title: Clinically relevant issues related to preheating composites.
abstract: BACKGROUND
  Issues regarding the use of composite preheating need to be investigated so that the clinician will better understand the variables associated with this method.
  
  
  OBJECTIVE
  To examine the multiple aspects of use of a commercial composite preheating device (Calset, AdDent Inc., Danbury, CT, USA).
  
  
  METHODS
  Temperature values of three heating units and composite compules were obtained using a K-type thermocouple and were recorded digitally in real time. The following parameters were measured: maximum heater and composite temperature and its stability upon storage, composite temperature change when removed from the heater and injected, the effect of delivery system on ejected composite temperature, and the effect of repeated and extended preheating on composite monomer conversion (using infrared spectroscopy). Monomer conversion was measured after repeated composite cycling (from room temperature [RT] to 60 degrees C, 10x) or extended preheating (24 hours at 60 degrees C), and values were compared with composite maintained at RT (control group). Among test parameters, data (N=5 for each parameter) were analyzed using Student's t-test, analysis of variance, and the Tukey-Kramer post-hoc test where appropriate (alpha=0.05).
  
  
  CONCLUSIONS
  Two of the three tested units achieved the stated preset temperatures. Composite attained temperature values close to the heating unit. Composite temperature drop upon removal from the heater was dramatic: within 2 minutes a 50% temperature drop was noted. Heating the compule while preloaded in the syringe provided higher delivery temperatures than heating the compule separately (p < 0.00). Optimum results were achieved when preheated composite was dispensed and used as quickly as possible. Neither repeated nor extended preheating of composite significantly affected monomer conversion.
  
  
  CONCLUSIONS
  Preheating composite has potential benefits, but should be used with knowledge of its limitations. Reheating of unused composite does not affect its degree of conversion, thus decreasing material waste. Heating of the composite preloaded in the delivery syringe enhances the temperature of extruded composite.
authors.affiliation: Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Márcia
authors.initials: M
authors.lastname: Daronch
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Rueggeberg
authors.forename: Linda
authors.initials: L
authors.lastname: Moss
authors.forename: Mario Fernando
authors.initials: MF
authors.lastname: de Goes
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006361:Heating / Q000295:instrumentation*; D006358:Hot Temperature; D011140:Polyurethanes / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D003764:Dental Materials; D011140:Polyurethanes