Measurements for restorative dentistry: shrinkage and conversion degree of bulk-fill composites

The paper deals with a measuring approach based on Raman Spectroscopy and micro-CT imaging for correlating the degree of conversion of bulk-fill composites to the contraction shrinkage and consequently to the internal gap formation in high c-factor dental cavities. The developed study was performed on extracted molars in which a first-class cavity was prepared. A micro-CT scan was performed before and after composite lightcuring to tridimensionally measure the interfacial gap between the composite material and the cavity walls. After the complete polymerization of the composite, each sample was sectioned vertically to expose the lateral surface of the restorative material. Raman Spectroscopy measurements were performed along the cross-section of the cavity filled with the restorative material, every 0.5 mm from the occlusal surface. The obtained results showed a minimal gap opening after light-curing and a degree of conversion which was not affected by the bulk-fill composite thickness. Thanks to the 3D rendering, it should be observed that gaps were mostly concentrated at the cavity floor and despite the reduction in the degree of conversion detected in the deeper portions of the restoration, a three-dimensional opening of an interfacial gap was not observed. Therefore, it is possible to assume the presence of a correlation between the degree of conversion and the volumetric interfacial gap could. Further studies are actually in progress to compare these preliminary results with those obtained on other dental composite materials

The effect of ultrasonic access cavity preparation on dentinal inner walls: a micro-CT study on cadaveric samples

ObjectiveThe objective of this study is to evaluate the occurrence of coronal dentinal micro-cracks after access cavity refinement using high-speed burs and ultrasonic tips by means of micro-computed tomography (micro-CT) analysis.MethodsIn this study, 18 mandibular cadaveric incisors were divided into two groups according to the protocol of the preparation of the conventional access cavity. The diamond bur 802 # 12 was used until the perforation of the pulp roof. Then, the Endo-Z bur was used for the group #1 and the ultrasonic tip Start-X # 1 for the group #2 to finish and refine the access cavity. The preparation time of each access cavity has been recorded. The teeth underwent a micro-CT scan before and after the preparation of the access cavity. Fisher's exact test, the Chi-square test, the Kolmogorov-Smirnov test, the Mann-Whitney test, and the Student's test were used for statistical evaluation.ResultsThe percentage of teeth with new micro-cracks is not significantly different between the two groups (-p-value < 0.5). The number of newly formed micro-cracks and extension size were not significantly different between the two groups. The direction of extension of the micro- cracks was occluso-apical. The average duration of the access cavity is significantly smaller with the Endo-Z system (-p- value < 0.001). The roughness of walls surfaces has no statistically difference between the two groups.ConclusionThe use of ultrasound, although slower, is considered safe in the creation of dentinal micro-cracks, in the preparation of the access cavity

INTERACTION BETWEEN NANOFILLED COMPOSITES AND POLYWAVE MULTILED CURING LAMPS: AN IN VITRO STUDY

8nonenoneBattaglia V; Bergantin E; Paolino D; Coero Borga FA; Cadenaro M; Breschi L; Berutti E; Scotti N.Battaglia, V; Bergantin, E; Paolino, D; Coero Borga, Fa; Cadenaro, Milena; Breschi, Lorenzo; Berutti, E; Scotti, Nicol

Case report: "C-SHAPED MANAGEMENT with THERMAFIL SYSTEM£

RiassuntoObiettiviL’anatomia del secondo molare mandibolare è altamente variabile. I canali C-Shaped rappresentano una sfida per il clinico nella sagomatura, detersione, ma soprattutto durante la fase di otturazione. Lo scopo del seguente lavoro è illustrare la versatilità del sistema Thermafil in questo tipo di anatomie canalari.Materiali e MetodiViene presentato un case series di 3 secondi molari mandibolari C-Shaped destinati altrattamento endodontico. Glide path e sagomatura sono stati eseguiti con PathFile e ProTaper fino ad F2. EDTA 10% e NaOCl 5% sono stati usati come irriganti. L’otturazione è stata eseguita con sistema Thermafil.Risultati e ConclusioniI controlli radiografici mostrano un’adeguata distribuzione della guttaperca ed un omogeneo sigillo apicale. A due anni i casi risultano asintomatici e si evidenzia la guarigione periradicolare. La tecnica presentata sembra facilitare la gestione della complessa anatomia canalare C-Shape.SummaryAimThe anatomy of mandibular second molar is highly variable. C-Shaped canals rapresent a challenge for the clinician in saping, cleaning, but mainly during obturation. The aim of this study is to illustrate the versatility of Thermafil System in such complex anatomy.Material and MethodsA case series of 3 C-shaped mandibular second scheduled for root canal treatment is presented. Glide path and shaping were performed with PathFile e ProTaper up to F2. EDTA 10% and NaOCl 5% solutions were utilised as irrigants. Obturation was accomplished with Thermafil system.Results and ConclusionRadiographic imaging showed an adequate distribution of thermoplasticised guttapercha with homogeneous apical seal. At 2 years follow up all cases appeared symptoms-free and showed periradicular health. The present technique appeared user-friendly and reliable in managing complex C-Shaped anatomy