The Effect of Cementation Load, Unload Time, and Storage Time on Film Thickness and Microtensile Bond Strength Durability of Dual-Cure Resin Cements: An In Vitro Study

Abstract

Objectives

This article aims to evaluate the effect of load weight, unload time, and storage duration on microtensile bond strength (µTBS) of dual-cure resin cement to CAD/CAM composite.

Materials and Methods

Forty-eight composite blocks (Grandio Blocs, n = 24 shade A1, and n = 24 shade A4) were randomly assigned to eight groups (n = 3 shade A1, and n = 3 shade A4) based on load weight (1, 3, 5, and 15 kg), and unload time (immediately before light curing or 10 minutes during/after light curing). Bonded blocks (n = 3/group) were sectioned into multiple sticks. Half of the sticks (n = 21) were tested after 24 hours, while the remaining 21 were stored in distilled water at 37°C and tested after 6 months. Sticks for film thickness were evaluated using a stereomicroscope (60 × ). However, the sticks for µTBS were pulled in tension at a 0.5-mm/min crosshead speed.

Statistical Analysis

Data were analyzed using ANOVA and the Games–Howell post hoc test (α = 0.05).

Results

There was no correlation between µTBS and FT (r = 0.035; p = 0.737). For the FT, only “unload time” had a significant effect (p < 0.001). For µTBS, “load weight,” and “unload time” had no significant impact (p = 0.948 and p = 0.948, respectively). However, “storage time” significantly influenced the results (p < 0.001). Adhesive mode was significantly predominant (56.85%).

Conclusion

Unload time is a crucial factor controlling the film thickness of the dual-cure resin cement. However, it does not affect the resin cement µTBS to CAD/CAM composite.

Clinical Significance

Excessive seating load should be avoided when positioning CAD/CAM composite restorations, while a controlled short time may assist in preventing restoration rebound.

Keywords

load - unload time - film thickness - microtensile bond strength - dual-cure resin cement - CAD/CAM composite

Introduction

As digital technologies in dentistry continue to advance, CAD/CAM restorations have emerged as one of the most efficient and time-saving options in daily practice. For teeth with extensive carious lesions, large defective restorations, or those that are endodontically treated, direct restorations are often less practical and more time-consuming than CAD/CAM-fabricated solutions.[1]

Several studies have shown that the seating load applied to indirect restorations lacks standardization among researchers and in clinical scenarios.[2] [3] [4] [5] Indeed, dental practitioners typically rely on finger pressure to seat extracoronal restorations during final cementation. This applied force can vary considerably, not only among operators but also within the same operator during a treatment session, ranging from approximately 1 to 6 kg.[6] [7] [8] In contrast, maximum adult molar biting forces have been reported to reach around 28 kg.[9] These discrepancies suggest that the ISO-recommended loading force for seating extracoronal restorations may not accurately replicate clinical conditions.

The amount of seating load has been shown to influence the film thickness (FT) of resin cements.[10] [11] However, another study has demonstrated that this effect is material-dependent, with variations in load weight affecting FT differently among different resin cements.[12] The relationship between FT and resin cement's microtensile bond strength (µTBS) to CAD/CAM composites has also been investigated.[5] [13] While the study reported no significant correlation between FT and µTBS,[5] others found a strong positive association.[13] In both cases, a fixed seating load of 1 kg was used, raising the question of whether varying the load could influence FT sufficiently to establish a positive correlation with µTBS.

Furthermore, previous findings suggest that sustaining the seating load during resin cement polymerization improves bond strength compared with immediate load removal.[14] However, increasing the applied load during seating is not without risk. Despite proper occlusion during the try-in stage, clinicians may experience occlusal discrepancies in indirect restorations following light curing. This may result from elastic strain and subsequent rebound of the restoration after resin cement curing,[15] leading to slight elevation and occlusal disturbances. It has been reported that higher seating forces reduced the retention of extracoronal restorations compared with low seating forces.[16] Nevertheless, the extent to which variations influence restoration rebound in load weight or unloading time has not been thoroughly investigated.

Therefore, this study aimed at evaluating the effects of seating load and unloading time on the FT of a dual-cure resin cement and assessing the influence of these variables, along with storage duration, on the µTBS of the same resin cement bonded to CAD/CAM composite blocks. The null hypothesis posited that none of the variables would exert a statistically significant influence on either FT or µTBS.

Materials and Methods

A total of eight intact CAD/CAM composite blocks, four in shade A1 and four in shade A4, measuring 14.5 × 14 × 18 mm³, were sectioned both vertically and horizontally into smaller blocks (7 × 14 × 4 mm³) using a low-speed diamond-coated abrasive cutting disc (Isomet, Buehler Ltd., Lake Bluff, Illinois, United States). Each pair of smaller blocks was bonded together using a dual-cured resin cement. Details regarding the materials, including their descriptions, compositions, manufacturers, and lot numbers (Lot #), are presented in [Table 1].

Table 1 Materials' description, composition, manufacturer, and lot number (Lot #)

Materials	Description	Composition	Manufacturer	Lot number
Grandio blocs 14L (shades A1 and A4)	CAD/CAM composite blocks	Dimethacrylates, glass ceramics, silica. Filler content: 89 wt%	VOCO GmbH, Cuxhaven, Germany	1950657
Bifix QM resin cement (universal shade)	Dual-cured adhesive resin cement	Catalyst: dimethacrylate, BPO, silica, barium-aluminum-silicate-glass ceramics, BHT. Base: dimethacrylate, CQ, amine, silica, barium-aluminum-silicate-glass ceramics, BHT. Filler content: 70.2 wt%	VOCO GmbH	2248584
Ceramic bond	Silane coupling agent	Organic acid, 3-methacryloxypropyltrimethoxysilane, acetone	VOCO GmbH	2249262

Sample Size Calculation

The sample size was determined using G*Power software (version 3.1.9.4). For the FT and µTBS tests, the calculation was based on the means and standard deviations reported in previous studies,[5] [16] respectively. A total of 24 bonded blocks (n = 3/group) were recommended, based on an effect size of 1.17 and 0.96 for FT and µTBS, respectively, a statistical power of 95%, and a significance level of 0.05.

Study Design

For both FT and µTBS, 48 small blocks (n = 24 from shade A1 and n = 24 from shade A4, representing top and base blocks, respectively) were randomly selected from eight sectioned intact blocks. These were then randomly divided into eight experimental groups (n = 3 from shade A1 and n = 3 from shade A4 per group) based on two factors: (1) loading weight (1, 3, 5, or 15 kg) and (2) unloading time (either 20s immediate removal before light curing of the resin cement or removal 10 minutes after light curing). In µTBS, for the variable “storage duration,” sticks retrieved from each group were equally and randomly assigned to either 24 hours or 6 months of storage.

CAD/CAM Blocks Surface Treatments

The small blocks from each group were designated as either the top block (shade A1, n = 24) or the base block (shade A4, n = 24) for subsequent procedures. The bonding surfaces of the top and base surfaces of the CAD/CAM blocks were manually polished under continuous water irrigation using #1,000-grit silicon carbide (SiC) paper for 10 seconds to obtain standardized flat surfaces. The prepared surfaces were then air-abraded for 10 seconds using a dental unit-mounted air-abrasion handpiece (MicroBlaster; Bio-Art, São Carlos, Brazil) with 50-μm aluminum oxide (Al₂O₃) particles at a pressure of 0.2 MPa. The nozzle was held at a 45° angle and positioned 10 mm from the surface. The handpiece was moved continuously across the bonding surface to ensure uniform treatment.

Following air abrasion, the blocks were ultrasonically cleaned in a 70% alcohol bath at 37°C for 2 minutes using an ultrasonic cleaner (Sun, China), per the manufacturer's instructions. The specimens were then air-dried using oil- and water-free compressed air for 10 seconds. A silane coupling agent was applied with a Single-Tim micro-brush (as supplied by the manufacturer), left undisturbed for 60 seconds, and subsequently air-dried for 10 seconds.

Cementation Procedures

The dual-cured resin cement was applied according to the manufacturer's instructions. The material was dispensed onto the base blocks using the supplied auto-mix tip, after which the top blocks were carefully positioned over the uncured cement layer. The assembled block pairs were then placed into a custom-designed loading device and subjected to one of four predetermined loading conditions: 1, 3, 5, or 15 kg, depending on the assigned experimental group.

In the immediate unloading groups, the applied load was removed after 20 seconds to allow for the removal of excess cement prior to light curing. In the 10-minute unloading groups, the load was maintained during light curing and continued for 10 minutes post-curing.

Each cemented block was light cured using three irradiation cycles: two 20-second exposures on the long sides and one 20-second exposure on each short side, resulting in a total curing time of 120 seconds. An LED light-curing unit (Celalux 3, VOCO GmbH, Cuxhaven, Germany) with an output intensity of 1,300 mW/cm² was used, and its performance was routinely verified using the device's built-in radiometer. Following light curing, the specimens were stored in distilled water at 37°C for 48 hours in an incubator before µTBS testing.

After 48 hours of storage, each cemented block was sectioned along both the x- and y-axes using a diamond-coated abrasive disc, producing 18 sticks per block, each with an approximate cross-sectional area of 1 mm². This yielded 54 sticks per experimental group.

Evaluation of Resin Cement Film Thickness

A total of 12 sticks per group, which were not assigned for bond strength testing, were used to evaluate resin cement FT. Each stick was mounted on a glass slide using a thin layer of cyanoacrylate adhesive to facilitate surface preparation. The bonded interfaces were wet-polished in a circular motion using #1,000—and #1,200-grit silicon carbide (SiC) papers, each for 20 seconds. After polishing, the specimens were ultrasonically cleaned in distilled water for 5 minutes to eliminate residual debris.

Film thickness was measured under a stereomicroscope at 60× magnification. Using RI Viewer imaging software, three measurements were taken per stick at 250-µm intervals along the bonded interface. The average FT per stick was calculated from these three values, and the mean FT for each experimental group was determined based on the measurements from all 12 sticks.

Microtensile Bond Strength Testing

In total, 42 sticks per group were randomly selected for µTBS testing. Half of the specimens (n = 21) were tested after 24 hours, while the remaining 21 were stored in distilled water at 37°C (Incubator Model BT 1020, Biotec Company, Egypt) and tested after 6 months.

For µTBS testing, each stick was individually mounted in a notched metallic jig using cyanoacrylate adhesive (Pattex, Henkel AG & Co. KGaA, Düsseldorf, Germany). Tensile testing was performed using a universal testing machine (Instron 3345, Norwood, Massachusetts, United States) at a 0.5-mm/min crosshead speed. The µTBS value (MPa) was calculated by dividing the applied load (N) by the cross-sectional area (mm²) of each stick.

Failure Mode Analysis

All debonded sticks were analyzed for fracture mode using a stereomicroscope (SMZ 745T, Nikon, Tokyo, Japan) at 60× magnification. Failure modes were classified into four categories: (1) adhesive failure: fracture occurred at the interface between the resin cement and the CAD/CAM composite; (2) mixed failure: fracture occurred at the resin cement/composite interface, accompanied by partial cement remnants on the composite surface or partial fracture of the CAD/CAM composite; (3) cohesive failure in resin cement: fracture occurring within the resin cement itself; and (4) cohesive failure in CAD/CAM composite: fracture occurring within the CAD/CAM composite material.

Statistical Analysis

Data normality was assessed using the Shapiro–Wilk test, and homogeneity of variance was evaluated with Levene's test. Two-way and three-way ANOVA were used to assess the effects of load and unload time on FT, and the effects of load, unload time, and storage duration on µTBS, respectively. A one-way ANOVA and Games-Howell post hoc test were used to compare the pair. Additionally, for the µTBS, Student's t-tests were used for direct comparisons between the two storage times. For FT, Student's t-tests were used to compare the two unload conditions. The level of statistical significance was set at α = 0.05.

Results

The normal distribution for the µTBS and FT data was confirmed (p > 0.05); however, the homogeneity of variance was not assumed (p < 0.05). Only one pre-test failed stick was observed when a 5-kg load was applied, sustained for 10 minutes, and stored for 6 months. The value of the pre-test failed stick was recorded as zero and included in the statistical analysis. Pearson's correlation revealed no correlation between the µTBS and FT (r = 0.035, p = 0.737).

For FT, two-way ANOVA revealed that “unload time” had a significant effect on the FT (p < 0.001). However, “load weight” had no significant impact (p = 0.093). As shown in [Table 2], no significant differences were observed among the tested load weights, regardless of whether the load was removed immediately or after 10 minutes of light curing. However, only for the 15-kg weight specifically, a significant difference was found between the two unload times (p < 0.05), with immediate unloading resulting in a higher FT.

Table 2 Means ± SD in µm for the effect of unload time within each load weight, and load weight within each unload time on FT of the dual-cured resin cement

	Immediate unload time	10-min unload time	p-Value
1 kg	34.6 ± 6.7A	30.3 ± 7.3a	0.145
3 kg	36.9 ± 6.8A	30.7 ± 9.4a	0.077
5 kg	31.8 ± 10.7A	24.9 ± 5.7a	0.064
15 kg	42.2 ± 15.5A	26.6 ± 5.5a	0.006

Notes: The means with the same capital and small letters within each column had no statistically significant difference in FT at p = 0.05.

p-Value: Independent t-test between immediate and 10-minute unload times at p = 0.05.

For failure mode analysis, the stick that failed before testing was classified as an adhesive failure. The chi-square test revealed no significant difference in the distribution of failure modes among the experimental groups (p > 0.05), indicating an equal distribution across conditions. However, when evaluating the overall frequency of failure types, adhesive failure was the most prevalent (56.85%), followed by mixed failure (34.52%) and cohesive failure within the resin cement (8.63%). This distribution showed a statistically significant difference among failure modes (p < 0.05). Notably, no cohesive failures within the CAD/CAM composite were observed (0.00%). The percentage distribution of failure modes for each experimental group is illustrated in [Fig. 1].

Fig. 1 Fracture mode distribution (%) within each experimental group.

Three-way ANOVA revealed that factors “load weight” and “unload time” had no significant effect on the µTBS (p = 0.842 and p = 0.948, respectively). In contrast, factor “storage duration” showed a significant impact on the µTBS (p < 0.001).

For the immediate bond strength ([Table 3]), under the immediate unloading condition, the 15-kg load group exhibited a significantly lower µTBS compared with the other load groups (p < 0.05). However, no significant differences were observed among the 1-, 3-, and 5-kg load groups (p > 0.05). Under the 10-minute unloading condition, µTBS values did not significantly differ among the load weights tested (p > 0.05). A significant difference between immediate and 10-minute unloading was observed only for the 15-kg load group (p < 0.05). In contrast, no significant differences were found between unloading times for the 1-, 3-, and 5-kg groups (p > 0.05).

Table 3 Means ± SD in MPa for the effect of unload time within each load weight of immediate dual-cured resin cement to CAD/CAM composite bond strength

	Immediate unload time	10-min unload time	p-Value
1 kg	50.8 ± 18.4A (21/14/7/0/0)	44.5 ± 13.5a (21/13/5/3/0)	0.512
3 kg	51.2 ± 20.5A (21/8/9/4/0)	44.6 ± 14.3a (21/10/8/3/0)	0.228
5 kg	48.4 ± 14.7A (21/8/9/4/0)	46.6 ± 13.1a (21/9/8/4/0)	0.673
15 kg	32.2 ± 10.2B (21/10/9/2/0)	52.2 ± 12.7a (21/14/7/0/0)	<0.001

Notes: Means with the same capital letters within the immediate removal and small letters within the 10-minute removal had no statistically significant difference at p = 0.05.

p-Value: Independent t-test between immediate and 10-minute load removal at p = 0.05. (Total no. of tested sticks/adhesive/mixed/cohesive in cement/pre-test failed sticks.)

As shown in [Table 4], after 6 months of storage, the 3- and 15-kg loading groups exhibited significantly lower µTBS values than the 5-kg group (p < 0.05). However, no significant differences were observed between the 1-, 3-, and 15-kg groups, or between the 1- and 5-kg groups (p > 0.05). Under the 10-minute unloading condition, the 15-kg load group demonstrated the highest µTBS value, which was significantly greater than the other load groups (p < 0.05). No significant differences were found among the 1-, 3-, and 5-kg groups under this condition (p > 0.05). When comparing unloading times, significant differences in µTBS were observed between the immediate and 10-minute conditions for the 5- and 15-kg groups (p < 0.05). No significant differences were found for the 1- and 3-kg groups (p > 0.05).

Table 4 Means ± SD in MPa for the effect of unload time within each load weight of 6-month dual-cured resin cement to CAD/CAM composite bond strength

	Immediate unload time	10-min unload time	p-Value
1 kg	42.3 ± 14.0A,B (21/17/4/0/0)	33.8 ± 17.4b (21/14/5/2/0)	0.090
3 kg	35.4 ± 8.7B (21/10/8/3/0)	34.9 ± 11.0b (21/11/9/1/0)	0.870
5 kg	48.2 ± 19.1A (21/9/8/4/0)	31.6 ± 21.0b (20/9/10/2/1)	0.011
15 kg	32.1 ± 15.7B (21/12/8/1/0)	51.6 ± 25.8a (21/15/6/0/0)	0.006

Notes: Means with the same capital letters within the immediate removal and small letters within the 10-minute removal had no statistically significant difference at p = 0.05.

p-Value: Independent t-test between immediate and 10-minute load removal at p = 0.05. (Total no. of tested sticks/adhesive/mixed/cohesive in cement/pre-test failed sticks.)

Regarding the effect of storage time ([Table 5]), under the immediate unloading condition, a significant difference in µTBS between 24 hours and 6 months was observed only for the 3-kg load group (p < 0.05). In contrast, under the 10-minute unloading condition, significant differences were found between the two storage times for the 1-, 3-, and 5-kg load groups (p < 0.05).

Table 5 Means ± SD in MPa for the effect of storage time of dual-cured resin cement to CAD/CAM composite bond strength

		24-hour	6-month	p-Value
Immediate unload time	1 kg	50.8 ± 18.4	42.3 ± 14.0	0.100
	3 kg	51.2 ± 20.5	35.4 ± 8.7	0.003
	5 kg	48.4 ± 14.7	48.2 ± 19.1	0.969
	15 kg	32.2 ± 10.2	32.1 ± 15.7	0.982
10-minute unload time	1 kg	44.5 ± 13.5	33.8 ± 17.4	0.032
	3 kg	44.6 ± 14.3	34.9 ± 11.0	0.019
	5 kg	46.6 ± 13.1	31.6 ± 21.0	0.009
	15 kg	52.2 ± 12.7	51.6 ± 25.8	0.915

Note: p-Value: Independent t-test between 24 hours and 6 months at p = 0.05.

Discussion

Based on the results obtained in the current study, the null hypothesis must be only partially accepted: unload time significantly influenced the FT of the dual-cure resin cement, while storage duration had a significant impact on µTBS.

Dental composites exhibit non-Newtonian behavior, with viscosity decreasing as shear rate increases.[17] [18] When resin cement is pressed between two flat CAD/CAM blocks, it mimics a “parallel plate geometry,” where shear rate is highest at the specimen edges and zero at the center.[19] This may explain why variations in load did not affect the FT of the dual-cure resin cement. This was in contrast with the study of White et al.[12] They concluded that the increase in seating load led to a significant decrease in the FT of the resin cement used in their study. In the study of White et al,[12] they used a newly developed resin cement, which was used in conjunction with bonding agents. In all applied loads used, except the 15- and 23-kg, where the FT of resin cement was higher than the FT recorded in this study. This discrepancy in the results could be due to the difference in the resin cement used. However, increased load enhances shear rate and reduces cement viscosity; the findings suggest that viscosity reduction may reach a threshold beyond which further decreases in FT no longer occur.

Additionally, Pinto et al[11] observed reduced FT with increased pressure using a self-adhesive resin cement bonded to zirconia. In the current study, the applied load did not affect the FT of the dual-cure resin cement. The difference in materials tested may explain the discrepancy. Furthermore, FT reduction with increased pressure appears to be material-dependent, as Tsukada et al[10] reported. Nevertheless, Pinto et al[11] emphasized that controlling seating pressure is crucial for achieving optimal bond strength.

When extracoronal restorations are seated under pressure, restoration elevation is likely due to cement rebound after setting.[4] [15] This study showed a gradual increase in FT of the dual-cure resin cement when unloaded immediately compared with a 10-minute unload time. The rebound effect increased gradually with the increase in the applied loads. A significant FT increase (58%) was observed when specimens were immediately unloaded after using a 15-kg load—more than double the increase recorded with 1-, 3-, or 5-kg loads. It has been reported that the application of a sudden high load may induce elastic rebound to a degree that can cause partial dislodgement of the restoration.[14]

When a 15-kg load was removed immediately before light curing, bond strength significantly decreased after 24 hours of storage. When resin cement bonded two flat CAD/CAM surfaces, the free surface area was limited to the edges of the interface.[5] Given the volumetric nature of resin cement shrinkage, increased FT likely results in greater volumetric contraction. Higher seating loads can also induce elastic strain,[15] which can potentially increase contraction stresses as FT rises. These combined effects may reduce bond strength between resin cement and CAD/CAM composites. A previous study reported that high seating forces significantly decrease the retention of extracoronal restorations compared with low seating forces.[16] Despite the difference in resin cement tested, sustained load time, and substrate of bonding, the results of the current study agreed with the results of Chieffi et al. They reported that sustained load led to a significantly higher bond strength compared with the immediate removal of load.[13]

Long-term resin cement bond strength reduction is commonly attributed to water sorption.[20] [21] [22] [23] The present study observed a significant drop in bond strength after 6 months of storage when a 10-minute unloading period was applied, particularly under low loading weights (1–5 kg). However, the findings suggest that water sorption alone may not be the main factor for this reduction. Increasing the loading weight seemed to cause greater elastic strain, leading to cement rebound linked to the development of contraction stresses.[15] When the load was held for 10 minutes, the rebound of resin cement was prevented, and these stresses likely remained within the cement matrix. Water uptake gradually offset them during storage.[20] [24] As FT remained unaffected by the applied weight, it can be postulated that higher elastic strain facilitates greater stress relaxation over time, potentially explaining the bond strength stability observed with a 15-kg load. Further investigation is warranted to verify this proposed mechanism.

The findings of this study indicate that unloading time is a critical factor affecting the FT of resin cement and, consequently, may influence resin cement–to–CAD/CAM composite bonding. When the tested resin cement was subjected to different loading weights and loading durations, the bond strength was not affected. All applied loads, whether released after 20 seconds or after 10 minutes, resulted in FT values that were not significantly different. A significant effect of unloading time on µTBS was observed only when a sudden, high load (15 kg) was removed after 20 seconds prior to light curing of the resin cement; otherwise, unloading time showed no significant effect on µTBS. The expected high rebound elastic strain may not only lead to partial dislodgement of the restoration, resulting in an increased resin cement FT, but may also increase stresses at the resin–CAD/CAM interface, thereby leading to a reduction in bond strength. Although low seating loads seemed sufficient to achieve acceptable FT values and improve restoration seating, researchers have no consensus regarding the ideal seating load, making inter-study comparisons difficult. Developing a standardized application load for seating indirect restorations would improve the reproducibility and comparability of future research. This study has several limitations. First, only a single dual-cure resin cement and a single light-curing mode were evaluated; including a purely chemical-curing mode in future research would offer a more comprehensive evaluation. Second, the applied load was limited to a 10-minute during and following light curing, with no intermediate unloading periods assessed. Additionally, further research is necessary to clarify the role of water sorption as a potential stress-relief mechanism and to determine whether it is the only factor influencing the long-term durability of resin cement bonding to CAD/CAM composites.

Conclusion

Within the limitations of this study, several key conclusions can be made:

1. The timing of unloading was identified as the most critical factor affecting the FT of the resin cement. Delayed unloading allowed improved material flow and adaptation, resulting in thinner cement layers. In contrast, immediate release of the load prior to light curing of the resin cement may not only increase cement FT but also cause partial dislodgement of the restoration and occlusal discrepancies, which are generally associated with compromised mechanical properties of the resin cement and reduced clinical longevity of the restoration.

2. Furthermore, releasing higher seating forces immediately before light curing was shown to have a detrimental effect on the bond strength between the resin cement and the CAD/CAM composite. This finding indicates that premature unloading may disrupt the adhesive interface before polymerization is sufficiently initiated, resulting in compromised bonding and potentially reduced restoration durability. However, maintaining the high load weight preserves the resin cement-to-CAD/CAM composite μTBS after a 6-month storage period.

3. The decrease in µTBS was influenced not only by the magnitude of the applied load but also by the precise timing of its release. These results emphasize the complex interaction between mechanical pressure and curing dynamics, highlighting the importance of carefully controlled cementation protocols. Clinicians should recognize that excessive force and premature unloading can negatively impact the adhesive performance of resin cements and thus should adopt strategies that optimize both parameters to ensure reliable and durable restorations.

Overall, this study enhances understanding of how procedural variables during cementation affect the physical and adhesive properties of dual-cure resin cements. Future research may further examine these interactions under varying clinical conditions to refine best practices for CAD/CAM restorative procedures.

Conflict of Interest

None declared.

Acknowledgment

The authors would like to thank VOCO GmbH, Cuxhaven, Germany, for supplying the materials in this study. This study was presented as a poster presentation at the Academy of Dental Materials (ADM) meeting, Torino, Italy (October 2–5, 2024).

• References

• 1 Mainjot AK, Dupont NM, Oudkerk JC, Dewael TY, Sadoun MJ. From artisanal to CAD-CAM blocks: state of the art of indirect composites. J Dent Res 2016; 95 (05) 487-495
• 2 Mitchell CA, Pintado MR, Geary L, Douglas WH. Retention of adhesive cement on the tooth surface after crown cementation. J Prosthet Dent 1999; 81 (06) 668-677
• 3 Segreto DR, Naufel FS, Brandt WC, Guiraldo RD, Correr-Sobrinho L, Sinhoreti MA. Influence of photoinitiator and light-curing source on bond strength of experimental resin cements to dentin. Braz Dent J 2016; 27 (01) 83-89
• 4 Tjan AH, Li T. Seating and retention of complete crowns with a new adhesive resin cement. J Prosthet Dent 1992; 67 (04) 478-483
• 5 El-Askary F, Tadros N, Hassanein A, Aboalazm E, Kamel M, Özcan M. Is there a correlation between physical properties and film thickness of dual- and photo-polymerized resin cements and CAD/CAM- dentin micro-tensile bond strength?. Journal of Adhesion Science and Technology 2024; 38: 4116-4136
• 6 Zortuk M, Bolpaca P, Kilic K, Ozdemir E, Aguloglu S. Effects of finger pressure applied by dentists during cementation of all-ceramic crowns. Eur J Dent 2010; 4 (04) 383-388
• 7 Almustafa N, Ricketts D, Chadwick G, Saunders W. Force applied by dentists during cementation of all zirconia three unit bridges and its impact on seating. International Journal of Dental Science and Research 2020; 8: 112-118
• 8 Black S, Amoore JN. Measurement of forces applied during the clinical cementation of dental crowns. Physiol Meas 1993; 14 (03) 387-392
• 9 Palinkas M, Nassar MS, Cecílio FA. et al. Age and gender influence on maximal bite force and masticatory muscles thickness. Arch Oral Biol 2010; 55 (10) 797-802
• 10 Tsukada G, Tanaka T, Kajihara T, Torii M, Inoue K. Film thickness and fluidity of various luting cements determined using a trial indentation meter. Dent Mater 2006; 22 (02) 183-188
• 11 Pinto P, Carvalho Ó, Ferreira R, Madeira S, Silva FS. Influence of applied pressure and thickness variation on the bond strength between 3Y-TZP zirconia and self-adhesive resin cement. J Biomed Mater Res B Appl Biomater 2025; 113 (03) e35563
• 12 White SN, Yu Z, Kipnis V. Effect of seating force on film thickness of new adhesive luting agents. J Prosthet Dent 1992; 68 (03) 476-481
• 13 Chieffi N, Chersoni S, Papacchini F. et al. The effect of application sustained seating pressure on adhesive luting procedure. Dent Mater 2007; 23 (02) 159-164
• 14 Wassell RW, Barker D, Steele JG. Crowns and other extra-coronal restorations: try-in and cementation of crowns. Br Dent J 2002; 193 (01) 17-20 , 23–28
• 15 Karipidis A, Pearson GJ. The effect of seating pressure and powder/liquid ratio of zinc phosphate cement on the retention of crowns. J Oral Rehabil 1988; 15 (04) 333-337
• 16 Bagheri R. Film thickness and flow properties of resin-based cements at different temperatures. J Dent (Shiraz) 2013; 14 (02) 57-63
• 17 Loumprinis N, Maier E, Belli R, Petschelt A, Eliades G, Lohbauer U. Viscosity and stickiness of dental resin composites at elevated temperatures. Dent Mater 2021; 37 (03) 413-422
• 18 Lee IB, Son HH, Um CM. Rheologic properties of flowable, conventional hybrid, and condensable composite resins. Dent Mater 2003; 19 (04) 298-307
• 19 Ibraheem R. Rheological properties of resin composite. Biomat J 2022; 1: 13-17
• 20 Sokolowski G, Szczesio A, Bociong K. et al. Dental resin cements—the influence of water sorption on contraction stress changes and hydroscopic expansion. Materials (Basel) 2018; 11 (06) 973
• 21 Kazak M, Toz Akalin T, Esen F. Comparison of water sorption and water solubility properties of current restorative materials with different contents. Eur J Dent 2025; 19 (01) 248-254
• 22 Takahashi N, Kurokawa H, Wakamatsu K. et al. Bonding ability of resin cements to different types of CAD/CAM composite blocks. Dent Mater J 2022; 41 (01) 134-141
• 23 Tekçe N, Tuncer S, Demirci M. The effect of sandblasting duration on the bond durability of dual-cure adhesive cement to CAD/CAM resin restoratives. J Adv Prosthodont 2018; 10 (03) 211-217
• 24 Feilzer YJ, Feilzer AJ, Noack MJ, Kleverlaan CJ. Release of contraction stress of dental resin composites by water sorption. Dent Mater 2024; 40 (10) 1697-1701

Publication History

Article published online:
16 February 2026