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Final_Lec3 14-April-2013

Periapical radiograph (Bisecting angle technique)

We will continue talking about periapical radiograph of radiology. Parallel technique is that putting the film parallel to the tooth.

HOW can that be done?

You put the film far away from the tooth and toward the middle of the palate or the mid surface of the tongue.

My aim in Periapical radiographs is to see the periapical area at least 2mm around the apex.

Periapical radiograph is done by parallel technique or bisecting angle technique.

Bisecting angle technique:- Bisecting angle means there must be an angle

and I want to bisect it (divide it into two equal triangles)

The ideal position requirement we need parallelism between the tooth and the film. We need close contact as possible, minimum film to tooth distance, etc

In parallel technique we could not put the film in close contact to the tooth. So we lost this requirement. While now in bisecting angle technique we want to put the film in close contact to the tooth.

1. It is the point where the film contact the tooth, the plane of the film and the long axis of the tooth form an angle.

2. The central ray of the x-ray beam perpendicular to the imaginary bisector.

3. The film must be placed in the lingual surface of the tooth.

4. Imaginary bisector: the dental radiographer must visualize a plane that division half or bisects, the angle formed by the film and the long axis of the tooth.

5. The two imaginary triangle that result are right triangle and congruent , one represented by the long axis of the tooth and the other by the plane of the film .

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Rule of isometry: states that two triangular are equal if they have two equal angles and share a common side. We depend on this rule to detect the real dimension of the tooth.

We assumed that the length (the real dimension of the tooth) of the tooth on the film is accurate but it is not.

As in parallel technique we have several film holders, as parallel technique you set the patient in correct position and the film too. The vertical angulation should be central to the beam.

Film holders: is a device used to position an intraoral film in the mouth and return the film in position during exposure. With the bisecting technique, film holders are recommended because the need for the patient to stabilize the film with their finger is eliminated. This will reduce the patient exposure to radiation.

Examples of commercially available film holders:

- Rinn BAI instruments.

- Stabe bite-block (Rinn).

- EEZEE-Grip film holder (Rinn).

Finger-holding Method is the least desirable method for exposing films using the bisecting technique. Disadvantages of this method:

1. The patient's finger is in the path of primary beam, resulting in unnecessary radiation exposure.

2. The patient may use excessive force to stabilize the film, causing the film to bend and resulting in image distortion.

3. The patient may allow the film to slip from its position, resulting in inadequate exposure of the prescribed area.

4. Without the use of a film holder with aiming ring, the dental radiographer may align the PID incorrectly, causing a partial image or cone-cut.

Vertical angulation: refer to the position of the PID in a vertical or up and down, plane vertical angulation is measured in degrees and is registration on the outside of

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the tubehead. 5 degrees is added to the vertical angulation because of teeth inclination.

The vertical angulation differs according to the radiograph technique used as follows:

1. With the paralleling technique, the vertical angulation of the central ray is directed perpendicular to the film and the long axis of tooth.

2. With the bisecting technique, the vertical angulation is determined by imaginary bisector; the central ray is directed perpendicular to the imaginary bisector.

When using film holders no need to remember the vertical angulation because it is already correct while when using finger holding methods you have to remember it.

Incorrect vertical angulation results in a radiographic image that is not the same length as the tooth; instead, the image appears longer or shorter.

Elongated or foreshortened image are not diagnostic (distortion). Foreshortened image results from excessive vertical angulation (too steep). Elongated image results from insufficient vertical angulation (too flat). Distortion means not normal shape, especially with finger holding method.

Horizontal angulation refers to the positioning of the tube head and direction of the central ray in a horizontal or, side-to-side, plane. It does not differ according to the radiographic technique used.

Correct horizontal angulation: the central ray directed perpendicular to the curvature of the arch all through the contact areas of the teeth.

Incorrect horizontal angulation results in overlapped contact areas.

o Size 2 intraoral film is used with the bisecting technique for posterior teeth and size 1 for anterior teeth.

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Vertical angulation of the film for anterior teeth Horizontal angulation of the film for posterior teeth

There are:

- 5 films for upper anterior- 3 films for lower anterior- 8 films for posterior teeth- 4 bitewing films

There's no need to memorize angulation unless you use finger technique (specially vertical angulation).

Bisecting technique advantages:

1. Close contact between tooth and film. 2. Decreased exposure time when a short PID is used with the bisecting technique, a

shorter exposure time is recommended.But in parallel technique we use long cone to compensate for magnification

3. It can be use without a film holder when the anatomy of the patient (shallow palate, bony growths, sensitive mandibular premolar areas.

4. In edentulous patient because the muscle tens when he open his mouth an area in partially edentulous patients when the holder is not stable we can use cotton.

In the bisecting technique we lose two ideal requirements:

1. Parallelism2. The central ray of the x-ray beam must be directed perpendicular to the film and the

long axis of the tooth. (This principle will be lost)

Some students in the clinic use the same holder of the parallel technique in the bisecting technique but they put the film perpendicular to the tooth which is wrong of course we have to use special holder in bisecting technique.

Bisecting technique disadvantages:

1. Image distortion.

2. Angulation problems.

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3. Excess radiation exposure to patient’s hands. If a film holder is not used, as result of using finger holding method we may end with phalangioma on radiograph

We have intra oral radiograph:-

Periapical radiograph-parallel technique

-bisecting technique

Bite-wing technique

Is an intraoral radiographic technique that is used to examine the interproximal surfaces of teeth.

A bite-wing radiograph shows the crowns of the maxillary and mandibular teeth and the areas of crestal bone on the same film.

The main advantage of the bitewing technique is to detect interproximal caries that are not clinically evident.Bitewing radiograph are also useful in examining the crestal bone levels between teeth.

The indication of bitewing technique:-1. Indicate caries (interproximal examination). 2. Assessment of restorations and overhanging.3. Assessment of periodontal status.4. Detection of interproximal calculus.5. Pulp chamber examination6. Examining crestal bone levels between teeth.7. Overlapped contact: where the contact area of one tooth is super imposed over the

contact area of the adjacent tooth.8. Open contact: open contacts appear as thin radiolucent line between adjacent tooth

surfaces.9. Alveolar bone: bone that support and encases the root of the teeth.10.Crestal bone: coronal portion of alveolar bone found between the teeth (alveolar

crest).

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11. Contact area: area of a tooth that touches an adjacent tooth, the area where adjacent tooth surfaces contact each other.

In bitewing we achieve some parallelism and in the same time it will be interocclusal, so this point gives the Bitewings superiority in detecting carious lesions,

Angulation of PID Horizontal angulation: Positioning of the central ray in a horizontal or side to

side, plane. Correct horizontal angulation: the central ray directed perpendicular to the

curvature of the arch all through the contact areas of the teeth. As a result the contact area will appear opened and we can examine the caries.

Incorrect horizontal angulation results in overlapped contact areas.

We use horizontal angulation to detect caries for maxillary and mandibular together.

Vertical angulation: refer to the position of the PID in a vertical or up and down, plane. Vertical angulation may be positive or negative and is measured in degrees on the outside of the tubehead. If the PID is positioned above the occlusal plane and the central ray is directed downward -the vertical angulation is positive.

If the PID is below the occlusal plane and the central ray directed upward the vertical angulation is negative.

Incorrect vertical angulation results in distorted image. Vertical bitewing used to examine the level of alveolar bone loss in the mouth.

(Mild, moderate, severe). When the loss is more I need to put the film vertically to cover more area

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Film for bitewing technique:-

Size 0 film: is used to examine the posterior teeth of children with primary dentitions this film is always placed with the long portion of the film in a horizontal (sideways) direction.

Size 1 film: is used to examine posterior teeth of children with mixed dentition.

Posterior region size 1 film -- > placed in horizontal direction.

Anterior teeth size 1 film -- > placed in a vertical (up and down) direction.

Size 2 film: used to examine the posterior teeth in adults and may be placed horizontally or vertically.

*** Size 2 film is placed in horizontal direction, it is used for most bitewing exposures.

Size 3 film: is not recommended because overlapped contacts result, because of the difference in the curvature of the arch between the premolar and molar areas. In addition, the crestal bone areas may not be adequately seen on the radiograph. (Bone loss not seen because of the narrow shape of the film).

Film holder and bitewing tab:-In the bitewing technique either we use a film holder or bite-wing tab.

Film holders: is a device used to position an intraoral film in the mouth and retain the film in position during exposure (They are color coded red one use for bitewing).

Rinn XCP bitewing instrument: include plastic bite-blocks , plastic aiming rings , and metal indicator arms to reduce the amount of radiation the patient receives , a snap–on ring collimator can be added to the plastic aiming ring. These film holders are reusable and must be sterilized after each use.

BITE-WING TAB: readymade or can you made by yourself. As an alternative to a film–holding device, a film can be fitted with a bite wing tab.

The bitewing tab: is a heavy paper-board tab or loop fitted around a periapical film and used to stabilize the film during the exposure. The periapical film is oriented in

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the bite loop so that the tab portion extends from the white side (tube side) of the film.

Bite loops are available in various sizes; adhesive bite tabs are also available.

Ideal exposure factors 1. Assessment of caries and restoration-high kV which ensures good contrast to

allow differentiation between enamel, dentin and allow EDJ to be seen2. Assessment of periodontal status- low kV to avoid burn-out of the thin alveolar

crestal bone3. In the X-ray machines with fixed kV and mA these results are achieved through

exposure time

Rules for bite-wing technique:-

1. Film placement: the bitewing film must be positioned to cover the prescribed area of teeth to be examined .specific film placements are detailed in the following procedures.

2. Film position: the bitewing film must be positioned parallel to the crowns of the both the upper and the lower teeth .the film must be stabilized when the patient bites on the bitewing tab or bitewing holder.

3. Vertical angulation: the central ray of the x-ray beam must be directed at +10 degrees.

4. Horizontal angulation: the central ray of the x-ray beam must be directed through the contact areas between the teeth. (Perpendicular to the curvature of the arch).

5. Film exposure: the x-ray beam must be centered on the film to ensure that all areas of the film are exposed .failure to center the x ray beam results in a partial image on the bitewing film or a cone-cut.

We have anterior bitewing and posterior bitewings, posterior bitewing we have two films one for the premolar and one for molar because of the difference in the curvature of the arch.

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Premolar bitewing you have to put the anterior edge of the film in the distal part of the canine and the premolar have to be in the middle of the film.

Molar bitewing you have to see all the molars than you put the anterior edge of the film in the distal part of the second premolar.

In the bitewing film the maxillary and the mandibular teeth equally detect on the film and the occlusal plane must divide the film into half.

We put the vertical angulation in +10 degrees is used to compensate for the slight bend of the upper portion **** curve of monson***

Advantages of Bitewing technique:1. Simple2. Inexpensive3. The tabs are disposable, so no extra cross- infection control procedures

required4. Can be used easily in children

Disadvantage of the bitewing technique:1. Operator-dependent assessment of horizontal and vertical

angulation of the X-ray tubehead 2. Radiographs are not reproducible3. Cone cutting is common4. The tongue can easily displace the film packet 5. Difficulty in vertical and horizontal angulation when you use loop or

tab.

Patient preparation for bitewing technique:1. Briefly explain the radiographic procedure to the patient before the procedure begins.2. Position the patient upright in the chair; adjust the level of the chair to a comfortable working height for the dental radiographer.

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3. Adjust the headrest to support and position the patients head .the patients head must be positioned so that the upper arch is parallel to the floor and the midsagittal (midline) plane is perpendicular to the floor.4. Place and secure the lead apron with the thyroid collar on the patient.5. Remove all the object from the mouth (denture retainers, chewing gum) that may interfere with film exposure, eyeglasses must also remove.

In the clinic most of the time the student make gag reflex to the patient why??? Because they slowly or move the film.

The patient must be watched during the exposure because you have leaded glass window in the door because the patient maybe move or the cone this result incorrect radiograph.

Occlusal technique The occlusal technique is a method used to examine large areas of the upper or lower jaw. The film is so named because the patient "occludes" or bite on the film.Size 4 intraoral film is used in the occlusal technique.The occlusal radiograph is not common. When there is difficulty in making periapical radiograph, I can make an occlusal one, useful in very young children who cannot keep periapical film in place.It is also used to localize an object in three dimensions. Because the

periapical and bitewings are 2D radiographs. The occlusal radiograph shows us: mesiodistal dimension, occlusoapical dimension, buccolingual dimension (only seen in the occlusal radiograph)

Maxillary occlusal projections:

1. Maxillary topographic (also called standard cross sectional radiograph in UK): is used to examine the palate and the anterior teeth of the maxilla. (size 4 film). Angulation +65

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2. Maxillary pediatric: used to examine the anterior teeth of the maxilla and use for children 5 years old or younger. (Size 2 film). Angulation +65

3. Maxillary lateral (right or left) (also called oblique in UK): used to examine the palatal roots of the molar teeth from one side only. It may also be used to locate foreign bodies or lesion on the posterior maxilla. (Size 4 film). Angulation +60

Mandibular occlusal projections:

Here you ask the patient to tilt his head so that the mandible will be parallel with the floor. About 45 degress,

1. Mandibular topographic: is used to examine the anterior teeth of the mandible. (Size4 film)

2. Mandibular cross sectional projection: used to examine the buccal and lingual aspects of the mandible. And it is used to locate foreign bodies or salivary stones in the region of the floor of the mouth. (Size 4 film)3. Mandibular pediatric: used to examine the anterior teeth of the mandible and use for children 5 years old or younger. (Size 2 film)

You have to check the procedures for each projection; the Dr mentioned them very fast.

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The occlusal radiograph includes:1. Localization of roots, impacted teeth, unerupted teeth, foreign bodies, and salivary stone.2. Evaluation of size of lesion, boundaries of maxillary sinus, nasal fossa and jaw fracture.3. Examination of patient who cannot open their mouths.4. Measurement of changes in size and shape of jaws.

To detect mandibular gland:- Anterior 2/3 we can use occlusal radiographPosterior 1/3 we can use panoramic radiograph lateral oblique technique.

Done By: Fatma BdearChecked By: Sawsan Jwaied

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