Increased growth potential in the mandibular condylar head results in mandibular asymmetry. Obwegeser and Makek's classification was the first to identify the hemimandibular hyperplasia (HH), an abnormal self-limiting condylar growth, resulting in pathological one-sided bone overgrowth of the entire mandible on the affected side (Gateno et al., 2021; Ghawsi et al., 2016; Higginson et al., 2018; Ji et al., 2017). The presenting pathology manifests when one condyle is enlarged and bigger than the healthy one, which is the most common characteristic feature of Wolford et al.‘s HH/unilateral condylar hyperplasia (UCL) classification. Over time, one-sided mandibular overgrowth of the ramus and body occurs (Frączek et al., 2016; Gallagher et al., 2021; Gateno et al., 2021).

Bone activity is measured by scintigraphy with 99mTc-MDP (Wen et al., 2014; Willems et al., 2014; Wolford et al., 2014a, Wolford et al., 2014b; Sembronio et al., 2020). Nuclear studies are used to determine whether the growth is still occurring (AG+) or has ceased (GC−). Bone density studies indicate various factors relating to condylar bone differences between edentulous and dentulous patients, along with masticatory intensity, occurrence of TMJ symptoms/malfunctions, and occlusal force. However, thus far, no accurate measurements of bone density in active condylar hyperplasia and their clinical outcomes have been noted (Wolford et al., 2014a, Wolford et al., 2014b; Sembronio et al., 2020; Gallagher et al., 2021; Gateno et al., 2021). On the other hand, the density of condylar cortical and medullary bone can be easily measured using CT/LDCT (Hounsfield units [HU]) and compared with other bone structures and age-related changes (Cascone et al., 2021; Di Luzio et al., 2017; Fariña et al., 2016). Direct studies on histopathological and scintigraphic data are lacking.

Mandibular bone density (MBD/BD) can be easily measured with CT, CBCT, or LDCT. Density values measured in HU are often relative. The CT approach is a valuable diagnostic tool for evaluating any changes in edenteolous patients before dental implant placement, or even to evaluate bone changes during orthodontic treatement (Attili et al., 2015; Kim et al., 2022; Jolly et al., 2015; Morar et al., 2022; Katsumata et al., 2022). Bone density in both the cortical and cancellous bone can be easily measured; however, the density distribution within the bone structures can be different. Some studies have shown that the posterior mandibular area has characteristically lower bone density values, while the left and right side of the mandible do not differ from each other (Kim et al., 2022; Jolly et al., 2015). According to Morar et al., the Hounsfield scale is a quantitative measurement and provides an exact density value for each tissue type (Morar et al., 2022; Katsumata et al., 2022).

Previous studies involving histological examinations have revealed normal condylar bone appearance once growth has ceased, while a proliferation in condylar cartridge during growth has been noted in excised specimens (Aggarwal et al., 2015; Arora et al., 2019). Other studies have suggested that bone density measurements do not correspond with mandibular condyle changes, and previously used color schemes are nowadays less popular.

More recently developed methods enable easier evaluation of affected condyle bone architecture. New radiological insights into the affected condyle structure in hemimandibular hyperplasia are now possible with low-dose computed tomography (LDCT) (Aggarwal et al., 2015; Olate et al., 2013). In the current study, based on our own protocol, the measured values of bone density are not absolute values, but only relative, allowing estimation of the percentage changes in index values.

There have been limited studies describing changes in radiological structure of the mandibular condyles in comparison with histopathological data from excised specimens. The purpose of our study was therefore to retrospectively estimate whether our own protocol, based on radiological measurements of index ratios of bone density in mandibular condyle hyperplasia cases, corresponded with histopathological specimen data following condylectomy.