Luciano Bachmann

Color stability, opacity and degree of conversion of pre-heated composites

OBJECTIVESnTo assess color stability and opacity associated with the degree of conversion of a pre-heated nanohybrid composite (Tetric N-Ceram, Ivoclar/Vivadent, Schaan, Liechtenstein).nnnMETHODSnTwenty-seven specimens were prepared (n=9) using a Teflon matrix following storage of compules containing the composite at temperatures of 8°C, 25°C or 60°C. After photoactivation and polishing, baseline readings of six specimens were taken regarding their color and opacity (Spectrophotometer PCB 6807, Byk Gardner, Geretsried, Germany). Then, the specimens were submitted to artificial ageing for 384 h (C-UV, Adexim Comexim, São Paulo, SP, Brazil), after which the final readings were taken. Three specimens for each temperature were submitted to analysis of degree of conversion (Nicolet 380, Thermo Scientific, Waltham, MA, USA). The results were analysed by 1-way ANOVA/Tukey (p<0.05).nnnRESULTSnThere was no significant difference in color stability and opacity variation amongst the temperatures evaluated. The composite pre-heated at 60°C had a higher degree of conversion (65.13%), with statistically significant difference compared to the other temperatures (p<0.05).nnnCONCLUSIONSnComposite pre-heating does not promote changes in the optical properties, despite the increase in the degree of conversion.

Enamel mineralization in the absence of maturation stage ameloblasts

The role of maturation stage ameloblasts is not clear yet. The aim of this study was to verify to which extent enamel mineralizes in the absence of these cells. Maturation stage ameloblasts and adjacent dental follicle cells from rat lower incisors were surgically removed and the limits of this removal were marked by notches made in the enamel. Histological analysis confirmed that the ameloblasts had been removed within the limits of the notches. The teeth erupted and when the notches appeared in the mouth, the enamel in the experimental teeth was hard but whitish compared to the yellowish colour of the contralateral incisors used as control. SEM images revealed similar enamel rod arrangement in both groups. Decreased mineral content was observed in some specimens by polarized light microscopy, and microhardness values were much lower in the experimental teeth. FTIR analysis showed that higher amounts of protein were found in most experimental teeth, compared with the control teeth. Enamel proteins could not be resolved on 15% SDS-PAGE gels, suggesting that most of them were below 5kDa. These results suggest that the enamel matured in the absence of ameloblasts has increased protein content and a much lower mineral content, suggesting that maturation stage ameloblasts are essential for proper enamel mineralization.

Temperature rise during Er:YAG cavity preparation of primary enamel

This study aimed to assess in vitro thermal alterations taking place during the Er:YAG laser cavity preparation of primary tooth enamel at different energies and pulse repetition rates. Forty healthy human primary molars were bisected in a mesio-distal direction, thus providing 80 fragments. Two small orifices were made on the dentin surface to which type K thermocouples were attached. The fragments were individually fixed with wax in a cylindrical Plexiglass® abutment and randomly assigned to eight groups, according to the laser parameters (nu2009=u200910): G1u2009–u2009250xa0mJ/ 3xa0Hz, G2u2009–u2009250xa0mJ/ 4xa0Hz, G3u2009–u2009250xa0mJ/ 6xa0Hz, G4u2009–u2009250xa0mJ/10xa0Hz, G5u2009–u2009250xa0mJ/ 15xa0Hz, G6u2009–u2009300xa0mJ/ 3xa0Hz, G7u2009–u2009300xa0mJ/ 4xa0Hz and G8u2009–u2009300xa0mJ/ 6xa0Hz. An area of 4xa0mm2 was delimited. Cavities were done (2xa0mm longxa0×xa02xa0mm widexa0×xa01xa0mm thick) using non-contact (12xa0mm) and focused mode. Temperature values were registered from the start of laser irradiation until the end of cavity preparation. Data were analyzed by one-way ANOVA and Tukey test (pu2009≤u20090.05). Groups G1, G2, G6, and G7 were statistically similar and furnished the lowest mean values of temperature rise. The set 250xa0mJ/10 and 15xa0Hz yielded the highest temperature values. The sets 250 and 300xa0mJ and 6xa0Hz provided temperatures with mean values below the acceptable critical value, suggesting that these parameters ablate the primary tooth enamel. Moreover, the temperature elevation was directly related to the increase in the employed pulse repetition rates. In addition, there was no direct correlation between temperature rise and energy density. Therefore, it is important to use a lower pulse frequency, such as 300xa0mJ and 6xa0Hz, during cavity preparation in pediatric patients.

Oral aspects in celiac disease children: clinical and dental enamel chemical evaluation

OBJECTIVEnThe aim of this study was to evaluate the oral manifestations of celiac disease (CD), the chemical composition of dental enamel, and the occurrence of CD in children with dental enamel defects (DEDs).nnnSTUDY DESIGNnIn the study, 52 children with CD and 52 controls were examined for DEDs, recurrent aphthous stomatitis (RAS), dental caries experience, and salivary parameters. In addition, 10 exfoliated primary enamel molars from each group were analyzed by energy dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy. Fifty children with DEDs were submitted to CD diagnosis.nnnRESULTSnAmong the children with CD, a higher prevalence of DEDs (P = .00001) and RAS (P = .0052), lower caries experience (P = .0024), and reduction of salivary flow (P = .0060) were observed. Dental enamel from the children with CD demonstrated a lower calcium-to-phosphorus ratio (P = .0136), but no difference in the carbonate-to-phosphate ratio (P = .5862) was observed. In the multivariate analysis, CD was a protective factor for caries (OR = 0.74) and a risk factor for RAS (OR3.23).nnnCONCLUSIONSnThe children with CD presented with more RAS, DEDs, reduction of salivary flow, and chemical alterations in the enamel.

Tissue dissolution and modifications in dentin composition by different sodium hypochlorite concentrations

ABSTRACT Sodium hypochlorite (NaOCl) remains the most used irrigation solution during root canal preparation because of characteristics such as wide-spectrum antimicrobial activity and organic tissue dissolution capacity. However, these solutions can alter dentin composition and there is no consensus on the optimal concentration of NaOCl to be used. Objectives To determine the organic matter dissolution and changes in dentin chemical composition promoted by different concentrations of NaOCl over time. Material and Methods: Fragments of bovine muscle tissue were weighed before and after 5, 10, and 15 min of immersion in the groups (n=10): G1- 0.9% saline solution; G2- 1% NaOCl; G3- 2.5% NaOCl; and G4- 5% NaOCl. Bovine dentin fragments were subjected to the same irrigants and absorption spectra were collected by Attenuated Total Reflectance of Fourier Transform Infrared Spectroscopy (ATR-FTIR) before and after 0,5, 1, 2, 3, 5, 8, and 10 min of immersion in the solutions. The ratios of the amide III/phosphate and carbonate/phosphate absorption bands were determined. The tissue dissolution and carbonate/phosphate ratios were submitted to the two-way analysis of variance (ANOVA) with Tukey’s multiple-comparison test (α<0.05) and to the one-way analysis of variance with Tukey’s (α<0.05). The amide III/phosphate ratio was analyzed by Friedman test (α<0.05) and the Kruskal-Wallis test with Dunn’s post-hoc (α<0.05). Results The increase in NaOCl concentration and contact time intensified the dissolution of organic matter and dentin collagen with reduction in the amide III/phosphate ratio. Significant differences between all groups (p<0.05) were observed in the dissolution of organic matter at 10 min and in the amide III/phosphate ratio between the saline solution and 5% NaOCl at 5 min. The carbonate/phosphate ratio decreased significantly in G2, G3, and G4 after 0,5 min of immersion (p<0.05), but more alterations did not occur in the subsequent periods (p>0.05). Intergroup differences were not observed in this ratio (p>0.05). Conclusions The increase in the exposure time and in the concentration of NaOCl solution lead to an increase in the tissue dissolution and dentin collagen deproteination. Furthermore, some carbonate ions are removed from the dentin inorganic phase by the NaOCl.

CO2 laser as auxiliary in the debonding of ceramic brackets.

This study evaluated the temperature in the bonding composite and in the pulp chamber, the shear bond strength after the irradiation of CO2 lasers, and the Adhesive Remnant Index (ARI) after debonding of ceramic bracket. A hundred and five premolars were used: 30 to evaluate the temperature and 75 to test the resistance to shear and the ARI. To assess the temperature, different irradiation times (3 and 5xa0s), pulse duration (0.001 and 0.003xa0s), and output power (5, 8, and 10xa0W) were tested (total of 12 groups). During all the irradiation, specimens were immersed in thermal bath water at 37xa0°C. In the test and ARI evaluation, premolars were divided into five groups (nu2009=u200915) and were submitted to the following regimens of CO2 laser irradiation: I (5xa0W, pulse durationu2009=u20090.01xa0s, application timeu2009=u20093xa0s), II (5xa0W, 0.03xa0s, 3xa0s), III (8xa0W, 0.01xa0s, 3xa0s), and IV (1 0xa0W, 0.01xa0s, 3xa0s). Group C (control) was not subjected to irradiation. ARI was measured after debonding of the bracket. Following irradiation of the lasers, the pulpal temperature was not higher than 5.5xa0°C in four of the study groups. Results were submitted to the ANOVA and Duncan’s test. CO2 laser irradiation regimen IV was one in which the strength of debonding is 7.33xa0MPa. Therefore, CO2 laser may aid removal of ceramic brackets; it decreased the bond strength without increasing the excessive temperature excessively.

Organic and inorganic content of fluorotic rat incisors measured by FTIR spectroscopy

Details on how fluoride interferes in enamel mineralization are still controversial. Therefore, this study aimed at analyzing the organic contents of fluorosis-affected teeth using Fourier Transformation Infrared spectroscopy. To this end, 10 male Wistar rats were divided into two groups: one received 45 ppm fluoride in distilled water for 60 days; the other received distilled water only. Then, the lower incisors were removed and prepared for analysis by two FTIR techniques namely, transmission and micro-ATR. For the first technique, the enamel was powdered, whereas in the second case one fluorotic incisor was cut longitudinally for micro-ATR. Using transmission and powdered samples, FTIR showed a higher C-H content in the fluorotic enamel compared with control enamel (p<0.05, n=4 in the flurotic, and n=5 in the control group). Results from the micro-ATR-FTIR spectroscopic analysis on one longitudinally cut incisor carried out at six points reveal a higher C-H bond content at the surface of the enamel, with values decreasing toward the dentine-enamel junction, and reaching the lowest values at the subsuperficial enamel. These results agree with the morphological data, which indicate that in the rat incisor the fluorotic lesion is superficial, rather than subsuperficial, as in the case of human enamel. The results also suggest that the increased C-H bond content may extend toward the more basal enamel (intraosseous), indicating that fluorotic enamel may intrinsically contain more protein. Finally, particularly when coupled to ATR, FTIR is a suitable tool to study the rat incisor enamel, which is a largely used model of normal and abnormal amelogenesis. Further studies along this line may definitely answer some questions regarding protein content in fluorotic enamel as well as their origin.

Loss of structural water and carbonate of Nd:YAG laser-irradiated human enamel

The objective of this study was to use Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) to assess whether Nd:YAG laser irradiation associated with a dye or not alters the chemical constitution of the enamel. Fourteen enamel sections were randomly divided into two groups: (1) Nd:YAG and (2) dyeu2009+u2009Nd:YAG. First, the untreated enamel surfaces were analyzed by FTIR to acquire the control absorption spectrum. Next, Group 2 received a layer of inactivated coal diluted in deionized water before laser treatment. Enamel samples belonging to groups 1 and 2 were then irradiated with a 1,064-nm Nd:YAG laser (80xa0mJ, 10xa0Hz) in the contact mode; the carbonate absorption band and the water absorption band were measured in each sample after irradiation. The water band was measured again 24xa0h, 48xa0h, and 7xa0days after irradiation. Group 1 had statistically similar water and carbonate contents before and after irradiation. Group 2 displayed significantly lower (p < 0.05) water content after irradiation, which remained constant along time at 24 and 48xa0h. After 7xa0days, the water content increased slightly, being statistically higher than in the other experimental periods, except for the control. The carbonate/phosphate ratio was measured only at the beginning, and after irradiation, it decreased only in Group 2 indicating carbonate loss (p < 0.05). Irradiation with 1,064-nm Nd:YAG laser associated with a dye reduces the carbonate and structural water content in the enamel.

Thermal effects and morphological aspects of varying Er:YAG laser energy on demineralized dentin removal: an in vitro study

The aim of this study was to evaluate thermal changes, dentin ablation removal capacity, and morphological aspects of sound and demineralized human dentin surface irradiated with different output energies of an erbium: yttrium-aluminium-garnet (Er:YAG) laser. Eighty sound human tooth specimens were assigned into two groups: demineralized dentin and sound dentin (control group). The dentin groups were subdivided into four subgroups (nu2009=u200910) according to the irradiation energy used (120, 160, 200, or 250xa0mJ) at a constant frequency level of 6xa0Hz, in focused mode, and under refrigeration. Quantitative analysis of the sound and carious dentin ablation was performed using light microscopy (LM) by measuring (mm) the remaining demineralized tissue with the Axion Vision™ software. Qualitative analysis was performed using the images obtained with a scanning electron microscope (SEM), and the temperature increase was recorded with an infrared digital thermometer. The Er:YAG laser promoted a gradual increase in temperature for all groups, and no difference was observed between the sound and demineralized dentin. The groups of 200 and 250xa0mJ showed the highest values, yet a variation in temperature did not exceed 5xa0°C. The energy output of 120xa0mJ selectively removed demineralized tissue when compared to 250xa0mJ, while also providing more regular surfaces in the cavity preparation. It was concluded that the temperature increase during sound and demineralized dentin removal had a strong positive correlation with the Er:YAG laser energy level output. However, the higher energies used did not present selectivity to the demineralized tissue, and the parameters used did not cause an increase in temperature over 5xa0°C.

Analysis of the effects of several decalcifying agents alone and in combination with sodium hypochlorite on the chemical composition of dentine

AIMnTo investigate the effects of several decalcifying agents alone and in combination with sodium hypochlorite (NaOCl) on the organic and inorganic components of dentine using attenuated total reflectance in Fourier transform infrared spectroscopy (ATR-FTIR).nnnMETHODOLOGYnDentine slices from bovine teeth were submitted to (nxa0=xa05) the following: 0.9% saline, 9% and 18% etidronic acid (HEDP), 5% and 10% tetrasodium EDTA (EDTANa4 ), 17% trisodium EDTA (EDTAHNa3 ), and 0.5% and 2.0% peracetic acid (PAA) for 0.5-10xa0min; and to the combinations: G1 - mixture 5% NaOClxa0+xa018% HEDP (5 and 10xa0min); G2 - mixture 5% NaOClxa0+xa010% EDTANa4 (5 and 10xa0min); G2 - 2.5% NaOCl (5xa0min)xa0+xa017% EDTAHNa3 (1xa0min); G3 - 2.5% NaOCl (5xa0min)xa0+xa00.5% PAA (1xa0min); G4 - 2.5% NaOCl (5xa0min)xa0+xa09% HEDP (5xa0min). Specimens of G2, G3 and G4 received final flushes with 2.5% NaOCl for 0.5-10xa0min. Amide III/phosphate and carbonate/phosphate ratios of the spectra collected from the dentine specimens before and after immersion in the solutions were determined. Data were submitted to one-way repeated measures and one-way anova.nnnRESULTSnFor the same decalcifying agent, the higher the concentration and immersion time the greater the removal of phosphate, exposure of collagen matrix and consequently the increases in amide III/phosphate ratio. However, significant differences were found only between the two concentrations of PAA (Pxa0<xa00.05). PAA caused greater increases in this ratio, followed by EDTAHNa3 , EDTANa4 and HEDP, and this order was retained in the combinations with NaOCl. This ratio was significantly reduced in G1 (Pxa0<xa00.05) and not altered in G2 (Pxa0>xa00.05). Due to collagen degradation, the amide III/phosphate ratio reduced significantly after the use of NaOCl in G3, G4 and G5 (Pxa0<xa00.05). NaOCl required approximately 0.5xa0s to deproteinate the collagen matrix exposed after phosphate removal by EDTAHNa3 and PAA. The carbonate of dentine was removed more rapidly than phosphate by all decalcifying agents alone and in G3, G4 and G5. In the combinations with NaOCl, the last irrigant used defined the dentine amide III/phosphate and carbonate/phosphate ratios.nnnCONCLUSIONSnHEDP and EDTANa4 caused minor whilst EDTAHNa3 and PAA caused greater demineralization of dentine; both effects were time and concentration dependent. NaOCl degraded the dentine organic matrix more rapidly when it was exposed. Combinations of NaOCl and decalcifying agents can be used to create dentine surfaces with varying compositions for interaction with endodontic sealers.