BIOMATERIALS IN ODF
Plan :
1-Introduction and definitions.
2- Biomaterials used in Dento-Facial Orthopedics
2.1 Imprint materials
2.2 Wires and arches:
– Gold-based alloys.
– Stainless steel.
– The elgiloy.
– The Australian thread.
– The TMA
– Nickel-Titanium alloys.
2-3 Metal locks and rings
2-4 Ceramics
2-5 Brazing and soldering
2-6 Polymer materials
– Thermoformed gutter
– Acrylic resin
– Elastomeric materials
Conclusion
Introduction :
All the materials around us are made up of atoms and molecules, the arrangement and relationship between them explains some of their properties.
ATOM: is the fundamental constituent of matter. The term comes from a Greek word meaning “indivisible”, when two atoms bond, they can form a molecule.
The MOLECULE: represents, on a microscopic scale, the smallest part of a body likely to exist in a free state in nature, the molecule is an assembly of at least two identical atoms (simple body) or not (compound body).
Atoms and molecules are the “building blocks” of matter; from the moment that matter is intended for a specific use, we speak of materials; in the medical field we speak of biomaterials.
The term “BIOMATERIALS” refers to materials intended to be in temporary or permanent contact with different tissues, organs or fluids of a living being, for diagnostic, preventive or therapeutic purposes. They can have a benign function (used to replace heart valves), as they can be bioactive and used for more interactive purposes, such as total hip prostheses covered with a layer of hydroxyapatite (materials composing bones, it allows a better compatibility with body tissues).
The definition of a biomaterial does not only include artificial biomaterials that are constructed from metals or ceramics, a biomaterial can also be an autograft or an allograft.
In orthodontics, the behavior in the oral environment of biomaterials used in dentofacial orthopedics is based on a two-way mechanism:
The effects of the biomaterial on the environment (biocompatibility) but also the effects of the environment on the biomaterial (biodegradation).
Biocompatibility:
Biocompatibility includes corrosion resistance and tissue tolerance to the alloys used. It corresponds to the ability of a biomaterial to fully fulfill the function for which it was designed, without harming the vitality of the biological environment in which it is inserted.
Biodegradation:
Biodegradation is defined as the degradation of the characteristics of a biomaterial created by the biological environment in which it functions. The origin of the degradation can be electrochemical (corrosion) or biological, mainly by microbial attack. The biomaterial can no longer perform its function correctly and it can become dangerous (release of degradation products).
2. Biomaterials used in Dentofacial Orthopedics
The general principle of orthodontics is to move the teeth in the three dimensions of space in order to establish a final occlusion that is as functional, aesthetic and stable as possible. These dental movements will be carried out in particular by placing an orthodontic device in the mouth.
The orthodontist can mainly use removable therapy or multi-attachment fixed therapy and has a wide variety of biomaterials at his disposal, namely
Alginates and plasters
Bonding materials (sealing cement / composites)
Locks (brackets) and rings ..
The arches
Ceramics
Polymer materials
Removable therapy Fixed therapy
2.1 Imprinted biomaterials
The impression allows to create a perfect replica of the maxillary and mandibular structures and their relief. By pouring plaster into the impression thus obtained, we obtain a faithful and precise replica of our dental arch, this is what is called the study model or working model.
Several impression materials are used in dentistry, irreversible hydrocolloids or alginates, are the most used impression products in ODF.
Alginate is a salt of alginic acid extracted from certain brown algae, it generally comes in the form of a powder in a metal box or in sachets.
Alginate preparation is done by mixing alginate powder with water in a plastic bowl using an alginate spatula. Once the impression has been taken, it must be poured. In ODF, the material of choice for pouring impressions is soft plaster (of Paris) for study models and hard plaster for working models.
2.3 Metal alloys used in ODF (Wires & Arcs)
Historically few alloys have been used to make orthodontic wires, we find
- gold-based alloys,
- iron-based alloys (stainless steel),
- cobalt-based alloys (Elgiloy) and
- titanium-based alloys.
The choice of the wire best suited to each orthodontic situation depends on knowledge of the properties of orthodontic wires and the processes that allow them to be modified. This choice also depends on the section, length and composition of the wire.
2-3-1 Gold-based alloys:
Gold-based alloys were the first to be used despite their high cost, they were used in the practice of the classic Edgewise advocated by Edward Angle. They are composed of 15 to 65% gold, copper, palladium silver and platinum, these gold alloys have made it possible to vary the coefficient of elasticity while maintaining the ability to bend with pliers and the exercise of light forces. From 1936, for economic reasons, less expensive iron-based alloys replaced noble alloys in the manufacture of orthodontic wires.
2-3-2 Stainless steel:
Steel is any alloy whose main component is iron. For biomedical use, it had to be made perfectly stainless so that it would not corrode in the oral environment, which is very aggressive due to its high temperature, pH variations and the presence of enzymes.
Orthodontic steels are made stainless by the presence in the alloy of metals with particular characteristics: nickel and chromium.
Nickel increases stainlessness, tensile strength and wear resistance;
Chromium increases hardness and gives shine to steels.
Stainless steel wires commonly used in orthodontics contain approximately 18% chromium, 8% nickel and 0.2% carbon in addition to iron.
They can be welded or brazed for the manufacture of orthodontic devices. Stainless steel wires can be presented in round or rectangular section in single-strand or multi-strand forms.
Multi-strand wire
As early as 1934, Johnson reported that it was possible to obtain a more flexible arc by using two thin wires instead of one thick wire.
Multi-strand wires are available with a round outline or a rectangular outline:
– Round-contour multi-strand wires are either twisted or coaxial: using several strands increases the elastic limit without changing the load/bending ratio of the arch
– Multi-strand wires with a rectangular outline are either twisted or braided.
For braided rectangular contour wires, using multiple strands does not increase the elastic limit without changing the load/deformation ratio of the arch.
These wires have a low load/bending ratio, they are recommended in the leveling phase, however they have greater friction forces given their more rigorous and irregular surface condition.
2-3-3 The Elgiloy:
Elgiloy, was developed by the Elgin Watch Company around 1950 to produce watch springs,
In orthodontics, elgiloy contains 40% cobalt, 20% chromium, 15% nickel, 16% iron, 7% molybdenum, 2% manganese, 0.15% carbon and 0.04% beryllium,
It is therefore not a steel (name reserved for alloys of which iron is the main component)
This alloy, like stainless steel, resists corrosion well thanks to the formation of the passive oxidation layer produced by chromium.
On the other hand, Elgiloy is very malleable and allows the creation of multiple loops in Ricketts’ bioprogressive technique.
Elgiloy is available in four grades with the same chemical composition, but with different elastic limits depending on the wire machining method. From the most plastic to the least plastic we have:
- The blue Elgiloy;
- Yellow Elgiloy;
- Green Elgiloy;
- The red Elgiloy.
2-3-4 The TMA:
TMA for Titanium Molybdenum Alloy is an alloy that contains 79% titanium and 11% molybdenum.
It was first introduced in orthodontics in 1980 by Burstone. It has the advantage of having a lower modulus of elasticity than steel and being able to be shaped with pliers, it allows greater deformation than stainless steel and restores a softer and more continuous force.
Its surface has a satin appearance (linked to its crystalline structure), so it has a higher coefficient of friction compared to steel and elgiloy (which have a polished surface).
2-3-5 Ni-Ti alloys:
There are currently a wide variety of Ni-Ti bows, but their qualities and properties are not always identical:
– Nitinol: Composed of: Nickel: 52%, Titanium: 45%, Cobalt
Known for its shape memory property and low modulus of elasticity. Nitinol offers a definite advantage over steel during the leveling and alignment phases, and correction of rotations.
– Chinese Nitinol: has greater elasticity than American Nitinol. It can be bent four times more than a steel wire without showing permanent deformation.
– Japanese Ni-Ti: It is currently marketed under the names Bioforce, Sentalloy and Neosentalloy. This wire is characterized by its superelasticity and its shape memory effect.
– Copper Ni-Ti: It is a quaternary alloy (composed of Nickel, Titanium, Copper and Chromium) with superior superelasticity and shape memory properties, compared to classic Ni-Ti, Copper Ni-Ti delivers a constant force over a greater activation range, it is also more resistant to permanent deformation.
2-4- Metal locks and rings:
The orthodontic attachment or lock, bracket in English, is a device fixed to each of the teeth of an arch which can be glued to the tooth or welded to a ring and serves as an intermediary between the tooth to be moved or immobilized, and the mechanical effector which constitutes the active part of the orthodontic appliance.
Materials used for manufacturing locks:
Stainless steel, Titanium, Chrome cobalt alloys
Ceramic locks:
Plastic or polycarbonate locks appeared in the sixties to improve the unsightly appearance of metal multi-attachment devices; they are indicated for adolescents and adults sensitive to aesthetic factors.
Ceramic attachments are made of 2 metal oxides:
– zirconium oxide (ZrO2).
-Aluminum oxide (Al2O3), which is most used for the manufacture of fasteners.
Ceramics are chemically inert to air, oral fluids, acids and bases; they are biocompatible, non-allergenic, do not absorb water, do not stain or discolor. Ceramics have very low fracture toughness, making them extremely brittle.
2-5 Brazing and soldering:
Brazing is the conventional joining method used in orthodontics.
It consists of joining metallic elements together by the interposition of a filler material. In orthodontics, silver solder is used with a deoxidizing flux, incorporated or not, and with a gas torch.
Soldering is therefore a source of breakage, oxidation of devices and in some cases of allergies in the mouth.
Laser welding is of great interest in ODF innovation, compared to traditional brazing. It corresponds to the assembly of two metal parts carried out by thermal means. Unlike brazing, it is possible with laser welding to obtain an exact positioning of the elements without the possibility of deformation. It ensures a punctual fusion of the material, without heating the bordering areas to ensure an unmatched quality of the welded parts.
2-6_Polymeric materials:
Physical classification of polymers:
- Thermoplastics (polyethylene, PVC, nylon)
- Thermosetting polymers or resins (epoxy, polyurethane, silicone)
- Elastomers or rubbers
- Natural polymers (cellulose, proteins
2-6-1 Thermoformed gutter:
2-6-2Acrylic resin:
Acrylic resin is a well-known material that has been used for a long time in Dento-Facial Orthopedics, it is most often presented in liquid-powder form.
Powder (polymer): This is pre-polymerized methyl methacrylate in the form of small spherical particles.
The liquid (monomer): it is a monomer of methyl methacrylates. Orthodontic resin is composed of polymethyl methacrylate, it can come in different forms, translucent or colored.
Its preparation is carried out by mixing the liquid and the powder (a plastic paste is formed which can be molded into the desired shape), followed by a hardening cycle (heating in hot water under pressure to polymerize and harden the resin).
The use of acrylic resin for the manufacture of removable plates can be risky for patients because, if the polymerization is incomplete, the residual monomeric components are skin irritants that can cause allergic reactions.
Resin plates
Its mechanical properties are good: hardness, tensile strength.
However, its abrasion resistance is low.
2-6-3_Elastomeric materials:
An elastomer is a polymer called: elastic, it supports very large deformations, almost totally reversible.
The term elastomer thus designates all synthetic rubbers, possessing so-called rubbery elasticity.
Aging and biodegradation:
Functional biodegradation: Elastomeric components are unable to exert a force of constant intensity for a long period of time.
Environmental biodegradation: the degradation of physical and chemical properties within the humid and aggressive environment of the oral cavity is a factor in the worsening of the aging and porosity of elastomers.
In the mouth, different factors will influence:
-Chemical factors: saliva, food and hygiene.
-Thermal factors: variation in food temperature.
-PH variations.
-Mechanical factors: chewing and brushing.
_Orthodontic use of elastomers:
The rubber bands.
Elastomeric chains.
Elastomeric ligatures.
Elastomeric gutters
Conclusion :
In dentofacial orthopedics, dental movements and action on the bony bases are obtained using intraoral devices which constitute the bulk of the mechanical therapeutic arsenal.
The materials used in orthodontic appliances must meet mechanical criteria, but above all they must be biocompatible and have chemical stability allowing for fairly prolonged use in the oral environment.
Bibliography:
1-Jean-Pierre Attal: BioClinical Dental Materials
Dental Information Review 02.03.2016.
2-F.Bassigny Manual of dentofacial orthopedics
Edition Masson 1996
3- G. Burdairon: Summary of dental biomaterials,
Masson Edit, (1981).
4- J. Jacques Guyonnet, J. Champion, G. Gregoire, B. Grosgogeat, P. Millet, F. Moya, P. Rocher,
5-Dental alloys, French Dental Association, (Paris,) 2004 Marie José Boileau: Orthodontics for children and young adults volume 1
Principles and therapeutic methods
Edition Elsevrier Masson 2011
6-M.Chateau: Dento-facial orthopedics. Volume 1
Edition Cdp 1992
7- P. MILLET, P. WEISS: Physical properties of dental materials
French-speaking Society of Dental Biomaterials 2010
BIOMATERIALS IN ODF
Deep cavities may require root canal treatment.
Dental veneers correct chipped or discolored teeth.
Misaligned teeth can cause uneven wear.
Dental implants preserve the bone structure of the jaw.
Fluoride mouthwashes help prevent cavities.
Decayed baby teeth can affect the position of permanent teeth.
An electric toothbrush cleans hard-to-reach areas more effectively.