Final answer:
Pain provoked by hot or cold after an amalgam filling is often due to the different expansion rates of the metal filling and the tooth enamel, which can cause thermal stress and sensitivity.
Step-by-step explanation:
When a patient complains of pain provoked by hot or cold sensations after receiving an amalgam dental filling, this may be due to the differing expansion rates between the metal filling and the tooth enamel causing thermal stress. The metal in the amalgam can expand or contract more than the surrounding tooth when exposed to temperature changes, potentially leading to tiny cracks or gaps between the tooth and the filling. This mismatch can allow for temperature extremes to reach the sensitive inner parts of the tooth, resulting in pain. Modern composite fillings, made of porcelain, have expansion coefficients that are more similar to natural teeth, reducing this effect. For example, when the patient consumes hot food or drink, the amalgam filling expands more than the surrounding tooth enamel. This expansion can create stress on the tooth structure and potentially cause the filling to crack or fracture. The same applies when cold substances are consumed, causing the amalgam filling to contract more than the tooth enamel, resulting in stress and potential discomfort.