Effect of high energy X-ray irradiation on the nano-mechanical properties of human enamel and dentine

Abstract Radiotherapy for malignancies in the head and neck can cause common complications that can result in tooth damage that are also known as radiation caries. The aim of this study was to examine damage to the surface topography and calculate changes in friction behavior and the nano-mechanical properties (elastic modulus, nanohardness and friction coefficient) of enamel and dentine from extracted human third molars caused by exposure to radiation. Enamel and dentine samples from 50 human third molars were randomly assigned to four test groups or a control group. The test groups were exposed to high energy X-rays at 2 Gy/day, 5 days/week for 5 days (10 Gy group), 15 days (30 Gy group), 25 days (50 Gy group), 35 days (70 Gy group); the control group was not exposed. The nanohardness, elastic modulus, and friction coefficient were analyzed using a Hysitron Triboindenter. The nano-mechanical properties of both enamel and dentine showed significant dose-response relationships. The nanohardness and elastic modulus were most variable between 30-50 Gy, while the friction coefficient was most variable between 0-10 Gy for dentine and 30-50 Gy for enamel. After exposure to X-rays, the fracture resistance of the teeth clearly decreased (rapidly increasing friction coefficient with increasing doses under the same load), and they were more fragile. These nano-mechanical changes in dental hard tissue may increase the susceptibility to caries. Radiotherapy caused nano-mechanical changes in dentine and enamel that were dose related. The key doses were 30-50 Gy and the key time points occurred during the 15th-25th days of treatment, which is when application of measures to prevent radiation caries should be considered.

Factors influencing the development of ulcers and strictures in carcinoma of the esophagus treated with radiotherapy with or without concurrent chemotherapy.

PURPOSE: To ascertain factors that could influence the development of ulcers and strictures in the definitive management of squamous cell carcinoma (SCC) of esophagus treated with external beam radiotherapy (EBRT), high-dose-rate (HDR) intralumenal radiotherapy (ILRT) with or without concurrent weekly cisplatin (CDDP @ 35 mg/m2) chemotherapy (CT). MATERIALS AND METHODS: Between 1990-2005, 244 patients with inoperable SCC of esophagus were identified from our database and grouped into one of the following: those receiving at least 60 Gy EBRT (Gp E, n=44); EBRT followed by HDR-ILRT (Gp E+I, n=98); at least 50 Gy EBRT with CT (Gp E+C, n=68); EBRT+HDR-ILRT + CT (Gp E+I+C, n=34). Ulcers (discovered on endoscopy) and strictures evident on a barium swallow (which needed dilatations) were scored as treatment induced, if the biopsy was negative. Factors likely to influence their outcome were analyzed. RESULTS: The groups were matched for all patient and disease characteristics except pretreatment hemoglobin and Karnofsky performance score (KPS), which were lower in Gp E. The incidence of ulcers was 7%, 8%, 6% and 21% (P=0.08) while that of strictures was 14%, 9%, 21% and 41% (P=0.00) for the groups E, E+I, E+C and E+I+C respectively. On univariate analysis, patients with better KPS (P=0.03), treated with narrow applicators (6 mm vs. 10 mm, P=0.00), received CT (P=0.00) or assigned to Gp E+I+C (P =0.00) were more likely to develop strictures, with a trend for development of ulcers in Gp. E+I+C (P=0.08). Logistic regression retained only Gp E+I+C for development of ulcers (OR 10.36, 95% CI 1.2-89.1, P=0.03) and strictures (OR 4.2, 95% CI 1.4-12.6, P=0.00). CONCLUSION: Treatment intensification as in Gp E+I+C results in about a three-fold increase in treatment induced late morbidity which can adversely impact on swallowing function and therefore emphasizes the need for optimisation of HDR-ILRT when used in a CT+RT protocol.

Risk factors for anastomotic leakage after preoperative chemoradiation therapy and low anterior resection with total mesorectal excision for locally advanced rectal cancer / Factores de riesgo para la fuga anastomótica después de quimio-radioterapia preoperatoria y resección anterior baja con excisión total de mesorrecto para cáncer de recto localmente avanzado

Background. Risk factors for anastomotic leakage after preoperative chemoradiation plus low anterior resection and total mesorectal excision remain uncertain. Objective. To analyze, the associated risk factors with colorectal anastomosis leakage following preoperative chemo-radiation therapy and low anterior resection with total mesorectal excision for rectal cancer. Materials and methods. Between January 1992 and December 2000, 92 patients with rectal cancer were treated with 45 Gy of preoperative radiotherapy and bolus infusion of 5-FU 450 mg/m² on days 1-5 and 28-32, six weeks later low anterior resection was performed. Univariate analysis was performed as to find the risk factors for colorectal anastomotic leakage. Results. There were 48 males and 44 females, mean age was 55.8 years. Mean tumor location above the anal verge was 7.4 ± 2.6 cm. Preoperative mean levels of albumin and lymphocytes were 3.8 g/dL and l,697/mL, respectively. Mean distal margin was 2.9 ± 1.4 cm. Multivisceral resection was performed in 11 patients (13.8%), 32 patients (35%) had diverting stoma. Mean preoperative hemorrhage was 577 ± 381 mL, and 27 patients (24%) received blood transfusion. Ten patients (10.9%) had anastomotic leakage. No operative mortality occurred. Risk factors for anastomotic leakage were: gender (male) and tumor size > 4 cm. Three patients of the group without colostomy required a mean of six days in the unit of intensive care; mean time of hospital stay of patients with and without protective colostomy was 12.4 ± 4.5 days vs. 18.3 ± 5.2 days (p = 0.01). Conclusion. In male patients with rectal adenocarcinoma measuring > 4 cm, treated by preoperative chemoradiotherapy + low anterior resection with total mesorectal excision, a diverting stoma should be performed to avoid major morbidity due to anastomotic leak.

Antecedentes. Los factores de riesgo para la fuga de anastomosis colo-rectal después de quimio-radioterapia preoperatoria con excisión total de mesorrecto permanecen aún inciertos. Objetivo. Analizar los factores de riesgo asociados con la fuga o filtración de anastomosis colorrectal que sigue a la terapia de radiación química y a la extirpación anterior baja con total excisión mesorrectal para el cáncer rectal. Materiales y métodos. Entre enero de 1992 y diciembre de 2000, 92 pacientes con cáncer rectal fueron tratados con 45 Gy de radioterapia preoperativa e infusión del bolo de 5'FU450 mg/m² administrados los días 1-5 y del 28-32; seis semanas más tarde, se realizó la extirpación anterior baja. Se llevó a cabo un análisis univariado en cuanto a encontrar los factores de riesgo de la fuga anastomótica colorrectal. Resultados. Se trató a 48 varones y 44 mujeres cuya media etaria fue de 55.8 años. La localización media del tumor arriba del borde anal fue de 7.4 ± 2.6 cm. Los niveles medios preoperativos de albúmina y linfocitos fueron de 3.8 g/dL y 1,697/mL, respectivamente. El margen distal medio fue de 2.9 ± 1.4 cm. La extirpación multivisceral fue realizada en 11 pacientes (13.8%); 32 pacientes (35%) tuvieron una colostomía derivativa. La hemorragia preoperativa media fue de 577 ± 381 mL, y 27 pacientes (24%) recibieron transfusión sanguínea. Diez pacientes (10.9%) tuvieron fuga anastomótica. No hubo ningún deceso quirúrgico. Los factores de riesgo para la fuga anastomótica fueron: el género (masculino) y el tamaño del tumor > 4 cm. Tres pacientes del grupo sin colostomía requirieron una media de seis días en la UTI (Unidad de Terapia Intensiva); el promedio media de la duración hospitalaria de pacientes con y sin colostomía protectiva fue de 12.4 ± 4.5 días contra 18.3 ± 5.2 días (p = 0.01). Conclusión. En pacientes masculinos con adenocarcinoma rectal que mide > 4 cm, tratados mediante radioterapia química preoperativa + extirpación anterior baja con excisión total mesorrectal, debería realizarse una abertura que se desvíe a fin de evitar una mayor mortalidad debida a fuga anastomótica.

Procedimentos para pacientes portadores de marcapasso e submetidos à radioterapia / Procedures for radiation therapy in patients using cardiac pacemarkers

Os modernos marcapassos cardíacos podem falhar quando submetidos a radiaçäo ionizante da ordem de 10 Gy e exibir alteraçös funcionais com doses täo baixas quanto 2 Gy. A interferência eletromagnética também pode afetar seu desempenho, mas este efeito näo é problema sério quando consideramos os equipamentos de radioterapia atuais. Devido ao aumento significativo de aceleradores lineares no Brasil e, com isto, um aumento da probabilidade de tratamento de pacientes portadores de marcapassos cardíacos permanentes com esses equipamentos, apresentamos uma revisäo e discussäo dos problemas em potencial associados e sugerimos alguns cuidados que adotamos e praticamos no Serviço de Radioterapia do Hospital Israelita Albert Einstein