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

• A No. 0 receptor

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

5 -Deciduous Mandibular Molar Projection.

• A No. 0 receptor

• 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

• A No. 1 receptor

• centered on the embrasure between the central incisors in the

2 -Mandibular Anterior Periapical Projection

• A No. 1 receptor

• 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