|Year : 2020 | Volume
| Issue : 1 | Page : 2-7
Retentive strength of luting cements for stainless steel crowns: A systematic review
Shruti Virupaxi, Ramya Pai, Praveen Mandroli
Department of Paediatric and Preventive Dentistry, Maratha Mandal's NGH Institute of Dental Sciences, Belagavi, Karnataka, India
|Date of Submission||22-Oct-2019|
|Date of Decision||09-Jan-2020|
|Date of Acceptance||05-Feb-2020|
|Date of Web Publication||12-Mar-2020|
Dr. Ramya Pai
Department of Pediatric and Preventive Dentistry, Maratha Mandalfs NGH Institute of Dental Sciences, Bauxite Road, Belagavi - 590 010, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Stainless steel crowns (SSCs) are unique coronal restorative materials used commonly in the management of primary teeth with extensive caries. Aim: The aim of this study was to perform a systematic review to evaluate the retentive strength of luting cements for SSCs. Materials and Methods: Two reviewers performed a database search of the studies published from 2004 till date. The inclusion criteria were papers published in the English language andin vitro studies on retentive strength of SSC on primary molars. All potentially relevant studies were identified by the title and the abstract. After the full-text analysis, the selected studies were included in the systematic review. Results: Sixteen nonduplicated studies were found. However, after reviewing the articles, only seven were included. Risk bias was assessed. Out of seven studies included in the systematic review, five studies presented medium risk of bias and two studies showed high risk of bias. Conclusion: Within the limitations of this study, thein vitro literature seems to suggest that the use of self-adhesive resin cements shows higher retentive strength, followed by resin-modified glass-ionomer cement (RM-GIC) and conventional GIC. However, RM-GIC can be a preferred luting agent due to its clinical advantages over resin cements. Thus, it can be concluded that choice of cement will depend on individual patient needs and clinical situation.
Keywords: Luting cement, retentive strength, stainless steel crown
|How to cite this article:|
Virupaxi S, Pai R, Mandroli P. Retentive strength of luting cements for stainless steel crowns: A systematic review. J Indian Soc Pedod Prev Dent 2020;38:2-7
|How to cite this URL:|
Virupaxi S, Pai R, Mandroli P. Retentive strength of luting cements for stainless steel crowns: A systematic review. J Indian Soc Pedod Prev Dent [serial online] 2020 [cited 2020 Jul 7];38:2-7. Available from: http://www.jisppd.com/text.asp?2020/38/1/2/280515
| Introduction|| |
Stainless steel crowns (SSCs) were first introduced in the 1950s by Dr. Humphrey. These are unique coronal restorative materials used commonly in the management of primary teeth with extensive caries. Many studies have reported that SSCs are most-efficient solution in managing multisurface carious lesions in primary teeth.,,,
Although the clinical success rate of SSCs is high, the main reason for its lack of longevity is loss of the crown due to cementation failure., The key retentive feature of SSC depends on the close adaptation of crown margin to the tooth surface in undercut area and utilization of suitable luting cement which fills the gap between tooth structure and crown.,
The ideal properties of luting cement include biocompatibility, low solubility, good marginal seal, minimal film thickness, low viscosity, easy manipulation, and sufficient working time with rapid set. Other crucial properties for the overall success of luting cements are high tensile strength and maximum compressive and retentive strength.,
There are various materials used for luting of crowns over the years, both nonadhesive (zinc phosphate cement and polycarboxylate cement) and adhesive cements (glass-ionomer cement [GIC], resin-modified [RM] GIC, and resin cement).
Although there are several studies that investigate the retentive strength of various luting cements for SSC, they present heterogeneous methodology and results are variable.,,,,,, Therefore, our aim was to systematically and critically review the studies that evaluated the retentive strength of various cements used for luting of SSC on primary molars.
| Materials and Methods|| |
This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The following electronic databases were used for the selection of the primary studies: PubMed and Cochrane (from 2004 till date). The population, intervention, comparison, and outcome as a search strategy are presented in [Table 1].
|Table 1: Population, intervention, comparison, and outcome as a search strategy in databases|
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The search was conducted using the following terms: “(Deciduous molar OR primary molar) AND (Stainless steel crown) AND (luting cements).” To ensure the wide search, no language filters were applied. In addition, the bibliographies of the final selected articles were hand-searched to identify any relevant publications that were not identified earlier.
- Papers published in the English language from 2004 till date
- In vitro studies on retentive strength of SSC on primary molars.
- Studies conducted on luting cements for cast metal crowns
- Studies comparing mechanical retention methods (sand blasting/groves) with luting cements
- Studies evaluating other than retentive strength (micro leakage, marginal fit, and tensile strength)
- Unpublished manuscripts and thesis, book chapters, case studies, and literature reviews were excluded.
Literature search and search strategy
Two reviewers independently screened all retrieved titles and abstracts. If one reviewer considered a publication as having met the inclusion criteria, the full text was obtained. Abstracts considered as potentially eligible, as well as those with not enough information, were considered for full-text assessment. Any differences regarding eligibility were resolved through consensus, and in case of disagreement, a third reviewer was consulted before a final decision was reached [Figure 1].
Two reviewers independently extracted data simultaneously using a standardized outline. General information such as authors and year of publication were collected from each study. In addition, the following specific characteristics were also collected: (i) sample size, (ii) type of tooth, (iii) cements included, (iv) testing method, and (v) results. Later, critical review of the included studies was performed by the authors [Table 2].
Risk of bias
Risk of bias was evaluated according to the article's description of the following parameters for study quality assessment: randomization of teeth, teeth free of caries or restoration, materials mixed according to the manufacturer's instructions, use of similar teeth, description of sample size calculation, testing method specified, and blinding of the operator. If the authors reported the parameter, the article had a “Y” (yes) on that specific parameter; if it was not possible to find the information, the article received an “N” (no). If the data were not reported clearly enough, the article received an NC (not clear). Based on the amount of Ys presented by the article, articles that reported one to three items were classified as having high risk of bias, four or five items as medium risk of bias, and six or seven items as low risk of bias.
| Results|| |
Risk of bias
Out of seven studies included in the systematic review, five studies presented medium risk of bias and two studies showed a high risk of bias. The results are described in [Table 3], according to the parameters considered in the analysis.
|Table 3: Risk of bias considering aspects reported in the materials and methods section|
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| Discussion|| |
This systematic review is the first to evaluate retentive strength of various luting cements used for cementation of SSC on primary molars.
There are several studies done to test the retentive strength of various luting cements such as zinc phosphate, zinc polycarboxylate, glass-ionomer, resin-modified glass-ionomer, and adhesive resin cements. Hence, this systematic review was done to obtain collective data which were analyzed together, giving support for the clinician on evidence-based decision-making.
Out of seven studies included in the systematic review, two studies have evaluated the retentive strength of zinc phosphate, zinc polycarboxylate, and GIC., The results showed that zinc phosphate presented the highest retentive strength compared to other two cements. The probable cause for the highest retentive strength of zinc phosphate cement is mainly due to three reasons: low solubility; low initial pH, which has an etching effect on enamel, thereby improving bond strength; and its thin film thickness (<25 μ), creating an intimate adaptation in interfaces and better sitting of the crown.,
However, the film thickness is of significance when tooth structure is sound and caries free; thus, the tooth can be prepared in a standardized manner. However, in most clinical situations, there is extended caries in teeth and conditions do not exactly represent those seen in anin vitro condition. Furthermore, zinc phosphate is brittle, has a relatively high solubility in the mouth, and it does not adhere to tooth structure. They are also a potentially caustic substance, to vital pulp tissue due to their low pH.
The remaining five studies have compared glass-ionomer, RM-GIC, and adhesive resin cement. The results showed that adhesive resin cements had higher retentive strength compared to GIC, but no statistical significant differences was seen between adhesive resin cement and RM-GIC.,,,,
One of the studies has shown that GIC has better retentive strength over RM-GIC. The reason for this result could be because RM-GIC was used without a bonding agent as per the manufacturer's instruction.
GIC may be a wise choice for crown cementation in pediatrics due to its advancements such as fluoride release, anticariogenic property, adhesion to tooth and base metal, optimum mechanical characteristics, and high compressive strength.
However, GIC shows variation in its retentive strength value due to its sensitivity during manipulation of powder: liquid ratio. Another reason for low retention of GIC could be due to spontaneous cohesive fracture of cement, due to stress created by contraction on setting and low tensile strength and fracture toughness.
Both conventional and RM-GIC dehydrate and contract in air or humidity. Addition of resin to the brittle composition of conventional GIC significantly increases its fracture toughness. Furthermore, if RM-GIC specimens are kept in extended storage in distilled water, it could improve the bond strength. It has been reported that water sorption and hygroscopic expansion of RM-GIC are useful in improving bonding ability and marginal seal.
Resin luting cements have higher mechanical properties than both GICs and RM-GICs., The resin cement contains a phosphoric acid ester monomer such as 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate) and 5-NMSA (N-methacryloyl-5-aminosalicylic acid). When primer is applied on tooth structure, phosphate esters in the primer would decalcify dentin or enamel, thus improving the micromechanical bonding between the tooth and resin cement. In addition, ionic bonding may occur between the negatively charged phosphate ester monomer and the positively charged calcium ions on the tooth. Therefore, similar chemical interaction can occur between metal crown and phosphate ester monomer, resulting in improved retentive strength.
Furthermore, compressive strength, flexural strength, and modulus of elasticity of resin cements are significantly higher than conventional GIC and RM-GIC. However, this advantage is overlooked by the ability of RM-GIC to release fluoride and lesser clinical steps in the cementation of crown, low technique sensitivity, and low cost.
All the studies included in the review followed the same methodology. The teeth were tested in mechanical testing machine subjected to load until the first sign of dislodgement seen and the value was recorded. Only one study recorded two different values, i.e., first dislodgement which is recorded as retentive strength and complete dislodgement recorded as “peak force.” The difference between first dislodgement and “peak force” was recorded as “delta.” The higher this difference is, the more capable the cement is to tolerate intraoral forces. It is equally important that microleakage increases when first dislodgement happens and allows cement dissolution. If delta is low and is accompanied by delayed visit to a dentist, it may lead to failure in crown.
The results of the present review should be interpreted considering the fact thatin vitro studies have intrinsic limitations when trying to simulatein vivo conditions. Well-designed randomized controlled trials with long-term follow-up periods are needed to provide data for choosing better luting cements for cementation of SSCs.
| Conclusion|| |
Although the articles included in this systematic review showed high heterogeneity and medium to high risk of bias, thein vitro literature seems to suggest that self-adhesive resin cement is a superior luting cement compared with RM-GIC and conventional GIC. However, RM-GIC can be a preferred luting agent due to its clinical advantages over resin cements. Hence, the choice of cement will depend on the individual patient needs and clinical situation.
We acknowledge Dr. Ravi Shirahatti (Professor and Head, Department of Public Health dentistry) for providing support and assistance in review methodology design and statistical analysis.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]