An in vitro comparison of the enamel remineralisation potential of bioactive glass, hydroxyapatite and CPP-ACP

The objective of this research was to investigate the comparative in vitro enamel remineralisation potential of commercial toothpastes containing bioactive glass (BG) particles, hydroxyapatite (HAP) particles or casein phosphopeptide – amorphous calcium phosphate (CPP-ACP) nanocomplexes. Eighteen extracted permanent teeth were coated with varnish leaving a window on the buccal surface and placed in demineralising solution for 24 h to create artificial caries-like white spot lesions (WSLs). The teeth were randomly assigned to six groups and sectioned longitudinally through the WSLs. The roots were removed and the teeth were re-varnished, leaving the WSLs exposed. Groups A, B and C were subjected to an optimum remineralisation protocol in which the “control” half of each tooth was incubated in artificial saliva for 24 h at 37 ◦C and the “treatment” half of each corresponding tooth was cyclically exposed to artificial saliva and to 1:2 toothpaste solution containing either BG, HAP or CPP-CAP, respectively. Groups D, E and F were subjected to an acid-challenge remineralisation protocol which was similar to that of Groups A, B and C but which also incorporated cyclic exposure to demineralising solution. Scanning electron microscopy and energy dispersive X-ray analysis were used to compare the remineralisation of the surface and depth of the control and treatment WSLs. Under optimum conditions BG and CPP-ACP provided sub-surface repair by diffusion of calcium and phosphate ions into the WSLs. HAP did not influence remineralisation under neutral pH conditions. Conversely, under acid-challenge conditions, HAP was able to dissolve to release calcium and phosphate ions which diffused in to the WSLs and also protected the enamel surface from further erosion. BG and CPP-ACP both coated the enamel surface under acidic conditions, although their ability to remineralise the body of the lesion was compromised at low pH

Prevention of enamel demineralization after tooth bleaching by bioactive glass incorporated into toothpaste

Background: The aim of this study was to determine the effects of bleaching on the structure of the enamel layer of teeth and the potential of the commercial bioactive glass NovaMin® in two different toothpastes to remineralize such regions of the enamel. Three aspects were considered: the extent and nature of the alterations in the enamel after application of the bleaching agents; the extent of remineralization after application of two commercial toothpastes containing bioactive glass; and whether or not there were differences between the toothpastes in terms of their effectiveness in promoting remineralization. Methods: Bleaching agent based on 16% carbamide peroxide was applied to the enamel surface of freshly extracted human molars for 8 minutes, once a day for 7 days. After the bleaching cycles, the enamel surface was analysed by SEM and EDX. Results: The results obtained in the study lead to the conclusion that application of 16% carbamide peroxide causes distinct morphological changes to the enamel surface which vary from mild to severe. Subsequent treatment with either of the toothpastes containing the bioactive glass NovaMin® resulted in the formation of a protective layer on the enamel surface, consisting of bioactive glass deposits, with only slight differences between the two brands. Application of these dentifrices also caused increases in the Ca and P content of the enamel layer, returning it to that of undamaged enamel. Conclusions: Remineralizing toothpastes should be used after bleaching, in order to repair any damage to the mineral tissue caused by these procedures

Incorporation of antimicrobial agents can be used to enhance the antibacterial effect of endodontic sealers

**Aim** The antibacterial activity of five endodontic sealers against three different microorganism strains alone and following incorporation of 2% benzalkonium chloride (BC) and 2% cetylpyridinium chloride (CPC) was evaluated. **Methodology** The agar diffusion method was used to determine the inhibitory effect of the following endodontic sealers: RoekoSeal, Endomethasone N, N2, Apexit Plus and AH plus, on Streptococcus mutans – ATCC 25175, Lactobacillus casei – ATCC 4646 and Actinomyces viscosus – ATCC 19246. Bacterial strains were inoculated into BHIB, and incubated in an anaerobic atmosphere (37 °C). From the bacteria grown in the liquid medium, the density of the inoculum was set to be equivalent to McFarland 2 standard. In Shaedler agar, 350 μL of the bacterial suspension were equally spread. Specimens (4 mm × 6 mm) were prepared from each material without and with addition of 2% BC or 2% CPC. The inhibition zones were determined after 2 days, after 7 days and after 21 days of incubation. **Results** The largest inhibition zones were shown at zero time in all cases, with progressively less inhibition at 7 and 21 days. Endomethasone N and N2 showed the most intense antimicrobial activity, while RoekoSeal showed the least antimicrobial effect. The most susceptible microorganism was A. viscosus. Greater antimicrobial effects were found following incorporation of BC or CPC, and generally, BC gave greater inhibition zones than CPC. **Conclusions** Adding either BC or CPC has the potential to improve clinical outcomes with endodontic sealers, as these substances enhance the short-term antimicrobial effects of the sealers

Interfacial properties of three different bioactive dentine substitutes

Three different bioactive materials suitable as dentine substitutes in tooth repair have been studied: glass-ionomer cement, particulate bioglass, and calcium-silicate cement. On 15 permanent human molars, Class V cavities were prepared and the bottom of each cavity was de-mineralized by an artificial caries gel. After the de-mineralization, the teeth were restored with: (1) Bioglass (R) 45S5 and ChemFil (R) Superior; (2) Biodentine (TM) and ChemFil (R) Superior; and (3) ChemFil (R) Superior for a complete repair. The teeth were stored for 6 weeks in artificial saliva, then cut in half along the longitudinal axis: the first half was imaged in a scanning electron microscope (SEM) and the other half was embedded in resin and analyzed by SEM using energy-dispersive X-ray analysis. The glass-ionomer and the bioglass underwent ion exchange with the surrounding tooth tissue, confirming their bioactivity. However, the particle size of the bioglass meant that cavity adaptation was poor. It is concluded that smaller particle size bioglasses may give more acceptable results. In contrast, both the glass-ionomer and the calcium-silicate cements performed well as dentine substitutes. The glass-ionomer showed ion exchange properties, whereas the calcium silicate gave an excellent seal resulting from its micromechanical attachment