Maxillary overdentures supported by four or six implants in the anterior region: 10-year randomized controlled trial results

Metal-Free Custom-Made Zirconia Implants-A Prospective 5-Year Follow-Up Single-Arm Clinical Trial

BACKGROUND

Dental implants made of zirconia (ZrO2) are a potential alternative for titanium implants in dentistry because of their good biocompatibility, mechanical properties and excellent aesthetic results. However, solid long-term scientific data to prove clinical success of ZrO2 implants are scarce.

AIM

The aim of this study was to describe and to examine the clinical performance of custom-made two-piece ZrO2 implants, to identify possible influencing factors: a) manipulation of the implant after placement and b) the occlusal scheme on the survival rate, and to evaluate the performance of the implant-supported crown. This follow-up study collected and examined the 5-year data to answer the main question: What are the survival and the success rates of custom-made ZrO2 implants in the maxillary premolar region after 5 years?

MATERIAL AND METHODS

Of the 31 included patients in this prospective 5-year follow-up single-arm clinical trial, 30 received a custom-made ZrO2 implant to replace a missing single maxillary premolar, which was subsequently restored with a lithium disilicate crown. Parameters regarding clinical performance, marginal bone-level (MBL) changes, and patient-related outcome measures (PROMs) were assessed preoperatively, at the baseline, as well as 1 and 5 years after crown placement. Chances of survival and success of the implant were calculated and displayed using Kaplan-Meier statistics. Kaplan-Meier survival analysis was also performed with stratification based on the variables "manipulation of the implant prior to impression taking" and "occlusal scheme" and compared using log-rank tests. Bone-level moderation in time was compared using a paired samples t-test. Patient's expectations and satisfaction after 5 years were compared as a measure of fulfilled expectations, using a Wilcoxon signed-rank test. Performance of the implant-supported crowns was evaluated using validated criteria.

RESULTS

Survival and success probabilities after 5 years were, respectively, 75.8% (95% CI [60.0%; 91.0%]) and 71.0% (95% CI [54.0%; 88.0%]) for the custom-made ZV3 implants. No significant differences in survival rate were found after stratification on "manipulation of the implant" and on "occlusal scheme." Mean bone-level alteration between baseline and the first follow-up was +0.06 mm (95% CI [-0.23 mm; 0.12 mm]; SD = 0.42 mm) and between baseline and the second follow-up was +0.04 mm (95% CI [-0.35 mm; 0.26 mm]; SD = 0.54 mm). Patients' satisfaction for patients with implants still in function after 5 years was 91.7% (IQR = [90.5%-97.3%]), indicating satisfaction with the treatment. Pooled satisfaction in patients with successful implants after 5 years was significantly higher than patients' expressed expectations before treatment. None of the crowns failed, and no interventions were required.

CONCLUSION AND CLINICAL IMPLICATIONS

Survival rate of these particular ZV3 implants in our study was lower than expected and clinically not acceptable. Hence, ZV3 implant placement as applied in this study cannot be recommended for clinical practice. Further research on the different appearances of mechanical failure in ZrO2 implants would be highly recommended before a larger prospective randomized clinical trial is conducted to evaluate treatment with custom-made ZrO2 dental implants.

Two or four implants for maxillary overdentures in edentulous patients: 1-year results of a randomized controlled trial

INTRODUCTION

Maxillary implant overdenture therapy is a good treatment option for treating patients experiencing problems with their conventional maxillary denture. Retaining the overdenture with four implants and a bar attachment system serves as the current gold standard. However, there is a demand for less costly and less invasive treatment options. The aim of this randomized controlled trial was to compare marginal bone level change (MBLC), implant and overdenture survival, clinical, masticatory, and patient-related outcomes (PROMs) of maxillary implant overdentures with either two or four implants and a bar attachment system.

MATERIALS AND METHODS

Forty edentulous participants were randomly allocated to two groups (n = 20), to receive either two or four implants in the maxilla. After healing, all the participants received an implant overdenture retained by a bar attachment system. All the participants were evaluated 1 and 12 months after overdenture placement. The primary outcome was MBLC. Secondary outcomes were implant and overdenture survival, clinical, masticatory, and PROMs. The outcomes were analyzed using parametric and non-parametric tests.

RESULTS

MBLC was -0.03 mm in the 2-implant group and -0.16 mm in the 4-implant group (p = 0.21). Implant survival was 83.3% in the 2-implant group and 94.4% in the 4-implant group (p = 0.03). The median pocket depth change and clinical outcomes were low, and masticatory performance along with PROMs improved in both groups and did not differ significantly between them.

CONCLUSION

Maxillary 4-implant overdentures perform better than maxillary 2-implant overdentures with a bar attachment system in terms of implant and overdenture survival and therefore remains the gold standard. However, both overdentures perform similarly in terms of MBLC, clinical, masticatory, and PROMs.

Long-term treatment outcomes with zygomatic implants: a systematic review and meta-analysis

PURPOSE

The purpose of this study was to perform a systematic review with meta-analysis on the long-term survival rates of zygomatic implants (ZI). ZI success, prostheses survival and success, sinus pathology and patient reported outcomes were also investigated.

METHODS

Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines were followed. Embase and OvidMedline databases were searched alongside the grey literature. The systematic review was recorded in PROSPERO (CRD42022358024). Studies reporting titanium/titanium alloy ZI survival data, ZI-supported prosthesis data, ZIs directly compared to any other implant therapy including grafted sites, a minimum follow-up time of 3 years and a minimum number of 10 patients were included. All study designs were considered if they met the inclusion criteria. Studies not involving ZIs, ZIs not made from titanium/titanium alloy, a follow-up time of < 3 years or < 10 patients, animal studies and in vitro studies were excluded. Long-term follow-up has not been defined in the literature. A minimum of 3 years follow-up was considered acceptable to capture survival after initial healing, alongside in-function prosthesis data via delayed or immediate load protocols. ZI success, was predominantly defined as ZI survival without biological or neurological complications. Meta-analyses were performed for ZI survival, ZI failure incidence, ZI success, loading protocol, prosthesis survival, and prevalence of sinusitis using random effects models. Descriptive analysis was used for ZI success, prosthesis success and patient reported outcome measures.

RESULTS

Five hundred and seventy-four titles were identified, of which 18 met the inclusion criteria. Eligible studies included 1349 ZIs in 623 patients. Mean follow-up period was 75.4 months (range 36-141.6). The mean survival of ZIs was 96.2% [95% CI: 93.8; 97.7] at 6 years. Mean survival for delayed loading was 95% [95% CI: 91.7; 97.1] and 98.1% [95% CI: 96.2; 99.0] for immediate loading (p = 0.03). Annual incidence rate of ZI failure was 0.7% [95% CI 0.4; 1.0]. Mean ZI success was 95.7% [95% CI 87.8; 98.6]. Mean prosthesis survival was 94% [95% CI 88.6; 96.9]. Sinusitis prevalence was 14.2% [95% CI 8.8; 22.0] at 5 years. Patients' reported increased satisfaction with ZIs.

CONCLUSIONS

ZIs have long-term survival comparable to conventional implants. Immediate loading showed a statistically significant increase in survival over delayed loading. Prosthesis survival was similar to that of prostheses supported by conventional implants, with similar complications. Sinusitis was the most frequently encountered biological complication. Patients reported improved outcome measures with ZI use.

The performance of two-implant overdentures in the atrophic maxilla: a case series with 1-year follow-up

PURPOSE

To assess the implant and prosthesis survival rates, the clinical, radiographical and patient-related outcome measures, and the masticatory performance of maxillary overdentures supported by two implants in patients with an atrophic maxilla.

METHODS

In this case series, 15 consecutive patients who were eligible for maxillary implant overdenture therapy, but who had insufficient bone volume to place at least four implants and were unwilling to be treated with reconstructive surgery were asked to participate. After giving consent, participants received two implants in the maxilla under local anaesthesia. After 3 months of osseointegration, a maxillary overdenture with palatal coverage and solitary attachments was fabricated. Implant and overdenture survival, marginal bone level change, clinical outcome measures, masticatory performance and patient-related outcomes were evaluated at baseline and 1 year after overdenture placement.

RESULTS

Fourteen out of 15 participants completed the follow-up period of 12 months. Implant and overdenture survival rate were 89.3% and 85.7%, respectively. Change in marginal bone level (- 0.5 ± 0.7 mm), change in probing depth (0.0 ± 1.0 mm), and clinical outcomes were favourable. Masticatory performance and patient-related outcomes improved significantly compared to baseline. Complications were minimal.

CONCLUSIONS

Within the limitations of this study, it can be concluded that patients with extreme resorption of the maxilla that are unwilling to be treated with reconstructive surgery, benefit from two-implant maxillary overdentures retained by solitary attachments in terms of improved masticatory functioning and denture satisfaction. However, they have relatively high risk of implant loss.

TRIAL REGISTRATION

UMCG Trial Register (RR201900060), registered 22 January 2019.