Optident highlights five reasons for post-operative sensitivity when using adhesives and resin composites, and explains how Peak Universal Bond and Mosaic Universal Composite from Ultradent could help.
1. The dentine is too wet or overdried after etching
When the dentine is too wet, this may cause microscopic water blisters and resin globules to occur inside the dentinal tubules. When under occlusal compression, these blisters then may force dentinal fluid toward the pulp and cause post-operative sensitivity.
When dentine is too dry, the surrounding collagen fibres collapse and it becomes difficult to impregnate the resin into the dentine; causing sensitivity during chewing.
2. The dentine has been etched for too long
Etching dentine too long may result in etch patterns that extend too deep for the adhesive resins to reach. Depths of about 2 to 2.5 µm are the limit; deeper etching creates voids that may result in a weak link or tooth sensitivity. Always use an etchant with a limited penetration depth, even when left longer than the recommended 15 seconds.
3. Under or overcuring
Undercuring leaves the bonding resin only partly polymerised, which again leads to sensitivity. Choose a curing light powerful enough to reach the full distance from the tip of the light to base of the cavity. Use lights with at least 400Mw/cm2, or preferably over 1.000 Mw/cm2.
A study carried out in 2006 (Kim et al, 2006) proved that when the adhesive resin layer was cured longer than recommended, defects formed between the adhesive layer and the composite resin. The lesson? Always follow the manufacturer’s guidelines for curing times.
4. Using phosphoric acid in deep dentine
Using total-etch in deep dentine carries the risk of over drying the collagen layer, which again prevents the adhesive from penetrating correctly into the collapsed fibres of the intertubular dentine. In self-etch, the etching depth and the depth of the adhesive’s penetration into the dentine is the same, meaning the collagen fibres are prevented from collapsing.
5. Curing before proper adhesive application
Allowing too little time for adhesive application may result in poor penetration of the bonding agent. Make sure rubbing, brushing in and agitating of the product is given enough time. Air thin to allow the solvent to evaporate. If the curing light is used before the solvent evaporates, this may result in an incomplete cure.
How can Peak Universal help?
Neil Jessop, director of research and development at Ultradent says: ‘We have chemistry inside (Peak) that allows us to have a priming type agent. This primer allows us to have a wettable, or hydrophilic type component that goes in and finds the most microscopic details you can imagine, while after being polymerised becomes substantially hydrophobic. This ensures a long-term bond, dealing with sensitivity well.’
Peak came out top in a recent study: the microshear bond strength (μSBS) of universal adhesive systems were tested by application onto five different indirect restorative materials. The study proved Peak Universal Bond to be the only adhesive for which the mean μSBS reached the highest ranking of statistical significance for all five substrates (Siqueira et al, 2016).
How does Mosaic Universal combat sensitivity?
Mosaic is a nano-hybrid, which has the advantage of being low shrinkage, therefore helping to eliminate chances of marginal gaps forming after polymerisation. As Mosaic is a nanohybrid composite, it not only has low shrinkage, but it also performs well when it comes to aesthetics, wear characteristics and polishability.
Prepare for the switch
The growing requests to replace amalgam fillings with new, more aesthetically pleasing restorations shows testament to the evolution of aesthetic dentistry. Of course, amalgam doesn’t have the same post-operative sensitivity implications as composite, therefore the use of adhesives with resin composites comes under the spotlight.
Universal Bond and Mosaic Universal Composite are the perfect tools to use when post-op sensitivity is a concern. Use a system that is loved by dentists; we have these testimonials, and many more, to prove it.
‘Love the way the material handles and I love the realistic and beautiful look…Mosaic composite is a winner! Can’t wait to do more cases!’ – Dr Hal Stewart.
‘I haven’t had to replace a restoration due to patient sensitivity since I started using the Peak bonding system over five years ago. I use Peak exclusively and recommend it highly to all my colleagues!’ – Dr Thomas Germino.
Kim JS1, Choi YH, Cho BH, Son HH, Lee IB, Um CM and Kim CK (2006) Effect of light-cure time of adhesive resin on the thickness of the oxygen-inhibited layer and the microtensile bond strength to dentin J Biomed Mater Res B Appl Biomater Jul;78(1): 115-23
Siqueira F, Cardenas AM, Gutierrez MF, Malaquias P, Hass V, Reis A, Loguercio AD and Perdigão J. Laboratory Performance of Universal Adhesive Systems for Luting CAD/CAM Restorative Materials J Adhes Dent 18(4):331-40