Biocompatibility of Dental Materials

TOPIC 1. BIOCOMPATIBILITY BIOCOMPATIBILIT Y It relates to the fact that a material that is placed on parts of the human body comes into close contact with living tissues:  Interaction between material and tissue: release of substances  Tissue involvement BIOCOMPAT...

TOPIC 1. BIOCOMPATIBILITY BIOCOMPATIBILIT Y It relates to the fact that a material that is placed on parts of the human body comes into close contact with living tissues:  Interaction between material and tissue: release of substances  Tissue involvement BIOCOMPATIBILITY Nanoparticles generated during the processing of materials: INTERACTION with cells (polishing, carving or removal of restorations)  Amalgam (mercury release) BIOCOMPATIBILIT Y PHILLIPS. Ciencia de los materiales dentales: , 13e BIOCOMPATIBILIT Y Therefore, the main objective of the biocompatibility of dental materials is:  Patient Protection  Personnel protection  Environmental protection BIOCOMPATIBILIT Y Adverse reactions caused by dental restorative materials can be classified into three groups:  Systemic effects  Local effects  Allergies SYSTEMIC EFFECTS Those where the application location is far from the action site(e.g., mercury vapor)  LOCAL EFFECTS In the proximity of the applied material (e.g., inflammation of the dental pulp) PHILLIPS. Ciencia de los materiales dentales: , 13e ALLERGIES Antibody-antigen immune reaction  BIOACTIVITY It can be considered as a positive local effect (e.g., restorative dental tissues) Bioactive effects are primarily related to material-induced and cell- mediated effects on living tissues (e.g., induction, formation of new dentin, or antimicrobial activity)  Materials that release calcium or fluoride are called bioactive materials  Safety: No damage.  But... absolute security is not possible. RISK AND Possibility of adverse events Risk: purely intuitive perception of the SECURITY patient  ISO 14971:2019 standard (real risk combination probability & severity of damage)  Always consider risk versus benefit  BIOLOGICAL EFFECTS 5 entries through which harmful substances can enter the body: 1. Absorption through the skin/mucosa/dentin 2. Filtration through the apex of the tooth 3. Direct contact with the bone (implants) 4. Inhalation 5. Ingestion Skin They act as a protective barrier Mucos If it breaks (abrasions, lacerations)  Toxic substances can reach the internal environment. a Exposure to inorganic acids can increase the permeability of this Dentin barrier  SYSTEMIC EFFECTS OF MATERIALS The final systemic response depends on 6 variables: 1. The place of the exhibition 2. Toxicity 3. Concentration of the substance 4. Exposure Time 5. Excretion rate 6. Target organ EXCRETIO If excreted slowly: N RATE  Their critical concentrations are reached more quickly GENOTOXICITY Adverse effect on an organism's DNA caused by a chemical or physical agent MUTAGENICITY When the adverse effect is transferred to the next generation of cells (heritable) Genotoxicity can be considered the first necessary step for mutagenicity ESTROGENICIT Y Ability of a chemical to act like the hormone estrogen in the body.  If these chemicals are not specific to the body, they are called xenoestrogens  Bisphenol A: Xenoestrogen used in composite formulations and dental sealants XENOESTROGEN S It is feared that the release of these substances will aggravate exposure to other (non-dental) sources of endocrine disruptors  This fact could lead to diseases such as diabetes 2, obesity, premature puberty and even breast cancer (Highly controversial claims) Local effects of materials Effects on nearby oral tissues, such as the oral mucosa, periodontium, or tongue, are usually evident on visual inspection There are also local effects which we can not see in the pulp tissue, the tooth restoration and bone-implant interface interfaces. PHILLIPS. Ciencia de los materiales dentales: , 13e  Postoperative tenderness or pain that may occur after treatment can be due to several factors: PULP  Thermal trauma  Chemical injuries  Microfiltration  Allergy TISSUE Hipersensitivity related to the movement of extracellular fluid in the dentin tubules and its influence on odontoblastic processes (Hydrodynamic theory)  The movement of extracellular fluid in the dentin tubules stimulates the cellular receptors of odontoblastic processes Odontoblasts transfer this signal to HYDRODYNAM afferent nerves IC THEORY  Therefore, sealing the dentinal tubules during the procedure is essential to prevent or reduce the movement of intratubular fluid, reducing postoperative hipersensitivity PERIODONTIUM Periodontal attachment to the tooth is an important bond between the outside of the body and the inside of the body Periodontal tissues are the target of potential adverse effects of dental materials, as these materials are in close proximity to these tissues  The gingival sulcus can accumulate biofilms that can cause inflammatory reactions PHILLIPS. Ciencia de los materiales dentales: , 13e TOOTH- RESTORATION INTERFACE Restorative materials interface with each other and with dental hard tissues This interface is critical for the transfer of leach substances to the dentin fluid PHILLIPS. Ciencia de los materiales dentales: , 13e  Disbonding of the dentin adhesive layer (e.g. due to the polymerization contraction) It can cause fluids to enter along Microfiltrati the slits It can lead to unwanted events on Promotes material breakdown and secondary caries It causes marginal spots and compromises aesthetics  The resin in the adhesives does not fully penetrate the collagen NANOFILTRATIO network, developing a smaller slit (less than 0.1 microns) N Results in fluid exchange that can degrade the resin, reducing the longevity of the interface BONE-IMPLANT INTERFACE The success of dental implants depends on the stability of the implant's attachment to the bone Primary (initial) stability is achieved by inserting the implant into the bone Secondary (final) stability is achieved by growing and integrating newly formed bone into the implant Surface  This process is called osseointegration BIOINTEGRATI ON It consists of the adaptation of bone or other tissue to the implanted material without any appearance of slits along the tissue-material interface.  ALLERGIC REACTIONS The body recognizes a substance as foreign and the immune system reacts specifically against that substance. There are four types of allergic reactions (Gell and Coombs classification): 1. Type I reaction: Mediated by IgE and IgG4. Immediate reaction or anaphylactic reaction. 2. Type II reaction: caused by cytotoxic antibodies IgM and IgG. 3. Type III reaction: Tissue injury due to immune complexes. 4. Type IV reaction: Delayed hypersensitivity (bodies reacts with a host molecule e.g. metal ions). It is associated with allergic contact dermatitis. In dentistry, type IV reaction is usually the most frequent An allergic reaction ONLY occurs after the patient has become sensitized during a first contact  ALLERGIC REACTIONS An allergic reaction ONLY occurs after the patient has become sensitized during a first contact After sensitization to the substance, even brief contact with that allergen can precipitate the allergic reaction. Signs of contact allergies: 1. Reddish skin with swelling and itching. 2. Blisters. 3. Scaly areas. 4. Darkening of the affected tissue. 5. Leathery skin. 6. Cracked skin. IMMUNOTOXICIT Y Substances with the ability to alter the immune system. It can be caused by the direct toxic effect of a leach substance. Substances released by dental materials, such as metal ions or monomers, can disrupt the immune system in subtoxic concentrations.  Establishment of generally accepted standardized test methods(1980) Main objective:  Protecting Dental Patients, Dental Staff, and the Environment. BIOCOMPATIBILIT A clinical risk assessment is necessary before testing: Y TESTING  Material function in the mouth.  Physical and chemical characteristics.  Release of substances from the material. For example: cement and its effects on surrounding tissues  The location.  Exposure Time.  Each biomaterial can degrade and release components. The environment-material SUBSTANC interface is an active site for corrosion. There may also be a drop in pH at E RELEASE the biofilm-material interface that favors corrosion or release of substances. High-pH environments can increase the dissolution of some materials.  DOSE-RESPONSE RELATIONSHIP OF TOXICITY Toxicity depends on the dose. A specific dose of a substance may be:  Toxic.  Non-toxic.  Beneficial.  TYPES OF BIOCOMPATIBILITY TESTS Three different types of tests are used: 1. in vitro testing. 2. Animal testing. 3. Use trial (humans or animals)  An extract of the material is placed in direct or indirect contact with some biological system outside of in vitro an organism in a container. Indirect contacts simulate TESTING anatomical barriers for certain clinical situations. They lack the ability to simulate the complex interactions that exist in an organism.  An healthy animal is used. The advantage of these tests lies in ANIMAL their ability to allow biological systems to respond to or interact with a candidate material. TESTING The disadvantages are its high cost, the difficulty of controlling the factors and the time of realization/response.  The materials are applied directly to the animal as well as to the patient. The ultimate relevance of a use USE trial depends on the extent to which the trial simulates the clinical use of the product. There are limitations in humans: TRIAL  Histologic evaluations are not performed very often.  Design complexity.  Difficulty controlling variables.  High cost.  They take time.  Legal and confidentiality issues. RISK CLASSES The FDA classifies all medical devices according to three classes:  Class I: They usually present the least risk.  Class II: Moderate risk.  Class III: Higher risk. EVIDENCE-BASED DENTISTRY EVIDENCE-BASED DENTISTRY “It is defined as an approach to oral health care that requires the reasonable integration of systemic assessments of clinically relevant scientific evidence” The highest form of scientific evidence is the randomized controlled clinical trial.  Randomization eliminates the effect of multiple patient variables, which can skew results. Laboratory or standardized tests are the lowest level of evidence.  LEVEL OF EVIDENCE 1. Professional Association Position Statements. 2. Systematic reviews and meta-analyses of randomized controlled clinical trials. 3. Randomized clinical trials. 4. Cohort Studies. 5. Case Control and Crossover Case Studies. 6. In vitro laboratory tests. PHILLIPS. Ciencia de los materiales dentales: , 13e  in vitro laboratory test They evaluate a limited number of variables and are not representative of the true oral environment.  They cannot be correlated with what occurs in the oral environment. In vitro testing is ranked as the lowest evidence test according to the classification of evidence-based dentistry. OBSERVATIONA L STUDIES In vivo observational tests constitute the second level of evidence in dentistry according to evidence-based dentistry. They include: retrospective studies, prospective studies, case-control studies, and cohort studies.  They look back in time to identify the interventions performed and RETROSPECTIV examine the outcome today. Advantages: easily obtained data. E STUDIES – in Disadvantages: no standardization. the exam  Higher probability of error. CASE- Observational studies and are CONTROL usually retrospective. Study group and control group. STUDIES  Observational or randomized controlled. PROSPECTIV These are planned longitudinal experiments. ES STUDIES They are more expensive, since they have to be planned and monitored by the groups (cohorts).  Randomly assign participants to RANDOMIZED groups and (minimizing biases and confounding variables) they are CONTROLLED controlled (existence of a control group) Longitudinal and prospective CLINICAL studies. TRIALS Expensive and logistically very difficult to perform.