INTRODUCTION:

A veneer is a thin sheet of material placed on the front surface of the tooth, used for aesthetic purposes and protection. It is usually a thin layer of restorative material replacing the enamel. When multiple thin layers of wafer thin shells are chemically bonded to the tooth structure it is called laminate veneer. "lamination" is the process which refers to joining the materials together [1]. The difference between a veneer and laminate is that a veneer is a layer material placed over the tooth to change the colour of the tooth as they are tooth coloured restorations, whereas laminates maintain the colour[2]. Veneers are usually the material of choice for a conservative, esthetic approach as they are tooth coloured restorations in order to the give the patient a perfect smile. This in turn improves the self esteem, confidence thus boosting the social life of the patient. They were first used in 1928 by a California dentist Charles Pincus for changing the appearance of an actors teeth temporarily for a film shooting[3]. Since then there has been an increasing demand for the veneers as an effective esthetic alternative.

They have been made from various materials like ceramic, porcelain, composite resin, microfilled composite resin, preformed acrylic laminates, glass ceramic veneers etc.[4]. Veneers can be direct or indirect depending on the method of production. They can also be classified as direct or indirect veneers depending the coverage.

Indications:

· localised defects

· generalised defects

· intrinsic discolouration[5]

· diastema

· Chipped tooth

· worn dentition

· ->malaligned teeth

· excessively discoloured teeth

· ->hypocalcification

· peg laterals

· lingually positioned tooth[6][7]

Advantages:

They are extensively used as they are biocompatible, strong, durable, stain resistant, show longetivety, little recovery time, good clinical performance and are minimally invasive compared to crowns[8]. The recent years there have been various advancements in dental laminates and veneers with the aim of overcoming the previous shortcomings and for a more conservative feasible approach. The various recent advancements in dental laminates and veneers have been discussed in this review article.

Over the years there have been various advancements in laminates and veneers in dentistry. The recent advancements are:

· stacked/feldspathic teeth veneers

· thick monochromatic teeth veneers

· teeth veneers with reinforced leucite

· lithium disilicate teeth veneers

· ->lumineers

· ->Durathin veneers

· ->vivaneers

· da Vinci veneers

· MAC veneers

· zirconia veneers

Stacked/feldspathic teeth veneers:

These veneers contain many stacks of porcelain giving rise to multiple layers in the veneer. Feldspars are naturally occurring aluminium silicate containing sodium or potassium. The feldspars contain fluoroapatite crystals improving the optical appearance of the tooth[6].It has a polychromatic appearance and high translucency, hence closely resembles the natural tooth. Hence it is of great esthetic value[9].It is the highest quality cosmetic veneers.They are not as thick as monochromatic veneers.However the downside of these feldspar veneers is that they are not strong due to their low mechanical properties as the flexural strength is from 60-70 MPA[10].

Teeth veneers with reinforced leucite:

They are thinner veneers, having good aesthetics and used when teeth require minimal preparation. These veneers are patented and are available only from a lab in California and are not widely available. Reinforced Leucite has a flexural strength of 120-140 MPa and a moderate compressive strength.

Thick monochromatic teeth veneers :

These are usually thicker than the normal veneers, hence contributing to its strength and durability. They are present in one colour and can be customised according to the patients preference. They are used when the teeth has to be lengthened due to age or other factors. How ever these monochromatic veneers require more preparation to implement.

Lithium disilicate veneers :

They are the most widely used true glass ceramics. It is versatile and is stronger than other porcelain veneers . It has a high flexural strength and available in a variety of shades. It has high resistance to thermal shock thus managing the problem between two similar materials. It is used for teeth which requires minimal reshaping. It can be used to correct the shape of a malformed tooth[11]. It can be used in all areas of the mouth with some exceptions. They can be conventionally cemented or adhesively bonded[12]. IPS Emax (Ivoclairvivadent) is an example of these veneers.

Minimally invasive veneers or no prep veneers :

These veneers are ultrathin having a thickness similar to contact lenses of about 0.3-0.5 mm and hence get are called "contact lenses of teeth".These help in greatly conserving the tooth structure as previously used porcelain veneers needed a mandatory 0.5mm to 1 mm removal of tooth structure so that the thin layer of porcelain does not fracture[13]. They consist of lumineers, durathin veneers and vivaneers.

a). Lumineers :

They are exceptionally thin veneers (0.3mm) made of a special cerinate porcelain. Cerinate is material made of feldspathic porcelain reinforced with leucite crystals. They have low thermal expansion[14].They can be easily placed with minimal invasion and pain. They have high strength and resilience despite being exceptionally thin. They can be directly placed on the tooth without any anesthesia. They can be showed according to the patients wishes and can be placed with minimal visits to the dentist. They can be placed within two visits to the dentist. How ever the disadvantage of lumineers is that they have an opaque appearance interfering with the aesthetics of the patient.

b). Durathin veneers:

These veneers are exceptionally thin and are about 0.2 mm whereas the traditional veneers are usually about 0.5 mm thick. These veneers have gained popularity due to its good esthetic effects as it gives a natural translucency to the teeth closely resembling natural teeth. This is one of the advantages that durathinveneers have over lumineers as lumineers have an opaque appearance thus failing to give a natural effect. It is of high quality and requires the work of any highly artistic dental lab ceramist.

c). Vivaneers:

These are extra tough veneers with a thickness of about 0.3 mm and hence need a minimal thickness of about 0.3 mm[15].They are manufactured inGlidewell laboratories.

d). MAC veneers:

(Microadvanced Cosmetic Division veneers)

They are pressed ceramic veneers. They are manufactured in Microdental laboratories. They have high strength and are denser than other veneers. They are a bit thicker when compared to other veneers which ensures that these veneers can firmly adhere to the tooth surface and are not displaced from the teeth. They are also stain resistant. They can be placed over other teeth which are undergoing treatment at the same time. They are made by highly skilled technicians and give an excellent aesthetic outcome[16]. However these teeth need some amount of tooth preparation.

e). Da Vinci veneers :

They are high quality, ultra thin veneers. These porcelain veneers are hand crafted and are of tooth colored ceramics. They are manufactured in Da Vinci Dental Studios, California. They are indicated for chipped teeth,mishapen teeth, discolored teeth, gaps between the teeth and also for crowded teeth. They have fluorescent porcelain that enhances the aesthetic quality and the strength of the veneer. They have the ability to resist stains. They require little or no anasthesia. They have a firm bonding within the teeth structure ensuring that they have good longetivety. How ever these veneers need some amount of tooth preparation[17].[18].

Zirconia veneers:

Zirconia is a polycrystalline ceramic which is acid resistant with no amorphous silica which does not react to traditional glass etching treatments[19][20]. Zirconia veneers have excellent aesthetics. It is a versatile material. They are high strength materials having fluxural strength of 1000 MPa. They are resistant to fracture having a fracture toughness of 8-10 MPa. They can be used for discoloured tooth as they are opaque and easily mask the colour of the underlying tooth[21]. The zirconia veneers are layered with or without porcelain. They can be adhered to the tooth using surface adhesive primers which are phosphate comonomers covalently bound to the oxide [22]

CONCLUSION:

Veneers is a minimally invasive option for the treatment of discoloured and malformed teeth. The recent advancements in veneers and laminates in dentistry have given rise to an excellent alternative for a conservative approach for the teeth. It closely resembles the natural teeth and hence has good aesthetics. It's placement is a minimally invasive procedure and hence is widely accepted by patients. The recent advancements having good biocompatibility, high strength, durability and stain resistance has increased the demand for laminates in dentistry. However they do have some disadvantages like high cost, they cannot be used for malaligned teeth and have to be replaced every few years due to shrinkage which have to be taken into account for the future advancements made in order to improve the quality of the treatment and for the better aesthetics of the patient.

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Received on 29.07.2016 Modified on 18.09.2016

Research J. Pharm. and Tech 2018; 11(2):785-787.

DOI: 10.5958/0974-360X.2018.00148.8