Influence of pretreatment strategies on the tensile bond strength of 3D printed composite resins for definitive cementation to dentin

Statement of problem: Little is known about factors influencing the bond strength of additively manufactured materials in dentistry. The impact of diverse pretreatment strategies on the bond strength of 3-dimensionally (3D) printed composite resins indicated for definitive cementation to dentin has scarcely been investigated. Purpose: The aim of this study was to evaluate the adhesive bond strength of two 3D printed definitive fixed restoration materials to dentin by using different pretreatment protocols. Material and methods: Composite resin rods (2×2×10 mm, n=20/group) were 3D printed with 3Delta Crown and saremco print CROWNTEC. Half of the rods were airborne-particle abraded (APA), the other half of the rods were untreated. All rods were chemically conditioned with 1 of 3 adhesives (Adhese Universal, Heliobond, Monobond Plus). Dentin rods (2×2×5 mm) were cut from bovine teeth, pretreated with Adhese Universal, and bonded to the composite resin rods with Variolink Esthetic LC. The specimens were thermocycled (10 000 cycles) before testing for tensile bond strength (TBS) and the assessment of the failure mode. Surface roughness (SR) and degree of conversion (DC) were examined with laser scanning microscopy and Raman spectroscopy. Data were statistically analyzed with 1-, 2-, and 3-way analyses of variance (ANOVAs) and Weibull analysis (α=.05). Results: TBS values ranged from 6.57 to 10.58 MPa, without significant differences among the groups (P>.05). All groups demonstrated a comparable Weibull modulus and predominant adhesive failure. SR increased significantly (P<.05) upon APA, and the DC ranged from 70.1% to 71.9%. Conclusions: Regardless of the 3D printable material, SR was increased by APA, and the DC was around 70%. Different mechanical and chemical pretreatments appear to exert relatively little influence on TBS.