Challenges and opportunities in preparing dentists for primary care.

With the growing understanding of the relationship between oral and systemic diseases there is an increasing interest in integrating dental providers more completely into the health care delivery system. Technology advancements in traditional dental disease diagnosis and management as well as in salivary diagnostics for systemic disease provide great opportunities for the profession but numerous challenges for dental educators who are impacted by the intersection of numerous, sometimes competing interests. While economic factors play a significant role in curricular innovation and change, in the United States the accrediting process for dental education programs can be an equally vexing challenge. Movement away from primarily a competency-based assessment model to a model focusing on the establishment of Entrustable Professional Activities (EPAs) may provide a needed catalyst to enhance dental education to graduate dentists who embrace an expanded role as primary care providers.

Scanning electron microscopy observation of dentin bond interfaces in different types of resin luting cements.

This study aimed to observe and compare the resin luting cement (RLC)/dentin interfaces of different types of RLC systems with scanning electron microscopy (SEM). This study evaluated six self-adhesive resin luting cement systems (SARLCs), four systems combining a SARLC with a tooth primer (SARLCPs), and six conventional resin luting cement systems (CVRLCs). Cured resin composite rods were bonded to bovine dentin using RLCs in different etching modes. The morphological features at the interfaces were observed using SEM. Although all RLCs in etch-&-rinse (ER) mode showed a clear hybrid layer, most SARLCs had a thinner and more porous hybrid layer than the SARLCPs and CVRLCs. All SARLCPs with primer and CVRLCs showed a thin high-density layer below the primer layer in both etching modes. CVRLCs and SARLCPs with primer treatment systems may be more versatile and reliable when compared to simplified RLC systems.

Bond durability of a two-step adhesive with a universal-adhesive-derived primer in different etching modes under different degradation conditions.

This study investigated the enamel and dentin bond durability of a two-step adhesive system, using a universal adhesive-derived primer (G2-Bond Universal [GU]), and compared it with the two conventional, two-step, self-etch adhesive systems (Clearfil SE Bond 2 [CS] and OptiBond XTR [OX]) under thermal cycling (TC) and long-term water storage (WS). The shear bond strengths to bovine enamel and dentin were determined using the etch-and-rinse and self-etch modes. Twelve specimens per test group were prepared and further divided into the following subgroups: 1) subjected to TC, 2) long-term WS, and 3) WS for 24 h (baseline). The enamel and dentin bond durability of GU was superior to those of CS and OX in different etching modes and under different degradation conditions. The latest two-step adhesive system, which utilizes universal adhesives' benefits in its primer, might offer durable clinical bonding performances and can be widely used in a clinical setting.

Early Phase Enamel Bond Performance of a Two-step Adhesive Containing a Primer Derived from a Universal Adhesive.

PURPOSE: To investigate the changes in the enamel bond performance of a two-step adhesive containing a primer derived from a universal adhesive in the early phase before 24 h and compare them to those of other adhesives. The Knoop hardness number (KHN) of the cured adhesive layers and resin composite was measured. MATERIALS AND METHODS: A new two-step adhesive using universal adhesive technology, G2-Bond Universal, was tested. Two conventional two-step adhesives, Clearfil SE Bond 2 and OptiBond eXTRa, and an established universal adhesive, Scotchbond Universal Plus Adhesive, were used as comparison materials. Twelve specimens per group were used to measure the shear bond strength (SBS) to bovine enamel in different etching modes. The bonded specimens were stored in distilled water at 37°C for 5 min or 1, 6, 12, or 24 h before SBS testing. The KHN of the adhesive layer and resin composite was determined after the same storage periods as for SBS testing. RESULTS: All adhesives exhibited increased SBS with prolonged storage periods, irrespective of the etching mode. The KHN of the adhesive layer and resin composite increased over time. CONCLUSIONS: There were strong positive correlations between the SBS and KHN of the adhesive layer and resin composite. Phosphoric acid pre-etching of enamel effectively increases enamel bond performance. The two-step adhesive G2-Bond Universal demonstrated significantly higher bond strength in the early phase than the other adhesives in self-etch mode.

Bond Durability of Two-Step HEMA-Free Universal Adhesive.

The purpose of this study is to compare bond durability, in terms of fatigue bond strength, of a two-step HEMA-free universal adhesive and representative adhesives in each systematic category. The adhesives used in this study were OptiBond FL, Prime&Bond NT, Clearfil SE Bond 2, G2-Bond Universal, and Scotchbond Universal Plus Adhesive. Fatigue bond strength testing and scanning electron microscopy analysis of adhesively bonded enamel and dentin interfaces were performed. For the adhesives in etch-and-rinse mode, the enamel fatigue bond strength of the G2-Bond Universal adhesive was significantly higher than those of other adhesives, and the dentin fatigue bond strength of Prime&Bond NT was significantly lower than the others. For adhesives in self-etch mode, the enamel fatigue bond strengths of Clearfil SE Bond 2 and G2-Bond Universal were significantly higher than that of the Scotchbond Universal Plus Adhesive, and the dentin fatigue bond strength of G2-Bond Universal was significantly higher than Clearfil SE Bond 2 and the Scotchbond Universal Plus Adhesive. The two-step HEMA-free universal adhesive showed higher enamel and higher or equal dentin fatigue bond strength than other selected representative adhesive systems in etch-and-rinse mode and higher or equal enamel and higher dentin fatigue bond strength than adhesive systems in self-etch mode.

Fatigue bond strength of dental adhesive systems: Historical background of test methodology, clinical considerations and future perspectives.

Numerous laboratory evaluations have been conducted since Dr. Rafael Bowen introduced a method for determining the bond strengths of adhesive systems to dental substrates in 1965. Most of the past studies have been conducted using static bond strength tests, such as shear and tensile bond strength testing with either macro or micro sized specimens. These static bond strength tests are conducted using a monotonically increasing load in which stress is applied continuously until failure occurs. Although the type of stress that develops in static bond strength tests is not typically encountered in clinical situations, over the years clinicians have based their choice of adhesive systems for use in daily practice on the results of such tests. However, some well-known researchers have reported that the results obtained from static bond strength testing may have limited clinical relevance and should not be used only by themselves to make recommendations for clinical use. In clinical situations, restorations undergo cyclic stress during mastication at stress levels well below the breaking stress used in static bond strength tests. Thus, dynamic bond strength tests, using cyclic loading, should be more clinically relevant than static bond strength tests. Over 15 years, a testing method designed to assess fatigue bond strengths of dental adhesive systems has been developed through inter-collegial and international collaborative efforts. This review discusses the development of fatigue bond strength testing methodology, provides both a historical perspective and current information regarding available testing data for all categories of adhesive systems to enamel and dentin and perspectives on the future development of both adhesive systems and testing methods.

Effect of mold enclosure and chisel design on fatigue bond strength of dental adhesive systems.

To examine the effect of mold enclosure and chisel design on macro shear fatigue bond strengths of dental adhesive systems. The fatigue bond strength testing was conducted with two commercially available dental adhesive systems, (1) OptiBond eXTRa and (2) Scotchbond Universal, for bonding a resin composite (Filtek Supreme Ultra) to both enamel and dentin using a mold enclosure and a non-mold enclosure with a knife-edge and two sized notched-edge chisel assemblies for loading. As a loading reference for the fatigue testing, macro shear bond strengths of the adhesive systems to enamel and dentin were conducted using a mold enclosure and a knife-edge chisel assembly. The shear bond strengths with the mold enclosure using knife-edge chisel assembly did not exhibit a significant difference between the adhesive systems for either enamel or dentin. The fatigue bond strengths of bonded specimens demonstrated significant differences when comparing the mold enclosure and non-mold enclosure, but not between knife-edge and notched-edge chisel assemblies. The fatigue bond strengths of dental adhesive systems demonstrated significantly higher values when using mold-enclosed bonded specimens than a non-mold enclosure, regardless of type of chisel assembly.

Characterization of Ag-Ion Releasing Zeolite Filled 3D Printed Resins.

There has been profound growth in the use of 3D printed materials in dentistry in general, including orthodontics. The opportunity to impart antimicrobial properties to 3D printed parts from existing resins requires the capability of forming a stable colloid incorporating antimicrobial fillers. The objective of this research was to characterize a colloid consisting of a 3D printable resin mixed with Ag-ion releasing zeolites and fumed silica to create 3D printed parts with antiviral properties. The final composite was tested for antiviral properties against SARS-CoV-2 and HIV-1. Antiviral activity was measured in terms of the half-life of SARS-CoV-2 and HIV-1 on the composite surface. The inclusion of the zeolite did not interfere with the kinetics measured on the surface of the ATR crystal. While the depth of cure, measured following ISO4049 guidelines, was reduced from 3.8 mm to 1.4 mm in 5 s, this greatly exceeded the resolution required for 3D printing. The colloid was stable for at least 6 months and the rheological behavior was dependent upon the fumed silica loading. The inclusion of zeolites and fumed silica significantly increased the flexural strength of the composite as measured by a 3 point bend test. The composite released approximately 2500 µg/L of silver ion per gram of composite as determined by potentiometry. There was a significant reduction of the average half-life of SARS-CoV-2 (1.9 fold) and HIV-1 (2.7 fold) on the surface of the composite. The inclusion of Ag-ion releasing zeolites into 3D-printable resin can result in stable colloids that generate composites with improved mechanical properties and antiviral properties.

Influence of Different Application Methods on the Bonding Effectiveness of Universal Adhesives to Dentin in the Early Phase.

PURPOSE: To investigate the changes in the dentin bond strengths of universal adhesives during the early phase and evaluate the effect of a double-layer adhesive application on the performance of the dentin bond. MATERIALS AND METHODS: Three universal adhesives and a two-step self-etch adhesive were employed to ascertain the shear bond strengths (SBS) of specimens to bovine dentin with the use of the etch-and-rinse or self-etch mode. The specimens were further divided into two groups based on adhesive application in a single or a double layer. The bonded specimens were stored in distilled water at 37°C for 5 min or 1, 6, 12, or 24 h prior to SBS measurement and the adhesives' Knoop hardness number (KHN). RESULTS: All the adhesives showed increased SBS with prolonged storage periods regardless of the adhesive layer (single or double) or etching mode. Most universal adhesives in the double adhesive layer groups showed significantly higher SBS than single adhesive layer groups for the same storage period. All the adhesives also showed increased KHN with increased storage period. CONCLUSION: The SBS and KHN values of the adhesives increased with increasing storage duration over a 24-h period. Double adhesive layer application mediated increased dentin bond strength in the early phase.

Influence of light irradiation for in-office tooth whitening: A randomized clinical study.

PURPOSE: To evaluate the influence of light irradiation on the clinical efficiency of an in-office whitening agent. METHODS: The in-office whitening agent (Opalescence Boost 35%) was used in this study. Two whitening regimens were evaluated on maxillary anterior teeth: (1) with light irradiation; and (2) without light irradiation. The ΔE*, changes of L*, a*, b*, and the best shade match on the central incisor before, immediately after, and 6 months after whitening procedures were evaluated using a dental spectrophotometer. RESULTS: The ΔE and shade had no significant differences with or without light irradiation. In addition, the ΔE, changes of L*, a*, b*, and shade did not change over 6 months after bleaching at a level detectable to the naked eye. The results suggested that the in-office whitening agent using 35% hydrogen peroxide without photocatalysts can improve tooth color with or without light irradiation for 6 months after whitening. CLINICAL SIGNIFICANCE: In office whitening using 35% hydrogen peroxide without photocatalysts should be considered as a good treatment option for vital teeth whitening.

Bonding and wear properties of self-adhesive flowable restorative materials.

The purpose of this study was to evaluate the bonding and wear properties of self-adhesive flowable restorative materials. Five self-adhesive flowable restorative materials were used. The study parameters were: (i) shear bond strengths; (ii) microleakage; (iii) occlusal wear; and (iv) qualitative evaluation of the bonding interface. The range of shear bond strengths of the materials was as follows: 7.4-12.2 MPa to ground enamel, 22.5-32.5 MPa to etched enamel, and 1.3-4.2 MPa to dentin. The microleakage scores of the materials did not show any statistically significant differences regardless of the presence or absence of etching. The wear facets on the materials showed 0.099-0.447 mm3 of volume loss and 148.6-365.3 µm maximum depth, with statistically significant differences between materials. Scanning electron microscopic images of the interfaces of the materials showed good adaptation regardless of substrate. The bonding and wear properties of self-adhesive flowable restorative materials were still limited and showed lower values than previously reported results for nanofilled composites with an adhesive system. Selective enamel etching can improve the bonding performance of these materials.

Bond durability of universal adhesives to intact enamel surface in different etching modes.

This study aimed at determining the enamel bond durability of universal adhesives to intact enamel (IE) and ground enamel (GE) in different etching modes under thermal cycling (TC) and fatigue stresses. Two universal adhesives and a two-step self-etch adhesive were used. Enamel specimens were divided into four groups by treatment: (i) GE in etch-and-rinse, (ii) IE in etch-and-rinse, (iii) GE in self-etch, and (iv) IE in self-etch. Bonded specimens were subjected to TC, and then shear bond strengths (SBS) were conducted. SBS tests were also conducted after storage in 37°C water for 24 h (baseline). For shear fatigue strength (SFS) testing, bonded specimens were subjected to fatigue stress at a frequency of 10 Hz for 50,000 cycles. At baseline, all adhesives showed significantly higher SBS values with GE than IE in self-etch mode in contrast to in etch-and-rinse mode. After TC, the universal adhesives with IE showed lower SBS values than the baseline, regardless of the etching mode. Universal adhesives showed significantly lower SFS values with IE in etch-and-rinse, but not in self-etch mode. Phosphoric acid pre-etching or grinding of the aprismatic enamel may be helpful in establishing reliable initial and long-term bonds to enamel when using universal adhesives in self-etch mode.

Effect of double-layer application on the early enamel bond strength of universal adhesives.

OBJECTIVES: The present study aimed to investigate the changes in the enamel bond strengths of universal adhesives in the early phase of specimen creation and evaluate the effect of double-layer application on enamel bond effectiveness using different etching modes. METHOD: Four universal adhesives, namely Clearfil Universal Bond Quick, G-Premio Bond, Scotchbond Universal, and Tokuyama Universal Bond, were used. Clearfil SE Bond two-step self-etch adhesive system was used as a comparison. Fifteen specimens per group were used for determining the shear bond strength (SBS) to bovine enamel in the etch-and-rinse or self-etch mode. The adhesive was applied to specimens in accordance with the manufacturers' instructions (single-layer application), or the adhesive was applied twice (double-layer application). The bonded specimens were stored in distilled water at 37 °C for 5 min or 1, 6, 12, or 24 h before SBS testing. The flexural properties of the resin composite Clearfil AP-X were measured for the same storage periods. RESULTS: All universal adhesives exhibited increased SBS values with prolonged storage periods regardless of the application technique or etching mode used. Double-layer application was associated with higher SBS values than single-layer application for most universal adhesives over the same storage period. CONCLUSION: Phosphoric acid pre-etching and double-layer application of universal adhesives resulted in increased enamel bond strength in the early phase of specimen bonding. CLINICAL RELEVANCE: Care should be taken when using universal adhesives in the self-etch mode for enamel bonding because the enamel adhesion is sensitive to the duration after filling.

Comparison of different etch-and-rinse adhesive systems based on shear fatigue dentin bond strength and morphological features the interface.

OBJECTIVES: The aim of this study was to investigate dentin bonding durability of different etch-and-rinse (ER) adhesive systems under fatigue stress and to compare morphological features of resin/dentin interfaces using SEM. METHODS: Two three-step ER adhesives, a two-step ER adhesive, and a universal adhesive in ER mode were evaluated. Before application of either primer or adhesive, phosphoric acid etching of human dentin was completed. Fifteen bonded specimens for each adhesive system were stored in distilled water at 37 °C for 24 h, then subjected to a shear bond strength (SBS) test. Bonding durability was assessed from the perspective of biomechanical stress. 25 bonded specimens for each adhesive system were subjected to shear fatigue strength (SFS) testing with a repeated subcritical load at a frequency of 20 Hz for 50,000 cycles or until failure. RESULTS: Mean SBS and SFS values ranged from 33.3 to 41.2 MPa, and from 18.3 to 20.3 MPa, respectively. Three-step adhesives showed higher SBS and SFS values than the other adhesive systems. Under SEM, resin tags in different adhesive systems showed similar features, but morphology below the hybrid layer was material dependent. The universal adhesive in ER mode showed an obvious thin, high-density reaction layer below the hybrid layer. SIGNIFICANCE: Three-step adhesives showed higher dentin bond durability than the other ER adhesives; no significant differences in SFS were found between the universal adhesive in ER mode and the three-step ER adhesives. The results of this in vitro study indicate that some ER adhesives might establish chemical bonding with intact dentin below the hybrid layer in addition to micromechanical retention.

Chair-side CAD/CAM fabrication of a single-retainer resin bonded fixed dental prosthesis: a case report.

This clinical report describes designing and fabricating a single-retainer resin-bonded fixed dental prosthesis with a chair-side computer-aided design/computer-aided manufacturing system. The whole procedure, from tooth extraction to final placement of the prosthesis, was completed in one day, and a single clinic visit. No clinical complications were found at the 2-year follow-up after placement of the restoration, and satisfactory functional and esthetic results were achieved.

Influence of 38% silver diamine fluoride application on bond stability to enamel and dentin using universal adhesives in self-etch mode.

In order to evaluate the influence of 38% silver diamine fluoride (SDF) application on enamel and dentin bond stability of universal adhesives in self-etch mode, a 38% SDF and three universal adhesives were used in this study. Initial shear bond strength (ISBS), fatigue bond strength (FBS), and shear bond strength of survivors (SBSS) to enamel and dentin of universal adhesives in self-etch mode, with and without SDF application, were determined. SDF was applied to the polished enamel or dentin surface for 1 min, water-rinsed and air-dried for comparison with controls. The universal adhesives were applied to the prepared samples and composite resin was bonded using a mold-enclosed method. Enamel bond stability of universal adhesives with SDF (ISBS: 14.7-20.4 MPa; FBS: 5.5-7.4 MPa and SBSS: 14.4-21.5 MPa) was significantly weaker than those without SDF (ISBS: 28.0-29.2 MPa; FBS: 12.1-15.6 MPa and SBSS: 28.4-34.4 MPa). Dentin bond stability with SDF (ISBS: 14.8-20.9 MPa; FBS: 7.1-8.2 MPa and SBSS: 17.3-21.8 MPa) was also significantly weaker than without SDF (ISBS: 19.3-36.1 MPa; FBS: 11.0-13.7 MPa and SBSS: 22.2-34.6 MPa). The results suggest that SDF application on enamel and dentin reduces the bond stability of universal adhesives in self-etch mode.

Comparison of occlusal wear between bulk-fill and conventional flowable resin composites.

PURPOSE: To investigate the occlusal wear of bulk-fill and conventional flowable resin composites. METHODS: Four bulk-fill flowable resin composites: (1) Filtek Bulk Fill Flowable Restorative (FB); (2) G-ænial Bulk Injectable (GB); (3) SDR Flow+ (SD); and (4) Tetric EvoFlow Bulk Fill (TB), and four conventional flowable resin composites: (1) Clearfil Majesty IC (CM); (2) Filtek Supreme Ultra Flow (FF); (3) G-ænial Universal Flow (GF); and (4) Herculite XRV Ultra Flow (HF) were evaluated. Localized wear was simulated using 400,000 cycles in a Leinfelder-Suzuki (Alabama) device with a stainless-steel ball bearing antagonist. Volume loss and maximum depth of wear facets were measured using a Proscan 2100 noncontact profilometer in conjunction with analyzing software. Scanning electron microscopy observations were also conducted on the wear specimens. RESULTS: Simulated occlusal wear was significantly different (P< 0.05) among the materials tested. FF, GB and GF showed significantly less wear than the other tested resin composites. The rank order of volume loss and maximum depth was GF-GB-FF-FB-CM-HF-TB-SD. CLINICAL SIGNIFICANCE: Bulk-fill flowable resin composites showed a much wider range of wear properties than conventional flowable resin composites. Some composites of each type may be suitable for use in occlusal contact areas of posterior restorations, but care must be taken when selecting such a resin.

In Vitro Wear Resistance of Self-Adhesive Restorative Materials.

PURPOSE: To investigate simulated localized and generalized wear of self-adhesive restorative materials. MATERIALS AND METHODS: Three commercially available restorative materials and one experimental material with self-adhesive properties were evaluated. The experimental material was tested in both light-cured and self-cured conditions. Activa (A), Fuji II LC (F), and Equia Forte (E) and the experimental material ASAR-MP4 (S) were investigated. Two kinds of wear were simulated in an Alabama wear machine. Localized wear was simulated with a stainless-steel ball bearing antagonist and generalized with a flat-ended stainless-steel cylinder antagonist. The wear challenge was carried out in an aqueous slurry of polymethyl methacrylate beads. Material volume loss was measured on polyvinyl siloxane replicates of each worn surface using a Proscan 2100 noncontact profilometer in conjunction with Proscan and AnSur 3D software. RESULTS: There were significant differences (p < 0.05) among the materials for both generalized and localized wear. The experimental material in both curing modes exhibited significantly less localized wear than F and A and significantly less generalized wear than F and E. CONCLUSION: Self-adhesive materials offer unique handling properties for direct placement of posterior restorations in permanent teeth. The experimental material ASAR-MP4 generated similar wear values to the other self-adhesive materials tested.

Bond Strength of Self-Adhesive Restorative Materials Affected by Smear Layer Thickness but not Dentin Desiccation.

PURPOSE: To use shear bond strength (SBS) testing to determine the effect of surface moisture and smear layer thickness on the adhesion of self-adhesive restorative materials and a universal adhesive. MATERIALS AND METHODS: One single-step self-etch universal adhesive, Prime & Bond Active (PA), was used to bond Ceram.x Spectra ST HV composite resin to dentin and enamel using the self-etching technique. Three commercially available restorative materials and one newly developed material with self-adhesive properties, Activa (A), Fuji II LC(F), Equia Forte (E), and ASAR-MP4 (S), respectively, were also bonded to enamel and dentin prepared moist and dry and to dentin prepared with a thick smear layer. Shear bond testing was performed using an Ultradent bonding apparatus. RESULTS: The universal adhesive generated the highest SBS to dentin and enamel, followed by the newly developed material. None of the materials tested were significantly affected by the moisture conditions on enamel or dentin. The thickness of smear layer significantly affected SBS to dentin for S, F, and E. However, S and F still exhibited higher shear bond strength to dentin with the thicker smear layer compared to the other self-adhesive materials. Only the universal adhesive in self-etch mode was not affected by the thicker smear layer and maintained significantly higher SBS. CONCLUSION: None of the materials tested were affected by bonding to overdried dentin or enamel. All of the self-adhesive materials exhibited lower SBS to specimens with a thicker smear layer. The newly developed material ASAR-MP4 compared favorably to the other self-adhesive materials tested under all test conditions.

Enamel and Dentin Bond Durability of Self-Adhesive Restorative Materials.

PURPOSE: To use shear bond strength (SBS) and shear fatigue strength (SFS) testing to determine the durability of adhesion of self-adhesive restorative materials compared to composite resin bonded with a universal adhesive. MATERIALS AND METHODS: A universal adhesive, Prime & Bond Active, was used in self-etch mode to bond Z-100 composite resin to enamel and dentin. Three commercially available restorative materials and one experimental material with self-adhesive properties, Activa (A), Fuji II LC(F), and Equia Forte (E) and ASAR-MP4 (S) were also bonded to enamel and dentin. The SBS and SFS were determined for all materials. A staircase method was used to determine the SFS with 10 Hz frequency for 50,000 cycles or until failure occurred. RESULTS: On enamel, S generated similar values to the adhesive/composite materials and higher values than F, E, and A. On dentin, the composite/universal adhesive showed significantly higher SBS and SFS than the self-adhesive materials. S, F, and E generated higher values than A on dentin. CONCLUSION: SBS and SFS values to enamel were similar for all materials tested except Activa which generated lower enamel values. On dentin surfaces, the self-adhesive materials generated similar SBS and SFS, with the exception of Activa. Those values were lower than that generated with composite resin and a universal adhesive.