Influence of intraradicular post and crown ferrule on the fracture strength of endodontically treated teeth

The aim of this study was to investigate the fracture strength of endodontically treated teeth restored with different posts and variable ferrule heights. Sixty freshly extracted human canines were treated endodontically and randomly assigned to 6 groups (n=10), being restored with custom-made cast post-and-core (CP0 and CP3 groups), prefabricated post and composite resin core (PF0 and PF3 groups), and composite resin (CR0 and CR3 groups). The CP0, PF0 and CR0 groups presented no ferrule and the CP3, PF3 and CR3 presented 3 mm of coronal structure. All teeth were restored with full metal crowns. The fracture strength was measured in a universal testing machine at 45o to the long axis of the tooth until failure. Data were analyzed statistically by 2-way ANOVA and Tukey's test (?=0.05). When the mean fracture strength values were compared (CP0 group - 820.20 N, CP3 group - 1179.12 N; PF0 group - 561.05 N; PF3 group - 906.79 N; CR0 group - 297.84 N; and CR3 group - 1135.15 N) there was statistically significant among the groups (p<0.05), except for the three groups with 3 mm of coronal remaining, which were similar to each other. The results of this study showed that the ferrule in crowns promoted significantly higher fracture strength in the endodontically treated teeth.

O objetivo neste estudo foi avaliar a resistência à fratura de dentes tratados endodonticamente restaurados com diferentes pinos e diferentes alturas de remanescente dentinário da coroa. Sessenta caninos recém-extraídos foram tratados endodonticamente, separados em 6 grupos (n=10) e restaurados com núcleo metálico fundido (CP0 e CP3), pino pré-fabricado e núcleo em resina composta (PF0 e PF3) ou resina composta (CR0 e CR3). Os grupos CP0, PF0 e CR0 não possuíam férula e os grupos CP3, PF3 e CR3 apresentaram 3 mm de remanescente coronário. Todos os dentes foram restaurados com coroas totais metálicas. A resistência à fratura foi medida em máquina universal de ensaios com o longo eixo do dente posicionado a 45 graus em relação ao carregamento axial, até que ocorresse fratura. A análise de variância 2 critérios (?=0,05) mostrou diferença estatisticamente significativa entre os grupos. Quando as médias das forças para fratura foram comparadas (CP0 = 820,0 N; CP3= 1179,12 N; PF0 = 561,05 N; PF3 = 906,79 N; CR0 = 297,84 N; e CR3 = 1135,15 N) não foram observadas diferenças significativas entre os 3 grupos com 3 mm de remanescente coronal. Os resultados mostraram que a presença de férula em coroas aumenta significantemente a resistência à fratura de dentes tratados endodonticamente.

Longitudinal arch stress distribution of the foot following plantar ligament injury / 中华创伤杂志

Objective To measure stress distribution of the main bone architecture of the normal adult cadaveric foot and discuss the effect of plantar ligament injury on stress distribution. Methods Seven fresh adult cadaveric feet were used and 10 strain gauges attached to the bones of the longitudinal foot arch,including the calcaneus,navicular,medial cuneiform,1-5 metatarsal trunk,the distal part of the tibia and fibular,respectively.After the loading Was added to 700 N by almighty test machine,resistance strainmeter was used to measure surface strain of these bones.The results were processed statistically. Results The strain was varied based on different bone segments attached and increased with loading.Tensile force was always found at the medial part of the navicular,the distal part of the tibia and fibular,while the others showed compression all the time.Peak strain was found at calcaneus.followed by the second and third metatarsal.Strain on the surface of the bone segments changed greatly with different ligament injury(P＜0.05).Conclusion The bone surface stress of the longitudinal foot arch changes significantly when the plantar ligament is injured.

CLINICAL ANALYSIS OF STRESS FRACTURE OF THE PUBIC RAMUS CAUSED BY MILITARY TRAINING: A REPORT OF 66 CASES / 解放军医学杂志

To investigate the clinical diagnosis and treatment of stress fracture of the pubic ramus caused by military training, clinical data of 66 cases (18 males and 48 females, ranging from 18～21 years, mean age 19 6 years ) with stress fracture of the pubic ramus were retrospectively analysed. 55 cases were military recruits undergoing basic training, 11 army veterans undergoing intensive goose step training. 66 cases complained of chronic groin pain which increased in activity and relieved while at rest. The symptom occurred 3～10 weeks after the training began. The pain often lasted 1 week ～14 months. 22 cases who sought medical advice in medical team were mistaken for muscular injury. There were 76 stress fractures of the pubic ramus in 66 soldiers. 56 had stress fractures of one inferior pubic ramus, 6 both inferior pubic rami, and four had ipsilateral inferior and superior pubic rami fractures. Stress fracture of the pubic ramus is not rare, but it's quite easy to be neglected or misdiagnosed. The key to its diagnosis is getting a deeper understanding and making an adequate and early imaging examination in light of the clinical data.

X-ray diagnosis of stress fracture of the pubic ramus / 中华放射学杂志

Objective To study the X-ray findings and evaluate the value of X-ray in diagnosis of stress fracture of the pubic ramus. Methods The X-ray findings of 66 cases (18 males and 48 females, ranging in age from 18-21 years, mean age 19.6 years) with stress fracture of the pubic ramus were retrospectively analyzed. Fifty-five cases were military recruits undergoing basic training, and 11 army veterans were undergoing intensive goose step training. Results Sixty-two cases had stress fractures of the inferior pubic ramus including right-sided in 26, left-sided in 30, and bilateral in 6. Four had ipsilateral inferior and superior pubic rami fractures. With 2 weeks after onset, the radiographs were normal in 3 cases. The 66 cases had either a slight transverse fissure (34 cases) or a small dense callus (65 cases) or both during the examination period of 4 weeks to 8 months. Then the calcium resorbed at the margins of the fracture and at the same time the callus increased and surrounded the bone. Finally, the resorptive zone disappeared and the callus became homogeneous. This callus formation persisted for several months and disappeared gradually. Conclusion X-ray examination is the first imaging method of choice for detecting stress fracture of the pubic ramus. With combining clinical data, correct diagnosis can be made in the majority.

MR Imaging Findings of Fatigue Fractures of Lower Extremity in Young Soldiers

PURPOSE: To evaluate the MR imaging findings of fatigue fractures of the lower extremity in young soldiers. MATERIALS AND METHODS: In 22 cases of fatigue fractures of the lower extremity in young soldiers proven byclinical findings and radiological follow up, the MRI findings were retrospectively evalvated. All patients weremale and aged between 19 and 21 years. As seen on MRI, the bone marrow edema, intramedullary low signal intensityband, cortical fracture line, periosteal reaction, surrounding soft tissue edema, and enhancement pattern wereanalyzed and the site of involvement was determined in the axial plane. RESULTS: The locations of fatiguefractures of the lower extremity were the tibia (n=12), fibula (n=8), femur (n=1) and second metatarsus (n=1). Alloccurred in diaphyses: the junction of the proximal and middle (n=10), middle (n=9), proximal (n=2), and distalshaft (n=1). The sites of involvement were the posteromedial (n=6) and medial side (n=6) of the tibia, and theentire portion of the fibula(n=5) in the axial plane. MRI findings were bone marrow edema in 20 cases,intramedullary low signal intensity band in 14 (which were continuous with the cortex or cortical fracture line),cortical fracture line in 13, and periosteal reaction and surrounding soft tissue edema in all. Ongadolinium-enhanced images, enhancement was seen in the bone marrow in 19 cases, in the subperiosteal region in18, and in the surrounding soft tissue in 22. CONCLUSION: In fatigue fractures of the lower extremity in youngsoldiers, the main locations were the tibia and fibula, and characteristic MR imaging findings were intramedullarylow signal intensity bands, which were continuous with the cortex or cortical fracture line and often accompaniedby bone marrow edema, periosteal reaction, and surrounding soft tissue edema.

Stress Fracture in Posterior Aspect of the Tibia

PURPOSE: To determine correlation between stress fracture of the posterior tibia and flexor digitorum longusmuscle injury caused by athletic or sporting activity during adolescence. MATERIALS AND METHODS: Eleven casesdiagnosed as stress fracture after X-ray and MR imaging of the lower leg were reviewed. With regard to eachfracture, the following features were noted: age, sex, and athletic or sporting activity of the patient, and site.Using MR imaging techniques, axial and sagittal T1 and T2 weighted images were obtained in all cases and T1-GdDTPA images in seven. RESULTS: The activities undertaken were running (n=3), football (n=2), ballet (n=2),taekwando (n=1), badminton (n=1), field hockey (n=1), and basketball (n=1). MR images revealed localized corticalthickness (n=11), linear intramedullary callus showing a low signal on T1 and T2 weighted images (n=9), marrowhyperemia (n=7), and flexor digitorum longus muscle injury showing a high signal on T1-Gd DTPA and T2 weightedimage (n=7). CONCLUSION: Stress fracture of the posterior tibia might be induced by flexor digitorum longusmuscle activity induced by athletic or sporting activities during adoleseence.