dental materials PRINCIPLES OF BONDING

define bonding

process of attaching restorative materials to the tooth by adhesion

bonding involves...

-preparing the surface
-removing decay, plaque, and debris
-etching or conditioning tooth (with phosphoric acid)
-conditioning removes microns of tooth to provide a rough surface to which bonding can occur

bonding to an etched surface

when bonding agent is flowed over etched surface= PENETRATES INTO MICROSCOPIC PORES
- when bonding agent cures= forms RESIN TAGS that adhere to etched surface of tooth
- then will chemically bond to other resins placed over it such as COMPOSITE RESIN

the primary or chemical bond occurs through....?

ADHESION when the bonding agent and composite resin material ADHERE TO EACHOTHER
-chemical bond is stronger than a secondary or physical bond

surface wetting
etching creates a?
good wetting?
poor wetting?

etching increases the ability of the bonding material to wet the tooth surface by creating a HIGH SURFACE ENERGY
-good wetting increases contact of material, poor wetting prevents contact
- BONDING AGENTS are typically made of a LOW VISCOSITY material (ca

define bond strength

amount of force needed to break the two materials apart
- AN ENAMEL BOND IS TYPICALLY STRONGER THAN A DENTINAL BOND

enamel etching does what?

removes small portion of the surface, reduces enamel rods, and OPENS POROSITIES between rods
-removes SMEAR LAYER

etching takes how long?

takes approx 20-60 sec
- either LIQUID or GEL
- rinsed approx for 10 sec to remove etch

smear layer

made of bacteria, salivary components, and tooth dust
-MUST BE REMOVED BEOFRE THE BONDING PROCEDURE IS PERFORMED

dentin etching

phosphoric acid dissolves smear layer first
then portions of hydroxyapatite crystals from surface of dentin creating...
A POROUS SURFACE AND EXPOSING COLLAGEN FIBRILS
-opens dentinal tubules leaving a rough, porous surface
- only needs to be etched for 10

bonding agents are?
enamel requires?
dentin requires?

LOW VISCOSITY RESINS
-penetrate porosities in tooth surface created by etching
- enamel only requires single component= low viscosity liquid
- dentin two types= primer and bond

preparing to bond
(enamel, dentin)

-if only enamel etched= surface dried to frosty finish
-when dentin bonded= LEFT MOIST (do not want to overdry) to keep COLLAGEN FIBRILS FROM COLLAPSING
- primer placed first and dried before curing

oxygen inhibited layer

on surface of polymerized bonding resin= thin coating of UNCURED RESIN
- polymerization is INHIBITED when surface is EXPOSED TO OXYGEN in the air
-NEEDS TO BE POLISHED OFF

types of bonding agents

self etching= two component bonding agents that incorporated acidic groups in primer without needing to rinse and dry (combo of acid etch and bond)
-called SELF ETCHING PRIMERS

what are the three modes of curing?

self cure
light cure
dual cure

microleakage

when rest not completely sealed at margins, they can leak
- allowing fluids, bacteria to enter cavity prep
- can result in recurrent decay

tooth hypersensitivity is?
causes?

some pt experience TRANSIENT tooth sensitivity, USUALLY ONLY LASTS A SHORT TIME
- causes
- tooth is overdried (desiccation)
- tooth over etched
- composite cured in large segments

clinical application of bonding to....
(porcelain, metal, amalgam)

porcelain= stronger retention if bonded rather than cemented
metal= used to create a stronger bond before cementation of a crown or bridge
amalgam= helps seal out microleakage

what cure is used for orthodontic bonding of brackets?

dual cure material

the light wavelength needed to activate the curing process lies somewhere within the range of __________nm. This means that the light emitted from the typical dental curing light will have a __________ coloration.

420 to 450-470nm
violet to blue

a ____________ bond is based on an interlocking of the cured liquid plastic bonding agent within the nooks and crannies of the etched enamel surface.

micro mechanical

each additional layer of dental composite that is placed creates a ___________ bond with the bonding agent sublayer and/or a previous layer of dental composite.

chemical

the acid etchant is usually supplied in a ______% _________ solution.

37%
(ortho) phosphoric acid