Optimizing Dental Bond Strength: Insights from Comprehensive Literature Review and Future Implications for Clinical Practice

This review examines the modifying factors affecting bond strength in various bonding scenarios, particularly their relevance to the longevity of dental restorations. Understanding these factors is crucial for improving clinical outcomes in dentistry. Data were gathered from the PubMed database, ResearchGate, and Google Scholar resources, covering studies from 1992 to 2022. The findings suggest that for dentin-resin bonds, minimizing smear layers and utilizing MMP inhibitors to prevent hybrid layer degradation are essential. In the case of resin-resin bonds, reversing blood contamination is possible, but preventing saliva contamination is more challenging, underscoring its critical importance during clinical procedures. Additionally, while pretreatment on ceramics has minimal impact on bond strength, the influence of specific colorings should be carefully considered in treatment planning. This comprehensive review highlights that although established practices recognize significant bond strength factors, ongoing research provides valuable insights to enhance the clinical experience for patients. Once confirmed through rigorous experimentation, these emerging findings should be swiftly integrated into dental practice to improve patient outcomes.

Effect of surface treatments on optical, topographical and mechanical properties of CAD/CAM reinforced lithium silicate glass ceramics

OBJECTIVES

To investigate the effect of different surface treatments on optical, topographical and mechanical properties of CAD/CAM lithium silicate-based glass ceramics (LSC's) and their combined effect on the output of a light curing unit (LCU).

METHODS

Four CAD/CAM LSC's were investigated: Lithium Disilicate (Emax CAD; EC), Zirconia-reinforced silicates (Vita Suprinity; VS and Celtra Duo;CD) and Lithium Aluminum Disilicate (CEREC Tessera; CT). Ceramic specimens (n = 240) were divided into six subgroups according to their surface treatment: (a) Control, (b) Hydrofluoric acid (HF) 5%, (c) HF 5% + Neutralizing agent (N), (d) HF 9%, (e) HF 9% +N and (f) Self-etching ceramic primer (SEP). Irradiance, power and radiant exposure of a LCU were measured with MARC-LC following ceramic specimen interposition. Direct light transmission (T%) and absorbance (Abs%) of the specimens were measured with UV-Vis spectrophotometry. Roughness (Sa, Sq) and wettability (θ°) were measured with optical profilometry and sessile drop profile analysis, respectively. Biaxial flexural strength (σ) of the ceramic specimens was measured by the ball-on-three-balls method and ceramic specimens were examined microscopically. Statistical analyses was performed by two-way ANOVA followed by post hoc multiple comparisons (α = 0.05).

RESULTS

Acid neutralization decreased T% and increased Abs% in all LSC's and highest T% was exhibited with VS. Neutralized EC, VS and CD displayed higher Sa in HF9, while neutralized CT displayed higher Sa in HF5. Self-etch primer significantly reduced θ° (p < 0.001). σ was observed in the followed ascending order: HF9 +N < HF9 < HF5 +N < HF5 < SEP < Control for all LSC's.

SIGNIFICANCE

Optical, topographical and mechanical properties of the CAD/CAM ceramic blocks were strongly dependent on the type of surface treatment. Results of neutralization post-etching indicate promising potential for future investigations.

Influence of Low-Pressure Plasma on the Surface Properties of CAD-CAM Leucite-Reinforced Feldspar and Resin Matrix Ceramics

The introduction of new ceramic materials for dental restorations is currently a reality; however, little information is available on their surface treatment for the bonding process. Furthermore, surface treatment with plasma on ceramic materials has been recently introduced, although not many studies are available. The aim of this study was to evaluate the surface properties of a leucite-reinforced feldspar ceramic (LIC) and resin matrix ceramic (RMC) after low-pressure plasma treatment. From each material, 48 discs were prepared and subject to surface treatment. The LIC group was treated by hydrofluoric acid (HF) (LIC-HF), plasma with oxygen (LIC-O2), and plasma with argon (LIC-Ar). The RMC group was treated by sandblasting with alumina (RMC-SB), plasma with oxygen (RMC-O2), and plasma with argon (RMC-Ar). The groups whose surfaces were not subjected to treatment were considered as the control group. Surface wettability and roughness was analyzed. The results showed significant differences among the treatments for both ceramics regarding wettability and roughness. Plasma treatments increased the wettability and had a very low effect on the roughness. Plasma treatments achieved similar values for both surface properties in each ceramic group with no differences between both treatments. Plasma treatment seems to be a promising alternative for ceramic surface treatments since it increased the surface energy of the ceramics analyzed and hardly affects the roughness. Further studies are necessary to evaluate the effect of plasma treatment on the bond strength of ceramics.

Orthodontic Bonding: Review of the Literature

BACKGROUND

Patients seeking orthodontic treatment are increasing, and clinicians often have to place brackets on various surfaces aside from enamel. It is crucial to know what materials or instruments are required to bond brackets to each surface.

OBJECTIVE

This study aims to serve as a clinical guideline for the safest and most effective approaches taken to condition various surfaces for bonding to orthodontic brackets and provide background knowledge on the subject.

MATERIALS AND METHODS

PubMed and EBSCO databases were searched, along with the use of Google Scholar search engine, to obtain relevant articles published in English in peer-reviewed journals, from 1955 to 2020. Keywords used were Shear bond strength; Orthodontic bracket; Base design; Etching; Sandblasting; Laser; Conditioning; Enamel; Ceramic; Porcelain; Gold; Amalgam; Composite.

CONCLUSION

Even though orthophosphoric acid is the most widely used enamel conditioning agent, laser etching should be considered to avoid enamel decalcification. Hydrofluoric acid is the current standard for ceramic conditioning; however, its use intraorally should be minimized due to its toxicity. Orthophosphoric acid, CoJet-Sand air abrasion, and laser etching are viable alternatives for conditioning ceramic. Monobond Etch & Prime is toxic and should not be used intraorally. Composite can be conditioned by bur roughening, and the use of ceramic brackets is recommended. Amalgam and gold surfaces can be conditioned adequately by air abrasion. Despite the claims of many authors, the maximum shear forces that orthodontic brackets are subjected to are not 6-8 mega pascal (MPa). Further investigation is required in that regard. More in vivo studies need to be performed to confirm the in vitro results.

Marginal gap and fracture resistance of CAD/CAM ceramill COMP and cerasmart endocrowns for restoring endodontically treated molars bonded with two adhesive protocols: an in vitro study

Endocrowns represent a conservative and esthetic restorative alternative to full coverage crowns. They can be constructed using various CAD/CAM materials that can provide a modulus of elasticity similar to that of teeth. The ability to use of such materials in composite blocks that can be easily repaired is also an advantage, provided appropriate bonding performance is ensured. This study, therefore, evaluated the marginal gap and fracture resistance of two CAD/CAM endocrown materials using two bonding protocols. Thirty-two mandibular molars were evaluated in two groups based on the material type: a Cerasmart group (GC America Inc; n = 16) acting as the control and a Ceramill COMP group (Amann Girrbach, Germany; n = 16). These groups were then classified according to the bonding protocol used: a total-etch bonding protocol (n = 8) and a self-etch bonding protocol (n = 8) implemented using RelyX ultimate adhesive resin cement (3M ESPE). The samples were then subjected to aging by simulating a 1-year thermo-mechanical process. The marginal gap results were statistically insignificant across the material and bonding protocol groups before thermo-mechanical aging. Thermo-mechanical aging significantly reduced the marginal gap distance for Ceramill COMP endocrowns cemented using the total-etch protocol (p = 0.002). No statistically significant difference was recorded for the fracture resistance in either the material or bonding protocol groups (p ≥ 0.05). Both materials and bonding protocols can, therefore, be used in the posterior region providing conservative treatment, adequate marginal gap and fracture resistance.

Effect of Different Neutralizing Agents on Feldspathic Porcelain Etched by Hydrofluoric Acid

Objective The aim of this study was to evaluate the effect of neutralizing agents on the shear bond strength of hydrofluoric (HF)–etched porcelain in nonaging and aging conditions.

Subjects and Methods One hundred and twenty feldspathic porcelain specimens were prepared and divided into six groups to undergo different surface conditioning methods—group 1: control; group 2: HF; group 3: HF + calcium hydroxide; group 4: HF + calcium carbonate; group 5: HF + calcium gluconate; and group 6: HF + ultrasonic. All samples were immersed in 37°C distilled water for 24 h. Half of the samples were thermocycled in water for 5,000 cycles. The shear bond strength test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. Data were statistically analyzed by two-way ANOVA and Tukey's multiple comparison test at a 95% confidence level. The surface micromorphology and surface elements were analyzed using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively.

Results The shear bond strengths of groups 2–6 were significantly higher than the control group in both aging and nonaging conditions ( p < 0.05). There were no significant differences among all of the HF-etched porcelain groups ( p > 0.05). SEM images of groups 2–6 illustrated similar patterns of irregularity on the specimen surfaces. Elemental analysis of EDX demonstrated identical elements on surfaces of specimens of groups 2–6.

Conclusion Within the limitations of this study, shear bond strength values between HF-etched porcelain, HF-etching followed by application of neutralizing agents, and HF-etching followed by ultrasonic cleaning were not significantly different in both nonaging and aging conditions.

Bond and topography evaluation of a Y-TZP ceramic with a superficial low-fusing porcelain glass layer after different hydrofluoric acid etching protocols

Abstract Introduction Despite being one of the most studied ceramics today, zirconia still does not have a well-defined adhesion protocol. Objective Evaluate the influence of different etching times and hydrofluoric acid (HF) concentrations on the zirconia surface and bond strength between a vitrified Y-TZP ceramic and a resin cement. Materials and method The zirconia surface treatments were: sandblasting with silica-coated alumina (Co); glaze application + 5% HF etching for 5s (G5-5s), 10s (G5-10s) or 20s (G5-20s); glaze application + 10% HF etching for 5s (G10-5s), 10 (G10-10s) or 20s (G10-20s) . Then, cement cylinders (3.3 × 3.3 mm) were built up for shear bond test on all specimens. The specimens were subjected to 6000 thermal cycling before the test. Fractures were analyzed by stereomicroscope. Data were statistically analyzed by Kruskal-Wallis and Dunn statistical tests (5%). Extra samples of each group were made to obtain profilometry and scanning electron microscopy (SEM). Result Zirconia-cement bond strength was affected by the ceramic surface treatments (p = 0.001). G10-5s (2.71 MPa) recorded the highest bond strength values, followed by the Co (2.05 MPa) while G5 groups had the lowest bond value. Adhesive failure of the samples predominated. The image analysis revealed G5 groups seem to have a lower roughness when compared to groups treated by 10% HF. The creation of pores in the low-fusing porcelain glass layer surface occurred only when 10% HF was used. Conclusion The low-fusing porcelain glass layer application was able to overcome the sandblasting and obtain a greater adhesive bond to the resinous cement, however, only when 10% HF was used for an interval of 5 seconds.

Effect of two-step and one-step surface conditioning of glass ceramic on adhesion strength of orthodontic bracket and effect of thermo-cycling on adhesion strength

PURPOSE

The adhesion strength of orthodontic brackets bonded to dental glass ceramics was evaluated after ceramic surface was treated with two-step and one-step surface conditioning systems, and subjecting to thermo-cycling.

MATERIALS AND METHOD

A total of forty specimens were fabricated from silica based glass ceramic (lithium disilicate) by duplicating the buccal surface of maxillary first premolar. The specimens were randomly assigned to two experimental groups (n = 20), group one specimens were treated with two-step surface conditioning system (IPS ceramic etching gel™ and Monobond plus™) and group two specimens were treated with one-step surface conditioning system (Monobond etch and prime™). The surface roughness of the specimens after treatment with two-step and one-step surface conditioning system was measured using non-contact surface profilometer. Ten randomly selected specimens from each group were subjected to thermo-cycling and the remaining ten served as baseline. The shear bond strength of the specimens was measured using universal material testing machine. The adhesive remnant index score was calculated, and the results of surface roughness and bond strength were tabulated and subjected to analysis of variance and post hoc tukey's test at a significance level of p < 0.05.

RESULTS

The results of the study showed that the specimens treated with two-step conditioning system had higher surface roughness and bond strength than one-step conditioning system. The majority of the specimens treated with both two-step and one-step conditioned specimens showed adhesive failure after subjecting thermo-cycling.

CONCLUSIONS

Traditional two-step conditioning provides better bond strength. The clinical importance of the study is that, the silane promoted adhesion significantly reduces on exposure to thermo-cycling.

Comparison of access-hole filling materials for screw retained implant prostheses: 12-month in vivo study

BACKGROUND

Screw retained implant prostheses seem to be an efficient restorative method to prevent peri-implantitis caused by cement excess around the abutment. The drawback of the screw-retained prostheses is the difficulty to realize an efficient access-hole filling functionally and aesthetically. Up to now, few in vitro and in vivo studies were reported in the literature. The aim of this study was to evaluate clinical performances of two direct filling materials through a period of 12 months.

METHODS

To pursue a previous in vitro evaluation, this in vivo 12 months prospective study followed up and compared the access-hole filling integrity of a modified 4-META (4-methacryloxyethyl trimellitate anhydride)/MMA-TBB (methyl methacrylate-tri-n-butyl borane) - based resin (M4M) and a photo-polymerizing nano-hybrid composite resin (CR). Twenty-eight access-holes were filled with both materials respectively, then impressions and intra-oral photographs were taken at T = 0, T = 1 M (month), 3, 6, and 12 M. The access-hole surface measurement and the margin analysis (depth and angle) were carried out. The VAS (visual analogue scale) value on marginal discoloration and integrity at the baseline T = 0 and T = 12 M was recorded.

RESULTS

The mean values of the surface areas changes from T = 1 to T = 12 M were 83.3 ± 11.5% for group CR and 77.1 ± 13.1% for group M4M, respectively. (Mann-Whitney test p < 0.05, p = 0.046). The mean marginal depth at T = 12 M for group CR were 141.2 ± 125.5 μm and 132.1 ± 107.8 μm for the group M4M, respectively. (Mann-Whitney test p > 0.05, p = 0.58). The mean values of the angle formed at the margin (T = 12 M) were for group CR 39.5 ± 19.4° and 28.2 ± 17.2° for group M4M, respectively (Mann-Whitney test p < 0.0001). The photographical analysis by VAS values showed no significant difference between CR and M4M groups (Mann-Whitney test p > 0.05, p = 0.848).

CONCLUSIONS

Based on intra- and extra-oral evaluations with the limitation, both CR and M4M combined with a ceramic primer are indicated as promising materials to fill the access-hole. Further long-term investigation is necessary to confirm this finding.

Enamel and Dentin Surface Finishing Influence on the Roughness and Microshear Bond Strength of a Lithium Silicate Glass-Ceramic for Laminate Veneers

Objectives. This study evaluated the influence of cavity surface finishing with diamond burs of different grit mounted on high-speed turbine and ultrasound on the roughness and microshear bond strength (MBS) of a lithium silicate glass-ceramic to enamel and dentin. Methods. Enamel and dentin specimens were divided into seven groups, according to the type of surface finishing: 1200-grit sandpaper (control), two different brands of medium-grit and fine-grit diamond burs in a high-speed turbine; medium-grit and fine-grit CVD (chemical vapor deposition) tips in an ultrasonic device. Roughness parameters (n = 5) and MSBS to a glass-ceramic (n = 10) were determined. Data were analyzed using ANOVA and Tukey's test (α = 5%). Results. Control group showed lower mean roughness readings and groups that used medium-grit diamond burs showed the highest mean roughness values. Regarding MSBS, there was no statistical difference when comparing the groups gritted with the same brand of medium- and fine-grit burs and tips. Conclusions. Cavity surface finishing influenced the roughness parameters and MSBS of a glass-ceramic to enamel and dentin. Medium-grit diamond burs in high-speed turbine showed the highest mean roughness values. Fine-grit CVD tips in ultrasound presented the highest MSBS values for both enamel and dentin.