Contemporary dentistry dictates a new paradigm in restoring posterior teeth. Historically, since the middle 1800s, teeth have been restored with either gold or a material customarily known as amalgam.
To this day, cast gold and to a degree, gold foil, is the best material known to restore teeth. In order for a material to be used for posterior restorations, certain factors must be considered. Biocompatibility is a major consideration, as well as physical properties of the material. Gold is an excellent material for restoring teeth because it is the most biocompatible material we have to use in these restorations. Gold has physical properties nearly the same as natural teeth and is very kind to the opposing dentition.
Amalgam was accidentally discovered around 1833, and was used as an alternative filling material for cast gold and gold foil.12 Subsequently, it was discovered that the material lasted longer than anticipated, and it became the standard of care restorative material.
Now we are in the 21st century. We don’t criticize the use of amalgam as a dangerous material; however, we have better materials for restoring posterior teeth,1-3 including composite resins developed from the original of Bowens formula through the microhybrids of today.4
Composite resins can be divided into 5 main categories:5
(1) Microfills,
(2) Microhybrids,
(3) Hybrids,
(4) Packables, and
(5) Flowables.
The microfill composites are highly polishable and appropriate for use in anterior veneers and bonding, class V, and anterior veneering where strength is not as important as high polishability.
The microhybrids and hybrids differ primarily based upon the average particle size of their filler material. The microhybrid has an average particle size of 0.6 m (submicron size), whereas the hybrids tend to have average particle sizes of around 1 m. This is a semantic issue, as they both behave very similarly and are used in the same manner for the same types of restorations, specifically, class II and IV restorations where heavy wear is likely to ensue.
Packable materials have a very large average particle size (5 to 20 m) and are very highly filled (77% to 80% by weight or volume). This affords the material a great deal of strength, especially in heavy mastication, and is also appropriate for class II and IV restorations. The main disadvantage of the packable systems is that they do not polish well and poorly maintain what little polishability they do possess.
POSTERIOR RESTORATIONS
One of the main challenges of posterior restorations is achievement of adequate contact area.
How many times have we clinicians placed what we thought was a very fine class II restoration, and then upon testing the contact with floss found that the thick dental tape we used went through the contact like limp spaghetti. No contact at all. Wow! What a nuisance. Now we have to remove some of the material and attempt to gain better contact by adding composite interproximally, or even worse, replacing the restoration completely.
In the following case report, I will demonstrate a technique whereby achievement of snug contact areas is predictable and foolproof.
CASE REPORT
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| Figure 1. Molar demonstrating fracture and recurrent caries. |
This is typical of the type of case we see on a daily basis a young patient with a fractured amalgam restoration, including recurrent decay (Figure 1). This tooth is nearly broken down to the point where a lab-processed restoration would be more sensible. Why? Because one of the drawbacks of composite resin is that the matrix of the composite shrinks significantly upon polymerization5 (ergo polymerization shrinkage). This is the phenomenon that occurs when the large linked polymers convert from a plastic state to a solid state in the presence of light. Why is this of consequence? The reason is that the composite will adhere to the sides of the restoration tenaciously, and when the polymerization continues the walls of the tooth will torque towards the light-curing source, therefore incurring a significant amount of energy and pressure, squeezing the tooth together. This can cause a high amount of pain due to the pinching of the Odonto blastic fibers, which are small projections of pulpal tissue inside the dentin tubules.
In this case, the decision was made to place a direct composite resin restoration.
Postoperative sensitivity has been a big problem with the use of composites. There are several reasons for this phenomenon, including the following:
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| Figure 2. Fiesta rubber dam clamps. | Figure 3. Flexi-Dam nonlatex rubber dam. |
(1) improper isolation of the tooth, not using rubber dam5-7 (Figures 2 and 3);
(2) unpolymerized resin on the floor of the preparation;
(3) over-etching with phosphoric acid (etch for 15 seconds only);
(4) nonvolatilized solvent from the primer bonding agent;
(5) bacterial contamination on the surface of the preparation; and
(6) polymerization shrinkage.
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| Figure 4. The 845KR-016 diamond (Axis Dental). | Figure 5. Molar isolated under rubber dam. |
We applied the rubber dam first (Fiesta Clamps, Coltene/Whaledent;Flexi-Dam, Roeko) (Figures 2 and 3). I then removed the old amalgam and caries using an 845KR-016 diamond (Figure 4). I use diamonds (Axis Dental, Brasseler, Alpen, Coltene/Whaledent) for removal of old amalgam to minimize the jumping of the handpiece, which occurs with the use of carbides (Figure 4). Notice that the rubber dam is applied prior to removal of amalgam (Figure 5). This has a 2-fold purpose. First, the amalgam particles will not collect in the patients throat and mouth. Second, the isolated teeth can be disinfected, and therefore the aerosol produced by the drill will be reduced and the microbiological contamination to the office surroundings will be nearly eliminated.6
Notice that the dam is not in full contact with the tooth distal to the preparation (Figure 5). This is acceptable at this point, however I will not place my restoration until the dam is in complete contact with both the tooth undergoing treatment as well as the surrounding teeth. Patients find the use of the dam pleasant for 2 reasons. First, they recognize that this is something extra that I am using to protect them from swallowing amalgam (and mercury debris). Second, they become aware that I am a state-of-the-art clinician and take pride in my work.7
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| Figure 6. Preparation completed under rubber dam. |
The preparation was completed and the rubber dam was replaced. Notice that the area of the dam in contact with the prepared tooth is inverted under the sulcus (Figure 6). This is important in order to minimize and hopefully eliminate the crevicular seepage, which could contaminate the preparation and final restoration. If we have difficulty in seating the rubber dam, a waxed dental floss ligature can be used to secure the dam and hold the dam subsulcularly.
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| Figure 7. Auto-matrix (DENTSPLY Caulk). | Figure 8. Matrix placed and tooth prewedged with GDS flexi-wedges. |
A Mylar contoured matrix (Auto-matrix, DENTSPLY Caulk) was applied and pre-wedged in place (GDS flexi-wedge, Common Sense Dental Products) (Figures 7 and 8). Careful examination is done to make sure that the matrix is in tight apposition to the proximal box and walls of the preparation. The wedges are placed for 2 reasons. First, to pre-wedge for acceptable contacts, and second, to make sure that the matrix is snug against the gingival cavosurface.8
The tooth was then ready for etching, disinfecting, and bonding agent. The tooth need not be dry, and to the contrary, a moist field is important to keep the tooth hydrated. All bonding agents are hydrophilic and require a moist field for percolation of the bonding agent into the dentin tubules.9
The tooth was etched with a suitable agent, such as phosphoric acid 35%, for 15 seconds only. This is a very important step. Clinicians have historically etched for up to 60 seconds or more, thinking that if a little etching is good, then more etching is better. This is incorrect. The dentin matrix (protein, hydroxyapatite, and water) and the collagen matrix will be damaged if etched for longer than 15 seconds. This will cause the underlying dentin to be less stable, and if the restoration is placed over this soft dentin, the patient will experience postoperative sensitivity upon mastication. The floor of the preparation will depress, and the hydrodynamic theory will cause pinching of the Tomes fibers, and therefore pain.
The etching was completed (15 seconds) and then rinsed for 60 seconds with water. High-speed evacuation allows the tooth to be sufficiently dried prior to disinfection. Remember, we still want a moist surface prior to applying the disinfecting agent and bonding agent. Many suitable disinfecting agents can be used. Consepsis, Tubulicid Red, and sodium hypochlorite are some of the more popular agents. I prefer Tubulicid Red (Global Dental Products). It is comprised of cocoamphodiacetate benzalkonium chloride and fluoride in aqueous solution. This allows disinfection, fluoride treatment, and an aqueous residual, which is beneficial for bonding agents.10
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| Figure 9. Prime and Bond NT (DENTSPLY Caulk). |
With the surface of the tooth left moist with the disinfectant, I then applied my bonding agent, Prime and Bond NT (DENTSPLY Caulk) (Figure 9). This 5th generation bonding agent has a nanofiller and excellent bond strength as well as ease of use and placement.11 The material was applied with a microbrush and cured with the spectrum curing light for 10 seconds. The surface was checked to make sure that there was a glossy surface.
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| Figure 10. Esthet-X Composite (DENTSPLY Caulk). |
The next step is critical. Esthet-X flow (DENTSPLY Caulk) was applied in a thin layer covering the base of the preparation and up the sides of either the mesial or distal proximal box9 (Figure 10). Then, the selected shade of Esthet-X was immediately applied to fill the rest of the box. It is unnecessary to fill the opposite box with composite at this time. Blend the composite in the middle of the preparation and feather the material down towards the opposite box as in incremental loading. This will allow a smooth interface when completing the restoration.
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| Figure 11. Contact Pro (CEJ Dental). | Figure 12. Contact Pro demonstration on model. |
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| Figure 13. Mesial aspect of preparation completed with Contact Pro. | Figure 14. Mesial and distal aspect of the preparation completed with Contact Pro. |
The appropriate (mesial or distal) end of the Contact Pro instrument (CEJ Dental) (Figure 11) was inserted and torqued towards the adjacent tooth contact area, and cured through the Contact Pro (Figure 12) using the Allegro LED curing light (Den-Mat Corp). The Contact Pro was gently rocked until it popped free from the box, leaving an island of composite and a predictable snug contact area (Figure 13). The process was repeated for the other side of the preparation and cured (Figure 14). Then, the areas buccal and lingual to the island of composite were filled and cured with the Allegro LED curing light.
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| Figure 15. Enhance polishing system. |
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| Figure 16. Enhance disc on slow speed. |
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| Figure 17. Enhance cup, point, and disc. |
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| Figure 18. Final polished restoration. |
Adjustment and polishing were accomplished with diamonds, carbides, Enhance rubber cups (DENTSPLY Caulk), discs with Prisma Gloss (3 m then 1 m), and finally PoGo (DENTSPLY Caulk) (Figures 15 through 17). PoGo gives a mirror gloss to the final restoration (Figure 18).
CONCLUSION
Composite resins are much more technique sensitive than other types of materials used in direct placement. Care in following manufacturers instructions for the use of each material selected, from etchant (remember, 15-second etch only) to bonding agents, and finally the selected composite system (in this case Esthet-X and Esthet-X flow), will increase the rate of success and patient satisfaction with the new, tooth-colored restorative materials.
Happy bonding!
References
1. Wiggin LL. Composites vs amalgams. J Am Dent Assoc. 2001;132:150-152. [letter of response to Leinfelder KF. Do restorations made of amalgam outlast those made of resin-based composite? J Am Dent Assoc. 2001;131:1186-1187.]
2. Perry R, Kugel G, Kunzelmann KH, et al. Composite restoration wear analysis: conventional methods vs three-dimensional laser digitizer. J Am Dent Assoc. 2000;131:1472-1477.
3. Hickel R. Restorative Materials: an evidence-based review. Dent Prod Rep. 2001;35:36-45.
4. Bowen RL. Dental filling material comprising vinyl silane treated fused silica and a binder consisting of the reaction product of bis phenol and glycidyl acrylate. US patent 3,066,112. Nov 27, 1962.
5. Deliperi S, Bardwell DN. An alternative method to reduce polymerization shrinkage in direct posterior composite restorations [published correction appears in J Am Dent Assoc. 2002;133(12):1614.] J Am Dent Assoc. 2002;133(10):1387-1398.
6. Samaranayake LP, Reid J, Evans D. The efficacy of rubber dam isolation in reducing atmospheric bacterial contamination. ASDC J Dent Child. 1989;56:442-444.
7. Strassler H. The dental dam is tricky to place but patients appreciate the effort. Dent Off. 1992;11(12).
8. Yetto RJ. Creating tight anatomically contoured proximal contacts in class II direct composite resin restorations. J Cosmet Dent. 2003;19:28-34.
9. Arellano A, Pires Lopes LM, Lopez-Areal B, et al. Effect of moisture on shear bond strength of dentin adhesives. Abstract for CED of IADR Berlin. 1996:128.
10. Gwinnett AJ. Effect of cavity disinfection on bond strength to dentin. J Esthet Dent. 1992;4(suppl):11-13.
11. Barkmeier WW, Hammesfahr PD, Latta MA. Bond strengths of composite to enamel and dentin using Prime & Bond 2.1. J Dent Res. 1997;76:136. Abstract 979.
12. Ring ME. Dentistry: An Illustrated History. Philadelphia, Pa: Mosby; 1985:206. ISBN 0801641462.
Dr. Abel is a pioneer and trendsetter in the field of cosmetic dentistry. Recognizing the importance of continuing education, Dr. Abel has attended every course available in the discipline and applied his knowledge and skill in his clinical practice in Rockville, Md. He is the first accredited member of the American Academy of Cosmetic Dentistry and American Society for Dental Aesthetics, and the first to achieve diplomat status in the American Board of Aesthetic Dentistry in the state of Maryland. He is a fellow in the Academy of General Dentistry and a fellow in the International Academy of Dental and Facial Esthetics. Dr. Abel is a published author both nationally and internationally and lectures at dental schools in the United States and abroad. He can be reached at (301) 770-1447.
Disclosure: The author has adapted this article from an article he originally published in Dentistry, a United Kingdom publication, adapted by permission of Dentistry.
