Replacing Amalgams With Porcelain Onlays – Illustration

illustration of a healthy tooth
HEALTHY TOOTH: A healthy tooth with its three layers: enamel, dentin and pulp. Enamel is the hardest substance in the body. Dentin is made up of live tissue, similar to bone, however it does not have a blood supply. It receives its nutrition through millions of tiny tubules extending from the nerve (pulp) chamber all the way to the enamel junction.
The pulp is made up of tiny arteries and veins, nerves and a matrix which includes stem cells for regeneration. The extension of the pulp into the root is called the “root canal”.
illustration of a tooth with decay
DECAY: as a cavity forms through the pit, it spreads radially once it enters dentine. This is technically an “infection”, since it represents bacteria invading dentin (live tissue).
illustration of a tooth with amalgam filling
AMALGAM FILLING: this is basically a primitive “prosthetic” method of cutting (or drilling) out infected dentine and filling the space with a substance which hardens and “restores” the missing part of the tooth. Amalgam is an unstable metallic alloy which is not bonded to tooth structure. Instead, it is packed into the cavity using undercuts so it stays put.
illustration of tooth with deterioration and recurring decay
DETERIORATION AND RECURRENT DECAY Over the years, as amalgam corrodes, its surface is rusted and its marginal integrity is damaged, allowing moisture and bacteria to leak into the space between it and the tooth. The constant expansion and contraction from temperature fluctuations also causes cracks inside the tooth, weakening its structural integrity. What is known as “recurrent” decay sets in, which spreads towards the pulp, and along the enamel and dentin interface, weakening the tooth even more.
illustration of safe amalgam removal
SAFE AMALGAM REMOVAL is carried out using strict precautions to avoid mercury vapor release and ingestion. (see video Safe Amalgam removal by Dr Sarkissian) One such precautionary protocol is called the “chunk removal” method, which involves drilling trenches along key points in the amalgam, and removing the “chunks” mechanically. This is to avoid drilling out the whole mass of the amalgam, which releases high quantities of mercury vapor and amalgam dust.
illustration of tooth decay removal
DECAY REMOVAL: Most of the decay is removed using a slow electric drill.
illustration of deep tooth decay emoval with the laser
DEEP DECAY REMOVAL is carried out with the laser “waterlase” to avoid traumatizing the pulp (nerve) area. This reduces the risk for root canals. To see a video of the laser in action, watch the video How does the Dental Laser work.
illustration of a tooth core buildup after decay removal
CORE BUILDUP is intended to insulate the dentin and fill in the undercuts. Restoring this tooth follows the biomimetic principle of replacing parts of the tooth not only using the most conservative approach, but also using materials that are bonded throughout, and which are close to the properties of the tooth itself. A bonded biocompatible bioceramic is applied over the area of dentin closest to the pulp, which is then sandwiched in a layer of composite, which also fills in the undercuts.
illustration of the onlay design after removal of tooth decay
ONLAY DESIGN: The tooth is then shaped for an onlay with fine diamond burs, and is digitally scanned with our CEREC camera, creating a virtual model. An onlay is digitally designed in the computer program, and is sent to a CAD-CAM device, which mills the onlay on the same day.
illustration of the onlay placement after removal of tooth decay
ONLAY PLACEMENT: The onlay is tried in, glazed, and bonded in place. The whole procedure between scan and cementation takes 40 minutes. The rationale of the onlay is as follows: It basically covers the whole chewing surface and holds together the pieces of the tooth segments, weakened from the amalgam filling. It also preserves the bulk of the walls which are healthy and valuable as part of the natural tooth structure.

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