Two 3D-printed crown materials (Crown and Ceramic Crown) were examined to determine the best surface treatment and primers for bonding. Discs of the two materials were printed and mounted with their “intaglio” surfaces untouched. Half the specimens from each group were sandblasted with 50 µm alumina. Then, specimens were divided into four groups (n = 10): Gr1—no further treatment; Gr2—one coat of silane; Gr3—one coat of universal adhesive; Gr4—one coat of silane, then one coat of universal adhesive. Bond strength specimens were prepared with an Ultradent shear bond strength apparatus using Filtek Supreme composite. Specimens were stored for 8 weeks in 37 °C water. The specimens were debonded with a circular notched-edge blade applied at 1 mm/min, and the shear bond strength was calculated. The data were compared with a two-way ANOVA (factors: surface treatment and primer) and a Tukey post hoc analysis for both materials independently, with p < 0.01 considered meaningful. The filler content (burned ash) and resin content (FTIR) of the materials were determined. For both materials, factors surface treatment and primer were significant (p < 0.01), but their interaction was not (p = 0.43 for Crown and p = 0.34 for Ceramic Crown). Alumina air particle abrasion improved the bond strength for both materials. The Tukey post hoc analysis grouped primer treatments into the same statistically different groups for both materials: Gr1 and Gr2 < Gr3 and Gr4. The filler percentage of Crown was 32.7% and Ceramic Crown was 48.2%. Resin content was similar for both materials. The most effective method to bond to 3D-printed crowns (regardless of filler percentage) was to sandblast with 50 µm alumina and apply a layer of adhesive (with or without previous application of silane).

The aim of this study was to evaluate and compare the surface roughness and gloss—both initially and after simulated toothbrushing—of three 3D-printed crown materials subjected to different surface treatments: varnishing, polishing with diamond-impregnated rubber polishers, and polishing with a bristle brush and paste. Disc-shaped specimens (n = 90) were 3D-printed using three commercially available crown resins (Rodin Sculpture, VarseoSmile TriniQ, and OnX Tough 2) and post-processed per manufacturers’ instructions. Specimens were divided into three surface treatment groups: application of a light-cured varnish, polishing with a two-step diamond-impregnated rubber polisher, or polishing with a bristle brush and abrasive paste. Surface roughness and gloss were measured after treatment and again following 20,000 cycles of simulated toothbrushing. Additional specimens were prepared for Vickers microhardness testing and determination of filler weight percentage (wt%). Statistical comparisons were performed using two-way ANOVA with significance set at p < 0.05. Results: The varnish provided the statistically lowest roughness of all surface treatments for all materials. The bristle brush and abrasive paste polishing protocol produced the greatest gloss for the softest material (VarseoSmile TriniQ) and lowest gloss for the hardest material (Rodin Sculpture), whereas the two-step diamond-impregnated rubber polisher produced an equivalent gloss on all materials. Following toothbrushing, roughness was minimally affected; however, gloss was considerably reduced. Conclusions: All tested polishing and varnishing methods achieved clinically acceptable surface roughness (Ra < 0.2 µm) that persisted after simulated toothbrushing. Notably, the two-step diamond-impregnated rubber polisher produced consistent gloss across all materials, while the bristle brush and abrasive paste polishing protocol performed better on softer materials, and varnish application resulted in equal or superior gloss and roughness retention compared to polishing.

Additive manufacturing has expanded the fabrication of occlusal splints; however, the influence of printing technology and build orientation on accuracy remains unclear. This study evaluated the effect of printing technology (Liquid Crystal Display [LCD] and Digital Light Processing [DLP]) and build orientation (0°, 45°, and 90°) on the trueness of additively manufactured occlusal splints under standardized conditions. A maxillary occlusal splint was digitally designed from a scanned typodont and used as the reference model. Specimens (n = 10/group) were fabricated using two LCD printers (Ackuretta SOL, Phrozen Mini 8K S) and one DLP printer (SprintRay Pro 95S) with a single photopolymer resin (KeySplint Soft). All samples were printed at 100 µm layer thickness and subjected to standardized post-processing. Trueness was assessed by comparing scanned splints to the reference STL using Geomagic Control X and expressed as root mean square (RMS) values. Data were analyzed using two-way ANOVA and Tukey post hoc tests (α = 0.05). Printing technology and build orientation significantly affected trueness (p < 0.001), with RMS values increasing as build orientation increased, and no significant interaction between factors (p > 0.05). LCD systems demonstrated lower RMS values than the DLP system across all orientations. Within the limitations of this study, both factors influenced trueness; however, all systems produced clinically comparable results, supporting the use of LCD technology as a cost-effective option for occlusal splint fabrication.