Numerous materials with individual characteristics are used today for restorations with the direct technique: these characteristics include differences in viscosity, presentation as a single dose or in a syringe, and restoration with a single shade or using a layering technique.

Moreover, these materials have a wide and varied range of indications, extending from minimally invasive restoration of initial carious lesions to comprehensive restorations in the anterior or posterior regions.

In view of this variety of treatment fields/options, it is quite possible to construct specific instruments for each type of material and indication. However, it appears more rational to offer a versatile solution that is ergonomic on the one hand, yet on the other hand, confers unlimited functionality, even for unusual applications.

General aims
An important objective is optimised use of the dentist's time with regard to a clinically high-quality result and high working efficiency. Contrary to what can be expected from the term "light-curing composites", the processing time must be short in order to avoid premature hardening due to the general lighting or even faster setting due to the treatment lamp. Following contact between the sculpting instrument and the composite increment, a few seconds are needed to produce even distribution. This is a crucial phase for closing any gaps that may have arisen and achieving good adaptation to the cavity walls.

Under these circumstances, the dentist's workflow must not be constantly interrupted by changing between different forms of instruments. Instead, a few forms should be available in sizes suitable for the clinical situation and the employed materials. The choice of two instrument forms - a plugger and a spatula - appears logical. Two double-ended pluggers mean that four sizes are available but in contrast for the same selection of spatulas, four double-ended instruments are required so that the differently sized working ends each come with a curved edge and a curved flat surface.

Important criteria for instrument design
With instruments used for composite applications, it must be possible to place all types of composite materials and sculpt them by gentle contact. The composite must on no account stick to the instruments. There are different surface coatings on the market to counteract this phenomenon, for instance Teflon and titanium nitride. These coatings are sensitive - in the case of Teflon, they lead to thicker instruments and are always associated with a certain rigidity of the spatulas. An at least equally good non-stick effect can be achieved with highly polished stainless steel. Its elastic flexibility makes the consistency of the materials palpable for the dentist during sculpting.

For the aforementioned reasons, a plugger must be smooth with rounded contours, corresponding to the shape of the rotaries (ISO 830) used for cavity preparation.

The smallest plugger diameter allows use in minimally invasive cavities, for instance simple fissure opening, tunnel preparation or cavities prepared with sono-abrasive instruments. The biggest plugger should facilitate placement of larger amounts of composite, which is important especially in large cavities in order to control the highly- associated contraction strain.

A fine spatula can be introduced into the approximal spaces, used for sculpting the cusps and for shaping the outer surface of the marginal ridge. With its working end, a small increment of composite can be picked up.

A large spatula is suitable for working material on the vestibular surface of an anterior tooth, whether this involves only a cervical filling or a major restoration involving the incisal margin.

Hints on use
A rationally designed spatula is a versatile instrument. With regard to ergonomy, two principles should be emphasised:

• The number of instruments employed should be limited.
• If necessary change to an instrument of a different size but not of a different shape. This improves the workflow by avoiding delays due to the dentist switching instruments.
  A spatula is an extremely versatile instrument:
• With its slightly tapered working end it can be used to apply the
  composite material precisely.
• The flat surface allows material to be applied and shaped
• Excess can be removed with the edge,cusp contours can be shaped or the marginal lobes of an incisal edge can be recreated. Naturally it does not make sense to use a complete new set of instruments for each case. Every dentist can make his selection according to his experience and working habits.
  A few suggestions:
  
• A posterior set with one plugger and one or even two spatulas    
  
• An anterior set with two spatulas

Maintenance of the instruments
Instruments for sculpting composites should not be used for any other purpose in order to keep their surface intact. In particular, they must never be used for working with glass ionomer cement or amalgam. Composite instruments must be protected from scratches. Storage in cases is always to be preferred.

During use, monomer traces always remain on the part of the instrument that is placed in contact with the composite material. With a disposable paper napkin at hand, the instruments can be wiped regularly for greater working efficiency.