Radiological examinations in Odontostomatology
- Introduction
Radiological examinations represent a part of the complementary examinations. These are the extension of a precise and meticulous clinical examination and must be justified. They imply a good knowledge of their principles and their indications.
- X- ray radiography :
- Unprepared shots:
2.1.1 Intraoral images:
Intraoral radiography is a method of exploring the dental system which aims to highlight the different dental and maxillary elements, avoiding the superposition of other dental or bony planes, and avoiding as much as possible the deformations of these elements.
- Oblique projection method:
These are the retro-alveolar incidence and the dysocclusal incidences.
The retroalveolar
It gives a real projection of the tooth, its interest lies in the details it offers. It provides the practitioner with invaluable information on a daily basis on the anatomy of the roots, canals and apices as well as on the alveolar bone, the lamina dura and the desmodontal space. It is an indispensable tool for the diagnosis, control and monitoring of root canal treatment.
There are two techniques:
*The bisector technique : The film is placed in contact with the tooth, and the ray is sent perpendicularly to the bisector of the angle formed by the main axis of the tooth and the film.
*The parallel plane technique: This consists of placing the undeformed film parallel to the longitudinal axis of the teeth and sending the central ray perpendicular to the subject and the film.
The latter is currently replaced by radiovisiography (RVG). The film is replaced by a digital sensor. It eliminates the development step and saves a lot of time.
The occlusal biter
The horizontal reference plane is the occlusal plane, the film is held by biting between the arches, the anatomical structures examined are interposed between the radiation source and the film.
The latter is indicated in:
-Study of dental anomalies (Location of an included or ectopic tooth).
– Palatal or vestibular inclusion of canines
-Study of velopalatine clefts
-State of fractures in the horizontal plane.
-Submaxillary salivary stones.
b) Orthogonal projection method:
This method gives a faithful image, in their shapes and dimensions, of the structures examined.
“BITE WINGS” film
The rays are orthogonal thanks to a paper tab glued to the film and perpendicular to it, this tab will be maintained in the occlusal plane by biting. The film will be located behind the crowns.
This method makes it possible to highlight interproximal lesions, lesions of the neck, and it gives valuable information on the state of the periodontal structures.
Its disadvantage lies in the sacrifice of the periapical region in favor of better precision of the pericoronal region.
2.1.2 Extraoral images:
A) Front incidences
1) Incidence of BLONDEAU “NMP”
This is a postero-anterior incidence, the main ray makes an angle of -50° with the standard reference plane (orbitomeatal plane),
2) Face to face incidence “NFP”:
*High face: This is a posteroanterior incidence, the main ray makes an angle of -25° with the orbitomeatal plane. It allows to highlight:
-The frontal sinuses.
-Ethmoidal cells.
-The nasal cavities (septum, middle and inferior turbinate).
-Roof and side walls of the orbit.
– Front part of the vault.
-Lower edge of the maxillary sinuses.
-Symphysis and ascending branch of the mandible
*Low face: This is a postero-anterior incidence, the main ray passes through the mucosa and comes out in the middle of the nasal bridge. It makes an angle of +25° with the orbitomeatal plane. It allows to visualize:
-The ascending branch of the mandible.
-Horizontal branch (posterior region).
-Posterior walls of the maxillary sinuses.
-Spheno-maxillary cleft.
-The sphenoid sinus.
3) HIRTZ incidence: “axial incidence”
The main ray follows the path of the retro-symphyseal region. It makes an angle of +195° with the orbitomeatal plane. The purpose of this incidence is the study of the base of the skull:
-Forward and outward: Orbit and maxillary sinus are superimposed.
-In the center: the nasal cavities (septum, vomer, turbinate) come out superimposed on the ethmoidal cells.
-Behind: The sphenoid sinus is projected into the lumen of the cavum.
– Laterally: the oval holes (inferior maxillary nerve), and the small round holes (middle meningeal artery) are clearly visible.
4) Incidence of the nasal pyramid: Allows you to visualize
-The nasal structures.
-Rising process of the upper jaw.
-The proper bones of the nose.
-Nasal spine of the frontal and upper jaw.
b) Profile incidence
1) Incidence of previous profile, or strict profile:
-The frontal sinuses.
-The maxillary sinuses.
-The bony palate.
-The cavum.
-The mandible
2) Paralleled maxillary incidence: the head is inclined towards the side to be examined, allowing a satisfactory study of a hemi-mandible (horizontal branch up to the condyle).
3) SCHULLER incidence (temporo-tympanic): this unilateral incidence allows the study of the ATM, and possibly the mandible and condyles during opening and closing of the mouth.
4) Unilateral incidence of the malar: Allows visualization of the malar by spreading its body and its three processes
5) TLR profile: This incidence is used in ODF and to a lesser extent in maxillofacial surgery. It is used for cephalometric analyses allowing an analysis that is both diagnostic and prognostic.
E) Panoramic or Orthopantomography: Large tomographic section allowing a global visualization owes its name to the fact that it explores:
– The whole dental arches (tooth and periodontium),
-The entire mandible, the ATMs and, incidentally, the zygomatic arches.
Radiological examinations in Odontostomatology
INDICATIONS OF THE MAIN BASIC INCIDENCES ACCORDING TO THE STRUCTURES TO BE EXPLORED:
-Maxillary sinuses: BLONDEAU, HIRTZ, profile view
-Frontal sinuses: High face, hyper axial HIRTZ.
-Sphenoid sinus: BLONDEAU, HIRTZ, lateral incidence
-Ethmoidal cells: Upper face, HIRTZ.
-Nasal cavities: High face, HIRTZ, BLONDEAU.
-The mandible: Panoramic, lower face, maxilla, SCHULLER
2. CLICHES WITH PREPARATION:
2.1. Sialography:
This is an X-ray of the salivary glands previously opacified by ascending ductal routes using a radiopaque liquid called iodine-based contrast. The principle consists of opacifying and visualizing the salivary glands, the product is injected using a fine needle into the saliva excretion duct. It lines its walls which will be visible on the images thanks to its radiopaque properties.
The first shot should be taken within one minute of opacification.
The second shot is taken 1 hour later (parotid) and 24 hours later (submaxillary).
X-ray:
*for the parotid: Lower face, HIRTZ, profile, panoramic.
*For the submaxilla: decapitated maxilla, profile, low face, BLONDEAU, panoramic, occlusal bite.
The sialogram:
The X-ray images must be subject to careful analysis, which will focus on the appearance of the duct and the parenchyma. The sialogram of a normal gland includes two types of elementary images, parenchyma and duct (the diameter of the Stenon duct is 2 mm, the Wharton duct is 3 mm).
The evaluation sialogram: a normal parotid empties almost completely in 1 hour and the submaxilla in 24 hours.
2.2. Scintigraphy:
This is a precise technique that allows the functional value of all or part of the salivary system to be assessed. The principle consists of injecting the patient with a radioactive product, which varies according to the organ examined (Thallium, Tchnetium, Iodine). This substance presents no danger to the patient, because it is administered in very small quantities, which will attach to the organ to be studied.
Once the injection has been carried out, it is often necessary to wait several hours before the practitioner turns on the device, which analyses the radiation emitted which depends on the more or less good vascularisation of the organ studied.
Directions:
-Lithiasis of the salivary glands: prolonged excretion.
-Parotitis and submaxillitis: Hyperfixation of Technetium 99 in the acute phase.
2. 3. Variants: “Bone scintigraphy”
Bone scintigraphy is a simple, non-invasive, reproducible method providing information on the metabolic viability of bone. The uptake of the radiotracer depends on the preservation of a satisfactory nutritional vascular supply and a network of osteocytes and osteoblasts.
Indication:
-Search for bone metastasis
-Search for osteoarthritis foci
2.4. Angiography:
Allows the diagnosis to be confirmed, in order to begin treatment.
Determine the relationships of a vascular tumor with neighboring vessels.
2.5. Arteriography:
This is the X-ray of the arteries and branches, after direct injection into the vessels of a product opaque to X-rays, it allows:
– A hemodynamic assessment of the lesion (parenchymography).
-To represent the blood vessels at the level of the face (external carotid and its branches)
– Detect vascular tumors.
2.6. Arthrography:
It is the opacification of the ATM by a contrast product, to allow the study of structures not opaque to radiography, it finds its indication in the study of menisco-condylar pathologies
3. SPECIFIC EXPLORATION:
3.1. Tomography:
This technique uses a multidimensional scanning device which allows very fine sections of 1 to 0.5 cm to be made in the three directions of space. It is useful for identifying in depth, at different levels, the extent of bone destruction or a tumor.
3.2. Computed tomography “scanography” :
It is a radiological examination that consists of exploring the inside of the body by combining an X-ray source, a detector, an amplifier and a computer. The device used is called a “scanner”. The source emits X-rays and rotates around the organ to be studied. Scanography is capable of giving a spatial image of the organ studied, it is indicated in:
-Traumatology.
-Tumor and inflammatory pathology.
-Cranial malformation.
Radiological examinations in Odontostomatology
3.3. Cone beam volumetric tomography :
This is a new digital radiography technique that appeared towards the end of the 90s. As its name suggests, it uses a conical-shaped irradiation beam . This device has the advantage of being more precise than the dental panoramic by offering a resolution similar to, or even superior to, that of the scanner, with the added possibility of a 3D reconstruction. But it has its limits; it does not allow the study of soft tissues or the measurement of density.
Indication
-Pre-implant radiological study,
-Examination of the temporomandibular joints,
-Exploration of the maxillary sinuses,
-Assessment of third molars, included and ectopic teeth, tumor pathology of the mandible and maxilla and finally the orthodontic radiological assessment.
3.4. Magnetic resonance imaging “MRI”:
It is part of the complementary medical imaging examinations, just like X-rays , ultrasounds or scanners. The images are produced using a magnetic field produced by a magnet, through which radio waves pass, which will make hydrogen atoms in the body “resonate”.
It is a computer system which, based on the information sent back to the body, will create a digital image which will be printed on film.
Indication in maxillofacial pathology and stomatology: Allows two types of complementary approaches:
– The first with an anatomical morphological aim, therefore allows the study of the anatomy of the facial mass: Bones, muscles, fat, vessels, glandular parenchyma, teeth
– The second is aimed at diagnosis, see post-therapeutic, by determining: craniofacial malformations, inflammatory tumor processes, detection of cervicofacial adenopathy, sinus inflammation.
3.5. Ultrasound:
Ultrasound is based on the idea of sonar (Sound navigation and ranging). A probe emits ultrasonic pulses that propagate through the body, reflecting on obstacles encountered, forming “echoes” that constitute information captured in return by the probe, transformed into a video signal displayed on a monitor. The echoes at the origin of the ultrasound image result from the acoustic properties of matter.
Indications:
-They are dominated in stomatology by the exploration of the salivary glands and their excretory ducts, the cervical soft parts with in particular the lymphatic chains and the elements of the tongue (mobile, base and floor)
– Assessment of the extension of malignant tumor processes (cervical adenopathy).
– Diagnosis of sinus conditions.
Radiological examinations in Odontostomatology
Conclusion :
X-rays have an undeniable place in the treatment plan. However, they remain a complementary examination that will never replace the clinical sense of the practitioner. It will be up to the latter to master the basics without abusing them.
Radiological examinations in Odontostomatology
Bibliography
- Ruhin-Poncet B, Martin-Duverneuil N. Behavior to adopt in front of a radiolucent image of the jaws. Actual Odonto-Stomatol. 1 Nov 2014;(270):412.
- Barnes L. Surgical Pathology of the Head and Neck. CRC Press; 2001. 836
- Lim AA-T, Peck RH-L. Bilateral mandibular cyst: lateral radicular cyst, paradentalcyst, or mandibular infected buccal cyst? Report of a case. J Oral Maxillofac Surg Off J AmAssoc Oral Maxillofac Surg. Jul 2002;60(7):8257.
- Case Archive – School of Dental Medicine – Case Western Reserve University[Internet]. [cited 6 Nov 2017]. Available at: https://dental.case.edu/ommds/case-archive/
- Fowler CB, Brannon RB, Kessler HP, Castle JT, Kahn MA. Glandular OdontogenicCyst: Analysis of 46 Cases with Special Emphasis on Microscopic Criteria for Diagnosis.Head Neck Pathol. Sep 14, 2011;5(4):3647
Radiological examinations in Odontostomatology
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