METHODS OF DETERMINING PULP VITALITY

what is vitality

vitality: having an intact blood supply

what are characteristics of an ‘ideal’ pulp tester

• must be effective on both anterior and posterior teeth (single/ multi-rooted)

• must be effective if the tooth is carious or if it has been restored

• must be effective when secondary dentine has been deposited

• must be effective in unusual circumstances (re-implanted, transplanted teeth)

what are current methods of vitality testing

what are conventional principals of conventional pulp testing (4)

• patient indicates a response

• tests the whole of the pain pathway, not just the pulp

• sensation uncomfortable at detection threshold, but not painful (pre-pain?)

• confirm by questioning that it is the pulp that is being stimulated, not the gingiva or PDL

what are difficulties in pulp testing

• the pulp is in an enclosed chamber, making access difficult

• the pulp chamber is practically opaque - except for dentinal tubules

• electrical resistance (impedance) varies widely

• pulp size diminishes due to secondary dentine

what is a false positive

false positive: when pulp testing indicates that the tooth is vital when it actually is not (better than false -ve)

what is a false negative

false negative: when pulp testing indicates that the tooth is non-vital when in reality it is vital

what sensation results from an electrical pulp tester

the sensation is uncomfortable but not painful at threshold

what are the criteria for using an EPT (3)

• avoid gingival margin and metal restorations (current spread)

• need good electrical contact

• teeth must be isolated

outline how good electrical contact can be achieved

good electrical contact

• toothpaste, not prophylactic paste (glycerine)

• electroconductive rubber

• indifferent electrode (monopolar stimulation) in hand or via handle and operator - NO RUBBER GLOVES

outline how tooth isolation can be achieved

• no saliva between teeth

• no dentures or other appliances

how do electric pulp testers work

• EPTs directly activate pulpal nerve fibres (bypass receptors)

• pulp testers achieve this by depolarising pulpal nerve fibres so that they generate action potentials

• for a nerve fibre to be depolarised, electrical current has to flow into it

• but most pulp testers generate voltage pulses, not current pulses

• therefore, the electrical resistance (impedance) of the tooth is important

what features would cause a tooth to have a high electrical resistance

• large and deep fillings

• old patient

what are the options for EPT

1. monopolar VS bipolar stimulation

2. constant current VS constant voltage

diagram showing monopolar VS bipolar stimulation

outline monopolar VS bipolar stimulation

• nerve fibres are excited where current density is highest

• is this in the dentinal tubules, at the pulp-dentine junction or at the apex?

• use cathodal stimulation for monopolar testing

outline constant current VS constant voltage

• most commercial pulp testers are of the constant voltage type

  • these often cause false positives because of stimulus spread to the gingival margin and PDL

• with constant current devices there are few false positives but more false negatives

sensation and perception graph

outline heat thermal testing

• hot gutta percha

• sticks to teeth when surface is dry - use vaseline

• difficult to control temperature and distribution

outline cold thermal testing

• ethyl chloride spray (evaporative cooling)

• apply with cotton wool pledget to single tooth

• avoid soft tissues

• Moody et al. (1989): 80% correct, 2 false +ve

  • better than electrical testing

recording pulpal blood flow

outline Laser-Doppler flow meters

what are problems with Laser-Doppler methods

Soo-Ampon et al. (2003)

summary slide