Biomaterials Lecture 1
Restorative materials:
Oldest and one of the best; gold (used in bridges, crowns, inlays, overlays)
Full coverage: overlay over an area / Partial coverage: veneer [fixed, non-removable prosthetics or
restorative materials]
Partial or full (acrylic or metallic) dentures [removable]
Implants (fixed restorative materials) are usually three parts: 1. Titanium implant 2. Abutment 3. Crown
(ex of implants: full prosthetic part over implants)
Abutments over implants: Acrylic material/denture or fixed ceramic material can be placed on implants;
each have their own properties
Composite (bulk-fill, flowable, injectable) ex: amalgam
Direct gold or amalgam fillings can be done
Cements like glass ionomer, resin, zinc phosphate, zinc oxide eugenol, and calcium hydroxide
Aim of a Restorative Material
- Remove diseased tooth substance
- Prevent recurrence of caries
- Restore tooth back to its function (aesthetically and functionality)
Ideal Requirements of a Restorative Material:
1. Easy to manipulate (mixing, easily applied)
2. Long lasting
3. Adequate strength
4. Insoluble and non-corrodible in the mouth
5. Low exotherm (ma betal3o 7arara) and negligible change of volume upon setting (no expansion
or shrinking because margins become compromised causing recurrent/secondary caries)
6. No toxic and non-irritant to pulp and gingival tissues
7. Trimmed and easily polished
8. Coefficient of thermal expansion similar to that of enamel and dentin
9. Low water sorption
10. Adhesive to tooth substance
11. Radiopaque (to be seen in X-rays)
12. Long shelf life
13. Inexpensive
Long ago, dual cure composite or chemically cured composites were used.
Example of a case where manipulation properties improved:
- Chemically cured composites are placed in the cavity and while you’re working on it and shaping
it, it might get cured and you won’t have control over its setting time anymore
- That’s why photo initiators were introduced, and now we have photo initiated composite resin
which can be shaped and carved and cured by LCU when you want it to
- Mechanical properties and aesthetics were not improved ONLY manipulation properties did
The oral cavity has saliva therefore metals cannot be used because corrosion (rusting) will occur
1. Their function will be compromised
2. They will cause systemic effects (ex: iron in bloodstream causes toxicity)
If enamel and dentin expand by x amount, the material should also expand by x amount
Classification of Dental Materials
- Location of Fabrication (Clinic/Lab)
1. Direct restorative material (while patient is on the chair; resin composite, amalgam, GIC)
2. Indirect restorative material (not while patient is on the chair metals, ceramics)
3. Semi-direct restorative material
Fabricate restoration directly in the clinic; cavitated tooth is drilled and caries is removed and cavity is
filled)
Indirect restorative material needs high temperatures; ex: metals need to be molded which will cause pulp
death/ burning; so labs fabricate them by furnaces (ovens with high temp); impressions are taken in the
clinic and a lab fabricates the restoration, you then cement the restoration [INDIRECT]
Composites can be direct or indirect
Dentures; indirect, only fittings done in clinic, the rest done by lab technicians
[Semi-direct; rare] Impression taken, fabricated in clinic and cemented in clinic or filling with separating
medium (like Vaseline/glycerin gel or something that will later be removed inside patient’s mouth, then
surface treatment occurs and material is cemented. Basically using the patient’s mouth as a model. Does
not include labs
Longevity of Use
- Permanent (years, approx. 4-5-6 years) [ex: composite resin]
- Temporary (few days to few weeks)
- Interim (in-between; lasts a few months) [using GIC or zinc oxide eugenol in the form of a
putty/paste]
State of Restorative Material at Time of Placement
- Rigid [indirect]
- Plastic (moldable) [like composite; direct; placed then cured]
Biological Compatibility
- In contact with soft tissues (tongue, cheeks) must have the bare minimum of safety
- Could affect vitality (life) of dental pulp (ex: melted metal causes pulp necrosis [death] which
leads to root canal treatment)
- Used as root canal filling material (have special properties because they’re in contact with the
periodontium)
- Those which affect hard tissues of teeth
- Those which are laboratory handled and may be accidentally ingested or inhaled (ex: models that
are trimmed or cut release dust particles that are biologically and environmentally hazardous
(harm lungs) like aluminum oxide)
Material shouldn’t be toxic, but position of placement makes it vary. Some materials have a small toxic
effect, but if it’s near the pulp, it could have damaging effects; for example it could be put on the tooth,
but not in contact with the pulp or root canal filling material
Dental Cements: Uses, Requirements, and Classifications
What is a cement? It is a substance that hardens from a viscous state to a solid state to join two surfaces.
Liquid then it solidifies. Not a chemical bond because it’s not a part of those 2 surfaces, it only fills up the
porosities.
Why does a tongue stick to a cold surface? Water enters the papillae of the tongue and saliva freezes to
the surface; it is resolved by pouring hot water over it.
Same principle is followed in cementation: filling micro-porosities present and sealing them with a
cement to fix the crown [mechanical bond].
Cement is placed on crown, and excess is removed (after curing if it’s like resins and needs curing; in
case of GIC, zinc oxide eugenol, zinc phosphate, polycarboxylate, cement doesn’t need to be cured by
LCU). If not removed, excess cement could carry food debris and be harmful.
Uses of Cements
- Cementation (luting; la 7ata nlaze2 ; on the fitting or antagonist surface of the crown)
- Liner and pulp capping (most commonly Calcium hydroxide (CaOH) and mineral trioxide
aggregates(MTA) because they’re not acidic and not irritating to the pulp)
- Root Canal Treatment (RCT) sealer
- Surgical dressing (krmel jer7 ba3d surgery in the case of pain or preservation of sutures)
- Gingival tissue pack (to separate gums from margins of the tooth and expose the margins while
taking impressions; in the form of cords or injectable paste that helps to retract the gums)
- Temporary restoration (sets when in contact with water/saliva, but stays soft enough to remove;
could be made from resin or could be curable)
Cements need to have adequate viscosity to properly fill the porosities, they need to have low surface
tension and low viscosity
Cementation quality is compromised if otherwise, it could leave out porosities or not spread properly
throughout
When the pulp is visible, you CANNOT immediately put filling materials because it could result in the
DEATH OF THE PULP or infections and other complications, so 2 options are to be considered:
1. Root canal treatment (kill the tooth)
2. Cap and preserve the tooth (keep the pulp living) using a certain cement then place
composite/amalgam
Sometimes this works, other times it doesn’t
In RCT you have to drill, remove all the tissue and fill up the cavity; if not removed thoroughly,
retrograde infection occurs. The material used to fill up the empty space is NOT composite or hard
materials, you should use a rubbery material along with a sealer to ensure proper closure of the space (ex:
zinc oxide eugenol or certain resins)
Temporary cements are used to adhere a crown temporarily. Temporary filling materials are used for
filling not adhesion. Both are made out of cements.
Requirements
- Safe to use around pulpal tissues
- Insoluble in the oral environment
- Provide adhesion if possible
- Antibacterial effect
- Obtundent effect
