Post-operative sensitivity is one of the most frustrating complications in restorative dentistry. Almost every dentist has experienced a case where a patient returns the next day complaining, “Doctor, my filling hurts when I bite or when I drink something cold,” even though the procedure seemed perfect.
While mild sensitivity may resolve on its own, persistent cases can impact patient satisfaction and treatment success. Understanding the causes and applying preventive measures is key to reducing its occurrence.
The Main Theory Behind Post-Operative Sensitivity
The most accepted explanation is the Hydrodynamic Theory. According to this theory, movement of fluid within the dentinal tubules (DT) stimulates mechanoreceptors near the odontoblastic processes, leading to pain or discomfort.
This movement can be triggered by thermal, chemical, or mechanical stimuli — and it can be caused by physiological, pathological, or iatrogenic factors.
Types and Causes of Tooth Sensitivity
1. Physiological Causes
Caries
Cracks
Erosion
2. Pathological Causes
Caries progression
3. Iatrogenic Causes (Dentist-Induced)
This is the most relevant in post-operative sensitivity after composite placement. The patient arrives comfortable, you perform the restoration, and they leave with discomfort — indicating an issue that occurred during the procedure.
Common Iatrogenic Causes and How to Avoid Them
1. Cavity Preparation
Heat generation can cause irreversible pulp damage. A rise in pulp temperature of just 5°C can lead to necrosis.
Always use adequate water coolant during preparation.
Four-hole turbines are preferred over single-hole turbines for better cooling.
2. Adhesive Systems
Many believe self-etch adhesives cause less sensitivity than total-etch systems — some studies support this, especially in deep cavities, while others find no significant difference.
3. Desensitizers
Applying multiple adhesive layers does not guarantee reduced sensitivity; in fact, excessive layers can reduce shear bond strength.
4. Light Curing Units and Technique
Incomplete polymerization due to low-intensity light can cause sensitivity.
Keep the curing light as close as possible to the composite.
Use incremental layering (≤ 2 mm) unless using a bulk-fill composite.
5. Composite Type and Placement
Polymerization shrinkage (1.7–5.7% of total volume) can pull resin away from cavity walls, creating gaps and allowing microleakage — a major cause of sensitivity.
Poor adaptation to cavity walls (especially in Class II) leaves voids.
Occlusion must be checked before dismissal; high spots can cause immediate discomfort.
High C-factor cavities (e.g., Class I, Class V) increase shrinkage stress — use layering to reduce it.
Flowable composites as the first layer can improve adaptation and reduce stress.
Prevention Strategies
Control heat during preparation.
Use adhesives and desensitizers appropriately.
Cure in thin increments with optimal light intensity.
Understand the composite material’s properties before use.
Maintain good adaptation and coverage of dentin.
Management Protocol for Post-Operative Sensitivity
1- Check occlusion — remove any high spots.
2- If pain persists, remove the composite and place a temporary restoration such as GIC or ZOE.
3- Once symptoms resolve, replace with a new composite restoration following proper protocols.