Generations of Dental Adhesives: From Etching to Universal Systems

Adhesive dentistry has undergone a revolution over the past seventy years. From the first acid etching of enamel, described by Buonocore in 1955, to today's single-bottle universal systems — each generation has brought a new compromise between ease of application, bond strength, and long-term stability. Understanding this evolution is not merely an academic exercise: the choice of adhesive directly affects the clinical outcome of every composite filling, indirect restoration, and orthodontic bonding.

01Historical ContextWhy Generations Matter

The classification of adhesives into "generations" is well established in the literature, even if not entirely uniform. In their review, Sofan et al. (2017) [1] describe the evolution from the 4th generation (three-step etch-and-rinse) through the 5th–6th generation (simplified systems) to the 7th generation (all-in-one). Van Meerbeek et al. (2020) [2], in an extensive status perspective, point out that generational numbering is a marketing construct — clinically more relevant is the division into etch-and-rinse (E&R) and self-etch (SE) systems, each approach having clearly defined indications and limits.

Even so, the generational view remains a useful didactic tool, because it maps how the philosophy of adhesion has changed: from maximum control over the smear layer, through an effort to simplify, to an effort to achieve universality.

Arandi (2023) [3] stresses that the choice of adhesive should be based on an understanding of the substrate (enamel vs. dentin), not on the marketing label of a generation. Enamel requires acid etching for optimal microretention; dentin is more sensitive to the aggressiveness of the acid.

02Generations 4–5Three-Step and Two-Step Etch-and-Rinse

The 4th generation represents the gold standard of adhesion to enamel. The protocol involves three steps: etching with phosphoric acid (37 %), rinsing, application of a primer, and then bonding. Van Meerbeek et al. (2020) [2] describe the three-step E&R system as the "gold standard" for adhesion to enamel, with consistently the highest microtensile bond strength values.

The 5th generation simplified the protocol by combining the primer and bond into a single bottle (so-called one-bottle systems). Heintze et al. (2011) [4], in a study correlating laboratory data with clinical outcomes, demonstrated that three-step and two-step E&R systems achieve higher bond strength values than self-etch systems — especially on dentin after a longer period of water exposure.

Ivoclar Vivadent — ExciTE F DSC: This total-etch bond (separate phosphoric-acid etching, primer and bond in a single step) is a representative of the 5th generation with an added dual-cure capability. The key innovation is a patented applicator brush coated with a chemical initiator — thanks to which it requires no separate activator even when used with dual-cure or self-cure materials. ExciTE F DSC is indicated primarily for the adhesive cementation of indirect ceramic and composite restorations and for the luting of endodontic posts in combination with dual-cure or self-cure cements (e.g., Variolink® Esthetic).

03Generations 6–7Self-Etch Systems and All-in-One

The 6th generation brought two-step self-etch systems: an acidic primer conditions the smear layer without rinsing, and the bond is applied separately. The advantage is lower postoperative sensitivity on dentin; the disadvantage is weaker adhesion to unetched enamel. Erickson et al. (2009) [5] demonstrated that pre-etching enamel with phosphoric acid before applying SE systems increases bond strength by 27–86 % and brings it in line with the E&R approach.

The 7th generation (all-in-one) combined etching, primer, and bond into a single step. Guéders et al. (2006) [6], in an in vitro microleakage study, showed that all-in-one self-etch systems exhibit statistically higher microleakage than E&R systems — with the exception of moderately strong SE adhesives, which approached E&R.

Ivoclar Vivadent — AdheSE: A two-step SE system (6th generation). An acidic primer conditions the dentin and smear layer without the need for rinsing. Indicated for direct composite fillings, especially in cervical regions where dentin predominates.

04Generation 8Universal (Multi-Mode) Adhesives

Universal adhesives, brought to market from 2011 onward, represent the most flexible category to date: a single product can be used as E&R, SE, or selective-etch. Alsaeed (2022) [7] summarizes that universal systems have become the most popular category on the market, with the key functional monomer being 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate), which forms a stable ionic bond with hydroxyapatite.

Francois et al. (2026) [8], in the largest practice-based study to date (31 201 standardized tests, 90 adhesives/application modes over 25 years), demonstrated that the performance of an adhesive cannot be predicted from its generational category or from the presence of 10-MDP — what is decisive is the individual chemical formulation. Single-dose packaging delivered statistically higher bond strength than bottle systems (p < 0.01).

Universal adhesives offer clinical flexibility, but their true potential depends on the correct choice of application mode according to the substrate — selective-etch on enamel and self-etch on dentin remains the recommended strategy.

Ivoclar Vivadent — Adhese Universal: Ivoclar's flagship product in the 8th-generation category. It contains the 10-MDP monomer and is available in the VivaPen (dosing pen) format as well as the classic bottle. It can be used in all three application modes. The manufacturer declares compatibility with light-cure, dual-cure, and self-cure composites and cements without the need for a separate activator — an advantage over many competing systems. Dantagnan et al. (2026) [9], in a systematic review, confirmed that UA systems provide sufficient bond strength to enamel and to restorative materials, with pre-etching of enamel with phosphoric acid for 15 s further improving performance.

05Practical RecommendationHow to Choose an Adhesive for a Specific Situation

The choice of adhesive is not a question of fashion, but of substrate and clinical situation:

• Enamel-dominant cases (anterior teeth, surface fillings): Three-step E&R or the selective-etch mode of a universal adhesive — enamel requires acid etching for optimal microretention [2].
• Dentin-dominant cases (cervical lesions, deep cavities): SE mode or a two-step SE system — reduces the risk of postoperative sensitivity [3].
• Indirect restorations (e.max, zirconia): Adhese Universal in E&R mode combined with Monobond Plus (silane + 10-MDP primer) — chemical adhesion to the substrate is just as important here as micromechanical retention [7].
• Dual-cure cements: Adhese Universal and ExciTE F DSC are compatible with dual-cure activation without a separate activator — verify compatibility with other systems [2].
• Packaging: Francois et al. (2026) [8] recommend single-dose packaging (VivaPen for Adhese Universal) for consistent results — bottle systems are more prone to formulation degradation from repeated opening.

06Reference

1. Sofan E, Sofan A, Palaia G, Tenore G, Romeo U. Classification review of dental adhesive systems: from the IV generation to the universal type. Annali di stomatologia. 2017. Available from: https://pubmed.ncbi.nlm.nih.gov/28736601/
2. Van Meerbeek B, Yoshihara K, Van Landuyt K, Yoshida Y, Peumans M. From Buonocore's Pioneering Acid-Etch Technique to Self-Adhering Restoratives. A Status Perspective of Rapidly Advancing Dental Adhesive Technology. J Adhes Dent. 2020. Available from: https://pubmed.ncbi.nlm.nih.gov/32030373/
3. Arandi NZ. The Classification and Selection of Adhesive Agents; an Overview for the General Dentist. Clin Cosmet Investig Dent. 2023. Available from: https://pubmed.ncbi.nlm.nih.gov/37692095/
4. Heintze SD, Thunpithayakul C, Armstrong SR, Rousson V. Correlation between microtensile bond strength data and clinical outcome of Class V restorations. Dent Mater. 2011. Available from: https://pubmed.ncbi.nlm.nih.gov/20947156/
5. Erickson RL, Barkmeier WW, Kimmes NS. Bond strength of self-etch adhesives to pre-etched enamel. Dent Mater. 2009. Available from: https://pubmed.ncbi.nlm.nih.gov/19473695/
6. Guéders AM, Charpentier JF, Albert AI, Geerts SO. Microleakage after thermocycling of 4 etch and rinse and 3 self-etch adhesives with and without a flowable composite lining. Oper Dent. 2006. Available from: https://pubmed.ncbi.nlm.nih.gov/16924985/
7. Alsaeed AY. Bonding CAD/CAM materials with current adhesive systems: An overview. Saudi Dent J. 2022. Available from: https://pubmed.ncbi.nlm.nih.gov/35692241/
8. Francois P, Le-Goff S, Attal JP, Gouze H, Lapostolle B. Battle of the bonds: Practice-based standardized dental adhesive testing of immediate dentin shear bond strength over 25 years. J Dent. 2026. Available from: https://pubmed.ncbi.nlm.nih.gov/41687956/
9. Dantagnan CA, Boudrot M, Bosco J, Dot G, Nassif A. Effectiveness of universal adhesives for orthodontic bonding to enamel and restorative materials: A systematic review. Int Orthod. 2026. Available from: https://pubmed.ncbi.nlm.nih.gov/41270430/

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Editorial · Cicero

Tým za platformou Cicero. Píšeme o digitalizaci ordinací, klinickém workflow a o tom, jak technologie mění každodenní praxi.