Adriana Lemos Mori Ubaldini

Hydrogen Peroxide Diffusion Dynamics in Dental Tissues

The aim of this study was to investigate the diffusion dynamics of 25% hydrogen peroxide (H2O2) through enamel-dentin layers and to correlate it with dentin’s structural alterations. Micro-Raman Spectroscopy (MRS) and Fourier Transform Infrared Photoacoustic Spectroscopy (FTIR-PAS) were used to measure the spectra of specimens before and during the bleaching procedure. H2O2 was applied to the outer surface of human enamel specimens for 60 minutes. MRS measurements were performed on the inner surface of enamel or on the subsurface dentin. In addition, H2O2 diffusion dynamics from outer enamel to dentin, passing through the dentin-enamel junction (DEJ) was obtained with Raman transverse scans. FTIR-PAS spectra were collected on the outer dentin. MRS findings revealed that H2O2 (O-O stretching µ-Raman band) crossed enamel, had a more marked concentration at DEJ, and accumulated in dentin. FTIR-PAS analysis showed that H2O2 modified dentin’s organic compounds, observed by the decrease in amides I, II, and III absorption band intensities. In conclusion, H2O2 penetration was demonstrated to be not merely a physical passage through enamel interprismatic spaces into the dentinal tubules. H2O2 diffusion dynamics presented a concentration gradient determined by the chemical affinity of the H2O2 with each specific dental tissue.

Factors That Drive Dentists towards or Away from Dental Caries Preventive Measures: Systematic Review and Metasummary

Background Dental caries is a serious public health concern. The high cost of dental treatment can be avoided by effective preventive measures, which are dependent on dentists’ adherence. This study aimed to evaluate the factors that drive dentists towards or away from dental caries preventive measures. Methods and Findings This systematic review was registered in PROSPERO (CRD42012002235). Several databases as well as the reference lists and citations of the included publications were searched according to PRISMA guidelines, yielding 18,276 titles and abstracts, which were assessed to determine study eligibility. Seven qualitative studies and 41 surveys (36,501 participants) remained after data extraction and interpretation. A total of 43 findings were abstracted from the reports and were grouped together into 6 categories that were judged to be topically similar: education and training, personal beliefs, work conditions, remuneration, gender, place of residence and patients. The main findings for adherence based on their calculated frequency effect sizes (ES) were teamwork (21%) and post-graduation (12%), while for non-adherence were biologicism (27%), and remuneration for preventive procedures (25%). Intensity ES were also calculated and demonstrated low prevalence of the findings. Quality assessment of the studies demonstrated that the methodological quality, particularly of surveys, varied widely among studies. Conclusions Despite the questionable quality of the included reports, the evidence that emerged seems to indicate that further education and training coupled with a fairer pay scheme would be a reasonable approach to change the balance in favor of the provision of dental caries preventive measures by dentists. The results of this review could be of value in the planning and decision making processes aimed at encouraging changes in professional dental practice that could result in the improvement of the oral health care provided to the population in general.

Fourier transform infrared photoacoustic spectroscopy study of physicochemical interaction between human dentin and etch-&-rinse adhesives in a simulated moist bond technique

The purpose of this study was to provide the physicochemical interactions at the interfaces between two commercial etch-&-rinse adhesives and human dentin in a simulated moist bond technique. Six dentin specimens were divided into two groups (n=3) according to the use of two different adhesive systems: (a) 2-hydroxyethylmethacrylate (HEMA) and 4-methacryloxyethyl trimellitate anhydrate (4-META), and (b) HEMA. The Fourier transform infrared photoacoustic spectroscopy was performed before and after dentin treatment with 37% phosphoric acid, with adhesive systems and also for the adhesive systems alone. Acid-conditioning resulted in a decalcification pattern. Adhesive treated spectra subtraction suggested the occurrence of chemical bonding to dentin expressed through modifications of the OH stretching peak (3340 cm(-1)) and symmetric CH stretching (2900 cm(-1)) for both adhesives spectra; a decrease of orthophosphate absorption band (1040 to 970 cm(-1)) for adhesive A and a better resolved complex band formation (1270 to 970 cm(-1)) for adhesive B were observed. These results suggested the occurrence of chemical bonding between sound human dentin and etch-&-rinse adhesives through a clinical typical condition.

Analytical method to estimate resin cement diffusion into dentin

Abstract. This study analyzed the diffusion of two resin luting agents (resin cements) into dentin, with the aim of presenting an analytical method for estimating the thickness of the diffusion zone. Class V cavities were prepared in the buccal and lingual surfaces of molars (n=9). Indirect composite inlays were luted into the cavities with either a self-adhesive or a self-etch resin cement. The teeth were sectioned bucco-lingually and the cement–dentin interface was analyzed by using micro-Raman spectroscopy (MRS) and scanning electron microscopy. Evolution of peak intensities of the Raman bands, collected from the functional groups corresponding to the resin monomer (C─O─C, 1113  cm−1) present in the cements, and the mineral content (P─O, 961  cm−1) in dentin were sigmoid shaped functions. A Boltzmann function (BF) was then fitted to the peaks encountered at 1113  cm−1 to estimate the resin cement diffusion into dentin. The BF identified a resin cement–dentin diffusion zone of 1.8±0.4  μm for the self-adhesive cement and 2.5±0.3  μm for the self-etch cement. This analysis allowed the authors to estimate the diffusion of the resin cements into the dentin. Fitting the MRS data to the BF contributed to and is relevant for future studies of the adhesive interface.

Study of the chemical interaction between a high-viscosity glass ionomer cement and dentin

Abstract Objective To investigate the chemical interactions between a high-viscosity glass ionomer cement (GIC) (KetacTM Molar Easymix, 3M ESPE, Seefeld, Bavaria, Germany) and human dentin. It was also analyzed the dynamics of GIC setting mechanism based on the time intervals required for the GIC and the GIC mixed with dentin to achieve stability. Material and Methods Each constituent of GIC – powder (P) and liquid (L) – and powdered dentin (D), as well as the associations P+L, D+L, and P+L+D in the concentrations of 29%, 50%, 65%, 78%, 82%, and 92% of GIC were analyzed with Fourier transform infrared (FTIR) and Raman spectroscopy. Results New optical absorption bands and/or Raman bands, which were not present in P, L, or D, were observed in the associations. The concentrations of 29% and 50% of GIC showed higher interaction, revealing that the amount of dentin influences the formation of new optical absorption or scattering bands. FTIR bands showed that the setting time to achieve bond stability was longer for the high-viscosity GIC (38±7 min) than for the sample with 29% of GIC (28±4 min). Conclusions The analysis revealed the formation of new compounds or molecular rearrangements resulting from the chemical interactions between GIC and dentin. Moreover, this study provides an effective method to evaluate the dynamics of the setting mechanism of GICs.

Influence of immediate dentin sealing and interim cementation on the adhesion of indirect restorations with dual-polymerizing resin cement

Statement of problem: Dentin surface contamination before the cementation of indirect restorations may impact bonding effectiveness. Purpose: The purpose of this in vitro study was to analyze the influence of immediate dentin sealing (IDS) and interim cementation on the adhesion of indirect restorations with a dual‐polymerizing resin cement. Material and methods: Composite resin inlays were placed in class V cavities prepared in the buccal and lingual surfaces of 30 extracted human molars with a dual‐polymerizing resin cement in 3 different ways (n=10): CG, directly on dentin; PG, after 14 days interim cementation; SG, after IDS and 14 days interim cementation. Buccal restorations were sectioned into sticks and submitted to the microtensile bond strength (&mgr;TBS) test. Lingual restorations were submitted to micro‐Raman spectroscopy (MRS). Data were analyzed with 1‐way ANOVA and the Tukey‐Kramer post hoc test (&agr;=.05). Results: Significantly higher &mgr;TBS results were found for SG (35.7 ±8.2 MPa) when compared with CG (23.1 ±7.1 MPa) and PG (17.0 ±6.0 MPa) (P<.05), but no differences were observed between CG and PG. MRS showed that the diffusion zone in SG (3.7 ±0.5 &mgr;m) was significantly thicker than that of CG (1.8 ±1.2 &mgr;m) or PG (1.5 ±0.3 &mgr;m) (P<.05). Additionally, a new interface peak (at approximately 1330 cm‐1) was found in SG, indicating a chemical interaction. Conclusions: The use of IDS before cementation resulted in a chemical interaction at the interface and significantly higher &mgr;TBS and diffusion zone thickness values. Interim cementation did not interfere with adhesion quality when compared with the control group.

Challenges in luting fibre posts: Adhesion to the post and to the dentine

OBJECTIVE To investigate the relationship between physicochemical interactions of resin luting cements with dentine and retention of fibre posts in root canals. METHODS Retention of fibre posts (RelyX Fiber Post) was assessed by the pull-out method. The diffusion zone of the cements and their chemical interaction with dentine were estimated by micro-Raman spectroscopy. Resin luting cements employing etch-and-rinse (Rely X Ultimate and Variolink II), self-etch (Rely X Ultimate and Panavia F2.0), or self-adhesive (RelyX Unicem 2) modes were investigated. Data were analyzed by analysis of variance followed by Tukey HSD tests. RESULTS The retention of the fibre posts decreased in the following order: RelyX Ultimate, etch-and-rinse mode>RelyX Unicem 2≥RelyX Ultimate, self-etch mode≥Panavia F2.0≥Variolink II (p<0.05). One of the etch-and-rinse mode cements presented the deepest diffusion zone, while the other, along with the self-adhesive cement, produced the shallowest zone. Cements used in the self-etch mode showed intermediary diffusion into dentine (p<0.05). All resin luting cements showed some degree of chemical interaction with dentine, the highest recorded for RelyX Ultimate used in the etch-and-rinse mode and the lowest for Panavia F2.0 (p<0.05). The retention of fibre posts in the root canal could be attributed neither to the mode of interaction of the luting cements with dentine nor to their ability to diffuse into dentine. SIGNIFICANCE Chemical interaction between the resin luting cement and the dentine paired with adequate post pretreatment contribute positively to the retention of fibre posts.