite promising [12].

The aim of this in vivo study was to compare the access-hole filling integrity of two different filling materials, M4M and CR, during 12 months. The null hypothesis was that superficial and marginal deterioration of M4M and CR would not be significantly different.