75 Years Ago: Discovery of Resin Adhesion to Acid-etched Enamel - A Comparison of the 1949 and 1955 Methods.

PURPOSE: This paper describes previously unknown details about the discovery of resin adhesion to acid-etched human enamel. MATERIALS AND METHODS: A literature review was performed through manual assessments. Primary sources revealing the discovery of resin curing on etched enamel were analyzed considering the research objectives and methodological procedure during that era, including the type of teeth used, preparatory measures, acid-etching process, type of resin and its application, and follow-up observations. Additionally, the political and economic contexts were examined. RESULTS: In 1949, acid etching was found to promote adhesion with acrylic resin, a finding described again in 1955. The 1949 studies utilized nitric acid for enamel etching and the acrylate resin Paladon from the Kulzer company (Germany). Conversely, the 1955 investigations employed phosphoric acid and an unnamed acrylate, likely a self-curing resin supported by Kulzer in the late 1930s. Disparities in the 1949 and 1955 findings can be ascribed to varying objectives and test conditions amidst a turbulent political backdrop, significantly impacting the Kulzer company. CONCLUSION: The discovery of resin adhesion to acid-etched enamel, approaching its 75th anniversary in 2024, is a landmark in 20th-century adhesive dentistry. Paladon represents a pioneering compound, exemplifying the influence of political, ideological, and economic factors on scientific advancements during that period.

The effect of repair protocols and chewing simulation on the microtensile bond strength of two resin matrix ceramics to composite resin.

BACKGROUND: To assess the micro tensile bond strength (µTBS) of two resin matrix ceramic (RMC) blocks bonded to composite resin by using different repair protocols with and without chewing simulation (CS). MATERIALS AND METHODS: Two resin matrix ceramic blocks (Vita Enamic and Lava Ultimate) were divided into 4 groups according to the surface treatments: Bur grinding (control), Bur grinding + silane, 9.5% HF acid etching, and 9.5% HF acid etching + silane. The single bond universal adhesive was applied on all specimens after the surface treatments according to the manufacturer's instructions, it was administered actively on the treated surface for 20 s and then light cured for 10 s, followed by incremental packing of composite resin to the treated surface. Each group was further divided into 2 subgroups (with/without chewing simulation for 500,000 cycles). A micro tensile bond strength test was performed for each group (n = 15). The effect of surface treatments on the materials was examined by using a scanning electron microscope (SEM). The micro tensile bond strength (MPa) data were analyzed with a three-way ANOVA, the independent t-test, and one-way ANOVA followed by the Tukey post-hoc test. RESULTS: µTBS results were significantly higher for Lava Ultimate than Vita Enamic for all the surface treatment protocols with (p < 0.01). The chewing simulation significantly negatively affected the micro-tensile bond strength (p < 0.001). Bur grinding + saline exhibited the highest bond strength values for Lava Ultimate, both with and without chewing simulation. For Vita Enamic, bur grinding + saline and HF acid + saline showed significantly higher bond strength values compared to other surface treatments, both with and without chewing simulation (p ≤ 0.05). CONCLUSION: Bur grinding + silane could be recommended as a durable repair protocol for indirect resin matrix ceramics blocks with composite resin material.

To etch or not to etch, Part III: On the hydrophobic-rich content and fatigue strength of universal adhesives after long-term ageing.

OBJECTIVES: To examine whether dentin-etching extension and/or the hydrophobic-rich content of hybrid layers would affect fatigue strengths of a mild universal adhesive after long-term aging. METHODS: Twin-bonded resin-dentin interfaces were produced by etching sound midcoronal dentin beams with 32 % ortho-phosphoric acid for 15 s (OPA15s), 3 s (OPA3s) or 10 % meta-phosphoric acid for 15 s (MPA15s). Samples were bonded with a mild universal adhesive with or without additional coating using a solvent-free bisGMA-based bonding resin. Self-etch application served as control. Composite buildups were made with a nanofilled composite. Bar-shaped twin-bonded interfaces (0.9 × 0.9 × 12 mm) were aged for two years in artificial saliva at 37 â„ƒ and tested under 4-point flexure at quasi-static (n = 16) and cyclic loads (n = 35) until failure. The stress-life fatigue behavior was evaluated using the staircase method at 4 Hz. Crack initiation and fracture patterns were evaluated by SEM. Cyclic-loaded data was analyzed by Kruskal-Wallis on Ranks (α = 0.05). RESULTS: Significantly higher fatigue life distributions and higher endurance limits were observed for less aggressive etch-and-rinse protocols (OPA3s and MPA15s) after long-term ageing. Hydrophobic-rich coating produced 20-32 % higher endurance limits, prevented micrometer-sized porosities at bonded interfaces, reduced etching-associated variability and lowered crack formation. Significance Long-term hydrolysis produces detrimental effects on the fatigue strength of resin-dentin interfaces. The bond-promotion effect of less aggressive etch-and-rinse protocols and the creation of hybrid layers with higher hydrophobic-rich content are critical to extend the durability of mild universal adhesives. Therefore, current oversimplification trends in adhesive dentistry may limit resin-dentin bonding performance.

Influence of Application Modes on Increasing Bond Strength Longevity of Self-etching and Universal Adhesive Systems to Enamel.

The present study aimed to evaluate the influence of application mode on the short-term microshear bond strength longevity of self-etching and universal adhesive systems to enamel, the failure mode, and the resulting enamel surface micromorphology. Ninety enamel surfaces were obtained from sound third molars, planed, and randomly assigned to nine groups, according to the application mode and the adhesive system (n=10). There were three primer application modes: according to the manufacturer's recommended application time (control), using double the application time recommended for the primer and selective enamel etching. The adhesive systems used were: Clearfil SE Bond (Kuraray), FL-Bond II (SHOFU), and Futurabond U (Voco). At least two resin-bonded composite cylinders (Grandioso Light Flow, Voco) were placed on each enamel surface, and then evaluated for microshear bond strength at 24 hours and 180 days of storage in solution body fluid (SBF) at pH 7.4. Failure modes were evaluated with a stereoscopic microscope at 20× magnification. A micromorphological analysis of the enamel surface was performed under a scanning electron microscope at 5000× magnification before and after the treatments. Mixed models for repeated measures over time showed significant interaction among application modes, adhesive systems, and time periods (p=0.0331). The bond strength of FL-Bond II adhesive to enamel observed after performing selective enamel etching was significantly higher than that observed after applying the control treatment (p=0.0010) at both 24 hours and 180 days. However, no significant difference was observed between the application of this same adhesive at double the time recommended by the manufacturer and the other two application modes (p>0.05). There was also no significant difference in the microshear bond strength for the enamel treatments applied using Clearfil SE Bond and Futurabond U (p>0.05). A significant reduction in bond strength to enamel was observed at the 180-day storage time for all the adhesive systems when selective enamel etching was performed (p<0.0001). No significant association was observed between the adhesive system failure mode and the enamel treatments (p=0.1402 and p=0.7590 for 24 hours and 180 days, respectively). The most prevalent failure was the adhesive type.

Ultrathin Feldspathic Ceramic Veneers: A Pilot SEM Evaluation of Etched Intaglio Surfaces.

Ultrathin ceramic veneers are a viable therapeutic option to manage esthetic challenges in the anterior zone. Proper conditioning of the intaglio surface of porcelain veneers is essential to achieve an adequate bonding. In clinical practice, this is typically done with chemical etching using an acid-containing agent, such as hydrofluoric acid. While it is well established that the etching effect is dependent on etching time and the acid concentration, little is known about the impact of etching time and the veneer fabrication method. The purpose of this pilot study was to evaluate, using scanning electron microscopy (SEM), the effect that different etching-time protocols have on the intaglio surface characteristics of ultrathin ceramic veneers fabricated with either the platinum foil technique or the refractory die technique. Several replicas of an ultrathin feldspathic ceramic veneer for a maxillary central incisor were fabricated. Individual specimens were processed according to different intaglio surface-etching protocols: no etching, etching for 90 seconds, etching for 120 seconds, and etching for 150 seconds (9.6% hydrofluoric acid used for all etching groups). It was observed that the 120-second etching protocol resulted in a favorable microroughness surface pattern in the platinum foil group. This pattern was comparable to that obtained by etching for 90 seconds with hydrofluoric acid the intaglio surface of veneers fabricated with the refractory die technique. Increasing the etching time to 150 seconds did not result in a more favorable roughness pattern.

Scanning electron microscope analysis to evaluate the effect of pretreatment with ozone and sodium hypochlorite on pits and fissures of primary teeth.

Introduction: The cornerstone of preventative therapy is made up of pit and fissure sealants and fluorides. Resin sealants have been shown to help reduce fissure decay in both primary and permanent teeth. Etching of primary molars is not effective due to prismless enamel, higher organic content, and diversity in fissure shape. Methods of pretreatment of pits and fissures have been hypothesized to promote microporosities in etched enamel and hence sealant adherence. Examining the etching pattern and surface roughness of the enamel surface can be used to gauge these. Objective: This study aimed to evaluate the effect of pretreatment with ozone gas and 5.25% sodium hypochlorite solution on pits and fissures of primary teeth to check for the etching pattern and surface roughness. Materials and Methods: Thirty noncarious primary molars were sectioned to retain the crowns, and randomly divided into three groups, sodium hypochlorite, ozone gas, and control. Each sample was pretreated with the agent, washed, followed by etching with 37% phosphoric acid. Samples were sectioned and subjected to scanning electron microscope analysis to evaluate the etching pattern and surface roughness. Results: Comparison of the etching pattern in three groups showed a statistically insignificant difference (P=0.364). Surface roughness was highest in the hypochlorite group followed by ozone and control which showed a statistically significant difference (P = 0.001). The surface area between the three groups showed a statistically insignificant difference. Conclusion: Sodium hypochlorite is a better pretreatment agent compared to ozone gas and acid etching alone. However, as all results were not statistically significant further research must be carried out to prove the effectiveness of these agents.

Does the application of dimethyl sulfoxide improve resin bonding to eroded dentine? Four-year in vitro evaluation.

OBJECTIVE: To evaluate the effect of dimethyl sulfoxide (DMSO) on the microtensile bond strength (µTBS) and nanoleakage (NL) of universal adhesives on eroded dentine, immediately and after four years of water storage. METHODS: Sixty-four sound human molars were distributed into 16 groups according to (1) Dentine surface (sound and eroded dentine); (2) dimethyl sulfoxide application (with or without); (3) Application mode (etch-and-rinse or self-etch) and (4) Storage time (immediate and four years). One mild universal adhesive was used (Scotchbond Universal). The restoration was then performed with a composite resin and the specimens were sectioned into resin-dentine bonded sticks. Resin-dentine bonded sticks were tested (immediately and after four years of water storage) for µTBS (0.5 mm/min) or used to assess NL. Data on µTBS and NL were analyzed using four-way ANOVA and Tukey's test (α = 0.05). RESULTS: Only the 3-way cross-product interaction 'substrate vs DMSO vs time' was statistically significant (p = 0.007). Eroded dentine showed a lower mean of µTBS and a higher mean of NL values than sound dentine. However, when DMSO was applied, no significant decrease of µTBS or NL values was observed after four years of water storage, regardless of adhesive strategies, or dentine evaluated, when compared to immediate results. SIGNIFICANCE: Water-based DMSO pre-treatments not only prevent degradation of MDP-containing simplified adhesives but also serve as a potential alternative to improve long-term bonding properties to eroded dentine. The versatility of using a single pre-treatment for both self-etch or etch-and-rinse bonding to eroded dentin may facilitate future clinical applications.

Randomized Clinical Split-Mouth Study on Partial Ceramic Crowns Luted with a Self-adhesive Resin Cement with or without Selective Enamel Etching: Long-Term Results after 15 Years.

PURPOSE: This follow-up of a randomized clinical split-mouth study aimed to investigate the influence of selective enamel etching on the long-term clinical performance of partial ceramic crowns (PCCs) luted with a self-adhesive resin cement. MATERIALS AND METHODS: 43 patients received two PCCs (Vita Mark II; Cerec 3D) each for the restoration of extensive lesions with multiple cusp coverage, inserted with a self-adhesive resin cement (RelyX Unicem, RXU). Using a split-mouth design, one PCC received additional selective enamel etching (RXU+E) and one did not (RXU-E). Patients were clinically evaluated at baseline and after up to 15 years (median observation period 176 months) using modified USPHS and FDI criteria. The data were analyzed non-parametrically (chi-squared tests, α = 0.05). Clinical survival of all restorations after 15 years was evaluated using the Kaplan-Meier analysis. RESULTS: After 15 years, 19 patients were available for clinical assessment (recall rate: 56%). Kaplan-Meier analysis showed a cumulative survival of 78.1% for RXU+E and of 42.9% for RXU-E, indicating a significantly higher survival rate for RXU+E (p = 0.004). Regarding the clinical performance of PCCs available for the 15-year evaluation, no statistically significant differences were found between RXU+E and RXU-E using modified USPHS and FDI criteria. Both groups revealed significant deterioration over time regarding surface luster, marginal adaptation, and marginal discoloration. RXU+E resulted in significantly inferior anatomic form over time and a significant improvement in post-operative hypersensitivity compared to baseline. CONCLUSION: For posterior PCCs, selective enamel etching can be recommended based on higher survival rates after 15 years. Clinically, deterioration due to aging is similar in both groups.

Preheated Composite as an Alternative for Bonding Feldspathic and Hybrid Ceramics: A Microshear Bond Strength Study.

PURPOSE: To evaluate the bond strength between alternative or conventional luting agents and indirect restorative materials. MATERIALS AND METHODS: Blocks of a polymer-infiltrated ceramic network (PICN, Vita Enamic) and a feldspathic ceramic (FEL, Vita Mark II) were sliced and divided according to the luting agent: resin cement (PICN-RC, FEL-RC), flowable composite (PICN-FC, FEL-FC), or preheated composite (PICN-PH, FEL-PH). The ceramic surfaces were polished, etched with 5% hydrofluoric acid for 60 s, and then a silane layer was applied. Cylinders of the luting agents were built up on the ceramic surfaces. In half the samples, the microshear bond strength (µSBS) was tested after 24 h (baseline). The other half was tested after 5000 thermocycles (5°C-55°C) (aging). The failure modes were determined using a stereomicroscope, and the ceramic surfaces were analyzed using a scanning electron microscope. Data were statistically analyzed with two-way ANOVA. RESULTS: Thermocycling reduced the bond strength values of all experimental groups. Regarding FEL, the preheated composite obtained the highest results. Resin cement showed results similar to the flowable composite at baseline and after aging. The highest results of PICN were obtained from the preheated composite followed by resin cement and flowable composite. Significant differences among the three luting agents were observed before and after aging. The most frequent failures among the experimental groups were adhesive and cohesive in the ceramic. CONCLUSION: Bond strength results indicate that the preheated composite can be an alternative for adhesive cementation when applied on the tested feldspathic ceramic or PICN.

Noninvasive diagnostic method using optical coherence tomography detected a vulnerable dentin enamel junction created by phosphoric acid etching.

To investigate the influence of phosphoric acid etching on the dentin enamel junction (DEJ) using optical coherence tomography (OCT). Human teeth were assigned to four groups: 1. control, no additional treatment (CT); 2. The primer of "SE Bond2" was applied (SE), 3. "Enamel Conditioner" was applied (EC), 4. "K-etchant syringe" was applied (KE). After treatment, the DEJ was observed using a laser microscope (CLSM), OCT, and scanning electron microscopy (SEM). Additionally, an ultimate tensile strength (UTS) test at the DEJ was performed. No cracks were observed by CLSM. In contrast, cracks were observed all samples by SEM. Additionally, OCT revealed a white line along the DEJ in all KE specimens and some EC specimens. The UTS test showed a significant difference between CT and KE. This study found that phosphoric acid etching may cause excessive demineralization and weaken the DEJ. This fragility was observed using a non-invasive diagnostic method using OCT.

38. Effect of Chlorhexidine Rinsed Blood Contamination on Bond Strength of Brackets Bonded with Self-etch Primer- An in Vitro Study.

The present invitro type of study has done to check the effect of blood contamination & chlorhexidine combination on the bond strength of brackets bonded with self-etch primer technique. The study consisted of ninety sound human upper premolars (extracted for orthodontic purpose) fixed in a self-cure acrylic block and segregated into three groups of 30 samples each. 0.022 slot metal MBT brackets (Gemini series-3M unitek) were bonded with self-etch primer using Transbond XT composite, CA, USA and light cure for 40 seconds) on clean buccal surface. Teeth were divided into 3 groups-Group A/Control group, Group B, Group C. A computer was used to record the force applied to debond the bonded bracket in the unit of Newton. The analysis of variance indicated that there were significant differences (F value = 6.891, p value=0.002) in bond strengths between the various groups tested. The highest value of shear bond strength occurred when chlorhexidine (Group C) was used to remove the blood contamination (mean=15.874 MPa). When bonding was done in ideal condition (Group A), shear bond strength obtained was slightly lower (mean=14.497 MPa) as compared to Group C. On the other hand, lowest shear bond strength among all three groups occurred when blood contamination (Group B) was removed with water (mean=11.059 MPa). Analysis of the study showed that shear bond strength of orthodontic brackets to enamel significantly decreased during bonding with self-etch primer in blood contamination condition. Self-etch primer displayed considerably superior performance with the use of chlorhexidine instead of water to wash the blood contamination.

Effect of different adhesive systems on dental defects and sensitivity to teeth in composite resin restoration: a systematic review and meta-analysis.

OBJECTIVES: This meta-analysis aimed to elucidate the effects of various acid etching patterns on the sensitivity of teeth and their clinical effectiveness following composite resin repair. MATERIALS AND METHODS: PubMed, Cochrane Library, Web of Science, and Embase databases were searched for relevant studies on the postoperative sensitivity (POS) of composite resin restorations after using different bonding systems. The retrieval was from the inception of the databases to August 13, 2022, with no filter of written language. Literature screening was conducted by two independent researchers. The Cochrane risk-of-bias assessment tool was adopted for quality evaluation, and Stata 15.0 for analysis. RESULTS: Twenty-five randomized controlled trials were included in the present study. Following resin composite restoration, 1309 restorations were bonded by self-etching (SE) adhesives, whereas 1271 restorations were bonded by total-etching (TE) adhesives. The meta-analyses showed that there is no evidence to prove the SE and TE will affect POS at present when measured using the modified United States Public Health Service (USPHS) criteria [RR = 1.00 (95% CI: 0.96, 1.04)], the World Dental Federation (FDI) [RR = 1.06 (95% CI: 0.98, 1.15)], or the visual analog scale (VAS) [SMD = 0.02 (95% CI: -0.15, 0.20)] scales. At a certain follow-up time, TE adhesives provide better outcomes in terms of color match, marginal staining, and marginal adaptation. In other words, TE adhesives have better esthetic results. CONCLUSIONS: The type of bonding technique (ER and SE) does not affect the risk and degree of POS in class I/II and class V restorations. Further research is required to verify whether these findings apply to different forms of composite resin restorations. CLINICAL RELEVANCE: Besides the fact that TE barely increase postoperative sensitivity, it also yields superior cosmetic results.

Efecto del tratamiento de la morfología oclusal con materiales para restauraciones preventivas / Effect of treating occlusal morphology with materials for preventive restorations

Introducción: las fosas y fisuras son áreas formadas por delgadas irregularidades de la capa del esmalte de la superficie oclusal. La compleja morfología en dientes posteriores es un determinante biológico asociado al desarrollo de caries. Objetivo: evaluar el efecto de diversas formas de tratar la morfología oclusal en la adaptación y penetración de materiales utilizados en restauraciones preventivas. Material y métodos: diseño experimental e in vitro. Sesenta terceros molares fueron distribuidos aleatoriamente en dos grupos: surco sin ameloplastia y con ameloplastia; además, contaban con acondicionamiento del esmalte que se subdividió en tres subgrupos: 1) sellador de fosas y fisuras, 2) adhesivo/sellador de fosas y fisuras y 3) adhesivo/ resina Flow. Resultados: los subgrupos adhesivo/sellador y adhesivo/ Flow alcanzaron mayores valores de adaptación íntima a las paredes del surco. Las diferencias fueron significativas entre los materiales (p = 0.0009). Las mayores zonas de desadaptación resultaron para el sellador sin y con ameloplastia. La penetración de los materiales fue mayor en los surcos con ameloplastia. En los surcos tratados con ameloplastia, el adhesivo/Flow reveló el mayor porcentaje de penetración y la mejor adaptación a las paredes del surco. Conclusiones: la penetración del material está positivamente correlacionada con la profundidad del surco. El sellador con y sin ameloplastia mostró pobre adaptación a las paredes del surco (AU)

Introduction: pits and fissures are areas formed by fine irregularities in the enamel layer of the occlusal surface. The complex morphology in posterior teeth are biological determinants associated with the development of caries. Objective: to evaluate the effect of various ways of treating occlusal morphology on the adaptation and penetration of materials used in preventive restorations. Material and methods: experimental design, in vitro. Sixty third molars were randomly distributed into two groups: groove without ameloplasty and with ameloplasty, with enamel conditioning with three subgroups: 1) pit and fissure sealer, 2) adhesive/pit and fissure sealer, 3) adhesive/resin flow. Results: the adhesive/sealant and adhesive/flow subgroups reached higher values of intimate adaptation to the furrow walls. The differences were significant between the materials (p = 0.0009). The largest areas of maladjustment were found for the sealant without and with ameloplasty. The penetration of the materials was greater in the grooves with ameloplasty. In the grooves treated with ameloplasty, the adhesive/flow revealed the highest percentage of penetration and the best adaptation to the walls of the groove. Conclusions: the penetration of the material is positively correlated with the depth of the furrow. The sealant with and without ameloplasty showed poor adaptation to the sulcus walls (AU)

Resin Cement/Enamel Interface: A Morphological Evaluation of the Acid-Base Resistant Zone, Enamel Etching Pattern, and Effect of Thermocycling on the Microshear Bond Strength.

PURPOSE: To evaluate the effects of etching mode (self-etch and etch-and-rinse) on acid-base resistant zone (ABRZ) formation at the resin cement/enamel interface and enamel etching pattern, as well as the effects of thermocycling (0, 5000, and 10,000 cycles) on the enamel microshear bond strength (µSBS) mediated by dual-cure resin cements (DCRC). MATERIALS AND METHODS: Two DCRC were used in 4 groups: Panavia V5 in self-etch (V5NE) and etch-and-rinse mode (V5E); and Estecem II in self-etch (ENE) and etch-and-rinse mode (EE). For ABRZ observation, the bonded interface was subjected to a demineralizing solution. The morphological attributes of the interface and etching patterns were observed using FE-SEM. For µ-SBS, cylinders with a 0.79-mm internal diameter and 0.5-mm height were made with DCRC and tested in shear after 0, 5000, and 10,000 thermal cycles (TC) (5°C and 55°C) (n = 10). RESULTS: The formation of an enamel ABRZ was observed in all groups with different morphological features between self-etch and etch-and-rinse groups. A funnel-shaped erosion beneath the interface was present using V5NE and ENE modes where enamel was dissolved, while ABRZ formation was confirmed and no funnel-shaped erosion was noticed using V5E and EE. No significant differences in µSBS were observed between resin cements. However, significantly lower µSBSs were recorded when the self-etching mode was used. Thermocycling resulted in a significant reduction in µSBS for all groups. CONCLUSION: Selective enamel etching should be recommended to improve the interfacial quality when dual-cure resin luting cements are used.

Pre-cementation treatment of glass-ceramics with vacuum impregnated resin coatings.

OBJECTIVE: The study aimed to investigate the effectiveness of a vacuum impregnation process to eliminate the porosity at the ceramic-resin interface to optimize the reinforcement of a glass-ceramic by resin cementation. METHODS: 100 leucite glass-ceramic disks (1.0 ± 0.1 mm thickness) were air-abraded, etched with 9.6 % HF acid, and silanated. Specimens were randomly allocated to 5 groups (n = 20). Group A received no further treatment (uncoated control). Groups B and D were resin-coated under atmospheric pressure, whereas groups C and E were resin-coated using vacuum impregnation. The polymerized resin-coating surfaces of specimens in groups B and C were polished to achieve a resin thickness of 100 ± 10 µm, while in groups D and E no resin-coating modification was performed prior to bi-axial flexure strength (BFS) determination. Optical microscopy was undertaken on the fracture fragments to identify the failure mode and origin. Comparisons of BFS group means were made by a one-way analysis of variance (ANOVA) and post-hoc Tukey test at α = 0.05. RESULTS: All resin-coated sample groups (B-E) showed a statistically significant increase in mean BFS compared with the uncoated control (p < 0.01). There was a significant difference in BFS between the ambient and vacuum impregnated unpolished groups (D and E) (p < 0.01), with the greatest strengthening achieved using a vacuum impregnation technique. SIGNIFICANCE: Results highlight the opportunity to further develop processes to apply thin conformal resin coatings, applied as a pre-cementation step to strengthen dental glass-ceramics.

Aesthetic caries infiltration - Long-term masking efficacy after 6 years.

OBJECTIVES: This study aimed to evaluate the masking efficacy of caries infiltration technique of initial caries lesions (ICL) six years after debonding and single treatment. METHODS: In 10 adolescents, 74 ICL (ICDAS 2) in 74 teeth were treated by resin infiltration (Icon, DMG) at a mean (SD) of 1.2 (1.2) months after bracket removal. The etching procedure was performed up to 3 times. Standardized digital images were taken before treatment (T0), seven days (T7) and 6 years (T2190) after treatment. Outcomes included the evaluation of the color differences between carious and healthy enamel at T0, T7 and T2190 by quantitative colorimetric analysis (ΔE), ICDAS scores, quantitative light-induced fluorescence (QLF; ΔF,ΔQ,WS Area) and qualitative visual evaluation (5-point Likert-scale [deteriorated (1), unchanged (2), improved, but not satisfying (3), improved and no further treatment required (4), completely masked (5)). RESULTS: The median color difference ΔΕ0 (25th/75th percentiles) at T0 was 10.3 (8.56/13.0). At T7 a significant decrease was observed (ΔΕ7=3.7 (2.0/5.8); p<0.001; Friedmann-test; ICDAS p<0.001; Chi-square test). No significant changes based on ΔΕ (p=0.972; Friedmann-test) and ICDAS grading (p=0.511, chi-square test) were observed between T7 and T2190 (ΔΕ2190=2.9 (1.8/4.2)). Furthermore, at T2190 four experienced dentists classified 50% and 37% of the lesions as "improved and no further treatment required" and "completely masked", respectively (Fleiss kappa: T2190: 0.782 (substantial agreement)). CONCLUSION: Aesthetic caries infiltration can effectively mask post-orthodontic initial caries lesions for at least 6 years. These results for most of the teeth could not only be observed by quantitative but also by qualitative analysis. CLINICAL SIGNIFICANCE: Resin infiltration efficaciously masks post-orthodontic initial carious lesions. The optical improvement can be observed directly after treatment and remains stable for at least six years.

Progress in Dental Adhesive Materials.

There have been significant advances in adhesive dentistry in recent decades, with efforts being made to improve the mechanical and bonding properties of resin-based dental adhesive materials. Various attempts have been made to achieve versatility, introducing functional monomers and silanes into the materials' composition to enable the chemical reaction with tooth structure and restorative materials and a multimode use. The novel adhesive materials also tend to be simpler in terms of clinical use, requiring reduced number of steps, making them less technique sensitive. However, these materials must also be reliable and have a long-lasting bond with different substrates. In order to fulfill these arduous tasks, different chemical constituents and different techniques are continuously being developed and introduced into dental adhesive materials. This critical review aims to discuss the concepts behind novel monomers, bioactive molecules, and alternative techniques recently implemented in adhesive dentistry. Incorporating monomers that are more resistant to hydrolytic degradation and functional monomers that enhance the micromechanical retention and improve chemical interactions between adhesive resin materials and various substrates improved the performance of adhesive materials. The current trend is to blend bioactive molecules into adhesive materials to enhance the mechanical properties and prevent endogenous enzymatic degradation of the dental substrate, thus ensuring the longevity of resin-dentin bonds. Moreover, alternative etching materials and techniques have been developed to address the drawbacks of phosphoric acid dentin etching. Altogether, we are witnessing a dynamic era in adhesive dentistry, with advancements aiming to bring us closer to simple and reliable bonding. However, simplification and novelty should not be achieved at the expense of material properties.

Ceramic surface conditioning, resin cement viscosity, and aging relationships affect the load-bearing capacity under fatigue of bonded glass-ceramics.

This study aimed to evaluate the influence of ceramic surface treatments, resin cement viscosities, and storage regimens on the fatigue performance of bonded glass-ceramics (lithium disilicate, LD; feldspathic, FEL). Ceramic discs (Ø = 10 mm; thickness = 1.5 mm) were allocated into eight groups per ceramic (n = 15), considering three factors: "ceramic surface treatment" in two levels - 5% hydrofluoric acid etching and silane-based coupling agent application (HF), or self-etching ceramic primer (E&P); "resin cement viscosity" in two levels - in high or low viscosity; and "storage regimen" in two levels - baseline, 24 h to 5 days; or aging, 180 days + 25,000 thermal cycles. Adhesive luting was performed onto glass fiber-reinforced epoxy resin discs (Ø = 10 mm; thickness = 2 mm) and the bonded assemblies were subjected to cyclic fatigue tests: initial load = 200 N; step-size = 25 N (FEL) and 50 N (LD); 10,000 cycles/step; 20 Hz. Scanning electron microscopy (SEM) inspections were performed. Regarding the LD ceramic, the fatigue behavior was reduced after aging for HF_HIGH and E&P_LOW conditions, while stable performance was observed for HF_LOW and E&P_HIGH. Regarding the FEL results, aging negatively affected HF_HIGH, E&P_HIGH, and E&P_LOW, being that only the HF_LOW condition presented a stable behavior. The failure initiated from defects on the etched surface of the ceramics, where the cross-sectional analysis commonly revealed unfilled areas. Long-term aging might induce a decrease in mechanical behavior. The 'ceramic microstructure/surface conditioning/resin cement viscosity relationships' modulate the fatigue performance of lithium disilicate and feldspathic glass-ceramics.

The Impact of Different Surface Treatments on Topography and Bond Strength of Resin Cement to Lithium Disilicate Glass Ceramic.

OBJECTIVE: To evaluate the influence of different surface treatments on topography, surface roughness, surface energy, and microtensile bond strength stability of resin cement to lithium disilicate glass ceramic. METHODS AND MATERIALS: Seventy disc-shaped specimens of IPS e.max Press were divided into seven groups according to the surface treatment: NT - non-treated (control); FSil - hydrofluoric acid (HF) + silane; FPSil - HF + phosphoric acid (HP) + silane; FUSil - HF + ultrasonic bath (U) + silane; FPUSil - HF + HP + U + silane; MEP - Monobond Etch and Prime (MEP); and MEPH - MEP + heating. Topography and surface roughness were evaluated using a 3D laser confocal microscope (3DLCM) and scanning electron microscopy (SEM) and surface energy with a goniometer. The microtensile bond strength (µTBS) was evaluated after storage in distilled water at 37°C for 24 hours and after thermocycling (5,000 cycles, 5°-55° C, 30-second dwell time). Data were analyzed using one-way ANOVA (surface roughness and surface energy), two-way ANOVA (µTBS), Tukey's HSD post-hoc test, and Student t-test (α=0.05). RESULTS: FUSil, FPSil, and FSil presented similar and highest surface roughness, whereas NT, FPUSil, MEP, and MEPH showed similar, and lowest, roughness values (p<0.05). FPUSil, FPSil, FUSil, and FSil presented a similar and highest surface energy. NT, MEP, and MEPH showed similar and lowest surface energy. CONCLUSION: Only FSil, FPSil, and MEPH maintained bond strength stability after thermocycling, with FPSil leading to less bond strength reduction, suggesting this protocol is more reliable for bonding resin cements to lithium disilicate glass ceramics.

Evaluation of the masking efficacy of caries infiltration in post-orthodontic initial caries lesions: 1-year follow-up.

OBJECTIVES: This study aimed to qualitatively and quantitatively assess the masking efficacy and color stability of resin infiltration on post-orthodontic ICL after 1 year. MATERIALS AND METHODS: In 17 adolescents, 112 ICL (ICDAS-1: n = 1; ICDAS-2: n = 111) in 112 teeth were treated by resin infiltration (Icon, DMG) 3 to 12 months after bracket removal. The etching procedure was performed up to 3 times. Standardized digital images were taken before treatment (T0), 7 days (T7) and 12 months (T365) after treatment. Outcomes included the evaluation of the color differences between infiltrated and healthy enamel at T0, T7, and T365 by quantitative (colorimetric analysis (ΔE), ICDAS scores) and qualitative methods (5-point Likert scale (deteriorated (1), unchanged (2), improved, but not satisfying (3), improved and no further treatment required (4), completely masked (5)).) Differences between time points were analyzed by using Friedman test (ΔΕ) and chi-square tests (ICDAS). RESULTS: The median color difference (25th/75th percentiles) between carious and healthy enamel at baseline (ΔΕ0) was 10.2(7.7/13.6). A significant decrease was observed 7 days after treatment (ΔΕ7 = 3.1(1.8/5.0); p < 0.001; ICDAS; p < 0.001). No significant changes based on ΔΕ (p = 1.000), and ICDAS grade (p = 0.305) were observed between T7 and T365 (ΔΕ12 = 3.4 (1.8/4.9)). Furthermore, at T365 four experienced dentists classified 55% and 39% of the lesions as "improved and no further treatment required" and "completely masked," respectively (Fleiss kappa: T365 = 0.851 (almost perfect)). CONCLUSION: Resin infiltration efficaciously masked post-orthodontic ICL 7 days and 12 months after treatment. These results for most of the teeth could not only be observed by quantitative but also by qualitative analysis. CLINICAL RELEVANCE: Resin infiltration efficaciously masks post-orthodontic initial carious lesions. The optical improvement can be observed directly after treatment and remains stable for at least 12 months.