3M Scotchbond Universal Adhesive

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3M Scotchbond Universal Adhesive

April 2020

Modern dentistry is minimally invasive dentistry. The progress in adhesive dentistry in the last few decades allows clinicians to confidently bond onto tooth substrate without utilising any retentive and resistive form in our tooth preparations. In other words, we are conserving more tooth structure than ever before and hence promoting the longevity of the tooth.


What do we look for in an ideal bonding system?

  • Provide adequate bond strength to different types of dental substrates (i.e. sound, affected dentine, sclerotic dentine as well as enamel).

  • Resist wear and water sorption

  • Resists microleakage

  • No post-op sensitivity


When comparing the different generation of adhesives, 3 bottle adhesive systems (4th generation adhesives) has the greatest bond strengths to enamel e.g. 3M Scotchbond Multipurpose (3M ESPE, St. Paul., MN, USA). These systems create the thickest hybrid layer without the presence of a smear layer. When used correctly, 4th generation adhesives are the gold standard of adhesive systems (Hamouda et al 2011).


However, the 4th generation adhesives are also the most technique sensitive as they require multiple steps and the presence of moist dentine. They require etch, rinse, drying and application of hydrophilic primers followed by a hydrophobic adhesive layer. There are potential errors that may occur during any of these steps and as such, these systems can be very technique sensitive. Significant clinical issues occur with either over etching or over drying the dentine as it results in collapse of the collagen fibres, which impedes the primer/monomer penetration. Prolonged etching can form a deep demineralised dentine zone that may not be fully impregnated by the primer and adhesive. This can decrease bond strength and increase post-operative sensitivity (Sofan et al 2017, Carrilho et al 2019).


Bonding systems can generally be grouped into 2 categories: etch-and-rinse and self-etch systems. The universal or multi-mode adhesive (8th generation) has been clinically used since 2011 and is termed the ‘all-in-one’ dental adhesive system. They essentially fall into the family of self-etching adhesive materials. The process is potentially simplified with one bottle containing the conditioner, primer and adhesive. These types of adhesives may be used in either an etch-and-rinse, selective etch or a self-etch modality (Sofan et al 2017).


Scotchbond Universal Adhesive

Scotchbond Universal Adhesive (3M ESPE, St. Paul., MN, USA) is different to self-etching 7th generation adhesive in that it contains functional monomers that are capable of producing chemical and micromechanical bond adhesion to the dental substrates. They also contain nano-fillers that increases the penetration of the resin monomers and the hybrid layer thickness (Toshniwal et al 2019).


Scotchbond Universal contains the functional monomer - Methacryloyloxydecyl Dihydrogen Phosphate (10-MDP). This is a polymerizable methacrylate group and a phosphate group capable of forming a stable salt with calcium in hydroxyapatite (Lawson et al 2015). This functional monomer has mild-etching properties that allows its application without a separate etching step and produces an ionic bond to hydroxyapatite through nano-layering with calcium present in the hybrid layer (Haak et al 2019, Lawson et al 2015). This enables it to be used with any bonding technique.


It also contains another functional monomer, polyalkenoic acid copolymer and also hydroxyethylmethacrylate (HEMA) as a monofunctional resin monomer cosolvent. It also contains initiators and solvents in the form of water and ethanol. Further promoting the bond is the polyalkenoic acid copolymer which has a chemical infinity for hydroxyapatite. (Haak et al 2019, Lawson et al 2015). It has been suggested that these other components may compete for calcium against 10-MDP (Carrilho et al 2019).


Scotchbond is mildly-acidic (pH 2.7) that serves to partially dissolve the smear layer and demineralize hydroxyapatite enhancing monomer penetration, and imparting the adhesives with potentiation for chemical interactions with 10-MDP and polyalkenoic acid copolymer (Carrilho et al 2019).


Scotchbond also contains silane which may increase the bonding effectiveness to ceramics and tooth structure (Michaud et al 2018). Silane increases the surface energy of ceramic and the wettability of resin cements. It possesses a methacrylate end to co-polymerize with the adhesive and/or resin cement and the silane group to covalently bond the ceramic glass phase. In theory, clinicians do not need to apply a separate silane solution after the glass-ceramic is etched with hydrofluoric acid. Yoshihara et al 2016 found that the silane-coupling agent found in universal adhesives was not very effective and stable, most likely because the mildly acidic nature of the universal adhesives promoted dehydration condensation that prevented bonding to glass. Clinically, the use of a separate silane primer remains recommended to achieve enough silane-coupling effect on etchable ceramics.


A critical step during the application of any water-based adhesive, including universal adhesives, is the water and solvent evaporation time after application of the adhesive. Increasing the evaporation time from the manufacturers’ recommended 5 seconds to 25 seconds results in a significant increase in the 24-hour dentine bond strengths (Luque-Martinez et al 2014). They found entrapment of residual water in the resin-dentine interface compromises the performance of the universal adhesives.

Bonding Protocols


Protocol I: Self-etch


In this modality, we do not use phosphoric acid at all and simply apply the universal adhesive on the tooth surface.



  • If there is clearly no enamel present e.g. root surface restoration

  • Bonding fibre posts

  • Limited time or poor patient compliance e.g. very young patients or dental phobic patients

When used in a self-etch mode, they are essentially one-step self-etch adhesives. Traditional one-step self-etch adhesives (7th generation adhesives) have not performed well in laboratory and clinical studies when compared to two-step self-etch adhesives. The biggest difference with Scotchbond Universal is the presence of 10-MDP (Perdigao et al 2015). 10-MDP contains a polymerizable methacrylate group and a phosphate group capable of forming a stable salt with calcium in hydroxyapatite (Lawson et al 2015). Another chemical reaction occurs between polyalkenoic acid copolymer and calcium in hydroxyapatite.


Adequate bonding can be achieved with either an etch-and-rinse or a self-etch technique.

Studies have shown that there is no improvement in bond strengths to dentine with prior acid etching in mild universal adhesive. For the dentine, the self-etch technique eliminates the possibility of over-etching or over-drying the dentine that may occur in the etch-and-rinse technique.


Chen et al 2015 examined in vitro performance of universal adhesives bonded to human dentine. They found that Scotchbond Universal was able to produce similar bond strengths to dentine when used in either an etch-and-rinse or self-etching mode. The study utilised a thermocycling regime that approximated 1 year of physiological ageing in the oral cavity. In the etch-and-rinse group the bond strength dropped by 8.6 MPa to 47.1 MPa and in the self-etch mode the bond strength dropped 4.1 MPa and remained relatively high at 55.8 MPa.


The bonding effectiveness of Scotchbond Universal may be the result of a two-fold mechanism: micro-mechanical interlocking at the dentine surface and chemical bonding between the functional monomer 10-MDP and residual apatite on the collagen fibrils. In addition, the favourable bonding to dentine may be partially be due to the affinity of polyalkenoic acid copolymer for calcium in hydroxyapatite (Haak et al 2019).


Universal adhesives are now increasingly used in paediatric dentistry. The hybridization that these materials create in primary dentine is consistent with and similar to the hybridization provided by total etch dentine adhesives.


Haak et al 2019 found that Scotchbond Universal performed better than a 4th generation adhesive in treating non-carious cervical lesions. It was likely that this was due to insufficient mechanical and chemical conditioning of sclerotic dentine. Hence, it may be advantageous to use a Universal adhesive in sclerotic dentine situations.




  1. Apply adhesive and rub it in for 20 s with a microbrush applicator.

  2. Gently dry with water-free and oil-free air for 5-25 s to evaporate the solvent or until the adhesive doesn’t move.

  3. Light cure for 10 s (> 1000 mW/cm2).


Figure 1. Scotchbond Universal used in a self-etching protocol. Post preparation made for a fibre post and no enamel identified. A self-etching protocol indicated. Fibre post cemented in place with RelyX Ultimate and subsequent placement of a dual-cure core material and a lithium disilicate CADCAM crown.

Protocol II: Total etch


This mode involves applying phosphoric acid on the total preparation on enamel and dentine.


Indication for total-etch

  • Bonding to unground enamel or if the preparation is solely in enamel.

  • Bonding attachments for clear aligner therapy


The main disadvantage with the self-etching modality is the inability to deeply etch the enamel compared to phosphoric acid etching. This leads to inferior bond durability and higher rates of marginal discolouration, especially when compared to the gold-standard 4th generation adhesives (Sofan et al 2017).


Scotchbond Universal performs well on dentine, however, as it is a mild adhesive it is unable to etch enamel well. Scotchbond Universal bond strength to enamel has been reported as 28.7 MPa in self-etch mode and 40.1 MPa in etch-and-rinse mode. This reduction in bond strength results in marginal staining and marginal leakage.


Rosa et al 2015 found that Scotchbond Universal (pH – 2.7 compared with pH – 0.1 – 0.4 of 37% phosphoric acid) and prior acid etching with phosphoric acid increases enamel bond strength. They found that mild-adhesive systems both etch-and-rinse or self-etching modes created adequate bond strengths to dentine.



  1. Apply etchant for 15 s. Up to 30 s is required for primary teeth and teeth with fluorosis.

  2. Rinse thoroughly with water for 20 s and dry with water-free and oil-free air or with a cotton pellet; do not overdry.

  3. Apply adhesive and rub it in for 20 s.

  4. Gently dry with water-free and oil-free air for 5-25 s to evaporate the solvent or until the adhesive doesn’t move.

  5. Light cure for 10 s (> 1000 mW/cm2).


It is always advisable to etch enamel in either a total etch technique or a selective-etch technique.

Summary Total Etch.JPG

Figure 2. Scotchbond Universal used in a total-etch protocol. Minimal preparation made for composite resin veneers. Preparation was largely in enamel and sclerotic dentine.

Protocol III: Selective-etch


This mode involves applying phosphoric acid on the enamel only.



  • Whenever there is the presence of enamel and dentine


Whenever bonding to enamel is necessary, etching of the enamel is definitely preferred because of the micromechanical interaction appears to achieve a durable bond to enamel.


The weakest property of mild adhesives is their bonding potential to enamel. In order to create sufficient retentive etching pattern at enamel an additional selective etching of the enamel margins is highly recommended. Therefore, selective enamel etching prior to the application of Scotchbond Universal is an advisable strategy for optimizing bonding (Rosa et al 2015). This results in higher bond strengths to enamel, clinically better marginal integrity and absence of marginal discolouration (Haak et al 2019).


There is some debate whether universal adhesives should be applied as a total etch technique on both enamel and dentine as the etching process removes calcium from dentine. This removal of calcium from the interface may eliminate the potential ionic bonding between calcium and 10-MDP and polyalkenoic acid copolymer in Scotchbond Universal (Perdigao et al 2015, Chen et al 2015). By using a selective-etch technique will still provide calcium for potential bonding with 10-MDP and polyalkenoic acid copolymer.


  1. Apply etchant to enamel for 15 s. Up to 30 s is required for primary teeth and teeth with fluorosis. Aovid accidental etching of dentine.

  2. Rinse thoroughly with water for 20 s and dry with water-free and oil-free air or with a cotton pellet; do not overdry.

  3. Apply adhesive and rub it in for 20 s.

  4. Gently dry with water-free and oil-free air for 5-25 s to evaporate the solvent or until the adhesive doesn’t move.

  5. Light cure for 10 s (> 1000 mW/cm2).

Selective Etch.JPG

Figure 3. Scotchbond Universal used in a selective-etch protocol. Carious lesion identified and removed, selective etching of enamel and placement of Filtek Universal Restorative.


An advantage of Scotchbond Universal Adhesive over other types of adhesives is that it is indicated for a wider variety of restorative procedures and adhesive modalities (Perdiago et al 2015). The clinical applications for Scotchbond Universal Adhesive ranges from bonding crowns, inlays, onlays, fibre posts, direct restorations and dual-cure resin core materials. The presence of 10-MDP allows chemical bonds to be formed with hydroxyapatite in dentine when used in self-etch mode. Where enamel is present, the literature supports the selective etching of enamel with a scrubbing technique to apply the adhesive system on dental substrates (Carrilho et al 2019).


In practice, we carry a 4th generation adhesive and Scotchbond Universal Adhesive. We have found that there is an advantage of an adhesive that can operate effectively in different modalities of application. It allows the clinician to choose their procedure according to the case.


Regardless of the type of adhesive, it is always incumbent on the clinician to learn and understand their specific adhesive system, it’s idiosyncrasies, it’s strengths and weaknesses and how to maximise its performance (Alex 2009).



Alex G. Adhesive dentistry: the good, the bad, and the ugly. Compend Contin Educ Dent. 2009;30(8):553-568.


Carrilho E, Cardoso M, Ferreira MM, Marto CM, Paula A, Coelho AS. 10-MDP based dental adhesives: Adhesive interface characterization and adhesive stability – A systematic review. Materials 2019;12:790.


Chen C, Niu LN, Xie H, Zhang ZY, Zhou LQ, Jiao K, Chen JH, Pashley DH, Tay FR. Bonding of universal adhesives to dentine – Old wine in new bottles? Journal of Dentistry 2015; 43:525-536.


Farias DCS, Andrada MAC, Boushell LW, Walter R. Assessment of the initial and aged dentin bond strength of universal adhesives. Int J of Adhesion and Adhesives 2016; 70:53-61.


Haak R, Hahnel M, Schneider H, Rosolowski M, Park KJ, Ziebolz D, Hafer. Clinical and OCT outcomes of a universal adhesive in a randomized clinical trial after 12 months. Journal of Dentistry 2019;90.


Hamouda IM, Samra NR, Badawi MF. Microtensile bond strength of etch and rinse versus self-etch adhesive systems. J Mech Behav Biomed Mater 2011;4:461-466.


Lawson NC, Robles A, Fu, CC, Lin CP, Sawlani K, Burgess JO. Two-year clinical trial of a universal adhesive in total-etch and self-etch mode in non- carious cervical lesions. Journal of Dentistry 2015; 43:1229-1234.


Luque-Martinez IVL, Perdigao J, Munoz MA, Sezinando A, Reis A, Loguericio AD. Effects of solvent evaporation time on immediate adhesive properties of universal adhesives to dentin. Dent Mater 2014;30:1126-1135.

Michaud PL, Brown MB. Effect of universal adhesive etching modes of bond strength to dual-polymerizing composite resin. J Prosthet Dent 2018; 119:657-62.

Moro AFV, Ramos AB, Rocha GM, Perez CR. Effect of prior silane application on the bond strength of a universal adhesive to a lithium disilicate ceramic. J Prosthet Dent 2017;118:666-671.


Perdiago J, Swift EJ. Universal Adhesives. J Esthet Restorative Dent 2015;26(6):331-334.

Rosa WL, Piva E, Silva AF. Bond strength of universal adhesives: A systematic review and meta-analysis. Journal of Dentistry 2015; 43:765-776.


Sofan E, Sofan A, Palaia G, Tenore G, Romeo U, Migliau G. Classification review of dental adhesive systems: from the IV generation to the universal type. Annali di Stomatologia 2017;VIII(1):1-17.


Toshniwal N, Singh N, Dhanjani V, Mote N, Mani S. Self etching system v/s conventional bonding: Advantages, disadvantages. Int J Applied Dent Sciences 2019;5(3):379-383.


Yoshihara K, Nagaoka N, Sonoda A, Maruo Y, Makita Y, Okihara T, Irie M, Yoshida Y, Meerbeek BV. Effectiveness and stability of silane coupling agent incorporated in ‘universal’ adhesives. Dent Mater 2016;32:1218-1225.

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