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Purpose: To evaluate the effect of titanium base height on torque loss of monolithic zirconia, lithium disilicate, and polymer-infiltrated ceramic hybrid abutment restorations for an offset placed implant., Materials and Methods: A total of 42 hybrid abutment restorations supported by offset implant placement (4.2-mm diameter, 10-mm length) were divided into six groups: short titanium base and zirconia (SZ), long titanium base and zirconia (LZ), short titanium base and lithium disilicate (SE), long titanium base and lithium disilicate (LE), short titanium base and polymer-infiltrated ceramic (SP), and long titanium base and polymer-infiltrated ceramic (LP). An adhesive resin cement was used to bond the restoration to the titanium base. The restoration was secured with a titanium screw, tightened to 30 Ncm using a calibrated torque meter device. The specimens were exposed to thermocycling (5,000 cycles at 5°C to 55°C), then cyclic loading (120,000 cycles, 50 N, 1.6 Hz), where the load was placed vertically in the mesial fossa of the restoration. The loosening torque value of the abutment screw was measured by the torque meter device, and then the torque loss and its percentage were calculated. Two-way and one-way ANOVA and post hoc Tukey tests were used for statistical data analysis (α = .05)., Results: Two-way ANOVA showed significant differences in loosening torque, torque loss, and percentage of torque loss across the restorative material (P < .001), with no significant difference across the height of the titanium base (P = .213) and no significant interaction (P = .845) between the restorative material and titanium base height. Regarding the restoration type, one-way ANOVA showed a significant difference (F ratio = 15.95, P < .001) in torque loss between groups. The mean torque loss was significantly higher for monolithic zirconia than for lithium disilicate (P = .039) and polymer-infiltrated ceramic (P < .001). A significant difference (P = .013) was also found between the lithium disilicate and polymer-infiltrated ceramic., Conclusions: The restorative material had a major effect on the torque maintenance in hybrid abutment restorations supported by offset implant placement, while the titanium base abutment height had no influence on torque maintenance. Compared to lithium disilicate and polymer-infiltrated ceramic materials, monolithic zirconia induced higher torque loss when used as a hybrid abutment restoration.

Statement of Problem: The use of multilayered monolithic zirconia ceramics is becoming popular because it simplifies the production of esthetic restorations. The effect of clinical adjustment on the optical properties of these ceramics, especially strength-gradient zirconia, remains unclear., Purpose: The purpose of this in vitro study was to evaluate the color and translucency of gradient multilayered zirconia brands after grinding and polishing., Material and Methods: Sixty 10×10×1-mm monolithic zirconia specimens were milled from 6 zirconia brands (Ceramill Zolid HT White, Ceramill Zolid HT Preshade, Ceramill Zolid FX Multicolor, VITA YZ XT Multicolor, IPS e.max ZirCAD Prime, and KATANA YML). The zirconia specimens were milled to include all layers of A2 preshaded multilayered zirconia blanks (A2 shade) except Ceramill Zolid HT White and Ceramill Zolid HT Preshade. Ceramill Zolid HT White specimens were milled from a white zirconia blank with subsequent shading. The color coordinates and the relative translucency parameter after glazing and after grinding and polishing were determined with a reflectance spectrophotometer, and the relative translucency parameter and contrast ratio were measured. The differences in color and translucency were calculated. The data were analyzed using 2-way ANOVA and 1-way ANOVA tests followed by the post hoc Tukey test (α=.05)., Results: Statistically significant changes (P<.001) in the color coordinates measured before and after grinding and polishing were detected for each zirconia brand except for the KATANA YML that showed no significant difference (P=.686) in lightness. The highest color difference after grinding and polishing was detected in group KATANA YML. The 2-way ANOVA test showed a statistically significant interaction (P<.001) between the zirconia brand and the grinding and polishing regarding the relative translucency parameter. The zirconia brand had a significant impact on the relative translucency parameter before and after grinding and polishing (both P<.001)., Conclusions: Except for KATANA YML, the color change in multilayered zirconia after clinical adjustment with polishing was not beyond the clinically acceptable limit of the color difference. Although clinical adjustment with polishing reduced the translucency of gradient zirconia, the change in translucency was below the clinically detectable threshold value of the translucency difference., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the impact of various preparation designs and the material type on fracture resistance of minimally invasive posterior indirect adhesive restorations after aging using a digital standardization method., Materials and Methods: One-hundred sixty human maxillary premolars free from caries were assigned into 16 groups (n = 10): bevel design on enamel substrate with mesial box only (VEM), butt joint design on enamel substrate with mesial box only (BEM), bevel design on enamel substrate with mesial and distal box (VED), butt joint design on enamel substrate with mesial and distal box (BED), bevel design on dentin substrate with mesial box only (VDM), butt joint design on dentin substrate with mesial box only (BDM), bevel design on dentin substrate with mesial and distal box (VDD), and butt joint design on dentin substrate with mesial and distal box (BDD). Each group was restored with pressable lithium disilicate (LS 2 ) or disperse-filled polymer composite (DPC) materials. Adhesive resin cement was used to bond the restorations. The specimens were aged for 10,000 thermal cycles (5°C and 55°C), then 240,000 chewing cycles. Each specimen was subjected to compressive axial load until failure. A two-way analysis of variance (ANOVA) test followed by a post hoc Tukey test was used to analyze the data (α = 0.05)., Results: The two-way ANOVA test revealed a significant difference among designs (p < 0.001) and materials (p < 0.001) with no interaction effect (p = 0.07) between the variables. The Post hoc Tukey test revealed that the VEM group exhibited the highest mean fracture resistance value, while the BDM group had the lowest. The LS 2 groups showed the highest mean fracture resistance values. The DPC groups showed a restorable fracture pattern compared to the LS 2 groups., Conclusions: Bevel and butt joint designs with mesial or distal boxes are recommended for conservative posterior indirect adhesive restorations in premolar areas. Enamel substrate improved load distribution and fracture resistance. DPCs have restorable failure patterns, while pressed LS 2 may harm underlying structures., (© 2024 by the American College of Prosthodontists.)

Objectives: The development of dental adhesives with enhanced bond strength has assisted minimally invasive dentistry. The aim of this study was to evaluate the fracture load and stress distribution pattern of two retainer designs for posterior cantilever resin bonded fixed dental protheses (RBFDPs)., Materials and Methods: Forty human mandibular molars were divided into two groups according to the retainer design; lingual coverage (LC) and occlusal coverage (OC) retainers. Each main group was then divided according to the number of inlay boxes (n = 10); one inlay and two inlay boxes. High translucency (3Y) zirconia was used to manufacture all restorations, and a dual-polymerizing adhesive resin cement was used for bonding. All specimens underwent 10,000 cycles of thermocycling (5-55°C), 240,000 cycles of dynamic loading (50 N, descending speed v = 30 mm/second, frequency = 1.6 Hz), and failure load test. Both one-way and two-way ANOVA tests were used to analyze the data. The four models included in the in-vitro study are part of the finite element analysis (FEA). When the restorations failed, maximal principal stress values on restorations, enamel, dentin, and luting resin were investigated., Results: A statistically significant (p = 0.018) higher failure load was recorded for OC1 (627.00 ± 153.4 N) than the other groups; (548.0 ± 75.6 N, 521.20 ± 11.3 N, and 509.20 ± 14.9 N for LC1, LC2, and OC2, respectively). With regard to failure mode, one inlay box designs showed more favorable failure pattern than those of two inlay boxes. FEA showed higher stress magnitude transmitted to the tooth structure in models LC2 and OC2., Conclusions: Lingual coverage and occlusal coverage retainers are promising designs capable to withstand the normal occlusal force for cantilever RBFDP in premolar area. The use of two inlay boxes decreased the fracture load of the two retainer designs and increased the stress transmitted to the tooth and resulted in high incidence of catastrophic failure., Clinical Significance: Monolithic high translucent zirconia RBFDP could be considered as a viable treatment option to substitute missing posterior tooth, with improved esthetics and biocompatibility., (© 2023 Wiley Periodicals LLC.)

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., (© 2023. The Author(s).)

Statement of Problem: Preserving and strengthening the remaining tooth structure of compromised flared root canals after endodontic treatment is challenging., Purpose: The purpose of this in vitro study was to compare the adaptation of milled polymer- infiltrated ceramic, fiber-reinforced composite resin, and high-performance semicrystalline thermoplastic resin posts as used to restore mandibular premolars with flared root canals., Material and Methods: Forty sound mandibular premolars were randomly divided into 4 groups: custom Vita Enamic (CV), custom fiber-reinforced composite resin (CF), custom polyetherketoneketone (CP), and prefabricated fiber (RF) posts. After endodontic treatment, each tooth was sectioned 1.5 mm occlusal to the cementoenamel junction. Then, the post space was prepared and flared, except the RF group, to a depth of 9 mm. The post space in RF group was prepared with a post drill. For the CV, CF, and CP groups, the posts were milled, finished, and cemented to their corresponding teeth. Each tooth was scanned using a microcomputed tomography device, and the reconstructed images were analyzed in mesiodistal, buccolingual, and horizontal planes. The cement thickness, cement volume, and volume of voids were measured. The data were analyzed using 3-way ANOVA (cement thickness) and 2-way ANOVA (cement volume and voids volume) tests followed by the post hoc Tukey test (α=.05)., Results: The 3-way ANOVA test revealed a significant interaction (P<.001) between material type, section, and surface on the cement thickness. The mean cement thickness in the RF group was significantly higher than in the CV group (P=.001) and CF group (P=.005). The least mean cement thickness was at the apical section followed by the cervical and middle sections. Regarding cement volume, the 2-way ANOVA test showed statistically significant interaction between material type and section. The mean cement volume in the RF group was significantly lower than in the CV group (P=.001), CF group (P=.001), and CP group (P=.001). The highest mean cement volume was in the cervical section followed by the middle and apical sections. The 2-way ANOVA test showed statistically significant interaction (P<.001) between material type and section on the volume of voids. Significant differences were found between the mean volume of voids at the cervical and middle sections (P=.001) and the cervical and apical sections (P=.002)., Conclusions: Compared with prefabricated fiber posts, digitally fabricated polymer-infiltrated ceramic and fiber-reinforced composite resin posts had a thinner cement layer with minimal thickness at the apical section. The digitally fabricated posts had higher cement volume, especially at the cervical section, than prefabricated fiber posts. High volumes of voids were related to the cervical section of all tested posts., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Background: The purpose of the current study was to assess the impact of three esthetic CAD/CAM material, titanium base height and their interaction on the retention strength of a hybrid-abutment-crown., Methods: A total of 42 hybrid-abutment crowns with identical external geometries were designed in CAD software to fit two different Ti-Base abutment heights (n = 42/abutment height): either short (S) with 4 mm (n = 21) or long (L) 7 mm (n = 21) height. Each main group was divided into 3 subgroups (n = 7), according to esthetic crown material, Zirconia (Z), Lithium disilicate (L) and Hybrid ceramic (V). A universal primer and an adhesive resin cement were used for bonding according to the manufacturer instructions. Artificial aging in form of water storage (30 days), chewing simulation (50,000-cycles, 49 N, 1.67 Hz) and thermal cyclic (5000 cycles at 5-55 °C) were applied, specimens were pulled-out under tension load in (N) using a universal testing machine. Two and one-way ANOVA and Post Hoc Tukey test were used for statistical analysis., Results: Long lithium disilicate (LL) group showed the highest retention (738.7 ± 178.5) followed by short lithium disilicate (LS) group (688.6 ± 169.9). Meanwhile, short zirconia (ZS) showed the lowest retention strength (231.1 ± 86.9)., Conclusion: CAD/CAM fabricated lithium disilicate hybrid-abutment-crown can be used instead of conventional crowns over implant abutment. Etchable ceramics are recommended as a material of choice for CAD/CAM fabricated hybrid-abutment-crowns instead of zirconia in terms of retention durability., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Purpose: 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.

Objectives: This clinical study aimed to investigate the outcomes and survival rates of different variations of inlay-retained fixed dental prostheses (IR-FDPs) composed of monolithic zirconia ceramic. The IR-FDPs with a single-retainer design were used for replacing missing mandibular second premolars. The research evaluated the effectiveness and longevity of these prostheses in clinical settings., Methods: A total of 30 IR-FDPs (n = 30) were placed for 27 female patients who presented with missing mandibular second premolar teeth. For this study, the mandibular first molar was chosen as a retainer for the cantilever IR-FDPs and the study involved a random assignment of participants into three distinct groups, each comprising 10 individuals (n = 10). The criterion for the grouping was the retainer design: inlay ring (IR), lingual coverage (LC), and occlusal coverage (OC). The three groups included mesial inlay box with the same dimensions (3 mm height, 3 mm width and 2 mm depth). All IR-FDPs were manufactured using monolithic high translucent 3Y zirconia and the connector area to the cantilever pontic was adjusted to dimensions of 3 × 3 mm for all designs. The restorations were bonded using adhesive resin cement. The clinical and radiographic evaluations of the restorations were conducted for a duration of 18 months, following the modified FDI (World Dental Federation) criteria., Results: The restorations were observed in stage one for a period of 18 months. Only one restoration in group LC was debonded after 10 months and re-bonded. The clinical quality of all crowns and the patient's satisfaction were high. No adverse soft tissue reactions around the crowns were observed and only one abutment in group IR was endodontically treated after 12 months., Conclusions: Zirconia cantilever IR-FDPs offer a viable short-term treatment option for replacing missing posterior teeth, providing esthetic and functional benefits while minimizing invasiveness. Over an 18-month observation period, these prostheses have demonstrated a remarkable survival rate of 100% and a success rate of 96.6%. These findings suggest the effectiveness and reliability of zirconia cantilever IR-FDPs as a short-term solution for replacing missing posterior teeth., Clinical Significance: Zirconia cantilever IR-FDPs could present a practical solution for addressing posterior tooth loss, especially in cases where implant placement is not recommended and conventional fixed dental prostheses entail excessive invasiveness., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Objectives: This study aimed to evaluate the maximum bite force (MBF) and satisfaction of patients restored with implants, combined tooth-implants, and teeth-supported monolithic zirconia fixed dental prostheses (FDPs)., Materials and Methods: Thirty partially edentulous patients in need of three units of FDPs in their mandibular posterior region were divided into three equal groups (n = 10) as follows: Group-1 patients received two implants for each at the second premolar and second molar regions, Group-2 patients received one implant for each at the second molar region, and Group-3 patients with missing lower first molar. All the restorations were constructed from monolithic zirconia. Patients were evaluated 1 week after placement of restorations (baseline) and then after 6, 12, and 24-month intervals for MBF using force transducer occlusal force meter and satisfaction (function, esthetic, and overall satisfaction) using a visual analog scale., Results: The mean MBF for Group 1 was higher than Group 2 (p = .044) but not that of Group 3 (p = .923). Additionally, Group 3 displayed a higher MBF than Group 2, although this difference was not statistically significant (p = .096). Concerning patient satisfaction, all study groups reported high levels of satisfaction across all satisfaction elements, and no significant differences were observed between the groups., Conclusion: Within the limitations of this study, it can be concluded that Group 1 gives comparable anticipated treatment outcomes as Group 3 concerning biting force and patient satisfaction. However, Group 2 gives comparable satisfaction results with biting force value within the normal range; thus, it might be used as a treatment option in a specific situation., (© 2023 The Authors. Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.)

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 between 5 and 55°C, followed by cyclic load (50 N) for 240,000 cycles. Each specimen was subjected to a static axial load until fracture using universal testing machine and the fracture load was recorded. The fracture mode studied and recorded. The fracture load results were analyzed using two-way ANOVA test (α = 0.05)., Results: A significant interaction (P = 0.038) of combining MDP-containing zirconia primer and cement type on fracture resistance of monolithic zirconia crown was detected. The mean fracture load values of zirconia crown were significantly influenced by the combined application of the MDP-containing zirconia primer with Calibra Universal (P = 0.01), RelyX U200 (P < 0.001), and Multilink Speed (P = 0.038), while there was no significant difference with Panavia SA Cement Plus (P = 0.660). There was significant difference (F = 20.69, P < 0.001) between the mean fracture loads of groups with self-adhesive cements (C, R, P, and M groups). The highest fracture load was recorded with RZ group (2446.90 ± 126.72 N) while the lowest fracture load was recorded with C group (1623.18 ± 149.86 N)., Conclusions: The self-adhesive resin cement with different acidic functional monomer affects the fracture resistance of monolithic zirconia crown. Application of MDP-containing primer could improve the fracture resistance of monolithic zirconia crown with most self-adhesive cements. The application of an MDP-containing primer had no impact on the fracture resistance of monolithic translucent zirconia crown bonded by MDP-containing self-adhesive resin cement., (© 2023. BioMed Central Ltd., part of Springer Nature.)

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).

Purpose: To evaluate the effect of finish line design (chamfer and feather-edge) and ceramic type on the internal and marginal fits of fixed partial dentures on abutment teeth., Materials and Methods: Two typodont mandibular casts, missing right first premolar tooth, received tooth preparation on canine and second premolar abutments (one cast with chamfer finish line and the other cast with feather-edge finish line). The preparation segment of each typodont model was scanned, 3D printed in resin, and then invested and casted in metal to obtain two metal models. Polyvinyl siloxane impressions were made for the metal models and poured in type IV stone. The stone models (n = 40) were randomly assigned into four groups (n = 10): chamfer finish line with heat-pressed zirconia reinforced lithium disilicate fixed partial denture (CL), chamfer finish line with monolithic zirconia fixed partial denture (CZ), feather-edge finish line with heat-pressed zirconia-reinforced lithium disilicate fixed partial denture (FL), and feather-edge finish line with monolithic zirconia fixed partial denture (FZ). After the fabrication of ceramic restoration, micro-computed tomography was used to evaluate the internal and marginal fits of each fixed partial denture. Data were statistically analyzed with three-way ANOVA (α = 0.05)., Results: There were no significant interactions between preparation type, material type, and tooth type at any of the areas assessed. There was significant difference (p = 0.01) between CZ (59.15 ± 4.6 µm) and FZ (73.6 ± 17.1 µm) groups at the finish line area. Regarding the horizontal marginal discrepancy area, there were significant differences between CZ (62.65 ± 10.5 µm) and FZ (90.05 ± 5.6 µm) groups (p < 0.001), CL (77.45 ± 8.1 µm) and CZ (62.65 ± 10.5 µm) groups (p < 0.001), and FZ (90.05 ± 5.6 µm) and CL (77.45 ± 8.1 µm) groups (p < 0.001). At finish line area, there was a significant difference (p = 0.018) between feather-edge with canine (72.75 ± 13.3 µm) and chamfer with canine (59.05 ± 5.8 µm); however, there was no significant difference (p = 0.774) between feather-edge with premolar (69.45 ± 12 µm) and chamfer with premolar (65.1 ± 7.4 µm). Moreover, there was no significant difference (p = 0.886) between feather-edge with canine and feather-edge with premolar., Conclusions: The internal and marginal fits of the ceramic fixed partial dentures can be affected by the finish line design and ceramic type. The feather-edge finish line had a negative impact on the marginal and internal fits of ceramic fixed partial dentures at certain measurement points. Regarding the effect of finish line design on abutment teeth, the difference in fit was only detected at the finish line area of the anterior abutment (canine) with the feather-edge finish line., (© 2023 by the American College of Prosthodontists.)

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.

Objective: To study the fracture resistance and stress distribution pattern of translucent zirconia and fiber-reinforced composite cantilever resin-bonded fixed dental prostheses (RPFDPs) with two retainer designs., Materials and Methods: Forty human mandibular molars were divided into two groups according to the retainer design. The restorations included a premolar pontic and 2 retainer designs: (D1) inlay ring retainer and (D2) lingual coverage retainer. Each main group was then divided according to the material used (n = 10): zirconia (Z) or fiber-reinforced composite (FRC) (F). Restorations were cemented using dual polymerizing adhesive luting resin. All specimens were thermo-cycled (5-55 °C for 10,000 cycles), then subjected to dynamic loading (50 N, 240,000, and 1.6 Hz) and fracture resistance test. The finite element analysis includes the two models of retainer designs used in the in vitro test. Modified von Mises stress values on enamel, dentin, luting resin, and restorations were examined when the restorations failed., Results: A significantly higher failure load was recorded for zirconia groups (505.00 ± 61.50 and 548.00 ± 75.63 N for D1Z and D2Z, respectively) than for FRC groups (345.00 ± 42.33 and 375.10 ± 53.62 N for D1F and D2F, respectively) (P = 0.001). With regard to failure mode, D2 showed a more favorable failure pattern than D1. Model D2 resulted in lower stresses in tooth structure than model D1, and zirconia transmitted more stresses to the tooth structure than FRC., Conclusions: The lingual coverage retainer (D2) enhanced the biomechanical performance of the restoration/tooth complex. Considering the failure mode and tooth stress, FRC is a promising treatment option when constructing a cantilever RPFDP., Clinical Relevance: Dentists should be aware of the biomechanical behavior during the selection of the material and for the replacement of a single missing mandibular premolar tooth with minimally invasive RBFDP., (© 2022. The Author(s).)

Purpose: To 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 Methods: Fifty 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 < 0.001)., Results: A statistically significant difference (p < 0.001) was found between all groups except between IR and LC and between OW and TW designs, with the highest mean failure load detected for OC (534.70 N) and the lowest detected for OW (129.80 N). With regard to failure mode, OW, TW, and LC showed more incidences of favorable failure patterns than IR and OC designs. FEA showed that FRC transmitted low stresses in tooth structure and high stresses to the luting resin., Conclusions: LC and OC designs can be used to design cantilever RBFDPs in premolar area. IR design transmitted more stresses to the tooth structure and resulted in 30% catastrophic failure. OW and TW were below the normal occlusal force and should be carefully used., (© 2022 by the American College of Prosthodontists.)

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 found between ceramic types and cement types after cementation, and after soaking in coffee was found. All groups showed a clinically acceptable difference in translucency parameters after soaking in coffee. The resin cement affects the color and translucency of ceramic laminate veneers used for diastema closure, and ceramic laminate veneers bonded with Variolink Esthetic LC resin cement are more translucent, while ceramic laminate veneers bonded with RelyX Veneer resin are more resistant to coffee staining. The lithium disilicate laminate veneer is more resistant to coffee staining than zirconia reinforced lithium silicate and translucent zirconia laminate veneers used for diastema closure., (© 2022. The Author(s).)

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., (© 2022. The Author(s).)

Background: The purpose of this in vitro study was to assess the influence of different cement systems with different ceramic primers on the retention strength of zirconia crowns., Methods: Thirty extracted molars were prepared with flat occlusal surfaces, 20 degrees taper, and 3 mm axial wall height. A zirconia crown with an occlusal bar was fabricated for each tooth. All specimens were divided (n = 10) into; Group M: Multilink Speed/Monobond N, Group P: Panavia V5/Clearfil Ceramic Primer Plus, Group D: Duo-Link universal/Z-Prime Plus. The intaglio surfaces of crowns were air-abraded using 50 µm alumina at 2.5 bar for 10 s. Then each crown was cemented onto its corresponding tooth. All specimens were thermocycled for 10,000 cycles between 5 and 55 °C. Each crown was subjected to gradually increasing vertical load along the path of insertion through hooks engaging the occlusal bar using a universal testing machine until failure. The force at dislodgment was recorded and retention strength was calculated for each specimen. The failure modes were recorded for each specimen. The data were statistically analyzed using one way ANOVA test followed by Tukey HSD test (α = .05)., Results: Group D showed lowest strength (1.42 ± 0.23 MPa) and differed significantly (P < .001) from Group M (2.71 ± 0.45 MPa) and Group P (2.47 ± 0.41 MPa). There was no significant difference (P = .34) between Group M and Group P. The failure modes for Groups M and Group P were mainly cohesive, while Group D showed adhesive failure., Conclusions: The retention strength of zirconia crowns was improved with Multilink Speed and Panavia V5 cement systems, while the use of the Duo-Link Universal cement system only showed half of those retention strength values., (© 2022. The Author(s).)

This paper assesses the effect of cement type and cement preheating on the marginal and internal fit of lithium disilicate single crown. Methods: 40 maxillary premolars were selected, restored with lithium disilicate single crowns. Teeth were randomly assigned into four groups (n = 10) based on cement type (Panavia SA or LinkForce) and preheating temperature (25 °C or 54 °C). After fabrication of the restoration, cements were incubated at 25 °C or 54 °C for 24 h, and each crown was cemented to its corresponding tooth. After 24 h, all specimens were thermally aged to (10,000 thermal cycles between 5 °C and 55 °C), then load cycled for 240,000 cycles. Each specimen was then sectioned in bucco-palatal direction and inspected under a stereomicroscope at x45 magnification for marginal and internal fit evaluation. The data were statistically analyzed (significance at p ≤ 0.05 level). Re sults: At the mid-buccal finish line, mid-buccal wall, palatal cusp, mid-palatal wall, mid-palatal finish line, and palatal margin measuring points, there was a significant difference ( p ≤ 0.05) between the lithium disilicate group cemented with Panavia SA at 25 °C and the group cemented with LinkForce at 25 °C, while there was no significant difference ( p > 0.05) at the other points. At all measuring points, except at the palatal cusp tip ( p = 0.948) and palatal margin ( p = 0.103), there was a statistically significant difference ( p ≤ 0.05) between the lithium disilicate group cemented with Panavia SA at 54 °C and the group cemented with LinkForce at 54 °C. Regardless of cement preheating, statistically significant differences were found in the buccal cusp tip, central groove, palatal cusp tip, and mid-palatal wall ( p ≤ 0.05) in the lithium disilicate group cemented with Panavia SA at 25 °C and 54 °C, as well as the mid-palatal chamfer finish line and palatal margin in the LinkForce group cemented with Panavia SA at 25 °C and 54 °C. At the other measurement points, however, there was no significant difference ( p > 0.05). Conclusions: The type of resin cement affects the internal and marginal fit of lithium disilicate crowns. At most measuring points, the cement preheating does not improve the internal and marginal fit of all lithium disilicate crowns.

This study assesses the effect of the material type (lithium disilicate, zirconia, and polymer-infiltrated ceramic) and dental bonding substrates (dentin, dentin with intra-coronal cavity, and dentin with composite filling) on the fracture resistance and failure mode of molars restored by occlusal veneers., Methods: Ninety occlusal veneers, fabricated from either lithium disilicate, zirconia, or polymer-infiltrated ceramic, were adhesively bonded to teeth prepared with either dentin, dentin with intra-coronal cavity, or dentin with composite filling. All specimens were thermally aged (5000 cycles), then load cycled (120,000 cycles). Each specimen was subjected to a compressive load through fracture, then was examined (×20) to identify the fracture type. Data were statistically analyzed., Results: Material type and dental substrate had no significant effect on the fracture resistance of adhesively retained occlusal veneer restorations. For each material, no significant differences were found between veneers bonded to dentin, dentin with intra-coronal cavity, and dentin with composite filling. Additionally, within each bonding substrate, there were no significant differences between lithium disilicate, zirconia, and polymer-infiltrated ceramic veneers. The adhesive failure was recorded mainly with zirconia occlusal veneer restorations., Conclusions: Considering the fracture results, lithium disilicate, zirconia, and polymer-infiltrated ceramic occlusal veneers perform well whatever the type of dental bonding surface. When the dental bonding surface varies, different occlusal veneer materials should be considered. Occlusal veneers bonded to dentin, dentin with composite filling, or dentin with an intra-coronal cavity exhibited a fracture resistance exceeding the average human masticatory forces in the molar area.

This paper assesses the impact of preheating of adhesive cement on the fracture resistance of lithium disilicate and zirconia restorations. Methods: A total of 80 human maxillary premolar teeth were assigned into 8 groups ( n = 10) according to material type (either lithium disilicate or zirconia) and type of resin cement (either LinkForce or Panavia SA) with preheating temperature at 54 °C or at room temperature (25 °C). Teeth were prepared and restored with either lithium disilicate or zirconia restorations. After cementation, specimens were thermal cycled (10,000 cycles, 5 °C/55 °C), then load cycled for 240,000 cycles (50 N). Each specimen was statically loaded until fracture and the load (N) at fracture was recorded, then the failure mode was detected. Statistical analysis of data was performed ( p ≤ 0.05). Results: There was no significant difference ( p = 0.978) in fracture mean values between LinkForce and Panavia SA. Statistically significant difference ( p = 0.001) was revealed between fracture resistance of lithium disilicate restorations cemented with LinkForce at 25 °C and at 54 °C; however there was no significant difference ( p = 0.92) between the fracture resistance of lithium disilicate restorations cemented with Panavia SA used at 25 °C and at 54 °C. Regarding the interaction between ceramic material, cement type, and cement preheating, there was no significant effect ( p > 0.05) in fracture resistance. The cement type does not influence the fracture resistance of ceramic restorations. Preheating of resin cement has negatively influenced the fracture resistance of all tested groups, except for lithium disilicate cemented using LinkForce cement.

Purpose: To assess the impact of abutment angulation on loosening torque, torque loss, and percentage of torque loss in the prosthesis and abutment screws after aging of the implant-supported prosthesis., Materials and Methods: Fifty epoxy maxillary casts with missing central, lateral, and canine teeth were used, and each cast received two implants. All casts were divided into five groups (n = 10): (1) both implants received straight abutments (0-0); (2) the central implant received a straight abutment and the canine implant received a 17.5-degree angled abutment (0-17.5); (3) the central implant received a straight abutment and the canine implant received a 35-degree angled abutment (0-35); (4) both implants received 17.5-degree angled abutments (17.5-17.5); and (5) both implants received 35-degree angled abutments (35-35). For each cast, a three-unit zirconia restoration was fabricated, and a torque meter was utilized to tighten the abutment screw (25 Ncm) and prosthesis screw (18 Ncm). The reverse torque value was recorded for each screw. All restorations were subjected to 3,500 thermal cycles between 5°C and 55°C and load cycled for 150,000 cycles with 50-N load. After the loosening torque was measured for each screw, the torque loss and percentage of torque loss were calculated., Results: There was a statistically significant difference in the torque loss of the central prosthesis screw (P < .001) and canine prosthesis screw (P < .001) between study groups. The 35-35 group showed the highest percentage of torque loss, while the 0-0 group showed the lowest value. A significant difference was found regarding the torque loss of the central abutment screw (P < .001) and canine abutment screw (P < .001). The abutment screws of the 35-35 group showed the highest percentage of torque loss, while the 0-0 groups showed the lowest percentage of torque loss., Conclusion: Screw loosening of the prosthesis and abutment screws increases with increasing abutment angulation after aging. In the same fixed prosthesis, the torque loss in the prosthesis and abutment screws was higher in canine screws employing different angled abutments.

Objective: Optimizing monolithic zirconia (ZrO 2 ) 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 ZrO 2 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 ZrO 2 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., (Copyright © 2021 The Academy of Dental Materials. All rights reserved.)

Background: The aim of this study was to test the impact of hot acids etching and two types of adhesive cement on the retention of zirconia crowns., Methods: Forty maxillary premolars were prepared, and zirconia crowns were designed and fabricated with proximal extensions, then divided into 4 groups (n = 10). Group AP; the crowns were air-abraded and cemented using Panavia SA Cement. Group AL; the crowns were air- abraded and cemented using GC LinkForce. Group AHP; the crowns were air-abraded, etched with the hot acids (48% hydrofluoric acid and 69% nitric acid), and cemented using Panavia SA Cement. Group AHL; the crowns were air-abraded, etched with the hot acids, and cemented using GC LinkForce. Each zirconia crown was pre-treated and bonded to its corresponding tooth. After thermocycling (5-55 °C/10,000), the retention test was performed and the load required to dislodge the crown was reported in Newton (N), and mode of failure was recorded. The retention strength (MPa) was calculated for each tested variable and statistically analyzed., Results: Group AHP showed the highest mean value of the retention strength, followed by group AP then group AHL. Group AL showed the lowest value. A statistically significant effect ( p = 0.001) of the hot acids etching on the retention of zirconia crown was found. Also, there was a significant effect ( p = 0.000) of the cement type. The interaction between surface treatment and the cement type has no significant impact ( p = 0.882). The main mode of failure for Panavia SA Cement is mixed mode of failure, while for G-CEM LinkForce is adhesive failure. Conclusions : Hot acid etching pre-treatment improved the retention of zirconia crown. Usage of Panavia SA Cement with hot acids etching is effective can be used for adhesive cementation of zirconia crown.

Statement of Problem: Chairside and laboratory adjustments of translucent monolithic zirconia restorations sintered by short cycles are inevitable. Therefore, the optical properties of these materials should be evaluated under conditions similar to those in the oral environment., Purpose: The purpose of this in vitro study was to evaluate the color stability and the translucency changes of translucent monolithic zirconia after the sintering procedure, simulated clinical adjustment, and coffee thermocycling., Material and Methods: Eighty monolithic zirconia disks (diameter: 10 mm; thickness: 1 mm) were milled from 4 zirconia brands (Zolid FX Preshaded, Zolid FX White, DD Cubex 2 , and DD Bio ZX 2 ). Two sintering procedures (standard or speed) were performed for each zirconia brand. The color coordinates and the translucency after sintering, clinical adjustment, and after 5000 cycles in a coffee solution were analyzed with a reflectance spectrophotometer, and the translucency parameters and contrast ratio were measured. The color differences and the translucency variations were calculated for each tested variable and statistically analyzed with 2-way ANOVA and pairwise comparison (α=.05)., Results: Both clinical adjustment procedure and coffee thermocycling had significant influence on color differences (P<.001). For translucency, 2-way ANOVA showed a significant interaction between sintering procedure and zirconia brand after coffee thermocycling (P<.001) while no significant interaction was recorded after the clinical adjustment procedure (P=.247). For all evaluated groups, the translucency parameter values decreased after either clinical adjustment procedure or coffee thermocycling (P<.001). For tested zirconia, group DD Cubex 2 showed higher translucency parameter regardless of the variables tested., Conclusions: The color and the translucency of the translucent zirconia can be affected by the type of the zirconia brand and the sintering protocol. Furthermore, the color and the translucency were affected by both the clinical adjustment procedure and the coffee thermocycling, but not beyond the clinically acceptable limit of the color difference., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objective:  The aim of this study was to assess the impact of implant platform diameters on ultimate force to failure of zirconia abutments with different angulation., Materials and Methods:  Forty-two zirconia abutments with either 0 degree (ST) or 15-degree (AN) angulation were assembled on tapered internal connection titanium implants (Direct's Legacy; 13 mm Implant Direct, LLC, Las Vegas, United States) with a platform diameter of Ø3.0, Ø3.5, and Ø4.5 mm (14 per group). Zirconia crowns (Ceramill Zolid; Amann Girrbach GmbH) were fabricated and cemented using self-adhesive resin cement (MaxCem Elite, Kerr). The specimens were thermomechanically loaded (TCML= 6,000 cycles of 5 to 50°C for 2 minutes/cycle followed by cyclic loading 600,000 cycles) followed by static loading until fracture. The data of load (N) at which fracture occurred were statistically analyzed by using Kruskal-Wallis analysis of variance and Mann-Whitney U tests at 5% significance level., Results:  Higher load to fracture was reported for zirconia crowns in straight abutments groups and a platform of 4.5, 3.5, and 3 mm diameter was 438.2± 85.4, 345.5± 71.3, and 331.1± 59.1 N, respectively. However, the groups restored with zirconia crowns in angulated abutments groups and a platform of 4.5, 3.5, or 3 mm diameter showed a fracture load of 411.4 ± 49.8, 354.2 ± 52.5, and 302.8 ± 52.5 N, respectively., Conclusion:  Straight and angulated zirconia abutments presented similar load to fracture on 3 and 3.5 mm platform diameters yet being significantly less for 4.5 mm diameter., Competing Interests: None declared.

Purpose: To evaluate the tightening torque maintenance with zirconia, lithium disilicate, and polyetheretherketone (PEEK) hybrid-abutment-crowns after thermal aging, in addition to assess the fracture resistance of hybrid-abutment-crowns fabricated with different materials., Materials and Methods: Thirty implants were restored with identical hybrid-abutment-crowns, resembling the maxillary first premolar, fabricated from zirconia (Zr), lithium disilicate (L2), or ceramic-reinforced PEEK (PE). The three groups (n = 10) were constructed utilizing a Ti-base. After bonding, each restoration was secured in its respective implant with a torque of 25 Ncm. All restorations were subjected to thermal aging for 7000 cycles. The loosening torque was assessed utilizing the digital torque meter. Each restoration was subjected to fracture testing and the mode of failure was determined., Results: Zr group displayed the highest mean torque loss value (2.70 ± 0.59 Ncm) with the mean loosening torque value of 22.38 ± 0.68 Ncm. PE group displayed the lowest mean torque loss (2.55 ± 0.50 Ncm) with mean loosening torque value of 22.61 ± 0.59 Ncm. There was no significant difference between study groups regarding loosening torque (p = 0.68), torque loss (p = 0.80), and percentage of torque loss (p = 0.79). There was significant difference regarding the mean fracture load value between Zr and PE groups. However, there was no significant difference (p = 0.05) regarding mean fracture load value between L2 and PE groups., Conclusion: The hybrid-abutment-crown material does not affect the torque maintenance after thermal aging. Based on fracture load, zirconia hybrid-abutment-crown can be used, while lithium disilicate and PEEK hybrid-abutment-crowns may cautiously serve in premolar region.

Purpose: To assess the 10-year clinical retention and survival rates of metal-ceramic (MC) and all-ceramic (AC) cantilever resin-bonded fixed dental prostheses (CRBFDPs)., Materials and Methods: Forty CRBFDPs constructed from either cobalt-chromium ceramic (MC group; n = 20) or glass-infiltrated alumina ceramic (AC group; n = 20) were placed in 40 patients between August 2007 and December 2009. After baseline recordings, the patients were followed up using modified United States Public Health Services (USPHS) criteria after 6 months and thereafter annually for 10 years. Data were statistically analyzed using Kaplan-Meier estimation with log-rank (Mantel-Cox) test., Results: The 10-year clinical retention rate was 95.0% in the MC group and 70% in the AC group. The difference was statistically significant (P = .02, log-rank test). Three all-ceramic CRBFDPs fractured at 6, 12, and 84 months after insertion. No statistically significant difference in survival rate was observed between the MC and AC groups over the 10 years of clinical observation (MC: 100%; AC: 85%; P = .075) (Kaplan-Meier method, confidence interval = 92.5% to 97.5%)., Conclusion: Although glass-infiltrated alumina ceramic anterior CRBFDPs exhibited a lower clinical retention rate compared to metal-ceramic CRBFDPs, the debonded prostheses were recemented and continued in function over the observation period. Additionally, an acceptable 10-year clinical longevity was recorded.

Purpose: To analyze the impact of microthreads on the stresses generated in peri-implant bone surrounding reduced-diameter zirconia and titanium implants under loading., Materials and Methods: Two custom-made zirconia implants, microthreaded or smooth neck, and two titanium replicas were made. Strains were recorded in the peri-implant region under 200-N vertical load. Two three-dimensional finite element models were created. Zirconia and titanium implants were tested under 200-N vertical load and 150-N oblique load at 30, 45, and 60 degrees., Results: The lowest peri-implant strain (40 ± 6 με) under vertical load was related to the microthreaded zirconia implant. Oblique load showed higher von Mises stress on bone in comparison with vertical load. The von Mises stress increased by increasing the load angle by approximately 2 MPa per degree. Under oblique load, implants showed more stress in peri-implant bone and the implant itself. On the other hand, total strains were within physiologic limits in all tested cases., Conclusion: Stresses within the peri-implant cortical bone around the reduced-diameter implant with microthreads appeared to be superior compared with the smooth-neck one. Reduced-diameter zirconia implants induced less stress on bone in comparison with the titanium implants, suggesting that zirconia is a feasible alternative for titanium.

The purpose of this study was to assess the effect of pre-etching time and material on shear bond strength (SBS) of self-adhesive resin cements to eroded and sound enamel. Eroded enamel specimens were assigned into 5 groups (n=20 each) based on enamel surface treatment as follow: Group N, eroded enamel (without surface pre-treatment); Group PH15, 35% H 3 PO 4 etching for 15 s; Group PH30, 35% H 3 PO 4 etching for 30 s; Group L30, 20% lactic acid etching for 30 s and Group L60, 20% lactic acid etching for 60 s.Composite blocks were fabricated and cemented to enamel surfaces with one of two self-adhesive cements. Notched-edge SBS was assessed. Bond strength of self-adhesive cement to eroded enamel surface significantly enhanced following application of 20% lactic acid for 30 s.

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.