Msmiline - Proeclain Inlays
Inlays
Sometimes, a tooth is treatment planned to be restored with an intracoronal restoration, but the decay or fracture is so extensive that a direct restoration, such as amalgam or composite, would compromise the structural integrity of the restored tooth by possibly undermining the remaining tooth structure or providing substandard opposition to occlusal (i.e. biting) forces. In such situations, an indirect gold restoration may be indicated, such as the gold inlay shown below. When gold is used, the tooth-to-restoration margin may be finished and polished to such a super-fine line of contact that recurrent decay will be all but impossible. It is for this reason that some dentists recommend gold as the restorative material of choice for pretty much any and all restorations. While these restorations might be ten times the price of direct restorations, the superiority of gold as a restoration in terms of resistance to occlusal forces, protection against recurrent decay, precision of fabrication, marginal integrity, proper contouring for gingival (tissue) health, ease of cleansing and many other aspects of restorative quality offers an excellent alternative to the direct restoration. For this reason, some patients request gold restorations so they can benefit from its wide range of advantages even when an amalgam or composite will suffice. The only true disadvantage of gold is the higher cost.
Types of Inlays
Silver (amalgam) fillings: Silver fillings have been used reliably for many years. Typically, silver fillings are placed on back teeth (molars). They are an economical way of providing a lasting restoration for most cavities. The material is specially formulated to withstand years of chewing pressure.

White fillings: White fillings are an alternative to silver (amalgam) fillings. White fillings are made of a strong composite resin that is matched to the surrounding tooth colour. In the past, white fillings were placed only on front teeth, but recently a stronger more durable material has been developed that can withstand the chewing pressure of back teeth

Gold inlay or onlay: A gold inlay or onlay is
used when the cavity is too big for a silver filling, but isn't so
big that a crown is required. An inlay is a filling within the cusp
tips of the tooth. Onlays (also known as overlays) will overlay one
or more cusps in order to protect and strengthen the tooth.

An impression of preparation for restoration
with a DO gold inlay on tooth #5. The "DO"
designation indicates that the gold serves as a restoration for
the distal and occlusal surfaces of the tooth. This tooth was
prepared and the inlay will be fabricated according to the
R.V. Tucker method of gold inlay preparation.
Notice how the line angles of the impression for the inlay are
very sharp and precise; this is achieved using carbon-tipped
stainless steel instruments. The salmon-colored polyvinylsiloxane
impression material is less viscous than the blue and is able to
capture better detail for the tooth being restored.
Onlays
Additionally, when decay or fracture incorporate areas of a tooth that make amalgam or composite restorations essentially inadequate, such as cuspal fracture or remaining tooth structure that undermines perimeter walls of a tooth, a gold onlay might be indicated. Similar to an inlay, a gold onlay is an indirect restoration which incorporates a cusp or cusps by covering or onlaying the missing cusps. All of the benefits of a gold inlay are present in the onlay restoration. The onlay allows for conservation of tooth structure when the alternative is to totally eliminate cusps and perimeter walls for restoration with a crown. Because onlays have a very long margin (i.e. the line of tooth-to-restoration contact is much longer than that of a crown because of the many turns and curves that an onlay makes in contacting the tooth), some dentists feel that an onlay is a fundamentally inferior restoration. This is because it is primarily the marginal adaptation of any dental restoration that will decide whether or not it will successfully remain in the mouth without exhibiting recurrent decay. The increase in marginal length consequently provides a further likelihood of failure.
An MO gold inlay on tooth
#3, the "MO" designation indicating that the gold serves as a
restoration for the mesial and occlusal surfaces of the tooth.
This tooth was also restored according to the R.V.
Tucker method. Notice how the gold appears to flow into
the tooth structure, almost perfectly mimicking the natural
contours and even allowing the specular reflection to continue
over the margin from tooth to gold.