Introduction to dental naterial science and the basic classification of dental materials

1. DENTAL MATERIALS AND
TECHNOLOGY
Dental students 2nd year
2012/2013
Dr. Kinga Turzó
4th of September 2012

2. Lectures:
Faculty of Dentistry, Lecture Hall
Tuesday 13:00-15:00 (2 hours /week), Examination, 3 credits
Sept. 4.: Introduction to dental materials science. Importance of dental material
knowledge in dentistry. History of dental materials. International standards for
materials used in dentistry (ISO, DIN, etc.). Classification of dental materials
based on structure and utilization.
Sept. 11.: Basic physical properties of materials. Test methods for materials in
dental material science.
Sept. 18.: Types, classifications and applications of impression materials.
Presentation of elastic impression materials.
Sept. 25.: Examining, treating and preventive methods used in dentistry from
technological point of view. Die materials and methods of model preparation.
Oct. 2.: Polymers used in dentistry (1st part). Practical aspects of polymers used in
dentistry (2nd part).

3. Lectures:
Oct. 9.: Waxes. Occlusion papers and foils. Artificial teeth (acrylic and ceramic)
Oct. 16.: 1st WRITTEN TEST
Oct. 30.: Filling materials and adhesive technologies. Dental cements and
endodontic materials.
Nov. 6.: Structure and properties of metals and alloys used in dentistry.
Electroforming. Corrosion of metals.
Nov. 13.: Investment, investment materials, metal casting. Processing of surfaces
of dental appliances, polishing. Burs and polishing instruments in dentistry.
Nov. 20.: Amalgam. Allergic reactions to dental materials.
Nov. 27.: 2nd WRITTEN TEST
Dec. 4.: Materials used for porcelain-fused-to-metal restorations. All-ceramic
systems, composition, characteristics, processing

4. Conditions for accepting the
semester and the credits:
Active participation on lectures and practices, based on the study and exam
regulations of the University and of the Faculty of Dentistry.
Requirements of participation on lectures and practices and replacement of
absenteeism based on the study and exam regulations of the Faculty of Dentistry.
Method of proof of the absence on practices and lectures based on the study and
exam regulations of the University and of the Faculty of Dentistry.
Accomplishment of the tasks in the practices.
The safety rules of the laboratory should be kept.
It is mandatory the fulfillment of the WRITTEN TESTS (1st and 2nd). The
average mark of the tests should be at least 2.0. Unsatisfactory test should
be corrected; there is only ONE possibility for the correction during the
semester! The date of this correction Test is given by the responsible of the
subject. Failed Written tests are also included in the average. The absence
from the Written tests can be certified with a medical certificate. In absence
of this certificate the students Written test will be considered failed.

5. Requirements of signing the
Practice:
Active participation on the practices based on the study and exam
regulations of the Faculty of Dentistry and the average mark of the practice
written tests and oral questions should be at least 2.0.
The practice teachers are continuously checking the knowledge of the
students with written tests and oral questions. These tests are performed
during the practice hours and their number can be equal with the number of
practice hours. The subject of these practice tests contain topic of the
lectures and the practice itself. It is compulsory the knowledge of the
theoretical subjects related to the practices, and the average mark of all the
tests should be at least 2.0. The mark of small tests may be max. 3 times 1.
Failed written tests and oral questions are also included in the average. If the
student already has three failed marks during the semester, then he will have
only ONE opportunity to correct these tests. If the student fails on this last
correction the Practice will not be signed. The correction can be written or
oral. The date of the correction will be given by the practice teachers.

6. Mark of the Examination (Lectures) is
established in the following way:
If the average of the Written test and the practice written tests and
oral questions is between 4.0 and 5.0 then an offered mark can be
given to the student.
Calculation of the average: [1st Written test + 2nd Written Test +
practice written tests and oral questions average]/3.
If the average is between 4.0-4.50 then good (4) is given, if the
average is between 4.51-5.0 then excellent (5) can be given. In
case the average is below 4.0 the student will perform an oral exam
(Examination).
Recommended literature:
Dental Materials and Their Selection: Edited by W.J. O’Brien.
Quintessence Publishing Co, Inc.

7. Subject of the 1st lecture:
Introduction to dental materials science.
Importance of dental material knowledge in
dentistry.
Historical overview.
International standards for materials used in
dentistry.
Classification of dental materials based on
structure and utilization.

8. Introduction to dental materials science. The
importance of dental material knowledge in dentistry.
The goal of dentistry: to maintain and improve the health of the
human teeth (oral cavity) in order to improve the quality of life of
the dental patient.
Activities:
- preventing disease,
- tooth replacements,
- replacement of missing portions of tooth structure,
- improving mastication efficiency,
- enhancing speech, improving appearance and
- relieving pain.
All these activities require the replacement or alteration of existing
tooth structure and also the development of auxiliary dental
appliances.

9. Introduction to dental materials science. The
importance of dental material knowledge in dentistry.
Dentistry includes:
- curing the diseases of teeth and oral cavity,
- selection of the needed materials and instrumentation,
- the knowledge of medicaments used in dentistry,
- dental technology.
The science of dental materials is critically important. A great deal
of the daily practice of dentistry involves the selection and use of
dental materials, either for the treatment procedure or in the
instrumentation required.
The dentist has to possess the knowledge from various disciplines, to know
the properties of these materials:
- chemical and physical-chemical structure,
- mechanical properties,
- technological, processing features,
- biological properties, the interaction of the material with the surrounding
medium and the host reactions of the biological system.

10. Hierarchy of evidences for dental
materials
Scientific/published
- Long-term clinical trials
- Other clinical studies
- Animal studies importance
- In vitro studies amount
- Physical properties data
Speculative/unpublished
– Deductions from clinical literature
– Deductions from scientific theories
– Product manufacturer literature
– Popular media
– Rumors and myths

11. EBD - Evidence Based Dentistry
Definition:
Scientific An approach to oral health care
evidence that requires the judicious
integration of systematic
Experience assessments of clinically relevant
Patient
and
needs
scientific evidence, relating to
Judgment patient’s oral and medical
condition and history, with the
dentists’ clinical expertise and
Clinical/Patient the patient’s treatment needs
Circumstances
and preferences.
American Dental Association

12. Example: replacement of missing
portions of tooth structure
In case of tooth filling only materials having no harmful biological effect on
their environment can be used.
Questions arising :
Does it dissolve in the mouth?
Does it produce electrochemical effects?
Does it disturb or even damage compounds of normal biochemical
processes (e.g. enzymes)?
Does it have any irritating effect?
Does it have any poisonous effect when absorbed (e.g. fluoride)?
At the same time it is useful to know:
- Abrasion resistance, hardness and corrosion resistance of the material
concerning its durability and function.
- The technological suitability (easy processing) of the material.

13. Biocompatibility
The main challenges for centuries have been the development and
selection of biocompatible prosthetic materials that can withstand
the adverse conditions of the oral environment: extreme
temperatures (5-55oC), acidic pH, abrasion, high magnitude forces,
bacteria.
Biocompatibility: Acceptance of a synthetic material or an
artificial implant by the surrounding tissues and by the body as
a whole.
Does not irritate the surrounding structures.
Does not provoke an abnormal inflammatory response.
Does not incite allergic or immunologic reactions.
Does not cause cancer.
„Biocompatibility is a dynamic, always changing phenomenon.”
J.E. Lemons, Journal of Prosthetic Dentistry, 2001

14. Utility of dental research
C. Bedos, P. Allison: Do Canadian Dentists find Dental Research useful?
Journal of Canadian Dental Association, 68(9): 540, 2002.
450
dentists

15. Historical overview
• 3000 B.C. : dentistry begun • 1756: Pfaff, described a method for
making impressions of the mouth in wax
• 2500 B.C.: gold bands and wires
were used by the Phoenicians for the • 1792: de Chamant patented a process for
construction of partial dentures the construction of porcelain teeth
• 700 B.C.: Etruscans used tooth • 1850 years: first studies on amalgam
implant material (ivory)
• 1915: areas of Colorado, observations on
• 600 A.D.: the Mayans used implants the effect of fluoride to prevent tooth
consisting of seashell segments (1931, demineralization
Honduras, Dr. Wilson Popenoe)
• 1935: introduction of polymerized acrylic
• 1728: modern dentistry began, resin as a denture base material to support
Fauchard „father of dentistry” artificial teeth
published a treatise describing many
types of dental restoration • 1944: controlled water fluoridation (1 ppm)
to reduce tooth decay

16. International standards for materials
used in dentistry
The standard of a product contains:
1. General properties, classification, field of application.
2. Requirements (appearance, color, etc.).
3. Usage, processing, packaging and storage instructions.
4. Specific testing requirements.
5. Scientific, published data.
• Describes: composition, purity, physical, chemical features, for e.g.:
- binding time, stress strength, solubility, the correct
processing form, usage instructions, instructions regarding
package and storage.
Data’s provided by the manufacturer: name, date of production and expiration,
weight, appearance, color.

17. International standards for materials
used in dentistry
A performance standard is mandatory, any
deviation from it has to be approved by the
National Standard Organization. The task of these
Organizations is to develop standards and to
certify products.
Hungary: M.Sz. (Magyar Szabványügyi Hivatal)
Germany: DIN (Deutsches Institute für Normung)
France: FDI (Fédération Dentaire International)
International (agreement between ~ 60 countries, harmonization): ISO
(International Organization for Standardization)
USA: ADA (American Dental Association Specifications)
British Standards, Australian Standards

18. International standards for materials
used in dentistry
Dental materials – beside the quality and physical/chemical
requirements – have to fit the needs of applicability in practice. This
has to be supported by a comprehensive scientific study. Norms give
the required features of a material and the methods of testing them.
Goals of the performance standards are:
1. To protect the public from hazardous or ineffective dental devices.
2. Proper information of the dentist/dental technician -> selection of the product
3. Information of the merchant -> indications for the consumer
4. Information of the producer -> production of a quality material, method of
quality control
Every standard has a number, which has to appear on the product.

19. Dental implants – Guidelines for fabricating dental implants
(ISO/TR 11175:2003)
Forces acting on
transmucosal dental
implants
gingiva
Forces acting on
totally embedded
dental implants

20. Dentistry. Fatigue testing of dental implants (ISO
14801:2003)
F
force
The patent beside
determining the general
definitions, the
Supporting
system
requirements for writing
Implant the records defines also
Implant
the exact geometry and
holding elements used in the
element
testing device.
2b: nominal bone level

21. Classification of dental materials
based on utilization
Tooth replacements: Replacement of
missing portions of
Animal teeth tooth structure:
Human teeth
Seashells Metals
Ivory Ceramics
Bone Polymers
Hydroxyapatite Composites
Co-Cr alloy
Titanium

22. Classification of dental materials based
on structure
Metals
Ceramics
Polymers
Composites
Other classifications for e.g.:
- non-metallic and
- metallic materials

23. Metals
Classification:
• precious metals (e.g.: gold, silver, Platinum)
• non-precious metals (e.g.: Co, Cr, Ni, Ti)
• alloys (e.g.: amalgam, Co-Cr, stainless steel)
Advantages: strength, hardness, easy to shape, ductile
Disadvantages: susceptible to corrosion, high density, expensive
production
Fields of application: denture base material, orthodontic arch wires,
dental implant (total hip and knee joints, fracture healing aids as
bone plates and screws, etc.)
O’Brien classification: alloys (e.g.: gold-copper) and intermetallic
compounds (e.g.: amalgam phases)

24. Osseointegrated dental implants replacing
missing teeth

25. Ceramics
Definition: refractory, polycrystalline compounds, usually
inorganic materials (silicates, metallic oxides, and various
refractory hydrides, sulfides and selenides)
Advantages: high melting temperature, very biocompatible,
inert, strong in compression, aesthetic appearance
Disadvantages: brittle, not resilient, difficult to make
Fields of application: coating of dental and orthopedic
implants (femoral head of hip replacement, etc.)
O’Brien classification: inorganic salts (e.g.: gypsum, zinc phosphate),
crystalline ceramics (e.g.: SiO2, Al2O3), glasses (e.g.:
dental porcelain)

26. Classification of ceramics used in
fabricating implants
Nonabsorbable, bioinert (dense and porous aluminum
oxides Al2O3, zirconium ceramics ZrO2, single phase
calcium aluminates)
Bioactive or surface reactive, sem-inert (dense
nonporous glasses, Bioglass, Ceravital and dense
hydroxyapatites HAP)
Biodegradable or resorbable, non-inert (calcium-
phosphates Ca-P, calcium sulfate (CaSO4, plaster of
paris), calcium aluminates Al-Ca-P, corals, tricalcium
phosphate TCP, etc.)

27. Comparison of metals and ceramics

28. Polymers
Definition: very long chain molecules which are formed by covalent
bonding along the backbone chains. The long chains are held
together either by secondary bonding forces (van der Waals and
hydrogen bonds) or primary bonding forces through crosslink
between chains.
Classification:
natural (cellulose, yeast, natural rubbers, DNA)
synthetic (polyesters, polyamides (nylons), silicon, polyvinylchloride
PVC, polyethylene PE, polypropylene PP, polymethylmethacrylate
PMMA)
O’Brien classification: rigid polymers (e.g.: PMMA), waxes, elastomers,
(rubbers, e.g.: impression materials)
Advantages: resilient, easy to fabricate (polymerization)
Disadvantages: not strong, deforms with time, may degrade

29. Polymers and applications
- prosthetic materials,
- dental materials,
- implants
(sutures, blood vessels,
hip socket, ear nose,
other soft tissues,
sutures, encapsulants,
polymeric drug delivery
systems, etc.)

30. Composites
Definition: contain two or more distinct constituent materials
or phases, on a scale larger than the atomic.
Advantages: strong, stiff, tailor-made, lightweight
Disadvantages: difficult to make, the interface between the
constituents can be degraded by the body environment
Two big classes:
fibrous and particulate composites
Natural composites:
bone, dentin, cartilage, skin, lung

31. Composites
Field of application: dental filling composites, orthopedic
implants with porous surfaces, reinforced methyl
methacrylate bone cement and ultrahigh molecular weight
polyethylene, joint implants, heart valves, etc.
Scanning electron
micrograph of a fracture
fixation plate.
Laminae buckling and
delamination (D)
between lamina in a
carbon fiber-reinforced
PLA fracture fixation
plate