Additively manufactured resin-based endocrowns: Effect of material type, margin configuration, and pulp chamber depth on fabrication trueness and fit

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OBJECTIVE: To evaluate the effects of margin configuration and pulp chamber depth on the fabrication trueness and internal fit of resin-based endocrowns fabricated with additive (AM) and subtractive manufacturing (SM). METHODS: Four mandibular first molar typodonts prepared with butt joint or 1 mm-wide shoulder margins and 2 mm or 4 mm pulp chamber depths were digitized to design reference endocrowns. These designs were used to fabricate endocrowns with AM (Crowntec [AM-CT], FREEPRINT Crown [AM-FP], Tera Harz TC80DP [AM-GR]) or SM (Tetric CAD [SM-TC]) (n = 7). Surface deviations (external, intaglio, and marginal root mean square, RMS) and triple scan protocol (average gap) were used for digital analyses. Data were analyzed with generalized linear models (α = 0.05). RESULTS: Intaglio RMS was affected by the interaction of all main factors, while all surface deviations were affected by material type-margin configuration interaction. Material type-pulp chamber depth interaction affected intaglio RMS and average gaps, whereas margin configuration-pulp chamber depth interaction affected all outcomes, except intaglio RMS (P ≤ 0.001). AM-GR mostly led to lower intaglio and marginal RMS, while SM-TC mostly led to lower external RMS (P ≤ 0.022). SM-TC endocrowns with 4-mm depth had the highest and AM-GR endocrowns with 4-mm depth mostly had lower average gaps (P ≤ 0.024). CONCLUSIONS: The interactions among the main factors affected the trueness of the tested endocrowns. However, no clear trend emerged that would highlight any subgroup as having the highest trueness. Most endocrowns demonstrated clinically acceptable internal gaps. CLINICAL SIGNIFICANCE: Tested additively manufactured resin-based endocrowns had favorable internal adaptation. However, they may require more chairside adjustments on external surfaces compared to tested subtractively manufactured endocrowns.