- Email: [email protected]
Posterior composites: Update on cavities and filling techniques
Accepted Manuscript Title: Posterior composites: update on cavities and filling techniques Author: J. Sabbagh R.J. McConnell M. Clancy McConnell PII: DOI: Reference:
S0300-5712(16)30242-1 http://dx.doi.org/doi:10.1016/j.jdent.2016.11.010 JJOD 2704
To appear in:
Journal of Dentistry
Received date: Revised date: Accepted date:
16-3-2016 2-11-2016 21-11-2016
Please cite this article as: Sabbagh J, McConnell RJ, McConnell M.Clancy.Posterior composites: update on cavities and filling techniques.Journal of Dentistry http://dx.doi.org/10.1016/j.jdent.2016.11.010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Posterior composites: update on cavities and filling techniques
J. Sabbagh; Restorative and Aesthetic Dentistry Department, School of Dentistry. Lebanese University. BeirutLebanon R.J. McConnell; Restorative Dentistry, University Dental School and Hospital. Cork. Ireland M. Clancy McConnell; Restorative Dentistry, University Dental School and Hospital. Cork. Ireland
Corresponding author: Professor Robert J McConnell. [email protected]
Address: Helvic, Ardfoyle Avenue. Ballintemple. Cork. Ireland
Posterior composites: update on cavities and filling techniques
Abstract Objectives: The aim of this paper is to examine cavity design for posterior resin composite restorations and to discuss various resin composite filling techniques. Data: Literature with regard to cavity preparation for amalgam and resin composite restorations has been reviewed. An overview of available bulkfill resin composite systems is provided and a categorization of these systems according to their clinical application and their intended use is outlined. Sources; A literature search was carried out by the authors in Medline Study selection; Pre-defined inclusion criteria based on keywords were included and reviewed. Conclusions: Minimum cavity preparations are advised for posterior resin composite restorations, preserving the greatest amount of healthy tooth structure. For resin composite restorations only the caries lesion needs to be removed with all remaining tooth structure protected for the bonding process. The anticipated outcome of this philosophy will result in the longer survival of teeth.
Newer bulkfill restorative resins allow the operator to complete the restoration in a similar time to the placement of a dental amalgam restoration. Keywords Cavity; Minimal; Amalgam; Resin Composite; Bulkfill;
Introduction:
When placed in optimal conditions and in low caries risk patients, resin composite restorations demonstrate comparable or even higher clinical performance to that of dental amalgam restorations1. Resin composites materials offer the potential of extended survival of the tooth and are more aesthetic than amalgam 2. Resin composites require different clinical skills and operative techniques to that used with dental amalgam restorations. These techniques have now been introduced into many undergraduate dental education programmes. Recent graduates are more competent in using resin composite materials for the restoration of posterior teeth3.
Resin composite restorations support the use of minimum cavity design 4. In contrast to dental amalgam, resin composites do not require a minimum thickness; and when bonded they support the remaining enamel and dentine requiring no additional retentive features5.
The main disadvantage associated with the use of resin composite for restoring posterior teeth is shrinkage on polymerization. Stresses produced during polymerization are a leading cause of adhesive failure, resulting in postoperative sensitivity, marginal staining, and recurrent caries 6 . This polymerization shrinkage creates stresses as high as 13 MPa between the resin composite material and tooth interface exceeding the tensile strength of the enamel often resulting in stress cracking and fracturing of the enamel7. When a resin composite is cured, the surrounding tooth structure may deform 8. This deflection can range from 4 to 6 μm, depending on the filling technique used9. The higher the intensity of the light source, the greater the contraction force at the composite-tooth interface and so the use of high intensity plasma lights is not recommended. Intermittent or lower intensities lights improve the marginal integrity of the restoration because it permits dissipation of the polymerization stress10. To achieve clinically successful posterior resin composite restorations, it is vital to maintain the integrity of the bond and the marginal adaptation to tooth enamel and dentin 10 . Other shortcomings of resin composites are the long placement procedure and achievement of an adequate contact point.
The incremental technique is considered as the standard technique for posterior restorations. The thickness is limited to 2 mm maximum for optimal polymerization and degree of conversion11 . Combined with a three step total
2
etch bonding technique, the restoration of a posterior cavity with resin composite can take twice as long to complete as an equivalent procedure using dental amalgam 2. With the development and use of self-adhesive bonding systems the operator can shorten the bonding procedure and at the same time reduce postoperative sensitivity12 13. Using bulk filling resin composite materials the total time taken to restore a posterior tooth with resin composite is similar to that of a dental amalgam restoration14.
Cavity Design: Greene Vardiman Black (1836–1915), published his concepts and ideas of cavity design for dental amalgam in his text Manual of Operative Dentistry in 1896. Further, he organized 'Black's Classification of Caries Lesions' which is still in use today. He established guidelines for cavity preparation, extension, retention and resistance form which applied to the mechanical requirements of dental amalgam. Design is based on the extent of the disease process and on the physical properties of amalgam. This means that the cavity must be at least 2 mm deep with design features such as undercuts, parallel walls and flat floors. It is also important that while finishing the cavity that the surface enamel is supported. In many cases, amalgam also requires the placement of a lining material.
A new cavity classification was published in 1998 in response to adhesive restorations by Mount et al 15. This emphasized the principle of minimum extension. An FDI review of minimal intervention was published in 200016. Further publications in 200117, 2002 18 and 2003 19 lead eventually in 2006 to a publication which introduced the SiSta classification of cavity design20. Cavities for resin composite restorations are not predetermined by the physical properties of the material. The only criterion for the cavity design is the removal of the diseased tissue and as a result there are no standard cavities for resin composite restorations.21 Cavities can be of minimal depth 4,can have unsupported enamel at the cavo- surface margin, proximal walls and the cervical floor and do not require the placement of a base material. Unsupported enamel in the interproximal box is not removed with a bur or chisel as this can lead to bleeding from the interproximal papilla. The papilla can also be protected by pre-wedging which also assists in the development of a good interproximal contact. The cavosurface margins of 3
proximal boxes to be restored with resin composite are smoothed and finished, but not bevelled22.
In the following table the authors suggest cavity designs for posterior resin composite restorations. These designs are based on the most frequent presentation of caries. Further, these designs may assist students and educators in standardizing resin composite techniques.
4
Table 1. Classification of composite cavities
Description
Preparation 1
Early occlusal caries lesion. Minimal preparation to remove early caries in enamel and dentine.
Occlusal caries lesion Minimal cavity design. No removal of unsupported enamel
Occlusoproximal caries lesion Access to caries through marginal ridge. Shape of cavity is “C” shaped with no extension occlusally or laterally. Unsupported enamel remains on cervical floor of box Occlusoproximal lesion involving occlusal fissures ( replacement of an amalgam) Box is “C” shaped with no removal of unsupported enamel or dentine,
5
Preparation 2
Caries lesion involving cusp Caries cusp is removed with no attempt to remove unsupported tooth structure. Retention is gained using bonding technique
Table 1.
Adhesive process: Management of Operatively Exposed Dentine In most cases, liners/bases are not required under resin composite restorations, as they prevent the bond to dentine. There is evidence of no difference in outcome in terms of post- operative sensitivity when a resin composite is ‘‘bonded’’ or ‘‘based’’23 . Placement of a liner for therapeutic purposes may be required in areas close to the pulp. A recent review on direct and indirect pulp capping concludes that exposure of the vital pulp should be avoided at all times24 . Should a pulpal exposure occur, emerging evidence suggests that MTA is superior to calcium hydroxide 25 22 . Newer products such as Biodentine have potential use in this situation 26 27 28 29
Bonding The bonding of resin composite to tooth structure can be achieved with one of four different etching systems: total-etch 3 step, total-etch 2 step, self-etch 2 step, and self-etch 1 step. The self-etch adhesives have increased in popularity due to their simplified technique and lower incidence of postoperative sensitivity30 . However, the acidic nature and permeability of simplified, self-etch adhesives make them incompatible with self-cured and dual-cured composites 31 . One-step adhesives have a lower bonding 6
effectiveness, attributed in part to the dissolution of hydrophilic and hydrophobic monomers in a highly concentrated solvent, which jeopardizes
7
bond durability32 . Tay33 has demonstrated that single-bottle adhesives, due to the lack of a more hydrophobic bonding resin layer, behave as permeable membranes after polymerization. They permit the continuous transudation of dentinal fluid and do not provide a hermetic seal for vital deep dentin. This may interfere with optimal polymerization of composites and resin cements. The shear bond strengths of self-etching primer/adhesive systems and totaletch, 1-bottle systems to enamel have been shown to be much lower than the other systems, resulting in increased leakage and staining at the enamelcomposite interface. The bonding of these self-etching primers to enamel may depend on their specific composition (pH)34 . The conventional, 3-step, etch-and-rinse adhesives still perform favorably and are the most reliable in the long-term. Multiple studies comparing contemporary adhesives reveal that these adhesives remain the gold standard in terms of durability; whereas simplifying the clinical procedure results in loss of bonding effectiveness35 . The 2-step total-etch systems exhibit slightly lower bond strengths than the 3step systems after aging36 , the introduction of filled, 2-step total-etch systems demonstrate good bond strengths. These filled adhesives provide better coverage of the dentinal substrate. Filled adhesives are associated with a reduction in microleakage when compared to unfilled adhesives 37, 38.
Selection and placement of restorative resin using incremental technique The selection of resin composite is important for the success of the composite restoration. Hybrid and certain nano-particle hybrid resin composites are, in general, appropriate for use in posterior load-bearing situations. As a general rule, the resin composite selected should contain at least 60% filler by volume. Careful technique is required during the placement of resin composite to limit the adverse effects of polymerization shrinkage. According to Feilzer, et al 39 the stress relieving flow is affected by the configuration of the restoration, known as the C-factor. The C-factor is the ratio of bonded (flowinactive) to unbonded or free (flow-active) surfaces. An increase in the number of bonded surfaces results in a higher C-factor and greater contraction stress on the adhesive bond. The Class I restoration is the most common restoration to have post-operative sensitivity due to incorrect filling technique. Class I cavities have five bonded surfaces and have a high C-factor 39 . Joining the opposing walls, buccal and lingual, in one-increment concentrates the contraction forces in the centre of the bulk of the resin composite. By avoiding the union of the buccal and
8
lingual walls in any one increment the centre of contraction is directed towards the walls and away from the centre of the restoration. One study has questioned the clinical significance of the C-factor for Class 1 cavities. However, in this study extensive cavities were used which may have influenced the results 40
Other advantages of the incremental technique are the improved shade and shape control of the restoration and complete curing of the composite. This technique tends to concurrently enhance the depth and adequacy of cure of the resin composite 5. (Photo 1)
Photo 1:
Class I molar restored using incremental technique
Bulk fill resin materials
Reduced polymerization shrinkage resin composites are now available and recent publications would suggest that these perform as ideal as the conventional composite resin systems . 41 , 42 . These resin materials are indicated in medium to deep posterior cavities, can be light cured up to 4-5 9
mm thickness43 and are classified as bulk fill resin restoratives. The major advantages of bulk filled composite resins are increased depth of cure; the percentage of fillers, the translucent shades, the use of some specific photoinitiators and monomers43,44. Their increased depth of cure reduces the clinical application time compared to regular composite restorations 45. Flowable bulk-fill materials: These materials are used to fill the deeper aspects of the cavity up to 4 mm depth with the addition of a conventional resin composite occlusally. They should not be in occlusal contact with the opposing tooth structure because of their low percentage of fillers and low mechanical properties. Fiber bulk fill base material: One material available in this category cannot be placed in open contact areas such as occlusally or interproximaly as fibres need to be protected by a conventional resin composite.
High viscosity bulk-fill materials: These are heavily filled resin composite materials used to fill a cavity up to 5mm deep. They can be dispensed classically from a syringe such as the Xtra Base (Voco); Filtek™ Bulk Fill Posterior Restorative (3M) or activated sonically, Sonicfill (Kerr and Kavo). The use of these systems combined with a self-etch adhesive, represent a reduction in operator time when compared to the incremental technique or the flowable and fibre filled bulk systems. The mechanical properties of some of the currently available paste and flowable forms bulk-fill resin composites have been studied comparing them to commercially available nano-hybrid conventional composites. Leprince et al concluded that bulkfill composites have the advantages of clinical time saving and easy handling when compared to nano-hybrid composites 46. Didem et al investigated the mechanical properties of different types of bulk-filled composites and concluded that the sonically activated system had the highest score among the tested materials and can be used as an alternative to regular resin composite for posterior teeth restoration47 . Other studies have compared the light-curing efficiency and mechanical properties of the some commercially available bulk-fill composite. One such study looked at three bulk filled paste materials and found that the microhardness values of high viscosity bulk-fill materials can differ compared to each other but all showed sufficient depth of cure at 4 mm depth and no significant difference in their flexural strength. The bulk fill materials exhibit less polymerization stress at the tooth-composite interface than the conventional composites 48. Flowable bulkfill materials in
1 0
increments of 4mm demonstrate lower shrinkage force than conventional flowable resin composites 49 Similarly, a sonic activated bulkfill material showed low shrinkage as compared to conventional composite resin materials 50. Unlike conventional Resin composite materials, filling a class I cavity in one increment using a bulk-fill material does not result in postoperative sensitivity. A recently published randomized controlled clinical trial compared the incidence of postoperative sensitivity between teeth filled using an incremental technique with teeth filled using a bulk fill technique. The authors found no significant difference between the two groups in terms of postoperative sensitivity.51 Dentists are seeking a fast and reliable technique to achieve good posterior restorations. Placing a bulk fill restorative restoration using a self etch adhesive technique allows the operator to achieve a high standard posterior resin composite restoration in a similar time to a dental amalgam restoration.
Conclusions The success of composite resin restorations is dependent on an understanding of the physical properties and management of the material and the clinical management of the caries process. For resin composite restorations only the caries lesion needs to be removed with all remaining tooth structure protected for the bonding process. The anticipated outcome of this philosophy will result in the longer survival of teeth. Newer bulkfill restorative resins allow the operator to complete the restoration in a similar time to the placement of a dental amalgam restoration. This paper advises the use of minimum cavity preparations, preserving the greatest amount of healthy tooth structure and introduces the newer bulk-fill resin composite restorative materials.
10
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Tyas MJ, Anusavice KJ, Frencken JE, Mount GJ. Minimal intervention dentistry-a review. FDI Commission Project 1-97. Int Dent J 2000 Feb;50(1):1-12. 17
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Mount GJ, Tyas JM, Duke ES, Hume WR, Lasfargues JJ, Kaleka R. A proposal for a new classification of lesions of exposed tooth surfaces. Int Dent J 2006 Apr;56(2):82-91. 21
Kidd E. Clinical Threshold for caries removal. Dent Clin North Am. 2010.54:541-549
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Opdam NJ, Roeters JJ, Kuijs R, Burgersdijk RC. Necessity of bevels for box only Class II resin composite restorations.Journal of Prosthetic Dentistry 1998;80:274–9. 23
Burrow MF, Banomyong D, Harnirattisai C, Messer HH. Effect of glass-ionomer cement lining on postoperative sensitivity in occlusal cavities restored with resin composite – a randomized clinical trial. Operative Dentistry 2009;34:648–55. 24
21. Bjørndal L, Reit C, Bruun G, Markvart M, Kjaeldgaard M, Näsman P, Thordrup M, Dige I, Nyvad B, Fransson H, Lager A, Ericson D, Petersson K, Olsson J, Santimano EM, Wennström A, Winkel P, Gluud C. Treatment of deep caries lesions in adults: randomized clinical trials comparing stepwise vs. direct complete excavation, and direct pulp capping vs. partial pulpotomy. Eur J Oral Sci 2010 Jun;118(3):2907 25
Hilton TJ, Ferracane JL, Mancl L, Northwest Practice-based Research Collaborative in evidence-based dentistry (NWP). Comparison of CaOH with MTA for direct pulp capping: a PBRN randomized clinical trial. J Dent Res 2013;92:16S–22S. 26
Mouawad S, Artine S, Hajjar P, McConnell R, Fahd J, Sabbagh J. Frequently asked Questions in Direct Pulp Capping: Dent Update 2014 May;41(4):298-300, 302-4.298-304 27
Hashem D, Mannocci F, Patel S, Manoharan A, Brown JE, Watson TF, Banerjee A . Clinical and radiographic assessment of the efficacy of calcium silicate indirect pulp capping: a randomized controlled clinical trial. J Dent Res 2015 Apr;94(4):562-8. 28
Tziafa C, Koliniotou-Koumpia E, Papadimitriou S, Tziafas D. Dentinogenic Activity of Biodentine in Deep Cavities of Miniature Swine Teeth. J Endod 2015 Jul;41(7):1161-6. 29
Martens L, Rajasekharan S, Cauwels R Pulp management after traumatic injuries with a tricalcium silicate-based cement (Biodentine™): a report of two cases, up to 48 months follow-up. Eur Arch Paediatr Dent 2015 Dec;16(6):491-6 30
Unemori M, Matsuya Y, Akashi A,et al. Self-etching adhesives and postoperative sensitivity. Am J Dent 2004; 17: 191-195 31
Carvalho RM, Garcia FC, E Silva SM, et al. Critical appraisal: adhesive-composite incompatibility, Part 1: J Esthet Restor Dent 2005; 17: 129-134 32
Van Meerbeek B, Van Landuyt K, De Munck J, et al. Technique-sensitivity of contemporary adhesives. Dent mater J. 2005; 24: 1-13 33
Tay FR, Frankenberger R, Krejci L, et al. Single bottle adhesives behave as permeable menbranes after polymerization, In vivo evidence. J Dent 2004; 32: 611-621 13
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Lopes GC, Marson FC, Viera LC, et al. Composite bond strength to enamel with self- etching primers. Oper Dent 2004: 29; 424-429 35
De Munck J, Van Landuyt K, Peumans M, et al. A critical review of the durability of adhesion to tooth tissue: methods and results. J Dent Res 2005: 84; 118-132
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Frankenberger R, Strobel WO, Lohbauer U, et al. The effect of six years of water storage on resin composite bonding to human dentine. J Biomed Mater Res B Appl Biomater 2004: 69: 25-32 37
Deliperi S, Bardwell DM, papathanasiou A, et al. Microleakage of resin-based liner materials and condensable composites using filled and unfilled adhesives. Am J Dent 2003: 16; 351-355 38
Pamir T, Turkun M, Factors affecting microleakage of a packable resin composite: an in vitro study. Oper Dent 2005: 30; 338-34 39
Feilzer AJ, De Gee Aj, Davidson CL. Setting stress in composite resin in relation to configuration of the restoration. J Dent Res 1987; 66; 1636-163 40 van
Dijken JW. Durability of resin composite restorations in high C-factor cavities: a 12-year follow-up J Dent 2010 Jun;38(6):469-74. 41
Roggendorf MJ, Kra¨ mer N, Appelt A, Naumann M, Frankenberger R. Marginal quality of flowable 4-mm basevs. conventionally layered resin composite. Journal of Dentistry 2011;39:643–7. 42
Goracci C, Cadenaro M, Fontanive L, et al. Polymerization efficiency and flexural strength of low-stress restorative composites. Dent Mater 2014 Jun;30(6):688-94 43
Li X, Pongprueksa P, Van Meerbeek B, De Munck J. Curing profile of bulk-fill resin-based composites. J Dent. 2015 June; 43(6): 664-72 44
Alrahlah A, Silikas N, Watts DC. Post-cure depth of cure of bulk fill dental resin- composites. Dent Mater. 2014 Feb;30(2):149-54 45
Czasch P, Ilie N. In vitro comparison of mechanical properties and degree of cure of bulk fill composites. Clin Oral Investig 2013 Jan;17(1):227-35. 46
Leprince JG, Palin WM, Vanacker J, Sabbagh J, Devaux J, Leloup G. Physico-mechanical characteristics of commercially available bulk-fill composites. J Dent 2014 Aug;42(8):993- 1000. 47
Didem, A., Gözde, Y., & Nurhan, Ö. Comparative Mechanical Properties of Bulk-Fill. Open
Journal of Composite Materials 2014;4:117–121. 48
Kim RJ, Kim YJ, Choi NS, Lee IB. Polymerization shrinkage, modulus, and shrinkage stress related to toothrestoration interfacial debonding in bulk-fill composites. J Dent 2015 Apr;43(4):430-9. 49
Marovic D, Tauböck TT, Attin T, Panduric V, Tarle Z. Monomer conversion and shrinkage force kinetics of low-viscosity bulk-fill resin composites. Acta Odontol Scand 2015 Aug;73(6):474-80. 50
Ibarra ET, Lien W, Casey J, Dixon SA, Vandewalle KS. Physical properties of a new sonically placed composite resin restorative material. Gen Dent 2015 May-Jun;63(3):51-6
51. Hickey D, Sharif O, Janjua F, Brunton PA. Bulk dentine replacement versus incrementally
15
16
S0300-5712(16)30242-1 http://dx.doi.org/doi:10.1016/j.jdent.2016.11.010 JJOD 2704
To appear in:
Journal of Dentistry
Received date: Revised date: Accepted date:
16-3-2016 2-11-2016 21-11-2016
Please cite this article as: Sabbagh J, McConnell RJ, McConnell M.Clancy.Posterior composites: update on cavities and filling techniques.Journal of Dentistry http://dx.doi.org/10.1016/j.jdent.2016.11.010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Posterior composites: update on cavities and filling techniques
J. Sabbagh; Restorative and Aesthetic Dentistry Department, School of Dentistry. Lebanese University. BeirutLebanon R.J. McConnell; Restorative Dentistry, University Dental School and Hospital. Cork. Ireland M. Clancy McConnell; Restorative Dentistry, University Dental School and Hospital. Cork. Ireland
Corresponding author: Professor Robert J McConnell. [email protected]
Address: Helvic, Ardfoyle Avenue. Ballintemple. Cork. Ireland
Posterior composites: update on cavities and filling techniques
Abstract Objectives: The aim of this paper is to examine cavity design for posterior resin composite restorations and to discuss various resin composite filling techniques. Data: Literature with regard to cavity preparation for amalgam and resin composite restorations has been reviewed. An overview of available bulkfill resin composite systems is provided and a categorization of these systems according to their clinical application and their intended use is outlined. Sources; A literature search was carried out by the authors in Medline Study selection; Pre-defined inclusion criteria based on keywords were included and reviewed. Conclusions: Minimum cavity preparations are advised for posterior resin composite restorations, preserving the greatest amount of healthy tooth structure. For resin composite restorations only the caries lesion needs to be removed with all remaining tooth structure protected for the bonding process. The anticipated outcome of this philosophy will result in the longer survival of teeth.
Newer bulkfill restorative resins allow the operator to complete the restoration in a similar time to the placement of a dental amalgam restoration. Keywords Cavity; Minimal; Amalgam; Resin Composite; Bulkfill;
Introduction:
When placed in optimal conditions and in low caries risk patients, resin composite restorations demonstrate comparable or even higher clinical performance to that of dental amalgam restorations1. Resin composites materials offer the potential of extended survival of the tooth and are more aesthetic than amalgam 2. Resin composites require different clinical skills and operative techniques to that used with dental amalgam restorations. These techniques have now been introduced into many undergraduate dental education programmes. Recent graduates are more competent in using resin composite materials for the restoration of posterior teeth3.
Resin composite restorations support the use of minimum cavity design 4. In contrast to dental amalgam, resin composites do not require a minimum thickness; and when bonded they support the remaining enamel and dentine requiring no additional retentive features5.
The main disadvantage associated with the use of resin composite for restoring posterior teeth is shrinkage on polymerization. Stresses produced during polymerization are a leading cause of adhesive failure, resulting in postoperative sensitivity, marginal staining, and recurrent caries 6 . This polymerization shrinkage creates stresses as high as 13 MPa between the resin composite material and tooth interface exceeding the tensile strength of the enamel often resulting in stress cracking and fracturing of the enamel7. When a resin composite is cured, the surrounding tooth structure may deform 8. This deflection can range from 4 to 6 μm, depending on the filling technique used9. The higher the intensity of the light source, the greater the contraction force at the composite-tooth interface and so the use of high intensity plasma lights is not recommended. Intermittent or lower intensities lights improve the marginal integrity of the restoration because it permits dissipation of the polymerization stress10. To achieve clinically successful posterior resin composite restorations, it is vital to maintain the integrity of the bond and the marginal adaptation to tooth enamel and dentin 10 . Other shortcomings of resin composites are the long placement procedure and achievement of an adequate contact point.
The incremental technique is considered as the standard technique for posterior restorations. The thickness is limited to 2 mm maximum for optimal polymerization and degree of conversion11 . Combined with a three step total
2
etch bonding technique, the restoration of a posterior cavity with resin composite can take twice as long to complete as an equivalent procedure using dental amalgam 2. With the development and use of self-adhesive bonding systems the operator can shorten the bonding procedure and at the same time reduce postoperative sensitivity12 13. Using bulk filling resin composite materials the total time taken to restore a posterior tooth with resin composite is similar to that of a dental amalgam restoration14.
Cavity Design: Greene Vardiman Black (1836–1915), published his concepts and ideas of cavity design for dental amalgam in his text Manual of Operative Dentistry in 1896. Further, he organized 'Black's Classification of Caries Lesions' which is still in use today. He established guidelines for cavity preparation, extension, retention and resistance form which applied to the mechanical requirements of dental amalgam. Design is based on the extent of the disease process and on the physical properties of amalgam. This means that the cavity must be at least 2 mm deep with design features such as undercuts, parallel walls and flat floors. It is also important that while finishing the cavity that the surface enamel is supported. In many cases, amalgam also requires the placement of a lining material.
A new cavity classification was published in 1998 in response to adhesive restorations by Mount et al 15. This emphasized the principle of minimum extension. An FDI review of minimal intervention was published in 200016. Further publications in 200117, 2002 18 and 2003 19 lead eventually in 2006 to a publication which introduced the SiSta classification of cavity design20. Cavities for resin composite restorations are not predetermined by the physical properties of the material. The only criterion for the cavity design is the removal of the diseased tissue and as a result there are no standard cavities for resin composite restorations.21 Cavities can be of minimal depth 4,can have unsupported enamel at the cavo- surface margin, proximal walls and the cervical floor and do not require the placement of a base material. Unsupported enamel in the interproximal box is not removed with a bur or chisel as this can lead to bleeding from the interproximal papilla. The papilla can also be protected by pre-wedging which also assists in the development of a good interproximal contact. The cavosurface margins of 3
proximal boxes to be restored with resin composite are smoothed and finished, but not bevelled22.
In the following table the authors suggest cavity designs for posterior resin composite restorations. These designs are based on the most frequent presentation of caries. Further, these designs may assist students and educators in standardizing resin composite techniques.
4
Table 1. Classification of composite cavities
Description
Preparation 1
Early occlusal caries lesion. Minimal preparation to remove early caries in enamel and dentine.
Occlusal caries lesion Minimal cavity design. No removal of unsupported enamel
Occlusoproximal caries lesion Access to caries through marginal ridge. Shape of cavity is “C” shaped with no extension occlusally or laterally. Unsupported enamel remains on cervical floor of box Occlusoproximal lesion involving occlusal fissures ( replacement of an amalgam) Box is “C” shaped with no removal of unsupported enamel or dentine,
5
Preparation 2
Caries lesion involving cusp Caries cusp is removed with no attempt to remove unsupported tooth structure. Retention is gained using bonding technique
Table 1.
Adhesive process: Management of Operatively Exposed Dentine In most cases, liners/bases are not required under resin composite restorations, as they prevent the bond to dentine. There is evidence of no difference in outcome in terms of post- operative sensitivity when a resin composite is ‘‘bonded’’ or ‘‘based’’23 . Placement of a liner for therapeutic purposes may be required in areas close to the pulp. A recent review on direct and indirect pulp capping concludes that exposure of the vital pulp should be avoided at all times24 . Should a pulpal exposure occur, emerging evidence suggests that MTA is superior to calcium hydroxide 25 22 . Newer products such as Biodentine have potential use in this situation 26 27 28 29
Bonding The bonding of resin composite to tooth structure can be achieved with one of four different etching systems: total-etch 3 step, total-etch 2 step, self-etch 2 step, and self-etch 1 step. The self-etch adhesives have increased in popularity due to their simplified technique and lower incidence of postoperative sensitivity30 . However, the acidic nature and permeability of simplified, self-etch adhesives make them incompatible with self-cured and dual-cured composites 31 . One-step adhesives have a lower bonding 6
effectiveness, attributed in part to the dissolution of hydrophilic and hydrophobic monomers in a highly concentrated solvent, which jeopardizes
7
bond durability32 . Tay33 has demonstrated that single-bottle adhesives, due to the lack of a more hydrophobic bonding resin layer, behave as permeable membranes after polymerization. They permit the continuous transudation of dentinal fluid and do not provide a hermetic seal for vital deep dentin. This may interfere with optimal polymerization of composites and resin cements. The shear bond strengths of self-etching primer/adhesive systems and totaletch, 1-bottle systems to enamel have been shown to be much lower than the other systems, resulting in increased leakage and staining at the enamelcomposite interface. The bonding of these self-etching primers to enamel may depend on their specific composition (pH)34 . The conventional, 3-step, etch-and-rinse adhesives still perform favorably and are the most reliable in the long-term. Multiple studies comparing contemporary adhesives reveal that these adhesives remain the gold standard in terms of durability; whereas simplifying the clinical procedure results in loss of bonding effectiveness35 . The 2-step total-etch systems exhibit slightly lower bond strengths than the 3step systems after aging36 , the introduction of filled, 2-step total-etch systems demonstrate good bond strengths. These filled adhesives provide better coverage of the dentinal substrate. Filled adhesives are associated with a reduction in microleakage when compared to unfilled adhesives 37, 38.
Selection and placement of restorative resin using incremental technique The selection of resin composite is important for the success of the composite restoration. Hybrid and certain nano-particle hybrid resin composites are, in general, appropriate for use in posterior load-bearing situations. As a general rule, the resin composite selected should contain at least 60% filler by volume. Careful technique is required during the placement of resin composite to limit the adverse effects of polymerization shrinkage. According to Feilzer, et al 39 the stress relieving flow is affected by the configuration of the restoration, known as the C-factor. The C-factor is the ratio of bonded (flowinactive) to unbonded or free (flow-active) surfaces. An increase in the number of bonded surfaces results in a higher C-factor and greater contraction stress on the adhesive bond. The Class I restoration is the most common restoration to have post-operative sensitivity due to incorrect filling technique. Class I cavities have five bonded surfaces and have a high C-factor 39 . Joining the opposing walls, buccal and lingual, in one-increment concentrates the contraction forces in the centre of the bulk of the resin composite. By avoiding the union of the buccal and
8
lingual walls in any one increment the centre of contraction is directed towards the walls and away from the centre of the restoration. One study has questioned the clinical significance of the C-factor for Class 1 cavities. However, in this study extensive cavities were used which may have influenced the results 40
Other advantages of the incremental technique are the improved shade and shape control of the restoration and complete curing of the composite. This technique tends to concurrently enhance the depth and adequacy of cure of the resin composite 5. (Photo 1)
Photo 1:
Class I molar restored using incremental technique
Bulk fill resin materials
Reduced polymerization shrinkage resin composites are now available and recent publications would suggest that these perform as ideal as the conventional composite resin systems . 41 , 42 . These resin materials are indicated in medium to deep posterior cavities, can be light cured up to 4-5 9
mm thickness43 and are classified as bulk fill resin restoratives. The major advantages of bulk filled composite resins are increased depth of cure; the percentage of fillers, the translucent shades, the use of some specific photoinitiators and monomers43,44. Their increased depth of cure reduces the clinical application time compared to regular composite restorations 45. Flowable bulk-fill materials: These materials are used to fill the deeper aspects of the cavity up to 4 mm depth with the addition of a conventional resin composite occlusally. They should not be in occlusal contact with the opposing tooth structure because of their low percentage of fillers and low mechanical properties. Fiber bulk fill base material: One material available in this category cannot be placed in open contact areas such as occlusally or interproximaly as fibres need to be protected by a conventional resin composite.
High viscosity bulk-fill materials: These are heavily filled resin composite materials used to fill a cavity up to 5mm deep. They can be dispensed classically from a syringe such as the Xtra Base (Voco); Filtek™ Bulk Fill Posterior Restorative (3M) or activated sonically, Sonicfill (Kerr and Kavo). The use of these systems combined with a self-etch adhesive, represent a reduction in operator time when compared to the incremental technique or the flowable and fibre filled bulk systems. The mechanical properties of some of the currently available paste and flowable forms bulk-fill resin composites have been studied comparing them to commercially available nano-hybrid conventional composites. Leprince et al concluded that bulkfill composites have the advantages of clinical time saving and easy handling when compared to nano-hybrid composites 46. Didem et al investigated the mechanical properties of different types of bulk-filled composites and concluded that the sonically activated system had the highest score among the tested materials and can be used as an alternative to regular resin composite for posterior teeth restoration47 . Other studies have compared the light-curing efficiency and mechanical properties of the some commercially available bulk-fill composite. One such study looked at three bulk filled paste materials and found that the microhardness values of high viscosity bulk-fill materials can differ compared to each other but all showed sufficient depth of cure at 4 mm depth and no significant difference in their flexural strength. The bulk fill materials exhibit less polymerization stress at the tooth-composite interface than the conventional composites 48. Flowable bulkfill materials in
1 0
increments of 4mm demonstrate lower shrinkage force than conventional flowable resin composites 49 Similarly, a sonic activated bulkfill material showed low shrinkage as compared to conventional composite resin materials 50. Unlike conventional Resin composite materials, filling a class I cavity in one increment using a bulk-fill material does not result in postoperative sensitivity. A recently published randomized controlled clinical trial compared the incidence of postoperative sensitivity between teeth filled using an incremental technique with teeth filled using a bulk fill technique. The authors found no significant difference between the two groups in terms of postoperative sensitivity.51 Dentists are seeking a fast and reliable technique to achieve good posterior restorations. Placing a bulk fill restorative restoration using a self etch adhesive technique allows the operator to achieve a high standard posterior resin composite restoration in a similar time to a dental amalgam restoration.
Conclusions The success of composite resin restorations is dependent on an understanding of the physical properties and management of the material and the clinical management of the caries process. For resin composite restorations only the caries lesion needs to be removed with all remaining tooth structure protected for the bonding process. The anticipated outcome of this philosophy will result in the longer survival of teeth. Newer bulkfill restorative resins allow the operator to complete the restoration in a similar time to the placement of a dental amalgam restoration. This paper advises the use of minimum cavity preparations, preserving the greatest amount of healthy tooth structure and introduces the newer bulk-fill resin composite restorative materials.
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