A case of mandibular fracture including coronoid process fracture

The incidence of mandibular fractures is the highest among facial bone fractures. Addi-tionally, most of mandibular fractures occur in the mandibular angle and condylar process. On the other hand, the incidence of fracture of coronoid process is extremely low. We experienced a case of mandibular fractures involving mandibular body, condylar process as well as the coronoid process in a man aged 3₉–years–old who had received strong direct external force to the mandible. Mandibular fractures usually occur in the condylar process and mandibular angle because direct external force is more likely to transmit to these re-gions. Based on the classification of mandibular fractures, the incidence of mandibularfractures involving coronoid process increases with an increased number of fractures lines that means complicated fracture. At the viewpoint of anatomical portion, direct external force dose not transmit to coronoid process; however, it is possible that direct external force may transmit coronoid process in the case of complicated fracture. In this case report, we considered the potential mechanism of fracture of coronoid process by using a three–dimensional finite element model of a human mandible stress distribution analysis

Measurement of alveolar bone mineral density (BMD) to evaluate chronic periapical lesions.

目的：歯槽骨の骨密度（bone mineral density, BMD）は、根尖病変の拡大と治癒の過程において変化する。DentalSCOPE（メディア、東京）は、歯槽骨のBMD値を計測するために開発された画像解析システムである。BMD値計測では、口内法デジタルＸ線撮影装置の機種による特性の違いが測定精度に影響する可能性がある。そのため本研究ではまず、輝尽性蛍光体（photo-stimulable phosphor, PSP）デジタル口内法Ｘ線撮影システムにおけるBMD計算キャリブレーションの方法を検討した。次に、根尖病変の大きさによるBMDの変化について実験的に検討した。 方法：三種類のPSPデジタル口内法Ｘ線撮影システム（以後、PSPシステムと略す）を使用してBMD値定量ファントムの口内法デジタルX線画像を撮影し、各PSPシステムに最適なソフトウェアパラメータ設定について検討した。続いて、乾燥下顎骨の根尖に実験的な模擬根尖病変を作成した。模擬病変が十分に大きくなるまで、根尖の骨を削除してＸ線撮影する作業を繰り返した。歯科用コーンビームCT（CBCT）画像上の根尖病変の大きさを計測してBMD値との相関を調べた。 結果：DentalSCOPEのパラメータ設定を最適化するためのキャリブレーション手順を実行しなかった場合、BMD値は使用したPSPシステムによって異なっていた。三種類のPSPシステム間のBMD値の違いは、イメージングシステム固有のキャリブレーションを適用することで最小限に抑えることができた。根尖周囲病変のBMD値に関して、病変の近遠心径とBMD値は中程度の相関を示した。頬舌の直径と病変の体積はBMD値と高い相関を示した。BMD値は歯根嚢胞のX線写真では観察が困難な小さな病変にも鋭敏に変化した。結論：歯槽骨のBMD値測定は、根尖周囲病変の段階を評価して歯内治療の予後を観察するのに有用と考える。Objectives : The bone mineral density (BMD) of alveolar bone should be changing following the growing and healing process of the lesion. The DentalSCOPE (Media Corporation, Tokyo, Japan) is an image analysis system developed to evaluate the BMD of alveolar bone. In this system, measurement accuracy may be aff ected by the individual characteristics of diff erent digital imaging systems. Therefore, this study aimed to examine calibration method for the BMD calculation in photo-stimulable phosphor (PSP) digital intraoral imaging systems. Then we performed an in-vitro study to compare the size of periapical lesions and their BMD. Methods : Intraoral digital radiographs of the standardized BMD phantoms were obtained using three PSP imaging systems. We studied the optimal software parameter for setting each PSP imaging system. Experimental pseudo-periapical lesions were created in the root apex of dried mandibles. We repeated the process of removing the bone and took images until the lesions were large enough. We examined whether the relationship exists between the size of periapical lesions in the dental CBCT images and BMD of periapical lesions or not. Results : Without a calibration to optimize the DentalSCOPEʼs parameter setting, the BMD values were diff erent depending on the PSP imaging systems used. The diff erences in the BMD value between three PSP imaging systems were minimized by application of the imaging system specifi c calibration. The mesio-distal diameter of the lesions and their BMD values showed a moderate correlation with each other. The bucco-lingual diameter and volume of the lesion showed a high correlation with the BMD. The BMD value responded sensitively to small lesions that were diffi cult to detect with a periapical radiograph. Conclusion : BMD measurement will be useful to evaluate the stage of periapical lesion and to observe the prognosis of endodontic treatmentjournal articl