EVALUATION OF THE EFFECT OF DIFFERENT LIGHT CURING AND ADHESIVES SYSTEMS ON THE POLYMERISATION SHRINKAGE OF DENTAL COMPOSITE: AN IN VITRO STUDY

Abstract

This study evaluated the effect of three types of light curing systems (quartz tungsten halogen, light emitting diode and softstart curing light) on three types of dental adhesives (Xeno® III, Prime and bond® NT™ and Unibond II). Sixty freshly extracted sound bicuspid teeth were used; two standardized cavities were created on the middle third of the buccal and lingual surfaces of each tooth. After storage for one day in normal physiological saline at 37oC, teeth were divided into four groups of fifteen teeth each. The three selected bonding and filling agents, as well as curing systems were applied according to the manufacturers’ instructions. The first group was considered as a control (without bonding agent) and cured by three different curing systems. The second, third and fourth groups were treated with one of the adhesive agents. Then all groups were coated with nail varnish and immersed in 2% aqueous solution of methylene blue dye for 24 hours, then washed, sectioned and scored under light microscope. The microleakage at the resin-based composite (Filtek™ Z250, 3M, ESPE) – tooth interface was assessed. Soft-start light-curing mode showed the lowest microleakage values among the curing modes, while the quartz tungsten halogen light curing revealed the highest values of microleakage in all types of bonding systems. Concerning the dental adhesives, the lowest microleakage values were observed when the Unibond II was used whereas Xeno III® exhibited the highest degree of microleakage. Resume Cette etude a evalue le degre de micro-infiltration a l’interface dent- composite lorsque trois systemes de lumiere bleue (« quartz tungsten halogen », « light emitting diode » et «softstart ») et trois types d’adhesifs dentaires (« Xeno® III », « Prime and bond® NT™ » et « Unibond II ») ont ete utilises. Soixante premolaires saines fraichement extraites ont ete utilisees; deux cavites ont ete creees au niveau du tiers median des faces vestibulaire et linguale / palatine de chaque dent. Les trois agents adhesifs choisis ont ete appliques selon les instructions du fabricant. Ensuite, les dents ont ete immergees pendant 24 heures dans du serum physiologique a 37 °C puis reparties en quatre groupes de quinze dents chacun. Le premier groupe a ete considere comme un groupe-temoin (sans adhesif); dans les second, troisieme et quatrieme groupes, un des trois types d’adhesifs a ete applique. Ensuite, toutes les dents ont ete recouvertes d’une couche de vernis et immergees pendant 24 heures dans une solution aqueuse a 2% de bleu de methylene, puis rincees, sectionnees et observees au microscope optique. Le degre de microinfiltration a l’interface dent-composite (Filtek™ Z250, 3M, ESPE) a ete evalue. La photopolymerisation utilisant le mode « soft-start » a montre la valeur la plus faible de micro-infiltration, tandis que la lumiere au tungstene de quartz a revele les valeurs les plus elevees de micro-infiltration quel que soit le type d’adhesif. En ce qui concerne les adhesifs dentaires utilises, le degre de micro-infiltration etait le plus faible avec « Unibond II » alors que le Xeno® III a presente le plus haut degre de micro-infiltration.