Effects of Er:YAG laser pre-treatment on dentin structure and bonding strength of primary teeth: an in vitro study.

BACKGROUND: To investigate the effects of Er:YAG laser pre-treatment on the dentin structure and shear bond strength of primary teeth. METHODS: Dentin specimens were prepared using freshly extracted intact primary molars and divided randomly into four groups based on the surface treatment applied. The control and etchant groups received no treatment and conventional acid etching treatment, respectively, while the energy and frequency groups received laser surface treatment with variable energy (50-300 mJ) and frequency (5-30 Hz) parameters. The morphology was observed using scanning electron microscopy. The surface-treated dentin slices were bonded to resin tablets, followed by thermocycle treatment. The shear strength was determined using a universal testing machine and de-bonded surfaces were observed using a stereomicroscope. RESULTS: SEM observation showed that the surface morphology of the dentin slices changed after etching as well as after Er:YAG laser pre-treatment with different energy and frequency values. The dentin tubules opened within a specific energy (50-200 mJ) and frequency (5-20 Hz) range. Beyond this range, the intertubular dentin showed cracks and structural disintegration. Shear strength tests showed no significant changes after acid etching. The shear strength increased significantly (P < 0.05) after Er:YAG laser pre-treatment compared with that of the control group. The shear strength increased within the same energy (50-200 mJ) and frequency (5-20 Hz) range as the tubule opening, but not significantly (P > 0.05). The most common mode of interface failure was adhesive (interface) failure, followed by mixed and resin cohesive failure. CONCLUSIONS: Pre-treatment using Er:YAG laser opens the dentinal tubules without the formation of a smear layer and improves the bonding strength between the primary teeth dentin and the resin composites.

Does prenatal maternal stress impair cognitive development and alter temperament characteristics in toddlers with healthy birth outcomes?

AIM: The aim of this study was to assess the cognitive and behavioural development of children with healthy birth outcomes whose mothers were exposed to prenatal stress but did not experience pregnancy complications. METHOD: In this prospective study, self-reported data, including the Prenatal Life Events Checklist about stressful life events (SLEs) during different stages of pregnancy, were collected at 32 to 34 weeks' gestation. Thirty-eight healthy females (mean age 27 y 8 mo, SD 2 y 4 mo) who were exposed to severe SLEs in the first trimester were defined as the exposed infant group, and 114 matched comparison participants were defined as the unexposed infant group (1:3). Maternal postnatal depressive symptoms were assessed with the Edinburgh Postnatal Depression Scale. The Bayley Scales of Infant Development and the Toddler Temperament Scale were used to evaluate the cognitive development and temperament characteristics of the infants with healthy birth outcomes when they were 16 to 18 months old. RESULTS: A randomized block multivariate analysis of covariance showed that the mental development index scores of the infants of mothers with prenatal exposure to SLEs in the first trimester averaged seven points (95% confidence interval 3.23-10.73 points) lower than those of the unexposed infants. Moreover, the infants in the exposed group achieved higher scores for regularity (adjusted mean [SD] 2.77 [0.65] vs. 2.52 [0.78], F(5,146) =5.27, p=0.023) and for persistence and attention span (adjusted mean 3.61 [0.72] vs. 3.35 [0.52], F(5,146) =5.51, p=0.020). INTERPRETATION: This study provides evidence that lower cognitive ability and less optimal worse behavioural response in infants might independently result from prenatal maternal stress.

Measurement of the morphological data of primary teeth in northwest China.

Objective: This study aims to digitally obtain the morphological data of children's primary teeth in northwest China and evaluate the reliability of digitally obtaining the anatomical morphological data of primary teeth. Methods: A total of 308 extracted primary teeth and cone-beam computed tomography (CBCT) images of 407 primary teeth were collected in northwest China. Electronic digital Vernier callipers (accuracy: 0.01 mm) were used to measure the mesiodistal and buccolingual diameters and crown length of the extracted primary teeth and calculate the crown area and crown index. Each sample was scanned with an intraoral scanner (Trios2 3shape, Denmark), and the resulting stl format files were imported into Geomagic Wrap 2015 to measure the axial and buccolingual diameters and crown length. The crown area and crown index were then calculated. After verifying the accuracy of the CBCT image measurement, the CBCT image data of 407 samples were measured in SmartV software using the "measure length" function by referring to the coronal, sagittal, and horizontal planes to adjust the position of the reference line. Results: Northern Chinese have larger primary teeth than other populations (Japanese, white American, African, Icelander, Spanish, and Dominican Mestizo) but smaller primary teeth than native Australians. Compared to Indian primary teeth, northwest Chinese's primary teeth have larger diameters on the central axis and smaller diameters on the buccolingual surface. Male teeth are usually larger than female teeth. Compared with the results of Wang Huiyun's study, the axial and buccolingual diameters and crown length of all native tooth types in this total sample were significantly smaller at the 0.1% level, and only the axial diameters of the upper first molar and lower second molar and the crown length of the lower lateral incisor were significantly smaller at the 1% level. The results of the intraclass correlation coefficient of 308 extracted primary teeth expressed an excellent degree of agreement between the callipers and intraoral scanner for the following: mesiodistal diameter (0.956-0.991), buccolingual diameter (0.963-0.989), crown length [0.864-0.992, except for the upper canine (0.690)], crown index (0.850-0.975), and crown area (0.946-0.993). Conclusion: The digital measurements of the intraoral scanner and CBCT image are in good agreement with the manual measurement of the Vernier calliper. The difference between the anatomical morphology size of the primary teeth measured in this study and the results of different populations could be due to different genetic backgrounds and environmental factors.

Stability of bonds made to superficial vs. deep dentin, before and after thermocycling.

OBJECTIVES: Bonding stability of resinous adhesives to dentin is still problematic and may involve regional variations in dentin composition. This study is to evaluate the effect of dentin depth on the stability of resin-dentin bonds under thermocycling challenge. METHODS: Dentin slabs with two flat surfaces parallel to the tooth axis were obtained from extracted human third molars. The slabs were randomized into eight groups according to the location of dentin [deep dentin (DD) or superficial dentin (SD)], the adhesive treatment (Single Bond 2 or Clearfil S(3) Bond), and the storage treatment (thermocycling for 5000 times vs. no). After the adhesive treatment and composite buildup on the dentin slabs, the micro-shear bond strength (µSBS) of each group was detected. The concentrations of cross-linked carboxyterminal telopeptide of type I collagen (ICTP) were also evaluated using an immunoassay to detect the degree of collagen degradation in each group. RESULTS: Dentin depth, adhesive treatment and storage treatment all showed significant effects on both the µSBSs and the ICTP values (P<0.05). Regardless of the adhesive type, thermocycling decreased the µSBSs and increased the ICTP values (P<0.05). The DD groups showed significantly lower µSBSs and higher ICTP values than SD groups after thermocycling aging (P<0.05). The treatment with Single Bond 2 significantly increased the ICTP values (P<0.05), whereas Clearfil S(3) Bond showed no effect on the ICTP values (P>0.05). SIGNIFICANCE: Deep dentin showed significantly more bond degradation after thermocycling than did superficial dentin.

[Effect of quaternary ammonium methacrylates incorporation into a dental adhesive on the resistance of enzymatic degradation of resin-dentine interfaces].

OBJECTIVE: To evaluate the effect of quaternary ammonium methacrylates incorporation into a dental adhesive on the resistance of enzymatic degradation of resin-dentine interfaces. METHODS: Thirty caries-free extracted human third molars were randomly divided into three groups (n = 10): 2-methacryloxylethyl dodecylmethyl ammonium bromide (MAE-DB) incorporated adhesive served as the experimental group, pre-treatment with chlorhexidine (CHX) served as a positive control, Adper(TM) Single Bond 2 served as a negative control. The resin-dentin interfaces were prepared using total etch bond system. After storage in distilled water at 37 °C for 24 h, the bonded teeth were vertically sectioned into beams. Beams were respectively immersed in artificial saliva containing 2 g/L MMP-8 at 37 °C for 0 h, 24 h and 120 h (n = 30). Micro-tensile bond strength, failure modes and nanoleakage were examined. RESULTS: There were no significantly differences of micro-tensile bond strength between groups before hydrolysis (P > 0.05). After the enzymatic hydrolysis of 24 h and 120 h, the micro-tensile bond strength of MAE-DB groups [(31.13 ± 8.77) MPa, (24.14 ± 6.64) MPa] were significantly higher than that of the negative control groups [(25.63 ± 6.90) MPa, (15.22 ± 6.57) MPa] (P < 0.05). Most of the failures were found in the base part of the hybrid layer in the negative control group, while failures occurred through the top of the hybrid layer in CHX and MAE-DB groups after the enzymatic hydrolysis.Specimens from each immediate group showed minor silver deposits in hybrid layer. After beams being enzymatic hydrolyzed for 120 h, it was shown that the silver nitrate uptake in the negative control group were significantly different from those in the CHX and MAE-DB groups (P < 0.05). CONCLUSIONS: Dental adhesive incorporation of MAE-DB could improve the anti-degrade ability of resin-dentin interfaces.

[Inhibitory effect of a novel crosslinking quaternary ammonium methacrylates on matrix metalloproteinases].

OBJECTIVE: To evaluate the anti-matrix metalloproteinase (MMP) activity of a novel crosslinking quaternary ammonium methacrylates, 2-methacryloxylethyl dodecylmethyl ammonium bromide (MAE-DB). METHODS: The effects of MAE-DB at different concentrations (1%, 3%, 5%, 7%) on soluble matrix metalloproteinase-8 (MMP-8) were investigated using fluorescent assay kit. Readings were taken every 20 min for 3 h. The 1, 10-phenanthroline provided by the assay kit served as control group. Demineralized dentin beams were randomly divided into three groups (n = 50) and immersed in different solutions: artificial saliva, MAE-DB incorporated artificial saliva and chlorhexidine incorporated artificial saliva. After temperature cycling, the changes of ultimate tensile strength were measured to determine the effect of MAE-DB on the activity of matrix-bound endogenous matrix metalloproteinases. The morphology of dentin collagen fibrils in the three groups was observed via transmission electron microscopy (TEM). RESULTS: MAE-DB could effectively inhibit the activity of soluble MMP-8. The inhibition percentage of 3% MAE-DB was 99.53% after 1 h, and it was significantly higher than that of 1, 10-phenanthroline (95.71%, P < 0.05). After temperature cycling, the ultimate tensile strengths of MAE-DB groups were significantly higher than those of the artificial saliva groups and the chlorhexidine groups (P < 0.05). TEM micrographs of MAE-DB group revealed that the microstructure of the collagen fibrillar was intact, while the fibrillar in the artificial saliva group was disrupted, indicating a protective function of MAE-DB on dentin collagen. CONCLUSIONS: MAE-DB can inhibit the activity of MMP and protect dentin collagen from enzyme degradation.

Maternal depressive symptoms related to Epstein-Barr virus reactivation in late pregnancy.

We examined the relationship between maternal depressive symptoms in late pregnancy and Epstein-Barr virus reactivation before delivery. In this prospective observational study, prevalence of Epstein-Barr virus reactivation within one week before delivery was compared between 163 pregnant women with depressive symptoms at 33 to 34 weeks of gestation and a computer-generated control group of 163 pregnant healthy women without depressive symptoms. Depressive symptoms at 33 to 34 weeks of gestation were significantly related to the prevalence of Epstein-Barr virus reactivation before delivery after adjustment for potential confounders (adjusted OR = 2.74, 95%CI: 1.23-6.08). Compared to that in the control group, the prevalence of Epstein-Barr virus reactivation was higher in women with depressive symptoms accompanied by higher negative coping (24.2% compared with 7.9%; adjusted OR = 3.67, 95%CI: 1.47-9.16). Maternal depressive symptoms in late pregnancy are associated with Epstein-Barr virus reactivation, and this association could be moderated by maternal coping style.

The inhibitory effect of a polymerisable cationic monomer on functional matrix metalloproteinases.

OBJECTIVES: This study examined the use of methacryloxylethyl cetyl dimethyl ammonium chloride (DMAE-CB) as a potential matrix metalloproteinases (MMPs) inhibitor on both soluble recombinant and dentine matrix-bound endogenous MMPs, meanwhile attempted to determine the effective anti-MMP group of quaternary ammonium methacrylates (QAMs). METHODS: The possible inhibitory effects of five DMAE-CB mass concentrations (0.1%, 0.5%, 1%, 3%, 5%) on soluble rhMMP-9 were measured using a colorimetic assay kit. Methyl methacrylate (MMA) and [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METMAC) were also screened against rhMMP-9 to compare the inhibitory effect with DMAE-CB. Matrix-bound endogenous MMP-activity was evaluated in completely demineralized dentine beams. Thirty beams were randomly divided into three groups (N=10) and respectively placed into 500µL of calcium- and zinc-containing media (CM; control), 0.2% chlorhexidine or 3% DMAE-CB in CM aged for 30 days. The changes in modulus of elasticity, loss of dry mass and solubilization of collagen peptides were measured via three-point bending, precision weighing and hydroxyproline assay, respectively. RESULTS: 0.5-5% mass concentrations of DMAE-CB were highly effective (P<0.05) in inhibiting rhMMP-9 varied between 76.56±6.44% and 97.06±3.24%, the inhibitory effect of MMA was much lower than that of METMAC and DMAE-CB at the same concentration (P<0.05). Dentine beams incubated in 3% DMAE-CB showed only a 26.34% decrease in the modulus of elasticity (75.74% decrease in control), a 1.72±1.56% loss of dry mass (29.70±9.12% loss in control), and significantly less solubilized hydroxyproline when compared with the control (P<0.05). CONCLUSIONS: DMAE-CB is effective in inhibiting both soluble recombinant MMPs and matrix-bound dentine MMPs. Quaternary ammonium group is the effective anti-MMP group of QAMs. CLINICAL SIGNIFICANCE: The incorporation of DMAE-CB into dental adhesives has the potential to enhance the durability of dentine bonding and thus increases the longevity of restorations.