Davide Prisco

Carbon fiber post adhesion to resin luting cement in the restoration of endodontically treated teeth

Carbon fiber posts (CFP) are widely used in the restoration of endodontically treated teeth to enhance the mechanical behavior in spite of metallic posts and to prevent vertical fractures of the tooth under chewing loads. The post is cemented inside the canal lumen using polymer resins with Youngs modulus lower than Dentine. In this conditions the stress concentration is located at the post-cement interface and in the cement bulk itself, preserving radicular Dentine from dangerous stress accumulation. The mechanical resistance of CFP posts cemented in human Dentine was evaluated by the means of mechanical pull-out tests assisted by the finite element analysis. The average bond strength and the critical stress values of the CHP-cement interface were 25 MPa and 50 MPa respectively. ©2000 Kluwer Academic Publishers

Mechanical strength of tooth fragment reattachment

The aim of this study was static and fatigue test investigation of the strength of a tooth fragment reattached with adhesives to the tooth body. Central bovine incisor teeth were used, and standardized fragments were obtained by cutting the incisal edge of the selected teeth. All the fragments were reattached using a multistep dentine adhesive system, and the specimens were randomly divided into two groups (A and B). Group B specimens underwent a further dental treatment: a circumferential double chamfer prepared around the external cut interface was filled with light cured composite restorative resin. Static and fatigue bending tests were performed and linear elastic equations were used to analyze and compare the strength of the treated teeth. The results indicated that the static and fatigue bending properties were improved by using reinforcement with composite restorative resin.

Effect of light curing and dark reaction phases on the thermomechanical properties of a Bis-GMA based dental restorative material

PURPOSE The effects of light curing units (LCU) and energy doses on the chemical and physical properties of a dental composite were investigated. METHODS The effects on the chemical and physical properties of a bisphenol A diglycidylether methacrylate (Bis-GMA) based dental restorative material were evaluated through photospectrometry, differential scanning calorimetry, and mechanical measurements. RESULTS The light curing conditions associated with direct and indirect restorations were replicated in vitro using optical investigation techniques. A slight attenuation resulted independently of the LCU and a strong attenuation was measured for the cement luting a thick inlay, as well as for the deepest layer of a composite filling increment. Calorimetric measurements indicated that the curing degree is very sensitive to the light energy dose rather than to the LCU. Mechanical testing showed a transient phase during which properties increased. The delay of the composite in reaching adequate properties is strongly dependent on the energy dose. CONCLUSIONS It is recommended that composites subject to unfavorable light curing conditions undergo a prolonged light curing process.

Temperature Profiles Along the Root with Gutta-percha Warmed through Different Heat Sources

Objectives: To evaluate temperature profiles developing in the root during warm compaction of gutta-percha with the heat sources System B and System MB Obtura (Analityc Technology, Redmond, WA, USA). Thirty extracted human incisor teeth were used. Root canals were cleaned and shaped by means of Protaper rotary files (Dentsply-Maillefer, Belgium), and imaging was performed by micro-CT (Skyscan 1072, Aartselaar, Belgium). Methods: Teeth were instrumented with K-type thermocouples, and the roots were filled with thermoplastic gutta-percha. Vertical compaction was achieved through the heat sources System B and System MB, and temperature profiles were detect-ed by means of NI Dac Interface controlled by the LabView System. With both heat sources, higher temperature levels were recorded in the region of the root far from the apex. When the warm plugger tip was positioned at a distance of 3 mm from the root apex, temperature levels of about 180°C were used to soften gutta-percha, and no statistically significant differences were observed between peak temperatures developed by the two heating sources at the root apex. However, a temperature level higher than 40°C was maintained for a longer time with System MB. Results: Statistically significant differences were observed in peak temperature levels recorded far from the root apex. Thus, with a temperature of about 180°C and the warm plugger positioned at 3 mm from the root apex, both heating sources led to a temperature slightly higher than 40°C at the apex of the root, suggesting that the gutta-percha was properly softened. Significance: A temperature level higher than 40°C was maintained for a longer time with System MB, thus providing an ad-equate time for warm compaction of the gutta-percha.

SLER (Soft Light Energy Release) - A Novel Curing Technology For Orthodontic Bracket Bonding

Bracket bonding procedures with composite photo-cured materials are commonly used in orthodontics to improve clinical performance and reduce treatment time. Ceramic brackets are frequently applied in combination with composite photo-cured materials to improve aesthetics. Since bond strength depends on the light curing process, in dentistry a new technology named Soft Light Energy Release (SLER®) has been introduced to allow thermal control of the curing process by softly decreasing light energy in the final step of the irradiation period. The aim of this study was to test the SLER® technology in orthodontics. Eighty ceramic brackets were bonded on the enamel facial surface of freshly extracted central lower bovine incisors with light cured composite materials. They were randomly divided into two groups: one using standard light curing (group A) and the other SLER® curing technology (group B), both providing the same energy dose. An Instron digital torsiometer determined the bonding strength. Statistical analysis showed a significant difference between the two groups. Group B with the SLER® showed a greater bonding strength compared to the Group A with standard light curing. The findings suggested that SLER® improves the bonding strength of orthodontic brackets when using light cured composite materials.

KAVİTE ŞEKLİ FAKTÖRÜ VE BİR ARA REZİN KAVİTE ÖRTÜCÜ MATERYALİN KALINLIĞININ, GERİLİM KUVVETLERİ ALTINDA BAĞLANMA DAYANIMLARINA ETKİSİ-THE THICKNESS OF A FLOWABLE COMPOSITE LINING MATERIAL AND CAVITY CONFIGURATION FACTOR (C FACTOR) IN RELATION TO THE TENSI

THE THICKNESS OF A FLOWABLE COMPOSITE LINING MATERIAL AND CAVITY CONFIGURATION FACTOR (C FACTOR) IN RELATION TO THE TENSILE BOND STRENGTHS Ozet Kompozit materyallerin polimerizasyonlari sirasinda olusabilecek polimerizasyon buzulme stresleri, ara rezin kompozit (bonding) materyaller ve kavite seklinin degistirilmesi ile azaltilabilir. Bu calismada ara rezin kompozit materyal kalinligi ve gerilim direnci arasindaki iliski olasiligi arastirilmis ve ayrica kavite sekli faktoru de degerlendirilmistir. Molar dislerin aproksimal yuzlerinde iki degisik derinlikte acilan Black II kaviteler, iki farkli teknikle restore edilmis ve gerilim stresleri karsisinda gingival duvarda baglanma dayanimlari degerlendirilmistir. Istatistiksel analizler sonucunda kavite sekli faktorunun baglanma direncine etkisi olmadigi ve ara rezin ortucu materyal kalinliginin baglanma dayanimi ile iliskisi olmadigi gozlenmistir. Bu sonuclarin alinmasinda, ara rezin kavite ortucu materyalin elastik bariyer olarak etkisi oldugu sanilmaktadir. SEM sonuclarina gore en fazla kirilmanin ara rezin kavite ortucu materyal icinde olmasinin ise materyalin asiri kalinlikta kullanimindan kacinilmasi gerektigi sonucunu vermektedir. Anahtar sozcukler: Ara rezin kompozit materyaller, kavite sekli faktoru, gerilim stresi Abstract The degree of stress development during the setting of the composite material can be controlled to some extent, by the flowable composite lining materials and by the cavity design. The purpose of the present work was to investigate a possible relationship between the thickness of a resin lining material and tensile bond strengths. Cavity configuration factor (C Factor) was also evaluated. Class II slot cavity praparations with two different cavity configurations were prepared on the proximal surfaces of caries free third molar teeth and restored with two different filling techniques. The thickness of lining cement was measured and the samples were tested under tensile stress loading. No relation was found between the thickness of lining material and tensile bond strengths. No statistical significant difference was also found between the groups due to cavity configuration and filling techniques (P>0.05). The elasticity of the resin lining material had an effect to get these results. Key words: Flowable composite resins, C Factor, tensile bond strengths