Lee, Jason DViera, Oliver2026-05-0620262026-05-062026Viera, Oliver. 2026. Effect of Customized CAD/CAM Geometry Versus Conventional Surface Treatments on Shear Bond Strength of Reline Material to 3D-Printed Provisional Resin. Masters Thesis, Harvard University School of Dental Medicine.32677505https://dash.harvard.edu/handle/1/42736758Statement of the Problem The interfacial bond between 3D-printed provisional resins and conventional polymethyl methacrylate (PMMA) reline materials is a critical determinant of clinical performance in modern prosthetic dentistry. Current strategies to enhance this bond rely primarily on post-fabrication surface treatments. Although these techniques can improve adhesion, they are often technique-sensitive and may introduce variability or unintended surface damage, potentially compromising clinical outcomes. Purpose
This in vitro study evaluated whether incorporation of a CAD/CAM-designed honeycomb macro-geometry into the surface of 3D-printed provisional resin could improve adhesion to conventional PMMA reline material when compared with commonly used mechanical and chemical surface treatment protocols. Materials and Methods
A total of 72 specimens (n=12 per group) were fabricated using a 3D-printed provisional resin and allocated to six surface modification groups: untreated control (C), sandblast (S), monomer application (M), CAD/CAM honeycomb geometry (H), combined sandblast–monomer treatment (SM), and combined honeycomb–sandblast modification (HS). For the honeycomb groups, a macro-geometric hexagonal pattern was incorporated into the “intaglio” treatment surface during the digital design phase prior to fabrication. All specimens were luted to an autopolymerizing PMMA resin. Mechanical testing was performed using a universal testing machine (UTM) at a crosshead speed of 0.5mm/min. Outcome measures included shear bond strength (MPa), peak load (N), and energy to yield (N·mm). Statistical analysis was conducted using one-way analysis of variance (ANOVA) followed by Tukey post hoc comparisons, with a significance level of α=.05. Results Statistically significant differences were observed among surface modification groups for shear bond strength and peak load (F(5,66)=22.01, P.001) as well as for energy to yield (F(5,66)=8.53, P.001). H demonstrated the highest mean shear bond strength (40.20 ± 7.28 MPa) and peak load (505.20 ± 91.43 N), corresponding to approximately a 2.7-fold increase in shear bond strength compared with C (15.00 ± 6.01 MPa). H also exhibited the greatest energy to yield (264.37 ± 194.94 N·mm), indicating increased energy absorption prior to failure. Conventional surface treatments improved bond strength, however, no modification protocol outperformed H. Conclusion Surface modification with honeycomb geometry significantly improves PMMA adhesion to printed provisional resin without compromising structural integrity and decreasing laboratory steps.application/pdfen3D PrintingCAD/CAMGeometryHoneycombPMMAShear bond strengthDentistryMaterials ScienceThesis or Dissertation2026-05-060009-0001-8533-0054