Esthetic dental crowns are restorative solutions designed not only to restore masticatory function but also to maintain a natural tooth-like appearance. In selecting materials for esthetic crowns, dentists must consider factors such as fracture strength, wear resistance, color matching, compatibility with surrounding tissues, and margin design (finishing line).
One notable experimental study compared the fracture resistance of zirconia-porcelain crowns and porcelain-fused-to-metal (PFM) crowns with chamfer and shoulder margin designs. The findings provide valuable insight for selecting optimal materials and designs in esthetic restorations.
Research Findings and Their Implications
A study published in the Jurnal Kedokteran Gigi (JKG) FKG UGM by Elka Ayu Amalia, under the supervision of drg. Herijanti Amalia Kusuma, SU, Sp.Pros(K) and Dr. drg. Endang Wahyuningtyas, M.S., Sp.Pros(K), entitled “Perbedaan Ketahanan Fraktur Mahkota Zirkonia-Porselen dan Porcelain Fused to Metal dengan Finishing Line Chamfer dan Shoulder”, tested 24 crown samples divided into four groups:
- Zirconia-porcelain with chamfer margin
- Zirconia-porcelain with shoulder margin
- PFM with chamfer margin
- PFM with shoulder margin
All samples were tested for fracture resistance using a Universal Testing Machine (UTM) until cracking or fracture occurred, followed by statistical analysis.
Key Results
- Zirconia-porcelain crowns demonstrated higher fracture resistance than PFM crowns.
- Chamfer margin design provided better fracture resistance than shoulder margins.
- No statistically significant difference was found between zirconia-porcelain crowns with chamfer and shoulder margins (p > 0.05).
- For PFM crowns, chamfer margins outperformed shoulder margins in terms of fracture resistance.
The study concluded that both material selection and margin design significantly influence the mechanical performance of esthetic crowns.
Important Factors in Selecting Esthetic Crown Materials
Based on the literature and the findings above, several key factors must be considered:
| Factor | Explanation | Clinical Implications |
|---|---|---|
| Fracture Strength | The material must withstand occlusal and lateral forces | Zirconia-porcelain offers superior fracture strength compared to PFM |
| Margin Design (Finishing Line) | Chamfer margins distribute stress more effectively and reduce stress concentration | Chamfer margins are recommended, particularly for esthetic restorations |
| Esthetics / Translucency | Materials should mimic natural teeth, especially in anterior regions | Modern zirconia can achieve sufficient translucency for esthetic use |
| Biocompatibility & Absence of Metal Margins | Materials should not irritate soft tissues or create dark marginal lines | Ceramic/zirconia materials are more advantageous than PFM in esthetic zones |
| Tooth Preparation Requirements | Minimizing tooth reduction is essential for conservative treatment | Strong materials allow thinner restorations, preserving tooth structure |
| Long-Term Durability & Wear | Materials must resist fracture and wear under oral conditions | Zirconia tends to be durable; PFM remains an option with a long clinical track record |
Case-Based Selection Strategies
- Tooth Location (Anterior vs Posterior)
- Anterior teeth require high esthetics (translucency, color), favoring zirconia with porcelain layering or full-contour ceramics.
- Posterior teeth prioritize strength due to higher occlusal loads.
- Margin Design and Preparation
- Chamfer margins are preferred when possible, as studies indicate better fracture performance.
- Proper material thickness, internal angles, and marginal adaptation are essential to avoid stress concentration.
- Tooth and Supporting Tissue Condition
- Teeth with weakened remaining structure require stronger materials and margin designs that minimize additional load.
- Periodontal health must be ensured prior to esthetic restoration.
- Oral Environment Factors
- Factors such as pH, moisture, dynamic occlusal forces, thermal cycling, and fatigue stress influence wear and fracture.
- Differences in thermal expansion coefficients between coping materials and porcelain (as in PFM) may create residual stresses that reduce fracture resistance.
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Material selection for esthetic dental crowns must consider multiple aspects, including mechanical strength, margin design, esthetics, tissue preservation, and the patient’s clinical condition. Based on research comparing zirconia-porcelain and PFM crowns with chamfer and shoulder margins, zirconia-porcelain crowns with chamfer margins demonstrated the best fracture performance. However, in clinical practice, no single solution fits all cases; each patient requires individualized assessment to ensure long-lasting esthetic and functional restorations.
References
Jurnal Kedokteran Gigi, Elka Ayu Amalia, drg. Herijanti Amalia Kusuma, SU, Sp.Pros(K), Dr. drg. Endang Wahyuningtyas, M.S., Sp.Pros(K), PERBEDAAN KETAHANAN FRAKTUR MAHKOTA ZIRKONIA-PORSELEN DAN PORCELAIN FUSED TO METAL DENGAN FINISHING LINE CHAMFER DAN SHOULDER, https://journal.ugm.ac.id/jkg/article/download/30008/18074
Author: Rizky B. Hendrawan | Photo: Freepik
