title: Mechanical and biological characterization of resin-modified glass-ionomer cement containing doxycycline hyclate.
abstract: OBJECTIVE
  To characterize the mechanical and biological properties of a resin-modified glass ionomer cement (RMGIC) containing doxycycline hyclate.
  
  
  METHODS
  The antibacterial effect of RMGIC containing 1.5, 3.0 and 4.5% doxycycline hyclate was assessed using two experiments - agar diffusion test for 24h and biofilm assay for 24h and 7 days - against some cariogenic bacteria. Briefly, base layers of BHI agar and 300μL of each inoculum were prepared in Petri dishes with 6 wells that were completely filled with materials. After 24h incubation, zones of bacterial growth inhibition were measured using a digital caliper. Biofilm assays were conducted using RMGIC specimens immersed in 24-well plates containing the inoculum in BHI broth. After 24h and 7 days, each specimen were removed, vortexed and the suspension diluted and inoculated in BHI plates for subsequent bacterial counting. Cytotoxicity tests used 50 specimens made in sterilized metal molds, including Vitrebond as positive control. Extracts from every specimen were applied on the MDPC-23 odontoblast-like cells for 24h. The MTT assay and SEM evaluation determined cell metabolism and morphology, respectively. 80 cylindrical specimens were made from the previously cited groups, and were submitted to testing with a universal testing machine (Instron 4411) using a crosshead speed of 1.0mm/min for compressive strength and 0.5mm/min for diametral tensile strength, respectively. Data from antibacterial and cytotoxic effects, and mechanical properties were submitted to appropriated statistical tests.
  
  
  RESULTS
  All tested groups showed growth inhibition of all tested strains (p<0.05) in 24h for both microbiological tests, but only 4.5% doxycycline have antibacterial effect after 7 days. None of doxycycline concentrations caused toxic effect to the MDPC-23 cells or presenting alterations to mechanical properties.
  
  
  CONCLUSIONS
  The incorporation of up to 4.5% doxycycline hyclate into RMGIC inhibits important oral microorganisms, without modifying biological and mechanical characteristics of the dental material, suggesting a new alternative for the treatment of dental caries.
authors.affiliation: Department of Pediatric Dentistry, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, São Paulo, Brazil.
authors.forename: Aline R F
authors.initials: AR
authors.lastname: de Castilho
authors.forename: Cristiane
authors.initials: C
authors.lastname: Duque
authors.forename: Thais de C
authors.initials: Tde C
authors.lastname: Negrini
authors.forename: Nancy T
authors.initials: NT
authors.lastname: Sacono
authors.forename: Andréia B
authors.initials: AB
authors.lastname: de Paula
authors.forename: Patrícia A
authors.initials: PA
authors.lastname: Sacramento
authors.forename: Carlos A
authors.initials: CA
authors.lastname: de Souza Costa
authors.forename: Denise M P
authors.initials: DM
authors.lastname: Spolidorio
authors.forename: Regina M
authors.initials: RM
authors.lastname: Puppin-Rontani
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001681:Biological Assay; D002460:Cell Line; D015169:Colony Count, Microbial; D003731:Dental Caries / Q000188:drug therapy*; D004318:Doxycycline / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D019279:Resin Cements / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D005899:Glass Ionomer Cements; D019279:Resin Cements; D004318:Doxycycline