American journal of dentistry最新文献

Purpose: To evaluate the impact of simplified or multi-step polishing techniques on the roughness, color, and susceptibility to staining of different resin composites.

Methods: Discs (Ø6 mm x 2 mm) were obtained from different resin composites [nanofilled (Z350XT), suprananofilled (Estelite Omega), and nanohybrid (Forma)]. The specimens (n= 15) were submitted to a simplified protocol using abrasive discs (Sof-Lex) and spiral discs (Diacomp Plus Twist), or a multi-step protocol using abrasive discs (Sof-Lex), abrasive points (Jiffy), silicon carbide brush and felt disc with diamond pastes (Diamond Polish). The specimens were evaluated initially for roughness (Ra) and color (CIEL*a*b*, CIEDE 2000), after completing the polishing protocol, and after exposure to a coffee solution (pH= 5.01). The data were analyzed according to the variables, using generalized linear models, and the Friedman, Nemenyi, Kruskal-Wallis, Dunn, and Mann-Whitney tests (α= 0.05).

Results: The nanohybrid resin composite showed an increase in Ra following use of both polishing methods (P= 0.038). Both techniques promoted an increase in L* values after polishing; however, the general color changes (ΔEab and ΔE₀₀) were greater after the multi-step polishing (P< 0.05). After immersion in coffee, the multi-step polished groups of the nanohybrid and suprananofilled resin composite showed higher L* values than the simplified polishing groups (P= 0.023), and the nanofilled resin composite showed higher ΔEab and ΔE₀₀ values than the other resin composites, regardless of the polishing technique (P< 0.05).

Clinical significance: The choice of the resin composite had a greater effect on roughness, color stability and susceptibility to staining than the polishing technique. However, luminosity after coffee staining was higher with the multi-step polishing technique.

Purpose: To assess the effects of adhesive resin cement, obturation material and dentin location on the retention of glass fiber-reinforced resin composite (FRRC) posts.

Methods: 60 root canals in single rooted teeth were obturated with three different protocols (n= 20), including no obturation material (Control), GuttaFlow and Gutta-percha. Spaces were prepared for glass (FRCR) posts. Subgroups of the roots (n=10) were allocated for receiving posts luted with RelyX Unicem or Calibra resin cements. The specimens were mounted in plastic molds using epoxy resin. They were sectioned transversely to obtain three 1 mm-thick coronal, middle and apical slabs. Post retention was measured using a universal testing machine. The push-out test was performed at a crosshead speed of 0.5 mm/minute until post dislodgement occurred. Dislodged posts were examined microscopically to evaluate the mode of failure. Data were analyzed using univariate tests to reveal the effects of dependent variables and their interactions on post retention. Tukey test was used to determine significant differences for post retention in obturation material and dentin location groups. P-values ≤ 0.05 were considered significant.

Results: The adhesive resin cement, obturation material, dentin location and cement obturation materials interaction affected post retention. The mean bond strength was higher for posts cemented with RelyX Unicem than for those cemented with Calibra resin cements. Post retention in coronal locations was significantly superior to middle or apical locations. The failure mode was primarily mixed.

Clinical significance: When using RelyX Unicem cement for luting glass fiber-reinforced root canal posts, complete removal of all obturation materials from the post space significantly improves the retention. Although Calibra cement is less technique sensitive than RelyX Unicem resin cement, it produces notably lower retention of fiber-reinforced glass root canal posts.

Purpose: To evaluate the amount of dentin loss following immersion in or toothbrushing with whitening toothpaste (WT) containing hydrogen peroxide (HP) and citric acid (CA). Additionally, the amount of dentin loss after brushing with a WT alone or in combination with a conventional toothpaste was assessed, and the effects of HP and CA solutions on the dentin surface were investigated.

Methods: Bovine dentin specimens (n= 350) were randomly assigned to seven solutions of various compositions as toothpaste: The specimens assigned to each solution were then further divided into five treatment groups (n=10 each) : Group A = 1-hour immersion in each solution (ES); Group B = 10,000 brushing in ES; Group C = 1-hour immersion in ES + 10,000 brushing in ES; Group D = 1-hour immersion in ES + 10,000 brushing in reference slurry (RS); Group E = 10,000 brushing in ES + 10,000 brushing in RS. The amount and pattern of dentin loss were determined, and the surfaces were observed using noncontact profilometry.

Results: The WT (pH 5.0) caused lower dentin loss than RS after a single brushing cycle; however, the extent of dentin loss after 1 hour of immersion in the WT was significantly greater than that in the RS. Among the specimens treated with WT, a significant difference in dentin loss was observed between Group C and Groups D and E (P< 0.05) but not between Groups D and E. The surfaces exposed to CAS1, CAPB, and WT exhibited U-shaped patterns of dentin loss after brushing or immersion, whereas a wedge-shaped pattern was observed in those that underwent brushing with the RS.

Clinical significance: The effects (dentin abrasion) of a whitening toothpaste containing hydrogen peroxide and citric acid when used in combination with a conventional toothpaste were similar to those seen with the continuous use of a conventional toothpaste alone.

Purpose: To evaluate the efficacy of COMORAL a new multi-channeled oral irrigation (MCOI) unit with pulsating water jet, in plaque score reduction and gingivitis.

Methods: This was a single-blinded clinical randomized controlled trial (NCT05031260). Forty-two healthy subjects between 18 to 35 years old were initially recruited, and the control group (n = 20) and the intervention group (n = 17) were randomly assigned. Both groups were asked to brush their teeth one or two times a day without any supplementary oral hygiene products while the intervention group used COMORAL 3 times a day, 5 days a week. Clinical indices including gingival index (GI), plaque index (PI), bleeding on probing (BOP), pocket depth (PD), gingival recession (GR), and clinical attachment loss (CAL) were obtained at the baseline (D0), day 14 (D14), and day 28 (D28). Saliva was collected to examine the presence of periodontal pathogens. The repeated measures analysis of variance or generalized estimating equation was used to compare the interaction between groups and time points. The independent t-test or Mann-Whitney test were used for intergroup differences at each time point.

Results: At V0, PI, GI, BOP, and PD scores showed no differences between the two groups. At V1 and V2, these scores showed significant difference between two groups (P < 0.05) such that the intervention group showed gradual decreases while the control group showed no change. There were no differences in GR, CAL, and periodontal pathogens between the two groups. COMORAL showed improvement in reducing gingival inflammation and dental plaque formation adjuvant to routine toothbrushing in healthy adults.

Clinical significance: The results of this study can be useful to clinicians when selecting oral hygiene devices that can help improve patients' routine oral hygiene practice and their overall oral health.

Purpose: To evaluate the shear bond strength of two different resin cements to zirconia after treatment with cold atmospheric pressure plasma (CAPP) and other surface modification methods.

Methods: 189 specimens fabricated from Vita YZ-HT zirconia discs were divided into nine surface treatment groups: (1) Untreated (U), (2) Sandblasting (S), (3) Laser (L), (4) Plasma (P), (5) Primer (PR), (6) Sandblasting + Primer (SPR), (7) Laser + Primer (LPR), (8) Plasma + Primer (PPR), (9) Laser + Plasma + Primer (LPPR). Surface roughness (Ra) and contact angles were measured (n= 10 each), and scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses were performed (n= 1 each). Specimens were cemented with RelyX Ultimate Clicker adhesive resin cement or Theracem self-adhesive resin cement. The specimens were subjected to shear bond strength (SBS) test. Modes of failure were examined under a stereomicroscope and visualized by SEM.

Results: The S, PR, SPR, PPR and LPPR groups showed significantly greater Ra values than the U group. Significantly lower contact angles were observed in the S, P and L groups versus the U group. The SBS values of SPR, PPR and LPPR groups were significantly greater than those of the U group. CAPP can improve zirconia-resin cement bond strength by increasing the wettability of zirconia surfaces pretreated with the 10-methacryloyloxydecyl dihydrogen phosphate (MDP) primer.

Clinical significance: The use of cold atmospheric pressure plasma in combination with a primer is a promising clinical procedure for improving resin cement bonding to zirconia surface.

Purpose: To compare the accuracy and reliability of cone-beam computed tomography (CBCT) and laser scanner in measuring minor volume changes such as the root canal space.

Methods: 35 maxillary incisors were endodontically prepared. A dimensionally stable silicone material was injected into the root canal space and scanned with CBCT. The root canal volume was measured using Romexis 3.0.1 R software. Replicas were carefully removed from the teeth and scanned using an extraoral laser scanner. These images were exported to the Rhinoceros software for volume measurement. The volume of each replica was also assessed using the gravimetric method. To determine the accuracy, the volume obtained from both devices was compared with the gravimetric method. Statistical analysis was done using a paired t-test. The reliability was assessed using the intraclass correlation coefficient.

Results: There was no statistically significant difference between the mean volume of CBCT 27.04 ± 7.25 mm³ and the mean volume of the gravimetric method 27.87 ± 7.17 mm³ (P< 0.05). A statistically significant difference was seen with the laser scanner at 25.31 ± 6.89 mm³ and the gravimetric method at 27.87 ± 7.17 mm³ (P< 0.05). CBCT showed a good degree of agreement (ICC 0.899), while the laser scanner showed a moderate degree of agreement (ICC 0.644) with the gravimetric method. CBCT proved accurate and reliable in measuring minor volumes like the root canal space, ideally in the range of 20-25 mm³. The laser scanner presented acceptable reliability.

Clinical significance: The laboratory data showed satisfactory outcomes, providing an evidence-based approach and potentially motivating clinicians to integrate cone-beam computed tomography for volume analysis into clinical practice. The accuracy and reliability of laser scanners for small-volume analysis have not previously been evaluated. Consequently, the findings from this study warrant further clinical investigations.

Purpose: To evaluate the effectiveness of a calcium phosphate-containing-desensitizer (Teethmate Desensitizer - TD), caries type, subject age, and preoperative hypersensitivity on postoperative sensitivity (POS) after composite restorations on deep or extremely deep lesions.

Methods: 50 subjects, having two teeth with deep or extremely deep caries, participated in this study. TD was applied randomly to one tooth of each participant, and all teeth were restored with composite resin (Filtek Z250). After 1 week, POS was evaluated according to NRS (numerical rating scale) and VAS (visual analogue scale) by using participant diaries. At 6 weeks, POS was assessed considering subjects' reports. The normality of data was analyzed with Shapiro-Wilk test. For analyses, Pearson's chi-squared test, Mann-Whitney U and the Wilcoxon Signed-Rank test were used, and the effect sizes (ES) were calculated (α= 0.05).

Results: 47 of the participants completed the 6-week study. There was a small effect size noted for TD for NRS and VAS (P> 0.05, ES < 0.30). Also, there was no statistically significant difference between POS and subject age (P= 0.294, ES= 0.161), type of caries (P= 0.680, ES= 0.042) and preoperative sensitivity (P= 1.000, ES= 0.138) after the first week.

Clinical significance: Teethmate Desensitizer had no significant effect on postoperative sensitivity occurrence with respect to caries type, subject age, and existence of preoperative sensitivity. The application of Teethmate Desensitizer demonstrated no significant relieving effect on postoperative sensitivity in deep or extremely deep cavities.

Purpose: To compare the microhardness values and bottom/top hardness ratios of different composites after being cured in 2 or 4 mm increments.

Methods: Two bulk fill composites, methacrylate-based and ormocer-based, and one conventional composite were tested. 36 cylindrical discs were prepared (n=12/composite, with six for 2 mm, and six for 4 mm thickness) by pressing each composite into a mold between two glass slides covered by Mylar strips. The top and bottom surfaces of each sample were evaluated using a Buehler hardness tester for Knoop microhardness, with a 50 g static load applied for 10 seconds at three different locations of the central part of each sample. The bottom/top hardness ratio was calculated for each sample. The Knoop microhardness data and bottom/top ratio percentages were analyzed using two-way repeated measures ANOVA and Holm-Sidak post hoc test, with significance at P< 0.05.

Results: The tested methacrylate-based bulk fill had the highest overall microhardness among the three tested composites. All three composite types showed a significant difference in microhardness between the top and bottom of the 4 mm discs. The bottom/top ratio percentages differed significantly for both tested bulk fill composites across different thicknesses. Both tested bulk fill materials had a bottom/top ratio of ≥ 80% at the deepest level of a 4 mm increment.

Clinical significance: The type of material significantly affected both the bottom and top microhardness values under the experimental conditions used. While both tested bulk fill composites showed a decline in microhardness at the bottom of the 4 mm depth, they had clinically acceptable microhardness ratios at greater depths.

Purpose: To evaluate the shear bond strengths (SBS) of permanent 3D-printed resin (PR) to primary dentin using different luting agents.

Methods: 90 primary teeth were prepared. 45 cylinders (3 x 3 mm) were printed using PR, and 45 cylinders were milled using a Z block (to control). The cylinders were bonded to primary dentin by using three types of luting agent [glass-ionomer cement (GIC), resin-modified glass-ionomer cement (RMGIC), and self-adhesive resin cement (SRC)]. The SBS values of the specimens were calculated, and the fracture modes were examined.

Results: There was a statistically significant difference between the three different luting agents that were used to lute the PR to primary dentin (P< 0.001). Changing the material (PR or Z) did not affect the SBS values of the luting agents (P> 0.05). The adhesive failure between cement and dentin in the PR-SRC group was significantly higher than the other groups (P< 0.001). The SBS values of the newly developed PR to primary dentin with RMGIC and SRC were similar, but GIC showed lower values than the others.

Clinical significance: This laboratory study suggests that bond strength of the permanent 3D-printed resin can be like that of zirconia. As the resin-modified glass-ionomer cement and self-adhesive resin cement showed higher bond strength to primary teeth making the 3D-printed resin a treatment option.

Purpose: To evaluate the capacity of highly opaque cements on masking titanium abutment background.

Methods: Dentin and titanium specimens were used to simulate respectively, a natural dental background and an implant abutment. To simulate the full-crowns, Y-TZP zirconia (ZC), lithium disilicate (LD), and resin composite (RC) blocks were used. The titanium specimens were divided into six cementation groups (n=10): two regular cements (BQM and RX); three opaque cements (MHA; VA and BHA); and a clear liquid (CL). The masking capacity of each cement was calculated as the color difference between the color of the crowns over dentin with clear liquid (reference) and the color of the crowns over the titanium with the different cements (ΔEab). Data were statistically analyzed using two-way ANOVA and Tukey test (α= 0.05).

Results: Significant differences (P= 0.0001) were observed for both factors, cement and crown, and for the interactions between them. The results of Tukey test for cement were: BHA-2.25(0.98), MHA-2.94 (1.03), VA-3.45 (1.67), BQM-9.55 (2.77), RX-9.88 (3.12), CL-10.41 (3.47). The cements BHA, MHA and VA showed significantly smaller means than BQM, RX and CL. The results for crown were: ZC-3.66 (2.37), LD-7.50 (4.08), RC-8.08 (4.67). The means for all crown materials were significantly different. Highly opaque cements were more efficient on background masking than regular cements. Zirconia promoted the higher color masking while the resin composite the lowest.

Clinical significance: The use of a highly opaque cement can reduce the color interference of the titanium abutment background, favoring the esthetic outcome of metal-free cemented crowns.