ABSTRACT
Background:
The durability of dental crowns is critical in pediatric dentistry to ensure long-term functionality and esthetics. Stainless steel crowns (SSCs) have been a staple in restorative pediatric dentistry, while zirconia crowns (ZCs) have emerged as an esthetic alternative.
Materials and Methods:
A total of 100 pediatric patients aged 4–8 years were included in the study and randomly divided into two groups: SSC (n = 50) and ZC (n = 50). Crowns were placed on primary molars requiring full-coverage restorations. Durability was evaluated over 12 months based on retention, marginal integrity, wear resistance, and fracture rates. Standardized clinical protocols were followed for crown placement and follow-up assessments at 3, 6, and 12 months. Data were statistically analyzed using a paired t-test and Chi-square test, with a significance level set at P < 0.05.
Results:
The retention rate after 12 months was 98% for SSCs and 92% for ZCs (P = 0.04). Marginal integrity remained optimal in 96% of SSCs and 88% of ZCs (P = 0.02). Wear resistance scores were comparable between the groups, with mean values of 8.5 ± 0.4 for SSCs and 8.2 ± 0.5 for ZCs (P = 0.21). Fracture rates were higher in ZCs, with 10% showing significant cracks or failure compared with 2% in SSCs (P = 0.03).
Conclusion:
Stainless steel crowns demonstrated superior durability in terms of retention, marginal integrity, and fracture resistance compared with zirconia crowns. Although zirconia crowns offer esthetic advantages, their higher fracture rates may limit their use in high-stress applications.
KEYWORDS: Crown retention, durability, marginal integrity, pediatric dentistry, stainless steel crowns, zirconia crowns
INTRODUCTION
The restoration of primary teeth is essential in pediatric dentistry to maintain function, esthetics, and arch integrity while preventing the premature loss of teeth.[1] Stainless steel crowns (SSCs) have been widely used for decades as the gold standard in full-coverage restorations for primary molars because of their durability, cost-effectiveness, and ease of placement.[2,3] However, the increasing demand for esthetic alternatives has led to the introduction of zirconia crowns (ZCs), which offer a more natural appearance while maintaining adequate strength.[4]
SSCs are characterized by their high fracture resistance and ability to withstand heavy masticatory forces, making them particularly suitable for children with parafunctional habits or extensive caries.[5] In contrast, ZCs have gained popularity for their superior esthetics, biocompatibility, and resistance to discoloration, although concerns about their fracture resistance and wear properties remain.[6] Despite these advantages, the selection of crown material often depends on clinical requirements, parental preferences, and the dentist’s expertise.[7]
Studies comparing SSCs and ZCs have shown mixed results regarding their durability, retention, and marginal adaptation.[8,9] Although SSCs are often favored for their proven longevity, ZCs have been reported to exhibit higher fracture rates, especially in high-stress areas.[10] The lack of consensus highlights the need for a comprehensive evaluation of these materials under clinical conditions to guide evidence-based decision making.
MATERIALS AND METHODS
Study design
This was a prospective, randomized clinical study conducted over a period of 12 months to compare the durability of stainless steel crowns (SSCs) and zirconia crowns (ZCs) in primary molars.
Study population
The study included 100 children aged 4–8 years attending the pediatric dental department. Inclusion criteria were primary molars requiring full-coverage restorations due to extensive caries or developmental defects, adequate tooth structure to support the crown, and cooperative behavior during treatment. Exclusion criteria included patients with systemic conditions affecting oral health, history of bruxism, or inadequate crown preparation.
Group allocation
Participants were randomly divided into two groups:
Group 1 (SSCs): Fifty primary molars restored with stainless steel crowns.
Group 2 (ZCs): Fifty primary molars restored with zirconia crowns.
Randomization was performed using a computer-generated random number table.
Crown preparation and placement
Teeth in both groups were prepared using standardized protocols. For SSCs, conventional crown preparation was followed, with occlusal reduction and minimal proximal reduction to allow crown placement. ZCs required additional reduction to achieve adequate clearance and passive fit due to their bulkier design. Cementation for both types of crowns was performed using glass ionomer cement.
Evaluation criteria
Crown durability was assessed at 3, 6, and 12 months based on the following parameters:
Retention: Evaluated as either present or lost.
Marginal Integrity: Assessed visually and with a dental probe for marginal adaptation.
Wear Resistance: Measured using a scoring system based on occlusal surface wear.
Fracture Rate: Recorded as the presence of cracks or fractures compromising crown function.
Clinical evaluations were performed by two independent examiners who were blinded to the crown type.
Statistical analysis
Data were analyzed using SPSS software (version 25.0).
RESULTS
The study evaluated the durability of stainless steel crowns (SSCs) and zirconia crowns (ZCs) in primary molars over 12 months. A total of 100 crowns were assessed, with equal distribution across the two groups.
Retention
Retention rates at the end of 12 months were 98% for SSCs and 92% for ZCs, showing a statistically significant difference (P = 0.04). The retention rates are summarized in Table 1.
Table 1.
Retention rates of SSCs and ZCs at 12 months
| Crown Type | Retention (%) | Lost Retention (%) | P |
|---|---|---|---|
| Stainless Steel | 98% | 2% | 0.04 |
| Zirconia | 92% | 8% |
Marginal integrity
Marginal integrity was optimal in 96% of SSCs and 88% of ZCs (P = 0.02). ZCs exhibited a higher frequency of marginal discrepancies compared with SSCs. Details are provided in Table 2.
Table 2.
Marginal integrity assessment
| Crown Type | Optimal Marginal Integrity (%) | Marginal Discrepancy (%) | P |
|---|---|---|---|
| Stainless Steel | 96% | 4% | 0.02 |
| Zirconia | 88% | 12% |
Wear resistance
The mean wear resistance scores for SSCs and ZCs were 8.5 ± 0.4 and 8.2 ± 0.5, respectively, with no statistically significant difference (P = 0.21). These findings are outlined in Table 3.
Table 3.
Wear resistance scores
| Crown Type | Mean Wear Score±SD | P |
|---|---|---|
| Stainless Steel | 8.5±0.4 | 0.21 |
| Zirconia | 8.2±0.5 |
Fracture rates
Fractures were observed in 2% of SSCs and 10% of ZCs, demonstrating a significant difference (P = 0.03). ZCs were more prone to fracture under high-stress conditions [Table 4].
Table 4.
Fracture rates of SSCs and ZCs
| Crown Type | Fractures (%) | No Fractures (%) | P |
|---|---|---|---|
| Stainless Steel | 2% | 98% | 0.03 |
| Zirconia | 10% | 90% |
DISCUSSION
Retention is a critical factor in the success of pediatric crowns. The higher retention rate observed in SSCs (98%) compared with ZCs (92%) aligns with earlier studies that reported the superior adaptability of SSCs to prepared tooth surfaces due to their malleability and precise fit.[3] In contrast, ZCs rely on passive fit, which may compromise retention in challenging clinical conditions.[4]
Optimal marginal integrity was observed more frequently in SSCs (96%) than ZCs (88%). This finding is consistent with the literature, where SSCs are noted for their ability to maintain excellent marginal adaptation even in cases of suboptimal preparation.[5] Marginal discrepancies in ZCs could be attributed to their rigid nature, which requires meticulous tooth preparation to achieve an ideal fit.[6]
The wear resistance scores were comparable between the two groups, with no statistically significant difference. Both materials have been shown to exhibit adequate resistance to occlusal wear under normal masticatory forces.[7] SSCs are known for their durable metal surface, while ZCs benefit from their high-strength ceramic composition, providing sufficient resistance to wear.[8]
A significant difference in fracture rates was observed, with ZCs showing a 10% fracture rate compared with 2% in SSCs. The higher fracture rates in ZCs may be attributed to their brittleness, particularly under high-stress conditions.[9] Similar findings were reported by Taran and Kaya, who noted the susceptibility of ZCs to fractures in pediatric patients.[10,11] Conversely, SSCs demonstrated superior fracture resistance due to their ductility and ability to absorb occlusal forces effectively.[3]
Although SSCs excel in durability and cost-effectiveness, their metallic appearance may not meet the esthetic demands of some parents and patients. ZCs offer a natural tooth-like appearance, making them a preferred choice in cases where esthetics are prioritized. However, clinicians must consider the higher likelihood of fractures and marginal discrepancies associated with ZCs, particularly in high-stress areas or uncooperative patients.
CONCLUSION
The findings suggest that SSCs are more durable than ZCs, making them suitable for high-stress applications in pediatric dentistry. ZCs, while esthetically pleasing, require careful case selection to minimize the risk of fractures and marginal discrepancies. Clinicians should balance esthetic and functional requirements when selecting crown materials for primary teeth.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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