Chinese Journal of Dental Research, 01/2011

Radiation therapy for malignant tumours in the head and neck region are inevitably associated with significant long-term injury to the salivary glands, often resulting in salivary gland hypofunction. The subsequent lack of saliva production leads to many functional and quality-of-life problems for affected patients and there is no effective method to eliminating this problem caused by radiation treatments. Although many studies have been done in animal models, the mechanism of this injury in humans is still unclear. In this review, an animal model (miniature pigs) used in irradiated research is mainly discussed. This review also presents the progress made to date on the gene transfer-mediated functional restoration of irradiated salivary glands and the possibilities provided by future interventions to prevent radiation damage to salivary glands. Keywords: gene transfer, miniature pig, radiation damage, salivary glands, xerostomia

Objective: To investigate the reinforcing effect of short E-glass fibre fillers on fracture related mechanical properties of dental composite resin with a semi-interpenetrating polymer network (IPN) polymer matrix. Methods: Experimental short fibre composite (FC) resin was prepared by mixing 22.5 wt% of short E-glass fibres, 22.5 wt% of IPN-resin and 55 wt% of silane treated silica fillers using a high speed mixing machine. Test specimens were made bar shaped (3 × 6 × 25 mm3), cylindrical (6 mm length × 3 mm diameter) and cubic (9.5 × 5.5 × 3 mm3) from the experimental FC resin and conventional particulate composite resin (Grandio) as control. The test specimens (n = 8) were either dry stored or water stored (37°C for 30 days) before the mechanical tests. A three-point loading test and compression test were carried out according to ISO 10477 and a static loading test was carried out using a steel ball (Ø 3.0 mm) with a speed of 1.0 mm/min until fracture. Results: Experimental fibre composite had a significantly higher mechanical performance for fracture toughness (14 MNm-1.5), compression strength (129 MPa) and static load-bearing capacity (1584 N) than the control composite (2 MNm-1.5, 112 MPa and 1031 N). Conclusion: The resin with short E-glass fibre fillers and IPN-polymer matrix yielded improved mechanical performance compared to the conventional particulate composite resin. Keywords: compression strength, fibre-reinforced composite, fracture toughness, restorative composite

Objective: To evaluate the morphological features of craniofacial structures in young patients affected by bilateral temporomandibular joint osteoarthrosis (TMJOA). Methods: Forty-three males and 189 females aged 15 to 25 years who had lateral cephalograms and temporomandibular joint (TMJ) radiological examinations were included. They were classified into a TMJOA group and a control group, according to TMJ bony status. Thirty-two variables from lateral cephalogram were analysed by t test to evaluate the cranial and dentofacial differences between the two groups. Results: TMJOA group showed a shorter posterior ramus height and shorter condyles, smaller SNB angle and larger ANB angle, smaller facial plane angle and larger angle of convexity, steeper mandibular plane angle and more vertical y-axis. Conclusion: Bilateral TMJOA is associated with dentofacial alterations characterised by a tendency toward retrognathism and shorter mandibles. However, the cause-and-effect relationship is yet to be clarified. Keywords: cephalometrics, osteoarthrosis, temporomandibular joint

Objective: To describe a multidisciplinary approach to ensure optimal treatment and timing of treatment for these patients. Methods: Ten patients with congenital missing teeth were treated with dental implants with a multidisciplinary approach, including orthodontics, prosthodontics, and/or orthognathic surgery, from 1997 to 2006 in the Department of Implant Dentistry, Peking University, Hospital of Stomatology. All patients were followed up over five years. Clinical and radiographic examinations were conducted for all the patients. A thorough diagnostic workup was used and the outline of the treatment planning was given from the prosthodontic point of view. Results: A total of 31 implants were placed and restored for the 10 patients involved. Followup averaged 108.4 months (61-155 months) after implant prosthetic functioning. With the multidisciplinary approach, a satisfactory treatment for these patients was acquired, with follow-up for more than 5 years. The peri-implant marginal bone level was stable with bone resorption averaged 1.97 mm. Peri-implantitis was found in one patient with two implants and effectively treated with local anti-infection. Ceramic chips were observed in two cases and the crowns were re-fabricated. Conclusion: Implant restoration with an interdisciplinary approach provides an alternative way with predictable clinical results for patients with congenitally missing teeth. Keywords: augmentation, congenital missing teeth, hypodontia, implant, rehabilitation

Objective: To evaluate the outcome of dissecting the styloid process via an extraoral approach combined with antidepressants for treating Eagle's syndrome. Methods: Twenty-two patients with Eagle's syndrome underwent resection of the elongated styloid processes under general anaesthesia via an extraoral approach. All patients completed a self-rating depression scale preoperatively, and a score over 49 was defined as depression. The patients with depression were treated with fluoxetine 20 mg/day for 3 weeks postoperatively. In all patients, the abnormal length of the styloid process was resected. Results: No surgical complications were observed. Eighteen (81.8%) patients had depression, and all 22 patients were followed for 7 to 26 months: 19 were symptom-free (86.4%), two patients with mild or moderate depression obtained almost complete remission of their symptoms, and one patient with severe depression obtained partial remission. No complications of medication occurred in any patient with depression, and all patients had a satisfactory cosmetic result and no paraesthesia. Conclusion: Dissection of the styloid process via an extraoral approach is simple and reliable; dissection of the styloid process combined with antidepressants (fluoxetine) is preferred for treating Eagle's syndrome. Keywords: antidepressants, depression, Eagle's syndrome, fluoxetine, Styloid-stylohyoid syndrome

Objective: To evaluate the effects of low-intensity swimming on radiation-induced leg contracture. Methods: Forty mice were randomly and equally divided into four groups: 1) irradiation; 2) swimming before irradiation; 3) swimming after irradiation; 4) swimming after contracture, and their left hind legs were exposed to gamma irradiation of 60 Gy. The mice were allowed to swim freely for 10 minutes, three times per day. For group 2, the mice were allowed to swim for only 1 week before irradiation. For group 3, the mice were allowed to swim immediately after irradiation until day 130, post-irradiation. For group 4, the mice were allowed to swim after leg contracture happened (on day 30 post-irradiation) until day 130, post-irradiation. The leg lengths and knee joint angles were measured. Leg contracture was defined as the decrease in the hind leg lengths and the knee joint angles of each animal. The ultrastructural changes of gastrocnemius muscles were observed using transmission electron microscopy. Results: The radiation could result in leg contracture and mitochondrial injury of the muscles. However, the group of swimming immediately after irradiation had less leg contracture and no vacuolar degeneration in the mitochondria, compared with the other groups. Conclusion: Low-intensity swimming that began immediately after the mice were irradiated could effectively prevent the irradiated legs from contracture. Patients with irradiated mastication muscles were recommended to begin mouth-opening exercises immediately after radiotherapy. Keywords: exercise therapy, radiation injuries, radiotherapy, trismus

Objective: To evaluate the effects of a commercial bleaching agent containing 36% hydrogen peroxide on the clinical plaque index and Streptococcus mutans and Lactobacilli counts in dental plaque and saliva in vivo. Methods: Twenty volunteers were recruited in the present study. Evaluation of plaque index and bacteria counts in plaque and saliva was performed before bleaching the teeth, and 3 days, 2 weeks and 4 weeks post-treatment. Results: Quigley-Hein Plaque Index and Modified Navy Plaque Index were significantly lower on day three after bleaching compared to that before bleaching and the other time points after bleaching. The total number of bacteria in the plaque on day three after bleaching was also less than that before bleaching and the other time points after bleaching. The Streptococcus mutans counts in the plaque and saliva four weeks after bleaching were decreased significantly compared to that before bleaching. Conclusion: Hydrogen peroxide bleaching can decrease plaque accumulation and cariogenic bacteria for a short period of time. Keywords: cariogenic bacteria, peroxide, plaque

Objective: To evaluate the level of psychosocial difficulties in patients with temporomandibular disorders (TMD) by using the Symptom Checklist 90 revised (SCL-90-R), and determine whether there is an association between psychosocial status and chronic pain severity. Methods: One hundred and sixty-two female patients who came to the Center for TMD and Orofacial Pain of Peking University Hospital of Stomatology were randomly included in this study. SCL-90-R was used to assess the psychological status of the TMD patients. This instrument was also used to assess psychological status and pain-related disability in chronic pain patients and a seven-item questionnaire was used to grade chronic pain severity (GCP). Univariate analysis of variance and correlation analysis were performed to determine the association between psychological status and chronic pain severity. Results: A total of 126 female TMD patients complained of pain in the temporomandibular joint. One hundred and sixteen patients had low disability, with 83 (51.3%) having low intensity pain (Grade I), 30 (18.5%) having high intensity pain (Grade II) and only 13 (8%) with high disability (Grade III pain). The patients were divided into four groups according to their GCP scores. The scores of all the factors of SCL-90-R were significantly different among the groups. The incidence of psychosocial symptoms was also significantly different among the groups. The psychosocial status of patients with high disability was the worst among the four groups. Conclusion: The GCP severity is a suitable tool to assess the psychosocial and physical status of TMD chronic pain. Some TMD patients have psychological problems and symptoms of psychopathology, especially those with high disability. Physicians should keep this possibility in mind when treating patients with TMD chronic pain. Keywords: chronic pain, disorders psychology, Symptom Checklist 90, temporomandibular

Objective: To report on a three-year clinical evaluation of the gingiva-coloured compomer (Comp Natur, Voco, Germany). Methods: Twelve patients with cervical lesions as a result of either gingival recession or worn root dentine were included in this study. In total, 106 restorations were evaluated by two examiners at baseline, 6-month and 3-year recalls. Results: Ninety-nine restorations (99/106, 93.4%) were reported with having a good retention in the oral cavity at the 3-year recall. Ninety-two of the 99 restorations were evaluated as excellent for colour match. Marginal discoloration was slightly higher at the 3-year recall, while surface texture and anatomic form were significant. Marginal adaptation was not statistically important at the 3-year recall. There was no problem related to caries and postoperative sensitivity. Conclusion: Comp Natur is an acceptable treatment choice for cervical defects with recessed gingiva. Keywords: cervical defect, class 5, Comp Natur, compomer, gingival recession

Desmoplastic ameloblastoma (DA) is a benign but locally invasive variant of the solid/multicystic ameloblastoma (SMA). In the recent World Health Organization classification of odontogenic tumours, DA has been characterised as a variant, with specific clinical, radiographic and histopathological features. A possible 'transitional' form of DA, showing microscopic features of the desmoplastic variant together with areas typical of classic follicular or plexiform ameloblastoma, has been described as a 'hybrid' lesion of ameloblastoma (HLA). A unique case with synchronous emergence of desmoplastic and unicystic ameloblastoma (different growth patterns) in the mandible of a 50-year-old male is reported. Keywords: desmoplastic ameloblastoma, growth pattern, mandible, unicystic ameloblastoma