Conventional panoramic oral radiographs
Modern panoramic oral radiography achieves decent images suitable, with perhaps only modest intra-oral supplementation, for periodontal treatment planning purposes. The differences in any “yield”, even with an older generation of panoramic radiograph machines and technology, in comparison with periapicals,29 and bitewings,30 and bitewings and periapicals,31 and periapicals and clinical probing32 were small, and for newer panoramic radiograph technologies difference in any “yield” are apparently even smaller.33 Panoramic radiography in a group of periodontal maintenance patients, that is patients previously affected by periodontal disease which had been treated and who were undergoing supportive periodontal care, showed “great agreement” with long cone intra-oral radiographs.34 Two of the recent reviews1,6 have dealt with the issue of paralleling periapical series versus panoramic oral radiographs. The features of interest for periodontal assessment noted on periapical radiographs are also capable of being noted on panoramic radiographs (Table 5). For many practitioners the radiographic features of interest on a panoramic, supplemented where necessary by a small number of intra-oral views, is sufficient for the management of periodontal diseases. Tugnait and Camichael6 note how there has been a pragmatic shift by many towards panoramic radiographs in the investigation of patients with periodontal diseases, in view of time efficiency, greater patient tolerance, and often a lower radiation exposure. Cost savings are also more and more an issue, and while the machinery for panoramic oral radiography is not cheap, it is nowadays relatively cheaper than formerly, and the time taken for producing a full-mouth periapical series is a costly investment if there is little by way of yield.
Table 5. (after Tugnait et al.1). Detectable features of interest on radiographs
| – even||Yes||Yes|
| – angular||Yes||Yes|
|Radio-opaque restorative margins||Yes||Yes|
| – deficiency||Yes||Yes|
| – overhang||Yes||Yes|
|Root length embedded in alveolar bone||Yes||Yes|
|Widened periodontal ligament space||Yes||Yes|
|Approximal root caries||Yes||Yes|
|Root canal fillings||Yes||Yes|
|Periapical periodontitis, cysts, granulomas||Yes||Yes|
|Impacted third molars||Yes||Yes|
The American Academy of Periodontology (AAP) in its 2000 Parameter on Comprehensive Periodontal Examination35 holds that “radiographs that are current, based on the diagnostic needs of the patient, should be utilized for proper evaluation and interpretation of the status of the periodontium … Radiographs of diagnostic quality are necessary for these purposes”. It further states “Radiographic abnormalities should be noted”.35 Panoramic radiographs fulfil these conditions (Table 5) and allow for the identification of radiographic abnormalities. The point made by the AAP that there should be some record made of what was detected on the radiographs is advice given in many jurisdictions. While available, the radiograph(s) reveal all that can be discerned, but if the radiograph(s) is(are) not available for whatever reason, then having some written record of the findings should obviate the need for any additional repeat radiograph to compensate for the temporary unavailability of the radiograph(s). The AAP in its 2001 Position Paper on “Guidelines for periodontal therapy”36 holds that “interpretation of a satisfactory number of updated, diagnostic quality periapical and bitewing radiographs or other diagnostic imaging needed for implant therapy” is required. The AAP contends that intra-oral radiographs, such as periapical films and vertical or horizontal bitewings, provide a considerable amount of information about the periodontium that cannot be obtained by any other non-invasive means.37 Panoramic radiographs certainly do provide a considerable amount of information (Table 5) and they also inform on treatment planning. The situation of the AAP becomes clear on viewing the AAP website* (“Search Our Site”: “Panoramic” in the gateway to “Members Only” AAP Insurance Policy Statement – Radiographs in Periodontics), where it is stated: “The American Academy of Periodontology believes that panoramic radiographs have limited value in the diagnosis of periodontal disease …” This, however, is only a “belief”. A casual view of the world reveals that not all share the same beliefs. The authors of this review do not share the same belief as the AAP. The expense, time and physical inconvenience in having all periodontitis patients subjected to a full-mouth series of periapical and bitewing radiographs on the basis of a belief can be questioned, as it is in this review. The American Board of Orthodontics is more reasonable in its advice, only requiring six intra-oral radiographs to supplement a panoramic view for adults for comparison of pre-treatment and post-treatment crestal bone levels and root status.38 One earlier study shows how dearly belief systems with respect to full-mouth periapical surveys can be held.39 In this American study, the proportion of patients who had the results from a screening clinical examination and a panoramic radiograph but who were still judged by independent examiners to be in need of full-mouth periapical series was the same as for those patients who only had the clinical screening results. In that study, patients were slated by the examiners for the full-mouth series of periapical radiographs on the basis of the case type into which they fell. Recommendations for the full-mouth periapical radiograph series was made on the basis of case type, and information available from the panoramic was not used because in the examiners’ opinions that particular case type demanded the full-mouth periapical series, because it seems that was what they had been taught. When dental teaching hospitals in the United Kingdom and Ireland were surveyed,40 the most commonly taken views to assess periodontal status were panoramic radiographs with selected periapical radiographs. Hopefully, graduates from these dental schools will follow their teaching, while constantly evaluating the state of knowledge and experience in this field and being prepared to change practice as new evidence emerges.
Further, panoramic radiographs have been shown to reveal in a majority (63 per cent) of periodontal patients some form of dental abnormality unrelated to periodontal disease.41 General radiologists in Australasia have had recent advice on the interpretation of dental panoramic radiographs42 and should thus be available for consultation, as would be other dental specialists in Australia, if abnormalities detected were to be out of the ordinary.
Panoramic radiographs may not reveal alveolar bony defects as accurately as periapical radiographs.43,44 However, that is not the issue. The issue must be whether there is any additional therapeutic yield from any greater accuracy in representation of alveolar bone destruction revealed on periapical radiographs.
A small study was conducted in Hong Kong in which part-time clinical dental teachers were asked to develop periodontal treatment plans on the basis of, in the first instance, a complete periodontal charting, study casts and a panoramic radiograph. The 35 patient records chosen were of adult patients with, what would now be diagnosed as, chronic periodontitis and who had at least six teeth per quadrant. After a one-year wash-out period, the same clinical records camouflaged, and study casts were given along with, on this second occasion, not the panoramic radiograph but a full-mouth series of paralleling periapical radiographs which at the time of the charting had been prescribed by a dental surgeon in the clinic in compliance with his previous teaching. The individual treatment plans derived on the first and second occasion were almost identical. Between examiners there was variation in treatment plans regarding periodontal surgery, as has been reported from elsewhere,45 and extractions. However, each individual part-time clinical dental teacher developed almost identical treatment plans from clinical findings and panoramic radiographs (of an earlier generation) as they did from the clinical findings and the full-mouth paralleling periapical radiograph series. Hence, there was no perceptible “therapeutic yield” from the additional full-mouth periapical radiograph series, such as that shown in Fig 4.
The full-mouth series of periapical radiographs shown in Fig 4 is mounted on a clear, not a traditionally black, background. The Australian Safety Guide for Radiation Protection in Dentistry20 suggests mounting radiographs on a “mask” which eliminates stray light around the radiograph, and provision for magnification is also suggested as being advisable. The periapical radiographs in Fig 4 are mounted on a clear background because each radiograph should be viewed against a light-box using a viewing box with in-built magnifying lens (Fig 5). Such viewing boxes are available and are highly recommended not only for conventional periapical and bitewing radiographs, but also for the study of conventional panoramic oral radiographs in assessing crestal bone loss and alveolar bony defects.
While panoramic radiography may be less accurate in the representation of bony defects than intra-oral radiography,43,44 this has little therapeutic effect in practice. For instance, many therapeutic decisions to do with the management of bony defects are not determined by the radiographic appearance, but rather by the intra-operative appearance of the tooth-roots and the bony defects. Guided tissue regeneration (GTR), it has been concluded in a systematic review,46 achieves 1.22 mm more gain in clinical attachment level at pocket sites than open flap (access flap) debridement. Narrow and deep infrabony defects have been shown to respond radiographically and, to some extent at least, clinically more favourably to GTR than wide and shallow defects, and depth was more indicative of favourable response than the angle of the defect.47 This finding was confirmed in a follow-up study.48 GTR requires a surgical approach to the defects. The surgical approach allows for direct intra-operative assessment of defect depths and angles. No reliance should be made on the radiographic assessment of the bony defect. The most that the radiographic assessment of defect depth and width might indicate would be a preparedness to consider GTR as a therapeutic alternative. The findings with respect to the defect on flap reflection – whether the defect is contained or circumferential, indeed whether the tooth is treatable and retainable or not – determine the applicability of the GTR approach. This is decided intra-operatively and not on the basis of the radiographic assessment alone, if indeed at all.
In a systematic review,49 Emdogain® (an enamel matrix derivative) was found to have improved probing attachment levels by 1.2 mm and probing pocket depth reduction by 0.8 mm compared to open (access) flap debridement, although these results have to be interpreted with caution. The effectiveness of Emdogain® is also dependent to an extent on defect depth and defect morphology. Emdogain® has been shown to be very successful, over a nine-year period, in deep defects50 and in angular defects.51,52 The depth of defect and its suitability for Emdogain® regeneration are all made intra-operatively. Questions of interest to the operator – such as “is the defect a deep defect?”, “is it contained or circumferential?”, “are the root surfaces amenable to debridement?”– can all be answered on the basis of the intra-operative direct assessment. The pre-surgical radiographic assessment again may only indicate that Emdogain® might be considered in the surgical treatment of that defect. Also, for Emdogain® regenerative therapy, as for GTR, often in the clinical situation on surgical reflection of flaps, defects reveal themselves to be topographically well suited to regenerative approaches, when the pre-surgical radiographic assessment had not suggested such. In these clinical circumstances, the radiographic assessment has not guided the eventual treatment approach adopted.
If an adjunctive regenerative approach had proved to work with non-surgical periodontal therapy for specific infrabony defect depths and configurations, but not for others, then pre-treatment radiographic accuracy in representing defects would be at a premium. Sadly, however, Emdogain® has been shown to offer no advantage when applied as an adjunct to non-surgical periodontal therapy.53–55 Hence for most therapeutic decisions, and thus offering satisfactory “therapeutic yield”, panoramic oral radiography is, notwithstanding its less accurate depiction of radiographically evident alveolar bone defects, of great therapeutic use.