Aesthetic and Functional Rehabilitation for Dentogingival Asymmetry Using Zirconia Restorations.

In an effort to improve dentogingival aesthetics, scientific research has been developing non-surgical techniques and dental restorative materials. A 45-year-old female reported to the hospital with a complaint of an unpleasant aesthetic in the anterior region of the maxilla. She has an irregular contour of the gingiva in her anterior region and no temporomandibular problems. There is a history of trauma, but she did not take any treatment for it, which caused discolouration. Plaque index was retained by the surface roughness. Due to this reason, the patient's appearance, self-esteem, and quality of life have decreased. The purpose of this case is to provide a system-based clinical example of oral rehabilitation for anterior teeth. The patient didn't like the way she looked, and hence aesthetic and functional rehabilitation was planned. Treating the dentogingival asymmetry was the first step in the therapeutic approach. An in-ceram zirconia permanent porcelain metal-free crown was positioned after the temporary crowns were cemented into place. It should be mentioned that in clinical situations, the integration of periodontal and prosthetic treatment is crucial. Additionally, it is stated that the in-ceram zirconia system can produce satisfactory results when applied appropriately. For the main anterior teeth, zirconia crowns have offered an alternate treatment option that addresses aesthetic concerns and facilitates the installation of extra-coronal restorations. This article describes a case involving the aesthetic and functional restoration of severely damaged maxillary incisors using zirconia crowns.

Degree of conversion and interfacial adaptation of touch-cure resin cement polymerized by self-curing or dual-curing with reduced light.

OBJECTIVES: The first aim of this study was to determine whether there is a difference in degree of conversion (DC) of touch-cure cements polymerized by self-curing with adhesive or dual-curing under reduced light. The second aim was to compare interfacial adaptation of zirconia restoration cemented using touch-cure cements self-cured or dual-cured by reduced light. METHODS: The DC of touch-cure resin cements with adhesive was measured continuously using Fourier transform infrared spectrometry. Experimental groups differed depending on touch-cure cement. Each group had three subgroups of polymerization method. For subgroup 1, the DC was measured by self-curing. For subgroups 2 and 3, the DCs were measured by dual-curing with reduced light penetrating 3 mm and 1 mm zirconia blocks, respectively. For interfacial adaptation evaluation, Class I cavity was prepared on an extracted third molar, and zirconia restoration was fabricated. The restoration was cemented using the same cement. Groups and subgroups for interfacial adaptation were the same as those of the DC measurement. After thermo-cycling, interfacial adaptation at the tooth-restoration interface was evaluated using swept-source optical coherence tomography imaging. RESULTS: The DC of touch-cure cement differed depending on the measurement time, resin cement, and polymerization method (p < 0.05). Interfacial adaptation was different depending on the resin cement and polymerization method (p < 0.05). CONCLUSION: For touch-cure cement, light-curing with higher irradiance presented a higher DC and superior interfacial adaptation than light-curing with lower irradiance or self-curing. CLINICAL RELEVANCE: Although some adhesives accelerate the self-curing of touch-cure cement, light-curing for touch-cure cement is necessary for zirconia cementation.

No-prep dentistry using the Simple Orthodontic Extrusion (SOE) technique to create occlusal space. Illustration in tooth wear and resin-bonded bridges

In restorative dentistry, the lack of occlusal space may lead to the mutilation of healthy tissue in order to provide sufficient space for the restorative material. Noprep dentistry can be achieved by placing high-bite restorations, followed by Simple Orthodontic Extrusion (SOE) of other teeth to close the created open bite. This rapid, partial orthodontic treatment is well accepted by patients as it can be easily performed using simple buttons, and it takes only a few weeks to reestablish occlusal contacts. The SOE technique is a further development of the Dahl concept. It has the advantages without the disadvantages. Two applications of this technique are presented in this article: the treatment of the severe wear of anterior teeth with no-prep palatal veneers made of Polymer-infiltrated Ceramic Network (PICN, 'hybrid ceramic') material and the realization of no-prep zirconia resin-bonded bridges (RBBs) to replace missing lateral incisors. An original 3D-printed resin guide for correctly positioning RBBs and facilitating the removal of excess composite cement is also presented. This work highlights the considerable advantages of multidisciplinary collaboration in the field of minimally invasive dentistry.

Effect of Er:YAG Laser Application and Sandblasting on Shear Bond Strength of Veneering Ceramic to Zirconia Core.

Objectives: Porcelain chipping and delamination are among the shortcomings of all-ceramic restorations. This study aimed to assess the effect of laser irradiation and sandblasting on shear bond strength (SBS) of zirconia to veneering porcelain. Materials and Methods: In this in vitro, experimental study, 60 zirconia blocks were randomly divided into three groups (n=20) for surface treatment with Er:YAG laser, sandblasting, and no surface treatment (control). Each group was randomly divided into two subgroups (n=10) for porcelain application by the layering or the pressing technique. The surface roughness, SBS, and failure mode were determined and analyzed using two-way ANOVA, Tukey's HSD test, Chi-square test, and Pearson's correlation test (alpha=0.05). Results: The mean SBS was 8.16±3.66 MPa, 9.32±2.7 MPa, and 11.85±3.06 MPa in the control, laser, and sandblasting groups, respectively. The SBS was significantly different among the three groups (P=0.002). The failure mode of the three groups was not significantly different (P>0.05). The sandblasted group showed significantly higher surface roughness than the control and laser groups (P<0.001). Conclusion: Sandblasting yielded higher SBS particularly when the porcelain was applied by the layering technique. Although laser irradiation increased the SBS, the difference with the control group was not statistically significant.

Does the internal surface treatment technique for enhanced bonding affect the color, transparency, and surface roughness of ultra-transparent zirconia?

PURPOSE: To investigate the effects of different surface treatments and thicknesses on the color, transparency, and surface roughness of ultra-transparent zirconia. METHODS: A total of 120 Katana ultra-translucent multi-layered zirconia specimens were divided into 12 groups according to the thickness (0.3, 0.5, and 0.7 mm) and surface treatment (control, airborne particle abrasion [APA], lithium disilicate coating, and glaze on). Color difference (ΔE00) and relative translucency parameter (RTP00) were calculated using a digital spectrophotometer. The surface roughness (Ra, Rq, Sa, and Sq) was measured using a non-contact profile scanner. The surface morphologies and microstructures of the samples were observed using a tungsten filament scanning electron microscope. Statistical analyses were performed by one-way and two-way analysis of variance (ANOVA) followed by post hoc multiple comparisons and Pearson's correlation (α = 0.05). RESULTS: The results showed that the surface treatment, ceramic thickness, and their interactions had significant effects on ΔE00 and RTP00 (p < 0.001). The surface treatment significantly altered the micromorphology and increased the surface roughness of the ceramic samples. APA exhibited the lowest transparency, largest color difference, and highest surface roughness. Zirconia with 0.3 mm and 0.7 mm thicknesses showed strong negative correlations between Sa and RTP00. CONCLUSIONS: The three internal surface treatments significantly altered the surface roughness, color difference, and transparency of ultra-transparent zirconia. As the thickness increased, the influence of the inner surface treatment on the color difference and transparency of zirconia decreased. CLINICAL IMPLICATIONS: For new zirconia internal surface treatment technologies, in addition to considering the enhancement effect on the bonding properties, the potential effects on the color and translucency of high-transparency zirconia should also be considered. Appropriately increasing the thickness of zirconia restorations helps minimize the effect of surface treatment on the optical properties.

Reverse scan body: Complete digital workflow for double full-arch zirconia prostheses.

During intraoral complete-arch digital implant scanning, one of the most technique-sensitive steps is the implant data acquisition and merging of different surface geometry data sets for prototype prosthesis fabrication due to the absence of fixed landmarks. Recently developed extraoral techniques have allowed for an alternative approach for the digital acquisition of implant position in completely edentulous patients. Specifically, extraoral digital scanning of the conversion prosthesis after connecting reverse scan bodies has been proposed as an efficient approach. The reverse scan body protocol digitally simulates the traditional back-pouring technique long utilized in analog workflows. The present article describes a technique for simplifying the digital workflow for the fabrication of passive-fitting definitive prostheses using the reverse scan body concept.

Alterations in internal threads of implant analog of different materials after multiple reuse.

The impact of multiple reuse on the alterations in internal threads of four different implant analogous composed of different materials (stainless steel (SS), aluminum (Al), titanium (Ti), and zirconia (Zr) by utilizing two die materials at different time durations is of interest to dentists. The spacing between the threads was measured using the impressions created for the interior threads of implant analogs, or replicas by stereomicroscope set to x50 at 0th, 3rd, 6th, 9th, and 12th interval. It was observed that there was decrease in distance between threads 1-2 as the increasing reuse at increasing time intervals in all implants analogs. However the decrease in distance between threads was low in Titanium implants analogs followed by Zircona implant analogs and the decrease was maximum in aluminum implants analogs followed by SS implant analogs. When there was evaluation of distance between threads 3-4 then it was observed that there was reduced decrease in distance between threads 3-4 as compared to threads 1-2 n all implant analogs. Similarly the reduction in distance between threads 5-6 was lesser as compared to threads 1-2 and threads 3-4. There was decrease in distance between threads 1-2 as the increasing reuse at increasing time intervals in all implants analogs. However, the reduction in distance between threads was lowest in Titanium implants analogs followed by Zircona implant analogs.

Comparison of polishing methods for two types of monolithic all-ceramic crowns after occlusal adjustments: Polishing paste versus glazed porcelain.

This study compared the effects of two surface preparation methods on two types of zirconia. Immediately prior to the placement of a monolithic zirconia crown, its morphology may be modified using a rotary cutting instrument for occlusal adjustments. The crown surface is scratched during the grinding process and, thus, requires polishing. Simplified zirconia crowns of 3Y and 5Y were fabricated and used as specimens. The surface roughness and gloss of the occlusal surfaces of specimens were measured and compared when a polishing compound was used after polishing points and when a silica-based coating was sintered. No significant differences were observed in surface roughness between 3Y and 5Y zirconia. The use of polishing compounds was effective because polishing points alone only resulted in a level of surface roughness that may cause wear on antagonist teeth. Although the silica-based coating improved surface properties, the polishing compound more effectively improved surface roughness.

Evaluation of vertical marginal discrepancy and load-to-failure of monolithic zirconia and lithium disilicate laminate veneers manufactured in different thicknesses.

OBJECTIVES: This study aimed to evaluate the feasibility of monolithic zirconia laminate veneers (MZLV) compared to lithium disilicate laminate veneers (LDLV). MATERIALS AND METHODS: Sixty resin replicas, each prepared with depths of 0.5 mm, 0.7 mm, and 1 mm, were produced using a 3D printer from acrylic teeth. Laminate veneers of these thicknesses were milled from pre-sintered monolithic zirconia (3rd generation) and lithium disilicate blocks. The intaglio surface of MZLV was treated with air abrasion using 110 µm diameter silica-modified aluminium oxide particles and ceramic primer, while LDLV was etched with etchant gel and treated with the ceramic primer before cementation with resin cement. Vertical marginal discrepancy (VMD) was assessed using a stereomicroscope, and a load-to-failure test was conducted using a universal testing machine. Failure modes were evaluated macroscopically on fractured surfaces. Data were analysed statistically using Two-way ANOVA and Bonferroni correction (α = 0.05). RESULTS: LDLV samples exhibited significantly larger VMD compared to MZLV samples across all thicknesses, especially in cervical, palatal, and mean data. Within the LDLV group, load-to-fracture values for 0.7 mm and 1.0 mm thicknesses were similar, whereas for 0.5 mm thickness, it was significantly lower. In the MZLV group, load-to-fracture values were lower for 0.7 mm and 1.0 mm thicknesses compared to LDLV, but higher for 0.5 mm thickness. CONCLUSIONS: Material choice and restoration thickness significantly influence laminate veneer restorations' success. MZLV generally exhibits superior vertical marginal fit compared to LDLV, with varying load-to-failure values across different thicknesses. Clinical management of debonding in MZLV is simpler compared to restoration fracture in LDLV. CLINICAL RELEVANCE: Considering clinical factors, MZLV may be a preferable option to LDLV for this restoration with the thickness of 0.5 mm.

Qualitative surface roughness of lithium disilicate endo-crown for pulpotomized primary molars.

Rehabilitation of pulpotomized primary molars with an appropriate restoration is essential for recovering function and safeguarding the durability of the treatment. This study aimed to assess and compare the surface roughness of stainless steel (ST) crowns, zirconia (ZR) crowns, fiberglass (FG) crowns, and lithium disilicate (LD) endo-crowns as a restoration for pulpotomized primary molars also, evaluating the surface roughness of their antagonists. Sixty pulpotomized primary mandibular first molars were used for qualitative surface roughness evaluation and divided into four groups (n = 15/group) according to the crown type (group-ST, group-ZR, group-FG, group-LD). While the other sixty sound, unprepared primary maxillary first molars were used for evaluation of their surface roughness against the tested crowns. Specimens' preparation and cementation were carried out according to each crown type and manufacturer's instructions. The surface roughness was done using a two-body wear test. The data were statistically analyzed. All tested crowns showed an increased change in surface roughness, except group-ZR, which had the least change in surface roughness after mechanical wear with no statistically significant difference(P = 0.681). All crown types significantly increased the surface roughness of their antagonists after mechanical wear, except group-ST which showed insignificant affection (p ≥ 0.05). Zirconia crowns and lithium disilicate endo-crowns had the least change in surface roughness compared to other groups while SSCs showed the least tooth loss in the antagonist enamel.

Fracture Resistance of Zirconia Surveyed Crowns With Digitally Designed and Hand-Modified Occlusal Rest Seats.

Background In light of the trend of using zirconia crowns, clinicians will likely face abutment included in removable partial dentures (RPD) designs with existing zirconia. However, the decision to replace the existing crown with a surveyed crown or modify the existing crown to accept the RPD is unclear. To the best of our knowledge, there is a lack of literature on the effect of preparing a rest seat on the existing monolithic zirconia crown in the patient's mouth on the fracture resistance of the crown. Therefore, in this study, we aimed to evaluate the fracture resistance of computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia surveyed crowns with digitally designed rest seats and hand-modified rest seats. Methods Thirty CAD/CAM zirconia surveyed crowns were digitally designed and fabricated and divided into groups (n=10 per group) as follows: Group 1 comprised surveyed crowns with no occlusal rest seat; Group 2 comprised surveyed crowns with a digitally designed mesial rest seat; and Group 3 comprised surveyed crowns with a hand-modified mesial rest seat. Then, with all the crowns cemented to metal dies, the specimens were subjected to a fracture resistance test using a universal testing machine (Model 8501 Instron, Norwood, MA, USA). Results Surveyed crowns without any rest seat and those with digitally created and hand-modified rest seats displayed different fracture resistances: crowns with no rest seat offered the highest fracture resistance (5831 ± 895.15 N), followed by those with a digitally designed and milled rest seat (5280 ± 1673.33 N). Crowns with a hand-modified rest seat provided the lowest fracture resistance (4976 ± 322.5 N). Based on our results, surveyed crowns without a rest seat displayed higher fracture resistance than those with a rest seat. Conclusion The fracture resistance of crowns with a digitally designed and milled rest seat was statistically similar to that of control crowns with no rest seat, whereas hand-modified rest seats significantly reduced the fracture resistance of surveyed zirconia crowns.

A Survey of Preferences for Ceramic Materials on Tooth-Supported Crowns Among Dental Practitioners in Chile.

Purpose: To evaluate the preferences of dental practitioners for tooth-supported crowns dental ceramics by means of an online survey and to assess the influence of age, gender, years of experience, and dental specialty on those preferences. Materials and Methods: An anonymous questionnaire was delivered online through Google Surveys, targeting 796 dentists. It contained 17 dichotomous, closed questions with two sections. The first section dealt with general characteristics, including age, gender, years of experience, training in prosthodontics, and hours worked per week. The second section included questions regarding preferences of different materials for crowns, and the use of digital workflows. Analyses were carried out with Stata 14.0 software (StataCorp, TX, USA). A significance level of p=0.05 was adopted. Results: 248 surveys were answered. Practitioners in Chile preferred lithium disilicate for the anterior region (55.2%) but also for the posterior area (40.7%), regardless of their age, gender, years since graduation, hours worked per week or any training in prosthodontics. Chilean dentists over 50 years old considered zirconia almost 4 times more than those under 30 years old for anterior crowns (51.85%). 59.68% of dentists take digital impressions, and 37.10% have access to chairside CAD/CAM technology. In this group, 54.4% preferred feldspathic ceramic for anterior and 23.9% for posterior crowns. Conclusions: While there is a wide range of dental ceramic materials, these results provide a snapshot of the current trends in Chile where lithium disilicate is the most preferred ceramic material for tooth-supported crowns, and metal-ceramic is the least preferred material.

Comparison of the Marginal and Internal Fit of Ceramic Laminate Veneers Fabricated with Four Different Computer-Aided Manufacturing Techniques.

Purpose: The improvement of computer-aided design and computer-aided manufacturing (CAD/CAM) has changed the methods of fabricating laminate veneers. The objectives of this study were to evaluate the marginal and internal fit of ceramic veneers manufactured with different CAD/CAM techniques. Materials and methods: A metal die was made by copying a prepared plastic maxillary central right incisor and scanned for designing a laminate veneer. One hundred laminate veneers were made with four different CAD/CAM techniques (n=25), including milled lithium disilicate (MLD), heat-pressed lithium disilicate with 3-dimensional (3D) printed wax patterns (PLD), milled zirconia (MZ), and 3Dprinted zirconia (PZ). The virtual marginal and internal fit of fabricated veneers was evaluated with digital crown fitting software. The actual marginal and internal fit was measured with the silicone replica method under a digital microscope. The measured data were analyzed using the one-way analysis of variance and the Turkey test. Results: There were significant differences in marginal and internal fit (P < 0.001) among manufacturing techniques. Both the virtual and actual marginal and internal gaps were higher in the PLD and PZ groups compared to the MLD and MZ groups. Conclusion: All four CAD/CAM techniques of manufacturing veneers, that is, milled lithium disilicate, heat-pressed lithium disilicate with 3D-printed wax patterns, milled zirconia, and 3D-printed zirconia, have clinically acceptable marginal and internal fit. Milled zirconia and lithium disilicate veneers demonstrated superior marginal and internal fit compared to 3D-printed zirconia and heat-pressed lithium disilicate veneers with 3D-printed wax patterns.

Flexural Strength of Different Yttrium Oxide Containing Monochrome and Multilayer Partially Stabilized Zirconia upon Various Sintering Rates.

Purpose: Sintering procedures influence the properties of zirconia. This study evaluated the effect of varying sintering rates on flexural strength (σ) of 3, 4, and 5 mol% yttria (Y) containing monochrome (Mo) and multilayer (Mu) zirconia. Materials and Methods: 270 specimens (width×length×thickness = 11.2×20×1.5 mm) were prepared from Mo and Mu of 3Y, 4Y, and 5Y zirconia and randomly sintered at regular (RS: 10 °C/min), fast (FS: 35 °C/min), and speed (SS: 70 °C/min) sintering (n = 15/group). Three-point bending test was determined for σ. ANOVA and Bonferroni test were analyzed for significant differences of σ (a=0.05). The microstructure and crystalline [monoclinic (m), tetragonal (t), and cubic (c)] phases were evaluated by SEM and XRD.Results: σ of zirconia was affected by zirconia type, shade pattern, and sintering rate. Significant higher σ for 3Y>4Y>5Y (p<0.05). Significant greater σ for Mu>Mo (p<0.05). Significant reduction of σ upon SS than RS and FS (p<0.05). However, no significant effect on σ upon varying sintering rates within each type of zirconia (p>0.05). SEM indicated greater grain size in 5Y than in 4Y and 3Y. XRD indicated higher t phase in 3Y, whereas higher c phase in 5Y. Mo indicated a higher c phase than Mu.Conclusions: σ was influenced by Y content (3Y>4Y>5Y), shade pattern (Mu>Mo), and sintering rate (RS@FS>SS). Nonetheless, no influence of varying sintering rates on σ for each type of zirconia, suggesting sintering zirconia with RS and FS for expecting higher σ and at SS for acceptable σ for chair-side cost-effective restoration.

Mandibular biomechanics rehabilitated with different prosthetic restorations under normal and impact loading scenarios.

BACKGROUND: Restorative treatment options for edentulous patients range from traditional dentures to fixed restorations. The proper selection of materials greatly influences the longevity and stability of fixed restorations. Most prosthetic parts are frequently fabricated from titanium. Ceramics (e.g. zirconia) and polymers (e.g. PEEK and BIOHPP) have recently been included in these fabrications. The mandibular movement produces complex patterns of stress and strain. Mandibular fractures may result from these stresses and strains exceeding the critical limits because of the impact force from falls or accidents. Therefore, it is necessary to evaluate the biomechanical behavior of the edentulous mandible with different restorations under different loading situations. OBJECTIVE: This study analyzes the biomechanical behavior of mandibles after four prosthetic restorations for rehabilitation under normal and impact loading scenarios. MATERIAL AND METHODS: The mandibular model was constructed with a fixed restoration, which was simulated using various materials (e.g. Titanium, Zirconia & BIOHPP), under frontal bite force, maximum intercuspation, and chin impact force. From the extraction of tensile and compressive stresses and strains, as well as the total deformation of mandible segments, the biomechanical behavior and clinical situations were studied. RESULTS: Under frontal bite, the anterior body exhibited the highest tensile (60.34 MPa) and compressive (108.81 MPa) stresses using restoration 4, while the condyles and angles had the lowest tensile (7.12 MPa) and compressive (12.67 MPa) stresses using restoration 3. Under maximum intercuspation, the highest tensile (40.02 MPa) and compressive (98.87 MPa) stresses were generated on the anterior body of the cortical bone using restoration 4. Additionally, the lowest tensile (7.7 MPa) and compressive (10.08 MPa) stresses were generated on the condyles and angles, respectively, using restoration 3. Under chin impact, the highest tensile (374.57 MPa) and compressive (387.3 MPa) stresses were generated on the anterior body using restoration 4. Additionally, the lowest tensile (0.65 MPa) and compressive (0.57 MPa) stresses were generated on the coronoid processes using restoration 3. For all loading scenarios, the anterior body of the mandible had the highest stress and strain values compared with the other segments. Compared to the traditional titanium restoration.2, restoration.1(zirconia) increases the tensile and compressive stresses and strains on the mandibular segments, in contrast to restoration.3 (BIOHPP). In addition, zirconia implants exhibited higher displacements than the other implants. CONCLUSION: In the normal loading scenario, the tensile and compressive stresses and strains on the mandible were within the allowable limits when all restorations were used. Under the chin impact loading scenario, the anterior body of the mandible was damaged by restorations 1 and 4.

In Vitro Assessment of a New Block Design for Implant Crowns with Functional Gradient Fabricated with Resin Composite and Zirconia Insert.

This study aims to evaluate and compare the mechanical resistance, fatigue behavior and fracture behavior of different CAD/CAM materials for implant crowns. Eighty-eight implant crowns cemented-screwed with four sample groups: two monolithic G1 Zirconia (control) and G3 composite and two bi-layered G2 customized zirconia/composite and G4 prefabricated zirconia/composite. All static and dynamic mechanical tests were conducted at 37 °C under wet conditions. The fractographic evaluation of deformed and/or fractured samples was evaluated via electron microscopy. Statistical analysis was conducted using Wallis tests, which were performed depending on the variables, with a confidence interval of 95%, (p < 0.05). The Maximum Fracture Strength values displayed by the four groups of samples showed no statistically significant differences. The crown-abutment material combination influenced the failure mode of the restoration, transitioning from a fatigue fracture type located at the abutment-analog connection for monolithic materials (G1 and G3) to a brittle fracture located in the crown for bi-layered materials (G2 and G4). The use of layered crown materials with functional gradients appears to protect the crown/abutment connection area by partially absorbing the applied mechanical loads. This prevents catastrophic mechanical failures, avoiding long chairside time to solve these kinds of complications.

Friction and Wear Behavior of Double-Walled Carbon Nanotube-Yttria-Stabilized ZrO2 Nanocomposites Prepared by Spark Plasma Sintering.

Double-walled carbon nanotube-yttria-stabilized ZrO2 nanocomposites are prepared by a mixing route followed by Spark Plasma Sintering. The double-walled carbon nanotubes (DWCNTs) have been previously subjected to a covalent functionalization. The nanocomposites present a high densification and show a homogenous dispersion of DWCNTs into a matrix about 100 nm in size. The DWCNTs are well distributed at the matrix grain boundaries but form larger bundles upon the increase in carbon content. The Vickers microhardness of the nanocomposites decreases regularly upon the increase in carbon content. Incorporation of carbon at contents higher than 2 wt.% results in significantly lower friction coefficients, both against alumina and steel balls, possibly because of the elastic deformation of the DWCNTs at the surface of the sample. Their presence also favors a reduction of the steel/ceramic contacts and reduces the wear of the steel ball at high loads. DWCNTs improve wear resistance and reduce friction without incurring any severe damage, contrary to multi-walled carbon nanotubes.

Comparative Clinical Behavior of Zirconia versus Titanium Dental Implants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Objective: The goal of this systematic review and meta-analysis was to assess whether there were clinically relevant differences in the treatment of edentulous areas comparing zirconia (Zr) and titanium (Ti) dental implants. The null hypothesis is that no differences can be observed in terms of the clinical parameters; the positive hypothesis I is that Zr implants have generally better results compared to Ti implants; and the positive hypothesis II is that Ti implants have a generally superior result than Zr implants. Methods: This review work was registered on the PROSPERO platform, and its development was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. The electronic search process was conducted on three databases (PubMed/Scopus/Web of Science), including randomized controlled trials (RCTs) from the past 10 years (up to April 2024). Identified articles were analyzed and included/excluded based on pre-defined selection and exclusion criteria. The quality assessment and risk of bias were evaluated using a Cochrane risk-of-bias assessment tool specifically designed for randomized trials (RoB2). A meta-analysis was conducted to correlate different treatment options based on the described outcomes; a random-effects model was used in the analysis of the variables. The analysis of heterogeneity was conducted by means of Cochran's Q-test and Higgins' I2 statistic. Results: Six RCTs were enrolled; 152 patients (90 males and 62 females) and 448 implants (267 Zr and 181 Ti) were included. Dental implant placement involved both the maxillary and mandibular arches. The implant sites showed heterogeneity in receiving Zr and Ti dental implants; in particular, 22 dental implants were placed in the mid-palatal region and 426 dental implants in the alveolar region (255 were in Zr and 171 in Ti). Regarding the success rate, it was better for Zr but with no statistical difference (p > 0.05); bleeding on probing had slight differences between Ti with 0.34% ± 0.42 and Zr with 0.26% ± 0.36 (p > 0.05); plaque score showed 0.46 ± 0.47 for Ti compared to 0.44 ± 0.49 for Zr (p > 0.05); no statistically significant difference was observed for pink esthetic score (PES). Statistically significant results were found for survival rate, which favored Ti implants (77.6%) compared to Zr (70.3%) (p < 0.05), and for marginal bone loss, which showed less loss in Ti implants (0.18 mm ± 0.47) compared to 0.42 mm ± 0.40 in Zr at 12 months (p < 0.001). Conclusions: The present systematic review and meta-analysis identified the positive hypothesis I and rejected the null and positive hypothesis II; it was possible to conclude that Ti dental implants have a better survival rate and less marginal bone loss than Zr dental implants after 1-year follow-up.

Zirconia full-arch implant prostheses: Survival, complications, and prosthetic space dimensions with 115 edentulous jaws.

PURPOSE: To assess the survival and complication rates of 115 monolithic zirconia implant-supported fixed complete dental prostheses (IFCDPs) with an up to 6-year follow-up. MATERIALS AND METHODS: One hundred fifteen edentulous jaws (71 patients) underwent complete-arch implant treatment with a digital workflow and were rehabilitated with monolithic zirconia IFCDPs. The primary outcome was to assess survival and complication rates while the secondary outcome was to measure the cross-sectional dimensions (prosthetic space) of those 115 monolithic zirconia IFCDPs and to correlate potential technical complications with the prosthetic space dimensions. RESULTS: Out of the 115 zirconia IFCDPs, 2 fractured, yielding a 98.6% survival rate up to a 6-year follow-up. The most commom minor technical complications were loss of screw access channel filling and porcelain chipping for the modified monolithic IFCDPs. There was no significant association between the count and type of complications and jaw location (maxilla vs. mandible) or prosthesis type (FP1 vs. FP3), according to Fisher's exact test. For maxillary zirconia IFCDPs, the mean square surface for the at the posterior abutment cross-sectional area was 25.18 mm2 at the lingual side of the abutment and 34.19 mm2 at the buccal side, respectively. The anterior abutment cross-sectional area was 33.92 mm2 at the lingual side of the abutment and 29.49 mm2 at the buccal side, respectively. For mandibular zirconia IFCDPs, the mean square surface at the posterior abutment cross-sectional area was 29.89 mm2 at the lingual side of the abutment and 39.05 mm2 at the buccal side, respectively. The anterior abutment cross-sectional area was 27.07 mm2 at the lingual side of the abutment and 56.50 mm2 at the buccal side, respectively. At the connector cross-sectional area, the mean square surface for the maxillary zirconia IFCDPs was 64.33 and 90.56 mm2 for the mandibular zirconia IFCDPs. The two fractures occurred in the midline (anterior area) for both maxillary FP1 prosthesis and mandibular FP3 prosthesis. The mean surface area at the connector for the maxillary FP1 prosthesis was 28.50 and 82.11 mm2 for the mandibular FP3 prosthesis, and was within the range of IFCDP connector square surface area. There was no significant association between the thickness of the zirconia prosthesis and the encountered prosthesis fractures. CONCLUSIONS: Monolithic zirconia IFCDPs yielded a 98.6% survival rate, after a mean observation period of 62 months with an SE of 3.1. The connector mean surface area in the two fractured IFCDPs was within the square surface range (minimum-maximum) as for the remaining 113 complication-free IFCDPs.

Effects of different plasma treatments on bonding properties of zirconia.

This in vitro study was to evaluate the effect of different non-thermal atmospheric pressure plasma (NTP) on shear bond strength (SBS) between yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and self-adhesive resin cement. In this study, The Y-TZP specimens were divided into 4 groups according to the surface treatment methods as follows: Control (no surface treatment), Sb (Sandblasting), AP(argon NTP), and CP(20 % oxygen and 80 % argon combination NTP). Y-TZP specimens were randomly selected from each group to observe and test the following indexes: scanning electron microscope to observe the surface morphology; atomic force microscope to detect the surface roughness; contact angle detector to detect the surface contact angle; energy spectrometer to analyze the surface elements. Then, resin cement (Rely X-U200) was bonded to human isolated teeth with Y-TZP specimens to measure SBS. The results showed that for the SE test, the NTP group was significantly higher than the control group (p < 0.05). The results of the SBS test showed that the SBS values of the NTP group were significantly higher than those of the other groups, regardless of the plasma treatment (p < 0.05). However, there was no significant difference between groups AP and CP in a test of SBS (p > 0.05). This study shows that non-thermal atmospheric pressure plasma can improve the shear bond strength of Y-TZP by increasing the surface energy. The addition of oxygen ratio to argon is more favorable to increase the shear bond strength and is worth further investigation.