title: The effect of disinfectants on the properties of dental gypsum, part 2: surface properties.
abstract: OBJECTIVE
  This study is part of an ongoing investigation to evaluate the surface properties of dental stones mixed with disinfection solutions, and to determine the effect of adding gum arabic and calcium hydroxide on the same properties.
  
  
  METHODS
  Aqueous solutions of 2 chemical disinfectants were used in mixing 2 types of dental stones (type III and type V). These dental stones were modified further by adding 1% gum arabic and 0.132% calcium hydroxide to their hemihydrate powders before mixing. Five specimens prepared from each type of dental stone were classified into 7 groups according to the hemihydrate powder modification and mixing liquid/powder ratio. Surface roughness was tested by 2-dimensional profilometery and scanning electron microscopy (SEM). Knoop hardness testing was carried out, and detail reproduction was assessed using ADA specification 25 in addition to SEM and 3-dimensional profilometer studies.
  
  
  RESULTS
  Dental stones mixed with chemical disinfectants showed higher average roughness (R(a)) values than those of the controls. However, adding gum arabic and calcium hydroxide to the hemihydrate powders before mixing restored values to the level of the control. The additives seemed to have a role in the improvement of surface hardness. There was no significant difference between the experimental and the control group in the terms of detail reproduction.
  
  
  CONCLUSIONS
  Using SEM, 3-dimensional profilometry, and ADA testing methods, we found that the surface roughness of stone casts was adversely affected by using the disinfectant solutions as mixing water substitutes. Gum arabic and calcium hydroxide additives can yield a harder stone surface without compromising other surface properties.
authors.affiliation: University of Minnesota, Minneapolis, USA.
authors.forename: Khalid M
authors.initials: KM
authors.lastname: Abdelaziz
authors.forename: Edward C
authors.initials: EC
authors.lastname: Combe
authors.forename: James S
authors.initials: JS
authors.lastname: Hodges
mesh_terms: D000704:Analysis of Variance; D002126:Calcium Hydroxide / Q000737:chemistry; D002133:Calcium Sulfate / Q000737:chemistry*; D016009:Chi-Square Distribution; D019551:Dental Disinfectants / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006170:Gum Arabic / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011206:Povidone-Iodine / Q000737:chemistry; D011208:Powders; D012973:Sodium Hypochlorite / Q000737:chemistry; D013223:Statistics as Topic; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D019551:Dental Disinfectants; D003764:Dental Materials; D011208:Powders; D014867:Water; D011206:Povidone-Iodine; D006170:Gum Arabic; D012973:Sodium Hypochlorite; D002126:Calcium Hydroxide; D002133:Calcium Sulfate