Kannan S K, Sandhya G, Selvarani R
Department of Oral Medicine & Radiology, Meenakshi Ammal Dental College & Hospital, Alapakkam Main Road, Maduravoyal, Chennai-602102, Tamil Nadu State, India.
Int J Paediatr Dent. 2006 Jan;16(1):59-64. doi: 10.1111/j.1365-263X.2006.00630.x.
Periostitis Ossificans (PO) is a non-suppurative type of Osteomyelitis, commonly occurring in children and young adults, in mandible. The most common cause for PO is periapical infection of mandibular first molar. Radiographically PO is characterized by the presence of lamellae of newly formed periosteal bone outside the cortex, giving the characteristic appearance of "onion skin".
Two male children 11 years of age reported to the Department of Oral Medicine with a painless and persistent bony hard swelling in the mandible, with a short duration (Figs 1, 5). Both the patients had grossly decayed mandibular permanent first molar tooth with periapical infection and buccal cortical plate expansion (Figs 2, 6). The radiographic study revealed different appearances, the Orthopantomograph of case I showed a single radiopaque lamella outside the lower cortical border, without altering original mandibular contour (Fig. 3) and in case II showed a newly formed bony enlargement on the outer aspect of the lower cortical border without altering the original mandibular contour (Fig. 7). Occlusal radiograph of both the patients showed two distinct radiopaque lamellae of periosteal bone outside the buccal cortex (Figs 4, 8). Kawai et al. classified PO of mandible into type I and type II, based on whether the original contour of mandible is preserved or not. Each type is further classified into two sub types (Table 1). In case I, the orthopantomographic appearance is characteristic of type I-1 (Fig. 3), but the appearance in occlusal radiograph is characteristic of type I-2 (Fig. 4). In case II, the appearances in both the radiographs are characteristic of type I-2 (Figs 7, 8).
Apart from the typical onion skin appearance, PO shows various other radiographic appearances. The radiographic appearance of Periostitis Ossificans may reflect the duration, progression and the mode of healing of the disease process. The radiographic classification of PO depends on the type of radiographs taken for evaluation.
骨化性骨膜炎（PO）是一种非化脓性骨髓炎，常见于儿童和年轻人的下颌骨。PO最常见的病因是下颌第一磨牙的根尖感染。在影像学上，PO的特征是皮质外出现新形成的骨膜骨板，呈现出“葱皮样”的特征外观。
两名11岁男性儿童因下颌骨无痛性持续性骨质硬肿胀就诊于口腔内科，病程较短（图1、5）。两名患者的下颌第一恒磨牙均严重龋坏，伴有根尖感染和颊侧皮质板膨隆（图2、6）。影像学检查显示出不同表现，病例I的全景片显示在下颌皮质边界外有一条不透光的骨板，未改变下颌骨的原始轮廓（图3），病例II显示在下颌皮质边界外侧有新形成的骨质增大，未改变下颌骨的原始轮廓（图7）。两名患者的咬合片均显示颊侧皮质外有两条明显的不透光骨膜骨板（图4、8）。Kawai等人根据下颌骨的原始轮廓是否保留，将下颌骨PO分为I型和II型。每种类型又进一步分为两个亚型（表1）。在病例I中，全景片表现符合I-1型的特征（图3），但咬合片表现符合I-2型的特征（图4）。在病例II中，两张片子的表现均符合I-2型的特征（图7、8）。
除了典型的葱皮样外观外，PO还表现出各种其他影像学表现。骨化性骨膜炎的影像学表现可能反映了疾病过程的持续时间、进展和愈合方式。PO的影像学分类取决于用于评估的X线片类型。
