Massimo Gagliani

Adhesive post-endodontic restorations with fiber posts: push-out tests and SEM observations

OBJECTIVES Nowadays, the restoration of endodontically treated teeth is based on the use of materials with a modulus of elasticity similar to that of dentin (18.6 GPa). Fiber posts, resin cements and some composite resins all have this characteristic. This study evaluated the bond strength between luting materials, root dentin and fiber posts through push-out tests and examined the integration among these three components through scanning electron microscopy. METHODS Endodontically treated extracted teeth and plastic plates were used to test the interface between luting agent and dentin and luting agent and post. RESULTS Chemical affinity between different components (luting materials and fiber posts) is extremely important in achieving high bond strength. The bond strength tests and SEM observations showed that in vitro, composite resins perform better than resin cements. SIGNIFICANCE The in vivo use of these materials may significantly reinforce residual tooth structure therefore reducing the risk for fracture and debonding.

The Outcome of Endodontic Retreatment: A 2-yr Follow-up

Retreatment is common in endodontics. The purpose of this article was to classify the different clinical situations encountered in retreatment cases and relate them to the outcome after an observation period of 24 months. A total of 425 patients (452 teeth) from 451 patients, consecutively admitted for root-canal retreatment, were monitored during a 24-month period. All teeth (254 molars, 107 premolars, and 91 single-root anterior teeth) were divided into two major categories: teeth with modified anatomy from previous endodontic treatment (root-canal-morphology altered) and teeth in which no significant anatomical changes were made by the former endodontic treatment (root-canal-morphology respected). Although the overall success was 69.03%, the success in the root-canal-morphology-respected group was 86.8% and in the root-canal-morphology-altered group 47% (Mann-Whitney U test p < 0.0001). The clinical success of an endodontic retreatment seems to depend on whether alterations in the natural course of the root canals were caused by previous root-canal treatment.

Single Versus Multiple Visits for Endodontic Treatment of Permanent Teeth: A Cochrane Systematic Review

The Cochrane Collaboration promotes evidence-based healthcare decision making globally through systematic reviews of the effects of healthcare intervention. The purpose of this systematic review was to investigate whether the effectiveness and frequency of short-term and long-term complications are different when endodontic procedure is completed in one or multiple visits. Randomized and quasi-randomized controlled trials enrolling patients undergoing endodontic treatment were identified by searching biomedical databases and hand-searching relevant journals. The following outcomes were considered: tooth extraction as a result of endodontic problems and radiologic failure after 1 year, postoperative discomfort, swelling, analgesic use, or sinus track. Twelve studies were included in the review. No detectable difference was found in the effectiveness of root canal treatment in terms of radiologic success between single and multiple visits. Neither single-visit root canal treatment nor multiple-visit root canal treatment can prevent 100% of short-term and long-term complications. Patients undergoing a single visit might experience a slightly higher frequency of swelling and refer significantly more analgesic use.

Ultrasonic root-end preparation: Influence of cutting angle on the apical seal

Apical resection is fundamental in obtaining a correct apical seal. The purpose of this study was to evaluate how the apical root resection angle and the cavity made by ultrasonic retrotips may influence the apical seal. A total of 48 extracted teeth were endodontically treated and sealed by guttapercha vertical compaction: 24 were resected with a 45 degrees angle and 24 with a 90 degrees one. An ultrasound source (P.M. 400 EMS) and a CT5 Scaler were used to make the retrograde cavity that was filled afterwards with EBA-zinc oxide-eugenol alumina-added cement. Apical leakage was determined using fuchsin and assessed after the roots were sectioned longitudinally. Linear dye penetration in dentin and at the interface between dentin and cement was measured with a stereomicroscope (x 12 magnification), and the results were statistically analyzed. Results showed that there was less infiltration both in dentin and in the space between the filling and the dentinal wall in the group with the 90 degrees angle, but this difference was statistically significant (p < 0.0001) only for the dentin. None of the samples showed leakage greater than the depth of the preparation. An apical cavity of 3 mm or more along the vertical axis can produce a safe and effective seal.

Degree of conversion of three composite materials employed in the adhesive cementation of indirect restorations: A micro-Raman analysis

OBJECTIVES Adhesive luting of indirect restorations can be carried out employing dual- or light-curing materials. This in vitro study evaluated the degree of conversion (DC) of the materials employed in this procedure, seeking how the combination of time and power of curing applied during polymerisation, as well as the temperature of the light-curing composite, influenced the DC. MATERIALS AND METHODS One hundred and eighty onlays of different thicknesses (2 mm, 3 mm, 4 mm) were luted with three different composites: two dual-curing cements (Variolink II and Calibra) and a light-curing composite (Venus). The same halogen lamp was used with three different modalities selected to provide a constant quantity of energy. The time/power combinations tested were 400 mW/cm(2) for 120 s, 800 mW/cm(2) for 60s and 1200 mW/cm(2) for 40 s. The light-curing composite was employed at room temperature and after preheating at 54 degrees C. Each sample was examined in three positions using the Micro-Raman Dilor HR LabRam spectrometer to evaluate the polymer conversion degree. The data were analysed using analysis of variance and the Student-Newman-Keuls test (p=0.05). RESULTS The dual-curing materials showed average conversion percentages close to 64%, although onlays thickness clearly influence the degree of conversion, the light-curing composite showed satisfactory results only when onlays thickness was thin, however preheating significantly improved the performance of the light-curing composite under onlays of great thickness. CONCLUSIONS Optimal luting of indirect restorations is clearly dependent from light source power, irradiation time and dual-cure luting cement or light-curing composite chosen. It should be calibrated for each material to acquire high DCs. Preheating of light-curing only composites allows for the materials to reach optimal conversion degrees.

Effect of different bur grinding on the bond strength of self-etching adhesives

This study compared the microtensile bond strength (MTBS) of three all-in-one adhesive systems and a two-step system using two types of burs to prepare the dentin surfaces. Flat coronal surfaces of 24 extracted human molars were produced using either regular-grit or superfine-grit diamond burs. Resin composite was then bonded to equal numbers of these surfaces using one of the four adhesives: Clearfil SE Bond (CSE), G-Bond (GB), SSB-200 (SSB) or Prompt L-Pop (PLP). After storage for 24 hours in 37 degrees C distilled water, the bonded teeth were sectioned into slices (0.7-mm thick) perpendicular to the bonded surface. The specimens were then subjected to microtensile testing and the bond strengths were calculated at failure. Bond strength data were analyzed by two-way ANOVA and the GamesHowell test for interaction between adhesive and type of cut dentin. The fractured surfaces were observed by SEM to determine the failure mode. In addition, to observe the effect of conditioning, equal numbers of the two bur-cut dentin surfaces of eight additional teeth were conditioned with the adhesives and observed by SEM. Based on the results, when CSE and SSB were bonded to dentin cut with a regular-grit diamond bur, the MTBS values were significantly lower than that of superfine bur-cut dentin; whereas, GB and PLP showed no significant differences in MTBS between the two differently cut surfaces. SEM observation of the fractured surfaces revealed a mixed mode (adhesive in some areas and cohesive in others in the same sample) of failure in all specimens except PLP, which showed cohesive failure within the adhesive for both types of bur preparation. Generally, SEMs of the conditioned surfaces using both types of burs showed partial removal of the smear layer for CSE, minimal for GB and SSB and complete removal for PLP. In conclusion, when cutting dentin, selecting the proper bur type is important for improving the bond strength of some self-etching adhesive systems.

Biofilm formation on composite resins for dental restorations: an in situ study on the effect of chlorhexidine mouthrinses.

Purpose Biofilm formation on the surface of dental restorative materials by oral bacteria is considered an important step in the development of secondary caries. The aim of this study was to evaluate the in situ effect of a chlorhexidine (CHX)-containing mouthrinse on the biofilm formation occurring on the surface of human enamel and of two resin-based commercially available materials: a silorane-based material (Filtek Silorane®) and a methacrylate-based material (Filtek Supreme XT®). Methods 53 disks were obtained for each of the two composites and 37 disks for enamel. The surface was characterized by determining the surface roughness and the surface free energy of 5 samples for each of the three materials tested, then the remaining samples were mounted on splints worn by 16 volunteers. The participants were randomly divided into two groups: an experimental group that used 0.12% CHX-based mouthrinse and a control group that used a placebo mouthrinse. Biofilm formation on the different surfaces after a 24 h period was assessed using MTT assay. Results The two composites in the group treated with the placebo mouthrinse showed a similar biofilm formation, which was significantly higher than that occurring on enamel surfaces. The CHX-based mouthrinse significantly reduced biofilm formation on the surfaces of the two resin-based materials when compared with the placebo mouthrinse. The reduction was particularly relevant on the Filtek Silorane surfaces. Conclusions The new silorane-based material seems to interact with CHX in a promising way from the point of view of biofilm formation control.

Hydrophilicity of dentin bonding systems influences in vitro Streptococcus mutans biofilm formation

OBJECTIVE To evaluate in vitro Streptococcus mutans (S. mutans) biofilm formation on the surface of five light-curing experimental dental bonding systems (DBS) with increasing hydrophilicity. The null hypothesis tested was that resin chemical composition and hydrophilicity does not affect S. mutans biofilm formation. METHODS Five light-curing versions of experimental resin blends with increasing hydrophilicity were investigated (R1, R2, R3, R4 and R5). R1 and R2 contained ethoxylated BisGMA/TEGDMA or BisGMA/TEGDMA, respectively, and were very hydrophobic, were representative of pit-and-fissure bonding agents. R3 was representative of a typical two-step etch-and-rinse adhesive, while R4 and R5 were very hydrophilic resins analogous to self-etching adhesives. Twenty-eight disks were prepared for each resin blend. After a 24h-incubation at 37°C, a multilayer monospecific biofilm of S. mutans was obtained on the surface of each disk. The adherent biomass was determined using the MTT assay and evaluated morphologically with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). RESULTS R2 and R3 surfaces showed the highest biofilm formation while R1 and R4 showed a similar intermediate biofilm formation. R5 was more hydrophilic and acidic and was significantly less colonized than all the other resins. A significant quadratic relationship between biofilm formation and hydrophilicity of the resin blends was found. CLSM and SEM evaluation confirmed MTT assay results. CONCLUSIONS The null hypothesis was rejected since S. mutans biofilm formation was influenced by hydrophilicity, surface acidity and chemical composition of the experimental resins. Further studies using a bioreactor are needed to confirm the results and clarify the role of the single factors.

Influence of MDPB-containing Primer on Streptococcus Mutans Biofilm Formation in Simulated Class I Restorations

PURPOSE To evaluate the activity of a methacryloyloxydodecylpyridinium bromide (MDPB)-containing self-etching primer (Clearfil Protect Bond) against Streptococcus mutans and its ability to reduce biofilm formation on standardized experimental Class I restorations in vitro. MATERIALS AND METHODS Forty experimental Class I round restorations were prepared on enamel-dentin slabs using different adhesive strategies: group 1 = MDPB-containing adhesive system (Clearfil Protect Bond); group 2 = MDPB-free self-etching adhesive system (Clearfil SE Bond); group 3: MDPB-containing self-etching primer in combination with a fluoride-free bonding agent; group 4: MDPB-free self-etching primer in combination with a fluoride-containing bonding agent; group 5: a three-step etch-and-rinse adhesive system (Adper Scotchbond Multi Purpose). A Streptococcus mutans biofilm was grown for 48 h on the restoration surfaces and subsequently evaluated using scanning electron microscopy on three different areas: enamel, composite, and interface surfaces. Statistical analysis was performed by multiple ANOVA after data transformation. RESULTS Specimens in groups 2, 4 and 5 showed greater biofilm formation than those in groups 1 and 3 (p < 0.001) on all investigated substrates (enamel, composite, and interface areas). CONCLUSIONS Specimens prepared with an MDPB-containing primer exhibited significant decreases in biofilm formation on Class I restorations in vitro. Further in vitro and in vivo studies are required to clarify the role of quaternary ammonium compounds in reducing bacterial biofilm formation on restoration surfaces.

Patient and Clinical Characteristics Associated with Primary Healing of Iatrogenic Perforations after Root Canal Treatment: Results of a Long-term Italian Study

INTRODUCTION There are few data on the long-term efficacy of mineral trioxide aggregate (MTA) in treating root canal perforations. We investigated the extent of primary healing after perforation repair with MTA and non-healing as a result of repair. We also investigated patient/clinical characteristics affecting treatment outcomes and long-term prognosis. METHODS This was a prospective cohort study that enrolled consecutive patients with a single dental perforation treated with MTA (January 1999-June 2009). Patients were followed up until December 2012 for a maximum of 13 years after treatment, with analyses carried out at 8 years. RESULTS Of the 110 patients (median age, 36 years; 54.5% male) eligible for inclusion, 101 were judged to have started to heal at the first (n = 98, 89%) or second (n = 3, 3%) annual post-treatment checkup, and 9 (8%, 4 women and 5 men, aged between 18 and 65 years) did not show any sign of healing. Patients >50 years had a higher percentage of non-healing perforations compared with those ≤ 50 years (12% versus 7%). The percentages of perforations at post-treatment analysis that failed to heal were 13% (intermediate/middle), 4% (coronal), and 0% (apical). The percentages of non-healing perforations according to size were 16% for >3 mm, 6% for 2-3 mm, and 0% for smaller perforations. Characteristics associated with probability of progressing after initial healing were gender, positive probing, size, and site of perforation. CONCLUSIONS Our results show that having obtained primary healing with MTA, the likelihood of progressing is very low. They provide good evidence of the combined effectiveness of experienced operators and use of state-of-the-art materials.