radiographic aids in diagnosing periodontal diseases ,various types of radiographs indications and contraindications ,recent advancements

2. RADIOGRAPHIC AIDS IN THE DIAGNOSIS OF
PERIODONTAL DISEASE
PRESENTER – PUNIT
PG
DEPARTMENT OF PERIODONTICS

3. CONTENTS
1. INTRODUCTION
2. SELECTION CRITERIA
3. RADIOGRAPHIC ASSESSMENTS OF
PERIODONTAL CONDITIONS
4. INTRAORAL RADIOGRAPHY
5. LIMITATIONS OF RADIOGRAPHY
6. RADIOGRAPHIC DIAGNOSIS IN
PERIODONTITIS

4. 7. RADIOGRAPHIC CHANGES IN SYSTEMIC DISEASE
8. DIGITAL IMAGING
9. DIGITAL SUBTRACTION RADIOGRAPHY
10.TUNED APERTURE COMPUTED TOMOGRAPHY
11. COMPUTED TOMOGRAPHY
12. PRESURGICAL PLANNING
13.EXTRA ORAL RADIOGRAPHY
14.NEW FRONTIERS
15.CONCLUSION
16. REFERENCES

5. Limited number of major tools for the diagnosis of periodontal
disease Patient’s history
• Visual inspection
• Periodontal probing and
•Radiographic examination
It is a valuable aid in the
•Diagnosis
•Prognosis
•Evaluation of treatment outcome
Image – info. of calcified tissues
Only clinical correlation will result in a accurate diagnosis.
IMAGE NEVER MAKES A DIAGNOSIS, THE CLINICIAN DOES.
However, it is an adjunct to the clinical examination, not a
substitute for it.
INTRODUCTION

6. RADIOGRAPHIC ASSESSMENT OF PERIODONTAL
CONDITIONS
1. Amount of bone present
2. Condition of the alveolar crests
3. Bone loss in the furcation areas
4. Width of the periodontal ligament space
5. Local initiating factors that cause or intensify periodontal disease
• Calculus
• Poorly contoured or overextended restorations
6. Root length and morphology and the crown to root ratio
7. Anatomic considerations
• Position of the maxillary sinus in relation to a periodontal deformity
• Missing, supernumary or impacted teeth
8. Pathologic considerations
• Caries
• Periapical lesions
• Root resorptions

7. SELECTION CRITERIA
The necessity for radiographs and their quantity depend solely on the
patient’s
1. Clinical findings
2. Oral anatomy
3. Treatment planning goals
Simply put no radiograph should be exposed on a patient without performing
a thorough clinical examination.
The selection of radiographic projections, number of films, speed of film,
and settings on the X-ray source are all under the control of the clinician.
Proper selection will increase the likelihood of obtaining the required
diagnostic information while limiting the risk to the patient due to
radiation exposure.
Radiographic survey – 14 intraoral films and 4 posterior bitewing films

8. RADIOGRAPHIC IMAGE TYPES AND TECHNIQUES
INTRAORAL(TRANSMISSION) EXTRAORAL
PERIAPICAL BITEWING PANORAMIC VIEW
HORIZONTAL VERTICAL

9. ADVANCED TECHNIQUES
1. Digital radiography
2. Digital substraction radiography (DSR)
3. Computed assisted densitometric image analysis system (CADIA)
4. Computed tomography (CT)
5. Cone beam computed tomography (CBCT)
6. Local computed tomography
7. Optical coherence tomography
8. Indirect digital radiography or Computed radiography (CR)

10. FILM PLACEMENT AND BEAM ALIGNMENT
The teeth will be depicted in their correct positions relative to the alveolar process
when there is
(1) No overlapping of the proximal contacts between crowns,
(2) No overlapping of roots of adjacent teeth, and
(3) Overlapping of the buccal and lingual cusps of molars.
(4) Image of the crest as distinct radioopaque line.

11. With the teeth in a close approximation of their normal occlusion, the angulation used
(positive 7 to 10 degrees) is favorable to projecting the image of both the maxillary and
mandibular posterior teeth in their most parallel orientation.
BITEWING TECHNIQUE
Properly positioned and exposed bitewing radiographs (horizontal or vertical) are
considered mandatory in the periodontal "hard-tissue" assessment for most patients,
because of the characteristics outlined below:
1. The alveolar crest height is as accurately depicted as possible.
2. The relation of the cementoenamel junction (CEj) to the alveolar crest can be
accurately determined.
3. The presence of vertical bony defects can be demonstrated more precisely than with
periapical images.
4. Early crestal bone loss in the posterior dentition can be found more readily than with
periapical images.

12. BITEWING TECHNIQUE
ADVANTAGES
1. The alveolar crest height is as accurately depicted as possible.
2. The relation of the cementoenamel junction (CEJ) to the alveolar crest can be accurately
determined.
3. Early crestal bone loss in the posterior dentition can be found more readily
4. Radiation dose is reduced.
5. To some extent standardized
DISADVANTAGE
Limited view of the osseous crest
Limited view of entire tooth & surrounding region

13. INDICATIONS FOR PERIAPICAL RADIOGRAPHY
1) Detection of apical infection /inflammation
2) Assessment of the periodontal status
3) After trauma to the teeth and associated alveolar bone
4) Assessment of the presence and position of unerupted teeth
5) Assessment of root morphology before extractions
6) During endodontics
7) Preoperative assessment and postoperative appraisal of apical surgery
8) Detailed evaluation of apical cysts and other lesions within the alveolar bone
9) Evaluation of implants postoperatively.

14. PERIAPICAL TECHNIQUE
• vertical bony defects can be demonstrated
• assessing the crown-to-root ratio,
• root morphology,
• periodontal ligament spaces, and
• periapical status
The two types of images discussed, bitewing and periapical, are
complementary and both image sets most likely will be necessary for
patients with periodontal problems.

15. PURPOSE AND USE OF EXTRAORAL RADIOGRAPHY
• As adjunct for full mouth IOPA
• Evaluation of tooth development (mixed dentition)
• Assist and assess orthodontic treatment
• Evaluate location of 3rd molar
• Extensive disease – large lesions which cannot be seen in the intra oral
radiographs
• Evaluation of developmental anomolies,cysts,tumors
• Evaluation of fractures following trauma
• Assess underlying bone for pre and post prosthodontic treatment
• Initial evaluation image in determining the need for other projections

16. EXTRAORAL RADIOGRAPHY(Panoramic radiography )
Advantages
1. Image acquisition is relatively fast and simple
2. No need for any intraoral manipulation.
3. It shows all dentoalveolar structures in a single image at a dose that is
considerably lower than for an intraoral full-mouth series .
Disadvantages
1. Lingual structures will be projected higher on the film than buccal structures.
2. Patient-positioning errors represent one of the main sources of error in
panoramic radiography.
3. It is technique sensitivity also.
4. Makes it difficult to reproduce the imaging geometry at a later date.
5. Images show less image detail than intraoral images.
6. Structures outside the image layer are not completely removed , cause so-called
ghost images.

17. RADIOGRAPHIC ANATOMY OF THE PERIODONTIUM

18. INTERDENTAL SEPTUM AND CRESTAL LAMINA DURA
The interterdental septum,
located between the roots of adjacent teeth
therefore more clearly visualized than bone that is located on the buccal or lingual
aspect of the tooth
Shape function of the morphology of the contiguous teeth.
Convex teeth Flatter, less convex
wider interdental space narrower interdental space
broader septa of larger mesiodistal width "septal peak"
seen in the anterior regions
Loss of this architecture results in "blunting" or loss of septal height and may
indicate early periodontitis (although evidence of clinical attachment loss will
precede radiographically evident bone loss).

19. LAMINA DURA
1) The interdental septum normally presents a thin radiopaque border, adjacent to the
periodontal ligament and at the crest, that is referred to as the lamina dura.
2) This appears radiographically as a continuous white line
3) At the top of the crest, it is known as the crestal lamina dura.
4) It has been suggested that loss of the crestal lamina dura may correspond to
periodontal disease activity.
Greenstein and co-workers report that the crestal lamina dura is not significantly
related to any of a number of clinical periodontal parameters.
Absence of the crestal lamina is not indicative of current or impending disease
activity,
Presence of a crestal lamina dura may be associated with clinical stability.
5) Increased density of the crestal lamina dura has been reported after successful
periodontal therapy.

21. 1) Normally, the alveolar crest meets
the lamina dura at a right angle
when teeth are tipped,
the appearance of the crestal lamina may
mimic a vertical bone defect because of the
Improper vertical angulation CEJ is inferior to
Adjacent tooth creating an impression of vertical defect but in reality no defect.
2) A similar "CEJ discrepancy" can occur as a anatomic variation
Some people have a mesial tilt to the posterior teeth
vertical defects adjacent to the mesial surfaces of multiple teeth
Ritchey and Orban report that lines drawn between the adjacent CEJs should
parallel the crestal lamina dura, and this simple test will readily distinguish
true vertical defects from "pseudo-defects" caused by tooth angulation.

22. PERIODONTAL LIGAMENT SPACE
1) Thin radiolucent line interposed between the root and the radiopaque
line that outlines the root.
2) The width of the PDL has been considered important in the diagnosis
of various conditions, including occlusal trauma .
3) However, the PDL width varies with varying tube/film geometry and
exposure conditions and with root morphology.
4) Occlusal trauma may be manifested as a widening of the PDL space or
may present as a funneling of the coronal aspect of the PDL space.

23. LIMITATIONS OF RADIOGRAPHS
 A two-dimensional view of a three-dimensional situation.
 Bony defects overlapped by higher bony walls may be hidden
 Overlapping tooth structure
However, subtle changes in the density of the root structure (which is more
radiolucent) may indicate bone loss on the buccal or lingual aspect of the tooth.
Furthermore, use of multiple images made at different angulations, as in a full-
mouth set, allows the viewer to use the buccal object rule to obtain three-
dimensional information
 Radiographs typically show less severe bone destruction than is actually
present. The earliest (incipient) mildly destructive lesions in bone do not cause
a sufficient change in density to be detectable.
 Radiographs do not demonstrate the soft-tissue-to-hard-tissue relationships and
thus provide no information about the depth of soft tissue pockets.

24.  Bone level is often measured from the cementoenamel junction; however, this
reference point is not valid in situations in which either overeruption or severe
attrition with passive eruption exists.
 It is not possible to render a definitive periodontal diagnosis by means of a
radiograph.
For example,
1. Advanced periodontitis
good clinical response to therapy. minimal probing depths,
but the radiographic bone levels will likely remain largely unchanged after
treatment
It will be impossible to determine whether that individual requires further treatment
by examining post-treatment radiographs alone.
Conversely, serial radiographs taken at baseline (pretreatment) and at subsequent
appointments may reveal ongoing bone loss but only in the context of
supplementing the findings from the clinical examination.

25. 2) Endodontically involved mandibular molar
reveals radiolucency in the furcation region
no increase in probing depth or clinical attachment loss ,there has been no apical
migration of epithelial attachment, sulcus is not continuous with furcation area.
This is strictly an endodontic problem unless and until the sulcus becomes
continuous with the furcation.
Nevertheless, the radiographic image may mimic the appearance of significant
furcation involvement caused by periodontal destruction.

26. ADDITIONAL RADIOGRAPHIC CRITERIA IN THE DIAGNOSIS OF
PERIODONTAL DISEASE
• Radiopaque horizontal line across the roots. This line demarcates the portion
of the root where the labial and/or lingual bony plate has been partially or
completely destroyed from the remaining bone supported portion.
• Vessel canals in the alveolar bone.
Hirschfeld described linear and circular
radiolucent areas produced by interdental
canals and their foramina, respectively.

27. RADIOGRAPHIC DIAGNOSIS IN PERIODONTITIS
a. Bone Destruction in Periodontal Disease
slight radiographic changes in the periodontal tissues mean that
the disease has progressed beyond its earliest stages
The Earliest Signs Of Periodontal Disease Must Be Detected Clinically

28. The radiographic image tends to show less severe bone loss than that actually
present.
the difference between the alveolar crest height and the radiographic appearance
0 to 1.6 mm,
accounted for by x-ray angulation
b. Distribution of Bone Loss
The distribution of bone loss is an important diagnostic sign. It points to the location
of destructive local factors in different areas of the mouth.

29. d) Pattern of Bone Destruction
interdental septa may be reduced in height,
crest horizontal and septa may have a angular defect
perpendicular to the long axis
horizontal bone loss angular or vertical bone loss

30. Page & Schroeder (1982)
2.5 mm range of influence of the subgingival plaque
“when the bone surface has been resorbed to about 2.5mm apical or lateral to site of
bacteria, bone loss appears to cease and bone production takes over”
infrabony lesions seldom develop on the buccal surface
Tal (1984)
<2.6mm rarely infrabony defect seen
Interdental distance
>3.1mm infrabony defect seen

31. RADIOGRAPHIC CHANGES IN PERIODONTITIS
• Fuzziness and a break in the continuity of the lamina dura
• A wedge-shaped radiolucency
• The height of the interdental septum is progressively reduced by the extension of
inflammation and the resorption of bone.

32. RADIOGRAPHIC APPEARANCE OF CRATERS
appear as angular or vertical defects
• do not indicate the internal morphology or
• depth of the craterlike interdental defects
• do not reveal the extent of involvement on the facial and lingual surfaces
Reasons for this
1. Facial and lingual surface bone destruction is obscured by the dense root structure,
and
2. Bone destruction on the mesial and distal root surfaces may be partially hidden by
a dense mylohyoid ridge.
 A reduction of 0.5mm or 1.0mm in the thickness of the cortical plate is sufficient
to permit radiographic visualization of destruction of the inner cancellous
trabeculae.
 In most cases it can be assumed that bone losses seen interdentally continue in
either the facial or lingual aspects creating a troughlike lesion.

33.  Gutta percha packed around the teeth increases the usefulness of the
radiograph for detecting the morphologic changes of osseous craters and
involvement of the facial and lingual surfaces. However, this is a cumbersome
technique and is seldom performed.
 The true lesion can only be detected by clinically probing the defect.
 Surgical exposure and visual examination provide the most definitive
information regarding the bone architecture produced by periodontal
destruction.

34. RADIOGRAPHIC CHANGES IN LOCALIZED, AGGRESSIVE
PERIODONTITIS
Juvenile periodontitis is characterized by a combination of the following
radiographic features:
• Bone loss may occur initially in the maxillary and mandibular incisor and/or
first molar areas, usually bilaterally, and results in vertical, arc like destructive
patterns .

35. b. Loss of alveolar bone may become generalized as the disease
progresses but remains less pronounced in the premolar areas.

36. RADIOGRAPHIC CHANGES IN TRAUMA FROM OCCLUSION
Trauma from occlusion can produce radiographically detectable changes in the
 lamina dura,
 morphology of the alveolar crest,
 width of the periodontal space, and
 density of the surrounding cancellous bone

37. PHASES OF TRAUMA FROM OCCLUSION
The injury phase
a loss of the lamina dura that may be noted in apices,
furcations, and/or marginal areas. The loss of lamina
dura results in widening of pdl space.
The repair phase
attempt to strengthen the periodontal structures
widening of the periodontal ligament space
More advanced traumatic lesions
result in deep angular bone loss when combined with
marginal inflammation lead to intrabony pocket.

38. RADIOGRAPHIC APPEARANCE OF PERIODONTAL ABSCESS
Abscess is that of a discrete area of radiolucency along the lateral aspect of the root .
However the radiographic picture is often not typical
• In the early stages presents no radiographic changes.
• The extent of bone destruction and the morphologic changes of the bone.
• The location of the abscess – lesion in the soft tissue wall of periodontal pocket
less likely to produce radiographic changes

39. FURCATION DEFECTS
Etiology
 periodontitis
 endodontic infection,
 root perforation during dental procedures, or
 occlusal trauma.
These changes are most readily seen in the mandibular molar region.
Maxillary molars have three roots, early change in their furcation areas are more
difficult to assess.
But 30% to 55% of grade 2 or 3 furcation involvements have a
furcation arrow present on the radiograph.

40. Diagnostic criteria are suggested:
• The slightest radiographic change in the furcation area should be investigated
clinically, especially if there is bone loss on adjacent roots .
• Diminished radiodensity in the furcation area in which outlines of bony
trabeculae are visible suggests furcation involvement.
• Whenever there is marked bone loss in relation to a single molar root, it may
be assumed that the furcation is also involved .

41. ROOT MORPHOLOGY
The radiograph is the only method, short of direct observation, of visualizing the
morphology of the roots.
Radiographic parameters help in clinical significance:
 length of the root trunk
 root length,
 root divergence/convergence
 root resorption, and
 root shape
 gemination or fusion
 root dilacerations

42. OPEN CONTACTS
a. When the mesial and distal surfaces of adjacent teeth do not touch, the patient
has an open contact. This condition is potentially dangerous to the
periodontium.
b. Similar potential situations in which periodontal disease may develop include
discrepancies in the height of two adjacent marginal ridges or tipped teeth.
LOCAL IRRITATING FACTORS
a. Calculus
b. Overhanging restoration margin

43. SKELETAL DISTURBANCES MANIFESTED IN THE JAWS
a. Osteitis fibrose cystica (Recklinghausen's disease of bone) develops in
advanced primary or secondary hyperparathyroidism and causes osteoclastic
resorption of bone with fibrous replacement and hemorrhage with hemosiderin
deposition, creating a mass known as brown tumor.
b. In Paget's disease, the normal trabecular pattern is replaced by a hazy, diffuse
meshwork of closely knit, fine trabecular markings, with the lamina dura
absent, or scattered radiolucent areas may contain irregularly shaped
radiopaque zones.
c. Fibrous dysplasia may appear as a small radiolucent area at a root apex or as an
extensive radiolucent area with irregularly arranged trabecular markings. There
may be enlargement of the cancellous spaces, with distortion of the normal
trabecular pattern ("ground glass" appearance) and obliteration of the lamina
dura.

44. d. Langerhans cell Histiocytosis they appear as single or multiple radiolucent
areas, which may be unrelated to the teeth or entail destruction of the tooth
supporting bone.
e. In osteopetrosis (marble-bone Albers-Schonberg disease) the outlines of the
roots may be obscured by diffuse radiopacity of the jaws. In less severe cases
the increased density is confined to the bone in relation to the nutrient canals
and the lamina dura.
f. In scleroderma, the periodontal ligament is uniformly widened at the expense
of the surrounding alveolar bone.

45. PRESURGICAL PLANNING FOR PLACEMENT OF IMPLANTS
Before surgical intervention, it is necessary to know the location of vital structures
that may be in proximity to the surgical site.
Many implant protocols call for a certain minimal space (e.g., 2 mm) between the
apical extent of the osteotomy site and any vital structure, such as the
mandibular canal.
Because this type of surgery often involves placing implants in relatively close
proximity to such structures, it is necessary to know the vertical and horizontal
magnification of the radiographic image.

46. DIGITAL RADIOGRAPHY
There are currently two competing technologies available for the implementation of
digital imaging. One uses solid-state detectors, the other photostimulable
phosphor

47. Digital imaging offers a number of advantages compared to film.
• The elimination of chemical processing is considered one of the main benefits.
• Shorter exposure-to-display time.
• Integration with existing electronic office and patient-management systems.
• Image processing can be used to enhance the perceived quality, either to
restore the subjective quality of the image as a whole or to enhance a selected
region in the image for a specific diagnostic task.
• Furthermore, the software offers a variety of measurement tools, most of
which are digital versions of existing analog tools.
• The benefits of digital imaging are obtained along with a reduction in radiation
exposure, although the amount of exposure reduction is dependent on the type
of receptor.

48. ADVANCED DIAGNOSTIC TECHNIQUES
Most assessment of bone loss in clinical practice today is achieved by visual
comparison of the radiographs.
The radiograph contains so much information that it is difficult for the human eye
to detect small changes in bone support in the presence of a busy background
containing the teeth and bone.
Studies have shown that a 30% to 50% change in bone mineral is needed to be
visible even to the experienced clinician.
Techniques have been developed that enhance our ability to “see” small changes
over time in the bone. These include
• Digital Substraction radiography
• Computer assisted densitometric image analysis

49. DIGITAL SUBTRACTION RADIOGRAPHY (DSR)
Zeidses des Plantes (1935) : 1st demonstrated use of
subtraction imaging
 Depends up on conversion of serial radiographs into digital
images.
 The serially obtained digital images are superimposed &
image intensities of corresponding pixels are subtracted
If change has occurred
The brighter area represents gain
Darker area represents loss

50. CONCEPT OF DSR
• When two images of the same object are registered and the image intensities of
corresponding pixels are subtracted, a uniform difference image will be
produced.
• If a change in the follow-up image has occurred, this change will show up as a
brighter area when the change represents gain and as a darker area when the
change represents loss.
• The strength of DSR is that it cancels out the complex anatomic background
against which this change occurs.

51. d. Subtraction images allow detection of mineral changes of as little as 5%. In
addition to early detection, a number of quantitative measurements can be
made, such as linear, area, perimeter and density measurement.
e. An early technical challenge in DSR was the requirement that the consecutive
images be closely aligned for an accurate comparison to be made. This was
accomplished using custom stents and other devices that made the technique
less practical.
f. For clinical use recent technologic enhancements have enabled
compensation for imprecision in placement, thereby allowing for the accurate
"superimposition" of the images, which is required for DSR. This has made
DSR much easier, and it is widely used in periodontal research. However, the
technique is still not commonly used by clinicians.

52. Overall contrast is
improved
Trabecular marrow
spaces are visualized
Enhancement of low
and high density
no objective description
High standardization of x
rays
No reduction in exposure
ADVANTAGES DISADVANTAGES

53. COMPUTER ASISTED DENSITROMETRIC IMAGE
ANALYSIS SYSTEM
Introduced by Urs Brägger et al 1988
 A video camera measures the light transmitted through
the a radiograph
 Signal are converted to grey scale images
 Camera is interfaced with computer and image
processor for storage and mathematic manipulation of
image
 Offers an objective method for studying alveolar bone
changes quantitatively
 High degree of sensitivity ,accuracy and reproducablity

54. Advantages
Objective method – Quantitative measurements
Higher sensitivity
reproducibility
Higher accuracy
Urs Brägger et al in 1988
 CADIA was more sensitive than subtraction radiography
 CADIA was capable of assessing differences in
remodeling activity over 4–6 weeks after periodontal
surgery
Objective method to quantify alveolar bone density

55. CONVENTIONAL X-RAY TOMOGRAPHY
PRINCIPLE
 Designed to image a slice or plane of tissue
 It consists of an x ray tube and radiographic film rigidly connected which
moves about a fixed axis and fulcrum
 As exposure begins tube and film move in opposite direction
simultaneously .
 Objects located with in the fulcrum remain in fixed positions and are
viewed clearly
ADVANTAGES
Offers true cross sectional images of the alveolar ridge
Useful during placement of single or multiple implants
LIMITATIONS
Blurring of structures on either side of focal plane
Time required for reposition of the patient for every image.
Cost is higher

56. COMPUTED TOMOGRAPHY
PRINCIPLE
A thin fan-beam of X rays rotates around the patient to generate in one revolution
a thin axial slice of the area of interest.
Multiple overlapping slices are obtained
With the help of a computer a 3 D digital map of the jaws is the advantage of the CT.
ADVANTAGES
1. Three dimensional
2. Precise detailed information
3. Images can be adjusted and printed without magnification.
4. Vertical & horizontal rulers adjacent to each image.
5. Digital format
6. Bone & soft tissue contrast
7. Excellent resolution

57. CT Image construction
Computer algorithms use photon counts to construct
digital images
Images are displayed in individual blocks -----VOXELS
Each square of the image is matrix----PIXELS
Each pixel is assigned a CT number representing tissue
density
CT number HOUNSFIELD units
Range -1000 to 1000

58. DISADVANTAGES
• Requires specialised equipment
• Much higher radiation dose to the patient
• Metallic restorations can cause artifacts.
• Cost is significantly high.

59. CONE BEAM COMPUTED TOMOGRAPHY (CBCT)
 Developed in 1982 for angiography
 Utilizes cone shaped source of ionizing radiation & 2D area detector fixed
on a rotating gantry .
 Multiple sequential images are produced in one scan
• Rotates 360° around the head
• Scan time typically < 1 minute

60. CT V/S CBCT
 Conventional CT scanners
make use of a fan-beam and
Provides a set of consecutive
slices of image
 Conventional CT makes use of
a lie-down machine with a
large gantry.
 Greater contrast resolution &
More discrimination between
different tissue types (i.e. bone,
teeth, and soft tissue
 Utilize a cone beam, which radiates
from the x-ray source in a cone
shape, encompassing a large
volume with a single rotation.
 a sitting-up machine of smaller
dimensions
 Commonly used for hard tissue
 Ease of operation
 Dedicated to dental
 Both jaws can be imaged at the
same time
 Lower radiation burden

61. TUNED APERTURE COMPUTED TOMOGRAPHY (TACT®)
The motivation behind the development of TACT® was to be able to achieve 3 D
with existing dental equipment and without the high cost and dose associated
with computed tomography.
PRINCIPLE
TACT® is built on the basic principles of tomosynthesis: by shifting and
combining a set of basic projections, arbitrary slices through the object can be
brought into focus.
The basic projections are conventional transmission radiographs. Each radiograph
is taken from a different angle relative to the object and the receptor.
Ongoing research seeks to further improve this technology and determine optimal
parameters for various clinical applications.

62. OPTICAL COHERENCE TOMOGRAPHY
 Optical coherence tomography (OCT) generates cross-sectional images of
biological tissues using a near-infrared light source.
 The light is able to penetrate into the tissue without biologically harmful
effects.
 Differences in the reflection of the light are used to generate a signal that
corresponds to the morphology and composition of the underlying tissues.
 The feasibility of its clinical use was demonstrated by capturing high-
resolution images of oral structures, including soft tissue and hard tissue
boundaries of the periodontium.
 While it is yet too early to judge the potential success of OCT as a routine
clinical tool, the initial results warrant keeping an eye on further developments
of this technology.

63. CONCLUSION
a. Radiographs can provide critical information for diagnosis and treatment
planning, which can also serve as baseline information for the assessment of
treatment outcomes.
b. Commonly used modalities include bitewing, periapical and panoramic
radiography.
c. One of the main limitations is the two-dimensional representation of three-
dimensional structures.
d. There also needs to be a substantial amount of mineral loss (30–50%) before
bone resorption can be detected. These limitations reduce the sensitivity of
conventional radiography and generally result in underestimating actual bone
loss even when high quality images are produced.
e. Misdirection of the central ray of the X-ray beam as well as exposure and
processing errors further limit accuracy.
f. The radiograph and clinical periodontal examination complement one another.
Neither is sufficient by itself, but together they can provide a sound
foundation for diagnosis and treatment planning.
g. Despite certain limitations, the conventional dental radiograph is an
indispensable adjunct in diagnosis and treatment planning.

65. REFERENCES
1. Carranza’s Clinical Periodontology 10th Edition.
2. Oral Radiology – White & Pharoah
3. Periodontics Medicine, Surgery,and Implants - Rose, Mealey
4. Periodontology 2000, vol-34, 2004, 34-48.
5. Clinical practice of dental hygienist, 9th edition, Wilkin’s
6. Fundamentals of periodontics – Wilson & Korman
7. Advances in periodontics – Wilson, Korman
8. Diagnosis & risk prediction of periodontal disease - Axelsson

66. KEY POINTS