X ray techniques and interpretations

DEPARTMENT OF PERIODONTICS

1. X-RAY TECHNIQUES AND INTERPRETATIONS T.HUDSON JONATHAN

2. Introdution Radiographic techniques -paralleling technique -bisecting angle technique Bitewing radiography Occlusal radiography Panaromic radiography CBCT(Cone Beam Computed Tomography) Magnetic resonance imaging Subtraction radiography Xeroradiography Digital radiography Radiographic assessment of periodontal condition Normal radiographic features of healthy alveolar bone CONTENTS

3. Radiographic appearance of periodontal diseases -horizontal bone loss -vertical bone loss -furcation involvement Chronic periodontitis Aggressive periodontitisa Periodontal abcess Nectrotizing ulcerative periodontitis Systemic disease affecting periodontium Limitations of radiographs in periodontal condition Conclusion Reference CONTENTS

4. X-ray is an electromagnetic wave of high energy and very short wave length,which is able to pass through many materials that are opaque to light. X-ray was discovered in 1895 by Wihelm conrad roentgen ( 1845-1923 ) who was a professor at wuzerberg university in germany. Working with a cathode ray tube in his laboratory,he observed a fluorescent glow of crystals on a table near his tube . Introduction

5. The tube that roentgen was working with consisted of a glass envelope(bulb) with positive and negative electrodes encapsulated in it. The air in the tube was evacuated and when a high voltage was applied,it produced a fluorescent glow. Roentgen shielded the tube with heavy black paper and discovered a green colored fluorescent light generated by a material located a few feet away from the tube. Roentgen also discovered that the ray could pass through the tissue of humans,but not bones and metal objects.

6. Intra oral - Paralleling technique - Bisecting angle technique Paralleling technique : - Patient preparation: Prior to starting to take flims,the patient must be positioned properly.Seat the patient and ask them to remove glasses and any removable appliances. Place the lead apron and thyroid collar on the patient and adjust the headrest to support the head while taking flims.Raise or lower the chair to a comfortable height for the operator. Radiographic techniques

7. The paralleling technique is accompained by placing the receptor parallel to the long axis of the tooth. After this parallel relationship has been established,the central ray must be directed perpendicular to both the tooth and the receptor . Because the receptor cannot always be placed as close as possible to the tooth due to flim holding device,image magnification may occur. It is said to be superior when performed correctly as it produce an image of linear and dimensional accuracy.To facilitate flim placement ,the flim may be tipped up to 20 degrees. Procedure

8. Paralleling technique

9. It has better dimensional accuracy as it results in less distortion. The alingment of x-ray beam is simplified. Due to positioning instrument,it is easier to standardize flims. Beacuse of paralleling instrument it is easy to align the x-ray beam irrespective of head position. Advantages

10. Less comfortable as the flim impinges on palate or floor of the mouth. More limited due to the anatomy of the palate or floor of mouth. Positioning the holder within the mouth can be difficult for inexperienced operators. The apices of the teeth can sometimes appear very near to the edge of the flim. Disadvantages

11. It is an alternative to paralleling technique for taking periapical flims.The paralleling technique is recommended for routine periapical radiography,but there are some instances where it is very difficult to patient anatomy or lack of co-operation. In this situation the bisecting angle technique is used.The flim can be held in the mouth with the thumb or index finger or a bisecting instrument may be used. In this technique x-ray beam is directed perpendicular to an imaginary line which bisects the angle formed by the long axis of the tooth and flim. Bisecting angle technique

12. Bisecting angle technique

13. Because of the flim placed at angle to long axis of the teeth,the flim doesn’t impinge on tissue as much,so it is more comfortable. Flim holder is not needed ,as patient can hold the flim using a finger. The flim can be angled to accomodate different anatomic situation using this technique. Advantages

14. Because the flim and teeth are angled to each other more distortion will occur. Patient acceptance of bisecting instrument is not much better than paralleling due to stress of finger retention. As there is basically no use of flim holder,it is difficult to visualize where x-ray beam should be directed. Flim is less stable as the retention is done using finger,which may cause chances of moving. Disadvantages

15. Bitewing radiography is used to detect interproximal caries and alveolar bone levels. The receptor is placed in the mouth parallel to the crowns of the maxillary and mandibular posterior teeth. The flim is stabilized as patient is asked to bite the tab or bitewing holder. The horizontal angle of the x-ray beam is then directed through the contacts of the posterior teeth at 5-10 degree. Bitewing Radiography

16. Receptors may be positioned in horizontal or vertical dimension with this technique,depending on the area to be examined. Bitewing may be taken in anterior segment as well.In periodontics it is prescribed to be of 4 vertical bitewing receptors posteriorly and 3 vertical bitewing receptors anteriorly . So it allows to evaluate both bone level and caries detection.

17. Bitewing radiography

18. Occlusal radiography is used to examine a large areas of upper and lower jaw.The palate and floor of the mouth may also be examined. It is generally taken as a supplementary radiography along with periapical and bitewing radiograph. The flims are bigger than IOPA as it has to cover the complete upper or lower jaw.It is of length 57mm and breadth 76mm. Occlusal radiography

19. The patient positioning is done prior to flim placement.Patient is seated such that the sagittal plane is perpendicular to floor and occlusal plane parallel to floor. The apron must be properly placed to avoid interference with the radiographic exposure. use a type 4 receptor with tube side of receptor toward the maxilla,the receptor is placed crosswise in the mouth like a cracker. The central ray is directed at an angle of +65 degree and a horizontal angulation of 0 degree. Technique

20. In maxilla it is used to view alveolar fractures, cyst, supernumerary teeth,impacted canines. In the mandible the image field includes buccal cortical plate,lingual cortical plate and teeth from 37-47. Projection of central ray is at the midline through the floor of mouth.It is approximately 3cm below the chin at 90 degree t o the receptor. The patient is placed tilted,that the occlusal plane is 45° above horizontal plane.Type 4 receptor is used with the tube of the receptor towards mandible.

21. Occlusal radiography

22. Salivary stones in the duct of submandibular gland. To evaluate the extent of lesions. Boundaries of maxillary sinus. Fracture of maxilla and mandible. Foreign bodies in maxilla and mandible. To examine cleft palate. Retained roots,supernumerary teeth,unerupted or impacted. Indications

23. Panaromic radiography or pantomography is a extra oral radiographic technique for producing a single tomographic image of the facial structures. It includes both maxillary and mandibular dental arches and their supporting structures in a single large flim. It is a curvilinear variant of conventional tomography,and is based on the principle of reciprocal movement of an x-ray source and an image receptor around a central point or plane called the image layer in which the object of interest is located. Panaromic radiography

24. Patient positioning: Remove all removable appliance,metallic objects, necklace, ear rings.Tongue and lip rings should also be removed if at all possible. Explain the procedure to the patient and make him/her to wear a lead apron without thyroid collar. The purpose of lead apron is to reduce the somatic exposure of radiosensitive tissues and minimize genetic exposure to the reproductive organs. The most radiosensitive regions of head and neck are thyroid and salivary glands.

25. The mid sagittal plane is positioned perpendicular to right angle to floor and centered right to left. The plane of occlusion is positioned parallel to the floor.The frankfort plane,tragal-canthus plane and ala-tragus are used to align the vertical position of the head. Anteroposterior plane is aligned with specific landmark that varies among panaromic machines.It is aligned between maxillary lateral and canine contact. Procedure

26. It is a technique of producing tomographic image by sectioning of the parts and simultaneous movement of x-ray tube head and flim cassette in opposite direction to produce the depth of the tissue. In the image the anterior part appears narrower than the posterior,so some patients seems to not match with it. Correct patient positioning is essential for optimal results.Image distortion occurs,when structures are anteriorly positioned which causes narrowing and when posteriorly positioned causes widening of image.

27. Panaromic radiography

28. For initial examination of new patients in all age groups that can provide required insight or idea in determining the need for other projections and general screening. In TMJ disturbances caused by malocclusion. In patients suffering from pain of unknown origin. In patients who are unable to open the mouth,with limited mouth opening,cannot tolerate intraoral radiography or patients suffering from severe gagging. Indications

29. To eliminate the presence of any underlying disease before complete or partial dentures are constructed. Suspected bony swelling or known large lesions and in cases of mandibular asymmetry. In patients with history of trauma to confirm or rule out the possibility of fractures,especially mandible. Before and after surgical intervention of lesions.

30. It is the most significant technological advancement in maxillofacial imaging.It is a form of x-ray computed tomography in which x-rays are divergent forming a cone. In this the 3D visualization of manifested disease or deformation gives diagnostic accuracy,which enables better understanding for planning of treatment. There are some technological factors that made it possible -The development of compact high quality flat panel detector arrays. -Reduction in the cost of computers capable of reconstruction CBCT(Cone Beam Computed Tomography)

31. -Development of inexpensive x-ray tube capable of continuous exposure. -Limited volume scanning. Specific application in dentistry CBCT technology has a substantial impact on maxillofacial imaging. It is not a replacement of panaromic or other radiographs but it should be considered as a complimentary for specific application.

32. Patient selection : There should be justification of the exposure to the patient, so that the total diagnostic benefits are greater than the individual determining the radiation may cause. Should be used only when a periapical or panaromic cannot provide necessary information for patient diagnosis and treatment planning. Cone beam computed tomography,should not be repeated routinely on a patient without a new risk/benefit assessment.

33. CBCT(Cone Beam Computed Tomography)

34. The more important of CBCT is of planning of dental implant placement which gives clear detail of that region. Ability to visualize the site of implant in the mesiodistal,faciolingual and superio-inferior dimensions. It has ability to allow reliable,accurate measurements. Capacity to evaluate trabecular bone dentisty and cortical thickness. Ability to determine axial orientation of the implant Gives cross sectional image of alveolar bone height, width,angulation and accuracy depicts vital structures such as IAN canal,sinus in maxilla. Implant assessment

35. Image accuracy Rapid scanning time Multiplanar reformating Better images with good spatial resolution E conomical,comfortable and safe Soft tissue assessment Assessing bone density Advantages

36. Magnetic resonance imaging was described by paul lauterbur in 1973 and peter mansfield further developed use of the magnetic field and developed for clinical use around 1980. To make a magnetic resonance image ,the patient is placed inside a large magnet.This magnetic field causes the nuclei of many atoms in the body,particularly hydrogen to align with the magnetic field. The scanner then directs a radiofrequency pulse into the patient,causing some hydrogen nuclei to absorb energy. Magnetic Resonance Imaging

37. When the RF pulse is turned off,the stored enery is released from the body and detected as a signal in a coil in the scanner. This signal is used to construct the magnetic resonance image,in essence a map of the distribution of hydrogen . It has an advantage of being non-invasive using non-ionizing radiation and making high quality images of soft tissues resolution in any imaging plane.

38. Because of its excellent soft tissue contrast resolution,MRI is useful for instance, the position and integrity of the disk in the condyle, for soft tissue disease especially neoplasia involving soft tissue such as tongue,cheek,salivary glands and neck determining malignant involvement of lymp nodes and determing perineural invasion of malignant neoplasia. Disadvantage include its high cost,long scan times and the fact that the various metals in the imaging field either will distort the image or may move in the strong magnetic field injuring the patient.

39. Magnetic Resonance Imaging

40. It is a method of imaging which uses the xeroradiographic coping process to record images produced by diagnostic x-rays. It is a method of x-ray imaging in which a visible electrostatic pattern is produced on the surface of a photoconductor. The xeroradiographic plate is made up of a 9 ½ to 14 inche sheet of aluminium,a thin layer of vitreous or amorphous selenium photoconductor,an interface layer,and an over cutting on the thin selenium layer. Xeroradiography

41. The XR plate is charged to high positive potential by corotron.It is then placed in a cassette and used in a manner similar to that with conventional flim in its cassette. A positive XR refers to image that is blue and white with blue representing dense areas. A negative XR refers to image that is blue and white but that has been reversed so that represents the dense areas.

42. Application: The radiography has found application in soft tissue imaging:in radiographic examination of the mammary glands,muscles,tendons and ligaments. The main advantage of xeroradiography include enhanced visualisation of the borders between images of different densities(edge effect),low contrast which enables differentiation between fat,muscle and bones.

43. Digital imaging is an method of imaging that creates an image that can be viewed or stored on a computer. Digital imaging incorporates computer technology in the capture,display,enhancement,and storage of direct radiographic images. Digital image offers some distinct advantages over film,but like any emerging technology,it presents new and different challenges for the practioner to overcome. Digital Radiography

44. Advantages: All the procedures can be visualised almost immediately. Any area of the picture can be enlarged . Provides necessary magnification. Good resolution. Conventional developing is not necessary. Bone pattern,its height and depth during implant placement can be visualised.

45. Most assessment of progressive alveolar bone loss in clinical practice today is achieved by interpretation ie visual comparision of radiographs taken over time. Unfortunately it is difficult to detect small changes that occur between examinations using interpretation because the radiograph contains a superimposed background of the teeth,cortical bone and trabecular bone. Digital subtraction radiography was introduced to dentistry in 1980’s.This technique is used to detect small changes in hard tissue that occur between examinations. Subtraction radiography

46. In brief,digital subtraction radiography uses specialized computer program to remove all structures that have not changed from a set of two x-ray flims taken at different examinations. This image processing procedure subtracts unchanging teeth,cortical bone and trabecular pattern leaving only the bone gain or loss standing out against a neutral grey background on the subtraction image. The area of change may be superimposed on the original radiograph to improve the ability of the clinician to interpret the subtraction image.

47. Additional software can determine the size,mass or density of the region of change.These technique have been shown to be more than 90./.sensitive and specific in determining small bony changes. More recently this quantitative method has been shown to co-relate highly with technique used to measure bone mass in medicine.

48. Subtraction radiography Pre-operative Post-operative

49. Radiographs are especially helpful in the evaluation of the following features. Amount of bone present. Condition of alveolar crest. Bone loss in the furcation area. Width of periodontal ligament space. Local irritating factors that increase the risk of periodontal disease. -calculus -poorly contoured or over extended restoration Radiographic assessment of periodontal conditions

50. Root length and morphology and the crown to root ratio. Open interproximal contacts which may be sites for food impaction. Anatomic considerations. -Position of maxillary sinus in relation to periodontal deformity. -Missing,supernumerary,Impacted and tipped. Pathologic considerations. -Caries,periapical lesion,root resorption.

51. Presence of thin evenly pointed margins in the interdental crestal bone in the anterior region.Anteriorly ,cortication at the top of the crest may not always be evident due to the small amount of bone present between the teeth. Presence of thin,smooth,evenly corticated margins in the interdental crestal bone in the posterior region. Interdental crestal bone is continuous with the lamina dura of the adjacent teeth,and the junction of the two forms a sharp angle. Loss of clarity or unsharpness of this angle may be an indication of periodontal involement. Thin even width of periodontal ligament space. Normal radiographic features of healthy alveolar bone

52. The direction of the bone loss or bone destruction is determined using the CEJ as the plane of reference.The bone destruction can be in the form of Horizontal bone loss :when the bone loss occurs on a plane that is parallel to a line drawn from the CEJ of a tooth to that of an adjacent tooth,it is called horizontal bone loss. Vertical bone loss :when there is greater degree of bone loss on the proximal aspect of one tooth than on the adjacent tooth,the bone level is angular or not parallel to a line joining CEJ.This type of bone loss is said to be vertical or angular bone loss. Radiographic appearance of periodontal diseases

53. Furcation involvement: Extension of periodontal pocket between the roots of multi-rooted tooth is called furcation involvement. Radiographs can be helpful in locating furcation involvement, however the furcation involvement cannot be seen unless the bone resorption extends apically beyond furcation.

54. It shows loss of corticated interdental crestal margin,the bone edges become irregular are blunted. Widening of PDL space at the crestal margin. Loss of normally sharp angle between crestal bone and lamina dura. Localised or generalised bone loss of alveolar bone. Loss of bone in furcation area of multi rooted tooth. Chronic periodontitis

55. In first molar region,radiographs shows localised deep pockets and vertical bone resorption that often is bilateral and symmetric. An arch shaped loss of alveolar bone extending from distal surface of second pre molar to the mesial surface of second molar is also seen.Similar involvement is apparently around the anterior teeth. There is usually a distolabial migration of the maxillary incisors with diastema formation. Clinically the patients are healthy except for periodontal disease and there is no association with any systemic disease. Aggressive periodontitis

56. A periodontal abscess often arises in a pre-existing periodontal lesion which is usually precipitated by alteration in the subgingival flora,host resistance or both. This is an acute exacerbation of a process occuring in a chronic periodontal pocket ,which may result from partial or complete occlusion of the orifice of the pocket,furcation involvement or diabetes. Radiographically,underlying bone changes may be indistinguishable from other forms of periodontal bone destruction. In an acute periodontal abscess there is no visible radiographic findings,and this is diagnosed clinically where the signs of acute inflammation and infection are evident. Periodontal abscess

57. Occurrence of an abscess in the buccal and lingual aspect shows a crater like radiolucency,which will make the root clearer in the affected area. In lateral periodontal abscess,it appears as a localised area of increased radiolucency with poorly defined margins. In the apical variety usually as a sequela of vertical bone loss,it appears as an area of increased radiolucency with hazy borders.

58. Necrotizing ulcerative periodontitis is similar to that of necrotizing ulcerative gingivitis,but it also shows loss of clinical attachment and alveolar bone. This destructive form of periodontitis may arise within the zone of pre-existing periodontitis or it may present a sequelae of single or multiple episodes of necrotizing ulcerative gingivitis. Patients affected are often younger than most patients affected with chronic periodontitis and often show immunosuppression and malnutrition. Necrotizing ulcerative Periodontitis

59. Systemic disease like hyperthyroidism,scleroderma,diabetes mellitus and esinophilic granules may show,refraction of bone and absence of lamina dura,which can mimic the appearance of periodontal disease. In scleroderma there is generalised widening of the periodontal ligament space. patient who are HIV positive and immunocompromised can present with distinct form of necrotizing gingivitis and periodontitis. Systemic Disease affecting periodontium

60. Radiography provides no direct evidence of the soft tissue involvement in gingivitis . However in severe cases of acute ulcerative gingivitis,where there have been extensive craters of the interdental papilla,inflammatory destruction of underlying crestal bone may be observed .

61. Radiograph provides a restricted two dimensional representation of the three dimensional anatomic structures. The changes that occur in the soft tissue cannot be preceived.They do not provide information about the health of soft tissues,presence of mucogingival defects or the position of the gingival marigin. The very earliest sign of periodontal disease cannot be detected radiographically,however this is possible by clinical examination. It is difficult to recognize any existing bony defects that are overlapped by existing bony walls on the resultant radiograph. Limitations of radiograph in periodontal condition

62. Periodontium can be considered healthy,when periodontal tissue exhibits no evidence of disease. Unfortunately this cannot be ascertained from radiographs alone.Dental radiographs must be used in conjugation with clinical examination to establish the existing condition. Clinical examination provides information about the soft tissue and radiographs permit evaluation of the hard tissues. Conclusion

63. Text book of oral radiology-white and paroah. Carranza clinical periodontology-12 th edition. Oral and maxillofacial radiology-kamal G pillai. Fundamental of periodontics-2 nd edition Thomas G,Wilson,Kenneth S.Kornman. Periodontics revisited-Shalu Bathla. Periodontology 2000 vol-73, 2017. References

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