Restoration of maxillary posterior teeth presents unique challenges due to the complex anatomy, high occlusal forces, and aesthetic requirements of this region. The selection of an appropriate crown material for rehabilitation in these cases is critical to ensure functional longevity, aesthetic satisfaction, and minimal complications [1]. The advent of modern materials and fabrication techniques has expanded the options available to clinicians, including porcelain-fused-to-metal (PFM), all-ceramic, and zirconia crowns, each offering distinct benefits and limitations. 

Porcelain-Fused-to-Metal (PFM) Crowns
PFM crowns have been a staple in restorative dentistry for decades, combining the strength of a metal substructure with the aesthetic potential of porcelain. The metal core provides durability, making PFM crowns suitable for high-stress areas such as maxillary molars and premolars [2]. However, they have notable drawbacks, including susceptibility to chipping of the porcelain veneer and potential for aesthetic compromises due to the opacity of the metal core [3]. Additionally, gingival recession over time can expose the metal margins, further impacting aesthetics [4].

All-Ceramic Crowns

All-ceramic crowns have gained popularity for their superior aesthetics, as they closely mimic the translucency and natural appearance of teeth. These crowns are particularly favored in cases where aesthetics are a primary concern, such as anterior teeth. However, their application in the posterior maxilla is often limited by concerns regarding their fracture resistance under high occlusal forces [5]. Advances in ceramic technology, including high-strength ceramics such as lithium disilicate, have improved the durability of these crowns, making them a viable option for posterior restorations in select cases [6].

Zirconia Crowns

Zirconia crowns represent a significant innovation in dental materials, offering a combination of high strength, biocompatibility, and acceptable aesthetics. Their mechanical properties make them highly resistant to fracture and wear, making them a preferred choice for posterior restorations where masticatory forces are considerable [7]. Furthermore, the introduction of translucent zirconia has enhanced the aesthetic appeal of these crowns, addressing previous concerns about their opacity [8]. However, challenges such as potential wear on opposing teeth and the need for precise bonding techniques remain areas of focus in clinical practice [9].

Comparative Considerations

The choice of crown material for maxillary posterior rehabilitation often depends on a balance of factors, including mechanical performance, aesthetics, cost, and patient preferences. Clinical studies have demonstrated varying survival rates and complication profiles for these materials, highlighting the need for individualized treatment planning [10]. For instance, zirconia crowns have shown superior survival rates compared to PFM and all-ceramic crowns, while the latter may be preferred for patients prioritizing aesthetics [11]. Cost also plays a pivotal role, with PFM crowns being more economical but requiring higher maintenance due to their propensity for complications such as chipping [12].

Purpose of the Study

Despite the wealth of options, there remains a lack of consensus on the optimal crown material for maxillary posterior rehabilitation. This study aims to provide a comprehensive comparison of PFM, all-ceramic, and zirconia crowns, evaluating their clinical performance, patient satisfaction, and cost-effectiveness over a five-year period. By analyzing survival rates, complication profiles, and patient-reported outcomes, this research seeks to inform evidence-based decision-making in restorative dentistry.

Study Design

This was a retrospective cohort study conducted at a tertiary dental care center, analyzing clinical data of patients who underwent maxillary posterior rehabilitation using crowns between 2015 and 2020. The study was approved by the institutional ethics committee and informed consent was obtained from all patients during their initial treatment for the use of their anonymized data in research.

Study Population

The study included 150 patients who received maxillary posterior crowns during the specified period. Patients were divided into three groups based on the type of crown used:

1. PFM crowns (n = 50)
2. All-ceramic crowns (n = 50)
3. Zirconia crowns (n = 50)

Inclusion Criteria

• Adult patients aged 18–70 years.
• Rehabilitation involving maxillary molars or premolars.
• Minimum follow-up period of five years.
• Complete treatment records with radiographs and clinical evaluations.

Exclusion Criteria

• Patients with systemic conditions affecting oral health, such as uncontrolled diabetes or osteoporosis.
• Cases with incomplete records or follow-up data.
• Crowns placed as part of implant-supported prostheses.

Data Collection

Patient records were reviewed to extract the following information:

1. Demographic details: Age, gender, and medical history.
2. Crown details: Type of material, tooth location, and date of placement.
3. Clinical outcomes: Survival rate, presence of complications, and maintenance requirements.
4. Patient-reported outcomes: Satisfaction levels using a validated 10-point Likert scale.

Radiographs and clinical examination notes were used to evaluate crown margins, wear, and overall integrity.

Outcome Measures

The study focused on the following primary and secondary outcomes:

• Primary Outcome
• Survival Rate: The proportion of crowns that remained functional without failure over five years.
• Secondary Outcomes
• Complications: Fracture, marginal discoloration, chipping, and wear on opposing dentition.
• Patient Satisfaction: Measured using a 10-point Likert scale, where 1 indicated extremely dissatisfied and 10 indicated highly satisfied.

Evaluation Parameters

1. Survival Analysis: Kaplan-Meier survival curves were constructed to analyze the longevity of different crown types.
2. Complication Rates: Each crown was assessed for complications such as fracture, discoloration, or wear on opposing teeth during follow-up visits.
3. Patient Satisfaction: Surveys conducted during follow-up visits provided quantitative data on aesthetic and functional satisfaction.

Statistical Analysis

Data were compiled in Microsoft Excel and analyzed using SPSS (Version XX). The following statistical tests were employed:

1. Kaplan-Meier Survival Analysis: To compare the survival rates of the three crown types. Log-rank tests determined the significance of differences.
2. Chi-Square Test: Used to compare the incidence of complications across the three groups.
3. One-Way ANOVA: Applied to analyze differences in patient satisfaction scores among the groups.
4. Post-hoc Analysis: Conducted using Tukey’s test for pairwise comparison of satisfaction scores.

Sample Size Calculation

A power analysis was conducted to ensure the sample size was adequate to detect statistically significant differences in survival rates and complication rates among the three groups. A minimum sample size of 50 per group was determined to achieve 80% power with a significance level of 0.05.

Follow-Up Protocol

Patients were recalled annually for clinical and radiographic evaluations. Follow-up assessments included:

• Inspection of crown margins for adaptation and discoloration.
• Assessment of occlusal wear and opposing tooth wear.
• Documentation of any repairs or replacements required.

Ethical Considerations

The study adhered to the principles of the Declaration of Helsinki. Confidentiality was maintained, and patient data were anonymized during analysis.

1. Survival Rates

The survival rates of crowns over a five-year period varied significantly among the three groups. Zirconia crowns exhibited the highest survival rate of 90%, outperforming both PFM (85%) and all-ceramic crowns (82%). Statistical analysis revealed a significant difference between zirconia crowns and the other two types, with a p-value of 0.032. These findings emphasize zirconia’s superior durability and long-term functionality in maxillary posterior rehabilitation. Table 1.

Table 1: Survival Rates

2. Complication Rates

Complications associated with the different crown types highlighted distinct material-specific challenges. PFM crowns showed the highest chipping rate (20%), followed by all-ceramic crowns (10%) and zirconia crowns (5%). Fracture rates were most prominent in all-ceramic crowns (18%), while zirconia crowns demonstrated the lowest fracture rate (5%). Marginal discoloration was most common in PFM crowns (15%) compared to all-ceramic (12%) and zirconia crowns (8%). Notably, zirconia crowns had a higher incidence of wear on opposing teeth (10%) than PFM (5%) and all-ceramic crowns (6%). All differences were statistically significant, with p-values ranging from 0.019 to 0.034. These results highlight zirconia’s strength and stability while underscoring its potential impact on opposing dentition. Table 2.

Table 2: Complication Rates

3.Patient Satisfaction Scores

Patient satisfaction was highest for zirconia crowns, with a mean score of 8.8 ± 1.0, followed by all-ceramic crowns at 8.4 ± 0.9, and PFM crowns at 7.5 ± 1.2. Statistical analysis indicated significant differences in satisfaction scores among the three groups (p = 0.045). The higher satisfaction associated with zirconia crowns can be attributed to their balance of durability and aesthetics, whereas PFM crowns scored lower due to aesthetic limitations and higher complication rates. Table 3.

Table 3: Patient Satisfaction Scores

4.Cost Analysis

Cost analysis revealed that zirconia crowns, while having the highest average cost ($600), offered the lowest maintenance cost over five years ($50). PFM crowns were the most economical upfront ($300) but had the highest maintenance cost ($100) due to frequent repairs. All-ceramic crowns fell in between with an average cost of $450 and maintenance cost of $80. The p-value for cost differences was significant at 0.040. These findings suggest that zirconia crowns, despite their higher initial cost, provide long-term value by reducing maintenance requirements. Table 4

Table 4: Cost Analysis

The present study provides a comprehensive comparison of porcelain-fused-to-metal (PFM), all-ceramic, and zirconia crowns in maxillary posterior rehabilitation, focusing on their survival rates, complications, patient satisfaction, and cost-effectiveness. The findings highlight the distinct advantages and limitations of each crown type, offering valuable insights for clinicians in selecting the most suitable material for posterior restorations.

1. Survival Rates

Zirconia crowns demonstrated the highest survival rate (90%) over a five-year period, significantly outperforming PFM (85%) and all-ceramic crowns (82%). These results are consistent with previous studies highlighting zirconia’s exceptional durability and resistance to fracture under high occlusal forces [1, 2]. The superior mechanical properties of zirconia, including its high flexural strength and fracture toughness, make it particularly suitable for maxillary posterior restorations, where chewing forces are considerable [3]. In contrast, PFM and all-ceramic crowns showed lower survival rates, attributed to the higher incidence of complications such as chipping and fracture.

2. Complications

The study revealed notable differences in complication rates among the three crown types. PFM crowns exhibited the highest chipping rate (20%), a well-documented drawback attributed to the brittle nature of the porcelain veneer used in these restorations [4]. Marginal discoloration was another significant issue with PFM crowns, occurring in 15% of cases, likely due to gingival recession and the exposure of the metal substructure over time [5].

All-ceramic crowns, while offering superior aesthetics, showed the highest fracture rate (18%), consistent with their lower fracture toughness compared to zirconia. Although advances in materials, such as lithium disilicate ceramics, have improved the strength of all-ceramic crowns, their application in posterior regions remains limited due to these durability concerns [6, 7].

Zirconia crowns demonstrated the lowest rates of chipping (5%) and fracture (5%), underscoring their robustness. However, they were associated with wear on opposing teeth (10%), a complication reported in other studies due to zirconia’s high hardness [8]. This wear, although less severe than anticipated, highlights the need for careful adjustment of occlusion and polishing to minimize its impact [9].

3. Patient Satisfaction

Patient satisfaction was highest for zirconia crowns (8.8 ± 1.0), followed by all-ceramic (8.4 ± 0.9) and PFM crowns (7.5 ± 1.2). The superior satisfaction scores for zirconia crowns can be attributed to their combination of durability, biocompatibility, and acceptable aesthetics. Advances in translucent zirconia have addressed previous concerns about opacity, making it a preferred choice for patients prioritizing both aesthetics and function [10].

All-ceramic crowns also scored high in patient satisfaction, primarily due to their excellent aesthetic properties. However, concerns about their durability may limit their widespread application in posterior regions, as patients may experience fractures over time [11]. PFM crowns, despite being the most economical option, scored the lowest in satisfaction, reflecting patient concerns about aesthetic limitations and the frequent need for repairs [12].

1. Cost Analysis

The cost analysis revealed significant differences in the financial implications of using the three crown types. Zirconia crowns had the highest upfront cost ($600) but offered the lowest maintenance cost over five years ($50), reflecting their minimal complication rates and superior longevity. This finding aligns with previous research suggesting that zirconia crowns, despite their higher initial expense, are cost-effective in the long term due to reduced maintenance needs [13].

All-ceramic crowns, with a moderate upfront cost ($450) and maintenance cost ($80), provided a balance between aesthetics and durability. PFM crowns, while the most affordable initially ($300), incurred the highest maintenance costs ($100) over five years due to frequent complications such as chipping and marginal discoloration. These results underscore the importance of considering not only initial costs but also long-term maintenance when selecting crown materials [14].

5. Clinical Implications

The findings of this study have several practical implications for clinical decision-making in maxillary posterior rehabilitation:

• Material Selection Based on Patient Needs: Zirconia crowns are the most suitable option for patients requiring high durability and minimal maintenance, particularly in regions of high masticatory load. For patients prioritizing aesthetics, all-ceramic crowns may be preferable, especially in less load-intensive areas. PFM crowns, while cost-effective, may be better suited for temporary or transitional restorations due to their higher complication rates.
• Customized Treatment Planning: Factors such as patient age, oral hygiene habits, and occlusal forces should be considered when selecting crown materials. For younger patients with strong occlusion, zirconia may be ideal, while all-ceramic crowns could be more appropriate for patients with lower occlusal forces or aesthetic concerns [15].
• Mitigation of Wear on Opposing Teeth: While zirconia crowns demonstrate excellent durability, their potential to cause wear on opposing teeth warrants careful occlusal adjustment and finishing. Polishing techniques and the use of surface-modified zirconia may reduce this risk, as suggested by recent studies [16].

6.Limitations and Future Directions

This study has some limitations. The retrospective design relies on existing patient records, which may introduce bias or incomplete data. Additionally, the sample size of 150 patients, though sufficient for statistical analysis, limits the generalizability of the findings. Randomized controlled trials with larger sample sizes and longer follow-up periods are needed to validate these results.

Future research should explore the impact of newer materials, such as monolithic zirconia and hybrid ceramic systems, on clinical outcomes in maxillary posterior rehabilitation. The role of digital dentistry, including CAD/CAM technology, in improving crown fabrication and reducing complication rates also warrants further investigation [17].

This study highlights the superior performance of zirconia crowns in terms of survival rates, complication profiles, and patient satisfaction, making them the most reliable option for maxillary posterior rehabilitation. However, all-ceramic crowns remain a valuable choice for aesthetics-sensitive patients, and PFM crowns offer an economical solution despite their limitations. The findings emphasize the need for individualized treatment planning to achieve optimal outcomes in restorative dentistry.

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