The unexpected loss of tooth structure due to caries, subsequent damage to the tooth due to extensive endodontic treatment and, particularly, missing anterior teeth create physical and functional problems and often psychologic and social disturbances as well.
Over the last decade, demand for treatment of unaesthetic anterior teeth has now become one of the most critical needs for patients attending dental clinics for the restoration of aesthetics as well as function.
Accordingly, several treatment modalities have been proposed so far including crowns/bridges, veneers etc. to restore the aesthetic appearance of the dentition. The demand for tooth-coloured restorations has grown considerably during the last decade.
In this context, dental ceramics/porcelain is widely used due to their ability to imitate the optical properties of enamel and dentin and their biocompatibility and chemical durability.
Although metal-ceramic and porcelain fused to metal crowns have been acknowledged with 94% success rates over 10 years, concern regarding limitations in biocompatibility and optical qualities has encouraged the use of full porcelain crowns.
Modifications in metal-ceramic systems dominated dental ceramics research during the past 35 years that resulted in improved alloys, porcelain metal bonding, and porcelains.
The full porcelain crown system, despite its aesthetic advantages, failed to gain extensive popularity until the introduction of alumina as a reinforcing phase in dental porcelain. This method was considered as one of the most important developments in dental ceramics, was first introduced in dentistry by McLean and Hughes in the 1960’s.
Despite being, strengthen by the addition of alumina, the transmission of the light decreases resulting in poor translucency and adaptation of the dental restoration. To overcome this limitation, a new aluminous porcelain was subsequently developed and introduced under the name of Hi-Ceram, however the disadvantages of both aluminous porcelain materials remained that the strength was inadequate to restore posterior teeth where these restorations are prone to brittle fracture and the dental restoration had a dull appearance.
The use of toughened ceramics such as yttrium-stabilized zirconia offers a more fracture resistant application of full-ceramic/porcelain crowns to the posterior region without sacrificing aesthetic qualities.
Zirconia ceramics are known to have physical properties that can accomplish twice the flexural strength and fracture toughness of densely sintered high purity alumina ceramics. Depending on the quantity, size, and chemical properties of the crystals within the ceramic matrix, light is more or less scattered and reflected causing the ceramic to look more opaque or translucent.
Different types of full-ceramic/porcelain such as In-Ceram Zirconia followed by In-Ceram Alumina, Procera AllCeram, IPS Empress 2, and In-Ceram Spinell have been shown to have increasing translucency, which may influence the aesthetic choice of restorative materials.
Several studies of full porcelain crowns have exclusion criteria for patients with severe parafunction, moderate gingival inflammation; high carries risks, and poor oral hygiene. There are no recognised health risks to patients from the use of full porcelain crown in prosthodontic and restorative dentistry, other than possible abrasive damage to opposing dentition and the potential for fracture.
Beside this, excessive exposure to acidulated fluoride can increase chemical degradation of porcelain surfaces, but the products of such degradation are usually not ingested.
The surface attack may perhaps result in greater plaque accumulation that affects soft tissue, but this seems more an exercise in speculation than a real health concern. Moreover, the major drawback in using full porcelain crown is the substantial removal of large amounts of sound tooth substance and possible adverse effects on adjacent pulp and periodontal tissues.
In search of more durable aesthetics and to overcome this major drawback, full porcelain veneers have been introduced in the market that is steadily increasing in popularity among today’s dental professionals for conservative restoration of unaesthetic anterior teeth.