Figure 13 . Cervical burnout visible on premolar teeth . |
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B |
Figure 14 . A : Mach band effect under coronal restoration . This appears as a thin radiolucent line following the restoration shape exactly . There is also extruded root filling material shown at the apex of the retained UL1 root . B ): Mach band effect around the post of this coronal restoration . |
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Figure 15 . Superimposition of zygomatic arch ( Black arrow ).
Superimposition of the floor of the maxillary sinus ( white arrow ).
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Figure 16 . Superimposition of the floor of the maxillary sinus ( white arrow ) and the floor of the nasal cavity ( black arrow ) showing the “ Y line of Ennis ”.
Figure 17 . Mental foramen ( black arrow ) lying inferior to the apicies of the premolars . There is a periapical radiolucency associated with the root filled LL7 .
Figure 18 . Nasopalatine foramen ( black arrow ) lying adjacent to the apices of the central incisors . .
Cervical Burn out / Mach band effect A radiolucent shadow is often evident at the neck of the teeth where no carious lesions are visibly present . It is an artefactual phenomenon called cervical burnout . At the cervical edge of the tooth , there is an area of dentine not covered by either enamel or alveolar bone . In this area , attenuation of the x-ray beam will be comparatively lower than the adjacent areas giving this area a relative radiolucent appearance . It can be distinguished from cervical caries by careful interpretation of the radiographic image . The “ lesion ” should be located at the neck of the tooth with its lines of demarcation being the enamel / restoration on one side and the alveolar bone level on the other , it is triangular in shape as the “ lesion ” progresses to the more attenuating centre of the tooth . Usually , all the teeth on the radiograph will be affected . ( Fig 13 )
The optical illusion that can be of particular confusion in interpretation of dental radiographs is the Mach Band effect . This is where there is a sharply defined density difference and there appears to be a more radiolucent region immediately adjacent to an area of radiopacity ( e . g . under a restoration ). This optical illusion can often be misinterpreted as secondary caries and incorrect interpretation can lead to overtreatment . In the case where there are no clinical signs of a lesion except the radiolucent line under a restoration , it is reasonable to monitor the area . ( Fig 14 )
NORMAL ANATOMY It is important to be aware of the normal anatomical appearance of areas within the mouth to avoid confusing normal anatomy with a pathological diagnosis . Some areas where clinicians may confuse normal anatomy with pathological appearances are shown in the following images . ( Fig 15,16 , 17 , 18 )
CONCLUSION Dental radiographs are of great use in the diagnosis and treatment of dental disease . However as with every radiological investigation the benefit of this exposure must outweigh the risk of ill effects of radiation . The benefit of the radiograph is correlated directly to the information the clinician can garner from it therefore careful interpretation of every radiograph must occur . Radiographic interpretation combines the clinician ’ s knowledge of how “ normal ” anatomy appears , detecting “ abnormal ” appearances and recognising the pathology that would likely cause this appearance . Radiographic interpretation must be combined with clinical history and careful examination of the patient to ensure accurate diagnosis .
MARK VINER , FCR , MSC , HDCR , DIPHSM , DIPFMS , DIPFHID , MCFS , CERTRP . SENIOR TUTOR – RADIOGRAPHY BARTS & THE LONDON SCHOOL OF MEDICINE & DENTISTRY , QUEEN MARY COLLEGE , UNIVERSITY OF LONDON
l M��� h�� ��e� 33 �e���� experience as a radiographer , radiology manager and NHS senior manager in London Teaching Hospitals . Throughout his career he has been actively involved in radiography education , as a visiting lecturer at a number of UK universities and presenting at national and international conferences . He took up the position of part time Senior Tutor in Dental Radiography in 2014 .
�e h�� � ��e��fi� ���e�e�� �� de���l & forensic imaging and forensic h���� �de���fi������ ��d h��
authored a number of papers and book chapters on the subject . He is co-editor of the second edition of ����d���� ���e���� ��d������h� and is a founder board member of both the International Association of Forensic Radiographers and The International Society of Forensic Radiology & Imaging .
He has extensive experience of forensic and archaeological radiography and disaster victim �de���fi������� �e h�� �d���ed �he �� ���e �ffi�e � G��e���e�� �ffi�e f�� ���d��� The ����ed Nations International Criminal
Tribunal for the Former Yugoslavia , The UN Special Tribunal for Sierra Leone and is currently radiography advisor to the Forensic Team of the UN International Criminal Court .
He has been awarded the Fellowship of the College of Radiographers , The Gold Medal of the Society & College of Radiographers and a Winston Churchill Fellowship .
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