Biomimeting agents are those which gives the dentist the power to work flawlessly and the patient recieves a life like result and working. It is the most discussed topics in the dental world at this time and indeed the most interesting too.
It's a metal that is solid and brittle at room temperature (if you strike it, it shatters like glass), but it melts at 86°F, so if you hold it in your hands for a few minutes it will melt. Unlike mercury, gallium is not toxic.
Final polishing is done after 24 hours. Many clinicians prefer to do even the initial contouring after 24 hours to avoid water from affecting the cement. The final finishing is done using "Sof-Lex" discs or discs with different gradation of abrasives from coarse to fine, in a series.
. The transformation of partially stabilized tetragonal zirconia into the stable monoclinic form can also occur under stress and is associated with a slight particle volume increase. The result of this transformation is that compressive stresses are established on the crack surface, thereby arresting its growth. This mechanism is called transformation toughening.
Experimental glass-ceramics in the system Li2O-Al2O3- CaO-SiO2 are currently the object of extensive research work.
Two modified porcelain compositions for the Inceram technique have been recently introduced. In- Ceram Spinell contains a magnesium spinel (MgAl2O4) as the major crystalline phase with traces of alpha-alumina, which seems to improve the translucency of the final restoration. The second material contains tetragonal zirconia and alumina.
Dental Biomimetic Materials
Guided by : Dr S. Prakasam Presented by: Dr K.C. Ponnappa Dr.Supratim Tripathi TOOTH CARE DENTAL CLINIC LUCKNOW, UTTTAR PRADESH. INDIA. 7800302984
Biomimetic dentistryProperties of biomaterialsAmalgamGold alloysComposite resinsGlass ionomerCeramicsArticlesReferences
What is biomimetic dentistry?Biomimetic dentistry, a type of tooth conserving dentistry, treats weak,fractured, and decayed teeth in a waythat keeps them strong and seals them from bacterial invasion.
• Biomimetic means to copy or mimic nature. • Nature is our ideal model to imitate. In order to mimic nature we must understand what nature looks like or feels like. We need to know how it moves or behaves. In other words, we can study natures properties so that we can better duplicate it.>> 0 >> 1 >> 2 >> 3 >> 4 >>
• Biomimetic dentistry is conservative.• One more important aspect about biomimetic dentistry needs to be addressed: less dentistry is the best dentistry; we can even say no dentistry is the best dentistry. Much of the surgical aspect of dentistry can be eliminated or prevented with modern science. Periodontal disease and caries (decays) can practically be eliminated with Ozone treatment, hygiene, and properly placed pit and fissure sealants. If caries or old fillings are existing, they can be treated with the most conservative materials and techniques. We can say that preservation and conservation lie at the heart of biomimetic dentistry. It is a win-win situation for everyone. Page 7
(Biomimicry)• Biomimics take clues from nature• Biomimicry (from bios, meaning life, and mimesis, meaning to imitate) is a design discipline that studies nature‟s best ideas and then imitates these designs and processes to solve human problems.• Bionics (short for Biomechanics) (also known as biomimetics, biognosis, biomimicry, or bionical creativity engineering) is the application of methods and systems found in nature to the study and design of engineering systems and modern Page 8
High fuel efficiency concept vehicle Based on the Body Shape of Boxfish Bionic car, 20 percent lower fuelconsumption and up to 80 percent lower nitrogen oxide emissionsphoto courtesy of DaimlerChrysler
Mollusk-inspired Fan: EnergySaver and Reduction of Noise
Beetle-inspired Material forwater harvester: the patterningNew material that copies the properties ofthe wing surface of the Namibian desertbeetle for collecting precious drinkingwater from an invisible mist. InventaPartners: Air Conditioning for recyclingwater. 2004 (Original research by MIT)
Eys of Moth to Autoflex MARAG (MothEye Anti-Reflective, Anti- Glare)These compound eye structures haveevolved to collect as much light aspossible without reflection, in order toprevent moths being detected by nighttime predators. Applications include flatpanel displays, touch screen interfaces,electroluminescent lamps and lenses formobile phones and PDAs.
Biologically inspired robots Six legged robot at the AI Lab, Univ. ofQuadruped Walking Machine to Climb Slopes at the Univ. of MichiganNagoya, Japan http://www.ai.mit.edu/ projects/leglab/home. htmlFully Contained 3D Bipedal Walking Dinosaur Robot atMIT Snake-like – by Mark Tilden
Robot that responds to human expressions Cynthia Breazeal and her robot Donna
Applications of biomimetic robots Mattel‟s Miracle Moves Baby doll making realistic behavior of a baby.Walking forest machine for complexharvesting tasks (Plustech Oy,Finland).[http://www.plustech.fi/Walking1.html] Multi-limbed robots LEMUR (Limbed Excursion Mobile Utility Robot) at JPL.
Romans and Chinese used gold in dentistry over 2000 years ago. Ivory & wood teeth Aseptic surgery 1860 (Lister) Bone plates 1900, joints 1930 Turn of the century, synthetic plastics came into use 1960- Polyethylene and stainless steel being used for hip implants
BACKGROUND Historically, biomaterials consisted of materials common in the laboratories of physicians, with little consideration of material properties. Early biomaterials : Gold: Malleable, inert metal (does not oxidize); used in dentistry by Chinese, Aztecs and Romans--dates 2000 years Iron, brass: High strength metals; rejoin fractured femur (1775) Glass: Hard ceramic; used to replace eye (purely cosmetic) Wood: Natural composite; high strength to weight; used for limb prostheses and artificial teeth Bone: Natural composite; uses: needles, decorative piercings
INTRODUCTION A biomaterial is a nonviable material used in a medical device, intended to interact with biological systems. is used to make devices to replace a part of a function of the body in a safe, reliable, economic, and physiologically acceptable manner. is any substance (other than a drug), natural or synthetic, that treats, augments, or replaces any tissue, organ, and body function. The need for biomaterials stems from an inability to treat many diseases, injuries and conditions with other therapies or procedures : replacement of body part that has lost function (total hip, heart) correct abnormalities (spinal rod) improve function (pacemaker, stent) assist in healing (structural, pharmaceutical effects: sutures, drug release)Williams, D.F. (1987) Definitions in Biomaterials. Proceedings of a Consensus Conference of the European SocietyFor Biomaterials, England, 1986, Elsevier, New York.
Restorative and Esthetic Materials• Restorative: To replace or bring something back to its natural appearance and function.• Esthetic: To replace or bring something back to its pleasing appearance. Page 29
Restorations• Restorative materials that are applied to the tooth while the material is pliable and able to carve and finish. – Amalgam – Gold alloys – Composite resins – Glass ionomer – Ceramics Page 30
Amalgam HISTORY : Dental amalgam is one of the oldest filling materials in use today. It is available to dental profession for over 150 years. The first dental silver amalgam was introduced into England by “Joseph Bell” in 1819 and was known as “BELLS PUTTY”. - SIR REGNART because of his extensive study is considered as the FATHER OF AMALGAM.
• First Amalgam War :• In 1843 American Society of Dental Surgeons condemned the use of all filling material other than gold as toxic, thereby igniting “first amalgam war‟. The society went further and requested members to sign a pledge refusing to use amalgam.• Second Amalgam War :• In mid 1920‟s a German dentist, Professor A.Stock started the so called “second amalgam war”.• He claimed to have evidence showing that mercury could be absorbed from dental amalgam which lead to serious health problems.• He also expressed concerns over health of dentists, stating that nearly all dentists had excess mercury in their urine.
• Third Amalgam War ;• The current controversy, sometimes termed as “Third Amalgam War‟ began in 1980 primarily through the seminars and writings of Dr.Huggins, a practicing dentist in Colarado.• He was convinced that mercury released from dental amalgam was responsible for human diseases affecting the cardiovascular system and nervous system.• He also stated that patients claimed recoveries from multiple sclerosis, Alzhemer‟s disease and other diseases as a result of removing their dental amalgam fillings.
• PRESENT :• Classification (Marzouk) :• The amalgam alloy can be classified in the following ways :• According to number of alloy metals :• Binary alloys (Silver-Tin)• Ternary alloys (Silver-Tin-Copper)• Quaternary alloys (Silver-Tin-Copper-Indium).• According to whether the powder consist of unmixed or admixed alloys.• Certain amalgam powders are only made of one alloy. Other have one or more alloys or metals physically added (blended) to the basic alloy. eg. adding copper to a basic binary silver tin alloy.• According to the shape of the powdered articles.• Spherical shape (smooth surfaced spheres).• Lathe cut (Irregular ranging from spindles to shavings).• Combination of spherical and lathe cut (admixed).•• According to Powder particle size.• Microcut• Fine cut• Coarse cut Page 35
• According to copper content of powder• Low copper content alloy – Less than 4%• High copper content alloy – more than 10%• According to addition of Nobel metals.• Platinum• Gold• Palladium• According to compositional changes of succeeding generations of amalgam.• First generation amalgam was that of G.V.Black i.e. 3 parts silver one part tin (peritectic alloy).• Second generation amalgam alloys - 3 parts silver, 1 part tin, 4% copper to decrease plasticity and increase hardness and strength. 1% zinc, as oxygen scavenger and decrease brittleness.• Third generation : First generation + Spherical amalgam .• Fourth generation : Adding copper upto 29% to original silver and tin powder to form ternary alloy. So that tin is bounded to copper.• Fifth generation : Quaternary alloy ie.. silver tin and copper and indium.• 6th generation (Eutectic alloy ). Page 36
• According to Presence of zinc.• Zinc containing (more than 0.01%).• Non zinc containing (less than 0.01%).• CLASSIFICATION ACCORDING TO STURDEVENT• According to Sturdevant amalgam is classified into :• Amalgam alloy particle according to geometry and size.• Copper content• Zinc content•• 1) Amalgam alloy particles according to Geometry and size :• A) Irregular powder particles (lathe cut) : In these more mercury is needed to fill the spaces between the particles. Mercury is later removed by wringing the mass in a squeeze cloth.• B) Spheroidal alloy particles. Page 37
• 2) Copper content :• A) High Copper (More than 11.9% to 28.3%)• B) Low copper (2.4% to 8.6%)• 3) Zinc content• A) Zinc containing• B) Zinc free Page 38
• STAGES OF DIMENSIONAL CHANGES :• Dimensional Changes occurs in 3 stages :• Stage I : Called initial contraction for approximately 20 minutes after beginning of trituration. It results from absorption of mercury, into interparticular spaces of alloy powder.• Stage II : Called as expansion stage. This is due to formation and growth of matrix crystals.• Stage III : Called as limited delayed contraction. This occurs due to absorption of unreacted mercury. Page 39
Indications for Using Amalgam In individuals of all ages. In stress-bearing areas of the mouth. When there is severe destruction of tooth structure. As a foundation. When personal oral hygiene is poor. When moisture control is problematic. When cost is an overriding patient concern.
Indications for Not Using Amalgam Esthetics is important. Patient has a history of allergy to mercury or other amalgam components. The cost of other restorative materials or treatment options is not a factor.
Chemical Makeup of Amalgam• Mercury (43% to 54%)• Alloy powder (57% to 46%) – Silver, which gives it its strength. – Tin for its workability and strength. – Copper for its strength and corrosion resistance. – Zinc to suppress oxidation. Page 42
Issues Concerning Amalgam Harm to patients: Essentially harmless. -The exception is with patients who have many amalgam restorations, or a high sensitivity to metals. Harm to Dental Personnel: - Health concerns with high exposure to mercury, not amalgam. Tremors Kidney dysfunction Depression Nervous system disorders
Amalgam Hygiene Do not contact mercury with your skin. Protect against spillage during trituration. Keep lid closed during trituration. Do not discard scrap amalgam into waste containers. Collect all scrap amalgam and store under water or photographic fixer solutions in a closed container.
Preparation of Amalgam Capsules (600 mg of alloy): For small or single-surface restorations. Capsules (800 mg of alloy): For larger restorations. Trituration: The process by which the mercury and alloy are mixed together to form the mass of amalgam.
Direct Application of Amalgam1. Mixed amalgam placed in amalgam well.2. Amalgam carried to the prepared tooth.3. Amalgam placed in increments in the prepared tooth.4. Each increment is condensed immediately.5. Carvers are used to carve anatomy into the amalgam.6. A burnisher is used to smooth the amalgam.7. The new restorations occlusion is checked.
RECENT ADVANCES IN DENTIN AMALGAM : Fluoride Containing Amalgam : Secondary caries is one of the most importantcause of failure in amalgam restoration. This was considerably low in case of silicate cement which was associated with the high fluoride content ofthat material. The addition of fluoride to amalgam was therefore attractive way to stimulate the anticariogenic properties of silicate cement. Stannous fluoride was added Results / Advantages :Studies showed that there was reduced solubility of enamel adjacent to fluoride containing amalgam. One study has shown that there was lowerincidence of secondary caries around the fluoride containing amalgam restoration.
• Disadvantages :• Invitro studies have shown that there is reduction in mechanical properties such as compressive strength and corrosion resistance when stannous fluoride is added to the amalgam.• INDIUM :• The possibility of adverse effects caused by exposure to mercury vapour caused researchers to experiment with alternative materials.• Indium was incorporated into the amalgam structure to minimize the vaporization of mercury from the amalgam surface.• Effects :• These Are :• Total reduction in the amount of mercury present.• More efficient oxidation of the surface of mercury releasing phase.• It is good wetting agent and adapts well to tooth surface. Page 48
• GALLIUM ALLOYS :• Silver amalgam, though an accepted restorative material, yet the mercury controversy limits it use. The toxic effects of mercury coupled with problems of mercury hygiene, led the researchers think of mercury free alloys.• Biological Considerations :• Biologically, the results are not promising. In early gallium alloys, surface roughness, marginal discoloration and fracture were reported. With the improvement in composition these defects were significantly reduced but not totally eliminated. Page 49
• BONDED AMALGAM RESTORATIONS :• To overcome one of the major disadvantage of silver i.e. it does not adhere properly to cavity walls, adhesive systems designed to bond amalgam to enamel and dentin have been introduced.• Some studies also suggest that the use of dual-cured filled liners may be beneficial for bonding amalgam to dentin.• The use of a self-cured filled adhesive liner has been shown to be as valuable under amalgam restorations as under composite restorations.• Another advantage from the use of dentin adhesives under amalgam restorations is that the residual tooth structure becomes more resistant to fracture than when teeth are restored with a copal varnish and amalgam. Page 50
• At present, the benefit of a bonded amalgam is two-fold:• 1. The reduction or elimination of microleakage afforded by sealing the prepared tooth structure with a bonding system.• 2. The reinforcement of the remaining tooth structure.• STEPS (steps 1 to 4 are common to the technique used for composite restorations)• 1. Etch enamel and dentin for 15 seconds• 2. Rinse, leave moist• 3. Apply two consecutive coats of Single Bond• 4. Gently air dry to evaporate the ethanol solvent• 5. Dispense a small amount (2-3 clicks) of Rely X ARC from the Clicker dispenser and mix it on a paper pad with a spatula• 6. Brush it on the preparation for 15 seconds• 7. Insert and condense the amalgam• Am J Dent 1993;6:173-5
GOLD ALLOYS• Noble metals:• The periodic table of elements shows eight noble metals• Gold (Au)• Platinum (Pt)• Palladium (Pd)• Rhodium (Rh)• Ruthenium (Ru)• Iridium (Ir)• Osmium (Os)• and Silver (Ag)
• Pure gold (Au) is a soft, malleable, ductile metal that has a rich yellow colour with a strong metallic luster.Au - 79 Atomic No.196.97 Atomic Mass19.32 gm/cm3 Density1064.4 C Melting point.
Alloy types by function (ISO 1562- year 2002) Type Yield str Min Elongtn % Use MPa (Min) Type I 80 18 Very low stress Low strength inlays. Type II 180 10 Moderate stressMedium strength inlays, onlays & Full crowns. Type III 270 5 High stress onlays, High strength thin coping, crowns & saddles Type IV 360 3 Very high stress Extra strength saddles, bars, clasps, partial dentures frameworks.
Composite Resins• Becoming the most widely accepted material of choice by dentists and patients because of their esthetic qualities and new advances in their strength .• Since the 1990‟s resin-based composite [RBC] sales have increased. The ability to mimic tooth structure gives RBC a distinct advantage for patients and dental professionals. As differences between amalgam and RBC properties narrowed, resin –based materials was placed in larger preparations. Page 57
Class of composite Particle size Clinical useTraditional 1-50 m glass High-stress areas(large particle)Hybrid (1) 1-20 m glass (2) 0.04 High-stress areas(large particle) m silica. requiring improved polishability (classes I, II, III, IV)Hybrid (midifiller) (1) 0.1-10 m glass (2) High-stress areas 0.04 m silica requiring improved polishability (classes III, IV)Packable hybrid Midifiller/minifiller Situations in which hybrid, but with lower improved condensability filler fraction is needed (class I, II)Flowable hybrid Midifiller hybrid, but with Situations in which finer particle size improved flow is needed distribution and /or where access is difficult (class II) as gingival increment or liner.
Indications for Using Composite Resins • Withstand the environments of the oral cavity. • Be easily shaped to the anatomy of a tooth. • Match the natural tooth color. • Be bonded directly to the tooth surface. Page 60
Chemical Makeup of Composite Resins• Resin matrix – Dimethacrylate, referred to as BIS-GMA • Monomer used to make synthetic resins – Polymerization additives • Allow the material to take form through a chemical process • Initiator • Accelerator • Retarder • Ultraviolet (UV) stabilizers Page 61
Chemical Makeup of Composite Resins cont’d • Fillers Add the strength and characteristics necessary for use as a restorative material. • Inorganic fillers – Quartz – Glass – Silica – Colorants • A coupling agent strengthens the resin by chemically bonding the filler to the resin matrix. – Organosilane compound Page 62
Direct Application of CompositeResins1. Select the shade of the tooth.2. Express the needed amount of material onto the treated pad or in the light-protected well.3. Material placed in increments.4. Material is light-cured.5. Material is finished and polished. Page 63
Steps in Finishing a CompositeRestoration1. Reduction of the material is completed by the use of a white stone or a finishing diamond.2. Fine finishing is completed with carbide finishing burs and diamond burs.3. Polish with medium discs and finish with the superfine discs.4. Finishing strips assist in the polishing of the interproximal surfaces.5. Use polishing paste with a rubber cup. Page 64
• INDIRECT POSTERIOR COMPOSITES:• Indirect composites inlays or onlays reduce wear and leakage and overcome some of the limitation of resin composites. Several different approaches to resin inlay construction have been proposed.• These include• 1) the use of both direct and indirect fabrication method• 2) the application of light, heat, pressure, or a combination of these curing systems• 3) the combined use of hybrid and microfilled composites Page 65
• In addition to conventional light and heat curing, laboratory processing may employ heat (140 c) and pressure (0.6 MPa for 10 min.).• The potential advantage of these materials is that a somewhat higher degree of polymerization is attained, which improves physical properties and resistance to wear.• Polymerization shrinkage does not occur in the prepared teeth, so induced stresses and bond failures are reduced, which reduces the potential for leakage. Page 66
Glass IonomerMaterials• Glass ionomer is a versatile material with chemical properties allowing it to be a restorative material, liner, bonding agent, and permanent cement.• Glass ionomer is the generic name of a group of materials that use silicate glass powder and an aqueous solution of polyacrylic acid. This material acquired its name from its formulation of a glass powder and an ionomeric acid that contains carboxyl groups. It is also referred as polyalkenoate cement. Page 68
• Micro mechanical adhesion to enamel was really recognized by Buonocore‟s classic paper in 1955. He defined the principles of the acid-etch technique to the extent that he is clearly regarded as the father of the concept.• The invention of the glass- ionomer cement in 1969 (reported by Wilson and Kent, 1971) resulted directly from basic studies on dental silicate cements and studies demonstrate that the phosphoric acid in dental silicate cements was replaced by organic chelating acids. Page 69
• CLASSIFICATION FOR GLASS IONOMER CEMENT•• A. According to Wilson and McLean in 1988• 1. Type I -Luting cements• 2. Type II -Restorative cements• -a. Restorative aesthetic• -b. Restorative reinforced•• B. According to application• 1. Type I -Luting cements• 2. Type II -Restorative cements• -a. Aesthetic filling materials• -b. Reinforced materials (Fuji IX)• 3. Type III -Lining or base cement• 4. Type IV -Fissure Sealant• 5. Type V -Orthodontic cement• 6. Type VI -Core build up cement Page 70
• C. According to characteristics specified by the manufacturer•1.Type I - Luting cement (e.g.) Fuji I, Ketac2.Type II - Restorative material (e.g.) Ketacfil, Fuji II, Fuji IX etc3.Type III -a. Bases & Liners-Weak with less acidic (eg.) GC lining cement, Shofu liner• b. Bases & Liners-Stronger but more acidic (eg.) Ketac bond, Shofu base, GC Dentin• c. Bases & liners-Strong even in thin layer (eg.) Light cure (vitrabond)4. Type IV -Admixtures (eg) Ketac Silver, Miracle Mix Page 71
• D . Newer classification•• 1. Traditional Glass Ionomer a. Type I - Luting cement b. Type II - Restorative cements c. Type III - Liners & Bases• 2. Metal modified Glass Ionomer a. Miracle Mix b. Cermet Cement 3. Light Cure Glass Ionomer HEMA added to liquid 4. Hybrid Glass Ionomer / Resin modified Glass Ionomer a. Composite resin in which fillers substituted with glass ionomer particles b. Pre-cured glasses blended into composites Page 72
• INDICATIONS OF GLASS IONOMER CEMENT:• 1. Restoration of erosion /abrasion lesions without cavity preparation• 2. Sealing and filling of occlusal pits and fissures.• 3.Dentin substitutes for the attachment of composite resins using the acid etch technique.• 4. Restoration of class 3 and 5 early carious lesions.• 5. Lining of all types of cavities where biological seal and cariostatic actions are required.• 6. Minimal cavity preparations where restoration is not exposed to high occlusal stress.• 7. Core build-up where there is residual dentin support.• 8. Restoration of deciduous dentin.• 9. Provisional restorations when future veneer crowns are contemplated.• 10. Repair of defective margins• 11. Sealing of root surfaces for overdentures.• 12. Cementation of crowns and inlays, particularly in patients with a high caries incidence Page 74
CHEMISTRY OF SETTING Stage I Dissolution Stage II Precipitation of salts, gelation and hardening Stage III Hydration of salts Stage I – Dissolution: When the solution or the water is mixed with the powder, the acid goes into solution and reacts with the outer layer of the glass. This layer becomes depleted in aluminum, calcium, sodium and fluoride ions so that only, a silica gel remains.
Stage II - Precipitation of Salts, Gelation and Hardening: During this stage, calcium and aluminum ions bind to polyanions via the carboxylate groups. The initial clinical set is achieved by cross-linking of the more readily available calcium ions with the carboxyl of the acid.
Stage III – Hydration of salts: Associated with the maturation phase, is a progressive hydration of the matrix salts, leading to sharp improvement in physical properties.
FLUORIDE RELEASE: One of the important properties that glass ionomers share with silicate is the release of fluoride ion throughout the life of the restoration. Glass ionomer also has a reputation for providing resistance to further demineralization to surrounding and adjacent tooth structure.
Indications for Using Glass Ionomers• Primary teeth.• Final restorations in non-stress areas.• Intermediate restorations.• Core material for a buildups.• Long-term temporary restorations. Page 81
Supply of Glass Ionomers• Powder and Liquid: Manually mixed together on a treated paper pad.• Light-Protected Tubes: Dispensed onto a treated paper pad.• Paste/Paste System: Mixed for application.• Premeasured Capsule: Triturated for application. Page 82
• RECENT ADVANCES• RESIN MODIFIED GLASS IONOMERS• Resin modified glass ionomer restorative cements are a relatively recent development. They were introduced to overcome the problems associated with the conventional glass ionomers and at the same time preserving the clinical advantages of the conventional materials.• The approximately 5% of resin that normally added is HEMA, along with a small quantities of a photoinitiator (camphoroquinone).
Classification of Resin Reinforced glass ionomers Depends on the curing mechanism Dual cure: Visible light cure free-radical polymerization and glass ionomer setting mechanism (Acid-base reaction). E.g. Geristore. Tri-cure: Visible light free radical methacrylate polymerization. Chemical cure of free radical methacrylate polymerization of composite resin. Conventional acid base reaction. E.g. Vitremer, Fuji II LC. Photocure: Visible light cure only. E.g. Polyacid modified composite resins, variglass, compoglass, Autocure: Chemical cure of the radical methacrylate polymerization only autocure. E.g. Prosthodont.
• Advantages of resin modified glass ionomer cement’s over conventional glass ionomer cements:• Sufficiently long working time controlled in command to a snap set by photocuring.• Improved setting characteristics.• Protects the acid base reaction from problems of water balance.• Rapid development of early strength.• Can be finished and polished immediately after set.• Repairs can be easily carried out, as the bond between old and new material is very strong.• Disadvantages:• Biocompatibility is controversial.• Setting shrinkage is higher microleakage is more, marginal adaptation is poor.• Low wear resistance compared to composite.• Poor fracture toughness.• Color that cannot compare to composite in its ability to match natural tooth coloration• Uses:• Used for luting stainless steel crowns, space maintainers, bands in pedo cases.• Used as a liner and base.• Pit and fissure sealant.
• COMPOMER (POLYACID MODIFIED COMPOSITE RESINS)• Compomers are the combination of composites (‘comp’) and glass ionomers (‘omer’).• Compomers contain dimethacrylate monomer and two carboxylic groups along with ion leachable glass. There is no water in the composition of these materials and the glass particles are partially silanated to ensure some bonding with the matrix. These materials set via free radical polymerization reaction and do not bond to hard tooth tissues.
• Indications• Sealing and filling of occlusal pits and fissures• Restoration of deciduous teeth• Minimal cavity preparation or tunnel preparation• Lining of all types of cavities where a biological seal and cariostatic action is required• Core-build up• Replacement of carious dentine for the attachment of composite resins• Repair of defective margins in restorations• Restoration of Class III cavities preferably using a lingual approach• Restoration of Class V carious lesions• Restoration of erosion (abrasion lesion without cavity preparation)• Sealing of root surfaces for over dentures• Provisional restoration where future veneer crowns are contemplated• Potential root canal sealers• Retrograde fillings materials in endodontic emergencies• Fine grain versions of glass ionomer cement, for luting purposes.
• Advantages• Superior working characteristics to resin modified glass ionomer cement• Ease of use• Easily adapts to the tooth• Good esthetics• Good fluoride release• Contraindications• Class IV carious lesions• Lesion involving large areas of labial surface where esthetics is of prime concern• Class II carious lesions where conventional cavities are prepared replacements of old amalgam restorations.• E.g. Compomer, Dyract (Dentsply), compoglass (Ivoclar), Hytac (Espe).• Lost cusp areas• Underneath metal/PFM crowns where light cannot penetrate
• GIOMER (PRE-REACTED GLASS-IONOMER)• Giomers are a relatively new type of restorative material. The name „giomer‟ is a hybrid of the words „glass ionomers‟ and „composite‟. They have the properties of both glass ionomers (fluoride release, fluoride recharge) and resin composites (excellent esthetics, easy polishability, and biocompatibility).• Indications:• Restoration of Class I. II. III. IV, & V• Restoration of cervical erosion and root caries• Laminate veneers and core build-up• Ideal for pedodontic restorations• Other dental applications such as repair of fractured porcelain and composite restoration
Ceramics Ceramics are compounds that involve a combination of metallic and nonmetallic elements, creating strength and aesthetics. Since the first use of porcelain to make a complete denture by Alexis Duchateau in 1774, numerous dental porcelain compositions have been developed. Porcelain compositions suitable for metal- ceramic restorations were introduced in 1962 (Weinstein and Weinstein, 1962) and led to the success of this technology. For the last ten years, the application of high-technology processes to dental ceramics allowed for the development of new materials such as heat pressed, injection-molded, slip-cast ceramics, and glassceramics.
CLASSIFICATION I] There are several categories of dental ceramics : a) Conventional leucite-containing porcelain b) Leucite - enriched porcelain c) Ultra - low fusing porcelain that may contain : Leucite Glass – ceramic Specialized core ceramics like (alumina, glass infiltrated alumina, magnesia and spinel) d) CAD-CAM ceramic
II] Dental ceramics can be classified by : I) Type : a) Feldspathic porcelain b) Leucite reinforced porcelain c) Aluminous porcelain d) Alumina e) Glass infiltrated alumina f) Glass infiltrated spinel g) Glass ceramic
II) Use : a) Denture teeth b) Metal - ceramics c) Veneers d) Inlays e) Crowns and anterior bridges III) By processing method a) Sintering b) Casting c) Machining IV) By substructure material : a) Cast metal b) Glass ceramic c) CAD-CAM ceramic d) Sintered ceramic core
III] Dental porcelains are also classified according to their firing temperatures as follows: a)High fusing - 1300 C b)Medium fusing - 1101 - 1300 C c) Low fusing - 850 -1100 C d) Ultra low fusing - < 850 C
REVIEW OF NEW MATERIALS AND PROCESSES • Sintered porcelains a) Leucite-reinforced feldspathic porcelain b) Alumina-based porcelain c) Magnesia-based core porcelain d) Zirconia-based porcelain • Glass-ceramics a) Mica-based b) Hydroxyapatite-based c) Lithia-based • Machinable ceramics a) Cerec system b) Celay system • Slip-cast ceramics a) Alumina-based (in-Ceram) • Hot-pressed, injection-molded ceramics a) Leucite-based b) Spinel-based Page 95
Leucite-reinforced feldspathic porcelain Optec HSP material (leneric/Pentron, Inc.) is a feldspathic porcelain containing up to 45 vol% tetragonal leucite. The large amount of leucite in the material contributes to a high thermal contraction coefficient.
Alumina-based porcelain Aluminous core porcelain is a typical example of strengthening by dispersion of a crystalline phase (McLean and Kedge, 1987). Alumina has a high modulus of elasticity (350 GPa) and high fracture toughness (3.5 to 4 MPa.m05). Its dispersion in a glassy matrix of similar thermal expansion coefficient leads to significant strengthening of the core.
Magnesia-based core porcelain Magnesia core ceramic was developed as an experimental material in 1985 (OBrien, 1985). Its high thermal expansion coefficient (14.5 x 106/°C) closely matches that of body and incisal porcelains designed for bonding to metal (13.5 x 10"6/°C). The flexural strength of unglazed magnesia core ceramic is twice as high (131 MPa) as that of conventional feldspathic porcelain (65 MPa).
Zirconia-based porcelain Mirage II (Myron International, Kansas City, KS) is a conventional feldspathic porcelain in which tetragonal zirconia fibers have been included. Partial stabilization can be obtained by using various oxides such as CaO & MgO which allows the high-temperature tetragonal phase to be retained at room temperature.
Glass-ceramics Mica-based The advantage of this process is that the dental restorations can be cast by means of the lost-wax technique, thus increasing the homogeneity of the final product compared with conventional sintered feldspathic porcelains. Dicor (Dentsply Inc., York, PA) is a mica- based machinable glass-ceramic.
Hydroxyapatite-based Cerapearl (Kyocera, San Diego, CA) is a castable glassceramic in which the main crystalline phase is oxyapatite, transformable into hydroxyapatite when exposed to moisture.
Lithia-based Glass-ceramics can be obtained from a wide variety of compositions, leading to a wide range of mechanical and optical properties, depending on the nature of the crystalline phase nucleating and growing within the glass.
Machinable ceramics Cerec system The evolution of CAD-CAM systems for the production of machined inlays, onlays, and crowns led to the development of a new generation of machinable porcelains. There are two popular systems available for machining all-ceramic restorations. The glass-ceramic contains 70 vol% of the crystalline phase.
Celay system As with the Cerec system, the starting material is a ceramic blank available in different shades. One ceramic material currently available for use with the Celay system is Vita-Celay. The alumina copings were further infiltrated with glass following the conventional ln-Ceram technique, resulting in a final marginal accuracy within 50 um.
Slip-cast ceramics Alumina-based (n-Ceram) ln-Ceram (Vident, Baldwin Park, CA) is a slip-cast aluminous porcelain. The alumina-based slip is applied to a gypsum refractory die designed to shrink during firing. This processing technique is unique in dentistry and leads to a high-strength material due to the presence of densely packed alumina particles and the reduction of porosity.
Hot-pressed, injection-molded ceramics Leucite-based IPS Empress (Ivoclar USA, Amherst, NY) is a leucite-containing porcelain. Ceramic ingots are pressed at 1150°C (under a pressure of 0.3 to 0.4 MPa) into the refractory mold made by the lost- wax technique. The ceramic ingots are available in different shades.
Spinel-based Alceram (Innotek Dental Corp, Lakewood, CO) is a material for injection-molded technology and contains a magnesium spinel (MgAl2O4) as the major crystalline phase (McLean and Kedge, 1987). This system was initially introduced as the "shrink-free" Cerestore system.
Among the currently available materials, slip-cast ceramics exhibit the highest values compared with all other products (378-604 MPa). The mean flexural strength of alumina or leucite-based materials, whether sintered or heat- pressed, is between 70 and 180 MPa. Among the machinable ceramic materials, the mica-based material (Dicor MGC) has the highest flexural strength value (229 MPa).
109 Advantages: - inert in body (or bioactive in body) - high wear resistance (orthopedic & dental applications) - high modulus (stiffness) & compressive strength - fine esthetic properties for dental applications Disadvantages: - brittle (low fracture resistance, flaw tolerance) - low tensile strength (fibers are exception) - poor fatigue resistance (relates to flaw tolerance)
• There is now occurring a movement amongst dentists to avoid doing root canals. Ultimately root canals give people enduring medical problems, pain and suffering.• Ozone will immediately kill off any trace of bacteria that may remain. There is also evidence that ozone gas will stimulate the growth of dental tissue. (see Julian Holmes)• Dr Allemen said that ozone will penetrate up to 2 mm into the pulp. 6th October 2009 by Arrow Durfee Posted in Disease, Revolutionary Therapies, Oxidative Therapies, Misc
Forisome based biomimetic smart materials• With the discovery in plants of the proteinaceous forisome crystalloid (Knoblauch et al.2003), a novel, non-living, ATP- independent biological material became available to the designer of smart materials for advanced actuating and sensing.• Natural systems have the capacity to sense their environment, process this data, and respond. For example, the Venus flytrap, a carnivorous plant,has prey-capturing behaviour and can execute repeatable reversible mechanical actions very swiftly.
Microstructures of an Amelogenin Gel Matrix• The thermo-reversible transition (clear ↔ opaque) of the amelogenin gel matrix, which has been known for some three decades, has now been clarified by microstructural investigations. A mixed amelogenin preparation extracted from porcine developing enamel matrix (containing “25K,” 7.4%; “23K,” 10.7%; “20K,” 49.5%; and smaller peptides, 32.4%) was dissolved in dilute formic acid and reprecipitated by adjusting the pH to 6.8 with NaOH solution• These observations suggest that the hydrophobic interactions among nanospheres and different orders of amelogenin assemblies are important in determining the structural integrity of the dental enamel matrix. Journal of Structural Biology Volume 126, Issue 1, 1 June 1999, Pages 42-51
Molecular biomimetics: Utilizing nature’s molecular ways in practical engineering• In nature, proteins are the machinery that accomplish many functions through their specific recognition and interactions in biological systems from single-celled to multicellular organisms.• The molecular biomimetic approach opens up new avenues for the design and utilization of multifunctional molecular systems with wide ranging applications, from tissue engineering, drug delivery and biosensors, to nanotechnology and bioremediation. Acta Biomaterialia Volume 3, Issue 3, May 2007, Pages 289-299 2nd TMS Symposium on biological materials science
Biomimetic mineral coatings in dental and orthopaedic implantology• Biomimetic techniques are used to deposit coatings of calcium phosphate upon medical devices. The procedure is conducted under near-physiological, or “biomimetic”, conditions of temperature and pH primarily to improve their biocompatibility and biodegradability of the materials. The inorganic layers generated by biomimetic methods resemble bone mineral, and can be degraded within a biological milieu.Frontiers of Materials Science in China Volume 3, Number 2 / June, 2009
Leonardo da Vinci• As wrote in 16th century, “Human ingenuity may make various inventions, but it will never devise any inventions more beautiful, nor more simple, nor more to the purpose than Nature does; because in her inventions nothing is wanting and nothing is superfluous”.
1. Operative dentistry – Gilmore 4th edition2. Operative dentistry – Marzouk3. Operative dentistry – Sturdevent’s 5th edition4. Science of dental material – Anusavice 11th edition5. Fundamentals of Operative Dentistry – Summit, Robbins, Schwartz; 2nd edition6. Dental material and their selection – William J. O’briean 3rd edition7. Introduction to Dental Materials – Van Noort 2nd edition• Dentistry news• World net