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Time dependence of composite shrinkage using halogen and LED light curing

Affiliation

  • 1 Friedrich Schiller University Jena, Institute of Materials Science and Technology (IMT), Löbdergraben 32, D-07743 Jena, Germany.
  • PMID: 15705435
  • DOI: 10.1016/j.dental.2004.03.010

Time dependence of composite shrinkage using halogen and LED light curing

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Authors

Affiliation

  • 1 Friedrich Schiller University Jena, Institute of Materials Science and Technology (IMT), Löbdergraben 32, D-07743 Jena, Germany.
  • PMID: 15705435
  • DOI: 10.1016/j.dental.2004.03.010

Abstract

Objectives: The polymerization shrinkage of light cured dental composites presents the major drawback for these aesthetically adaptable restorative materials. LED based light curing technology has recently become commercially available. Therefore, the aim of the present study was to investigate if there was a statistically significant difference in linear and volumetric composite shrinkage strain if a LED LCU is used for the light curing process rather than a conventional halogen LCU.

Methods: The volumetric shrinkage strain was determined using the Archimedes buoyancy principle after 5, 10, 20, 40 s of light curing and after 120 s following the 40 s light curing time period. The linear shrinkage strain was determined with a dynamic mechanical analyzer for the composites Z100, Spectrum, Solitaire2 and Definite polymerized with the LCUs Trilight (halogen), Freelight I (LED) and LED63 (LED LCU prototype). The changes in irradiance and spectra of the LCUs were measured after 0, 312 and 360 min of duty time.

Results: In general there was no considerable difference in shrinkage of the composites Z100, Spectrum or Solitaire2 when the LED63 was used instead of the Trilight. There was, however, a statistically significant difference in shrinkage strain when the composite Definite was polymerized with the LED63 instead of the Trilight. The spectrum of the Trilight changed during the experiment considerably whereas the LED63 showed an almost constant light output. The Freelight I dropped considerably in irradiance and had to be withdrawn from the study because of technical problems.

Significance: The composites containing only the photoinitiator camphorquinone showed similar shrinkage strain behaviour when a LED or halogen LCU is used for the polymerization. The irradiance of some LED LCUs can also decrease over time and should therefore be checked on a regular basis.

The composites containing only the photoinitiator camphorquinone showed similar shrinkage strain behaviour when a LED or halogen LCU is used for the polymerization. The irradiance of some LED LCUs can also decrease over time and should therefore be checked on a regular basis.

Investigation of polymerisation shrinkage strain, associated cuspal movement and microleakage of MOD cavities restored incrementally with resin-based composite using an LED light curing unit

Affiliation

  • 1 Materials Science Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, Trinity College Dublin, Dublin 2, Ireland. [email protected]
  • PMID: 16842899
  • DOI: 10.1016/j.jdent.2006.05.003

Investigation of polymerisation shrinkage strain, associated cuspal movement and microleakage of MOD cavities restored incrementally with resin-based composite using an LED light curing unit

  • Search in PubMed
  • Search in NLM Catalog
  • Add to Search

Authors

Affiliation

  • 1 Materials Science Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, Trinity College Dublin, Dublin 2, Ireland. [email protected]
  • PMID: 16842899
  • DOI: 10.1016/j.jdent.2006.05.003

Abstract

Objectives: To investigate the polymerisation shrinkage strain, associated cuspal movement, degree of conversion (DC) and cervical gingival microleakage of mesio-occlusal-distal (MOD) cavities restored with four resin-based composite (RBC) filling materials placed incrementally using a light emitting diode (LED) light curing unit (LCU).

Methods: Standardised extensive MOD cavity preparations on extracted teeth were performed on 40 sound upper premolar teeth. Restoration of the teeth involved the placement of RBCs in eight increments with the appropriate bonding system before irradiation using an LED LCU. Buccal and palatal cusp deflections at each stage of polymerisation were recorded using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in a 0.2% basic fuchsin dye for 24 h, sagittally sectioned and examined for cervical microleakage. The DC was determined using a Fourier transform infra-red (FT-IR) spectrometer.

Results: No significantly difference (P=0.677) in cuspal movement was recorded for Z100 (13.1+/-3.2 microm) compared with Filtek Z250 (8.4+/-3.5 microm), P60 (7.3+/-3.8 microm) and Admira (6.7+/-2.7 microm). The LED LCU deflections were compared with a halogen LCU used in a conventional (Fleming GJP, Hall D, Shorthall ACC, Burke FJT. Cuspal movement and microleakage in premolar teeth restored with posterior filling materials of varying reported volumetric shrinkage values. Journal of Dentistry, 2005;33:139-146) and soft-start mode (Fleming GJP, Cara RR, Palin WM, Burke FJT. Cuspal movement and microleakage in premolar teeth restored with posterior filling materials cured using ‘soft-start’ polymerization. Dental Materials, 2006, , in press) and a significant reduction in cuspal movement was identified for curing type and material type (P Significance: It would appear that irradiation of RBCs using the LED LCU offered a significant reduction in associated cuspal movement in large MOD cavities. However, the microleakage scores following polymerisation were significantly increased with dye penetration into the pulp chamber from the axial wall evident in teeth restored with the LED LCU.

It would appear that irradiation of RBCs using the LED LCU offered a significant reduction in associated cuspal movement in large MOD cavities. However, the microleakage scores following polymerisation were significantly increased with dye penetration into the pulp chamber from the axial wall eviden …