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. 2025 Jun 2;37(4-6):12. doi: 10.1007/s44445-025-00016-z

Mechanical properties of different types of composite resin used as clear aligner attachments: an in vitro study

Rana R Alshammari 1,2,✉, Nada Alshihah 3, Aljazi Aldweesh 3
PMCID: PMC12129878  PMID: 40455353

Abstract

Composite resin is often used as an orthodontic attachment due to its esthetic appearance, ease of clinical manipulation, and micromechanical bonding to etched enamel tooth structures. The aim of this study was to compare the Vickers microhardness (VMH) and shear bond strength (SBS) of six types of composite resins (Tetric PowerFlow, Filtek™ Supreme Flowable Restorative, Clearfil Majesty Flow, Tetric PowerFill, Filtek™ Supreme XTE Universal, and Estelite Sigma Quick). Twelve composite resin discs were fabricated for VMH test for each composite group. And 15 rectangular composite resin attachments were bonded on natural extracted premolars for each SBS test. VMH values were retrieved using an INOVATEST microhardness device at T1 and T2 after thermocycling and toothbrushing intervention. SBS values were retrieved using a Universal Testing Machine after thermocycling aging. The VMH values of all materials showed statistically significant differences (p =  < .01) between T1 and T2, as Clearfil Majesty Flow material did not show a significant difference and Filtek™ Supreme XTE Universal material showed a significant difference at (p =  < .05) but not at (p =  < .01). ANOVA revealed no statistically significant difference in the SBS values between the six composite resin materials. The Clearfil Majesty Flow composite resin was not affected by thermocycling or toothbrushing compared to all other composite groups.

Keywords: Clear aligner attachments, Composite resin attachments, Composite attachment SBS, Composite attachment VMH

Introduction

Previous survey studies have indicated that two-thirds of young adult patients reject orthodontic treatment, even though they are in need of esthetic or functional dental correction (Thai et al. 2020). These surveys found that esthetic impairment of visible brackets and speech disturbances resulting from lingual appliances were the primary causes of this rejection (Meier et al. 2003). In response, clear aligner trays were introduced to the market as an invisible alternative to fixed orthodontic brackets. The trays deliver orthodontic force via composite resin attachments, which are bonded on selective teeth following the proposed treatment plan (Shakir et al. 2018).

Composite resin is used as an attachment due to its esthetic appearance, ease of clinical manipulation, and micromechanical bonding to etched enamel tooth structures (Ilie and Hickel 2011). Many dental companies produce different products made of restorative composite resin, each with its own strength properties. For example, esthetic appearance and translucency to simulate natural dentition via enamel light transmitting can be controlled by adding glass, quartz, or fused silica filler to the resin (Roberson et al. 2002). However, these fillers have a major impact on material performance, including hardness and tooth bond strength (O’Brien 2002). Composite resin surface microhardness is a primary predictor of clinical success, as it quantifies a material’s competence to resist indentation or scratching when subjected to alteration force (Monteiro and Spohr 2015; Mandikos et al. 2001). Composite resin materials should be able to withstand various oral environments, which can be harsh as a masticatory force, habits, temperature fluctuation, and intraoral enzymes (Meier et al. 2003). The surface hardness of composite resins is affected by the type of organic matrix and the size, content, and arrangement of filler molecules (Bayne et al. 1998). Increase the percentage of filler in the composite generally leads to enhanced surface hardness (Mandikos et al. 2001). Furthermore, poor hardness may indicate either inadequate physical or chemical contact between the material matrix and fillers (Wilson et al. 2006).

When considering the endurance of composite resin restorations, the mechanical properties of the restorations are essential to the bond strength to the tooth in intraoral conditions (Heintze et al. 2017). Composite bond strength indicates the degree of adherence between a composite material and its base material, such as tooth enamel (Isolan et al. 2014). The bond is essential to the effectiveness of composite materials since inadequate bonding may lead to premature failure (Spencer et al. 2010). Numerous factors influence bond strength, including the way the surface is prepared, the adhesive technique employed, and the composite material’s composition (Brockmann et al. 2009). In clear aligner patients, repeated insertion and removal of aligners and mastication force can cause composite attachment bond failure, described as shearing (Kiran et al. 2012). Shear bond strength is defined as the quality of a material’s adhesive strength at the interface (Hasegawa 1994). Surface treatment techniques like etching or air abrasion improve adhesion by enhancing surface roughness, hence facilitating micro-mechanical retention (Bhadule et al. 2024).

Composite resin attachments are prone to wear, chipping, and debonding, which can be caused by mastication force or removal of the clear aligner tray (Ahmed et al. 2021). Many studies have evaluated the damage or failure rate of brackets, but limited research has examined the damage to composite attachments from microhardness deterioration or composite attachment debonding (Rossini et al. 2015). In practice, the choice of clear aligner attachment composite resin is mainly based on orthodontists’ clinical preference due to these limited comprehensive studies. Therefore, this research aimed to compare the mechanical properties as Vickers microhardness (VMH) and shear bond strength (SBS) in six types of resin composites. Three of them were low viscous flowable resin composites: Tetric PowerFlow (Ivoclar Vivadent AG), Filtek™ Supreme Flowable Restorative (3M™ ESPE), and Clearfil Majesty Flow (Kuraray Medical, Tokyo, Japan). The other three were high viscous restorative composites: Tetric PowerFill (Ivoclar, Vivadent AG), Filtek™ Supreme XTE Universal (3M™ ESPE), and Estelite Sigma Quick (Tokuyama Dental, Japan).

Materials and methods

Ethical approval

In accordance with the Declaration of Helsinki, the study protocol was approved by the Local Ethics Committee of King Saud University, Institutional Review Board with Reference Number 23/0228/IRB. Extracted premolars utilized in this study were originally collected after the extraction as part of comprehensive orthodontic treatment planning. Consequently, obtaining participants’ informed consent was considered unnecessary following the rules and regulations of the Kingdom of Saudi Arabia and the research policies and procedures of the KSU IRB. The research project was registered in CDRC of KSU # PR0146 and the study was conducted at physical lab, King Saud University, Riyadh, Saudi Arabia.

Vickers microhardness experimental sample

Based on 90% power and a 0.05 level of significance, a total of 72 composite discs were needed for the VMH testing, equaling 12 discs per group of the six composites. Each composite type was used to form disc shapes with a diameter of 5 mm and thickness of 1 mm that were compacted in a prefabricated stainless-steel mold for standardization. The discs were then pressed by a flat glass slide to remove any excess or voids and cured following each composite manufacturer’s instruction. For each group, the discs were numbered on the back side from 1 to 12 (Fig. 1) (Bowman Feinberg et al. 2016; Monteiro and Spohr 2015). All specimens were immersed in distilled water at 37ºC for 24 h for complete polymerization before baseline analysis using the INOVATEST microhardness tester device for VMH (Fig. 2) (Barakah 2021; Al-Angari et al. 2021; Monteiro and Spohr 2015). Three indentations were made with a diamond indenter at a load of 10 N and dwelling time of 10 s, 1 mm apart (Fig. 3) (García-Contreras et al. 2015). VMH was calculated for each indentation using an automated formula VMH=1.854F÷d2. The average value for each specimen was recorded as T1. After that, the intervention started, wherein each sample underwent thermocycling aging following ISO/TS 11405:2015 guidelines using SD Mechatronic TC 45 (Huber, Germany) in two distilled water baths for 30 s. The first bath had a temperature of 5 °C, and the second had a temperature of 55 °C. A 10-s transfer time was considered for 10,000 cycles, equal to 1 year of aging (ISO/TS 11405:2015 Dentistry—Testing of adhesion to tooth structure). Afterward, the samples were placed in a toothbrushing simulator ZM-3.8 (SD Mechatronik GMBH, Germany) using a toothbrush (Colgate Twister toothbrush, Vietnam) and toothpaste (Colgate Advanced Whitening toothpaste, UK) and set to circular brushing movement for 24 h, equal to 1 year of wear (Monteiro and Spohr 2015) (Fig. 4). Next, the discs were cleaned for 10 min using distilled water in an ultrasonic bath and assessed for T2 VMH using the INOVATEST VMH tester device.

Fig. 1.

Fig. 1

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VMH testing sample preparation

Fig. 2.

Fig. 2

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INOVATEST VMH tester device

Fig. 3.

Fig. 3

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Representative image of Vickers microhardness diamond pyramid indentation on composite resin surface

Fig. 4.

Fig. 4

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Discs mounted in tooth brushing simulator ZM-3.8 (SD Mechatronik GMBH, Germany)

Shear bond strength experimental sample

Based on 90% power and a 0.05 level of significance, a total of 90 natural teeth with bonded rectangular attachment were required for the SBS experiment, equaling 15 teeth with attachments for each composite group. A total of 90 natural teeth (premolars) free from cracks, caries, restoration, and dental anomalies were used for bonding with the attachments. The teeth were extracted for orthodontic treatment, cleaned from any debris, rinsed with distilled water, and preserved in a saline solution (0.90% of Sodium hypochlorite) at 4 °C until they were mounted on acrylic resin base dentoform. They were then randomly assigned to each experimental group using the Kutools randomization tool in MS Excel (16.0.12624, Proplus). Next, an intraoral iTero scanner (Element 2, iTero) was used to scan each model before they were imported as 3D digital models into the system to place digital rectangular attachments with dimensions of 2 mm (vertical) × 4 mm (horizontal) × 1 mm (thickness) using Meshmixer 3.5 software (Autodesk) on each tooth. Then, a 3D master model made from printable resin (ASIGA, USA) was printed using a printing machine (Phrozen Shuffle desktop 3D printer). This model was used to fabricate thermoplastic transfer attachment trays made of polyethylene with a pressure forming device (Henry Schein, Germany). The transfer attachment tray was wiped with 75% ethyl alcohol and air dried. Then, the manufacturer’s instructions for each composite material were followed for tooth etching, application of an adhesive layer, and composite loading and curing. The six types of composites (shade A1) were used based on their degree of viscosity, that is, either low viscous flowable resin composite such as Tetric PowerFlow, Filtek™ Supreme Flowable Restorative, and Clearfil Majesty Flow or high viscous restorative composite such as Tetric PowerFill, Filtek™ Supreme XTE Universal, and Estelite Sigma Quick (Table 1).

Table 1.

The tested composite resins *

Product Manufacturer Description Composition Filler size and load Filler type Significance
Tetric PowerFlow Ivoclar Vivadent AG Light-cure flowable composite

Bis-GMA,

Bis-EMA, UDMA,

DCP

Nanohybrid

71%

 Barium aluminium silicate glass, an Iso-filler copolymer mix, ytterbium fluoride Short curing time = 3 s
Tetric PowerFill Ivoclar Vivadent AG Light-cure restorative material

Bis-GMA,

Bis-EMA, UDMA,

PBPA, DCP,

β-allyl sulfone

Nanohybrid

79%

 Barium aluminium silicate glass, an Iso-filler copolymer mix, ytterbium fluoride and a spherical mixed oxide Short curing time = 3 s

Filtek™ Supreme Flowable

Restorative

 3M™ ESPE Light-cure flowable composite Procrylat, BisGMA, and TEGDMA resins

Nano

65%

Non-agglomerated/non-aggregated surface modified 20 nm silica filler, a non-agglomerated/non-aggregated surface modified 75 nm silica filler, a surface modified aggregated zirconia/silica cluster filler (comprised of 20 nm silica and 4 to 11 nm zirconia particles) and ytterbium trifluoride filler with a range of particle sizes from 0.1 to 5.0 μm

The aggregate has an average cluster particle size of 0.6 to 10 μm

 0% bubble formation due to unique tip design
Filtek™ Supreme XTE Universal 3M™ ESPE Light-cure restorative material

Bis-GMA (5–10 wt%), UDMA (5–10 wt%),

TEGDMA (5–10 wt%), Bis-EMA6 (1–10%), and polyethylene glycol

dimethacrylate (PEGDMA) resins

Nano

78.5%

Non-agglomerated nano silica of 20 nm filler size and

agglomerated zirconia/silica nanocluster with the size of 5–20 nm

 Exceptional handling properties
Clearfil Majesty Flow Kuraray medical Light-cure flowable composite

(TEGDMA)

Hydrophobic aromatic dimethacrylate

dl-Camphorquinone · Accelerators · Pigments · Others

 Nano 81% Silanated barium glass filler (average: 3 µm). Silanated colloidal silica (average: 20 nm) Super esthetic due to highest filler content
Estelite Sigma Quick Tokuyama Dental Light-cure restorative material Bis-GMA, TEGDMA

Supra-nano

82%

SiO2, ZrO2, PFSC

(200 nm)

 Unique blending effect due to spherical shape particles
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Bis-GMA: bisphenol A-diglycidyl dimethacrylate; Bis-EMA: ethoxylated bisphenol A dimethacrylate; UDMA: urethane dimethacrylate; DCP: tricyclodecane–dimethanol dimethacrylate; PBPA: propoxylated bisphenol A dimethacrylate; DMA: dimethacrylate; TEGDMA: triethylene glycol dimethacrylate; PEGDMA: polyethylene glycol dimethacrylate resins. *All information is supported by each manufacturer’s profile

After preparing the master model, thermocycling aging following ISO/TS 11405:2015 guidelines using SD Mechatronic TC 45 (Huber, Germany) was completed. Each tooth in the master model was sectioned interdentally and mounted on an acrylic resin base ring to be secured on a Universal Testing Machine (Instron 5965, Instron Corporation, MA, USA). A customized stainless steel road blade was directed occluso-gingivally to the parallel-aligned composite attachment. Shear force was generated at the composite attachment–tooth interface by transferring the vertical load at a speed of 1 mm/minute until failure was recorded at the composite attachment base (Figs. 5). At this point, the machine automatically stopped, and the maximum force was calculated electronically utilizing the formula SBS MPa=ForceN÷aream2 with Bluehill 3.22.1373 software; the data were exported in PDF format (Chen et al. 2021).

Fig. 5.

Fig. 5

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Bond strength sample preparation and SBS testing with Universal Testing Machine

Statistical analysis

SPSS version 23 (SPSS Inc., IBM, Chicago, Illinois, USA) was used to gather and analyze the data using the descriptive statistics as mean and standard deviation. The normality of the data was evaluated with the Kolmogorov–Smirnov test. A paired t-test was used to compare surface VMH, while a one-way ANOVA with significance set at p < 0.05 was used to compare SBS between the six composite groups.

Results

According to the Kolmogorov–Smirnov test, the data in the present experimental in vitro study showed a normal distribution.

Changes in microhardness

The mean VMH values of the six composite groups are summarized in Table 2. A paired t-test showed a highly statistically significant difference (p = < 0.01) in the microhardness of the composite resin tested between the baseline and after thermocycling and toothbrushing intervention in the Tetric PowerFlow, Tetric PowerFill, Filtek™ Supreme Flowable Restorative, and Estelite Sigma Quick composites. A significant difference (p = < 0.05) was also detected in the Filtek™ Supreme XTE Universal composite. In contrast, the Clearfil Majesty Flow composite showed insignificant differences in its microhardness values.

Table 2.

Mean and standard deviation of Vickers microhardness (VHN) of composite resins (n = 12)

Material N Mean (± SD) at T1 Mean (± SD) at T2 P value
Tetric PowerFill 12 53.91 (± 1.2) 39.33 (± 1) .000**
Tetric PowerFlow 12 34.76 (± 1) 32.59 (± 1.3) .000**
Filtek™ Supreme XTE Universal 12 80.01 (± 1.2) 78.18 (± 0.4) .03*
Filtek™ Supreme Flowable 12 57.15 (± 1) 51.56 (± 2) .000**
Clearfil Majesty Flow 12 47.87 (± 1.3) 47.08 (± 2) .31
Estelite Sigma Quick 12 62.67 (± 0.4) 54.61 (± 1) .000**
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**Shows highly statistically significant difference at p = < .01, *Shows statistically significant difference at p = < .05

Shear bond strength

The descriptive statistics from the SBS tests are shown in Table 3. The Tetric PowerFill composite had the highest SBS mean, while the FiltekTM Supreme XTE Universal composite had the lowest, even though an ANOVA revealed no discernible variation in SBS amongst the six composite groups (Table 4) (Fig. 6).

Table 3.

Mean shear bond strength (SBS) of composite resins (n = 15) in MPa

Material N Mean (± SD) Mx Min
Tetric PowerFill 15 43.52 (± 9.8) 57.78 24.49
Tetric PowerFlow 15 36.39 (± 9.1) 53.37 21.25
Filtek™ Supreme XTE Universal 15 34.50 (± 9.5) 50.70 16.18
Filtek™ Supreme Flowable 15 40.64 (± 5) 61.54 20.69
Clearfil Majesty Flow 15 40.66 (± 9.3) 47.63 33.63
Estelite Sigma Quick 15 36.74 (± 9.5) 44.85 22.16
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Table 4.

ANOVA OF shear bond strength (SBS) of composite resins (n = 15) in MPa

Sum of Squares df Mean Square F Sig
Between Groups 865.407 5 173.081 2.037 .082
Within Groups 7138.148 84 84.978
Total 8003.555 89
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Fig. 6.

Fig. 6

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Box plots represent the shear bond strength in different composite attachments group

Discussion

We chose the six composite resins according to their approval by their respective companies’ laboratory studies, short curing time (3 s), exceptional handling, and superior esthetic (Mantovani et al. 2018), in addition to other important advantages such as superior hardness, enhanced bond strength, and cost-effectiveness (Savignano et al. 2019; Mantovani et al. 2018). To date, there are no clinical or laboratory base recommendations for composite resins according to microhardness or bond strength for use as clear aligner attachments. Our research aimed to provide scientific guidance to answer this question about six various kinds of composite resin, both conventional and flowable.

The experimental composite resin specimens were prepared at 1 mm thickness and immersed in distilled water at 37ºC for 24 h to ensure maximum polymerization (Mowafy 2021). Adequate polymerization is critical for composite resin restorations’ functional and esthetic longevity in the oral cavity, as incomplete curing increases water sorption, decreases wear resistance, compromises strength, and increases residual monomer leaching (Da Silva et al. 2008).

Surface hardness is an important characteristic of composite resins to evaluate since it is considered a predictor of the material’s wear resistance (Shahdad et al. 2007). While surface hardness dictates the esthetic performance of composite resins, more importantly, it influences plaque retention and subsequent caries and periodontal problems. Various measurement methods are available to test surface hardness, such as the Vickers and Knoop tests. Vickers microhardness (VMH) is most used due to its simple sample preparation and testing via one diamond indenter, which can be used for materials like metals, polymers, and ceramics, with a test force ranging between 1 gf and 100 k gf (Ozcan et al. 2013). Previous studies have shown that VMH mean values of variable products of dental composite resins ranged from 30 to over 100 (Szczesio-Wlodarczyk et al. 2021a). In agreement with these findings, in the present in vitro study, the mean composite VMH values ranged from 34 to 80. However, a paired t-test showed insignificant differences in the VMH values of the Clearfil Majesty Flow composite group, meaning that the thermocycling aging and toothbrushing with whitening toothpaste interventions did not affect this composite resin’s VMH. This finding can be explained primarily by the adequate integration of triethylene glycol dimethacrylate (TEGDMA) into this resin’s matrix via fillers (Chladek et al. 2016). In contrast, the Tetric PowerFill, Tetric PowerFlow, Filtek™ Supreme XTE Universal, Filtek™ Supreme Flowable Restorative, and Estelite Sigma Quick composite groups showed statistically significant differences after thermocycling aging and toothbrushing interventions. Generally, Tetric PowerFill, Tetric PowerFlow, Filtek™ Supreme Flowable Restorative resin matrices contained different percentages of bisphenol A-glycidyl methacrylate (Bis-GMA), and a collection of other monomers compared to Clearfil Majesty Flow (Marovic et al. 2022; Elshazly et al. 2020; Ferooz et al. 2020; Lee et al. 2005). Moreover, Clearfil Majesty Flow uses “nano dispersion technology” in the filler to maximize its load, which can reach up to 81% wt (Al-Haj Husain et al. 2022). It has also added silanated barium glass filler in addition to the conventional silanated silica filler seen in other composites (Kuraray Dental 2008). The presence of hydrophobic rings in Clearfil Majesty Flow improves hardness values as well (Szczesio-Wlodarczyk et al. 2021b). In addition, the unique technique of surface treatment to enhance the wetting interaction between fillers and resin monomers can reduce air bubble entrapment compared with other flowable composite products (Kuraray Dental, 2008). In this study, we found that the specimens showed significantly different microhardness mean values, which was influenced by the different composition and filler particles of each composite resin group. One study found it is difficult to describe the exact filler content differences between commercial materials (Randolph et al. 2016).

Previous research has tried to simulate the harsh intraoral environment, which can include oral enzymatic degradation, water sorption, mastication, and parafunctional habits, using thermocycling in cool and hot water baths (Jaramillo-Cartagena et al. 2021; Nasoohi et al. 2017). One study found that a coupling agent had a hydrolysis effect on a composite that subsequently impacted the mechanical properties of the material by increasing its surface roughness and reducing its VMH (Delaviz et al. 2014). Chladek et al. evaluated the effects of thermocycling aging on VMH and found no statistically significant changes (p > 0.05). They attributed this to elevated temperatures during thermocycling, which potentially reduced the number of unreacted double bonds, promoting further polymerization and thereby enhancing the material's physical and mechanical properties (Chladek et al. 2016). Mechanical toothbrush abrasion acts as another option for aging, especially in combination with whitening toothpaste (Epple et al. 2019). Reports on the impact of whitening toothpaste on surface properties have stated conflicting results, however, with only some research finding reduced VMH values and increased surface roughness after its use (John and Author 2017; Da Rosa et al. 2016).

The second part of our experiment examined the shear bond strength (SBS) of the same six composite resins by contrasting the three high-viscosity restorative composites (Estelite Sigma Quick, Filtek™ Supreme XTE Universal, and Tetric PowerFill) with the three low-viscosity flowable composites (Tetric PowerFlow, Filtek™ Supreme Flowable Restorative, and Clearfil Majesty Flow). There were no statistically significant differences in SBS between the groups (p = 0.082), which could be explained by accurate adherence to each manufacturer's bonding protocol. As shown in Table 3, the Tetric PowerFill composite had the highest mean SBS, indicating that it better preserved attachment stability under applied force. This could be due to the material’s type of nanohybrid fillers it contains. These results are not consistent with other research that found significant differences in SBS between composite resins. For instance, a study comparing many resins discovered statistically significant variations in SBS (p < 0.01), suggesting that bond strength is significantly influenced by filler loading (Kircelli et al. 2023). These discrepancies may result from variations in the experimental materials, testing protocols, and material formulations, among other experimental conditions (Chen et al. 2021). This emphasizes the need for consistent evaluation processes to determine whether composite materials are appropriate for certain clinical applications.

Furthermore, because there were no statistically significant changes in SBS between the groups with low and high viscosities, it is possible that viscosity had limited influence on the bond strength of the investigated composites. However, increases in filler concentration have been shown to decrease polymerization shrinkage, which may lead to stronger bonding, as shown in the composites with high filler percentages that we experimented in the present study (Pereira et al. 2019). Compared to conventional composites, flowable composites have low viscosity and can be applied more quickly as aligner attachments (Shahin et al. 2024). Because they take on the shape of the attachment template, flowable composites are a preferred option for clear aligner attachment (Shahin et al. 2024; Kircelli et al. 2023). In conclusion, it is challenging to accurately evaluate the effect of different resin compositions based on filler size, type, or shape on specific physical or mechanical aligner attachments properties (García-Contreras et al. 2015).

Limitations

This is an in vitro study, so it was not possible to precisely simulate the temperature, humidity, or oral enzymes of the oral cavity. In addition, previous research has outlined that limiting the experiment materials to flowable composites is a preferred testing option (Shahin et al. 2024).

Clinical implications

The selection of clear aligner attachments composite resins significantly influences the esthetic appearance and the clinical durability of clear aligners orthodontic treatment. The findings of this study suggest that Clearfil Majesty Flow exhibits superior resistance to surface degradation following simulated aging, maintaining stable microhardness, which is essential for long-term esthetic and functional performance. Although all tested composites demonstrated comparable adhesive performance in terms of shear bond strength, clinicians should consider composite formulations with high filler content and optimized matrix composition to reduce wear, discoloration, and detachment risks.

Given the daily intraoral challenges faced by composite attachments—such as temperature fluctuations, masticatory forces, and oral hygiene practices—choosing materials with proven resistance to such factors may reduce the need for replacements or adjustment, as a result improving the clear aligners orthodontic treatment efficiency and patient satisfaction. These results support evidence-based decision-making in the selection of composite materials for clear aligner attachment protocols and highlight the need for further clinical validation to confirm in vivo behavior.

Conclusions

This in vitro study demonstrated significant differences in surface microhardness among the tested composite resins except Clearfil Majesty Flow following simulated aging and brushing, while no statistically significant differences were observed in their shear bond strength. Clearfil Majesty Flow revealed the most stable microhardness mean values post-intervention, potentially due to its high nano filler content and the optimized structure of the matrix formulation. Despite these findings, all materials showed comparable adhesive performance under standardized conditions.

Given the limited selection of composite resin material and the laboratory-based nature of the experiment, these results should be interpreted with caution. Clinical behavior may differ due to the complex intraoral environment. Therefore, further clinical studies are recommended to validate these findings and support evidence-based selection of composite materials for clear aligner attachments.

The following abbreviations are used in this manuscript

VMH

Vickers microhardness

SBS

Shear bond strength

MPa

Megapascal

Author contribution

R. R. A.: Conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project administration, resources, software, validation, visualization, and writing – original draft.

N. A.: Review, editing, and funding acquisition.

A. A.: Supervision, project administration, writing – review and editing, and funding acquisition.

Funding

This research received no external funding.

Data availability

Available upon reasonable request from the corresponding author.

Declarations

Competing interest

The authors declare no conflicts of interest.

Consent of publication

All authors agreed on publication at Saudi Dental Journal.

Consent of participate

Not applicable.

Footnotes

Publisher's Note

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

References

  1. Ahmed MA, AbdelAllah MM, Raslan EK, Gouda WR, Dawaba MM, Abd El-Ghafar IS, Ali AM, Abdelmonem MH (2021) Evaluation of clear aligners attachment success rate with different composite types. Int J Health Sci (Qassim) 533–541. 10.53730/ijhs.v5ns2.13071
  2. Al-Angari SS, Eckert GJ, Sabrah AHA (2021) Color stability, roughness, and microhardness of enamel and composites submitted to staining/bleaching cycles. Saudi Dent J 33:215–221. 10.1016/j.sdentj.2020.08.003 [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Al-Haj Husain N, Feilzer AJ, Kleverlaan CJ, Abou-Ayash S, Özcan M (2022) Effect of hydrothermal aging on the microhardness of high- and low-viscosity conventional and additively manufactured polymers. J Prosthet Dent 128:822.e1-822.e9. 10.1016/J.PROSDENT.2022.08.022 [DOI] [PubMed] [Google Scholar]
  4. Barakah H (2021) Effect of different curing times and distances on the microhardness of nanofilled resin-based composite restoration polymerized with high-intensity LED light curing units. Saudi Dent J 33: 1035–1041. 10.1016/j.sdentj.2021.05.007 [DOI] [PMC free article] [PubMed]
  5. Bayne SC, Thompson JY, Swift EJ Jr, Stamatiades P, Wilkerson M (1998) A characterization of first-generation flowable composites. J Am Dent Assoc 129(5):567–577. 10.14219/JADA.ARCHIVE.1998.0274 [DOI] [PubMed] [Google Scholar]
  6. Bhadule SN, Kalaskar R, Kalaskar A, Krishnakumar K, Joshi S, Balasubramanian S (2024) Clinical effectiveness of air abrasion when compared to conventional acid-etching technique in enhancing the retention of pit and fissure sealants: a systematic review. Int J Clin Pediatr Dent. 10.5005/jp-journals-10005-2782 [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Brockmann W, Geiß PL, Klingen J, Schröder B (2009) Adhesive bonding: materials, applications and technology. Adhesive Bonding: Mater Appl Technol 1–414. 10.1002/9783527623921
  8. Chen W, Qian L, Qian Y, Zhang Z, Wen X (2021) Comparative study of three composite materials in bonding attachments for clear aligners. Orthod Craniofac Res 24:520–527. 10.1111/ocr.12465 [DOI] [PubMed] [Google Scholar]
  9. Chladek G, Basa K, Żmudzki J, Malara P, Nowak AJ, Kasperski J (2016) Influence of aging solutions on wear resistance and hardness of selected resin-based dental composites. Acta Bioeng Biomech 18(3):43–52. 10.5277/ABB-00434-2015-03 [PubMed] [Google Scholar]
  10. Da Rosa GM, Da Silva LM, De Menezes M, Do Vale HF, Regalado DF, Pontes DG (2016) Effect of whitening dentifrices on the surface roughness of a nanohybrid composite resin. Eur J Dent 10:170–175. 10.4103/1305-7456.178305 [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Da Silva EM, Poskus LT, Guimarães JGA, Barcellos ADAL, Fellows CE (2008) Influence of light polymerization modes on degree of conversion and crosslink density of dental composites. J Mater Sci Mater Med 19:1027–1032. 10.1007/S10856-007-3220-5 [DOI] [PubMed] [Google Scholar]
  12. Delaviz Y, Finer Y, Santerre JP (2014) Biodegradation of resin composites and adhesives by oral bacteria and saliva: a rationale for new material designs that consider the clinical environment and treatment challenges. Dent Mater 30:16–32. 10.1016/j.dental.2013.08.201 [DOI] [PubMed] [Google Scholar]
  13. Elshazly TM, Bourauel C, Sherief DI, El-Korashy DI (2020) Evaluation of two resin composites having different matrix compositions. Dent J (Basel) 8. 10.3390/DJ8030076 [DOI] [PMC free article] [PubMed]
  14. Epple M, Meyer F, Enax J (2019) a critical review of modern concepts for teeth whitening. Dent J (Basel) 7. 10.3390/DJ7030079 [DOI] [PMC free article] [PubMed]
  15. Feinberg KB, Souccar NM, Kau CH, Oster RA, Lawson NC (2016) Translucency, Stain Resistance, and Hardness of Composites Used for Invisalign Attachments. J Clin Orthod 50(3):170–6. https://pubmed.ncbi.nlm.nih.gov/27117736/ [PubMed]
  16. Ferooz M, Bagheri R, Jafarpour D, Burrow M (2020) Physical properties of nanohybrid and microhybrid resin composites subjected to an acidic environment: a laboratory study. Oper Dent 45:E105–E113. 10.2341/18-319-L [DOI] [PubMed] [Google Scholar]
  17. García-Contreras R, Scougall-Vilchis R, Acosta-Torres L, Arenas-Arrocena C, García-Garduño R, de la Fuente-Hernández J (2015) Vickers microhardness comparison of 4 composite resins with different types of filler. J Oral Res 4:313–320. 10.17126/joralres.2015.061 [Google Scholar]
  18. Hasegawa TRD (1994) Laboratory evaluation of experimental restorative systems containing 4-META. Am J Dent 7:6–212 [PubMed] [Google Scholar]
  19. Heintze SD, Ilie N, Hickel R, Reis A, Loguercio A, Rousson V (2017) Laboratory mechanical parameters of composite resins and their relation to fractures and wear in clinical trials—a systematic review. Dent Mater 33:e101–e114. 10.1016/J.DENTAL.2016.11.013 [DOI] [PubMed] [Google Scholar]
  20. Ilie N, Hickel R (2011) Resin composite restorative materials. Aust Dent J 56:59–66. 10.1111/j.1834-7819.2010.01296.x [DOI] [PubMed] [Google Scholar]
  21. Isolan CP, Valente LL, Münchow EA, Basso GR, Pimentel AH, Schwantz JK, da Silva AV, Moraes RR (2014) Bond strength of a universal bonding agent and other contemporary dental adhesives applied on enamel, dentin, composite, and porcelain. Appl Adhesion Sci 2:1–10. 10.1186/S40563-014-0025-X/FIGURES/2 [Google Scholar]
  22. Jaramillo-Cartagena R, López-Galeano EJ, Latorre-Correa F, Agudelo-Suárez AA (2021) Effect of polishing systems on the surface roughness of nano-hybrid and nano-filling composite resins: a systematic review. Dent J (Basel). 10.3390/dj9080095 [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. John P, Author C (2017) Comparison of the effects of different toothpastes on the micro hardness of a nano hybrid composite resin-an in-vitro study. IOSR J Dent Med Sci 16:6–11. 10.9790/0853-1612050611 [Google Scholar]
  24. Kiran KM, Gopal T, Nujella SBP, Choudary MT, Reddy SP (2012) Comparison of shear bond strength of aesthetic restorative materials. Contemp Clin Dent 3:22–26. 10.4103/0976-237X.94541 [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Kircelli BH, Kilinc DD, Karaman A, Sadry S, Gonul EY, Gögen H (2023) Comparison of the bond strength of five different composites used in the production of clear aligner attachments. J Stomatol Oral Maxillofac Surg 124:101481. 10.1016/J.JORMAS.2023.101481 [DOI] [PubMed]
  26. Kuraray Dental (2008) CLEARFIL MAJESTY TM Esthetic CLEARFIL MAJESTY TM Posterior CLEARFIL MAJESTY TM Flow [WWW Document]. SCIENTIFIC PRODUCT INFORMATION - Kuraray Noritake kuraraynoritake.eu https://www.kuraraynoritake.eu › pub › media › pdfs. URL www.kuraray-dental.net (accessed 1.16.25)
  27. Lee YK, Lu H, Oguri M, Powers JM (2005) Changes in gloss after simulated generalized wear of composite resins. J Prosthet Dent 94:370–376. 10.1016/j.prosdent.2005.08.006 [DOI] [PubMed] [Google Scholar]
  28. Mandikos MN, McGivney GP, Davis E, Bush PJ, Carter JM (2001) A comparison of the wear resistance and hardness of indirect composite resins. J Prosthet Dent 85:386–395. 10.1067/MPR.2001.114267 [DOI] [PubMed] [Google Scholar]
  29. Mantovani E, Castroflorio E, Rossini G, Garino F, Cugliari G, Deregibus A, Castrofloriog T (2018) Scanning electron microscopy evaluation of aligner fit on teeth. Angle Orthod 88:596–601. 10.2319/120417-827.1 [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Marovic D, Par M, Macan M, Klarić N, Plazonić I, Tarle Z (2022) Aging-dependent changes in mechanical properties of the new generation of bulk-fill composites. Materials 15. 10.3390/ma15030902 [DOI] [PMC free article] [PubMed]
  31. Meier B, Wiemer KB, Miethke RR (2003) Invisalign® - Ein Patientenprofil. Auswertung einer prospektiven Befragung. J Orofac Orthop 64:352–358. 10.1007/s00056-003-0301-z [DOI] [PubMed] [Google Scholar]
  32. Monteiro B, Spohr AM (2015) Surface roughness of composite resins after simulated toothbrushing with different dentifrices. J Int Oral Health: JIOH 7(7):1 [PMC free article] [PubMed] [Google Scholar]
  33. Mowafy OEl (2021) Effect of dental composite increment thickness on hardening of bulk-fil resin composite restorative. Int J Clinic Stud Med Case Rep 13. 10.46998/ijcmcr.2021.13.000323
  34. Nasoohi N, Hoorizad M, Tabatabaei SF (2017) Effects of wet and dry finishing and polishing on surface roughness and microhardness of composite resins. J Dentistry (Tehran, Iran) 14(2):69 [PMC free article] [PubMed] [Google Scholar]
  35. O’Brien WJ (2002) Dental materials and their selection, 2nd edn. Quintessence books, pp 56–60. https://library.unmas.ac.id/repository/E-FKG0170.pdf
  36. Ozcan S, Yikilgan I, Uctasli MB, Bala O, Kurklu ZGB (2013) Comparison of time-dependent changes in the surface hardness of different composite resins. Eur J Dent 7:S20. 10.4103/1305-7456.119059 [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Pereira R, Lima DANL, Giorgi MCC, Marchi GM, Aguiar FHB (2019) Evaluation of bond strength, nanoleakage, and marginal adaptation of bulk-fill composites submitted to thermomechanical aging. J Adhes Dent 21:255–264. 10.3290/J.JAD.A42547 [DOI] [PubMed] [Google Scholar]
  38. Randolph LD, Palin WM, Leloup G, Leprince JG (2016) Filler characteristics of modern dental resin composites and their influence on physico-mechanical properties. Dent Mater 32:1586–1599. 10.1016/J.DENTAL.2016.09.034 [DOI] [PubMed] [Google Scholar]
  39. Roberson TM, Heymann HO, Swift EJ (2002) Sturdevant’s Art & Science of Operative Dentistry, 4th edn. Mosby Inc., Orlando, pp 476–483. https://www.scirp.org/reference/referencespapers?referenceid=1399136
  40. Rossini G, Parrini S, Castroflorio T, Deregibus A, Debernardi CL (2015) Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle Orthod. 10.2319/061614-436.1 [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Savignano R, Valentino R, Razionale AV, Michelotti A, Barone S, D’Antò V (2019) biomechanical effects of different auxiliary-aligner designs for the extrusion of an upper central incisor: a finite element analysis. J Healthc Eng 2019. 10.1155/2019/9687127 [DOI] [PMC free article] [PubMed]
  42. Shahdad SA, McCabe JF, Bull S, Rusby S, Wassell RW (2007) Hardness measured with traditional Vickers and martens hardness methods. Dent Mater 23:1079–1085. 10.1016/J.DENTAL.2006.10.001 [DOI] [PubMed] [Google Scholar]
  43. Shahin SY, AlQahtani N, Abushowmi TH, Siddiqui IA, Akhtar S, Nassar EA, Gad MM (2024) The effect of surface treatment and thermal aging on the bonding of clear aligner attachments to provisional resin-based material: shear bond strength analysis. Front Oral Health 5:1449833. 10.3389/FROH.2024.1449833 [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Shakir H, Al Noor S, Al-Joubori SK (2018) Retention of different orthodontic aligners according to their thickness and the presence of attachments. Int J Med Res Health Sci 7:115–121 [Google Scholar]
  45. Spencer P, Ye Q, Park J, Topp EM, Misra A, Marangos O, Wang Y, Bohaty BS, Singh V, Sene F, Eslick J, Camarda K, Katz JL (2010) Adhesive/Dentin interface: the weak link in the composite restoration. Ann Biomed Eng 38:1989–2003. 10.1007/S10439-010-9969-6 [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Szczesio-Wlodarczyk A, Domarecka M, Kopacz K, Sokolowski J, Bociong K (2021) An evaluation of the properties of urethane dimethacrylate-based dental resins. Materials 14. 10.3390/MA14112727 [DOI] [PMC free article] [PubMed]
  47. Szczesio-Wlodarczyk A, Domarecka M, Kopacz K, Sokolowski J, Bociong K (2021b) An evaluation of the properties of urethane dimethacrylate-based dental resins. Materials 14:2727. 10.3390/MA14112727 [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Thai J, Araujo E, McCray J, Schneider P, Kim K (2020) Esthetic perception of clear aligner therapy attachments using eye-tracking technology. Am J Ortho Dentofacial Orthoped 158. 10.1016/j.ajodo.2019.09.014 [DOI] [PubMed]
  49. Wilson N, Gordan V, Brunton P, Wilson M, Crisp R, Mjör I (2006) Two-centre evaluation of a resin composite/self-etching restorative system: Three-year findings. J Adhes Dent 8:47–51 [PubMed] [Google Scholar]

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