Overview

Did you know our teeth can feel heat, cold, and touch? Yes, the dental pulp inside our teeth does that. It means that particular teeth are vital.

The dental pulp is a vital part of the tooth. It plays a key role in tooth health, helps the tooth grow, and allows it to sense things like temperature and pressure. That’s why assessing tooth vitality is an important diagnostic task for dentists. Only a vital tooth can respond to external stimuli like temperature or pressure, which is essential for the tooth to function normally. Pulp vitality test gives a clear idea about the status of the tooth, whether the tooth is alive &  functioning normally, a crucial diagnostic tool for assessing accurate treatment planning.² The way the dental pulp responds can vary based on factors like the patient’s age, general health, tooth anatomy, and pain tolerance. Since we can't directly see or examine the pulp, dentists often use tests that involve heat, cold, or a mild electric current to check its health. In addition to these traditional methods, several newer diagnostic techniques are also available.

Patient history & clinical methods 

Patients with pulp problems often experience symptoms such as pain or sensitivity to hot and cold. Dentists may also observe signs like tooth discolouration, fractures, or the presence of small bumps (abscesses) near the affected tooth. Discomfort during percussion – tapping the tooth – can further indicate an issue. When external stimuli like heat or cold are applied, a normal, short-lasting response typically suggests reversible pulpitis, where the pulp is inflamed but still healthy. However, if the pain continues even after the stimulus is removed, it may indicate irreversible pulpitis, where the damage is more advanced. In cases where there is no response at all, it usually points to pulpal necrosis, meaning the pulp tissue is dead. Methods for how dentists test for pulp problems are discussed below:

Thermal test

The thermal test is performed in two steps: cold testing and heat testing. During the cold test, a dentist will apply cold products to see how the tooth responds. Ice and ethyl chloride are commonly used; proper assistance & isolation using rubber dams are required to avoid the thermal stimulation of multiple teeth. Recently, refrigerant sprays like DDM have been used. The application of refrigerant spray requires soaking a cotton pellet in the spray. Larger-sized cotton pellets will have a larger surface area, allowing more thermal conduction to pass between the cotton pellet and the tooth being tested.³

Another type of cold test involves applying carbon dioxide snow (dry ice) to the susceptible tooth. Dry ice is prepared from a pressurised carbon dioxide liquid cylinder. It comes out as ice at high atmospheric pressure, is collected in a pencil stick and applied to a tooth at a time using an applicator.³

During the heat test, heat products are applied to teeth to check for reaction or pain. Heated gutta-percha is applied to the tooth being tested with a lubricant so it can be easily removed after testing. Heat ball-ended metallic instruments, such as the burnisher, are used. They are placed near the teeth, but don't touch the tooth directly. Battery-powered controlled heating instruments, such as heat probes, and bathing the tooth in hot water while it’s isolated using a rubber dam, are also used.³

Electric pulp test ( EPT)

An electric current is applied to the teeth to produce a small electrical signal (called an action potential), eliciting a neurological response. A conducting medium, like toothpaste, is applied to a dried tooth, and the probe tip of the electric pulp tester is placed on the surface of the tooth closest to the pulp horn. The patient is asked to hold the end of the conducting probe to complete the circuit and asked to let go with the probe if a tingling sensation is felt.⁴

Cavity test

A cavity test is considered a last resort for checking pulp health as it is an invasive method that carries the risk of damage to an otherwise healthy tooth. The technique involves drilling into the dentin using a slow or high-speed burr without local anaesthesia. If the pulp tissue is healthy, the patient will experience pain once the dentin has been drilled. However, if the pulp tissue is dead, no sensation will be felt.

Dental X-ray

A dental X-ray can be used to detect:

• Cavities in their early stages 
• Small decay between the teeth
• Decay beneath existing fillings
• Bone loss in your jaws
• Areas of infection
• Cysts & tumours

Recent advances in pulp vitality testing

Laser Doppler flowmetry is a noninvasive, painless, electro-optic technique that allows semi-quantitative recordings of the pulpal blood flow. It measures blood flow even in the tiny blood vessels of the microvasculature. The source of light used to measure pulpal blood flow is a helium-neon laser, an infrared laser diode.⁶

Pulse oximetry uses an oxygen saturation monitoring device (pulse oximeter) to measure oxygen levels in circulating arterial blood. Pulse oximeters have two light-emitting diodes (LEDs), one that uses red light (visible) and one that uses infrared light (invisible) to detect oxygenated and deoxygenated blood. They’re commonly used in medicine on various body parts; however, in dentistry, pulse oximeters need to be adapted to the size, shape, and anatomical contour of the tooth. Once positioned, pulse oximeters determine pulp health by measuring oxygen saturation in the pulp’s circulating blood, where higher levels generally equal healthy pulp.^7,9

Dual wavelength spectrophotometry (DWS) is another minimally invasive method that can check pulp health using blood oxygen levels. Unlike pulse oximetry, DWS does not require circulating blood to detect pulp oxygen saturation, which can be harder to detect due to the tooth’s hard exterior (enamel and dentine). DWS measures oxygenation changes in the pulp’s capillaries based on the presence of haemoglobin.⁹

Transmitted light photoplethysmography is an optical measurement technique used to detect the blood volume changes in the microvascular bed of tissue. This requires a light source to illuminate the tissue and a photo detector.⁹ 

Summary

The assessment of pulp vitality is crucial for determining the health of the dental pulp and treatment planning. There are several diagnostic methods, each with a varying degree of sensitivity and specificity. Standard techniques include thermal testing and electric pulp testing. Advanced methods such as laser Doppler flowmetry and pulse oximetry offer more precise measurements of blood flow. Along with testing, patient history and clinical signs can help the clinician to assess pulp vitality and determine the best treatment and outcomes for the patient.