Chinese Journal of Dental Research, 01/2010

Members of the transforming growth factor-ß (TGF-ß) superfamily are critical regulators that control cell proliferation, differentiation and apoptosis. TGF-ß signalling also regulates the morphogenesis of many developing organs. The development of mouse tooth germ, which is a good model for organogenesis, provides a powerful tool for elucidating the molecular mechanisms that control organogenesis. As ectodermal appendages, the tooth organ arises from complex and progressive interactions between an ectoderm, the oral epithelium and an underlying mesenchyme. Their morphogenesis is regulated by conserved signalling pathways, including TGF-ß. In this review, the essential function of the TGF-ß superfamily will be discussed in detail, including TGF-ß, bone morphogenetic proteins (BMP), activin, etc, during tooth crown patterning and following tooth root development. The review also highlights recent advances in the understanding of Smad-dependent and Smad-independent pathways in regulating tissue-tissue interactions during patterning of tooth crown and root. Keywords: TGF-ß, tooth development, BMP, Smad, root development

Salivary gland ductal obstruction is traditionally treated by sialoadenectomy when conservative measures fail. During the last decade, sialendoscopy has become the preferred approach in the management of salivary ductal obstructions. Sialendoscopy can provide direct, accurate and reliable visualisation of the salivary duct lumen and ductal pathologies, and can eliminate pathologies with miniaturised instrumentation. Now, sialendoscopic surgery is a promising option for patients who can be offered a satisfactory clinical outcome while avoiding sialoadenectomy. The present article briefly outlines sialendoscopy-based diagnosis and treatment of salivary ductal obstructions. Keywords: sialendoscopy, diagnosis and treatment, salivary ductal obstructions

Objective: To determine the quality of the evidence for the uses of fluoroscopy in dentistry. Methods: A systematic review using Ovid and MEDLINE was conducted to identify papers showing the uses of fluoroscopy in dentistry published between 1953 and September 2009. Human, animal and phantom/skull/mannequin studies on fluoroscopy with regard to its diagnostic value, research performance, and clinical and safety applications in dentistry were included in this analysis. Studies that were not in English, as well as those that employed fluoroscopy in dentistry without the use of image intensification, were excluded. Articles were evaluated, classified and graded by levels of evidence. Results: Fifty-five out of 139 papers fulfilled the inclusion criteria. Amongst them, 19 were related to diagnosis, 15 to research, 12 to clinical and nine to safety applications. Fluoroscopy has contributed to nine different areas of dentistry. Also, it was used on 895 dental patients, 37 animals and 17 phantoms/skulls/mannequins. Two randomised controlled trials, two cohort studies, two case controls, 48 case reports and one expert opinion were found. Conclusion: Fluoroscopy with image intensification has been a useful, but not consistently used tool in dentistry for over 50 years. Several lines of evidence have shown fluoroscopy's diagnostic potential, research use, and clinical and safety applications in dentistry. Keywords: fluoroscopy, radiology, systematic review, evidence-based dentistry, dental imaging

Objective: To evaluate the application of cone-beam computed tomography (CBCT) in the detection of dental root fractures and to analyse the demographic profile of these fractures. Methods: The study group comprised 398 teeth that were examined by CBCT for determining whether they had a root fracture. Patient characteristics were recorded, and the location, fractured roots, fracture types and three-dimensional images of the related skeletal structures were analysed. Two experienced oral radiologists independently analysed each case and reached a consensus, and the diagnosis was graded in one of the following three categories: fracture definitely present (FDP), fracture probably present (FPP) and no visible fracture (NVF). Results: Among these teeth, 155 (39.0%) were diagnosed as FDP, 14 (3.5%) as FPP and 229 (57.5%) as NVF in the consensus reading. During follow-up, all teeth diagnosed as FDP and 4 of the 14 teeth diagnosed as FPP were intra-operatively demonstrated to be fractured. In FDP cases, 60.0% of the patients were aged from 50 to 69 years. In total, 107 FDP teeth were non-endodontically treated, and the remaining were endodontically treated with (n = 16) or without (n = 32) crown placement. The maxillary and mandibular molars were most frequently affected (81.9%). The fractured roots were mostly palatal (65.7%) in maxillary molars and mesial (84.2%) in mandibular molars. The fractures were characterised as vertical (n = 84), horizontal (n = 34), oblique (n = 5) and complicated (n = 32) fractures. Conclusion: The application of CBCT is valuable for the diagnosis of root fracture. Keywords: cone-beam computed tomography, dental root fracture, imaging diagnosis

Objective: To investigate the efficacy of functional training of facial mimic muscles for patients with incomplete peripheral facial nerve injury. Methods: Ninety-two patients with 241 injured branches of incomplete peripheral facial nerve injury were divided into a treatment group and a control group. The treatment group consisted of 58 cases that received functional training of facial mimic muscles. The rest of the cases served as controls. Assessment parameters included the House-Brackmann grading system, a quantitative facial nerve function estimating system and electroneurography. According to the three assessments, the facial nerve injury was divided into four grades: normal, minor, moderate and severe. The treatment group started training facial mimic muscle activity 2 weeks after facial nerve injury. After follow-ups of 1 to 4 years, the outcomes were statistically analysed. Results: In the minor facial nerve injury group, there was no significant difference in the time needed for initial recovery (Ti, the time needed for significant recovery of the facial nerve function after injury) and final recovery (Tf, the time point after which no further improvement of facial nerve function was obtained) between the two groups (P > 0.05). No adverse effect was found in these cases. In the moderate facial nerve injury group, the Ti and Tf of the treatment group were shorter than those of the control group (P 0.05). One case had synkinesis. In the patients with severe facial nerve injury, the recovery rate of facial nerve function in the treatment group was higher than that of the control group and the sequelae were less. Conclusion: Functional training of facial mimic muscles cannot shorten the time of recovery for the patients with minor facial nerve injury but it can speed up the recovery and reduce the undesirable sequelae such as synkinesis and hemifacial spasm for the patients with moderate and severe facial nerve injury. Keywords: facial mimic muscle, functional training, facial nerve injury

Objective: To evaluate whether the Notch signalling pathway is involved in the senescence of human dental pulp cells. Methods: Human dental pulp cells were isolated and cultured. The Notch signalling pathway was blocked by adding DAPT (N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester, γ-secretase inhibitor, 5 µmol/L) into the culture medium. Cell proliferation was evaluated by MTT assay. Cell senescence was evaluated through expression of senescenceassociated ß-galactosidase (SA-ß-Gal) using ß-galactosidase staining. Results: The proliferation of the human dental pulp cells decreased dramatically after treatment with DAPT, compared with the control. SA-ß-Gal positive staining cells were seen in the DAPT group, but not in the control group. Conclusion: The Notch signalling pathway is involved in the senescence of human dental pulp cells. Keywords: dental pulp cells, senescence, Notch signalling pathway

Objective: To evaluate xerostomia, mucositis and dental caries during head and neck radiotherapy. Methods: Twenty patients with nasopharyngeal carcinoma were included. Oral examinations were conducted before radiotherapy, after dosage of 2000 cGy irradiation, immediately after the termination of radiotherapy, and 1 month and 6 months after termination of the radiotherapy. Oral hygiene instruction, effective oral care and dental intervention were performed during the treatment. Salivary flow rate was evaluated by modified Schirmer's test. Xerostomia, mucositis and dental caries status were evaluated based on oral examinations. Results: Salivary flow rate decreased significantly after the first dosage of 2000 cGy, and was aggravated with the increase in irradiation dosage until the termination of radiotherapy. Xerostomia and mucositis were observed in parallel with the reduction of saliva flow rate, and were aggravated with the increase in irradiation dosage. Mucositis began to recover within 1 month after the termination of radiotherapy and fully recovered within 6 months after the termination of the radiotherapy. Six months after the termination of irradiation, new carious lesions were detected in two patients. Conclusion: Oral sequelae developed during radiotherapy of the head and neck. Oral health instructions and effective intervention were essential before, during and after the radiotherapy. Keywords: xerostomia, mucositis, dental caries

Objective: To assess the prevalence and factors associated with traumatic injuries to permanent incisors of 12-year-old school children in Davangere, India. Methods: In total, 1020 12-year-old school children were selected. Two trained and calibrated clinicians examined the children in the school environment using the World Health Organization Classification of Tooth Fracture (1978). Examination was also done for lip coverage and maxillary overjet using the Community Periodontal Index probe. Children were then interviewed using a structured questionnaire for demographic data and history of the injury. Results: The overall prevalence rate of traumatic dental injuries (TDI) to permanent incisor teeth was 15.1%. The prevalence of TDI was higher in boys compared to girls. The major cause of TDI was falling followed by collision. The maxillary incisors were commonly injured, involving mainly enamel fracture. Children with excessive overjet and inadequate lip coverage were more likely to have injuries. Conclusion: TDI could be a serious dental public health problem among children. Thus, there is an urgent need to collect local data on dental injuries in order to obtain a more comprehensive picture of dental health. Keywords: traumatic dental injuries (TDI), overjet, tooth fracture

A 70-year-old man who suffered from extensive extra and intraoral defects was rehabilitated with a prosthesis using multiple retaining means. The treatment was performed in two parts: externally involving the construction of an episthesis supported only by the remaining intact boundaries of the defect and retained by mini-dental implants and spectacle frame with a modified ear hook; and intraorally by an acrylic resin obturator to restore the function of the hemi-sectioned hard and soft palate. The episthesis was securely retained with minimal movement and/or dislodgment of the prosthesis during function. Multiple retentive techniques may be used to fix heavy external prostheses as an alternative to conventional implants or biological adhesives. Keywords: anaplastology, midface replacement, mini-dental implant, ear hook

A rare case of a male patient who suffered from noma with sequelae of ankylosis in bilateral temporomandibular joints for 52 years and a neoplasm in the right commissure of the lips for 1 year, was operated on to resolve the ankylosis, remove the neoplasm and reconstruct the soft tissue defect with a forearm flap through a one-stage operation. The neoplasm pathology was verrucous carcinoma. Keywords: noma, ankylosis, forearm flap, verrucous carcinoma

Hyperplastic dental follicle is an extremely rare lesion. The practitioner should be able to differentiate it from a dentigerous cyst. The present article will review related literature and report on two cases in one family. A 12-year-old white female and her 15-year-old brother were referred for exposure of unerupted canines. No systemic diseases or syndromes were present. Intra-oral examinations were unremarkable, except for the absence of all eight canines. Radiographic examinations revealed impacted canines with each unerupted tooth surrounded by a well-demarcated radiolucency, which passed beyond the cementoenamel junction. The teeth were surgically exposed and tissue specimens surrounding the unerupted teeth were analysed histologically. Histology revealed fibrous connective tissue with areas demonstrating some ground substance and multiple odontogenic epithelial rests. Some surfaces were partially lined by reduced enamel epithelium. A diagnosis of hyperplastic dental follicle was made. Sometimes, it is difficult to differentiate hyperplastic dental follicle from odontogenic fibroma, both simple and central forms. A correct diagnosis should be based on clinical, radiographic and histological findings. Keywords: hyperplastic dental follicle, unerupted canine