Table of Contents

Title Page

Copyright Page

Foreword

Acknowledgements

Chapter 1 Panoramic Radiography: History and Future Development

Aim

Outcome

Introduction

Development of the Technique

Panoramic Equipment Using an Intraoral Source of Radiation

Panoramic Equipment Using an Extraoral Source of Radiation

Further Developments

Digital Imaging

Charged Couple Device (CCD)

Photostimulable Phosphors (PSP)

Conclusion

Acknowledgements

Further Reading

Chapter 2 Dental Panoramic Radiographic Technique

Aim

Outcome

Introduction

Panoramic Image Formation

Tomography

Slit Beam Imaging

Image Magnification

Dental Panoramic Technique

Practical Procedures

Preparation

Radiography

Further Reading

Chapter 3 Anatomy

Aim

Outcome

Introduction

Hard Tissues

Mandible (Fig 3-1)

Maxilla, Antrum, Nasal Skeleton, Zygoma and Temporal Bone

Other Bony Structures

Soft Tissues

Air Shadows

Ghost Shadows

Further Reading

Chapter 4 Radiation Dose and Risk in Panoramic Radiography

Aim

Outcome

Introduction

The Biological Effects of Panoramic Radiography

Radiation Units

Measurement of Dose

Effective Dose and Risk in Panoramic Radiography

How Can We Reduce Dose to Our Patients?

Constant Potential (‘direct current’) X-Ray Generation

Field Limitation Techniques

The Use of Rare-Earth Screens

Digital Panoramic Systems

The Risks Associated with Panoramic Radiography

Conclusion

Further Reading

Chapter 5 The Use of Panoramic Radiography in General Dental Practice

Aim

Outcome

Introduction

The Development of Clinical Guidelines

The Limitations of the Panoramic Image

Magnification Variations

Overlap of Adjacent Teeth

Superimpositions

Diagnostic Accuracy and Efficacy of Panoramic Radiography

How do we Assess Radiographic Accuracy?

The Diagnostic Value of Panoramic Radiography for Common Dental Pathosis

Caries Diagnosis

Periodontal Disease

Periapical Inflammatory Pathology

The Diagnostic Value of Panoramic Radiography for Other Pathology

Prior to Oral Surgery

The Detection of Facial Fractures

Sinus Disease

Identification of Systemic Disease

The Assessment of Temporomandibular Joint Pathology

Conclusions

Routine Screening by Panoramic Radiography

Panoramic Radiography for the New Adult Patient

Edentulous Patients

Panoramic Radiography within Orthodontic Practice

Panoramic Radiography in Implantology

Conclusions

Reference

Further Reading

Chapter 6 Quality Assurance in Panoramic Radiography

Aim

Outcome

Introduction

How to Overcome Problems of Poor-Quality Images

Identifying the Problem - A Reject Film Analysis

How can we Improve Panoramic Film Quality?

Producing a DPR

Stage 1: The Darkroom

The dedicated dark room

Safe lights

Desktop processors

Film storage and film type

Cassettes

Stage 2: Operator Technique

Preparing the patient

Positioning the patient

Stage 3: X-Ray Equipment and the Image Receptor

X-ray equipment

The image receptor

Stage 4: Film Processing

Manual processing

Automatic processing

Monitoring of film processing

Stage 5: Viewing the Radiograph

Reporting of radiographs

Conclusions

Further Reading

Chapter 7 Radiographic Interpretation of Disease

Aim

Outcome

Introduction

Image Formation

Principles of Radiographic Interpretation

So How Should One Examine a DPR?

Use appropriate viewing conditions

Be familiar with the normal panoramic image

Assess image quality (see Chapter 6)

Examine the radiograph systematically

Familiarise yourself with disorders of the jaws

Relate what you see to the clinical findings

Use previous radiographs

Disorders of the Teeth

Hypodontia

Hyperdontia

Impacted Third Molars

Nature of impaction

Status of crown

Root morphology (Fig 7-5)

Association with the inferior alveolar (dental) canal

Other features to assess

Maxillary Canines

Radiographic assessment should include:

Dentinogenesis Imperfecta

Clinical features

Radiographic features

Periodontal Disease

Disorders Affecting the Jaws

Well Defined Radiolucencies of the Jaws

Radicular Cyst

Clinical features

Radiological features

Dentigerous Cyst

Clinical features

Radiological features

Odontogenic Keratocyst

Clinical features

Radiological features

Residual cyst

Clinical features

Radiological features

Ameloblastoma

Clinical features

Radiographic features

Solitary (Traumatic) Bone Cyst

Clinical features

Radiographic features

Stafne Bone Cavity

Radiographic features

Ill-Defined Radiolucencies of the Jaws

Osteomyelitis

Clinical features

Radiological features

Malignant Tumours

Mixed Density and Radiopaque Lesions of the Jaws

Sclerosing Osteitis

Radiographic features

Osteosclerosis (Dense Bone Island)

Osteoma

Bony Tori and Bony Overgrowths

Odontomes

Radiographic features

Fibrous Dysplasia

Cemento-Ossifying Lesions

Periapical Cemento-Osseous Dysplasia and Florid Cemento-Osseous Dysplasia

Clinical features

Radiological features

Cemento-Ossifying Fibroma

Clinical features

Radiological features

Trauma

Disorders in the Soft Tissues

Salivary Duct Calculi

Clinical features

Radiographic features

Calcified Lymph Node

Tonsilloliths

Foreign Bodies

Disorders of the Maxillary Sinus

Root Displaced Into the Maxillary Sinus

Clinical features

Radiographic features

Oro-Antral Fistula (OAF)

Clinical features

Radiographic features

Root-Filling Material

Radiological features

Mucous Cysts of the Maxillary Antrum

Clinical features

Radiographic features

Carcinoma of the Maxillary Sinus

Clinical features

Radiographic features

Disorders of the Temporomandibular Joint

Further Reading

Cover

Quintessentials of Dental Practice – 20
Imaging – 2

Panoramic Radiology

Authors:

Vivian E Rushton

John Rout

Editors:

Nairn H F Wilson

Keith Horner

cover
Quintessence Publishing Co. Ltd.

London, Berlin, Chicago, Paris, Milan, Barcelona, Istanbul, São Paulo, Tokyo, New Delhi, Moscow, Prague, Warsaw

Foreword

Panoramic radiology is extensively used in everyday clinical practice. It is therefore important that both existing and future practitioners are fully familiar with this imaging technique, the interpretation of panoramic images and very importantly, the indications and clinical justifications for such extraoral imaging. Practitioners using panoramic radiology must also have knowledge of relevant radiation doses, risks to patients and quality assurance protocols.

Panoramic Radiology, Volume 20 in the timely Quintessentials for General Dental Practitioners series, addresses all of these issues and, in addition, gives a great deal of practical guidance on panoramic radiology as it ought to be applied by practitioners. As with all forms of radiological examination each and every panoramic image should have a net benefit for the patient, with the exposure to ionising radiation having been optimised for the intended purpose. This excellent, succinct, generously illustrated book will assist practitioners in satisfying this requirement in relation to panoramic radiology.

As all members of the dental team should play their respective parts in ensuring the safe, appropriate and effective use of panoramic imaging, this book should find its way into the practice environment for all to study and use to good effect. An excellent addition to all practitioner and practice collections of reference texts.

Nairn Wilson
Editor-in-Chief

Acknowledgements

We would like to thank our respective families and colleagues for their help and encouragement during the writing of this book and also those patients whose clinical radiographs are integral to a book of this nature.

Chapter 1

Panoramic Radiography: History and Future Development

Aim

The aim of the chapter is to present an overview of the development of dental panoramic radiography during the past century.

Outcome

After studying this chapter, the reader should have a clear understanding of the historical development of panoramic radiography and of the more recent technological advances in panoramic image production, including digital imaging techniques.

Introduction

Dental panoramic radiography is a radiographic technique that produces an image of both jaws and their respective dentitions on a single extraoral radiographic film. The development of panoramic radiographic equipment represented a major innovation in the field of dental imaging as, prior to this, dental radiographic images consisted solely of intraoral and oblique lateral projections of the jaws taken using a conventional dental x-ray set.

Today panoramic radiographic equipment is found routinely both within most hospital radiology departments and in a high proportion of general dental practices. It has been estimated that around 60% of United Kingdom dentists have direct access to panoramic equipment. A similar level of use has been reported in other parts of the industrialised world.

Development of the Technique

In the early part of the 20th century, many researchers were developing techniques using movement of the x-ray tube and the film in order to visualise structures or foreign bodies (particularly bullets) situated within the patient. Andre Bocage, a French researcher, was the originator of the principles of body-section imaging. In Bocage’s seminal work, patented in 1922, the author mentions the possibility of imaging curved surfaces such as the jaws.

Further interest in this field of research did not resurface for another 20 years and resulted in the development of x-ray equipment using two quite different radiographic techniques to produce an overall image of the jaws. One group of researchers developed a small x-ray source which, when positioned intraorally, would directly expose an x-ray film moulded to the outside of the patient’s face. The other group relied upon the production of a tomographic image of the jaws with the tube positioned extraorally, combined with either an intraorally or an extraorally positioned film.

Panoramic Equipment Using an Intraoral Source of Radiation

Bouchacourt first proposed the possibility of using an intraoral source of radiation to image the jaws as early as 1898. This concept was finally developed almost half a century later when two separate groups of researchers applied for patents to develop intraoral panoramic equipment. These were, in 1943, the German company of Koch and Sterzel (Fig 1-1), followed in 1951 by the Swiss researcher Dr. Walter Ott. Dr. Sydney Blackman, a British radiologist, modified the principles proposed by Dr. Ott, leading to the commercial development by Watson and Sons Ltd. of the ‘Panograph’ panoramic equipment (Fig 1-2).

QE20_Rushton_fig002.jpg

Fig 1-1 Patent issued to the Koch and Sterzel Aktiengesellschaft of Düsseldorf, Germany, for x-ray equipment capable of imaging body cavities. Horst Bergen is named as the inventor of the equipment.

QE20_Rushton_fig003.jpg

Fig 1-2 Panograph intraoral panoramic unit showing the slender x-ray tube.

Intraoral panoramic equipment used a cone-shaped anode located at the end of a thin rod (Fig 1-2) with a focal spot (the source of the x-ray beam) that was extremely small (ca. 0.1 mm) compared to conventional x-ray equipment. The intraoral technique had several inherent problems. It was extremely time-consuming, requiring separate exposures for both the maxilla and mandible (Fig 1-3). The technique also resulted in severe geometric distortion and, more importantly, delivered high doses of radiation to the oral tissues, notably the tongue. Paradoxically, these factors appeared not to have deterred the development of an intraoral panoramic unit that relied upon a radioactive isotope as its source of radiation. Fortunately, common sense prevailed and further experimentation with this type of intraoral panoramic equipment was rapidly curtailed, not least because of the obvious radiation risk but also the cost of the isotope.

QE20_Rushton_fig004.jpg

Fig 1-3 Panograph intraoral panoramic unit. Patient positioned with the anode intraorally and the maxillary film moulded to face.

Further development of the intraoral type of panoramic equipment centred upon improving patient comfort and reducing image distortion. An eccentric positioning of the x-ray tube was an attempt to improve the latter; however, the problems of geometric distortion proved insurmountable. Finally, the unacceptable dose level delivered by this type of equipment led to legislation within the United Kingdom recommending its withdrawal from clinical practice.

Panoramic Equipment Using an Extraoral Source of Radiation

The records of the American Patent Office show that in 1922, a patent was issued to A.F. Zulauf for ‘Panoramic X-ray Apparatus’ (Fig 1-4). The equipment used a rotational narrow beam x-ray technique that scanned either the upper or lower jaw with an intraorally positioned waterproofed lead-backed film packet to receive the image. The x-ray generator was moved manually around the patient on a mobile carriage supported on a U-shaped table using a preformed track. The researcher clearly understood the principles of image production but also its limitations. Zulauf stressed that the exact speed of movement was ‘determined by experience and depends on the strength of the x-rays, the width of the collimator and its distance from the teeth being shadow-graphed’. While this patented design must qualify as the earliest example of rotational panoramic radiography, no further details concerning the subsequent development or the clinical use of the equipment have been found.

QE20_Rushton_fig005.jpg

Fig 1-4 Patent of rotational x-ray equipment issued to A.F. Zulauf in 1922. Upper diagram is a side view elevation of the equipment. Figures 4 and 5 (on the patent document) are the top and front views, respectively, of the x-ray collimator.

During the early 1930s, several researchers were active in pursuing and developing methods of imaging ‘curved’ structures such as the jaws. Numata proposed and discussed the principles of the panoramic technique as early as 1933, while at the same time constructing a suitable device for the clinical examination of the jaws. Numata’s prototype used a very narrow collimated beam of x-ray photons, often referred to as a slit beam. The x-ray equipment rotated around the patient’s head with the film positioned intraorally in the lingual sulcus.

Two researchers, Vieten and Heckmann, expounded the theoretical principles of imaging ‘curved’ structures without the superimposition of neighbouring structures. Both researchers experimented with a rotational slit beam technique to expose a film, but it was Olsson who refined the principles of an x-ray tube moving simultaneously to the detector, which is positioned behind the structure to be imaged.

In 1946, Dr. Yrjö Veli Paatero of the Institute of Dentistry, University of Helsinki, Finland, carried out similar work to that previously described by Olsson, although apparently unaware of this earlier research. The literature credits Paatero with developing and constructing the first working prototype of an extraoral rotational panoramic unit. The design of this unit was similar to that proposed by Numata in 1933. Paatero’s prototype positioned the film intraorally, requiring a separate film for each jaw. The equipment used a stationary slit collimated x-ray beam which scanned the teeth and jaws by manually rotating the patients around the x-ray source as they sat in the dental chair.

Further research by Paatero in 1949 resulted in the development of a single axis or concentric rotational panoramic system. This system incorporated a curved extraoral film cassette (Fig 1-5) rather than the time-consuming and uncomfortable intraoral placement of the image receptor. The equipment continued to use a slit collimated x-ray beam with the patient and the curved extraoral film cassette rotating around a stationary x-ray source, with the film exposed through a vertical slit. The method of exposure consisted of rotation of the patient in front of a stationary x-ray tube as the film was translated behind the vertical slit to achieve a sequential exposure.

QE20_Rushton_fig006.jpg

Fig 1-5 Patent 2,684,446 for an apparatus for x-ray photographing curved surfaces, issued to YV Paatero in 1954. The schematic shows how the equipment relied upon a cog wheel (10) to move the cassette holder (14) along with the curved cassette (5). The stationary x-ray source (6) is easily seen as is the lead shield labelled 16. The crank (7) rotated the chair either by hand or via an electric motor.