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Alfallaj H. Pre-prosthetic orthodontics. Saudi Dent J. 2020; 32:7-14
Dietschi D, Spreafico R. Current clinical concepts for adhesive cementation of tooth-colored posterior restorations. Prac Periodont Aesthet Dent. 1998; 10:47-54
Magne P, Spreafico R. Deep margin elevation: a paradigm shift. Am J Esthet Dent. 2012; 2:86-96
Frese C, Wolff D, Staehle HJ. Proximal box elevation with resin composite and the dogma of biological width: clinical R2-technique and critical review. Oper Dent. 2014; 39:22-31
Veneziani M. Adhesive restorations in the posterior area with subgingival cervical margins: new classification and differentiated treatment approach. Eur J Esthet Dent. 2010; 5:50-76
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Frankenberger R, Hehn J, Hajtó J Effect of proximal box elevation with resin composite on marginal quality of ceramic inlays in vitro. Clin Oral Invest. 2013; 17:177-183
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Coronal margin relocation (CMR) is a technique that is being increasingly used to manage subgingival defects in cavities in posterior teeth. The aim of this case report and literature review is to arm the dental practitioner with up-to-date scientific literature on this topic, such that they can appropriately incorporate CMR into their practice. Inclusion criteria for the literature review were the use of composite as the material used for CMR and a subsequent indirect restoration. Medline was searched and manual search of bibliographies was carried out. This yielded nine in vitro studies and 12 clinical reports that were considered in this review.
CPD/Clinical Relevance: The CMR technique is being used more widely in dental practice and it is important for dental practitioners to be aware of the evidence base on which to guide their practice.
Article
The management of subgingivally extending carious lesions in posterior teeth poses a common clinical scenario faced in dental practice. Traditionally, surgical and orthodontic crown lengthening has been used to increase crown height in such situations, although it may be considered that additional training would be needed for such techniques.1,2 The evolution of dental adhesive systems and restorative materials however, has led to the increased use of an alternative technique that first appeared in the literature in 1998: cervical margin relocation (CMR).3 It has since also been referred to as ‘deep margin elevation’ (DME) and ‘proximal box elevation’ (PBE), among other names. The technique advocates the direct addition of composite resin onto the cavity floors of posterior proximal subgingival defects to produce a supragingivally displaced margin,4 which can then be used as the margin for a further indirect or, less commonly, direct restoration.4,5 The rationale for this technique includes the improved ease of impression taking and isolation of the relocated margin, while being less invasive and more affordable than surgical crown lengthening options.4
The aim of this article is to present case reports using this technique and to provide a review of the existing literature. Medline was searched using the terms ‘cervical margin elevation’, ‘proximal box elevation’, ‘deep margin elevation’ and ‘coronal margin relocation’. A further manual search of the bibliographies of all selected articles was carried out. The search concluded on 1 April 2020. Inclusion criteria were the use of composite for the elevation of margins of posterior teeth, with subsequent use of an indirect restoration.
Case examples
In 2010, Veneziani proposed a useful classification of cervical cavities into three grades based on the ability to isolate them with rubber dam and on the distance of the cavity margin to the supracrestal connective tissue attachment (Table 1).6 The first case is an example of a grade 1 case according to Veneziani's classification because it could be isolated with rubber dam.
Grade
Definition
1
The prepared cervical margin can be adequately isolated with rubber dam only
2
The subgingival cervical margin cannot adequately be isolated with rubber dam but the biological width has not been violated (distance from margin of over 2mm to connective attachment or over 3mm to bone crest))
3
The subgingival cervical margin is violating the biological width (distance from margin of less than 2mm to connective attachment or less than 3mm to bone crest)
Case 1. CMR procedure
A 38-year-old male patient presented complaining of a 3 month history of a broken, but otherwise asymptomatic, LR5. On examination, a large disto-occlusal cavity was present with a subgingival distal extent involving some element of gingival overgrowth (Figure 1a). Disto-buccal, disto-lingual and mid-distal probing depths of 2 mm were present and there was no bleeding on probing. The tooth provided a negative response to sensibility testing. Radiographically, the cavity was deemed to be extending past the cementoenamel junction (CEJ) with no enamel present distally. The presence of peri-apical pathology was noted (Figure 1b).
Figure 1. (a) Pre-operative, distal cavity margin not visible due to gingival overgrowth. (b) Pre-operative radiographic views: bitewing LR45 (left), long cone peri-apical LR5 (right). (c) Pre-operative, initial rubber dam placement (occlusal view). (d) Pre-operative, initial rubber dam placement (buccal view). (e) Caries removal and inversion of rubber dam into gingival sulcus. (f) Assessment of adaptation of curved sectional matrix at cervical margin. (g) Long cone peri-apical post CMR and core build up, prior to onlay preparation. NB Composite resin used for core build up has inadvertently increased the thickness of composite resin at distal margin. (h) Following CMR, immediate dentine sealing, preparation for onlay and finishing and polishing of CMR composite NB Composite resin at distal margin has been reduced back to 1.5 mm, which was sufficient to give a margin just coronal to the level of the inverted rubber dam.
Following local anaesthesia, a rubber dam (medium gauge, latex free, UnoDent, Witham, UK) was placed to assess isolation of the cavity. At this stage there was less than ideal adaptation of the rubber dam distally, even with the aid of a B4 clamp (Medentra, UK). (Figure 1c,d) Caries removal was then carried out to expose the margin of the cavity and inversion of the rubber dam was performed with the aid of a flat plastic and 3-in-1 air until the rubber dam was inverted within the gingival sulcus, and the entire cavity margin could be clearly visualized (Figure 1e). Root canal treatment was completed using the WaveOne Gold (Dentsply Sirona, Charlotte, NC, USA) rotary system and adaptation of a curved metal matrix (TOR VM, Moscow, Russia) was checked (Figure 1f). Immediate dentin sealing7 was carried out using a selective enamel etching technique with self-etch adhesive (Universal Adhese, Ivoclar Vivodent, UK). The cavity margin was then relocated, while applying digital pressure to keep the matrix firmly in place, with a 0.5-mm increment of flowable composite (Tetric EvoFlow, Ivoclar Vivodent), which was also then used to seal all remaining dentine with a 0.5-mm thickness. The margin was relocated by a further 1 mm using conventional composite (Tetric Evoceram, Ivoclar Vivodent) and a composite core was built up in increments of 1 mm using the same material. Prior to onlay preparation, a radiograph was taken to ensure sufficient adaptation of the CMR composite with cervical dentine (Figure 1g). The tooth was then prepared for a ceramic onlay and the final CMR composite finishing and polishing was carried out using extra fine diamond burs (Schottlander Gold Diamond, UK) (Figure 1h). The marginal adaptation between the CMR composite and cervical margin of the tooth was deemed to be both clinically and radiographically acceptable.
Case 2. Impression and indirect restoration fit
Once cervical margin relocation and preparation of the tooth have been completed, the remaining clinical steps are similar to those normally carried out for indirect restorations. The main factor to consider is bonding of the indirect restoration to the relocated composite margin.
A 29-year-old female patient presented with a failed composite restoration on UL4 (Figure 2a,b). The distal extent of the cavity was subgingival, past the CEJ and a CMR procedure was carried out as in case 1. Unlike case 1, removal of minimal gingival tissue was required (Figure 2c) to enable a sufficient seal with rubber dam and this was carried out using a Thermacut bur (Dentsply Sirona). The need for removal of gingival tissue without ostectomy makes this a grade 2 case according to Veneziani's classification.6
Figure 2. (a) Pre-operative UR5, poor marginal adaptation of composite restoration and marginal staining. (b) Pre-operative long cone peri-apical radiograph UR5678, no clear radiographic enamel present distally. (c) Following gingivectomy, CMR and onlay preparation. NB CMR performed with individual tooth isolation but split dam used to polish CMR margin. (d) Two-stage putty wash impression. (e) Prior to onlay fit; following rubber dam isolation, air abrasion, selective enamel etching and application of self-etch adhesive (f) Immediately following onlay fit and initial polishing (g) Post-operative view following removal of rubber dam and polishing.
The impression was taken using a two-stage putty wash impression technique (Imprep ac light body and putty, UnoDent) (Figure 2d) and a lithium disilicate onlay (e.max, Ivoclar Vivadent) was fabricated in the laboratory. Prior to cementation, rubber dam was applied, the composite was air abraded with 50-μm aluminium oxide (AquaCare, Velopex International, UK), a selective enamel etching technique was carried out with a self-etch adhesive (Universal Adhese, Ivoclar Vivodent) (Figure 2e) and the fitting surface of the onlay was treated with Monobond Etch & Prime (Ivoclar Vivodent) and Universal Adhese (Ivoclar Vivodent) prior to being cemented using heated composite (Tetric Evoceram, Ivoclar Vivodent). Excess composite was removed after a tack cure and polishing was carried out with fine diamond burs. (Schottlander Gold Diamond) (Figure 2f,g).
Review of literature
For the purposes of this review, the literature available on CMR can be separated into in vitro studies and in vivo clinical reports.
In vitro studies on CMR technique
Marginal adaptation, fracture resistance and bond strength
Nine in vitro studies on CMR were found.8–16 All studies compared indirect restorations bonded directly to proximal dentine margins apical to the CEJ with those that were elevated superior to the CEJ with composite resin. Most of these focused on assessing ‘marginal quality’ by using scanning electron microscopy before and after thermomechanical loading (TML).9–12,14,15 Five of these six studies found no significant difference between marginal adaptation of indirect bonded restorations when bonded to elevated composite margins those bonded directly to dentine margins placed below the CEJ.9,11,12,14,15 Contrastingly, one study found poorer marginal adaptation of indirect restorations bonded to elevated margins than those bonded directly to dentine.10 In 2018, however, the first study to assess leakage, rather than marginal adaptation, as the indicator for marginal quality was carried out.13 This found increased nanoleakage between the elevated composite margins and indirect restorations, rather than when directly bonded to the dentine below the CEJ.
Two studies further investigated fracture resistance of teeth with CMR.14,15 Neither of these studies showed a significant difference in fracture resistance in teeth with CMR compared to those without.
One study focused on microtensile bond strength (MTBS) and used composite inlays bonded using either a total-etch or self-adhesive resin cement.16 The inlays bonded onto margins with CMR had an improved bond strength, but this was only statistically significant for those bonded with self-adhesive resin cement.
Choice of materials and placement
These studies used a variety of composite and ceramic indirect restorations and two studies explored the impact of the type of indirect restorative material when used on elevated composite margins, both using CAD/CAM produced restorations.8,14 Spreafico et al8 found no significant difference in marginal adaptation between composite resin and ceramic crowns on CMR margins. Ilgenstein et al14 found marginal adaptation, measured as percentage of continuous margin, did not significantly decrease following TML for composite onlays on elevated margins. However, ceramic onlays bonded to elevated composite margins did suffer a significant decrease in marginal adaptation following TML. This study found no significant difference in fracture resistance between composite and ceramic onlays when bonded to elevated composite margins, although for teeth without CMR, composite onlays had a higher fracture resistance.14
In terms of the material used to elevate the margin, Spreafico et al found no significant difference in marginal adaptation of crowns bonded to margins elevated with conventional composite versus flowable composite.8 The study focusing on leakage also found no difference in leakage when flowable or conventional composite was used.13
Three studies looked further into the effect of layering the composite material used for CMR. One study found no difference in marginal adaptation after TML when composite was layered in two 1.5-mm increments rather than when a single 3-mm composite increment was placed for CMR.12 The other two studies found layering the composite in three 1-mm increments gave better marginal adaptation following TML than if a single 3-mm increment were placed.10,11
In vivo clinical reports
Twelve clinical reports fulfilling the inclusion criteria were found.3,4,6,17–25 Two literature reviews focusing on CMR overall were identified.17,18 One further literature review focused on the periodontal impact of CMR.19 The available literature on this aspect has been expanding in recent times. The first controlled trial of CMR was published in 2018 by Ferrari et al on its influence on periodontal health.20 The first histological study focusing on the effects of CMR was published in 2019 by Bertoldi et al.21 Two studies explore a system of classification of subgingival defects to aid in deciding between CMR and surgical approaches and include case reports.6,23 The purpose of one study is to provide survival rates of teeth with CMR22 and the remaining clinical reports present the CMR clinical technique.3,4,24,25
Longevity of CMR
Bresser et al evaluated the survival rates of 197 teeth with CMR and indirect restorations over a period of up to 12 years.22 Modes of failure were set as secondary/root caries, fracture, debonding, pulpal necrosis and periodontal breakdown. The average evaluation time was 57.7 months and, of 197 indirect restorations, eight were deemed to have failed, giving a survival rate of 95.9%.22
Ghezzi et al reported that 100% of 15 indirect restorations with CMR remained functional after mean follow up of 5.7 years.23 Ten of these also had a surgical approach in conjunction with CMR.
Assessing cases for CMR versus a surgical approach
Two studies reported classifications to aid decision-making between CMR alone or additional use of a surgical approach for management of subgingival margins.6,23 Both articles give a classification into three groups based on three clinical scenarios. The first scenario is cervical margins that can be isolated with a rubber dam alone, and both articles recommend CMR with no surgical management.6,23 Both studies advocate a surgical approach for margins that cannot be isolated with dam alone and differentiate according to cases requiring bone removal or not. Both base this decision on ensuring sufficient biological width/space for supracrestal connective tissue attachment (STA). Veneziani gives set measurements (2 mm from margin to connective tissue or 3 mm to bone crest) to decide whether bone removal is needed.6 Ghezzi et al advocated an approach based on what is needed to obtain rubber dam isolation: if the margin can be isolated following raising of a flap only, then bone removal can be avoided, regardless of measurements.23
Impact of CMR on periodontal health
In their case series of 15 patients who had CMR with or without an additional surgical approach (based on the classification above), Ghezzi et al found a reduction in probing depths and bleeding on probing from baseline in all three groups with CMR after 1 year, with no significant difference between them.23 Bertoldi et al carried out CMR with composite resin on 29 teeth requiring subgingival restorations and found a significant reduction in probing depths and an increase in periodontal attachment at 3 months.21 Secondary flaps were also harvested and histological assessment showed no significant difference in levels of gingival inflammation adjacent to CMR composite and untreated root surfaces.21
However, in a 12-month controlled trial of 35 teeth restored with ceramic indirect restorations, Ferrari et al found significantly increased bleeding on probing around CMR margins compared with those where the indirect restoration was directly bonded to dentine below the CEJ.20
Choice of materials
The majority of the clinical reports advocate the use of rubber dam prior to CMR,4,6,23–25 with only one presenting a case report using cotton roll and dry angle isolation.17 Of the reports that specify the adhesive system used prior to CMR, most present the three-step total-etch adhesive system to be the gold standard,4,17,24 with one using selective enamel etching with a self-etch adhesive.23 The use of sectional or circumferential matrices is also recommended4,6,17,23–25 with curved matrices being specified in two articles.4,24
In terms of the type of composite resin used for CMR, flowable,6 conventional23 and a flowable composite base with overlying conventional composite17,25 have all been advocated with two studies stating either flowable or conventional composite can be used.4,24 Both ceramic4,17,20 and composite6,23–25 indirect restorations were used. Sandblasting/air abrasion4,24 and use of a primer17,23 onto the CMR composite prior to cementation of indirect restoration have also been carried out.
Discussion
Despite being introduced in the literature in 1998, the evidence base on CMR is still relatively limited. In vitro studies have shown positive results for marginal adaptation, fracture resistance and MTBS in teeth with CMR. Clinical survival rates are also promising, although there is a limited number of these studies. Studies on the impact on periodontal health have given conflicting results but the evidence in this area is expanding and an interesting area for research is to decide when surgical approaches are appropriate. There is also some question over leakage around CMR margins and further studies assessing this, particularly in vivo, would be beneficial.
There is little evidence to differentiate between use of flowable or conventional composite for CMR or to decide between composite or ceramic indirect restorations but layering of CMR composite is likely to be favourable.
Overall, there is still limited high-quality evidence on CMR with indirect restorations. There is a need for more randomized controlled clinical trials including on the periodontal impact of CMR and impact of leakage at the margin between the CMR composite and dentine on longevity. On the basis of the available literature, CMR offers a promising option to manage subgingival posterior defects as an alternative or in conjunction with surgical approaches. However, as concluded in the previous literature reviews,17,18 more scientific evidence is still required. It should be added that, as many cases of CMR are directly as a result of caries, patients requiring the use of this technique should be counselled regarding their diet and caries activity.
