35: Evaluating Esthetic Materials

Chapter 35 Evaluating Esthetic Materials

Relevance of Evaluating Materials and Techniques to Esthetic Dentistry

Important Terminology

AccuVol: Volumetric shrinkage of restorative composites is determined using this specialized scanning device designed by Bisco.

Bond strength: Bond strength tests are done with operators and assistants working together to simulate the clinical procedure.

Digitized microleakage: Microleakage at the margins of class V restorations is measured using an imaging algorithm reading from sectioned specimens viewed through a stereo microscope.

Fluorescence: Fluorescence of materials is tested intra-orally in a live subject in a custom-made black light cabinet. It is not possible to test fluorescence using extracted teeth or discs.

Hardness: Depth of cure of composites and curing time as it relates to hardness are tested in a digital hardness tester.

Modified molar for depth of cure: Modified class II preparation is used to determine depth of cure and gingival wall hardness instead of the much more common but clinically irrelevant metal cylinder technique.

Porosity: Trans-illuminating and digitizing disks of composite quantify porosity in composites. Materials with high levels of porosity can cause problems during the finishing and polishing phase of a restoration.

Specimen preparation: Specimens for bond strength testing are prepared on a dual-wheel model trimmer.

Thermocycler: A thermocycler is used to simulate the temperature extremes that a restoration would experience intraorally.

Translucency and opacity: Spectrophotometry determines the translucency and opacity of materials to allow more specific selection. These properties are important in choosing materials to replace enamel and dentin and to simulate incisal effects.

Unless there is some science behind the materials or methods used in dental trials, there is no way a clinician can know whether a product works as advertised. Experience in evaluating dental materials, including esthetic materials, devices, and equipment, reveals that many claims made by manufacturers are shaky or even untrue.

Numerous evaluations are available, so it is important to assess the source of the evaluation. The people doing the evaluation must be totally unbiased. If there is any commercial overtone in an evaluator’s profile, that tends to negate many of the findings. For example, the evaluator may be working under a grant from a manufacturer, suggesting bias. It is well known that those who pay the bills are more favorably treated, so it is very important to know who is doing the evaluation, what is behind it, and who is paying for it.

The methods by which evaluations are done are also important. For example, a facility tests a new nanocomposite restorative material and finds that the product does not light cure well at the bottom of a proximal box. If a clinician is using this in a class II situation and places it on a gingival wall and cures it for the manufacturer’s recommended time, most likely the material will be undercured. The manufacturer may not have ever performed a test under those conditions. Many products on the market have undergone testing but nothing that subjects the product to all the uses for which it is recommended. The issue of validation for the clinical dentist is one of confidence in use. To be confident that the material will function in a certain manner, the dentist must have an independent non-manufacturer, non-distributor evaluation that indicates the uses of the material and the results expected.

Many materials are good materials made by ethical, well-meaning manufacturers. As noted, the way the products are used is not always investigated by the manufacturer. Even when the manufacturer has a recommended technique, that technique may not be appropriate or may not optimize the material’s performance. In these cases, dentists using these products according to the manufacturer’s directions come up with less-than-optimal results. Often a manufacturer’s directions are based on outdated tests designed by the International Organization for Standardization (ISO), the American Dental Association (ADA), or other regulatory bodies. These tests may have been applicable years ago but no longer apply to modern materials. Tests must be adjusted frequently so they reflect how a product is being used clinically. The way to optimize the product’s use is not necessarily in the instruction manual that comes in the box. Most instruction manuals or, as manufacturers call them, the DFUs (directions for use), are poorly written, presented in extremely small type, and printed on paper that is not amenable to disinfection procedures. If the dentist picks up the instructions while using the material and his or her gloves are contaminated, the instructions can blur and become contaminated. The instructions may also be ambiguous. Probably the most egregious example is adhesives, because many adhesives today demand that the dentist use certain types of moisture substrates. Moist states range from the tooth glistening with moisture to being completely dry. The manufacturer’s description of what the dentist should achieve in the substrate condition is typically so ambiguous that it is virtually impossible to achieve.

Brief History of the Clinical Development and Evolution of Evaluating Esthetic Materials

The ADA and ISO have testing programs and regulations in place for materials presumably before they can go on the market. Because these quasi-governmental bodies are somewhat slow in responding to changes, many products are not tested properly or involve old materials. In the 1970s, Clinical Research Associates (CRA) started a private testing program. Although its testing program is acceptable, there are flaws in it because dentists do not conduct the tests, so they are not always clinically relevant.

In the early 1980s the Dental Advisor offered a testing program along the same lines as those used by CRA or universities. The main researcher behind that program was not a dentist. REALITY Publishing Company (www.realityesthetics.com) came on the scene in 1986. The goal of REALITY is to test products in a more clinically relevant manner, as used by normal dentists in normal practices.

REALITY follows a three-pronged attack method. First, the products are tested in the REALITY research lab, which is staffed primarily by research dentists plus some auxiliaries who handle non-dental activity. The products are tested in a controlled manner using techniques that match clinical techniques as closely as possible. There is always a gap between laboratory and clinical views, but the techniques are designed to simulate the clinical situation as closely as possible. Second, 38 clinical evaluators throughout the world, with various types of experience and academic credentials, are used to obtain a good geographic balance between clinical and academic, scientific and practical assessments. This yields a variety of opinions on these materials, products, and equipment. Third, the scientific literature is reviewed even though much of it has little relevance to clinical practice.

Jan 3, 2015 | Posted by in Esthetic Dentristry | Comments Off on 35: Evaluating Esthetic Materials
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