What type of material is tooth bonding? What are the properties of dental composite?

Dental composite is a plastic.

You might be curious as to the composition of dental composite (the restorative material that is utilized with dental bonding technique). We could tell you that the compounds formulating the core structure of dental composite are "high molecular weight monomers that when cured create rigid cross-linked polymers." Certainly that would be technically correct but in laymen's terms it's easiest just to say that dental composite is a plastic.

The physical properties of this core plastic leave a lot to be desired. And for this reason fillers and modifiers are added so to enhance the composite's overall characteristics (such as strength, wear resistance, how easily it handles, and even its precise shade of white). While each manufacturer will develop their own special formulation for their brand of dental composite, usually the fillers that are added are some combination of finely ground particles of quartz, glass, zirconium, silica, barium, and strontium.

The types and specific amounts of fillers that are included in the dental composite's formulation will depend on the specific application in which the composite will be utilized. As an example, if the composite will be used to create white fillings for back teeth then those fillers that enhance physical properties related to strength and wear resistance will be bulked up. In comparison, if the dental composite will be used in a cosmetic dental bonding application for a front tooth then fillers that enhance the composite's color and polishing characteristics will be emphasized in the formulation.

More about the characteristics of dental composite.

When tooth-bonding products were first brought to the marketplace dental composites came as two separate putty-like pastes (a base and catalyst). The dentist would take equal amounts of each of these pastes and mix them together just prior to their use. The combination of the two pastes would activate the composite's curing reaction, so once mixed the dentist would know that they had just a few minutes to get the composite in place before it would set. This method of curing (self-cure) meant that the dentist had to be quick in placing and shaping the composite before it hardened. As you can imagine, this time limitation could prove to be quite an inconvenience.

Now days most dental composites are formulated as a single putty-like paste with a curing catalyst that has already been mixed in. The key here is that the setting catalyst only becomes activated when the dentist exposes the dental composite to the output of a "curing light." The great convenience of using this form of dental composite is that the dentist can work with and shape the composite at their leisure, and then when satisfied with their efforts expose the composite to a curing light so to activate its set. Usually dental composite becomes fully hardened within 20 to 40 seconds of exposure with the curing light. (Possibly you have had tooth bonding placed and during the procedure you have heard a beeping sound. The sound is probably coming from your dentist's curing light, marking off 10 second intervals, so they can keep track of the composite's total exposure time.)

More about the curing lights dentist use to harden dental bonding.

Dental "curing lights" are hand-held units that produce visible spectrum output (light) that lies within a specific wavelength range. The idea is that the setting catalyst (a photo initiator) contained in the dental composite is sensitive to and activated by this particular color (wavelength) of light.

Actually, dentists use curing lights to activate the set of a wide range of different types of dental materials. With most dental products, including most dental composites, the light wavelength needed to activate the curing process lies somewhere within the range of 420 to 450 nm. This means that the light emitted from the typical dental curing light will have a violet to blue coloration.