title: Effect of Different Firing Temperatures on Structural Changes in Porcelain.
abstract: OBJECTIVE
  To study the structural changes occurring in the dental porcelain mass fired at various firing temperatures using scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectroscopy. Also, additional tests, namely compressive strength, abrasion resistance analysis, and the amount of oxides released, were conducted at different firing temperatures.
  
  
  METHODS
  Six groups (40 specimens in each group) of porcelain mass were prepared. The dimensions and weight of all the specimens were kept constant. The specimens were then heat treated at different firing temperatures (660°C, 760°C, 860°C, 900°C, 960°C, 990°C). Half of the specimens of each group were subjected to a compressive strength test on a universal testing machine and then finely ground using an electrochemical grinder to prepare for XRD analysis. The other half of the specimens was weighed to analyze the amount of oxides released after each firing cycle. Following this, the specimens underwent an abrasion resistance test on a Nanovea Tribometer. The unaltered surface was scanned using SEM. The data (numerical and graphical) for all the tests were recorded and analyzed using one-way ANOVA and post hoc Tukey test.
  
  
  RESULTS
  The specimens fired at 900°C exhibited superior compressive strength and abrasion resistance. The quantity of oxides released by the specimens fired at 900°C was the least compared to specimens heat treated at the other firing temperatures. XRD analysis proved that the oxide released by the porcelain mass was calcium aluminum chromium oxide. Also, the fewer peaks obtained in the XRD graphs of specimens fired at 900°C signified lesser porosities in the porcelain specimens. SEM analysis depicted a homogeneous mass of porcelain at 900°C.
  
  
  CONCLUSIONS
  All the above findings validate the objective of studying the physical and internal structural changes of dental porcelain when subjected to an increasing firing temperature gradient. The specimens fired at 900°C exhibited superior strength and abrasion resistance. SEM analysis depicted a homogeneous mass of dental porcelain, implying that firing was complete at 900°C.
authors.affiliation: Dean, Postgraduate Studies and Research, Saraswati Dental College and Hospital, Lucknow, India.
authors.forename: Arvind
authors.initials: A
authors.lastname: Tripathi
authors.affiliation: Department of Prosthodontics, Saraswati Dental College and Hospital, Lucknow, India.
authors.forename: Soumyojeet
authors.initials: S
authors.lastname: Bagchi
authors.affiliation: Department of Prosthodontics, Saraswati Dental College and Hospital, Lucknow, India.
authors.forename: Juhi
authors.initials: J
authors.lastname: Singh
authors.affiliation: Indian Institute of Technology, Saharanpur Campus, Roorkee, India.
authors.forename: Vivek
authors.initials: V
authors.lastname: Gaurav
authors.affiliation: Institute for Data Computing and Training, Lucknow, India.
authors.forename: Mahendra
authors.initials: M
authors.lastname: Pal Singh Negi
mesh_terms: D003776:Dental Porcelain; D006358:Hot Temperature; D008422:Materials Testing
chemical_list: D003776:Dental Porcelain
keywords: Porcelain; ceramic mass; firing cycle; firing temperature; porosity; temperature gradient