10.3 Dental implants and restorative materials
5 min read•august 16, 2024
Dental implants and restorative materials are crucial in modern dentistry, replacing missing teeth and restoring oral function. These biomaterials interact with living tissues, requiring careful consideration of their properties and to ensure successful integration and long-term performance.
From implants to ceramic , a variety of materials are used in dental restoration. Understanding their composition, mechanical properties, and biological interactions is key to selecting the right materials for each patient, ensuring optimal outcomes in terms of function, aesthetics, and durability.
Dental Tissues and Implant Materials
Composition and Structure of Dental Tissues
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- Dental tissues comprise enamel, dentin, cementum, and pulp, each with unique compositions and structural characteristics
- Enamel forms the hardest tissue in the human body composed primarily of hydroxyapatite crystals (96%) and a small percentage of organic material (4%)
- Dentin makes up the bulk of the tooth as a mineralized connective tissue consisting of collagen fibers and hydroxyapatite crystals arranged in a tubular structure
- Periodontal ligament anchors the tooth to the alveolar bone playing a crucial role in load distribution and proprioception
- Contains specialized fibers (Sharpey's fibers) that insert into both the cementum and alveolar bone
- Acts as a shock absorber during mastication
Bone-Implant Interface and Osseointegration
- Osseointegration creates a direct structural and functional connection between living bone and the surface of a load-bearing artificial implant
- Bone-implant interface characterized by complex biochemical and biomechanical interactions influenced by implant surface properties
- Surface roughness affects cell adhesion and bone formation (rough surfaces generally promote better osseointegration)
- Chemical composition impacts bioactivity and bone bonding (titanium oxide layer on titanium implants promotes osseointegration)
- Bioactive materials form a direct chemical bond with bone tissue enhancing implant integration
- Examples include bioactive glasses (45S5 Bioglass) and calcium phosphate ceramics (hydroxyapatite)
- These materials stimulate the formation of a hydroxycarbonate apatite layer, similar to bone mineral
Dental Implant Types and Materials
Classification and Materials of Dental Implants
- Dental implants classified based on placement location endosteal (within the bone), subperiosteal (on or above the bone), and transosteal (through the bone)
- Implant materials include titanium and its alloys, , and polymer-based materials each with specific advantages and limitations
- Titanium alloys (Ti-6Al-4V) offer excellent biocompatibility and mechanical properties
- Zirconia implants provide aesthetic advantages in cases of thin gingival biotype
- Restorative materials for dental crowns and include metals, ceramics, and polymer-based composites
- Metals (gold alloys, cobalt-chromium alloys) offer high strength and durability
- Ceramics (feldspathic porcelain, lithium disilicate) provide excellent aesthetics and biocompatibility
- Dental cements bond restorations to natural teeth or implants
- Examples include zinc phosphate (high compressive strength), glass ionomer (fluoride release), and resin cements (high bond strength)
Advanced Manufacturing Techniques
- CAD/CAM technology revolutionized the fabrication of dental implants and restorations allowing for precise, customized designs
- Enables the production of complex geometries and patient-specific implants
- Improves fit accuracy and reduces chairside adjustment time
- 3D printing techniques emerge as a promising method for manufacturing dental implants and restorative components
- Offers increased design flexibility and cost-effectiveness
- Allows for the production of porous structures to enhance osseointegration
Implant Material Properties
Mechanical and Aesthetic Properties
- Crucial mechanical properties for dental materials include strength, hardness, elastic modulus, fatigue resistance, and
- Compressive strength important for withstanding masticatory forces (enamel: ~384 MPa, dentin: ~297 MPa)
- Wear resistance crucial for maintaining occlusal stability and preventing material loss
- Elastic modulus mismatch between implant materials and surrounding bone can lead to stress shielding
- Titanium (110 GPa) vs. cortical bone (18-20 GPa) mismatch may cause bone resorption around the implant
- Aesthetic properties of restorative materials include color, translucency, and fluorescence which should mimic natural teeth
- Color matching systems (VITA classical shade guide) used to select appropriate restorative materials
- Translucency affects light transmission and overall natural appearance
Biological and Surface Properties
- Biocompatibility ensures dental materials do not elicit adverse local or systemic responses in the oral environment
- Cytotoxicity, genotoxicity, and allergenicity tests performed to evaluate biocompatibility
- prevents the release of potentially harmful ions and maintains structural integrity of metallic implants
- Passivation layer on titanium implants provides excellent corrosion resistance
- Surface properties influence cell adhesion, proliferation, and differentiation affecting osseointegration
- Surface roughness (Sa values) categorized as smooth (<0.5 μm), minimally rough (0.5-1 μm), moderately rough (1-2 μm), and rough (>2 μm)
- Wettability affects protein adsorption and cell attachment (contact angle <90° considered hydrophilic)
- Mechanical behavior under cyclic loading conditions (fatigue) crucial for predicting long-term performance
- Fatigue limit defines the stress level below which the material can withstand an infinite number of cycles
Factors for Implant Success
Patient-Related and Implant Design Factors
- Patient-related factors include overall health status, smoking habits, oral hygiene practices, and systemic diseases
- Smoking increases implant failure risk by 2-2.5 times compared to non-smokers
- Diabetes affects osseointegration through impaired wound healing and increased susceptibility to infection
- Implant design features impact initial stability and long-term osseointegration
- Thread geometry affects and stress distribution (V-shaped, square, buttress threads)
- Macro/microstructure influences bone-implant contact area and biological response
Bone Quality and Treatment Planning
- Quality and quantity of available bone at the implant site determine implant success
- Bone density classified using Hounsfield units (HU) on CT scans (D1: >1250 HU, D2: 850-1250 HU, D3: 350-850 HU, D4: 150-350 HU)
- Bone grafting techniques address deficiencies (autografts, allografts, xenografts, synthetic materials)
- Proper treatment planning including accurate imaging and surgical guides essential for optimal implant placement
- Cone-beam computed tomography (CBCT) provides 3D visualization of anatomical structures
- Surgical guides improve implant positioning accuracy and reduce risk of complications
Biomechanical and Maintenance Factors
- Biomechanical factors such as occlusal forces and load distribution play a critical role in longevity
- Proper occlusal scheme (mutually protected occlusion) reduces harmful lateral forces on implants
- Cantilever length affects stress distribution (general rule: cantilever length ≤ 1.5 times the anterior-posterior spread)
- Oral biofilms interact with implant and restorative materials potentially leading to peri-implantitis or secondary caries
- Peri-implantitis prevalence ranges from 1-47% depending on diagnostic criteria
- Surface roughness affects biofilm formation (smoother surfaces less prone to plaque accumulation)
- Regular professional maintenance and patient compliance with oral hygiene protocols crucial for preventing complications
- Recommended recall intervals typically 3-6 months for the first year, then adjusted based on individual risk factors
- Professional cleaning using appropriate instruments (plastic/carbon fiber scalers) to avoid damaging implant surfaces
Key Terms to Review (18)
Bioactive Glass: Bioactive glass is a type of glass material that can bond with bone and promote healing, often used in medical applications such as implants and tissue engineering. This unique characteristic allows bioactive glass to stimulate biological responses, making it a valuable component in regenerative medicine. By facilitating the formation of a hydroxycarbonate apatite layer on its surface when in contact with body fluids, bioactive glass encourages cell attachment and proliferation, which is crucial for successful integration into biological systems.
Biocompatibility: Biocompatibility refers to the ability of a material to perform its desired function in a medical application without eliciting any adverse effects on the surrounding biological environment. This concept is critical because it directly influences the design and selection of materials for medical devices, drug delivery systems, and tissue engineering applications, ensuring that they integrate well with biological tissues while minimizing immune response or toxicity.
Bridges: In dentistry, bridges refer to prosthetic devices used to replace one or more missing teeth by anchoring to adjacent natural teeth or dental implants. These restorations play a crucial role in maintaining oral function, aesthetics, and overall dental health by preventing the shifting of teeth and preserving the integrity of the jawbone.
Corrosion resistance: Corrosion resistance refers to the ability of a material to withstand degradation and deterioration when exposed to corrosive environments, such as moisture, acids, and salts. This property is crucial in ensuring the longevity and functionality of biomedical devices and implants, as they frequently come into contact with bodily fluids and other potentially harmful substances. A material's corrosion resistance can influence its selection, performance, and overall success in various medical applications.
Crowns: Crowns are dental restorations that encase a tooth to restore its shape, size, strength, and improve its appearance. They are commonly used in cases where a tooth has been damaged due to decay, trauma, or after root canal treatment. The integration of crowns with dental implants and restorative materials enhances their functionality and aesthetic appeal, providing a durable solution for tooth restoration.
Direct restoration: Direct restoration is a dental procedure that involves the immediate placement of a restorative material into a cavity or defect within a tooth. This method allows for the quick repair of tooth structure using materials such as composite resins or glass ionomers, providing an aesthetic and functional solution for damaged teeth. The process is typically performed in a single visit, making it a convenient option for both patients and dental professionals.
Endosteal implants: Endosteal implants are dental devices that are surgically placed directly into the jawbone to support prosthetic teeth. These implants serve as a stable foundation for replacement teeth, effectively integrating with the surrounding bone through a process called osseointegration. This type of implant is essential in restorative dentistry as it provides a more permanent solution for missing teeth compared to traditional dentures or bridges.
Indirect restoration: An indirect restoration is a dental procedure where a custom-made restoration, like a crown or bridge, is created outside of the mouth and then cemented onto the prepared tooth structure. This method contrasts with direct restorations, where the material is placed directly in the cavity. Indirect restorations are often preferred for their enhanced durability, esthetics, and ability to restore more extensive tooth damage.
Mechanical Strength: Mechanical strength refers to the ability of a material to withstand applied forces without failing or deforming. This property is crucial in determining how materials behave under stress, influencing their performance in various biomedical applications where durability and reliability are essential.
Plasma Spraying: Plasma spraying is a thermal spray coating process that involves using a plasma arc to melt and propel powder materials onto a substrate, creating a strong bond and protective layer. This technique is crucial in enhancing the performance and durability of dental implants and restorative materials, allowing for improved biocompatibility and wear resistance. By applying various materials such as ceramics or metals, plasma spraying can significantly enhance the surface properties of dental devices.
Primary Stability: Primary stability refers to the initial mechanical stability of a dental implant immediately after its placement in the bone. This stability is crucial as it ensures that the implant remains securely anchored in place during the healing process and facilitates osseointegration, where the bone grows around the implant, effectively integrating it into the jaw structure. Achieving adequate primary stability is essential for the long-term success of dental implants and influences subsequent restorative procedures.
Sandblasting: Sandblasting is a surface preparation technique that involves propelling fine particles, typically sand, at high velocity against a material's surface to clean, smooth, or etch it. This method enhances the surface properties of materials like metals and ceramics, making it particularly useful in applications such as dental implants and restorative materials where surface texture is crucial for adhesion and biocompatibility.
Secondary stability: Secondary stability refers to the enhanced mechanical anchorage that occurs after the initial placement of dental implants, which occurs as the surrounding bone integrates with the implant surface over time. This process, known as osseointegration, is crucial for the long-term success of dental implants and helps ensure that the implants remain secure and functional within the oral environment.
Self-healing materials: Self-healing materials are innovative substances that have the ability to autonomously repair damage without external intervention. This property enhances their longevity and performance, making them particularly valuable in applications where durability is essential, such as in dental implants and restorative materials. By mimicking biological healing processes, these materials can significantly reduce the need for repairs or replacements, ultimately leading to improved outcomes in various biomedical applications.
Subperiosteal implants: Subperiosteal implants are a type of dental implant that is placed under the periosteum, the connective tissue that surrounds the bones in the jaw. These implants are designed for patients who have inadequate bone height or volume to support traditional endosteal implants. By being placed directly under the periosteum, they provide a stable foundation for dental prosthetics while minimizing the need for extensive bone grafting procedures.
Titanium: Titanium is a strong, lightweight metal known for its excellent corrosion resistance and biocompatibility, making it a popular choice in medical applications like implants. Its unique properties, including a high strength-to-weight ratio and low density, allow it to be used effectively in both orthopedic and dental implants, where durability and the ability to integrate with bone are crucial for long-term success.
Wear Resistance: Wear resistance refers to the ability of a material to withstand the gradual removal of its surface due to mechanical action, such as friction, abrasion, or erosion. This property is crucial for materials used in biomedical applications, where long-term durability and functionality are essential, especially in implants that must endure dynamic body movements and interactions over time.
Zirconia: Zirconia, or zirconium dioxide (ZrO₂), is a white crystalline oxide of zirconium that is widely used in biomaterials due to its exceptional mechanical properties and biocompatibility. It is primarily classified as a ceramic biomaterial, recognized for its strength, toughness, and resistance to wear and corrosion, making it a popular choice in dental applications and various implant technologies.