The Dental Implant

Published on May 2016 | Categories: Types, Instruction manuals | Downloads: 50 | Comments: 0 | Views: 342
of 25
Download PDF   Embed   Report

biomaterials in the fabrication of dental implants

Comments

Content

The Dental Implant 1.What exactly are dental implants? Dental implants are artificial tooth replacements that are used to counter tooth loss due to decay, root canal failure, gum disease, congenital defects, or any other sort of trauma. 2.Skull Anatomy The skull contains some of the body’s most important and complex structures, including the brain, eyes, and mouth (including teeth). 22 bones make up an adult human skull. 2.1.Frontal Skull! Frontal Bone consists of two portions, a vertical portion corresponding with the region of the forehead and a horizontal portion which forms the roofs of the orbital and nasal cavities. Temporal Bone is situated at the sides and base of the skull and supports the temple. Sphenoid Bone is situated at the base of the skull in front of the temporals and basilar part of the occipital bone. Zygomatic Bone is situated at the upper and lateral part of the face and is commonly referred to as the cheekbone. Maxilla Bone is the upper jaw and is made of several bones fused together and holds the upper teeth in place. Inferior Nasal Concha is one of the turbinates in the nose. It extends horizontally along the lateral wall of the nasal cavity.

Nasal Bones consist of two small oblong bones that are placed side by side at the middle and upper part of the face. They form the “bridge" of the nose. Mandible Bone forms the lower jaw and holds the lower teeth in place. Teeth are small white structures found in the jaws of many vertebrates that are used to tear, scrape, and chew food. The roots of teeth are covered by gums. 2.2.Lateral Skull! Parietal Bones are bones in the human skull and form the sides and roof of the cranium. Frontal Bone consists of two portions, a vertical portion corresponding with the region of the forehead and a horizontal portion which forms the roofs of the orbital and nasal cavities. Temporal Bone is situated at the sides and base of the skull and supports the temple. Occipital bone is situated at the back and lower part of the cranium. It is trapezoid in shape and is pierced by the foramen magnum through which the cranial cavity communicates with the vertebral canal. Zygomatic Bone is situated at the upper and lateral part of the face and is commonly referred to as the cheekbone. Sphenoid Bone is situated at the base of the skull in front of the temporals and basilar part of the occipital bone. Mandible Bone forms the lower jaw and holds the lower teeth in place. Maxilla Bone is the upper jaw and is made of several bones fused together and holds the upper teeth in place.

Lacrimal bone is the smallest and most fragile bone of the face. It is situated at the front part of the medial wall of the orbit. Nasal Bones consist of two small oblong bones that are placed side by side at the middle and upper part of the face. They form the “bridge" of the nose. 3.Jaw Anatomy 3.1.Mandible • The Mandible, or inferior maxillary bone, forms the lower jaw and holds the lower teeth in place. • It is the largest and strongest bone in the face. 3.2. Mandible Body of the Mandible: The body is curved like a horseshoe and has two surfaces and two borders. The surfaces (external and internal) contain multiple foramen for the passage of nerves and vessels while the superior border is hollowed into cavities for the reception of teeth. Condyle: The condyle presents a surface for articulation with the articular disk of the temporomandibular joint; it extends farther on the posterior than on the anterior surface and contains a small tubercle for the attachment of the temporomandibular ligament. Coronoid Process: The Coronoid Process is a thin, triangular eminence that serves as the insertion point of the temporalis and masseter. 3.3.Maxilla The Maxilla, or upper jaw, is made of several bones fused together and holds the upper teeth in place.

Sinus: The maxillary sinus is a large pyramidal cavity found within the body of the maxilla. On the posterior wall are alveolar canals which transmit the posterior superior alveolar vessels and nerves to the molar teeth. Anterior Nasal Spine: The anterior nasal spine is a pointed projection at the anterior extremity of the maxilla. Zygomatic Process: The zygomatic process of the maxilla is a rough triangular eminence at the angle of separation of the anterior, zygomatic, and orbital surfaces. It marks the division between the anterior and infratemporal surfaces. Palate: The palate is the roof of the mouth in humans. It separates the oral cavity from the nasal cavity. 4.Salivary Glands • Produce saliva composed of water, electrolytes, mucus, enzymes, and proteins

Salivary Glands

4.1.Parotid Gland: The parotid gland is the largest of the salivary glands. It is wrapped around the mandibular ramus and helps with mastication and swallowing by secreting saliva into the oral cavity. 4.2 Submaxillary Glands: The submaxillary glands (also known as the submandibular glands) are located beneath the floor of the mouth. It produces viscous saliva composed of mucin and salivary amylase. Mucin aids in lubrication as food travels down the esophagus and salivary amylase aids in the breakdown of starches. 4.3. Sublingual Gland: The sublingual gland is a complex of salivary glands that lie anterior to the submaxillary glands. It is the smallest of the three major salivary glands and produces about 5% of the saliva that enters the oral cavity. 5.The Temporomandibular Joint (TMJ) is the movable joint between the lower jaw and the temporal bone of the cranium. • A foramen is an opening or hole in the skull. • Allows blood vessels and nerves to pass through bone. 6.Tooth Anatomy 6.1.Tooth Classification

• Incisors (8) – Cut and Shear Food • Canines (4) – Hold and Tear Food • Pre-Molars (8) – Help with Chewing • Molars (12) – Grind Food

• Crown – above the gum (visible part of tooth) • Neck – at the gum line • Root – below the gum 6.2.Enamel: • Hardest substance in body • 96% mineral, mostly hydroxyapatite (crystalline calcium phosphate) • Semitranslucent • Tooth enamel is the hardest and most mineralized substance of the human body.


Ranks 5 on the Mohs Hardness Scale

• The Mohs scale (ranges from 1-10) characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. • Diamond is at the top of the scale while talc is at the bottom. • Tooth enamel is on the middle of the scale with a hardness of 5. • Primarily consists of Hydroxyapatite • Contains water and proteins such as amelogenins and emaelins • Unlike dentin and bone, enamel does not contain any collagen. 6.3. Dentin: • Calcified Tissue • Yellow in appearance (somewhat shows through enamel) • 70% hydroxylapatite • 20% organic material

• 10% water • Dentin is the hard, yellow bone-like material that lies below the enamel and encloses the cavity of the tooth containing the nerves, pulp chamber, and root canals. • • Thousands of dentinal tubules run from the nerve and terminate at the enamel. Dentin composes the bulk of the tooth and is sensitive to touch and other stimuli

• Dentinal tubules originate from the inner surface of the nerve space and travel perpendicularly to the surface of the tooth terminating at the undersurface of the enamel. These contain tiny projections of cells (called odontoblasts “link to next page”) that line the inside of the nerve space. 6.4.Odontoblasts
• • • • Odontoblasts are tall columnar cells located at the periphery of the dental pulp. Their biological function is dentinogenesis, or the creation of dentin. Another type of dentin, tertiary dentin, is secreted by odontoblasts in reaction to chemical attacks. Tertiary dentin slows down the progress of caries.

6.5. Pulp: • Soft tissue at the center of the tooth containing odontoblasts • Contains nerve 6.6.Cementum: • Serves as a medium by which the periodontal ligaments can attach to for stability • Makeup is similar to bone 6.7.Root Canal: • Natural cavity within a tooth that consists of the dental pulp chamber and main canals to the blood stream 6.8.Periodontal Ligaments • Periodontal Ligaments are specialized connective tissue fibers that attach the tooth to the alveolar bone. • Help the tooth withstand compressive forces that occur during eating 6.9.Alveolar Bone • Alveolar bone is the thickened ridge of bone on the upper and lower jaws that contain the teeth. • Cortical bone, or compact bone, comprises the tooth socket into which the roots fit. 6.10.Gingiva • Consists of mucousal tissue that lies over the alveolar bone and surrounds the teeth. trunks and blood vessels

• Healthy gingiva is usually coral pink, but gingival and periodontal disorders are common and can change the color of gingiva. 7.Dental Implant Design

7.1.Titanium: High Strength-to-Weight Ratio -> prevents deformation under stresses of chewing while remaining light weight to preserve patient comfort Excellent Mechanical Properties -> Ductile so will not fail catastrophically, Malleable so it can easily be formed to desired shape, Tough so will not fatigue over time Great Corrosion and Erosion Resistance -> Thin oxide surface prevents corrosion, which preserves integrity of implant and does not release harmful products into body. Hardness prevents erosion and breaking off of particles. Biocompatible -> Will not elicit an immune response and will not cause any damage to the body Reasons for adding Aluminum:



It changes the crystal structure of the Titanium. When small percentages of aluminum go into solid solution in titanium, the crystal form results in that of alpha titanium. It results in an intermetallic compound having a high modulus, a low density, a high thermal conductivity, good oxidation resistance, and good creep resistance.



Reasons for adding Vanadium:


TiAl alloys are extremely brittle at temperatures below 100oC Adding Vanadium improves ductility and strength of TiAl alloy at lower temperatures



• Unalloyed (commercially pure) titanium can be found in two crystallographic forms: • •


1) Hexagonal close-packed (hcp) or alpha (α) phase is found at room temperature 2) Body centered cubic (bcc) or beta (ß) phase is found above 883 °C (1621 °F) The control of alpha (α) and beta (ß) phases through alloying additions is the basis for the titanium alloys

• The composition Ti6Al4V results in an Alpha Beta Titanium Alloy. • Alpha–beta titanium alloys such as Ti–6Al–4V are used increasingly in biomedical applications because their mechanical properties are much better than those of pure titanium. Moreover, the alloys have a high corrosion resistance equivalent to pure titanium and good biocompatibility

There are numerous reports that demonstrate that the surface roughness of titanium implants affects the rate of osseointegration and biomechanical fixation. 7.1.1.Physical Surface Treatments Grit-Blasting


Roughens surface by blasting implant with hard ceramic particles Drastically increases the biomechanical fixation strength of the implants when compared to smooth titanium Significantly improves bone-to-implant contact One problem is that blast particles my become embedded in titanium and reduce its resistance to corrosion



• •

Plasma-Spraying • Titanium powders are projected on to the surface of the implants at very high temperature • Particles condense and fuse together, forming a film about 30µm thick • Increases mechanical strength at bone/implant interface • Metallic wear particles have been shown to break off and produce toxic effects in the body Acid Etching
• •

Strong acids produce micro pits 0.5-2µm in diameter Promotes rapid osseointegration that lasts for very long periods of time

• • •

Increases cell adhesion and bone regeneration Greatly increases bone-to-implant contact Chemical treatments degrade mechanical properties of implant

Anodization • Nano- or Micro-porous surfaces can also be created by anodization treatment in acidic solutions at high current. • Enhances rate and quality of osseointegration of titanium dental implants. • Increases: - Protein adsorption - Osteoblast cell adhesion - Rate of bone healing 7.1.2.Chemical Surface Treatments • Biomimetic Calcium Phosphate Coatings on titanium dental implants


Incorporation of Biologically Active Drugs into titanium dental implants

Endosseous Root Form Endosseous implants are basically cylinders (with or without threads) and as such require a cylindrical osteotome (a round hole) to place them making them the easiest implants of all to place consistently. Since they approximate the general size of a normal tooth root. They can easily be placed in sites where roots existed making them very versatile for

replacing one or more teeth. Installation is very consistent across the group of implants in this category often allowing the dentist to simplify the armamentarium. These implants may be straight sided or tapered. The basic cylindrical shape is also very conducive to attaching a single tooth restoration while still allowing for the placement of bridges and overdenture restorations in multiple situations. The ability to precisely locate the implant in the position occupied by a root is also a tremendous advantage in prosthetic reconstruction. Abutment Healing Abutment: • Temporary (~5days) • Displace the gingiva from the space above the implant during the implant healing time and serve for proper gingiva shaping • They are offered in three different • shapes; cylindrical, wide body and bottleneck Definitive Abutment: • Anchors crown to post • Stabilizes soft tissue • Prevents soft tissue recession • Transfers mechanical stresses to post • Connects to post by ball and socket or screw Connects to crown by Dental Cement

• Made from a variety of materials including: titanium alloys, zirconia, etcetera. 8. Ceramic Crown Types of Ceramics Used in Dental Implants: • Felspathic porcelains are often used as a veneer material on ceramic and metal implants because of their more natural and aesthetic appearance. • • Sodium oxide or some other alkaline oxide is often used to improve its translucence. Fluxes are also added to the material to lower its melting point. This allows dental laboratories to handle these materials more easily.

Leucites are often used to modify the coefficient of thermal expansion. This becomes extremely important when ceramic is coated on metals. Differences in the coefficients of thermal expansion may create internal stresses, leading to the failure of the implant. Castable glass ceramics use various forms of mica to strengthen glass. The composition of the material is altered to ensure easy handling in dental laboratories 9.Materials 9.1.METALS Physical Properties in Dentistry • Strong - to sustain forces of chewing and not deform • Tough – to avoid fatigue over time • Ductile – to avoid catastrophic failure

• High Strength-to-Weight Ratio – mimic properties of bone, reduce self-loading – Mimicking properties of bone also enhances compliance and prevents detachment of implant from bone • Malleable – to be formed into desirable shape of implant with relative ease • Ductile failure is the preferred mode of failure because it is a more gradual process than catastrophic failure The material can be replaced before a devastating failure, which occurs in brittle materials Chemical Properties of Metals Very reactive with air, water, and acids Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form metal oxides. Anodizing or Galvanizing metals are good ways to prevent their corrosion. Galvanizing


Galvanization is a process of making metals resistant to oxidation.

• High oxidation-resistance achieved by adding chromium • Chromium forms a passivation layer that coats the surface, protecting the metal beneath. Also, this layer quickly reforms when the surface is scratched Anodizing



Anodizing is an Electro-Chemical process used to increase the thickness of the natural oxide layer.

• Creates a protective film on the surface of metal parts • Increases corrosion resistance and wear resistance • In the plating process a more reactive metal in the electrochemical series must be chosen as the coating. – The metal must not corrode within the body giving off harmful metal ions. – Furthermore, corrosion changes the mechanical properties of the prosthetic making them less desirable. • Solutions: – Metals are chosen that are less corrosive in bodily fluids. • For example, Cobalt, Chromium, and Titanium form an oxide layer that protects against corrosion • Measured by Pilling - Bedworth Ratio (PBR) – Metals can be coated to prevent corrosion. • Galvanization • Anodizing • Alloying with other metals induces passivation Metal Alloys • Most pure, elemental metals are either too soft, brittle or chemically reactive for practical use.



Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics.

• The aim of making alloys is generally to make them less brittle, harder, or resistant to corrosion. • Examples of alloys are steel (iron and carbon), brass (copper and zinc), bronze (copper and tin), and duralumin (aluminium and copper). • The melting point of alloys is dependent on the concentration of various metals in the alloy. • Alloying allows for the refinement of material properties to more closely resemble the replaced bone. Furthermore, alloying can have a profound effect on biocompatibility. With alloying, one can select the best available form of a material to be used in the body.

9.2.Ceramics Physical Properties of Ceramics • Very hard • Wear-resistant • Brittle, low toughness and ductility • Refractory • Thermal insulators • Electrical insulators • Limited by defects, stress concentrates at small imperfections leading to sudden crack propagation and failure

• • • • •

Nonmagnetic Oxidation resistant Prone to Thermal Shock Porous Fail Catastrophically

• Ductile Failure • Metals undergo gradual ductile failure • Metals are able to deform when stress is applied. • For example, when tension is applied metals will undergo necking, where the metal will start to narrow at point of failure. • In deformed state the mechanical properties of metals are attenuated. • However, because the metal is still intact it is able to partially support applied loads. • Catastrophic Failure • In ceramics, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. • These combine to give catastrophic failures, as opposed to the normally more forgiving failure modes of metals. • Ceramics do not deform under stress, but rather maintain their full strength up until failure, which usually occurs suddenly without warning.

Physical Properties Necessary for Dental Implants
• • • •

Hard – to avoid deforming under stress of chewing Tough – to prevent failing catastrophically, cracking, chipping Strong – to resist thermal shock Must have excellent wear properties so that implant does not disintegrate or get worn away under shear stresses of grinding. Lustrous and Translucent – to mimic appearance of natural teeth Appropriately colored – to remain aesthetically appealing

• •

Chemical Properties of Ceramics • Ceramics are primarily oxides (compounds of oxygen), but some are carbides (compounds of carbon and heavy metals), nitrides (compounds of nitrogen), borides (compounds of boron), and silicides (compounds of silicon). • Ceramics are chemically inert and nonreactive. • Ceramics are more resistant to corrosion than plastics and metals. • Ceramics generally do not react with most liquids, gases, alkalies, and acids. • Most ceramics have very high melting points, and certain ceramics can be used up to temperatures approaching their melting points. • Ceramics also remain stable over long time periods.


Biocompatibility: An implant must not degrade in the body or cause degradation of the body.

• •

Nonimmunogenic: The implant cannot elicit an immune response. Resistant to corrosion and abrasion: If the implant gets corroded or starts wearing out, it will become loose and ultimately fail. Chemically inert and stable: Ceramics are biocompatible and resistant to abrasion and corrosion; making them a good choice for dental implants.



Ceramic matrix composites (CMCs) combine reinforcing ceramic phases with a ceramic matrix to create materials with new and superior properties • In ceramic matrix composites, the primary goal of the ceramic reinforcement is to provide toughness to an otherwise brittle ceramic matrix • The desirable characteristics of CMCs include: • • • • • • • • High-Temperature Stability High Thermal-Shock Resistance High Hardness High Corrosion Resistance Light Weight Nonmagnetic Nonconductive Properties Versatility in providing unique engineering solutions

Osseointegration Osseointegration is the Formation of a Structural Connection Between Bone and a Weight-Bearing Material.

It improves implant fixation and reduces stress shielding -- a condition that occurs as the stiffer implant material bears more load than the healing bone Healing Time Line

Sponsor Documents

Or use your account on DocShare.tips

Hide

Forgot your password?

Or register your new account on DocShare.tips

Hide

Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in

Close