Chinese Journal of Dental Research, 02/2007

Classification of ameloblastomas into solid or multicystic, unicystic, peripheral and desmoplastic types based on the biological behaviour has gained recent recognition in the new WHO classification of head and neck tumours. The distinctive clinical and pathological features of the unicystic variant were reviewed. The variability of histological spectrum, diagnostic problems and choice of treatment for this subtype of ameloblastoma were discussed in the light of recent research interest and progress. Keywords: ameloblastoma, odontogenic tumour, unicystic variant

Objective: To study the close relationship between odontoblasts and intradental nerves in order to elucidate its role in the sensory mechanism that is responsible for dentinal pain. Methods: Jaws dissected from 40 mice and 35 rats, and 24 human molar teeth, were routinely embedded into paraffin or araldite®. Following embedding, the specimens were studied using immunohistochemistry for some common neuronal and neuropeptide markers or electron microscopy. Results: Strong immunoreactivity for synaptophysin reveals the presence of presynaptic vesicles in the odontoblast zone of the pulp. Immunoreactivity for nerve growth factor receptor (NGFR) shows clearly that the neurites enter the dentinal tubules together with the odontoblast processes as they share a similar course. Electron microscopy images of the neuro-odontoblast relationship demonstrate some morphological characteristics such as synapse-like contacts between neurites and odontoblast processes, the presence of numerous small granular vesicles (SGV) and some clear cored vesicles in the odontoblast process at the synaptic contact and a typical synaptic cleft, 15 to 20 nm in width. From all these features, we can describe these neuro-odontoblast relationships as synaptic, based on immunological and morphological characteristics. Conclusion: Although it has previously been proposed that odontoblasts also could act as a specialised receptor cell, to date no synaptic or gap junctions connecting them with the nerve fibres have been described. In this investigation of mouse, rat and human odontoblasts and intrapulpal and intradentinal nerves, we demonstrated the presence of chemical synapses using electron microscopy and immunohistochemistry. Keywords: immunohistochemistry, neural endings, synapse, odontoblast, transmission electron microscopy

Objective: To investigate the functions of the two heads of lateral pterygoid muscle in mouthopening and jaw-protruding resistance exercises with magnetic resonance imaging (MRI). Methods: Seven normal male subjects participated in the study. Four of the seven subjects did mouth-opening resistance exercises, while two did jaw-protruding resistance exercises and one did both mouth-opening and jaw-protruding resistance exercises over a period of two weeks. The oblique sagittal T2 -weighted MR images of lateral pterygoid muscle were obtained before and immediately after exercise and at 2, 4, 6, 8, 10, 15, 20 minutes after exercise. Signal intensity of the superior and inferior heads of lateral pterygoid muscle, cerebral grey matter, and masseter was also measured at these time points. Results: The signal intensity (SI) of the two heads of lateral pterygoid muscle in all the subjects was increased significantly and homogeneously after mouth-opening or jaw-protruding resistance exercise. The increased SI declined approximately to pre-exercise level in 20 minutes. No changes of SI were found in masseter and cerebral gray matter after exercises. Conclusion: The results of the present study strongly suggest that the two heads of the lateral pterygoid act synergistically and homogeneously during mouth-opening and jaw-protruding resistance exercise. The results do not support the concept that the two heads act antagonistically during jaw movements. Keywords: lateral pterygoid muscle, masticatory muscle, MRI, muscle recruitment, signal intensity

Objective: To evaluate the microtensile bond strength (µ-TBS) of short glass fibre-reinforced composite (FC) to dentine and the reliability of two adhesive systems and influence of water storage on bond strength. Methods: Experimental FC was prepared by mixing short glass fibres with a fraction of 22.5 wt% and IPN-resin 22.5 wt% with silane-treated particulate fillers 55 wt% using a high-speed mixing machine. FC composite and conventional restorative composite resins (PFC) (Grandio; control) were bonded incrementally to flat, midcoronal dentine from 40 human molars, using two different adhesives systems (total-etch [Scotchbond] and self-etch [Futurabond]). Teeth were sectioned both mesiodistally and buccolingually to obtain multiple bonded beam specimens. The specimens were stored in water at 37°C for 1 month or 6 months before being tested in tension at a crosshead speed of 0.5 mm/min until failure. The failure mode was analysed by SEM. The data were analysed using ANOVA. Results: The bond strength of experimental FC did not differ (p > 0.05) from conventional PFC. Bond strength values were significantly higher (p 0.05) with the total-etching system than with the self-etching system. Water storage decreased the bonding values. Conclusion: Short-FC with semi-IPN polymer matrix revealed similar bonding capacity to conventional PFC. Keywords: fibre-reinforced composite, microtensile bond, restorative composite

Objective: To evaluate the osteoinductive effects of adenoviral encoding human BMP-2 (AdBMP-2) gene modified goat bone marrow stromal cells (bMSCs) in nude mice. Methods: Primary cultured goat bMSCs were transduced with 50 pfu/ml AdBMP-2 and Ad- LacZ. Gene transfer efficiency was detected by X-gal staining 3 days after AdLacZ gene transduction. AdBMP-2 or AdLacZ gene modified bMSCs were injected into nude mice intramuscularly (number of injection sites: AdBMP-2 = 9; AdLacZ = 9). Three samples in each group were obtained after 2 weeks, and the remaining six were harvested after 4 weeks. All samples were evaluated by histology. MicroCT, BMP-2 immunohistochemistry and X-gal staining were performed for 4-week samples. Results: Gene transfer efficiency reached above 70%. Two weeks after injection into nude mice. AdBMP-2 samples demonstrated a combination of relatively mature bone formation and a lesser amount of cartilaginous tissue. In contrast, only fibroblastic-like tissue was detected in Ad- LacZ-transduced bMSCs samples. At week 4, all six AdBMP-2 sites had new bone formation, while in the AdLacZ group no obvious radiopaque area was detectable by microCT. Histologically, AdBMP-2 transduction induced a large bone mass with fatty marrow tissue. While the AdLacZ group showed mainly fibrotic tissue proliferation, X-gal staining confirmed the bMSCs origin in the AdLacZ group. Conclusion: bMSCs modified with AdBMP-2 gene can promote new bone formation in a nude mice model and could be used for further bone regeneration in the oral and maxillofacial region. Keywords: bone marrow stromal cells, bone morphogenetic protein, gene therapy

Objective: To investigate the effects of xylitol chewing gum containing calcium hydrogen phosphate and funoran (a polysaccharide extracted from seaweed) on initial enamel lesions. Methods: The clinical trial of the study was double blind. Human enamel blocks with artificial subsurface lesions were mounted in oral devices in 15 subjects. The subjects served as their own controls and were instructed to chew the three different gums, containing: (1) 79% sucrose (S), (2) 40% xylitol (X) and (3) 40% xylitol plus calcium hydrogen phosphate and funoran (X+2), 7 times daily, for a period of 1 week each respectively. Mineral content within the lesions after chewing each gum was analysed by quantitative microradiography. All data were analysed statistically using a one-way ANOVA test. Results: After chewing the gums, the amount of mineral at all depths of subsurface lesion was highest in the X+2 group, followed by the X group and then the S group. The difference between the groups was statistically significant (p 0.01), especially in the lesion body. Conclusion: Xylitol chewing gum containing calcium hydrogen phosphate and funoran significantly enhanced the remineralisation of initial human enamel lesions in situ. Keywords: calcium hydrogen phosphate, enamel subsurface lesion, funoran, remineralisation, xylitol chewing gum

Objective: To investigate the clinicopathologic characteristics of salivary duct carcinoma (SDC) in major and minor salivary glands and the possible role of MMP (matrix metalloproteinase)- 2 and MMP-9 in SDC. Methods: Clinicopathologic features of 10 SDCs were described. Immunohistochemical expressions of MMP-2 and MMP-9 proteins were examined in the paraffin samples of the 10 SDCs and 10 basal cell adenomas (BCA). The scoring of the immunoreactivity was estimated by integrated optical density (IOD) through a digital image analyser. Results: The patients of SDC presented clinically with a local mass or swelling, frequently painful (6 of the 10 cases). The symptoms of facial paralysis or lip numbness (3/10) and lymph node metastasis (6/10) were usually detected. SDCs showed increased expression in both MMP-2 and MMP-9 proteins as compared with BCAs. Moreover, MMP-2 and MMP-9 proteins were markedly increased in metastatic compared with non-metastatic SDCs. Conclusion: MMP-2 and MMP-9 may play an important role in invasion and metastasis of SDC. Toothache may be an important clinical characteristic of SDC originated in maxillary sinus. SDC histologically showed various proportions of papillary, comedo, cribriform and solid patterns. Keywords: immunohistochemisty, MMP-2, MMP-9, salivary duct carcinoma

Objective: To study long-term skeletal and dento-alveolar stability 15 years after surgical-orthodontic correction of skeletal open bite. Methods: Ten open bite patients (8 females and 2 males) who had undergone orthodontic treatment in combination with bimaxillary surgery at Hannover Medical School were reviewed. All patients underwent Le Fort I osteotomies combined with bilateral sagittal split osteotomy. The cephalometric records of these patients were examined at the start of orthodontic treatment (T1), before surgery (T2), immediately after surgery (T3), medium-term after surgery (average 1.5 years, T4) and long-term after surgery (average 15 years, T5). Eight skeletal and five dental cephalometric measurements were selected. Skeletal and dento-alveolar changes were evaluated. Results: Moderate skeletal relapse has been observed 15 years after surgery in skeletal open bite patients treated by bimaxillary surgery. Approximately half of the total surgical changes in PP-SN, MP-SN and ANS-Me remained. Two-thirds of surgical changes in N-Me, N-ANS and S-Go remained. Except that the anterior part of maxilla relapsed completely 1.5 years after surgery, other skeletal relapses occurred mainly in the late follow-up period. Overbite remained quite stable 15 years after surgery, which was mainly due to the upper and lower incisors eruption during the long-term period. Conclusion: Treatment of skeletal open bite via Le Fort I and bilateral sagittal split osteotomies appears to be a clinically successful and stable procedure.

Objective: To study the effect of Epimedium grandiflorum Morr (EG) on the prevention and treatment of bone loss of the mandible and femur in ovariectomised rats. Methods: A total of 114 adult female Sprague-Dawley (SD) rats were ovariectomised. The effects of EG and oestradiol (ES) on prevention and treatment of bone loss were evaluated. For prevention, both drugs were given the day after ovariectomy. For treatment, the drugs were given 3 months after ovariectomy, when the animal model of osteoporosis was established. The bone density was determined with a densitometer. Newly synthesised collagen was fluorescently labelled with procion red. Results: Three months after ovariectomy, the bone densities of the rat femurs and mandibles were markedly lower than those of the controls, indicating that osteoporosis was successfully established. Administration of EG and ES equally prevented osteoporosis of mandible and femur of ovariectomised rats, and to some extent increased bone density of osteoporosis rats. Conclusion: EG was effective in the prevention of osteoporosis of the mandibles and femurs. EG was also somewhat effective in the treatment of osteoporosis of femurs. Keywords: Chinese herbal medicine, Epimedium grandiflorum Morr, mandible bone loss, osteoporosis

Objective: To investigate the differences in 1H nuclear magnetic resonance (1H NMR)-based metabonomic analysis between oral squamous cell carcinoma (OSCC) and healthy control by principal component analysis (PCA); also, to evaluate this method in distinguishing different sample classes, and to detect the relationships between genotypes and phenotypes. Methods: 1H NMR resonances of plasmas were obtained from 20 OSSC subjects as well as 20 healthy subjects, and spectrally processed. Subsequent data were reduced by applying unsupervised PCA, one method of pattern recognition analysis, to detect the different spots corresponding to the low-molecular-mass metabolites. Results: Some important micromolecular species in plasma, including myo-inositol, praline, creatinine, arginine, and aspartic acid displayed great dissimilarity between OSCC and healthy control. Conclusion: The NMR metabonomic technique is feasible for studying the small molecule components of human blood plasma. Keywords: 1H NMR spectroscopy, metabonomics, oral squamous cell carcinoma

The aim of the study was to design a bracket structure that features two parallel rectangular slots. This Twin-slots bracket separates the embedment of two archwires and therefore forms a force-acting area between the archwires and the slots, creating a large amount of force moment. With the tooth displacement being guided and controlled within the track of two archwires, some modalities of tooth movement that require heavy force moment, such as mesio-distal bodily translation, de-rotation and uprighting, could be manipulated efficiently. A variety of options in the combination of two different archwires mean they function independently but integrally to fulfil complex teeth repositioning, e.g. relieving severe crowding in anterior teeth while reinforcing the anchorage in the molars, and retracting the anterior teeth by one archwire performing labial-lingual tipping while the other adjusts torque. A case report was provided to demonstrate its clinical application. This design is a preliminary attempt and further improvement in the slot structures, such as the built-in prescriptions, should be the subject of further research. Keywords: force moment, main and auxiliary archwires, twin-slots bracket