DENTAL MATERIALS AND TECHNOLOGY

Dental students 2nd year

2012/2013

Dr. Kinga Turzó

4th of September 2012

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).

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 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

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.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.

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 � 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.

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.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.

Subject of the 1st lecture:

� Introduction to dental materials science. Importance of dental material knowledge in 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.

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: � 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.

� Dentistry includes:- curing the diseases of teeth and oral cavity,

- selection of the needed materials and instrumentation,

- the knowledge of medicaments used in dentistry,

Introduction to dental materials science. The importance of dental material knowledge in dentistry.

- 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.

Hierarchy of evidences for dental materials

� Scientific/published- Long-term clinical trials

- Other clinical studies

Animal studies importance- Animal studies

- In vitro studies

- Physical properties data

� Speculative/unpublished– Deductions from clinical literature

– Deductions from scientific theories

– Product manufacturer literature

– Popular media

– Rumors and myths

importanceamount

EBD - Evidence Based Dentistry

� Definition:An approach to oral health care that requires the judicious

Scientific

evidence that requires the judicious integration of systematic assessments of clinically relevant scientific evidence, relating to patient’s oral and medical condition and history, with the dentists’ clinical expertise and the patient’s treatment needs and preferences.

American Dental Association

evidence

Experience

and

Judgment

Patient

needs

Clinical/Patient

Circumstances

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 :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.

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, temperatures (5-55 C), 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

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

450

dentists

Historical overview

• 3000 B.C. : dentistry begun

• 2500 B.C.: gold bands and wires

were used by the Phoenicians for the

• 1756: Pfaff, described a method for

making impressions of the mouth in wax

• 1792: de Chamant patented a process for were used by the Phoenicians for the

construction of partial dentures

• 700 B.C.: Etruscans used tooth

implant material (ivory)

• 600 A.D.: the Mayans used implants

consisting of seashell segments (1931,

Honduras, Dr. Wilson Popenoe)

• 1728: modern dentistry began,

Fauchard „father of dentistry”

published a treatise describing many

types of dental restoration

• 1792: de Chamant patented a process for

the construction of porcelain teeth

• 1850 years: first studies on amalgam

• 1915: areas of Colorado, observations on

the effect of fluoride to prevent tooth

demineralization

• 1935: introduction of polymerized acrylic

resin as a denture base material to support

artificial teeth

• 1944: controlled water fluoridation (1 ppm)

to reduce tooth decay

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.).

• 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.

2. Requirements (appearance, color, etc.).3. Usage, processing, packaging and storage instructions. 4. Specific testing requirements.5. Scientific, published data.

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 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

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 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.

Dental implants – Guidelines for fabricating dental implants (ISO/TR 11175:2003)

Forces acting on

transmucosal dental

implants

Forces acting on

totally embedded

dental implants

gingiva

Dentistry. Fatigue testing of dental implants (ISO 14801:2003)

F

force

The patent beside determining the general

Implant holding element

Supporting system

Implant

2b: nominal bone level

determining the general definitions, the requirements for writing the records defines also the exact geometry and elements used in the testing device.

Classification of dental materials based on utilization

� Tooth replacements:

Animal teeth

� Replacement of missing portions of tooth structure:

� Animal teeth

� Human teeth

� Seashells

� Ivory

� Bone

� Hydroxyapatite

� Co-Cr alloy

� Titanium

tooth structure:

� Metals

� Ceramics

� Polymers

� Composites

Classification of dental materials based on structure

� Metals

� CeramicsCeramics

� Polymers

� Composites

Other classifications for e.g.:

- non-metallic and

- metallic materials

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)

Osseointegrated dental implants replacing missing teeth

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)

Classification of ceramics used in fabricating implants

� Nonabsorbable, bioinert (dense and porous aluminum oxides Al2O3, zirconium ceramics ZrO2, single phase calcium aluminates)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.)

Comparison of metals and ceramics

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. 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

Polymers and applications

- prosthetic materials,- prosthetic materials,

- dental materials,

- implants

(sutures, blood vessels, hip socket, ear nose, other soft tissues, sutures, encapsulants, polymeric drug delivery systems, etc.)

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

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.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