dental bonding

[wise146]

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Could someone please explain to me the basics of dental bonding.

How and why is it performed? How common is it? How effective is it?

Thanks.

 

[UBTom]

You will learn it in your Biomaterials class at Stony that's fer sure... But here's the nutshell explanation:

Bonding works by mechanically locking a resin into the enamel or dentin. How this is achieved:

1) The enamel edges in a cavity prep needs to be beveled (around 45 degrees) to provide increased surface area and to allow the resin to be drawn to a fine edge upon finishing/polishing.

2) the enamel and dentin needs to be etched with an acid, such as 37% phosphoric acid. This creates microscopic spaces between enamel prisms and allows the bonding agent's resin to flow in and mechanically lock-in upon curing. The acid also dissolves the smear layer in dentin and leaves tufts of collagen fibers that can also lock with the resin. Bonding strength is far stronger with enamel than to dentin though, which is why we always try to keep a cavity prep's margins in enamel.

3) The bonding agent is applied and cured with a light. This polymerizes the fluid methacrylate in the bonding agent into a hard resin (polymerized methacrylate).

4) Once the bonding agent is cured, one can apply the tooth-colored resins (a shade you selected to match the patient's tooth before starting the procedure) and it will polymerize to the bonding agent and "stick on". The finished filling is then shaped and polished.

Properly done, a composite bonded resin filling blends in so well that one can hardly tell there is a filling there. Anyhoo that's the abbreviated version of how we do composite restorations for anterior teeth..

HTH!

 

[wise146]

Thank you Tom

--so it is only for appearance purposes?

 

[UBTom]

Well, no, there are many applications for etching & bonding.. For example, the brackets for orthodontic braces are usually bonded onto teeth. Another example would be sealants for kids-- the occlusal surfaces of molars are etched and the sealant flowed in and cured, which effectively seals off the deep pits and fissures in the biting surfaces to prevent decay from starting there. And many more..

You'll see, come Fall.

 

[Meggs]

Originally posted by wise146
Thank you Tom

--so it is only for appearance purposes?

It's also used in splinting in perio, and in fixed retainers in ortho.

 

[sadanand]

hi ,
to add to it ,
The field of bonding agents is one of the most researched now .
The main reason for application of etching procedures & application of bonding agents is for biological reasons these days . Microleakage at the junction of the restoration & the tooth structure is considered one of the main causes for restoration failure . Hence bonding the restorative material/restoration to the tooth structure r the walls of cavity reduces the leakage & prevents pulpal insults & also recurrent decay .
Hence bonding is being used not only for compostites , but also for amalgam , porcelain inlays , etc.

Apart from the ortho phosporic acid (37%) agents like citric acid, maleic acid & pyruvic acid r being used .
The primers r bifunctional compounds which have a hydrophillic & a hydrophobic ends.
The bonding agents r unfilled resins generally BISGMA ( bis phenol A glycidyl methacrylate )

The etching time which was initially about 60 secs is now reduced to 10 secs & its been noted that irrespective of the etching time (whether 10 secs r 60 secs ) the amount of irregularities produced remains the same .
The junction between the primer/bonding agents & the collagen in the etched dentin is referred to as the HYBRID layer .
The bond strength in dentin is relatively lower than that produced in enamel because of the moisture content in dentin & also the amonut of organic content in dentin .