Effect of Laser Irradiation Modes and Photosensitizer Types on Antimicrobial Photodynamic Therapy (aPDT) for Streptococcus sobrinus in the Crown Dentin of Bovine Teeth: An Experimental In Vitro Study.

This study aimed to assess the impact of different laser irradiation modes and photosensitizer types on the bactericidal efficacy of antimicrobial photodynamic therapy (aPDT). Dentin plates were prepared by sectioning the crown dentin of bovine teeth infected with Streptococcus sobrinus (n = 11). Nine aPDTs involving the combination of three 1% solutions of photosensitizers (brilliant blue, BB; acid red, AR; and methylene blue, MB) and three irradiation modes of semiconductor lasers (50 mW for 120 s, 100 mW for 60 s, and 200 mW for 30 s) were performed for each infected dentin plate, and the control consisted of the specimens not applied with aPDT. The bactericidal effects in 10 groups were evaluated using both assays of the colony count (colony-forming-unit: CFU) and adenosine triphosphate (ATP) (relative-light-unit: RLU). The data obtained were analyzed using the Kruskal-Wallis test (α = 0.05). The most aPDT groups exhibited significantly lower RLU and CFU values compared with the control (p < 0.05). The effect of irradiation modes on RLU and CFU values was significant in the aPDT group using BB (p < 0.05) but not in the aPDT group using AR or MB. The aPDT performed with AR or MB exerted a remarkable bactericidal effect.

Effects of Semiconductor Laser Irradiation on Differentiation of Human Dental Pulp Stem Cells in Co-Culture with Dentin.

This study aimed to determine the effect of photobiomodulation therapy induced by semiconductor laser irradiation on human dental pulp stem cell (hDPSC) proliferation and their differentiation into odontoblast-like cells (OLCs). The effects of various semiconductor laser irradiation conditions on hDPSCs were examined. Three groups were evaluated: a single laser irradiation at 6 h post-seeding, multiple laser irradiations up to four times every 4 days after the first dose, and a control with no laser irradiation. The cells were irradiated at 10, 30, and 150 mW using a semiconductor laser. The effect of laser irradiation on hDPSC differentiation into OLCs was also determined. Four groups were evaluated, including co-culture using basic medium and dentin discs, simple culture using OLC differentiation-inducing medium, co-culture using OLC differentiation-inducing medium and dentin discs, and control culture with basic medium. The expression of the nestin, ALP, DSPP, and DMP-1 genes was measured using real-time PCR. The multiple irradiation group irradiated at 30 mW exhibited significantly more cell proliferation than the control. The expression of nestin associated with differentiation into OLCs during each culture period tended to be lower, whereas DSPP and ALP expression was higher compared with that of the control. Multiple laser irradiations at a low power of 30 mW induced significant hDPSC proliferation and might induce differentiation into OLCs.

The Effects of Antimicrobial Photodynamic Therapy Used to Sterilize Carious Dentin on Rat Dental Pulp Tissue.

Antimicrobial photodynamic therapy (aPDT) used to sterilize carious dentin may irritate pulp tissues because of tissue-penetrating laser and singlet oxygen generation. This study aimed to assess the effects of aPDT on rat pulp tissues. A cavity formed in a rat maxillary first molar was treated with aPDT. The combined photosensitizer and laser irradiation conditions in the aPDT groups were as follows: methylene blue and 100 mW for 60 s, brilliant blue (BB) and 100 mW for 60 s, BB and 50 mW for 120 s, and BB and 200 mW for 30 s. Each cavity was treated with an all-in-one adhesive and filled with flowable resin. aPDT was not applied for the control. In each group, the rats were sacrificed on postoperative days 1 and 14, and thin sections of the treated teeth were prepared. Pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and tertiary dentin formation (TDF) were evaluated. At 1-day evaluation, there were significant differences between the aPDT group and controls with respect to PTD and ICI (p < 0.01); 14 days later, almost all specimens showed tertiary dentin formation. The application of aPDT caused reversible damage to the rat pulp, while in the long term, healing occurred with the formation of tertiary dentin.

The Effect of Laser Irradiation to Surfaces of Computer-Aided Design/Computer-Aided Fabrication Resin Blocks Coated with a Silane Coupling Agent on Bond Strength between the Resin Blocks and Composite Resin.

The aim of this study was to investigate the effect of laser irradiation to computer-aided design/computer-aided fabrication (CAD/CAM) resin blocks coated with a silane coupling agent on the bond strength between resin blocks and composite resin. The CAD/CAM resin blocks used in this study were Cerasmart 300 (GC) and Vita Enamic (Vita); they were cut into plates and then subjected to a series of treatments. After processing with a silane coupling agent, treatment with a semiconductor laser was performed at 3.0, 5.0, and 7.0 W, followed by bonding procedures. The control group included those exposed to silane and bonded without laser application. After bonding, a mold with a simulated cavity was formed on the specimen and filled with flowable composite resin, and they were stored for 24 h or stressed by thermal cycling for subsequent testing that assessed the shear bond strength (n = 10). The results revealed that the bond strength was significantly enhanced by laser irradiation after applying a silane coupling agent (p < 0.03), whereas significant increase was not detected between the materials (p > 0.05). Particularly, 7 W laser irradiation had a significant increase on the bond strength between the composite resin and Cerasmart block after thermal cycling (p = 0.009). The SBS of the composite resin to CAD/CAM resin blocks was significantly enhanced by laser irradiation after silane coupling agent application.

Effect of viscosity of experimental universal adhesive on bond strength to dentin prepared with Er:YAG laser.

The aim of this study was to clarify the effect of universal adhesive (UA) viscosity on the bond strength of resin composite to dentin prepared with Er:YAG laser. Four experimental UAs (SI-1, SI-2, SI-3, and SI-4) were developed by adding 1, 2, 3, and 4 wt/% nanosilica to BeautyBond Xtreme (Shofu), respectively. BeautyBond Xtreme was used as a control (SI-0). The viscosities of experimental UAs were measured using a B-type viscometer. After bovine mandibular anterior teeth were ground with #600 emery paper to obtain the flattened dentin surfaces, the dentin surfaces were cut thinly by irradiating the Er:YAG laser. Specimens were prepared using the respective UA and flowable resin composite and subjected to the microtensile bond strength (µTBS) test. The data from viscosity measurement and the µTBS test were statistically analyzed using the Kruskal-Wallis test. The mean values of viscosity significantly differed among the all experimental groups (p < 0.01). The µTBS of SI-1 and SI-2 was significantly higher than that of SI-0, SI-3, and SI-4 (p < 0.001). The µTBS of SI-0 was significantly lower than that of SI-4 (p < 0.001). The viscosities of the experimental universal adhesives significantly affected their bond strength to laser-cut dentin.

Effects of Sr2+, BO33-, and SiO32- on Differentiation of Human Dental Pulp Stem Cells into Odontoblast-Like Cells.

This study aimed to clarify the effects of strontium (Sr2+), borate (BO33-), and silicate (SiO32-) on cell proliferative capacity, the induction of differentiation into odontoblast-like cells (OLCs), and substrate formation of human dental pulp stem cells (hDPSCs). Sr2+, BO33-, and SiO32- solutions were added to the hDPSC culture medium at three different concentrations, totaling nine experimental groups. The effects of these ions on hDPSC proliferation, calcification, and collagen formation after 14, 21, and 28 days of culture were evaluated using a cell proliferation assay, a quantitative alkaline phosphatase (ALP) activity assay, and Alizarin Red S and Sirius Red staining, respectively. Furthermore, the effects of these ions on hDPSC differentiation into OLCs were assessed via quantitative polymerase chain reaction and immunocytochemistry. Sr2+ and SiO32- increased the expression of odontoblast markers; i.e., nestin, dentin matrix protein-1, dentin sialophosphoprotein, and ALP genes, compared with the control group. BO33- increased the ALP gene expression and activity. The results of this study suggested that Sr2+, BO33-, and SiO32- may induce hDPSC differentiation into OLCs.

Toothbrush Abrasion of Restorations Fabricated with Flowable Resin Composites with Different Viscosities In Vitro.

The purpose of this study was to examine toothbrush-induced abrasion of resin composite restorations fabricated with flowable resin composites of different viscosities in vitro. In this study, six types of flowable resin composites with different flowability (Beautifil Flow F02, F02; Beautifil Flow F10, F10; Beautifil Flow Plus F00, P00; Beautifil Flow Plus F03, P03; Beautifil Flow Plus X F00, X00; and Beautifil Flow Plus X F03, X03) were used. For the toothbrush abrasion test, the standard cavity (4 mm in diameter and 2 mm in depth) formed on the ceramic block was filled with each flowable resin composite (n = 10) and brushed for up to 40,000 strokes in a suspension containing commercial toothpaste under the conditions of 500 g load, 60 strokes/min, and 30 mm stroke distance. After every 10,000 strokes, the brushed surface of the specimen was impressed with a silicone rubber material. The amount of toothbrush-induced abrasion observed on each impression of the specimen was measured using a wide-area 3D measurement device (n = 10). The viscosity was determined using a cone-and-plate rotational measurement system. Because of the effect of different shear rates on viscosity and clinical use, the values 1.0 and 2.0 s-1 were adopted as data (n = 6). In this study, the results of the toothbrush abrasion test demonstrated no significant differences in the amount of toothbrush-induced abrasion among flowable resin composites used (p > 0.05). No significant correlation was reported between toothbrush-induced abrasion and viscosities of flowable resin composites.

Effect of the S-PRG filler content in the multi-ion releasing paste on the acid resistance of the enamel surface after polishing with the paste.

This study aimed to investigate the effect of the multi-ion releasing paste (MP) on the acid resistance of the enamel surface of an extracted human tooth. Five kinds of MP were prepared according to the content (wt%) of S-PRG fillers: 0 wt% (MP0, control), 1 wt% (MP1), 5 wt% (MP5), 20 wt% (MP20), and 30 wt% (MP30). The buccal coronal surfaces of the extracted anterior teeth were polished with each kind of MP for 1 min. After removing radicular parts, the coronal parts underwent a pH cycling, and then sliced to make thin sections. The lesion depth of each section was measured using a polarization microscope. Each lesion's depth of enamel polished with MP5, MP20, and MP30 was significantly shallower than that polished with MP0.

Clinical effectiveness of direct resin composite restorations bonded using one-step or two-step self-etch adhesive systems: A three-year multicenter study.

The purpose of this multicenter clinical study was to compare the mid-term clinical effectiveness of direct resin composite restorations using one-step or two-step self-etch adhesives (1-SEAs or 2-SEAs). In total, 352 restorations of class I-V cavities and non-carious cervical lesions in vital teeth (1-SEAs; 52 cases, 2-SEAs; 300 cases) were placed at nine university hospitals and evaluated according to the modified USPHS criteria at baseline, and after 1, 2, and 3 years. The recall rates were 86.6% (1 year), 80.1% (2 years), and 62.2% (3 years). Two restorations failed due to fracture during the follow-up, and there was no significant difference in survival rates between 1-SEAs (97.6%) and 2-SEAs (99.4%). However, 2-SEAs exhibited significantly lower occurrences of discoloration, marginal discoloration, fracture, and plaque retention. Moreover, the subjects reported a significantly lower postoperative hypersensitivity and higher overall satisfaction at all evaluation periods if 2-SEAs were used.

Dentin bond strengths of all-in-one adhesives combined with different manufacturers' flowable resin composites.

The present study aimed to evaluate the dentin bond strengths of all-in-one adhesives in combination with flowable-resin-composites of different manufacturers. The materials used in this study were two all-in-one adhesives (BeautiBond Multi, BM, and Clearfil Bond SE ONE, SE) and four flowable resin composites (Clearfil Majesty ES Flow, CME; Estelite Flow Quick, EFQ; MI Flow II, MIF; and Beautifil Flow Plus F03, BFP). By combining each all-in-one adhesive and flowable resin composite, eight experimental groups were established. The shear bond strengths (SBSs) in each group were measured, and the data were statistically analyzed using one-way analysis of variance. The SBSs of the group that used SE showed no significant differences among all flowable resin composites (p>0.05), whereas those of the group that used BM showed significant differences between BFP and CME, and CME and EFQ. The combinations showed dentin bond strength ranging approximately from 20 to 30 MPa.

Evaluation of Restorative Techniques for Vertically Fractured Roots.

The purpose of this study was to examine the effects of combining specific adhesive materials and various surface treatments on bonding durability and microleakage of vertically fractured roots. Adhesive models were prepared using bovine lower incisors. The experiment included the following five groups: SB-G group (control) (10% citric acid with 3% ferric chloride solution (10-3 solution) + an adhesive resin cement (4-META/MMA-TBB; Super-Bond®)), EC group (self-cure bonding agent (UB) + core composite resin (EC)), EC-G group (10-3 solution + UB + EC), EC-P group (40% phosphate solution + UB + EC), and EC-E group (18% ethylenediaminetetraacetic acid (EDTA) solution + UB + EC). After applying a load of 50,000 cycles, microleakage, microtensile bond strength (µTBS), and failure modes were examined. Microleakage of the EC, EC-G, and EC-E groups was significantly lower than that of the EC-P group. The µTBS of the EC-G group was significantly higher than that of the other groups. All EC groups showed that mixed (cohesive and adhesive) and adhesive failures were the most prevalent types of failure modes. The EC-G group showed the highest bonding durability and the lowest microleakage results, which indicates a possible alternative to current adhesive and tooth surface treatments.

Pulp tissue reaction to a self-adhesive, resin-based direct pulp capping material containing surface pre-reacted glass-ionomer filler.

OBJECTIVE: This study aimed to evaluate the effect of direct pulp capping using an experimental self-adhesive resin for direct pulp capping (SRD) containing silica and surface pre-reacted glass-ionomer (S-PRG) filler on pulpal healing and to monitor the dentin bridge formation in rat pulp 2-4 weeks after operation. METHODS: Five types of SRDs (SRD-0: S-PRG fillers 0 wt%; SRD-1: S-PRG fillers 9.1 wt%; SRD-2: S-PRG fillers 18.4 wt%; SRD-3: S-PRG fillers 27.8 wt%; and SRD-6: S-PRG fillers 57.4 wt%) were prepared, and mineral trioxide aggregate (MTA) was used as control (n = 8). Direct pulp capping was performed on rats that were sacrificed for further evaluation 2 or 4 weeks after the operation. The pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and reparative dentin formation were histopathologically evaluated; the data were statistically analyzed using the Kruskal-Wallis and the Mann-Whitney U tests. RESULTS: The histopathological evaluation of SRD-1-treated test animals 2 weeks post-operation revealed inferior PTD and ICI when compared with that of MTA. Even 4 weeks after the operation in SRD-1- and SRD-2-treated rats, the PTD and ICI were inferior when compared with those of MTA. The dental specimens of SRD-0 and MTA showed orthodentin formation, whereas SRD-treated test animals showed osteodentin formation at a position slightly deeper than the site of the pulpal exposure. SIGNIFICANCE: The reparative dentin formed by SRD-0 and MTA was genuine, whereas that formed by SRD-3 and SRD-6 was ossified and ectopic. SRD may have the potential to be utilized clinically as a direct pulp capping material.

Effect of various surface treatments on the bond strength of resin luting agent and the surface roughness and surface energy of CAD/CAM materials.

The aim of this study was to examine the effect of various surface treatments on the bond strength of a resin luting agent and the surface roughness and surface energy of computer-aided design and computer-aided manufacturing (CAD/CAM) materials. Four types of CAD/CAM blocks (Shofu Block HC: BHC; GC Cerasmart: CER; VITA Enamic: ENA; and Lava Ultimate: LAV) were used. All blocks were randomly divided into eight groups based on the surface treatment as follows: no surface treatment (C), airborne-particle abrasion (AA), hydrofluoric acid etching (HA), silane coupling agent application (SL), AA/SL, HA/SL, AA/HA, and AA/HA/SL. The microtensile bond strength (µTBS), surface roughness and surface energy were measured. Three-way ANOVA revealed that all surface treatments significantly influenced the µTBS between the resin luting agent and all types of CAD/CAM materials; however, the effect of each surface treatment on surface roughness and energy was dependent on the CAD/CAM materials.

Bactericidal effect of antimicrobial photodynamic therapy (aPDT) on dentin plate infected with Lactobacillus acidophilus.

This study aimed to examine bactericidal effects of a new antimicrobial photodynamic therapy (aPDT) on dentin plates infected with Lactobacillus acidophilus (L. acidophilus). First, we measured the amount of reactive oxygen species (ROS) produced when new photosensitizer (PS), acid red (AR), and brilliant blue (BB) were irradiated with a semiconductor laser. ROS generated from each PS solution by laser irradiation was calculated as the total light emission amount (Relative Light Unit, RLU) using a chemiluminescence measuring device. Second, we examined bactericidal effects of the aPDT on dentin plates infected with L. acidophilus. The bactericidal effects on each group were evaluated by colony count assay and adenosine triphosphate assay. The experimental groups comprised two laser irradiation groups (650 nm laser, 650laser; and 940 nm laser, 940laser), two PS groups (BB and AR), four aPDT groups (650 nm laser irradiation with BB, 650laser-BB; 650 nm laser irradiation with AR, 650laser-AR; 940 nm laser irradiation with BB, 940laser-BB; 940 nm laser irradiation with AR, 940laser-AR), and a control. The ROS in all aPDT groups was significantly higher than in the control. RLU in all groups applied with laser irradiation was significantly lower than that in the control. However, only 650laser-BB showed significantly lower colony counts than the control. 650laser-BB was the most effective in sterilizing the infected dentin plates.

Effect of silane coupling treatment and airborne-particle abrasion on shear bond strength between photo-cured bulk-fill flowable composite resin and silverpalladium-copper-gold alloy using self-adhesive resin cement.

The purpose of the present study was to examine the effects of silane coupling treatment and airborne-particle abrasion (APA) on shear bond strength (SBS) between photo-cured bulk-fill flowable composite resin and 12% silver-palladium-copper-gold (Ag-Pd-CuAu) alloy using self-adhesive resin cement. The six experimental groups were compared using two-way analysis of variance (ANOVA) followed by Tukey Kramer's post-hoc test to compare SBS values among the six groups at a 95% confidence level. The SBS of APA groups was significantly higher than non-APA groups. The SBS of the specimens with silane coupling treatment increased slightly compared with specimens without silane coupling treatment. The combination of resin coating with bulk-fill resin and self-adhesive resin cement could be clinically useful when restoring a cavity with a noble metal.

Effects of the percentage of air/water in spray on the efficiency of tooth ablation with erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation.

We aimed at examining the effects of a percentage of air/water in spray on the cutting efficiency of Er,Cr:YSGG laser for enamel and dentin. The intensity and frequency of irradiation were 3.0 W and 20 Hz for the enamel surface and 2.0 W and 20 Hz for the dentin surface, respectively. Flattened surfaces of enamel and dentin were irradiated at nine points for approximately 1 s under various percentages of air/water in spray using Er,Cr:YSGG laser. A high-speed video microscope was used to record each laser irradiation on the tooth surface. A slow video image was used to count the number of water micro-explosions yielded on the tooth surface during laser irradiation. A surface roughness tester was used to measure the depth of the dimple prepared with laser irradiation on each specimen. Each individual depth of dimple was divided by the number of water micro-explosions (pulse). This allowed for the calculation of the cutting depth per pulse. Following laser irradiation, several representative specimens were observed using an SEM. Two-way ANOVA was used as the statistical analysis. This revealed that there was no significant effect of the percentage of air/water in spray on the cutting depth for enamel surface (p > 0.05). On the contrary, a significant effect was observed in air-ratio for dentin cutting (p < 0.05). Both enamel and dentin were characterized by the presence of rough surfaces, as shown by the SEM images of the dimples. The percentage of air/water in spray was not significantly effective in laser cutting for enamel. Air-percentage was significantly effective in laser cutting for dentin.

Histopathological findings of an exposed human pulp carbonised by CO2 laser irradiation: A case report.

This report shows the healing process of an exposed pulp carbonised by CO2 laser irradiation prior to the application of a capping material. Six intact teeth from four volunteers were irradiated by CO2 laser and randomly capped with either an adhesive resin (SE bond) (n = 3) or calcium hydroxide-based cement (Dycal) (n = 3). The laser was operated in super-pulsed mode (power output, 0.5 W) for an irradiation time of 30 s. All cavities were restored with composite resin. Each tooth was extracted at approximately 30, 50 or 260 days post treatment and prepared for histological evaluation. CO2 laser irradiation controlled exudate and bleeding from each exposed pulp. Histological images revealed Dycal promoted complete dentine bridge formation at the carbonised pulp surface, and laser energy affected not only the pulp surface but also the deeper part of the pulp chamber.

Effect of filler size and filler loading on wear of experimental flowable resin composites.

The relationship between wear resistance and filler size or filler loading was clarified for the universal resin composite; however, their relationship in flowable resin composites has not been clarified. The purpose of this study was to investigate the effect of filler size and filler loading on wear of experimental flowable resin composites by using a cyclic loading device. Nine experimental flowable resin composites consisting of three different sizes (70, 200 and 400 nm) and loading (50, 55 and 60 wt%) of filler were prepared. Bowl-shaped cavities were prepared on a flat surface of ceramic blocks using a No. 149 regular cut diamond point. The cavities were treated with a silane coupling agent and an all-in-one adhesive and then filled with each experimental flowable resin composite. The restored surfaces were finished and polished with a 1500-grit silicon carbide paper. The specimens were subjected to an in vitro two-body wear test using a cyclic loading device. The localized worn surfaces were evaluated at 10,000, 20,000, 30,000, and 40,000 cycles using a computer-controlled three-dimensional measuring microscope (n=5). The volumetric wear loss of the materials was calculated automatically by the equipment. Data were statistically analyzed with two-way ANOVA and post hoc Tukey test. Two-way ANOVA showed that the filler size significantly influenced wear volume (p<0.003), but the filler loading did not have a significant effect (p>0.05). A post hoc Tukey test detected significant differences in filler size between 70 nm and 400 nm, and 200 nm and 400 nm (p<0.007). The experimental flowable resin composite containing a mean filler size of 400 nm exhibited significantly lower wear resistance in two-body wear compared with those containing mean filler sizes of 200 nm or 70 nm.

Effect of antimicrobial photodynamic therapy (aPDT) on the sterilization of infected dentin in vitro.

The aim of this study was to evaluate the bactericidal effect of antimicrobial photodynamic therapy (aPDT) on an infected dentin model. Dentin plates were prepared from extracted human molars and infected through immersion in a solution of Streptococcus mutans. The nine experimental groups consisted of two laser irradiation groups (650 nm laser: 650 laser and 940 nm laser: 940 laser), two photosensitizer groups (methylene blue: MB, and azulenocyanine: Azc), four aPDT groups (650 nm laser irradiation of MB: 650 laser-MB, 650 nm laser irradiation of Azc: 650 laser-Azc, 940 nm laser irradiation of MB: 940 laser-MB and 940 nm laser irradiation of Azc: 940 laser-Azc) and a control. The bactericidal effects on each group were evaluated by colony count and adenosine triphosphate (ATP) assays. Based on the results of the colony count assay, the 650 laser-MB and 940 laser-MB groups formed significantly fewer colonies than the other experimental groups. Significantly fewer colonies were observed in the 940 laser-Azc group than in the control, but significant differences in the numbers of colonies were not observed between the 650 laser-Azc and control groups. The 940 laser group formed slightly fewer colonies than the 650 laser group, but the difference was not significant. In addition, the number of colonies in the MB group was significantly less than the number in the Azc group. The results of the ATP assay were similar to those of the colony count assay. aPDT with MB showed a significant bactericidal effect on dentin plates infected with S. mutans.

Effect of filler size and filler loading on wear of experimental flowable resin composites

Abstract The relationship between wear resistance and filler size or filler loading was clarified for the universal resin composite; however, their relationship in flowable resin composites has not been clarified. Objectives: The purpose of this study was to investigate the effect of filler size and filler loading on wear of experimental flowable resin composites by using a cyclic loading device. Material and Methods: Nine experimental flowable resin composites consisting of three different sizes (70, 200 and 400 nm) and loading (50, 55 and 60 wt%) of filler were prepared. Bowl-shaped cavities were prepared on a flat surface of ceramic blocks using a No. 149 regular cut diamond point. The cavities were treated with a silane coupling agent and an all-in-one adhesive and then filled with each experimental flowable resin composite. The restored surfaces were finished and polished with a 1500-grit silicon carbide paper. The specimens were subjected to an in vitro two-body wear test using a cyclic loading device. The localized worn surfaces were evaluated at 10,000, 20,000, 30,000, and 40,000 cycles using a computer-controlled three-dimensional measuring microscope (n=5). The volumetric wear loss of the materials was calculated automatically by the equipment. Data were statistically analyzed with two-way ANOVA and post hoc Tukey test. Results: Two-way ANOVA showed that the filler size significantly influenced wear volume (p<0.003), but the filler loading did not have a significant effect (p>0.05). A post hoc Tukey test detected significant differences in filler size between 70 nm and 400 nm, and 200 nm and 400 nm (p<0.007). Conclusion: The experimental flowable resin composite containing a mean filler size of 400 nm exhibited significantly lower wear resistance in two-body wear compared with those containing mean filler sizes of 200 nm or 70 nm.