Search Results (72)

Background: Monolithic zirconia has attracted considerable interest in dentistry due to its favorable physical and mechanical properties, making it a promising alternative for crown fabrication. Nonetheless, a standardized finishing protocol for this material has yet to be established. Objective: This study aimed to evaluate the surface characteristics and in vitro biofilm formation of zirconia finished by either polishing or glazing. Methods: A total of 72 zirconia specimens were fabricated and divided into control, glazing, and polishing groups. Surface analysis included roughness, wettability, and surface free energy. Microbiological analysis included CFU (colony-forming units per mL) counts, microbial adhesion at 2, 4, 6, and 8 h, biofilm biovolume, and qualitative biofilm assessment via scanning electron microscopy (sEm). Results: The glazing group showed significantly greater roughness than the polishing (p = 0.006) and control (p = 0.016) groups, along with a lower contact angle (polishing—p = 0.002; control—p < 0.001) and higher surface energy (polishing—p = 0.005; control—p < 0.001). No significant differences were observed in CFU counts for the tested microorganisms (C. albicans, p = 0.158; L. casei, p = 0.610; S. mutans, p = 0.904). Regarding microbial adhesion, the polishing group showed a smaller biofilm-covered area compared to the control group for both total biofilm (p = 0.008) and viable biofilm (p = 0.005). no statistically significant difference was observed in biofilm biovolume (p = 0.082). Conclusions: These findings suggest that, despite the surface differences among the groups, biofilm formation was not significantly affected. Full article

Background/Objectives: Full-arch implant-supported prostheses have become a widely accepted solution for edentulous patients, yet long-term biological and mechanical complications remain a clinical concern. Methods: This retrospective study included 70 fully edentulous patients (362 implants) rehabilitated with either fixed or removable implant-supported prostheses. Data were collected on demographics, medical status, type and location of prostheses, implant type, abutments, method of fixation, and complications. Statistical analysis included Fisher’s exact test, the Mann–Whitney U test, and chi-squared tests, with a significance level set at p < 0.05. Results: Mechanical complications occurred in 41.4% of patients (29 out of 70), with framework fractures reported in eight cases (27.6%), ceramic chipping in six cases (20.7%), and resin discoloration in four cases (13.8%). The prostheses were fabricated using monolithic zirconia, metal–ceramic crowns, zirconia on titanium bars, and hybrid resin/PMMA on cobalt–chromium frameworks. Gingival inflammation was also noted in 41.4% of cases (n = 29), predominantly in posterior implant regions. Younger patients and those without systemic diseases showed a significantly higher incidence of mechanical complications. Conclusions: Two years post-treatment, mechanical and biological complications appear to be independent phenomena, not significantly associated with most prosthetic variables. Patient-specific factors, particularly age and general health status, may have greater predictive value than prosthetic design. Limitations of the study include its retrospective design and the lack of radiographic data to assess peri-implant bone changes. Full article

Purpose: The aim of this study was to compare the effect of rotary (air-driven, electric-driven) and oscillating (piezoelectric ultrasonic) handpieces on the quality of crown preparation, marginal integrity, and internal adaptation of monolithic zirconia crowns. Materials and Methods: Seventy-two standardized premolar preparations were performed using the air-driven handpiece with a guide pin-ended tapered fissure diamond bur on a modified dental surveyor. The finishing process utilized three handpiece types (n = 24/group) with fine/superfine diamond burs under controlled force with a fixed number of rotations and controlled advancement time. Marginal/internal adaptation was evaluated via the triple-scan technique; defects (marginal, axial, and occlusal) were quantified based on predefined criteria through the inspection of the Standard Tessellation Language (STL) file. Results: One-way ANOVA with Tukey HSD and Kruskal–Wallis with Dunn–Bonferroni tests were utilized. The marginal gap showed no significant differences (p > 0.05, η² = 0.04). The electric handpiece outperformed the ultrasonic (p = 0.023, η² = 0.105) in internal adaptation, while the air-driven showed no differences (p > 0.05). The ultrasonic handpiece produced fewer marginal defects than the air-driven (p = 0.039, ε² = 0.132), but more axial defects (median 9 vs. 6, p = 0.014, ε² = 0.168) than the electric handpiece and occlusal defects (5 vs. 3, 4 p = 0.007, p = 0.015, ε² = 0.227) than rotary handpieces. The air-driven handpiece exhibited comparable defect numbers to the electric handpiece without statistical significance (p > 0.05). Conclusions: Handpiece selection had a small effect on marginal adaptation but more pronounced effects on overall defect formations and internal adaptation. The ultrasonic handpiece’s decreased marginal defects but variable axial/occlusal results reveal technological constraints, whereas rotary handpieces’ consistency reflects their operator-dependent nature. Full article

Objective: This in vitro study aimed to evaluate the influence of cervical margin design—tangential versus chamfer—on the fracture resistance of monolithic crowns fabricated from lithium disilicate and zirconia ceramics. Materials and Methods: Forty extracted human molars were randomly assigned to two preparation types: chamfer and tangential. Each group was restored with CAD/CAM-fabricated crowns made from either zirconia (IPS e.max^® ZirCAD Prime) or lithium disilicate (IPS e.max^® CAD), resulting in four subgroups (n = 10). Standardized adhesive cementation protocols were applied. After 24 h storage in distilled water, the specimens underwent static load-to-failure testing using a ZwickRoell ProLine Z005 universal testing machine. Results: Zirconia crowns with chamfer margins exhibited the highest mean fracture resistance (2658 N), while lithium disilicate crowns with tangential margins showed the lowest (1862 N). Chamfer preparation significantly increased the fracture resistance of lithium disilicate crowns (p < 0.01), whereas margin design had no significant effect on zirconia. All restorations exceeded physiological masticatory forces, confirming their clinical viability. Conclusions: Cervical margin design significantly affected the fracture performance of lithium disilicate crowns but not zirconia. Chamfer preparations are recommended when using lithium disilicate to optimize mechanical strength. These findings underscore the importance of preparation geometry in guiding material selection for CAD/CAM ceramic restorations. Full article

This study aimed to evaluate prosthetic complications, implant survival rates, and marginal bone loss in implant-supported monolithic restorations compared to metal-ceramic restorations. The study was registered in PROSPERO (CRD420251022336) and conducted following the Cochrane Handbook for Systematic Reviews of Interventions and PRISMA guidelines. A systematic search was conducted in the electronic databases MEDLINE/PubMed, Web of Science, Scopus, Embase, and ProQuest for articles published up to December 2024. The inclusion criteria comprised studies evaluating only randomized clinical trials that evaluated implant-supported monolithic restorations directly compared to metal-ceramic restorations, considering any type of ceramic material and regardless of the fixation system (screw-retained or cemented), with a minimum follow-up of one year. A meta-analysis was performed using RevMan 5.4 software, and the risk of bias and certainty of evidence were assessed using the RoB 2.0 and GRADE tools, respectively. A total of six studies were included, all of which exclusively evaluated monolithic zirconia single crowns over follow-up periods ranging from 1 to 3 years. None of the included studies evaluated fixed partial dentures or restorative materials other than monolithic zirconia. In total, 267 patients (mean age range: 18–57 years) were analyzed, with a total of 174 implant-supported monolithic zirconia crowns and 165 metal-ceramic single crowns in the posterior region (premolars and molars). The meta-analysis revealed that implant-supported monolithic zirconia single crowns exhibited significantly fewer prosthetic complications compared to metal-ceramic single crowns (p < 0.0001; Risk Ratio [RR]: 0.26; Confidence Interval [CI]: 0.14–0.47). However, no statistically significant differences were observed between implant-supported monolithic zirconia and metal-ceramic single crowns regarding implant survival rates (p = 0.36; RR: 1.66; CI: 0.56–4.94) or marginal bone loss (p = 0.15; Mean Difference [MD]: −0.05; CI: −0.11–0.02). The risk of bias assessment indicated that four studies had a low risk of bias. However, the certainty of evidence was classified as low for prosthetic complications and implant survival rates and very low for marginal bone loss. Within the limitations of this review, it can be concluded that implant-supported monolithic zirconia single crowns can be considered a favorable treatment option as they show comparable implant survival and bone stability to metal-ceramic crowns, with a potential reduction in short-term prosthetic complications such as screw loosening and ceramic chipping. However, due to the limited number of studies included and low certainty of evidence, further long-term research is still needed to confirm their clinical performance over time. Full article

Objective: Selecting suitable materials and luting agents for single crowns is critical yet challenging, as dentists must consider different factors. This study aimed to assess dentists’ preferences for materials and luting agents under different clinical conditions and evaluate the nonclinical factors influencing their preferences. Methods: A paper-based survey supplemented with photographs illustrating anterior and posterior single-crown preparation designs was used, incorporating three clinical scenarios for each as examples. Participants provided demographic data and were asked to select their preferred material and luting agent for each scenario. Comparisons between the crown material/luting agent choices and dentist/practice characteristics were performed. Significant differences were determined using the chi-square test. Results: Overall, 262 (87.3%) dentists participated in this survey. The top-selected material for anterior preparation designs was lithium disilicate; monolithic zirconia was the most selected for posterior preparation designs. Dual-cure resin was the most selected luting agent for all anterior and posterior clinical scenarios, except for posterior subgingival preparation design. There was a significant association between the dentist’s age and the selection of material and luting agent (p < 0.05) in all clinical scenarios, except for the luting agent selection in the posterior subgingival preparation designs (p < 0.05). Other nonclinical factors yielded mixed results; some preparation designs showed significant differences, while others did not, depending on the clinical scenario. Conclusions: Reliance on new materials and luting agents that require minimally invasive treatment with dental ceramics and resin cement is increasing. However, the choice of materials and luting agents is influenced by clinical presentation and nonclinical factors, making it crucial for dentists to be aware of these factors when selecting materials for single-crown restorations. Clinical Implications: An overall trend was observed for the use of strong monolithic ceramics with adhesive resin cements. These findings could assist dentists in reviewing and re-evaluating material choices in their clinical practices, both at a national and regional level. Additionally, the findings could be useful for dental policy makers, wholesale suppliers, and retail distributors in making future decisions. Full article

Background: Modern dentistry demands accurate finish line designs for abutments. CAD/CAM systems enable the fabrication of thin prosthetic structures to fulfill this requirement. The aim of this study is to research the mechanical resistance of customized implant abutments with different types of marginal design in laboratory environment. The null hypothesis is there is no difference in fatigue loading and compression strength in custom implant abutments with chamfer or vertical marginal design. Methods: The study model includes 60 specimens of implant suprastructures, organized into four test groups, by the margin design and used material: Group A—suprastructures, made of monolithic zirconia implant crown and titanium custom abutment with vertical marginal design; Group B—suprastructures, monolithic lithium disilicate implant crown and titanium custom abutment with vertical marginal design; Group C—suprastructures, made of monolithic zirconia implant crown and titanium custom abutment with chamfer marginal design; and Group D—suprastructures, made of monolithic lithium disilicate implant crown and titanium custom abutment with chamfer marginal design. All samples were subjected to fatigue loading test in chewing Simulator CS-4 (SD-Mechatronik, Westerham, Germany) for 1250,000 cycles, at a frequency of 2 Hz. The specimens, which survived, was conducted to compressive strength test in universal testing machine Instron M 1185 (Instron, Norwood, MA, USA). Results: The results analysis highlighted Group A as the most resistant to compressive forces (4411 MPa). Group D was with lowest values (1864 MPa)—twice than Group A. Group B (3314 MPa) had lower results than Group A, but higher than Groups C (3130 MPa) and D. Conclusion: Compression strength significantly depends on the choice of marginal design of implant abutments. Vertical margin design has better performance, that chamfer one. Full article

Background/Objectives: Among the complications of endodontic treatment, root fractures are the most severe and may require tooth extraction. The objective of this study was to develop virtual models of mandibular molars with different endodontic restorations to assess the stress distribution in tooth structures based on the type of corono-radicular restoration, compared with the model of an intact molar. Methods: Four virtual models of a mandibular molar were created: (1) an intact molar with preserved enamel, dentin, dental pulp and cementum; (2) an endodontically treated molar restored with a composite filling; (3) a molar restored with a fiberglass post and monolithic zirconia crown; (4) a molar restored with a metal cast post and monolithic zirconia crown. External force loads from 0 to 800 N were simulated using Finite Element Method (FEM). Results: The highest displacement, strain and stress values were observed in the molar restored with a composite filling, whereas the lowest values were recorded in the molar restored with a fiberglass post and zirconia crown. Critical stresses were primarily concentrated on the pulp chamber floor. Conclusions: The pulp chamber floor was identified as the most vulnerable area for fracture. This underscores the importance of preserving tooth structure to enhance the strength and durability of molars throughout and beyond endodontic treatment. Full article

This study evaluated if the material, the substrate, and the cement have no influence on the color of pre-shaded monolithic zirconia crowns. The specific effect of the cement over each substrate/brand group was also studied. Two commercial brands of zirconia, Amann Girrbach (AG) and Zirkonzahn (ZZ), were used to produce crowns that were placed over three substrates (natural tooth, zirconia, metal) using two different resin cements (Ivoclar AG (Shaan, Liechtenstein) Neutral and Light) or glycerol (as the control) (n = 10). Lightness (L*), chroma (C*), hue (h*), and color difference (ΔE) of each crown were measured using a VITA Easyshade V^® spectrophotometer (VITA Zahnfabrik, Bad Säckingen, Germany), following the standardized reference. Since normality was not verified by the Shapiro–Wilk test, data were statistically analyzed using the Kruskal–Wallis test for group comparisons and Tukey’s post-hoc test for multifactorial variance analysis (α = 0.05). ΔE medians ranged between 1.3 in the AG/zirconia substrate/glycerol group and 8.0 in the ZZ/metal substrate/light cement group. In general, lower values of ΔE were recorded in AG restorations compared to ZZ (p < 0.05), zirconia, and natural tooth substrates compared to metal (p < 0.001) and neutral compared to light cements (p < 0.05). Specifically, over the metal substrate, AG crowns with neutral cement and ZZ crowns with neutral cement and glycerol showed lower ΔE values (p < 0.05). Over the zirconia substrate, light cement presented higher ΔE values than glycerol in both brands but similar to neutral cement. Over the natural tooth, no significant differences were observed between cements (p > 0.05) in the AG brand, while in the ZZ group, light cement showed higher ΔE values (p < 0.05). The final color of the restorations was significantly influenced by the zirconia brand, substrate type, and resin cement. Light cement led to greater color variations, particularly in ZZ restorations. These findings highlight the importance of material selection in achieving esthetically pleasing zirconia restorations. Full article

Background and Objectives: The manufacturing of single crowns using hybrid abutments is an alternative that may be interesting in clinical practice, combining the advantages of the different materials used in a personalized design for each case. The purpose of this in vitro study was to evaluate the torque loss, survival, reliability, failure mode, and strain distribution of implant-supported prostheses with zirconia (Zir) and cobalt–chromium (Co-Cr) hybrid abutments. Materials and Methods: Abutments were milled by CAD/CAM and divided into two groups according to the materials used, Zir and Co-Cr, and cemented on titanium bases screwed to dental implants. Monolithic zirconia crowns were cemented on the abutments. The implant/abutment/crown sets were subjected to thermomechanical cycling (n = 10) (2 Hz, 140 N, 1 × 10⁶ cycles, immersed in water at 5–55 °C) to evaluate the torque loss. The single load to fracture test (SLF) was performed to design the loading profiles (light, moderate, and aggressive) of the step-stress accelerated life testing (SSALT) (n = 21) to evaluate the survival and reliability. The representative fractured specimens were analyzed under optical and scanning electron microscopy. The digital image correlation (DIC) (n = 1) was performed using specimens embedded in polyurethane resin models that received static point loading, and the strain distribution was analyzed. Results: There was no difference in torque loss, survival, or reliability between zirconia and Co-Cr abutments. An analysis of the fractured surfaces showed that the abutments presented the same failure mode, where the fracture probably started in the titanium base/screw. The zirconia abutment model presented only compressive strains around the implant, while the Co-Cr abutment model showed tensile and compressive strains in the middle of the implant; however, all strains were within the clinically acceptable limits. There was a strain concentration in the titanium base close to the implant platform for both groups. Conclusions: Zirconia and Co-Cr hybrid abutments presented similar torque loss, survival, reliability, and failure modes, but the abutment material influenced the strain distribution around the implant. The titanium base screw was the weakest link in the system. Full article

The use of zirconia for full-arch Implant-Supported Fixed Complete Dental Prostheses (ISFCDPs) is common and reliable, with different techniques available for their design and fabrication. This retrospective study investigated prosthetic and implant survival/success rates and patients’ satisfaction for ISFCDPs produced with three different techniques: zirconia-on-titanium (milled zirconia arch glued to a titanium bar), progressive monolithic zirconia (entirely made of zirconia and directly screwed to the implants) and zirconia-on-zirconia (milled esthetic zirconia crowns glued to a milled high resistance zirconia frame). Fourteen patients (five males, nine females) aged 52–80 and treated with 14 ISFCDPs (86 implants) were included in this analysis. The mean follow-up at the time of recall was 36 months. Prosthetic and implant-related success rates were, respectively, 92.86% and 95.35%. No failures have been reported. One case of prosthetic chipping was observed; however, it was successfully repaired intraorally. Patients’ satisfaction was high: 78.57% were completely satisfied, 14.53% very satisfied and 7.14% satisfied. In conclusion, all the patients recommend treatment with ISFCDPs as full-arch prosthetic rehabilitation. The present study demonstrates positive clinical outcomes and high patients’ satisfaction. Further long-term, prospective studies with a larger cohort of patients are needed to confirm the advantages of the different prosthetic designs. Full article

Background: The present article describes a step-by-step maximally digitalized workflow protocol with computer-aided design and computer-aided manufacturing (CAD/CAM) in partial-arch edentulous patients rehabilitated with fixed dental prostheses and removable partial dentures (FDPs and RPDs). Methods: Facial digitalization, intraoral scans, and functional mandibular movement recordings were used to create a 4D virtual patient on commercially available CAD software. The fixed components including post-and-cores, both metal–ceramic with extra-coronal attachment and monolithic zirconia crowns, and the RPDs were manufactured by computer numerical controlled direct milling. Results: This innovative digital approach using the virtual patient and the superimposition of interim RPDs fitted in the mouth has been used to provide fixed and removable rehabilitation to the patient without clinical complications with 2 years of follow-up. Conclusions: Within the limitations of this report, the developed combined prosthesis fabrication technique allowed optimization of the production by decreasing the clinical steps and laboratory procedures in partial-arch edentulous rehabilitated with FDPs and RPDs. Full article

Objective: The aim of the present study was to evaluate the long-term clinical survival and success of chairside-fabricated single-tooth monolithic zirconia restorations on posterior teeth using the speed sintering process. Materials and Methods: Between 2012 and 2022, 250 single-tooth crowns were fabricated for 193 patients using the CEREC^® chairside workflow. Restorations were fabricated from monolithic 3Y-TZP zirconia (InCoris TZI, Dentsply Sirona©, Bensheim, Germany) as full-contour crowns. The same clinician performed all procedures. Luting was performed using self-adhesive resin-based cements or glass ionomer cement. Retrospective analysis was conducted, defining survival as crowns still in function regardless of any interventions, and success as crowns that remained functional without the need for intervention. Statistical analysis was performed using Kaplan–Meier analysis, considering “refabrication” and “intervention” as endpoints. Results: Of the 250 crowns, a total of 162 (64.8%) crowns showed success. Over the whole observation period, 44 crowns (17.6%) required refabrication, and 88 (35.2%) required intervention. Mean survival without refabrication was 7.43 years, with a 5- and 7.5-year survival of 86.9% and 76.6%. The mean survival without intervention was 6.5 years, with a 5- and 7.5-year survival of 70.8% and 59.9%. Conclusions: Under appropriate technical conditions, chairside-fabricated 3Y-TZP zirconia single-tooth crowns represent a viable fabrication method. Neither the cementation mode nor the crown position—whether on premolars or molars—significantly impacted the survival rates. Full article

Monolithic zirconia (MZ) crowns are widely utilized in dental restorations, particularly for substantial tooth structure loss. Inspection, tactile, and radiographic examinations can be time-consuming and error-prone, which may delay diagnosis. Consequently, an objective, automatic, and reliable process is required for identifying dental crown defects. This study aimed to explore the potential of transforming acoustic emission (AE) signals to continuous wavelet transform (CWT), combined with Conventional Neural Network (CNN) to assist in crack detection. A new CNN image segmentation model, based on multi-class semantic segmentation using Inception-ResNet-v2, was developed. Real-time detection of AE signals under loads, which induce cracking, provided significant insights into crack formation in MZ crowns. Pencil lead breaking (PLB) was used to simulate crack propagation. The CWT and CNN models were used to automate the crack classification process. The Inception-ResNet-v2 architecture with transfer learning categorized the cracks in MZ crowns into five groups: labial, palatal, incisal, left, and right. After 2000 epochs, with a learning rate of 0.0001, the model achieved an accuracy of 99.4667%, demonstrating that deep learning significantly improved the localization of cracks in MZ crowns. This development can potentially aid dentists in clinical decision-making by facilitating the early detection and prevention of crack failures. Full article

Multilayer monolithic zirconia, which incorporates polychromatic layers that mimic natural tooth gradients, offers enhanced aesthetics and functionality while reducing debonding risks and improving fabrication efficiency. However, uncertainties remain regarding the fracture characteristics of multilayer monolithic zirconia crowns under occlusal loading, whether composed of uniform or combined yttria levels. The current study investigated how variations in yttria levels and thicknesses affected the optical properties and fracture loads of multilayer monolithic zirconia. Samples of multilayer monolithic zirconia in the Vita A1 shade were used, while employing 3Y (SZ) and 4Y + 5Y (AZ) yttria levels. The optical properties, including the color difference (ΔE_WS) and translucency parameters (TP₀₀), were measured using a digital colorimeter. The fracture loads were analyzed using a universal testing machine, and fractured surfaces were examined under a stereomicroscope. Statistical analyses assessed the impacts of the yttria levels and sample thicknesses on the optical properties. The ΔE_WS values of SZ ranged 3.6 to 4.0, while for AZ, ΔE_WS at 0.5 mm was 3.9 and <2.6 for other thicknesses. The TP₀₀ values decreased with an increased thickness, with AZ generally exhibiting greater translucency than SZ. In the fracture load investigations, SZ (>1600 N) generally exceeded AZ (>1260 N), with fracture loads notably increasing with thickness, particularly for premolars (SZ > 3270 N, AZ > 2257 N). SZ predominantly exhibited partial and complete fractures, whereas AZ showed fewer non-fracture categorizations. Complete fractures began with dense, irregular cracks that extended outward to reveal smooth surfaces, while premolars subjected to higher loads exhibited concentric ripple-like structures. Partial fractures revealed radial textures indicative of areas of stress concentration. In summary, higher yttria levels were correlated with increased translucency, while variations in the fracture loads primarily stemmed from differences in the tooth position or thickness. Overall, multilayer monolithic zirconia incorporating combined yttria levels of 4Y + 5Y (AZ) offered high translucency, precise color matching, and substantial fracture resistance, rendering it highly suitable for aesthetic and functional dental applications. Full article