Evaluation of resin infiltration for inhibiting initial caries progression: An in vitro study using Micro-Computed Tomographic analysis.

Objective: To evaluate the changes in lesion depth and mineral density of resin infiltration-treated white spot lesions against a simulated oral environment using thermal and acidic challenges in vitro. Materials and methods: Two enamel slabs were prepared from each buccal surface of permanent human premolars, for a total of 56 slabs. Artificial white spot lesions were induced. One specimen was treated with resin infiltration, while the other was used as an untreated control. A micro-CT was used to assess the lesion depth and mineral density of each specimen. Subsequently, all specimens were subjected to 10,000 cycles of thermocycling and pH cycling for 10 days before being re-evaluated using the micro-CT. Lesion depth and mineral density were examined and compared between before and after aging procedures within each group by the paired sample t-test. The independent samples t-test was utilized to compare lesion depth progression and percentage change of mineral density between groups. Results: After aging, there was both a significant lesion depth progression and a mineral loss in the control and resin infiltration groups. Mean lesion depth progression was 132.88 ± 4.18 µm for the control group and 52.31 ± 4.16 µm for resin infiltration group. Percentage mineral density loss as a percentage for the control and resin infiltration groups were 16.1 ± 0.64 % and 8.83 ± 0.30 %, respectively. The resin infiltration group demonstrated a significantly lower mean lesion depth progression and percentage changes in mineral loss compared to the control group. Conclusions: The lesion depth and mineral density changes in the resin infiltrated-treated group were lower than untreated white spot lesions after aging procedures using thermal and acidic challenges. Clinical significance: Resin infiltration is a promising approach to inhibit the progression of white spot lesions related to the initial stage of dental caries.

Primer application technique and remaining dentin thickness affected microtensile bond strength of contemporary dentin adhesives under simulated pulp pressure.

OBJECTIVES: To evaluate the effect of application techniques, type of adhesives and remaining dentin thicknesses on microtensile bond strength (µTBS) of 3 adhesive systems. MATERIALS AND METHODS: 112 flat occlusal dentinal surfaces of third molar were randomly allocated into 16 groups based on 2 remaining dentin thicknesses (RDT), 2 application techniques, and 3 adhesive systems (Optibond FL, OFL; Clearfil SE Bond, CSE; and Single Bond Universal, SB); SB was applied in either etch-and-rinse (ER) or self-etch (SE) mode. Simulated pulpal pressure was performed during restorative procedure and water storage. The stick-shaped specimens from each tooth underwent µTBS testing. The data were evaluated using a paired t test and ANOVA followed by a post hoc test. The fractured specimens were evaluated for mode of failure using a stereomicroscope. RESULTS: The mean µTBS values were significantly affected by RDT, application technique, and types of adhesives. Neither RDT nor application technique affected µTBS of SB in ER mode, whereas application technique affected both conventional and universal self-etch adhesives. RDT also influenced µTBS of OFL. CONCLUSIONS: RDT and application technique differently affected the µTBS of dentin bonding which was product-related. Etch-and-rinse systems had higher bond strength to superficial than to deep dentin, whereas self-etch systems were more sensitive to both RDT and application technique. CLINICAL RELEVANCE: The universal adhesive is less sensitive to intrinsic wetness and can be used according to manufacturer's instructions.

Influence of fatigue load on various adhesive resin luting agents in a zirconia-reinforced lithium silicate ceramic bonded to dentin.

PURPOSE: To examine fatigue failure load value of etch-and-rinse and self-adhesive luting systems used to bond ZLS to dentin. Moreover, this study seeks to evaluate whether the application of unfilled resin on silanated ceramic intaglio surface could improve fatigue failure load value. METHODS: Vita Suprinity (VS) blocks were sectioned into a cylindrical shape (5 mm in diameter and 1.5 mm in height). All VS were crystallized, and bonded surfaces were either treated with Heliobond (HB) application after silanization or without application of HB. Each VS was cemented to each flat occlusal dentin surface of the extracted human molar, following the adhesive luting systems: Optibond FL (FL) with Nexus3 (NX3), RelyX Unicem (UC), and Maxcem Elite (ME). 24-hour mean fatigue failure load was determined using a staircase approach (500,000 cycles, 20 Hz, initial load = 844 N, step size = 42 N). Representatives of failed specimens were evaluated by a scanning electron microscope (SEM). RESULTS: The Behrens-Fisher T-test revealed that ZLS cemented to dentin using self-adhesive resin luting cements (UC and ME) had a statistically significantly lower mean fatigue failure load value than etch-and-rinse resin luting cement (FLNX3) (alpha= 0.05). Meanwhile, the HB application groups did not achieve a statistically significant difference in fatigue failure load value when compared to non-application groups (alpha= 0.05). CLINICAL SIGNIFICANCE: Fatigue strength evaluation of ZLS bonded to dentin suggested that self-adhesive luting systems may not be the material of choice compared to a 3-step etch and rinse luting system.

Deep margin elevation with resin composite and resin-modified glass-ionomer on marginal sealing of CAD-CAM ceramic inlays: An in vitro study.

PURPOSE: To evaluate the marginal sealing ability of different restorative materials used in deep margin elevation (DME) on zirconia-reinforced lithium silicate CAD-CAM ceramic restorations. METHODS: A total of 30 Class II cavities were prepared in freshly extracted human molars with the proximal margin located 1 mm below the cemento-enamel junction (CEJ). All specimens were randomly assigned to one of three groups (n=10): control group, resin composite group (Filtek Z350 XT), and resin-modified glass-ionomer group (RMGI) (Vitremer Tricure). In Group 1, control group, no DME was performed. The inlay margin of the control group was placed directly on the dentin. In Groups 2 and 3, DME was used to elevate the margin to 1 mm above the CEJ with resin composite and RMGI, respectively. Zirconia-reinforced lithium silicate CAD-CAM ceramic restorations were manufactured and bonded on all specimens with universal bonding and resin luting cement. All specimens were aged by water storage for 6 months. Marginal sealing ability at different interfaces was evaluated with a stereomicroscope at 40x magnification by scoring the depth of silver nitrate penetrating along the adhesive surfaces. Statistical differences between groups were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. RESULTS: At the dentin interface, there was no significant difference in microleakage scores in the control group and resin composite group (P= 0.577); however, the RMGI group had significantly higher microleakage compared to the control group (P= 0.004) and resin composite group (P= 0.007). CLINICAL SIGNIFICANCE: Deep margin elevation can be achieved with resin composite. Resin-modified glass-ionomer must be used with caution due to the high microleakage scores.

Dentin microshear bond strength of various resin luting agents to zirconia-reinforced lithium silicate ceramics.

STATEMENT OF PROBLEM: The performance of adhesive and resin luting cements used to bond zirconia-reinforced lithium silicate (ZLS) ceramics to dentin has not been well established. PURPOSE: The purpose of this in vitro study was to examine the microshear bond strength (µSBS) of an etch-and-rinse adhesive system, a universal adhesive, and a self-adhesive resin cement that were used to bond ZLS to dentin. MATERIAL AND METHODS: VITA Suprinity (VS) and Celtra Duo (CD) blocks were sectioned into 36 and 72 microbars (1×1×3 mm). All VS were crystallized, while half of CD were additionally fired and defined as fired-Celtra Duo (FCD). The others were defined as unfired-Celtra Duo (UCD). Each microbar was cemented to each flat occlusal dentin surface of a human first premolar, following the adhesive luting systems: Scotchbond Multi-purpose (SM), Single Bond Universal (SU) combined with RelyX Ultimate, and RelyX Unicem (U2) (n=12 per group). µSBS at 24 hours was then determined, and the data were analyzed by using 2-way ANOVA and a Tukey post hoc test (α=.05). Failure modes were analyzed under a stereomicroscope at ×40 magnification. RESULTS: Two-way ANOVA revealed that the type of ZLS had no influence on µSBS (P=.699). However, the kinds of adhesive luting cements and their interaction had a statistically significant effect on µSBS (P<.001 and P=.002). U2 had a statistically significant lower mean µSBS, regardless of the type of ZLS, than SM and SU (P≤.05), while UCDU2 did not show a statistically significant difference in µSBS from UCDSU (P=.478). CONCLUSIONS: Resin cement used with an etch-and-rinse and a universal adhesive agent demonstrates higher bond strength for the cementation of zirconia-reinforced lithium silicate ceramics to dentin than a self-adhesive resin cement.

Grape Seed Extract Reduces Active Gelatinases Using an Etch-and-Rinse Mode Universal Adhesive.

PURPOSE: To examine the effect of grape seed extract (GSE) pretreatment on the reduction of active gelatinases when using universal adhesives in etch-and-rinse mode. MATERIALS AND METHODS: Fifty extracted non-carious human teeth were used in this study. Dentin powder was prepared for analysis of active MMP-2 by ELISA. Resin-dentin slices were prepared for in situ zymography in order to localize active gelatinases by quenched fluorescein-conjugated gelatin under a confocal microscope. Fluorescence intensity was analyzed quantitatively. Specimens were allocated into 6 groups: a non-treated control, phosphoric acid etched (PA), PA followed by Single Bond Universal (SBU, 3M Oral Care) or G-Premio Bond (GPB, GC), and PA followed by GSE for 1 min prior to SBU or GPB. The data were analyzed with one-way ANOVA and Bonferroni's test at a significance level of 0.05. RESULTS: Application of the universal adhesives SBU and GPB in etch-and-rinse mode reduced active MMP-2 in dentin matrices. However, the only further significant reduction was found in GPB pre-treated with GSE, as analyzed by ELISA. In situ zymography demonstrated the location of active gelatinases, and fluorescence intensity analysis confirmed significant reduction of active gelatinases in the hybrid layer of GPB pre-teated with GSE compared to GPB alone. CONCLUSION: The present study demonstrated the potential advantage of applying GSE to reduce active gelatinases especially at the hybrid layer, with greater benefit achieved for hydrophobic adhesives. Nevertheless, the mechanism of action, analysis of bond strength, and long-term efficacy require further study.

Compromised alveolar bone cells in a patient with dentinogenesis imperfecta caused by DSPP mutation.

OBJECTIVES: Dentin sialophosphoprotein (DSPP) plays an important role in the mineralization of both dentin and bones. The Dspp null mice developed periodontal diseases. Patients with DSPP mutations have dentinogenesis imperfecta (DGI), but very little is known about their bone characteristics. This study aims to characterize alveolar bone cells of a DGI patient with DSPP mutation. MATERIALS AND METHODS: Pathogenic variants were identified by whole exome and sanger sequencing. Cells isolated from the alveolar bones of a DSPP patient were investigated for their characteristics including cell morphology, attachment, spreading, proliferation, colony formation, mineralization, and osteogenic differentiation. RESULTS: We identified a Thai family with three members affected with autosomal dominant DGI harboring a heterozygous pathogenic missense mutation, c.50C > T, p.P17L, in exon 2 of the DSPP gene. The patients' phenotypes presented deteriorated opalescent teeth with periapical lesions, thickening of lamina dura, furcation involvement, alveolar bone loss, and bone exostoses. The alveolar bone cells isolated from DSPP patient exhibited compromised proliferation and colony formation. Scanning electron microscope revealed altered cellular morphology and spreading. The DSPP cells showed deviated mRNA levels of OCN, ALP, and COL1 but maintained in vitro mineralization ability compared to the control. CONCLUSIONS: We demonstrate that the DSPP p.P17L mutant alveolar bone cells had compromised cell spreading, proliferation, colony formation, and osteogenic induction, suggesting abnormal bone characteristics in the patient with DGI caused by DSPP mutation. CLINICAL RELEVANCE: DSPP mutation can induce the behavior alterations of alveolar bone cells.

Cyclophilin-B Modulates Collagen Cross-linking by Differentially Affecting Lysine Hydroxylation in the Helical and Telopeptidyl Domains of Tendon Type I Collagen.

Covalent intermolecular cross-linking provides collagen fibrils with stability. The cross-linking chemistry is tissue-specific and determined primarily by the state of lysine hydroxylation at specific sites. A recent study on cyclophilin B (CypB) null mice, a model of recessive osteogenesis imperfecta, demonstrated that lysine hydroxylation at the helical cross-linking site of bone type I collagen was diminished in these animals (Cabral, W. A., Perdivara, I., Weis, M., Terajima, M., Blissett, A. R., Chang, W., Perosky, J. E., Makareeva, E. N., Mertz, E. L., Leikin, S., Tomer, K. B., Kozloff, K. M., Eyre, D. R., Yamauchi, M., and Marini, J. C. (2014) PLoS Genet 10, e1004465). However, the extent of decrease appears to be tissue- and molecular site-specific, the mechanism of which is unknown. Here we report that although CypB deficiency resulted in lower lysine hydroxylation in the helical cross-linking sites, it was increased in the telopeptide cross-linking sites in tendon type I collagen. This resulted in a decrease in the lysine aldehyde-derived cross-links but generation of hydroxylysine aldehyde-derived cross-links. The latter were absent from the wild type and heterozygous mice. Glycosylation of hydroxylysine residues was moderately increased in the CypB null tendon. We found that CypB interacted with all lysyl hydroxylase isoforms (isoforms 1-3) and a putative lysyl hydroxylase-2 chaperone, 65-kDa FK506-binding protein. Tendon collagen in CypB null mice showed severe size and organizational abnormalities. The data indicate that CypB modulates collagen cross-linking by differentially affecting lysine hydroxylation in a site-specific manner, possibly via its interaction with lysyl hydroxylases and associated molecules. This study underscores the critical importance of collagen post-translational modifications in connective tissue formation.

Microtensile bond strength of silorane-based resin composite and its corresponding adhesive in Class I occlusal restorations.

PURPOSE: To determine the performance of a silorane-based resin composite, compared to that of a methacrylate-based resin composite, when used with their corresponding adhesive systems, and to determine the effects of c-factor and water storage time in Class I occlusal preparation, by means of microtensile bond strength (microTBS) test. METHODS: Extracted human third molars were ground flat to expose dentin, and randomly divided into eight groups, according to the type of resin composite, c-factor, and water storage time: (1) Filtek P90/ high c-factor/24 hours, (2) Filtek P90/low c-factor/24 hours, (3) Filtek Z250/high c-factor/24 hours, (4) Filtek Z250/low c-factor/24 hours, (5), Filtek P90/ high c-factor/3 months, (6) Filtek P90/low c-factor/3 months, (7) Filtek Z250/high c-factor/3 months, and (8) Filtek Z250/ low c-factor/3 months. After 24 hours or 3 months of water storage, the bonded hourglass specimens were tested for microTBS, and failure types were also noted. Data were analyzed using three-way ANOVA and Tamhane post-hoc test (alpha = 0.05). RESULTS: Filtek Z250/low c-factor/24 hours exhibited the highest microTBS (54.19 +/- 9.05 MPa), and Filtek P90/high c-factor/3 months exhibited the lowest (6.94 +/- 2.07 MPa). All groups tested in high c-factor (> 4) preparations and 3-month water storage time showed significant decrease in microTBS, except when comparing between Filtek P90/high c-factor/24 hours and Filtek P90/high c-factor/3 months as there was no statistical difference.

Different roles of dexamethasone on transforming growth factor-beta1-induced fibronectin and nerve growth factor expression in dental pulp cells.

During pulp injury, it has been hypothesized that transforming growth factor-beta1 (TGF-beta1) is released from dentin into pulp tissue and promotes pulp tissue healing. Dexamethasone is a glucocorticoid that has been used to treat pulp injury and shown to induce differentiation of hard tissue forming cells. However, the interaction between dexamethasone and TGF-beta1 is still unknown. This study aimed to examine the effects of dexamethasone on human pulp cells in the presence of TGF-beta1. TGF-beta1 increased expression and synthesis of both fibronectin and nerve growth factor (NGF), whereas dexamethasone stimulated fibronectin synthesis but inhibited NGF expression. The application of both TGF-beta1 and dexamethasone resulted in an additional effect on fibronectin; however, dexamethasone inhibited the TGF-beta1-induced NGF expression. Dexamethasone promotes fibronectin synthesis and suppresses NGF secretion, suggesting that this reagent could be used clinically to reduce pain and promote dental pulp tissue healing.

Clinical evaluation of a resin-modified glass-ionomer liner for cervical dentin hypersensitivity treatment.

PURPOSE: To evaluate the effectiveness of two agents for treating cervical dentin sensitivity associated with gingival recession or noncarious cervical lesions. METHODS: 44 patients with at least mild sensitivity affecting cervical dentin were enrolled in a longitudinal randomized clinical trial. A resin-based desensitizer or an experimental glass-ionomer was assigned to treat at most two teeth from each side of the mouth. Sensitivity was assessed by tactile and cold tests, measured with a Visual Analogue Scale at baseline, after treatment, and at 1 week, 1, 3, 6, and 12 months after treatment. Other noteworthy clinical observations were recorded. RESULTS: Both treatments effectively reduced dentin sensitivity (mixed linear model analysis). Sensitivity score for the glass-ionomer was significantly lower than for the resin-based desensitizer after treatment and at all follow-up periods (P < 0.0001). Some overhanging margins were observed in the glass-ionomer group, which could accumulate plaque and cause gingivitis. Despite material loss from some teeth treated with the glass-ionomer, the follow-up sensitivity scores were still lower than baseline scores.