intraoral projection

C H A P T E R 7

Intraoral Projections

Intraoral images can be divided into three categories:

• (1) periapical projections• should show all of a tooth, including the

surrounding bone.

• (2) bitewing projections• show only the crowns of teeth and the adjacent

• (3) occlusal projections. • show an area of teeth and bone larger than

periapical images.

CRITERIA OF QUALITY

1-Radiographs should record the complete areas of interest

• the full length of the roots and at least 2 mm of periapical bone must be visible.

• If evidence of a pathologic condition is present, the area of the entire lesion plus some surrounding normal bone should show on one radiograph.

• Bitewing examinations should demonstrate each posterior proximal surface at least once.

2-Radiographs should have the least possible amount of distortion.

• Most distortion is caused by improper angulation of the x-ray beam rather than by the curvature of the structures being examined or inappropriate positioning of the receptor.

3-Images should have optimal density and contrast to facilitate interpretation.

• milliamperage (mA), peak kilovoltage (kVp), and exposure time

• faulty processing

PERIAPICAL IMAGING

• To obtain a view of entire tooth and its surrounding structures. • 2 techniques:

paralleling technique (preferred) bisecting technique

•Paralleling technique: less image distortion, reduces excess radiation •

• Bisecting technique :• for patients unable to accommodate the

positioning of paralleling technique, low palatal vaults and children

GENERAL STEPS FOR MAKING AN EXPOSURE• Prepare unit for exposure.• Greet and seat the patient.• Adjust the x-ray unit setting.• Wash hands thoroughly.• Examine the oral cavity. • Position the tube head. • Position the receptor.• Position the x-ray tube. • Make the exposure.

A) PARALLELING TECHNIQUE• •Principle: The central concept of the

paralleling is that “the x-ray receptor is supported parallel to the long axis of the teeth and the central ray of the x-ray beam is directed at right angles to the teeth and receptor”.

Benefits:• This orientation of the receptor, teeth, and

central ray minimizes geometric distortion and presents the teeth and supporting bone in their true anatomic relationships.

• The use of a long source-to-object distance reduces the apparent size of the focal spot, thus increasing image sharpness, and provides images with minimal magnification.

Instruments

Receptor Placement

Angulation

ModificationsIf the lack of parallelism does not exceed 20, the radiograph is generally

acceptable�.̊

Place 1 or 2 cotton rolls on bite block.

Increase the vertical angulation by 5 to 15

degrees

Shallow

palate

ModificationsFor maxilla, place

the film on far side of the film.For mandible,

place film between the tori

and tongue

Bony growth

s

BISECTING ANGLE TECHNIQUE

• The bisecting-angle technique is based on a simple geometric theorem, Cieszynski ’ s rule of isometry, which states that two triangles are equal when they share one complete side and have two equal angles.

Receptor-Holding Instruments

• It is undesirable to have the patient support the receptor from the lingual surface with his or her forefinger.

• Patients often use excessive force and bend the receptor, causing distortion of the image.

Positioning of the Patient

• For images of the maxillary arch, the patient’s head should be positioned upright with the sagittal plane vertical and the occlusal plane horizontal.

• For mandibular teeth are to be radiographed, the head is tilted back slightly to compensate for the changed occlusal plane when the mouth is opened.

Receptor Placement

• The occlusal or incisal edge is oriented against the teeth with an edge of the receptor extending just beyond the teeth.

• If necessary for the patient’s comfort, the anterior corner of a film can be softened by bending it before it is placed against the mucosa. Care

Angulation of the Tube Head

• 1) Horizontal Angulation. • the radiation beam is also centered on the

receptor. This angulation usually is at right angles (in the horizontal projection) to the buccal or facial surfaces of the teeth in each region.

• 2) Vertical Angulation.• the clinician’s goal is to aim the central ray of the

x-ray beam at right angles to a plane bisecting the angle between the receptor and the long axis of the tooth.

• Excessive vertical angulation results in foreshortening of the image.

• insufficient vertical angulation results in image elongation.

MAXILLARY CENTRAL INCISOR PROJECTION

Image Field .

• The field of view on these radiographs (shaded area) should include both central incisors and their periapical areas.

Receptor Placement.• receptor at about

the level of the second premolars or first molars to take advantage of the maximal palatal height so that the entire length of the teeth can be projected on it.

Projection of Central Ray• . Because the axial

inclination of the maxillary incisors is about 15 to 20 degrees, the vertical angulation of the tube should be at the same positive angle. The tube should have 0 horizontal angulation.

Point of Entry• on the lip, in the

midline, just below the septum of the nostril.

MAXILLARY LATERAL PROJECTION

Image Field.• . Include the mesial interproximal area with the

distal aspect of the central incisor on the radiograph so that no overlap is evident.

Receptor Placement• Place a No. 1

receptor deep in the oral cavity parallel withthe long axis and the mesiodistal plane of the maxillary lateral incisor.

Projection of Central Ray.• Direct the central ray

through the middle of the lateral incisor, with no overlapping of the margins of the crowns at the interproximal space on its mesial aspect. Do not attempt to visualize the distal contact with the canine.

Point of Entry• Orient the central

ray to enter high on the lip about 1 cm from the midline.

MAXILLARY CANINE PROJECTION

Image Field.• Open the mesial contact area. Ignore the distal

contact because it will be visualized on other projections.

Receptor Placement.• Receptor Placement.

Place a No. 1 receptor against the palate, well away from the palatal surface of the teeth. Orient the receptor packet with its anterior edge at

Projection of Central Ray.• Position the holding

instrument so that it directs the beam through the mesial contact of the canine.

Point of Entry.• . The point of entry

is at about the intersection of the

• distal and inferior borders of the ala of the nose.

MAXILLARY PREMOLAR PROJECTION

Image Field• should include the images of the distal half of

the canine and the premolars, with room for at least the first molar.

Receptor Placement .• The packet should

also include the premolars and the first molar and maybe the mesial portion of the second molar.

Projection of Central Ray.• The horizontal

angulation of the holding instrument should be adjusted to permit the beam to pass through the interproximal area between the first and second premolars.

Point of Entry.• This point usually

is below the pupil of the eye.

MAXILLARY MOLAR PROJECTION

Image Field• The radiograph of this region should show

the images of the distal half of the second premolar, the three maxillary permanent molars, and some of the tuberosity.

Receptor Placement.• The anterior

border should just cover the distal aspect of the second premolar.

Projection of Central Ray• Adjust the

horizontal angulation of the receptor-holding instrument to direct the beam at right angles to the buccal surfaces of the molar teeth.

Point of Entry• The point of entry

of the central ray should be on the cheek below the outer canthus of the eye and the zygoma at the position of the maxillary second molar.

MANDIBULAR CENTROLATERAL PROJECTION

Image Field• Center the image of the mandibular central

and lateral incisors and their periapical areas on the receptor.

Receptor Placement• Place the long

dimension of the No. 1 receptor vertically behind the central and lateral incisors with the contact area centered and the lower border below the tongue.

Projection of Central Ray• Orient the central

ray through the interproximal space between the central and lateral incisors.

Point of Entry• The central ray

enters below the lower lip and about 1 cm lateral to the midline.

MANDIBULAR CANINE PROJECTION

Image Field• This image should show the entire mandibular

canine and its periapical area. Open its mesial contact area. The distal contact is included on other projections.

Receptor Placement• Place a No. 1

receptor packet in the mouth with its long dimension vertical and the canine in the midline of the receptor.

Projection of Central Ray• Projection of Central Ray.

Direct the central ray through the mesial contact of the canine without regard to the distal contact.

Point of Entry• The point of entry is

nearly perpendicular to the ala of the nose, over the position of the canine, and about 3 cm above the inferior border of the mandible.

MANDIBULAR PREMOLAR PROJECTION

Image Field• The radiograph of this area should show the

distal half of the canine, the two premolars, and the first molar.

Receptor Placement.• Bring the No. 2

receptor into the mouth with its plane nearly horizontal. Rotate the lead edge to the floor of the mouth between the tongue and the teeth with the anterior border near the midline of the canine. Place the receptor

Projection of Central Ray• Position the receptor-

holding instrument to project the central ray through the second premolar-molar area. The vertical angulation should be small, nearly parallel with the occlusal plane.

Point of Entry• The point of entry of

the central ray is below the pupil of the eye and about 3 cm above the inferior border of the mandible.

MANDIBULAR MOLAR PROJECTION

Image Field• The radiograph of this region should include the

distal half of the second premolar and the three mandibular permanent molars.

• In the case of an impacted third molar or a pathologic condition distal to the third molar, a distal oblique molar projection or even additional extraoral projections (panoramic or lateral ramus) may be required to demonstrate the area adequately.

• If the molar area is edentulous, place the receptor far enough posterior to include the retromolar area in the examination.

Receptor Placement• Place the No. 2

receptor in the mouth with its plane nearly horizontal. Rotate the inferior edge downward beneath the lateral border of the tongue, displacing it medially.

Projection of Central Ray• Projection of Central

Ray. Proper placement of the holding instrument directs the central ray through the second molar.

• Adjust the horizontal angulation to project the beam through the contact areas.

Point of Entry• Direct the point of

entry of the central ray below the outer canthus of the eye about 3 cm above the inferior border of the mandible

• Bitewing (also called interproximal ) radiographs include the crowns of the maxillary and mandibular teeth and the alveolar crest on the same receptor.

Bitewing (interproximal)

• interproximal caries in the early stages.• secondary caries below restorations.• Overhanging restorations.• evaluating the periodontal condition.

(alveolar bone crest)• detecting calculus deposits.

Indications

• Parallel with the occlusal plane.• The aiming cylinder is positioned about

+7 to +10 degrees to project the beam parallel with the occlusal plane.

Vertical Bitewing

Horizontal Bitewing

Receptor-holding device for bitewing images.

Set of vertical bitewing views

PREMOLAR BITEWING PROJECTION

Image Field• This projection should cover the distal portion of

the mandibular canine anteriorly and show equally the crowns of the maxillary and mandibular premolar teeth.

Receptor Placement• Place the receptor

between the tongue and the teeth, far enough from the lingual surface of the teeth to prevent interference by the palate on closing and parallel to the long axes of the teeth. The anterior border of the receptor

Projection of Central Ray.• Projection of Central

Ray. Adjust the horizontal angulation of the cone to

• project the central ray to the center of the receptor through the premolar contact areas.

• To compensate for the slight inclination of the receptor against the palatal mucosa, the vertical angulation should be about +5 degrees. (In the drawing, the mandibular teeth are shown in dashed lines.)

Point of Entry• Identify the point of

entry by retracting the cheek and determining that the central ray will enter the line of occlusion at the point of contact between the second premolar and the first molar.

MOLAR BITEWING PROJECTION

Image Field• This projection should show the distal surface

of the most posterior erupted molar and equally the crowns of the maxillary and mandibular molars.

Receptor Placement• Receptor Placement.

Place the receptor between the tongue and teeth as far lingual as practical to avoid contacting the sensitive attached gingiva. The distal margin of the receptor should extend 1 to 2 mm beyond the most posterior erupted molar.

Projection of Central Ray• Project the central ray

to the center of the receptor and through the contact of the first and second maxillary molars.

• Angle the central ray slightly from the anterior because the molar contacts usually are not oriented at

• right angles to the buccal surfaces of these teeth.

• A vertical angulation of +10 degrees is recommended. (In the drawing, the mandibular teeth are shown in dashed lines.)

Point of Entry• Point of Entry. The

central ray should enter the cheek below the lateral canthus of the eye at the level of the occlusal plane.

• An occlusal radiograph displays a relatively large segment of a dental arch.

• when patients are unable to open the mouth.• localization of objects.• To locate precisely roots and

supernumerary, unerupted, and impacted teeth (this technique is especially useful for impacted canines and third molars)

• To localize foreign bodies in the jaws and stones in the ducts.

Occlusal View

• To demonstrate and evaluate the integrity of the outlines of the maxillary sinus

• To demonstrate and evaluate the integrity of the anterior, medial, and lateral outlines of the maxillary sinus

• To determine the medial and lateral extent of disease (e.g., cysts, osteomyelitis, tumors) and to detect disease in the palate or floor of the mouth.

ANTERIOR MAXILLARY OCCLUSAL PROJECTION

Image Field• The primary field of

this projection includes the anterior maxilla and its dentition and the anterior floor of the nasal fossa and teeth from canine to canine.

Receptor Placement

Adjust the patient’s head so that the sagittal plane is perpendicular and the occlusal plane is horizontal to the floor.

• Place the receptor in the mouth with the exposure side toward the maxilla, the posterior border touching the rami, and the long dimension of the receptor perpendicular to the sagittal plane.

• The patient stabilizes the receptor by gently closing the mouth or using gentle bilateral thumb pressure.

• Projection of Central Ray. Orient the central ray through the tip of the nose toward the middle of the receptor with approximately +45 degrees vertical angulation and 0 degrees horizontal angulation.

• Point of Entry. The central ray enters the patient’s face approximately through the tip of the nose.

TOPOGRAPHICAL MAXILLARY OCCLUSAL PROJECTION

Image Field• This projection shows

the palate, zygomatic processes of the maxilla, anteroinferior aspects of each antrum, nasolacrimal canals, teeth from second molar to second molar, and nasal septum.

Receptor Placement• Seat the patient

upright with the sagittal plane perpendicular to the floor and the occlusal plane horizontal.

• Place the receptor, with its long dimension perpendicular to the sagittal plane, crosswise in the mouth. Gently push the receptor in backward until it contacts the anterior border of the mandibular rami. The patient stabilizes the receptor by gently closing the mouth.

• Projection of Central Ray. Direct the central ray at a vertical angulation of +65 degrees and a horizontal angulation of 0 degrees to the bridge of the nose just below the nasion, toward the middle of the receptor.

• Point of Entry. Generally, the central ray enters the patient’s face through the bridge of the nose.

LATERAL MAXILLARY OCCLUSAL PROJECTION

Image Field• This projection shows

a quadrant of the alveolar ridge of the maxilla, inferolateral aspect of the antrum, tuberosity, and teeth from the lateral incisor to the contralateral third molar.

Receptor Placement• Place the receptor

with its long axis parallel to the sagittal plane and on the side of interest, with the tube side toward the side of the maxilla in question. Push the receptor posteriorly until it touches the ramus.

• Position the lateral border parallel with the buccal surfaces of the posterior teeth, extending laterally approximately 1 cm past the buccal cusps. Ask the patient to close gently to hold the receptor in position.

• Projection of Central Ray. Orient the central ray with a vertical angulation of +60 degrees, to a point 2 cm below the lateral canthus of the eye, directed toward the center of the receptor.

• Point of Entry. The central ray enters at a point approximately 2 cm below the lateral canthus of the eye.

ANTERIOR MANDIBULAR OCCLUSAL PROJECTION

Image Field• This projection

includes the anterior portion of the mandible, the dentition from canine to canine, and the inferior cortical border of the mandible.

Receptor Placement• Seat the patient tilted

back so that the occlusal plane is 45 degrees above horizontal.

• Place the receptor in the mouth with the long axis perpendicular to the sagittal plane and push it posteriorly until it touches the rami.

• Projection of Central Ray. Orient the central ray with −10 degrees angulation through the point of the chin toward the middle of the receptor; this gives the ray −55 degrees of angulation to the plane of the receptor.

• Point of Entry. The point of entry of the central ray is in the midline and through the tip of the chin.

TOPOGRAPHICAL MANDIBULAR OCCLUSAL PROJECTION

Image Field• This projection

includes the soft tissue of the floor of the mouth and reveals the lingual and buccal plates of the mandible from second molar to second molar.

• When this view is made to examine the floor of the mouth (e.g., for sialoliths), the exposure time should be reduced to half the time used to create an image of the mandible.

Receptor Placement• Seat the patient in a

semireclining position with the head tilted back so that the ala-tragus line is almost perpendicular to the floor.

• Place the receptor in the mouth with its long axis perpendicular to the sagittal plane and with the tube side toward the mandible.

• The anterior border of the receptor should be approximately 1 cm beyond the mandibular central incisors.

• Ask the patient to bite gently on the receptor to hold it in position.

• Projection of Central Ray. Direct the central ray at the midline through the floor of the mouth approximately 3 cm below the chin, at right angles to the center of the receptor.

• Point of Entry. The point of entry of the central ray is in the midline through the floor of the mouth approximately 3 cm below the chin.

LATERAL MANDIBULAR OCCLUSAL PROJECTION

Image Field• Image Field. This

projection covers the soft tissue of half the floor of the mouth, the buccal and lingual cortical plates of half of the mandible, and the teeth from the lateral incisor to the contralateral third molar.

Receptor Placement.• Seat the patient in a semireclining position with

the head tilted back so that the ala-tragus line is almost perpendicular to the floor. Place the receptor in the mouth with its long axis initially parallel with the sagittal plane and with the pebbled side down toward the mandible

• Projection of Central Ray. Direct the central ray perpendicular to the center of the receptor through a point beneath the chin, approximately 3 cm posterior to the point of the chin and 3 cm lateral to the midline.

• Point of Entry. The point of entry of the central ray is beneath the chin, approximately 3 cm posterior to the chin and approximately 3 cm lateral to the midline.

IMAGING OF CHILDREN

• Radiation protection is most important for children because of their greater sensitivity to irradiation.

• The best way to reduce unnecessary exposure is for the dentist to make the minimal number of receptors required for the individual patient. These

• The frequency should be determined partly by the patient’s caries rate.

• The relatively shallow palate and floor of the mouth may require further modification of receptor placement.

EXAMINATION COVERAGE

• Also, an exposure appropriate to the child’s size should be used.

• example, a 50% reduction in the mA used for an average young adult gives the proper density for patients younger than 10 years.

Primary Dentition (3 to 6 Years)

• This examination may consist of two anterior occlusal receptors, two posterior bitewing receptors, and up to four posterior periapical receptors as indicated

1- Maxillary Anterior Occlusal Projection.

• A No. 2 receptor

• its long axis perpendicular to the sagittal plane and the pebbled surface toward the maxillary teeth.

• central ray is directed at a vertical angulation of +60 degrees through the tip of the nose toward the center of the receptor.

2- Mandibular Anterior Occlusal Projection• A No. 2 receptor

• occlusal plane is about 25 degrees above the plane of the floor.

• The central ray is oriented at −30 degrees vertical angulation and through the tip of the chin toward the receptor.

3 -Bitewing Projection• A No. 0 receptor• The image field :the distal half of the

canine and the deciduous molars. • A positive vertical angulation of +5 to +10• The horizontal angle :direct the beam

through the interproximal spaces.

4 -Deciduous Maxillary Molar Periapical Projection


• The image field of this projection should include the distal half of the primary canine and both primary molars.

5 -Deciduous Mandibular Molar Projection.


• The exposed radiograph should show the distal half of the mandibular primary canine and the primary molar teeth.

Mixed Dentition (7 to 12 Years)

• A complete examination of the mixed dentition, consists of

• two incisor periapical views, four canine periapical views, four posterior periapical views, and two or four posterior

• For the maxillary and interproximal projections, the child should be seated upright with the sagittal plane perpendicular and the occlusal plane parallel to the floor.

• For the mandibular projections, the child should be seated upright with the sagittal plane perpendicular and the ala-tragus line parallel to the floor. XC

1 -Maxillary Anterior Periapical Projection


• centered on the embrasure between the central incisors in the

2 -Mandibular Anterior Periapical Projection


• positioned behind the mandibular central and lateral incisors.

3 -Canine Periapical Projection

• A No. 1 receptor should be positioned behind each of the canines.

4 -Deciduous and Permanent Molar Periapical Projection

• A No. 1 or No. 2 receptor (if the child is large enough)

• should be positioned with the anterior edge behind the canine.

5 -Posterior Bitewing Projection.• No. 1 or No. 2 receptor

• Four bitewing projections should be exposed when the second permanent molars have erupted.

MOBILE IMAGING

• This machine uses a high-frequency, constant potential x-ray generator (60 kilowatt constant potential)

• short focal spot-to-skin • small focus spot (0.4 mm).

operator dose

• The operator dose is mitigated by the use of

1- internal shielding materials in the unit to reduce leakage exposure

2- and a shield on the aiming cylinder to minimize backscatter from the patient.

SPECIAL CONSIDERATIONS

INFECTION

• Infection in the orofacial structures may result in edema and lead to trismus of some of the muscles of mastication. As a result, intraoral radiography may be painful to the patient and difficult for both the patient and the radiologist.

• Under such circumstances, extraoral or occlusal techniques may offer the only possibility of an examination.

• In the case of edema in an area to be examined, exposure time should be increased to compensate for the tissue swelling.

TRAUMA

• Dental fractures are best appreciated by using periapical or occlusal radiographs. Special care must be taken when making these views because of the condition of the patient.

• Skeletal fractures are usually best seen with panoramic or other extraoral views or a computed tomography examination.

PATIENTS WITH MENTAL DISABILITIES

• When the radiographic examination is performed speedily, unpredictable moves by the patient can be minimized.

• In some cases, sedation may be required.

PATIENTS WITH PHYSICAL DISABILITIES

• These patients usually are cooperative and eager to assist.

• Members of the patient’s family often are very helpful in assisting the patient into and out of the examination chair and in receptor positioning and holding, inasmuch as they usually are familiar with the patient’s condition and accustomed to coping with it.

GAG REFLEX

• the radiologist should make an effort to relax

• The gag reflex often is worse when a patient is tired.

• Stimulating the posterior dorsum of the tongue or the soft palate usually initiates the gag reflex.

• Sliding the film, along the palate or tongue is likely to stimulate the gag reflex.

• In extreme cases, topical anesthetic agents in mouthwashes or spray can be administered to produce temporary numbness of the tongue and palate to reduce gagging.

• The most effective approach is to reduce apprehension, minimize tissue irritation, and encourage rapid breathing through the nose.

IMAGING FOR ENDODONTICS

• In these cases, when it is necessary to separate the roots on multirooted teeth, a second projection may be made. The horizontal angulation is altered 20 degrees mesially for maxillary premolars, 20 degrees mesially or distally for maxillary molars, or 20 degrees distally for an oblique projection of mandibular molar roots.

• If a sinus tract is encountered, its course is tracked by threading a No. 40 gutta percha cone through the tract before the radiograph is made.

PREGNANCY

• radiographic examination is limited during pregnancy to cases with a specific diagnostic indication.

EDENTULOUS PATIENTS

• To discover roots, residual infection, impacted teeth, cysts, or other pathologic entities that may adversely affect the usefulness of prosthetic appliances or the patient’s health.

• After a determination has been made that these entities are not present, repeated examinations to detect them are not warranted in the absence of signs or symptoms.

• If available, a panoramic examination of the edentulous jaws is most convenient.

• If panoramic equipment is unavailable, an examination consisting of 14 intraoral views provides an excellent survey.

• . The exposure required for an edentulous ridge is approximately 25% less than that for a dentulous ridge.

• This examination consists of seven projections in each jaw (adult No. 2 receptor) as follows:

• Central incisors (midline): one projection• Lateral canine: two projections• Premolar: two projections• Molar: two projections

intraoral projection

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