title: Glass ionomer cements functionalised with a concentrated paste of chlorhexidine hexametaphosphate provides dose-dependent chlorhexidine release over at least 14 months.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Oral Nanoscience, School of Oral and Dental Sciences, University of Bristol, Lower Maudlin St BS1 2LY, UK.
authors.forename: Candice A
authors.initials: CA
authors.lastname: Bellis
authors.affiliation: Oral Microbiology, School of Oral and Dental Sciences, University of Bristol, Lower Maudlin St BS1 2LY, UK.
authors.forename: Angela H
authors.initials: AH
authors.lastname: Nobbs
authors.affiliation: Oral Nanoscience, School of Oral and Dental Sciences, University of Bristol, Lower Maudlin St BS1 2LY, UK.
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: O'Sullivan
authors.affiliation: Oral Nanoscience, School of Oral and Dental Sciences, University of Bristol, Lower Maudlin St BS1 2LY, UK; Kemdent, Associated Dental Products Ltd., Purton, Swindon SN5 4HT, UK.
authors.forename: James A
authors.initials: JA
authors.lastname: Holder
authors.affiliation: Oral Nanoscience, School of Oral and Dental Sciences, University of Bristol, Lower Maudlin St BS1 2LY, UK. Electronic address: m.e.barbour@bristol.ac.uk.
authors.forename: Michele E
authors.initials: ME
authors.lastname: Barbour
mesh_terms: D000890:Anti-Infective Agents / Q000008:administration & dosage; D002710:Chlorhexidine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000737:chemistry*; D019245:Compressive Strength; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D004338:Drug Combinations; D005459:Fluorides / Q000737:chemistry / Q000494:pharmacology; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008422:Materials Testing; D009824:Ointments / Q000737:chemistry; D010710:Phosphates / Q000008:administration & dosage / Q000737:chemistry*; D012464:Saliva, Artificial; D013295:Streptococcus mutans / Q000187:drug effects / Q000254:growth & development; D013718:Tensile Strength; D014867:Water / Q000737:chemistry
chemical_list: D000890:Anti-Infective Agents; D004338:Drug Combinations; D005899:Glass Ionomer Cements; D009824:Ointments; D010710:Phosphates; D012464:Saliva, Artificial; D014867:Water; C005035:hexametaphosphate; C012980:fluorophosphate; C010882:chlorhexidine gluconate; C009285:sodium polymetaphosphate; D005459:Fluorides; D002710:Chlorhexidine
keywords: Antimicrobial; Biomaterials; Chlorhexidine; Glass ionomer; Restorative