Glass ionomer cements functionalised with a concentrated paste of chlorhexidine hexametaphosphate provides dose-dependent chlorhexidine release over at least 14 months.

OBJECTIVES: The aim of this study was to create prototype glass ionomer cements (GICs) incorporating a concentrated paste of chlorhexidine-hexametaphosphate (CHX-HMP), and to investigate the long-term release of soluble chlorhexidine and the mechanical properties of the cements. The purpose is the design of a glass ionomer with sustained anticaries efficacy. METHODS: CHX-HMP paste was prepared by mixing equimolar solutions of chlorhexidine digluconate and sodium hexametaphosphate, adjusting ionic strength, decanting and centrifuging. CHX-HMP paste was incorporated into a commercial GIC in substitution for glass powder at 0.00, 0.17, 0.34, 0.85 and 1.70% by mass CHX-HMP. Soluble chlorhexidine release into artificial saliva was observed over 436 days using absorbance at 255nm. Diametral tensile and compressive strength were measured after 7 days' setting (37°C, 100% humidity) and tensile strength after 436 days' aging in artificial saliva. 0.34% CHX-HMP GICs were tested for their ability to inhibit growth of Streptococcus mutans in vitro. RESULTS: GICs supplemented with CHX-HMP exhibited a sustained dose-dependent release of soluble chlorhexidine. Diametral tensile strength of new specimens was unaffected up to and including 0.85% CHX-HMP, and individual values of tensile strength were unaffected by aging, but the proportion of CHX-HMP required to adversely affect tensile strength was lower after aging, at 0.34%. Compressive strength was adversely affected by CHX-HMP at substitutions of 0.85% CHX-HMP and above. CONCLUSIONS: Supplementing a GIC with CHX-HMP paste resulted in a cement which released soluble chlorhexidine for over 14 months in a dose dependent manner. 0.17% and 0.34% CHX-HMP did not adversely affect strength at baseline, and 0.17% CHX-HMP did not affect strength after aging. 0.34% CHX-HMP GICs inhibited growth of S. mutans at a mean distance of 2.34mm from the specimen, whereas control (0%) GICs did not inhibit bacterial growth. CLINICAL SIGNIFICANCE: Although GICs release fluoride in vivo, there is inconclusive evidence regarding any clinical anticaries effect. In this study, GICs supplemented with a paste of chlorhexidine-hexametaphosphate (CHX-HMP) exhibited a sustained release of chlorhexidine over at least 14 months, and small additions of CHX-HMP did not adversely affect strength.

Chlorhexidine hexametaphosphate nanoparticles as a novel antimicrobial coating for dental implants.

Dental implants are an increasingly popular solution to missing teeth. Implants are prone to colonisation by pathogenic oral bacteria which can lead to inflammation, destruction of bone and ultimately implant failure. The aim of this study was to investigate the use of chlorhexidine (CHX) hexametaphosphate (HMP) nanoparticles (NPs) with a total CHX concentration equivalent to 5 mM as a coating for dental implants. The CHX HMP NPs had mean diameter 49 nm and composition was confirmed showing presence of both chlorine and phosphorus. The NPs formed micrometer-sized aggregated surface deposits on commercially pure grade II titanium substrates following immersion-coating for 30 s. When CHX HMP NP-coated titanium specimens were immersed in deionised water, sustained release of soluble CHX was observed, both in the absence and presence of a salivary pellicle, for the duration of the study (99 days) without reaching a plateau. Control specimens exposed to a solution of aqueous 25 µM CHX (equivalent to the residual aqueous CHX present with the NPs) did not exhibit CHX release. CHX HMP NP-coated surfaces exhibited antimicrobial efficacy against oral primary colonising bacterium Streptococcus gordonii within 8 h. The antimicrobial efficacy was greater in the presence of an acquired pellicle which is postulated to be due to retention of soluble CHX by the pellicle.

Development of a novel antimicrobial-releasing glass ionomer cement functionalized with chlorhexidine hexametaphosphate nanoparticles.

BACKGROUND: Glass ionomer cements (GICs) are a class of dental biomaterials. They have a wide range of uses including permanent restorations (fillings), cavity linings, fissure sealants and adhesives. One of the most common reasons for replacing a dental restoration is recurrent bacterial tooth decay around the margins of the biomaterial. Therefore, a dental biomaterial which creates a sustained antimicrobial environment around the restoration would be of considerable clinical benefit. In this manuscript, the formulation of a GIC containing novel antimicrobial nanoparticles composed of chlorhexidine hexametaphosphate at 1, 2, 5, 10 and 20% powder substitution by mass is reported. The aim is to create GICs which contain chlorhexidine-hexametaphosphate nanoparticles and characterize the nanoparticle size, morphology and charge and the release of chlorhexidine and fluoride, tensile strength and morphology of the GICs. RESULTS: The GICs released chlorhexidine, which is a broad spectrum antimicrobial agent effective against a wide range of oral bacteria, over the duration of the experiment in a dose-dependent manner. This was not at the expense of other properties; fluoride release was not significantly affected by the substitution of antimicrobial nanoparticles in most formulations and internal structure appeared unaffected up to and including 10% substitution. Diametral tensile strength decreased numerically with substitutions of 10 and 20% nanoparticles but this difference was not statistically significant. CONCLUSION: A series of GICs functionalized with chlorhexidine-hexametaphosphate nanoparticles were created for the first time. These released chlorhexidine in a dose-dependent manner. These materials may find application in the development of a new generation of antimicrobial dental nanomaterials.

Teaching dental pain with and without underlying oral physiology: learning implications.

This study investigated whether teaching undergraduate dental students the diagnosis and management of acute dental pain alongside the underpinning oral physiology helped them to understand the topic better than teaching them acute dental pain as a separate entity. Each of three clinical years of dental students at the same dental school was taught in two groups. Each group was taught the signs/symptoms of five acute dental pain conditions by the same member of the staff. However, the teaching for one group of students in each year reminded the students about the physiology that underpinned the clinical symptoms. One week later, the students completed an open-ended questionnaire that required them to list signs/symptoms of the five dental pain conditions. For each year of dental students that was examined, the mean student marks were significantly higher (p<0.05) for those who were taught dental pain and the underlying physiology compared with students who were only taught dental pain as a stand-alone subject. This suggests that integrating biomedical science and clinical teaching is beneficial.

Differential adhesion of Streptococcus gordonii to anatase and rutile titanium dioxide surfaces with and without functionalization with chlorhexidine.

The majority of dental implants are composed primarily of titanium and have an outer layer of titanium dioxide. Crystalline titanium dioxide most commonly exists in one of the two structures, anatase and rutile, and both of these have been observed on commercially available dental implants. Early implant failure can be associated with postoperative infection due to implant contamination during or immediately after surgery. The impetus of this study was to investigate whether functionalization of anatase and rutile titanium dioxide surfaces with chlorhexidine-reduced subsequent colonization of the surface by Streptococcus gordonii. Exposure to 100 mg x L(-1) chlorhexidine for 60 s resulted in a fivefold reduction in S. gordonii coverage on anatase and a twofold reduction on rutile. This may be related to a preferential adsorption of chlorhexidine to anatase compared with rutile. The reduction in bacterial coverage was not due to desorption of chlorhexidine into solution. More bacteria were observed on anatase than rutile surfaces without chlorhexidine functionalization, indicating that crystal structure may have a significant effect on bacterial colonization. In conclusion, functionalization with chlorhexidine reduced bacterial coverage on titanium dioxide surfaces, and anatase surfaces may be more amenable to such treatment than rutile.

The effects of polishing methods on surface morphology, roughness and bacterial colonisation of titanium abutments.

Bacterial colonisation of exposed implant and abutment surfaces can lead to peri-implantitis, a common cause of oral implant failure. When an abutment becomes exposed in the oral environment the typical recommendation is to debride it, to obtain a smoother surface which might be expected to reduce bacterial colonisation. The aim of this study was to evaluate, in vitro, a conventional polishing protocol (PP1) and a simplified polishing protocol (PP2), suggested to have advantages over PP1. The surface morphology and roughness of titanium abutments were characterised at each stage of polishing, and adhesion of oral bacteria was evaluated, using atomic force microscopy, environmental scanning electron microscopy and optical profilometry. PP1 and PP2 methodologies resulted in indistinguishable surface finishes, with fewer scratches than the unmodified surface, and equal roughness values. PP2 resulted in less disruption and less removal of surface material. Early biofilm formation by Streptococcus mutans was reduced on surfaces polished using PP2, but not PP1. Biofilms of Actinomyces naeslundii were more extensive on polished abutment surfaces. Simplified protocol PP2 may be preferable to conventional protocol PP1, since less material is removed, and there is less chance of rough areas remaining. Polishing, however, does not necessarily reduce oral bacterial colonisation.