2.1 Introduction

It is very important to form diagnosis, if we want to manage a problem accurately. Over the years, there has been tremendous advancement that help to make the diagnosis and then design our treatment plan. Now is the age of virtual reality. The “godfather” of digital dentistry is the French Professor Francois Duret, who invented dental CAD CAM in 1973. The new image reconstruction techniques provide a faster and more accurate workflow.

Conventional techniques in dentistry have worked successfully for decades and is still being used effectively. However, to keep with the changing technologies and for a faster, more accurate, and more efficient workflow, there is a large potential in digital dentistry. There are many areas of digital dentistry available, and many more are being researched. Some (but not limited to) of the commonly used techniques are as follows:

Currently, digital dentistry is an umbrella topic that covers almost all the areas of dental specialties ranging from diagnosis, record keeping, surgical aspects, and computer-aided design or computer-aided manufacturing (CAD/CAM), and 3D printers. While each aspect is important in its own way, it is their incorporation as a whole that makes dental care effective and successful. Most of the topics mentioned above will be covered separately in great detail as individual chapters in this book. This chapter will only deal in detail about topics that are not covered elsewhere in the book. Others will be introduced and touched upon briefly.

2.2 Caries Detection Methods

Some of the caries detection units have lasers that cause fluorescence of tooth, while others use transillumination to see through enamel. While some of these technologies are standalone units, a few may also be integrated into intraoral cameras. Some examples include Microlux Dental Caries Detection System, Cam X Spectra Caries Detection System, DOE Transilluminator, LUM G2, Ortek-ECD, and The Canary System. A few are discussed here although the evidence supporting new systems is currently limited.

2.2.1 Intraoral Television Camera (IOTV)

The probe or wand of the camera projects a magnified digital image of teeth on the screen of computer. This helps in visualizing the oral cavity better and at the same time the diagnosis can be explained to the patient (Fig. 2.1a, b).

2.2.2 Visible Light

These techniques are based upon the phenomenon of light scattering and utilize different light sources.

2.2.3 Fiber-Optic Transillumination (FOTI)

First designed by Friedman and Marcus in 1970, this technique is based on the principle that carious enamel has a lower index of light transmission than the enamel that is intact [1]. Fibre-optic transillumination (FOTI) uses a light emitted from a handheld device which illuminates the tooth. Any changes in the mineralization of the tooth will appear as shadows in the tooth. FOTI technique is indicated in detecting occlusal and proximal caries. Enamel and optical disruption can occur by penetrating photons of light through densely packed hydroxyapatite crystals.

2.2.4 Digital Imaging Fiber-Optic Transillumination

Digital imaging fiber-optic transillumination (DIFOTI) was developed in an attempt to reduce the disadvantages of FOTI, by combining FOTI with a digital CCD camera. It consists of two handpieces: one for occlusal surface and one for smooth surface and interproximal areas. Its main indications are detection of incipient and frank caries in all tooth surfaces and detecting cracks, and secondary caries around restorations [2–4]. An example of this system is DIAGNOcam.

Other examples of LED-based caries detection system for detecting and quantifying caries include Midwest Caries ID™ (MID) and Vista Proof-VP. In MID, a specific fiber-optic signature captures the resulting reflection and refraction of the light in the tooth. This data gets converted to electrical signals which pass through the software algorithm already installed in the computer and helps to detect the presence of any carious activity [1].

2.2.5 Electrical Caries Monitor (ECM)

Electrical impedance measurement is a measure of degree at which an electric circuit resists electric current flow when a voltage is applied across two electrodes. Caries tissue has a lower impedance than sound tooth. It is also known as electronic caries monitor [5]. ECM measures the electrical resistance of the area of tooth under controlled drying. This method helps in differentiating between sound and carious dental tissues, through electrical conductivity [2].

CarieScan is a device that uses alternating current impedance spectroscopy. Insensitive level of electric current is passed through the tooth to check for the location and presence of any carious lesion. CarieScan provides a qualitative value of diseased tooth as it is not affected by optical factors like discoloration or staining [1].

2.3 Lasers

2.3.1 Quantitative Light-Induced Fluorescence (QLF)

Fluorescence (green and red) is a phenomenon by which an object is excited by particular wavelength of light, and the fluorescent (reflected) light is of a larger wavelength [6]. QLF is based on the principle of fluorescence. It provides a fluorescent image of a tooth surface within yellow-green spectrum of visible light that quantifies mineral loss and size of the lesion. The QLF devices shown in Figs. 2.2 and 2.3 use blue light to illuminate the tooth. This causes the teeth to fluoresce in green (so-called autofluorescence). The resulting QLF images show a higher contrast between sound and demineralized tooth tissue.

It is suitable for detecting early enamel lesions (in clinically inaccessible areas) particularly progression or regression of white spots of smooth surface lesions (Figs. 2.4 and 2.5).

2.3.2 DIAGNOdent Laser System

DIAGNOdent laser was first introduced in 1998 by Hibst and Gal and is a variant of QLF system. It uses infrared laser fluorescence of 655 nm for the detection of occlusal and smooth surface caries by using a simple laser diode to compare the reflection wavelength against a well-known healthy baseline to uncover decay. Unlike the QLF system, the DD does not produce an image of the tooth; instead it displays a numerical value on two LED displays. It has a pen handpiece that is suitable for diagnosis of dental caries without radiographs and any mechanical damage to the tissues. This system uses a low-power laser directed onto the tooth. Healthy tooth structure displays little or no fluorescence resulting in very low-scale readings on the display whereas carious teeth structure displays fluorescence, giving elevated scale readings on the display. Use of laser fluorescence device provides results that are more consistent with tactile examination comparing with other methods.

The device’s inability to determine the depth of the carious lesions has been mentioned [7]. Some recent studies claim that fluorescence-based intraoral devices do not contribute to a better detection of early carious lesions [8, 9]. Nevertheless, they can be used in conjunction with the International Caries Detection and Assessment System (ICDAS), a relatively new technique for the measurement of dental caries [10]. DIAGNOdent pen is a latest advancement to the DIAGNOdent technology and is used to detect pit and fissure and smooth surface caries accurately.

2.3.3 Ultrasonography

Ultrasound caries detection method (UCD) was first suggested over 30 years ago; however, it has been used more in the last decade [11] for detecting early carious lesions on smooth surfaces. The principle is that images of tissues can be collected by reflected sound waves. Demineralization of natural enamel is assessed by ultrasound pulse-echo technique. It is observed that there is a definite correlation between the mineral content of the body of the lesion and the relative echo amplitude changes [12].

Studies have shown that UCD could differentiate between cavitated and non-cavitated proximal lesions [13]. It has also been shown that UCD reduces patient exposure to radiation and has higher sensitivity and lower specificity than the radiographs in diagnosis of interproximal caries [14]. Research has also shown UCD can be used successfully in the determination of thickness changes in enamel [15].

2.4 Diagnosis in Endodontics: Pulp Vitality Tests

2.4.1 Laser Doppler Flowmetry (LDF)

The technique uses a light beam from a helium-neon (He-Ne) laser emitting at 632.8 nm. Other wavelengths of semiconductor laser have also been used: 780 and 780–820 nm (Fig. 2.6) [16]. Laser light is transmitted to the dental pulp by means of a fiber-optic probe placed against the tooth surface. Backscattered reflected light has a different frequency with respect to the static surrounding tissues and is considered as the output signal. Signal is recorded as the flux (velocity and concentration) in an arbitrary term, perfusion units (PU), for example, 2.5 V of blood flow is equivalent to 250 PU (Fig. 2.7a, b). It should be emphasized that the optical properties of a tooth change when the pulp becomes necrotic, and this can produce changes in the LDF signal that are not due to differences in blood flow [17].

Various studies have been performed to investigate the preferred testing parameters for LDF. Gazelius et al. stated that though 750 nm laser penetrated deeper, they were associated with signal contamination of non-pulp origin from surrounding tissues [18]. Later studies showed that the problem of signal contamination was associated with the extensive scattering of light with longer wavelength lasers. The laser beam produced should be low-power beam ranging from 1 to 2 Mw [19].

Calibration of probes is another important criteria to get accurate readings [20]. The probe, when in contact with tooth, contains both receiving and sending optic fibers, with two detectors placed in a triangular arrangement at one end of probe, while the other being the source (Fig. 2.8). It was noted that with larger optical fiber separation distance on the probes, higher was the signal output (as larger area was covered), which increases the chances of blood flow signal contamination from non-plural sources [21]. Hence, 0.5 or 0.025 mm separation distances are preferred [22].

The advantages of LDF are many including being noninvasive in nature, painless, accurate, and reproducible. It is most useful in pediatric and medically compromised patients where their responses may not be relied upon. There are few drawbacks as well, such as high economic cost and the sensor should be completely stable to be able to record accurate reading. Discolored tooth crown may give a false positive response due to blood pigments that may interfere with laser light transmission. This method makes it difficult to measure vitality in teeth with large restorations, such as metal inlay, crown or orthodontic brackets, and requires individual stabilizing devices for the probe (such as splint or silicone). Any stimulation or effect of supporting tissues, such as gingival or oral, may interfere with accurate recordings [23].

2.4.2 Pulse Oximetry

Compared to laser Doppler flowmeters, pulse oximeters are relatively inexpensive and commonly used in general anesthetic procedures. The term oximetry means determining the percentage of oxygen saturation of the circulating arterial blood [23]. It helps in differentiating between nonvital and vital tooth. Since oxygenated and deoxygenated hemoglobin have different colors, they absorb different amounts of red and infrared light. Pulse oximeter, with the help of probes, emit red and infrared light to transilluminate the concerned vascular area. This allows the photodetectors to identify the absorbance peak and hence calculate the pulse rate and oxygen saturation levels [2].

2.4.3 Other Noninvasive Experimental Tests for Pulp Vitality