CHAPTER 15 Dental Biomaterials
|Calculus on teeth||86|
KHN, Knoop hardness number.
|Sex||Male Female||The patient is in the dental office because of a fractured tooth. Visual examination of tooth #18 reveals a fracture of the ML cusp. The remainder of the tooth holds a large MOD (mesio-occlusal-distal) amalgam restoration. After the dentist removes all of the old amalgam, some caries is discovered that will result in a near pulpal exposure. Patient also has amalgam restorations in teeth #2, #14, #19, and #31, and full gold crowns on teeth #3 and #30.|
|Chief Complaint||“I bit down on a popcorn kernel and my tooth broke.”|
Physical properties depend primarily on the type of atoms and bonding that is present in a material. Allows clinician to understand how given material will withstand oral environment (i.e., temperature fluctuations, biting forces, moisture).
|Silicone impression material||210.0|
Biological properties refer to the biological response of the human body to various materials and the continued examination of the host–foreign body response. Response of both patients and clinicians can involve allergy, microleakage, and toxicity factors.
Function of impression and replication materials is to accurately record hard and soft tissues in the oral cavity. Impressions produce negative reproduction, which then can be used by clinician for construction of restorations to replace missing tooth structure and for fabrication of preventive devices. Vary in accuracy and ease of use, especially in removal from the mouth, such as around tooth undercuts, portion of tooth that lies between its height of contour and attached gingiva. Replication materials to preserve the impressions are discussed in next section.
|Calcium sulfate||16||Reacts with potassium alginate to create gelation|
|Potassium alginate||15||Reacts with calcium sulfate to create gelation|
|Potassium titanium fluoride||3||Accelerates setting of gypsum|
|Agar-agar||8-15||Substance is extracted from a type of seaweed whose fibrils form a colloid that results in a partially rigid but elastic gel|
|Water||80-85||Main component that occupies the spaces between the agar-agar fibrils|
|Borax||Trace amounts||Increases the strength of the gel (also can retard the setting of gypsum; requires the addition of an accelerator)|
|Potassium sulfate||2||Accelerates the setting of gypsum|
|Gypsum||Water (mL/100 g powder)|
|Model plaster (type II)||37-50|
|Dental stone (type III)||28-32|
|High-strength dental stone (type IV-V)||19-24|
Many procedures cannot be completed in one appointment because of need for lab work or because of complications of infections. In these instances, temporary (provisional) restoration that is placed over preparation is indicated. Materials such as acrylics, stainless steel, composites, or cements are used in preparation to maintain relationship in occlusion until permanent restoration can be placed.
Permanent restorations are composed of dental materials whose properties allow them to function in the oral cavity for a greater length of service than that of temporary restorations. Include both esthetic and amalgam restorations.