Papers by walid abdelghafar
BMC Oral Health
Objectives Successful ceramic restorations depend on the strong bonding with resin cement and eve... more Objectives Successful ceramic restorations depend on the strong bonding with resin cement and even stress distribution. The aim of this study was to evaluate the impact of adding MDP-containing zirconia primer before self-adhesive resin cements with different functional acidic monomers on fracture resistance of monolithic zirconia crown. Materials and methods Eighty defect-free human maxillary premolars were divided according to the cement type and application of MDP-containing zirconia primer into eight groups (n = 10): Calibra Universal (C), Calibra Universal combined with zirconia primer (CZ), RelyX U200 (R), RelyXU200 combined with zirconia primer (RZ), Panavia SA Cement Plus (P), Panavia SA Cement Plus combined with zirconia primer (PZ), Multilink Speed (M), and Multilink Speed combined with zirconia primer (MZ). After teeth preparation and fabrication of zirconia crowns, each crown was bonded to its corresponding tooth. All specimens were subjected to 10,000 thermocycles betwe...
PubMed, May 11, 2023
Aim: To evaluate the influence of resin cement on the color stability of lithium disilicate and z... more Aim: To evaluate the influence of resin cement on the color stability of lithium disilicate and zirconia restorations immersed in coffee after aging. Materials and methods: Eighty maxillary premolars were classified into eight groups (n = 10) based on restorative material type (lithium disilicate or zirconia), resin cement type (G-CEM LinkForce; GC Corporation or Panavia SA Cement Plus Automix; Kuraray Noritake Dental), and preheating temperature (25°C or 54°C). Following tooth preparation, each restoration was bonded to its corresponding substrate. Using a reflectance spectrophotometer, Commission Internationale de l'Éclairage (CIE) tristimulus values were detected and calculated (D65 standard illumination, 10-degree observer angle). All specimens were aged (240,000 load cycles followed by 10,000 thermal cycles), then immersed in coffee (18 h). Following that, the second measurements of the color coordinates were determined. The total color differences were measured, and the data were statistically analyzed (α = 0.05). Results: The temperature had a significant effect on ΔL΄ (P < 0.001), ΔC΄ (P < 0.001), and ΔH΄ (P < 0.001). The lithium disilicate restorations were more color stable than the zirconia restorations. Also, there was a significant difference (P = 0.047) between the LinkForce (2.28 ± 0.48) and Panavia SA (2.15 ± 0.46) cement. The restorations cemented at a temperature of 54°C (1.76 ± 0.11) showed significant color differences (P < 0.001) compared with those cemented at a temperature of 25°C (2.67 ± 0.15). A three-way analysis of variance (ANOVA) test revealed that the interaction between the ceramic material, cement type, and temperature had no statistically significant effect (P = 0.611) on the color stability of the ceramic restorations. Conclusions: Cement type has a significant effect on the color stability of lithium disilicate and zirconia restorations. Cement at a temperature of up to 54°C enhances the color stability of lithium disilicate and zirconia restorations.
Journal of Adhesive Dentistry, 2016
Purpose: To test the effect of surface conditioning protocols on the reparability of CAD/CAM zirc... more Purpose: To test the effect of surface conditioning protocols on the reparability of CAD/CAM zirconia-reinforced lithium silicate ceramic compared to lithium-disilicate glass ceramic. Materials and methods: Zirconia-reinforced lithium silicate ceramic (Vita Suprinity) and lithium disilicate glass-ceramic blocks (IPS e.max CAD) were categorized into four groups based on the surface conditioning protocol used. Group C: no treatment (control); group HF: 5% hydrofluoric acid etching for 60 s, silane (Monobond-S) application for 60 s, air drying; group HF-H: 5% HF acid etching for 60 s, application of silane for 60 s, air drying, application of Heliobond, light curing for 20 s; group CO: sandblasting with CoJet sand followed by silanization. Composite resin (Tetric EvoCeram) was built up into 4 x 6 x 3 mm blocks using teflon molds. All specimens were subjected to thermocycling (5000x, 5°C to 55°C). The microtensile bond strength test was employed at a crosshead speed of 1 mm/min. SEM was employed for evaluation of all the debonded microbars, the failure type was categorized as either adhesive (failure at adhesive layer), cohesive (failure at ceramic or composite resin), or mixed (failure between adhesive layer and substrate). Two-way ANOVA and the Tukey's HSD post-hoc test were applied to test for significant differences in bond strength values in relation to different materials and surface pretreatment (p < 0.05). Results: The highest microtensile repair bond strength for Vita Suprinity was reported in group CO (33.1 ± 2.4 MPa) and the lowest in group HF (27.4 ± 4.4 MPa). Regarding IPS e.max CAD, group CO showed the highest (30.5 ± 4.9 MPa) and HF the lowest microtensile bond strength (22.4 ± 5.7 MPa). Groups HF, HF-H, and CO showed statistically significant differences in terms of all ceramic types used (p < 0.05). The control group showed exclusively adhesive failures, while in HF, HF-H, and CO groups, mixed failures were predominant. Conclusions: Repair bond strength to zirconia-reinforced lithium silicate ceramics and lithium-disilicate glass ceramic could be improved when ceramic surfaces are sandblasted with CoJet sand followed by silanization.
PubMed, Jul 18, 2023
Aim: The present study aimed to evaluate the retention strength of nonretentive zirconia occlusal... more Aim: The present study aimed to evaluate the retention strength of nonretentive zirconia occlusal veneers bonded to different bonding surfaces (enamel, enamel and dentin, and enamel with composite filling) using two adhesive resin cement systems that use either organophosphate carboxylic acid or organophosphate monomers as a ceramic primer. Materials and methods: Sixty extracted mandibular molars were prepared to receive occlusal veneers as follows (n = 20): 1-mm reduction within enamel; 2-mm reduction within enamel and dentin; 1-mm reduction within enamel with composite filling. Each occlusal veneer was designed with an occlusal bar to aid in the retention test, then milled from a zirconia block, and sintered. Within each group, the zirconia occlusal veneers were bonded using either Duo-Link Universal or Panavia V5 (10 specimens each). All specimens were thermocycled for 5000 cycles. After the pull-off test, the retention strength was calculated for each specimen. Each specimen was examined under magnification to determine its mode of failure. Representative specimens were examined using a scanning electron microscope. Data were analyzed using the two-way analysis of variance (ANOVA) and Tukey HSD tests (P = 0.05). Results: Both bonding substrate and cement type had a significant influence on retention strength values (P < 0.05). The two-way ANOVA showed a significant interaction between bonding substrate and cement type (P = 0.003). There were significant differences in the retention strength between the cements in both the enamel and enamel and dentin substrates (P < 0.05), but no significant difference between the cements in the enamel with composite filling substrate (P > 0.05). The predominant mode of failure was cement remaining principally in the restoration surface (adhesive failure), followed by cement adhesion to both the tooth and the restoration surface (mixed failure). Conclusions: Among the studied substrates, enamel was the optimal dental bonding surface. However, bonding to dentin was not a limiting factor for the retention of zirconia occlusal veneers. The resin cement using an organophosphate (Panavia V5) provided superior retention strength compared with the cement using organophosphate carboxylic acid monomer (Duo-Link Universal).
Research Square (Research Square), Dec 8, 2022
Background The purpose of this in vitro study was to evaluate the effect of phosphotungstic acid ... more Background The purpose of this in vitro study was to evaluate the effect of phosphotungstic acid pre-treatment on the surface properties of zirconium oxide ceramics and the microtensile bond strength (µTBS) between zirconium oxide ceramics and resin cement. Methods A total of 26 sintered zirconia blocks were randomly divided according to surface pre-treatment into four groups; group C (n = 6): no treatment (control), group S (n = 6): airborne particle abrasion followed by Silano Pen treatment, group P1 (n = 7): Phosphotungstic acid 1gm/ 50 mL, and group P2 (n = 7): Phosphotungstic acid 2gm/50 mL. From each group, one zirconia block was examined using X-Ray Diffraction and scanning electron microscope. Also, one zirconia block from groups P1 and P2 was examined using Fourier-transform infrared spectroscopy. A total of 20 zirconia blocks were bonded to corresponding pre-constructed composite blocks using adhesive resin cement. Each zirconia-composite assembly was sectioned to obtain microbars of 1 mm 2. A 20 microbars from each group were selected and aged (3500 thermocycles between 5°C and 55°C), then the µTBS test was performed using a universal testing machine (0.5 mm/min). The µTBS results was analyzed using one-way ANOVA test. Results Group P2 recorded the highest µTBS (23.824 ± 5.9 MPa) between all studied groups, while Group C recorded the lowest µTBS (12.19 ± 4.67 MPa). One-way ANOVA revealed a signi cant difference (P < 0.05) between all groups. The mode of failure was predominantly adhesive in Groups C, P1, and S, while group P2 showed cohesive and adhesive failures. Conclusions The phosphotungstic acid (2gm/50 mL) improved the bond strength of zirconia ceramics without phase transformation and composition changes.
BMC Oral Health, Nov 24, 2022
Background: To evaluate the clinical and radiographic assessment of customized fusion-sputtered o... more Background: To evaluate the clinical and radiographic assessment of customized fusion-sputtered one-piece zirconia implants. Methods: Twenty-eight patients received either fusion sputtered one-piece zirconia implants (n = 14) or one-piece titanium implants (n = 14). All implants were one-piece designs. After 4 months of immediate loading, all implants were restored with a monolithic zirconia crown. All implants were evaluated at baseline, 6 months, 1 year, 2 years, and 5 years. Implant mobility, plaque index, and gingival index evaluations were performed. The measurements of marginal bone level were calculated radiographically. Results: All implants were well maintained through the evaluation period with a 100% survival rate without any clinical complications. Regarding gingival index, there was no statistically significant difference (P = .364) between zirconia (3.3 ± 0.7 mm) and titanium (3.5 ± 0.6 mm) implants, after 5 years. There was no statistically significant difference (P = .470) between zirconia (1.77 ± 0.039 mm) and titanium (1.80 ± 0.28 mm) implants regarding marginal bone loss, after 5 years. Conclusions: One-piece fusion-sputtered zirconia implant represents a reliable treatment modality in replacing a missing tooth in the esthetic zone.
Egyptian dental journal, Jul 1, 2021
Purpose: To assess the effect of chemical pre-treatments (piranha, hot acid, and heteropolyacid) ... more Purpose: To assess the effect of chemical pre-treatments (piranha, hot acid, and heteropolyacid) on the bond strength (μTBS) to zirconia. Materials and Methods: A total of 8 sintered zirconia blocks were randomly assigned into 4 groups; Group I: Air abrasion, Group II: Air abrasion and etching using piranha solution (3H 2 SO 4 : 1H 2 O 2), Group III: Air abrasion and etching using hot acid solution (1HNO 3 : 1HF), and Group IV: Air abrasion and etching using heteropolyacid solution (2gm/50 mL). Zirconia blocks were bonded to their corresponding pre-constructed composite blocks using adhesive resin cement. For each group, each assembly was sectioned to obtain 20 microbars. All microbars were thermocyled (10,000), then the μTBS test was done with the aid of a Universal Testing machine. To determine the mode of failure, each specimen was examined under stereomicroscope (x40). One-way ANOVA and Post Hoc Tukey tests were used. Results: The piranha pre-treatment displayed the lowest bond strength (16.82 ±5.97 MPa), while heteropolyacid pre-treatment had higher bond strength (26.22 ±4.05 MPa). One-way ANOVA test indicated statistical significant difference between the studied groups (P<.001). No significant difference was observed between control and piranha groups, also between hot acid and heteropolyacid groups. However, there were statistical significant differences between the control and heteropolyacid groups, and between piranha and heteropolyacid groups. Conclusions: According to the current findings; The novel surface pre-treatment with heteropolyacid (2gm/50 mL) performed well to improve bonding to air-abraded zirconia-based ceramics. The hot acids etching pre-treatment enhanced the bonding to zirconia.
International Journal of Prosthodontics, May 1, 2020
ingle-tooth replacement in the anterior maxillary area presents the ultimate esthetic challenge. ... more ingle-tooth replacement in the anterior maxillary area presents the ultimate esthetic challenge. 1 Although a single-tooth implant-supported restoration does not necessitate preparation of abutment teeth, 2 the implant approach is sometimes impossible and restricted because of accessibility to the bone volume at the inclusion site and the risk factors related to participants, such as smoking, radiotherapy, anxiety, occlusal function, and economic costs. Moreover, the clinical life span of single-tooth implant-supported restorations following 5 years of clinical follow-up extended from 91% to 96.3% 3,4 and 89.4% after 10 years. 4 The main advantage of resin-bonded fixed dental prostheses (RBFDPs) over fullcoverage fixed dental prostheses (FDP) is that they require minimally invasive tooth preparation on the lingual and proximal surfaces. Additional advantages include the supragingival margins and reduced cost due to decreased chairtime. 5-7 In 1991, a design similar to that of metal-ceramic RBFDPs with ceramic wings was introduced to overcome the esthetic drawbacks of conventional metal-ceramic RBF-PDs. 8 Unfortunately, early reports about the durability of the two retainers showed connector fractures in one-third of the restorations during the first year of clinical service. 9-15 The ceramic fracture was mainly related to the propagation of a crack through one connector (between the retainer wing and the pontic), leaving the pontic
Journal of Prosthodontics
PurposeTo evaluate the fracture load and stress magnitude of different retainer designs of minima... more PurposeTo evaluate the fracture load and stress magnitude of different retainer designs of minimally invasive cantilever resin‐bonded fixed dental prostheses (RBFDPs) after artificial aging.Materials and methodsFifty caries‐free human mandibular molars were prepared as abutments for cantilever fixed dental prostheses using different retainer designs: one wing (OW), two wings (TW), inlay ring (IR), lingual coverage (LC), and occlusal coverage (OC). Computer‐aided design and computer‐aided manufacturing were used for milling the RBFDPs using fiber‐reinforced composite (FRC), and the restorations were adhesively bonded. The specimens were then subjected to thermomechanical aging and loaded until failure. The 3D finite element analysis (FEA) was performed with five models of retainer designs similar to the in vitro test. Modified von Mises stress values on enamel, dentine, luting resin, and restorations were examined. Data were analyzed with Kruskal–Wallis and Mann–Whitney U tests (p &l...
Odontology, Aug 5, 2023
A total of 20 lithium disilicate glass-ceramics (IPS e.max CAD, Ivoclar Vivadent) and 20 resin na... more A total of 20 lithium disilicate glass-ceramics (IPS e.max CAD, Ivoclar Vivadent) and 20 resin nano-ceramic (Voco Grandio Blocks) onlay restorations were performed in 20 patients using a split-mouth design to compare the two-year clinical performance of lithium disilicate and resin nano-ceramic onlay restorations. Both restorations were evaluated at baseline, one-year, and two-year clinical follow-ups based on the modified United States Public Health Service (USPHS) criteria. Chi-square and Fisher's exact tests showed no statistically significant difference between Voco Grandio and IPS e.max ceramic restorations for all evaluated parameters during the different follow-up periods (p > 0.05). Cochrane's and MC-Nemar's tests indicated statistically significant differences regarding color match within the Voco Grandio group. They also indicated statistically significant differences in marginal discoloration, marginal adaptation, surface texture, and postoperative hypersensitivity within both ceramic material groups (p < 0.05). Kaplan-Meier curve indicated that the survival rate of both ceramic materials was 90%. After two years of clinical service, IPS e.max CAD and Voco Grandio onlay restorations exhibited similar clinical performance.
Journal of Prosthodontics
Journal of Prosthodontic Research
To evaluate the influence of retainer design and ceramic materials on the durability of minimally... more To evaluate the influence of retainer design and ceramic materials on the durability of minimally invasive cantilever resin-bonded fixed dental prostheses (RBFDPs) after artificial aging. Methods: One hundred caries-free human mandibular molars were prepared as abutments for all-ceramic cantilevered fixed dental prostheses using the following retainer designs: One wing (OW), Two wings (TW), Inlay ring (IR), Lingual coverage (LC), and Occlusal coverage (OC). Two ceramic materials were used: monolithic high translucent zirconia(z) and zirconia-reinforced lithium disilicate (ZLS 2) (n=10). All restorations were adhesively bonded with resin cement. The thermocycling of the specimens were performed between 5°C and 55°C for 10,000 cycles and then exposed to 240.000 cycles of dynamic loading on a chewing simulator. All surviving specimens were loaded onto the pontic until failure using a universal testing machine. Results: The mean failure load ranged from 124.00 to 627.00 N for the zirconia groups and from 133.30 to 230.00 N for the ZLS 2 groups. Regarding the materials, a significantly higher failure load was recorded in the zirconia groups than in the ZLS 2 groups (P<0.001), except for OW (P=0.748). Regarding the retainer designs, a significant different failure load was recorded between the different designs except for IR and LC in the zirconia groups, IR and OC, OW and TW, and TW and LC in the ZLS 2 groups (P<0.001). Conclusions: Zirconia IR, LC, and OC can be used as cantilever RBFDP in the premolar region. The fracture resistance of the ZLS 2 design was below the normal bite force and should not be recommended as the first option.
Egyptian Dental Journal
Statement of problem: Longer-term clinical trials with success data are required to validate the ... more Statement of problem: Longer-term clinical trials with success data are required to validate the current design options of Ti base as viable abutments. Objective: The aim of this clinical research was to investigate the influence of abutment designs on the clinical outcome of screw-and cement-retained, implant-supported monolithic zirconia crowns. Material and methods: A total of 28 patients with missing 30 single maxillary premolar areas were implanted (4.1x12mm), and random classified into 3 equal groups (n =10): Group (A) (VC): patients receiving hybrid Ti base abutments (Variobase, Straumann, Switzerland) with cementretained crowns, Group (B) (VS): patients receiving hybrid Ti base abutments (Variobase) with screw-retained crowns, Group (C) (DS): patients receiving non-segmented screw-retained crown (cemented onto Dess Ti Base). The monolithic zirconia crowns were CAD/CAM fabricated, cemented, and evaluated at baseline, 3, 6, 12 and 18 months clinically and radiographically. All data were collected and statistically analyzed. Results: All 30 implants remained stable and reached osseointegration (100% cumulative success rate ⁅CSR⁆). The highest mean average crestal bone level (BL) measured 1.23+0.72mm (median: 1.40mm, range: 0.00-2.25mm) (P=0.09 NS) in group (C) (DS), and the least mean BL measured 1.00+0.55mm (median: 1.10mm, range: 0.00-2.00mm) and (median: 1.00mm, range: 0.10-1.90mm) (P=0.83 NS) and (P=0.52 NS) in the groups (B and A) (VS and VC) respectively. Conclusions: Under the conditions of this study, using a prefabricated (Variobase or Dess) Ti base as an abutment for an implant-supported zirconia crown is an alternative procedure for FPDs. It promotes healthy and stable hard and soft tissues.
Scientific Reports
To investigate the effect of resin cements on the color stability and translucency of ceramic lam... more To investigate the effect of resin cements on the color stability and translucency of ceramic laminate veneers used for diastema closure. Sixty resin abutments were prepared for ceramic laminate veneers and divided into six groups according to the ceramic type (lithium disilicate, zirconia-reinforced lithium silicate, and translucent zirconia) and the cement type (Variolink Esthetic LC and RelyX Veneer). Color coordinates and translucency were analyzed after cementation and after soaking in the coffee solution. Differences in color and translucency were estimated, and results were statistically assessed (α = 0.05). Ceramic materials showed a significant impact on color changes after soaking in coffee within Variolink Esthetic groups. Translucent zirconia showed the highest color change, followed by zirconia reinforced lithium silicate and lithium disilicate. Ceramic materials showed a significant impact among the RelyX Veneer groups. A significant interaction in color changes was fo...
Background The purpose of this in vitro study was to evaluate the effect of phosphotungstic acid ... more Background The purpose of this in vitro study was to evaluate the effect of phosphotungstic acid pre-treatment on the surface properties of zirconium oxide ceramics and the microtensile bond strength (µTBS) between zirconium oxide ceramics and resin cement. Methods A total of 26 sintered zirconia blocks were randomly divided according to surface pre-treatment into four groups; group C (n = 6): no treatment (control), group S (n = 6): air-borne particle abrasion followed by Silano Pen treatment, group P1 (n = 7): Phosphotungstic acid 1gm/ 50 mL, and group P2 (n = 7): Phosphotungstic acid 2gm/50 mL. From each group, one zirconia block was examined using X-Ray Diffraction and scanning electron microscope. Also, one zirconia block from groups P1 and P2 was examined using Fourier-transform infrared spectroscopy. A total of 20 zirconia blocks were bonded to corresponding pre-constructed composite blocks using adhesive resin cement. Each zirconia-composite assembly was sectioned to obtain ...
Mansoura Journal of Dentistry, 2021
Objective: To evaluate effect of veneering thickness and repeated firing on the flexural strength... more Objective: To evaluate effect of veneering thickness and repeated firing on the flexural strength and translucency of lithium disilicate glass ceramic. Materials and methods: Sixty-three-disc specimens were divided; each group have 21 discs specimens. First group was lithium disilicate core 1 mm with no veneering coverage, second group the lithium disilicate core was veneered by 0.5 mm nano flouroapatite glass ceramic. Third group was lithium disilicate core veneered by 1 mm nano flouroapatite glass ceramic. Each group was subjected to repeated firing cycles (3, 5, 7). Seven-disc specimens for each firing cycle were used to measure translucency then flexural strength. The degree of color difference between the compared colors was expressed in ∆E units. The total color difference, according to L*, H*, C* coordinates, was calculated. Then change in TP (∆TP) which is the difference between first and second sample regarding thickness and firing cycles was measured to determine the acceptability threshold. Then fracture load was applied to all specimens fixed on 3 balls fixture under static compressive loading using universal testing machine to determine the flexural strength. The results were tabulated and statistical analysis was performedusing repeated way ANOVA method. Results: Regarding value, chroma and hue, in 3 firing cycles value means revealed a significant difference in the comparison between 1 mm, 1.5 mm (P=0.001) thickness and between 1 mm, 2 mm (P=0.001) but non-significant difference was shown between 1.5 mm and 2 mm (P=0.325). While chroma and hue showed significant difference in comparison between 1 mm, 1.5 mm and 2 mm (P=0.001). However, in 5 firing cycles, value showed significant difference between 1 mm, 1.5 mm and 1 mm, 2 mm (P=0.001) and also between 1.5 mm, 2 mm (P=0.016), and chroma also showed significant difference between 1 mm, 1.5 mm, 2 mm (P=0.001), and hue showed significant difference between 1 mm, 1.5 mm (P=0.027), and also between 1 mm, 2 mm and 1.5 mm, 2 mm. However, in 7 firing cycles, value showed significant difference in comparison between 1 mm, 1.5 mm (P=0.001) and 1 mm, 2 mm (P=0.001) but non-significant difference was revealed between 1.5 mm, 2 mm (P=0.053). While chroma showed significant difference between 1 mm, 1.5 mm and 2 mm (P=0.001), while hue showed significant difference in comparison between 1 mm, 1.5 mm (P=0.001) but non-significant difference was found between 1 mm, 2 mm (P=0.11) and 1.5 mm, 2 mm (P=0.148). Translucency parameters revealed a significant difference (P=0.001) between different firing cycles with different thickness. Flexural strength showed no significant decrease with increasing firing cycles from 3 to 5 firing cycles in the same 1 mm thickness (P=0.153) and showed significant decrease on increasing firing cycles from 3 to 7 cycles (P=0.001) and 5 to 7 cycles (P=0.005). While in 1.5 mm thickness showed significant decrease in flexural strength on increasing firing cycles from 3 to 5 cycles (P=0.013) and from 3 to 7 cycles (P=0.001) and showed no significant decrease on increasing firing cycles from 5 to 7 cycles (P=0.073). While in 2 mm thickness showed significant decrease in flexural strength on increasing firing cycles from 3 to 5 cycles (P=0.015), 3 to 7 cycles (P=0.001) and 5 to 7 cycles (P=0.03). Conclusions: 1-Translucency decreased on increasing the firing cycles and increasing the veneering thickness. 2-Flexural strength increased on increasing veneering thickness and decreased on increasing the firing cycles.
Dental Materials, 2021
OBJECTIVE Optimizing monolithic zirconia (ZrO2) aesthetically without affecting the unique mechan... more OBJECTIVE Optimizing monolithic zirconia (ZrO2) aesthetically without affecting the unique mechanical properties remains a major ongoing interest. The purpose of this review is to evaluate the improvement of recent monolithic ZrO2 generations to meet aesthetic optimization qualities. Additionally, for how the extent of the former modifications negatively affected their mechanical properties and the impact on their clinical indications. METHODS The current literature examines in-vitro studies evaluating both monolithic ZrO2 translucency and mechanical properties. The electronic search was done within these databases: Web of Science, ScienceDirect, Scopus, and PubMed within the period between 2009/10/01 and 2019/10/31. Search results that met eligibility criteria were classified into four groups; one for translucency parameter, two for uniaxial flexural strength and one for biaxial strength. RESULTS Articles that remained for comprehensive analysis were fifty-three. They reported a significant impact of composition, microstructure and surface treatment on translucency and flexural strength assessment. Aging was found to be of no concern for zirconia structures with high yttria content. Smooth surface polish was found to significantly enhance strength while coarse grinding and mechanical fatigue was found to do the reverse. SIGNIFICANCE Based on analyzing the previous in-vitro studies the following was found: Although significant improvement has occurred with recent monolithic zirconia types with higher yttria content having higher cubic/tetragonal ratio, they are still inferior to glass-ceramics' unique translucency. With improving zirconia aesthetically, some of mechanical performance was sacrificed. Care must be taken when dealing with thin sections of aesthetic zirconia structures especially when used in high bearing stress areas.
Egyptian Dental Journal, 2019
Purpose: The current in-vitro investigation analyzed the impact of speed sintering and different ... more Purpose: The current in-vitro investigation analyzed the impact of speed sintering and different finish line width on marginal adaptation, internal fit and microleakage of translucent monolithic zirconia crowns. Materials and Methods: Sixty maxillary premolars were reduced based on basic guidelines of tooth preparation for a zirconia crown with either 0.5, 0.8 and 1.2 mm chamfer width (n=20 ̸ each finish line width). After digital scanning and milling of zirconia crowns, the sintering procedure was performed in special furnace for two different sintering programs (n =10 per group) following either standard or speed sintering procedure. Each crown was cemented to its corresponding prepared tooth utilizing self-adhesive-resin cement. After 15000 thermal cycles between 5°C and 55°C, specimens were submersed in methylene blue for 12 hours. After sectioning buccolingually, marginal gap and cement film thickness values were recorded at nine sites using a digital microscope followed by microleakage scores examination. Results: Tested groups with 0.5 mm chamfer widths had the greatest mean marginal gap values of 47.9±5.4 and 50.1±5.6 µm for both conventional and speed sintering respectively, while groups with 1.2 chamfer widths had the lowest mean gap values of 42.3±5.6 and 44.5±5 µm for both standard and speed sintering, respectively. Two-way ANOVA revealed statically insignificant impact of sintering procedure on crown adaptation (p=.08). The greatest mean microleakage score (3±088 µm) was obtained from the 0.5 mm chamfer width group, while the smallest (2±0.78 µm) score was obtained from the 1.2 mm chamfer width group. Conclusions: Marginal adaptation and internal fit of translucent monolithic zirconia crowns are affected by width of the preparation margin while sintering protocol has little impact on adaptation.
The Journal of Adhesion, 2013
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Papers by walid abdelghafar