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. 2025 May 24;25:785. doi: 10.1186/s12903-025-06174-0

Evaluating the effect of surface treatments and adhesive systems on shear bond strength and microleakage in 3D permanent resin denture bases

Emel Arslan 1,✉, Hatice Sevmez 1, Merve Hatice Arslan 2
PMCID: PMC12102799  PMID: 40413442

Abstract

Objective

The objective of this study was to evaluate and compare microleakage and bond strength values resulting from various surface treatments and adhesive system processes applied to different resin materials.

Methods

270 samples of two different 3D resin materials (Saremco Crowntec-Saremco Denture) were prepared by various surface treatments (control: Group C, hydrofluoric acid application: Group A, tribochemical sandblasting: Group T), adhesive systems (bond: Group B, resin cement: Group R, resin: Group P) (n = 30). Microleakage and bond strength tests were performed, and the data obtained were analyzed by a two-way ANOVA.

Results

The findings revealed statistically significant differences among the analyzed groups (p < 0.001). While the mean values of microleakage in Group C were the highest (0.15 ± 0.04 mm2), no significant difference was found between Group A (0.13 ± 0.05 mm2) and Group T (0.14 ± 0.03 mm2). When the bond strength was compared, Group B showed the highest bond strength value (8.50 ± 1.79 MPa) while Group P showed the lowest bond strength value (3.08 ± 1.61 MPa).

Significance

The study found that applying Group A (2.50 ± 1.47 MPa) weakened the bond, while Group T (3.78 ± 2.63 MPa) had lower values than Group C (13.52 ± 1.37 MPa). Among the adhesive systems, bond application showed the best performance. The application of surface treatment decreases bond strength with reduced microleakage. These findings emphasize the importance of selecting appropriate adhesive systems for 3D-printed complete dentures in clinical applications. It shows the best ways for both clinicans and patients to bond in order to meet the mechanical and aesthetic needs that come up with long-term prostheses use.

Keywords: Adhesive systems, 3D printer, Denture base resin, Microleakage, Surface treatment

Introduction

Despite significant advancements in dental implants, complete dentures remain a crucial treatment option for individuals who have lost all of their teeth [1]. This is because they are complicated, require surgery, and are expensive [2].

Poly-methyl-methacrylate (PMMA) resin, introduced in the 1930 s, has been the standard material because of its predictable physical properties. But problems like monomers that don’t react, the ability for Candida albicans to colonize, and long prosthetic procedures can cause problems for patients [3]. Therefore, researchers are continuously exploring alternative materials and techniques to improve the durability and biocompatibility of dental prosthetics. These limitations necessitate the adoption of modern techniques such as computer-aided design (CAD)/computer-aided manufacturing (CAM) systems [4].

By mechanically or chemically treating the ridge-lap surface of the dentures, researchers have tried to make it easier for denture teeth and denture base resins (DBRs) to stick together. The glaze on the ridge-lap surface of the tooth is broken up by mechanical preparation, which can be done by using techniques like bur roughening and microblasting to make grooves and cavities in the tooth. Chemical treatments with PMMA monomer, acetone, ethylene, methylene chloride, dichloromethane (DCM), and solvents that don’t polymerize have been looked into by researchers. Additionally, the type of DBR and the material used for the artificial teeth can influence bond strength. Studies indicate that surface treatment of ridge-lap areas can significantly improve bonding between artificial teeth and DBRs.

However, research focuses on enhancing this bond because resin denture teeth made from stronger materials, such as composites or those incorporating cross-linking agents, have demonstrated lower bond strength than traditional acrylic denture teeth [5]. In conventional dentures, debonding is a common issue, accounting for approximately one-third of all denture repairs [6]. Ensuring a strong bond between artificial teeth and DBRs is essential for the durability and longevity of dental prostheses. Traditionally, methacrylate-based bonding agents bond resin denture teeth to milled denture bases [7]. Resin teeth with dentures frequently adhere to a milled denture base using methacrylate-based bonding solutions. Suzuki et al. [8] found that using 4-META adhesive makes the bond between cross-linked prosthetic teeth stronger. However, there is still not a lot of research on how long the bond between teeth and CAD/CAM-fabricated prosthetic bases lasts.

Choi et al. [9] found that heat-polymerized denture base resins (DBRs) have a stronger bond with false teeth than CAD/CAM DBRs. This shows how important it is to choose the right DBR. Using methacrylate-based bonding agents and ridge-lap conditioning techniques can help the fake teeth and DBRs stick together better [10]. Saavedra et al. [11]found that bonding agents based on methyl methacrylate (MMA) make bonds stronger when exposed to air abrasion, no matter what kind of DBR was used. The same thing was shown by Han et al. [10], who found that MMA-based resin cement with 4-META can bond prepolymerized DBRs well enough.

The CAD/CAM technology facilitates the production of resin teeth and prosthesis bases in a single piece [4, 12]. However, resin teeth are prone to rapid wear. To maintain proper vertical dimension and occlusion, these teeth must resist wear. Therefore, traditional acrylic resin denture teeth have incorporated various fillers and cross-linking agents to enhance their physical properties [3, 13, 14]. Advances in technology now allow for the separate fabrication of denture bases and teeth using 3D printers. Although prostheses produced with three-dimensional printers provide aesthetic and rapid production advantages, debonding artificial teeth from the prosthesis base is still a common problem [15]. The effect of different surface treatments and adhesive systems on this connection remains unclear. There is a need to determine the ideal method and material combination. However, studies on the durability and long-term success of the bond between artificial teeth and prosthesis bases in dental prostheses produced by three-dimensional printers are still limited.

The goal of this study was to find out how different surface treatments on the crestlap surface, adhesive systems, and polymerization techniques affected the shear bond strength (SBS) and microleakage between DBRs and false teeth. According to the null hypothesis, there were no appreciable differences in SBS between the different treatments. The alternate hypothesis posited that the administered therapies would influence microleakage.

Material and method

Specimen preparation

Two types of three-dimensional (3D) resin materials were used: Saremco Crowntec (Saremco Dental AG, Rebstein, Switzerland) for the crown fabrication and Saremco Denture Base Resin (Saremco Dental AG, Rebstein, Switzerland) for denture base material. The required sample size was calculated using G*Power v3.1.9.2, ‘f test- ANOVA: Fixed effects, special effects, main effects, and interactions,’ was used for power and sample size assessment. The 95% confidence level (1-α), 95% test power (1-β), effect size f = 0.25, and the results of the analysis of variance (ANOVA) test were used to determine a sample size of 251. The study planned for a sample size of 540 specimens. These specimens were allocated as follows: 270 for microleakage testing and 270 for bond strength testing. To assess microleakage, 270 specimens (diameter: 15 mm; thickness: 1.2 mm) were produced using AutoCAD (Autodesk Inc., USA), and 30 specimens were allocated to each group. In addition, 270 specimens were prepared to check the bond strength. Saremco Crowntec (5 mm long, 2 mm thick) and Saremco Denture Bases (10 mm wide, 2 mm long) were rectangular specimens simulating crown and base structures were fabricated [12]. The thickness of the specimens was verified using a digital caliper (TorQ 150 mm × 0.01-mm Digital Caliper, China). To ensure surface cleanliness before treatment, all specimens were immersed in isopropyl alcohol and sonicated in an ultrasonic bath (Euronda, Sassuolo, Italy) for 5 min. Specimens intended for microleakage testing were stained with methylene blue and thus were excluded from bond strength testing. Therefore, the total sample count was distributed across two separate groups to avoid cross-testing contamination.

Surface treatment

The samples have been split into three groups according to the surface treatments administered:

  • Group C (control): This group consists of untreated samples used as a reference.

  • Group A (hydrofluoric acid treatment): The specimens were subjected to 9% hydrofluoric acid (Ultradent Porcelain Etch, Utah, USA) for 60 s, washed for 2 min, and subsequently coated with silane (Ultradent Silane), which was allowed to dry for 60 s.

  • Group T (tribochemical sandblasting): The samples were roughened via tribochemical sandblasting utilizing 30-µm silica-coated Al2O3 (3 M ESPE, Seefeld, Germany). The particles were blasted at a pressure of 3 bars for 15 s, maintaining a distance of 10 mm between the sandblasting apparatus and the sample. The treated samples were cleaned with 96% isopropyl alcohol (ARPI) in an ultrasonic device (Euronda, Sassuolo, Italy). All procedures were conducted by a sole operator to guarantee uniformity. All procedures were performed by a single operator to ensure consistency [16].

Adhesive system application

After surface treatment, the specimens were divided into three groups according to the adhesive system used:

  • Group B (Universal Adhesive Group): Tetric N-Bond Universal (Ivoclar Vivadent, Schaan, Liechtenstein), and polymerization was performed with an LED light device (Bredent GmbH & Co. KG, Senna, Germany).

  • Group R (Resin Adhesive Group): Using Saremco Crowntec resin, polymerization was performed under Dentafab curing light for 10 min.

  • Group P (Resin Cement Group): Using Panavia SA Cement (Kuraray Noritake Dental, Tokyo, Japan), curing was performed with an LED light device (Bredent GmbH & Co. KG, Senna, Germany) for 120 s according to the manufacturer’s recommendation.

To establish a uniform and consistent adhesive thickness, polymerization was standardized using a specialized device applying 0.94 kg of force [17]. The adhesives were applied using an active brushing technique for 20 s with a microbrush. Excess adhesive was gently removed using a dry microbrush before polymerization [10]. Group B and Group P specimens were polymerized using an LED light unit (Bredent GmbH & Co. KG, Senna, Germany). Group R specimens were cured using the DentaFab UV curing system for 10 min. To control the adhesive layer thickness and standardize the bonding area, a static load of 0,94 kg was applied during the bonding procedure until the curing was completed. The leftover excess cement was carefully removed with a dental explorer after polymerization. Curing procedures varied depending on the adhesive system (Table 1).

Table 1.

Materials used in the study, their contents and application methods

Product Composition Application Method
Saremco Crowntec (Saremco Dental AG, Rebstein, Switzerland) Bisphenol A ethoxylate dimethacrylate (Bis-EMA), Dental glass, pyrogenic silica, catalysts, inhibitors The samples produced in Asiga printer were cured in Dentafab curing device for 1 × 10 min. Cleaning in ultrasonic bath 3 min
Saremco Denture Base resin (Saremco Dental AG, Rebstein, Switzerland)

Bisphenol A ethoxylate dimethacrylate (Bis-EMA), Urethanmethylcrylate (UMA)

Triethylene glycol dimethacrylate (TEGDMA), pyrogenic silica, catalysts, inhibitors, pigments

 The samples produced in Asiga printer were cured in Dentafab curing device for 1 × 10 min. Cleaning in an ultrasonic bath for 3 min
Hydrofluoric acid (Ultradent Porcelain Etch, Utah, USA) 9% Buffered hydrofluoric acid After the surface is acidified for 90 s, the surface is thoroughly rinsed and dried. Silane is applied to the surface and left for 60 s
Air-abrasion (3 M ESPE, Seefeld, Germany) Silica-coated aluminum trioxide particles (30 µm) The equipment operated at a pressure of 3 bar for 15 s, maintaining a 10 mm distance from the sample
Tetric N-Bond Universal (Ivoclar Vivadent, Schaan, Liechtenstein) Ethanol, phosphonic acid acrylate, Bis-GMA, HEMA, UDMA, diphenyl (2,4,6- trimethylbenzoyl) phosphine oxide The bond light-cured for 10 s at a light intensity of 750 mW/cm2
Panavia SA Cement (Kuraray Noritake Dental, Tokyo, Japan) MDP, Bis-GMA, TEGDMA, Hydrophobic aromatic dimethacrylate, HEMA, Silanated barium glass filler, Silanated colloidal silica, dl, Camphorquinone, Peroxide, Catalysts, Pigments, Hydrophob ic aliphatic dimethacrylate, Surface treated sodium fluoride, Accelerators After light curing for 2 s, remove excess cement and cure for 2 min
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Microleakage evaluation

Before testing, all specimens were subjected to thermal aging to simulate clinical conditions. Specimens were subsequently exposed to 10,000 temperature cycles (Gökçeler Makine, Sivas, Turkey) ranging from 5 to 55 °C, with a transfer duration of 10 s and a dwell duration of 30 s. This aging process is critical for mimicking the long-term clinical performance of the resin interfaces [18]. Two coats of nail varnish (Flormar, Kocaeli, Turkey) were applied to the sample surfaces, disclosing 1 mm of the connection areas. The samples prepared for microleakage were submerged in a 1% methylene blue solution at 37 °C for 24 h to evaluate marginal leakage. After staining, the samples were bisected for microleakage analysis. Coloration at the microleakage areas was examined under a stereomicroscope (SZx10 Olympus, Tokyo, Japan) at 25 × magnification (Fig. 1). The images were measured using computer program (Pycharm 3.12.3, Prague, Czech Republic) for dimensional measurement in square millimeters (mm2) (Fig. 2). The images were measured using Python and OpenCV (Python: a high-level programming language for data processing and automation; OpenCV: an open-source computer vision library for image analysis). The analysis was performed in PyCharm (an integrated development environment (IDE) for Python programming). The process was carried out in the following steps. Images were loaded using the cv2.imread function. Lower and upper thresholds for the pink color were defined in the HSV color space, and the pink regions were masked using cv2.inRange. Contours of the pink regions in the mask were identified using cv2.findContours, and the area of each contour was calculated. The calculated area was converted into square millimeters (mm2), assuming each pixel represents 0.1 mm. The results were transferred into a Pandas DataFrame and saved as an Excel file. Through this process, the sizes of pink-colored regions in the images were measured in square millimeters and recorded in an Excel file [19, 20].

Fig. 1.

Fig. 1

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Examination of the obtained images under stereomicroscope

Fig. 2.

Fig. 2

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Analyzing the measurements of the obtained images in a computer program

Bond strength testing

The samples were put through thermal aging and then tested for bond strength on an Instron Model 3340 universal testing machine (Instron Corp., Wycombe, UK) with a crosshead speed of 1 mm/min. The ISO recommendation (TR 11405) advises a crosshead speed that varies between 0.45 and 1.05 mm/min [21]. The blade tip applied a load parallel to the adhesive interface between the denture base and the crown, with the maximum shear load prior to rupture being documented. The bond strength was determined utilizing the subsequent formula: Bond Strength (MPa) = Breaking Load (N)/Bond Area (mm2) (N/mm2 = MPa). All specimens were tested by a single operator to minimize variability. Each specimen was analyzed using a stereomicroscope (SZx10 Olympus, Tokyo, Japan) at 25 × magnification to identify the fracture type. The specimens are categorized into three types: adhesive, cohesive, and mixed.

Statistical analysis

Statistical analyses were performed using SPSS software (IBM SPSS Statistics for Windows, version 25.0; IBM Corp., USA). The Shapiro–Wilk test was employed for each group (n = 30) to assess the homogeneity of variance distributions for surface treatment and adhesive system to assess whether the data followed a normal distribution. The analysis of surface treatment and adhesive treatment was conducted using a two-way ANOVA test, using the Tukey post-hoc test. The criterion for statistical significance was set at p < 0.05.

Results

A two-way ANOVA showed significant differences in both microleakage and bond strength depending on the surface treatments and adhesive systems used (Tables 2 and 4). The descriptive statistics for microleakage and bond strength are presented in Tables 3 and 5.

Table 2.

Investigation of the effect of surface treatments, adhesive systems and curing processes on microleakage values

Source Type III Sum of Squares df Mean Square F Sig Partial Eta Squared
Surface Treatment 0,014 2 0,007 7,054  < 0,001 0,055
Adhesive System 0,094 2 0,047 47,071  < 0,001 0,279
Surface_Treatment * Adhesive System 0,016 4 0,004 4,110 0,003 0,063
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R2 = 0,375

Table 4.

Investigation of the effect of surface treatments and adhesive systems on bond strength values

Source Type III Sum of Squares df Mean Square F Sig Partial Eta Squared
Surface Treatment 6533.517 2 3266.758 142.711  < 0,001 0.540
Adhesive System 1674.770 2 837.385 36.582  < 0,001 0.231
Surface Treatment* Adhesive System 3775.909 4 943.977 41.238  < 0,001 0.404
R2 = 0.760
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Table 3.

Descriptive statistics of microleakage values (mm2)

Adhesive System Group C Group A Group T Total
Group B 0.12 ± 0.03c 0.09 ± 0.03d 0.12 ± 0.03c 0.11 ± 0.03X
Group P 0.17 ± 0.04a 0.14 ± 0.05a,b,c 0.14 ± 0.02b,c 0.15 ± 0.04Y
Group R 0.16 ± 0.04a,b 0.16 ± 0.03a,b 0.15 ± 0.03a,b 0.16 ± 0.03Y
Total 0.15 ± 0.04A 0.13 ± 0.05B 0.14 ± 0.03B 0.14 ± 0.04
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A-B: No difference between surface treatments with the same letter in the horizontal direction

X–Y: There is no difference between adhesive system and curing process with the same letter in vertical direction

a-d: There is no difference between surface treatments and adhesive systems with the same letter

Table 5.

Descriptive statistics of bond strength values (MPa)

AdhesiveSystem Group C Group A Group T Total
Group B 19.44 ± 1.54a 2.01 ± 0.66 b 5.06 ± 3.24b 8.50 ± 1.79X
Group R 18.43 ± 8.26a 3.07 ± 2.19 b 2.14 ± 1.06b 8.21 ± 3.79X
Group P 2.68 ± 0.68 b 2.43 ± 0.90 b 4.13 ± 2.23b 3.08 ± 1.61Y
Total 13.52 ± 1.37A 2.50 ± 1.47B 3.78 ± 2.63B 6.60 ± 1.78
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A-B: There is no difference between surface treatments with the same letter

X–Y: There is no difference between adhesive system and curing process with the same letter in vertical direction

a-b: There is no difference between surface treatments and adhesive systems with the same letter

Microleakage results

The data showed that surface treatments, particularly adhesive systems, had a significant impact on microleakage values (p < 0.001). The highest mean microleakage was recorded in Group C (0.15 ± 0.04 mm2). No statistically significant difference was found between Group A (0.13 ± 0.05 mm2) and Group T (0.14 ± 0.03 mm2) (p > 0.05). Group B exhibited the lowest microleakage among the adhesive systems, with a mean value of 0.11 ± 0.03 mm2. No significant difference was observed between Group R (0.16 ± 0.03 mm2) and Group P (0.15 ± 0.04 mm2; p > 0.05). The interaction between surface treatment and adhesive system did not show a significant effect on microleakage when analyzed separately (p > 0.05). However, a statistically significant interaction effect emerged when the combined influence of surface treatments and adhesive systems was analyzed (p < 0.001; Table 2). The lowest microleakage value was observed in Group B with Group A (0.09 ± 0.03 mm2), whereas the highest microleakage was found in Group R with the Group C resin adhesive (0.17 ± 0.04 mm2). Detailed pairwise comparisons are shown in Table 3 (Fig. 3).

Fig. 3.

Fig. 3

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Graphical representation of average values of microleakage

Bond strength results

The bond strength data also revealed statistically significant differences among the surface treatments and adhesive systems (p < 0.001, Table 4). Group C exhibited the highest mean bond strength value (13.52 ± 1.37 MPa), whereas Group A (2.50 ± 1.47 MPa) and Group T (3.78 ± 2.63 MPa) demonstrated significantly lower bond strengths. When comparing the adhesive systems, both bonded and resin-treated specimens showed higher bond strength values (8.50 ± 1.79 MPa and 8.21 ± 3.79 MPa, respectively) than the resin cement-treated specimens (3.08 ± 1.61 MPa). A statistically significant interaction between the surface treatments and adhesive systems was observed (p < 0.001). The highest bond strength value was recorded in Group B with Group C (19.44 ± 1.54 MPa), while the lowest was obtained in Group B with Group A (2.01 ± 0.66 MPa). Additional multiple comparisons are presented in Table 5 (Fig. 4).

Fig. 4.

Fig. 4

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Graphical representation of average values of bond strength

The predominant failure mode was adhesive. However, Group CB, Group AB, Group AP, Group TB also showed mixed failures. Other groups showed adhesive failures (Fig. 5). No cohesive failure was observed in the tested specimens (Table 6).

Fig. 5.

Fig. 5

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Failure between 3D permanent resin denture base and permanent resin. a Mixed failure, b Adhesive failure

Table 6.

Modes of failure in each group of specimens

Failure Mode
Groups Adhesive Cohesive Mix Total
Group C Group B 12 0 18 30
Group R 17 0 13 30
Group P 19 0 11 30
Group A Group B 7 0 23 30
Group R 16 0 14 30
Group P 12 0 18 30
Group T Group B 10 0 20 30
Group R 16 0 14 30
Group P 19 0 11 30
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Discussion

The research assessed the bond strength and microleakage characteristics of CAD/CAM denture base resins in conjunction with resin denture teeth. The study involved a comparative analysis of different adhesive techniques and surface treatments applied to enhance bonding. The experimental groups demonstrated variations in bond strength and microleakage values compared with the control groups. The null hypothesis was rejected due to the significant differences observed in bond strength across the various surface treatments and adhesive systems. Moreover, surface treatments significally influced microleakage values, thereby supporting the acceptance of the alternative hypothesis.

In this study, microirregular structures were created through surface treatments to improve the mechanical interlocking between denture teeth and bases. Previous research has demonstrated that HF etching causes surface degradation and increases microirregularities, which may interfere with bonding [22, 23]. Although the application of silane primer is recommended by manufacturers to promote chemical adhesion [24], the present study found that HF-treated samples showed reduced bond strength compared to the control group. This reduction may be attributed to the acid’s chemical interaction with the denture base resin, altering its surface integrity. Similarly, Bayati et al. [25] reported that primer-treated PMMA or UDMA specimens from bubbles during chemical reactions can initiate fractures and reduce bond strength. When comparing the microleakage values, the highest leakage was observed on acid-treated surfaces Group A (0.13 ± 0.05 mm2).

Another surface treatment applied in this study was tribochemical sandblasting. This process involves blasting high-pressure aluminum oxide particles onto the surface of the material to increase surface area and promote mechanical interlocking. As a result, Group T showed lower microleakage values (0.14 ± 0.03 mm2) compared to Group C (0.15 ± 0.04 mm2), although the bond strength of Group T (3.78 ± 2.63 MPa) was significantly lower than that of Group C. This finding indicates that while tribochemical treatment may reduce microleakage, it may also compromise bond strength. The loss in bond strength may be due to the disruption of the resin matrix by abrasive particles, which interferes with the chemical bonding potential of the surface. Most studies have reported that the chemical structure is more important than the form of polymerization and that base materials provide a stronger bond with materials of similar chemical structure [26, 27].

The bond formed between conventional denture resins and resin teeth primarily relies on mechanical retention achieved through intimate contact, alongside chemical bonding that occurs via the diffusion of monomers into the denture resin. The combination of increased temperature and pressure enhances bonding between denture resins and resin denture teeth. Prior research has shown that this approach enhances bond strength compared to the control group when the PMMA surface is modified [5, 28]. The results of this study demonstrate that the Group T (3.78 ± 2.63 MPa) exhibited a significant decrease in bond strength compared to Group C (13.52 ± 1.37 MPa). Surface treatments negatively affected the bond strength of permanent resins; therefore, it is recommended that clinicians avoid applying surface treatments to denture bases and permanent dental resins, as they may compromise the bond strength of these materials.

Although surface treatments resulted in lower bond strength between the denture base and permanent resin, they also showed reduced microleakage values. Prior research indicates that increased surface roughness facilitates the infiltration of fluid adhesives into uneven surfaces produced by sandblasting, hence enhancing mechanical adhesion [29, 30]. Comparisons of microleakage revealed that samples treated with surface modifications exhibited less staining. Additionally, the adhesive system used, especially the bond adhesive (0.11 ± 0.03 mm2), demonstrated higher fluidity than other systems, which may contribute to reducing microleakage.

This study utilized denture base resin to model the cementation between the denture base and teeth. Research indicates that increased chemical similarity among the denture base and the relining material correlates with enhanced bond strength [31]. However, in this study, Group P (0.15 ± 0.04 mm2) exhibited higher microleakage than the group B (0.11 ± 0.03 mm2). The bond between denture base resin and denture teeth is mainly attributed to the presence of unreacted methyl-methacrylate groups [32]. However, this phenomenon is less reliable in cold-cured materials due to residual unreacted double bonds at room temperature. Prior studies have demonstrated that elevated temperatures during polymerization enhance physical properties [33, 34], as heat facilitates polymer network mobility, which promotes bond formation. The impact of heat produced by polymerization and LED light sources on the degree of conversion in the post-curing process remains to be fully evaluated [35]. In addition, Bis-GMA in Panavia SA Cement causes the viscosity to increase [36]. Due to this feature and the high polymerization shrinkage of the TEGDMA monomer in its structure, microleakage values may be high [37].

In this study, microleakage and bond strength between 3D-printed base material and artificial teeth were investigated. Factors such as curing time, the photopolymer used, and the polymerization machine were found to affect polymerization outcomes. While the distance between the light source and the cured object in a light-curing unit can be controlled by the clinician, this is not possible in desktop post polymerization units where multiple LED lamps are placed on the inner walls of the polymerization chamber [35]. Furthermore, light-curing units are commonly available in dental clinics, offering an accessible option for post-polymerization of 3D-printed restorations, provided their mechanical performance is comparable to benchtop curing systems [38, 39]. Additionally, it was observed that microleakage increased with the thickness of the adhesive material used during curing. Because the resin and resin cement are denser than the bond adhesive system, light may not sufficiently penetrate the inner surface, resulting in excessive microleakage due to inadequate curing. Studies on curing have shown that light rapidly weakens as it passes through the resin, leading to insufficient polymerization because the material is not fully activated [35]. In such cases, extending the polymerization time or using more intense light sources is recommended to compensate for light attenuation [40]. However, according to the results of the present study, LED light was applied in Group B (0.11 ± 0.03 mm2) and Group R (0.16 ± 0.03 mm2) in accordance with the manufacturer’s recommendation, while a curing device was used in Group P (0.15 ± 0.04 mm2). While microleakage can be observed in material due to the effect of cold curing, the reason for more microleakage in Group R may be due to the thickness of the cement. The low viscosity of UDMA in Group B may be important for improving the processability of dental composite resins and replacing high-viscosity monomers [41].

Thermal cycling enables researchers to replicate intraoral circumstances while examining the mechanical characteristics of denture base materials. Thermal cycling causes water absorption in denture base resins, resulting in the degradation of polymeric chains and diminished mechanical characteristics [42, 43]. In this study, microleakage and bond strength values were analyzed after subjecting the samples to thermal cycling for 10,000 cycles, representing 1 yr of usage [44]. It is recommended that in vitro testing be conducted for a minimum of 7,000 cycles to produce a significant fatigue effect at the bonding interface [45].

Although no material can completely prevent microleakage, the ideal scenario would be a material that fully adapts and adheres to the tooth structure without microleakage [46]. In this study, 1% methylene blue dye was employed to assess microleakage. This dye is effective because it rapidly penetrates the tooth’s water compartment, does not interact with hard tissues, and is easily discernible under visible light due to its smaller molecular size than bacteria [47]. To ensure objectivity, the microleakage values in this study were analyzed using PyCharm 3.12.3 software, rather than traditional scoring methods. Although AutoCAD software has been used in previous studies, PyCharm provided automatically calculated numerical data [20, 48].

The limitation of this study is that bond strength and microleakage values were assessed without applying occlusal loading. The oral environment presents variables such as saliva, humidity, and thermal changes during food intake, all of which may influence the mechanical performance of dental polymeric materials. Therefore, further research is needed to assess how these conditions affect the bond strength between 3D-printed denture bases and permanent resin [49].

Conclusion

In the results obtained, the application of HF acid as a surface treatment between the denture base produced with a 3D printer and the teeth plays a critical role in reducing microleakage while reducing the bond strength. While bond application minimizes the risk of microleakage. Consideration of these findings in clinical applications is of great importance for the durability of complete dentures produced with 3D printers. This study will also guide future in vivo and in vitro studies in terms of adhesion and surface treatments.

Authors’ contributions

Conceived and designed the analysis: EA, HS, MHA; Data collection or data entry: EA, HS; Contributed data/analysis tools: EA, MHA; Performed the analysis: EA, MHA; Writing: EA, HS. All authors read and approved the final version of the manuscript.

Funding

There is no financial support in the study.

Data availability

Data sets generated and/or analyzed during the current study are not publicly available due to [Data are not publicly available as additional analyses are ongoing] but are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for Publication

Not applicable.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

Data sets generated and/or analyzed during the current study are not publicly available due to [Data are not publicly available as additional analyses are ongoing] but are available from the corresponding author upon reasonable request.

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