Do Different Pretreatments of Dentine Surface Affect the Bond Strength with a Self-adhesive Resin Cement?

PURPOSE: To evaluate the microtensile bond strength of dentine/self-adhesive resin cement interface after several treatments on a dentine surface. MATERIALS AND METHODS: Twenty-eight human molars were selected and divided into four groups: no treatment (control (C)); 2% chlorhexidine digluconate (CHX); 25% polyacrylic acid (PA); and 23 ppm dispersive solution of silver nanoparticle (SN). Prepolymerised TPH resin composite (Dentsply) blocks were luted on the dentine surface using RelyX U200 self-adhesive resin cement (3M ESPE). Microtensile bond strength was measured (MPa) in a universal testing machine 24 h and 6 months after the bonding process. The fractured specimens were examined in an optical microscope and classified according to the fracture pattern. A representative sample of each group was observed by scanning electronic microscope. Data were submitted to analysis of variance (ANOVA) and Tukey's test to compare the mean among the groups (p <0.05). RESULTS: The highest microtensile bond strength values after 24 h were found for the PA group (13.34 ± 6.36 MPa), with no statistically significant difference for the C group (9.76 ± 3.11 Mpa). After 6 months, the highest microtensile bond strength values were found for the C group (9.09 ± 3.27 Mpa), with statistically significant difference only for the CHX group (2.94 ± 1.66 MPa). There was statistically significant difference only for the PA group when comparing the periods studied. Regardless of the surface treatment applied, there were more adhesive failures in both periods of time. CONCLUSION: Dentinal pretreatment with PA, as well as use of SN before the bonding procedure of self-adhesive resin cement to dentine, may be alternative bonding protocols.

Effect of glass fiber post customization on the mechanical properties of resin cement and underlying dentin.

This study evaluated the Martens hardness (HM) and elastic modulus (EIT) of resin cement and dentin underlying the bonding interface of customized glass fiber posts luted to intraradicular dentin and subjected to mechanical cycling. Two null hypotheses were tested: (1) no differences in the mechanical properties (HM and EIT) of the resin cement and underlying dentin would be found between customized and noncustomized glass fiber post groups, with or without mechanical cycling; and (2) no differences in the mechanical properties of the resin cement or underlying dentin would be found between the cervical, middle, and apical thirds of the intraradicular dentin. Forty single-rooted premolars were divided into 4 groups: customized or noncustomized glass fiber post, with or without mechanical cycling. The noncustomized posts were cemented in their original state to prepared canals, while the customized posts were modified with composite resin according to the geometry of the root canal. The specimens in the mechanical cycling groups were positioned at a 45-degree angle in an electromechanical fatigue testing machine and subjected to loading with a steel tip with a 4-mm diameter for 1,200,000 cycles at 50 N. After the specimens were prepared according to the appropriate group protocol, they were sectioned into thirds, and HM and EIT values of the resin cement and dentin underlying the bonding interface were determined using an ultramicrohardness tester under a load of 5 mN. A 2-way repeated-measures analysis of variance with post hoc Tukey test was performed. For resin cement in the cervical region, the highest HM and EIT values were observed in the noncustomized group after mechanical cycling. Similarly, in the underlying dentin, specimens in the noncustomized group after mechanical cycling had the highest HM values in the cervical region. Therefore, customization of glass fiber posts with composite resin is not essential for bonding to intraradicular dentin.

Emergence profile customization technique during implant transfer.

This case report aimed to describe the clinical considerations in oral rehabilitation with prostheses on implants in the anterior region, using emergence profile customization technique during implant transfer. A patient presented with a missing left upper central incisor and with not satisfactory esthetic in the other upper incisors. After diagnosis, a treatment plan was elaborated: implant placement in this region; ceramic laminates for teeth 11 and 22, and full crown for tooth 12. During the impression procedure, the implant transfer was customized by copying the gingival profile. The prostheses were made using IPS e.max ceramic system and luted with resin cement. The patient was submitted to annual follow-up examinations that did not show any irregularity or deficiency in the prostheses. The technique performed is a viable alternative that can be used in oral rehabilitation with implants involving anterior teeth because it allows a predictable level of adaptation.

Influence of Light-curing Units on Surface Microhardness and Color Change of Composite Resins after Challenge.

AIM: The aim of this study was to evaluate microhardness and color change (ΔE) of composite resins, light cured with different light emission diodes (LEDs) and submitted to artificial accelerated aging (AAA). MATERIALS AND METHODS: Two composite resins with lucirin- TPO photoinitiator were selected: Tetric N-Ceram (Ivoclar Vivadent, A1) and Vit-l-escence (Ultradent, WO).A resin with the only camphorquinone photoinitiat or was chosen as a negative control: Filtek Z350XT (3M ESPE, WD). Disc-shaped specimens were prepared (5 mm diameter; 1.5 mm thick) and photopolymerized with an LED with one wavelength (Radii-Cal, SDI) or multiple wavelengths (Valo, Ultradent), for each composite resin (n = 10). Surface microhardness and color evaluations were performed immediately after specimen preparation and after AAA. Microhardness results were analyzed using Kruskal-Wallis and Mann-Whitney tests for multiple comparisons. To compare the evaluation of microhardness at different times, the Wilcoxon test was used. Mean values of ΔE, ΔL, Δa, and Δb were evaluated using two-way analysis of variance (ANOVA), and Tukey test for multiple comparisons (a = 0.05). RESULTS: Regarding microhardness, a statistically significant difference between the two LEDs was observed for Vit-lescence after AAA. When comparing composite resins that were light-cured with the same device, FiltekZ350XT obtained the greatest microhardness. All groups presented a statistically significant decrease in microhardness from the initial time to the AAA. Regarding ΔE, no statistically significant difference between the two LEDs was observed. When comparing composite resins, FiltekZ350XT showed the highest ΔE values. CONCLUSION: In general, an LED with multiple wavelengths influenced the microhardness of only one resin containing lucirin-TPO after AAA. The ΔE was more influenced by the composite resin than the LED device. CLINICAL SIGNIFICANCE: The knowledge of composite resin with deficiencies in the polymerization mechanism could contribute to preventing restorations to become more susceptible to color change and reduction of the mechanical strength.

Mechanical and surface properties analysis of restorative materials submitted to erosive challenges in situ.

OBJECTIVE: This study aims to evaluate the effect of acidic solutions (AS) on surface roughness (Ra) and microhardness of restorative materials (RM). MATERIALS AND METHODS: Eight volunteers wore intraoral palatal devices (IPD) containing samples of RM: Ketac Nano (KN); Ketac Nano + Biscover LV (KN-B); Esthet-X (EX); Esthet-X + Biscover LV (EX-B); Supreme XT (SXT); Supreme XT + Biscover LV (SXT-B); and bovine enamel. The samples were submitted to three phases: (1) immersion in 0.01M hydrochloric acid (HCl) - 10 min, three times/day (14 days); (2) immersion in soft drink (Sprite®) - 10 min, three times/day (14 days); and (3) keeping in saliva (14 days). Changes in Ra/microhardness were measured before/after the three phases. STATISTICAL ANALYSIS: ANOVA (α = 0.05) and Fisher's test. RESULTS: Materials sealed with Biscover LV (B) presented lowest values in all periods. KN glass ionomer cement showed highest Ra values after exposure in AS. Application of B did not reduce the Ra for the composites studied, except for EX after immersion in HCl. AS promoted changes in Ra/microhardness of RM, except for sealed materials. CONCLUSIONS: The acids used were able to change the Ra and microhardness of RM, except of the sealed materials. The resin-modified GIC showed the most significant changes after immersion in AS; and the composites sealed with B, even after immersion in acidic solutions (AS), showed the lowest Ra values and the least degradation in microhardness, especially when subjected to low pH solutions.

Minimum intervention management of diastema closure using cordless displacement system and laminate veneers: A 2-year follow-up.

This case report presents a minimally invasive diastema treatment using cordless gingival displacement system allowing a very conservative intervention. A 32-year-old female patient who presented with diastema in her upper front teeth opted for a treatment using laminate veneers to ensure achieving adequate tooth proportion and gingival levels. Having a displacement material that exerts excessive pressure during the displacement process can lead to disruption of the junctional epithelium and damage to periodontal tissues. This case report focuses on the effectiveness of the use of a minimally invasive method of gingival management. Two-year follow-up no infiltration, sensitivities, or fractures were detected on teeth, and indirect restorations, the purposed treatment allowed a quick, effective, and durable resolution for diastema.