Maurizio D’Amario

The effect of resin cement film thickness on the pullout strength of a fiber-reinforced post system.

STATEMENT OF PROBLEM Debonding is a common cause of failure encountered with fiber posts and usually occurs along the post space-dentin adhesive interface. The ideal thickness of the resin cement needed to improve retentive bond strength is unknown. PURPOSE The purpose of this study was to evaluate the effect of 4 different post-space diameters and related resin cement film thicknesses on the bond strength between fiber posts and root dentin. MATERIAL AND METHODS Eighty human maxillary central incisors with similar root lengths were selected, sectioned at the cemento-enamel junction, and the roots were treated endodontically. The roots were divided into 4 groups (n=20), and the post spaces were prepared to a depth of 8 mm using 1 of 4 different drills with a different diameter: Torpan drill ISO 90 for the control group (D90); and Torpan Drill ISO 100 (D100), Torpan Drill ISO 120 (D120), or Enapost Drill ISO 140 (D140) for the 3 test groups. Quartz fiber posts (Endo Lightpost), 0.9 mm in apical diameter, were luted (Panavia 21) in each specimen after dentin bonding procedures. The specimens were then subjected to a pullout test using a universal testing machine at a crosshead speed of 1.0 mm/min, and the maximum force required to dislodge each post was recorded (N). Data were analyzed using 1-way ANOVA and Tukey multiple comparisons tests (a=.05). RESULTS The mean bond strength values (SD) in N for the experimental groups D100 (181.7 (55.3)) and D120 (210.7 (55.0)) were higher (P=.036 and <.001, respectively) than that obtained for the D90 control group (138.5 (49.2)). The lowest mean value was recorded for the D140 group (91.1 (36.0)). All experimental groups showed significantly different results, when compared to the control group. A multiple comparison between experimental groups showed significant differences (P<.001). Only the comparison between D100 versus D120 was not significant. CONCLUSIONS Data suggest that the resin cement film thickness influences the pullout strengths of fiber-reinforced posts. For the selected quartz fiber-reinforced post and resin luting cement, the highest bond strength values were not obtained when the thinnest cement layer was tested (D90) but when oversized post spaces were used (D100-D120). However, when the cement film thickness was too great (D140), the dislocation resistance of fiber-reinforced posts was significantly decreased.

Bond strengths of three types of fibre‐reinforced post systems in various regions of root canals

AIM To evaluate the bond strengths of three adhesive/resin cement/fibre post systems to coronal, middle and apical thirds of post space dentine. METHODOLOGY Three types of glass-fibre post systems were selected for the study. Saremco Post Non-stop Fibre (Saremco), FRC Postec Plus (Ivoclar Vivadent) and Anatomical Post (Dentalica) were luted in prepared root canals using adhesive system and resin cement provided by the respective manufacturer. The luting agent was placed into the root canal using a specific syringe with needle. A push-out test was performed on sections from the apical, middle and coronal parts of each specimen to measure bond strength. All fractured specimens were observed using a stereomicroscope to identify the modes of failure. RESULTS Bond strength values were significantly affected both by the post-adhesive-cement system used and by root region (P < 0.05). Additionally, there was no significant interaction between the post system and region of canal factors (P > 0.05). The highest bond strength values were found in the coronal third for all experimental groups. The middle and apical thirds exhibited similar bond strengths with no statistically significant differences amongst them. Saremco and Precision post systems had the highest retentive strengths, whilst the Ivoclar post system had the lowest values. Microscopic analysis of the specimens revealed a prevalence of post-cement and mixed failures. CONCLUSIONS Type of post-adhesive-cement system and root position had a significant effect on fibre post retention. The coronal region of the canals was characterized by significantly higher bond strengths.

An evaluation of luting agent application technique effect on fibre post retention

OBJECTIVE Aim of the study was to assess the bond strengths of three adhesive/resin cement/fibre post systems by using different application methods of the luting agent. METHODS Three types of fibre post systems were selected for this study. ENA Post (Micerium), Anatomical Post (Dentalica), and Endo Light-Post (RTD) were luted in prepared root canals, using proprietary adhesive system and resin cement. Each group was divided into three subgroups (n=10). For each subgroup, a different technique was used to place the luting agent into post space: using a lentulo spiral; applying the cement onto the post surface; injecting the material with a specific syringe. A push-out test was performed on sections from apical, middle and coronal parts of each specimen. All fractured specimens were observed using a scanning electron microscope to identify the types of failure. RESULTS Bond strengths were not statistically influenced by root region (p>0.05) but were significantly affected both by post/adhesive/cement system and by the application technique of the luting agent (p<0.05). The microscopic analysis of the specimens revealed a prevalence of post/cement and mixed failures. CONCLUSIONS The best results with the push-out test were obtained when the luting agent was brought into the post space with lentulo spirals or specific syringes. Only ENA Post system showed similar bond strength values independently from the application method of the luting agent.

The cytotoxic effects of resin-based sealers on dental pulp stem cells

AIM To evaluate the effect of four current resin-based adhesives on expanded ex vivo human dental pulp mesenchymal stem cells (DP-MSCs). METHODOLOGY Dental pulp mesenchymal stem cells were derived from dental pulps of ten donors. After in vitro isolation, dental pulp stem cells were analysed using flow cytometry. The immunophenotype of DP-MSCs disclosed the homogeneous expression of the mesenchymal-related antigens CD29, CD44, CD73, CD90, CD105, CD166. DP-MSCs were exposed to four different commercially available bonding systems (CMF Bond, Prime&Bond NT, Clearfil S(3) Bond, XP Bond), and after 24, 48 and 72 h of incubation the morphological features and the cell growth were analysed. Moreover, the cell viability was evaluated at the same times by MTT assay. Data were statistically analysed using a two-way anova and Holm-Sidak method (alpha set at 0.05). RESULTS Significant differences were observed between the four groups when comparing DP-MSCs appearance. DP-MSCs survived and proliferated without inhibition in the presence of CMF Bond adhesive. On the contrary, microscopic evaluation of the other three groups revealed extensive cytotoxic effects from the dentine bonding agents. The MTT assay revealed no statistically significant differences in cell viability after 72 h between the control group and CMF Bond group. All the other experimental groups had statistically lower optical density values. CONCLUSIONS CMF Bond adhesive allowed human dental pulp stem cells to survive and proliferate. All of the other dentine bonding agents had extensive cytotoxic effects.

Effect of Airborne Particle Abrasion on Microtensile Bond Strength of Total-Etch Adhesives to Human Dentin

Aim of this study was to investigate a specific airborne particle abrasion pretreatment on dentin and its effects on microtensile bond strengths of four commercial total-etch adhesives. Midcoronal occlusal dentin of extracted human molars was used. Teeth were randomly assigned to 4 groups according to the adhesive system used: OptiBond FL (FL), OptiBond Solo Plus (SO), Prime & Bond (PB), and Riva Bond LC (RB). Specimens from each group were further divided into two subgroups: control specimens were treated with adhesive procedures; abraded specimens were pretreated with airborne particle abrasion using 50 μm Al2O3 before adhesion. After bonding procedures, composite crowns were incrementally built up. Specimens were sectioned perpendicular to adhesive interface to produce multiple beams, which were tested under tension until failure. Data were statistically analysed. Failure mode analysis was performed. Overall comparison showed significant increase in bond strength (p < 0.001) between abraded and no-abraded specimens, independently of brand. Intrabrand comparison showed statistical increase when abraded specimens were tested compared to no-abraded ones, with the exception of PB that did not show such difference. Distribution of failure mode was relatively uniform among all subgroups. Surface treatment by airborne particle abrasion with Al2O3 particles can increase the bond strength of total-etch adhesives.

Orthodontic brackets removal: morphological in vitro evaluation

Debonding procedure is a fundamental stage in the orthodontic treatment (1). Adhesive removal should lead to a complete polished enamel in order to prevent the plaque accumulation and enamel injures (2). Aim of this study is to evaluate in vitro by use of Scanning Electron Microscopy (SEM) the enamel surface after the bracket removal and the enamel polishing with four different techniques. Two groups of teeth, group A (n=12) and group B (n=12) were evaluated. The images were analyzed by the Image J software. After the debonding procedure the two groups were subcategorized in four groups (1A, 1B, 2A, 2B 3A, 3B and 4A, 4B, n.=3). The discriminant between the two main categories was the use of a magnification system (Group A) during the polishing stages. From the qualitative and quantitative images analysis the most conservative technique resulted to be the use of tungsten carbide bur, followed by the final polishing using the soft-polisher tip for composites. In group A, the percentage of the residual adhesive resulted 8% and the damages on the enamel surface showed to be 7%. In group B the percentage of the residual adhesive resulted 35% and the damages on the enamel surface showed to be 15%. This analysis showed how the use of a magnification system aids in significant way during the debonding procedures in the enamel surfaces’ preservation.The authors are grateful to Dr. M. Gianmatteo and to Dr. E. Nazaj, University of L’Aquila, for their help in the sampling and microscopy procedures.

Protocollo digitale di chirurgia implantare guidata mininvasiva a carico immediato: presentazione di un caso clinico

Riassunto Obiettivi L’integrazione di dati da fonti diverse di imaging diagnostico tridimensionale e la tecnologia guidata da computer rappresentano importanti ausili per lo sviluppo di metodiche affidabili e predicibili nella pianificazione e realizzazione della protesi su impianti. Materiali e metodi La metodica presentata si basa sull’integrazione di immagini da scansione radiografica tridimensionale (Cone Beam Computed Tomography, CBCT) e immagini da scansione ottica di superficie. Risultati Nel follow-up a 18 mesi e evidente il successo clinico del caso presentato. Conclusioni Nell’ambito di un trattamento implantare con approccio mininvasivo e protesizzazione a carico immediato, la pianificazione del caso eseguita su accurata ricostruzione delle superfici anatomiche consente di ottenere risultati esteticamente e funzionalmente predicibili.