|Year : 2012 | Volume
| Issue : 4 | Page : 155-158
Restoration of non-carious cervical lesions with ceramic inlays: A possible model for clinical testing of adhesive cements
Michal Staninec, Grant H Tsuji
Department of Preventive and Restorative Dental Sciences, UCSF School of Dentistry, 707 Parnassus Ave, San Francisco, CA, USA
|Date of Web Publication||5-Feb-2013|
Grant H Tsuji
Department of Preventive and Restorative Dental Sciences, UCSF School of Dentistry, 707 Parnassus Ave, San Francisco, CA
Source of Support: None, Conflict of Interest: None
Introduction: There are many luting cements coming to market which claim to be adhesive, but there is no clinical protocol currently for testing these claims. There is a standardized protocol for testing direct restorations bonded to dentin and it is used extensively. Case Report: We describe a clinical procedure for restoring a non-carious cervical lesion (NCCL) with a ceramic inlay using Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) technology and an adhesive resin cement.The procedure was straightforward and the result was good at one month. Discussion: NCCL's can be restored with CAD-CAM technology in one appointment. This technique can be used to clinically test adhesion of luting cements to dentin, similarly to the current standard for direct restorations.
Keywords: Bonding agents, Computer-Aided Design and Computer-Aided Manufacturing, cementation, clinical protocols, dental adhesives, dental bonding, dental materials, dentin-bonding agents, evidence-based dentistry, inlays
|How to cite this article:|
Staninec M, Tsuji GH. Restoration of non-carious cervical lesions with ceramic inlays: A possible model for clinical testing of adhesive cements. Dent Hypotheses 2012;3:155-8
|How to cite this URL:|
Staninec M, Tsuji GH. Restoration of non-carious cervical lesions with ceramic inlays: A possible model for clinical testing of adhesive cements. Dent Hypotheses [serial online] 2012 [cited 2019 Dec 12];3:155-8. Available from: http://www.dentalhypotheses.com/text.asp?2012/3/4/155/106842
| Introduction|| |
The technology of dental luting cements is advancing rapidly with many new cements coming on the market with various claims of adhesive properties. Since most indirect restorations such as crowns, inlays and onlays incorporate a significant amount of mechanical retention and cement failures are rare in the short term, there is no practical clinical testing protocol currently which can give us data on the relative adhesive/retentive properties of various cements. The preparation for porcelain veneers generally lacks significant mechanical retention, but usually consists mostly of enamel, which is etched prior to cementation with resin cements, providing good long term retention.  The longevity of porcelain veneers can give us clinical information about adhesion of cements to enamel, but not to dentin.
When a sufficient amount of tooth structure remains for an indirect restoration, any cement will retain a restoration over the long term. However, there are often challenging clinical situations where the amount of existing tooth structure has been severely compromised by caries, fractures, and previous restorations. In these situations it is often necessary to use build-ups with pin or slots, or possibly elective root canal therapy with a post to gain additional retention. In some situations the inter-occlusal space is reduced to the point that a build-up is not possible.
Luting cement with the strongest long-term adhesion to tooth structure, particularly dentin, and to the restoration would be of great help in these challenging situations and could minimize the need for more invasive procedures.
Adhesive dentistry started with Buonocore's discovery of acid etching to enhance retention of acrylic filing materials to enamel.  Eventually, dentin bonding was developed with glass ionomers and resin-based dentin bonding agents. A large body of literature has been produced dealing with in vitro testing of dentin bonding in various ways. Later, a clinical protocol was developed in conjunction with the ADA Council on Scientific Affairs for clinical testing of dentin bonding agents.  This standardized protocol involves restoring non-carious cervical lesions (NCCL's) with glass ionomer or composite and following the restorations for 18 months. If a material demonstrates 90% retention at the end of the observation period, the material is granted acceptance as a dentin adhesive material.
The existence of this clinical testing and acceptance program has led to an explosion of very clinically relevant knowledge of dentin adhesives. Recent reviews of the literature point to hundreds of clinical studies all over the world which have used the ADA protocol to test dentin adhesives.  It is clear from these studies that a later generation of adhesives does not always bring improved clinical adhesion.
With the widespread use of CAD-CAM technology in dentistry, it is possible to restore NCCL's with this technique in one appointment and use any of the adhesive cements to bond the inlays to the tooth structure. This paper presents a clinical technique using the CEREC system that could be used as a model for clinical testing of adhesive cements.
| Case Report|| |
A patient in private practice had an NCCL restored with the CEREC system (Sirona Dental Systems LLC, Charlotte, NC). [Figure 1]a shows a pre-operative view of tooth #12. The dentist (author GHT) isolated the tooth utilizing the Isolite System and retraction cord [Figure 1]b and prepared the site for a digital impression by first applying CEREC Imaging Liquid (polysorbate liquid) to the surface to enhance powder adhesion.He then dried the wet surface until a uniform sticky film was observed and then he applied the reflective CEREC Powder (titanium dioxide) with the Powder Perfect System onto the tooth [Figure 1]c. Next, he recorded an optical image with the CEREC 3D camera and followed CEREC CAD-CAM protocol to design and mill the definitive restoration [Figure 1]d.
|Figure 1: (a) Pre-operative photo of NCCL. (b) Retraction cord packed (c) Impression powder in place (d) Design of restoration (e) Inlay with etching gel (f) Bonding primer applied to the tooth (g) Inlay pressed into place with cement (h) Immediately after finishing (i) Final result after one month|
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The sprue was preserved to serve as a small handle on the middle of the outer surface. Next, the dentist treated the internal surface of the inlay with 5% hydrofluoric acid gel for one minute [Figure 1]e, thoroughly rinsed with water spray for 15 seconds and dried with a stream of oil-free air. Next, he applied Monobond-S to the clean ceramic surface and allowed it to react for 60 seconds prior to final drying.
The dentist placed retraction cord to help isolate the restorative site and treated the dentin surface by scrubbing Multilink Primer A and Primer B mixed in a 1:1 ratio on the surface for 15 seconds [Figure 1]f. He then applied Multilink Automix luting composite to the inner aspect of the restoration prior to seating it onto the tooth. After coating the inlay and pressing it into place using the small handle [Figure 1]g he applied light pressure to the restoration to minimize voids and to ensure complete seating. Next, he removed gross excess cement with a rubber tip hand instrument and light-cured the cement for 3 seconds prior to removal of residual excess and final light curing of 30 seconds. He then removed the handle using a diamond point, and finished and polished the restoration using the NTI Cera Glaze System. [Figure 1]h shows the results immediately after placement. [Figure 1]i shows the inlay one month later.
| Discussion|| |
The technique presented here is simple and applicable to long term study of retention using adhesive cements.Indirect restoration of NCCL's may not be cost effective as a routine procedure, as direct restorations for these lesions are quite successful without any preparation.However, clinical studies of dentin adhesives are generally sponsored by the manufacturer, so there would be no cost to the patient. It may turn out that the clinical service life of NCCL inlays is as long as that of direct restorations, some of which can last more than five years. That may still not make them cost effective, as an indirect procedure is more time consuming for the dentist.
The main application of this technique would be for long term clinical observation of cement performance in retaining inlays bonded mostly to dentin. As there is generally no mechanical retention in an NCCL, all of the retention is derived from the adhesive properties of the restorative material. In the case of composite resin restorations, the interface is composed of the dentin-resin hybrid layer, the boning agent, and the composite resin. In the case of glass ionomer, the hybrid layer is in direct contact with the restorative material. In the case of a ceramic inlay, the interface is more complex: the hybrid layer, possibly a bonding agent, the luting cement, and then the ceramic material.
Failure mode is an important piece of information for evaluating and improving adhesion. In the case of ceramic inlays, it is possible that the failure could occur between the cement and the inlay. Part of the evaluation of clinical failure should be a high magnification examination of the tooth surface to look for any remnants of the cement. The testing of the cement-ceramic interface should be amenable to in vitro testing by making ceramic-cement-ceramic specimens and subjecting them to accelerated aging procedures such as water immersion and thermal cycling, as is done for dentin-composite specimens. These specimens could also be aged concurrently with the clinical cases.
The current knowledge about direct bonding to NCCL's is abundant and has been reviewed in recent papers.  Overall, the clinical data favors glass ionomer restorative cements for having the best long term retention. The three-step etch-prime-bond systems as well as the two step self-etch primer followed by bonding resin systems also give quite good results. The least reliable systems are one component self-etch systems, which are a more recent development, owing to the desire to simplify the procedure.
The published studies of self-adhesive resin cements are mainly laboratory studies, and meaningful clinical data on retention are lacking.  The relative retentive strength of cements can be tested in vitro on standardized crown restorations,  but it is not known how well laboratory data correlates with clinical retention. Unlike knowledge about direct adhesive restoratives, knowledge about the true clinical adhesive properties of luting cements is virtually non-existent. The ADA specifications for dental cements come from the pre-adhesive era and lack any meaningful tests of adhesion.
Many factors can contribute to failures in adhesive NCCL restorations, including occlusal mechanical stress.  A study testing adhesive cements should be designed so that the cement is the only variable tested.We will not know how long these restorations will last until a long term clinical study is done, but if two or more cements are as the only variables, a comparison of adhesive properties can be made.
Recommendations for a particular clinical procedure or material should be supported by the highest level of evidence available. The hierarchy of evidence generally places meta-analyses and systematic reviews of prospective randomized clinical trials at the top. ,, The best evidence comes from the evaluation actual clinical outcomes that are most relevant to question being asked. The technique presented here could provide the basic data and thus contribute to an evidence-based approach to evaluating adhesive dental cements.
| Conclusion|| |
Non-carious cervical lesions can be restored with indirect ceramic inlays in one appointment using CAD-CAM technology and this procedure can be used to test clinical adhesion of luting cements.
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