Fundamental Concepts of Enamel and Dentin Adhesion (Part 2) PDF

Fundamental Concept Of Enamel And Dentin Adhesion (2) By: Dr. Rehab Alwakeb Operative Dentistry Division Refrence: Art and Science of operative dentistry 6th edition, chapter 4; page: 114. ILOs: I. Differentiation between Current Strategies for Adhesion of Resins to...

Fundamental Concept Of Enamel And Dentin Adhesion (2) By: Dr. Rehab Alwakeb Operative Dentistry Division Refrence: Art and Science of operative dentistry 6th edition, chapter 4; page: 114. ILOs: I. Differentiation between Current Strategies for Adhesion of Resins to Dentin. II. Case discussion ( selection of adhesive system according to prepared cavity with justification) II. Current Strategies for Adhesion of Resins to Dentin Classification of contemporary adhesive systems. Three step total etch system (etch and rinse)  Etchant Primer Bonding agent E P B Three-step Removes the smear Includes bifunctional Includes hydrophobic etch-and-rinse layer molecules monomers such E+P+B Exposes intertubular (simultaneously as Bis-GMA and peritubular collagen hydrophilic & Dentin is Opens the tubules in a and hydrophobic) Small percentage of demineralized funnel configuration hydrophilic monomers, by up to 7.5 Decreases surface free Envelops the external such as HEMA μm, energy of dentin surface of collagen fibrils Co-polymerizes with Examples : the primer molecules, 1. Scotch Bond Re-establishes surface Penetrates and MultiPurpose free energy to levels polymerizes (3M), compatible with a more into the inter-fibrillar 2. All hydrophobic restorative spaces to form Bond2,(bisco) material Hybrid layer 3. Panavia 21 (resin-dentin interdiffusion zone) They also penetrate and polymerize in the open dentinal tubules, forming resin tags.  Two-step etch-and-rinse (E + [PB]) Rationale: Simplification of the bonding procedure. Examples: One-Step Plus (Bisco, Inc.), Prime & Bond NT (DENTSPLY Caulk), Adper Single Bond Plus (3M ESPE), OptiBond SOLO Plus Main drawbacks of total etch system Moisture content of dentin after rinsing: 1. excessive dryness If the dentin surface is dried with air Collagen fiber network undergoes immediate collapse Bonding resin monomers fail to penetrate Moist bonding  2. Excessively wet dentin Pooled moisture (excess water) Dilute the primer Render it less effective. Accepted moisture A study showed that the excess water after rinsing the etching gel can be removed with: 1. Damp cotton pellet. 2. High-volume suction. 3. Disposable brush, or 4. Laboratory tissue paper without adversely affecting bond strengths Self etching adhesives: It is described as non-rinsing conditioners or self-priming etchants. Types: 1. 2-step self etching adhesive. (2 bottle) 2. 1 step self etching adhesive. (1 bottle) or all in one. 2 step self etching adhesives  Main advantages compared to total etch systems: 1. More simplified technique (less technique sensitive). 2. Elimination of rinsing and drying steps reduces the possibility of over-wetting or over-drying, either of which can affect adhesion adversely. 3. Do not remove the smear layer from dentin completely which result in less postoperative sensitivity compared with etch-and-rinse adhesives. It should be noted that also restorative technique affects post-operative sensitivity.  one-Step Self-Etch Systems, all in one systems or single bottle systems All of its components are included in one bottle. Tends to behave as semi-permeable membranes Do not provide a hermetic seal for vital deep dentin due to transudation of dentinal fluid across the polymerized adhesives to form fluid droplets on the surface of the adhesive.  To overcome this problem: 1. Extra coat of a hydrophobic bonding layer can be added. Or 2. Applying thin layer of flowable composite liner.  SEPs have been classified according to Ph value into three categories: mild, moderate, and aggressive. Mild and Ultramild SEPs tend to provide excellent dentin bond strengths and poorer enamel bonds, whereas Aggressive self-etch systems provide the reverse with no need for selective etching of enamel.  Universal adhesives. They are termed so because they bond to various substrates besides dentin such as indirect ceramic and resin-based restorations (crowns, inlays, onlays, and veneers). They are considered mild or ultra-mild one step self- etching adhesive. Selective enamel etching is mandatory Case based discussion A 40-year-old woman presents to the Dental Clinic complaining of food collecting in lower back tooth. Clinical examination reveals large occlusal caries in tooth # 47. compound Class I tooth preparation is done as shown. Hard discolored dentin is left on pulpal floor of the preparation as shown. Composite restoration is the restoration of choice What is the best used adhesive systems? 1. What is the best used bonding system in the class II preparation in tooth # 16 shown in the image below? 2. justify your choice. 1. What is the best used bonding system to restore tooth # 11? 2. justify your choice. Thank You