Pain Management Flashcards

What is the 'gate control theory' of pain and how does it explain pain relief from transcutaneous electrical nerve stimulation (TENS)?

Answer: Large diameter A-beta fibres (non-painful sensory) can inhibit nociceptive transmission at the spinal cord 'gate' — TENS activates A-beta fibres, closing the gate and reducing pain signals to the brain

Melzack and Wall's gate control theory proposes that non-painful sensory input via A-beta fibres can inhibit nociceptive transmission in the dorsal horn. TENS uses this mechanism by activating tactile A-beta fibres, reducing pain signal transmission.

What is the 'intrapulpal injection' technique and when is it used in dentistry?

Answer: Direct injection of local anaesthetic into the exposed pulp chamber — used as a last resort supplement when all other techniques fail, effective but extremely painful to administer requiring counter-pressure

Intrapulpal injection delivers LA directly into the root canal/pulp chamber using slow counter-pressure, providing profound anaesthesia even in inflamed pulp. It is painful to administer but immediately effective, used when all other supplemental techniques have failed.

Why can inferior dental block (IDB) fail in acute pulpitis?

Answer: Inflammation lowers local tissue pH, converting the LA from lipid-soluble base form (which crosses membranes) to ionised form — reducing LA efficacy; also peripheral sensitisation lowers nociceptor thresholds

Inflamed tissue has a lower pH. LA (pKa ~7.8) requires unionised base form to cross nerve membranes. In acidic inflamed tissue, more LA is in the ionised form, reducing membrane penetration and block efficacy. Also, sensitised C fibres fire at lower thresholds.

What is 'maxillary sinus pain' and how does it mimic dental pain?

Answer: Sinus infections/congestion cause referred pain to upper posterior teeth (premolars and molars) because these teeth share innervation proximity with the maxillary sinus — tests show teeth are vital

Maxillary sinusitis commonly causes dull aching pain in the upper posterior teeth (usually multiple teeth) due to shared innervation (posterior superior alveolar nerve). Teeth test vital, pain is bilateral/positional, and multiple teeth are affected — unlike pulpitis which affects a single tooth.

What role do endorphins and endogenous opioids play in dental pain?

Answer: Endorphins (beta-endorphin) and enkephalins bind to opioid receptors in the brain and spinal cord, activating descending inhibitory pathways that reduce nociceptive transmission — the basis of placebo analgesia and acupuncture effects

The endogenous opioid system (beta-endorphins, enkephalins, dynorphins) activates mu, delta, and kappa receptors, inhibiting pain transmission in the dorsal horn and activating descending pain inhibitory pathways. This system underpins placebo analgesia and contributes to anxiety-pain links.