Written by Dino S. Javaheri, DMD Wednesday, 28 February 2007 19:00
Advances in adhesive dentistry combined with new developments in composite materials offer an option for patients who demand durable, aesthetic posterior direct restorations. While amalgam restorations have many advantages, such as being inexpensive, easy to place, and long-lasting, patients frequently request an alternative. Patients may desire to do away with the many “metal” fillings they have in an attempt to improve the overall appearance of their smile. Also, patients are more likely to request a tooth-colored restoration when replacing a defective restoration or when faced with the need to treat new decay.
In addition to aesthetics, another concern that many patients have is the perception of mercury leakage from amalgam restorations. Despite ADA and CDC efforts to provide accurate research and documentation that amalgam is safe, the perception among patients of mercury leakage and toxicity is still common. A large part of the public sensitivity to amalgam is due to consumer reports and Web sites that claim mercury poisoning or toxicity is responsible for a multitude of diseases. Diseases associated with amalgam by anti-amalgam groups include multiple sclerosis, amyotrophic lateral sclerosis, Lou Gehrig’s disease, autism, colitis, gastrointestinal problems, changes in blood pressure, chronic or frequent headaches, dizziness, fine tremors, persistent cough, emphysema, congestive heart failure, idiopathic dilated cardiomyopathy, trigeminal neuralgia, eczema, psoriasis, muscle weakness, fatigue, hypoxia, edema, joint pain, rhinitis, sinusitis, memory loss, depression, hair loss, swollen lymph nodes in neck, cold, clammy hands and feet, excessive perspiration, and loss of appetite.
The debate over amalgam safety is not a new issue. Patients and a number of healthcare professionals have been influenced by anecdotal case reports in the medical and dental literature, research published in refereed literature, and media stories concerning the alleged dangers of amalgam restorations. In 1990 the news program 60 Minutes ran a shocking exposé on amalgam, alleging that because of its mercury content, it was poisonous and was responsible for many of the diseases that have not yet been cured by medical science. More recently a Smart Money article titled “10 Things Your Dentist Doesn’t Want You to Know,” which was also listed as major news and a feature on aol.com, stated that old metal fillings may be leaking toxic waste. It also stated that there is a sponsored bill in California to phase out mercury in fillings by 2009. On the Internet, listing “mercury amalgam dental” in any search engine will yield hundreds of sources. It is not my intention to discuss or debate the safety of amalgam; rather, it is my intention to point out that many people perceive amalgam as unhealthy, and knowing another option (composite) is available to them, they would prefer that.
It is also interesting to note that some research indicates that composites may not be totally biocompatible. Recent research conducted at the University of Rochester School of Medicine and Dentistry on 85 young males found that increased exposure to phthalate, a man-made ingredient in plastics, may lead to deficiencies in development and an increased risk of cancer.1 In another recent study appearing in Endocrinology, mice that were exposed to bisphenol-A were more likely to develop cancer-related mammary duct abnormalities.2 Again, it is not my intent to discuss the safety of composites, but rather to point out that questions may arise in the future as to their biocompatibility.
In regard to the health of a tooth, adhesive technology has revolutionized tooth preparation by allowing minimal tooth reduction without large retentive undercuts. Composite restorations are conservative in nature, as their preparation necessitates the removal only of decayed tooth structure. The adhesive bond provides sufficient strength and retention for the restoration. Current resin materials have the required strength and wear resistance to withstand the forces of mastication.
Patients often request composite restorations due to aesthetics, and most dentists enjoy providing cosmetic services to their patients. However, before a dentist is able to routinely do the “caviar and champagne” cosmetic procedures such as porcelain veneers, they need to master posterior composite. Posterior composites are a relatively simple aesthetic restoration that can be considered a “bread and butter” procedure for the aesthetic/restorative practice. If a dentist does not place tight contacts or has problems with postoperative sensitivity when placing a posterior composite, then patients are less likely to have confidence in that doctor performing a complex cosmetic procedure. Therefore, good technique and predictable results with posterior composites are vital in promoting other aesthetic procedures.
Composites have become an integral part of dentistry; however, their evolution has not been without growing pains. The most common problems dentists face when placing posterior composites are postoperative sensitivity and open contacts.
Postoperative sensitivity may be due to many factors. The most common causes are moisture contamination, over-heating the pulp, prolonged desiccation, adhesion protocol, polymerization shrinkage stress, and inadequate cure. Postoperative sensitivity can be greatly reduced, even eliminated, with proper materials and technique. The steps involved in avoiding these pitfalls are as follows:
(1) Place a rubber dam. Rubber dams have many advantages, one of which is reducing the risk of moisture contamination. Rubber dams also serve to protect the patient from swallowing “stuff,” improve the field of vision, reduce procedure time, and protect the practitioner by reducing aerosol bacteria contamination.
(2) Use lots of water while preparing the tooth. Do not let the tooth dry out.
(3) Use a self-etching adhesive system such as AdheSE (Ivoclar Vivadent), Clearfil SE Bond or Clearfil Protect SE Bond (Kuraray), OptiBond Solo Plus Self Etch (Kerr), One-Up Bond F Plus (J. Morita), or Prompt L-Pop (3M ESPE). As opposed to the technique-sensitive total-etch/wet-bonding systems, self-etch systems are simple to use with minimal steps. Since self-etch does not etch as deeply and does not remove the smear layer, postoperative sensitivity from the adhesive is eliminated.
(4) To reduce the effects of polymerization shrinkage, composite should be placed in small increments not to exceed 2 mm.
(5) Inadequate cure will lead to a softer and porous composite. The restoration will be more susceptible to chemical degradation and increased solubility. Curing lights should be checked regularly with a radiometer to ensure effectiveness. Composites cannot be overcured, so when in doubt always cure longer.
A common symptom noticed at follow-up appointments is that the occlusion is now “off.” This is probably a secondary issue that arose from inflammation caused by another source of irritation. Of course, the occlusion must be readjusted.
ANATOMICALLY CORRECT TIGHT CONTACTS
Conventional techniques that incorporate a Tofflemire band often result in a restoration with a point of contact near or at the marginal ridge of the adjacent tooth. This weak area is subsequently subject to fracture at the marginal ridge or loss of contact during occlusal adjustment. A tight anatomical contact is achieved with a sectional matrix system (eg, Composi-Tight [Garrison Dental Solutions], Contact Matrix [Danville Materials], Palo-dent Matrix [DENTSPLY Caulk]). Incorporation of such a system provides a broad contact at the tooth’s natural height of contour, with a strong marginal ridge that is resistant to fracture. A sectional, precontoured, biplanar concave matrix band should be positioned and stabilized with a wedge at the gingival margin of the box. Minimal pressure is used during placement of the wedge, which seals the gingival margin of the box. The wedge should not cause tooth displacement or separation. The retaining ring gives a slight tooth separation and maintains placement of the matrix band during the restorative procedure.
To apply a retaining ring, the main body of the ring is engaged with ring placement forceps and placed over the band. For ring placement around a small or medium tooth, rubber dam forceps will usually work. When possible, the wedge is engaged with the retaining ring to ensure closure at the gingival margin of the box. While placement of the ring between the band and the wedge will impart separation of the contact area, it may also separate the band from the wedge and release the gingival seal. An open gingival seal may result in a gingival overhang or postoperative sensitivity from leakage of the etching material onto the root. Following placement of the matrix system, the band is burnished against the adjacent tooth in order to limit spring-back of the band.
Figure 1. Preoperative view of failing restorations on teeth Nos. 18 to 20.
Figure 2. Rubber dam placement on lower left quadrant.
Figure 3. After removal of old restorations and decay.
Figure 4. A retaining ring was placed for a tight, anatomically correct contact.
Figure 5. Composite is placed in small increments to reduce polymerization shrinkage.
Figure 6. Hybrid composite layer is built to within 1 mm of final restoration.
Figure 7. Per request of patient, stains are placed into grooves.
Figure 8. A translucent microfill composite is placed for the final layer.
Figure 9. After removal of retaining ring, prior to any adjustment.
Figure 10. Final polished restorations with occlusion adjusted.
A patient was scheduled for replacement of amalgam restorations in teeth Nos. 18 and 19. Tooth No. 20 had an existing composite restoration with decay on both the mesial and distal (Figure 1). Preocclusal stops were recorded with articulating paper in order to serve as a finishing reference. Shade selection and pit and fissure color mapping were also done. A dentin body and translucent enamel shades were selected to facilitate the achievement of a 3-dimensional appearance and illusion of depth.
Following the administration of anesthesia, a rubber dam was used to ensure moisture control as well as proper and predictable bond strength (Figure 2).
Preparation for a posterior composite restoration only requires the removal of the previous restoration, decay, bases, and liners (Figure 3). There is minimal reduction of healthy tooth structure, and undercuts are not required. Removal of slightly unsupported enamel is not necessary, since the bonded restoration will support the tooth structure.
To achieve a tight, anatomically correct contact a sectional matrix system was placed (Composi-Tight). Two sectional, precontoured, bi-planar concave matrix bands were placed. The size was selected to be level with the marginal ridge when placed. If a size is used that is not level with the marginal ridge when placed, then the contact will be in the wrong place. A wedge was then placed to stabilize the sectional matrix and help seal the gingival margin of the box. Minimal pressure was used during placement of the wedge, as the wedge should not cause tooth displacement or separation. The retaining rings were then placed to provide a tight contact (Figure 4). The rings have different lengths and therefore can be placed on top of each other. When possible the wedge is engaged with the retaining ring to ensure closure at the gingival margin of the box. Following placement of the matrix system, the band was burnished against the adjacent tooth in order to limit spring-back of the band.
For the adhesive step a self-etching system was used to reduce the possibility of postoperative sensitivity (Clearfil SE Bond). First, the self-etching primer component was applied for 20 seconds. The volatile elements of the primer were evaporated with a mild air flow. The adhesive component was then applied and light-cured. A dentin-shaded hybrid composite (4 Seasons [Ivoclar Vivadent]) was used to provide strength for the body of the restoration. The composite was placed in small increments not exceeding 2 mm in order to minimize the effects of shrinkage stress. The layers were also built against the walls of the preparation to minimize the effects of stress during shrinkage (Figure 5). The dentin-shaded hybrid layer was built up to approximately 1 mm of the final restoration (Figure 6). At this point, if the patient and clinician had preoperatively determined that pit and fissure stains are desired, then stains (eg, Kolor+ Plus [Kerr/Sybron]) should be embedded into the final layer of the hybrid material with a thin instrument, and then cured (Figure 7). For the final layer a microfill composite was placed. Since microfill composites result in less wear than hybrid composites and retain their polish more effectively, an enamel-shaded microfill composite (Heliomolar RO [Ivoclar Vivadent]) was placed as the final layer (Figure 8). The microfill layer gives the restoration an aesthetic appearance that matches the effect of enamel over dentin. This final layer should be placed close to the desired contours to minimize the extent of the finishing procedures (Figure 9).
The restoration was then given the final cure, the rubber dam was removed, and the occlusion was verified. Any necessary adjustments are performed with light pressure using a fine carbide or diamond bur and water irrigation. Excess interproximal composite should be removed with a No. 12 blade, a sharp scaler, or a finishing strip. Polishing was performed with rubber points (Jiffy points [Ultradent Products]) at high torque/low speed to maintain the occlusal anatomy. The postoperative result following direct restoration with composite resin presents enhanced aesthetics and significant preservation of the natural form (Figure 10).
Although placement of posterior composites may be challenging, clinicians can easily incorporate direct composite techniques and materials for the mutual benefit of the patient and clinician.
1. Swan SH, et al. Decrease in anogenital distance among male infants with prenatal phthalate exposure. Environ Health Perspect. 2005;113(8):1056-61.
2. Vandenberg LN, et al. Exposure to environmentally relevant doses of the xeno-estrogen bisphenol-A alters development of the fetal mouse mammary gland. Endocrinology. 2007;148(1):116-27.
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