[ Periodontal ]
[ Prosthodontics ]
[ Orthodontics ]
[ Oral/Maxillofacial Surgery ]
The role of gingival mechanoreceptors in the reflex control of human jaw-closing muscles
Christos Loucaa,b, Steven D. Vidgeon,b, Samuel W. Caddenc,Roger W. A. Linden a. Accepted 19 August 1997.Archives of oral biology.
Abstract Electromyographic (EMG) experiments were undertaken to investigate the jaw reflexes evoked by activation of gingival receptors in 12 humans. EMG recordings were made from an active masseter muscle whilst ramp plateaumechanical stimuli were applied to the gingiva. Stimuli with a constant rate of rise (0.2 N/msec) and a variable pla-teau force (up to 2 N), evoked a complex set of short and long latency inhibitory and excitatory responses.
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.
The effect of altered functional forces on the expression of bone-matrix proteins in developing mouse mandibular condyle
Kenichi Sasaguri, Heping Jiang, Jinkun Chen * Department of Pediatric Dentistry, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284-7888, USA
Accepted 20 July 1997.Archives of oral biology.
Abstract Mechanical forces are known to have an effect on bone formation, maintenance and remodelling, and there is evidence that the development of the mandibular condyle in the rat is influenced by the consistency of the diet. Here a mouse model was used to investigate the relation between food, condylar development and the expression of bone sialoprotein (BSP), osteopontin (OPN), osteocalcin (OC) and type I collagen (COL I). Twenty-four 19-day-old male mice were randomly divided into three groups. Groups 1 and 2 were fed hard pellets and soft powdered food, re- spectively, for 2 weeks. Group 3 mice were fed soft food for 1 week followed by a week of hard pellets. Incisors of mice in groups 2 and 3 were trimmed twice a week to reduce occlusal forces. After killing the animals, mandibular condyles were collected for RNA extraction, in situ hybridization and immunohistochemical analyses. Histological sections showed that the condyles of mice in group 2 were underdeveloped, with a thinner layer of cartilage and fewer bone trabeculae. Northern hybridization of total RNA of the condyle from mice in this soft-food group also exhibited a significant decrease in the amounts of BSP, OPN, OC and COL I, representing 79%, 75%, 77% and 79% respectively, of that from mice fed hard food. In situ hybridization of these bone-matrix proteins demonstrated signals in bone-forming cells and BSP mRNA was also seen in the hypertrophic cartilage cells in the developing con- dyle. Immunohistochemical study demonstrated an obvious difference in the intensity of staining, especially for BSP.Results from group 3 were similar to those from group 1. The observed decrease in bone matrix-protein expression confrms that the consistency of the diet affects the development of the mouse mandibular condyle and that a soft diet diminishes the rate of bone formation.
Keywords: Bone-matrix proteins; Dietary; Gene expression; Mandibular
Pain relief in children
( 23 May )
EditorialsDoing the simple things better
Paediatric pain management has undergone significant change during the past decade, more so than many other areas of medical practice. Development has grown out of improved understanding of the physiological and psychological effects of unrelieved pain in children, greater insight into the benefits and risks of an aggressive approach to pain management, and greater knowledge of the clinical pharmacology of analgesic drugs in children. The trend towards specialised paediatric units staffed by professionals with training and experience in managing children's diseases has accelerated progress towards optimal pain management, whether for acute, chronic, or cancer pain. Unfortunately current practice still falls short of the ideal of safe and effective pain relief for all children.
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.
Searching for MB2|
Implants #18, #19
Molars with lesions
Lower incisor retreatment
Peri radicular healing
2 upper molars
2 Anterior teeth
File broken in tooth
2 year trauma
Squirt on mesials|
Palatal root exits
Color map 3