The effect of deviations in sintering temperature on the translucency and color of multi-layered zirconia.

OBJECT: This study aimed to investigate the changes in the translucency and color of four different multi-layered zirconia materials when the sintering temperature were inaccurate. MATERIALS AND METHODS: Two hundred zirconia samples (11 × 11 × 1.0 mm) of four multi-layered zirconia, Upcera TT-GT (UG), Upcera TT-ML (UM), Cercon xt ML (CX), and Lava Esthetic (LE), were divided into five subgroups according to the sintering temperature: L1 (5% lower temperature), L2 (2.5% lower temperature), R (recommended sintering temperature), H2 (2.5% higher temperature), H1 (5% higher temperature). After sintering, color coordinates were measured. Then the translucency parameter (TP) values, and the color differences (between the inaccurate sintering temperature and the recommended temperature) of each zirconia specimen were calculated. Statistical analysis was performed by using three-way ANOVA tests, the one-way ANOVA, and Tukey's post hoc test. RESULTS: Three-way ANOVA results showed that material type, sintering temperature, specimen section, and their interactions significantly influenced the TP values (except for the interactions of specimen section and sintering temperature) (P < .05). TP values of zirconia specimens were significantly different in the inaccurate sintering temperatures (P < .05), except for the cervical and body sections of UG group (P > .05). Compared with recommended sintering temperature, higher sintering temperature caused higher TP values for CX, but lower for LE. Three-way ANOVA results showed that material type, sintering temperature, and their interactions significantly influenced the ∆E00 values (P < .05). There were no significant differences in ∆E00 values of UM and CX groups at different inaccurate sintering temperatures, and were clinical imperception (except for UM-L1) (∆E00 < 1.25). ∆E00 values of all zirconia specimens showed clinically acceptable (∆E00 < 2.23). CONCLUSION: The deviations in sintering temperature significantly influenced the translucency and color of tested multi-layered zirconia. The trends of translucency in the multi-layered zirconia depended on material type and the color changes of all zirconia materials were clinically acceptable at inaccurate sintering temperatures.

Effect of ceramic type and thickness on the masking ability of chairside machinable all-ceramic crowns.

OBJECTIVES: This study aimed to evaluate the influence of ceramic type and thickness on the masking ability and final aesthetic effects of chairside machinable all-ceramic crowns. METHODS: Six kinds from three types chairside machinable ceramic materials (IPS e.max CAD HT/MT/LT, IPS Empress LT, and VITA Suprinity HT/T) in shade A2 were fabricated to slice specimens into 1.0, 1.5, and 2.0 mm-thick sections (n=10). The color parameters of the specimens against black and white tiles and four resin substrates (A2, A4, B3, and C4 shade) were measured with a spectrophotometer. The translucency parameter (TP) was calculated using color parameters measured over standard white and black backgrounds. The color differences (ΔE) were calculated between there substrate shades (A4, B3, C4 ) and A2 shade (control group). Two-way analysis of variance (ANOVA) was performed on the TP values. The two va-riables were ceramic type and ceramic thickness. Three-way ANOVA was used to determine the effects of ceramic materials, ceramic thickness, and substrate shades on the ΔE values, followed by Tukey test for multiple comparisons (α=0.05). RESULTS: Ceramic type, ceramic thickness, and substrate shade significantly affected the ΔE values (P<0.001). The L* and b* values of the specimens increased with increasing ceramic thickness, except in substrate A2, whereas the ΔE values decreased. The color difference of all 1.0 mm-thick specimens or all specimens over the substrates C4 shade exceeded the clinically acceptable threshold (ΔE>3.3). CONCLUSIONS: The masking ability of chairside machinable all-ceramic crowns is influenced by ceramic type and thickness, and ceramic material. The thickness of ceramic less than 2.0 mm cannot mask the gray shade abutment.

Comparison of the efficacy and safety of first-line treatments for of advanced EGFR mutation-positive non-small-cell lung cancer in Asian populations: a systematic review and network meta-analysis.

Background: According to the 2023 guidelines for treating non-small-cell lung cancer (NSCLC), first-line treatment and recently developed agents for the treatment of epidermal growth factor (EGFR) mutation-positive locally advanced or metastatic NSCLC were compared in this meta-analysis. Treatment regimens involved in the included studies included first, second, and third-generation tyrosine kinase inhibitors (TKIs), TKIs plus chemotherapy, TKIs plus angiogenesis inhibitors, and platinum-containing doublet chemotherapy with or without bevacizumab. Considering the varying efficacy and safety of drugs in people of different ethnic origins, the optimal regimen should be determined, and the safety of first-line treatments should be assessed in the Asian population specifically. Methods: PubMed, Embase, the Cochrane Library, Web of Science, and the China National Knowledge Infrastructure (CNKI) were systematically searched to retrieve reports on randomized controlled trials (RCTs) with research data published from inception to 1 February 2023. Adopting Asian patient populations as the target (including studies in which Asian patients accounted for more than 50% of the sample), a network meta-analysis (NMA) was conducted for comparison of treatment regimens and treatments were ranked based on the surface under the cumulative ranking curve (SUCRA). Results: A total of 19 RCTs involving 5,824 patients and covering 14 treatment regimens were included. The primary outcome measure examined in this study was progression-free survival (PFS); other outcome measures examined were overall survival (OS), disease control rate (DCR), objective response rate (ORR), occurrence of any adverse events (AE), occurrence of adverse events of grade 3 or above (≥3AE), and occurrence of serious adverse events (SAE). In terms of PFS, all regimens including TKIs (as a monotherapy or in combination with other therapies), as well as bevacizumab (Bev) plus chemotherapy (Ch) were found to be significantly superior to basic chemotherapy (HRs: 0.09-0.61, p < 0.05 in all cases compared with Ch alone). The highest-ranking therapies were erlotinib (Erl) plus Bev (SUCRA: 0.94) and Erl plus ramucirumab (Ram) (SUCRA: 0.93). Regarding OS, no significant differences was observed between first-line treatment strategies; the top four treatments based on SUCRA, in rank order, were Bev + Ch (0.87), gefitinib (Gef) plus Ch (0.81), dacomitinib (Dac) (0.79), and osimertinib (Osi) (0.69). Additionally, there were no significant differences between first-line treatment strategies in terms of DCR. Regarding ORR, the top three treatments based on SUCRA were Erl + Bev (0.85), Erl + Ram (0.76), and Gef + Ch (0.74). No significant difference between first-line treatment strategies was observed in terms of the risk of AE. However, based on SUCRA, Erl ranked highest on avoidance of ≥ 3AE (0.97), and Osi ranked highest on avoidance of SAE (0.91). Conclusion: Based on these analyses of survival benefits, tumor burden response, and safety, furmonertinib (Fur), Osi, and aumolertinib (Aum) may represent the best treatment regimen options for Asian patients, significantly prolonging survival (as measured by median PFS/OS), eliciting a greater tumor burden response, and exposing patients to a lower risk of adverse events. Although Erl + Bev and Erl + Ram are associated with the best survival benefits in terms of PFS, further clinical studies are still needed to identify ways to reduce the risk of adverse events. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php? ID=CRD42023407994, identifier CRD42023407994.

Effect of CAD-CAM ceramic materials on the color match of veneer restorations.

STATEMENT OF PROBLEM: With the different translucency levels and types of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic materials, choosing the most appropriate CAD-CAM ceramic materials to better reproduce the color appearance of natural teeth can be challenging. PURPOSE: The purpose of this in vitro study was to analyze the color differences between natural teeth and milled veneers fabricated with the different types of CAD-CAM ceramic materials. MATERIAL AND METHODS: Ten extracted maxillary central incisor teeth with the A2 shade in the body region were prepared for ceramic veneers. The veneer restorations were designed by using the duplicating method and fabricated from 9 milling blocks (IPS e.max CAD HT/LT, Lava Ultimate CAD HT/LT, VITA SUPRINITY HT/T, IPS Empress CAD HT/LT/Multi) in a dental milling unit (n=10). The bonding surface of the abutment tooth was coated with a thin layer of a separating agent, and the veneer specimen with resin cement was then bonded to the corresponding abutment tooth. A clinical spectrophotometer was used to measure the Commission Internationale de l'Eclairage Lab values of natural teeth, abutment teeth, and milled veneers in the cervical, body, and incisal regions. Color differences between the natural tooth and A2 shade tab (ΔE1) and between the milled veneer and natural tooth (ΔE2) were calculated. The ΔE2 values were compared with the perceptibility threshold (ΔE=2.6) and acceptability threshold (ΔE=5.5). The paired-samples t test, 1-way analysis of covariance, and 2-way ANOVA were used to analyze data (α=.05). RESULTS: The results of 1-way analysis of covariance showed that ceramic materials significantly affected the a∗ and b∗ values of the milled veneers (P<.001) but did not affect the L∗ values of the milled veneers (P>.05). The results of 2-way ANOVA indicated that the ΔE2 values were not significantly affected by different CAD-CAM ceramic materials (F=1.560, P=.138), while statistically significant differences were found in the veneer regions (F=6.588, P=.002). The ΔE2 values ranged from 2.41 to 5.36, less than the clinically acceptable color threshold of 5.5. CONCLUSIONS: The color parameters of milled veneers were affected by the different types of CAD-CAM ceramic materials. The color of the veneer restoration was able to match that of the natural tooth.

[Impact assessment on enamel remineralization after orthodontic treatment with casein phosphopeptide calcium phosphate complex].

PURPOSE: To compare the effect on enamel demineralization following fluoride rinse or casein phosphopeptide calcium phosphate complex (CPP-ACP) after fixed appliance orthodontic treatment. METHODS: The study population consisted of 21 post-orthodontic patients (13 females, 8 males, 84 affected teeth) with white spot lesions (WSL). They were divided into 3 groups with 28 affected teeth in each group. Participants in the control group were brushed with fluoride toothpaste twice a day. Participants in the fluoride group were instructed to rinse the mouth with 20mL 0.01% sodium fluoride rinse in addition to brushing twice a day. Participants in CPP-ACP group were instructed to use tooth moss after brushing their teeth twice a day for 6 months. SPSS 17.0 software package was used to analyze the data. RESULTS: Within 6 months after orthodontic treatment, white spot lesions areas of the three groups caused by enamel demineralization were all reduced in different degrees, and the differences of success rate were significant among three groups (P<0.05). CPP-ACP group achieved the highest success rate (51%) than the other group, the fluoride group (44%) and the control group (42%). CONCLUSIONS: Brushing teeth, fluoride rinse and CPP-ACP have certain effect on remineralization of demineralized teeth in 6 months after orthodontic treatment. Compared with brushing and fluoride rinse, CPP-ACP can reduce the area of enamel demineralization more effectively.

The effect of ceramic thickness and resin cement shades on the color matching of ceramic veneers in discolored teeth.

The objective of this study was to analyze the effects of ceramic material thickness and resin cement shade on the color matching of ceramic veneers at the gray tooth structures. Seventy-two artificial maxillary right central incisor teeth (C2 shade) were prepared according to veneer tooth preparation in practice. Ceramic materials (LT, A2 shade, IPS e.max Press) were selected to fabricate the 0.50- and 0.75-mm thick veneers at the body region. The ceramic veneer specimens were bonded to the artificial teeth by the 6 shades of resin cements (Variolink Veneer: shades of HV+3, LV-2, LV-3; and RelyXTM Veneer: shades of WO, TR, A3). A clinical spectrophotometer (Crystaleye, Olympus) was used to measure the color parameters. The color differences (ΔE values) of ceramic veneers and A2 shade tab (Vitapan Classical, Vita) and C* ab values were calculated. The results of three-way ANOVA indicated that the ΔE values of ceramic veneer and A2 shade tab were significantly different in the thickness of ceramic materials, shades of resin cements, and measuring regions (p < 0.001). There were significant differences in 0.50-mm-thick ceramic veneers that exhibited higher ΔE values compared with veneers that were 0.75-mm thick. Tukey's HSD test showed that the average ΔE values in body region were significantly smaller than that in cervical and incisal regions. The color matching of ceramic veneers was significantly influenced not only by the ceramic thickness and the resin cement shades but also the tooth regions.

The influence of resin cements on the final color of ceramic veneers.

PURPOSE: To evaluate the effect of three brands of resin cement on the final color of ceramic veneers. METHODS: 50 disk-shaped ceramic specimens (IPS e.Max, 0.6mm×8.0mm diameter) and disk-shaped composite resin background specimens (4.0mm×8.0mm diameter) were prepared and divided into 10 groups (n=5). These paired specimens were bonded using ten shades of resin cement (Variolink Veneer, shades LV-3, LV-2, MV, HV+2, HV+3; Panavia F, shades light and brown; and RelyX™ Veneer, shades WO, TR, A3). A spectrophotometer (VITA Easyshade) was used to measure the color parameters (CIE L*a*b* values) of the paired disks before and after cementation. The color differences (ΔE values) after cementation were calculated and statistically analyzed by the One-way ANOVA (at the significant level p<0.05). RESULTS: The color parameters of the ceramic disks were measured in terms of the increase in L* value, and the decrease in Cab(*) value after bonding with the resin cement. The ΔE values of ceramic disks after cementation ranged from 1.38 to 7.16. The ΔE values were more than 3.3 when the ceramic disks were cemented with resin cements in shade HV+3 (4.90) and shade WO (7.16). One-way ANOVA of ΔE values revealed significant differences in the resin cement shades. CONCLUSIONS: Resin cements can affect the final color of ceramic veneer restorations, and the extent of this effect varies according to the resin cement shades.

[Evaluation of the esthetic effect of resin cements on the final color of ceramic veneer restorations].

OBJECTIVE: To evaluate the influence of various shades of resin cements on the final color of an improved lithium-disilicate pressed glass ceramic veneers and analyze the agreement of resin cements and corresponding try-in pastes. METHODS: Forty-eight artificial maxillary central incisor teeth were sequenced according to the measured color parameters and divided at random into 8 groups (n = 6). These artificial teeth were prepared following veneer preparation protocol. An improved lithium- disilicate pressed glass ceramic materials (IPS e.max Press, Ivoclar Vivadent) were selected as the veneer material. The shape and curvature of each veneer wax pattern were duplicated with the same impression to guarantee the similarity. The ceramic veneer specimens were delivered on the artificial teeth using the corresponding try-in pastes of 8 shades (Variolink Veneer, shades of LV-3, LV-2, MV, HV+2, HV+3; and 3M RelyXTM Veneer, shades of WO, TR, A3) and bonded with the resin cements. A clinical spectrophotometer was used to measure the color parameters of the ceramic veneers before the try-in, during the try-in procedure, and after cementation. ΔE values and C*ab values were calculated. RESULTS: The result of one-way ANOVA indicated that the color changes of ceramic veneer cementation with resin cements were statistically significantly different in the shades of resin cements (P < 0.001). The ΔE values of ceramic veneer after cementation ranged from 0.93 to 6.79. The color changes of ceramic veneer specimens using the shades of LV-3, HV+3, WO were 3.31, 4.90 and 6.79, respectively (ΔE>3.3). The ΔE values of the ceramic veneer specimens between the resin cements and corresponding try-in pastes were from 0.72 to 1.79 (except the shade of HV+3). CONCLUSIONS: The LV-3, HV+3, WO shades were able to change the final color of a ceramic veneer. The color of resin cements and corresponding try-in pastes achieved high agreement (except the shade of HV+3).

[Effect of bleaching agents on the color of indirect and direct composite resins].

OBJECTIVE: To evaluate the effect of bleaching agents on the color of indirect and direct composite resins. METHODS: Five resin composite materials were tested in this in vitro study. The five composites were as follow: two indirect composite resins (Adoro SR, Ceramage) and three direct composite resins (Filtek Z350, Clearfil Majesty Esthetic, and Gradia Direct Anterior). For each material, twenty disk-shaped specimens were prepared and randomly divided into five groups according to the color parameters of specimens before bleaching treatment. The composite resin specimens were treated by one of five sample solutions which were at-home bleaching agents (10% and 15% carbarmide peroxide), in- office bleaching agents (38% H(2)O(2) and 35%H(2)O(2)) and deionized water (control group). The color parameters of specimens were measured by spectrophotometer at baseline and after bleaching treatments. The color differences (ΔE values) between baseline and post-treatments were calculated. The data of color differences were evaluated statistically using two-way analysis with a significance level of 0.05. RESULTS: The color changes of the resin composites were less than 2.0 after bleaching agent treatment, therefore were not perceptible. Slight increase of L(*) values and decrease of C(*)ab values in color parameters of specimens were observed. There were statistically significant differences in ΔE values for different bleaching treatments and resin materials (P = 0.001). CONCLUSIONS: The bleaching agents did not affect the color of indirect and direct composite resins tested.

Effect of in-office bleaching agents on the color changes of stained ceromers and direct composite resins.

PURPOSE: To evaluate the effect of two in-office bleaching agents on the color changes of two ceromers (Ceramage and Adoro SR) and one direct composite resin (Gradia Direct Anterior) after staining by tea and coffee. MATERIALS AND METHODS: Twenty-four disk-shaped specimens were fabricated for each resin material and randomly divided into three groups (n = 8). The specimens were immersed in tea, coffee or deionized water, respectively, for 7 days. Each group was then equally divided into two sub-groups (n = 4), which were subjected to two in-office bleaching agents (BEYOND and Opalescence Boost), respectively. The color of the specimens was measured by a spectrophotometer at baseline, after staining and after bleaching. The color differences (ΔE values) between baseline and after treatments were calculated. RESULTS: Statistical analysis indicated that the staining solution had significant influence on the color change of resin composites tested (p < 0.001). The discolorations of resin composites were perceptible after immersing in tea or coffee solutions (ΔE>2.0). There was no statistically significant difference between BEYOND and Opalescence Boost in stains removal from discolored resins (p = 0.550). The color changes in ΔE value between baseline and after bleaching were less than 2.0 for all resin composite groups. CONCLUSIONS: Tea solution produces severe discoloration of three resin composites tested. The two in-office bleaching agents can effectively remove the stains from two ceromers and one direct composite resin tested in this study.

In vitro evaluation of halogen light-activated vs chemically activated in-office bleaching systems.

OBJECTIVES: To compare the tooth whitening efficacy, temperature and HP concentration changes induced by halogen light-activated and chemically activated in-office bleaching systems. MATERIALS AND METHODS: Twenty-four extracted premolars were randomly divided into two groups (n = 12): Group BL (35% HP with halogen light activation) and Group OP (38% HP with chemical activation). Tooth color was measured by a spectrophotometer according to the CIE L*a*b* color space system. Temperatures of bleaching gels and pulp chambers during the bleaching process were monitored and recorded by a digital multimeter with K-type thermocouple. HP concentrations were tested before and after treatments by iodometry. ANOVA and paired t-test were used for statistical analyses at the significance of p < 0.05. RESULTS: Tooth whitening resulted in the increase of ΔL* and ΔE and reduction of Δb*. Paired t-tests revealed groups BL had greater ΔE than group OP, however, there was no statistically significant difference in ΔE between them after 3 weeks post-treatment. Maximal temperature rise (ΔT) was found only in group BL, showing the increment of 2.55 and 2.02°C for bleaching gels and pulp chambers, respectively. HP concentrations were higher than baseline values for group OP (p < 0.001) rather than group BL. CONCLUSIONS: Halogen light and chemically activated in-office bleaching systems were both effective for tooth whitening, but halogen light activation could improve the immediate whitening effect. In contrast, chemical activation was a more conservative method due to the little temperature rise in pulp chambers.

Nerve-targeted desensitizing toothpastes occlude dentin tubules and induce mineral precipitation.

PURPOSE: To examine the laboratory dentin tubules occlusion and mineral precipitation capability of two potassium salts-containing desensitizing toothpastes. METHODS: 40 dentin disks were obtained and divided into four groups, including artificial saliva (AS), distilled water (DW), Sensodyne Freshmint (SF) and Colgate Sensitive (CS). Dentin permeability measurement was performed after EDTA etching, initial brush, 3-day brush, 7-day brush and citric acid challenge, respectively. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to monitor the variation of mineral content before and after treatments. The ultra-morphology of dentin surface was examined using scanning electron microscopy (SEM) to evaluate tubule occlusion. RESULTS: The two potassium salts-containing desensitizing toothpastes significantly reduced dentin permeability to less than 40% after 7-day treatment (P<0.05). The ATR-FTIR analysis showed increase of the intensity of the phosphate peak after a 7-day brushing period using both of the tested toothpastes. However, the dentin permeability significantly increased and the intensity of phosphate peak decreased after acid etching for all groups. The SEM examination revealed partially occluded dentin tubules after toothpaste treatments, but after the acid challenge the tubules were opened again.

Dentine remineralization induced by two bioactive glasses developed for air abrasion purposes.

OBJECTIVES: The present study aimed to evaluate dentine remineralization through a 7-day period of artificial saliva (AS) storage induced by bioactive glass 45S5 (BAG) and by bioactive glass modified with soda-lime spherical glass. METHODS: Partially demineralized dentine disks were treated by BAG or the spherical-glass modified bioactive glass (M-BAG) and subsequently immersed in AS for 7 days. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) was used to quantitatively analyse the mineral variation of the dentine surface by calculating the spectra parameters. X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDX) were performed on completely demineralized dentine to confirm the apatite formation. The roughness of the dentine surface was evaluated by atomic force microscopy (AFM) and the morphology was also examined by scanning electron microscopy (SEM). RESULTS: ATR-FTIR showed a significant increase of the mineral matrix area ratio in dentine specimens treated with the two bioactive glasses subsequent to 7 days of AS storage. The XRD spectrum exhibited apatite growth and mineral elements could be found on completely demineralized samples analysed by EDX after remineralization treatments. The dentine specimens treated with bioactive glass showed lower roughness, and most of the dentinal tubules appeared completely occluded during the AFM and SEM examination. CONCLUSIONS: Although the concentration of bioactive glass in the M-BAG is 60% of that contained in the original version, both formulations have similar potential in dentine remineralization. These bioactive powders developed for air-abrasive use may be considered as innovative bioactive materials for therapeutic remineralization of dental hard tissues.

Evaluation of the esthetic effect of resin cements and try-in pastes on ceromer veneers.

OBJECTIVE: To evaluate the influence of various shades of resin cements on the final color of ceromer veneers and analyse the agreement of resin cements and corresponding try-in pastes. METHODS: Ceromer disks (Ceramage, 1.0mm×10mm diameter) were bonded to resin background disks (3.0mm×10mm diameter) using five shades of resin cements (RelyX Veneer), whilst butylphthalate was placed between ceromer and resin background as the control group (n=5). The corresponding try-in pastes were placed between ceromer and resin background disks using the specimens of the control group. After colorimetric evaluations, the thickness of ceromer disks was reduced to 0.8 and 0.5mm. Color measurements were repeated at each thickness. To analyse masking ability of the cement, resin background disks with 0.1mm thick cement layer were fabricated using five shades of resin cements (n=5). RESULT: Two-way ANOVA of ΔE values of cement shades and control group revealed significant differences in cement shade and thickness, and their interaction (p<0.001). The 0.5mm thick Ceramage specimens yielded the highest mean ΔE values (2.44±1.12) for all cement shade groups. A3, WO, and B05 shade of resin cements created perceptible color differences (ΔE>2.0) in 0.5mm thick specimens and WO shade in 0.8mm thick specimens. There were no perceptible color differences between resin cements and corresponding try-in pastes. CONCLUSION: The effect of resin cements on the final color of ceromer veneers depended on cement shades and thickness of ceromer. The color of resin cements and corresponding try-in pastes achieved high agreement.

Effect of desensitising toothpastes on dentinal tubule occlusion: a dentine permeability measurement and SEM in vitro study.

OBJECTIVES: The purpose of this study was to evaluate the in vitro effectiveness of a new bioglass-containing and two commercial desensitising toothpastes on dentinal tubule occlusion after citric acid challenge or artificial saliva (AS) immersion. METHODS: One hundred dentin discs from human third molars were used. Specimens were randomly divided into five groups (n=20), Group 1: EDTA-treated dentin; Group 2: brushing with distilled water; Group 3: brushing with Novamin; Group 4: brushing with Sensodyne Freshmint; Group 5: brushing with Colgate Sensitive. In each group, samples were then equally split into two subgroups (n=10) to test two post-treatments: 6% citric acid challenge or 24h immersion in artificial saliva. Dentine permeability of each specimen was measured before and after each treatment using a hydrostatic device working at 20cm H(2)O pressure. Data were analysed by two-way repeated measures ANOVA to determine if there were any significant differences within or between groups. Dentine morphology and surface deposits were observed by SEM. RESULTS: All three desensitising toothpastes significantly reduced dentine permeability and created precipitates on the treated dentine surfaces. Moreover, the reductions in dentine permeability showed partial recovery after a citric acid and artificial saliva immersion. Sensodyne showed significant resistant to acid attack and Novamin exhibited the lowest permeability after artificial saliva immersion for 24h. CONCLUSIONS: The application of the three toothpastes resulted in effective dentinal tubule occlusion. However, the new bioglass-containing toothpaste (Novamin) represented excellent occlusion effects after brushing treatment and AS immersion, while Sensodyne demonstrated more reduction in permeability when citric acid challenged.

[Effect of the shade and thickness of luting agent on the color of solidex resin].

OBJECTIVE: To evaluate the effect of the shade and thickenss of luting agent on the final color of different thickness Solidex resin in vitro. METHODS: Five specimens of Solidex resin were fabricated at thickness of 0.5, 1.0 and 1.5 mm. The pieces of Ni-Cr alloy, two shade composite resin and opaque porcelain veneered Ni-Cr alloy were used as backgrounds. The CIE L*a*b* values of specimens were measured by a colorimeter (ShadeEye NCC) to determine the colorimetric difference, when different thickness of specimens were overlaid the different shade and thickness of luting agent at the same backgrounds. RESULTS: The final color difference of specimens was significantly influenced by the factors of luting agent and the interaction of specimens thickness, backgrounds and luting agent(P< 0.001). Regarding the thickness of luting agent, A3 shade luting agents produced clinically unacceptable difference (deltaE*>2) in the final color of Solidex specimens at the thickness of 0.5 mm. Regarding the shade of luting agent, the color difference was more than 2 when the Solidex specimens at the thickness of 0.5 mm or 1.0 mm were against the 0.2 mm thick luting agent. CONCLUSION: The final color of thinner Solidex specimens was significant affected by the change of the shade and thick of luting agent.

[Effect of three backgrounds on the final color of Solidex with six different thickness].

OBJECTIVE: To analyze the final color of Solidex in six thickness interacting with three different backgrounds. METHODS: Five specimens of Solidex in each shade A1, A3, and C2 were fabricated at thickness of 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0 mm. The CIE L(*)a(*)b(*) values of specimens were measured using a colorimeter (ShadeEye NCC) to determine the colorimetric difference, when the specimens overlaid on different backgrounds. RESULTS: When the thickness was more than 1.8 mm, the color difference (DeltaE(*)ab < 1) was not perceived by human observers. When the thickness was 1.4 mm or less than 1.4 mm, the color difference (DeltaE(*)ab > 2.72) was considered clinically unacceptable between alloy background and two types of composite resin background. CONCLUSIONS: Alloy background had more evident influence on the final color of Solidex than composite resin background. When making metal-free crown restoration using Solidex, it was advisable to make the composite resin more than 1.8 mm thick.