Multiple coatings can improve the bond durability of one-step self-etching adhesive to primary dentin.

OBJECTIVE: To investigate whether multiple coatings can improve the bond durability of one-step self-etching adhesive to primary dentin. METHODS: Twelve caries-free human primary molars were randomly divided into 2 groups. In group 1, each tooth was hemisected into 2 halves. One half was assigned to the control subgroup 1, which was bonded with a commercially available one-step self-etching adhesive according to the manufacturer's instructions; the other half was assigned to experimental subgroup 1, in which the adhesive was applied three times before light curing. In group 2, one split half tooth was bonded with a commercially available one-step self-etching adhesive according to the manufacturer's instructions; for the other half, three layers of adhesive were applied with each successive layer of light curing. Specimens were stored in 0.9% NaCl containing 0.02% sodium azide at 37℃ for 18 months and then were subjected to microtensile bond strength test and the fracture mode analysis. RESULTS: When the adhesive was applied three times before light curing, the bond strength of the experimental subgroup 1 was significantly higher than that of the control subgroup 1 (47.46∓13.91 vs. 38.12∓11.21 MPa, P<0.05). When using the technique of applying multiple layers of adhesive with each successive layer of light curing, no difference was observed in bond strength between the control subgroup and the experimental subgroup (39.40±8.87 vs. 40.87±9.33 MPa, P>0.05). CONCLUSION: Multiple coatings can improve the bond durability of one-step self-etching adhesive to primary dentin when using the technique of light-curing after applying 3 layers of adhesive.

[Precision and accuracy of a dental spectrophotometer in gingival color measurement of maxillary anterior gingival].

OBJECTIVE: To explore a gingival shade matching method and to evaluate the precision and accuracy of a dental spectrophotometer modified to be used in gingival color measurement. METHODS: Crystaleye, a dental spectrophotometer (Olympus, Tokyo, Japan) with a custom shading cover was tested. For precision assessment, two experienced experimenters measured anterior maxillary incisors five times for each tooth. A total of 20 healthy gingival sites (attached gingiva, free gingiva and medial gingival papilla in anterior maxillary region) were measured,the Commission Internationale de I' Eclairage (CIE) color parameters (CIE L*a*b*) of which were analyzed using the supporting software. For accuracy assessment, a rectangular area of approximately 3 mm×3 mm was chosen in the attached gingival portion for spectral analysis. PR715 (SpectraScan;Photo Research Inc.,California, USA), a spectroradiometer, was utilized as standard control. Average color differences (ΔE) between the values from PR715 and Crystaleye were calculated. RESULTS: In precision assessment,ΔL* between the values in all the test sites and average values were from(0.28±0.16)to(0.78±0.57), with Δa*and Δb* from(0.28±0.15)to (0.87±0.65),from(0.19±0.09)to( 0.58±0.78), respectively. Average ΔE between values in all test sites and average values were from (0.62 ± 0.17) to (1.25 ± 0.98) CIELAB units, with a total average ΔE(0.90 ± 0.18). In accuracy assessment, ΔL* with control device were from(0.58±0.50)to(2.22±1.89),with Δa*and Δb* from(1.03±0.67)to(2.99±1.32),from(0.68±0.78)to(1.26±0.83), respectively. Average ΔE with the control device were from (2.44±0.82) to (3.51±1.03) CIELAB units, with a total average ΔE (2.96 ± 1.08). CONCLUSION: With appropriate modification, Crystaleye, the spectrophotometer, has demonstrated relative minor color variations that can be useful in gingival color measurement.

[Effect of Shofu gingival matrices which simulate the gingival color on spectrophotometric tooth color measurement].

OBJECTIVE: To investigate the effect of gingival color on spectrophotometric color measurement in a standardized model. METHODS: Shofu gingival matrices were used to simulate the soft tissue and VITA Classical shade tabs were fixed into them. Both the gingival matrices and shade tabs were measured with Crystaleye spectrophotometer in a black box. Regions of the shade tabs, gingival color and their combinated effect on measurements were analyzed, Pearson correlation analysis was used to identify the correlation of the gingival color difference with the shade tabs color difference. RESULTS: The ranges of color difference were 1.01-2.26 in the cervical, 0.93-1.27 in the body and 1.67-2.97 in the incisal regions, respectively. Statistical analysis revealed that there was significant difference among all the gingival groups in the cervical region. Color differences were similar in the body and the incisal regions. The color measurement with Crystaleye was influenced by the regions of the shade tabs, the gingival color and their combination (P<0.001). Pearson Correlation Coefficient was 0.646 in the cervical, 0.386 in the body and 0.217 in the incisal regions respectively(P<0.001). CONCLUSION: The color measurement in the cervical region with the spectrophotometer was influenced by the color of the simulated gingiva. Such influence was not obvious in the body and incisal regions. Color coordinates changed regularly with the gingival color.

Effect of multiple coatings of one-step self-etching adhesive on microtensile bond strength to primary dentin.

OBJECTIVE: To investigate the effect of multiple coatings of the one-step self-etching adhesive on immediate microtensile bond strength to primary dentin. METHODS: Twelve caries-free human primary molars were randomly divided into 2 groups with 6 teeth each. In group 1, each tooth was hemisected into two halves. One half was assigned to control subgroup 1, which was bonded with a single-step self-etching adhesive according to the manufacturer's instructions; the other half was assigned to experimental subgroup 1 in which the adhesive was applied three times before light curing. In group 2, the teeth were also hemisected into two halves. One half was assigned to control subgroup 2, which was bonded with the single-step self-etching adhesive according to the manufacturer's instructions; the other half was assigned to experimental subgroup 2 in which three layers of adhesive were applied with light curing each successive layer. Microtensile bond strength was immediately tested after specimen preparation. RESULTS: When the adhesive was applied three times before light curing, the bond strength of the experimental subgroup 1 (n=33, 57.49 +/-11.61 MPa) was higher than that of the control subgroup 1 (n=31, 49.71 +/-11.43 MPa, P<0.05). When using the technique of applying multiple layers of adhesive with light curing each successive layer, no difference of immediate bond strength was observed between the control subgroup 2 and the experimental subgroup 2 (P>0.05). CONCLUSION: strength to primary dentin when using the technique of light-curing after applying three layers of adhesive.

[H(2)O(2) treatment improves the bond strength between glass fiber posts and resin cement].

OBJECTIVE: To evaluate the effect of etching with H2O2 on the bond strength between epoxy-based glass fiber posts and resin cement. METHODS: Sixteen epoxy-based glass fiber posts were randomly divided into 4 groups (4 posts in each group) for different surface treatments. Group 1, no surface treatment (Control group); Group 2, treated with silane coupling agent for 60 s; Group 3, immersed in 10% H2O2 for 10 min then treated with silane coupling agent for 60 s; Group 4, immersed in 30% H2O2 for 10 min then treated with silane coupling agent for 60 s. Resin cement was used for the post cementation to form resin slabs which were then sectioned and trimmed into dumbbell shape to obtain microtensile specimens. Microtensile bond strengths were tested and the failure modes were examined with a stereomicroscope. Statistical analysis of microtensile bond strengths was performed with Kruskal-Wallis test. RESULTS: The microtensile bond strengths (standard deviation) were 18.81 (4.04) MPa for Group 1, 26.70 (9.63) MPa for Group 2, 39.07 (6.47) MPa for Group 3, 46.05 (5.97) MPa for Group 4. CONCLUSION: Etching with H2O2 followed by silanization could significantly improve the bond strength between epoxy-based glass fiber posts and resin cement.

[Clinical evaluation of denture made of pure titanium].

OBJECTIVE: To evaluate the clinical effect of pure titanium used for complete denture and removable partial denture. METHODS: Sixty edentulous patients were selected. Thirty patients in the test group for pure titanium denture and the other 30 in control for Co-Cr Alloy denture. RESULTS: No significant differences in clinical effect between dental casting pure titanium and casting Co-Cr alloy used for complete denture or removable partial denture. CONCLUSION: Due to the properties and biocompatibility, pure titanium can be used for denture base and frameworks of removable partial denture.

Effect of Provisional Restorations with Ovate Pontics on Preservation of the Ridge after Tooth Extraction: Case Series.

OBJECTIVE: To evaluate the effect of provisional restorations using ovate pontics on the hard and soft tissues of the alveolar ridge after tooth extraction. METHODS: Patients with intact buccal bone after extraction of a maxillary incisor underwent a series of treatments. The protocol included tooth extraction and provisional restoration using ovate pontics. The outcomes were assessed 1, 3 and 6 months after the procedure, regarding changes in bone volume and soft tissue dimension. RESULTS: A total of 11 patients (6 female and 5 male) were treated using an ovate pontic provisional restoration after tooth extraction. After 6 months, bone loss at level 1, 3 and 5 mm below the most coronal section of the bone crest was 2.28 ± 0.53 mm, 1.51 ± 0.30 mm and 1.46 ± 0.41 mm, respectively. Changes in bone volume of these three levels were significantly lower (P < 0.01) than changes previously reported in the literature. The mesial and distal papillae recessed 0.47 ± 0.24 mm and 0.88 ± 0.57 mm, respectively, whereas the midfacial shrinkage was 0.86 ± 0.44 mm. The dimension of the ridge contour around the socket reduced mostly at 3 and 5 mm below the coronal section and the gingival mucosa, with values of 1.68 ± 0.48 mm and 1.61 ± 0.48 mm, respectively. CONCLUSION: Using a provisional restoration with ovate pontics after tooth extraction may preserve the alveolar ridge by sustaining the soft tissue, in particular the gingival papilla.

Effects of a modified cold atmospheric plasma jet treatment on resin-dentin bonding.

The radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma is a novel cold atmospheric plasma (CAP) source, which has low energy characteristic. This study investigated the effect of RF-APGD plasma on the mechanical properties of dentin collagen and resin-dentin bonding. The scanning electron microscopy analysis was performed before and after a novel RF-APGD plasma and a conventional CAP treatment and a tensile test was carried out for the stiffness of dentin collagen. The microtensile resin-dentin bond strength was tested either immediately or after a 50,000-cycle thermocycling process. Dentin collagen maintained an intact structure after a 45-s RF-APGD plasma treatment, whereas even a 10-s treatment with the conventional CAP collapsed the collagen scaffold. When compared with control groups, the RF-APGD plasma treatment showed: (i) an improved stiffness of dentin collagen; (ii) a significant improvement in the bonding strength before/after artificial aging. Thus, RF-APGD plasma treatment has excellent prospects as a resin-dentin bonding protocol.

[Coverage errors of five shade guide systems to vital natural teeth].

OBJECTIVE: To compare the coverage errors (CE) of five different shade guides in anterio vital natural teeth of selected people. METHODS: Anterior vital natural teeth were measured with Crystaleye spectrophotometer, color coordinates of the teeth and five shade guides A (VITA Classical), B (VITA 3D-Master), C (Chromascop), D (Shofu Vintage Halo NCC) and E (Noritake)were analyzed with the supporting software. The CE of the five shade guide systems to natural teeth were evaluated in cervical, body and incisal regions, and difference in CE among shade guides was determined. RESULTS: In the cervical region, shade guide A had the maximal CE value (3.09 ± 0.97) and shade guide D had the minimal CE value (1.62 ± 0.75).In the body region, CE of shade guide B (1.65 ± 0.64) and shade guide D (1.52 ± 0.74) were lower than those of shade guides A (2.04 ± 0.80), C (2.04 ± 0.90) and E (2.02 ± 0.84) (P < 0.05).In the incisal part, all CE were below 2.00, and again shade guide A had the maximal CE value (1.81 ± 0.86) and shade guide D had the minimal CE value (1.28 ± 0.55). CONCLUSIONS: Within the limitation of the study, shade guide D had better color coverage of natural teeth in cervical, body and incisal regions.

An internet evaluation of Chinese public preferences for asymmetrically altered incisor angulations.

OBJECTIVE: To evaluate the Chinese public preferences for asymmetrically altered incisor angulations, with the goal of linking preferences to gender. METHODS: Five variations of 5 separate digital smiling photographs were used in this survey. The alterations included discrepancy between the dental and facial midlines, inclination of dental midline and two central incisors, inclination of left central incisor (mesially or distally) and occlusal cant. The raters used a 100-point visual analogue scale to evaluate each image on a web page. RESULTS: Overall 1,022 raters joined the evaluation and they were reliable (intraclass correlation coefficient = 0.76-0.80). Raters identified range of approval for several smile characteristics. A 2 mm dental to facial midlines discrepancy was the maximum acceptable deviation for females and 3 mm was the maximum for males. Females could accept a 4-degree occlusal cant and males could accept a 6-degree cant. These two characteristics were related to gender. The dental midline and relevant two central incisors with a 5-degree slope or less were generally acceptable. The approval of a left central incisor inclination was 5 degrees mesially and 10 degrees distally. These three characteristics were unrelated to gender. CONCLUSION: The approval for five smile characteristics could be identified reliably. The ranges of acceptability were large and slight changes in the angulations of incisors did not influence the smile attractiveness.

Reliability and accuracy of Crystaleye spectrophotometric system.

OBJECTIVE: to develop an in vitro shade-measuring model to evaluate the reliability and accuracy of the Crystaleye spectrophotometric system, a newly developed spectrophotometer. METHODS: four shade guides, VITA Classical, VITA 3D-Master, Chromascop and Vintage Halo NCC, were measured with the Crystaleye spectrophotometer in a standardised model, ten times for 107 shade tabs. The shade-matching results and the CIE L*a*b* values of the cervical, body and incisal regions for each measurement were automatically analysed using the supporting software. Reliability and accuracy were calculated for each shade tab both in percentage and in colour difference (ΔE). Difference was analysed by one-way ANOVA in the cervical, body and incisal regions. RESULTS: range of reliability was 88.81% to 98.97% and 0.13 to 0.24 ΔE units, and that of accuracy was 44.05% to 91.25% and 1.03 to 1.89 ΔE units. Significant differences in reliability and accuracy were found between the body region and the cervical and incisal regions. Comparisons made among regions and shade guides revealed that evaluation in ΔE was prone to disclose the differences. CONCLUSION: measurements with the Crystaleye spectrophotometer had similar, high reliability in different shade guides and regions, indicating predictable repeated measurements. Accuracy in the body region was high and less variable compared with the cervical and incisal regions.