长春市某小学7～12岁儿童福赛斯坦氏菌和中间普氏菌分布状态调查

目的 应用聚合酶链反应(PCR)法对儿童口腔内福赛斯坦氏菌(Tannerella forsythus,Tf)和中间普氏菌(Prevotella intermedia,Pi)进行检测,探讨检出结果与牙周临床指标之间的关系.方法 选取长春市自强小学151名7至12岁儿童为研究对象,选择右上颌中切牙和第一磨牙为被检牙位,取龈上菌斑、记录探诊出血(bleeding on probing,BOP)、探诊深度(probing depth,PD)、牙龈指数(gingival index,GI),应用PCR法对儿童龈上菌斑中的Tf和Pi进行检测.结果 儿童龈上菌斑中Tf、Pi的检出率分别为40.3%(1 18/293)、46.4%(136/293);6颊面Tf、Pi的检出率分别为55.2%(80/145)、53.8%(78/145)均显著高于(1)唇面的Tf和Pi的检出率[分别为25.7%(38/148)、39.2%(58/148)],差异有统计学意义(P＜0.01);Pi检出率随年龄增长呈逐渐减低趋势,Tf检出率在7～8岁组最高,其次为11～12岁和9～10岁组;BOP阳性部位的Tf、Pi检出率[分别为43%(35/81)、49%(40/81)]均高于BOP阴性部位二者的检出率[分别为37%(72/194)、45%(87/194)].在BOP阳性部位,随PD加深Tf检出率逐渐增高,特别是在PD 4 mm以上时Tf检出率明显增高(P＜0.01),Tf检出率与BOP阳性、PD增加呈正相关.结论 7～12岁儿童龈上菌斑中高频度分布着Tf和Pi;上颌前牙区与磨牙区菌丛构成不同,Tf、Pi在磨牙区检出率更高,Tf的检出率与PD呈正相关,Tf检出率在7～8岁组最高,Pi检出率随年龄增长呈减低趋势,儿童时期进行牙周病早期预防是非常必要的.

Abstract：

Objective To detect the presence of Tannerella forsythus(Tf)and Prevotella intermedia (Pi) using polymerase chain reaction(PCR) in the oral plaque samples from children and investigate the relationship between bacteria and clinical parameters. Methods A total of 151 children aged 7 to 12 years were selected from Changchun primary school. The supragingival plaque sample was collected from the mesiobuccal and labial surfaces of the right maxillary central incisor ( FDI 1 ) and the right maxillary first molar ( FDI 6 ). Extracted DNA from plaque samples was used for PCR analysis. Intraoral examination,probing depth (PD) and bleeding on probing (BOP) were performed and recorded. Results The detection rate for Tf was 40. 3% ( 118/293 ) and Pi was 46. 4% ( 136/293 ) in supragingival plaque. The detection rates for Tf and Pi in molars were much higher than those in incisors( P ＜0. 01 ). The detection rate of Tf and Pi was positively related to BOP + and PD. The detection rate for Pi decreased gradually with age, and the detection rate for Tf was highest in the group aged 7 to 8 and the detection rates for Tf and Pi were higher in the gingiva with BOP + than that with BOP - ( P ＞ 0. 05 ). The detection rates for Tf increased remarkably with BOP + and especially when PD was greater than 4 mm. Conclusions Detection rates of putative periodontal pathogens from healthy children of 7 to 12 years of age were high. The detection rates for Tf and Pi in molars were much higher than those in incisors, and the presence of Tf and Pi in supragingival plaque was related to periodontal parameters.     

Mechanical evaluation of space closure loops in orthodontics

This study evaluated the mechanical performance of teardrop-shaped loops and teardrop-shaped loops with helix used in orthodontic space closure. Sixty retraction loops made with 0.019" x 0.025" stainless steel (SS) and beta-titanium (BT) wires were used. They were attached to a testing machine to measure the magnitudes of the sagittal force and the load-deflection ratio necessary for 1 mm, 2 mm and 3 mm activation. The results demonstrated that the BT alloy presented significantly smaller mean values (p < 0.01) of sagittal force and load-deflection than the SS alloy. The loop with the highest mean value of sagittal force and load-deflection was the teardrop-shaped loop (p < 0.01). Differences were observed in the mean values of sagittal force and load-deflection among activations, and the highest mean value was found in the activation of 3 mm, while the smallest mean value was evident in the activation of 1 mm (p < 0.01). It could be concluded that the metallic alloy used and the presence of a helix in configuration of the loops may have a strong influence on the sagittal force produced and on the load-deflection ratio; the teardrop-shaped loops and teardrop-shaped loops with helix in BT presented the release of lighter forces; the teardrop-shaped loop in SS generated a high load-deflection ratio, providing high magnitudes of horizontal force during its deactivation.     

A thick frame decreases the fracture toughness of veneering ceramics used for zirconia-based all-ceramic restorations

Purpose

To investigate the influence of firing condition and thickness of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) frame on the fracture toughness of veneering ceramics.

Biomechanical comparison of straight and staggered implant placement configurations

The effect of buccolingual staggered implant placement on stress distribution within the supporting structure was examined photoelastically. Two photoelastic models of a human mandible, edentulous distal to the canine, were fabricated. Three screw-type implants were embedded into the edentulous region of each model. The implants were placed in a straight line in one model and in a buccolingual staggered configuration in the other. Vertical and lateral loads were applied to a fixed partial denture superstructure. No clear biomechanical advantage to a staggered 1.5 mm buccal and lingual offset placement configuration was observed.     

Resorbable poly-L-lactide plates and screws for the treatment of mandibular condylar process fractures: a clinical and radiologic follow-up study.

PURPOSE: The purpose of this study was to determine whether a resorbable poly-l-lactide (PLLA) miniplate system could be used to treat mandibular condylar process fracture. PATIENTS AND METHODS: Fourteen patients (12 males, 2 females, aged 23.1 +/- 5.7 years) who had mandibular condylar process fractures treated with PLLA implants were recalled for follow-up clinical and radiologic examinations at 3 years. RESULTS: Mouth opening recovered to more than 35 mm and occlusion was stable in all patients. There was no facial asymmetry 3 months postoperatively. Two patients had mild chronic postoperative tenderness at the implantation site; however, there was no wound infection. All fractured mandibular condyles showed anatomic good reduction and long-term stability with the use of resorbable miniplates and screws. Bone healing was satisfactory in all patients, and there was no evidence of abnormal resorption of the condylar process. The screw holes remained evident after 3 years. Screw holes in 2 patients showed enlargement on radiographic examination. CONCLUSION: The PLLA miniplate system provides reliable stability when used for the fixation of mandibular condylar process fractures.     

Salivary duct carcinoma in the mandible: a case report

Salivary duct carcinoma (SDC) is a distinctive and aggressive neoplasm. The most frequent site of origin is the parotid gland, followed by the submandibular gland. SDC originating in the minor salivary glands, particularly in the ectopic glands within the mandible, is extremely rare. We describe a 62-year-old man with SDC in the mandible, who presented with a painless lump in the right submandibular region (later identified as lymph node metastasis) and ipsilateral mental nerve palsy. Histologic examination after ablative surgery revealed SDC originating in the mandible and cervical nodal metastases spreading to levels I-III. The patient remains alive 59 months after presentation as a result of postoperative full-dose irradiation and regular intensive chemotherapy using TXT, 5-FU, and CDDP. However, the patient has local recurrence and distant metastases to the lung and brain. In this report, we also discuss the specific diagnostic criteria and developmental theories of intraosseous salivary gland tumors.