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Objective:To investigate the influence of 3 methods of fiber posts on fracture resistance of maxillary anterior teeth with flared root canals.Methods:32 human maxillary central incisors were assigned randomly to 4 groups(n =8).The crowns of the teeth were removed at a level 2 mm incisal to the cementoenamel junction(CEJ).After root canal therapy,flared canals were simula-ted in 3 groups.The flared canals were reinforced with resin cement(group A),resin composite(group B)and accessory posts (group C)respectively.In group D flared canals were not created.The same size fiber posts were cemented with resin cement in all groups.After posts cementation and composite resin core formation,all teeth were restored with metal crowns.Then the roots of the teeth were embedded in acrylic resin blocks up to 2 mm below the CEJ.The samples were loaded in a testing machine until failure occurred.Results:The maximum load value(N)for fracture of group A,B,C and D was 295.94 ±69.11,450.51 ±54.68, 479.37 ±77.81 and 618.51 ±87.42 respectively(F =118.127,P =0.000);group B vs C,P >0.05,between each 2 of the other groups,P 0.05). Conclusion:Reinforcement of flared canal with resin composite and accessory posts can increase the fracture restance of the tooth root and the most of fracture patterns are beneficial for the second repair.
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BACKGROUND:Recent years, fiber posts and resin cores have been widely used in repairing the endodonticaly treated teeth with satisfactory effect. Erbium:yttrium aluminum garnet (Er:YAG) laser is a new type of water power laser system, which can be used for surface treatment of fiber posts. But studies on the effect of Er:YAG laser surface treatment on the bond strength of fiber posts are rarely reported. OBJECTIVE: To evaluate the effect of surface treatment utilizing Er:YAG laser irradiation with different parameters on the bond strength of fiber posts to root canal dentin. METHODS: Fifty human maxilary central incisors that had similar dimensions were used. After endodontic treatment, removal of the crown and canal preparation, ParaPost FIBER LUX glass fiber posts were cemented into the root canals. According to the method of surface treatment, 50 teeth were randomly divided into: no surface treatment as control group; four groups undergoing surface preparation with Er:YAG laser with four different power settings (150, 250, 350 and 450 mJ at 10 Hz for 60 s at 100-μs pulse duration), named 1.5, 2.5, 3.5, and 4.5 W Er:YAG laser irradiation groups, respectively. RESULTS AND CONCLUSION: The mean bond strength values reduced from the cervical to the apical root canal, and the bond strength of the dental cervix was significantly different from that of middle and apical thirds (P 0.05). Regardless of the different part of the root slices, the bond strength was highest in the 4.5 W Er:YAG laser irradiation group, showing significant difference from other groups (P < 0.05). These findings indicate that 4.5 W Er:YAG laser irradiation significantly increases the bond strength of the fiber posts to root canal dentin.
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BACKGROUND:Although incidents of organophosphate-induced delayed neurotoxicity have been documented for over a century, the molecular mechanisms underlying the axonopathy remain poorly understood. OBJECTIVE:To discuss the effects of tri-ortho-cresyl phosphate (TOCP) on homeostasis of the glutamate-glutamine cycle and the expression of key enzymes in the brains of hens. METHODS:Twenty-four adult hens were randomly divided into three groups (n=8). TOCP group was treated with TOCP by gavage at a single dosage of 1 000 mg/kg, and control group was given an equivalent volume vehicle by gavage, while hens in the phenylmethylsulfonyl fluoride (PMSF)+TOCP group were subcutaneously injected with 40 mg/kg PMSF fol owed by 1 000 mg/kg TOCP 24 hours later. The hens were kil ed on days 5 and 21 post-dosing. The brains were taken out quickly and preserved in a-80℃deep freezer. ELISA was used to determination the content of glutamine synthetase and glutaminase and the activity of glutamine synthetase. Corresponding kits were used to measure the level of glutamate and glutamine. Fluo3-AM was used to measure cytosolic calcium concentration. RESULTS AND CONCLUSION:The activity and content of glutamine synthetase and the concentration of glutamine were down-regulated, while the concentrations of the intracellular Ca2+and glutamate were up-regulated in the early stage after TOCP administration. It is also suggested that the downregulated expression of glutamine synthetase may be associated with organophosphate-induced delayed neurotoxicity through the disruption of homeostasis of the glutamate-glutamine cycle and cytosolic calcium concentration.
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BACKGROUND:The elastic modulus of the fiber post is close to that of the dentine, so it can form a homogeneous whole and share the masticatory force, which can ease the stress concentration of dentine and prevent from tooth fracture. ＜br> OBJECTIVE:To investigate the effect of alveolar bone height and fiber post length on the fracture resistance of endodontical y treated maxil ary central incisors. ＜br> METHODS:Forty-eight human maxil ary central incisors were assigned randomly to six groups (n=8) of three different post insertion depths (5, 7, 9 mm) and two alveolar bone levels (2 and 5 mm) from the cement-enamel junction. Al of them were restored by glass fiber posts with composite resin core and cast metal crown. The samples were loaded in a testing machine with a crosshead speed of 1 mm/min at a 45° angle to the long axis of the tooth on the palatal surfaces until tooth fracture occurred. The maximum load and failure mode were recorded. ＜br> RESULTS AND CONCLUSION:Alveolar bone height had a significant influence on the fracture resistance (F=560.943, P>0.05), but fiber post length did not have a significant influence on it (P>0.05). Significant differences were found between the normal and resorbed alveolar bone groups in the number of repairable fracture patterns (χ2=5.689, P＜0.05). Under the circumstance of lowered alveolar bone height, lengthening fiber post cannot enhance fracture resistance of the teeth.
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BACKGROUND:The elastic modulus of the fiber post is close to that of the dentine, so they can form a homogeneous whole and share the masticatory force, which can ease the stress concentration of dentine and prevent from tooth fracture. OBJECTIVE:To observe clinical effects of anterior teeth with flared root canals restored by fiber posts using three application methods. METHODS:Anterior teeth with flared root canals from 48 patients were involved. They were divided into three groups, then restored with three post-core crowns respectively: a single fiber post, rehabilitation with composite resin, and fiber post combined with accessory post. Al patients were folowed up for 2 years to observe post and core loosening, fracture and root fracture. RESULTS AND CONCLUSION:The group of a single fiber post was failed in eight teeth including four cases of post and core loosening and four cases of post and core fracture, with a successful rate of 64%. The group of rehabilitation with composite resin was failed in three teeth including two cases of post and core loosening and one case of post and core fracture, with a successful rate of 90%. The group of fiber post combined with accessory post was failed in two teeth of post and core loosening, with a successful rate of 93%. The successful rate of the group of a single fiber post was lower than that of the groups of rehabilitation with composite resin and fiber post combined with accessory post (P 0.05). The clinical effects of rehabilitation with composite resin and fiber post combined with accessory post are better than that of a single fiber post. But the method of combination fiber post with accessory post is recommended because of easy operation.
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BACKGROUND:Although incidents of organophosphorus poisoning-induced delayed neuropathy (OPIDN) have been documented for over a century, the molecular mechanisms underlying the axonopathy remain poorly understood. Therefore, OPIDN treatment has been increasingly concerned. OBJECTIVE:To construct the OPIDN hen model induced by triorthocresyl phosphate (TOCP) and to explore the effect of phenylmethylsulfonyl fluoride (PMSF) intervention. METHODS:Adult hens were randomly divided into four groups: two TOCP groups, a PMSF group and a control group. TOCP groups were treated with TOCP by gavage at a single dosage of 1 000 mg/kg and 750 mg/kg respectively; control group was given an equivalent volume of saline by gavage while hens in the PMSF group were subcutaneously injected with 40 mg/kg PMSF 24 hours after 1 000 mg/kg TOCP injection. OPIDN neurological signs were assessed by a six-point graded scale. The changes of the hen weight were recorded. The hens were kiled on day 5 and 21 post-dosing. The samples were cut into 50 nm thick sections and examined by transmission electron microscopy. RESULTS AND CONCLUSION:OPIDN neurological signs such as abnormal gaits progressed in severity with time (P < 0.05), and the hen weight was significantly decreased in TOCP groups (P < 0.05). However, no clinical signs of delayed neurotoxicity were observed in hens of the PMSF group and the control group during the experiment period. The mild mitochondrial sweling and the fragmentation of microfilament and microtubule arrangement in axons were observed on day 5 post-dosing, leaving the other organeles remained unchanged. On day 21, neuronal degeneration was apparent, including sweling of endoplasmic reticulum, abnormal change of mitochondria, and disordered arrangement of cytoskeleton. The optimal dose of TOCP was 1 000 mg/kg. Experimental findings indicate that, OPIDN hen model induced by TOCP and PMSF intervention hen model were successfuly constructed. PMSF intervention significantly improved the pathologic changes and clinical symptoms of OPIDN induced by TOCP in hens.
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Objective To discuss the effects of applying electric heating pattern instrument in experimental teaching of fixed partial denture technology.Methods Totally 98 prosthodontic undergraduates of 2008 and 2009 grades were selected in this study； 46 students of 2008 grade were taken as control group and 52 students of 2009 grade were taken as experimental group.Students in experimental group made wax patterns with electric heating pattern instruments to melt inlay wax while those in control group made wax patterns with instruments heated by alcohol lamps.Teaching effects were evaluated by experimental test scores and questionnaires.Results Test scores of experimental group were (22.6± 1.8),obviously higher than those of (22.6-± 1.8) in control group (P ＜ 0.05).Satisfaction degree of experimental group were increased significantly compared with that of control group based on the resuits of questionnaire.Conclusions Applying electric heating pattern instrument in making wax patterns in experimental teaching of fixed partial denture technology is easy to operate and can improve the quality of wax pattern and working efficiency as well as enhance students' confidence,therefore it is worthy further spreading.
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The clinical practice is a very important link for medical students to relate theory with practice and to be trained comprehensively.Stomatology is an applied science,so clinical practice is more outstanding and important during the stomatological education.This thesis discusses how to improve stomatological students' comprehensive skill in the clinical practice.