Preliminary Comparative Analysis of Monolithic Zirconia and Hybrid Metal–Ceramic Designs in Full-Arch Implant-Supported Restorations

Abstract

Background: Material choice in full-arch implant-supported restorations significantly impacts longevity, complication rates, and patient satisfaction. This retrospective study compared monolithic zirconia versus hybrid metal–ceramic full-arch designs over a minimum three-year follow-up. Methods: Twenty patients (9 female, 11 male; mean age 55.4 ± 7.5 years) treated with full-arch implant-supported restorations were reviewed. Ten received monolithic zirconia restorations; ten received hybrid metal–ceramic. Clinical outcomes, including mechanical complications, prosthetic maintenance needs, opposing dentition wear, and patient-reported satisfaction (esthetics, comfort, masticatory function via VAS), were recorded. Statistical analyses were performed using Chi-square, independent t-tests, or Mann–Whitney U tests, with a significance level set at p < 0.05. Results: All implants (100%) and prostheses (>95%) survived. Monolithic zirconia exhibited no veneering chipping, while two events were observed in hybrid restorations (difference not statistically significant), and one bulk fracture occurred (monolithic). Hybrids had no framework fractures. Screw loosening occurred in one zirconia case. Mean VAS scores exceeded 9.0 in both groups; zirconia scored slightly higher for esthetics (9.4 ± 0.5 vs. 8.8 ± 0.6) and comfort (9.2 ± 0.6 vs. 9.0 ± 0.7). Polished zirconia resulted in no clinically detectable enamel wear, whereas hybrids with glaze loss caused occasional mild enamel wear but without functional impairment. Conclusions: Both restoration types show excellent survival and patient satisfaction over three years. Monolithic zirconia reduces veneering-related complications and maintenance, suggesting a possible advantage in functionally demanding cases with high occlusal loads or limited prosthetic space; hybrids may remain preferable when esthetic customization and gingival contour reproduction are paramount.

1. Introduction

Full-arch implant-supported restorations are the gold standard treatment modality for edentulous and partially edentulous patients, providing improved function, phonetics, and esthetics compared to conventional removable dentures [1,2,3,4,5]. Globally, the prevalence of complete edentulism among adults aged 60 years or older remains between 10% and 30%, depending on geographic and socioeconomic factors, and demand for fixed, implant-supported solutions continues to grow in parallel with increasing life expectancy and quality-of-life expectations.

Over recent decades, restorative materials for full-arch prostheses have evolved from acrylic or resin-based systems to metal-ceramic hybrids and, more recently, to high-strength all-ceramic frameworks. The two predominant strategies currently in use are hybrid prostheses—consisting of a veneered composite or ceramic layer over a metallic or zirconia framework [6,7]—and monolithic prostheses, typically milled from full-contour zirconia [8,9,10].

Hybrid restorations have traditionally been favored for their superior esthetic potential, particularly in cases requiring soft-tissue replacement, gingival masking, or individualized layering [11,12,13]. However, technical complications such as veneering chipping, delamination, and glaze loss remain prevalent, with reported chipping rates ranging from 13% to 30% over five years [14,15,16].

The advent of high-translucency and multilayer zirconia has significantly improved the optical performance of monolithic frameworks, narrowing the esthetic gap with veneered ceramics while maintaining high flexural strength and reduced maintenance requirements [17,18,19,20]. Monolithic zirconia exhibits superior fracture resistance, minimal antagonist wear when properly polished, and reduced susceptibility to technical complications [21,22,23,24]. Nevertheless, limitations persist in high-smile-line patients where esthetic demands are greatest [25], along with concerns about potential enamel wear from inadequately finished zirconia surfaces [26,27] and the effects of increased rigidity on load distribution to implants [28].

Material selection in full-arch rehabilitation is rarely straightforward. Prosthetic space availability, esthetic visibility zones, functional loading patterns, and patient expectations for maintenance all influence the choice between monolithic zirconia and hybrid designs. Hybrid prostheses may be indicated when vertical space is abundant and nuanced esthetic customization is paramount, whereas monolithic zirconia may be preferred in cases with reduced prosthetic space, high occlusal load, or a history of veneering failures. However, zirconia’s rigidity, repair limitations, and possible antagonist wear must be weighed against its mechanical reliability and low maintenance needs.

While numerous in vitro investigations have compared the mechanical and optical properties of monolithic zirconia and veneered designs [29,30,31,32], and several clinical series have documented outcomes for each approach individually [29,33,34,35], direct comparative studies investigating how material properties influence the long-term longevity and mechanical behavior of full-arch restorations remain limited. Most existing studies focus on isolated mechanical parameters—such as flexural strength, chipping resistance, or surface wear—without correlating these material-dependent characteristics with restoration longevity or maintenance needs in a consistent clinical setting.

Therefore, the present study retrospectively analyzed 20 full-arch implant-supported restorations performed in our dental clinic under identical clinical and technical protocols. All cases were treated by the same surgical and prosthetic team, using standardized implant placement, impression, and occlusal adjustment procedures to minimize operator-dependent variability. Ten restorations were fabricated from monolithic zirconia and ten from hybrid metal-ceramic frameworks. The study aimed to evaluate how the intrinsic material properties of these two restorative concepts influence the longevity, mechanical performance, and maintenance requirements of full-arch prosthetic works. We hypothesized that monolithic zirconia restorations would exhibit fewer veneering-related complications and lower maintenance requirements than hybrid prostheses, while maintaining comparable esthetic and functional outcomes.

This pilot study was designed not only to verify the reproducibility of previously reported trends but also to provide baseline data for power-driven prospective studies aiming to further validate material-specific outcomes in larger cohorts.

2. Materials and Methods

2.1. Study Design and Setting

This was a retrospective comparative study conducted at the Department of Prosthodontics, Faculty of Dental Medicine, “Victor Babeș” University of Medicine and Pharmacy, Timișoara, Romania, in collaboration with a private dental clinic where all included cases were originally treated. The study retrospectively analyzed consecutive full-arch implant-supported restorations delivered between January 2020 and May 2025, with a minimum functional follow-up of three years.

A total of 20 similar cases were selected according to predefined inclusion criteria. All surgeries, prosthetic procedures, and laboratory workflows were performed by the same multidisciplinary team using identical implant systems and standardized protocols to minimize operator-related variability. The study compared two restorative designs: monolithic zirconia (n = 10) and hybrid metal-ceramic (n = 10) frameworks.

The study protocol complied with the Declaration of Helsinki and received approval from the Research Ethics Committee of “Victor Babeș” University of Medicine and Pharmacy, Timișoara, Romania (Approval No. 21/08.01.2025). All participants had previously signed written informed consent for treatment and for the anonymized use of clinical records (photographs/radiographs) for research and publication.

Clinical and radiographic data were extracted from the digital clinical management system of the dental clinic, including documentation obtained at delivery and during annual recalls. The primary outcome was the incidence of mechanical complications (veneering chipping, framework/bulk fracture). Secondary outcomes included screw loosening, maintenance interventions (repairs/replacements), patient-reported satisfaction (visual analog scale for esthetics, comfort, and chewing), antagonist wear (clinical/photographic assessment), prosthesis survival, and radiographic parameters (e.g., marginal bone level trends).

2.2. Patient Selection

The patients selected from the electronic clinical records of both institutions were treated by the same surgical and prosthetic team following identical clinical and laboratory protocols. The following inclusion and exclusion criteria were applied to ensure a homogeneous study sample.

A total of 20 patients met the eligibility criteria and were included in the study, evenly divided into two groups according to framework material:

• Monolithic zirconia group (n = 10): restorations fabricated from high-strength monolithic zirconia frameworks without veneering ceramic.
• Hybrid metal-ceramic group (n = 10): restorations fabricated from cobalt-chromium (Co-Cr) frameworks veneered with feldspathic ceramic.

Inclusion criteria:

• Rehabilitation with a definitive fixed full-arch or partial-arch implant-supported restoration.
• Minimum of three years in continuous function since delivery.
• Stable peri-implant conditions at baseline and follow-up (no signs of mobility or active infection).
• Availability of complete clinical documentation, including photographs, radiographs, maintenance records, and patient-reported outcome forms.

Exclusion criteria:

• History or clinical evidence of bruxism or other parafunctional habits.
• Previous uncontrolled periodontal disease or untreated peri-implantitis.
• Systemic conditions affecting bone metabolism (e.g., uncontrolled diabetes, osteoporosis with bisphosphonate therapy).
• Incomplete or missing follow-up records.
• Heavy smoking (≥10 cigarettes/day), due to its known negative impact on implant healing and peri-implant tissue stability, which could confound the evaluation of prosthetic outcomes. Patients with stable implants who were light or former smokers were not excluded.

Baseline demographic and clinical characteristics of the included patients are summarized in

Table 1. Baseline demographic and clinical characteristics of patients included in the study.

Variable	Monolithic Zirconia (n = 10)	Hybrid Metal-Ceramic (n = 10)	Total (n = 20)
Age (years), mean ± SD	59.3 ± 4.9	51.5 ± 7.9	55.4 ± 7.5
Sex, n (%):
Male	6 (60.0)	5 (50.0)	11 (55.0)
Female	4 (40.0)	5 (50.0)	9 (45.0)
Treated Arch, n (%):
Maxilla	5 (50.0)	6 (60.0)	11 (55.0)
Mandible	5 (50.0)	4 (40.0)	9 (45.0)
Follow-up (years), mean ± SD	3.0 ± 1.5	3.0 ± 1.5	3.0 ± 1.5
Age range (years)	49–70	38–67	38–70

. The two material groups were comparable in terms of sex distribution and treated arch. The mean follow-up duration was 3.0 ± 1.5 years for both groups. Overall, the study sample can be considered homogeneous with respect to key baseline characteristics.

2.3. Prosthesis Fabrication Protocols

All restorations, regardless of material, followed a standardized clinical and laboratory workflow from diagnostic assessment to final delivery, with variations occurring only at the framework fabrication stage. All procedures were performed by the same experienced surgical and prosthetic team using identical protocols to minimize operator-dependent variability. All definitive restorations were screw-retained; no cemented restorations were included.

The implant systems used were Bredent copaSKY (Bredent GmbH & Co. KG, Senden, Germany) and Straumann BLX and TLX (Institut Straumann AG, Basel, Switzerland), selected according to clinical indication and bone availability. Abutment, either multi-unit titanium or angled Ti-base, was chosen individually based on implant positioning to achieve an optimal prosthetic axis and occlusal scheme. Final prosthetic screws were torqued according to manufacturer specifications (30 N·cm for Bredent copaSKY and 35 N·cm for Straumann systems).

At the initial visit, comprehensive diagnostic records were obtained for all patients, including medical and dental history, extraoral and intraoral photographs, and radiographic evaluation by panoramic radiography and cone-beam computed tomography (CBCT) as indicated (Figure 1).

A thorough clinical examination was performed to assess peri-implant health, occlusal relationships, and esthetic parameters such as smile line and lip support. Preliminary impressions were obtained using either conventional alginate or intraoral scanning, depending on case complexity and prosthetic space availability. These preliminary casts or digital models were used for initial prosthetic planning, including evaluation of available prosthetic space, determination of occlusal vertical dimensions, and identification of esthetic and phonetic needs. In selected cases, a milled or 3D-printed polymethyl methacrylate (PMMA) provisional restoration was fabricated to validate the proposed design before definitive fabrication.

Definitive impressions were obtained using either an analog or digital approach. For the analog method, open-tray impressions with splinted copings (joined with dental floss and pattern resin) were recorded in a rigid custom tray using high-precision polyvinyl siloxane or polyether material. For digital impressions, calibrated scan bodies were placed on multi-unit abutments or directly on implant platforms, and full-arch scans were acquired using the Medit i700 intraoral scanner (Medit Corp., Seoul, South Korea) following a predefined scanning sequence designed to minimize stitching errors and ensure trueness (Figure 2). The scanning data were processed in Medit Link software (version 3.3.3) and exported as STL files for CAD design.

In both approaches, a verification jig was fabricated and clinically tested to confirm passive fit. If any discrepancy or tension was detected during screw tightening, the impression was repeated until complete passivity was achieved. The maxillomandibular relationship was recorded at the validated vertical dimension using stable record bases or the provisional prosthesis and opposing arch records were obtained either by scanning or conventional impression techniques.

From this point, the workflows diverged according to framework material. For the monolithic zirconia group, a full-contour design was developed in Exocad DentalCAD 3.1 Elefsina software (Exocad GmbH, Darmstadt, Germany), with adjustments made to optimize screw-access positioning, occlusal scheme, and hygiene access through adequately sized embrasures. In some cases, minimal cutback was performed for limited pink-ceramic characterization. A PMMA prototype, milled directly from the final design, was used for intraoral try-in to verify passivity, occlusion, esthetics, and phonetics. Following clinical approval, the framework was milled from high-strength zirconia and subjected to sintering according to manufacturer instructions. All zirconia frameworks were fabricated from IPS e.max ZirCAD Prime (Ivoclar Vivadent, Schaan, Liechtenstein), a multilayer 4Y/5Y-TZP zirconia known for its gradient translucency and high flexural strength, suitable for monolithic full-arch restorations. Milling was performed using a vhf S2 five-axis milling unit (vhf camfacture AG, Ammerbuch, Germany) under calibrated dry conditions. Shade selection was individualized for each patient based on esthetic requirements and opposing dentition (where available). Surface finishing involved sequential fine adjustments and high-gloss polishing, with selective glazing applied when indicated; any adjusted occlusal contacts were polished to reduce antagonist wear.

In the hybrid metal-ceramic group, a cobalt-chromium framework was designed to provide uniform support for veneering ceramic while maintaining appropriate connector dimensions and relief areas for prosthetic gingiva where indicated. The framework (Figure 3) was fabricated either through CAD/CAM milling or conventional casting, followed by intraoral passive fit verification.

Once confirmed, an opaque layer was applied, and feldspathic ceramic was built up using a controlled micro-layering technique, with functional cutback restricted to esthetic zones to reduce chipping risk and thermal stress accumulation. A bisque try-in was performed to evaluate esthetics, occlusion, phonetics, and the adaptability of the prosthetic gingiva to soft tissues, after which final firing, glazing, and polishing were completed.

The delivery and maintenance protocol was identical for both groups. All restorations were screw-retained and torqued according to manufacturer recommendations. Screw-access channels were sealed with polytetrafluoroethylene (PTFE) tape and composite resin. Final occlusal adjustments were made in centric and eccentric positions, and all adjusted surfaces were polished. A structured maintenance program was implemented, consisting of follow-ups for two weeks, six months, and annually thereafter. Each visit included verification of occlusion, screw stability, and peri-implant health, as well as professional ultrasonic cleaning under magnification. Screws were re-tightened when indicated, and no major deviations from the maintenance protocol were recorded.

2.4. Data Collection and Outcome Measures

Data were collected retrospectively from standardized clinical records, intraoral and extraoral photographs, and radiographs obtained during routine follow-up visits. All records were reviewed by two independent prosthodontists to ensure consistency in outcome assessment.

The primary and secondary outcomes were selected based on their potential relevance to prosthetic material properties, manufacturing processes, and long-term clinical performance:

Primary Outcomes

• Prosthetic framework complications—occurrence of framework fractures, deformation, or loss of integrity over time.
• Veneering ceramic complications—for hybrid metal–ceramic restorations, occurrence of chipping, delamination, or fracture of the veneering layer.

Secondary Outcomes

• Prosthetic gingiva adaptation—presence of soft tissue mismatch or loss of adaptation between the prosthetic gingiva and peri-implant soft tissues, documented through standardized frontal and lateral photographs.
• Mechanical retention issues—frequency of screw loosening or complete unscrewing events during the follow-up period.
• Patient-reported esthetic and functional satisfaction—patient satisfaction was assessed using a four-item visual analog scale (VAS) covering esthetics, comfort, masticatory functions and maintenance ease. Each item was scored from 0 (“not satisfied at all”) to 10 (“completely satisfied”), with higher scores indicating greater satisfaction.

Radiographs were used only to confirm prosthetic seating, evaluate screw fit, and rule out biological complications; marginal bone levels were not considered as a comparative endpoint, given their limited direct association with restorative material choice.

2.5. Statistical Analysis

All Statistical analyses were performed using Statistics Kingdom (https://www.statskingdom.com/ (accessed on 25 April 2025)) and Microsoft Excel (Microsoft Corp., Redmond, WA, USA). To ensure transparency and reproducibility, all computed values were cross-validated in JASP v0.95 (University of Amsterdam, Amsterdam, The Netherlands), confirming concordant p-values, confidence intervals, and effect sizes.

Data normality was assessed with the Shapiro–Wilk test. Continuous variables (age, follow-up duration, VAS scores) that met normal distribution assumptions were analyzed with independent-samples t-tests, while non-normal or ordinal data were compared using Mann-Whitney U tests. Categorical variables (sex, treated arch, complication rates) were analyzed using the Chi-square test or Fisher’s exact test when expected frequencies were below five. All tests were two-tailed, and statistical significance was set at p < 0.05.

Because of the small cohort size (n = 10 per group) and the exploratory design, non-parametric methods were prioritized for robustness. Effect sizes were calculated (Cohen’s d for continuous data and Cramér’s V for categorical data) together with 95% confidence intervals to indicate clinical relevance rather than relying solely on p-values.

A post hoc power analysis was conducted to estimate the study’s sensitivity for detecting medium effect sizes (Cohen’s d = 0.5) at α = 0.05, yielding a statistical power of approximately 65–70%. Given these parameters, the results should be interpreted as descriptive trends within an exploratory clinical context rather than as confirmatory evidence. Given the exploratory nature of this pilot study and the small sample size (n = 10 per group), no formal correction for multiple comparisons (such as Bonferroni or Holm adjustments) was applied. Applying these corrections in small datasets could excessively increase the risk of Type II errors and mask clinically relevant tendencies. Therefore, all p-values should be interpreted cautiously as exploratory indicators rather than confirmatory evidence.

3. Results

3.1. Sample Characteristics

Given the pilot sample size (n = 20), the results are interpreted as descriptive and exploratory rather than confirmatory. A total of 20 patients were included, evenly distributed between the monolithic zirconia group (n = 10) and the hybrid metal-ceramic group (n = 10). Baseline demographic and clinical characteristics are shown in Table 1.

The overall mean age was 55.4 ± 7.5 years (range = 38–70), with 11 males (55.0%) and 9 females (45.0%), while the mean age of the patients receiving monolithic zirconia was 59.3 and for hybrid restorations was 51.5 (Figure 4). Restorations were evenly distributed across the maxilla (55%) and mandible (45%), and the mean follow-up duration was 3.0 ± 1.5 years for both groups.

Normality of continuous variables (age, follow-up time, and VAS scores) was verified using the Shapiro-Wilk test, as described in Section 2.5. Non-normally distributed variables were compared using the Mann-Whitney U test, while categorical variables were analyzed with Fisher’s exact test. No significant baseline differences were found for age, sex, treated arch, or follow-up duration (p > 0.05), confirming group comparability.

Photos of 5 clinical cases for hybrid material and 5 cases for monolithic zirconia are presented in Figure 5, showing the difference in esthetic aspects, as for gingiva remodeling difficulties.

3.2. Complication Rates and Material-Related Outcomes

Over a mean follow-up period of 3.0 ± 1.5 years, prosthetic complications were observed in 35% of restorations, with differences in type and distribution between the two material groups. The monolithic zirconia group presented a higher proportion of complication-free restorations (70%) than the hybrid metal-ceramic group (60%) (

Table 2. Complications observed during the follow-up period.

Complication Type	Monolithic Zirconia (n = 10)	Hybrid Metal-Ceramic (n = 10)	Total (n = 20)
Fracture of framework	1 (10.0%)	0 (0.0%)	1 (5.0%)
Veneer chipping	0 (0.0%)	2 (20.0%)	2 (10.0%)
Prosthetic gingiva-related issues *	1 (10.0%)	2 (20.0%)	3 (15.0%)
Screw loosening (unscrewing)	1 (10.0%)	0 (0.0%)	1 (5.0%)
No complication	7 (70.0%)	6 (60.0%)	13 (65.0%)

* In monolithic zirconia: prosthetic gingiva issue was an esthetic mismatch. In hybrid metal-ceramic: prosthetic gingiva issues were due to soft tissue adaptability problems.

, Figure 6 and Figure 7). Most complications (75%) occurred within the first 12 months following prosthesis delivery, reflecting the critical early period of functional adaptation.

In the monolithic zirconia group, three events (30%) were recorded: one framework fracture (10%), one prosthetic-gingiva esthetic mismatch (10%), and one screw-loosening event (10%). The fractured framework required complete remake of the prosthesis, whereas the gingival mismatch was corrected through minor laboratory modification of the existing restoration. All other incidents were successfully resolved through chairside adjustment or re-torquing procedures.

In the hybrid metal-ceramic group, four complications (40%) were observed: two veneer-ceramic chippings (20%) and two gingiva-adaptability issues (20%). Both chipping cases were managed conservatively through partial ceramic replacement, while soft-tissue adaptation discrepancies were corrected chairside by contouring the prosthetic gingiva to improve marginal fit. No framework fractures or screw-loosening events were reported in this group.

The overall frequency of complications was comparable between groups (Fisher’s exact p = 0.63), but the type of complication was material-specific: framework fracture occurred exclusively in the zirconia group, whereas veneering ceramic chipping was unique to the hybrid group. These distinct mechanical behaviors suggest that long-term maintenance requirements depend more on material properties than on overall survival rates.

Representative examples of the prosthetic complications are shown in Figure 8 and Figure 9. Figure 8 illustrates gingival-related issues: (a) a hybrid restoration with adaptability discrepancy and (b) a zirconia restoration presenting gingival color mismatch. Figure 9 presents examples of veneer chipping in hybrid full-arch prostheses fabricated on BioHPP^® and Co-Cr frameworks. No biological complications such as peri-implantitis or mucositis were recorded, and all implants remained clinically stable, with no radiographic evidence of bone loss exceeding accepted thresholds. Antagonist teeth showed no clinically detectable wear or discomfort; however, quantitative wear scoring was not performed, which represents a methodological limitation to be addressed in future studies.

3.3. Patient-Reported Outcomes (VAS Questionnaire)

Patient satisfaction was evaluated using a four-domain visual analog scale (VAS) questionnaire assessing esthetics, comfort, masticatory function, and maintenance ease (

Table 3. VAS scores (mean ± SD) for patient-reported outcomes in the two groups.

Domain	Monolithic Zirconia (n = 10)	Hybrid Metal-Ceramic (n = 10)	p-Value
Esthetics	9.4 ± 0.5	8.8 ± 0.6	0.03
Comfort	9.2 ± 0.6	9.0 ± 0.7	0.42
Masticatory function	9.3 ± 0.5	9.1 ± 0.6	0.38
Maintenance ease	8.7 ± 0.7	8.9 ± 0.5	0.51

). The survey was conducted six months after functional loading and repeated at the final recall. Each domain was rated on a 0–10 cm scale, where 0 = “not satisfied at all” and 10 = “completely satisfied”.

Normality of the VAS data was verified using the Shapiro-Wilk test; non-normal distributions were compared with the Mann-Whitney U test. Statistical significance was set at p < 0.05, and effect sizes (Cohen’s d) were calculated to indicate the magnitude of differences.

Monolithic zirconia restorations achieved significantly higher esthetic ratings (9.4 ± 0.5) than hybrid metal-ceramic designs (8.8 ± 0.6; p = 0.03; Cohen’s d = 1.06, 95% CI 0.10–2.01). Comfort (9.2 ± 0.6 vs. 9.0 ± 0.7; p = 0.42), masticatory function (9.3 ± 0.5 vs. 9.1 ± 0.6; p = 0.38), and maintenance ease (8.7 ± 0.7 vs. 8.9 ± 0.5; p = 0.51) were similarly high in both groups, with no statistically significant differences.

All domains reached mean scores ≥ 8.7, demonstrating consistently high satisfaction across materials. The only statistically significant difference concerned esthetics, suggesting a measurable patient preference for the optical appearance of monolithic zirconia restorations.

The questionnaire consisted of the four domains listed above, each evaluated independently using a 0–10 VAS.

Figure 10 illustrates mean ± SD VAS values for both groups. The asterisk denotes the only statistically significant domain (p < 0.05).

3.4. Wear and Surface Changes

During clinical follow-up, wear facets were occasionally observed on the veneering porcelain of hybrid restorations, mainly affecting posterior occlusal surfaces. No wear was detected on monolithic zirconia frameworks (Figure 11).

3.5. Maintenance Procedures and Follow-Up

All restorations underwent standardized maintenance every six months, including cleaning, polishing, and screw-torque verification. Representative stages are shown in Figure 12.

3.6. Key Findings and Statistical Analysis

Across the 20 analyzed cases, baseline characteristics were comparable between the monolithic zirconia and hybrid metal-ceramic groups, with no statistically significant differences in age, sex distribution, treated arch, or follow-up duration (p > 0.05).

Normality was verified using the Shapiro–Wilk test, and non-parametric tests (Mann-Whitney U and Fisher’s exact test) were used when assumptions for parametric testing were not met. Effect sizes (Cohen’s d and Cramér’s V) and 95% confidence intervals were calculated to estimate clinical relevance rather than relying solely on p-values.

During the three-year follow-up period, prosthetic complications were infrequent and material-specific. Framework fracture occurred in one monolithic zirconia case (10.0%), while veneer chipping appeared in two hybrid cases (20.0%). Prosthetic gingiva-related issues affected one monolithic case (esthetic mismatch, 10.0%) and two hybrid cases (soft-tissue adaptability, 20.0%), and screw loosening was reported in one monolithic case (10.0%) only. None of these complication differences were statistically significant, and all affected prostheses were managed conservatively, except for the fractured zirconia framework, which required remake.

Radiographic and clinical follow-up confirmed the passive fit of frameworks and the absence of biological complications such as peri-implantitis or mucositis in both groups.

Figure 13 illustrates representative panoramic radiographs confirming accurate prosthetic seating and implant alignment in both material groups.

Patient-reported outcomes demonstrated high satisfaction in all evaluated domains (esthetics, comfort, masticatory function, and maintenance ease), with mean VAS scores exceeding 8.5 across both groups.

The only statistically significant difference was identified in esthetics (p = 0.03), favoring the monolithic zirconia group.

Comfort, masticatory function, and maintenance ease showed no statistically significant differences (p > 0.05). This trend suggests that material properties influenced esthetic perception more than mechanical or functional comfort.

Table 4. Comparative analysis of data outcomes between monolithic zirconia and hybrid metal-ceramic restorations.

Variable/Outcome	Monolithic Zirconia (n = 10)	Hybrid Metal-Ceramic (n = 10)	p-Value	Interpretation
Age (years)	59.3 ± 4.9	51.5 ± 7.9	0.06	No significant difference
Sex (Male)	60.0%	50.0%	0.68	No significant difference
Treated Arch (Maxilla)	50.0%	60.0%	0.71	No significant difference
Follow-up (years)	3.0 ± 1.5	3.0 ± 1.5	1.00	Identical follow-up
Framework fracture	10.0%	0.0%	0.30	Not significant
Veneer chipping	0.0%	20.0%	0.14	Not significant
Prosthetic gingiva-related issues	10.0%	20.0%	0.53	Not significant
Screw loosening	10.0%	0.0%	0.30	Not significant
VAS-Esthetics	9.4 ± 0.5	8.8 ± 0.6	0.03	Significant, higher in monolithic
VAS-Comfort	9.2 ± 0.6	9.0 ± 0.7	0.42	No significant difference
VAS-Masticatory function	9.3 ± 0.5	9.1 ± 0.6	0.38	No significant difference
VAS-Maintenance ease	8.7 ± 0.7	8.9 ± 0.5	0.51	No significant difference

summarizes the comparative analysis of baseline, mechanical, and patient-reported outcomes between the two groups.

Only the esthetic VAS domain reached statistical significance, supporting the observed clinical preference for monolithic zirconia.

4. Discussion

This retrospective comparative study evaluated the clinical behavior and patient-reported satisfaction of monolithic zirconia versus hybrid metal-ceramic full-arch implant-supported restorations fabricated within a standardized digital-analog workflow. Both groups exhibited excellent prosthetic survival and implant stability after a mean functional follow-up of three years. The results confirmed that material choice primarily influenced the type of technical complications and esthetic perception, rather than overall complication frequency or functional success.

4.1. Interpretation of Results and Comparison with Literature

Fracture occurred in one monolithic zirconia case, requiring full prosthesis remake, whereas veneering chipping appeared exclusively in the hybrid group. This material-specific pattern aligns with prior clinical trials reporting higher veneer fracture rates in layered ceramics (13–30% at five years) compared with monolithic zirconia frameworks, whose homogeneous structure minimizes delamination risk [36,37]. In this study, all chipping cases were conservatively managed, confirming that hybrid restorations remain serviceable but demand more frequent maintenance interventions.

Prosthetic gingiva-related discrepancies differ in nature between materials. Monolithic zirconia occasionally presented shade mismatch due to uniform coloring and limited pink ceramic layering, while hybrid restorations showed soft-tissue adaptability challenges. These observations corroborate reports that monolithic systems, despite advances in shade gradient technology, still offer reduced flexibility for gingival morphology customization compared with veneered designs [38,39]. Patient-reported outcomes confirmed this contrast between visual and functional domains.

The esthetic domain reached statistical significance (p = 0.03), favoring monolithic zirconia, whereas comfort, masticatory function, and maintenance ease remained equally high for both materials. These findings reinforce that optical quality and material homogeneity directly enhance patient perception, consistent with recent RCTs using multilayer zirconia (2023–2024) that demonstrated comparable or superior esthetics to veneered alternatives when proper polishing and surface finishing are applied.

4.2. Material Properties and Surface Management

The zirconia restorations in this study were milled from high-strength, gradient mul-tilayer zirconia blocks (IPS e.max ZirCAD Prime, Ivoclar Vivadent, Schaan, Liechtenstein) using a calibrated five-axis vhf S2 milling unit (vhf camfacture AG, Ammerbuch, Germany). Following sintering under manufacturer-specified conditions, the frameworks were manually finished and sequentially polished with diamond-impregnated rubber wheels and fine polishing pastes to obtain a smooth, glaze-free surface that minimizes antagonist enamel wear.

Hybrid metal-ceramic frameworks were fabricated from CAD/CAM-milled Co-Cr (Bredent BioBase) and veneered with feldspathic porcelain through a controlled micro-layering and double firing cycle.

These technical parameters directly influence wear potential and long-term durability. Polished monolithic zirconia demonstrates wear behavior comparable to metal-ceramic restorations, while glazed or roughened surfaces may accelerate antagonist enamel loss [36,38].

Therefore, the polishing stage is crucial, especially in screw-retained restorations subjected to heavy occlusal loading [40].

4.3. Maintenance and Functional Considerations

Both materials exhibited low maintenance requirements and no biological complications, confirming the effectiveness of standardized hygiene and torque protocols.

Monolithic zirconia’s dense surface facilitates plaque control and may reduce peri-implant inflammation risk, whereas hybrid frameworks can accumulate biofilm at the metal–ceramic junctions if not meticulously cleaned [36,41].

In this cohort, professional maintenance was performed biannually, with screw verification and occlusal adjustments when needed. No temporomandibular disorders were recorded, suggesting that proper occlusal equilibration can mitigate the potential stiffness of zirconia frameworks.

4.4. Statistical and Methodological Limitations

The present analysis should be interpreted as exploratory due to the small sample size (n = 10 per group). While such pilot designs are common in full-arch prosthetic research, the absence of a priori power calculation increases the likelihood of Type II errors. A post hoc power analysis indicated that the study could detect medium effect sizes (Cohen’s d ≈ 0.5) with 65–70% power at α = 0.05. Additionally, despite normality testing (Shapiro-Wilk), non-parametric tests were preferred for robustness. No correction for multiple comparisons was applied, and results should therefore be regarded as descriptive trends. Additionally, no adjustment for multiple testing was performed because of the limited sample size and the exploratory framework of the analysis; this omission is acknowledged as a source of potential Type I error inflation.

Nevertheless, the consistency between statistical and clinical trends, fewer veneer complications and higher esthetic scores in zirconia—strengthens the interpretive reliability.

4.5. Contribution to Current Evidence and Future Perspectives

This study adds to the limited pool of post-2023 comparative clinical data by integrating both mechanical and patient-centered outcomes for monolithic and hybrid full-arch systems fabricated under identical clinical protocols. Unlike prior publications focusing solely on mechanical fatigue or esthetic ratings, the current analysis simultaneously evaluated complication profiles, maintenance frequency, and subjective satisfaction, providing a holistic perspective on long-term performance.

Future prospective trials should include larger cohorts, quantitative wear measurements (e.g., volumetric scanning of opposing dentition), and standardized fatigue testing to clarify whether the observed advantages of zirconia persist beyond the medium term.

Such studies could also explore surface coating technologies or hybrid polymer–zirconia composites to improve resilience and esthetic adaptability.

5. Conclusions

Over a three-year period, both monolithic zirconia and hybrid metal-ceramic full-arch implant restorations showed outstanding patient satisfaction and dependability. Rather than the frequency of complications, the type of complications was influenced by the composition of the material. While hybrid designs provided better soft-tissue and esthetic customization, monolithic zirconia demonstrated superior esthetics, lower maintenance, and minimal antagonist wear. A patient’s occlusal load, prosthetic space, and esthetic requirements should all be taken into consideration when choosing materials. These results offer clinically applicable recommendations for evidence-based material selection in prosthodontics for full-arch implants.