title: Comparison to the scanning electron microscope of professional dental hygiene methods on metal-free layered structures and metal-free monolithic structures processed by different polymerization cycles.
abstract: OBJECTIVE
  Aim of the study was to find effective instrumental methodologies and procedures for scaling and deplaquing without compromising the structure of metal-free, monolithic lithium disilicate and layered zirconia prosthetics.
  
  
  METHODS
  Of 14 decontaminated, extracted teeth in good anatomical condition, 7 veneers lithium disilicate monolithic and 7 layered zirconia crowns were prepared for testing and divided into 6 treatment groups. Each group was composed of a veneer and a crown. The division of the groups was carried out according to the type of treatment performed- instrumental carbon fiber and steel tips, prophylaxis paste with high and low RDA (Relative dentin abrasion), bicarbonate powder. Samples were examined and observed through a scanning electron microscope (SEM). Afterwards a detailed comparison of the images of treated and untreated samples was performed. The images were at the same magnification, thus showing the differences in the treated samples.
  
  
  RESULTS
  The monolithic lithium disilicate presents minor damage to the surface but no excessive changes to the structure in general post treatment. The layered zirconia resulted in notable damage with evident abrasions on the layered ceramic structure after the use of ultrasound with a steel tip and air flow with bicarbonate. Carbon fibre tips and prophylaxis paste containing perlite and low RDA did not create notable changes to the properties of the materials in question.
  
  
  CONCLUSIONS
  The results of the disilicate monolithic appear to show it to be a much more resistant material compared to layered zirconia in ceramic. Its resistance is demonstrated by the lack of notable damage in all the treatment groups.
authors.affiliation: Department of Dental Hygiene University of Pavia, Pavia, Italy - martaermetici@hotmail.it.
authors.forename: M
authors.initials: M
authors.lastname: Ermetici
authors.forename: M
authors.initials: M
authors.lastname: Segù
authors.forename: A
authors.initials: A
authors.lastname: Butera
mesh_terms: D000537:Aluminum Oxide; D002244:Carbon; D000077482:Carbon Fiber; D002516:Ceramics; D003442:Crowns; D003775:Dental Polishing / Q000009:adverse effects / Q000379:methods*; D003776:Dental Porcelain; D012534:Dental Scaling / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D003799:Dental Stress Analysis; D003801:Dental Veneers; D003802:Dentifrices; D006244:Hardness; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009757:Nylons; D017640:Silicates; D012822:Silicon Dioxide; D017693:Sodium Bicarbonate; D013193:Stainless Steel; D013499:Surface Properties; D015040:Zirconium
chemical_list: D000077482:Carbon Fiber; D003802:Dentifrices; D009757:Nylons; D017640:Silicates; C493120:lithia disilicate; C003076:Perlite; D003776:Dental Porcelain; D013193:Stainless Steel; D002244:Carbon; D012822:Silicon Dioxide; D017693:Sodium Bicarbonate; D015040:Zirconium; D000537:Aluminum Oxide; C005144:pumice; C028541:zirconium oxide