Coronal Leakage From Alkaline Endodontic Cements Versus Resin Sealers

Objectives: Coronal leakage causes long term failure of root fillings. This laboratory study used a saliva challenge model to assess leakage characteristics of alkaline cements with conventional root filling materials.
Methods: 140 human roots with single straight canals prepared to standard length and canal size with rotary NiTi instruments were allocated into 7 groups. Canals were obturated with GP and AH-Plus, GP and Zirmix (Ozdent) (a non-staining resin sealer chemically similar to AH 26), Nex MTA (GC), MTA-Mix (a non-staining white MTA cement based on Portland cement, Supercal (Ozdent) – an alkaline calcium hydroxide and glycerol-based hard setting alkaline cement. Negative controls were sealed with wax and positive leakage controls were left open. The test devices were gamma sterilized, then the coronal root face was exposed daily to fresh stimulated saliva diluted 1:5 in BHI medium. Leakage was determined by bacterial growth in sterile BHI medium in contact with the root apex. Samples were kept for up to 90 days at 37^oC in a humid atmosphere. Leakage was indicated by turbidity in the BHI medium. Survival was compared using Kaplan-Meier analysis.
Results: In order of survival, the groups were ranked as follows from highest to lowest: Negative control (sealed with wax), Supercal, Nex MTA, Zirmix, MTA-Mix, GP+AH Plus, and the positive control (open canal). At 90 days, 5 out of 20 roots obturated with Supercal did not show leakage. Differences between the two resin sealers became apparent at 2 weeks, and likewise between the two MTA cements. Intense root staining was seen with Nex MTA but not other materials.
Conclusions: Alkaline cements can show impressive resistance to fluid leakage from a constant saliva challenge. This property could reflect their interactions with radicular dentine as well as release of hydroxyl ions on contact with fluid.