Comparison of the Flexural Strength of Four Core Built up Materials

The aim of this study is to compare the flexural strength of 4 commonly used core build up materials in clinics. Four core built up materials, a cermet cement (ketac silver), a light cure composite, conventional silver amalgam (control group) and zirconomer (zirconia reinforced GIC) were used and were divided into Group A, B and C and D respectively. The root canal of 90 extracted mandibular molars with similar anatomy and morphology were selected. Highest flexural strength was shown by Group A followed by group C, group B and then group D.

Does pigment incorporation into regular composite resins for posterior buildups alter their bond strength?

Abstract Posterior build-ups are auxiliary devices to orthodontic treatment which are made with resin-based or glass ionomer composites. Their removal requires care to protect the tooth surface, therefore, pigmented materials are preferred for a better visualization. This study proposed a pigmentation experimental technique of a regular composite resin, evaluating the microshear bond strength test (µ-SBT) of this experimental pigmented resin and comparing with a blue-colored polyacid-modified composite resin, used for posterior buildups. Forty-eight buccal and lingual surfaces of human teeth were used and randomly divided into 4 groups (n=12). The groups were divided into: C (control), regular composite resin; P, regular composite resin pigmented; UBL, Ultra Band Lok™; OB, Ortho Bite™. The composites were bonded using a matrix to obtain microcylinders and prepared for each experimental groups. The samples were then stored in distilled water for 24h at 37°C followed by a µ-SBT. The types of bond failures were evaluated using a stereoscopic magnifying glass (10×). The data were analyzed by ANOVA with Fisher post hoc and Dunnett´s test. Means of µ-SBT± standard deviation (MPa) were: C (39.98a±13.0), P (40.09a± 14.3); UBL (33.26ab±8.6); OB (28.70b±5.5). The most prevalent type of failure was adhesive (80.4%). Further, was not observed a statistically significant correlation between the bond strength values and failure patterns. The pigmentation of a commercially available resin did not alter the µ-SBT and exhibited similar adhesiveness as a polyacid-modified composite resin.

Resumo Levantes de mordida posterior são dispositivos para o tratamento ortodôntico confeccionados com resinas compostas ou materiais ionoméricos. Cuidado com a remoção destes se faz necessário para proteção da superfície dentária; para tanto, materiais pigmentados são preferidos por proporcionar melhor visualização. Este estudo propõe uma técnica de pigmentação experimental de resinas compostas convencionais, avaliando a resistência ao microcisalhamento (µ-SBT) na interface de união da resina experimental e superfície de esmalte dental e comparando-a com materiais comercialmente disponíveis para a confecção de levantes de mordida. Quarenta e oito superfícies de dentes humanos foram selecionadas aleatoriamente e divididos em quatro grupos (n=12), de acordo com o material adesivo utilizado: C (Controle, resina composta convencional); P (pigmentação experimental da resina composta convencional); UBL (Ultra Band Lok®); OB (Ortho Bite®). Microcilindros foram preparados para cada tipo de compósito utilizando uma matriz de silicone. As amostras foram mantidas em água destilada por 24h a 37°C, antes da realização do µ-SBT. Os padrões de fratura foram avaliados através de uma lupa estereoscópica com magnificação de 10x. ANOVA com pós teste de Fisher e teste de Dunnett foram utilizados para avaliar os dados. As médias obtidas do µ-SBT ± desvio padrão (MPa) foram: C (39.98a±13.0), P (40.09a± 14.3); UBL (33.26ab±8.6); OB (28.70b±5.5). O tipo de fratura mais prevalente foi a adesiva (80.4%). Além disso, não foi observada correlação estatisticamente significante entre os valores de resistência de união e os padrões de fratura. A técnica de pigmentação experimental não alterou os resultados de µ-SBT da resina composta convencional e mostrou adesividade semelhante à dos compósitos modificados por poliácidos utilizados neste estudo.

The Experimental Assessment Of Build Up Factor And Attenuation Coefficient Of Brass Compensator Applied In Intensity-Modulated Radiation Therapy (Imrt) For 6mv Photon Beam

Introduction: Recent compensators are commonly applied in IMRT. The precise properties of applied compensators such as thickness, attenuation coefficient and build up factor are intensively important for IMRT calculations. Method: The brass compensator used for 6 MV photon beam was studied to estimate the relative effect of thickness and field size on IMRT calculations. Various field size together with several compensator thicknesses were examined. Result: The average reduction of effective attenuation coefficient (EAC), for the fields of 10×10 cm2 to 20×20 cm2, was 9.94%. By increasing the field size, EAC was decreased. The major reduction of EAC due to increasing field size was found to be 9.62%. The build up factor was increased by 2% to 21.8% respect to field size and compensator thickness. Also, the build up factor was increased by adding up the thickness. The rate of changes ranged from 24% to 48 %.Conclusion: The compensator thickness and field size are significantly important to calculate the effective attenuation coefficient and build up facto

Periodontal Supportive Care: Aesthetic and Functional Restoration with Acrylic Gingival Veneer

@#This case involved periodontal supportive care after non-surgical management of localized, severe chronic periodontitis (possibly with a history of aggressive periodontitis) and periodontal abscess. This included maintaining the current periodontal health, and rehabilitation of patient’s oral function and aesthetic concern using simple, economical and reversible direct restorations without further damaging the patient’s dentition for example composite resin as splint. Besides that, to address the patient’s complaint of unsightly gaps in between the teeth, an acrylic gingival prosthesis with denture tooth incorporated was constructed.

Establishment of linear accelerator-based image guided radiotherapy for orthotopic 4T1 mouse mammary tumor model / 한국실험동물학회지

This study was conducted to assess the feasibility of image guided radiotherapy (IGRT) for orthotopic 4T1 mouse mammary tumor using linear accelerator (LINAC). Eighteen Balb/C mice were inoculated with 4T1 cells on left mammary fat pad and nine of them were irradiated using LINAC. Tumors, planning target volumes (PTV), bowels adjacent to tumors, bones and lungs were delineated on planning CT images. IGRT plans were generated to irradiate prescription dose to at least 90% of the PTV and then compared with conventional 2-dimensional plans with anterior-posterior and posterior-anterior beams with 5 mm margins (2D AP/PA plan). Homemade dose-build-up-cradle was designed to encompass mouse bed for homogeneous dose build up. To confirm the irradiated dose, tumor doses were measured using diode detector placed on the surface of tumors. Plan comparison demonstrated equivalent doses to PTV while sparing more doses to normal tissues including bowel (from 90.9% to 40.5%, median value of mean doses) and bone marrow (from 12.9% to 4.7%, median value of mean doses) than 2D AP/PA plan. Quality assurance using diode detector confirmed that IGRT could deliver 95.3-105.3% of the planned doses to PTV. Tumors grew 505.2-1185.8% (mean 873.3%) in the control group and 436.1-771.8% (mean 615.5%) in the irradiated group. These results demonstrate that LINAC-based IGRT provides a reliable approach with accurate dose delivery in the radiobiological study for orthotropic tumor model maintaining tumor microenvironment.

The effect of thermocycling on fracture toughness and hardness of different core build up materials.

Introduction: Core build up materials are routinely used to restore grossly decayed teeth and in the oral environment they are subjected to changes in the temperature due to consumption of hot and cold food. Aims: The purpose of this study was to determine the effect of thermocycling on the fracture toughness and hardness of 5 core build up materials. Materials and Methods: Fifteen specimens were prepared for each of the following materials: DPI alloy, Miracle‑mix, Vitremer, Fuji II LC and Photocore. American Standard for Testing Materials guidelines were used for the preparation of single‑edge notch, bar‑shaped specimens. Ten specimens of each material were thermocycled for 2000 cycles and the other 5 specimens were not thermocycled (non‑thermocycled group). All specimens were subjected to 3-point bending in a universal testing machine. The load at fracture was recorded and the fracture toughness (KIC) was calculated. Vickers hardness test was conducted on the thermocycled and non‑thermocycled group specimens. Results: Photocore had the highest mean KIC in both thermocycled and non‑thermocycled groups. Miracle‑mix demonstrated the lowest mean fracture toughness (KIC) for both thermocycled and non‑thermocycled groups. By applying Mann Whitney ‘U’ test the Vickers hardness value in all materials used in the study is highly superior in non‑thermocycled group as compared to thermocycled group (P < 0.01). Non‑thermocycled Photocore showed highest hardness values of 87.93. Vitremer had lowest hardness of 40.48 in thermocycled group. Conclusion: Thermocycling process negatively affected the fracture toughness and hardness of the core build‑up materials.

Crown fractures in maxillary central incisors: 24 months follow-up and clinical outcome in children / Fracturas coronarias en incisivos centrales maxilares: seguimiento de 2 años y resultado clínico en niños

The purpose of this study is to present the results of a group of 5 patients from 7-12 years old for complicated and uncomplicated crown fractures in their maxillary central incisors. A cross sectional survey of series of 5 clinical cases was desined. Re-attachment of coronal fragments and composite restoration the affected teeth were performed. The patients have been recalled for 24 months follow-up period. All teeth to show adequate clinical and radiographic evolution. In relation to the aesthetic considerations, the outcome has been satisfactory. The treatment requires adequate knowledge about diagnosis, treatment plan and biological, aesthetical, functional and economic aspects. Currently, there is great evidence that pulp, restorative and aesthetic prognosis is good, and has improved in the last years. An immediate first emergency attention, to avoid and/or minimize risk of bacterial invasion through dentinal tubules to the pulp tissue should be performed.

El propósito de este estudio es mostrar los resultados de tratamiento por fracturas coronarias complicadas y no complicadas en incisivos centrales maxilares, en un grupo de 5 niños entre 7 y 12 años. Fue realizada una descripción de una serie de 5 casos. Los dientes afectados fueron restaurados con la técnica de reposición de fragmento y/o restauración coronaria con composite. Los pacientes han sido citados a control durante un periodo de seguimiento de 24 meses. Todos los dientes comprometidos han presentado una evolución clínica y radiográfica adecuada. Desde el punto de vista estético, el resultado lo consideramos satisfactorio. El adecuado tratamiento de esta patología, requiere necesariamente tener el conocimiento sobre aspectos de diagnóstico, planificación de tratamiento, aspectos biológicos, estéticos, funcionales y económicos. Actualmente existe una enorme evidencia que el pronóstico pulpar, restaurador y estético para esta patología es muy bueno, y que ha mejorado considerablemente en los últimos años. En condiciones ideales, es necesario realizar una atención de urgencia inmediata para evitar y disminuir el riesgo de invasión bacteriana del complejo dentino-pulpar.

Characteristics of Detectors for Measurements of Photon Depth Doses in Build-Up Region / 의학물리

To determine the appropriate method out of various available methods to measure build-up doses, the measurements and comparisons of depth doses of build-up region including the surface dose were executed using the Attix parallel-plate ionization chamber, the Markus chamber, a cylindrical ionization chamber, and a diode detector. Based on the measurements using the Attix chamber, discrepancies of the Markus chamber were within 2% for the open field and increased up to 3.9% in the case of photon beam containing the contaminant electrons. The measurements of an cylindrical ionization chamber and a diode detector accord with those of the Attix chamber within 1.5% and 1.0% after those detectors were completely immersed in the water phantom. The results suggest that the parallel-plate chamber is the best choice to measure depth doses in the build-up region containing the surface, however, using cylindrical ionization chamber or diode detector would be a reasonable choice if no special care is necessary for the exact surface dose.

A study on the material properties of various composite resins for core build-up / 대한치과보존학회지

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.

A study on the material properties of various composite resins for core build-up / 대한치과보존학회지

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.

Evaluation of the fracture resistance of all-ceramic zirconia posts by 3 different methods / 대한치과보철학회지

STATEMENT OF THE PROBLEM: All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal build-ups. In certain clinical cases, however, fractures at the joint between the post and core build-up have been reported. PURPOSE: The objective, therefore, is to improve the joint between the post and the core build-up. MATERIAL AND METHODS: Three different methods were used to prepare all-ceramic post-andcore restorations; pressing IPS Empress core build-ups to CosmoPost zirconia posts, cementing IPS Empress core build-ups to CosmoPost zirconia posts and Celay-milling of zirconia blanks. A series of ten restorations was prepared for each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded. RESULTS: The highest breaking load and highest deflection were recorded for the cementing technique with values of 25.3 N and 394 micrometer, respectively. The corresponding values for the pressed core build-ups and the milled zirconia core build-ups were 22 N and 301 micrometer, and 13 N and 160 micrometer, respectively. All the differences are statistically significant (p=0.05). Regarding the load-dependence of the deflection, the cemented core build-ups again demonstrated the highest value with 15.5 micrometer/N. The difference in the values of 13.6 micrometer/N and 13 micrometer/N recorded for the pressed-on and milled core build-ups, respectively, were statistically insignificant. CONCLUSION: In regard to the high fracture resistance of zirconia post, adhesive cementing the core build-up to the post offers a viable alternative to the conventional pressing technique. The elastic bond between the rigid high-strength zirconia post and the core build-up presents an additional advantage.

Dosimetric Characteristics of the KCCH Neutron Therapy Facility / 대한치료방사선과학회지

For the physical characterization of neutron beam, dosimetric measurements had been performed to obtain physical data of KCCH cyclotron-produced neutrons for clinical use. The results are presented and compared with the data of other institutions from the literatures. The central aixs percent depth dose, build-up curves and open and wedge isodose curve values are intermediate between that of a 4 and 6 MV X-ray. The build-up level of maximum dose was at 1.35 cm and entrance dose was approximately 40%. Flatness of the beam was 9% at Dmax and less than+/-3% at the depth of 80% isodose line. Penumbra begond the 20% line is wider than corresponding photon beam. The output factors ranged 0.894 for 6 x 6 cm field to 1.187 for 30 x 30 cm field. gamma contamination of neutron beam was 4.9% at 2 cm depth in 10 x10 cm field.