Blood or Saliva on Dentin in the Middle of Bonding: What Should We Do?
∆ Why contamination matters
Rubber dam isolation is the gold standard, but with subgingival margins, deep proximal cavities, freshly operated areas, or uncooperative patients it is not always possible. In these conditions saliva, blood, or gingival crevicular fluid can settle on the dentin at one of the steps of bonding. Saliva is mostly water with some enzymes and glycoproteins that coat the dentin surface and impair the wetting of the adhesive. Blood creates a worse situation, because plasma proteins form a layer on the dentin that blocks resin infiltration into the tubules and the formation of the hybrid layer, and the resin tags become shorter and fewer. That is why the damage blood does to bond strength is greater than that of saliva. This framework is written for the dentin surface.
∆ One simple rule for every step
The response to contamination depends on two things: at which step it happened and which adhesive system you are working with. But if you want to keep one rule in mind, it is this: rinse, dry, and redo the step you were on. Up to the point of curing the adhesive, this rule works in most systems and restores the bond substantially, often to close to the uncontaminated level. After the adhesive is cured, especially if the contaminant is blood, the rule is not reliable, and the safest route is to remove the adhesive layer and start again. Hemostatic agents are a separate exception, covered at the end. There is also one general point: no decontamination method guarantees a complete and reliable return of the bond to the uncontaminated level; these methods reduce the loss, they do not eliminate it.
Below, each step is written out separately for four common systems: etch-and-rinse (two- or three-step, with separate phosphoric acid), two-step self-etch (separate primer and adhesive), one-step self-etch (all-in-one), and a universal adhesive in self-etch mode.
∆ Step one: prepared dentin, nothing applied yet
This is the simplest situation, and the solution is the same in every system: rinse with water spray (about ten seconds of running water is enough), dry, and continue as usual.
Etch-and-rinse: after rinsing, the routine phosphoric acid etch itself removes the blood residues from the dentin surface, and no extra work is needed.
Two-step self-etch: rinsing and drying, or even blot drying with absorbent paper, before the primer has been reported to be enough.
One-step self-etch: a brief rinse with running water before applying the adhesive is enough.
Universal: rinsing and drying is enough. With heavy blood contamination, sodium hypochlorite together with an antioxidant (sodium ascorbate or proanthocyanidin) before the adhesive also has positive reports, but it is an additional option, not a replacement for rinsing.
∆ Step two: the dentin has been etched, then contamination occurs
This step exists only in etch-and-rinse (and in a universal adhesive used in etch-and-rinse mode). Etched, uncovered dentin is highly sensitive to contamination. For saliva, rinsing and drying again is usually enough. For blood, rinsing with water does not work, and you have to etch again, rinse, and dry. Re-etching at this step is the most effective measure and restores the bond to close to the uncontaminated level.
∆ Step three: primer or adhesive applied, not yet cured
This is the most common event in everyday work: the adhesive is on the dentin, your hand is reaching for the curing light, and in that interval the gingiva bleeds or saliva gets into the cavity. There are two things you should not do in any system: air-dry and cure, or apply another coat of adhesive over the contaminated layer. The shared principle is that the contaminated layer has to be rinsed off with water and then the step repeated.
Etch-and-rinse: rinse, dry with absorbent paper or a gentle air stream, then reapply the adhesive and cure. If the contaminant was blood, a short re-etch before the adhesive improves the result and restores the bond to close to the uncontaminated level.
Two-step self-etch: rinse, dry, then reapply the primer and then the adhesive, and cure. The result depends on the product; in some systems this restores the bond, and in others no method has been effective.
One-step self-etch: this group depends most on the product; one adhesive recovers well with rinsing and reapplication, while another shows an even greater loss with the same protocol. The safest course is to rinse and dry the surface thoroughly and redo the bonding from the start, rather than simply adding a layer.
Universal: rinse, dry, then reapply the adhesive and cure. In universal adhesives this protocol has given the most consistent result and restores the bond to close to the uncontaminated level.
∆ Step four: the adhesive has been cured, then contamination occurs
This time the adhesive layer has hardened, and the contaminant sits on its surface, not on the dentin. The composite has to bond to this surface, and a layer of saliva or blood now lies between the two. This is the most challenging situation, and the greatest loss of bond is seen at this step.
If the contaminant is saliva, in every system rinse, dry, apply a fresh coat of adhesive and cure; this is usually enough.
If the contaminant is blood, rinsing and reapplying adhesive on its own does not work, because blood proteins have adhered to the resin surface and do not come off with water. Here the systems part ways:
Etch-and-rinse: re-etching the cured surface with phosphoric acid and then applying fresh adhesive gives a partial improvement, but the bond still stays well short of the uncontaminated level. If the restoration is in a high-stress area, remove the layer and start again.
Two-step and one-step self-etch: in these two groups no conservative method after curing has compensated for the bond. The simple solution: remove the adhesive layer with a diamond bur and redo the bonding from the start.
Universal: the only group for which a conservative method with a result close to the uncontaminated level has been reported. Phosphoric acid or sodium hypochlorite on the cured surface, followed by rinsing, drying and fresh adhesive, and in one report rinsing with 2% chlorhexidine, have restored the bond. Still, in some other reports with this same group no method was effective, so if you are unsure, removing the layer and starting again is the safer option.
Removing the layer with a diamond bur fully restores the bond in every system, but some sound tooth structure is lost; that is why it is the last option, not the first.
∆ Hemostatic agents: not a solution, part of the problem
When there is bleeding, reaching for a hemostatic agent seems natural, but agents containing aluminum chloride or ferric sulfate themselves leave deposits on the dentin and reduce bond strength, especially in self-etch and universal systems. These agents are for controlling gingival bleeding, not for decontaminating dentin, and using them as a way to clean off blood is not recommended. If a hemostatic agent inadvertently reaches the dentin, rinsing with water is not enough and you need a chemical agent:
Etch-and-rinse: the routine phosphoric acid etch removes the effect of the hemostatic agent, and no extra work is needed.
Self-etch (both types) and universal: because they have no acid step, you need to add one: a short etch with phosphoric acid or EDTA, or a rinse with chlorhexidine, then rinse, dry, and continue as usual.
Ferric sulfate has an additional problem as well: the possibility of dentin discoloration in esthetic restorations.
∆ Summary
Whenever contamination occurs, rinse, dry, and redo the step you were on. Up to the point of curing the adhesive, this rule restores the bond substantially in most systems, and in etch-and-rinse, phosphoric acid is the most effective tool for correcting a contaminated surface. After curing, if the contaminant is saliva, the same rule is enough; if it is blood, in universal adhesives phosphoric acid or hypochlorite on the cured surface has a chance of recovery, and in the other systems the reliable route is to remove the layer and start again. Do not use hemostatic agents to clean off blood, and if they reach the dentin, clean them off with acid or chlorhexidine. And finally, no decontamination method reliably returns the bond to the uncontaminated level; prevention through proper isolation is still the main solution.