Dental radiography can be used to detect alveolar bone levels around periodontal and peri-implant structures. Periodontal radiographic images can assess alveolar bone height, periodontal ligament, furcation involvement, and evidence of bone destruction. Peri-implant radiographic images can assess the alveolar bone height in relation to the implant structure. As an adjunct to patient care, radiography can aid in the diagnosis of non-health.
Key points
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Radiographs can be use to aid with identifying sites of periodontal and peri-implant health, nonhealth, and progression of disease.
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Radiographs can monitor evidence of changes in the underlying alveolar structures, because this indication can aid in the diagnosis of a site of nonhealth.
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Accepted forms of radiographic assessment of periodontal and peri-implant hard and soft tissues include periapical and bitewing radiographs and cone beam computed tomography.
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The progression from a state of health to periodontitis and peri-implantitis can present as radiographic bone loss, which may be site specific and pattern specific, depending on the etiology.
Introduction
In the field of periodontics, radiography can be used to detect alveolar bone levels with respect to the pattern and extent. Crestal bone levels and osseous defects can be measured from the cementoenamel junction (CEJ) to the crest of the alveolar bone and from the CEJ to the osseous defect base, respectively. Through radiographs, the periodontal ligament (PDL) space, periapical region, and lamina dura can be viewed and are adjunctively useful to help identify risk factors, such as defective restorations and calculus. The value of radiographs for periodontal disease diagnosis lies in the ability to estimate severity and degree of progression, determine prognosis, and evaluate treatment outcomes. Radiographs, however, cannot replace the need for clinical examinations. Through radiographs, calcified tissue changes can be visualized. Although they cannot detail cellular activity, they can show the effects of previous cellular experiences with the bone and roots. Radiographs provide crucial diagnostic and treatment planning information to serve as baseline information from which an assessment of treatment outcomes can be prognosticated. An understanding of the advantages and disadvantages of diagnostic imaging, however, as well as the cost and benefits is needed. This involves an appropriate prescription for radiograph type and quantity in order to optimize the effects of radiographs on treatment outcomes. The adaption of digital imaging as a type of radiographic assessment has the ability to change the way periodontal tissues are visualized.
Periodontal radiograph techniques
Currently, periapical and bitewing radiographs have been used widely to form the basis of radiographic diagnostic information. This combination is used for the evaluation of periodontal diseases in conjunction with a clinical examination. Using these images, clinicians can assess the status of the periodontal bone and predict prognosis and diagnosis accurately. Features, such as the relative alveolar bone height, PDL space around teeth, and bone destruction pattern, can be observed from radiographic images. Alveolar trabecular pattern, radiodensity, and contours of interdental bone can vary, however, depending on x-ray angulation and type of film. The bisection-of-angle technique distorts an anatomic structure’s true appearance because it elongates the radiographic image. As a result, the level of the facial bone becomes distorted compared with the lingual, and alveolar bone margin may appear closer to the anatomic crown of the tooth. Horizontal angulation errors that occur result in overlapping tooth images, changes in radiographic PDL space width, and distortion of furcation involvement. In an attempt to avoid these errors, Prichard proposed four criteria for adequate angulation of periapical graphs. These include the following: (1) periapical radiograph should show cusps of molars with occlusal surface, (2) enamel and pulp chambers should be seen and distinct, (3) interproximal spaces should be open, and (4) contacts between adjacent teeth should not overlap unless teeth are out of line. Following these guidelines will help reproduce and standardize reliable radiographs for treatment.
Normal interdental bone
The basis of bone change evaluation in periodontal disease is based mainly on the appearance of the interdental alveolar bone. Radiographically, this is the main observation because the root structure overlaps and obscures both the facial and lingual alveolar bone structure. Interdental bone normally is represented by a radiopaque line, which is located at the alveolar bone margin and adjacent to the PDL. A change in the angulation of an x-ray beam, however, produces changes in appearance. The interdental alveolar crest varies due to the convex anatomy of tooth surfaces and the location of the CEJ. The horizontal width of the bone relative to the width of the proximal root surface also is a factor that causes variation. It is more common for the angulation of the interdental crest to form a parallel line similar to that formed by the CEJs of adjacent teeth ( Figs. 1–5 ). In some radiographs, this may result in an angulated appearance of the interdental bone. In certain periodontal conditions, such as medication-induced gingival hyperplasia, radiographic bone presentation appears normal or abnormal. The clinical presentation, however, demonstrates pathology ( Figs. 6 and 7 ).
Radiographic appearance of periodontal disease
The destruction of alveolar bone in periodontitis has some generalizable characteristics. These features may be present alone or in combinations. Typically, there is disruption of lamina dura. Fuzziness of crestal aspect of the alveolar bone may be present. This appearance is a result of resorption due to the advancement of gingival inflammation to the periodontal bone. The presence of crestal lamina dura also may indicate periodontal health. The radiographic feature of periodontitis recognized most commonly is the reduction in height of bone due to increasing osteoclastic activity. The interdental septum height is reduced due to the resorption of bone. The wedge shape at the interproximal aspects of the crest is created via the widening of the periodontal space, which is apically pointed toward the root. Lastly, a widening of periodontal space creating a wedge shape at the interproximal aspects of the crest. The apex of the wedge pointed apically toward the root.
The surface architecture of the alveolar bone in periodontal disease that was once thought to be of a linear pattern now has been described as “complex” with the advancement of imaging and diagnostic modalities. The visualization of this topology is crucial for both diagnostic and treatment planning. For example, certain areas, such as interradicular areas, are more prone to loss of bone with increasing likelihood during disease progression. As a result, the treatment options vary accordingly. The clinician decides whether or not periodontal osteoplasty surgery with or without ostectomy is appropriate. As a result, bone regeneration would be beneficial and prove to have a positive and predictable outcome. Although the decision for bone regeneration is determined once a surgical flap has been raised for clinical visualization, the advancements of radiological imaging modalities have proved useful in this regard. Two-dimensional imaging has its limitations; portraying a 2-dimensional structure in a planar perspective, visualization of the architecture cannot be predicted as accurately as three-dimensional imagery.
Bone destruction in periodontal disease
The earliest signs of periodontal disease can be detected only clinically due to specific features of early periodontal disease and the limitations of radiographic imaging. Radiographs are unable to capture the initial destructive alveolar bone changes. Once there is evidence of some structure changes, however, this is an indication that the disease may have progressed beyond the initial stages of periodontal disease. According to Thomas, radiographic imaging underestimates bone loss severity. The range of variation may be up to 1.6 mm of difference when observing alveolar crest height. This is apparent especially during angulation of radiographs. Radiographs aid the clinician’s determination of the remaining bone amount rather than bone loss, indirectly determining the amount of bone loss in periodontal disease. The clinician estimates the amount of bone from the height of the remaining bone to the approximated original physiologic level of the alveolar crest. In some cases of periodontal disease, the location and distribution of periodontal disease may result in a particular diagnosis. To reach a particular diagnosis, radiographic evidence of bone loss around similar locations in different areas of the mouth and at particular surfaces of teeth. This has been included localized periodontal disease, such as Stage III, grade C, localized periodontitis in an adolescent patient where there is an incisal-molar pattern of bone loss ( Fig. 8 ).
Furcation involvement
A complex aspect of periodontal radiograph is the diagnosis of disease of teeth with furcation involvement ( Figs. 9 and 10 ). The extent of periodontal disease involvement with furcated teeth is important in determining therapy. Decisions related to the extent and morphology of bone loss can change a potential treatment from a regenerative therapy to tooth extraction, followed by implant placement. The combination of clinical evaluation and radiographic imaging often provides the clinical with information to make the proper diagnosis and plan. Clinical examination with a specific furcation detection probe, such as the Nabers, is used to definitively diagnose furcation involvement. Radiographs may aid this diagnosis; however, due to some limitations, such as improper positioning, anatomic variations, and root superimposition, a furcation may not be visible on a radiograph image. A tooth may appear bifurcated at one angle; however, when adjusted, it may not appear; therefore, it is recommended that radiographs should be taken at different angles to increase the chances of observing a furcation involvement. Walter and colleagues recommend the guideline for assisting furcation detection with radiographs. First, a radiographic observation of furcation should be evident clinically, using a probe, especially if there is no evidence of adjacent root bone loss. The reduction in radiodensity of a proposed furcation area may suggest a furcation involvement of the teeth. Lastly, the investigators noted that a marked bone resorption at the site of a single molar root suggests that there may be a furcation involvement.
Pattern of bone destruction
The progression of periodontal disease results in physiologic changes of interproximal bone. Such physiologic changes include the different height and contour of the alveolar bone, size and shape of the alveolar medullary space, and the radiodensity of alveolar crest. The height of interdental bone inevitably reduces as disease progresses. The patterns of interdental bone loss could be horizontal, angular, or vertical. There are limitations of radiographic imaging, however, which cannot determine the depth of crater defects as well as the buccal and lingual surface bone destruction. Additionally, if superimposed, mesial and distal bone destruction of a tooth may not be observed. Bone loss, however, interdentally tends to continue on buccal and lingual surfaces. This interdental bone loss forms a trough-like defect that can be difficult to observe in radiographs. Deep craterlike defects may not be observed in radiographs if there are dense plates of interdental bone on buccal and lingual plates. According to Svärdström and Wennström, to allow for sufficient visualization of inner cancellous trabecular bone, a 0.5-mm to 1.0-mm thickness of cortical plate is needed. The classification of periodontal diseases recently has been revised to follow criteria related to progression, complexity, extent of disease, time, tooth loss, and systemic modifiers. According to the American Academy of Periodontology/European Federation of Periodontology 2017 classification, periodontal diseases and condition have been modified to a multidimensional staging and grading system. The staging and grading of periodontitis begin with mild bone attachment of loss (stage 1) before progressing to a more severe form with attachment loss equal to or greater than 5 mm and to loss of 5 or more teeth (stage IV) ( Figs. 11–16 ). Health and gingivitis are not included as classification categories.
