Intraoral Radiographic Views

INTRAORAL DENTAL EQUIPMENT

Intraoral dental equipment varies in size and appearance but have similar structural components and electrical parts (Figure 1). All these parts may vary in size, shape and arrangement. The standard structural parts include a control panel, which may be a cabinet like a structure, a panel mounted on the wall, or a portable control box. Next is a tube head, which houses the x-ray tube and a flexible extension arm from which the tube head is suspended. The extension arm is hollow to permit the passage of electrical wires to the tube. It folds up like a bracket and can be swiveled from side to side. The tube head is attached to the extension arm by means of a yoke that can revolve 360 degrees horizontally where it is connected. In addition, the tube head can rotate vertically within the yoke. The tube is made of cast metal (often aluminum) and protectively lined with the lead to prevent the escape of radiation in any direction except towards the position indicating device (PID).

The fundamental electrical parts of the x-ray machine are the x-ray tube, the electrical circuits (low-voltage or filament circuit and the high-voltage or cathode-anode circuit); and the timer. The electric circuit enters the control panel either through the cord plugged into a grounded outlet in the wall or through a direct connection to a power line in the wall. It continues to and through the hollow extension arm and the yoke, entering the tube head from one or both sides at a point where the tube head attaches to the yoke. All areas are heavily insulated to protect the patients and the operator from electric shock.   

Figure 1. Typical wall mounted dental x-ray machine.

EXAMPLES OF IMAGE OF THE MACHINE

POSITIONING GUIDELINES FOR INTRAORAL RADIOGRAPHS

                    

Accurate positioning is the key for diagnostic radiographs and helps avoid retakes. Intraoral radiographs are taken using paralleling, bisecting, and bite-wing techniques. Devices used to accomplish this include receptor instruments with ring guides, standard bite blocks, and bite-wing tabs.

Paralleling Technique

The paralleling technique is used for both periapical and bite-wing radiographs and is the most accurate technique for taking these projections. For film or digital radiographs, the receptor should be placed vertically and horizontally parallel with the teeth that are being radiographed. The X-ray beam should be directed at right angles to the teeth and receptor. In the case of periapical radiographs, the film or digital receptor should be placed parallel to the full length of the crown and root of the teeth being imaged. The paralleling technique for bite-wing radiographs is simpler in the sense that the radiograph is more easily placed in the patient’s mouth even if the palate is shallow or the patient gags easily. 

Figure 2. Paralleling technique

Bisecting Technique

The Bisecting Angle Technique is an alternative to the paralleling technique for taking periapical films.  The paralleling technique is recommended for routine periapical radiography, but there are some instances when it is very difficult due to patient anatomy or lack of cooperation. In these situations, the bisecting angle technique may be used.  The film can be held in the mouth with the bite block or a bisecting instrument may be used.  Note: patient acceptance of the bisecting instrument is not much better than for the paralleling instrument. In the Bisecting Angle Technique, the x-ray beam is directed perpendicular ( T shape) to an imaginary line which bisects (divides in half) the angle formed by the long axis of the tooth and the long axis of the film.

Figure 3. Bisecting Technique

Bite-wing techniques    

Bitewing X-rays show the upper and lower back teeth and how the teeth touch each other in a single view. These X-rays are used to check for decay between the teeth and to show how well the upper and lower teeth line up. They also show bone loss when severe gum disease or a dental infection is present.

Figure 4. Bite-wing techniques

FILM AND DIGITAL RECEPTOR INSTRUMENTS

Receptor instruments with X-ray beam ring guides improve the accuracy of the PID (Position indicating device, or X-ray cone) alignment to ensure correct beam angulation and beam centering. Receptor instruments combine a receptor holder with an arm that has an attached ring indicating the position for the PID. This helps the operator avoid common errors by specifically directing the X-ray beam toward the receptor. Regardless of the instrument used, the placement of the receptor relative to the teeth must be correct. Instruments are available for paralleling, bisecting, and bite-wing techniques, as well as for endodontic imaging where endodontic files and instruments may otherwise impede proper positioning of the receptor behind the tooth. Great care is necessary when placing the X-ray beam at right angles to the receptor, to avoid common errors. Incorrectly directing the beam in the horizontal plane will result in overlapping proximal contacts on bite-wing or periapical radiographs, making them diagnostically useless and resulting in a retake. Similarly, if the X-ray beam is not correctly centered over the receptor, cone cuts can occur on the image, with a clear zone where the X-rays did not expose the receptor. Central ray entry points help to identify the center of the receptor by using an external landmark. In the case of periapical radiographs, improper vertical angulation can produce image foreshortening and elongation that misrepresents the actual length of all structures including the teeth.

Reasons for requests

Figure 5. X-ray beam guide ring

•        helpful during instrumentation as a guide for detection of calculus deposits or faulty restorations
•    diagnosis of dental caries
•    alveolar bone loss
•    pulpal changes
•    anatomical imperfections in tooth and root surfaces

    ADVANTAGES AND DISADVANTAGES 

ADVANTAGES FOR CONVENTIONAL RADIOGRAPHY	DISADVANTAGES FOR CONVENTIONAL RADIOGRAPHY
Low cost	Have to process the image manually
Low dose of ionizing radiation	Difficulty in placing the film inside the mouth
Better resolution	Requires longer time

For further understanding, please kindly refer the following video clips :