INTRODUCTION

In recent years, the progress made in operational techniques and the continuous improvement of the physical, chemical  and  mechanical  characteristics of reconstruction materials have made it  possible for dentists to focus their attention on the constant pursuit of the best aesthetic restoration results. Patients asking for aesthetic restorations  want  them to integrate with their natural teeth. Dentists, therefore, should not only rely on scientifically validated techniques to restore dental biology but also be guided by their sense for  aesthetics  in order to reproduce the polychromatic and anatomical characteristics of teeth, so that restorations are ultimately unnoticeable.

In philosophical terms, the word ‘aesthetics’ indicates the “science of beauty, liberal arts and gnoseology, closely related to logics”, i.e. the beauty and outward appearance of something. In dentistry, a restoration is aesthetic when it best matches the color, shape and function of what it replaces. The physiological behavior of teeth, in fact, is the result of a close interaction between mechanical, biological, functional and aesthetic properties. This is where composite inlays come into play. The current composite resin formulations have improved the characteristics of materials through the size, shape, concentration and type of filler used. Shrinkage caused by curing has been reduced while tensile and flexural strength as well as resistance to abrasion and long term color stability have increased. Add to all this the benefits of high power curing lights, in combination with heat and pressure, that improve the quality of the polymerization reaction.

In recent years, two factors, at least, have contributed to the development of aesthetic inlays  and onlays:

• continuous innovation in enamel and dentin adhesives, which provide a high bond strength of the composite to dentin and enamel
• increased and constant request for aesthetic restorations on the part of patients.

MATERIALS AND METHODS

Composite offers several advantages: it does not require large thicknesses, it provides a good marginal precision and the possibility to correct shape and color, it  is easy to  repair, and  lab procedures are not complex. Indeed, it (almost) matches  several of the most significant qualities of ceramic materials (resistance to wear, long-term aesthetics, high stability) while offering remarkable advantages in terms of lower investment and less complex laboratory procedures, the possibility to perform intraoral corrections and repair, a more conservative cavity preparation, effective polishing, and a lower frailty and tendency to fracture. In particular, the modulus of elasticity (a body’s rigidity or flexure), resilience (the ability to absorb stress up to the breaking/failing point) and fatigue  strength (rupture after dynamic stress is applied) are the mechanical properties that, unlike with ceramic systems, make it possible to work with lower thicknesses  of composite material, which is also less subject to breakage. Indirect composite restorations such as inlays, onlays and overlays can be made with both dental  office and laboratory composites, without distinction.

Composite has three phases: matrix, filler and bonding agent. The most commonly used organic phase in composite materials mainly consists of Bis-GMA and/or UDMA together with other resins with a lower molecular weight. Fillers are those substances that are added to increase the  strength of the resin:

• macro particles (8-25 microns)
• fine particles (1-8 microns)
• micro particles (0.04-0.2 microns)

The composite used for this clinical case was Estelite Sigma Quick by Tokuyama Dental. Estelite Sigma Quick is a light- curable and radiopaque, submicron-filled composite resin, containing 82% by weight (71% by volume) of composite filler and zirconia/silicate filler. Thanks to these filler particles, shrinkage caused by curing is reduced. Each inorganic particle in the composite is submicronic (average size of the particles is 0.2 µ, in a range   from 0.1 to 0.3 µm) and this preserves brightness and resistance to wear to a very high degree. The monomeric matrix contains Bis- GMA and triethylene glycol dimethacrylate.

DR. ALBERTO PUJIA and ODT. PAOLO RICCIONI

To be continued...