Acid neutralizing and remineralizing orthodontic adhesive containing hydrated calcium silicate

Bioceramic micro-fillers reinforce antibiofilm and remineralization properties of clear aligner attachment materials

Introduction: Clear aligners, while offering a more hygienic alternative to fixed appliances, are still associated with challenges including plaque accumulation and enamel demineralization. The aim of the present study was to investigate the antibiofilm and remineralization effectiveness of innovative flowable composite attachments containing bioceramic micro-fillers. Methods: Four experimental attachments were formulated and bonded to human enamel specimens: 3M Filtek Supreme flowable composite (Filtek SF) + 10% bioactive glass 45S5 (BAG), Filtek SF + 30% BAG, Filtek SF + 10% Bredigite (BRT), Filtek SF + 30% BRT. Plaque biofilms were grown on the bonded enamel using a standardized protocol and the biofilm-killing effect was assessed by confocal laser scanning microscopy and scanning electron microscopy. Vickers microhardness was measured to evaluate the remineralization effect of the attachments containing bioceramic fillers after acid challenge. Shear bond test was performed to assess the bonding strength. Results: Attachments with bioceramic fillers significantly inhibited plaque biofilm growth in 3 weeks on enamel, contributing over 20% bacterial cell killing in 10% filler groups and over 30% killing in 30% filler groups. All four experimental groups demonstrated significantly higher microhardness values than the control group without fillers on the attachment side. The shear bonding strength was not compromised in the attachments with micro-fillers. Discussion: Proper incorporation of bioceramic micro-fillers in attachments provides an innovative approach for clear aligner therapy with reinforced antibiofilm and remineralization effects without weakening shear bonding strength.

A novel orthodontic adhesive containing zinc-doped phosphate-based glass for preventing white spot lesions

OBJECTIVES

This study aimed at demonstrating the remineralization effect of the enamel around the brackets to aid reduction in white spot lesions (WSLs) with use of zinc-doped phosphate-based glass (Zn-PBG) containing orthodontic adhesives.

METHODS

Zn-PBG powder was synthesized, and particle morphology, size, and density were evaluated. Orthodontic adhesives with increasing loading percentage of Zn-PBG powder were prepared: ZnPG3 (3 wt.%), ZnPG6 (6 wt.%), and ZnPG9 (9 wt.%). Brackets were bonded on the etched enamel surface and stored in distilled water (DW) for 1 h. Following, Shear bond strength (SBS) along with adhesive remnant index were analyzed. The release of calcium (Ca), phosphorus (P), and zinc (Zn) from adhesive specimens in DW was evaluated after 7, 15 and 30 days of immersion. The remineralization effect was confirmed by microhardness and surface morphology analysis with scanning electron microscopy.

RESULTS

The SBS value was observed between 20 and 22 MPa on enamel surface. The concentration of Ca, P and Zn released in DW increased with loading percentage of Zn-PBG. The microhardness increased in the experimental groups after immersion in artificial saliva for 7 days. Apatite-like crystal formation was observed after 30 days in the ZnPG 9 group.

CONCLUSIONS

The orthodontic adhesive containing Zn-PBG with an optimal SBS performance has an enamel remineralization effect, and therefore can aid in prevention of WSLs.

CLINICAL SIGNIFICANCE

The orthodontic adhesive containing Zn-PBG is clinically advantageous as it can promote remineralization and resist the formation of WSLs that may occur during orthodontic therapy.

Effect of bacterial resistant zwitterionic derivative incorporation on the physical properties of resin-modified glass ionomer luting cement

Biofilms induce microbial-mediated surface roughening and deterioration of cement. In this study, zwitterionic derivatives (ZD) of sulfobetaine methacrylate (SBMA) and 2-methacryloyloxyethyl phosphorylcholine, were added in concentrations of 0, 1, and 3% to three different types of commercially available resin-modified glass ionomer cement (RMGIC) (RMC-I: RelyX Luting 2, RMC-II: Nexus RMGI, and RMC-III: GC FujiCEM 2). The unmodified RMGICs served as the control group for comparison. The resistance of Streptococcus mutans to ZD-modified RMGIC was evaluated with a monoculture biofilm assay. The following physical properties of the ZD-modified RMGIC were assessed: wettability, film thickness, flexural strength, elastic modulus, shear bond strength, and failure mode. The ZD-modified RMGIC significantly inhibited biofilm formation, with at least a 30% reduction compared to the control group. The addition of ZD improved the wettability of RMGIC; however, only 3% of the SBMA group was statistically different (P < 0.05). The film thickness increased in proportion to the increasing ZD concentrations; there was no statistical difference within the RMC-I (P > 0.05). The experimental groups' flexural strength, elastic modulus, and shear bond strength showed an insignificant decrease from the control group; there was no statistical difference within the RMC-I (P > 0.05). The mode of failure differed slightly in each group, but all groups showed dominance in the adhesive and mixed failure. Thus, the addition of 1 wt.% ZD in RMGIC favorably enhanced the resistance to Streptococcus mutans without any tangible loss in flexural and shear bond strength.

Ceramic Nanomaterials in Caries Prevention: A Narrative Review

Ceramic nanomaterials are nanoscale inorganic metalloid solids that can be synthesised by heating at high temperatures followed by rapid cooling. Since the first nanoceramics were developed in the 1980s, ceramic nanomaterials have rapidly become one of the core nanomaterials for research because of their versatility in application and use in technology. Researchers are developing ceramic nanomaterials for dental use because ceramic nanoparticles are more stable and cheaper in production than metallic nanoparticles. Ceramic nanomaterials can be used to prevent dental caries because some of them have mineralising properties to promote the remineralisation of tooth tissue. Ceramic minerals facilitate the remineralisation process and maintain an equilibrium in pH levels to maintain tooth integrity. In addition, ceramic nanomaterials have antibacterial properties to inhibit the growth of cariogenic biofilm. Researchers have developed antimicrobial nanoparticles, conjugated ceramic minerals with antibacterial and mineralising properties, to prevent the formation and progression of caries. Common ceramic nanomaterials developed for caries prevention include calcium-based (including hydroxyapatite-based), bioactive glass-based, and silica-based nanoparticles. Calcium-based ceramic nanomaterials can substitute for the lost hydroxyapatite by depositing calcium ions. Bioactive glass-based nanoparticles contain surface-reactive glass that can form apatite crystals resembling bone and tooth tissue and exhibit chemical bonding to the bone and tooth tissue. Silica-based nanoparticles contain silica for collagen infiltration and enhancing heterogeneous mineralisation of the dentin collagen matrix. In summary, ceramic nanomaterials can be used for caries prevention because of their antibacterial and mineralising properties. This study gives an overview of ceramic nanomaterials for the prevention of dental caries.

A remineralizing orthodontic etchant that utilizes calcium phosphate ion clusters

This study aimed to investigate whether a phosphoric acid (H3PO4) solution containing calcium phosphate ion clusters (CPICs) could minimize enamel damage during long-term bracket bonding by dissolving the enamel surface and promoting enamel remineralization. The experimental design is as follows: first, three experimental etchants (H3PO4, CPICs-incorporated H3PO4 solution-I, and CPICs-incorporated H3PO4 solution-II) and two bonding resins (conventional orthodontic resin and self-adhesive orthodontic resin) were used in combination to create six groups, respectively. Each of these six groups was then divided into two sub-groups based on the presence or absence of thermocycling (TC). Twenty samples were assigned to each of the 12 groups (independent variables), and thus a total of 240 metal bracket-attached human premolars were used in this experiment. Bracket debonding was performed on each of 20 premolars in 12 groups, and shear bond strength (SBS) and adhesive remnant index (ARI) values were measured as dependent variables. Next, the three experimental etchants were applied (independent variables) to each of the three enamel samples, and the remineralization of the enamel surface was investigated as a dependent variable. The enamel surface was observed using electron scanning and atomic force microscopy. Furthermore, X-ray diffraction, energy dispersive spectroscopy (EDX) spectrum X-ray spectroscopy, and elemental mapping were performed, and the Knoop microhardness scale was measured. Therefore, the experiment was performed in two steps: SBS and ARI measurements for 12 groups, followed by observation of the enamel surface and microhardness measurements, according to the three types of etchants. As a result of the experiment, first, when the bracket was debonded, SBS did not decrease, and residual adhesive was hardly observed in the C2A group (before TC), C2A, and C1C groups (after TC) (p &lt; 0.001). Second, the experimental etchant containing CPICs achieved remineralization while demineralizing the enamel. This was verified through SEM/EDX, element mapping, XRD, and AFM. Also, the roughness and microhardness of the enamel surface were better in the remineralized surface by the experimental etchant containing CPICs (p &lt; 0.017). The CPICs-incorporated H3PO4 solution reduced ARI while maintaining SBS during bracket debonding, regardless of whether TC was performed or the type of resin. The etchant containing CPICs was also shown to remineralize the enamel and increase its microhardness.