Morphology and bacterial colonisation of tooth/ceramic restoration interface after different cement excess removal techniques

Effect of different techniques on removal of residual resin cement and marginal roughness of porcelain laminate veneers

STATEMENT OF PROBLEM

A consensus regarding how to effectively remove residual resin cement and polish the restoration margin during the cementation of porcelain laminate veneers (PLVs) is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of different cleaning and polishing techniques on the removal of residual resin cement and margin surface roughness of PLVs.

MATERIAL AND METHODS

PLVs were bonded to prepared buccal surfaces of extracted human premolars. All specimens were randomly divided by using a random number table into 8 groups (n=6): curette (C); brush (B); curette + polisher (CP); curette + rotary instrument (CR); curette + rotary instrument + polisher (CRP); brush + polisher (BP); brush + rotary instrument (BR); brush + rotary instrument + polisher (BRP). The relative amount of residual cement along the PLV margins were observed with a stereomicroscope and evaluated with a software program of Image J. The surface roughness and 3-dimensional (3D) morphology of the restoration margins were evaluated with a 3D topography scanner. Scanning electron microscopy (SEM) was used to detect the microscopic morphological characteristics of the restoration margins. Statistical analysis was performed by 2-way analysis of variance (α=.05).

RESULTS

Different techniques were associated with significantly different efficiencies in terms of removing residual cement and the surface roughness at the restoration margins (P<.001). The lowest relative amount of residual cement, as well as the lowest surface roughness, was detected in the BRP group (P<.001). SEM observation indicated that the BRP technique also maintained the integrity of the cement layer.

CONCLUSIONS

The removal of excess cement before polymerization using a brush, followed by sequential polishing with high-speed rotary instruments and low-speed polishers represents an effective technique in the removal of residual cement and smoothing the restoration margin without impairing the integrity of the bonded interface.

Effect of Two Different Intraoral Polishing Systems on Surface Roughness, Color Stability, and Bacterial Accumulation of Zirconia-Reinforced Lithium Silicate Ceramic

OBJECTIVE

 The aim of this study was to investigate the effects of two intraoral polishing methods on zirconia-reinforced lithium silicate ceramic after ultrasonic scaling.

MATERIALS AND METHODS

 Thirty disc-shaped samples of zirconia-reinforced lithium silicate were constructed. Freshly extracted bovine teeth were collected and cleaned then the discs were cemented into a cavity prepared onto their labial surface. The samples were divided into three groups (10 samples per group); S: Scaling only, SE: Scaling followed by polishing using Eve Diapro lithium disilicate polishers, SD: Scaling followed by polishing using Diatech ShapeGuard ceramic polishing plus kit. The surface roughness was evaluated after scaling and polishing the samples. For color stability, the samples were stored for 12 days at 37°C in an incubator to simulate 1-year consumption of coffee. L*a*b* color parameters were assessed using VITA Easyshade Advance 4.0 before and after the staining procedure and the color difference was measured. Finally, bacterial accumulation was evaluated by incubating the samples with a suspension of Streptococcus mutans ( S. mutans), after that the S. mutans colonies were counted to obtain the values of colony-forming units (CFU). The final overall roughness, change in color and bacterial count were compared between all groups using one-way ANOVA and Tukey's post-hoc analysis. The Pearson correlation coefficient was used to determine the correlation between continuous variables. The cutoff for significance was chosen at p ≤ 0.05.

RESULTS

 Scaling induced surface roughness of the zirconia-reinforced lithium silicate ceramic was significantly decreased after using both intraoral polishing systems and this was accompanied by a significant decrease in color change and bacterial count.

CONCLUSION

 Intraoral polishing techniques can reduce the roughness of the surface of zirconia reinforced lithium silicate restorations induced due to scaling and subsequently reduce the stainability and bacterial accumulation.

Evaluation of the ceramic laminate veneer-tooth interface after different resin cement excess removal techniques

OBJECTIVES

To compare, in vitro, resin cement excess removal techniques at the veneer-tooth interface.

MATERIALS AND METHODS

Anterior human teeth were restored with ceramic veneers and randomly divided according to the following techniques (n = 10): removal of excess resin cement with brush and dental floss, followed by light-curing with Valo (Group 1) or Elipar (Group 2) for 1 min and 40 s; tack-curing with Valo (Group 3) or Elipar (Group 4) for 1 s; and tack-curing with Valo (Group 5) or Elipar (Group 6) for 5 s. The tack-curing was followed by removal of excess with probe and dental floss and light-curing for 1 min and 40 s. The area of excess resin cement (mm2) was measured in micro-CT images using AutoCAD program. The failures at the cervical margin in the X, Y, and Z axes (µm) of greater value were measured using the DataViewer program. The specimens were submitted to microleakage with 2% basic fuchsin.

RESULTS

According to the Kruskal-Wallis and multiple comparison test, the highest area of excess resin cement was found in Group 1 (5.06 mm2), which did not differ statistically from Groups 2 (3.70 mm2) and 5 (2.19 mm2). Groups 2, 3 (1.73 mm2), 4 (1.14 mm2), and 5 (2.18 mm2) did not differ statistically. Group 6 (0.77 mm2) obtained the lowest value, which did not differ statistically from Groups 3 and 4. According to the Kruskal-Wallis and Dunn test, there was no significant difference in failures in X (p = 0.981), Y (p = 0.860), and Z (p = 0.638) axes and no significant difference in microleakage (p = 0.203) among the groups.

CONCLUSIONS

Tack-curing for 1 s or 5 s, followed by removal of excess resin cement using a probe and a dental floss, tended to result in a lower amount of excess material around the margin.

CLINICAL RELEVANCE

The technique used for resin cement excess removal influences the amount of excess leaved at the veneer-tooth interface. Tack-curing for 1 s or 5 s is recommended to mitigate the excess resin cement.

Effect of sintering speed, aging processes, and different surface treatments on the optical and surface properties of monolithic zirconia restorations

STATEMENT OF PROBLEM

Advances in dentistry have led to more esthetic and biocompatible restorative materials such as translucent zirconia and to faster and more accurate manufacturing methods. How changes in the surface and optical properties of translucent zirconia affect the esthetics and durability of these restorations under different conditions and manufacturing processes is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of the sintering speed, aging process, and different surface treatments on the translucency and surface structure of monolithic zirconia restorations.

MATERIAL AND METHODS

Prepared typodont teeth were scanned, and 40 three-unit fixed partial dentures (FPDs) and 40 disk specimens were designed and prepared from monolithic zirconia blanks. The specimens were divided into traditional or speed sintering groups (20 FPDs and 20 disks each); half of each group (10 FPDs and 10 disks) was polished with a handpiece at 10 000 rpm, and the other half was glazed. Half of the specimens were thermocycled with 3500 cycles in 5 °C and 55 °C water baths, and the remaining half were not thermocycled. Translucency was measured with a spectrophotometer. Surface free energy was calculated in mNm with a contact angle device; surface roughness was measured in nm with an atomic force microscope. Translucency data were analyzed by the Kruskal-Wallis and Mann-Whitney tests, while surface free energy and surface roughness data were analyzed by 3-way ANOVA (α=.05).

RESULTS

The highest transmittance was in the speed sintered, polished, nonthermocycled group, and the lowest transmittance was in the speed sintered, polished, thermocycled group (P=.029). The transmittance of the traditionally sintered, polished, nonthermocycled group was significantly higher than that in all the speed sintered, glazed groups; the traditionally sintered, glazed groups; and the traditionally sintered, polished, thermocycled group (P=.029). The transmittance of the traditionally sintered, polished, thermocycled group was significantly higher than that of all traditionally sintered, glazed groups (P=.029). The mean surface free energy in the traditionally sintered groups was higher than that in the speed sintered groups (P=.002); also, it was higher in the glazed groups than in the polished groups (P<.001). The aging process decreased surface free energy (P=.023). The mean surface roughness in the speed sintered groups was significantly lower than that in the traditionally sintered groups (P=.004). No significant difference in surface roughness was found between the polished and glazed groups and between the 2 variables of the aging process (P>.05).

CONCLUSIONS

Speed sintering and polishing may decrease the surface free energy and increase the translucency of the monolithic zirconia restoration. Also, speed sintering creates a smoother surface. Aging had a more significant effect on decreasing the surface free energy of the specimens and could make the least translucent restorations.

Assessment of physical/mechanical properties and cytotoxicity of dual-cured resin cements containing Sr-bioactive glass nanoparticles and calcium phosphate

The aim was to develop dual-cured resin cements containing Sr-bioactive glass nanoparticles (Sr-BGNPs; 5 or 10 wt%) and monocalcium phosphate monohydrate (MCPM; 3 or 6 wt%). Effects of additives on degree of monomer conversion (DC), biaxial flexural strength/modulus, shear bond strength (SBS), mass/volume change, color stability, ion release, and cytotoxicity were examined. Controls included material without reactive fillers and Panavia SA Plus (PV). Experimental cements showed higher DC than PV regardless of light activation (p<0.05). Mean SBS and color stability were comparable between experimental cements and PV. Cell viability upon the exposure to sample extracts of experimental cements was 80%-92%. High additive concentrations led to lower strength and modulus than PV (p<0.05). The additives increased mass change, reduced color stability, and promoted ion release. The experimental resin cements demonstrated acceptable mechanical/chemical properties and cytotoxicity. The additives reduced the strength but provided ion release, a desirable action to prevent recurrent caries.

Clinical Performance of Minimally Invasive Monolithic Ultratranslucent Zirconia Veneers: A Case Series up to Five Years of Follow-up

There is a lack of reports in the literature on the long-term clinical performance of ultratranslucent zirconia, especially considering its use in manufacturing monolithic veneers. The purpose of this case series is to describe the aesthetic treatment steps of three patients with minimally invasive ultratranslucent zirconia veneers and to report the clinical findings up to five years. Three patients (woman: 2, man: 1; mean age: 30 years) unsatisfied with their dental aesthetics sought dental treatment. The treatment plan involved cementing ultratranslucent zirconia veneers. Air-abrasion was performed on the internal surface of zirconia with alumina particles coated by silica (silicatization), followed by silane and adhesive applications for the adhesive cementation. All veneers were adhesively cemented to enamel with resin cement (Variolink Esthetic, Ivoclar). The patients were clinically evaluated annually considering the Ryge modified/ California Dental Association criteria. After a mean follow-up of 4.33 years (4-5 years), a survival rate of 100% was detected for the 28 minimally invasive ultratranslucent zirconia veneers cemented in the 3 patients. There were no absolute failures such as debonding, veneer fracture, or secondary caries. Superficial marginal discoloration was observed in one element (maxillary left lateral incisor) of one patient. Ultratranslucent zirconia is a viable option for manufacturing veneers due to its excellent clinical performance and longevity. However, further long-term clinical studies are essential to consolidate this material as an option for esthetic restorations.

Clinical performance of monolithic polymer-infiltrated ceramic and lithium disilicate posterior crowns: A controlled, randomized, and double-blind clinical trial

STATEMENT OF PROBLEM

The success rate of monolithic polymer-infiltrated ceramic posterior crowns after 1 year is unclear.

PURPOSE

The purpose of this controlled, randomized, and double-blind clinical trial was to evaluate the performance of posterior complete crowns in polymer-infiltrated and lithium disilicate ceramics and to assess the impact of oral rehabilitation on esthetic satisfaction, quality of life, and periodontal health.

MATERIAL AND METHODS

A total of 33 crowns were provided in 18 participants allocated to 2 groups: Control (Lithium disilicate-IPS e.max CAD; Ivoclar AG) and Experimental (Polymer-infiltrated ceramic-Vita Enamic; Vita Zahnfabrik). The crowns were evaluated before treatment (T0) and after 1 (T1), 6 (T2), and 12 (T3) months by using modified United States Public Health Service (USPHS) criteria, visual analog scales (VASs), oral impacts on daily performances (OIDP), and periodontal parameters. Survival analysis was performed by using Kaplan-Meier followed by the log-rank test (α=.05). The OIDP and USPHS data were analyzed descriptively while VASs for esthetic satisfaction and periodontal parameters were statistically evaluated by using the Mann-Whitney Friedman, and Wilcoxon post hoc tests.

RESULTS

For 18 participants with a mean age of 47.2 years, 19 crowns were manufactured in lithium disilicate and 14 in polymer-infiltrated ceramic. The Kaplan-Meier test revealed similar survival rates of 92.5% for polymer-infiltrated ceramic and 94.7% for lithium disilicate (P>.05). The analysis of periodontal parameters revealed a significant increase in the bleeding on probing (BOP) for polymer-infiltrated ceramics (P=.032) but for lithium disilicate, it was not significant (P=.387).

CONCLUSIONS

Survival rates between the evaluated materials were not significantly different, with acceptable clinical performance after 1 year of follow-up.

Effect of staining layer on roughness after progressive wear of monolithic ceramics

PURPOSE

The aim of this study was to evaluate staining layer behavior applied to high-translucency zirconia (YZHT), feldspathic ceramics (FD), and zirconia-reinforced lithium silicate (ZLS) surfaces against different antagonists.

METHODS AND MATERIALS

Monolithic ceramic discs (n = 120) (ø 12 mm; thickness, 1.2 mm; ISO 6872) were obtained, 30 from YZHT and FD, and 60 from ZLS CAD/CAM blocks (staining layer applied before or after the crystallization procedure). The specimens were divided into 12 subgroups (n = 10) according to the antagonists: steatite, polymer-infiltrated ceramic, or zirconia. Mechanical cycling (1.5 × 104  cycles; 15 N; horizontal displacement, 6 mm; 1.7 Hz) and flexural strength tests (1 mm/min-1000 kg cell) were performed. The differences between final and initial roughnesses (Ra, Rz, and Rsm), the mass loss, and the flexural strength data were individually analyzed by two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

The roughnesses of all ceramics did not present a statistically significant difference before wear simulation: Ra (p = 0.3348), Rz (p = 0.5590), and Rsm (p = 0.5330). After the wear simulation, the Ra parameter was not affected by an interaction between ceramic and antagonist (p = 0.595). The Rz and Rsm parameters were affected only by the antagonist pistons (both, p = 0.000). The ceramics used in this study showed statistically significant differences in mass loss after the wear test (p < 0.0001). The additional firing (2 steps) of the ZLS2 led to a higher lost mass quantity.

CONCLUSION

All ceramics presented similar initial roughnesses and similar roughnesses after the wear simulation. The zirconia antagonist showed better performance against ceramics with high crystalline content.

CLINICAL SIGNIFICANCE

It is clear that restorative materials must be carefully selected by dental practitioners according to indications, properties, and antagonists. The steatite antagonist, that is, an enamel analog, showed better performance against vitreous ceramics, while the zirconia antagonist showed better performance against ceramics with high crystalline content. Wear affects the surface roughnesses of the ceramics. Additional firing for the staining of the zirconia-reinforced lithium silicate ceramic led to a greater loss of mass.

Influence of the Scalpel Finishing Technique on Marginal Gap Formation in Class II Resin Composite Restorations

OBJECTIVES

Modern adhesives and composites allow the restoration of deep defects. In such cases, the matrix technique is particularly challenging, and excess composite is a common problem. Removing such overhangs with a scalpel has already been described as a substance preserving or selective finishing technique. Clinically, restoration margins may appear as a white line after scalpel finishing, and it is unclear whether this line represents a marginal gap and/or whether scalpel finishing promotes marginal gap formation. Therefore, the aim of this study was to investigate the influence of scalpel finishing of deep Class II composite restorations on marginal gap formation.

METHODS AND MATERIALS

Standardized mesioocclusal-distal (MOD) cavities were prepared and restored in 60 human molars randomly divided into six finishing protocol groups: G1, scalpels (SC); G2, oscillating files (OF); G3, finishing strips (FS); G4, scalpels and finishing strips (SC+FS); G5, scalpels and polishing discs (SC+PD); G6, polishing discs alone (PD, controls). The groups were additionally assigned to finishing and polishing in a phantom head (groups 1-4) or hand-held setting (groups 5-6) to simulate clinical and in-vitro research conditions, respectively. After restoration, artificial aging was performed by thermocycling (5-55°C, 2500 cycles) and mechanical loading (50 newtons (N) with 500,000 cycles) prior to scanning electron microscopy analysis of proximal restoration margin quality on the mesial and distal surfaces (n=120) of each tooth. Outcomes (perfect margin, marginal gap, overhang, marginal fracture) were statistically analyzed by t-test, Mann-Whitney U test, single-factor analysis of variance, post-hoc t-test, Kruskal-Wallis test and Dunn-Bonferroni correction for multiple group comparisons. Cohen's effect size d(Cohen) was calculated to show the strength of the relationship between variables.

RESULTS

Overall, marginal quality was significantly better in the hand-held setting (SC+PD and PD) than the phantom head setting (SC, OF, FS, SC+FS). The best marginal quality was achieved with oscillating files in the phantom head setting and with scalpels plus polishing discs in the hand-held setting. Marginal gaps occurred significantly more often with scalpels, but the proportion of gaps was very low and clinically insignificant. Finishing strips were the least effective instruments for removing overhangs but performed better in combination with scalpels.

CONCLUSIONS

Scalpel finishing can effectively and gently remove overhangs from enamel. However, blades should be used with caution as they can cut the dentin and cementum. Scalpel finishing does not lead to a clinically relevant increase in marginal gaps, but should be followed by polishing, whenever possible, to eliminate any marginal fractures that might be present.

Effect of Surface-Etching Treatment, Glaze, and the Antagonist on Roughness of a Hybrid Ceramic after Two-Body Wear

Stains and glaze are effective procedures for achieving an aesthetic smoothness on indirect restorations. Thus, the effect of surface-etching treatments previous to the stain layer and the glaze application on the occlusal and antagonist wear of a hybrid ceramic were evaluated against different antagonists. Disc-shaped samples were prepared from polymer-infiltrated ceramic network (PICN) blocks. The specimens were divided into eight groups, according to the surface-etching treatment and glaze application: P (polished specimens); PG (polishing plus glaze); E (hydrofluoric acid etching plus stain); EG (acid etching plus stain plus glaze); A (aluminum oxide sandblasting plus stain); AG (sandblasting plus stain plus glaze); S (self-etching primer plus stain); SG (self-etching primer plus stain plus glaze). Half of the samples were subjected to a wear simulation with a steatite antagonist, and the other half was tested using a PICN antagonist. The test parameters were: 15 N, 1.7 Hz, 6 mm of horizontal sliding, 5000 cycles. The discs and the antagonists' masses were measured before and after the wear tests. The average roughness and spacing defects were evaluated. The etching treatment affected the surface and antagonist mass loss when tested against steatite. AG showed the highest mass loss. This influence was not detected when using the PICN antagonist. The glaze application after staining ensures a smoother surface and avoids antagonist wear.

Influence of surface treatment and curing mode of resin composite cements on fibroblast behavior

BACKGROUND

Human gingival fibroblast (HGF-1) cells in the connective tissue provide an effective barrier between the alveolar bone and the oral environment. Cement margins of restorations with intrasulcular preparation or cemented implant restorations are in contact with HGF cells. However, it is unknown to what extend the cement surface finish affects the behavior of HGF cells. The purpose of this study was to compare the behavior of HGF-1 cells in contact with two different resin composite cements with three different surface treatments after light-curing and autopolymerization, respectively.

METHODS

Disks of one adhesive (Multilink Automix, Ivoclar Vivadent [MLA]) and one self-adhesive (RelyX Unicem 2 Automix, 3 M [RUN]) resin composite cement were either light-cured or autopolymerized. Specimen surfaces were prepared with the oxygen inhibition layer intact, polished with P2500-grit silicon carbide paper or treated with a scaler. Cells were cultivated on the specimens for 24 h. Viability assay was performed, and cell morphology was examined with scanning electron microscopy. Additionally, roughness parameters of the specimen were analyzed with a 3D laser scanning microscope. Three-way ANOVA was applied to determine the effect of cement material, curing mode and surface treatment (a = 0.05).

RESULTS

Overall, cement material (p = 0.031), curing mode (p = 0.001), and surface treatment (p < 0.001) significantly affected relative cell viability of HGF. The autopolymerized specimen with the oxygen inhibition layer left intact displayed the lowest relative cell viability (MLA 25.7%, RUN 46.6%). Removal of the oxygen inhibition layer with a scaler increased cell viability but also resulted in higher surface roughness values.

CONCLUSIONS

HGF cell viability is affected by the surface treatment and the curing mode. The oxygen inhibition layer is an inhibitory factor for the viability of HGF cells. Autopolymerization enhances the cytotoxic potential of the oxygen inhibition layer.

The Influence of Cement Removal Techniques on In Situ Bacterial Adhesion and Biodegradation at the Marginal Interface of Ceramic Laminates

Objectives

This in situ study aimed to analyze the influence of different resin cement removal techniques on bacterial adhesion and biodegradation at the marginal interface of ceramic laminates.

Methods and Materials

Eighty feldspathic ceramic (F) blocks were prepared and cemented onto bovine enamel slabs (7×2.5×2 mm). Excess cement was removed using a microbrush (MBR), a scalpel blade (SCP), or a Teflon spatula (TSP). For the biodegradation analysis, 40 disc-shaped resin cement specimens were prepared (7×1.5 mm) using a Teflon mold. The specimens were randomly allocated into two groups: (1) No finishing procedure (only Mylar strip), and (2) with finishing and polishing procedures using the Jiffy system (Ultradent, South Jordan, UT, USA) (n=20). The in situ phase consisted of using an intraoral palatal device by 20 volunteers for 7 days. Each device contained five cylindrical wells (8×3 mm), where three dental blocks and two cement specimens were included in the wells. Surface roughness (Ra) was measured using a contact profilometer. A micromorphological analysis was performed under a stereomicroscope and a scanning electron microscope. Bacterial adhesion was quantitated based on the number of colony-forming units (CFU/mL) and their biofilm development potential.

Results

The cement removal techniques directly affected surface roughness at the marginal interface (p&lt;0.001), and the SCP technique produced higher mean roughness, regardless of the surface area analyzed. Surface polishing protected cement specimens from further biodegradation (p=0.148). There were no differences in CFU counts between the groups after the in situ phase (p=0.96). All specimens showed CFU with a strong ability to develop a biofilm.

Conclusions

The techniques used for cement removal increased the surface roughness of ceramic laminates, particularly SCP, but they did not affect bacterial adhesion at the marginal interface. Surface polishing of the resin cement is recommended to mitigate biodegradation.

Potent Antibacterial and Antibiofilm Activities of a Synthetic Remineralizing Preparation of Nano-Hydroxyapatite Against Cariogenic Streptococcus mutans Using an Ex-vivo Animal Model

Aim

The aim to this study is to evaluate the biocompatibility and antibiofilm actions of two nano-hydroxy apatite (NHA).

Methodology

Nano-hydroxy apatites are biomaterials use in direct contact with living tissues. Therefore, they should be tested for their safety beside assessment of their minimum inhibitory (MIC) and minimum bactericidal concentration (MBC) using broth microdilution method. One hundred and twenty extracted bovine incisors were collected and cleaned to ensure the absence of any defects. Enamel blocks with different size (2 × 2 × 3 mm) and (5 × 5 × 2 mm) were prepared from their labial surfaces using an isomet saw. Enamel blocks are used for detecting the suitable concentration will be used in the following experiments using energy dispersive X-ray analysis (EDX). The remaining enamel blocks divided into 5 equal groups to detect inhibitory effect against bacterial adhesion to the initial enamel caries like lesions using viable count technique beside the antibiofilm activity against mature biofilm of Streptococcus mutans (S. mutans) using confocal laser microscopy. The remaining enamel blocks were used as a representing data for detecting surface topography for each group by using the scanning electron microscopy (SEM).

Result

The data showed safety of NHA suspensions. Additionally, only NHA suspension of large nanoparticle size (NHA-LPS) had MIC of 1.25 mg/ml against S. mutans. Also, have the higher percentages of Ca and P in the enamel blocks. Furthermore, the lowest level of bacterial adhesion was recorded in (group III) treated by NHA-LPS which was non-significantly different with the positive control group V. Biofilm thickness in group IV treated with NHA-small particle size (SPS) recorded high biofilm thickness followed by group III. Interestingly, group III showed greater killing effect against mature biofilm which is slightly higher than the positive control group V. In group III, surface topography revealed very smooth enamel surface with closed pores. Accordingly, NHA-LPS suspension had antiadhesive, antibacterial, and antibiofilm effect against cariogenic S. mutans representing a promising possibility to be recommended for safe effective remineralization.

Antibacterial Activity and Biofilm Inhibition of New-Generation Hybrid/Fluoride-Releasing Restorative Materials

The antibacterial activity, and the effect of the application of additional topical fluoride on the bacterial activity, biofilm formation, and surface roughness of new-generation hybrid/fluoride-releasing materials were investigated. Two hundred and forty specimens were prepared in split Teflon molds (8 × 2 mm) from a resin composite (as negative control: G-aenial A’Chord/GC), Equia Forte HT Fil(GC), Equia Forte HT Fil+Equia Forte Coat, Riva Self-Cure (SDI), Riva Self-Cure+Equia Forte Coat, Zirconomer (Shofu), Beautifil II (Shofu), and Riva Silver (Shofu). Penicillin G,1U was used as positive control. The antibacterial activity was evaluated by the agar diffusion test immediately after the materials set using Streptococcus mutans (S. mutans) and Lactobacillus casei (L. casei), and repeated after application of 0.20% w/w (900 ppm) topical fluoride. The biofilm formation of S. mutans on each material was quantified by crystal violet staining. Surface roughness of the specimens was measured by a profilometer. The data were analyzed by Kruskal–Wallis, Dunn’s, one-way ANOVA, and Tukey’s HSD tests (p < 0.05). None of the tested restorative materials showed antibacterial activity and no inhibition zones were observed after treatment of the restoratives with additional topical fluoride. There were significant differences among the groups in terms of biofilm formation (p < 0.005). Equia Forte HT Fil with and without coating showed the lowest, while Riva self-cure without coating and Zirconomer showed the highest biofilm accumulation. None of the new-generation hybrid/fluoride-releasing materials demonstrated antibacterial activity and additional topical fluoride application did not make any change. Biofilm formation of the tested materials differed. All tested materials showed different surface roughness values (p < 0.005). Characteristics and compositions of the materials seemed to be more effective than the surface roughness.

Influence of different zirconia surface treatments on biofilm formation in vitro and in situ

OBJECTIVES

To determine if the surface treatment of zirconia affects biofilm formation in an in vitro three-species biofilm model and in situ.

MATERIAL AND METHODS

Zirconia surfaces considered for the transmucosal portion of a zirconia implant were compared with polished pure titanium grade 4 (Tp). Discs 13 mm in diameter of either polished (Zp), polished and heat-treated (Zpt), machined (Zm), machined and heat-treated (Zmt) and sandblasted, etched and heat-treated (Z14) zirconia were fabricated. Surface roughness and wettability of specimens was measured. Biofilm formation was evaluated by safranin staining and scanning electron microscopy (SEM) using a three-species model, and intraorally with 16 volunteers carrying oral splints in two independent experiments. Relative biofilm formation was compared with Kruskal-Wallis followed by Bonferroni post-hoc test (α=0.05).

RESULTS

In vitro biofilm formation with optical density values on Zp (0.14±0.01), Zpt (0.14±0.02), Zm (0.13±0.01) and Zmt (0.13±0.01) was significantly lower than on Tp (0.21±0.05) and Z14 (0.20±0.04) (p<0.05). In situ biofilm formation was significantly higher on Z14 (0.56±0.45) (p<0.05), while no significant differences in optical density were observed among Zp (0.25±0.20), Zm (0.36±0.34) and Tp (0.28±0.22). SEM analysis supported quantitative findings.

CONCLUSIONS

In the in vitro three-species biofilm model differences in material and surface roughness affected biofilm formation. In situ biofilm formation was mainly affected by the surface roughness of the specimens. Polishing of zirconia is recommended to reduce biofilm formation while heat-treatment has no significant effect.

Does Resin Cement Type and Cement Preheating Influence the Marginal and Internal Fit of Lithium Disilicate Single Crowns?

This paper assesses the effect of cement type and cement preheating on the marginal and internal fit of lithium disilicate single crown. Methods: 40 maxillary premolars were selected, restored with lithium disilicate single crowns. Teeth were randomly assigned into four groups (n = 10) based on cement type (Panavia SA or LinkForce) and preheating temperature (25 °C or 54 °C). After fabrication of the restoration, cements were incubated at 25 °C or 54 °C for 24 h, and each crown was cemented to its corresponding tooth. After 24 h, all specimens were thermally aged to (10,000 thermal cycles between 5 °C and 55 °C), then load cycled for 240,000 cycles. Each specimen was then sectioned in bucco-palatal direction and inspected under a stereomicroscope at x45 magnification for marginal and internal fit evaluation. The data were statistically analyzed (significance at p ≤ 0.05 level). Results: At the mid-buccal finish line, mid-buccal wall, palatal cusp, mid-palatal wall, mid-palatal finish line, and palatal margin measuring points, there was a significant difference (p ≤ 0.05) between the lithium disilicate group cemented with Panavia SA at 25 °C and the group cemented with LinkForce at 25 °C, while there was no significant difference (p > 0.05) at the other points. At all measuring points, except at the palatal cusp tip (p = 0.948) and palatal margin (p = 0.103), there was a statistically significant difference (p ≤ 0.05) between the lithium disilicate group cemented with Panavia SA at 54 °C and the group cemented with LinkForce at 54 °C. Regardless of cement preheating, statistically significant differences were found in the buccal cusp tip, central groove, palatal cusp tip, and mid-palatal wall (p ≤ 0.05) in the lithium disilicate group cemented with Panavia SA at 25 °C and 54 °C, as well as the mid-palatal chamfer finish line and palatal margin in the LinkForce group cemented with Panavia SA at 25 °C and 54 °C. At the other measurement points, however, there was no significant difference (p > 0.05). Conclusions: The type of resin cement affects the internal and marginal fit of lithium disilicate crowns. At most measuring points, the cement preheating does not improve the internal and marginal fit of all lithium disilicate crowns.

Laboratory Characterization of In-Service Full-Mouth Rehabilitation with Monolithic Translucent Zirconia Restorations

The chance to critically and microscopically inspect the quality of bonded restorations once they are delivered to the patient after several pre-cementation steps is rare or nonexistent. Replicas of in-service restorations can provide a wealth of information on the integrity of the restorations and moreover make it possible to bring this information to the laboratory for further detailed analysis. This study aimed to characterize the epoxy replicas of 27 cemented monolithic yttria-stabilized zirconia crowns of the maxillary and mandibular arch to assess surface roughness, topography, and symmetry. The topography of the facial, lingual, and occlusal/incisal surfaces of each crown was observed under the optical microscope and further characterized using the scanning electron microscope. Surface roughness measurements were performed using the atomic force microscope. The optical microscope was used to measure the golden proportion and visible width of the anterior maxillary crowns. Surface damage consistent with unpolished adjustment was identified mostly in the occlusal surface of the posterior teeth. Other irregularities, such as scratch marks, small pits, and coarse pits were also found. The surface roughness had great variability. Not all of the anterior maxillary and mandibular teeth followed the golden proportion concept. This study design allows in vitro characterization of in-service restorations. It provides a framework for using replicas for early identification of patterns or features that can trigger fracture and for analysis of morphology and symmetry.

Incorporation of Hybrid Nanomaterial in Dental Porcelains: Antimicrobial, Chemical, and Mechanical Properties

Biofilm formation on biomaterials is a challenge in the health area. Antimicrobial substances based on nanomaterials have been proposed to solve this problem. The aim was to incorporate nanostructured silver vanadate decorated with silver nanoparticles (β-AgVO3) into dental porcelains (IPS Inline and Ex-3 Noritake), at concentrations of 2.5% and 5%, and evaluate the surface characteristics (by SEM/EDS), antimicrobial activity (against Streptococcus mutans, Streptococcus sobrinus, Aggregatibacter actinomycetemcomitans, and Pseudomonas aeruginosa), silver (Ag+) and vanadium (V4+/V5+) ions release, and mechanical properties (microhardness, roughness, and fracture toughness). The β-AgVO3 incorporation did not alter the porcelain's components, reduced the S. mutans, S. sobrinus and A. actinomycetemcomitans viability, increased the fracture toughness of IPS Inline, the roughness for all groups, and did not affect the microhardness of the 5% group. Among all groups, IPS Inline 5% released more Ag+, and Ex-3 Noritake 2.5% released more V4+/V5+. It was concluded that the incorporation of β-AgVO3 into dental porcelains promoted antimicrobial activity against S. mutans, S. sobrinus, and A. actinomycetemcomitans (preventing biofilm formation), caused a higher release of vanadium than silver ions, and an adequate mechanical behavior was observed. However, the incorporation of β-AgVO3 did not reduce P. aeruginosa viability and increased the surface roughness of dental porcelains.

Two-year Follow-up of Ceramic Veneers and a Full Crown Treated With Self-etching Ceramic Primer: A Case Report

CLINICAL RELEVANCE

The Monobond Etch & Prime seems to be an efficient option for adhesive cementation of ultrathin veneers and full crown ceramic with good properties after two years of clinical follow-up.

SUMMARY

The use of the self-etching ceramic primer combines the stages of acid conditioning and silanization in cementation procedures of ceramic restorations. The protocol is a simpler and safer alternative to the conventional protocol for surface treatment of silica-based ceramics. This case report describes the steps of an esthetic rehabilitation with ultrathin veneers and full crown based on lithium disilicate treated with a ceramic primer (Monobond Etch & Prime, Ivoclar Vivadent, Schaan, Liechtenstein). After two years of clinical follow-up, the restorations presented satisfactory esthetic and functional performance, color stability, surface and marginal integrity, and absence of cracks and debonding. More research is needed to investigate the clinical performance and longevity of the ceramic restorations treated with self-etching ceramic primers.

Mechanical properties of toothpastes with diamond abrasives

OBJECTIVE

The aim of this study was to evaluate and compare surface roughness, gloss, and color change of dental enamel after being brushed with toothpastes containing diamond powder and traditional abrasives.

MATERIALS AND METHODS

Seventy enamel slabs were derived from 70 bovine incisors. The slabs were brushed with six different toothpastes and artificial saliva as a negative control. The specimens were then stained with black tea mixed with citric acid (3 days, pH = 4) and again brushed with the same toothpastes. R_a (contact profilometer), gloss (glossmeter), and color (CIE L* a* b* system) values were measured after each step.

RESULTS

Emoform-F Diamond (contains diamond powder and traditional abrasives) offered significantly the best improvement of R_a and gloss values after the first brushing sequence and the best recovery of the brightness of enamel after staining and second brushing sequence (P < .05). AMC 2.5 (contains only diamond powder as abrasive) was not able to offer such improvement.

CONCLUSION

Diamond powder as an additional abrasive in toothpastes could be able to offer a further improvement of R_a , gloss, and color values of enamel.

Influence of Material and Surface Roughness of Resin Composite Cements on Fibroblast Behavior

Clinical Relevance

A well-polished cement surface increases the viability and spreading of gingival fibroblasts. The tested resin composite cements did not reveal any cytotoxic effects.

SUMMARY

Objective: This in vitro study aimed to investigate the effect of cement type and roughness on the viability and cell morphology of human gingival fibroblasts (HGF-1).

Methods and Materials: Discs of three adhesive (Panavia V5 [PV5], Multilink Automix [MLA], RelyX Ultimate [RUL] and three self-adhesive (Panavia SA plus [PSA], SpeedCem plus [SCP], RelyX Unicem [RUN]) resin composite cements were prepared with three different roughnesses using silica paper grit P180, P400, or P2500. The cement specimens were characterized by surface roughness and energy-dispersive X-ray spectroscopic mapping. A viability assay was performed after 24 hours of incubation of HGF-1 cells on cement specimens. Cell morphology was examined with scanning electron microscopy.

Results: The roughness of the specimens did not differ significantly among the different resin composite cements. Mean Ra values for the three surface treatments were 1.62 ± 0.34 μm for P180, 0.79 ± 0.20 μm for P400, and 0.17 ± 0.08 μm for P2500. HGF-1 viability was significantly influenced by the cement material and the specimens’ roughness, with the highest viability for PSA ≥ RUN = MLA ≥ SCP = PV5 &gt; RUL (p&lt;0.05) and for P2500 = P400 &gt; P180 (p&lt;0.001). Cell morphology did not vary among the materials but was affected by the surface roughness.

Conclusion: The composition of resin composite cements significantly affects the cell viability of HGF-1. Smooth resin composite cement surfaces with an Ra of 0.2–0.8 μm accelerate flat cell spreading and formation of filopodia.

Dual-curing resin cement with colour indicator for adhesively cemented restorations to dental tissues: Change of colour by curing and some physical properties

The study was aimed to investigate a color indicator containing dual curing resin composite luting cement and to plot the color change to the time of solidification of the cement. In addition some physical properties were studied. Specimens were made of a dual-cure resin cement (Maxcem Elite™ Chroma, Kerr, Orange, CA, USA) and polymerized by autopolymerization only, or with light initiated polymerization. A spectrophotometer was used to quantify the color change of the cement as plotted with the curing time. The efficacy of the curing process was studied by measuring water sorption and the ultimate flexural properties of the cement. The results showed that the flexural strength of cement after autopolymerization was 27.3 MPa and after light initiated polymerization 48.1 MPa. Young’s modulus of bending was 2089.3 MPa and 3781.5 MPa respectively for the same cement samples. Water sorption after two weeks for the autopolymerization cement samples was −1.12 wt% and for the light initiated polymerization samples 0.56 wt%. Non-parametric Spearman’s correlation was measured for autopolymerized cement samples between variables for color and solidification load (N), which showed a strong correlation between curing process and color change (p < 0.05). There was a correlation between the color change and degree of monomer conversion of the dual curing resin composite luting cement which contained a color indicator system for polymerization reaction. The study also suggested that autopolymerization only resulted in suboptimal polymerization of the cement. By additional light curing considerably higher flexural properties were obtained.

Can Dental Cement Composition Affect Dental Implant Success?

Cement-retained restorations on dental implants are a well-established method to replace missing teeth. However, undetected residual cement left during crown cementation procedures encourages microorganism growth, and it has been identified as a risk factor for peri-implant disease. Currently, there is no official guidance for dental cement selection, and the increasing variety of available compositions intensifies the complexity of the clinicians' decision process. The present study aimed to evaluate the in vitro host and bacterial cellular response to four different commercial dental cements as well as their effects on cement surface morphology. Disk specimens (n = 3) of bioceramic, zinc phosphate, resin-modified glass ionomer, and resin cements were exposed to host (murine pre-osteoblasts, human gingival fibroblasts, and undifferentiated human macrophages) and oral bacterial (Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguinis, and Aggregatibacter actinomycetemcomitans) cells. Results indicated that oral bacteria degraded the cement surface, but bacterial viability was not significantly affected by the presence of dental cement. Conversely, the biocompatibility and morphology of host cells were severely impacted by the cement composition. Only the bioceramic cement achieved >70% viability for all cell lines investigated. Within the limitations of this study, the results indicated the importance of considering the biological interactions of a dental cement composition during selection as it played a significant role in the host cellular response and the degree of surface degradation due to bacterial attack.

Y-TZP surface behavior under two different milling systems and three different accelerated aging protocols

BACKGROUND

To evaluate the influence of aging and milling system on zirconia surface roughness (SR) and phase transformation.

METHODS

Eighty crowns were divided in two groups according to yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic milling system (CAD-Neodent or MAD-Zirkonzahn). The crowns were submitted to different aging protocols (N.=10): 1) no aging; 2) autoclaving; 3) pH cycling; or 4) thermocycling. Next, the samples were submitted to an optical profilometry analysis to determine differences in the SR (µm). An X-ray diffraction analysis (XRD) was performed to quantify the percentage of monoclinic phase transformation. SR data was analyzed by two-way ANOVA (α=0.5%).

RESULTS

Aging protocol (P=0.42) and milling system (P=0.08) had no influence on the SR. However, the number of monoclinic phases was influenced by the autoclaving and pH cycling.

CONCLUSIONS

The surface roughness of zirconia-based crowns was not influenced by low temperature degradation or milling system. Regarding the phase transformation, autoclaving and pH-cycling aging presented a monoclinic phase increase when compared to the control group and thermocycled groups.

Effect of finishing condition on fracture strength of monolithic zirconia crowns

This study was to evaluate the load bearing capacity of monolithic dental zirconia crowns, and the effect of surface finishing on fracture strength. (1) The zirconia plates were divided into 5 groups and polished by various types of polishing bur, every specimen was analyzed by surface roughness testing, and X-ray diffraction (XRD). (2) The zirconia crowns were classified into 4 groups corresponding to different surface treatments and thickness. All the crowns were cemented and subjected to a load of 7 kg for 5 min. Stored in distilled water at 37°C for 24 h. Observe the typical surface using field emission scanning electron microscopy (FE-SEM). The cycling and fracture tests were carried out. The data was statistically analyzed. The groups had better fracture strength after polishing. This suggests the monoclinic phase can be eliminated by optimizing the polishing process. Moreover, the fracture strength increased with occlusal thickness (p<0.05).

Effects of Manufacturing and Finishing Techniques of Feldspathic Ceramics on Surface Topography, Biofilm Formation, and Cell Viability for Human Gingival Fibroblasts

Purpose:

Feldspathic ceramic restorations can be obtained by different techniques (stratification or computer-aided design/computer-aided manufacturing [CAD/CAM] blocks) and finishing procedures (polishing or glaze application). This study evaluated the effects of techniques and finishing procedures on surface properties, biofilm formation, and viability of human gingival fibroblasts (FMM-1) in contact with these materials.

Methods and Materials:

Ceramic specimens were obtained through a stratification technique (Vita VM9) and from CAD/CAM blocks (Vita Blocs Mark II; both Vita Zahnfabrik) and their surfaces were finished by polishing (ceramisté diamond rubbers + polishing paste; “p” subgroups) or glaze spray application + sintering (“g” subgroups). Roughness (Ra and RSm parameters) and surface free energy (SFE) were measured. Early biofilm formation of Streptococcus mutans, Streptococcus sanguinis, and Candida albicans was evaluated by counting colony-forming units (CFU). MTT (3-[4.5-dimethyl-thiazol-2-yl-]-2.5-diphenyl tetrazolium bromide) cytotoxicity test evaluated cellular viability for the growth of FMM-1 after 24 hours and seven days of contact. Scanning electron microscopy (SEM) and three-dimensional optical profilometry were performed to qualitatively analyze the surface. Data were analyzed by analysis of variance, Tukey test, and t-test (all α=0.05).

Results:

Polished samples presented lower roughness (Ra, p=0.015; RSm, p=0.049) and higher SFE (p=0.00). Streptococci had higher CFU in all groups, but the CFU of C albicans was lower for polished samples. Biofilm formation was influenced by the interaction of all factors (p=0.018), and the materials showed no cytotoxicity to FMM-1 growth.

Conclusions:

Polishing resulted in the lowest values for surface roughness and higher SFE values. Polished ceramics showed less C albicans adherence while the adherence of Streptococci was greater than C albicans in all conditions.

Influence of Dental Prosthesis and Restorative Materials Interface on Oral Biofilms

Oral biofilms attach onto both teeth surfaces and dental material surfaces in oral cavities. In the meantime, oral biofilms are not only the pathogenesis of dental caries and periodontitis, but also secondary caries and peri-implantitis, which would lead to the failure of clinical treatments. The material surfaces exposed to oral conditions can influence pellicle coating, initial bacterial adhesion, and biofilm formation, due to their specific physical and chemical characteristics. To define the effect of physical and chemical characteristics of dental prosthesis and restorative material on oral biofilms, we discuss resin-based composites, glass ionomer cements, amalgams, dental alloys, ceramic, and dental implant material surface properties. In conclusion, each particular chemical composition (organic matrix, inorganic filler, fluoride, and various metallic ions) can enhance or inhibit biofilm formation. Irregular topography and rough surfaces provide favorable interface for bacterial colonization, protecting bacteria against shear forces during their initial reversible binding and biofilm formation. Moreover, the surface free energy, hydrophobicity, and surface-coating techniques, also have a significant influence on oral biofilms. However, controversies still exist in the current research for the different methods and models applied. In addition, more in situ studies are needed to clarify the role and mechanism of each surface parameter on oral biofilm development.

Adhesion of Streptococcus mutans and Streptococcus sanguinis on Er:YAG Laser-Irradiated Dental Enamel: Effect of Surface Roughness

Objective: To determine surface roughness caused by Er:YAG laser irradiation and its effect on the increase in bacterial adhesion. Background: Er:YAG laser was proposed as a strategic device to reduce caries by its ability to generate chemical and structural changes in tooth enamel; in turn, it produces undesirable effects on the tooth surface that could increase its roughness and allow a greater accumulation of microorganisms. Methods: Eighty-four samples of human enamel were divided into seven groups (n = 12): G1_control (no laser irradiation); G2_100/H₂O, G3_200/H₂O, and G4_300/H₂O were irradiated with Er:YAG laser (12.7, 25.5, and 38.2 J/cm², respectively) under water irrigation. In addition, G5_100, G6_200, and G7_300 were irradiated with the energy densities described above and no water irrigation. Surface roughness measurements were recorded before and after treatment using a profilometer. Afterward, three samples per group were incubated in a microorganism suspension for the tetrazolium salt (XTT) assay. Biofilm morphology was observed using scanning electron microscopy and confocal laser scanning microscope. One-way analysis of variance and t-tests were performed for statistical analysis (p < 0.05). Results: There were no statistically significant differences in roughness values in the G5_100 group before and after treatment, but there were statistically significant differences observed in the other groups evaluated (p < 0.05). No significant differences in adhesion of both strains were detected in irradiated groups compared with G1_control. Conclusions: The increase in roughness on dental enamel surfaces was proportional to the irradiation conditions. However, the increase in surface roughness caused by Er:YAG laser irradiation did not affect Streptococcus mutans and S. sanguinis adhesion.

Monolithic Ceramics: Effect of Finishing Techniques on Surface Properties, Bacterial Adhesion and Cell Viability

INTRODUCTION

This study evaluated the morphology, biofilm formation, and viability of human gingival fibroblasts in contact with two monolithic ceramics after two different finishing techniques: polishing or glazing. For this, 92 blocks (4.5 × 4.5 × 1.5 mm) of each ceramic were made using high translucency zirconia partially stabilized by yttrium (YZHT) and lithium silicate reinforced by zirconium (ZLS).

METHODS AND MATERIALS

Blocks were sintered and then divided into glazing (g) or polishing (p) surface finish. Surface roughness (Ra and RSm) was evaluated through a contact rugosimeter and profilometry. Specimens were contaminated for heterotypic biofilm formation with Streptococcus mutans, Streptococcus sanguinis and Candida albicans for 16 hours. Biofilm was quantified by counting the colony forming units (CFU/mL) and analyzed by scanning electron microscopy (SEM). Fibroblast viability was evaluated by MTT assay. Surface free energy (SFE) was also determined. Roughness data were evaluated using nonparametric tests, while SFE, MTT and CFU results were evaluated by analysis of variance and Tukey test, and MTT data were also submitted to t-test (all, α=0.05).

RESULTS

Results showed that polished samples presented a lower high profile mean ( p<0.001); however, YZHTg presented less space between defects ( p=0.0002). SFE showed that YZHT presented higher SFE than ZLS. Profilometry evidenced more homogeneity on polished surfaces. The interaction of finishing technique and microorganisms influenced the CFU ( p=0.00). MTT assay demonstrated initial severe cytotoxic behavior for polished surfaces. SEM images showed homogeneous surfaces, except for glazed YZHT.

CONCLUSION

Glazed surfaces have a greater roughness and tend to accumulate more biofilm. Polished surfaces have higher SFE; however, they are temporarily cytotoxic.

Novel Microscalpels for Removing Proximal Composite Resin Overhangs on Class II Restorations

Introduction:

Limited access to interdental spaces complicates removal of excess material when placing class II composite resin restorations. Evidence-based recommendations on interproximal finishing are rare. We present novel microscalpels for this indication. The aim of the study was to test their fracture strength and cutting ability and to compare microscalpels with the use of a scaler, oscillating devices (G5-ProShape, G5-Proxocare), finishing strips and scalpels of sizes 12, 15, and 21 in a standardized in vitro model.

Methods and Materials:

Fracture strength (LOAD) and cutting forces (CUT) of microscalpels were evaluated at different angles (15, 30, 60, and 75 degrees; n=30 each) in a universal testing machine. Devices were compared in vitro using standardized composite overhangs. Marginal quality (QUAL; n=30) and quantity of excess/deficit (QUAN; n=30) were evaluated using scanning electron microscopy (SEM) for each device (explorative data analysis, Student t-test or analysis of variance; post hoc Scheffé).

Results:

Microscalpels showed the highest LOAD (95.8 [5.0] N) (mean [standard deviation]) and easiest cutting (CUT) (7.6 [1.5]) at 15 degrees. At all angles, LOAD was significantly higher than CUT (p&lt;0.001). Perfect margins were seen most often with scalpel size 12 (QUAL: 37% relative frequency), while most excess (73.4%) was observed with finishing strips. QUAN was lowest with microscalpels (19.3 [4.4] μm) and highest with finishing strips (116.0 [18.8]). Use of scalers led to fractures and crack formation.

Conclusion:

Microscalpels are able to cut composite at a lower force than necessary to fracture the blades at all angles. Small and/or curved scalpels yield the best-quality margins.

Streptococcus mutans forms xylitol-resistant biofilm on excess adhesive flash in novel ex-vivo orthodontic bracket model

INTRODUCTION

During orthodontic bonding procedures, excess adhesive is invariably left on the tooth surface at the interface between the bracket and the enamel junction; it is called excess adhesive flash (EAF). We comparatively evaluated the biofilm formation of Streptococcus mutans on EAF produced by 2 adhesives and examined the therapeutic efficacy of xylitol on S mutans formed on EAF.

METHODS

First, we investigated the biofilm formation of S mutans on 3 orthodontic bracket types: stainless steel preadjusted edgewise, ceramic preadjusted edgewise, and stainless steel self-ligating. Subsequently, tooth-colored Transbond XT (3M Unitek, Monrovia, Calif) and green Grengloo (Ormco, Glendora, Calif) adhesives were used for bonding ceramic brackets to extracted teeth. S mutans biofilms on EAF produced by the adhesives were studied using the crystal violet assay and scanning electron microscopy. Surface roughness and surface energy of the EAF were examined. The therapeutic efficacies of different concentrations of xylitol were tested on S mutans biofilms.

RESULTS

Significantly higher biofilms were formed on the ceramic preadjusted edgewise brackets (P = 0.003). Transbond XT had significantly higher S mutans biofilms compared with Grengloo surfaces (P = 0.007). There was no significant difference in surface roughness between Transbond XT and Grengloo surfaces (P >0.05). Surface energy of Transbond XT had a considerably smaller contact angle than did Grengloo, suggesting that Transbond XT is a more hydrophilic material. Xylitol at low concentrations had no significant effect on the reduction of S mutans biofilms on orthodontic adhesives (P = 0.016).

CONCLUSIONS

Transbond XT orthodontic adhesive resulted in more S mutans biofilm compared with Grengloo adhesive on ceramic brackets. Surface energy seemed to play a more important role than surface roughness for the formation of S mutans biofilm on EAF. Xylitol does not appear to have a therapeutic effect on mature S mutans biofilm.

Marginal Adaptation and Quality of Interfaces in Lithium Disilicate Crowns — Influence of Manufacturing and Cementation Techniques

Purpose: To evaluate the cement line thickness and the interface quality in milled or injected lithium disilicate ceramic restorations and their influence on marginal adaptation using different cement types and different adhesive cementation techniques.

Methods and Materials: Sixty-four bovine teeth were prepared for full crown restoration (7.0±0.5 mm in height, 8.0 mm in cervical diameter, and 4.2 mm in incisal diameter) and were divided into two groups: CAD/CAM automation technology, IPS e.max CAD (CAD), and isostatic injection by heat technology, IPS e.max Press (PRESS). RelyX ARC (ARC) and RelyX U200 resin cements were used as luting agents in two activation methods: initial self-activation and light pre-activation for one second (tack-cure). Next, the specimens were stored in distilled water at 23°C ± 2°C for 72 hours. The cement line thickness was measured in micrometers, and the interface quality received scores according to the characteristics and sealing aspects. The evaluations were performed with an optical microscope, and scanning electron microscope images were presented to demonstrate the various features found in the cement line. For the cement line thickness, data were analyzed with three-way analysis of variance (ANOVA) and the Games-Howell test (α=0.05). For the variable interface quality, the data were analyzed with the Mann-Whitney U-test, the Kruskal-Wallis test, and multiple comparisons nonparametric Dunn test (α=0.05).

Results: The ANOVA presented statistical differences among the ceramic restoration manufacturing methods as well as a significant interaction between the manufacturing methods and types of cement (p&lt;0.05). The U200 presented lower cement line thickness values when compared to the ARC with both cementation techniques (p&lt;0.05). With regard to the interface quality, the Mann-Whitney U-test and the Kruskal-Wallis test demonstrated statistical differences between the ceramic restoration manufacturing methods and cementation techniques. The PRESS ceramics obtained lower scores than did the CAD ceramics when using ARC cement (p&lt;0.05).

Conclusions: Milled restorations cemented with self-adhesive resin cement resulted in a thinner cement line that is statistically different from that of CAD or pressed ceramics cemented with resin cement with adhesive application. No difference between one-second tack-cure and self-activation was noted.

Bacterial Colonization in the Marginal Region of Ceramic Restorations: Effects of Different Cement Removal Methods and Polishing

This study evaluated the effects of excess cement removal techniques, with or without subsequent polishing, on biofilm formation and micromorphology in the marginal region of the tooth/restoration. From bovine teeth, 96 dentin blocks (4 × 8 × 2 mm) were produced, molded, and reproduced in type IV gypsum, on which 96 pressed ceramic blocks (Vita PM9, Vita Zahnfabrik; 4 × 8 × 2 mm) were produced via the lost wax technique. The dentin blocks and their respective ceramic blocks were cemented with a self-adhesive resin cement (RelyX U200, 3M ESPE), and cement excess was removed from the margin using four different techniques, followed or not by polishing with silicone rubber tips: MBr, removal with microbrush and photoactivation; MBr-Pol, MBr + polishing; Br, removal with brush and photoactivation; Br-Pol, Br + polishing; Photo-Expl, 5 seconds of initial photoactivation, removal with explorer, and final curing; Photo-Expl-Pol, Photo-Expl + polishing; Photo-SB, 5 seconds of initial photoactivation, removal with scalpel, and final curing; and Photo-SB-Pol, Photo-SB + polishing. After 24 hours, the roughness in the marginal region was analyzed using a profilometer (three measurements on each sample). Micromorphological analyses of the region were performed by stereomicroscope and scanning electron microscopy (SEM). Then the samples were contaminated with sucrose broth standardized suspension with Streptococcus mutans, Staphylococcus aureus, and Candida albicans and incubated for a period of 48 hours. The samples were quantitatively analyzed for bacterial adherence in the marginal region by confocal laser scanning microscopy and counting of colony-forming units (CFUs/mL) and qualitatively analyzed using SEM. Roughness data (Ra) were submitted to two-way analysis of variance, Tukey test at a confidence level of 95%, and Student t-tests. CFU, biomass, and biothickness data were analyzed by Kruskal-Wallis, Mann-Whitney, and Dunn tests. The removing technique statistically influenced Ra (MBr, p=0.0019; Br, p=0.002; Photo-Expl, p=0.0262; Photo-SB, p=0.0196) when comparing the polished and unpolished groups. The MBr and MBr-Pol technique differed significantly for CFU/mL values (p=0.010). There was no significant difference in the amounts of biomass and biothickness comparing polished and unpolished groups and when all groups were compared (p&gt;0.05). Different morphological patterns were observed (more regular surface for polished groups). We conclude that margin polishing after cementation of feldspar/pressed ceramic restorations is decisive for achieving smoother surfaces, as the excess cement around the edges can increase the surface roughness in these areas, influencing bacterial adhesion.

Effect of enamel morphology on nanoscale adhesion forces of streptococcal bacteria : An AFM study

We explore the influence of enamel surface morphology on nanoscale bacterial adhesion forces. Three dimensional morphology characteristics of enamel slices, which were treated with phosphoric acid (for 0 s, 5 s, 10 s, 20 s, and 30 s), were acquired. Adhesion forces of three initial colonizers (Streptococcus oralis, Streptococcus sanguinis, and Streptococcus mitis) and two cariogenic bacterial strains (Streptococcus mutans and Streptococcus sobrinus) with etched enamel surfaces were determined. Comparison of the forces was made by using bacterial probe method under atomic force microscope (AFM) in adhesion buffer. The results showed that enamel morphology was significantly altered by etching treatment. The roughness, peak-to-valley height, and valley-to-valley width of the depth profile, surface area, and volume increased linearly with acid exposure time, and reached the maximum at 30s, respectively. The adhesion forces of different strains increased accordingly with etching time. Adhesion forces of S. oralis, S. mitis, S. mutans, and S. sobrinus reached the maximum values of 0.81 nN, 0.84 nN, 0.73 nN, and 0.64 nN with enamel treated for 20s, respectively, whereas that of S. sanguinis at 10s (1.28nN), and dropped on coarser enamel surfaces. In conclusion, enamel micro-scale morphology may significantly alter the direct adhesion forces of bacteria. And there may be a threshold roughness for bacterial adhesion on enamel surface.