Loi Clinical evaluation of an improved cementation technique for implant-supported restorations : a randomized controlled trial

Background: Cement remnants were frequently associated with peri-implantitis. Recently, a shoulderless abutment was proposed, raising some concern about cement excess removal. Aim: To compare different cementation techniques for implant-supported restorations assessing the amount of cement remnants in the peri-implant sulcus. Additional aim was to compare the effect of these cementation techniques using two different abutment designs. Material & methods: Forty-six patients requiring double implant-supported restoration in the posterior maxilla were randomly divided in two groups according to the cementation modality: intraoral and extraoral. According to the abutment finishing line, implants in each patient were randomly assigned to shoulderless or chamfer subgroup. In the intraoral group, crowns were directly seated onto the titanium abutment. In the extraoral group, crowns were firstly seated onto a resin abutment replica and immediately removed, then cleansed of the cement excess and finally seated on the titanium abutment. After cement setting, in both groups, cement excess was carefully tried to remove. Three months later, framework/abutment complexes were disconnected and prepared for microscopic analysis: surface occupied by exposed cement remnants and marginal gaps were measured. Additionally, crown/abutment complexes were grinded, and voids of cement were measured at abutment/crown interface. Related-samples Friedman’s two-way analysis of variance by ranks was used to detect differences between groups and subgroups (P ≤ 0.5). Results: At the end of the study, a mean value of 0.45 mm ( 0.80), 0.38 mm ( 0.84), and 0.065 mm ( 0.13) and 0.07 mm ( 0.15) described surface occupied by cement remnants in shoulderless and chamfer abutment with intraoral cementation and shoulderless and chamfer abutment with extraoral cementation, respectively. A mean value of 0.40 mm ( 0.377), 0.41 mm ( 0.39) and 0.485 mm ( 0.47) and 0.477 mm ( 0.43) described cement voids at the abutment/ crown interface; a mean value of 0.062 mm ( 0.03), 0.064 mm ( 0.35), 0.055 mm ( 0.016) and 0.054 mm ( 0.024) described marginal gaps. Statistics showed tendency of intraoral cementation to have significantly higher cement remnants compared with abutments with extraoral cementation groups. At the same time, the presence of voids was significantly higher in case of extraoral cementation. No significant differences between groups for the variable “gap”. Conclusions: Despite the presence of more voids, extraoral cementation reduces cement excess. However, using low adhesivity cement and careful cement removal, a very limited quantity of cement remnants was observed also in the intraoral cementation. Implant-supported prostheses can be subdivided into screw-retained or cement-retained. In literature, there is actually no consensus on which of these techniques provide better mechanical or biological performances though advantages and disadvantages have been identified (Wittneben et al. 2014). Screw-retained prostheses are more easily retrievable (for instance, in case of loosening of the retaining screw or chipping of the veneering material) and, due to the reduced vertical amount of space needed, they are more indicated in cases with limited interocclusal distance (Torrado et al. 2004). Cement-retained reconstructions provide easier passivation on multiple implants Date: Accepted 4 March 2015 To cite this article: Canullo L, Cocchetto R, Marinotti F, Oltra DP, Diago MP, Loi I. Clinical evaluation of an improved cementation technique for implant-supported restorations: a randomized controlled trial. Clin. Oral Impl. Res. 00, 2015; 1–8. doi: 10.1111/clr.12589 © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 1 splinted frameworks, better esthetics (due to the lack of occlusal openings) and lower costs (Michalakis et al. 2003). On the other hand, literature suggests that, even after a careful removal procedure, some residual cement may remain in the periimplant sulcus (Chaar et al. 2011; Sailer et al. 2012). The risk of such event increases as the restorations’ margins are located deeper subgingivally (Linkevicius et al. 2011, 2013a,b). Cement remnants have been frequently associated with peri-implant disease (Wilson 2009; Linkevicius et al. 2013a, Korsch et al. 2014), and for this reason, screw-retained restorations have been suggested as a first choice in daily practice by some authors (Br€agger et al. 2005). An original cementation technique for implant-supported restorations has been proposed (Wadhwani et al. 2009) as a mean to reduce cement remnants in peri-implant sulcus: a silicon abutment replica is used as an initial “extraoral “cementation with the purpose to extrude excess cement from the crown, clean it and then place it onto the abutment intraorally to complete setting. An in vitro study (Chee et al. 2013) seemed to confirm the efficacy of the method compared with three other cementation methods. The abutment and crown design may play a role in increasing the risk of cement remnants in the peri-implant sulcus. In fact, to minimize cement remnants, undercuts should be reduced to a minimum (Vindasiute et al. 2013). Recently, a new prosthetic protocol aiming to improve esthetic outcomes of prosthetic restorations on natural teeth was presented (Loi & Di Felice 2013). This approach is based on a feather-edge preparation of abutment teeth and the gingival adaptation to crowns contours. The same principles and concepts are suggested by the authors for cemented implant restorations through the use of a shoulderless abutment design. However, such geometry presents increased undercuts, raising some concern about the difficulty to completely remove the excess cement. The aim of the present study was to compare in vivo two different cementation techniques for implant-supported restorations in relation to the amount of cement remnants in the peri-implant sulcus. Additional aim was to compare the effect of these cementation techniques using two different abutment design, chamfer and shoulderless. The article was written following the CONSORT statement for improving the quality of RCTs. Material and methods The present randomized controlled prospective study was performed following the principles outlined in the Declaration of Helsinki on experimentation involving human subjects. All procedures and materials in the present prospective study were approved by the Ethical Committee of the University of Valencia (# H1406287295470). Patients were required to sign a consent form after being informed about the study. Between Sept 2013 and Sept 2014, according to the power analysis, 46 consecutive patients needing two adjacent implant-supported restorations in the posterior maxilla were selected. Ninety implants (Premium SP; Sweden & Martina, Padua, Italy) were inserted in a two-stage modality. In all patients, Premium SP implants (Sweden & Martina) were used (Fig. 1). For every case, after implant osseointegration was achieved (2 months), healing abutments were connected (Fig. 2). After soft tissue healing, a silicon impression was taken at implant level. The working cast was scanned in laboratory (Echo, Sweden & Martina), and prosthetic components were designed and constructed with CAD CAM technology (Echo, Sweden &Martina) (Fig. 3). Abutment randomization Every implant in each case was randomly assigned to receive either an abutment with a chamfer finish line or an abutment with a shoulderless (feather edge) design: if the first implant received one kind of abutment design, the second would receive the other design. Random assignment was performed using a free dedicated software (www.examplerand omxxx.com).