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Article

Microgap Formation between a Dental Resin-Matrix Computer-Aided Design/Computer-Aided Manufacturing Ceramic Restorative and Dentin after Various Surface Treatments and Artificial Aging

by
Alexandros Galanopoulos
,
Dimitrios Dionysopoulos
*,
Constantinos Papadopoulos
,
Petros Mourouzis
and
Kosmas Tolidis
Department of Operative Dentistry, Faculty of Dentistry, School of Health Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
*
Author to whom correspondence should be addressed.
Appl. Sci. 2023, 13(4), 2335; https://doi.org/10.3390/app13042335
Submission received: 25 January 2023 / Revised: 7 February 2023 / Accepted: 10 February 2023 / Published: 11 February 2023
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Abstract

:
The potential formation and the size of microgaps at the material/dentin interface after various surface modifications of a resin-matrix computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic following artificial aging was investigated. Fifty human third molars were used, and a resin-matrix CAD/CAM ceramic, Lava Ultimate, and a resin cement material, Rely X Ultimate, were tested. CAD/CAM blocks were sectioned, and each slab was luted on the tooth surface using the same resin cement. The surface material was modified using the following treatments: Group 1—no treatment (control); Group 2—hydrofluoric acid (HF) + silane; Group 3—air abrasion with Al2O3 particles (29 μm); Group 4—air abrasion with Al2O3 particles (53 μm); and Group 5—erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) (2780 nm) laser treatment. The specimens were submitted to thermocycling (5000 cycles: 5 °C–55 °C) and then transversely cut in the middle and examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Larger microgaps were observed in the control and laser-treated groups, with no significant differences (p = 0.452). By contrast, the other three groups presented lower microgap formation, and in some cases, no microgaps were detected. Air-abrasion groups exhibited the lowest microgap formation (p < 0.05). Different surface modifications of the material presented significant differences in the formation of microgaps at the adhesive interface after artificial aging, implying differences in bond strengths among the groups. Air-abrasion pretreatments with Al2O3 particles presented more beneficial results regarding microgap formation.

1. Introduction

During the past few years, innovative technologies and materials have caused an increase in the use of computer-aided design/computer-aided manufacturing (CAD/CAM) restorations for structurally compromised teeth [1]. More recently, a significant development in dental materials has unfolded with the introduction of resin-matrix CAD/CAM ceramics, which can provide high aesthetics and long-term clinical survival rates of indirect restorations in one single session [2,3,4].
Considering that time is one of the most important factors in modern society, due to professional or other personal obligations, patients demand a shorter number of dental sessions. Modern ways of communication, combined with the use of digital technology, can also reduce anxiety and phobia for dentists, increasing, at the same time, the need for preventive dentistry. In addition, advertisements, marketing, social media, and new therapeutical protocols have also been developed over the last several years that make dental offices a friendlier environment. Various studies have also shown that the digital, compared to the analog way of dental practices, offers a higher impact and better patient compliance [1,5].
Resin-matrix CAD/CAM ceramics (RMCs) present some advantages compared with their ceramic counterparts, including higher Weibull modulus and lower hardness and stiffness, and as a consequence, they produce less wear to the antagonistic teeth, and the milling machine can prepare the restorations easier and faster [6,7]. Moreover, RMCs can be easily repaired, and due to the fact that they present lower brittleness than ceramics [7], they undergo chipping and crack propagation less frequently during fabrication [8] and exhibit sufficient marginal adaptation [9,10]. They contain UDMA monomers with dispersed fillers and are fabricated with the methods of high-temperature/-pressure polymerization, providing a higher degree of conversion in comparison with resin composites for direct restorations [11,12]. Lava Ultimate (LV) that was tested in this investigation belongs to this category of resin-based CAD/CAM materials with dispersive fillers. In particular, it contains bisphenol A diglycidylmethacrylate (Bis-GMA), urethane dimethacrylate (UDMA), ethoxylated bisphenol A dimethacrylate (Bis-EMA), and triethylene glycol dimethacrylate (TEGDMA) as basic monomers and silica (SiO2) and zirconia (ZrO2) nanoclusters as dispersed filler particles.
Nowadays, dental research has focused on the bonding of CAD/CAM restoratives to dental tissues by applying various techniques. The bonding process can be implemented using appropriate cement materials that are able to fill the area between the surface of the restorative materials and the tooth tissues and form chemical bonds between them. Different adhesive strategies have been suggested for CAD/CAM restoratives to reach adequate bond strength on the cement/material interface [13]. In particular, mechanical or chemical surface modification methods have been proposed for this reason [14]. The chemical bonding between resin cement and RMC material [15] and the application of primer (silane) for facilitating the wetting of the polymeric surface of restoratives have been reported to increase the bond strength significantly [16,17]. Furthermore, the micromechanical modification of the material’s surface by applying hydrofluoric acid (HF) [3], air abrasion with aluminum oxide (Al2O3) particles [18], or laser radiation [19,20] can enhance the bonding as well. These surface-treatment methods induce microretentive irregularities on the material’s surface [21]. Moreover, the application of a coupling agent after surface modification improves chemical adhesion prior to the application of the bonding agent [22].
In the oral environment, significant tensions can be developed at the cement/material interface during thermal changes that can result from the daily diet. Moreover, the hydrolysis of the resin cement due to moisture may lead to the disruption of the monomer bonds, attributed to the action of water. These conditions can weaken the bond between cement and material and may lead to bond failure, the formation of microgaps, and microleakage, as demonstrated in previous reports [23,24,25].
The aim of this research was to investigate the potential formation and size of microgaps at the material/dentin interface following four surface treatments of a resin-matrix CAD/CAM ceramic after artificial aging, using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). These methods provide sufficient morphological and compositional analyses, respectively, of the tooth/restorative interface and have been used in previous similar studies. The surface treatments that were investigated included air abrasion with 29 and 53 μm Al2O3 particles, the application of HF gel and erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser radiation (2780 nm). The first null hypothesis (H01) of the study was that after artificial aging, no microgap formation would be detected at the restorative/dentin interface. The second null hypothesis (H02) was that after artificial aging, no differences in microgap formation would be observed among the surface-treatment groups.

2. Materials and Methods

2.1. Materials

A resin-matrix CAD/CAM ceramic (Lava™ Ultimate, 3M ESPE, Seefeld, Germany) and a dual-cure resin cement material (RelyX™ Ultimate, 3M ESPE, St. Paul, MN, USA) were tested in this study. Their technical characteristics are shown in Table 1.

2.2. Sample Preparation

Ten CAD/CAM blocks (10 × 12 × 14 mm) were cut in four slabs of 3 mm thickness each, utilizing a low-speed, water-cooled diamond saw (Isomet 11-1180 Buehler, Lake Bluff, IL, USA). The top surfaces of the resulting forty slabs were polished on a grinding machine (Jean Wirtz TG 250, Dusseldorf, Germany) with 200 rpm under water cooling (50 mL/min) gradually using 600-, 800-, 1000- and 1200-grit silicon carbide abrasive papers (Apex S system, Buehler, Lake Bluff, IL, USA) for 20 s each.
Forty sound human molars, which were extracted for periodontal reasons, were stored in a 0.5% chloramine T solution at 6 °C for up to 3 months. The exposure of the dentin surface was achieved by cutting the enamel at the middle of the occlusal–cervical dimension of the crown with a water-cooled diamond saw.

2.3. Experimental Groups

Forty slabs of the tested CAD/CAM blocks were randomly distributed to five groups (n = 8). Each group of eight slabs received one of the following treatments on their polished surface:
Group 1—intact surfaces (CR): no surface treatment of the specimens was applied (control group);
Group 2—sandblasting with 29 μm Al2O3 particles (SB1): The top surfaces of the specimens were air-abraded using Aquacare Twin™ (Velopex Int, Medivance Instruments Ltd., London, UK) with 29 μm Al2O3 particles (Aqua AbrasionTM, Velopex Int, London, UK). The tip of the handpiece was vertically directed to the surface from a distance of 10 mm for 20 s with 0.3 MPa air pressure;
Group 3—sandblasting with 53 μm Al2O3 particles (SB2): the same surface treatment as Group 2 was implemented using 53 μm Al2O3 particles;
Group 4—HF and silane treatment (HF): The top surfaces were etched with 9% HF (Porcelain Etch, Ultradent, South Jordan, UT, USA) for 90 s and rinsed for 60 s. Subsequently, the specimens were immersed in an ultrasonic bath with distilled water for 5 min and air-dried for 20 s. The top surfaces were then coated with a silane (Silane, Ultradent, South Jordan, UT, USA) and remained undisturbed for 60 s;
Group 5—Er,Cr:YSGG laser treatment (LR): The surfaces were irradiated with an Er,Cr:YSGG (2780 nm) solid-state laser system (Waterlase MD Turbo, BIOLASE, Irvine, CA, USA). A Z-type glass cylindrical tip (MZ8) with 800 μm diameter and 6 mm length, which was adapted to a gold handpiece of the laser system, was positioned 1 mm from the specimen’s surface. The irradiation time was 90 s, and the average output power was 2.7 W, yielding a fluence of 202.5 J/cm2. The pulse repetition rate was 30 Hz with 90% water and 70% airflow, and the pulse duration was adjusted to 700 μs (S-mode).
To ensure consistent spot size with the hand irradiation, an endodontic file was fixed at the handpiece and kept a distance of 1 mm from the surface during irradiation. The handpiece was positioned perpendicularly to the enamel surface, and the samples were irradiated by hand once in each direction in a scanning mode, moving the handpiece slowly for 45 s horizontally and 45 s vertically with a speed of 2 mm/s, to promote homogeneous irradiation and to cover the entire specimen area. All the specimens were irradiated by the same operator.

2.4. Bonding Procedure to Dentin

A commercially available universal adhesive system (Single Bond™ Universal Adhesive, 3M ESPE, Seefeld, Germany) was used for the bonding procedures to dentin (Table 1). The adhesive agent was applied on the surface of the dentin by brushing with a microbrush and then left intact for 20 s and gently air-dried for 3 s. Subsequently, the light-curing of the adhesive was implemented for 10 s according to the manufacturer’s instructions, using a LED light-curing unit (Elipar Deep Cure S, 3M ESPE, St. Paul, MN, USA)at 1470 mW/cm2. Then, the pretreated surfaces of the slabs were luted to the dentin using dual-cure resin cement (RelyX™ Ultimate, 3M ESPE, St. Paul, MN, USA), according to the manufacturer’s instructions. A standard portion of the resin cement (1 mL) was applied on the material’s surface, and the slab was pressed on the surface of the dentin with a standard force of 150 N for 3 min. The resin cement was light-cured for 20 s on each side using the LED device.

2.5. Thermocycling

After bonding procedures, the specimens were stored in artificial saliva for 24 h in the dark at 37 °C [26]. Then, the samples were thermocycled for 5000 cycles at 5 °C and 55°C and a dwell time of 15 s.

2.6. Evaluation of Microgaps Formation

Following thermocycling, the specimens were sectioned using mesiodistal dimensions in the middle of the occlusal surfaces with a low-speed diamond saw under water irrigation, and the sections were prepared for SEM observations. In particular, each section was mounted on aluminum stubs with the cut surface facing up, sputter-coated with carbon to a thickness of approximately 200 Å in a vacuum evaporator (at low vacuum), and examined under a scanning electron microscope (JEOL Ltd., JSM-840, Tokyo, Japan) at an accelerated voltage of 20 kV. SEM photomicrographs were acquired at ×100 magnification. The maximum width of the formed microgaps at the interface between the restorative material and the dentin after thermocycling was recorded in μm using the software of the microscope in the backscattered mode (Figure 1). Each photomicrograph was evaluated using energy-dispersive X-ray spectroscopy (EDS) for the elemental analysis to define the structures and the mode of bond failure (Figure 2). Moreover, additional specimens were prepared for SEM observations in ×50 and ×500 magnifications to compare the effectiveness of the tested surface modifications (Figure 3).

2.7. Statistical Analysis

For statistical analysis of the data, the SPSS 24.0 software (SPSS, Inc., Chicago, IL, USA) was used. The data of microgap size in μm were statistically analyzed using one-way ANOVA to define how the surface pretreatment of the restorative material affected the mean size of the microgaps formed after thermocycling. The Bonferroni test was used to explore the significant differences in between-group comparisons at a level of significance of α = 0.05. The normality and homogeneity of the data distribution were preliminary checked using Kolmogorov–Smirnov and Levene tests, respectively.

3. Results

3.1. Observations of the Surfaces after the Treatments

Representative SEM images in ×50 and ×500 magnifications of the surface of the specimens after each surface pretreatment and before bonding to dentin are presented in Figure 3. The SEM observations revealed alterations in the surface morphology of the treated groups compared with the control group (CR). In particular, the untreated surfaces of the material exhibited a smooth appearance, while the mechanical treatments (SB1 and SB2) created a morphologically roughened surface, with the presence of irregular craters with different shapes and sizes. The chemical conditioning treatment (HF) induced irregular surfaces with craters of a different shape to that shown by the mechanical treatment and areas where the amorphous silica particles were partially dissolved or exposed upon the material’s surface. Laser-treated (LR) surfaces showed multiple large craters dispersed on the entire surface with intermediate intact areas due to the pulped mode of the irradiation.

3.2. Width of the Formed Microgaps after Thermocycling

The means and standard deviations of the maximum width of the formed microgaps in μm at the dentin/material interface after thermocycling are shown in Table 2. In addition, the representative SEM images for each experimental group at the material/dentin interface revealing microgap formation are illustrated in Figure 4. Statistically significant differences were detected among the experimental groups (p < 0.05). The highest mean width of microgaps was observed with CR and LR treatments, which did not differ from each other (p = 0.452), while the lowest were the two air-abrasion treatments (SB1 and SB2), which also did not show a significant difference (p = 0.118).

4. Discussion

Based on the results of the current research, H01, which stated that after artificial aging, no microgap formation would be detected at the restorative/dentin interface, was rejected. In the current study, the thermocycling protocol that was followed allows for the simulation of the oral environment over almost 6 months [27]. During the process of dimensional changes in restorative materials and tooth tissues, which are different due to the discrepancies in their thermal expansion coefficients, stresses are developed at the restorative/tooth interface deteriorating the bond between them, depending on the number of applied cycles [28]. Although no standard protocol regarding thermocycling has been established for evaluating microgap formation, in the present investigation, the selected protocol was adopted similarly to previous reports [28,29,30].
It has been claimed that the weakening in bonding between the restorative material and tooth tissues may also be attributed to the decomposition of the components at the interface area through hydrolysis [31,32]. Although it is not certain that the influence of thermocycling on bond strength is equal to that of long-term water storage, limited data are available regarding the synergistic effect of thermocycling and long-term water storage on microgap formation. The formation of microgaps raises concerns because they let the fluid or bacteria invade the dentin–pulp complex, which may lead to postoperative sensitivity and the formation of tooth caries [33].
The size of the microgaps is affected by the magnitude of the internal stresses that are developed during the contractions and expansions of the materials and tissues when temperature fluctuations take place. Thadathil Varghese et al. [34], who focused on the effect of thermal stimuli on the restorative/dentin interface, found significant changes in the developed stresses in this area. These stresses impair the bond strength at the adhesive interface, and when they exceed a critical threshold, they may result in fracture, fatigue damage, interfacial debonding, and microgap formation [35]. The physical–mechanical properties of teeth and restoratives such as the elastic modulus, the coefficient of thermal expansion, and thermal conductivity, as well as oral conditions, can crucially affect the progress of these defects, which may lead to the failure of tooth restoration [34]. It has been reported that restoratives with lower elastic modulus and coefficient of thermal expansion but higher thermal conductivity develop lower tensions on the adhesive interface, and as a consequence, restorative materials should be cautiously selected by the dental practitioner [34].
The outcomes of the current research demand the rejection of H02 stating that after artificial aging, no differences in microgap formation would be observed among the surface-treatment groups. The present research focused on the effect of the surface modification of RBC CAD/CAM blocks on the size of the formed microgaps at the material/dentin interface. Considering that the surface pretreatment of the restorative improves the bond strength to the dentin and that microgaps are formed when there is a bonding failure, the outcomes of the current study aimed to indicate an optimal treatment for the sufficient bonding of the tested material to dentin in order to achieve long-term survival. As a consequence, the parameters that may affect the results, such as the composition of the restorative material, the resin cement, and the adhesive strategy, were eliminated, and the only variable was the surface treatment of the material.
Surface pretreatments increase the impregnated surface area by the resin cement during the adhesive procedure [36]. When etching the ceramic components using hydrofluoric acid, sandblasting creates a roughened surface through the collision of Al2O3 particles, while laser irradiation modifies the material’s surface via the microexplosions of water molecules in order to increase micromechanical retention. Furthermore, silane-coupling agents enhance bonding by coupling inorganic fillers with the resin matrix of the restorative material [37]. Previous studies reported that micromechanical treatments using air-abrasion can improve bonding to the surface of resin-based CAD/CAM blocks more than chemical treatments, which may partially justify the smaller size of the microgaps that were found in the current research [14,24]. In the present investigation, mechanical surface modifications were performed using two distinguished sizes of Al2O3 particles (29 μm and 53 μm) with the same operation parameters (air pressure, duration, and distance from the surface). These settings were chosen foraverting superficial cracks on the surface of the tested materials and to confirm a uniform surface modification [38,39].
Hydrofluoric acid etching increases surface roughness, which is necessary for improving micromechanical retention and the wettability of the utilized coupling agent, resulting in stronger bonding [13]. Taking apart the surface layer of a glassy matrix containing silica (SiO2) and silicates (SiO4)−4, a porous surface is formed with a mean pore size of approximately 3–4 μm that is able to be infiltrated by adhesive agents [40]. It has also been well documented that bond strength is dependent on the developing interfacial stresses between the restorative and the bonding agent, as well as the surface energy of the restorative [41,42]. In the present study, HF induced a roughened surface similar to that reported in previous studies in polymeric silica-based CAD/CAM blocks [14].
Sandblasting treatments should be implemented with a mean particle diameter of around 50 μm, because previous reports demonstrated the creation of microcracks when larger particles were used, and the time of air abrasion should not overcome 30 s [43]. More specifically, in a previous study [44], it was reported that air abrasion with 50 μm Al2O3 particles at 2 bar air pressure increases surface roughness up to 225% without creating surface defects, while another study [43] found that with over 30 s of air abrasion, superficial microcracks were formed, expanding up to 3 μm into the material. This is consistent with the findings of the current research.
Laser surface modification did not show improved behavior regarding microgap formation compared with the control group. It has been postulated that laser surface modification may provide enhancement in the bonding of RBC CAD/CAM blocks [45,46,47]. Nonetheless, the laser parameters of the treatment such as average power, repetition rate, duration of irradiation, laser tip/surface distance, and the size of the irradiated area may induce differences in surface topography [48]. As SEM observations revealed in the current study, the laser-treated surfaces showed large, intact areas among the craters, which means that the surfaces were not uniformly modified to increase the micromechanical interlocking of resin cement materials in their irregularities. This might have an impact on the bonding between the material’s surface and the luting agent, resulting in the formation of large microgaps comparable to those of the control group. Presumably, different laser parameters (i.e., increased irradiation time) may offer improved surface modification and bonding performance.
The mechanism of action of the Er,Cr:YSGG laser involves high absorption of laser energy from water molecules, and as a consequence microexplosions, which lead to the removal of the particles from the surface of the restorative, especially inorganic components, and the creation of microporosities, as observed in the SEM images of this research [46]. The Er,Cr:YSGG laser beam has the advantage of the minimum generation of a thermal damaged layer, which is attributed to its hydrokinetic structure and the absence of smear layer formation [47]. Moreover, this laser wavelength is considered a less hazardous micromechanical treatment in comparison with sandblasting, due to the fact that Al2O3 aerosols have been implicated in inducing detrimental effects on the human body [49]. Although the findings of this investigation revealed larger microgap formation following laser treatment than when using the other mechanical surface treatments, in a previous report [50], the aforementioned treatments did not exhibit significant differences regarding bond strength. Additionally, it has been noted that erbium lasers are also capable of removing the glass phase of CAD/CAM materials, unlike sandblasting [51].
Some of the drawbacks of this in vitro research include the evaluation of only one restorative material, environmental conditions (temperature and humidity) that did not coincide with the oral conditions, the testing of only one laser protocol for the surface treatments, and the sectioning of the specimens for evaluating microgap formation using SEM. Presumably, a non-destructive microscopic technique such as microcomputed tomography could make more accurate measurements.

5. Conclusions

Within the limitations of this investigation, it could be deduced that the surface modifications of an RBC CAD/CAM material may affect microgap formation at the adhesive interface of the restorations, possibly due to differences in bonding performance. The mechanical surface treatment using air abrasion with Al2O3 particles presented lower microgap formation compared with the other treatments. The Er,Cr:YSGG-laser-treated group showed similar microgap formation to the control group. Nevertheless, different laser settings may result in more favorable outcomes. Hydrofluoric acid in combination with silane exhibited larger microgaps after artificial aging in comparison with sandblasting treatments. Further studies are necessary to confirm the findings of this research and especially the evaluation of the restorations in vivo.

Author Contributions

Conceptualization, D.D. and C.P.; methodology, A.G., C.P., and D.D.; software, A.G.; validation, P.M. and K.T.; formal analysis, A.G.; investigation, D.D.; resources, D.D.; data curation, C.P.; writing—original draft preparation, A.G. and D.D.; writing—review and editing, P.M. and K.T.; visualization, C.P.; supervision, D.D. and K.T.; project administration, D.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Ethics Committee of Aristotle University of Thessaloniki (protocol code 142/10-03-2022).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The data of this study are available after request to the corresponding author.

Acknowledgments

The authors thank Stavros Oikonomidis for his contribution to SEM observations and EDS analysis of the specimens for the purposes of this study, which were implemented at the Solid-State Physics Division, Department of Physics, Aristotle University of Thessaloniki, Greece.

Conflicts of Interest

The authors declare no conflict of interest.

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Applsci 13 02335 g001 550
Figure 1. Representative SEM image in backscattered mode for evaluation of the maximum width of the formed microgap in μm using the software of the microscope.
Figure 1. Representative SEM image in backscattered mode for evaluation of the maximum width of the formed microgap in μm using the software of the microscope.
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Applsci 13 02335 g002 550
Figure 2. Representative SEM images of the material/dentin interface, where the structures were defined by using energy-dispersive X-ray spectroscopy: (a) elemental analysis of the right side of the SEM image indicating composite material; (b) elemental analysis of the left side of the same SEM image indicating dentin.
Figure 2. Representative SEM images of the material/dentin interface, where the structures were defined by using energy-dispersive X-ray spectroscopy: (a) elemental analysis of the right side of the SEM image indicating composite material; (b) elemental analysis of the left side of the same SEM image indicating dentin.
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Figure 3. Representative SEM images of the treated surfaces of each experimental group in ×50 ((a–e) images) and ×500 ((f–j) images) magnifications. CR: control; SB1: air abrasion with 29μm Al2O3 particles; SB2: air abrasion with 53 μm Al2O3 particles; HF: hydrofluoric acid gel + silane; LR: Er,Cr:YSGG laser treatment.
Figure 3. Representative SEM images of the treated surfaces of each experimental group in ×50 ((a–e) images) and ×500 ((f–j) images) magnifications. CR: control; SB1: air abrasion with 29μm Al2O3 particles; SB2: air abrasion with 53 μm Al2O3 particles; HF: hydrofluoric acid gel + silane; LR: Er,Cr:YSGG laser treatment.
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Figure 4. Representative SEM images (×100 magnification) for each experimental group at the material/dentin interface revealing the microgap formation: (a) CR: control; (b) SB1: air abrasion with 29μm Al2O3 particles; (c) SB2: air abrasion with 53 μm Al2O3 particles; (d) HF: hydrofluoric acid gel + silane; (e) LR: Er,Cr:YSGG laser treatment.
Figure 4. Representative SEM images (×100 magnification) for each experimental group at the material/dentin interface revealing the microgap formation: (a) CR: control; (b) SB1: air abrasion with 29μm Al2O3 particles; (c) SB2: air abrasion with 53 μm Al2O3 particles; (d) HF: hydrofluoric acid gel + silane; (e) LR: Er,Cr:YSGG laser treatment.
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Table
Table 1. The technical characteristics of the tested materials according to the manufacturers.
Table 1. The technical characteristics of the tested materials according to the manufacturers.
MaterialManufacturerTypeComposition
Lava™ Ultimate3M ESPE, Seefeld, GermanyRBC
CAD/CAM
blocks		Bis-GMA, UDMA, Bis-EMA, TEGDMA, SiO2 (20 nm), ZrO2 (4–11 nm), aggregated ZrO2/SiO2 cluster
(SiO2: 20 nm, ZrO2: 4–11 nm)
RelyX™ Ultimate3M ESPE, St. Paul, MN, USADual-cure resin cementBase: methacrylate monomers, radiopaque, silanated fillers, initiator components, stabilizers, and rheological additives
Catalyst: methacrylate monomers, radiopaque alkaline (basic) fillers, initiator components, stabilizers, pigments, rheological additives, fluorescence dye, and dark polymerize activator for Single Bond™ Universal Adhesive
Single Bond™ Universal Adhesive3M ESPE, Seefeld, GermanyUniversal adhesive system10-MDP monomer, dimethacrylate resins, HEMA, polyalkenoic acid copolymer, fillers, ethanol, water, initiators, and silane
Bis-GMA: bisphenol A diglycidylmethacrylate; Bis-EMA: ethoxylated bisphenol A dimethacrylate; CAD/CAM: computer-aided design/computer-aided manufacturing; HEMA: hydroxyl–ethyl methacrylate; RBC: resin-based composite; TEGDMA: triethylene glycol dimethacrylate; UDMA: urethane dimethacrylate; SiO2: silica; ZrO2: zirconia; 10-MDP: 10-methacryloyloxydecyl dihydrogen phosphate.
Table
Table 2. Means and standard deviations (SDs) of the width of microgaps of each experimental group formed after thermocycling. CR: control; SB1: air abrasion with 29 μm Al2O3 particles; SB2: air abrasion with 53 μm Al2O3 particles; HF: hydrofluoric acid gel + silane; LR: Er,Cr:YSGG laser treatment.
Table 2. Means and standard deviations (SDs) of the width of microgaps of each experimental group formed after thermocycling. CR: control; SB1: air abrasion with 29 μm Al2O3 particles; SB2: air abrasion with 53 μm Al2O3 particles; HF: hydrofluoric acid gel + silane; LR: Er,Cr:YSGG laser treatment.
Experimental GroupsMean and SD of the
Microgap Size (μm)		Free Microgap Interfaces (%)
CR170.72 ± 79.06 A0%
SB16.83 ± 3.02 B25%
SB22.31 ± 1.61 B50%
HF22.46 ± 9.29 C25%
LR163.44 ± 59.23 A0%
Same uppercase superscripts in the middle column indicate no statistically significant difference (p <0.05).
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MDPI and ACS Style

Galanopoulos, A.; Dionysopoulos, D.; Papadopoulos, C.; Mourouzis, P.; Tolidis, K. Microgap Formation between a Dental Resin-Matrix Computer-Aided Design/Computer-Aided Manufacturing Ceramic Restorative and Dentin after Various Surface Treatments and Artificial Aging. Appl. Sci. 2023, 13, 2335. https://doi.org/10.3390/app13042335

AMA Style

Galanopoulos A, Dionysopoulos D, Papadopoulos C, Mourouzis P, Tolidis K. Microgap Formation between a Dental Resin-Matrix Computer-Aided Design/Computer-Aided Manufacturing Ceramic Restorative and Dentin after Various Surface Treatments and Artificial Aging. Applied Sciences. 2023; 13(4):2335. https://doi.org/10.3390/app13042335

Chicago/Turabian Style

Galanopoulos, Alexandros, Dimitrios Dionysopoulos, Constantinos Papadopoulos, Petros Mourouzis, and Kosmas Tolidis. 2023. "Microgap Formation between a Dental Resin-Matrix Computer-Aided Design/Computer-Aided Manufacturing Ceramic Restorative and Dentin after Various Surface Treatments and Artificial Aging" Applied Sciences 13, no. 4: 2335. https://doi.org/10.3390/app13042335

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