Developing anti-inflammatory mineral trioxide aggregate as dental implant crown cement to reduce peri-implantitis incidence

Abstract

Background/purpose

Dental resin cement residue around periodontal tissue is one of the causes of peri-implantitis. Severe cases may cause the implant to loosen or fall off. Therefore, the goal of this study was to modify mineral trioxide aggregate as an anti-inflammatory dental implant crown cement (ICC).

Materials and methods

The effects of deionized water solution (Daq), hydroxyapatite solution (Haq), and calcium chloride solution (Caq) on the setting time, compressive strength, adhesion strength, and biocompatibility of ICC were evaluated. One-way analysis of variance (ANOVA) was performed for each analysis to determine differences (P< 0.05) between experimental groups.

Results

The surface microstructure showed that the addition of Haq and Caq contributes to the binding between ICC particles. Surface element analysis showed that Haq addition increased the Ca ion content. Setting time results demonstrated that compared to Daq, Caq and Haq accelerated the final setting time by 46.5% and 34.7% respectively (P< 0.05). The compressive strength of Caq was 35.1% and 13.4% higher than those of Daq and Haq, respectively (P< 0.05). The adhesion strength results of the three ICC groups revealed that the resin cement had the same effect (P> 0.05). Biocompatibility and scavenging activity tests showed that ICC was superior to resin cement.

Conclusion

ICC combined with Caq can shorten the setting time, improve compressive strength, increase biocompatibility, and reduce the possibility of inflammation. Therefore, the ICC system combined with Caq may serve as an alternative to dental resin cements.

Introduction

Humans can lose teeth due to natural factors or man-made factors. In severe cases, pronunciation, food intake and interpersonal relationships may be affected.1 When patients lose their natural teeth, they often require restoration through dental implants, which are placed via dental surgery to support upper crown restorations.2 However, these implants are surrounded by soft tissue and alveolar bone. Diseases can develop in the surrounding tissues if not properly cleaned or exposed to other risk factors.3 Poor cleaning and maintenance, or the presence of factors affecting periodontal health, can cause inflammation and destruction of these tissues, leading to peri-implantitis.4 Severe peri-implantitis can destroy the osseointegration and cause the dental implant to fail. Therefore, periimplantitis presents a significant clinical challenge. Studies have indicated that many cases of peri-implantitis are related to contact with dental cements.5 Consequently, the choice and use of dental cements are crucial factors in reducing the incidence of peri-implantitis.

Dental implant treatment uses dental cements to bond and secure the crown restoration to the upper structure of the dental implant.6 However, traditional cement can lead to excessive overflow from the crown space during bonding, making removal difficult.7 Most of these cements include phosphate, phenate, polycarboxylate, polymethylmethacrylate, and resin polymer.8,9 Phosphate cements are strongly acidic and can irritate the dental pulp. They have a strong exothermic reaction during mixing and require a short operating time.10 Phenolic cement may irritate soft tissues, causing adverse reactions such as softening, damage, and discoloration.11 Polycarboxylate cements bond effectively with metal, but using metal adjusting tools can make it difficult to clean the appliance. 12 Resin polymer cements are polymerized by mixing monomers and polymers.13 The solid resin fills the gap between the crown restoration and the dental implant to serve as a fixation. However, residual monomers after polymerization or the formation of rough surfaces can facilitate bacterial adhesion. Consequently, these excess cement can irritate periodontal tissue (gingiva), leading to gums’ redness, swelling and inflammation. In severe cases, peri-implantitis may develop. Thus, the reliable removal of excess cement is a major challenge in dental implant surgery.14

In addition to cement removal strategies, the use of low-irritation dental cements would be another solution to mitigate these issues. Currently, mineral trioxide aggregate (MTA), also known as calcium silicate cement, is commonly used as a material for dental root canal treatment.15 It has good sealing and durability.16 Through the mixing reaction of powder and liquid, it will be solidified in the crown space. Therefore, trioxide mineralization is a potential choice as an alternative resin cement. The main ingredients of MTA are 75% portland cement, 20% bismuth oxide and 5% gypsum. Portland cement is used as filling material and bismuth oxide is mainly used as X-ray developing agent. However, bismuth oxide powder will cause discoloration over a long period of time after hydration reaction.17 Therefore, the addition of bismuth oxide was eliminated in this study. A new implant crown cement (ICC) system was developed through modification of MTA.

While mineral trioxide aggregate (MTA) shows promise as a dental implant cement, its hardening time must be reduced for practical application.18 Previous studies have indicated that calcium silicate compounds undergo hydration reactions with aqueous salt solutions. During the early stages, this hydration reaction causes the cement to set quickly, and in the later stages, it increases the mechanical strength.19 Therefore, controlling the coagulation time of MTA by manipulating the mixed salt aqueous solution is a viable approach. Common aqueous salt solutions in the human body include calcium chloride and hydroxyapatite. Research has demonstrated that calcium chloride can serve as a setting accelerator for Portland cement slurry. Adding calcium chloride to MTA can enhance hydration, shorten setting time, and increase compressive strength. Literature also suggests that CaCl₂/MTA composite cements exhibit a similar ability to induce bone-like apatite formation in simulated body fluid (SBF). The CaCl₂/MTA extract has been shown to stimulate cell proliferation within a certain concentration range. Moreover, hydroxyapatite (HA) is a phosphate with properties similar to human bone20 and possesses osteoconductive properties.21 It is frequently added to biomedical materials to enhance strength and biocompatibility. Therefore, incorporating HA is expected to increase the mechanical strength of the cement and improve both setting time and osteogenic properties.22 Thus, even in the presence of excess cement, dental implant cements formulated with these modifications not only suppress inflammation but also stimulate osteoblast growth. This study aims to modify the composition of MTA and control coagulation time and other properties through the use of calcium chloride and HA aqueous solutions. Explore the optimal conditions for dental implant cements.

Based on the above, this study aims to develop a dental implant cement (ICC) formulated with calcium silicate cement, calcium hydroxide, calcium sulfate, and calcium chloride solution. The setting time and mechanical properties of the cement will be controlled through various aqueous salt solutions. The effect of these additives on enhancing setting speed and mechanical strength will be evaluated. This new formulation aims to replace resin cements, thereby reducing the risk of irritation and inflammation of periodontal soft tissue. This study proposes two hypotheses: (1) the setting time and mechanical properties of dental implant cements will not be affected by aqueous salt solutions and (2) the dental implant cement can be effectively used for crown adhesion.

Materials and methods

This study employed a solid-state synthesis method to prepare C2S and C3S powders (Fig. 1). C2S was synthesized by combining CaCO₃ (Showa Chemical Industry, Tokyo, Japan) and SiO₂ (Showa Chemical Industry, Tokyo, Japan) at a molar ratio of 2:1 in 25 mL of ethanol (99%, ECHO CHEMICAL, Miaoli County, Taiwan) within a ball mill tank. The mixture was subjected to ball milling for 12 h using a ball mill (CHANG-YIH, Changhua, Taiwan). Subsequently, the mixed powder was dried in an oven at 40 °C for 6 h. The dried powder was then placed into a high-temperature sintering furnace and calcined at 1330 °C for 4 h, thereby completing the solid-state synthesis of C2S. For the preparation of C3S powder, CaCO₃ and SiO₂ were combined at a molar ratio of 3:1 in 25 mL of ethanol. The mixture was ball-milled for 12 h, followed by drying in an oven (DO-60N, Yotec Service, New Taipei City, Taiwan) at 40 °C for 6 h. The dried powder was subsequently sintered in a high-temperature furnace at 1600 °C for 4 h, completing the solid-state synthesis of C3S.

Figure 1.

Schematic diagram of dental implant crown cement synthesis. L/P ratio: The ratio of liquid to powder. Daq: Distilled water. Haq: hydroxyapatite solution. Caq: Calcium chloride solution.

In this study, tricalcium silicate (72.3 wt.%), dicalcium silicate (23.2 wt.%), calcium sulfate (2.1 wt.%), and calcium hydroxide (2.4 wt.%) were combined and placed into a ball mill. The mixture was ball-milled for 12 h according to the proportions shown in Fig. 1 to produce the ICC powder used in this study.

Calcium chloride aqueous solution (Caq) and hydroxyapatite aqueous solution (Haq) were subsequently prepared. The calcium chloride aqueous solution was prepared by adding calcium chloride dihydrate (27 wt.%) (ECHO CHEMICAL, Miaoli County, Taiwan) to deionized water and stirring the mixture uniformly using a magnetic stirrer. The hydroxyapatite (SigmaAldrich, St. Louis, MI, USA) aqueous solution was prepared by adding hydroxyapatite (10 wt.%) to deionized water and stirring the mixture uniformly with a magnetic stirrer. Deionized water (Daq) was used as the control group. The three solutions (Daq, Caq, and Haq) were mixed with the ICC powder at a fixed water-to-powder ratio of 0.31 mL/g to produce the implant crown cement.

In this study, a scanning electron microscope (SEM; JSM-7610F, JEOL, Tokyo, Japan) was used to examine the microstructure of the powder surface. To enhance electrical conductivity and facilitate observation of the surface morphology of the ICC particles, the specimens were gold-coated at 30 kV for 30 s prior to imaging. The elemental composition of the powder surface was analyzed using energy-dispersive X-ray spectroscopy (EDS; JEOL, Tokyo, Japan). The setting time of the cement was evaluated in accordance with the CNS 785 standard test method. The initial and final setting times were measured at 5-min intervals after sample preparation using a Gillmore needle apparatus. The needles were composed of stainless steel with copper weight blocks. The initial setting needle had a mass of 113.4 ± 0.5 g and a diameter of 2.12 ±0.05 mm, and the initial setting time was defined as the time at which the needle failed to penetrate the specimen surface. The final setting needle had a mass of 453.6 ±0.5 g and a diameter of 1.06 ±0.05 mm, and the final setting time was defined as the time at which no visible indentation remained on the specimen surface.

The compressive strength of the implant crown cement was evaluated in accordance with ISO 9917-1. Cement from each group was poured into a metal mold to produce cylindrical specimens with a height of 6 mm and a diameter of 4 mm. The specimens were allowed to set at room temperature for 24 h to ensure complete hardening. After the setting period, compressive strength was measured using a universal testing machine (AGX-V, Shimadzu, Kyoto, Japan) at a crosshead speed of 0.01 mm/s.

In this study, CAD software (inLab WS16, Dentsply Sirona, Charlotte, NC, USA) was used to design a digital dental crown for simulated clinical treatment based on the morphology of the implant abutment (Commed D5.0 AH5.0) (Fig. 2A and B). The designed crown file was fabricated using a dental resin (Printin, Printin3D, Taoyuan, Taiwan) and a liquid crystal display (LCD)—type 3D printer (Veribuild, Whip Mix, Louisville, KY, USA). The printed resin crowns were cleaned and post-cured for 20 min according to the manufacturer’s instructions using an ultraviolet light polymerization chamber (Printin3D, Taoyuan, Taiwan). Each group of implant crown cement was then used to bond the resin crown to the implant abutment, and the specimens were allowed to set for 24 h. Subsequently, the specimens were mounted on a universal testing machine (EZ-SX, Shimadzu, Kyoto, Japan) and subjected to tensile loading at a crosshead speed of 1 mm/s until fracture (Fig. 2C). An additional dental resin cement group (RelyX U200 Clicker, 3M, Saint Paul, MN, USA) was included as a control for adhesion strength. Furthermore, aging tests were conducted to evaluate the adhesive performance of the implant crown cement under simulated intraoral conditions. The specimens were subjected to thermal cycling between 5 °C and 55 °C using a double-tank thermal cycling machine (TBN-971105, TEN Billion, Tainan, Taiwan). Each temperature was maintained for 30 s, with a transfer time of 5 s between baths, and the procedure was repeated for 10,000 cycles.23

Figure 2.

Schematic diagram of adhesion strength. (a) Dental crown digital design file. (b) Digital file of implant abutment teeth. (c)Adhesion strength test.

In this study, two cell lines were used: a mouse-derived established fibroblast cell line (L929) and a mouse calvarial preosteoblast cell line (MC3T3-E1), in accordance with the relevant specifications of ISO 10993-5. Sample extraction solutions were prepared to evaluate cell viability after 24 h of exposure. Specimens with a diameter of 5 mm and a height of 5 mm were immersed in 1 mL of deionized water and incubated at 37 °C for 7 days. After incubation, the samples were centrifuged at 1500 rpm for 10 min, and the supernatant was collected and freeze-dried. Following drying, 10 mL of Dulbecco’s Modified Eagle Medium (DMEM) was added to each tube, and the solution was filtered using a 0.22 μm sterile filter to obtain the extraction medium for cell testing. L929 and MC3T3-E1 cells were seeded in 24-well culture plates at a density of 5 × 10⁴cells per well and incubated at 37 °C in a humidified atmosphere containing 5% CO₂ for 18 h. The culture medium was then replaced with the prepared extraction solution, and the cells were further incubated for 24 h. At the designated time points, 10 μL of Cell Counting Kit-8 (CCK-8) reagent was added to each well and incubated in the dark for 4 h. The absorbance was subsequently measured at 450 nm using a microplate reader.

Radical trapping capability was used as a preliminary screening method to evaluate the resistance of the materials to oxidative stress. The radical scavenging activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. A DPPH radical solution was prepared by dissolving 0.02 g of DPPH powder (Sigma—Aldrich) in 100 mL of methanol, followed by incubation in the dark for 45 min. A rinsing solution was prepared by mixing 150 mL of methanol with 50 mL of deionized water. For the assay, 1 mL of deionized water (control group) or a specimen with fixed dimensions (5 mm in diameter and 5 mm in height) was added to 3 mL of the DPPH radical solution and allowed to react at room temperature for 90 min. The absorbance of the reaction mixture was subsequently measured at 517 nm using a UV—visible spectrophotometer. The radical trapping efficiency was calculated using Equation (1), as described in previous studies.24

$$\text{Scavenging\hspace{0.17em}ratio\hspace{0.17em}}(\%)=\left[1-\left(\frac{\text{Absorbance\hspace{0.17em}of\hspace{0.17em}test\hspace{0.17em}sample}}{\text{absorbance\hspace{0.17em}of\hspace{0.17em}control}}\right)\right]\times 100\%$$ formula(1)

All data are presented as mean ± standard deviation (SD) from 5 replicate samples. Statistical analysis was performed using JMP 13 software (Statistics Analysis System, Charlotte, NC, USA). Significance was determined using a one-way ANOVA followed by Tukey’s HSD post hoc test, with a significance level set at P< 0.05.

Results

The hardened microstructures of the three cement groups (Daq, Caq, and Haq) exhibited a granular morphology (Fig. 3). In the Daq group, no apparent interparticle coating was observed. In contrast, the addition of Caq and Haq resulted in visible interparticle adhesion, leading to particle agglomeration. Surface elemental analysis indicated that the Daq and Caq groups showed similar elemental compositions, whereas chlorine was detected on the surface of the Haq group (Fig. 3 and Table 1).

Figure 3.

Surface morphology and composition of implant crown cement synthesis. Daq: Distilled water. Haq: hydroxyapatite solution. Caq: Calcium chloride solution.

Table 1.

Surface elements of implant crown cement synthesis by energy-dispersive X-ray spectroscopy (EDS).

Atomic%	Group
	Dqa	Hqa	Cqa
O K	51.55	44.33	63.75
Si K	11.54	11.73	8.84
Ca K	36.91	43.94	22.36
Cl K	N.D	N.D	5.06

Daq: Deionized water solution, Haq: hydroxyapatite solution, Caq: Calcium chloride solution.

The initial setting time of the Daq group was significantly longer than those of the Caq and Haq groups, being approximately 2.6-fold and 2.4-fold higher, respectively (P< 0.001; Table 2). A similar trend was observed for the final setting time, with the Daq group showing values approximately 1.5-fold and 1.8-fold higher than those of the Caq and Haq groups, respectively (P< 0.001). The compressive strengths of the Daq, Haq, and Caq groups were 46.7 ± 2.8 MPa, 55.6 ± 3.9 MPa, and 63.1 ± 3.0 MPa, respectively, and significant differences were observed among the groups (P< 0.001) (Table 3).

Table 2.

Setting time of implant crown cement synthesis.

Group	Initial setting time (min)	Final setting time (min)
	Mean ± SD	Mean ± SD
Daq	18.6 ± 1.1A	32.2 ± 0.8A
Haq	7.0 ± 0.7B	21.0 ± 0.7B
Caq	7.6 ± 1.1B	17.2 ± 0.8C
P	<0.001*	<0.001*

Daq: Deionized water solution, Haq: hydroxyapatite solution, Caq: Calcium chloride solution. Note: Different capital letters indicate differences between groups.

^*P = Indicates significant difference (P< 0.001).

Table 3.

Compressive strength of implant crown cement synthesis.

Group	Compressive strength (MPa)
	Mean ± SD	Lower 95%	Upper 95%	F Ratio	P
Daq	46.7 ± 2.8C	43.3	50.2		<0.001*
Haq	55.6 ± 3.9B	50.7	60.5	31.1053
Caq	63.1 ± 3.0A	59.4	66.8

Daq: Deionized water solution, Haq: hydroxyapatite solution, Caq: Calcium chloride solution. Note: Different capital letters indicate differences between groups.

^*P ± Indicates significant difference (P< 0.001).

Before aging, the adhesion strength of the specimens ranged from 91 N to 119 N (Fig. 4). The Haq group exhibited the highest adhesion strength (119 N) and showed a significant difference compared with the U200 group (91 N) (P< 0.001). After the aging test, the adhesion strength ranged from 80 N to 95 N, and no significant differences were observed among the groups (P> 0.001).

Figure 4.

Adhesion strength to implant crown cement-bonded crowns. Different capital letters indicate differences between groups (P < 0.001, mean ± SD, n = 5). Daq: Distilled water. Haq: hydroxyapatite solution. Caq: Calcium chloride solution. U200: Automix self-adhesive resin cement refill.

The biocompatibility results after 24 h of exposure to the extracts are shown in Fig. 5. In L929 cells, the cell viability of the Daq, Haq, Caq, and U200 groups was 101.1%, 103.9%, 102.9%, and 78.0%, respectively (Fig. 5A). In MC3T3-E1 cells, the corresponding cell viability values were 97.1%, 98.9%, 109.9%, and 87.0%, respectively (Fig. 5B). The radical scavenging activity of the Daq, Haq, Caq, and U200 groups was 20.0 ± 1.2%, 23.0 ± 2.0%, 25.0 ± 1.3%, and 13.0 ± 1.4%, respectively (Fig. 6), and significant differences were observed among all groups (P< 0.001).

Figure 5.

Biocompatibility of implant crown cement synthesis. Different capital letters indicate differences between groups (P < 0.001, mean ± SD, n = 5). Daq: Distilled water. Haq: hydroxyapatite solution. Caq: Calcium chloride solution. U200: Automix self-adhesive resin cement refill.

Figure 6.

Scavenging activity of implant crown cement synthesis. Daq: Distilled water. Haq: hydroxyapatite solution. Caq: Calcium chloride solution. U200: Automix self-adhesive resin cement refill. Different capital letters indicate differences between groups (P < 0.001, mean ± SD, n = 5).

Discussion

Dental resin cements have been used clinically for many years.25 However, the potential for periodontal soft tissue inflammation associated with residual resin monomers has remained controversial.26 In this study, a modified mineral trioxide aggregate was used as the base material and combined with different salt aqueous solutions to develop a novel implant crown cement (ICC). The optimal formulation was identified through systematic evaluation of setting time, compressive strength, and biocompatibility.

Microstructural observations indicated that the Daq group exhibited clusters composed of relatively small particles (Fig. 3). In contrast, the Haq and Caq groups contained calcium and chloride ions, which interacted with the ICC during mixing and promoted interparticle bonding, resulting in the formation of larger aggregated structures. This phenomenon was comparable to the wet deposition process involved in calcium phosphate crystal synthesis, in which electrostatic attraction between positively and negatively charged ions in an aqueous environment facilitated particle deposition and growth.27 Surface elemental analysis further confirmed that ions from the aqueous solutions were successfully incorporated into the ICC matrix (Table 1). Consequently, the Haq group exhibited approximately 19% higher calcium content than the Daq group. In addition, the effective interaction between Caq and ICC was supported by the detection of chloride ions on the material surface.

Dentistry has required rapid bonding when cementing crowns to implant abutments; therefore, accelerating the setting time of ICC was considered a critical factor for its application as a dental cement. The setting time results indicated that the presence of additional particles or ions in the aqueous solutions accelerated the hardening process of ICC (Table 2). Although no significant difference was observed in the initial setting time between the Haq and Caq groups, both exhibited setting times approximately 2.6-fold shorter than that of the Daq group. Significant differences among the solutions were observed only in the final setting time of ICC (P< 0.001). This difference was likely attributable to variations in ion concentration and mobility within the solutions. An increased availability of nucleation species during cement hydration has been reported to shorten hardening time by promoting crystal growth.28 Previous studies have demonstrated that the addition of calcium chloride accelerated the hydration of tricalcium silicate (C3S) and effectively reduced setting time.22,29 Moreover, Behnam Bolhari et al. reported that incorporating 10% fluorohydroxyapatite into mineral trioxide aggregate significantly shortened the setting time.30 These findings were consistent with the results of the present study, in which the use of Haq or Caq effectively reduced the setting time of ICC.

The compressive strength results demonstrated that the Caq group exhibited significantly higher values than the Daq and Haq groups (P< 0.001) (Table 3). According to ISO 9917-1 specifications, the compressive strength of hand-mixed or mechanically mixed cement used as a luting or repair material should fall within the range of 45–55 MPa.31,32 Although differences were observed among the three groups, all specimens met the relevant standard requirements. SEM observations indicated that the Caq group exhibited a denser microstructure with fewer voids compared with the other two groups. A reduction in porosity and enhanced interparticle bonding have been associated with increased compressive strength, which may explain the superior mechanical performance observed in the Caq group. In addition, previous studies have reported that the incorporation of fillers improved the mechanical properties of Portland cement. David Yong et al. demonstrated that the addition of bovine bone—derived hydroxyapatite enhanced the compressive strength of Portland cement.33 Mahima et al. further reported that the use of calcium chloride solution improved the compressive strength of mineral trioxide aggregate. These findings were consistent with the results of the present study, suggesting that both Caq and Haq effectively enhanced the compressive strength of ICC.

Adhesion strength was a critical factor influencing the clinical performance of crown restoration.34 In the present study, the ICC system primarily functioned to fill the gap between the crown and the implant abutment, thereby providing mechanical retention after cement hardening. A commercially available resin cement was included as a control to facilitate comparison with current clinical materials. In addition, because the intraoral environment is subjected to repeated thermal fluctuations, thermocycling was used to simulate the durability of bonded crowns under alternating hot and cold conditions.23 Before aging, the adhesion strength of the three ICC formulations ranged from 105.2 ± 12 N to 119.0 ± 8 N (Fig. 4). Among them, the Caq group exhibited an adhesion strength approximately 1.3-fold higher than that of the U200 group (P< 0.05). This result may have been attributed to two factors. First, the denser microstructure of the Caq group, characterized by fewer interfacial gaps, may have contributed to improved sealing and enhanced adhesion strength. Second, the presence of chloride ions in the Caq formulation may have facilitated interaction with the metal implant surface. Nevertheless, further investigation is required to clarify the dominant mechanisms responsible for the observed differences in adhesion strength. After thermocycling, a reduction in adhesion strength was observed in all groups. This decrease was likely associated with water penetration at the crown margins induced by repeated thermal stress. Despite this reduction, the ICC system demonstrated adhesion strength comparable to that of the resin cement control (U200), indicating its potential suitability for clinical application.

During crown bonding procedures, excess cement has often remained in close proximity to periodontal tissues.35 Historically, clinical efforts have focused on the removal of residual cement to minimize postoperative complications. The ICC system used in this study was designed to achieve crown retention through complete filling. The material surface did not exhibit intrinsic adhesiveness. Therefore, in clinical application, it was easily removed. In contrast, the present study was directed toward the development of a non—resin-based dental cement to address concerns related to periodontal inflammation. Accordingly, the biocompatibility of the ICC system and a conventional resin cement was evaluated using two cell viability assays (Fig. 5). In L929 cells, no significant differences were observed between any of the ICC groups and the control group (P> 0.05), whereas the U200 group exhibited significantly lower cell viability compared with the control (P< 0.05). Similar trends were observed in MC3T3-E1 cells exposed to the corresponding extracts. Although the U200 group maintained cell viability above 80% in both assays, previous studies have reported increased cytotoxicity in osteoblasts following exposure to dental cements. Freya Diemer et al. demonstrated a significant reduction in osteoblast viability after cement exposure, emphasizing the importance of complete polymerization and thorough removal of cement residues in clinical applications.36 In addition, Stefano Pagano et al. reported that several universal resin cements caused cellular damage in human gingival fibroblasts.37 Taken together, these findings suggested that the ICC formulations evaluated in this study exhibited superior biocompatibility compared with conventional resin-based cement, supporting their potential advantage in reducing periodontal tissue irritation during crown restoration procedures.

In addition to the intrinsic biocompatibility of dental materials, surrounding free radicals have also been recognized as contributing factors to tissue inflammation. Previous studies have demonstrated that excessive free radical production induced inflammatory responses. 38 Therefore, the ability to scavenge excess free radicals may reduce the risk of periodontal tissue inflammation. Earlier reports have indicated that hydroxyapatite and certain metal ions possessed radical scavenging capabilities, with scavenging efficiency increasing as concentration increased.24 Consistent with these findings, the scavenging activity of the Caq and Haq groups was significantly higher than that of the other groups in the present study (Fig. 6). Nevertheless, a reduction in free radical levels alone was insufficient to conclusively demonstrate the inhibition of inflammatory responses, and further investigations are required to clarify the biological relevance of this effect. Based on these results, the first hypothesis of this study was rejected, as the setting time and compressive strength of dental implant cement were influenced by the use of aqueous salt solutions. In contrast, the second hypothesis was accepted, indicating that the developed dental implant cement exhibited mechanical and biological properties suitable for crown cementation. The limitations of this study were that the cement was not directly applied intraorally for clinical testing. In addition, only one type of metal abutment was evaluated. Therefore, future studies will investigate the clinical performance of the cement with different types of dental metal abutments.

Based on the above results, the modified implant crown cement (ICC) was suitable for use as a dental cement and provided stable retention and adequate cement strength. The incorporation of Haq and Caq improved the compressive strength of ICC and effectively shortened its setting time. Among the tested formulations, ICC mixed with Caq exhibited favorable biocompatibility and enhanced free radical scavenging activity, which may contribute to a reduced risk of inflammatory responses. Therefore, the combination of ICC and Caq was a potentially suitable formulation and demonstrated potential for use in anti-inflammatory mineral trioxide aggregate—based cements for dental implant crown cementation.

Funding Statement

This research was funded by University System of Taipei Joint Research Program, via grants USTP-NTUT-TMU-112-03 to Wei-Chun Lin.