Chinese Journal of Dental Research, 01/2020

Salivary adenoid cystic carcinoma (ACC) and pleomorphic adenoma (PA) are the most common types of salivary gland tumours; the former is malignant and the latter is benign but with features of a border tumour. Proteoglycans (PGs) produced by neoplastic myoepithelial cells are ubiquitous in both types of tumours. However, normal myoepithelial cells of salivary glands do not have the ability to secrete PGs. When the synthesis of PGs is blocked, the pulmonary metastasis and perineural growth of salivary ACC as well as the implanting growth of salivary PA are inhibited, highlighting the important functions of PGs in the tumourigenesis and development of these two tumours. In this review, we summarise literature from the past 40 years, including more recent findings from our laboratory, to clarify the pivotal roles of PGs produced by neoplastic myoepithelial cells in both the histogenesis and biological behaviours of ACC and PA. Keywords: adenoid cystic carcinoma, pleomorphic adenoma, proteoglycans, RNA interference, xylosyltransferases

Skull base surgery is an interdisciplinary subject. The anatomical structures in the skull base related to oral and maxillofacial surgery include the parapharyngeal space, the pterygopalatine fossa and the infratemporal space. This operative area is one of the most challenging surgical areas in oral and maxillofacial surgery due to its deep site, complex anatomy and high risk. Obtaining pathological information of the tumour preoperatively may help surgeons optimise their treatment plan. Needle biopsy is one of the major minimally invasive techniques that allows preoperative pathological results to be obtained. The navigation technology, which is developing rapidly nowadays, provides a reliable assistance for deep tissue biopsy surgery. Experts from the Society of Oral and Maxillofacial Surgery, Chinese Stomatological Association formulated an expert consensus on the procedures and operations of navigation-guided needle biopsy techniques for skull base tumours, so as to standardise and promote the application and operation of navigation-guided needle biopsy for skull base tumours. Keywords: skull base tumour, biopsy, surgical navigation, expert consensus

Deformities of the maxillofacial region following trauma and ablative surgery are devastating and not uncommon. Reconstruction of such defects is a surgically challenging procedure. Conventionally, reconstruction of dental arch defects lacks preoperative customised planning and relies heavily on the surgeon experience to ensure optimum surgical outcomes. The restoration of the dental arch shape and function has taken precedence after an extensive tumour resection surgery, especially in the current age of technological advancement. Thus, personalised and accurate reconstruction of dental arch defects has become a new goal. Computer-assisted surgery, especially navigation-assisted surgery, has gained popularity of late, in reconstructing deformities and restoring facial symmetry, appearance and function in the maxillofacial region. This technology provides a clearer three-dimensional visualisation of the area of interest and its relationship with the adjacent vital structures. Together with preoperative virtual surgical planning, it allows more specific and accurate osteotomies, thus reducing the ischemia and total operating times substantially. The risk of complications is also minimised whilst improving the final surgical outcomes. The use of the intraoperative navigation system and other computer-assisted surgical techniques during surgery can significantly improve the precision of the reconstruction of dental arch deformities, and achieve personalised and functional reconstructive goals while enhancing the quality of life of patients postoperatively. The Society of Oral and Maxillofacial Surgery, Chinese Stomatological Association provides the present professional perspective and treatment protocol for navigation-guided reconstruction of dental arch defects, to allow standardisation of the technique while promoting its application among oral and maxillofacial surgeons. Keywords: bone remodelling, jaw defect, reconstruction, navigation technique, digital surgery, expert consensus

The zygoma is located in the medial and lateral parts of the face, supporting the midfacial contour. The forward projection of the zygoma and the zygomatic arch often expose them to injury. Fractures of the zygoma can lead to the displacement of the zygoma and the zygomatic arch, causing facial collapse deformity. For delayed zygomatic fractures, the loss of normal anatomical landmarks caused by the malunion of the fracture lines and remodelling of the bony contour makes it difficult to determine the correct positions of the zygomatic bones. In such cases, ideal and steady outcomes with satisfactory midface symmetry have been difficult to obtain using traditional surgical methods. Nowadays, the application of digital surgical software and surgical navigation helps surgeons to perform accurate preoperative simulations to obtain ideal three-dimensional virtual surgical plans and achieve accurate reduction by intraoperative navigation systems, which increase the accuracy and predictability of fracture reduction outcomes. Experts from the Society of Oral and Maxillofacial Surgery, Chinese Stomatological Association have fully discussed and formulated an expert consensus on navigation-guided unilateral delayed zygomatic fracture reconstruction techniques to standardise the clinical operation procedures and promote the application. Keywords: delayed zygomatic fractures, digital navigation, unilateral

Orbital fracture and orbital floor reconstruction surgery is characterised by limited surgical exposure and high risks. Before the advent of digital technology, the design and implementation of the surgical scheme for orbital floor reconstruction surgery mainly depended on the intuitive understanding of imaging and the clinical experience of surgeons, with strong unpredictability and experience dependence. Surgical navigation systems with real-time positioning and imaging functions, when used in orbital reconstruction surgery, can detect the real-time intraoperative position, avoid risks, and assist in locating the reconstruction position to ensure the accuracy of orbital reconstruction, with the help of a preoperative surgical plan. Many studies have confirmed its effect. Unilateral orbital fracture and orbital floor reconstruction surgery is one of the earliest and most widely used surgical techniques in maxillofacial surgery. Experts from the Society of Oral and Maxillofacial Surgery, Chinese Stomatological Association have fully discussed and formulated this expert consensus on navigation-guided unilateral orbital fracture and orbital floor reconstruction techniques to standardise the clinical surgical procedures and promote its application. Keywords: navigation technique, orbit fractures, unilateral

The newly emerged coronavirus disease (COVID-19) is a respiratory disease caused by a novel coronavirus (2019-nCoV) which was first identified in China in December 2019. It is a highly contagious infection that can spread from person to person through close contact and respiratory droplets. The healthcare personnel of the Department of Oral and Maxillofacial Surgery are especially vulnerable to the infection due to their extensive and close exposure to patients' oral and nasal cavities and secretions. As one of the busiest specialised hospitals in the world, the Department of Oral and Maxillofacial Surgery of Peking University School and Hospital of Stomatology summarised the experience with disease prevention and control and clinical recommendations on the examination, diagnosis and treatment processes, clinical management, healthcare personnel protection and disinfection amid the continued spread of the pandemic. Keywords: diagnosis and treatment process, new coronavirus, oral and maxillofacial surgery, protection

Objective: To determine the effects of different polishing protocols and curing times on the surface roughness (SR), surface gloss (SG) and surface hardness (SH) of a bulk-fill composite resin (BCR). Methods: A total of 30 block-shaped specimens (40 mm long × 10 mm wide × 2 mm thick) were made from Filtek Bulk-Fill composite resin and divided into two groups (n = 15) according to curing time (10 and 40 seconds). Each group was subdivided into five groups (n = 3) according to the polishing protocol: laboratory polishing with different silicon paper grits (G1:1200) → (G2:2400) → (G3:4000). Chairside polishing was performed using a series of Sof-Lex spiral (G4) and Jiffy Polisher (G5) points. The SR was measured by a surface profilometer. A Vickers indenter was used to test the SH, and a glossmeter was used to determine the SG at 60 degrees. The SR, SG and SH were quantified before and after polishing. A scanning electron microscopy (SEM) evaluation was then performed. Results: The curing time did not affect the surface properties of the BCR (P > 0.05). Significant differences in SR (ranging from 0.1 to 2 μm) and SG (ranging from 20 to 90 GU [gloss unit]) were found according to the type of polishing protocol (P 0.05). The SH values following different polishing protocols were significantly higher (ranging from 82 to 95 VH [Vickers hardness]) than the polishing values obtained before the polishing protocols (P 0.05). Conclusion: The tested chairside polishing protocols presented lower SG and higher SR values than the laboratory polishing protocols. Keywords: bulk-fill composite resin, curing time, polishing protocol, surface properties

Endoscopic techniques have been applied to oral and maxillofacial surgeries. Previous studies have proved their practicability in the treatment of osteomyelitis of the mandible and displaced residual roots in the maxillary sinus. In this report, two patients with dentigerous cysts in the maxillary sinus underwent endoscope-assisted curettage. Both patients were successfully cured without recurrent lesions or any complications. The follow-up found that the bone cavities had shrunk. An endoscope-assisted Caldwell-Luc operation provided clear visibility of the surgical field and preserved the mucosa of the maxillary sinus. Keywords: Caldwell-Luc operation, dentigerous cyst, endoscopic-assisted surgery, maxillary sinus