Patients today are demanding cosmetic restoration not only of their anterior teeth, but of their posterior teeth as well. We are moving from a “Disease Centred” approach in the dental profession i.e. fillings to a more “Health Centred” approach i.e. restorations. To restore anything is to “improve, repair or retouch so as to bring back to original condition; to bring back to a healthy state”. We must be versed in all the techniques and materials that are available to enable us to produce predictable posterior restorations. The introduction of acid etching and bonding to enamel by Buonocore in 1955,1,2 and to dentin,3,4 along with the introduction of composite resins as possible alternatives to metallic posterior restorations, has lead to the direct posterior composite resin restoration being one of the most commonly placed restorations today.
However, there have been numerous clinical problems associated with this popular restorative procedure. “Clinicians must understand the concept of polymerization contraction stress and realize that the quality of composite resin restorations depends on successful management of these stresses”.5 These contraction stresses can lead to disruption of the bond to tooth structure6-8 resulting in poor marginal seal,9-13 sensitivity to biting and temperature,14-18 and poor contacts.19,20 There is a steep learning curve for proper technique. Excellent isolation and excellent matrix technique is required, and these restorations are time consuming to place and finish. Compared to the typical amalgam restoration, composite restorations are more difficult and technique sensitive. We have to understand the limitations of this material and perform a meticulous step-by-step procedure to ensure success.
This article will discuss a predictable step-by-step process that will lead to aesthetic and functional posterior composite restorations.
DIAGNOSIS
As in any aspect of dental or medical treatment, everything must start with a diagnosis. As Morton Amsterdam once stated “There may be different ways of treating a disease, but there can be but one correct diagnosis”. Using evidence- based dentistry, this diagnosis will lead us to the proper restorative material for that particular tooth and clinical situation. Many times we are pressured to place composite resin restorations in teeth that cannot support the material. We then act surprised when the restoration fails or worse, the tooth fails (Fig. 1). We need to reduce restorative risks in order to increase the positive prognosis of the teeth in question.
From the restorative and prosthetic literature we have been taught certain criteria to allow us to determine whether to place a direct or indirect restoration. Larson has stated that to fracture an intact tooth takes a 530 pound load,21 and when an MOD preparation is placed that is greater than 1/3 the intercuspal distance (ICD), it only takes a load of 216 pounds to fracture a tooth.22 By placing an intra-coronal restoration in a tooth that has a preparation of ICD greater than 1/3 of the tooth ICD, it will still fracture.23 These teeth require complete cuspal coverage. It is the width of the occlusal portion of a preparation that affects the strength of the tooth. Vale showed that fracture resistance of teeth decreases with increases in intra-coronal preparation size.24 Therefore, if the ICD of the preparation is 1/4 or less of the tooth ICD, a direct restoration is indicated. Furthermore, we also know that if more than 75% of a non-functional cusp and more than 50% of a functional cusp is destroyed, an indirect restoration is indicated.25 If we can determine which type of restoration to place based on research knowledge, and follow those guidelines, the success of posterior composite restorations will increase dramatically.
ADHESION
The cornerstone to successful aesthetic dentistry is proper execution of adhesive technology. Elimination of sensitivity depends on the proper application of current dentin bonding agents. Enamel provides a very predictable substrate to which we can bond to.26-28 Unfortunately, dentin is less predictable.29-31 However, with proper technique and understanding of the chemistry of each system we use, we can increase our rate of success. The advantages of adhesively placed restorations are that they are minimally invasive, there are decreased pulpal risks, the remaining tooth structure is stronger and there can be reduced microleakage. Failure of composite restorations can be linked to the breaking of the seal at the tooth-restoration interface. This is usually due to the increased forces of polymerization shrinkage or occlusion. This microleakage can result in bacterial ingress, which leads to pulpal inflammation (pain and sensitivity) and recurrent decay. Being able to understand polymerization shrinkage and adhesion will lead to the relief of stress placed on the tooth and composite material resulting in a longer lasting restoration.
THE C-FACTOR
Polymerization shrinkage or curing contraction is the amount of volumetric decrease a composite undergoes because of the curing process.32 A stress is created that is then transferred to the tooth structure because the cavity walls restrict the volumetric changes of the composite. The C-factor is the ratio of bonded (flow-inactive) to unbonded or free (flow-active) surfaces.33 If the C-Factor is high, the stress created is usually greater than the bond strength resulting in delamination of the adhesive bond.34-36 This leads to gap formation between the dentin and restorative material. The 3 techniques for placement of posterior composite restorations will be reviewed in the next section and how the C-Factor is affected by each technique.
TECHNIQUES
There are 3 basic techniques for the placement of composite restorations. These are the Bulk Fill Technique, Incremental insertion, and the Direct Shrinkage with Incremental Buildup Technique also known as the directed contraction shrinkage technique.
With the Bulk Fill Technique, one places the entire amount of composite resin into the preparation at one time and then trans-enamel polymerization is used to cure the composite. The composite material then shrinks towards the light source. This creates internal stresses in the composite material leading to increased polymerization stresses, which then challenge the bond to dentin and leads to microleakage. If the C-Factor is high, as in an occlusal restoration, bulk filling the restoration places enormous stresses on the tooth and material. This can lead to major temperature and biting sensitivity. This is why a “simple occlusal” can cause us so much post-operative grief. Therefore the Bulk Fill Technique can not be recommended for use in posterior restorations.
Incremental placement of posterior composites has been advocated for a long time as an answer to polymerization contraction. Many methodologies have been suggested, including using no liner, the use of a low modulus flowable, or some type of glass ionomer cement. Since there are many viscosities of composites available with various degrees of polymerization contraction, the adaptive quality of the composite or its flow as well as inherent volumetric properties will affect the final marginal adaptation and leakage patterns with these placement techniques. The use of a low modulus liner can decrease the C factor due to flex, and the placement of a glass ionomer, which has little contraction shrinkage away from the dentin, serves to volumetrically decrease the amount of composite placed, and hence decrease the total amount of contraction. Boksman et al give an overview on the factors influencing these variables in their article37 but a discussion of these techniques and all the variables involved is beyond the scope of this article
.
The Direct Shrinkage with Incremental Buildup technique first introduced by Bertolotti,20 uses a self-cured low viscosity base posterior composite followed by an enamel replacement of light cured composite. This self-cured composite reaches its gel point very slowly, thereby avoiding stress build-up and shrinkage, the two biggest contributors to posterior composite failure. A light-cured wear resistant composite is then placed in small 2mm increments and light cured using trans-enamel polymerization. This technique controls the amount of stress created by polymerization shrinkage as well as leaving very little composite to trim and polish. Furthermore, this allows layering and stratification of composite shades and translucencies, leading to a more aesthetic posterior composite restoration. The clinical cases presented will focus on this technique.
CLINICAL PROCEDURES
Case 1
This patient presents with a failing amalgam restoration. Radiographs indicated recurrent decay as well as interproximal decay (Fig. 3.). Appropriate local anaesthesia was delivered and the rubber dam was placed. The rubber dam is a must for the control of moisture contamination in the placement of composite resin restorations. The existing amalgam was removed and the decay was removed. Then a sectional matrix was placed (Fig. 5). The Palodent System (Clinical Research Dental) or the Composi-Tight Gold System (Clinical Research Dental) are two sectional matrix systems that allow easy placement and ensure tight interproximal contacts.
After cleaning the preparation with Consepsis Scrub (UltraDent) and air abrasion, the enamel and dentin surfaces were etched with 32% phosphoric acid for 10-15 seconds, rinsed and lightly air dried. The surface has to be re wetted with a dentin/enamel wetting agent. The agent of choice is Aqua-Prep F (Bisco) and it was applied with a Micro Brush and gently dried. Numerous layers of One Step Plus(Bisco) were applied, the solvent evaporated and then light cured for 20 seconds. The resulting glossy surface was then lined with a self-cured low viscosity base composite, BisFil 2B (Bisco), to the DEJ surface (Fig. 6).
Dentin shade A3 Vit-L-Essence (UltraDent) was placed in increments starting with the palatal cusps, curing each 2mm increment for 10 seconds then layering the buccal cusps in the same manner. An ochre tint was placed in the central fossa of the mesial and distal pits (Fig. 7). The entire restoration was then cured for another 40 seconds. The sectional matrix was removed and De-Ox (UltraDent) was then placed over the entire surface and cured for another 20 seconds (Fig. 7). Note the lack of excessive composite material in Figure 7. This is another advantage of the Incremental Buildup Technique in that gross cutting of composite is not required. Finishing is quicker, easier, and places less stress on the composite. This also reduces the occurrence of white line margins and decreases wear rates. The final restoration is seen in Figure 8.
Case 2
This case demonstrates recurrent interproximal decay. The final size of the preparation is about the maximum isthmus width that is indicated for a direct restoration. Figure 9 shows the preoperative status of the tooth. The steps for the restoration are essentially the same as the previous case therefore they do not need to be repeated. Figure 10 demonstrates the use of Caries Detector (Kuraray) to expose the decayed dentin surface. This is used on every tooth prior to starting the adhesive process. The interproximal decay is clear (Fig. 11). This step is repeated until all the decay is removed (Fig. 12).
As in the previous case, the appropriate sectional matrix is placed, proper adhesive technique is followed and BisFil 2B (Bisco) is then placed using a Centrix Needle Tip Syringe (Fig. 13.) Figure 14 demonstrates the level of BisFil 2B that is needed to allow for the incremental placement of the enamel and dentin shades of composite. In the case of a Class II restoration, the first composite layer placed is an enamel shade. This anatomically builds up the tooth in the manner that a natural tooth is layered. The marginal ridge is built up to contour using Vit-L-Essence (UltraDent) shade Pearl Frost (Fig. 15).
The cusps are built up one segment at a time using Dentin Shade A3 (Fig. 16). The final enamel layer is placed, Pearl Frost. De-Ox (UltraDent) is again placed over the entire surface and light polymerized for 20 seconds (Fig. 17). The final polished restoration is seen in Figure 18. Note the excellent anatomy that was created by the incremental buildup of each cusp. The central grooves are the points of termination of each cusp and were not created with contouring and polishing burs thus not stressing the composite and there is no risk to scar the enamel surface.
Case 3
This case will demonstrate 2 Class II restorations and the importance of proper matricing. Figure 19 shows 2 failing amalgam restorations with radiographic interproximal decay. After the amalgams have been removed along with the decay, the final preparations are visualized (Fig. 20). Many times the proximal box is just a bit too wide for the Sectional Matrix. When the ring is placed the matrix collapses into the preparation. To solve that problem, a Omni Matrix (UltraDent) is used along with a BiTine ring (Fig. 21). A similar procedure as discussed above is followed to restore the missing dentinal tooth structure, and then the next composite layer is in an enamel shade Pearl Frost, along the mesial marginal ridge and the buildup of the buccal cusp was completed (Fig. 21). The dentin lobes are placed along the buccal cusps, polymerized then the lingual cusps are placed and polymerized (Fig. 22). The immediate post-op is shown in Figure 23.
Case 4
This final case will introduce a newly formulated composite Amelogen Plus (UltraDent) which is an improvement in the world of aesthetically shaded composites in that there are only 3 enamel shades and the usual dentin shades. It makes it less confusing than the Vit-L-Essence array of shaded enamels. Figure 24 shows the pre-operative condition of the lower first molar. After the use of Caries Detect (Fig. 25), the final preparation is shown in Figure 26. Placement of the Sectional Matrix and etching the entire tooth is demonstrated in Figure 27. BisFil 2B (Bisco) is placed in the proximal box in the usual manner (Fig. 28). Incremental buildup is accomplished through the use of a dentin shade A3. The A3 is used because it is the closest shade to the natural dentin. If the patient was much older, an A4 or A6 dentin shade may be indicated (Fig. 29). The enamel shade EN was used to ensure that the underlying dentin shade would impart proper colouring to the tooth (Fig. 30). The aesthetic final result is seen in Figure 31.
SUMMARY
By understanding basic restorative principles and applying them to direct composite restorations we can achieve predictable results. The introduction of new materials will improve the way we practice dentistry. We cannot, however, forget the basic principles of adhesion and restorative dentistry.
This article provides a technique that should make the placement of aesthetic direct posterior composite restorations a quick and predictable option for our patients.
Acknowledgements
The author wishes to thank Dr. Len Boksman for his excellent editorial assistance in the preparation of this article.
Dr. Marangos has no financial interest in any of the products used in this article.
Dr. Marangos maintains a private practice in Toronto with emphasis on aesthetic and restorative dentistry and orthodontics. He is the principal doctor at the Yorkville TMJ Centre, a practice that focuses on the management of head, neck and TMJ related pain. Dr. Marangos is a certified Ivoclar speaker. Dr. Marangos can be reached at 416-465-9343 or by email at dmarangos@rogers.com.
Oral Health welcomes this original article.
REFERENCES
1.Buonocor
e MG. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res, 1955; 34:849
2.Buonocore MG, Matsui A, Gwinnett AJ. Penetration of resin dental materials into enamel surfaces with references to bonding Arch oral Biol. 1968 Jan;13(1):61-70
3.Brudevvold F, Buonocore M, Wileman W. A report on a resin composition capable of bonding to human dentin surfaces. J Dent Res, 1956 Dec;35(^):846-51
4.Buonocore MG, Quigley M. Bonding of a synthetic resin material to human dentin: preliminary histological study of the bond area J Am Dent Assoc. 1958 Dec;57(6):807-11
5.Kinomoto Y, Torii M, Takeshige F, Ebisu S. Polymerization contraction stress of resin composite restorations in a model Class I cavity configuration using photoelastic analysis. J Esthet Dent. 2000;12(6): 309-19
6.Ilie N, Kunzelmann KH, Hickel R. Evaluation of micro-tensile bond strengths of composite materials in comparison to their polymerization shrinkage. Dent Mater. 2005 Nov11
7.Ilie N, Felten K, Trixner K, Hickel R, Kunzelmann KH. Shrinkage behavior of a resin-based composite irradiated with modern curing units. Dent Mater. 2005 May;21(5);483-9
8.Keverlaan CJ, Feilzer AJ. Polymerization shrinkage and contraction stress of dental resin composites. Dent Mater. 2005 Dec;21(12);1150-7
9.Stansbury JW, Trujillo-Lemon M, Lu H, Ding X, Lin Y, Ge J. Conversion-dependant shrinkage stress and strain in dental resins and composites. Dent Mater. 2005 Jan;21(1):56-67
10.Braga RR, Ferrance JL. Alternatives in polymerization contraction stress management Crit Rev Oral Biol Med. 2004 Jun 4;15(3):176-84
11.Ferracane JL. Developing a more complete understanding of stresses produced in dental composites during polymerization. Dent Mater. 2005 Jan;21(1):36-42
12.Uctasli S, Shortall AC, Bruke FJ. Effect of accelerated restorative techniques on the microleakage of Class II composites. Am J Dent. 2002 Jun;15(3):153-8
13.Loguercio AD, de Oliveira Bauer JR, Reis A, Grande RH. In Vitro microleakage of packable composites in Class II restorations. Quitessence Int. 2004 Jan;35(1): 29-34
14.Sarrett DC. Clinical challenges and the relevance of materials testing for posterior composite restorations. Dent Mater. 2005 Jan;21(1):9-20
15.Prati C, Chersoni S, Acquaviva GL, Breschi L, Suppa P, Tay FR, Pashley DH. Permeability of marginal hybrid layers in composite restorations Clin Oral Investig. 2005 Mar;9(1):1-7
16.Ward DH. Treating patients with CARE (comfortable aesthetic restorations): reducing postoperative sensitivity in direct posterior composite restorations. Dent Today. 2004 Aug;23(8):60, 62, 64-5
17.Perdigao J, Geraldeli S, Hodges JS. Total-etch versus self-etch adhesive: effect on postoperative sensitivity. J Am Dent Assoc. 2003 Dec;134(12):1621-9
18.Borgmeijer PJ, Kreulen CM, van Amerongen WE, kerboomHB, Gruythuysen RJ. The prevalence of postoperative sensitivity in teeth restored with Class II composite restorations. ASCD J Dent Child. 1991 Sep-Oct;58(5):378-83
19.Loomans BA, Opdam NJ, Roeters FJ, Bronkhorst EM, Burgersdijk RC, Dorfer CE. A randomized clinical trial on proximal contacts of posterior composites. J Dent. 2005 Sep 10; {Epub ahead of print}
20.Bertolotti RL. Posterior composite technique utilizing directed polymerization shrinkage and a novel matrix. Pract Periodontics Aesthet Dent 1991 Jun-Jul;3(4);53-58
21.Larson TD, Douglas WH, Geistfeld RE. Effect of Prepared Cavities on the Strength of Teeth. Operative Dent 1981;6:2-5
22.Larson TD, Douglas WH, Geistfeld RE. Effect of Prepared Cavities on the Strength of Teeth. Operative Dent 1981;6:2-5
23.Vale, British Dental Journal 1959
24.Vale, Irish Dental Review, 1956
25.Shillingburg et al, Fudamentals of Fixed Prosthodontics Second Edition. Quintessence Publishing Co. 1981
26.Hadad R, Hobson RS, McCabe JF. Micro-tensile bond strength to surface and subsurface enamel. Dent Mater. 2006 Jan 21;{Epub ahead of print}
27.Erickson RL, De Gee AJ, Feilzer AJ. Fatigue testing of enamel bonds with self-etch and total-etch adhesive systems. Dent Mater. 2005 Dec 16; {Epub ahead of print}
28.Van Landuyt KL, Kanumilli P, De Munck J, Peumans M, Lambrechts P, Van Meerbeek B. Bonds strength of a mild self-etch adhesive with and without prior acid-etching J Dent. 2006 Jan;34(1) 77-85
29.Sadek FT, Goracci C, Cadoso PE, Tay Fr, Ferrari M. Microtensile bond strength of current dentin adhesives measured immediately and 24 hours after application. J Adhes Dent. 2005 Winter;7(4):297-302
30.Peumans M, Kanumilli P, De Munck J, Van Landuyt K, Lambrechts P, Van Meerbeek B. Clinical effectiveness of contemporary adhesives: A systematic review of current clinical trials Dent Mater. 2005 Sep;21(9):864-81
31.R, Vanden Abbeele A. Sealing ability and bond strength of four contemporary adhesives to enamel and to dentine. Eur J Paediatr Dent 2005 Dec;6(4):185-90
32.Terry, Douglas, A. Restoring Posterior Teeth Using a New Low-Shrinkage Composite. Restorative Quarterly April 2002;Vol 5, (1):3-14
33.Feilzer AJ, De Gee AJ, Davidson CL. Setting stress in composite resin in relation to configuration of the restoration. J Dent Rs. 1987;66:1636-1639
34.De Munck J, Van Landuyt K, Coutinho E, Poitevin A, Peumans M, Lambrechts P, Van Meerbeek B. Micro-tensile bond strength of adhesives bonded to Class I cavity bottom dentin after thermocycling. Dent Mater. 2005 Nov;21(11):999-1007
35.Choi KK, Ryu GJ, Choi SM, Lee MJ, Park SJ, Ferracane JL. Effects of cavity configuration on composite restoration. Oper Dent. 2004 Jul-Aug;29(4): 462-9
36.Nikolaenko SA, Lohbauer U, Roggendorf M, Petschelt A, Dasch W, Frankenberger R. Influence of c-factor and layering technique on microtensile bond strength to dentin. Dent Mater. 2004 Jul;20(6):579-85
37.Boksman L, Pensak T. An Integrated Systems Approach to the Placement of Posterior Composite Resins. Dentistry Today Jan 2006 Vol 25, No. 1:54-59
