title: Atmospheric moisture effects on the testing rate and cementation seating load following resin-strengthening of a soda lime glass analogue for dental porcelain.
abstract: OBJECTIVE
  To investigate if resin-cementation of a soda lime glass dental analogue could elucidate information regarding the pattern of resin-reinforcement when coated in an environment actively scavenged of moisture.
  
  
  METHODS
  192 soda lime disc-shaped specimens (alumina particle air abraded, hydrofluoric acid-etched and silane coated) were randomly assigned to eight groups (n=24 per group) prior to resin-coating at seating loads of 5 N (Groups A-D) and 30 N (Groups E-H) in an environment where moisture was actively scavenged and maintained below 15 ppm. Following one week storage the discs were tested in biaxial flexure at crosshead rates of 0.01, 0.1, 1 and 10mm/min. Analysis of group means was performed utilising a general linear model univariate analysis and post hoc all paired Tukey tests (P<0.05).
  
  
  RESULTS
  The general linear model univariate analysis identified the mean biaxial flexure strength (BFS) was significantly influenced by the factors resin-cementation seating load (P<0.001) and crosshead speed of the applied load (P<0.001) with a significant interaction (P=0.008) between both factors. The linear logarithmic regression curves fitted to the group mean BFS data plotted against the crosshead speed highlighted significant differences between the pattern of resin-strengthening for the cementation loads and testing conditions.
  
  
  CONCLUSIONS
  The decrease in resin-penetration expected within the 'resin-ceramic hybrid layer' following removal of the 30 N seating load was proposed as the modifying resin-strengthening parameter. These observations are supported by the viscoelastic and creep behaviour of resins at slow testing rates which becomes the dominant or determining phenomenon.
authors.affiliation: Materials Science Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Lincoln Place, Trinity College Dublin, Ireland. Electronic address: paul.hooi@dental.tcd.ie.
authors.forename: Paul
authors.initials: P
authors.lastname: Hooi
authors.forename: Owen
authors.initials: O
authors.lastname: Addison
authors.forename: Garry J P
authors.initials: GJ
authors.lastname: Fleming
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry*; D002484:Cementation / Q000379:methods*; D055117:Curing Lights, Dental / Q000145:classification; D045662:Dental Etching / Q000379:methods; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003890:Desiccation; D004780:Environment, Controlled; D005898:Glass / Q000737:chemistry*; D006801:Humans; D006813:Humidity; D006858:Hydrofluoric Acid / Q000737:chemistry; D008422:Materials Testing; D010087:Oxides / Q000737:chemistry*; D018583:Pliability; D019279:Resin Cements / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D019279:Resin Cements; D012821:Silanes; D003776:Dental Porcelain; C004569:soda lime; D012972:Sodium Hydroxide; D000537:Aluminum Oxide; D006858:Hydrofluoric Acid
keywords: Biaxial flexure strength; Resin-based composite; Soda-lime glass