Intraoral Radiographic Techniques- Introduction (Chapter 1)

Introduction
Radiography involves the use of x-radiation and thus is potentially dangerous if mishandled. For your own sake, and that of the staff, patient, and public, it is essential that you gain adequate knowledge of radiographic techniques and radiation health and safety, prior to performing clinical procedures.
This course is intended to provide current, vital information on film and tube head placement, to serve as a guide to acquire new skills or refine current skills, and allow you to test yourself as you progress through the pages.
When you complete a continuing education course on the Dental ResourceNet, a form will come up that requests your name, address, etc.  If you are a member of the AGD, make sure to fill out the field that asks for your AGD membership number (if you are not an AGD member, leave blank).  When you hit submit, a copy of the "proof of completion" is e-mailed directly to the AGD and P&G. For your records, make sure to print a copy of the "proof of completion" certificate.

Overview
Radiography involves the use of x-radiation and thus is potentially dangerous if mishandled. For your own sake, and that of the staff, patient, and public, it is essential that you gain adequate knowledge of radiographic techniques and radiation health and safety, prior to performing clinical procedures.
This course is intended to provide current, vital information on film and tube head placement, to serve as a guide to acquire new skills or refine current skills, and allow you to test yourself as you progress through the pages

Objectives of this Article
Upon the completion of this Article, the dental professional will be able to:

• Understand the basic principles and concepts of intraoral procedures.
• Demonstrate the paralleling technique of intraoral radiology.
• Explain the bisecting angle technique of intraoral radiology.
• Identify proper techniques for bitewing radiography.
• Describe intraoral occlusal techniques.

Article Contents

• Introduction
• Intraoral Procedures
• Paralleling Technique
• Paralleling Technique Methodology
• The Bisecting Angle Technique
• Bisecting Angle Methodology
• Bitewing Radiography
• Intraoral Occlusal Radiography
• Digital Radiology
• Summary
• Glossary
• Course Test
• About the Authors

Introduction

Radiography involves the use of x-radiation and thus is potentially dangerous if mishandled.  For your own sake, and that of the staff, patient, and public, it is essential that you gain adequate knowledge of radiographic techniques and radiation health and safety, prior to performing clinical procedures. 
This course is intended to provide current, vital information on film and tube head placement, to serve as a guide to acquire new skills or refine current skills, and allow you to test yourself as you progress through the pages.

Intraoral Procedures

Introduction
The intraoral radiograph, when correlated with the case history and clinical examination, is one of the most important diagnostic aids available to the dental practitioner.  When examined under proper conditions, diagnostic-quality intraoral radiographs reveal evidence of disease that cannot otherwise be found. They also play a major role in forensic identification.
Two of the fundamental rules of radiography are that 1) the central beam should pass through the area to be examined, and 2) the x-ray film should be placed in position so as to record the image with the least amount of image distortion. Each of three types of intraoral radiologic examinations commonly used in dental practice—periapical, bitewing (interproximal), and occlusal examinations—depend on the operator’s adherence to these two rules even though specific techniques, processes, and indications differ widely among them.
Another aspect that these three examinations have in common pertains to the film packet.  The film packet has two sides, a tube side and a tongue side.  The tube side may be plain or textured.  When placed intraorally, the tube side always faces the radiation source, the tube head.  The tongue side may be colored and has a flange to open the packet and remove the film.  When placed intraorally, the tongue side always faces the patient’s tongue, except in the case of the mandibular occlusal examination.
Because of patient anatomic variations such as narrow arches, missing teeth, or the presence of tori, and limitations of the patient’s ability to open sufficiently (caused by age or other factors), or maintain the film placement, a clinical examination must precede the taking of films.  After the clinical examination, the operator can determine the number and size of films to expose, the technique modifications necessary, and the type of film retention devices to be employed.
Advancements are continually being made in the development and manufacturing of the actual film packet.  These advancements have helped to decrease radiation exposure.  Whenever possible the "fastest" film speed should be used.

Periapical Radiographs

The purpose of the intraoral periapical examination is to obtain a view of the entire tooth and its surrounding structures, as in Figure 1.  Two exposure techniques may be employed for periapical radiography: the paralleling technique and the bisecting angle technique.  The paralleling technique is the preferred method.  This technique provides less image distortion and reduces excess radiation to the patient.  The paralleling technique should always be attempted before other techniques.  The bisecting technique can be employed for patients unable to accommodate the positioning of the paralleling technique.  Candidates may include those with low palatal vaults and children.  Disadvantages to the bisecting technique include image distortion and excess radiation due to increased angulations involving the eye and thyroid glands.  Regardless of the technique, however, the rules of radiography referred to earlier must be followed.

 

Figure 1

Bitewing Radiographs
Bitewing examinations were introduced by Raper in 1925.  The greatest value of bitewing radiographs is the detection of interproximal caries in the early stages of development, before it is clinically apparent.  The arrows in Figure 2 indicate areas of interproximal caries.  Bitewing projections also reveal the size of the pulp chamber and the relative extent to which proximal caries have penetrated.
Bitewings also provide a useful adjunct to evaluating periodontal conditions, offer a good view of the septal alveolar crest, and, in addition, permit changes in bone height to be accurately assessed by comparison with adjacent teeth.  Bitewings do not show the apices of the teeth and cannot be used to diagnose in this area.

 

Figure 2

Occlusal Radiographs

Occlusal radiography is a supplementary radiographic examination designed to provide a more extensive view of the maxilla and mandible (Figure 3).

 

Figure 3

The occlusal radiograph is very useful in determining the buccolingual extension of pathologic conditions, and provides additional information as to the extent and displacement of fractures of the mandible and maxilla.  Occlusals also aid in localizing unerupted teeth, retained roots, foreign bodies, and calculi in the submandibular and sublingual salivary glands and ducts.  It should be noted that when imaging soft tissues exposure time needs to be appropriately reduced.

Dentulous Adult Survey
The number of films needed for a full mouth series varies greatly.  Some practitioners may prefer 10 films, while others may prefer 18, 20 or more exposures.
The selection of film sizes used in a full mouth series also varies.  A full survey can consist of narrow anterior film (size #1); standard adult film (size #2); #2 bitewing film or long bitewing film (size #3), (Figure 4) and may include anterior bitewings.  It is generally recommended to use 20 films --- four bitewings and 16 periapicals.  Eight anterior #1 films will allow for ease of film placement on patients with narrow palates.  However, in some cases six anterior periapicals will cover the area needed.  

By using #3 film only one film is used on both the right and left sides and opening both the premolar and molar contacts on one film is very difficult. (Figure 5)  With the use of #2 films for bitewings, the operator uses a total of four films. 

Each film is assigned either premolars or molars. (Figure 6)  Use of the #2 films instead of #3 films for bitewings is not only more comfortable for the patient but is easier for the operator to open the contacts.

Figure 5

Figure 6

Edentulous Adult Survey
By definition, an edentulous patient is one without the natural dentition, and a partially edentulous patient is one who retains some, but not all of the natural dentition.  Merely because a patient’s clinical exam reveals an edentulous state does not disqualify him or her from diagnostic radiographic examination.  In fact, it is commonly accepted that certain areas of the patient’s jaws may contain tooth roots or impacted teeth.  Residual infection, tumors, cysts, or related pathology may also be found, which, while not visible to the clinician, would hinder the effectiveness and comfort of an appliance such as a denture and could potentially cause life threatening conditions to the patient.  In addition to the hidden pathology mentioned above, edentulous surveys reveal the position of the foramina and the type of bone present.
In the case of the partially edentulous patient, placement of the film holding device may be complicated by its tendency to tip or slip into the voids which would normally be occupied by the crowns of the missing teeth.  This can usually be overcome by placing cotton rolls between the patient’s alveolar ridge and the film holder, thereby supporting the film holding device in position.
A 14 or 16 film intraoral periapical survey will usually examine the tooth bearing region in most edentulous patients (Figure 7).  Bitewings are not needed because there are no interproximal areas to be examined.

Figure 7

The use of film holders allow the paralleling technique to be used with edentulous patients.  The operator may be able to reduce radiation exposure in the edentulous patient by 25% by using the paralleling technique.  The film can be held in biteblocks to which cotton rolls have been taped.  To prevent patient discomfort on biting due to missing teeth and resultant over-closing of the arches, the cotton rolls can be attached to the upper and lower surfaces of the biteblocks.  Opposing arch denture or partial denture appliances can be left in place to make contact with the biteblock.
The radiographic film should be positioned with approximately one-third of the film’s vertical dimension protruding beyond the alveolar ridge; that is, the radiographic image should occupy two-thirds of the film. The horizontal angulation of the central beam is perpendicular to the film in the horizontal plane.  If bisecting, the vertical angulation of the central beam is much increased for an edentulous patient with minimal ridges.  The film placement may be similar to that of an occlusal film, and this flat film placement is the principal cause of dimensional distortion.  To determine vertical angulation it is necessary to estimate the long axis of the ridge instead of the tooth.



Mixed Dentition Survey
The full mouth survey for pediatric patients may vary, depending on the patient’s age, eruption pattern, behavior, and the size of the child’s mouth. In the six to nine-year-old group, a 12 film survey, using #1 narrow film is recommended, and would include:

• Maxillary:
• Central incisors
• Right and left lateral incisors and canines
• Right and left primary/permanent molars
• Mandibular:
• Central incisors
• Right and left lateral incisors and canines
• Right and left primary/permanent molars
• Bitewings:
• Right and left primary/permanent molars

An adult-sized periapical film is used in the posterior region if the child’s first permanent molar is fully developed.  The size of the tooth requires the use of a large periapical film to capture the complete image.

Pre-School Child Survey
Since pre-school children have smaller mouths, reduced size pediatric films (film size #0) are used to examine the posterior teeth, and adult films are used for anterior examinations in children who have only primary (deciduous or "baby") teeth.  For this group, an eight film survey is recommended.

• Maxillary:
• Central incisors
• Right and left primary molars
• Mandibular:
• Central incisors
• Right and left primary molars
• Bitewings:
• Right and left primary molars 
  

The paralleling technique should be used whenever possible.  This technique delivers the lowest dose of radiation possible.  The bisecting angle technique is a viable alternative for pediatric radiography because the apices of the permanent molar teeth tend to lie above the palate and below the floor of the mouth in the undeveloped mandible.  These positions prevent the image of the apices of the teeth from being projected into the oral cavity when the x-ray beam is perpendicular to the long axis of the teeth as it is when using the paralleling technique.

Quiz

1. What should be done before any radiographic examination?
2. What are the fundamental rules of radiography?
3. What is the purpose of the intraoral periapical examination?
4. What are the two primary techniques used in periapical radiography?
5. What is the primary purpose of bitewing radiographs?
6. What else can be accurately assessed with bitewings?
7. List five indications for taking occlusal radiographs.
8. What sizes of periapical films are commonly used in a dentulous adult survey?
9. Why should a radiographic examination be performed for a clinically edentulous patient?
10. How should film be positioned relative to the alveolar ridge?

Answers

1. A good clinical examination should be carried out before every radiographic examination.
2. The central beam should pass through the area to be examined and the x-ray film should be placed in position to record the image with the least amount of distortion.
3. To obtain a view of the entire tooth and surrounding structures.
4. Paralleling and bisecting angle technique.
5. The detection of caries in the early stages of development.
6. The detection of periodontal disease in the early stages.
7. Detection of pathological lesions; fractures of the mandible and maxilla; foreign bodies; salivary calculi; localizing unerupted teeth.
8. Number 1, 2 and 3 film.
9. It is commonly accepted that certain areas in the jaws may contain roots, impacted teeth, residual infections, tumors, cysts, etc.
10. The film should be placed with approximately one-third of the vertical dimension protruding beyond the alveolar ridge.

Vital Signs: Respiratory Rate

There  is  only  limited  research  relating  to monitoring  respiratory  rate,  and  these studies  focused  on  issues  such  as  the inaccuracy of respiratory rate measurement and  respiratory  rate  as  a  marker  for respiratory dysfunction. 

Inaccuracies  in  respiratory  measurement have  been reported in the literature. One study  compared  respiratory  rate  counted using a 15 second count  period, to  a full minute,  and  found  significant  differences in the rates. Respiratory rates measurement in children under five years, for a 30 second  or  60  second  period,  suggesting the 60 seconds resulted in the least variability. 

Another study found that rapid respiratory rates  in  babies,  counted  using  a  stethoscope, were 20% to 50% higher than those counted from beside the cot without the aid of the stethoscope. 

The value of respiratory rate as an indica- tor of potential respiratory dysfunction has been investigated but findings suggest it is of limited value. One study found that only 33% of people presenting to an emergency department  with  a  oxygen  saturation  below 90% had an increased respiratory rate. 

An  evaluation  of  respiratory  rate  for  the differentiation  of  the  severity  of  illness  in babies under  6 months found it  not  to be very useful. Approximately half of the babies  had  a  respiratory  rate  above  50 breaths per minute, thereby questioning the value  of having a "cut-off" at 50 breaths per minute as the indicator of serious respiratory illness. It has also been reported that factors such as crying, sleeping, agitation and age have a significant influence on the respiratory rate. As a result of these and  similar  studies  the  value  of  respiratory rate as an indicator of serious illness is limited.

Vital Signs: Pulse Rate

There  has  been  very   little  research evaluating the measurement of pulse rates. It  is  likely,  that  when  heart  rate  is  of concern,  cardiac  monitors  are  used  to determine not  only rate, but  also rhythm. The  role  of the "pattern of the pulse", for example  regular  pulse  versus  irregular pulse  or  strong  pulse  versus  weak  pulse, have not been addressed in the context of vital signs or patient observations. On this basis,  an  important  role  of  pulse  rate monitoring will likely be  to  identify when more advanced monitoring is required. 

Measurement  of  a  person's  pulse  rate  in the  presence  of  atrial  fibrillation  was evaluated  and  results  suggest  that  pulse rate,    measured    apically    using    a stethoscope for a 60 second count period, is likely to be the most accurate rate. This study  noted  that  86%  of  nurses  underestimated  the  pulse  rate,  and  that  as  the heart rate increased the magnitude of error also      increased.      Another      study recommended a 30 second count  period as the most accurate and efficient way of measuring  pulse  rate,  noting  that  the  15 second count time was the least accurate. A  third  study  found  that  there  was  no advantage in using the longer 60 seconds, over  the  15 or  30 second count  periods. These researchers suggest that counting an accurate pulse rate may be more difficult than commonly recognised. 

A study assessing infants apical pulse rate using a stethoscope, suggested that length of  time  may  not  be  the  primary  factor  in errors, and that like respiratory rate, pulse rate also appears to be influenced by infant states in addition to illness.

While these studies have identified that the accuracy  of  pulse  rate  measurements  is influenced by the number of seconds that the   pulse   is   counted,   the   clinical significance of these findings is unclear. The contradictory  findings  of  studies  suggest that  the  count  period  used  to  determine pulse rate is of only limited significance.

Vital Signs : Temperature measurement

The largest volume of research identified during the  literature search   addressed   various aspects     of      temperature measurement.  These  studies highlight  the  large  range  of methods  and  body  sites  that are used for the measurement of  temperature  (see  table three).  Because  of  the  volume of  research,  comparisons  of different  temperature measurement  methods  will  be summarised  as  a  separate systematic review. Summarised in  this  practice  information sheet  are  studies  addressing aspects of oral, rectal axillary and tympanic temperatures. 

General Issues

While  much  attention  has focused   on   measurement accuracy, one study evaluated touch as a screen for fever and found  that  while  mothers  and medical students overestimated the  incidence  of  fever  when using touch, they rarely missed its  presence  in  a  child.  The results  of  this  study  perhaps challenge  the  current  focus  of research  on  the  accuracy  of measurements  using  tenths  of a  degree,  when  simple  touch is  an  accurate  measure  for fever.  The  use  of  temperature as a discharge criterion for an ambulatory  surgical  unit  has been   studied,   but   results suggest  it  is  not  useful  in neither     rapid     or     deep differentiating  readiness  for Oral Temperatures Studies  evaluating  measurements from the different areas of the mouth recommend using either the right or left posterior sublingual  pocket,  as  these result   in   higher   recorded temperatures. 

Evaluation  of  the  impact  of oxygen    therapy    on    oral temperatures  have  reported contradictory results regarding its  statistical  significance, however  no  study  reported  a clinically  significant  effect. 

Similarly, different  rates  of oxygen flow, from 2 litres to 6 litres per minute, and warmed or  cooled  inspired  gas,  were found not to have an influence on oral temperature measurements.  Two  studies found  that  rapid  respiratory rates had a small influence on oral  temperatures,  but  these results  were  contradicted  by another   study   that   found breathing,     alone     or in combination, had any significant   effect   on   oral temperatures.

Studies   have   shown   that drinking hot or cold water has a    significant    impact    on recorded  oral  temperatures, and  it  has  been  suggested waiting 15 to 20 minutes after drinks  to  ensure  accuracy. Smoking does not change oral temperature measurements.

Researchers have evaluated the of the temperature accuracy time  required  for  mercury thermometers  to  accurately record   the   person's   oral temperature. One study found that with healthy adults, using a  two  minute  insertion  time resulted    in    27%    of    the temperature  readings  having an  error  of  at  least  0.3°C.  A study  assessing  thermometer insertion  time  in  afebrile  and febrile adults, suggested a six minute  insertion  time  as  a compromise  between  optimal time  and  clinical  practicality while another recommended a seven minute insertion time to ensure the majority of afebrile and  febrile  temperatures  are correctly recorded. However, a survey  of  nurses  showed  that most     left     the     mercury thermometer  in  the  mouth  for less than 3 minutes.

Axillary Temperature

There has been only limited re- search  focusing  on  axillary temperatures.   One   study evaluated axillary temperature measurements  in  elderly  females, and found great variation  between  individuals.

While  the mean axillary temperatures were approximately 36°C, the wide range of tem- peratures  encountered  prevented  the  identification  of  a single figure that could be considered  the  "normal"  axillary temperature.  Another  study evaluated  the  influence  of  intravenous infusions, via upper limbs of neonates, on axillary temperatures and found there was little significance in terms

Tympanic Temperature

There has been considerable research addressing tympanic temperature measurements ranging from the influence of infection and cerumen on measurement accuracy, to optimal technique. Studies have evaluated the impact of otitis media on tympanic temperatures and suggest it has little effect. While some studies have reported a statistically significant difference in tympanic temperatures between ears in people with unilateral otitis media, this difference was approximately 0.1°C and so of little clinical importance. The presence of cerumen  does  influence  tympanic  temperature  readings,  and  while  results  are  variable,  they  suggest  a significant  proportion  of the  temperature readings taken from  the occluded ear  will be  more  than 0.3°C lower than the ear that is not occluded.

Studies  evaluating  technique  suggest  an  ear  tug  should  be  used  during  the  measurement  of  tympanic temperatures, as this is reported to straighten the external auditory canal. Failure to use the ear tug means infrared thermometers are only partially directed at  the  tympanic membrane. The tug technique  in adults has  been described  as  pulling  the  pinna  (auricle  of  ear)  in  an  upward  and  backward  direction,  and  in infants it is pulling the pinna in a backward direction.

Evaluations  of  the  impact  of  ambient  temperatures  on  tympanic  temperatures  suggest  that  while  a  hot environment can significantly affect readings, cold appears to have little effect.

Cost  analyses of the different  temperature measurement methods suggest  infrared measurements may be the  most  cost  effective  despite  the  greater  initial  costs.  These  savings  are  the  result  of  the  rapid  reading capabilities of these instruments, and the labour cost savings that result.

Rectal Temperature

Many  studies  have  compared  the  different  methods  of  temperature  measurement,  and  commonly  rectal temperatures are used as the standard comparison. However, these studies will be summarised in a separate systematic  review.  The  most  common  reported issue  related  to  rectal temperature  measurement  is  that  of rectal perforation, which appears to be a risk primarily for the newborn and very young. Other reported complications include peritonitis secondary to rectal perforation, and one case of intra-spinal migration of a rectal thermometer in a two year old, which broke during routine rectal temperature measurement. A ten year  review of hospital records identified 16 children admitted to a surgical unit  with broken or  retained rectal thermometers. In response to this problem axillary temperature measurements have been recommended in  preference  to  the  rectal  measurements.  With  the  advent  of  infrared  tympanic  thermometers,  these complications are likely to become less common.

Vital Signs: Blood Pressure Measurement

Studies  addressing  the  measurement  of blood pressure with a sphygmomanometer have  focused on issues such as the  accuracy of indirect blood pressure, palpation versus  auscultation  cuff  size,  position  of arm during measurements and health care workers technique. 

Direct versus Indirect

Several studies have compared direct (intra-arterial)  and  indirect  (auscultation) measurements  of  blood  pressure.  There appears  to  be  little  significant  difference in  systolic  pressures  measured  by  either method,  with  differences  ranging  from  3 mmHg in two studies to 12mmHg in a third.

Differences in diastolic blood pressure are greater, and  are  influenced  by  the  refer- ence point that is used. When the phase V Korotkoff's sound is used (disappearance of the sound), both methods provide similar pressures. However when the phase IV Korotkoff's sound (muffling), is used, auscultated measurements are significantly greater  than  intra-arterial  pressures  (see table  one).  A  study  in  children  reported the use of either auscultation or palpation overestimated systolic pressure. See table two for current recommended practice for the measurement of blood pressure.

Palpation versus Auscultation

A comparison between systolic blood pressure  measurements  taken  by  auscultation and  palpation  found  both  were  within  8 mmHg. While palpation has been commonly limited to the measurement of systolic blood pressure,  one  study  reported  that  diastolic pressures could be accurately palpated using the brachial artery to identify the sharp phase  IV  Korotkoff's  sound,  However,  the value  of  this  technique  in  clinical  practice, and its accuracy when used by health care workers, has yet to be demonstrated.

Cuff Size

The length and width of the inflatable cuff (bladder)   that   is   used   during   the measurement of blood pressure may be a source of error. Much of the research has focused on  cuff  width,  (the  dimension across along the bladder) as the potential source of this error. The standard width of currently available cuffs is approximately 12cm, with both larger and smaller sizes also available. Studies have shown that the use  of  a cuff  that  is  too  narrow  results in an overestimation of blood pressure, and a cuff that is too wide underestimates blood pressure.  Length of cuff  appears  to  have little influence on accuracy.

For  obese  people  it  has  been  suggested that  large  cuffs  (15cm  width)  will  be required    when    the    person's    arm circumferences is between 33 -35cm, and a thigh cuff (18cm width) may be needed if  the  arm  circumferences  is  greater  than 41cm.  However,  difficulties  in  applying thigh cuffs to large arms have been reported. Cuff width may also be important when  measuring   blood   pressure   in neonates  and  a  cuff    width  equal  to approximately     50%     of     the     arm circumference has been recommended.

Arm and Body Position

Comparisons of blood pressures measured in  the  sitting  person  with  their  arm  supported  horizontally  or  with  the  arm  resting  at  their  side,  have  found  an average difference in systolic pressure of 11mmHg and diastolic pressure of 12mmHg. When the  arm  was  placed  above  or  below  the level  of  the  heart,  blood  pressure  measurements   changed   by   as   much   as 20mmHg. As a result  of  this, it  has been recommended  that  blood  pressures  be taken in the sitting position with arm supported horizontally at approximately heart level.

Bell versus Diaphragm

The accuracy of blood pressures measured with  the  bell  or  the  diaphragm  of  the stethoscope  have been investigated. One study  found  the  bell  of  the  stethoscope resulted  in  higher  readings  than  those taken using the  diaphragm. These  results were  supported  by  another  study,  with researchers recommending the use of the bell for all blood pressure measurements. 

Health Care Workers Technique

The  technique  used by  health care  workers  to  measure  blood  pressure  has  been shown to differ from recommended practice.  Using  the  American  Heart  Association Guidelines as the standard, one  study found that 57% of nursing students failed to  comply  with  these  guidelines  in  areas such  as  cuff  placement,  estimation  of systolic pressure by palpation, calculation of  proper  inflation  pressure,  and  proper stethoscope  placement.  Another  study  of 172  health  care  workers  concluded  that nurses  and  physicians  evaluated  blood pressure in an inadequate, incorrect and inaccurate way, and that only 3% of general  practitioners  and  2%  of  nurses  obtained reliable  results. Two studies evaluating  the  impact  of  education  programs on  blood  pressure  measurement,  found they increased agreement between the different  blood  pressure  readings  and  also significantly reduced differences in operator technique.

Limitations

A  descriptive  study  of  blood  pressures in critically  ill  patients  who  had  suffered  a cardiac arrest highlighted some limitations to these measurements. Of the 15 patients investigated,  5  patients  had  adequate intra-arterial   blood   pressures,   but unreadable  cuff  pressures.  Four  patients had  cuff  pressures  approaching  normal, but had an inadequate cardiac output. This study suggests that indirect blood pressure measurements  do  not  always  accurately reflect haemodynamic status of critically ill people.