This study investigates whether unusual jaw contours of edentulous jaw sections, which are not visible in 2D images, could be detected in the transverse plane of CBCT images. Using the CBCT images, a further step is to measure the height difference of the alveolar ridge between lingual and buccal aspects in the planned implant position and edentulous jaw areas.
The hypothesis was that no difference was observed in assessing the contour in edentulous jaw sections or in measuring the buccolingual height in both 2D and 3D-dimensional images.
CBCT-based implant planning showed a vertical bone deficit on the buccal side of the planned implant in the maxilla of 307 patients and the mandible of 265 patients. The mean was 2.09 mm (SD ± 2.25 mm) in the maxilla with a maximum deficit of 13 mm, and 3.97 mm (SD ± 3.45 mm) in the mandible with a maximum deficit of 12.5 mm (Table 5). Slight height discrepancies (0–1 mm) were measured in 133 cases in the maxilla and 90 cases in the mandible. At 4.1 mm, the 50 percentile in the lower jaw was more than twice as high as in the upper jaw at 2.0 mm. Larger discrepancies (5–12 mm) were observed much more frequently in the mandible.
The findings indicate that an unusual jaw contour in the implant position is detected in 2.4% of cases on the left and 3% on the right in the maxilla. However, an unusual jaw contour in the implant position was detected in 12.1% of the left and 12% right in the mandible. However, these were not detected by panoramic radiography.
A total of 335 pairs of images were compiled and included for further analysis. In the preliminary stages, measurement integrity was verified by an expert. The measurements were repeated at 2-week intervals. Both intra-observer reliability of the principal examiner and inter-observer reliability between the principal examiner and expert were significantly high, resulting in a Cohen’s kappa coefficient of 1.0 and a 95% confidence interval for kappa [0.92; 1.00]. The high intra- and inter-observer reliability support the reliability of the results.
Since Mozzo et al.’s description of CBCT in 1998 , numerous scientific studies have addressed the question of the CBCT necessity before surgical procedures. More specifically, the necessity for obtaining a CBCT scan for implant surgery has remained controversial [1, 11].
Few studies [24,25,26,27] compare panoramic radiography and CBCT for detecting height differences between the lingual and buccal ridges of edentulous jaw sections. Wolff et al.  conducted a comparative study of panoramic radiography and CBCT scans in 253 patients to ascertain whether CBCT scans affected the planning of dental implants. While CBCT images yielded more useful information, they did not influence the operative plan of this study, based on a pre-existing panoramic radiography image. Nevertheless, no direct comparison was made between panoramic radiography and CBCT. The results showed a bone deficit on the buccal side of these jaw sections in CBCT. Before the planned implantation, additional information provided by the CBCT can play an important role in the decision of the surgeon and the patient. Particularly, the CBCT seems to leave little room for interpretation of the findings, which is substantiated by Malina-Altzinger et al. . In their comparative study, they concluded that certain findings in panoramic radiography could be based on the assessment of the examiner. Compared with panoramic radiography, the authors conclude that CBCT allows examiner-independent assessment of specific findings, relevant to planned subsequent surgical interventions.
Deeb et al. , Dagassan-Berndt et al.  and Guerrero et al.  show similar results. The latter study also revealed that CBCT-based preoperative implant planning facilitated a significantly higher prognosis regarding augmentation than panoramic radiography-based planning.
Our findings are consistent with those of the above-cited studies [22, 26, 27]. In cases with more extensive bone deficits, CBCT-based implant planning has a substantial additional value for diagnostics. Additional information can provide a positive outcome for assessing implantation feasibility, augmentation and evaluation of costs and risks, which could offer possible forensic evidence.
Other aspects examined in the current study were unusual jaw contours, such as funnel-shaped or pronounced retraction of the edentulous sections of the jaw. Moreover, corresponding panoramic radiographs and CBCT images of edentulous sections of the jaw were compared. This information is vital for planning before implantation to minimise the risk associated with damaging adjacent structures.
Rajput et al.  used CBCT to assess the lingual concavities in the submandibular fossa in patients with missing posterior teeth, requiring dental implants. In 62% of the patients, a concavity depth of 2–3 mm was present; whereas in 15% of the cases, a concavity depth greater than 3 mm was determined. These authors conclude that CBCT remains the most effective imaging technique for providing sufficient information when planning posterior implant surgery. Another study used a design similar to that of Nickenig et al.  and showed that the undercut of edentulous mandibles was detected in the molar region of 68% of the patients.
Our results showed that an unusual jaw contour in the planned implant position could be detected by CBCT in 2.4% of cases on the left and 3% on the right in the maxilla. The results also show 12.1% on the left and 12.1% on the right in the mandible, otherwise not detected by panoramic radiography, which may be significantly lower than the values presented by the abovementioned studies. The discrepancies could appear because we did not measure the depth of the concavity. In our study, it was important to determine whether implant planning in the edentulous section of the jaw was possible without causing perforation. Thus, minor undercuts were not accounted for. The small number of undetected unusual jaw contours should not conceal the serious complications during implant surgery. Perforation of the lingual wall while preparing the implant bed can cause profuse bleeding, concomitant swelling and infection in the parapharyngeal space [10, 29]. Precise information on the anatomical structures can considerably mitigate perforation risks . Comparable results were published by Shelley et al. . Eight clinicians performed implant planning in the anterior mandible using panoramic radiography and CBCT. In challenging cases, narrower implants were selected when CBCT was available, presenting a little risk of lingual cortical perforations. In cases with known unusual jaw contours, another strategy was to use short implants. This might reduce the risk of perforations or the requirement for augmentation. The findings of a recent study showed that short implants exhibit a high success rate, even after 5 years . This minimises the risk of perforation and the requirement for augmentation.
Dau et al.  took different positions by comparing the subjective quality assessment of panoramic radiography and CBCT for the planning of dental implants by dentists with varying educational backgrounds. Their results showed significant subjective advantages for additional CBCT for planning dental implant procedures, particularly in the anterior and posterior maxilla. Above all, participants with only basic training requested CBCT more frequently. Other studies show that subjective factors, such as practitioner opinion or experience, are instrumental in assessing the viability of CBCT [22, 26].
Thus, our results indicate that useful information can be obtained by performing a CBCT before implant planning. This is crucial when assessing aspects such as risks, costs, duration of treatment or even forensic issues for the surgeon and patient. Consequently, our hypothesis may be rejected, which shows no difference is identified when assessing the contour in edentulous jaw sections or measuring the buccolingual height in both 2D and 3D images.