These occurred as a sequence of inhibition,excitation,inhibition,excitation, although not all of these elements were seen on every occasion. The median thresholds of these four responses ranged from 0.5 to 1 N but overall there were no significant differences between them ( p > 0.05, Friedman's ANOVA). In other experiments, the same reflexes were recorded in response to application to the gingiva of 1 N ramp plateau stimuli (5 msec rise time) and 1 N tap stimuli applied to the adjacent tooth. The application of a local anaesthetic agent to the stimulated gingiva produced reductions in the mean magnitude of almost all the responses but these were significant ( p < 0.05; ANOVA) only for the long-latency inhibitions evoked by ramping the gingiva and the long-latency excitations evoked by either stimulus. It is concluded that mechanoreceptors in the gingiva can mediate long-latency inhibitory and excitatory jaw reflexes, and that these receptors may also contribute to long-latency reflexes evoked by tapping teeth. The scarcity of effects of gingival anaesthesia on the short latency reflexes may be due to such responses being mediated by receptors deeper in the periodontium.

Keywords: Bone-matrix proteins; Dietary; Gene expression; Mandibular

A longstanding problem in paediatric pain management has been the difficulty of objectively assessing pain. Assessment in infants before they can speak is particularly challenging and may have been responsible for perpetuating the myth that infants experience less pain than adults. As a result paediatric pain therapy has developed slowly compared with its adult counterpart. Several studies have shown that health professionals consistently underestimate the amount of pain experienced by young children. In response, many pain assessment scales have been developed and validated for use in children using both behavioural and self reporting assessments. The "OUCHER" scale is a simple approach where the child identifies his or her level of pain from pictorial representations of a child's face in various degrees of distress.¹

The move to earlier discharge after surgery has shifted some of the burden of pain assessment and treatment to parents Although most parents are concerned that their children should not suffer pain, they too may underestimate the amount of pain experienced by children. Little is known about the reliability of the cues parents use to assess pain, and scales such as the postoperative pain measure for parents (POPMP) are not widely used at home despite their potential to improve assessment.²

Although development of sophisticated analgesic techniques (continuous epidural analgesia, opioid infusions, patient controlled opioid analgesia) for inpatient use in specialised paediatric centres continues, simpler methods incorporating local anaesthetic techniques (wound infiltration, nerve blocks) in combination with simple analgesic drugs are used extensively for postoperative pain relief after common surgical procedures. Great scope exists for relieving pain for many children by optimising the use of simple analgesic regimens which can be used in the community by parents and primary healthcare professionals.

A recent advance has been recognition that the simplest and most useful of analgesics, paracetamol, has in the past been used at subtherapeutic doses. Previously recommended regimens of 10 mg/kg four times daily do not achieve therapeutic blood concentrations. Recent pharmacokinetic data suggest that an initial loading dose of up to 40 mg/kg rectally may be required.³ The loading dose should be followed by regular oral or rectal dosing within the recommended maximum daily dose. The maximum daily dose of paracetamol in children remains controversial. An upper limit of 90 mg/kg/day with a loading dose of 30 mg/kg is becoming more widely accepted,⁴ particularly for otherwise healthy children. Doses above 150 mg/kg/day cause severe liver toxicity and should not be used. ^{5 6} Possible causes of overdose include miscalculated doses given by parents, inadvertent coadministration of other medications containing paracetamol, and inadvertent administration of adult formulations to children.⁷

This limitation on the maximum dose of paracetamol has shifted attention to other simple analgesics which can be combined with paracetamol to improve pain relief. Paracetamol and codeine combinations have been shown to be better than paracetamol alone in treating pain after minor operations. Non-steroidal anti-inflammatory drugs have also received increased attention. Ketorolac, ibuprofen, and diclofenac have all been investigated in children, particularly after surgery, and all have been found to possess useful analgesic effects without the emetic and other side effects of strong opioid analgesics. The reported low incidence of side effects with these drugs has strengthened arguments in favour of their inclusion in paediatric analgesic regimens.

There is no simple solution to the problem of treating pain in young patients. Doing the simple things well will enhance therapeutic efficacy, particularly in the majority of children who require pain relief but are managed outside specialised paediatric inpatient units. Accurate assessment of pain, improved parent education, and multimodal analgesic regimens incorporating drug combinations given in safe and effective regimens all have the potential to improve the quality of care offered to our younger patients.

1. Beyer JE, Wells N. The assessment of pain in children. Pediatr Clin North Am 1989; 36: 837-854
2. Chambers CT, Reid GJ, McGrath PJ, Finley GA. Development and preliminary validation of a postoperative pain measure for parents. Pain 1996; 68: 307-317
3. Birmingham PK, Tobin MJ, Henthorn TK, Fisher MD, Berkelhamer MC, Smith FA, et al. Twenty-four hour pharmacokinetics of rectal paracetamol in children. An old drug with new recommendations. Anesthesiology 1997; 87: 244-252
4. Paediatric pharmacopoeia. , 12th ed. Melbourne: Royal Children's Hospital , 1997.
5. Heubi JE, Bien JP. Acetaminophen use in children: more is not better. J Pediatr 1997; 130: 175-177
6. Rivera-Penera T, Gugig R, Davis J, McDiarmid S, Vargas J, Rosenthal P, et al. Outcome of acetaminophen overdose in pediatric patients and factors contributing to hepatotoxicity. J Pediatr 1997; 130: 300-304
7. Heubi J, Barbacci MB, Zimmerman HJ. Therapeutic misadventures with acetaminophen: hepatotoxicity after multiple doses in children. J Pediatr 1998; 132: 22-27.