Abstract
Objectives
The concept of Cervical Margin Relocation (CMR) consists on placing a base layer of direct resin composite to elevate supra-gingivally the proximal indirect bonded restorations. The aims of this clinical study were to evaluate 1. Bleeding on Probing (BoP) on posterior indirect restorations with one interproximal margin relocated cervically, and 2. possible correlation between depth of the interproximal margins and BoP.
Methods
CMR (Group 1) and shoulder preparations (Group 2) were performed in 35 posterior teeth and evaluated after 12 months (T12). Cavities’ margins were placed below the Cemento-Enamel-Junction (CEJ). CMR was applied in one interproximal box-slot preparation using G-Premio Bond, for dentin hybridization, and universal flow resin composite (GC Co. Tokyo, Japan). Pressed lithium disilicate crowns (LS2) (LiSi Press, GC Co. Tokyo, Japan) were made and placed with proprietary luting material. At baseline and after 12 months, clinical surrogate parameters were assessed; and measurements were recorded for the restorative margin position in relation to margo gingivae by probing, and radiographically, the distance from the bone crest was calculated (in mm). Statistical analysis was performed.
Results
CMR was associated with statistically significant increased BoP scores compared to shoulder preparation at T12 (53.0% vs. 31.5% per site, respectively) (p = 0.10). Gingival Index (GI) and Plaque Index (PI) were not statistically different between both groups. The linear distance between the bone crest and the restorative margin was 2 mm in 13 out of 19 experimental sites of Group 1, and 6 out of 11 of Group 2.
Conclusions
Higher incidence of BoP can be expected around teeth treated with the concept of CMR and in coincidence with deep margins placed at or closer than 2 mm from the bone crest.
Clinical significance
CMR is a clinically sensitive-technique, especially when performed on deep subgingival margins.
1
Introduction
The Cervical Margin Relocation (CMR) was proposed more than 15 years ago, and in the last decade became more and more popular among dental practitioners .
CMR is indicated when the gingival margin of a Class II interproximal cavity cannot be isolated with rubber dam alone, in alternative to perform surgical crown lengthening. CMR consists on placing a base of direct resin composite using a metal interproximal matrix to elevate the interproximal underneath indirect bonded restorations. Consequently, margins can be predictably caught by a conventional impression and/or intraoral optical scanning (IOS) .
A few trials described clinical steps of CMR and others mainly evaluated ‘quality margins’ through SEM observations of the external margins relocated coronally at lower magnifications .
The clinical success in restorative/prosthodontic dentistry can be based on different technical parameters, such as esthetics, precision of the margins, proper function on occlusion, preservation of vitality and fractures of the abutments . It seems mandatory, but beside this feature, healthy periodontal tissues, defined by a Probing Pocket Depth (PPD) less/equal than 4 mm without Bleeding on Probing (BoP).
It might be argued that even slightly subgingival located margins may affect the periodontal health ; and therefore, subgingivally located margins should be avoided whenever possible. Therefore, it has to be emphasized that the extent of the biological width between the cervical aspect of the interproximal composite box and the alveolar bone should be respected .
Recently, Paniz et al. evaluated in a 12 month clinical trial, the periodontal response (BoP and gingival recession) of different full crowns placed with subgingival margins, with teeth prepared alternatively with feather edge or chamfer finishing lines. After one year, both experimental groups displayed more deep inflammation (BoP) in respect to baseline.
Unfortunately, the literature does not report any clinical trial evaluating periodontal tissue response on indirect adhesive restorations placed on posterior teeth with CMR .
Differently, the literature reports about the influence of approximal restorations extension on the development of secondary caries, showing that restorations ending below the CEJ showed significantly increased risk for failure .
The primary aim of this clinical trial was to evaluate BoP on single adhesive indirect restorations made on posterior teeth with one interproximal margin relocated cervically; and secondary, to analyse the correlation between depth of the interproximal margins and BoP. The null hypothesis tested was that there is no statistically significant difference between margins with or without CMR regarding periodontal tissue inflammation (BoP).
2
Materials and methods
A consecutive sample of 35 restorations in 35 patients ( Table 1 ) in need of one single partial crown (onlay) on posterior teeth was placed between January and April 2016. A partial restoration was performed from the pool of patients accessing the Department of Prosthodontics and Dental Materials of the University of Siena, Italy. All of them had an old restoration and some carious tissue to be replaced.
| Age 42 (±16.5) years | Sex (19F, 16M) |
Patients written consent to the trial was obtained after having provided a complete explanation of the aim of the study. Ethical approval was achieved beforehand by the University of Siena, Italy (ClinicalTrials.gov #NCT01835821).
2.1
Inclusion criteria
A total of 35 patients (19 men/16 women, aged 27–54 years, mean age of 45.1 years) received 35 partial-coverage restorations. All patients were periodontally healthy or have been treated successfully before rehabilitation with indirect restorations on posterior teeth (molars or premolars).
Positive response to vitality testing by a one second application of air from a dental unit syringe (at 40–65 p.s.i. at approximately 20° C), directed perpendicularly to the root surface at a distance of 2 cm and by tactile stimuli with a sharp #5 explorer.
2.2
Exclusion criteria
Patients with the following factors were excluded from the clinical trial: 1) not proper age (<18years); 2 pregnancy; 3) disabilities; 4) potential prosthodontic restoration of the tooth; 5) pulpitic, non-vital or endodontically treated teeth; 6) (profound, chronic) periodontitis; 7) deep defects (close to pulp, <1 mm distance) or pulp capping;8) heavy occlusal contacts or history of bruxism; 9) systemic disease or severe medical complications; 10) allergic history concerning methacrylates; 11) rampant caries; 12) xerostomia; 13) lack of compliance; 14) language barriers; 15) plaque index higher than 20.
2.3
Patient selection
After recruitment, oral hygiene instructions were given to the patients and prophylaxis was performed by a Periodontist to establish optimal plaque control and gingival health. After 1 week, the following periodontal measurements were registered by two experienced operators: PPD at two different facial sites (mesial and distal) with a periodontal probe (UNC periodontal probe, Hu-Friedy), rounding the measurements to the nearest millimetre, plaque index (PI), according to Löe and Silness ; gingival index (GI), according to Löe and Silness ; gingival bleeding on probing (BoP), according to Ainamo and Bay . Intra-examiner calibration took place before initiation of the study by examination of ten patients twice, hours apart . The sequence of examiners was random. Measurements were accepted as calibrated if 90% of the recordings could be reproduced within a difference of 1 mm.
The inter-examiner agreement for the assessment of the variables was determined with the intra-class correlation coefficient (ICC). For the two examiners, t -test (α = 0.05) revealed no statistically significant differences. All restorative procedures were performed under local anaesthesia (Articaine with 1:100.000 epinephrine) by a single experienced prosthodontist (Faculty member, MF). Intraoral X-rays were made before starting the treatment.
Following anaesthesia, rubber dam was placed, caries detector was applied and all detected carious structures were excavated, and any restorative material was removed.
The preparation was performed using conventional diamond burs in a high-speed hand piece, with no bevel on margins. The preparation design was dictated by the extent of decay, pre-existing restorations and the preparation guidelines define by the manufacturer of the restorative materials ( Fig. 1 a and d). Cavities’ preparation must provide at least 1 mm space at the cervical margin and 1.0–1.5 clearance occlusaly. At least one occlusal cusp was covered. The Residual Dentin Thickness (RDT) was evaluated on a periapical radiograph, and teeth with RDT thinner than 0.5 mm were excluded. Interproximal margins were located below cementum-enamel junction into cementum-dentin. The decision where to place CMR was taken flipping a coin for each tooth.
Consequently, two groups were allocated: Group 1 corresponded to the interproximal margin in which CMR was performed and Group 2 to the other interproximal margin in which the crown was luting directly to dental structures.
Caries cleaning of the affected area was performed after placing a first matrix band to retract and simultaneously protect the soft tissue, the curvature of the metal matrix was properly adapted to the curvature of the tooth to achieve the best cervical fit was possible . In one proximal box CMR procedure was performed using G-Premio Bond, simultaneously used to perform for hybridization of entire exposed dentin of the entire cavity, and universal flow resin composite applied in two or three thin layers depending the depth and size of the cavity (GC Co. Tokyo, Japan) ( Fig. 2 a and d). After final cavity’s preparation, an impression was taken (Ex’lance, GC Co., Tokyo, Japan) ( Fig. 2 e) and sent to the laboratory in order to make the restoration using lithium disilicate (LS2) press material (LiSi Press, GC Co. Tokyo, Japan) ( Fig. 3 a). A temporary restoration was made with heat-polymerizing polymethylmethacrylate (PMMA) acrylic resin and luted. Patients were instructed to use a 0.2% chlorhexidine gluconate solution for 7 days until they could perform regular oral hygiene and returned 12 weeks later for the impression procedures, giving enough time for soft tissue adaptation and maturation after teeth preparation. The restorations were milled made in the laboratory, then tried-in, and margins were examined and carefully verified for fit and extension. Rubber dam was always placed to isolate the abutment ( Fig. 3 b). The restorations were luted following manufacturer’s instructions using proprietary’s cement (Link Force, GC Co., Tokyo, Japan) after being sandblasted, etched with fluoridric acid at 5% for 60 s and a coat of multi primer being applied and left to evaporate for 1 min.
Cement excess was carefully removed, and occlusion was slightly adjusted when needed. Intra-sulcular margin position was verified, and oral hygiene instructions were given to the patients. Patients were recalled 2 weeks later and then 3 months after for evaluation and oral hygiene measures reinforcement.
The restorations were placed in the time period between January 2016 and April 2016 and examined for (BoP) at baseline (cementation of the restorations), and after 12 months by two calibrated operators (EFC, ND) ( Fig. 4 a and b).
At baseline, the restorative margin position in relation to the gingival margin was recorded quantifying by probing in mm , and the linear distance from the bone crest was calculated in mm by intraoral x-ray. In addition, intraoral x-rays were made at the 12 month recall as well.
All clinical procedures were made using ∼3.5/4.5 magnification.
2.4
Data analysis
Descriptive statistics were expressed as mean (SD) and valid percentage for continuous and categorical data, respectively. The baseline comparisons between study groups were performed using chi-square test (Fisher exact test with observed frequencies <5) for categorical variables whereas continuous variables were tested using t -test (U-Mann Whitney test if the variables were not normally distributed).
Outcomes were analysed using analysis of covariance (ANCOVA), once assumptions for the convenience were confirmed, with baseline values and age as covariates and study group as independent variable. Least square (LS) mean ± standard error (SE) was calculated for variables involving each outcome. Paired t -test or McNemara test (if applicable) was used to compare outcomes at baseline and 12 months. Level of significance was set at 0.05. SPSS version 21 software (IBM) was used for all calculations.
2
Materials and methods
A consecutive sample of 35 restorations in 35 patients ( Table 1 ) in need of one single partial crown (onlay) on posterior teeth was placed between January and April 2016. A partial restoration was performed from the pool of patients accessing the Department of Prosthodontics and Dental Materials of the University of Siena, Italy. All of them had an old restoration and some carious tissue to be replaced.
| Age 42 (±16.5) years | Sex (19F, 16M) |
Patients written consent to the trial was obtained after having provided a complete explanation of the aim of the study. Ethical approval was achieved beforehand by the University of Siena, Italy (ClinicalTrials.gov #NCT01835821).
2.1
Inclusion criteria
A total of 35 patients (19 men/16 women, aged 27–54 years, mean age of 45.1 years) received 35 partial-coverage restorations. All patients were periodontally healthy or have been treated successfully before rehabilitation with indirect restorations on posterior teeth (molars or premolars).
Positive response to vitality testing by a one second application of air from a dental unit syringe (at 40–65 p.s.i. at approximately 20° C), directed perpendicularly to the root surface at a distance of 2 cm and by tactile stimuli with a sharp #5 explorer.
2.2
Exclusion criteria
Patients with the following factors were excluded from the clinical trial: 1) not proper age (<18years); 2 pregnancy; 3) disabilities; 4) potential prosthodontic restoration of the tooth; 5) pulpitic, non-vital or endodontically treated teeth; 6) (profound, chronic) periodontitis; 7) deep defects (close to pulp, <1 mm distance) or pulp capping;8) heavy occlusal contacts or history of bruxism; 9) systemic disease or severe medical complications; 10) allergic history concerning methacrylates; 11) rampant caries; 12) xerostomia; 13) lack of compliance; 14) language barriers; 15) plaque index higher than 20.
2.3
Patient selection
After recruitment, oral hygiene instructions were given to the patients and prophylaxis was performed by a Periodontist to establish optimal plaque control and gingival health. After 1 week, the following periodontal measurements were registered by two experienced operators: PPD at two different facial sites (mesial and distal) with a periodontal probe (UNC periodontal probe, Hu-Friedy), rounding the measurements to the nearest millimetre, plaque index (PI), according to Löe and Silness ; gingival index (GI), according to Löe and Silness ; gingival bleeding on probing (BoP), according to Ainamo and Bay . Intra-examiner calibration took place before initiation of the study by examination of ten patients twice, hours apart . The sequence of examiners was random. Measurements were accepted as calibrated if 90% of the recordings could be reproduced within a difference of 1 mm.
The inter-examiner agreement for the assessment of the variables was determined with the intra-class correlation coefficient (ICC). For the two examiners, t -test (α = 0.05) revealed no statistically significant differences. All restorative procedures were performed under local anaesthesia (Articaine with 1:100.000 epinephrine) by a single experienced prosthodontist (Faculty member, MF). Intraoral X-rays were made before starting the treatment.
Following anaesthesia, rubber dam was placed, caries detector was applied and all detected carious structures were excavated, and any restorative material was removed.
The preparation was performed using conventional diamond burs in a high-speed hand piece, with no bevel on margins. The preparation design was dictated by the extent of decay, pre-existing restorations and the preparation guidelines define by the manufacturer of the restorative materials ( Fig. 1 a and d). Cavities’ preparation must provide at least 1 mm space at the cervical margin and 1.0–1.5 clearance occlusaly. At least one occlusal cusp was covered. The Residual Dentin Thickness (RDT) was evaluated on a periapical radiograph, and teeth with RDT thinner than 0.5 mm were excluded. Interproximal margins were located below cementum-enamel junction into cementum-dentin. The decision where to place CMR was taken flipping a coin for each tooth.
Consequently, two groups were allocated: Group 1 corresponded to the interproximal margin in which CMR was performed and Group 2 to the other interproximal margin in which the crown was luting directly to dental structures.
Caries cleaning of the affected area was performed after placing a first matrix band to retract and simultaneously protect the soft tissue, the curvature of the metal matrix was properly adapted to the curvature of the tooth to achieve the best cervical fit was possible . In one proximal box CMR procedure was performed using G-Premio Bond, simultaneously used to perform for hybridization of entire exposed dentin of the entire cavity, and universal flow resin composite applied in two or three thin layers depending the depth and size of the cavity (GC Co. Tokyo, Japan) ( Fig. 2 a and d). After final cavity’s preparation, an impression was taken (Ex’lance, GC Co., Tokyo, Japan) ( Fig. 2 e) and sent to the laboratory in order to make the restoration using lithium disilicate (LS2) press material (LiSi Press, GC Co. Tokyo, Japan) ( Fig. 3 a). A temporary restoration was made with heat-polymerizing polymethylmethacrylate (PMMA) acrylic resin and luted. Patients were instructed to use a 0.2% chlorhexidine gluconate solution for 7 days until they could perform regular oral hygiene and returned 12 weeks later for the impression procedures, giving enough time for soft tissue adaptation and maturation after teeth preparation. The restorations were milled made in the laboratory, then tried-in, and margins were examined and carefully verified for fit and extension. Rubber dam was always placed to isolate the abutment ( Fig. 3 b). The restorations were luted following manufacturer’s instructions using proprietary’s cement (Link Force, GC Co., Tokyo, Japan) after being sandblasted, etched with fluoridric acid at 5% for 60 s and a coat of multi primer being applied and left to evaporate for 1 min.
