Abstract
Background:
The long-term success of implant-supported prostheses relies not only on osseointegration but also on the prevention of prosthodontic complications. Two common retention methods—screw-retained and cement-retained crowns—exhibit distinct clinical advantages and potential drawbacks.
Materials and Methods:
A prospective observational study was conducted on 100 patients receiving implant-supported single crowns—50 with screw-retained and 50 with cement-retained designs. All patients were followed up for 12 months to evaluate complications, such as screw loosening, crown fracture, marginal gap, cement washout, peri-implantitis, and prosthesis decementation. Data were analyzed using Chi-square and t-tests (P < 0.05 considered significant).
Results:
Screw loosening was more prevalent in screw-retained crowns (18%) compared to cement-retained (4%) (P = 0.032). Marginal discrepancies and cement washout were more common in the cement-retained group (marginal gap: 20%, cement washout: 14%) than in screw-retained (8%, 2%, respectively) (P < 0.05). Peri-implantitis was higher in cement-retained crowns (10%) versus screw-retained (4%) (P = 0.146, not significant). No significant difference was found in crown fractures (screw-retained: 4%, cement-retained: 6%, P = 0.712).
Conclusion:
Both systems have distinct complication profiles. Screw-retained crowns showed higher mechanical issues, while cement-retained crowns demonstrated increased biological complications. Appropriate case selection and clinical protocols can minimize these issues.
KEYWORDS: Cement-retained crowns, dental implants, implant-supported restorations, prosthodontic complications, screw-retained crowns
INTRODUCTION
Dental implant restorations have become a predictable and routine solution for replacing missing teeth, offering high survival rates and improved patient satisfaction.[1] Among the critical determinants of prosthetic success are the design and method of retention of the prosthesis—primarily divided into screw-retained and cement-retained types.[2] Each design presents specific advantages and disadvantages in clinical practice.
Screw-retained crowns facilitate retrievability and ease of maintenance but are often associated with aesthetic limitations and mechanical complications such as screw loosening.[3] In contrast, cement-retained crowns are more aesthetic and simpler to fabricate but carry a risk of residual cement, which can induce peri-implant inflammation and biological complications.[4]
Several studies have explored the comparative performance of these two designs, but findings remain inconsistent. For instance, Wittneben et al.[5] reported higher technical issues with screw-retained crowns, whereas cement-retained restorations were more often linked with peri-implantitis due to excess cement. Despite this, a consensus on their complication profiles remains elusive, particularly in single-unit restorations.
This study aims to prospectively assess and compare the incidence and nature of prosthodontic complications in screw-retained and cement-retained implant crowns over a 12-month period, providing evidence for better clinical decision-making.
MATERIALS AND METHODS
Sample size and grouping
A total of 100 patients requiring single-unit implant-supported crowns in the posterior region were enrolled and divided equally into two groups:
Group A: 50 patients received screw-retained crowns.
Group B: 50 patients received cement-retained crowns.
Inclusion criteria
Adults aged 20–60 years.
Good general health and adequate bone volume.
Single missing posterior tooth requiring implant rehabilitation.
Exclusion criteria
Systemic diseases affecting bone healing.
Smoking habits (>10 cigarettes/day).
Bruxism or parafunctional habits.
Poor oral hygiene.
Procedures
All implants were placed by a single experienced surgeon. After three to four months of osseointegration, patients were rehabilitated with either screw-retained or cement-retained zirconia crowns based on clinical indication. Follow-up evaluations were performed at 3, 6, and 12 months post-loading.
Outcome measures
The following prosthodontic complications were assessed:
Screw loosening
Crown fracture
Marginal gap/discrepancy
Decementation
Cement washout
Peri-implantitis.
Statistical analysis
Data were analyzed using SPSS v24. Descriptive statistics were expressed as mean ± SD and percentage. Chi-square test and independent t-test were used to compare outcomes between the groups. A P-value < 0.05 was considered statistically significant.
RESULTS
A total of 100 patients (mean age 43.7 ± 8.4 years, 52 males and 48 females) completed the study.
Screw-retained crowns demonstrated higher rates of mechanical complications like screw loosening (P = 0.032), while cement-retained crowns showed increased marginal discrepancies (P = 0.045), cement washout (P = 0.029), and decementation (P = 0.041). The difference in peri-implantitis was not statistically significant (P = 0.146) [Table 1].
Table 1.
Frequency of prosthodontic complications (n=50 per group)
| Complication | Screw-retained (%) | Cement-retained (%) | P | |||
|---|---|---|---|---|---|---|
| Screw loosening | 9 (18%) | 2 (4%) | 0.032* | |||
| Crown fracture | 2 (4%) | 3 (6%) | 0.712 | |||
| Marginal discrepancy | 4 (8%) | 10 (20%) | 0.045* | |||
| Cement washout | 1 (2%) | 7 (14%) | 0.029* | |||
| Decementation | 0 (0%) | 4 (8%) | 0.041* | |||
| Peri-implantitis | 2 (4%) | 5 (10%) | 0.146 |
*Significant at P<0.05
DISCUSSION
The present study highlights distinct prosthodontic complication profiles between screw-retained and cement-retained crowns over a 12-month period. The findings align with previous literature indicating increased mechanical issues in screw-retained crowns and biological complications in cement-retained designs.
The observed 18% incidence of screw loosening in screw-retained crowns is comparable to earlier findings by Weber et al.,[6] who reported a 19.5% rate in a one-year follow-up. Despite the retrievability advantage, screw loosening remains a technical drawback that may impact prosthesis stability.
Cement-retained crowns demonstrated a significantly higher rate of marginal discrepancy (20%) and cement washout (14%). These findings support the hypothesis that excess or poorly managed cement can contribute to microleakage and subsequent peri-implant tissue complications.[7] This risk emphasizes the need for meticulous cementation protocols or the use of radiopaque cements to identify and remove excess.[8]
Interestingly, peri-implantitis was more common in cement-retained restorations, though not statistically significant. This trend is consistent with findings by Linkevicius et al.,[9] who demonstrated that subgingival cement remnants can serve as a nidus for inflammation.
Crown fracture rates were low and not significantly different, reflecting the durability of contemporary monolithic zirconia restorations.
While both systems showed acceptable performance over 12 months, the findings suggest that screw-retained crowns may be preferred in scenarios requiring retrievability and minimal biological risk, while cement-retained crowns offer superior aesthetics at the cost of higher maintenance and biological vigilance.
CONCLUSION
This study demonstrates that prosthodontic complications vary based on the type of implant crown retention used. Screw-retained crowns were associated with higher mechanical issues, such as screw loosening, while cement-retained crowns presented more frequent biological complications, including marginal gaps, cement washout, and peri-implant inflammation. These findings underscore the importance of individualized treatment planning and stringent clinical protocols to mitigate risks associated with each retention type.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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