Dental Literature Watch · RCT · Prosthodontics
Definitive 3D-printed resin posterior crowns: six times the wear of zirconia and 6 of 28 fractured within a year
TL;DR
- Definitive 3D-printed resin posterior crowns fractured more and wore far more than monolithic zirconia at one year, with equal marginal fit, periodontal outcomes and patient satisfaction.
- Six of 28 resin crowns and 2 of 28 zirconia crowns fractured: fracture-free survival 78.6% (95% CI 58.4-89.8%) versus 92.9% (74.3-98.2%), P = 0.12.
- Seven of the eight fractures were on the most-posterior restored tooth, and that position was associated with fracture (P = 0.002).
- Wear: 92.33 ± 69.81 µm depth and 4.31 ± 3.68 mm³ volume for resin versus 14.48 ± 7.95 µm and 0.47 ± 0.31 mm³ for zirconia (P < 0.05).
- Marginal and axial gaps did not differ; axio-occlusal and occlusal gaps were smaller for resin (P < 0.05).
- The authors' own conclusion: durability concerns, longer studies needed before broader use as definitive posterior restorations.
The study
| Element | Detail |
|---|---|
| Design | Randomised controlled prospective study, 1:1, 1 year |
| Population | 56 adults requiring a tooth-supported posterior single crown |
| Intervention | Definitive 3D-printed resin crown versus monolithic zirconia crown |
| Outcomes | Marginal and internal gap (replica technique before cementation); occlusal wear from intraoral scans at 1 week and 1 year; fractures; periodontal outcomes; patient satisfaction |
| Result: fracture | Resin 6 of 28, zirconia 2 of 28; fracture-free survival 78.6% vs 92.9%, log-rank P = 0.12; 7 of 8 fractures on the most-posterior restored tooth (P = 0.002) |
| Result: wear | Depth 92.33 vs 14.48 µm; volume 4.31 vs 0.47 mm³ (P < 0.05) |
| Result: fit | Marginal and axial gaps equal; axio-occlusal and occlusal gaps smaller for resin (P < 0.05) |
| Result: other | Periodontal outcomes and patient satisfaction did not differ |
💎 Insight — what this means chairside
The terminal tooth is where printed resin fails
Seven of eight fractures sat on the most-posterior restored tooth in the arch.
If a printed resin crown is used anywhere, that is the position to avoid.
Seven of eight fractures sat on the most-posterior restored tooth in the arch.
If a printed resin crown is used anywhere, that is the position to avoid.
Good fit does not predict durability
The resin crowns fit at least as well as zirconia at the occlusal surface.
Fit is what is checked at delivery; wear and fracture are what the patient brings back a year later.
The resin crowns fit at least as well as zirconia at the occlusal surface.
Fit is what is checked at delivery; wear and fracture are what the patient brings back a year later.
Wear of 92 microns in a year is a bite change, not a surface mark
Six-fold the wear of zirconia, on a material the opposing dentition will also wear against differently.
A long-term provisional with a planned replacement date is a different proposition from a definitive crown.
Six-fold the wear of zirconia, on a material the opposing dentition will also wear against differently.
A long-term provisional with a planned replacement date is a different proposition from a definitive crown.
⚠️ The catch
Why this sits at 2 of 5
It is a caution against adopting something, not a change to current standard care, and most practices are not yet placing printed definitive crowns.
It is here because labs and manufacturers are now marketing exactly this indication.
It is a caution against adopting something, not a change to current standard care, and most practices are not yet placing printed definitive crowns.
It is here because labs and manufacturers are now marketing exactly this indication.
Twenty-eight crowns per arm, one year, and a non-significant survival difference
Six versus two fractures gives P = 0.12 on the log-rank test; the trial is too small to call the survival difference real.
The wear difference is large and significant; the fracture signal is suggestive and position-linked.
Six versus two fractures gives P = 0.12 on the log-rank test; the trial is too small to call the survival difference real.
The wear difference is large and significant; the fracture signal is suggestive and position-linked.
One resin, one printer, one protocol
Printed resins differ in filler load and post-processing; the abstract does not name the material, so the result cannot be extended to every printed crown product.
Printed resins differ in filler load and post-processing; the abstract does not name the material, so the result cannot be extended to every printed crown product.
Abstract only
Tooth type, opposing dentition, parafunction screening and cementation protocol are not in the abstract.
Tooth type, opposing dentition, parafunction screening and cementation protocol are not in the abstract.
⚡ Bottom line
- Definitive crown on a terminal molar → zirconia; that is where 7 of 8 fractures occurred and where resin wear will matter most.
- Lab offers a printed resin crown as "definitive" at lower cost → this trial's authors say longer studies are needed first; treat it as a long-term provisional with a replacement plan.
- Printed resin as an interim or transitional crown → not what this trial tested, and nothing here argues against that use.
- Checking a printed crown at delivery → fit will look fine; the problems are wear and fracture, which appear later.
🧪 Questions
Tap an answer — instant grade, deciding line, and the trap.
A 40-year-old needs a definitive crown on a terminal mandibular second molar. The laboratory offers a 3D-printed resin crown as a definitive restoration at a lower fee. Based on this trial, which choice is best supported?
The most-posterior restored tooth was significantly associated with fracture (P = 0.002), and resin wear depth was 92 versus 14 µm, so a terminal molar is the worst case for printed resin. Equivalence is not what the trial found; wear differed significantly and fractures ran 6 to 2. Better fit is true and irrelevant to durability. Confirming a smaller occlusal gap is a delivery check that says nothing about one-year wear or fracture. Trap: the fit argument, which is the measurable advantage the resin crowns did have.
What was the one-year fracture-free survival of the definitive 3D-printed resin crowns in this trial?
Resin crowns had 78.6% fracture-free survival (95% CI 58.4-89.8%) at one year. 92.9% is the zirconia figure. 58.4% is the lower bound of the resin confidence interval and 98.2% the upper bound of the zirconia interval. Trap: 92.9%, the number that belongs to the comparator.