As materials and techniques in dentistry have become ever more sophisticated, the sense of responsibility the industry holds for its patients has arguably evolved too. Modern developments are subjected to far more extensive testing and proving than was the case in the past.
Although time consuming, this has many benefits. As well as achieving its chief goal of enhancing patient wellbeing, such thorough testing also means that dental practitioners have far more data than ever before. They are able to compare and contrast a myriad of products and procedures, and thus employ them in the most appropriate way in their general practice. The wide availability of research documents online makes this even easier.
Composite filling materials provide an excellent example of the point. When composite resins were introduced in the 1980s they were met not with a blind acceptance, but with cautious requests for more information and more extensive research, as practitioners speculated about the clinical performance of the products.
In particular, practitioners needed convincing that composite materials were sufficiently wear resistant and that polymerisation shrinkage would not occur. These justified concerns prevented composites being used extensively in posterior restorations for many years, though they did become popular quickly in anterior regions. However, advances in the available materials coupled with extensive and objective testing have now seen that situation change. Modern composites are used extensively in posterior locations.
If anything, the testing regime has become even more demanding as newer products come to market. In vitro tests designed to predict durability levels of a restorative dental material in clinical practice are only stepping stones to negotiate on the way to in vivo tests. These are now considered essential to measure more accurately the functional stresses that restorations will be put to when patients start biting, chewing and grinding their teeth. The more demanding tests also reflect more accurately how restorations will cope with constant changes in temperature and pH balance.
Evaluations of how restorations perform in real use can take place over periods ranging from weeks to years. They also need to use comparable procedures and measures, which is why the United States Public Health Services (USPHS) evaluation system, also known as Ryge’s criteria, has become the most commonly used method. These were set out in 1971 to provide a systematic approach to the clinical assessment of restorative dental materials.
Such tests, even relatively short term ones, have increased acceptance of composite materials among dentists, by providing more tangible results in terms of predicting outcomes.
For example, Ceram.X from Dentsply, was included in a six month evaluation which showed it to provide outstanding colour matching results which lasted for the duration of the test period.
The study used 25 patients, all from the 18-40 age group. All had class I or class II cavities in posterior teeth indicated for composite restoration. The patients were considered to have oral health within acceptable ranges for their age. No more than three teeth per patient were included in the study.
Patients with para-functional habits such as bruxism were excluded from the study, as were those with restorations requiring cuspal coverage. Those with mental disabilities or other conditions that might prevent later cooperation were also omitted from the study.
All restorations were undertaken by a single operator, who followed standard procedures and adhered to manufacturer’s instructions for use of the materials tested: the nano-hybrid composite Ceram.X Duo and the micro-filled composite Heliomolar (Ivoclar Vivadent).
The restorations in the trial could all be classed as small to moderate in size. The operative area was isolated with a rubber dam, cotton rolls and saliva ejector, and the cavity prepared using tungsten carbide burs. Calcium hydroxide was used to cover deeper cavities, and all enamel and cavosurface margins were acid etched and coated with bonding agent.
In the case of class II restorations, a contoured sectional matrix band was applied and wedged to adapt to the gingival margin, providing a degree of tooth separation. The composite fillings were inserted incrementally by no more than 2mm thickness at a time. Restorations were light cured according to the material’s instructions for use.
Two clinicians evaluated the results, at intervals of one, three and six months. Although the colour matching of both materials was clinically acceptable, Ceram.X showed more consistent colour matching. Measured on this parameter, an Alfa (A) rating was given to 100 per cent of the class I restorations using Ceram.X, and to 90 per cent of the class II restorations using the product.
In keeping with the trend for more research, the slight differences in colour matching measured between the two materials prompted an immediate request for a longer-term study.
References available on request.