Dental Luting Cements: An Updated Comprehensive Review.

The cementation of indirect restoration is one of the most important steps in prosthetic and restorative dentistry. Cementation aims to bond the prosthetic restoration to the prepared enamel or enamel and dentine. Successful cementation protocols prevent biofilm formation at the margin between tooth and restoration and minimize mechanical and biological complications. With the advancements in dental cements, they have been modified to be versatile in terms of handling, curing, and bond strengths. This review presents updates on dental cements, focusing on the composition, properties, advantages, limitations, and indications of the various cements available. Currently, dental restorations are made from various biomaterials, and depending on each clinical case, an appropriate luting material will be selected. There is no luting material that can be universally used. Therefore, it is important to distinguish the physical, mechanical, and biological properties of luting materials in order to identify the best options for each case. Nowadays, the most commonly used dental cements are glass-ionomer and resin cement. The type, shade, thickness of resin cement and the shade of the ceramic, all together, have a tangible influence on the final restoration color. Surface treatments of the restoration increase the microtensile bond strength. Hence, the proper surface treatment protocol of both the substrate and restoration surfaces is needed before cementation. Additionally, the manufacturer's instructions for the thin cement-layer thickness are important for the long-term success of the restoration.

Luting indirect restorations with resin cements versus composite resins: Effects of preheating and ultrasound energy on film thickness.

OBJECTIVE: This study aims to evaluate and compare the film thickness obtained with a resin cement and two composite resins, preheated and/or ultrasonically vibrated, as luting agents. MATERIALS AND METHODS: One hundred and twenty-six (126) pairs of resin discs were randomly assigned to six experimental groups (n = 21) according to luting agent (Variolink Esthetic LC, IPS Empress Direct or Estelite Omega) and cementation technique (preheating at 68°C and/or ultrasonic vibration). Specimens were luted by applying a controlled force. Following sectioning and film thickness measurement through field emission gun scanning electron microscopy, statistical analysis was carried out considering a 5% significance level. RESULTS: Statistically significant lower film thickness was observed in Variolink Esthetic LC group when compared to all composite resin groups (p < 0.001), except IPS Empress Direct preheated and ultrasonically vibrated group (p = 0.073). IPS Empress Direct with ultrasonic vibration yielded statistically lower film thickness values than Estelite Omega groups, regardless of luting technique (p < 0.05). Ultrasonically vibrated Estelite Omega groups showed statistically lower film thickness values than solely preheated groups (p < 0.05). CONCLUSIONS: Both Variolink Esthetic LC and IPS Empress Direct preheated and ultrasonically vibrated provided the lowest film thickness. The addition of ultrasonic vibration during cementation proved to be effective in reducing film thickness of both tested composite resins. CLINICAL SIGNIFICANCE: The cementation technique will have variable results depending on the luting material. Adhesive cementation protocols with composite resins should mainly consider ultrasonic vibration, but also preheating, as strategies for reducing film thickness. The tested resin cement, alongside with IPS Empress Direct composite resin preheated and ultrasonically vibrated, provided the lowest film thickness among the tested materials and techniques.

Effect of Thermocycling on the Bond Strength of Self-Adhesive Resin Cements Used for Luting CAD/CAM Ceramics to Human Dentin.

The aim of the study was to evaluate the influence of thermocycling on the shear bond strength of self-adhesive, self-etching resin cements luted to human dentin and computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Three modern self-adhesive dental cements (Maxcem Elite, RelyX U200, Panavia SA) were used to lute three CAD/CAM ceramics (IPS Empress CAD, IPS e.max CAD, IPS e.max ZirCAD) onto the dentin. One conventional cement (Panavia V5) served as a control. After preparation, the samples were subjected to thermocycling as a method of artificial aging of dental materials applied to simulate long-term use in oral conditions. Shear bond strength was evaluated according to PN-EN ISO 29022:2013-10 and failure modes were observed under a light microscope. Statistical analysis was performed. The study demonstrated that a combination of ceramics and cements directly impacts the bond strength. The highest bond strength was observed in Panavia V5, lower in Panavia SA and Maxcem Elite and the lowest-in RelyX U200. Adhesive failure between human dentin and cements was the most common failure mode. Moreover, thermocycling highly decreased bond strength of self-adhesive, self-etching cements.

In Vitro Comparative Evaluation of Bond Strength of CAD/CAM Monolithic Zirconia Copings Influenced by Luting Agents and Finish Line Design.

AIM: The aim of the in vitro study was to comparatively evaluate the bond strength of CAD/CAM monolithic zirconia copings using three luting agents and two different finish lines. MATERIALS AND METHODS: For the evaluation of bond strength, 60 extracted human maxillary first premolars were prepared to receive CAD/CAM monolithic zirconia copings. They were randomly divided into six groups of 10 samples each to receive CAD/CAM monolithic zirconia copings to bond with three different luting agents on two different finish lines. The luting agents used were RelyX U200, RMGIC, and Maxcem Elite with finish lines which were incorporated were 90° shoulder and radial shoulder finish lines. The tensile bond strength for all 60 samples was tested using the universal testing machine. RESULTS: Between and within the group differences in tensile bond strength were analyzed using one-way ANOVA test of significance with Tukey's post-hoc analysis. The statistical analysis revealed that the CAD/CAM zirconia copings used a combination of 90° shoulder and RelyX U200 as the luting agent (Group II) which offered the maximum bond strength. CONCLUSION: Within the constraints of this study, it could be concluded that CAD/CAM monolithic zirconia copings luted with RelyX U200 cement on a 90° shoulder finish line is the preferred method, taking the bond strength into consideration. CLINICAL SIGNIFICANCE: The results of this study can be extrapolated into a clinical scenario to help the clinician decide the most apt combination of finish line design and the luting agent to achieve superior bond strengths in CAD/CAM zirconia crowns and fixed dental prosthesis.

Comparison of two curing protocols during adhesive cementation: can the step luting technique supersede the traditional one?

This study aims to compare the degree of conversion of two different curing protocols used during adhesive cementation. The following resin luting agents were tested: Hri Flow (MF) and pre-heated Hri Micerium (MH); light-cure Nexus Third Generation (NX3L) and dual-cure Nexus Third Generation (NX3D); dual cured RelyX Ultimate (RXU) and light-cure RelyX Veneers (RXL). For each tested material, ten samples were prepared and divided into two groups which had different curing protocols (P1 and P2): in P1, samples were cured for 40 s; in P2, samples were cured for 5 s, and then, after 20 s, cured again for additional 40 s. The degree of conversion (DC) was evaluated both during the first 5 min of the curing phase and after 1, 2, 7, 14 and 28 days (p = 0.05). Different trends were observed in DC values after 5 min by comparing P1 and P2. In both P1 and P2, DC decreased as follows, MH > MF > NX3L > RXL > RXU > NX3D. There were significant differences of DC values among all resin luting agents (p < 0.05) in P1, while no significant differences existed between MH and MF, and NX3L and RXL in P2. At 1, 2, 7, 14 and 28 days the light curing luting agents had a higher DC than the dual luting agents (p < 0.05). P1 and P2 were not statistically different at each time point (p > 0.05). Both P1 and P2 protocols let achieve an acceptable DC after 28 days. The tested P2 can be safely used to lute indirect restorations, simplifying the removal of cement excesses.

The influence of LED irradiance on the degree of conversion of resin luting agents under translucent zirconia.

This study aimed to evaluate the effect of different LED irradiance levels on the degree of conversion (DC) of dual-cured resin luting agents photocured through a high-translucency zirconia disc. Fifty-four disc specimens (approximately 0.1 × 6.0 × 6.0 mm) were prepared using 3 dual-cured resin luting agents (Panavia F 2.0, RelyX Unicem 2 Automix, and Calibra). Eighteen groups (n = 3) were evaluated. Test specimens were photocured through a 0.7 × 10.0-mm, high-translucency zirconia disc for 20 seconds using 1 of 3 different LED irradiances (mean output of 855, 1330, or 1750 mW/cm2 after 3 consecutive measurements with an LED radiometer). Specimens photocured directly, without a zirconia disc, were used as controls. Microattenuated total reflectance/Fourier-transform infrared spectroscopy was used to evaluate the extent of polymerization of all specimens prior to curing (baseline) and 24 hours after curing. Data were analyzed by 3-way analysis of variance and Tukey multiple comparisons test (α = 0.05). The RelyX Unicem 2 Automix and Panavia F 2.0 specimens showed no statistically significant difference in the mean DC after the use of different LED irradiance levels (P = 0.15 and P = 0.91, respectively) or when photocured with or without the use of a zirconia disc (P = 0.56 and P = 0.86, respectively). The Calibra specimens cured at the lowest irradiance level (855 mW/cm2) presented a significantly lower mean DC (P = 0.001). However, there was no statistically significant difference in the mean DC values when Calibra was photocured directly or through a zirconia disc (P = 0.33). The interpositioning of a high-translucency zirconia material did not reduce the DC of the tested resin luting agents compared to directly irradiated resin luting agents. The influence of different LED irradiance levels on the DC of dual-cured resin luting agents was material dependent.

Comparative evaluation of bond strength of all-metal crowns with different luting agents after undergoing various modes of surface treatments: An in-vitro study.

AIM: This study includes a comparative evaluation of the various surface treatments of the intaglio surface of crowns in combination with various luting agents for maximal retention. MATERIALS AND METHODS: Totally, 150 dies of a standard complete crown preparation were fabricated. Wax pattern with a loop on the occlusal surface was prepared on each die using standard procedures, and then crowns were cast with nickel-chromium alloy. These crowns were randomly divided into five groups as per the surface of the intaglio surface of the metal copings. The crowns in each group were again subdivided randomly into three groups as per the luting agents used resin-modified glass ionomer cement, glass ionomer cement, and zinc phosphate cement. Retention was measured (MPa) by separating the metal crowns from the metallic die under tension on a Universal testing machine. STATISTICAL ANALYSIS USED: The data were recorded and statistically analyzed using one-way analysis of variance followed by Tukey's test. RESULTS: The retention differed both with surface treatment and type of luting agents. Untreated group showed the least bond strengths < sandblasting with 50 µm alumina < sandblasting with 50 µm alumina with ultrasonic cleaning < sandblasting with 110 µm alumina < sandblasting with 110 µm alumina along with ultrasonic cleaning. For luting agents, glass ionomer cement showed least bond strength because there was no chemical bonding present between metal crown and metallic die, followed by zinc phosphate cement and maximum bond strength were found for resin-modified glass ionomer cement. CONCLUSION: Among all types of surface treatments used in this study, maximum bond strength was yielded by sandblasting with 110 µm alumina + ultrasonic cleaning and the best luting agent was resin-modified glass ionomer cement.

Degree of conversion of dual-cured composite luting agents: The effect of transition metal-based touch-cure activators.

PURPOSE: The aim of the study was (a) to assess the effect of universal adhesives and tooth primers with novel touch-cure activators on the conversion of dual-cured resin composite luting agents (RLAs) polymerized under the self-curing mode, and (b) to investigate the source of the catalytic effect exerted by the activators. MATERIALS AND METHODS: The materials selected were the adhesive RLAs Panavia V5/Tooth Primer (PV5/TP5), Variolink Esthetic DC/Adhese Universal DC (VLE/ADC), and the self-adhesive RLAs GCem ONE/AE Primer (GCO/AEP), RelyX Universal/Scotchbond Universal Plus (RXU/SUP) and Panavia SA Universal/Clearfil Universal Bond Quick (PSU/CUQ), the later serving as a control with an aryl-sulfinate activator. Coronal dentin specimens were prepared (n = 5/material), treated with the corresponding primers/adhesives (non-irradiated) and covered with a 100 µm-thick RLA layer (SC+A group). Three specimen series were additionally prepared (n = 3 × 5/material): A self-cured without the primers/adhesives (SC group), a dual-cured (20 s irradiation) with the corresponding primers/adhesives (DC+A group) and a dual-cured without primers/adhesives (DC group). All specimens were stored for 15 min (37 °C/dark/60 %RH). After demolding the degree of C = C conversion (DC%, top RLA surfaces) was measured by ATR-FTIR spectroscopy. The primer/adhesive liquids were further analyzed by ICP-MS and the microbrush tips of ADC by SEM-EDS. RESULTS: The touch-cure activators increased the DC% in all self-cured RLAs but failed to reach the values of the corresponding dual-cured RLAs. The effect of the activators in dual-cured specimens was negligible. The ICP-MS analysis showed the presence of V (AEP, TP5, ADC) and Cu (SUP) transitional metals in the activators, with V been located at the free ends of ADC tip bristles. The V activators demonstrated the highest DC% improvement in self-cured specimens. CONCLUSION: The new touch-cure activators significantly increased the conversion of the self-cured RLAs. Therefore, this step should be considered as universally applicable and not selective, as currently proposed for the self-adhesive luting agents by the manufacturers.

Application of Bulk-Fill Composite to Simplify the Cementation of Indirect Restorations: The COMBO Technique.

This article proposes a technique to simplify the cementation of indirect restorations by exploiting the advantageous properties of bulk-fill composites (BFCs). The proposed technique consists of using a thin layer of a high-viscosity (HV) BFC in the interproximal margins of the preparation and applying low-viscosity (LV) resin luting agents (RLAs) to the rest of the prepared surface. The application of the HV BFC limits the extrusion of the LV RLAs in the interproximal area, deviating the excesses of LV RLAs only on the vestibular and lingual side. This deviation allows the management and control of the excess material in complicated interproximal spaces, simplifying the cementation procedure of indirect restorations and achieving a reliable final result in terms of removing excess in a safe and repeatable way. This technical report provides an alternative clinical approach for cementing indirect restorations using the consistency and viscosity of different RLAs.

Influence of the Composition of Provisional Luting Materials on the Bond Strength of Temporary Single-Tooth Crowns on Titanium Abutments.

In addition to zinc oxide-based cements, resin-based materials are also available for temporary cementation. The aim of this in vitro study was to determine the influence of the different material compositions on temporary bonds. In nine test series (n = 30), temporary bis-acrylate single-tooth crowns were bonded onto prefabricated titanium abutments with nine different temporary luting materials. After simulating an initial (24 h, distilled water, 37 °C), a short-term (7 days, distilled water, 37 °C) and a long-term provisional restoration period (12h, distilled water, 37 °C; thermocycling: 5000 cycles) in subgroups (n = 10), the bond strength was examined using a combined tensile-shear test. Statistical analysis was performed by univariate analysis of variance or a non-parametric Kruskal-Wallis test, followed by post hoc tests. Of the three resin-based materials, two showed significantly higher bond strength values compared to all other materials (p < 0.001), regardless of the storage procedure. The resin-based materials were followed by eugenol-free and eugenol-containing zinc oxide materials. Significant intragroup differences were observed between the composite-based materials after all storage periods. This was only observed for some of the zinc oxide-based materials. The results show that under in vitro conditions, not only the composition of the temporary luting materials but also the different storage conditions have a significant influence on temporary bonds.

Current Insights on Fiber Posts: A Narrative Review of Laboratory and Clinical Studies.

PURPOSE: The aim of this study was to review the literature related to the clinical performance and laboratory findings regarding fiber posts, as well as the cementation technique employed with their use. MATERIALS AND METHODS: A literature search was performed using an electronic database, PubMed/Medline, between 2010 and 2023. The terms used were "intra coronal post, fiber post, post cementation, and post length". Titles and abstracts were initially screened, and a full-text assessment was conducted for those that fulfilled the inclusion criteria. The reference list of the collected papers was also screened for further relevant citations. RESULTS: In this work, 135 potentially eligible studies were analyzed. Titles and abstracts of 90 studies followed the inclusion criteria and were selected for a full-text assessment, resulting in 50 studies selected. Moreover, additional studies from relevant citations were included, totaling 57 studies. CONCLUSION: According to the laboratory and clinical studies revised, the survival rate between fiber and prefabricated and cast metal posts was similar, and failures were mainly related to the loss of retention. The intra-canal post length of less than two-thirds of the root length presented successful results when ferrule was present. Furthermore, the ferrule increased the longevity of teeth restored with fiber posts. Additionally, the use of a surface treatment protocol for fiber posts and the adhesive cementation technique both contributed to the clinical success and longevity of the intra-canal post.

Retention force, translucency, and microstructural properties of translucent temporary luting cements: An in vitro study.

The aim of the study was to investigate the retention behaviour (pull-off force include adhesive remnant index = ARI) as well as translucency of various temporary luting cements and use microstructure elucidation methods to formulate explanatory approaches to their mode of action. The retention force of the temporary luting cements Provicol QM Plus (P+), Provicol QM Aesthetic (Pae), Bifix Temp (BiT), and as a reference a glass ionomer cement Meron (M) with a direct (Structur 3/S3) or an indirect (Structure CAD/SCAD) resin-based composite restauration was investigated after accelerated aging (thermocycling). Additional investigation of the physical properties was performed regarding to translucency and surface free energy. The microstructure was evaluated by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and micro X-ray computed tomography. All tested temporary luting cements showed different pull-off forces in the range between 3.0 and 16.8 N in combination with S3 or SCAD after thermocycling. Only BiT with S3 showed pull-off forces of 129.2 N and complete retention on the restoration (ARI = 0), which was significant (p < .001) to all other samples. High translucency (BiT > Pae > M > P+) was observed for materials with lower crystalline content and low residual mass (usally resulting from higher organic content). M showed the highest surface free energy with a predominantly polar fraction, while BiT had a predominantly dispersive fraction. The highest porosity was observed in the coronal region of the restoration. The results suggest that translucency of temporary luting cements can be increased with higher organic and lower cryristall content. All combinations of cements and temporary restorations (direct/indirect; with the exception of BiT/S3) showed pull-off forces below 17 N (equivalent to a weight force of ∼1.7 kg), which allows manual detachment of the restoration by the dentist.

An In Vitro Trial to Estimate the Retention Ability of Luting Agents Utilized with Dental Implant-Supported Prosthesis.

Aim: The trial's goal was to assess the retentiveness of specially formulated implant cement besides comparing it to dental cements that are widely utilized by means of implant systems. Materials and Procedures: Twenty implant analogs were implanted in auto-polymerizing acrylic resin blocks and bonded to titanium abutments. Fifty uniform copings were waxed and cast unswervingly onto the abutment. (1) Resin-bonded zinc oxide eugenol cement, (2) purposefully designed implant cement, (3) zinc phosphate cement, (4) zinc polycarboxylate cement, and (5) glass ionomer cement were the cements used. Following cementation, each sample was pulled out by utilizing a widespread testing machine, and the stresses necessary to confiscate the crowns were recorded. The ANOVA and Bonferroni tests were used to examine the mean values and standard deviations of cement failure loads. Results: Zinc polycarboxylate cement had the peak mean cement failure load, followed by glass ionomer cement. Zinc phosphate cement had the next highest mean cement failure load, followed by resin-bonded zinc oxide eugenol cement. The mean cement failure load for Premier implant cement was the lowest. The difference in mean cement failure loads across the groups was statistically significant (P < 0.001). Conclusion: The findings do not imply that one type of cement is superior to another, but they do present a ranking directive of cements based on their capacity to maintain the prosthesis and facilitate retrievability.

Color change of glass ceramic restorations cemented by four types of dual-cured resin luting agents with different initiator systems.

This study aimed to comprehensively evaluate the effect of dual-cured resin luting agents with different initiator systems on the color stability of glass ceramic restorations by simulating various clinical glass ceramic restorations. Three commonly used shades from each of the two dual-cured resin luting agents with an amine-initiation system or without it were studied. The individual specimens had different translucency and thickness and were artificially aged using a xenon light aging machine. The color was measured before and after aging using a digital spectrophotometer with the difference calculated and analyzed statistically. As results, the amine-free dual-cured resin luting agents were more color stable than those using amine-initiation systems for both uncovered and bonding groups. The translucency and thickness of the ceramic, and shade and type of the resin luting agent significantly affected the color stability of glass ceramic restorations.

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.

Evaluation of change in implant abutment after teeth surface modifications.

The surface modifications in teeth increase the retentive strength of cemented castings by providing micro as well as macro retentive ridge and groove patterns. Restoring the dental implants with cement-retained prosthesis is well known. Therefore, it is of interest to compare retentive property of implant abutments with and without circumferential grooves. Hence, 20 straight shoulder type titanium abutments were with abutment screws as well as prefabricated plastic copings and corresponding 12 mm-long stainless steel laboratory implant analogs were used. The abutments were divided into two subgroups of 10 abutments each: without grooves and with grooves. After thermocycling and storing the cemented abutments in water at 37°C water for 6 days they were assembled in the Universal testing machine and subjected to a pullout test (retention) at a crosshead speed of 5.0mm/min to record forces in Newton. Data suggest that the addition of grooves increased the retention. The mean retentive forces of standard machined abutments (plain) cemented with Resin modified GIC showed 339.34 N. Retention increased by 667.39N after addition of circumferential grooves. The surface modification of an implant abutment by means of circumferential grooves is an effective method of improving the retention of cast crowns cemented with resin modified GIC especially in short abutments.

Geometry of Implant Abutment Surface Improving Cement Effectiveness: An In vitro Study.

AIM: The aim of the study was to investigate whether the surface geometry or topography of implant abutments affects the retentive strength of prosthesis cemented with zinc phosphate on standard machined, sandblasted, and grooved implant abutments and to compare the results between them. MATERIALS AND METHODS: Fifteen similarly shaped implant abutments (MDcpk61; MIS Implant Technologies Ltd.,) (height 6.0 mm and 6-degree taper) were divided into three groups (n = 05): Group I - standard machined abutments without grooves, Group II - sandblasted abutments (same as Group I but sandblasted with 50 µ aluminum oxide), and Group III - abutment with prefabricated circumferential grooves. Further in these groups of 15 abutments, 5 abutments each are to be taken to check the retentive force of zinc phosphate cement. Fifteen identical cast copings was prepared to fit all 15 abutments. The castings will be cemented to each group of abutments with an above-mentioned luting agent. After thermal cycling and storage for 6 days in a water bath, a retention test is to be done with a tensile testing machine (Instron) (5 mm/min) and retentive forces will be recorded. Data will be subjected to one-way ANOVA test and Student's t-test. RESULTS: For zinc phosphate cement, F = 30.53 (>3.59 for P = 0.05) shows a statistically significant difference between all the three groups. CONCLUSION: Circumferential grooves on implant abutments give better retention when compared with standard machined (plain) and sandblasted abutments despite marked difference. CLINICAL SIGNIFICANCE: Retention of restoration depends on the surface of the abutment as well as the luting agents used. Incorporation of retentive grooves can enhance retention of prosthesis, especially in situation of short abutments.

Retention of Various Luting Agents Used with Implant-Supported Crowns.

BACKGROUND: Implant supported crowns can either be screw retained or cement retained. Recent advances in implant dentistry has improved the longevity of the implant restoration and has placed importance on esthetics and function. Cement retained restoration has added advantage of superior esthetics and is preferred by the clinician. However, selecting the ideal type of cement for luting implant supported crown has been a topic of debate. METHODOLOGY: A study was conducted at ESIC Dental College & Hospital, Kalaburagi to determine the retentive ability of three different luting agents. 30 samples were divided into three groups and luted with Zinc phosphate, Zinc Polycarboxylate and Glass ionomer cement. The retentive strength was evaluated using universal testing machine. RESULTS: Results proved that zinc poly carboxylate cement had the highest retentive value followed by glass ionomer and zinc phosphate.

Assessibility of different CAD/CAM ceramics with optical coherence tomography.

OBJECTIVES: To investigate the light penetration depth of various CAD/CAM ceramics and luting agents by spectral-domain optical coherence tomography (SD-OCT). METHODS: Six CAD/CAM ceramics: lithium disilicate (LS2), zirconia-reinforced lithium silicate (ZLS), lithium aluminosilicate (LAS), polymer infiltrated (PIC), feldspar (FEL) and zirconium oxide (ZRO) and five common luting agents, two self-adhesive and three adhesive materials, were included. SD-OCT wavelengths (1310/1550 nm) and frequencies (5/28 kHz) that are particularly suitable for these materials were investigated. Subsequently, a clinical simulation was performed with an adhesively or self-adhesively inserted partial crown made of a ceramic that had an OCT penetration depth of > 1.0 mm. RESULTS: Best SD-OCT penetration was obtained at 1550 nm and 28 kHz. For ZLS, LS2 and LAS, SD-OCT light penetration depth of > 4 mm was shown. In contrast, the penetration depth of ZRO, PIC and FEL was less than 1 mm. Adhesive and self-adhesive luting agents could be visualized up to ≥ 0.9 mm. All clinically relevant areas (ceramic restoration, luting area, interfaces and adjacent tooth structures) can be imaged when SD-OCT-suitable ceramics are used. CONCLUSIONS: SD-OCT can be used to analyze CAD/CAM ceramics based on ZLS, LS2 and LAS, whereas ZRO, PIC, and FEL had insufficient penetration depth for clinical application. The type of luting agent or its thickness played an insignificant role. With suitable ceramics, SD-OCT can be recommended as a non-invasive examination tool. CLINICAL SIGNIFICANCE: This study indicates that SD-OCT is a useful non-invasive examination method for monitoring lithium silicate-based ceramic restorations and adjacent structures.

Effect of Water Storage on Hardness and Interfacial Strength of Resin Composite Luting Agents Bonded to Surface-Treated Monolithic Zirconia.

BACKGROUND: Durable bonding between resin composite luting agents (CLA) and zirconia is still a matter of controversy. The purpose of this study was to evaluate the effect of water storage on hardness and interfacial strength of three CLA, a non-adhesive (Multilink Automix/ML), an adhesive (Panavia F 2.0/PF) and a self-adhesive (PermaCem 2.0/PC), bonded to polished (CL) and grit-blasted (AL: 50 µm alumina, SJ: Sil-Jet + Monobond Plus silane) monolithic zirconia surfaces. METHODS: CLA specimens (n = 5/cement, condition) were prepared, stored under dry conditions or immersed in water, and Vickers hardness (VH) measurements were obtained at 1 h, 24 h, 1 week and 3 weeks intervals. Optical profilometry was used to determine the roughness parameters (Sa, Sz, Sdr, Sci) of zirconia surfaces (n = 5/treatment). A shear strength test (SBS, n = 10 × 2/cement) was performed to assess the strength and fractography of the cements bonded to zirconia after isothermal water storage and thermal-cycling (TC). RESULTS: PF demonstrated significantly lower VHN after water storage at all time intervals, PC at 1 w, 3 w and ML at 3 w. SJ and AL showed significantly higher values from CL in all roughness parameters. Weibull analysis revealed the following significance in σο ranking within the same material: AL, SJ, ALTC > SJTC, CL > CLTC (PF); SJ, SJTC, AL, ALTC > CL, CLTC (PC) and SJ, SJTC > AL > ALTC > CL, CLTC (ML). Within the same surface treatment subgroups, the significance in σo ranking was PC, ML > PF (before/after TC) for SJ; PC > PF > ML (before TC), PC, PF > ML (after TC) for AL, and PC > PF > ML (before/after TC) for CL. For the m ranking, the only significant difference within each material group was found in PC (AL > ALTC) and for the same surface treatment in AL (PC > ML). CONCLUSION: There are significant differences in the water plasticization susceptibility of the CLA tested; the materials with adhesive monomers were the most affected. Tribo-chemical silica coating combined with a silane coupling agent was the most efficient bonding treatment for the non-adhesive and the self-adhesive materials. The adhesive CLA performed better on alumina-blasted than on tribo-chemically coated surfaces.