IPS e.max for All-Ceramic Restorations: Clinical Survival and Success Rates of Full-Coverage Crowns and Fixed Partial Dentures

The impact of Streptococcus mutans biofilms on the color stability and topographical features of three lithium disilicate ceramics

PURPOSE

Secondary caries around ceramic restorations is the most common reason for the replacement of fixed dental prostheses (FDPs). Therefore, it is important to examine the susceptibility of different ceramic materials to biofilm formation. This study aimed to evaluate biofilm development and associated roughness and color alterations in three lithium disilicate ceramics: Emax CAD (EC), Emax Press (EP), and LiSi Press (LP).

MATERIALS AND METHODS

Streptococcus mutans biofilms were grown on the three ceramics (n = 10 per group) for 7 days. Surface roughness values and color alteration were assessed before and after the biofilm using a non-contact profilometer and spectrophotometer, respectively. Biofilm growth was evaluated using colony-forming units (CFUs) and scanning electron microscope (SEM) images. The data were analyzed using one-way ANOVA and Tukey tests.

RESULTS

There was a significant (p ≤ 0.001) growth of S. mutans colonies on EC (6.75 ± 0.56) and EP (6.72 ± 0.54) specimens compared to LP, which showed no biofilm growth. The change in average surface roughness (∆Ra, nm) was significantly lower (p < 0.001) in the EC specimens (0.029 ± 0.003) compared to the EP (0.055 ± 0.012) and LP (0.041 ± 0.010). When the changes in the Rv and Rt values were investigated, no significant difference was observed among the groups. Following the biofilm challenge, the change in color (∆E00) was significantly lower (p = 0.005) in the LP group (1.68 ± 1.45) compared to the EC group (3.89 ± 1.50) and no significant difference was observed between the EP group (2.74 ± 1.01) and the other two ceramics (p ≥ 0.05).

CONCLUSION

LP ceramics exhibited superior resistance to S. mutans biofilm formation and associated changes in surface roughness and color compared to the Emax CAD and Emax Press ceramics. These findings suggest that the LiSi Press material may be more favorable to mitigate the risk of secondary caries.

Comparative Invitro Testing of the Tensile Bond Strength Under Artificial Aging Between Different Lithium Disilicate Ceramics to Composite Substrate: A Novel Methodology

Objective The purpose of this study is to compare the tensile bond strength values to composite substrate pre- and post-aging between IPS E.max CAD and Initial LiSi. Methods The study utilized four blocks of IPS E.max CAD LT/B1 C14 (Ivoclar Vivadent, Liechtenstein, Germany) (referred to as E) and four blocks of Initial LiSi LT/B1 (GC, Tokyo, Japan) (referred to as L). These blocks were milled to produce 76 ceramic bars measuring 2 mm × 2 mm × 10 mm (E = 38, L = 38/n = 19). After acid etching with hydrofluoric acid (BISCO, Schaumburg, IL, USA) and silane application (BIS-SILANE, BISCO), the specimens were embedded in putty (Express STD, 3M, Decatur, AL, USA) to create a mold for the resin cement (RelyX U200, 3M). Subsequently, one group of each brand underwent mechanical tensile testing (E0 and L0), while the other groups were subject to tensile testing after artificial aging involving 500 thermal cycles between 5 and 55°C (E5 and L5). The mean tensile strength for each group (E0, E5, L0, and L5) was determined using the Brown-Forsythe one-way ANOVA and Tamhane's post hoc tests. Results Initial LiSi showed a superior pre-aging mean (11.7 MPa). However, both materials had identical post-aging means (7.6 MPa). There were no statistically significant differences, except between the dependent Initial LiSi groups (L0-L5). Most failure modes were mixed (cohesive cement and adhesive). There were no cohesive failures on the cement side except in three specimens of Initial LiSi post-aging. Conclusion The tested conditions have shown that Initial Lisi exhibited the highest pre-aging mean; however, it exhibited inferior bond stability under aging conditions compared to IPS E.max CAD. Analyzing the microstructure before and after aging may provide insights into the greater decrease in bond strength observed in the Initial LiSi specimens.

Effect of multiple firings on optical and mechanical properties of Virgilite-containing lithium disilicate glass-ceramic of varying thickness

OBJECTIVES

To investigate the effect of multiple firings on color, translucency, and biaxial flexure strength of Virgilite-containing (Li0.5Al0.5Si2.5O6) lithium disilicate glass ceramics of varying thickness.

MATERIALS AND METHODS

Sixty discs were prepared from Virgilite-containing lithium disilicate blocks. Discs were divided according to thickness (n = 30) into T0.5 (0.5 mm) and T1.0 (1.0 mm). Each thickness was divided according to the number of firing cycles (n = 10); F1 (Control group): 1 firing cycle; F3: 3 firing cycles, and F5: 5 firing cycles. The discs were tested for color change (ΔE00) and translucency (TP00) using a spectrophotometer. Then, all samples were subjected to biaxial flexure strength testing using a universal testing machine. Data were collected and statistically analyzed (α = 0.5). For chemical analysis, six additional T0.5 discs (2 for each firing cycle) were prepared; for each firing cycle one disc was subjected to X-ray diffraction analysis (XRD) and another disc was subjected to Energy dispersive X-ray spectroscopy (EDX) and Scanning electron microscope (SEM).

RESULTS

Repeated firing significantly reduced the translucency of F3 and F5 compared to F1 in T0.5 (p < 0.001), while for T1.0 only F5 showed a significant decrease in TP00 (p < 0.001). For ΔE00, a significant increase was recorded with repeated firings (p < 0.05) while a significant decrease resulted in the biaxial flexure strength regardless of thickness.

CONCLUSIONS

Repeated firings had a negative effect on both the optical and mechanical properties of the Virgilite-containing lithium disilicate glass ceramics.

CLINICAL RELEVANCE

Repeated firings should be avoided with Virgilite-containing lithium disilicate ceramics to decrease fracture liability and preserve restoration esthetics.

Effect of surface pretreatment and artificial aging on the retention of lithium disilicate crowns cemented to zirconia implant abutments

STATEMENT OF PROBLEM

Recent advancements in restorative dentistry have seen an increase in the use of ceramic restorations and zirconia implant abutments. However, how the pretreatment of a zirconia abutment and different artificial aging protocols affect the bond strength of a cemented, monolithic lithium disilicate crown is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of surface pretreatment on the retentive strength of milled lithium disilicate crowns bonded to custom zirconia implant abutments with different resin cements after thermocycling and long-term aging.

MATERIAL AND METHODS

A total of 144 crowns (n=8) were milled and bonded to 144 abutments. In the experimental groups, 72 abutments were airborne-particle abraded with 50-μm aluminum oxide before bonding. All specimens were stored at 37 °C in 100% humidity for 24 hours. Forty-eight specimens were subjected to thermocycling, and another 48 were subjected to aging for 6 months. Retentive strength was measured by using a pull-off test with a universal testing machine. Retentive strength values were calculated and compared with 3-way analysis of variance and a Tukey-Kramer post hoc test (α=.05).

RESULTS

In the 24-hour aging group, retention for all experimental groups was significantly higher (P<.05) than for the control group, except for Panavia 21 with Clearfil Ceramic Primer. In the thermocycling and long-term aging groups, all cements in the experimental group displayed significantly higher retention than the control. The airborne-particle abrasion of custom zirconia implant abutments with 50-μm aluminum oxide before bonding to lithium disilicate crowns significantly increased the bond strength of the Multilink Hybrid Abutment with Monobond Plus and RelyX Ultimate with Scotchbond Universal cements after 24-hour aging, but not of Panavia 21 with Clearfil Ceramic Primer.

CONCLUSIONS

Airborne-particle abrasion significantly increased the bond strength of all 3 cements after thermocycling and long-term aging.

Recent advances in glass-ceramics: Performance and toughening mechanisms in restorative dentistry

The use of glass-ceramics in the medical field has grown significantly since the 1980s. With excellent aesthetic properties, semi-translucency, outstanding mechanical properties, corrosion resistance, wear resistance and great biocompatibility and workability glass-ceramics is one of the most commonly used materials in restorative dentistry and is widely used in veneers, inlays, onlays, all-ceramic crowns, and implant abutments. This review provides an overview of the research progress of glass-ceramics in restorative dentistry, focusing on the classification, performance requirements, toughening mechanisms and their association with clinical performance, as well as the manufacturing and fabrication of glass-ceramics in restorative dentistry. Finally, the developments and prospects of glass-ceramics in restorative dentistry are summarized and discussed.

Retrospective clinical study on the performance and aesthetic outcome of pressed lithium disilicate restorations in posterior teeth up to 8.3 years

OBJECTIVES

Evaluation of cumulative survival and complication rate of monolithic lithium disilicate inlays and partial crowns performed by supervised undergraduate students up to 8.3 years of clinical service.

MATERIALS AND METHODS

In this retrospective clinical study 143 lithium disilicate posterior restorations (IPS e.max Press) were examined according to the FDI criteria. A standardised questionnaire was used to determine patient satisfaction. The aesthetic outcome was evaluated by dentists and dental technicians using intraoral photographs. Data were descriptively analysed. Cumulative survival and success rates were calculated using Kaplan-Meier estimation.

RESULTS

The cumulative survival rate of lithium disilicate restorations was 97.5% after a mean service time of 5.9 years and 95.0% after 8.3 years. The cumulative success rate decreased from 94.4% after 5.9 years to 30.7% after 8.3 years. Repairs were required for 7 restorations (4.9%), and 5 (3.5%) were classified as failures. The results of the questionnaire indicate a high level of patient satisfaction. The subjective aesthetics were assessed more critically by dental technicians compared to dentists.

CONCLUSION

Lithium disilicate posterior restorations survived successfully up to 8.3 years when carried out by undergraduate students.

CLINICAL RELEVANCE

Pressed lithium disilicate glass ceramic inlays and partial crowns are reliable treatment options in posterior teeth.

Fatigue resistance of anterior monolithic crowns produced from CAD-CAM materials: An in vitro study

STATEMENT OF PROBLEM

Lithium disilicate and 5 mol% yttria partially stabilized zirconia (5Y-PSZ) are commonly used for anterior restorations. However, studies comparing the durability of 5Y-PSZ and lithium disilicates are sparse.

PURPOSE

The purpose of this in vitro study was to investigate the fracture load of anterior monolithic crowns made of 2 lithium disilicates and a 5Y-PSZ under dynamic loading.

MATERIAL AND METHODS

Titanium abutments of the maxillary incisors were prepared (N=48, 8 for each group). Monolithic anterior crowns were made from the lithium disilicates (e.max CAD, Rosetta SM) and 5Y-PSZ (Katana UTML). After cementation, the specimens were stored in water for 24 hours and then thermocycled 10 000 times. Dynamic loading (70 N, 200 000 cycles, 1 Hz) was applied to half the specimens. The fracture load was measured by using a universal testing machine. The fracture patterns were analyzed and fractography applied. Two-way ANOVA and the Fisher exact test were used for statistical analysis (α=.05).

RESULTS

The material and dynamic loading affected the fracture load of the anterior monolithic crowns (P<.05). However, there was no interaction between the material and the dynamic loading (P=.079). Both lithium disilicates had higher fracture loads than 5Y-PSZ (P<.05). The fracture load of each specimen was reduced after dynamic loading (P<.05). Lithium disilicate showed marginal and bulk fractures, and 5Y-PSZ presented catastrophic fractures (P<.001).

CONCLUSIONS

5Y-PSZ materials with large grains and low flexural strength may be less resistant to fractures under dynamic loading than lithium disilicates.

Load-bearing capacity and wear characteristics of short fiber-reinforced composite and glass ceramic fixed partial dentures

The aim of this study was to evaluate load-bearing capacity and wear performance of experimental short fiber-reinforced composite (SFRC) and conventional lithium-disilicate CAD/CAM fabricated fixed partial dentures (FPDs). Two groups (n = 12/group) of three-unit CAD/CAM fabricated posterior FPDs were made. The first group used experimental SFRC blocks, and the second group fabricated from lithium-disilicate (IPS e.max CAD). All FPDs were luted on a zirconia testing jig with dual-curing resin cement. Half of FPDs per group were quasi-statically loaded until fracture. The other half experienced cyclic fatigue aging (100.000 cycles, Fmax = 500 N) before loading quasi-statically until fracture. Fracture mode was examined using SEM. Wear test was performed using 15,000 loading cycles. Both material type and aging had a significant effect on the load-bearing capacity of FPDs. Experimental SFRC CAD without fatigue aging had significantly the highest load-bearing capacity (2096 ± 149N). Cyclic fatigue aging decreased the load-bearing capacity of the SFRC group (1709 ± 188N) but increased it for the lithium-disilicate group (1546 ± 155N). Wear depth values of SFRC CAD (29.3μm) were significantly lower compared to lithium-disilicate (54.2μm). Experimental SFRC CAD demonstrated the highest load-bearing capacity before and after cyclic fatigue aging, and superior wear behavior compared to the control material.

The Toothbrushing Effects on Surface Properties and Color Stability of CAD/CAM and Pressable Ceramic Fixed Restorations-An In Vitro Study

Pressable ceramic restorations have been introduced and investigated, and found comparable to CAD/CAM ceramic in terms of mechanical properties; however, the effect of toothbrushing on the pressable ceramic has not been thoroughly investigated. The objective of the current study was to assess the effect of artificial toothbrushing simulation on the surface roughness, microhardness, and color stability of different ceramic materials. Three lithium disilicate-based ceramics (IPS Emax CAD [EC], IPS Emax Press [EP]; (Ivoclar Vivadent AG), and LiSi Press [LP] (GC Corp, Tokyo, Japan)) were examined. For each ceramic material, eight bar-shaped specimens were prepared and subjected to 10,000 brushing cycles. Surface roughness, microhardness, and color stability (∆E) were measured before and after brushing. Scanning electron microscopy (SEM) was used for surface profile analysis. The results were analyzed using one-way ANOVA, Tukey's post hoc test, and paired sample t-test α = 0.05. The findings revealed a non-significant decrease in the surface roughness of EC, EP, and LP groups (p > 0.05), and both LP and EP have the lowest surface roughness values (0.64 ± 0.13, 0.64 ± 0.08 µm) after brushing, respectively. Toothbrushing showed a decrease in the microhardness of the three groups: EC and LP, p < 0.001; EP, p = 0.012). EP showed the lowest hardness value after brushing (862.45 ± 273.83). No significant changes (∆E) were observed in all groups (p > 0.05); however, the EC group was found to be considerably affected by color changes, in comparison to the EC and LP groups. Toothbrushing had no effect on surface roughness and color stability of all tested materials, but it decreased the microhardness. Material type, surface treatments, and glazing of ceramic materials contributed to the surface changes in the ceramic materials, necessitating further investigations in terms of the toothbrushing effect with different glazing as variables.

Fracture resistance of pressed ZLS crowns versus pressed LD crowns under thermo-mechanical cycling

The aim of this study was conducted to assess the fracture resistance of zirconia reinforced lithium silicate all ceramic material "Celtra Press" compared to lithium disilicate one "IPS e-max Press" under simulated oral conditions. Fourteen ceramic crowns were fabricated on epoxy dies which were duplicated from stainless steel master die and divided into two equal groups (n=7) according to the material of construction; Group A: Crowns fabricated with IPS e-max Press material and Group B: Crowns fabricated with Celtra Press material. The crowns were then cemented onto their corresponding dies with a self-adhesive resin cement and subjected to thermocycling and cyclic loading. Then they were loaded to fractur in a universal testing machine. The results were tabulated and statistically analyzed using Kolmogorov-Smirnov and Shapiro-Wilk tests. Student t-test used to compare mean values. The significance level was set at P ≤ 0.05 and 95% Confidence interval. Statistical analysis was performed using Graph Pad Instat (Graph Pad, Inc.) software for windows. The mean ± SD values of fracture resistance were recorded for lithium Disilicate group (1706.01 ±154.32 N) meanwhile the mean ± SD value recorded with celtra group were (1550.67±196.71 N). Zirconia reinforced lithium silicate ceramic crowns produced comparable fracture resistance values to lithium disilicate ceramic crowns and both tested materials are within the clinically acceptable values in the posterior area.

The 3-year cumulative survival rates of posterior monolithic zirconia crowns and their antagonist teeth, and their influencing factors

PURPOSE

The purpose of this study was to evaluate the 3-year cumulative survival rates of posterior single monolithic zirconia crowns (MZCs) and their antagonists, and to analyze the influencing factors.

METHODS

The clinical outcomes of posterior single MZCs and their abutment teeth with antagonists, and the antagonists between April 2014 and September 2020 were evaluated retrospectively. The 3-year cumulative survival rates were calculated and associations between the survival time and predictor variables ("Jaw", "Tooth", and "Pulpal condition") were also verified using Cox proportional hazards models and hazard ratios (HRs).

RESULTS

The 3-year cumulative survival rate of single MZCs was 89.8% (9 of 177 MZCs, 95% confidence interval (CI): 80.0-95.1%). Cox proportional hazards models showed non-vital teeth were significantly associated with failure (HR: 2.76e + 9, P = 0.012). The 3-year cumulative survival rate of antagonists was 94.8% (7 of 171 antagonists, 95% CI: 89.3-97.6%). Non-vital antagonists were also identified as an independent predictor for failure in Cox proportional hazards models (HR: 7.83, P = 0.03).

CONCLUSION

Although posterior single MZCs were clinically acceptable, non-vital pulpal condition could be a potential risk factor for failures in the abutment and antagonist teeth of MZCs.

Shear Bond Strength of Lithium Disilicate Bonded with Various Surface-Treated Titanium

Purpose

Retention is one of the most important factors for fixed dental prostheses, especially in implant dentistry. Accordingly, the goal of this study was to evaluate the level of shear bond strength between titanium (Ti) subjected to different surface treatments and lithium disilicate glass-ceramics.

Materials and Methods

In this work, 90 titanium alloy specimens were divided into six groups as follows: the control group (CT), 50 μm alumina airborne-particle abrasion group (SB), silica-coated group (CJ), anodization group (AN), anodization followed by alumina 50 μm airborne-particle abrasion group (ANSB), and anodization followed by silica coating group (ANCJ). Titanium specimens were bonded to lithium disilicate specimens with resin cement (Multilink N). The specimens were restored in water at 37°C for 24 h, and then, shear bond strength (SBS) tests were performed using a universal testing machine (Shimadzu, Japan). The SBS values were statistically analyzed. The failure mode of the debonded titanium was classified after viewing the samples under a stereoscope.

Results

The results demonstrated that the mean SBSs of CT and AN were significantly lower than those of the other groups (p < 0.05). The SB group showed the highest SBS (29.47 ± 2.41 MPa); however, there was no significant difference between SB, ANSB, ANCJ, and CJ. The stereoscopic analysis demonstrated that the failure mode of AN was predominantly adhesive failure; whereas, the other groups showed cohesive and mixed failures.

Conclusions

In this study, it was found that the surface treatment with 50 μm alumina airborne-particle abrasion, silica coating with Cojet™ sand, anodization followed by 50 μm alumina airborne-particle abrasion, and anodization followed by silica coating with Cojet™ sand improved the SBS between titanium and lithium disilicate luted with Multilink N resin cement.

Comparative Assessment of the Functional Parameters for Metal-Ceramic and All-Ceramic Teeth Restorations in Prosthetic Dentistry-A Literature Review

Simple Summary

In the last decades, the science and technology of all-ceramic teeth restorations witnessed the fastest-growing field of restorative materials in research and development for fixed prosthodontics. Due to their properties, characterized by a high level of biocompatibility, excellent optical properties, and high fracture resistance, all-ceramic material can also be used in the posterior areas of the dental arches. However, metal-ceramic fixed partial dentures are still perceived as the golden standard for those restorations, thanks to the positive clinical outcomes. Irrespective of the materials of which fixed partial dentures are performed, their success rates depend on the expected outcome and on how they perform in the oral environment. Such conditions of failure restorations may include biological factors (i.e., secondary decay, loss of vitality, periodontal disease, or abutment fracture) or technical factors (i.e., chipping, ceramic fracture, framework fracture, or loss of retention). Our aim is to provide the current evidence for the efficacy of metal-ceramics and all-ceramics in the treatment of multiple posterior edentulous spaces. Moreover, we aim to compare the survival rates of metal-ceramic and all-ceramic fixed partial dentures in terms of functionality and biocompatibility in all the aforementioned clinical situations. Our results have shown that all all-ceramic systems, especially densely sintered zirconia and reinforced glass ceramics, have a promising future to satisfy both practitioners and patients. However, technical and biological complications need to be taken into account when planning multi-unit fixed partial dentures for the posterior areas.

Abstract

The metal-ceramic fixed partial prosthesis is the golden standard for posterior tooth restorations. Following the demands of patients and clinicians for metal-free restorations, all-ceramic materials were developed as they offer an adequate alternative with better optical qualities and good mechanical properties. This study aims to carry out a bibliographic review to assess the survival rate and the biological and technical complications of all-ceramic and metal-ceramic fixed partial dentures. An electronic search for articles in the English language literature was performed using PubMed (MEDLINE). This literature review focused on research studies between 2010 and 2020 that performed clinical studies on tooth-supported fixed partial dentures with a mean follow-up of at least 3 years. All the studies, which analyzed the survival and complications of tooth-supported fixed partial dentures, were included. Thus, 14 studies reporting on 756 all-ceramic and 160 metal-ceramic fixed partial dentures met the inclusion criteria. A comparative analysis was carried out based on all the data existing in the studies included in this review. The metal-ceramic fixed partial dentures showed survival rates of 95% to 100% at 3-, 5-, and 10-year follow-up periods. Zirconia fixed partial dentures were reported to have survival rates of 81% to 100% at 3-, 5-, 9-, 10-year follow-up evaluations. The reinforced glass-ceramic fixed partial dentures showed survival rates of 70% to 93.35% at 5 years, while the alumina FPDs showed a survival rate of 68% at 3 years follow-up. The incidence of caries and loss of vitality were reported as higher for all-ceramic prostheses as compared to the metal-ceramic ones. A significant framework fracture was reported for glass-infiltrated alumina fixed partial dentures in comparison to metal-ceramic fixed partial dentures. All-ceramic and metal-ceramic restorations showed similar survival rates after 3 years, although all-ceramic restorations have problems with technical complications such as chipping, which can lead to framework fractures over time.

Bonding Strength of Lithium Disilicate Adhesive Crowns with Different Occluso-Cervical Preparation Heights and Cement Types

The aim of this study was to evaluate if adhesion technology with CAD/CAM can compensate for the reduction of occluso cervical preparation heights using different types of dental cement. The de-bonding failure types were then assessed. Here, 72 caries-free extracted human premolar teeth were prepared to have a remaining occlusal height of two, three, and four mm. IPS e.max lithium disilicate CAD/CAM crowns were cemented with adhesive resin cement Panavia SA, self-adhesive resin cement, RelyX Unicem Aplicap, and zinc phosphate cement. The cementation techniques were based on the manufacturer’s instructions. After thermocycling, all samples were tested for tensile bond strength via an Instron machine. One-way analysis of variance (ANOVA) with post hoc testing (P < 0.05) was performed. The means TBS for the two, three, and four-mm OCHP groups were 2.72±0.69, 3.06±0.82, and 3.25±0.79.0 MPa; ARC, SARC, and ZPC were 3.41±0.51, 3.45±0.41, 2.08±0.35 MPa, respectively with significant differences in both. The mixed cement had failures in the resin cement groups. Failure was predominantly cohesive in the zinc phosphate group. Resin cement had the highest SBS values versus ZPC values when both bonded to lithium disilicate crowns with different occlusal heights. The failure of the adhesive to the crown and/or to the tooth were the highest for the four types of resin cement. Around 25% were cohesive failures with resin cement, but this was predominately adhesive in crowns in zinc phosphate regardless of the preparation heights.

Impact of the Veneering Technique and Framework Material on the Failure Loads of All-Ceramic Computer-Aided Design/Computer-Aided Manufacturing Fixed Partial Dentures

Objectives: Zirconia (Y-TZP) ceramics are considered as posterior fixed partial denture (FPD) materials; however, their applications are limited due to chipping. The use of monolithic lithium disilicate (LiDi) glass ceramics in posterior FPDs can be advantageous. This in vitro study aims to compare the loads until failure of posterior Y-TZP-FPDs and LiDi-FPDs before and after aging.

Does Resin Cement Type and Cement Preheating Influence the Marginal and Internal Fit of Lithium Disilicate Single Crowns?

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). Results: 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.

Lithium disilicate and peek implant-retained single crowns - a randomized, prospective clinical study

Introduction/Objective. Comparing two materials under the same conditions is the best way to define differences between them. PEEK is a polymer that has many possible uses in dentistry as already well-known lithium disilicate ceramics. The aim of this study was to compare peri-implant soft tissue healing and evaluate patient satisfaction with esthetics in different observation periods, as well as the success and survival rate of both types of crowns. Methods. The study was conducted as a clinical, prospective, randomized split-mouth study on 17 patients with bilaterally missing upper teeth of the same type, replaced with dental implants. Study outcomes have been analyzed with subjective (VAS scale) and objective parameters (MBI, MPI and PPD) baseline, six and twelve months after fixing crowns onto the implants. Results. Comparison of the results between PEEK and lithium disilicate crowns showed no statistical differences in terms of MPI, MBI and PPD in the observed periods. Analyzing MPI during observation periods in the PEEK group of crowns, statistical significance was registered between baseline values and after 6 months. Also, statistical significance was noticed in terms of PPD during the observation time both in the study and control group of crowns. Results for VAS for the esthetics showed no statistically significant difference between the groups, while VAS for restoration satisfaction showed a statistically significant difference. Conclusion. This study showed that scores of the applied subjective and objective parameters can be a reliable tool to rate the clinical outcome of implant-retained single crowns over time.

The One-Year In Vivo Comparison of Lithium Disilicate and Zirconium Dioxide Inlays

The objective of the present study was to evaluate the one-year clinical performance of lithium disilicate (LD) and zirconium dioxide (ZrO₂) class II inlay restorations. Thirty healthy individuals who met the inclusion criteria were enrolled for the study. The patients were randomly divided into two study groups (n = 15): LD (IPS e.max press) and ZrO₂ (Dentcare Zirconia). In the ZrO₂ group, the internal surfaces of the inlays were sandblasted and silanized with Monobond N (Ivoclar, Leichsteistein, Germany). In the LD group, the internal surfaces of the inlays were etched with 5% hydrofluoric acid. The ceramic inlays were cemented with self-cure resin cement (Multilink N). Clinical examinations were performed using modified United State Public Health Codes and Criteria (USPHS) after 2 weeks, 4 weeks, 6 months and 1 year. The one-year survival rate was evaluated. In total, one failure was observed in the ZrO₂ group. The survival probability after 1 year for the ZrO₂ inlays was 93%, and for the LD inlays was 100%, which was statistically insignificant. The differences between both groups for most USPHS criteria (except for colour match) were statistically insignificant. Within the imitations of the present study, the lithium disilicate- and zirconia dioxide-based inlays exhibited comparable clinical performances. However, the colour and translucency match was superior for the lithium disilicate restorations.