Composite restorations - a different way of thinking

Question 1

What is a composite resin?

Answer 1

Complex material in which two or more distinct, structurally complementary substances, typically ceramics, glasses and polymers, combine to produce structural or functional properties not present in any individual component

Question 2

Composition of dental composite resins

Answer 2

Resin matrix (25%)
-monomer: TEGMA, BisGMA, UDMA (all methacrylate based)
-photo initiator: Camophorquinone (stops it from setting under natural light)
-accelerator: 4-dimethylaminobenzoate ester
-stabiliser: butilated hydroxytoluene
-inhibitor: 2-hydroxy-4-methoxybenzophenone
Filler (75%)
-silane treated silica (sticks to polymer on one end and glass on other)

Question 3

Novel light-cure low-shrinkage composite resins

Answer 3

Ormocers

Siloranes

Question 4

Classification of dental composite resins

Answer 4

Initiation technique: heat/ self/ light/ dual-cure
-dual cure e.g. for veneers, light just accelerates setting
Filler size: macro/ micro/ nanofilled, hybrid
Viscosity: flowable, packable
Clinical application: direct, indirect

Question 5

Advantages of composites

Answer 5

Aesthetics
Bonding to tooth structure
Tooth-sparing preparation
Less-costly and more conservative alternative to indirect restorations
Repairability
< quantity of mercury exposure and environmental release
Lack of corrosion

Question 6

Disadvantages

Answer 6

Composite shrinkage (up to 3%) & microleakage
Post-op sensitivity
Secondary caries
Chipping and lower wear resistance than amalgam
Technique sensitive
Adverse biological reactions

Question 7

Biological considerations

Answer 7

Direct composite resins
-oral lichenoid reactions
-allergic reactions
Dentine bonding agents
-some pulpal reactions have been reported
Indirect resin-based materials
-allergic reactions in pxs
-hand dermatitis in technicians

Question 8

Aesthetic considerations: colour

Answer 8

Value: brightness
Saturation: intensity
Hue: colour / shade

Question 9

Aesthetic considerations: translucency

Answer 9

How much light goes through
Towards incisal edge tooth is more translucent (enamel), on neck will be more opaque (dentine)
-dual-shade composite resins: 1 shade for dentine, 1 for enamel

Question 10

Bonding and adhesion

Answer 10

Remove smear layer and produce/ place tag of resin into dentinal tubule
Etch
Primer
Bond

Question 11

Benefits of adhesion

Answer 11

Creates strong attachment to tooth tissue
Resists polymerisation shrinkage and minimises leakage
Tooth prep limited to damaged/ lost tooth tissue - no need for mechanical undercut
Supports weakened tooth structure
Optical integrity at cavity margins

Question 12

Composite placement

Answer 12

Access to and and removal of diseased tissue
Minimal prep at all times
Minor enamel bevelling to enhance bonding & aesthetics anteriorly
Clean dry field essential throughout bonding and placement
-rubber dam
-high volume suction
-cotton wool rolls and/ or ‘dry guard’
-lip retractors
-matrices

Question 13

Matrices

Answer 13

Transparent strips for anterior teeth
Contoured circumferential bands or sectional matrices for posterior teeth
All used with wedges to secure matrices and control fluid in gingival region
Tight proximal contacts more difficult to achieve than with amalgam

Question 14

Composite placement and finishing

Answer 14

Select shade
Place increments no deeper than 2-3mm and shape
Minimise excess before light curing
Shape with abrasive discs burs and strips
Use increasingly fine abrasives to polish

Question 15

Indications

Answer 15

Restoration of caries
Repair of enamel and dentine fractures
Tooth wear rehabilitation
To mask mild discolouration
As temp restoration for indirect veneer preps

Question 16

Contraindications

Answer 16

Where insufficient tooth structure and enamel present for bonding
Deep subgingival caries where moisture control not possible
Indirect restorations may be more appropriate for severely damaged and heavily restored teeth
Allergic reaction to resin-based dental materials