Dental pulpal testing is a clinical and diagnostic aid used in
dentistry
Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions o ...
to help establish the health of the
dental pulp
The pulp is the connective tissue, nerves, blood vessels, and odontoblasts that comprise the innermost layer of a tooth. The pulp's activity and signalling processes regulate its behaviour.
Anatomy
The pulp is the neurovascular bundle cent ...
within the pulp chamber and root canals of a tooth. Such investigations are important in aiding dentists in devising a treatment plan for the tooth being tested.
There are two major types of dental pulp tests. Vitality testing assesses the blood supply to the tooth, whilst sensitivity testing tests the sensory supply.
Clinical application
Dental pulp tests are valuable techniques used to establish the pulpal health status of a tooth in dentistry. The diagnostic information obtained from pulpal testing is then used alongside a patient's history, clinical and radiographic findings to determine a diagnosis and prognosis of the tooth.
Pulp tests are useful for the following procedures in dentistry:
* diagnosis of
endodontic
Endodontics (from the Greek roots ''endo-'' "inside" and ''odont-'' "tooth") is the dental specialty concerned with the study and treatment of the dental pulp.
Overview
Endodontics encompasses the study (practice) of the basic and clinical ...
pathology,
* localisation of tooth pain,
* differentiating between odontogenic and non-odontogenic pain,
* assessing pulpal status following
dental trauma
Dental trauma refers to trauma (injury) to the teeth and/or periodontium (gums, periodontal ligament, alveolar bone), and nearby soft tissues such as the lips, tongue, etc. The study of dental trauma is called dental traumatology.''Textbook and C ...
,
* establishment of pulpal health prior to
prosthodontic
Prosthodontics, also known as dental prosthetics or prosthetic dentistry, is the area of dentistry that focuses on dental prostheses. It is one of 12 dental specialties recognized by the American Dental Association (ADA), Royal College of Sur ...
treatment.
Pulpal tests may be conducted via stimulation of the sensory fibres within the pulp (sensitivity testing) or by assessing pulpal blood flow (vitality testing). All available techniques are reported to have limitations in terms of accuracy and reproducibility and therefore require careful interpretation in clinical practice.
Sensitivity testing
Sensitivity tests assess the sensory response of a tooth to an external stimulus, results which may be extrapolated to indirectly determine pulpal health status. Sensory stimuli, such as heat, cold or an electrical current, are applied to the tooth in question in order to stimulate the
nocireceptors within the pulp. The type of sensory fibres activated and therefore the response felt by the patient depends on the stimulus used. Sensibility testing is based on Brännström's
hydrodynamic theory, which postulates that the activation of nocireceptors is caused by fluid movement within the
dentinal tubules
Bone canaliculi are microscopic canals between the lacunae of ossified bone. The radiating processes of the osteocytes (called filopodia) project into these canals. These cytoplasmic processes are joined together by gap junctions. Osteocytes do ...
in response to thermal, electrical, mechanical or osmotic stimuli.
Responses to sensitivity testing
There are three primary outcomes of a pulp sensitivity test:
* A normal response — healthy pulps respond to sensitivity testing by eliciting a short, sharp pain which subsides when the stimulus is removed, indicating that the nerve fibres are present and responsive.
* A heightened or prolonged response — an exaggerated or lingering response to sensitivity testing indicates some degree of pulpal inflammation. If the pain is pronounced yet subsides once the stimulus has been removed, a diagnosis of reversible
pulpitis
Pulpitis is inflammation of dental pulp tissue. The pulp contains the blood vessels, the nerves, and connective tissue inside a tooth and provides the tooth’s blood and nutrients. Pulpitis is mainly caused by bacterial infection which itself is ...
may be probable. However, a lingering pain which continues despite the removal of the stimulus is indicative of irreversible pulpitis.
* No response — lack of response to sensitivity testing suggests that the nerve supply to the tooth has been diminished, as in the case of pulpal
necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
or in previously root treated canals.
Types of sensitivity tests
Thermal tests
Thermal testing, which involves the application of either hot or cold stimuli to the tooth, is the most common form of sensibility test.
A number of products are available for cold testing, each with varying melting points. Although household ice () is cheap and easy to obtain, it is not as accurate as colder products.
Dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily a ...
() can be used, however there have been concerns regarding the damaging effects of using something so cold in the oral cavity
despite evidence to suggest that dry ice has no negative impact on mucosal or tooth structure. Refrigerant sprays, such as
ethyl chloride
Chloroethane, commonly known as ethyl chloride, is a chemical compound with chemical formula CH3CH2Cl, once widely used in producing tetraethyllead, a gasoline additive. It is a colorless, flammable gas or refrigerated liquid with a faintly sweet ...
(),
1,1,1,2-tetrafluoroethane
1,1,1,2-Tetrafluoroethane (also known as norflurane (INN), R-134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermodynamic properties s ...
() or a propane/butane/isobutane gas mixture are further commonly used cold tests. Cold testing is thought to stimulate
Type Aδ fibres in the pulpal tissue, which elicit a short, sharp pain.
Heat tests include using heated instruments, such as a ball-ended probe or
gutta-percha
Gutta-percha is a tree of the genus ''Palaquium'' in the family Sapotaceae. The name also refers to the rigid, naturally biologically inert, resilient, electrically nonconductive, thermoplastic latex derived from the tree, particularly from ' ...
, a rubber commonly used in root canal procedures. Such tests are less commonly used as they are thought to be less accurate than cold tests, and may be more likely to cause damage to the teeth and surrounding mucosa.
Electric pulp testing
An electrical current can be applied to the tooth in order to generate an
action potential
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...
in the Type Aδ fibres within pulp, eliciting a neurological response. Such tests are conducted by applying a conducting medium (e.g. toothpaste) on a dried tooth and placing the probe tip of an electric pulp tester on the surface of the tooth closest to the pulp horn(s). The patient is then directed to hold the end of the conducting probe to complete the circuit and asked to let go of the probe when a ‘tingling’ sensation is felt.
The use of electric pulp testing has been questioned in patients with traditional cardiac pacemakers despite no evidence of interferences in humans, particularly with more modern devices.
Care must be taken if using an electric pulp test on a tooth adjacent to metallic restorations, as these can create electrical conduction and yield false negative results.
Anaesthesia testing
When pulp testing results are inconclusive and that patients cannot localise or specify the pain or symptoms, an anaesthetic would be helpful and be used. The most posterior tooth in the area where the pain resonates undergoes anaesthesia by either infiltration or intraligamentary injection until pain diminishes. If the pain is still present, the procedure is repeated on the mesial teeth, one by one until the pain diminishes and is gone. If one can still not determine the source of the pain, the procedure will be repeated on the opposite arch. In the case that the pain cannot be localised to either the maxillary or mandibular arch, an inferior alveolar nerve block would be used. If the pain stops, such would imply that it involves teeth of the mandibular arch.
Test cavity
The test cavity technique is only used as a last resort when results produced by all other methods above are inconclusive. High-speed burs are used without anaesthetic, drilling through enamel, or restorations to dentine. Throughout the drilling process, the patient is asked whether a painful sensation is felt, which would indicate pulpal vitality. In the event of a vital pulp, a painful response is provoked when dentin is contacted by the bur and the procedure will be stopped. A restoration would be then placed. Contrarily, when compared with vital pulp, pulp with partial necrosis will not be stimulated as extensively. In the case of partial necrosis, access to and into dentine would be needed, with the dentist progressively invading and drilling deeper into dentine, checking the sensory response—which is usually without sensory response because of the partial necrosis. Due to the invasiveness and possible anxiety that it may generate in patients, the test cavity technique is generally avoided. Also, there is little literature supporting its effectiveness, and it has been relatively anecdotal within clinical practice.
Limitations of sensitivity testing
All tests have some limitations and test results should be interpreted by an experienced dentist under the bidirectional consideration of both clinical symptoms and radiography. Sensitivity tests only indicate the presence or absence of the nerve supply to an individual tooth. Even though a prolonged response to aforementioned tests indicate pulpal inflammation, the degree of inflammation or innervation cannot be inferred from these tests.
False positive or false negative results are possible when performing a sensitivity testing. A false positive response occurs when a patient is respondent to sensitivity testing despite a lack of sensory tissue in the tooth that is being tested. Such responses may occur due to innervation of adjacent teeth due to inadequate isolation of the tooth being tested, or in anxious patients who perceive pain despite no sensory stimulus, or in multi-rooted teeth which still have residual pulpal tissue residing in canals. False negative results occurs when innervated teeth do not respond to sensibility testing. Such can occur in individuals who have recently traumatised teeth, teeth with incomplete root development, teeth with heavy restorations or teeth that have significantly reduced pulp size due to production of tertiary or sclerotic dentine.
Pulpal sensitivity testing may be regarded as inferior to vitality testing as they do not definitively prove that the tooth has a blood supply and is vital. Nonetheless, electric pulp testing and cold testing tests have been found to be accurate and reliable in the case of assessing pulpal health, especially when tests are used in combination.
In addition, cold testing is also more accurate than electric pulp in the case of running tests upon immature or traumatised teeth.
Vitality testing
Vitality tests assess the vascular supply of a tooth. Vascular supply is generally accepted as the earliest indicator of pulpal health. However, vitality tests have limitations and require strict adherence to correct application techniques.
The diagnostic methods to assess the vascular response of the pulp include:
Laser Doppler flowmetry
Laser Doppler flowmetry
Laser Doppler velocimetry, also known as laser Doppler anemometry, is the technique of using the Doppler shift in a laser beam to measure the velocity in transparent or semi-transparent fluid flows or the linear or vibratory motion of opaque, ref ...
is able to assess blood flow within the dental pulp directly. A laser beam directed onto the tooth follows the path of dentinal tubules to the pulp.
The viability of the vascular supply of the pulp is determined by the output signal generated by the backscattered reflected light from circulating blood cells. The reflected light is Doppler-shifted and has a different frequency to those reflected by the surrounding tissues which are static. An arbitrary unit of measurement, ‘perfusion unit’ (PU, is used to measure the concentration and velocity (flux) of blood cells.
The output of laser Doppler flowmetry may be influenced by the blood flow in surrounding tissues, and therefore the test tooth must be adequately isolated to avoid inaccuracies.
Pulse oximetry
Pulse oximetry
Pulse oximetry is a noninvasive method for monitoring a person's oxygen saturation. Peripheral oxygen saturation (SpO2) readings are typically within 2% accuracy (within 4% accuracy in 95% of cases) of the more accurate (and invasive) reading of ...
utilises the difference in red and infrared light absorption by oxygenated and deoxygenated red blood cells within blood circulation to determine the
oxygen saturation level (SaO2). Pulse oximetry, as well as laser Doppler flowmetry vitality tests may not truly reflect the real state of health of the dental pulp. This mainly happens in clinical scenarios when the dental pulp is diseased, yet a viable blood supply is maintained.
Dual wavelength spectrophotometry
The use of dual wavelength light establishes the contents within the pulp chamber.
[{{cite journal , last1=Nissan , first1=R. , last2=Trope , first2=M. , last3=Zhang , first3=C. D. , last4=Chance , first4=B. , title=Dual wavelength spectrophotometry as a diagnostic test of the pulp chamber contents , journal=Oral Surgery, Oral Medicine, and Oral Pathology , volume=74 , issue=4 , pages=508–514 , date=October 1992, pmid=1408029 , doi=10.1016/0030-4220(92)90304-9 ]
References
Dentistry
Endodontics