Periodontics. Fernando Suarez

that can be obtained through radiographic examination includes subgingival calculus deposition, root length and form, crown-to-root ratio, presence of periapical lesions, periodontal ligament space, root proximity, and the destruction of alveolar bone.^2,7

      Clinicians should keep in mind the following limitations of conventional dental radiography when interpreting radiographs during the examination phase^3,7,25:

       Radiographs do not show periodontal pockets.25

       Radiographs cannot distinguish between posttreatment periodontitis and active periodontitis.25

       Radiographs do not show buccal and lingual aspects of tooth and alveolar bone.25

       Radiographs cannot detect tooth mobility.25

       Radiographs can provide evidence of past destruction to the periodontium, but they cannot identify sites with active or ongoing periodontal inflammation.7

       Clinical attachment loss always precedes visual radiographic changes by approximately 6 to 8 months, and clinical attachment variations are greater than radiographic changes.26

       Radiographic changes are detectable by simple visual inspection when approximately 30% to 50% of the bone mineral has been lost.27

      The presence or absence of the crestal lamina dura is another common interpretation of radiographs for diagnosing periodontitis. Rams et al²⁸ observed that the presence of intact crestal lamina dura is positively correlated to periodontal stability over a 2-year follow up period. However, no significant relationship could be found between future periodontal breakdown and lack of crestal lamina dura.²⁸ A recent publication by Rams et al also reported similar findings and concluded that patients with angular bony morphology and PD greater than 5 mm poses a significant risk of periodontitis progression after treatment. However, if intact crestal lamina dura is present, despite the bony morphology, clinical stability for at least 24 months can be anticipated.²⁹ Also, molar furcation involvement can sometimes be observed on radiographs. Hardekopf et al were the first to describe the radiographic features of maxillary molars with furcation destruction: a triangular radiographic shadow, commonly known as “furcation arrow,” can be noted over the mesial and distal proximal areas of maxillary molars.³⁰ The clinical reliability of the presence of furcation arrow can be subjective and also greatly dependent on the degree of destruction. For instance, when furcation arrows are present on radiographs, these can only predict actual furcation invasion 70% of the time. On the other hand, when there is true furcation involvement, a furcation arrow is seen in less than 40% of the sites.³¹ It has been reported that the presence of furcation arrow for diagnosing furcation involvement on maxillary molars has a low sensitivity (38.7%) and high specificity (92.2%).³¹ When mandibular molars suffer from furcation involvement, radiolucency can be noted at the area where roots start to separate.

      In recent years, the utilization of CBCT has been rapidly increasing in popularity. CBCT has become an integral tool for researchers and clinicians, mostly applied to the implant field. As such, the use of CBCT imaging for the diagnosis of periodontitis has also been studied. However, in 2017, the American Academy of Periodontology reported that even though its use may be beneficial in selective cases, there is limited evidence to support the use of CBCT for the different types of bony defects, and there are no guidelines for its application to periodontal treatment planning.³²

      Advanced and Emerging Examination

      Periodontitis is a multifactorial disease involving the combination of dysbiosis of oral bacteria and an overreacted immune response from the host.³³ One of the disadvantages of the clinical periodontal evaluation is that these examinations only record destruction that has already occurred, such as the bone loss pattern and periodontal pockets. Therefore, patients would greatly benefit from techniques that detect the development of periodontal inflammation before tissue breakdown occurs and prevent further complications such as bone loss, tooth mobility, and ultimately tooth loss. The major rationale to develop advanced methods for examination is to detect disease activity at a subclinical level in order to provide early diagnosis and create a treatment plan tailored to each individual.³⁴

      Researchers and scientists have been investigating possible periodontitis-related biomarkers that could be used to distinguish between healthy and diseased patients.³⁴ These biomarkers can be collected from saliva, which can demonstrate overall periodontal health at a subject level, or gingival crevicular fluid, which is site specific.³⁴ For instance, proportions of specific periodontal pathogens, pro- and anti-inflammatory cytokines, and tissue-degradation products have all been studied to differentiate between healthy and periodontitis subjects. Among all biomarkers, interleukin-1 (IL-1) is one of the most notable proinflammatory cytokines that has been extensively studied in the periodontal field.^34,35 Periodontal pathogens that have been extensively studied and proved to be closely linked to the development of periodontitis include Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, and more.^2,36 Research in the field of advanced examination and biomarkers is still ongoing, and the results have indicated a promising future for early detection of periodontitis. However, these examinations are still not routinely utilized, due at least in part to the additional costs and disassociation to treatment options (ie, the test results would not alter the treatment plan).³⁴

      Classifications of Periodontal Diseases and Conditions

      Classification systems are essential to properly study the diagnosis, etiology, pathogenesis, and treatment of the different diseases. As such, the field of periodontology has witnessed the creation and continued update of different classification systems since the early 1940s. The first World Workshop in Periodontics³⁷ was held in Ann Arbor, Michigan, on June 6 to 9, 1966, and the most recent World Workshop took place in Chicago on November 9 to 11, 2017, with the related publications released in June 2018.³⁸ Understanding the development and the variations among the different classifications is critical for comprehending the literature published in different eras.

      1989 WORLD WORKSHOP IN CLINICAL PERIODONTICS

      One of the first major and comprehensive classifications of periodontitis emerged from the World Workshop in 1989.³⁷ On this date, the World Workshop in Clinical Periodontics gathered scientists and researchers to develop a classification for periodontal diseases. There were essentially five different classifications, which are listed in Box 2-3.³⁷

BOX 2-3 Classification proposed in 1989 World Workshop in Clinical Periodontics³⁷

Adult periodontitis (> 35 y)Early-onset periodontitis (≤ 35 y)Prepubertal periodontitis (< 13 y)GeneralizedLocalizedJuvenile periodontitis (13 to 26 y)GeneralizedLocalizedRapid progressive periodontitis (25 to 35 y)Periodontitis associated with systemic diseasesNecrotizing ulcerative periodontitisRefractory periodontitis

      Under the 1989 classification system, age of onset and distribution of lesions were taken into consideration for classifying adult periodontitis and early onset periodontitis as well as the subforms of early-onset periodontitis that included prepubertal periodontitis (generalized/localized), juvenile periodontitis (generalized/ localized), and rapidly progressive periodontitis.³⁷

      1999 INTERNATIONAL WORKSHOP FOR A CLASSIFICATION OF