Often when I lecture on composite dentistry I get asked about improving the final surface texture, polish and sculptability when doing anterior teeth. In a previous blog I looked at the categories of composites and understanding their physical and handling properties based on composition. Microfill composites are an older material formulation that is still on the market for precisely the reason of it’s esthetic qualities. These materials have a lower filler percentage which means there are compromises in the areas of material strength, wear and durability under load. However, microfills to date still have the highest polishability of any composites. Not only are the easy and beautiful to polish in your office, but they maintain that polish over time due to normal hygiene with a toothbrush.
Sometimes it feels as if it is hard to stay ahead of the curve with updated technology and equipment. While many of our equipment purchases are discretionary, others are vital and this would include our curing lights. The majority of curing lights in use today are LED, with a smaller number of halogen and plasma arc units being used. In the world of LED the newcomer when looking at lights is called a poly wave LED. If your current LED light is working you may be wondering why you would upgrade to this newer technology.
Tissue management for an exquisite impression depends on two factors. The first goal is to move the gingival tissues away from the margins and create a space for the impression material. The ideal space allows the technician the opportunity to create emergence profile and properly contour the restoration. The next goal of tissue management is to control moisture, as almost all of our impression materials are hydrophobic. As part of this process we often have to manage the tissue bleeding.
Before the advent of pressing technology ceramic restorations were most commonly produced using a process of combining liquid and powder into a slurry and then stacking this porcelain on the die. The ceramic is applied this way in layers and then fired. This process is still commonly used today and understanding the properties can allow us to use it to our advantage to achieve the clinical results we are after. Ceramics fabricated in this way are typically feldspathic or leucite reinforced glass, and used primarily for anterior restorations. The fabrication process is challenging and time consuming and requires a skilled ceramist to create both the esthetic results and a precisely fitting restoration. An advantage of this type of ceramic restoration is the ability the technician has to layer material of varying color and opacity.
Earlier posts have discussed the difference in light and color properties between natural tooth structure (enamel & dentin) and their corresponding composite replacements. The difference in translucency, opacity and how the thickness of each layer impacts these properties and others like chroma and value become a challenge chairside when we try and replicate nature. One of the ways to understand and maximize the properties of the composite you are using is a simple bench top exercise. First create a silicone lingual matrix from a model of a patients upper anterior teeth. Next using the current composite that you would employ for a class four or anterior veneer you simply need to create a few teeth and play with the layers and their relative thicknesses.
All composite materials are a mix of organic resin matrix, filler particles and a coupling agent. The challenges we experience with composites like consistency and stickiness as well as characteristics like polymerization shrinkage, flexural strength and polishability are a result of the type and quantity of filler particles in relationship to the resin matrix. As the proportion of filler particles increase the physical properties of the material improves, but handling properties can be compromised. In a quest to create better composites with optimal physical properties and handling characteristics new advances have been made in filler particle science. As new categories of composites have come on the market some of the older types have continued to find applications and been preferred by some practitioners. With all the different types of composites on the market what should you use when, and do we have a universal material?
Several months ago an article came out in the news that linked composite fillings that contain BPA during childhood with social issues like depression, stress and anxiety. BPA or Bisphenol A is a chemical present in many plastic materials, and has been associated with numerous health issues, resulting in it’s removal from many products such as water bottles and baby bottles. One of the chemicals in composite filling materials is bisGMA and it is made from BPA. Last month’s issue of JADA included an article based on research that showed increased levels of BPA in both saliva and urine for a number of hours after the placement of composite fillings containing bisGMA.
With the increase n the amount of bonding procedures that we do everyday, tissue health has become an even more important conversation. There is nothing more disheartening than removing provisionals to seat the final restorations and looking at red, puffy inflamed gingival tissues. The tissue health is a critical factor to successful bonding and cementation. There are many factors that contribute to the gingival health at the seat appointment. One is the patients oral hygiene. Having myself had splinted provisionals I am clear that very few of my patients are going to use floss threaders. At best we can hope for patients brushing and even then if they are worried about knocking off their temps they will be skiddish about their oral hygiene.
I am old enough that I learned amalgam as the go to operative material. In those days when we encountered deep decay we followed a process of applying calcium hydroxide to the deep areas of the prep and expected good results in the formation of a dentinal bridge and survival of the pulp. When we transitioned to composite products like Dycal(Calcium Hydroxide) and Copalite disappeared. For me it has felt like there has been a void in my ability to pulp cap in the instance of deep decay under a composite. Using glass ionomer or RMGI is probably the most accepted technique. The challenges I have run into are the set time of the materials and the limited bond strengths to dentin. Earlier this year Bisco dental released a new product designed for just this purpose. I have been using it ever since and finally feel like I have a pulp capping product I can use with confidence.
Key to the long-term success of a posterior composite is the marginal seal and integrity. The margins are the area most likely to break down, evidenced by leakage, staining or recurrent decay. Interproximal margins are perhaps more subject to these issues than the margins we see easily on the occlusal surface. So how do we assure proper seal that will last over time. In the prior post of posterior composites I mentioned convenience form. I think this is a critical step in marginal integrity. Having adequate convenience form allows us to see, feel and finish the margins interproximally. In this way we can be certain the day of placement we have created sealed the margins.