Navigating the digital frontier: transforming endodontic diagnosis through digitization. Part 1

Digital electric pulp testers

In 1867, Magitot advocated the use of an induction current to locate carious teeth, following which Marshall, in 1891, and Woodward in 1896, used electric current to demonstrate vital and non-vital pulps.² In the mid-1950s, bipolar instruments were used, while all testers used today are monopolar.³ Manually operated pulp testers had drawbacks, such as being bulky and cumbersome units to use.⁴ To overcome this problem, electric pulp testers have evolved over the years into electronic digital pulp testers. The output increased automatically with digital readouts and provided comfortable tooth stimulation when in contact (Figure 1).⁵ The main challenge is interference with cardiac pacemakers. However, with improved pacemakers having stainless or titanium electromagnetic shields, the interference with the functioning of the pacemaker is reduced.^6,7 The electronic devices used in such patients must be properly grounded and away from the pacemaker leads.⁸

To record the pulp vitality of teeth with full coverage crowns or fixed partial dentures, an explorer tip can be placed on the enamel and dentine below the crown margin, while the electric pulp tester probe touches the other side of the explorer to establish the pulpal status of the teeth below the prosthesis.⁹ Clinically, the electric pulp tester assesses the neural response by stimulating sensory nerve fibres (A and C fibres). An exaggerated response denotes pulpal inflammation, and a delay in response denotes chronic conditions of the pulp, when compared to contralateral healthy teeth. When there is no sensation until the maximum output is reached, the pulp is considered necrotic.¹⁰ However, true vitality is not assessed because the pulpal vascularity has not been evaluated. However, pulp sensibility can be evaluated only by pulp testers. In traumatized teeth, such as those in concussion and subluxation, injuries can lead to a false-negative response because neural regeneration is slower than vascular regeneration, or can be absent. The tooth may remain vital even if it does not respond to sensitivity tests.¹¹ A false-negative response can be observed in healthy vital teeth undergoing orthodontic treatment because the sensory fibres can be disturbed during movement.¹¹

Laser Doppler flowmetry (LDF)

Since the use of the laser Doppler method by Yeh and Cummins in 1964 to estimate the velocity of red blood cells in capillaries, this technology has been widely adopted for the measurement of blood flow, especially in soft tissues.¹² The Doppler effect is the basis of LDF, and uses the frequency shift that a wave undergoes when it is emitted from an object that is either moving away from, or toward, an observer—in this case, the objects are red blood cells (Figure 2).¹²

Challenges associated with LDF include documented instances of falsepositive responses, as reported by Sooampson et al¹³ and Gopikrishna et al.¹⁴ These responses could be attributed to signals obtained from nearby gingival tissues and periodontium or interference from a discoloured tooth via laser transmission.^15,16,17 Although it aids in monitoring age-related changes, the long recording time makes its use in dentistry impractical. Clinically, the LDF has been proven to be accurate in the early diagnosis of transient alterations in the pulpal blood flow of a traumatized immature teeth. Additionally, replanted teeth can indicate vascularization much earlier than traditional vitality tests.^16,17

LDF tests assess pulpal blood flow, rather than the patient's neural response, as in the case of pulp sensibility tests, thus, LDF is a reliable objective diagnostic marker for evaluating traumatized teeth because it assesses vascularity, especially in cases of luxation injuries.¹⁹

Pulse oximetry

This is a reliable, objective method of measuring percentage of oxygen saturation levels of the circulating arterial blood and is considered a standard monitoring parameter in critical care settings and during anaesthesia.²⁰ Invented by Dr Takuo Aoyagi in 1974, this technology assesses various functional states of blood flow, and the results of saturation are objective and independent of the patient's responses.²¹ Kosturkov et al used a pulse oximeter and electric pulp tester to check the response of hyperaemic pulp, and found that pulse oximetry could detect changes in pulp microcirculation, which is a valuable tool for early detection of pulpitis, necrosis and in case of traumatized teeth.²² Oxygenated haemoglobin absorbs different amounts of red and infrared light when compared to deoxygenated haemoglobin. This principle is adapted in pulse oximetry, which uses special probes that emit red and infrared light to transilluminate a target vascular area. In vital pulp with circulating blood, absorbance peaks can be measured by the oximeter photodetector, from which the pulse rate and oxygen saturation level (SaO₂) are calculated.^23,24 Gopikrishna et al used a special probe to evaluate the pulpal status of teeth and compared the thermal and electric pulp test results with those of a pulse oximeter in recently traumatized teeth. They found that the thermal and electrical test results showed no response during initial appointments owing to nerve paraesthesia.²¹ However, pulse oximetry confirmed the presence of pulpal blood circulation and oxygen saturation throughout the follow-up visits, which indicated that pulse oximetry was a true indicator of tooth vitality. However, currently, there are no pulse oximeters specifically designed for dentistry.²⁵

The pulp is surrounded by hard tissues (enamel and dentine), which can have different thicknesses and morphologies, and will act as an obstacle to light, which scatters through the enamel prisms and dental tubules. The presence of restorative materials could give a false-negative response, so careful observation of the tooth and its surroundings is essential to ensure correct readings.²⁶

Clinically, oxygen saturation values vary among teeth with different inflammatory conditions, which helps in differential endodontic diagnosis.²⁷ This approach helps in diagnosing non-localized pain. Oxygen saturation values are greatest in teeth that are developing and have a large pulp chamber,²² and as the tooth develops, the oxygen saturation decreases.²¹ Thermal tests simulate oxygen-dependent A-delta fibres, providing a reliable indication of oxygen depletion in the pulp, but thermal tests could yield a false-negative response in the case of pulp necrosis.²⁸ Hence, pulse oximetry is a reliable tool for diagnosis of pulpal status, hence research should be directed towards development of special pulse oximeters for dentistry.

Digital intra-oral radiography

The advent of the digital age in dental radiography was in 1987 when radio visiography (RVG) was introduced by Dr Francis Mouyen.²⁹ Digital images are displayed rapidly, as no film is needed. The two most common detectors used for capturing digital images are direct image acquisition using a charged coupled device (CCD) and semi-direct image acquisition using a photo-stimulable phosphor (PSP).³⁰ (Figures 3 and 4) Wallace et al compared PSP, CCD and Ektaspeed plus film (EPF) for the detection of peri-apical lesions and concluded that the EPF images, followed by PSP and CCD images, had better diagnostic accuracy.³¹ Sakhdari et al reported that there was no significant difference in the diagnostic accuracy of the CCD receptor or PSP for the early detection of external resorption.³² Drawbacks associated with intra-oral CCDs include their lack of flexibility and bulkiness. Additionally, placing the sensor can be time-consuming for the operator and uncomfortable for the patient, particularly due to the presence of the cable.³⁰ In PSP, the number of steps needed to visualize the image is greater than that in other methods, and these plates can be easily damaged because of manual handling and deterioration of image quality.³² Contrast resolution is an important parameter in clinical practice for determining the diagnostic accuracy of caries detection. This software allows image manipulation by applying specific filters to detect carious lesions. For periodontal diagnosis, the high resolution of intra-oral radiography helps visualize the bony supporting tissues, including intricate details, such as the periodontal ligament space, lamina dura and bony trabecularization.³³

Digital subtraction radiography (DSR)

DSR has been used in dentistry for more than 20 years, although BG Zeides des Plantes introduced it in the 1920s.³⁴ In this modality, the unchanged structure is displayed in neutral grey, while changed surfaces appear in darker or lighter shades of gray. Kapralos et al reported that DSR has better diagnostic accuracy for detecting vertical root fractures than does conventional digital radiography. Stannous fluoride, a contrast agent, enhances radiographic density in demineralized regions, aiding in precise caries diagnosis.³⁵ DSR, along with barium sulphate, exhibits good potential for measuring the depth of carious lesions.³⁶ A successful DSR can be achieved by reproducing a similar exposure geometry and identical contrast and density of serial radiographs. This technique is extremely sensitive to any physical noise occurring between radiographs.³⁷ In clinical practice, it helps detect changes in bone density by evaluating the healing of peri-apical lesions, cysts or tumours that may increase in size over time. It facilitates the evaluation of the progression, arrest, or regression of a carious lesion, as well as the detection of vertical root fractures, root resorption, and the depth of carious lesions.³⁷

Computed tomography (CT)

In 1972, Dr GN Hounsfield introduced computed transverse axial scanning, which led to the emergence of CT.³⁸ A series of 2D sectional X-ray scans are taken using the imaging technique, known as computed tomography, to create 3D views of an object. It has clear and better-quality images of hard and soft tissue with low radiation exposure. Small field of view (FOV) CT is less invasive, and beneficial for pre-operative assessment, and exposure is minimized depending on the characteristics of the pathological lesion.³⁹ A variant of CT, known as spiral CT (SCT), has the inherent advantage of recreating overlapping structures at random intervals and enhancing the resolution of small objects.³⁸ The main drawbacks of these methods include high cost, dispersion from metallic objects, limited resolution in comparison to conventional radiography, and inability to use CT or SCT equipment during dental operations.³⁹ Clinically, 3D images with slice thicknesses ranging from 0.2 to 5.0 mm enable the evaluation of root canal intricacies and curvatures.⁴⁰ Smaller slices produce sharper images with finer details, facilitating early detection and treatment of any peri-radicular lesions.⁴⁰ In clinical practice, these modalities have been used to evaluate root canals, obturations, metal posts, caries, and the proximity of the maxillary sinus.⁴¹ This approach also helps to determine the need for surgery and diagnose a vertical fracture.⁴²

Spiral computed tomography (SCT)

It has the inherent advantage of recreating overlapping structures at random intervals and enhances the resolution of small objects.⁴³ SCT captures raw projection data with a spiral-sampling locus in a brief amount of time by using simultaneous patient movement via the X-ray source and continuous source-detector assembly rotation. These data may be seen as standard transaxial pictures, such as multiplanar reconstructions, without requiring any additional scanning time. In clinical practice, it was used to evaluate root canals, obturations, metal posts, caries, and proximity between the maxillary sinus. It also helps to determine the need for surgery and diagnose a vertical fracture.⁴⁴ it has some disadvantages that is the costs, availability, and the higher ionizing radiation exposure this can be overcome by the use of low dose protocols.⁴⁵

Cone-beam computed tomography (CBCT)

CBCT is a valuable tool for diagnosis, treatment planning, and follow-up because it creates 3D images of the area to be studied by providing comprehensive views of the entire arch or single tooth along with its surrounding skeletal structures (Figure 5).⁴⁶ The radiation dosage must always be considered when choosing the modality of diagnosis, even though CBCT has limitations.

CBCT has several applications in endodontics because of its visual clarity, which helps clinicians in treatment planning. Surgeons benefit from presurgical assessment of the proximity of the maxillary sinus and cortical plate distance to the palatal root. CBCT helps in the meticulous assessment of the extent of the peri-apical lesion into the sinus CBCT can be used. Additionally, it helps in understanding the bone topography and early detection of apical periodontitis even before it is evident on conventional radiographs, which enables better treatment outcomes.⁴⁷ In an in vivo study, Patel et al diagnosed, assessed, and compared resorptive defects via CBCT, and a 3D view of the defect was used to assess the size and type of lesion.⁴⁷

CBCT can be used to plan virtual treatments. The acquired images can be conveyed directly via image-guided navigation or indirectly via surgical guidance.⁴⁸ Clinical CBCT may also help in the detection of apical periodontitis, the evaluation of root canal treatment outcomes, presurgical assessment, the visualization of traumatic injuries, the assessment of the labio-palatal extent of resorptive lesions, and the understanding of complexities in root canal anatomy, which may overall impact treatment planning.⁴⁹ A small FOV is used for assessing endodontic lesions, cracks, or fractures and assessing presurgical implant sites. A large FOV is indicated for assessing extended pathologies such as tumors or cysts, bone diseases, and maxillary or mandibular fractures.

CBCT may also be used to evaluate the outcome of previous endodontic treatment and to diagnose vertical root fractures, external root resorption, root perforation, and calcified canals and in cases of dento-alveolar injury.^50,51 The drawbacks of the presence of metallic restorations, such as amalgam, posts, crowns, and guttapercha, can compromise the intricate details of canal anatomy due to scatter and beam hardening, resulting in diagnostic inaccuracies, especially for perforation.⁵² However, there are artefact reduction programs that smooth the image to identify the true details, but these resultant images may have less accurate details. These software packages have been shown to be effective at compensating artefacts near metal objects compared to guttapercha.⁵³ The American Association of Endodontists/American Academy of Oral and Maxillofacial Radiology joint position statement was updated in 2015/2016, which gives 12 recommendations for the use of CBCT in endodontic practice.⁵⁴

Ultrasound

Ultrasound examines healthy and pathological disorders affecting the oral and maxillofacial area of soft tissue and bones using sound frequencies that are too high for humans to hear (20 kHz). It is effective at distinguishing cystic from non-cystic lesions.⁵⁵ It appears as a white reflecting surface if the alveolar bone is healthy and the root outlines of the teeth seem even whiter (hyperechoic). A hyporeflecting (dark) surface arises when a fluid-filled cavity in the bone is present. A thick cortical plate is present in the posterior area of the mouth, which stops ultrasonic waves from getting through, making their application difficult.⁵⁶ In a case report, an ultrasound with a colour power doppler was used to confirm the diagnosis of a peri-apical cyst. The ultrasound revealed a hyperechoic area with an irregular border and dirty shadowing within the lesion that was suggestive of a cavity filled with air. This sign is not typical of a cystic lesion, so an orthopantomogram was taken, which revealed it to be a maxillary sinus extending from the maxillary canine to the maxillary first molar.⁵⁷

Clinically, It helps in detecting fractures in the facial region and assesses the pathological nature of the lesions pre- and post-surgery. Furthermore, it is used to supplement radiographs in monitoring the extent and healing of peri-apical lesions and bone formation post treatment.^58,59 The disadvantages are the long examination time, and the need for specialized software to visualize tissues with less water. Additionally, restorations and implants have shown to cause blurring of the image as a result of artefacts.⁶⁰

Hughes Probeye camera

In 1974, Hughes introduced the Probeye camera, which can detect temperature variations as low as 0.1°C. The viability of the pulp is also determined by monitoring the flow of blood in the pulp. It is a thermal video system with a silicon close-up lens with a 0.023-inch resolvable spot size.⁶¹

In this technique, the teeth to be examined are protected by a rubber dam and cooled by a cold air stream. The teeth are cooled symmetrically to approximately 22°C. After that, the teeth are warmed back to their previous temperature. Non-vital teeth require 15 seconds to rewarm, but vital teeth take 5 seconds. Teeth with adequate blood supply warm more quickly.⁶¹

Allodynia measuring devices

Clinicians normally percuss the tooth during the examination to diagnose apical periodontitis, peri-apical abscess, cracked tooth or occlusal trauma. Percussion is a subjective test, and it is sometimes difficult for patients to differentiate sensation. A digital bite force transducer was used to determine the intensity of the occlusal force applied.⁶² When used clinically, patients develop pain when biting on a digital bite force transducer, which is an objective metric of mechanical allodynia.⁶²

Practice management software (PMS)

PMS provides administrative and clinical support for both the dentist and the support team, with patient scheduling, practice marketing, patient information and clinical data records, electronic bill generation, patient communication and appointment reminders. It helps in coordinating and tracking multi-specialty treatment referrals and consultations, and helps in efficient communication between dentists. Dentrix was the first PMS developed in 1989 and was designed to automate function within a dental practice.⁶³ Some software, such as DentiMax, is integrated with digital imaging software, such as PSP, intra-oral cameras, and digital panoramic X-rays.⁶⁴ CareStack software helps in storing data on a cloudbased system, which eases the transfer of information from one dental practice to another, and the recovery of data in case of hardware or software failures.⁶⁵

These systems enhance patient care by providing online patient registration, customizing detailed treatment options in which patients can choose and accept the treatment plan, and providing convenient communication between the patient and doctor. The billing collection can be improved by sending payment reminders and decreasing missed appointments.

Digital photography

Dental digital photography helps in communicating with the patient, dentist, and laboratory technician. Abnormalities that are not visible to the patient can be visualized and help rationalize the need for treatment. Photography helps to record clinical deviation accurately and can also be used for documentation in cases of lawsuits, education, and marketing.⁶⁶

Standardized photographs for each patient can be taken according to the guidelines by American Academy of Cosmetic Dentistry (AACD) which can aid in the diagnosis and analysis of oral health status.⁶⁷ It is also essential in analysing tooth alignment, occlusal discrepancies, and gingival inflammation; monitoring the progress of the treatment rendered; and comparing pre- and post-treatment outcomes to help in patient education about various treatment options available.⁶⁸ It prepares staff to understand the treatment workflow and keeps them updated about the latest techniques and scientific breakthroughs. Budding dentists can be educated by providing photos in textbooks, journals, and articles and in marketing and creating clinic portfolios.⁶⁶