Veneer Application Research Articles

3D-Printed Ultra-Thin Non-Prep Lithium Disilicate Veneers: A Proof-of-Concept Clinical Case.

To test the clinical application of LCM-printed lithium disilicate veneers. A female patient with tooth wear was scanned with intraoral scanner (Prime Scan, Dentsply Sirona). The six non-prep veneers were designed (DentalCAD, Exocad) and printed from lithium disilicate with an LCM-printer with the thickness of 0.1-0.2 mm (CeraFab System S65 Medical, Lithoz GmbH). The green parts after printing were cleaned of the excess slurry and debindered in a furnace (Nabertherm, Lilienthal) until 430°C with a dwell time of 5 h to remove all polymeric binder. The resulting parts were sintered in an oven (Programat P510, Ivoclar Vivadent AG) at a temperature of 900°C. The supports were removed with a dental technician handpiece (Perfecta 900, W & H). The final restorations were stained (e-max Ceram, Ivoclar Vivadent AG) by a master dental technician. The six LCM-printed ultra-thin non-prep lithium disilicate veneers were tried-in on the patient using a try-in glycerin gel (Ivoclar Vivadent, Schaan, Lichtenstein) and demonstrated excellent fit and esthetics. LCM technology enabled the production of ultra-thin non-prep lithium disilicate veneers with layer thicknesses of down to 0.1 mm. The 3D-printing of ultra-thin non-prep veneers is technically feasible and provides an adequate clinical outcome. Additive manufacturing of ultra-thin non-prep lithium disilicate veneers may pose a valid alternative to conventional and subtractive manufacturing.

Veneers on Devitalized Teeth: The Role of Adhesive Dentistry in Aesthetic and Functional Therapies

Devitalized teeth present a unique challenge in aesthetic dentistry, often exhibiting aesthetic issues such as color variations, shape changes, or structural fragility. In response to these challenges, dental veneers emerge as a promising solution to restore both the aesthetics and functionality of devitalized teeth. While chemical teeth whitening is the primary treatment approach for dental discolorations, some prove resistant, occasionally necessitating prosthetic interventions. This article aims to explore the application of ceramic veneers as an aesthetic and conservative solution to address the challenges associated with devitalized teeth. We will delve into the procedural steps, technological advancements, and clinical considerations guiding this contemporary practice in aesthetic dentistry.

Marginal Accuracy of Monolithic and Veneered Zirconia Crowns Fabricated by Conventional and Digital Workflows.

To compare the marginal accuracy of zirconia crowns fabricated by different workflows (conventional and digital) and designs (monolithic and veneered). A prepared maxillary first molar was used for the study. Four workflow combinations were evaluated: (1) intraoral scanning and monolithic zirconia (IOS-M), (2) intraoral scanning and veneered zirconia (IOS-V), (3) conventional impression and monolithic zirconia (IMP-M), and (4) conventional impression and veneered zirconia (IMP-V). All of the specimens had similar designs. The veneered groups had a buccal cutback for esthetic veneer application. A total of 10 crowns were produced in each workflow. The vertical and horizontal marginal accuracies were measured with a traveling microscope. Depending on the normality of the data, one-way analysis of variance test or Kruskal-Wallis test were applied to evaluate the differences among the groups (α = 0.05). The most superior vertical marginal accuracy was observed for IOS-V (mean= 22.5μm; SD = 6.7μm), followed by IMP-V (mean= 23.9μm; SD = 7.8μm), IOS-M (mean = 28.7μm; SD = 10.3μm), and IMP-M (mean = 39.8μm; SD = 22.0μm), respectively (p < 0.001). The IOS-M had the greatest mean horizontal discrepancies (mean = 23.9μm; SD = 4.3μm) followed by IMP-M (mean = 21.3μm; SD = 5.7μm), IMP-V (mean = 19.2μm; SD = 5.3μm) and IOS-V (mean = 17.6μm; SD = 5.7μm) (p < 0.001). Monolithic zirconia crowns fabricated digitally had superior marginal accuracy than monolithic zirconia crowns fabricated conventionally. Esthetic buccal veneering of predominantly monolithic zirconia copings improved the vertical and horizontal marginal accuracies.

Prosthetically Guided Orthodontics (PGO): A Personalized Clinical Approach for Aesthetic Solutions Using Digital Technology.

Conformative rehabilitation generally involves the treatment of partial dentate or the application of veneers. In this regard, conformative rehabilitation aims to generate an aesthetic prosthetic solution minimizing the amount of tissue removal without generating occlusal input interfering with the equilibrium of neuro-muscular function. In fact, pre-prosthetic orthodontics aims to re-establishing the correct position/inclination of the neighboring or antagonist teeth, providing appropriate space for the prosthetic crown. Clear aligners therapy (CAT) represents a valuable tool in the management of prosthetic cases with a conformative approach, as it allows clinicians to plan orthodontic movements that are guided by the prosthetic outcomes. In the present manuscript, we argue the concept of prosthetic guided orthodontics (PGO) by presenting and discussing three cases treated with the Invisalign GO system, which has been developed for the clinical management of multidisciplinary orthodontic-prosthetic cases with a conformative approach. In this regard, the rationale of this paper is to address the effectiveness and predictability of the digital set-up and CAT for aesthetic conformative rehabilitations.

Fracture Resistance of Upper Central Incisors with Different Endodontic Accesses Restored with Lithium Disilicate Partial Laminate Veneers.

PurposeA treatment protocol involving the root canal treatment with conventional palatal access cavity and the partial veneer application may considerably reduce the fracture resistance of the teeth. On the other hand, labial access cavity within the partial veneer outlines followed with the partial veneer application may more successfully recover the lost fracture resistance of the endodontically treated teeth. In this regard, the present study aims to compare the fracture resistances of upper central incisors endodontically treated with palatal and labial accesses and restored with restorative resin composite and lithium disilicate partial veneers.Materials and MethodsThree groups consisting ten specimens each were prepared by using extracted sound human upper central incisors. Root canal treatments with palatal access, resin composite restoration of the access cavities and veneer restorations were applied to the first group (Group P). Root canal treatments with labial access, resin composite restoration of the access cavities and veneer restorations was applied to the second group (Group L). Veneer restorations were applied to the third group (Group C) without root canal treatment. Specimens were thermocycled and loaded to fracture in order to record their fracture resistances.ResultsThe mean fracture resistance of Group C was observed to be significantly higher, compared to Groups P and L (P < 0.05). Fracture resistance of Group L was observed to be higher, compared to Group P, but the difference was not found statistically significant. Light microscope revealed that the specimens fractured in five different modes.ConclusionAlthough the mean fracture resistance of the teeth that endodontically treated with labial access cavity prior to the ceramic partial veneer application was higher in comparison with the teeth that endodontically treated with palatal access cavity prior to the ceramic partial veneer application, the difference was found statistically insignificant (P < 0.05).

Haptic and Aesthetic Properties of Heat-Treated Modified Birch Wood

This paper deals with the effect of heat treatment on the selected physical properties of birch wood. Five stages of heat treatment were used, ranging from 160 °C to 200 °C, in 10 °C increments, having a peak treatment duration of 3 h for each level. Primarily, changes in thermal characteristics, namely conductivity, diffusivity, effusivity, volume heat capacity, changes in colour and gloss parameters, mass loss due to modification and different moisture content in wood under given equilibrium climatic conditions, were monitored. The ISOMET 2114 analyser was used to measure the thermal characteristics. The measurement principle of this analyser is based on the analysis of the thermal response of the analysed material to pulses of heat flow. Measurements of colour, gloss, density and moisture content were carried out according to harmonised EN standards. The aim was to experimentally verify the more or less generally known more positive perception of heat-treated wood, both by touch and sight, i.e., the warmer perception of darker brown shades of wood. In terms of thermal characteristics, the most interesting result is that they gradually decrease with increasing treatment temperature. For example, at the highest treatment temperature of 200 °C, there is a decrease in thermal conductivity by 20.2%, a decrease in volume heat capacity by 15.0%, and a decrease in effusivity by 17.7%. The decrease in thermal conductivity is nearly constant at all treatment levels, specifically at this treatment temperature, by 6.0%. The fact mentioned above is positive in terms of the tactile perception of such treated wood, which can have a positive effect, for example, in furniture with surface application of heat-treated veneers, which are perceived positively by the majority of the human population visually or as a cladding material in saunas. In this context, it has been found that the thermal modification at the above-mentioned treatment temperature of 200 °C results in a decrease in brightness by 44.0%, a decrease in total colour difference by 38.4%, and a decrease in gloss (at an angle of 60°) by 18.2%. The decrease in gloss is only one essential negative aspect that can be addressed by subsequent surface treatment. During the heat treatment, there is also a loss of mass in volume, e.g., at a treatment temperature of 200 °C and subsequent conditioning to an equilibrium moisture content in a conditioning chamber with an air temperature of 20 ± 2 °C and relative humidity of 65 % ± 5%, there was a decrease by 7.9%. In conclusion, the experiments clearly confirmed the hypothesis of a positive perception of heat-treated wood in terms of haptics and aesthetics.

Stepwise stress testing of different CAD-CAM lithium disilicate veneer application methods applied to lithium disilicate substructures

Statement of problemWhether a computer-aided design and computer-aided manufacture (CAD-CAM) fabricated high-translucency lithium disilicate veneer on a lithium disilicate substructure would increase the strength of the restoration compared with a traditional feldspathic porcelain veneer is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of different lithium disilicate veneer application methods on a lithium disilicate substructure on their biaxial flexural stress (BFS). Material and methodsLithium disilicate disks were fabricated so that when combined with the veneering disks, they had a dimension of 12×1.2 mm. Experimental groups were as follows (n=15): resin-bonded lithium disilicate veneer, lithium disilicate veneer adhesively cemented to lithium disilicate; sintered lithium disilicate veneer, lithium disilicate veneer sintered to lithium disilicate; sintered feldspathic veneer, feldspathic porcelain applied to lithium disilicate; and monolithic lithium disilicate, the control group. Weibull distribution survival analysis was used to compare the differences in the resistance to fracture after fatigue. The total number of cycles was analyzed by using 1-way ANOVA (α=.05). A finite element analysis (FEA) was also performed. The maximum principal stress (MPS) was used as the failure criterion. ResultsThe sintered feldspathic veneer group had significantly lower fatigue resistance than sintered lithium disilicate veneer or resin-bonded lithium disilicate veneer (P<.05). The resin-bonded lithium disilicate veneer group showed significantly more fractured fragments than the other groups. No statistical difference was observed in the number of cycles. The lithium disilicate veneered groups presented similar resistance to fatigue as the monolithic specimens of the same overall dimensions. Higher peaks of MPS were observed for groups monolithic lithium disilicate, sintered lithium disilicate veneer, and sintered feldspathic veneer than for resin-bonded lithium disilicate veneer. ConclusionsVeneering a lithium disilicate substructure with a lithium disilicate veneer, bonded or sintered, increased resistance to fatigue compared with a feldspathic porcelain veneer. The lithium disilicate veneer groups had similar fatigue resistance to that of the monolithic group.

Smile makeover with porcelain laminate veneer: A case report

Pincus is credited for evolution of porcelain veneers. He attached the thin labial porcelain veneers temporarily with denture adhesive powders to improve dental esthetic appearance. Improvement of patient’s lost natural dental esthetics have become important goal of discipline of dentistry and credited for wide ranging applications from improving common man’s appearance to filmstars. Esthetic problems may be result of interplay of complex factors like color, shape, and structural and position abnormalities of anterior teeth. Laminate veneers are used for purpose of improving esthetic deficiencies and discolorations as well as existing abnormalities.Successful application of porcelain veneers depends on multiple factors such as the clinical and laboratory steps involved, along with the understanding of the scientific background of procedure.Conservative and esthetic approaches, such as direct and indirect laminate veneer restorations are most preferred way chosen by dentist across world to improve compromised esthetics of human beings. Technological advancements such as intraoral scanner for impression making have significantly improved the success of prosthesis.

Comparison of CAD/CAM manufactured implant-supported crowns with different analyses

BackgroundPresent study compared the failure load of CAD/CAM-manufactured implant-supported crowns and the stress distribution on the prosthesis-implant-bone complex with different restoration techniques.MethodsThe materials were divided into four groups: group L-M: lithium disilicate ceramic (LDS, monolithic), group L-V: LDS ceramic (veneering), group ZL-M: zirconia-reinforced lithium silicate ceramic (ZLS, monolithic), group ZL-V: ZLS ceramic (veneering). Crown restorations were subjected to load-to-failure test (0.5 mm/min). Failure loads of each group were statistically analyzed (two-way ANOVA, post hoc Tukey HSD, α = 0.05). Finite element analysis (FEA) was used to compare the stress distribution of crown restorations.ResultsGroup L-M had the highest failure load (2891.88 ± 410.12 N) with a significant difference from other groups (p < 0.05). Although there was a significant difference between group ZL-M (1750.28 ± 314.96 N) and ZL-V (2202.55 ± 503.14 N), there was no significant difference from group L-V in both groups (2077.37 ± 356.59 N) (p > 0.05).ConclusionsThe veneer application had opposite effects on ceramics, increased the failure load of ZLS and reduced it for LDS without a statistically significant difference. Both materials are suitable for implant-supported crowns. Different restorative materials did not influence the stress distribution, but monolithic restorations reduced the stress concentration on the implant and bone.

Classification and application of veneer in the minimally invasive restoration of tooth defects

全瓷材料和粘接技术的发展，使得贴面等牙体预备量少、以粘接固位为主的微创修复体在临床得以广泛应用。与全冠等传统修复体相比，微创修复体的适用范围更窄。缺损牙需存留足够量的牙釉质为修复体提供粘接固位，同时为修复体提供良好的强度支撑。因此，牙釉质存留量是决定牙体缺损微创修复适用范围的关键因素。.

Laminados minimamente invasivos na reabilitação estética anterior

The search for a harmonious smile associated with minimally invasive and painless procedures, made the ceramic laminates take on a prominent role in facial aesthetics and consequently in smile aesthetics. The advances in adhesive techniques, ceramic materials and technologies associated with their manufacture, have made ceramic contact lenses a safe and predictable alternative for rehabilitation in cases of dental diastemas, restoring color, shape and position in the arch. Therefore, this case report aimed to demonstrate the application of porcelain veneers in closing diastemas in order to optimize the treatment. It was observed, with the clinical case presented, a very satisfactory result from the aesthetic and functional point of view.

In vitro color stainability and relative translucency of CAD-CAM restorative materials used for laminate veneers and complete crowns

Statement of problemAssessing the long-term stainability and durability of restorative materials is an important parameter for determining clinical success and longevity. Information remains limited regarding the color stainability and translucency of the recently introduced ceramic materials for restorative treatment. PurposeThe purpose of this in vitro study was to compare the effect of cyclic immersion in hot and cold coffee on the color stainability and translucency of 6 computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials at thicknesses which represent a laminate veneer and a complete crown. Material and methodsCAD-CAM restorative materials including zirconia-reinforced lithium silicate ceramic (Celtra Duo), lithium disilicate glass-ceramic (IPS e.max CAD), polymerized resin nanoceramic (Lava Ultimate), integrated ceramic and acrylate polymer network material (VITA ENAMIC), zirconia-reinforced lithium silicate (VITA SUPRINITY), and zirconia (VITA YZ HT) were studied in 2 thicknesses for laminate veneer (0.7 mm) and complete crown application (1.3 mm to 1.5 mm). For each specimen, color difference on a gray backing was calculated using a spectroradiometer between its baseline color and after 6000 cycles of coffee thermocycling. The colors of the specimens on the black and white backings were used to calculate the relative translucency parameter from the CIEDE2000 color difference formula. An ANOVA and the Bonferroni-corrected Student t tests were used for testing statistical significance (α=.05). ResultsNo difference was found among the means of color change after coffee thermocycling between any 2 materials for the crown thickness (P>.999), and no difference was found among the means of color change between the 2 thickness groups within each material (P≥.187). However, the mean color change of the resin nanoceramic material in laminate veneer application (0.7 mm) was greater than that of every other material in the veneer thickness group (P<.001), and the mean color change of the integrated ceramic and acrylate polymer network material was greater than that of the lithium disilicate glass-ceramic material studied at the veneer thickness (P=.014). Translucency was found to be lower for complete crown thickness compared with laminate veneer thickness within each combination of material and coffee thermocycling (P<.001). The translucency of the lithium disilicate glass-ceramic material studied at the laminate veneer thickness was also found to be higher after coffee thermocycling (P=.033). Furthermore, several differences among materials were found for each combination of thickness and coffee. ConclusionsColor change after coffee thermocycling of the resin nanoceramic material was beyond the acceptability threshold. The lower translucency found for crown thickness compared with veneer thickness was verified.

Pre-sintered Y-TZP sandblasting: effect on surface roughness, phase transformation, and Y-TZP/veneer bond strength.

Sandblasting is a common method to try to improve the Y-TZP/veneer bond strength of dental prostheses, however, it may put stress on zirconia surfaces and could accelerate the t→m phase transformation. Y-TZP sandblasting before sintering could be an alternative to improve surface roughness and bonding strength of veneering ceramic.Objectives.The aim of this study was to analyze the effect of Y-TZP pre-sintering sandblasting on surface roughness, phase transformation, and the Y-TZP/veneer shear bond strength.Material and Methods.The Y-TZP specimen surface underwent sandblasting with aluminum oxide (50 μm) pre-sintering (Z-PRE) and post-sintering (Z-POS). Z-CTR was not subjected to surface treatment. After ceramic veneer application, the specimens were subjected to shear bond testing. Surface roughness was analyzed by confocal microscopy. Y-TZP monoclinic and tetragonal phases were evaluated by micro-Raman spectroscopy. Shear bond strength and surface roughness data were analyzed by One-way ANOVA and Tukey tests (α=0.05). Differences in the wave numbers and the broadening bands of the Raman spectra were compared among groups.Results.Z-POS (9.73±5.36 MPa) and Z-PRE (7.94±2.52 MPa) showed the highest bond strength, significantly higher than that of Z-CTR (5.54±2.14 MPa). The Ra of Z-PRE (1.59±0.23 µm) was much greater and significantly different from that of Z-CTR (0.29±0.05 µm) and Z-POS (0.77±0.13 µm). All groups showed bands typical of the tetragonal (T) and monoclinic (M) phases. Y-TZP sandblasting before sintering resulted in rougher surfaces but did not increase the shear bond strength compared to post-sintering and increased surface defects.Conclusions.Surface treatment with Al3O2, regardless of the moment and application, improves the results of Y-TZP/veneer bonding and is not a specific cause of t→m transformation.

Effect of luting agent on the load to failure and accelerated-fatigue resistance of lithium disilicate laminate veneers

ObjectiveThe aim of this study was to investigate the influence of the luting agent on the application of laminate veneers (LVs) in an accelerated fatigue and load-to-failure test after thermo-cyclic aging. MethodsSound maxillary central incisors (N=40) were randomly divided into four groups to receive LVs (Li2Si2O5) that were adhesively bonded: Group CEMF: Adhesive cement (Variolink Esthetic LC), fatigue test; Group CEMLF: Adhesive cement, load-to-failure test; Group COMF: Resin composite (Enamel HFO), fatigue test; Group COMLF: Resin composite, load-to-failure test. The specimens were thermo-mechanically aged (1.2×106 cycles at 1.7Hz/50N, 8000 cycles 5–55°C) and then subjected to either accelerated fatigue (5Hz, 25N increasing after each 500 cycles) or load to failure (1mm/min). Failure types were classified and data analyzed using chi-square, Kaplan Meier survival, Log Rank (Mantel–Cox) and independent-samples t-test. ResultsAfter thermo-mechanical aging, fracture resistance (p<0.000) was higher in the composite groups. Kaplan Meier survival rates showed significant difference (p<0.001) between the composite (mean load: 1165N; mean cycles: 22.595) and the cement groups (mean load: 762.5N; mean cycles: 14.569). The same differences were observed in the load to failure test (cement M=629.4N, SD±212.82 and composite M=927.59N, SD±261.06); t (18)=−2.80, p=0.01. Failure types were observed as fractures and chipping in group CEMF, all other groups were predominantly adhesive failures between the luting agent and the laminate veneer. SignificanceThe delivery of laminate veneers using a direct restorative composite rather than a resin cement resulted in significantly less chipping and fractures, higher fracture strength in both accelerated fatigue and load-to-failure.

Minimally Invasive Aesthetic Solutions - Porcelain Veneers and Lumineers

Porcelain veneers present a conservative solution for patients who demand improvement of the shape, position and color of their anterior teeth without the removal of substantial amounts of tooth substance. No-or minimal-preparation veneers associated with enamel preservation offer an excellent results in aesthetic dentistry and become an essential component in creating restorations that are functional and have increased longevity. The current literature was reviewed to search for the most essential parameters which have influence on the long-term success and correct application of porcelain veneers.

Effect of core ceramic grinding on fracture behaviour of bilayered zirconia veneering ceramic systems under two loading schemes

ObjectiveThe aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes. MethodsInterfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal–Wallis and one-way ANOVA at a significance level of 0.05. ResultsAs grit size of the diamond disc increased, zirconia surface roughness decreased (p<0.001). Thermal veneering treatment reversed the transformation of monoclinic phase observed after initial grinding. No difference in initial (p=0.519 for subgroups Ac-Dc) and final fracture strength (p=0.699 for subgroups Ac-Dc; p=0.328 for subgroups At-Dt) was found among the four groups for both loading schemes. While coarse grinding slightly increased final fracture strength reliability (m) for subgroups Ac-Dc. Two different modes of fracture were observed according to which material was on the bottom surface. Components of the liner porcelain remained on the zirconia surface after fracture for all groups. SignificanceTechnician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its application on rough zirconia cores may be preferred to enhance bond strength.

Minimally invasive veneers: current state of the art.

Ceramic veneers are considered a conservative solution for patients requiring improvement of the shape, color, or position of their anterior teeth. Ceramic veneers have been extensively and successfully used to mask intrinsic staining, to give the appearance of straightening, and to correct minor malformations of anterior teeth without the removal of substantial amounts of sound tooth substance. The current literature was reviewed to search for the most important parameters determining the long-term success and correct application of ceramic veneers.

Effect of core ceramic grinding on fracture behaviour of bilayered lithium disilicate glass–ceramic under two loading schemes

ObjectivesThe purpose of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered lithium disilicate glass–ceramic (LDG) under two loading schemes. MethodsInterfacial surfaces of sandblasted LDG disks (A) were ground with 220 (B), 500 (C) and 1200 (D) grit silicon carbide (SiC) sandpapers, respectively. Surface roughness and topographic analysis were performed using a profilometer and a scanning electron microscopy (SEM), and then underwent retesting after veneer firing. Biaxial fracture strength (σf) and Weibull modulus (m) were calculated either with core in tension (subgroup t) or in compression (subgroup c). Failure modes were observed by SEM, and loading induced stress distribution was simulated and analyzed by finite element analysis. Statistical data analysis was performed using Kruskal–Wallis, one-way ANOVA, and paired test at a significance level of 0.05. ResultsAs the grits size of SiC increased, LDG surface roughness decreased from group A to D (p<0.001), which remained unchanged after veneer firing. No difference in σf (p=0.41 for subgroups At–Dt; p=0.11 for subgroups Ac–Dc), m values as well as failure modes was found among four subgroups for both loading schemes. Specimens in subgroup t showed higher σf (p<0.001) and m values than subgroup c. Stress distribution between loading schemes did not differ from each other. Cracks, as the dominant failure mode initiated from bottom tensile surface. No sign of interfacial cracking or delamination was observed for all groups. ConclusionsTechnician grinding changed surface topography of LDG ceramic material, but was not detrimental to the bilayered system strength after veneer application. LDG bilayered system was more sensitive to fracture when loaded with veneer porcelain in tension. Clinical significanceWithin the limitations of the simulated grinding applied, it is concluded that veneer porcelain can be applied directly after technician grinding of LDG ceramic as it has no detrimental effect on the strength of bilayered structures. The connector areas of LDG fixed dental prosthesis are more sensitive to fracture compared with single crowns, and should be fabricated with more caution.

Shape Retention of Furfurylated and Moulded Wood Veneer

High-value wood veneer is used in the furniture and automobile interior industries for decorative purposes. Due to mechanical restrictions, veneer application on surfaces is limited to simple shapes. In the last century, many approaches were developed to improve the moulding behaviour of veneer. However, all of these processes face several difficulties. Currently, water is primarily used for veneer plasticization, with the disadvantages of shrinkage and cracks due to drying. Furthermore, products often fail during material climate testing due to set recovery. Thus, a veneer modification process was considered combining plasticization, moulding, and shape fixation of veneer with reduced set recovery. To accomplish this, veneers were impregnated with furfuryl alcohol/maleic anhydride solutions to improve plasticization and moulding properties. Subsequently, veneers were moulded, and the realized shapes were fixed by temperature-induced acid-catalyzed polymerization. Due to the polymer in the cell wall, set recovery of all modified samples was noticeably reduced compared to reference samples plasticized with water prior to moulding. The degree of set recovery reduction due to modification varied with the modification intensity. Samples with higher weight percentage gain (WPG=126.4%) were more stable in the presence of moisture than samples with lower polymer yields (WPG=107.4%).

Influence of substructure design, veneer application technique, and firing regime on the in vitro performance of molar zirconia crowns

ObjectivesThe aim of this in vitro study was to evaluate the influence of substructure design, veneer application technique, and firing regime on the failure and fracture resistance of molar zirconia crowns. MethodsSix groups (n=8/group) of zirconia crowns were fabricated in simple core (SC) or anatomically reduced (AR) design, veneered with different feldspathic or glass ceramic materials, and defined according to the application technique and firing regime (LT: layering technique; LT_L: LT with long-term cooling; PT: press technique; DV: digital veneering technique). The following groups were investigated: SCLT, ARLT, SCLT_L, SCPT, ARPT, ARDV. Crowns were adhesively bonded to polymethylmethacrylate abutment teeth and subjected to thermal cycling (TC: 2×3000×5°/55°) and mechanical loading (ML: 1.2×106; 50N; 1.6Hz) in a chewing simulator with metal-ceramic molar crowns as antagonists. Failures were monitored and fracture resistance determined after aging. Data were statistically analyzed (one-way analysis of variance, ANOVA; post hoc Bonferroni, α=0.05). Crowns were subjected to scanning electron microscopy for fractographic failure analysis. ResultsFailures (chipping, cracks) during TCML were observed in groups SCLT (2×), ARDV (2×) and SCLT_L (1×). Defect sizes varied between 3.5mm (SCLT: crack) and 30.0mm2 (SCLT_L: chipping). Mean (SD) fracture forces ranged between 1529.0 (405.2)N for SCPT and 2372.3 (351.8)N for ARDV. SignificanceThe failure frequency of veneered zirconia crowns could be reduced by using anatomically reduced substructures, the press veneering technique, and an adapted cooling protocol. Fracture resistance increased with use of anatomically reduced substructures and the digital veneering technique.