Zirconia Prostheses Research Articles

Enhancing Fracture Toughness of Dental Zirconia through Incorporation of Nb into the Surface.

Our previous study found that the addition of pentavalent cations like niobium (Nb) to yttria-stabilized zirconia increased fracture toughness but also raised the coefficient of thermal expansion (CTE), and opacity also increased undesirably. A new surface treatment is required to boost fracture toughness without altering CTE or translucency. The surfaces of pre-sintered 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 4.2 mol% yttria-stabilized partially stabilized zirconia (4.2Y-PSZ) were treated with a Nb sol solution containing Nb2O5 nanoparticles. After drying and sintering, a high-Nb-content surface layer formed with a depth of approximately 1 mm. The Nb content in this surface layer matched that of a bulk material with 1 mol% Nb2O5. The tetragonality of the surface zirconia increased, enhancing the surface fracture toughness without changing the CTE or translucency. Adding Nb near the surface improved the fracture toughness without affecting the CTE or translucency. This method could strengthen zirconia prostheses, allowing more reliable dental restorations.

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

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. 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. 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 25.18mm2 at the lingual side of the abutment and 34.19mm2 at the buccal side, respectively. The anterior abutment cross-sectional area was 33.92mm2 at the lingual side of the abutment and 29.49mm2 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 39.05mm2 at the buccal side, respectively. The anterior abutment cross-sectional area was 27.07mm2 at the lingual side of the abutment and 56.50mm2 at the buccal side, respectively. At the connector cross-sectional area, the mean square surface for the maxillary zirconia IFCDPs was 64.33 and 90.56mm2 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 82.11mm2 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. 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 Nano-Diamond-Coated Milling Bits on Cutting Dental Zirconia

Hard alloy end mills are commonly employed for milling zirconia prostheses in dentistry. Nano-diamond-coated milling bits ensure high processing efficiency, accuracy, extended tool life, and reduced processing costs. This study aims at comparing various effects of cutting dental zirconia with nano-diamond-coated and ordinary milling bits. Two types of milling bits, one with nano-diamond coating and one without, were used to cut the dental zirconia green blanks (Ø98.5 mm, thickness: 25 mm) at three different speeds (1000, 1500, and 2000 rpm) in a dental milling machine. The unsintered and sintered zirconia surfaces were evaluated with glossmeter, optical profilometer for surface roughness, SEM, and EDX. The glossiness of the sintered zirconia block was statistically higher than that of the unsintered block (p < 0.05). For sintered zirconia, the nano-diamond-coated milling bit yielded a statistically (p < 0.05) higher glossiness in all spindle speeds than uncoated, save for the uncoated milling bit used at 1500 rpm. However, in terms of roughness, only sintering showed to be a statistically significant factor (p < 0.001) outweighing other two factors, and sintered zirconia always yielded lower surface roughness than the unsintered counterpart. Overall, the nano-diamond-coated milling bit can be operated at various speeds, resulting in a higher gloss on the sintered zirconia block, while an ordinary, uncoated milling bit can only achieve the same glossiness at a designated speed. The type of milling bits and the speeds have no significant effect on the surface roughness.

Does the choice of the measuring technique affect the comparison of fit between zirconia and cobalt-chromium prostheses?

The objectives of the study were to compare the adaptation of presintered zirconia and cobalt- chromium prostheses using microcomputed tomography (μCT), scanning electron microscopy (SEM), and stereomicroscope (SM). Twenty-four fixed dental prostheses (FDPs) were fabricated on metal abutments, duplicated from maxillary first premolar and first molar prepared on a typodont model. Teeth were reduced to obtain chamfer of 1.2 mm and reduction occlusaly of 2 mm occlusal. Scanning of the abutments was done with random assignment to two groups receiving the FDPs made from soft-milled Co-Cr (n = 12) and zirconia (n = 12). Marginal and internal gaps were assessed using three evaluation techniques (X-ray microcomputer tomography, SEM, and stereomicroscopy). Comparison of the results was made using Levene and analysis of variance tests (α =0.05). Irrespective of the material tested, statistical differences were found between the measuring techniques (P = 0.001 overall); the obtained mean gaps were for CT scan (92.60 ± 13.31), for SEM (101.92 ± 23.03), and for SM (113.44 ± 14.68): the multiple comparisons between techniques found a significant difference between CT and SM (P < 0.001), and SEM and SM (P = 0.025). When materials were compared within each measuring technique, Co-Cr showed lower values compared to zirconia in SEM (P < 0.001) and Stereo (P = 0.049); similar results were found in CT. Results values differed with the chosen measuring technique. Co-Cr prostheses had a better fit than zirconia prostheses in SEM and Stereo. µCT showed comparable results to SEM, smaller than SM results.

Analysis of subgingival microbiota and IL-1β, TNF-α and CX3CL1 levels in gingival crevicular fluid of fixed dental prostheses.

Prosthetic biomaterials can affect the composition of the subgingival microbiota and consequently the production of proinflammatory cytokines, causing damage to the periodontium. A total of 40 patients were divided into two groups: 20 with monolithic zirconia (MZ) prostheses and 20 with porcelain fused to metal (PFM) with nickel-chromium (Ni-Cr) alloy prostheses. Subgingival plaque and gingival crevicular fluid samples were taken. The Checkerboard technique for DNA-DNA hybridization and the enzyme-linked immunosorbent assay technique were performed. Teeth with MZ presented a lower percentage of bleeding on probing and tooth mobility compared to teeth with PFM with Ni-Cr alloy. Prosthodontic teeth harbored higher total levels of the 18 bacterial species than non-prosthodontic teeth. There was a higher prevalence of S. gordonii and V. parvula species in PFM with Ni-Cr alloy compared to MZ. There was an increase in IL-1β, TNF-α and CX3CL1 levels in PFM with Ni-Cr alloy compared to MZ. MZ is a candidate biomaterial with fewer negative effects on the periodontium, allowing for longer prostheses longevity in the mouth.

Comparing and Evaluating the Effect of Different Thickness of Two Metal-Free Restoration on Fracture Resistance in Molar Implant Prosthesis

Aim: The objectives of this article was to determine the minimum thickness of two monolithic materials for a posterior implant prosthesis. Materials and methods sixty monolithic IPS E.MAX CAD and zirconia crowns with different occlusa l thicknesses were made with the use of a computer-aided design/computer-aided manufacturing technique was divided into 3 experimental groups: group (1) 0.5 mm group (2) 0.7mm group (3)1mm. A universal testing machine was used to determine the fracture load value. The restoration was loaded until fracture; the fracture resistance was registered. Two-way ANOVA has been used to examine the data., followed by the least significant difference LSD test. One-way ANOVA variance analysis was used to examine the differences in fracture load of monolithic zirconia or IPS E.MAX CAD at various thicknesses (p=0.05). Results vertical load test revealed that the fracture resistance of monolithic zirconia higher than the lithium disilicate crown (E.MAX CAD). The results showed that the highest mean value of fracture load test was obtained in the ice zirconia translucent with 1mm thickness group (1880N), while the lowest mean value was in the E.MAX CAD with thickness 0.5mm Group (223N). Conclusions: The fracture resistance of CAD-CAM monolithic crowns is influenced by the occlusal thickness. zirconia prosthesis with occlusal thickness 0.7mm,1mm had a high fracture resistance when compared with E.MAX CAD.

Investigation of the structure and mechanical properties of a novel dental graded glass/zirconia ceramic

Constructing graded structure is a promising solution to reduce the occurrence of cracking and delamination of bilayered zirconia prosthesis. In this work, a novel graded glass/zirconia ceramic was developed by utilizing the interdiffusion between dense zirconia and a novel lithium disilicate glass in the SiO2-Li2O-Al2O3 system. Results demonstrated that a graded glass/zirconia structure with a depth of about 300 µm was constructed, which exhibited obviously gradient characteristics in microstructure, glass content and mechanical properties. The hardness (H) and elastic modulus (EM) values at the surface reduced significantly (64% for H and 79% for EM), and increased gradually with depth of graded layer. When the graded layer was subjected to loading force, the biaxial flexural strength increased. The mechanism of the evolution of graded structure and change of strength were also elucidated in detail. This study provides a promising strategy to improve the interface stability of bilayered zirconia restoration.

Marginal fit of monolithic versus layered zirconia crowns assessed with 2 marginal gap methods

Statement of problemZirconia can be used either monolithically or veneered with porcelain. However, whether veneering zirconia affects marginal fit is unclear. PurposeThe purpose of this in vitro study was to evaluate the marginal fit of the monolithic and layered zirconia prostheses using 2 different assessment methods. Material and methodsAn ideal complete crown with a chamfer finish line was prepared on an extracted maxillary central incisor. Two prosthesis designs, a framework and a monolithic design, and 2 marginal fit evaluation methods, the silicone replica and the triple scanning techniques, were used. In the first group, 10 crowns were fabricated with the framework design followed by porcelain veneering, and 10 crowns were fabricated monolithically in the second group. The marginal gap in each group was evaluated with both the silicone replica and triple scan methods. Data were statistically analyzed with a 2-way repeated measures ANOVA (α=.05). ResultsA significant difference was found in the mean marginal gap by design type (P=.003), with the monolithic prostheses having lower mean marginal gaps (31.0 and 84.0 µm). However, both groups showed clinically acceptable marginal fit. No significant difference was found between the assessment methods (P=.092). ConclusionsMonolithic zirconia crowns had a better marginal fit than veneered zirconia frameworks. Both the replica and triple scan techniques for marginal gap assessment yielded similar results.

Screw-retained ceramic-veneered/monolithic zirconia partial implant-supported fixed dental prostheses: A 5 to 10-year retrospective study on survival and complications.

To assess the clinical performance of screw-retained, ceramic-veneered, monolithic zirconia partial implant-supported fixed dental prostheses (ISFDP) over 5-10 years and to evaluate implant- and prosthesis-related factors influencing treatment failure and complications. Partially edentulous patients treated with screw-retained all-ceramic ISFDPs with 2-4 prosthetic units with a documented follow-up of ≥5 years after implant loading were included in this retrospective study. The outcomes analyzed included implant/prosthesis failure and biological/technical complications. Possible risk factors were identified using the mixed effects Cox regression analysis. A screened sample of 171 participants with 208 prostheses (95% of the restorations were splinted crowns without a pontic) supported by 451 dental implants were enrolled in this study. The mean follow-up duration after prosthesis delivery was 82.4 ±17.2months. By the end of the follow-up period, 431 (95.57%) of the 451 implants remained functional at the implant level. At the prosthesis level, 185 (88.94%) of the 208 partial ISFDPs remained functional. Biological complications were observed in 67 implants (14.86%), and technical complications were observed in 62 ISFDPs (29.81%). Analysis revealed only emergence profiles (over-contoured) as a significant risk factor for implant failure (P<0.001) and biological complications (P<0.001). Full-coverage ceramic-veneered zirconia prostheses had a significantly greater chance of chipping (P<0.001) compared with buccal-ceramic-veneered or monolithic zirconia prostheses. Screw-retained ceramic-veneered, monolithic partial ISFDPs have a favorable long-term survival rate. Over-contoured emergence profile is a significant risk factor associated with implant failure and biological complications. Buccal-ceramic-veneered and monolithic zirconia partial ISFDPs lower the initial prevalence of chipping compared with a full-coverage veneered design.

Retention of titanium copings to implant-supported fixed dental prostheses.

The aim of this in vitro study was to assess the effects of using different cements and titanium copings designs on the retention of implant-supported fixed dental prostheses (IFDPs) using a pull-out test. Fifty zirconia (ZirCAD; Ivoclar Vivadent) and 20 prepolymerized denture acrylic resin (AvaDent) rectangular (36mm × 12mm × 8mm) specimens were milled to mimic the lower left segmental portion of the All-on-Four IFDPs. Cylindrical titanium copings (Variobase; Straumann) (V) were used in 2 prepolymerized denture acrylic resin groups (n = 10) while conical titanium copings (Straumann) (C) were used as a control group for zirconia with 4 groups using cylindrical titanium copings. Before cementation, the outer surfaces of all titanium copings and the intaglio bonding surface of prosthetic specimens were airborne-particle abraded. All specimens were cemented following the manufacturer's recommendations and instructions according to the experimental design. After artificial aging (5000 cycles of 5°C 55°C, dwelling time 20s; 150 N, 1.5Hz in a 37°C water bath), all specimens were subjected to retention force testing using a pull-out test using a universal testing machine and a custom fixture with a crosshead speed 5mm/min. Modes of failure were classified as Type 1, 2, or 3. Retention force values were analyzed by the t-test for the prepolymerized denture acrylic resin specimen groups, and 1-way ANOVA and the Tukey test for the zirconia groups at α = 0.05. Mean and standard deviation retention force values varied from 101.1±67.1 to 509.0±65.2 N for the prepolymerized denture acrylic resin specimen groups. The zirconia groups ranged from 572.8±274.7 to 1416.1 ±258.0 N. There is no statistically significant difference in retention force values between V and C specimens cementing to zirconia with Panavia SA cement (Kuraray Noritake) (p = 0.587). The retention forces and failure modes were influenced by the cement used (p < 0.05). Modes of failure were predominantly Type 2 (mixed failure) and Type 1 (adhesive fracture from prosthetic materials) except for the quick-set resin group (Type 3, adhesive failure from coping). When bonding IFDPs onto titanium copings, quick-set resin provided significantly higher retention force for prepolymerized denture acrylic resin prostheses. Conical and cylindrical titanium copings performed similarly when cemented to zirconia with Panavia SA cement under the same protocol. The stability of the bonded interface and retention forces between zirconia prostheses and titanium copings varied from the cement used.

The Use of Zirconia for Implant-Supported Fixed Complete Dental Prostheses: A Narrative Review.

The success of implant-supported fixed complete dental prostheses (ISFCDPs) depends on multiple factors: some are related to the fixtures, such as fixture material, surface characteristics, positioning, and type of connection to prosthetic components; others are related to the prostheses, such as design and materials used. Zirconia is a material widely used in fixed prosthodontics, whether on natural teeth or on implants, with excellent results over time. Regarding the use of zirconia for ISFCDPs, the 2018 ITI Consensus Report stated that "implant-supported monolithic zirconia prostheses may be a future option with more supporting evidence". Since CAD/CAM technology and zirconia are being continuously innovated to achieve better results and performances over time, a narrative review of the literature seems necessary to focus research efforts towards effective and durable solutions for implant-supported, full-arch rehabilitations. The objective of the present narrative review was to search the literature for studies regarding the clinical performance of zirconia-based ISFCDPs. According to the results of this review, the use of zirconia for ISFCDPs showed good clinical outcomes, with high survival rates ranging from 88% to 100% and prosthetic complications that were restorable by the clinicians in most cases.

Influence of Occlusal Stress on Implant Abutment Junction and Implant Bone Interface: A Finite Element Analysis Study.

The aim of the present study was to assess the occlusal stress on the implant-abutment junction and implant-bone interface of a long-span implant-supported prosthesis made of two different prosthetic materials. A computerized tomography of the mandible was used to get the finite element model of the bone. The comparative groups were made as follows: S1 and S2 - 3.7 × 11 mm (44 region) and 4.5 × 11 mm (47 region), S1A and S2A - screw-retained porcelain-fused-to-metal prosthesis, S1B and S2B - cement-retained porcelain-fused-to-metal prosthesis, S1C and S2C - screw-retained zirconia prosthesis, and S1D - cement-retained zirconia prosthesis. Maximum stress generated on the implant-abutment interface of all the prostheses under vertical and oblique load was assessed. For all the comparative groups, maximum level of stress was generated at the cervical level of the implant-bone interface in comparison to the apical and middle-third level under both vertical and oblique load. No statistically significant difference between zirconia and porcelain-fused-to-metal prosthesis was seen at the implant-abutment interface and the cervical third of the implant-bone interface. A significant difference was found between all screw-retained and cement-retained groups. The present study concluded that the short implants in combination with standard-length implants using either porcelain-fused-to-metal or zirconia as prosthetic material in the form of long-span implant-supported prosthesis can be a viable treatment option in the posterior mandible. The accuracy of the diagnosis, examination, and knowledge of the site where the implant must be inserted, and the choice of superstructure is important for the stability and lifespan of the implant prosthesis.

Infiltrating fluorapatite glass-ceramics on the surface of dental 3 % yttria-stabilized zirconia to enhance bond strength

Zirconia is a material commonly used for denture repair due to its excellent mechanical properties. However, the low bond strength between zirconia dentures and natural teeth may cause the prosthesis to fall off, which is a major obstacle to its clinical success. Improving the bonding strength between dental zirconia and teeth and resisting the adhesive failure of zirconia prosthesis have been difficult problems in recent years. Thus, this study aims to infiltrate synthesized fluorapatite (Ca5(PO4)3F, FAp) glass-ceramics on an unsintered zirconia surface. The microstructure, phase characterization, surface morphology, mechanical properties, and bonding strength were comprehensively evaluated in this study. Scanning electron microscopy images of the cross-section of infiltrated zirconia revealed a residual FAp glass-ceramics coating on the surface, under which is the graded layer, demonstrating that the FAp glass-ceramics infiltrated the loose porous zirconia embryo to form a mechanical chimera. Energy dispersive spectroscopy results showed that silicon, which is the principal element of the FAp glass-ceramics, penetrated the zirconia to a depth of nearly 150 μm. These results verified the mechanical stability of the FAp glass-ceramics coating. Meanwhile, the shear strength test between the infiltrated zirconia and teeth showed that the bonding strength increased by approximately 3-fold, while the bond durability and flexural strength of the infiltrated zirconia also increased. As a new material for infiltrating zirconia, the application of the synthesized FAp glass-ceramics on the surface of unsintered zirconia with an appropriate coating time can ensure a high penetration depth and prevent stripping. Meanwhile, the bond strength and durability of the infiltrated zirconia can be significantly enhanced without reducing its mechanical properties.

Maxillary and mandibular complete-arch implant rehabilitation using a complete digital workflow: A case report.

This paper summarizes the clinical steps involved in maxillary and mandibular complete-arch implant rehabilitation using a complete digital workflow. The maxillary arch was recorded was using the double digital scan technique, and the mandibular arch using the triple digital scan technique. The digital protocol used in this case report allowed the recording of implant positions via scan bodies, soft tissues, and, most importantly, interocclusal relationship in the same visit. A new technique for mandibular digital scan was described that uses soft tissue landmarks by creating windows in the patient's provisional prostheses to superimpose the three digital scans and consequently fabricate and verify the maxillary and mandibular prototype prostheses and definitive complete-arch zirconia prostheses. This article is protected by copyright. All rights reserved.

Retrospective Cohort Evaluation of Full-Arch Zirconia Implant-Supported Fixed Prostheses.

Objective: To determine the median event-free survival and relative complication rates of monolithic and minimally layered full-arch zirconia prostheses, as well as to identify risk factors for prosthesis complications. Materials and Methods: In this retrospective cohort study, a total of 129 subjects (173 prostheses) were included in the chart review and 56 subjects (75 prostheses) participated in a clinical follow-up visit. All subjects had either single- or dual-arch monolithic or minimally layered zirconia implant-supported prostheses. Data related to patient, implant, and prosthesis factors were extracted from charts. The subgroup that presented for a clinical visit were asked to complete a satisfaction questionnaire. For this subgroup, the following clinical measures were assessed: routine intraoral examination, number of occluding units, cantilever length on each side of the prosthesis (right and left), prosthesis height, occlusal scheme, and oral hygiene methods. Periapical radiographs were obtained when the last radiographs of the patient were taken more than 12 months prior. Results: The follow-up period ranged from 12 months to 7.1 years (mean: 1.9 years). Observed complications included implant loss, peri-implantitis, mucositis, purulence, sinus tract formation, oroantral communication, implant fracture, titanium base debonding, ceramic chipping, prosthetic screw fracture or loosening, damage to opposing teeth, and clicking sounds. There was an insufficient number of complications to evaluate the effect of covariates on the risk of specific complications, such as titanium base debonding (eight events), ceramic chipping (nine events), and peri-implantitis (eight events). The unadjusted event-free median survival time was 5.8 years. The proportion of all prostheses with at least one complication was 30%. There were no observed prosthesis losses during the follow-up period. Conclusion: Monolithic and minimally layered zirconia full-arch implant-supported prostheses demonstrate an acceptable median event-free survival time. Event-free survival times were increased and the number of complications was reduced in prostheses with five to eight implants and conventional (as opposed to zygomatic) implants. There was a reduced hazard of complications with a regular recall regimen. Patient satisfaction with these prostheses was high.

The enhanced shear bond strength of resin cement to zirconia with ordered conical spots through the CO2 laser process.

In this study, a new shear bonding system was created that uses a CO2 laser to form a pattern of conical spots on a zirconia prosthesis surface to improve mechanical interlocking. Four types of zirconia substrates were employed, which underwent particle abrasion after being polished, machined, spotted, and spot-particle abraded. The surface roughness of each substrate was measured via scanning electron microscopy and X-ray diffraction (XRD). A shear bond strength test was performed with the zirconia-based material and a composite resin assuming abutment construction. XRD did not indicate that forming spots caused a phase transformation in zirconia with respect to machined zirconia. The shear bond strength was approximately twice that of the machined samples and approximately 2.3 times that of the samples that underwent particle and spot-particle abrasion. Surface modification by spotting improved the mechanical fitting force. However, no significant difference was observed between particle abrasion and spot-particle abrasion.

Degree of conversion of light-polymerized composite resin in implant prosthesis screw access opening.

The mechanical and physical properties of implant screw access opening deteriorate if composite resin is not polymerized properly. Therefore, this study aimed to analyze the effect of using composite resin in implant access opening on the degree of conversion (DC). Two prosthetic materials (Co-Cr and zirconia), two types of composite resin (low and high viscosity), two light-cured resin depths (2 and 3mm), and two polymerization methods (max-mode 10s and mid-mode 20s: 16 and 22J/cm2 , respectively) were considered (n=192). The DC of the polymerized composite resin was measured through Fourier-transform infrared spectroscopy. The top and bottom surfaces of the polymerized composite resin body were observed through scanning electron microscopy. Multiple linear regression analysis and analysis of variance were used to identify significant differences in DC (α=0.05). The DC was lower when the low-viscosity composite resin (β=-0.431), light-polymerized resin depth of 2mm (β=-0.430), zirconia prosthesis (β=-0.191), and mid-mode polymerization method (β=-0.164) were used. The resin type, depth of resin to be light-cured, prosthesis material, and polymerization method had an effect on the DC. Low-viscosity composite resin should be polymerized at a low irradiance and long polymerization time (such that the light-cured resin depth does not exceed 2mm) to ensure proper composite resin polymerization in implant screw access opening.

Simultaneous mandibular advancement, maxilla-mandibular all-on-four and immediate loading: a case report

Introduction: Full arch reconstruction with dental implants is considered as a reference for dental rehabilitation. However, there are some limitations with patient affected by severe maxilla, mandible atrophy and dento-skeletal-disharmony. These defaults can be corrected with orthognathic surgery and several bone grafts. Observations: A partially edentulous 65-year-old female patient with a skeletal class II by mandibular retrognathia was treated with mandibular advancement osteotomy and simultaneous insertion of four fully guided implants with immediate screwed zirconia prostheses loading in just one session. Conclusion: Simultaneous bilateral sagittal split osteotomy with a full arch rehabilitation by implant with immediate loading by zirconia prosthesis seems to be a reliable and predictable approach to treat skeletal class II patient with a fixed solution. Virtual planning was compulsory to be able to perform this surgery with accuracy.

Esthetic solutions with layered zirconia prostheses: A case series

One of the major clinical challenges in the rehabilitation of anterior teeth is achieving natural looking restorations for improper shape, size of the existing teeth, irregular gingival contour and unaesthetic shades. Increasing demand by patients for aesthetic and metal-free restorations has resulted in all-ceramic restorations such as dental zirconia that offer optimal aesthetics with desirable mechanical properties. A case series of clinical reports of layered zirconia fixed dental prostheses for anterior teeth is described. Prosthetic rehabilitation of endodontically treated and vital abutments are described and the influence of zirconia composition, design, layering technique, shade selection, occlusion and clinical challenges in each of the clinical conditions are discussed. Choice of zirconia composition, framework design and shade selection in layered zirconia prosthesis is influenced by abutments in layered zirconia prosthesis.

Effect of the nanofilm-coated zirconia ceramic on resin cement bond strength.

Background. New surface treatments have been proposed to expand the clinical indications of zirconia prostheses. This study aimed to evaluate the effect of silica and fluorine nanofilms on zirconia ceramic on the resin cement bond strength. Methods. Zirconia blocks and discs underwent different surface treatments: untreated zirconia (CON), sandblasted, silica-coated alumina particles (30 µm) (SC), silica nanofilm (SN), and fluorine nanofilm (FN). Nanofilm deposition was performed through plasma enhanced chemical vapor deposition (PECVD). Zirconia surfaces were characterized on disks by morphology (atomic force microscopy, AFM), chemical analysis (x-ray photoelectron spectroscopy, XPS), and contact angle analysis. A silane coupling agent was applied on each treated surface, and a cylinder of resin cement was built up. Half of the specimens in each group were submitted to 6000 thermal cycles (TC). Bond strength was analyzed using the shear test, and the fractographic analysis was performed with stereomicroscopy and SEM/EDS. Statistical analysis was performed through one-way ANOVA and Tukey test in the non-aged and aged specimens. Results. Nanofilms modified the zirconia surface, which became more hydrophilic and chemically reactive. Chemical bonding between Si-O was found in SN, and FN promoted a fluorination process on the ceramic surface, converting zirconia into zirconium oxyfluoride. Specimens of the SN (TC) group failed on pre-testing. FN (TC) bond strength (3.8 MPa) was lower than SC (TC) and CON (TC) after shearing. Adhesive failure predominated in the experimental groups. Silica nanofilm failure occurred after aging. Conclusion. Silica and fluorine nanofilms deposited by PECVD did not promote effective bonding between zirconia and resin cement.