White spot lesions around orthodontic brackets are the major complication during fixed orthodontic treatment. This study prepared orthodontic adhesives for promoting mineral precipitation and reducing bacterial growth. Adhesives with added calcium phosphate monohydrate/Sr-bioactive glass nanoparticles (Sr/CaP) and andrographolide were prepared. The physical/mechanical and antibacterial properties of the adhesives were tested. The additives reduced the monomer conversion of the materials (62 to 47%). The addition of Sr/CaP and andrographolide increased the water sorption (from 23 to 46 μg/mm³) and water solubility (from 0.2 to 5.9 μg/mm³) but reduced the biaxial flexural strength (from 193 to 119 MPa) of the adhesives. The enamel bond strengths of the experimental adhesives (19–34 MPa) were comparable to that of the commercial material (p > 0.05). The Sr/CaP fillers promoted Ca, Sr, and P ion release and the precipitation of calcium phosphate at the debonded interface. An increase in the Sr/CaP concentration enhanced the inhibition ofS. mutansby 18%, while the effect of andrographolide was not detected. The abilities of the adhesives to promote ion release, calcium phosphate precipitation, and the growth inhibition of cariogenic bacteria were expected to reduce the occurrence of white spot lesions. The additives reduced the physical/mechanical properties of the materials, but the corresponding values were within the acceptable range.

Enamel demineralization around orthodontic adhesive is a common esthetic concern during orthodontic treatment. The aim of this study was to prepare orthodontic adhesives containing monocalcium phosphate monohydrate (MCPM) and nisin to enable mineralizing and antibacterial actions. The physicomechanical properties and the inhibition of S. mutans growth of the adhesives with added MCPM (5, 10 wt %) and nisin (5, 10 wt %) were examined. Transbond XT (Trans) was used as the commercial comparison. The adhesive containing a low level of MCPM showed significantly higher monomer conversion (42–62%) than Trans (38%) (p < 0.05). Materials with additives showed lower monomer conversion (p < 0.05), biaxial flexural strength (p < 0.05), and shear bond strength to enamel than those of a control. Additives increased water sorption and solubility of the experimental materials. The addition of MCPM encouraged Ca and P ion release, and the precipitation of calcium phosphate at the bonding interface. The growth of S. mutans in all the groups was comparable (p > 0.05). In conclusion, experimental orthodontic adhesives with additives showed comparable conversion but lesser mechanical properties than the commercial material. The materials showed no antibacterial action, but exhibited ion release and calcium phosphate precipitation. These properties may promote remineralization of the demineralized enamel.

The aims of this study were to compare the chondroitin sulphate (CS) levels in gingival crevicular fluid (GCF) of moved canines using either 70 or 120g of orthodontic force, and to compare the rate of tooth movement and the amount of pain between these two force magnitudes. Sixteen patients (6 males and 10 females; aged 16.91±2.99 years), with class I malocclusion, who required orthodontic treatment with first premolar extractions, were recruited. The force magnitudes used to move the maxillary canines distally were controlled at 70 and 120g on the right and the left sides, respectively. GCF samples were collected with Periopaper^® strips before and during orthodontic tooth movement. Competitive ELISA with monoclonal antibody was used to measure the CS levels. The distance of tooth movement and the amount of pain assessed by visual analog scale (VAS) scores were evaluated. The medians of CS levels during the loaded period were significantly greater than those during the unloaded period (P < 0.05). The differences between the medians of CS levels of 70g and 120g retraction force during each 1 week period were not significant. There was no significant difference in the rates of canine movement between these two force magnitudes. However, using 120g, the medians of VAS scores were significantly greater than those with 70g (P < 0.05). Collectively, 70g retraction force appears to be sufficient and more suitable than 120g force as it causes no difference in biochemically-assessed bone remodelling activity, the same rate of tooth movement, reduced pain and better comfort.

Objectives This study aims to evaluate shear bond strength (SBS) of orthodontic brackets to enamel after resin infiltration pretreatment using different adhesive systems. Materials and Methods Sixty extracted maxillary first premolars were divided into five groups (n = 12). Group I: sound enamel + Transbond XT; group II: resin-infiltrated enamel (ICON) + Transbond XT; group III: ICON + Scotchbond Universal Plus; group IV: ICON + Assure PLUS; group V: ICON + Transbond Plus Self Etching. The SBS was measured using universal testing machine and analyzed using analysis of variance (ANOVA). The adhesive remnant index (ARI) score after debonding was determined under stereomicroscope with a 10× magnification. Statistical Analysis A one-way ANOVA and post hoc Tukey's test were used to compare the data. Further, the ARI scores were evaluated using a chi-squared test. The level of significance was set at p = 0.05. Results SBS of group I, II, III, IV, and V were 11.70 ± 3.17, 11.23 ± 3.06, 9.52 ± 1.73, 8.97 ± 1.12, and 9.14 ± 0.70 MPa, respectively. SBS of group IV and V was significantly lower than group I and II (p < 0.05). There was no significant difference in the ARI scores among the five groups (p > 0.05). Conclusion The SBS of enamel resin infiltration pretreatment depends on the adhesive system. The SBS of all groups was within adequate SBS range in clinical use. The most common ARI score was 2, which indicated lower risk of enamel fractures when debonding.

This study investigated the effects of miniscrew location on biomechanical performance of bone-borne rapid palatal expander (B-RPE) to midpalatal suture, using finite element (FE). Three cases of B-RPE with different miniscrew locations (3 and 6 mm from midpalatal suture and palatal interdental site) were simulated activations in partly ossified midpalatal suture maturation. This study compared the expansion amount and pattern along the suture line. Equivalent von Mises (EQV) stresses at appliance, miniscrew, midpalatal sutures, and elastic strain at the bone around miniscrew were evaluated. In all cases, they could not break the midpalatal suture of palatine bone. However, midpalatal suture at the maxilla was expanded. The expansion amount and unparallel expanding pattern were increased when miniscrews were positioned away from the suture. The interdental miniscrew position extended the suture more than the other 2 cases, but the pattern was unparallel. When the miniscrews were positioned away from the suture, the EQV stress at the appliance and elastic strain at the bone around the miniscrew were reduced. In the case of the palatal interdental miniscrew, all parameters were of lower magnitude. All cases could expand the partly ossified midpalatal suture maturation. The distance between the midpalatal suture and the miniscrew influenced appliance EQV stress, elastic strain at the bone around the miniscrew, and expansion characteristics.

This study examined the degree of monomer conversion (DC) and mechanical properties of experimental orthodontic adhesives containing monocalcium phosphate monohydrate (MCPM), Sr-bioactive glass (Sr-BAG) nanoparticles, and andrographolide. Experimental adhesives were prepared with a 4:1 powder-to-liquid ratio, containing methacrylate monomers with varying formulations of glass fillers and additives. DC was measured using ATR-FTIR (n = 5) with and without bracket placement under two curing protocols: conventional LED (1200 mW/cm², 20 s) and high-intensity LED (3200 mW/cm², 3 s). The biaxial flexural strength and modulus were tested after 4-week water immersion (n = 8). Transbond XT was used as the commercial comparison. Transbond XT exhibited higher DC (33–38%) than the experimental materials. Conventional LED curing produced higher DC than high-intensity LED, while bracket placement reduced DC by approximately 10% in the experimental materials but minimally affected Transbond XT. Transbond XT demonstrated a superior biaxial flexural strength (188 MPa) compared to the experimental adhesives (106–166 MPa, p < 0.05). However, the experimental formulations with low additive concentrations showed a comparable biaxial flexural modulus (5.0–5.5 GPa) to Transbond XT (5.6 GPa) (p > 0.05). Although the experimental adhesives exhibited lower DC and strength than the commercial product, their values still met the ISO standards, suggesting their potential clinical viability despite their modified compositions.