Various cements and their effects on bond strength of zirconia ceramic to enamel and dentin

Update on Dental Luting Materials

A dental luting material aids in the retention and stability of indirect restorations on the prepared tooth structure. In dentistry, clinicians are using a wide range of luting materials for the cementation of indirect restorations. Zinc oxide eugenol and non-eugenol cements, zinc phosphate cement, zinc polycarboxylate cement, glass ionomer cement and resin cements are common dental cements used in dentistry. Each luting material or cement possesses unique properties and clinical implications. An ideal luting cement should be biocompatible, insoluble, resistant to thermal and chemical assaults, antibacterial, aesthetic, simple and easy to use. It should have high strength properties under tension, shear and compression to resist stress at the restoration-tooth interface, as well as adequate working and setting times. So far, no luting material possesses all of these properties of an ideal cement. Scientists have been modifying the conventional luting cements to improve the material's clinical performance and developing novel materials for clinical use. To achieve the best clinical outcome, clinicians should update their knowledge and gain a good understanding of the luting materials so that they can make a wise clinical decision on the material selection and obtain an insight into the development of luting cements. Therefore, the objective of this study is to provide a discussion on the physical, chemical, adhesive and aesthetic properties of common luting materials. The clinical indications of these luting materials are suggested based on their properties. In addition, overviews of the modification of the conventional luting materials and the newly developed luting materials are provided.

In vitro evaluation of the shear bond strength and bioactivity of a bioceramic cement for bonding monolithic zirconia

STATEMENT OF PROBLEM

Adhesive cementation is the most common bonding strategy for zirconia restorations. Although cementation with a bioactive luting agent has been proposed as an alternative, how the bond strength compares is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate shear bond strength after cementing a monolithic zirconia ceramic to human dentin with a bioceramic cement, compare it with a traditional cement, and evaluate its bioactive properties.

MATERIAL AND METHODS

A total of 120 dentin specimens and 120 yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) (BruxZir) cylindrical specimens were used. Zirconia and dentin specimens were randomly divided into 8 study groups (n=15) based on 2 luting cement types (a bioceramic cement or glass ionomer cement as control), 2 airborne-particle abrasion protocols (50 μm or 110 μm), and 2 water storage durations (24 hours or 30 days). After the shear bond strength test using a universal machine at a crosshead speed of 1 mm/min, fracture patterns were evaluated under a stereomicroscope and a scanning electron microscope. Strength values were statistically analyzed with a 3-factor ANOVA model (α=.05). Bioactivity was evaluated in simulated body fluid (SBF).

RESULTS

The control glass ionomer cement achieved significantly greater shear bond strength compared with the tested bioceramic cement. Mean bond strength values ranged from 2.52 MPa to 5.23 MPa for the bioceramic cement tested and from 4.20 MPa to 6.61 MPa for the control cement. The duration of water storage played a significant role in the bond strength, with groups stored for 30 days reaching higher bond strength values, whereas the particle size of airborne-particle abrasion did not have a significant effect. Failure types were primarily mixed. No apatite formation was recorded on the surface of the specimens even after 30 days of immersion in SBF.

CONCLUSIONS

The evaluated cement did not develop apatite in SBF, and its bond strength values were below the control glass ionomer cement.

Effect of Immediate Dentin Sealing on the Bond Strength of Monolithic Zirconia to Human Dentin

Objective:

This study evaluated the shear bond strength (SBS) of pretreated monolithic zirconia surfaces bonded to human dentin following immediate dentin sealing (IDS) using two different self-adhesive resin luting agents.

Methods and Materials:

Sixty intact human third molars were collected, stored, sectioned appropriately, and molded according to ISO 29022:2013, resulting in 120 dentin specimens. Ceramic cylindrical specimens were fabricated using CAD/CAM technology and sintered as recommended (final bonding area A=2.56 mm2). Specimens were randomly assigned to eight groups (15≥n≥14) depending on dentin conditioning method (IDS or delayed dentin sealing [DDS]), zirconia surface pretreatment (airborne particle abrasion [APA] with 50 μm Al2O3 particles at 3 bar for 10 seconds or tribochemical silica coating [TBC] with 30 μm CoJet particles at 2.8 bar for 10 seconds), and adhesive luting agent type (Panavia F2.0 [PAN] or PermaCem Dual Smartmix [PER]). Bonded specimens were water-stored (37°C, 24 hours) and subjected to SBS testing (50-kgF load cell, 1 mm/min). Fracture type was evaluated with stereomicroscopy. Data (MPa) were statistically analyzed using three-way analysis of variance (α=0.05).

Results:

All factors significantly affected SBS values (p<0.001). Dentin conditioning method presented the greatest effect. Mean SBS values ranged from 12.603 MPa (PER-APA-DDS) to 40.704 MPa (PER-TBC-IDS). Based on the fracture type, adhesive failures at the luting agent–zirconia interface were the least common.

Conclusion:

Bonding strategies for monolithic zirconia restorations could potentially benefit from IDS, regardless of the adhesive luting agent system used.

Microleakage around zirconia crown margins after ultrasonic scaling with self-adhesive resin or resin modified glass ionomer cement

OBJECTIVES

To measure microleakage around zirconia crown margins cemented with self-adhesive resin or resin modified glass ionomer (RMGI) cement after ultrasonic scaling.

METHODS

16 molars were prepared for crowns (margin 0.5 mm coronal of cementum-enamel junction). Preparations were digitally scanned and zirconia crowns milled. Specimens were divided into two groups (n = 8): self-adhesive resin (RelyX Unicem 2) or resin modified glass ionomer (RMGI) (RelyX Luting Plus) cements. After cementation, specimens were ultrasonic scaled with a piezoelectric device (60 s, hand pressure). After thermocycling (20,000 cycles/5-55°C), specimens were immersed in 5 wt% fuchsine dye before sectioning bucco-lingually. Microleakage was examined under 40× light magnification. Statistical comparisons were made using a paired t test and a two-sample t test (α = .05).

RESULTS

Ultrasonic scaling did not alter microleakage at the margins of crowns (P = .31). There was no significant difference in microleakage of scaled and untreated margins with the use of different cements (P = .21). The amount of microleakage around margins that were scaled was not significantly different between cements (P = .14). Untreated margins of crowns cemented with RelyX Luting Plus showed a significantly higher microleakage than those cemented with RelyX Unicem 2 (P = .005).

CONCLUSIONS

Piezoelectric ultrasonic scaling did not increase microleakage at the margin of zirconia crowns cemented with self-adhesive resin or RMGI cements.

CLINICAL SIGNIFICANCE

Piezoelectric ultrasonic scaling around zirconia crowns did not impact marginal microleakage cemented with self-adhesive resin or RMGI cements.