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ImplementingSandwichTechniquewithRMGI(Resin-ModifiedGlassIonomer)

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Implementing Sandwich Technique with RMGI (Resin Modified Glass Ionomer)

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Implementing Sandwich Technique with RMGI(Resin-Modified GlassIonomer)

Dr. Lev Nudelman

Abstract

This lecture will cover the mechanics and scope of sandwich technique with RMGI and provide insightinto obtaining an optimal peripheral seal.

Learning Objectives

1. To understand what materials and techniques are available today for achieving desirable results inrestorations.

2. To understand problems faced in maintaining marginal integrity.3. Determine the suitability of implementing sandwich technique with RMGI in your practice.

One of the critical goals of adhesive dentistry is to restore the peripheral seal of dentin that isinterrupted when enamel is lost as a result of developmental sequelae, trauma, caries or operativeintervention such as preparatory excision. For coronal lesions the exposed strata may be bounded bydentin, enamel or both. Manufacturers continue to work vigorously on resin formulations that will restorethis peripheral seal with operative ease and absolute durability.

The sandwich technique is a layering of materials to create the optimal combination of desirableproperties in a restoration. Two variations of this type of restorations exist: the open and closedsandwich. In a closed sandwich, the dentin is covered with resin-modified glass-ionomer (RMGI)

lining cement. In an open sandwich, RMGI is used to replace the dentin and also to fill the cervicalpart of the box, which results in a substantial part of the glass-ionomer cement being exposed tothe oral environment

Enamel BondThe bond between resin and enamel is generally satisfactory. Most clinicians report that it is possible toachieve seemingly impeccable margins at the visible cavosurfaces when restoring posterior teeth with adirect composite-resin technique. Clinical experience, however, reveals that these resintoothinterfaces deteriorate as they age. More pertinently, in vitro studies have revealed the formidablechallenge of achieving a predictable seal at the proximal margins when tooth coloured restorations areused1.

Dentin BondThe bond between resin and dentin has been more of a challenge, and numerous generations of resin-bonding agents have been energetically touted as the ultimate dentin bonding agent. Regrettably,predictability of outcome has been trumped by simplicity of application; as a result, the newer bondingagents are certainly simple to use (Fifth Generation - one bottle; separate etching, priming and rinsingnot required, or Seventh Generation Self etch single step bonding agent) but are no better (in fact,they are far worse) than the 3-bottle systems of the 1990s.

1Brunton PA, Kassir A, Dashti M, Setcos JC. Effect of different application and polymerization techniques on themicroleakage of proximal resin composite restorations in vitro. Oper Dent 2004; 29(1):549.


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For dentin bonding, it appears far easier to achieve a seal than to maintain it, and in vivo studies haveconfirmed that resindentin bonds degrade in the oral cavity2.

Enamel Protecting DentinSeveral authors have concluded that resin bonded to enamel protects the resindentin bond againstdegradation. It follows from the data on the bond to enamel and dentin that the reliability of adhesiondepends on the peripheral seal to the enamel3.

The ProblemFor a lesion that is entirely bounded by enamel (i.e., an intra-enamel lesion), preserving the dentin sealbecomes a matter of establishing a lasting interface between the resin and the enamel. Unfortunately,not all lesions are of this type, and posterior proximal lesions commonly have gingival margins boundedby dentin. The strength and quality of the peripheral seal is therefore compromised and is susceptibleto hydrolytic degradation.

The SolutionFor a posterior tooth with a proximal margin that extends apical to the cementoenamel junction and forwhich a direct tooth-coloured restoration is planned, the solution is the open-sandwich technique. Thistechnique is not new, but it deserves to be revisited, given the commercial proclivity towardsimplification and the inability of many of the newer materials to bond reliably and permanently to thediverse and compromised dentin substrates that clinicians encounter in clinical practice4. Traditionally,the filler of the sandwich was a glassionomer cement, but resin-modified glass ionomer cements(RMGIC) have superior mechanical properties and bonding strength to dentin. A previous studyinvestigating the durability and cariostatic effect of a modified open-sandwich restoration using anRMGIC concluded that it had acceptable durability for the extensive restorations evaluated5.Furthermore, the open-sandwich technique allows the least amount of micro leakage of the variousdirect restorative options currently available6.

Lessons to be LearnedThe case illustrated here was specifically chosen to demonstrate how the immediate marginal integritywill invariably deteriorate with time (Fig. 18). Studies have confirmed that the visible margins have lowerleakage scores than those of the proximal gingival margins, which validates the additional effortinvolved in performing the sandwich technique. Currently available dentin bonding agents can maintainthe peripheral seal that is integral to all adhesive procedures only if the seal is bounded by enamel. It istherefore recommended that the sandwich technique be the restoration of choice when proximalgingival margins extend beyond the cementoenamel junction.

The Technique

2Hashimoto M, Ohno H, Kaga M, Endo K, Sano H, Oguchi H. In vivo degradation of resin-dentin bonds in humans over 1 to 3years. J Dent Res 2000; 79(6):138591.3De Munck J, Van Meerbeek B, Yoshida Y, Inoue S, Vargas M, Suzuki K, and other. Four-year water egradation of total-etchadhesives bonded to dentin. J Dent Res 2003; 82(2):13640.

4Suzuki M, Jordan RE. Glass ionomer-composite sandwich technique. J Am Dent Assoc 1990; 120(1):557.5Pereira LC, Nunes MC, Dibb RG, Powers JM, Roulet JF, Navarro MF. Mechanical properties and bond strength of glass-ionomer cements. J Adhes Dent 2002; 4(1):7380.

6Loguercio AD, Alessandra R, Mazzocco KC, Dias AL, Busato AL, Singer Jda M, and other. Microleakage in class IIcomposite resin restorations: total bonding and open sandwich technique. J Adhes Dent 2002; 4(2):13744.


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After removal of the caries and placement of the matrix, the tooth is conditioned with polyacrylic acidaccording to the manufacturers directions. A single gingival increment of RMGIC is applied by syringeand is allowed to cure or is subjected to light polymerization. The restoration is then completed withcomposite resin (Figs. 1 to 17).

Preparation of Cavity

1

When restoring 2 proximal lesionscontaining sound marginal ridges, it isprudent to gain access through thetooth that displays the largest lesionradiographically. Accordingly, a pear-shaped diamond drill was used topenetrate through the enamel of thesecond premolar.

2

A stainless steel protective matrix(InterGuard, Ultradent) was usedduring removal of the caries topreserve those portions of theadjacent tooth that were sound. Around #6 carbide bur was used for thebulk of the excision.

3

Intraoperative view of caries removal.The depth of the premolar lesion hasapproached the cementoenamel

junction, and the molar has asubstantial rim of enamel along thegingival margin.

Prior to Filling

4A wooden wedge is inserted in sucha way that it depresses theinterproximal tissue, revealing theextent of the decay. Round burs arethen used to remove the decay.

5A curved AutoMatrix retainerless band(Dentsply, Woodbridge, Ont.) is placedin a circumferential position and awedge is put into place before theseparating ring is applied. Theseparating ring will provideinterproximal separation, and thewedge will affect matrix adaptation asit is pressed into the proximal spacealong the gingival margin.

6When a G-Ring (Garrison DentalSolutions) is applied, the curve of thematrix becomes distorted. Becausethe position and form of the matrixwill determine the outline of thedefinitive restoration, it is important torefine the curve of the matrix beforeplacing the restorative material.


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Materials Application

7A 37% polyacrylic acid(ProEtch, Silmet Ltd.) isapplied to remove the smearlayer in preparation forapplication of the sandwichlayer of the resin-modifiedglassionomer cement

(ProBase, Silmet Ltd).

8

RMGIC (ProBase, SilmetLtd.) is placed into position.Place the RMGIC as accuratelyas possible to avoid placing iton the occlusal cavosurfacemargins.Once the RMGIC hasbeen polymerized, the entirecavity is etched with phosphoricacid in preparation for thecomposite resin restoration

9An ample amount of bondingagent (ProLink, SilmetLtd.) is applied on dentin.When the restoration retentionarea lies primarily within dentinit is necessary to apply asecond layer.

10The first increment ofcomposite resin (ProFilSilmet Ltd.) shade A2 isapplied. The separating ringhas been removed toaccommodate a slight verticalmovement of the matrix so thatthe margin can be slightlyoverextended.

11The final occlusal increment isshaped into the correctocclusal form using finecomposite instruments. Notethat no attempt was made toround the distal marginal ridgebefore polymerization.

12The band is disconnected, andexcess composite along theaxial margins is removed withfinishing disks. The disks areinserted laterally into theproximal space and are used tocut back the excess marginal

height.

13The tip of an Enhance polishingpoint is used to reduce themarginal ridge along theinterior to maintainphysiological roundnessocclusally.

14Completed RMGIC sandwichrestoration on the premolar.The absence of sharp anglesand the marginal ridge werecreated by the disk (used onthe external surface) andpolishing point (used on theinternal surface).

15A BiTine ring and anatomicallyprecontoured Palodent matrixwere used to restore theproximal border of the firstmolar. The sandwich techniquewas not needed here, as therewas a rim of enamelcircumferential to the lesion.

16The matrix is reflectedalongside the premolar to allowprotective access for finishingthe axial surfaces of the molarwith the disk. The reflectedmatrix prevents inadvertentgouging of the proximallyrestored tooth.

17Completed restorations displaythe appropriate physiologicalcontours. The interfacial (resinenamel) marginal fidelity is aconsequence of the meticulousfinishing sequence.

18Postoperative view of therestorations 26 months later.Overall, the physiological formhas been maintained.


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ObjectiveTo understand the mechanics, indications and science behind the Sandwich Restorative technique

utilizing Resin Modified Glass Ionomers.

Course Review Questions:1. One of the critical goals of adhesive dentistry is?

a) Restore the peripheral seal of dentin.

b) Eliminate the use of etch to adhere to dentin.

c) Match the color of enamel.

d) Absorb moisture over time.

2. True or False. For dentin bonding, it appears far easier to achieve a seal than to maintain it.

a) False

b) True

3. Traditionally, the filler of the Sandwich was a glass ionomer cement however ,

a) Zinc Phosphate Cement shows less wear against enamel.

b) RMGIC have superior mechanical properties and bonding to dentin.

c) Release NaCl into the surrounding dentin to prevent decay

d) Will be digested over time.

e) All of the above

4 The open sandwich technique allows the least amount

a) of mercury to wash out into the dentin preventing decay.

b) composite to be utilized in restoring a class VI restoration.c) recession around cervical class V lesions.

d) of microleakage of the various direct restorative options currently available.

5. Select the correct statement or statements:

a) Studies have confirmed that the visible margins have lower leakage scores than those of the

proximal gingival margins.

b) Currently available dentin bonding agents can maintain the peripheral seal that is integral to all

adhesive procedures only if the seal is bounded by enamel.

c) The proper sequence to the sandwich technique is 37% poly acid, RMGIC, composite

restoration.d) All of the above.

Caution: After reading this article, the techniques, procedures, theories and materials presented herein,you must make your own decisions about specific treatment for patients. Use your professional

judgment to determine your need for further clinical testing and education. You must use and rely onyour own clinical expertise before trying to implement new procedures. You are encouraged toparticipate in additional hands on participation courses.


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Handout Evaluation Questions

Please answer the following questions on a scale of 1-5. (5 being strongly agree, 3 neutral and 1strongly disagree)

1. The content in this article was relevant and valuable to your practice

2. Do you feel this handout communicates ideas and concepts clearly

3. The stated objectives were met

4. Material discussed was presented in sufficient depth

5. The quality of this article was what I expect of a self instruction article

How likely are you to use this information in your Practice? Please explain.

What other topics would you like covered?

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Option 1

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Address: Exp. Date:

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Option 2

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Send a copy of the completed survey, questions and an invoiceindicating purchase of any Pro-line dental products by SilmetLtd.of minimum value $100.00 to :

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