Vitality tests

PULP VITALITY TESTS Assessment of vitality using routine methods rely on the stimulation of Aδ nerve fibers and there is no direct indication of the blood flow. Three methods are used to stimulate the Aδ nerve fibers Thermal stimulation Electrical stimulation Direct dentin stimulation.

THERMAL STIMULATION Inexpensive The temperature used is 65.5ºC to elicit the response Can use Gutta percha – (base plate gutta percha) Cast metal crown restorations are too thick to allow heated GP to elicit response In such cases a rubber wheel is used to elicit the response.

COLD TEST Various materials used for cold test are Cones of ice -20ºC Ethyl chloride spray - 40ºC Carbon- di- oxide snow -70ºC Application of cold for 4 seconds lowers the temperature to between 26 and 30ºC eliciting pain. Within the pulp temperature is lowered by 0.2ºC.

Heat causes vasodilatation and increase in intra pulpal pressure (releases gaseous product of proteolysis) (VAN HASSEL). In an intact pulp specific pulpal temperature must be reached before there is pain from heat. Therefore, application of heat to normal teeth gives delayed response. In a tooth with inflamed pulp, increased intra pulpal pressure already exists. Therefore immediate painful response to gradual/sudden increase in heat.

Cold decreases intrapulpal pressure in normal intact pulp and there is no pain. The pain from cold is due to hydrodynamic mechanism. Contraction of fluid causes outward flow of fluid in dentinal tubules, deforms Aδ nerve and an action potential is generated. In advanced acute pulpitis, no Aδ receptors are present. Cold produces contraction and lowers the intrapulpal pressure to a sub threshold level and relieves pain due to still viable C fibers. Pain returns within 30 – 60 seconds as intra pulpal pressure returns to its former suprathreshold level.

ELECTRIC PULP TEST Electrolyte applied on the teeth to transmit current Jelly used for ECG is ideal When electrolyte contacts the tooth an electric charge is applied by pressing rheostat button. A small charge is released initially and increased until response is felt. Select control teeth – contra lateral teeth and adjacent teeth.

INTERPRETATION : If the current required to gain a response from a test tooth is same as that needed to excite the control – the pulp of the test tooth is considered normal. If less current is required for a response – Hyperactive If more current is required– delayed response/ high pain threshold Lack of response – Pulpal necrosis Two readings are recorded and the average value is taken. “Using EPT on any tooth more than 4 times can give wrong reading due to additive action.”

Only Aδ fibers are activated by electric tests Aδ fibers produce initial momentary sharp response to electric stimuli because of its peripheral location, low threshold & greater conduction velocity. Continuous constant pain is produced by the smaller C fiber stimulation as it is associated with tissue damage and inflammatory process.

DISADVANTAGES : DISADVANTAGES Battery plug in Electrical deficiencies Output current variations Battery run down and not delivering full current all these give variable results with EPT Molars give readings not indicative of the true pulpal condition.

LIMITATIONS : LIMITATIONS Tests are not reliable on immature teeth of young patients as these teeth contain fewer Aδ fibers than mature teeth and myelinated nerves do not reach their maximal depth of penetration into the pulp until the apex completes its development.

When comparing teeth in question with the control teeth, pulps of the control teeth may not be normal. Teeth with acute alveolar abscess may respond positively to EPT because the gaseous and liquefied elements within the pulp can transmit electric charges to periapical tissues. In traumatic injuries, in the cervical areas there will be temporary paraesthesia of the nerves. If pulp vitality remains, the pulp will respond within normal limits after 30 to 60 days.