The Closing Gap Technique. The perfect seal in Class 5 restorations

Debonding of class V restorations is probably the main issue concerning failure of cervical composites, as most clinicians have surely experienced in their daily practice. Class V restorations have been commonly approached as two-stage restorations for many years now. In particular, most clinicians attempt to seal the cervical margin as quickly as they can, usually by layering a very big amount of composite to cover the whole cavity from cervical to coronal, thus dramatically increasing the odds of violent shrinkage and marginal debonding from the very moment the patient is dismissed.

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Fig.1
With the aim of fighting and decreasing the risk of cervical debonding, we developed the Closing Gap Technique back in 2012. This layering protocol is aimed at reducing shrinkage-related complications exploiting strong enamel-composite bonding as a base to build a multi-layered anatomy, up to the cervical margin. In the case chosen to present this technique to the Styleitaliano community, three old restorations needed to be replaced. A different cavity configuration was found in each tooth.

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Fig.2
Let’s start by describing the Closing Gap technique. In order to reduce polymerization shrinkage, composite is layered in progressively smaller increments, from the coronal margin towards the cervical, up to leaving a small gap (about 1 mm). Each layer adheres on 2 surfaces, of which only one is dental structure. There is no stated limit to the number of layers, yet, size and dimensions of the cavity, and consistency of the composite, are factors influencing the number of layers needed to fill a cavity.

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Fig.3
The, final, closing gap is filled last, and virtually creates no contraction thanks to its reduced thickness. Among the advantages of this technique, the main ones are:
• Guided buccal shaping
• Early shade check
• Minimum shrinkage
• Full control over composite packing
• Single-mass technique

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Fig.4
Let’s go back to the clinical case. After removing the old restorations, the rubber dam was placed and a modified 212 clamp applied for maximum retraction. A bevel was created in the premolars, while the cavity on the canine already had a bevel-like configuration. When restoring this kind of lesion, polymerization shrinkage, and consequent debonding, often happen when layering from the cervical to the occlusal. Yet, this cervical detachment is not visible in all cases, which is the reason why it is very rarely acknowledged.

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Fig.5
Selective etching of the enamel was carried out, one tooth at a time.

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Fig.6
Cavity surface after bonding should look shiny and even. The application of the Closing Gap technique is based on the creation of a rounded increment from incisal to gingival, without adapting the composite to the cervical feather-edge margin.

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Fig.7
A first increment was placed using an A3 body shade from coronal to cervical.

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Fig.8
A second increment was placed building up as close as possible to the cervical margin, leaving a gap.

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Fig.9
Detail fo the closing gap about to be filled either with a paste composite or a flowable one, depending on the preference of the clinician.

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Fig.10
Detail of the closed gap. Of course, there are a few disadvantages, such as learning curve, residual cervical excess material, and the use of a single mass. Yet, most of these disadvantages are usually easily overcome.

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Fig.11
The premolars showed a flat profile. The anatomy of the crown allowed for use of the Closing Gap technique.

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Fig.12
Two progressive layers were needed to reach the “gap level”.

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Fig.13
Aspect immediately after rubber dam removal.

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Fig.14
2-year check-up. The surface and the soft tissues show optimal conditions, except for the small brown defect of 2.3.

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Fig.15
With an abrasive rubber tip, the micro defect disappeared immediately.

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Fig.16
Detail of 2.3 at the 2-year check-up.

Conclusions

Although the mechanism of cervical debonding has not been fully cleared yet, clinical findings have shown optimum results in the long term with regards to visible debonding lines and infiltration when the Closing Gap technique was used as a layering protocol for class V restorations. Scientific evidence is being gathered and studies are in progress due to the clinical interest this technique has shown.

Bibliography

1. Shisei Kubo a,*, Hiroaki Yokota b, Haruka Yokota b, Yoshihiko Hayashi Three-year clinical evaluation of a flowable and a hybrid resin composite in non-carious cervical lesions
2. Yazici AR, Baseren M, Dayangaç B. The effect of flowable resin composite on microleakage in class V cavities. Oper Dent. 2003 Jan-Feb;28(1):42-6
3. Mena-Serrano AP, Garcia EJ, Perez MM, Martins GC, Grande RH, Loguercio AD, Reis A. Effect of the application time of phosphoric acid and self-etch adhesive systems to sclerotic dentin. J Appl Oral Sci. 2013 Mar-Apr;21(2):196-202.
4. Borges AB, da Silva MA, Borges AL, Werkman C, Torres CR, Pucci CR. Microshear bond strength of self-etching bonding systems to ultrasound diamond burprepared dentin. J Adhes Dent. 2011 Oct;13(5):433-8.
5. McDonald NJ. Microleakage of Class 5 composite resin restorations: a comparison between in vivo and in vitro Oper Dent 1993 Nov-Dec;18(6):237- 45.
6. Krejci I, Lutz F. Marginal adaptation of Class V restorations using different restorative techniques. J Dent 1991 Feb;19(1):24-32.
7. Costa Pfeifer CS, Braga RR, Cardoso PE. In- fluence of cavity dimensions, insertion technique and adhesive system on microleakage of Class V restorations. J Am Dent Assoc 2006 Feb;137(2): 197-202.

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