Influence of attaching mechanical retentive devices onto frameworks on fracture resistance of implant-supported zirconia crowns.

This study investigated the fracture load of implant-supported zirconia crowns (IZCs), in which indirect composite resin or feldspathic porcelain was layered onto zirconia frameworks with mechanical retentive devices. Three different zirconia frameworks were assessed: attaching mechanical retentive devices on glaze and opaque porcelain materials (GL and OP groups, respectively), and no attaching mechanical retentive devices (ND group). The frameworks were layered using feldspathic porcelain (FP veneer) and indirect composite resin (IC veneer). Fracture load of the specimens was measured. In FP veneer, the GL group recorded the highest fracture load. In the IC veneer, the GL and OP groups had significantly higher fracture load than the ND group. The fracture resistance of IZCs can be enhanced by applying glaze material before attaching mechanical retentive devices for porcelain layering. The mechanical retentive devices effectively yielded mechanical interlocking between the zirconia frameworks and the IC veneer in GL and OP groups.

Influence of different convergence angles of abutment teeth and cement spaces on internal adaptation of anterior CAD-CAM fixed dental prostheses.

PURPOSE: The aim of this study was to investigate the influence of different convergence angles of abutment teeth and different cement spaces on internal adaptation of anterior fixed dental prostheses (FDPs) fabricated with a computer-aided design-computer-aided manufacturing (CAD-CAM) system. METHODS: Composite resin FDPs for 99 standardized maxillary central incisors were fabricated according to nine parameters: three total convergence angles (4 [DG4], 12 [DG12], and 20 degrees [DG20]) and three cement space settings (10 [CS10], 50 [CS50], and 90 µm [CS90]). Internal space values were measured with a cement space replica technique. The Kruskal-Wallis and Steel-Dwass tests were used to evaluate differences in the total convergence angles and luting agent spaces, respectively (α = 0.05). RESULTS: For all three cement spaces tested, the median marginal gap values between abutment teeth and FDPs decreased significantly as the total convergence angle increased (P < 0.05). For the CS10 and CS50 groups, the internal space values at the axial area increased significantly as the total convergence angles increased (P < 0.05). CONCLUSION: Total convergence angles of the abutment teeth and cement spaces affected the marginal and internal adaptation of anterior FDPs fabricated with a CAD-CAM system.

Clinical performance of laminate veneers: A review of the literature.

PURPOSE: This narrative review aimed to survey the clinical outcomes of laminate veneers (LVs), including their survival and success rates. STUDY SELECTION: An electronic search of MEDLINE/PubMed, Web of Science, Cochrane Library, and Google Scholar from 2000 to April 2023 was conducted using the keywords "laminate" OR "veneer" OR "porcelain" OR "feldspathic" OR "lithium disilicate" OR "composite resin" OR "zirconia" OR "survival" OR "success." Case reports, case series, reviews, abstracts, in vitro studies, and observational studies were excluded. Five researchers independently evaluated the titles and abstracts of all identified studies. RESULTS: A total of 55 studies were identified. None of the studies met the criteria for zirconia LVs. According to the studies in this review, LVs fabricated with feldspathic porcelain, leucite-reinforced glass ceramics (LRG), and lithium disilicate ceramics (LDS) exhibited satisfactory survival and success rates. Furthermore, hydrofluoric acid etching followed by silane priming of the surface of ceramic LVs is necessary for improved clinical outcomes. The extent of dentin exposure significantly decreases the success rate of ceramic LVs. An appropriate adhesive luting process is required to achieve the long-term success of ceramic LVs. Dentin exposure should be minimized or sealed during tooth preparation to achieve a reliable and durable bond between LVs and abutment teeth. CONCLUSIONS: Based on this narrative review of the literature, the use of silica-based ceramic feldspathic porcelain, LRG, and LDS is recommended for LVs.

Influence of an internal firing of feldspathic porcelain before or after sintering on adaptation of high-translucent zirconia laminate veneers.

The aim of the present study was to evaluate the influence of two different internal surface treatments, namely, the firing of feldspathic porcelain before or after zirconia sintering, on the marginal and internal adaptation of laminate veneers (LVs) made of high-translucent zirconia. A total of 33 zirconia LVs were fabricated using a CAD/CAM system and divided into three groups based on the internal surface treatment method: the pre-firing (PRE) group involved firing feldspathic porcelain before zirconia sintering, the post-firing (POS) group involved firing feldspathic porcelain after zirconia sintering, and the no treatment (NT) group involved no application of feldspathic porcelain. The adaptation of the LVs was measured using a silicone replica technique. Data were analyzed using the Kruskal-Wallis and Steel-Dwass tests (α = .05). The POS group showed significantly higher marginal discrepancy values than the PRE group across all sites. The internal space values of the PRE groups were significantly lower than those of the NT group at all sites. The internal firing of feldspathic porcelain before zirconia sintering resulted in better marginal adaptation of the high-translucent zirconia LVs than the internal firing of feldspathic porcelain after zirconia sintering. The internal firing of feldspathic porcelain before zirconia sintering can achieve uniform internal adaptation of high-translucent zirconia LVs.

Fracture strength of implant-supported hybrid abutment crowns in premolar region fabricated using different restorative CAD/CAM materials.

The present study investigated the fracture strength of hybrid abutment crowns (HACs) in the premolar region that were fabricated with different restorative computer-aided design/computer-aided manufacturing (CAD/CAM) materials. The abutment-implant structures were randomly assigned into four groups (n=11 per group): bi-layered zirconia restorations (BL), translucent zirconia (4Y-PSZ) restorations (TZ), lithium disilicate ceramic restorations (LD), and dispersed nanoparticle-filled composite resin restorations (CM). All restorations were adhesively bonded to the titanium abutments. After the restoration-abutment complex was tightened onto the implant, the fracture strength was measured. The TZ (2.06 kN) and LD (1.87 kN) groups had significantly higher median fracture strengths than the BL (1.12 kN) and CM (1.10 kN) groups. In terms of fracture resistance, the 4Y-PSZ and lithium disilicate ceramic monolithic restorations would be superior to bi-layered 3Y-TZP and composite resin monolithic restorations for HACs in the premolar region.

Bond strength between a veneering composite resin and zirconia frameworks with attached mechanical retentive devices.

The effects of mechanical retentive devices and various surface treatments on the shear bond strength between a veneering composite resin and zirconia was investigated. Zirconia disks were classified into three surface-treatment groups: airborne-particle abrasion, overglazing, and overglazing with white alumina particles of three different grain sizes (50, 70, and 105 µm) attached onto zirconia disks (ZR-50, ZR-70, and ZR-105, respectively). They were further divided into four groups (n=44): unprimed, Clearfil Porcelain Bond Activator (CA), Clearfil Photo Bond (CB), and CA+CB. An indirect composite resin was bonded to zirconia specimens. Shear bond strengths were measured. For the ZR-70 and ZR-105 groups, the CB and CA+CB specimens exhibited higher bond strengths than the other two specimens after thermocycling. The ZR-70 and ZR-105 groups achieved micromechanical interlocking, and priming with a phosphate monomer (MDP) yielded stable bond strengths between the composite resin and zirconia with alumina particles attached as retentive devices.

Effect of firing procedures and layering thickness of porcelain on internal adaptation of zirconia cantilever resin-bonded fixed dental prostheses.

PURPOSE: This study evaluated the influence of firing procedures and layering thickness of porcelain on internal adaptation of maxillary anterior cantilever zirconia resin-bonded fixed dental prostheses (RBFDPs). METHODS: The maxillary right central incisor on a model was prepared for a single-retainer zirconia RBFDP. A total of 36 frameworks of cantilever zirconia RBFDPs were classified into three groups (CB0.5, CB1.0, and CB2.0 groups) based on the thickness of the cut-back on the facial surface (0.5 mm, 1.0 mm, and 2.0 mm, respectively). Feldspathic porcelain was layered onto the facial surface of the zirconia RBFDP frameworks. Internal space widths between the abutment tooth and the framework were measured before and after porcelain firing by a replica technique. The internal space values before and after porcelain firings were compared using the paired t-test within the same group (α = 0.05). Differences in internal space values (distortion) between before and after porcelain firing were compared using one-way analysis of variance and Tukey multiple comparison tests. RESULTS: For all framework designs, internal space values after porcelain firing were significantly higher than those before firing. Among all groups, the CB0.5 group showed the lowest internal distortion values for the whole measured area. The CB2.0 group showed higher distortion values than the CB1.0 group. CONCLUSION: Porcelain firing procedures negatively impacted the internal space in cantilever zirconia RBFDPs. In addition, the increased volume of layering porcelain had a negative effect on the internal distortion of maxillary anterior cantilever zirconia RBFDPs.

Influence of roughening procedures and priming agents on shear bond strength of CAD/CAM materials to zirconia frameworks.

This study investigated the influence of roughening procedures and application of primers on shear bond strengths of CAD/CAM composite resin material or ceramic material to zirconia frameworks. A CAD/CAM composite resin block (Katana Avencia Block; AVE) and lithium disilicate glass-ceramic block (IPS e.max CAD; IEC) were used as veneer materials. The veneers were divided into three surface treatment groups; HF, hydrofluoric acid etching; AB, airborne-particle abrasion; and CON, no surface treatment. Each veneer was primed with four agents: Clearfil Porcelain Bond Activator (ACT), Clearfil Photo Bond (CPB), Clearfil Photo Bond with Porcelain Bond Activator (CPB+ACT), and no priming (UP). The zirconia frameworks and AVE or IEC veneers were resin-bonded. In the AVE specimen, AB treatment showed significantly higher shear bond strength than the other treatments at 0 and 20,000 thermocycles, except for UP and CPB+ACT groups at 20,000 thermocycles. Airborne-particle abrasion is necessary for resin bonding to Avencia blocks.

Shear bond strength between gingival composite resin and glazed gingival porcelain for implant-supported prostheses.

This study determined the shear bond strength (SBS) between an indirect gingival composite resin and glazed gingival porcelain after various surface treatments. A total of 176 porcelain disks with natural glazing were used and assigned to one of four groups: no surface treatment, airborne-particle abrasion, hydrofluoric acid etching, or a combination of airborne-particle abrasion followed by hydrofluoric acid etching. Each group was divided into two subgroups: one subgroup was unprimed, and the other was silanized. An indirect composite resin was then bonded to the porcelain disks. Half of the specimens in each group (n = 11) were exposed to 5000 thermocycles. SBSs were measured, and data were analyzed with the Kruskal-Wallis and Steel-Dwass tests. Among silanized specimens, those treated with the combination of airborne-particle abrasion and hydrofluoric acid etching exhibited the highest bond strengths both before and after thermocycling. However, the SBS values of the silanized and unprimed hydrofluoric acid etched specimens did not differ significantly. Airborne-particle abrasion followed by hydrofluoric acid etching with silane application yielded stronger, more durable bonds between the indirect gingival composite resin and glazed gingival porcelain.

Clinical outcomes of single crown restorations fabricated with resin-based CAD/CAM materials.

Computer-aided design/computer-aided manufacturing (CAD/CAM) restorative materials have been widely used owing to a number of advantages, including stable quality of the materials, lower costs, and time-saving factors. Resin-based CAD/CAM materials for definitive restorations are classified into two groups: dispersed nanoparticle-filled composite resin and polymer-infiltrated-ceramic-network materials. Resin-based CAD/CAM materials have been applied to single crown restorations as a monolithic structure for the posterior region. In addition, resin-based CAD/CAM restorations have been applied recently for the anterior area. This literature review summarizes clinical outcomes, such as survival rates and clinical complications of single crown restorations fabricated with resin-based CAD/CAM materials.

Effect of luting agent type on fracture loads of implant-supported ceramic premolar prostheses.

To investigate the effect of luting agent type on fracture loads of implant-supported ceramic prostheses in premolar region. Ninety-nine implant-abutment complexes were divided into three different implant-supported prostheses: monolithic yttria-partially stabilized zirconia (Y-PSZ) restorations (MPZ specimens), porcelain layered on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations (PLZ specimens), and monolithic lithium disilicate ceramic restorations (MLD specimens). Implant-supported prostheses were luted with adhesive resin luting agent (RLA), glass ionomer cement (GIC), or zinc phosphate cement (ZPC). For MPZ and MLD specimens, fracture loads were significantly higher for RLA group than for GIC and ZPC groups. For PLZ specimens, fracture loads did not significantly differ in relation to luting agent. Fracture loads were significantly higher for MPZ specimens than for other test specimens, regardless of luting agent. Use of an adhesive resin luting agent is recommended for placement of premolar implant-supported monolithic Y-PSZ and lithium disilicate ceramic prostheses.

Accuracy and practicality of intraoral scanner in dentistry: A literature review.

PURPOSE: The digitization of the dental field has been vigorously promoted in recent years. An impression using an intraoral scanner is considered to significantly change future dental treatment. The purpose of this review is to evaluate accuracy and practicality of various intraoral scanners and verification method of intraoral scanners. STUDY SELECTION: This review was based on articles searched through the MEDLINE and PubMed databases. The main keywords that were employed during the search were "Oral Scanner, Intraoral Scanners, Desktop Scanner, and Digital Impression". RESULT: It was reported that illuminance and color temperature affected trueness and precision of intraoral scanners. The repeatability of intraoral scanners indicated the possibility of producing fixed prostheses within the range of being partially edentulous. It is considered difficult to use intraoral scanners in fabricating cross-arch fixed prostheses. However, with intraoral scanners, it may be considered possible to fabricate mouth guards and dentures equivalent to those of desktop scanners. Current intraoral scanner scans are considered more comfortable than traditional impressions that use irreversible hydrocolloid and elastomeric impression materials. CONCLUSION: Since the intraoral scanner is an evolving device, further improvement in accuracy is expected in the future. In addition, verification of the accuracy of intraoral scanners must be conducted accordingly.

Fracture loads of screw-retained implant-supported zirconia prostheses after thermal and mechanical stress.

PURPOSE: The objective of the present study was to evaluate fracture loads of screw-retained implant-supported zirconia prostheses after artificial aging. METHODS: Four types of screw-retained implant-supported prostheses were fabricated (n=11 each); porcelain-veneered zirconia prosthesis (PVZ), indirect composite-veneered zirconia prosthesis (IVZ), porcelain-fused-to-metal prosthesis (PFM), and monolithic zirconia prosthesis (ML). The specimens were subjected to 10,000 thermocycles and cyclic loading for 1.2 million cycles. Fracture loads were measured, and the data were analyzed with the Kruskal-Wallis and Steel-Dwass tests (α=0.05). RESULTS: All specimens survived the artificial aging procedures. The fracture loads for the PVZ (1.52kN), IVZ (1.62kN), and PFM groups (1.53kN) did not significantly differ; however, the fracture load for the ML group (6.61kN) was significantly higher than those for the other groups. The fracture load for the IVZ group was comparable to those for the PVZ and PFM groups. CONCLUSIONS: The monolithic zirconia prostheses exhibited significantly higher fracture loads than the bilayered prostheses. All the investigated types of screw-retained implant-supported zirconia prostheses appear sufficient to resist posterior masticatory forces during long-term clinical use.

Bond strength of CAD/CAM-manufactured composite resin and ceramic veneers to a zirconia framework.

This study investigated bond strength of CAD/CAM-manufactured composite resin and ceramic veneers to a zirconia framework and analyzed the effect of treatments of veneer surfaces. A CAD/CAM resin-based (AVE) composite or lithium disilicate ceramic (IEC) block was used as the veneer material. AVE and IEC specimens were assigned to receive one of three surface treatments (n = 22): no surface treatment, acid-etching with 9.5% hydrofluoric acid gel, and airborne-particle abrasion with alumina particles. Zirconia disks and AVE or IEC specimens in each group were bonded with a resin-based luting agent, and shear bond strength of the specimens was measured at 0 and 20,000 thermocycles. Significant differences were assessed by the Steel-Dwass test for multiple comparisons and Mann-Whitney U-test (α = 0.05). As compared with other surface treatments, bond strengths were significantly higher at 0 and 20,000 thermocycles in the airborne-particle abraded AVE and acid-etched IEC specimens. Airborne-particle abrasion of the surface of AVE specimens increased bond strength between AVE veneers and zirconia frameworks, while hydrofluoric acid treatment enhanced bond strength between IEC veneers and zirconia frameworks.

Bond strengths between gingiva-colored layering resin composite and zirconia frameworks coated with feldspathic porcelain.

This study evaluated shear bond strengths of two gingiva-colored layering resin composites to zirconia frameworks coated with feldspathic porcelain. Airborne-particle abraded porcelain-coated zirconia disks were treated with one of the following primers: Clearfil Photo Bond, Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB+Activator), Estenia Opaque Primer, Porcelain Liner M Liquid B (PLB), or no primer. A light-polymerizing (CER) or a photo/heat-polymerizing gingiva-colored indirect resin composite (EST) was bonded to the porcelain-coated zirconia disks in each group (n=11). Shear bond strength was measured. For both CER and EST specimens, bond strengths in CPB+Act group were significantly higher than those in the other groups. In all priming groups, bond strength was significantly higher for EST specimens than for CER specimens. Combined application of a phosphate monomer and silane enhanced initial bond strength of light-polymerized and photo/heat-polymerized gingiva-colored layering resin composites to porcelain-coated zirconia ceramics.

Importance of interim restorations in the molar region.

Interim restoration protects abutment teeth and periodontal tissues until prosthetic treatment ends with the fabrication of a definitive prosthesis, restores and maintains the functions and morphology of the stomatognathic system, and preserves the occlusal contact relationship. Temporary prostheses are used for a short time, to confirm the diagnosis and treatment plan. However, because interim restorations are used only briefly, their importance in ensuring the success of definitive prostheses is often overlooked. This review includes a comprehensive literature review of interim restoration of molars and summarizes the current clinical understanding and status of this functionally important area. Peer-reviewed publications were identified by searching PubMed in November 2018. An interim restoration, even when used briefly, can help dentists evaluate many aspects of the treatment plan and contribute to accurate prognosis of prosthetic treatment.

Effect of veneering materials on fracture loads of implant-supported zirconia molar fixed dental prostheses.

PURPOSE: To determine the effect of veneering material and framework design on fracture loads of implant-supported zirconia molar fixed dental prostheses (FDPs). METHODS: Sixty-six zirconia FDPs were manufactured onto two implants and classified as uniform thickness (UT) or anatomic design (AD). These framework design groups were then further divided into three subgroups (n=11): feldspathic porcelain-veneered zirconia FDPs (PVZ), indirect composite-veneered zirconia FDPs (IVZ), and metal-ceramic FDPs (MC). The FDPs were luted on the implant abutments and underwent fracture load testing. Significant differences were assessed by the Kruskal-Wallis test and Mann-Whitney U-test (α=0.05). RESULTS: For UT group, median fracture load was significantly higher for the IVZ (1.87kN) and MC (1.90kN) specimens than for the PVZ specimens (1.38kN) (p<0.05). In the AD group, the IVZ specimens had the highest median fracture load (4.10kN) of the three groups tested. The AD group exhibited higher median fracture loads than the UT group in all subgroups. CONCLUSIONS: Indirect composite appears to be a useful alternative to feldspathic porcelain as the layering material for implant-supported zirconia FDPs. The AD group had higher fracture loads than UT group. In addition, implant-supported indirect composite-veneered zirconia-based FDPs appear to be clinically feasible.

Effect of preparation design on marginal and internal adaptation of translucent zirconia laminate veneers.

This study investigated the effect of preparation design on the marginal and internal adaptation of laminate veneers (LVs) fabricated from translucent zirconia. Thirty-three resin teeth were prepared for LVs of three designs: window preparation (WP); incisal shoulder preparation (ISP); and incisal palatal chamfer preparation (IPP). Marginal adaptation was evaluated by measuring the vertical discrepancy between the LV margin and the finish line at 60 points. The internal adaptation was assessed by measuring the internal space width as the distance between the LV and the tooth at cervical, central, and incisal sites after sectioning. At the incisal, mesial, and distal sites, mean marginal discrepancies were significantly lower in the WP group than in the other two groups; the IPP group had the highest marginal discrepancies. At incisal sites, the median internal space was significantly higher in the IPP group than in the WP and ISP groups and higher in the ISP group than in the WP group. At the incisal site, marginal and internal adaptations were better for the non-overlap translucent zirconia LV design (WP) than for the overlap designs (ISP and IPP). The characteristics of the translucent zirconia LVs used in the present study indicate acceptable clinical performance.

Effect of a silane and phosphate functional monomer on shear bond strength of a resin-based luting agent to lithium disilicate ceramic and quartz materials.

This study examined the effect of silane and phosphate functional monomer on bond strengths between a resin-based luting agent joined to a lithium disilicate ceramic (IPS e.max) and silica (quartz) materials. The e.max and quartz specimens were assigned to 6 groups with different priming/bonding agents, namely, Clearfil Porcelain Bond Activator, Clearfil Photo Bond, Clearfil Photo Bond Universal with Clearfil Porcelain Bond Activator, Clearfil Photo Bond Catalyst with Clearfil Porcelain Bond Activator, Clearfil Photo Bond with Clearfil Porcelain Bond Activator, and unprimed. The corresponding specimens were bonded by using a resin-based luting agent (Panavia V5). Shear bond strengths were determined before and after 5,000 thermocycles. For both the e.max and quartz specimens, the Clearfil Photo Bond Universal with Clearfil Porcelain Bond Activator group had the highest pre- and post-thermocycling bond strength values. Combined use of silane in the acidic environment of a phosphate functional monomer and initiators enhances bond strength of a resin-based luting agent to e.max ceramic and quartz materials.

An in vitro evaluation of fracture load of implant-supported zirconia-based prostheses fabricated with different veneer materials.

OBJECTIVES: The purpose of this in vitro study was to evaluate fracture loads of implant-supported zirconia-based prostheses fabricated with different veneer materials (resin-based material and lithium disilicate ceramics). MATERIAL AND METHODS: Forty-four zirconia-based molar prostheses were fabricated on dental implants and divided into four groups (n = 11): zirconia-based prostheses veneered with feldspathic porcelain (ZVF), zirconia-based prostheses bonded with the lithium disilicate glass-ceramic veneer (ZBD), zirconia-based prostheses veneered with indirect composite resin (ZVC), and zirconia-based prostheses bonded with composite materials fabricated from a CAD/CAM resin block (ZBC). The zirconia-based prostheses and abutments were adhesively bonded with a dual-polymerized resin-based luting material. Fracture load was determined using compression load to the prostheses with a universal testing machine. The data were analyzed with one-way analysis of variance (ANOVA) and Tukey's HSD test (α = .05). RESULTS: The mean fracture load was significantly higher in the ZBC group (3.95 kN) than in the ZVC group (3.28 kN). No significant difference in fracture load was found among the ZVF (3.52 kN), ZBD (3.48 kN), and ZVC groups. CONCLUSIONS: The adhesively bonded veneering technique enhances fracture resistance of implant-supported zirconia-based prostheses fabricated with a resin-based material. All implant-supported zirconia-based restorations tested should resist physiologic masticatory forces in the oral environment.