Classification of dental cements

Transcription

1 Classification of dental cements Type I: Luting agents* that include temporary cements Class 1: powder-liquid -> harden Class 2: paste-paste -> remain soft Type II: Luting agents for permanent applications Type III: Temporary liner or base applications Type IV: Permanent liner or base applications *) A material that acts as an adhesive to hold together the casting to the tooth structure. 576

2 Applications of dental cements Underfilling or liner (materials for protection of dental pulp against mechanical and chemical ) Temporary filling Cover filling (inserted into a prepared cavity in a tooth = Filling in general) Temporary or long-life anchorage for coronas or filling in root channels Healing cements, e.g. dental zinc oxide eugenol cement which is used as temporary sealing material having a anodyne, sedative and antiphlogistic effect upon oral disease 577

3 Requirements for dental cements Good thermal, chemical and bacterial isolation No or low toxicity Low or no tissue irritating effects Mechanical strength Chemical resistance Good sealing and adhesion properties No or low electrical conductivity Low film thickness Adaptable colour, haze... Good processability x-ray opacity 578

4 ROOT CANAL FILLING MATERIALS Root canal filling materials consist of tapered gutta-percha (right root) or silver (left root) (or titanium or polymer coated gutta-percha) points in standard sizes that match the size of the files used. The points are cemented in place with root canal sealer that is usually a zinc oxide and eugenol preparation. Root canal filling materials are used to fill previously prepared root canals. They are a part of root canal, or endodontic, therapy

5 GUTTA-PERCHA POINTS Gutta-percha points are made from the refined, coagulated, milky exudate of trees in the Malay peninsula. Gutta-percha is pink or gray in color. It is softened by heat and is easily molded. When cool, gutta-percha maintains its shape. Gutta-percha points are used as a root canal filling material. Advantages (1) They have a high thermal expansion. (2) They do not shrink unless used with solvent. (3) They are radiopaque, conduct heat poorly, and are easy to remove from the root canal. (4) They may be kept sterile in antiseptic solution, are impervious to moisture, and are bacteriostatic (prevent the growth or multiplication of bacteria). Disadvantages (1) They shrink when used with a solvent. (2) They are not always easy to introduce into the root canal

6 SILVER ROOT CANAL POINTS The dentist has the option to use silver root canal points in filling a root canal. Advantages (1) They are more easily inserted than gutta-percha points and they have all the same advantages. (2) Sight selection of silver points is easy because they come in the same sizes and tapers as standard root canal broaches and reamers. Disadvantages (1) They are more expensive than gutta-percha. (2) They do not adapt to contours of the root canal. (3) They tend to corrode if subjected to body fluids

7 Dental impression Impression materials rigid flexible irreversible reversible irreversible reversible ZnO-Eugenol paste, Plaster Thermoplastic compositon mass e.g. Guttapercha, Stent's, Kerr, Waxes Elastomers Alginate Hydrocolloids Polysulfide (Thiocols) Polyether Silicones condensation crosslinked addition crosslinked 582

8 Processing of Elastic Impression Materials Volume Effects Curing shrinkage Thermal shrinkage Storage time dependent shrinkage 583

9 Processing of Elastic Impression Materials Volume Effects (R. Marxkors/H. Meiners, 1993) 584

10 Artificial teeth 585

11 Artificial Teeth Waxs model Metal cuvette Hard plaster Functioning model Cut through a two-sectioned cuvette with embedded wax model on the functioning model (R. Marxkors/H. Meiners, 1993) 586

12 Artificial Teeth State of a thermoplastic material in dependence on the polymerisation grade degree of polymerisation (R. Marxkors/H. Meiners, 1993) 587

13 Artificial Teeth Processing Powder-liquid-technique: Pearl polymer: Monomer 2 : 1 Micrograph (grinded) of a Powder-Liquid Technique Polymerised Acrylate, Etched (75x) (R. Marxkors/H. Meiners, 1993) 588

14 Artificial Teeth Hot polymerisation Initiation by temperature increasing Heating by a water bath Residue monomer! Short time procedure: 30 min heating, 30 min holding time at 100 C Medium time procedure: 60 min at 75 C, 30 min at 100 C Long time procedure: 12 h at 50 C, 2 h at 120 C (R. Marxkors/H. Meiners, 1993) 589

15 Artificial Teeth Auto polymerisation Initiation by reduction agent Faster than hot polymerisation procedure Use of very fine grained powder Continuous change in residual monomer content (R. Marxkors/H. Meiners, 1993) 590

16 Dental Implants worldental.org/images 591

17 Conditions Biological system State of the bone and the soft tissues i.e., height and width of the jaw bone: the higher and thicker the better the conditions for a successful implantation Width < 5 mm and height < mm are critical dimensions because bone volume (mass) is to small for holding an implant 592

18 Conditions Sufficient bone density Gums (or Gingiva) state: Healthy soft tissue support for the implant and the supra construction Position of the upper jaw in relation to the lower jaw Deflection against ideal position can lead to loadings that can not be compensated by the materials and/or the design 593

19 Caution! Implantation site in the upper jaw The bone of the upper jaw flanks the maxillary sinus that is connected with the nose -> inflammation and implant loss if the implant penetrates the mucous membrane of the maxillary sinus Nervus mandibularis - Implantation site in the lower jaw N. mandibularis locates along the side of of the lower jaw -> numbness in the lower lip and the chin if this nerve is injured during the operation Maxillary sinus 594

20 Dental implants - Types Transosseous implants: Only used in mandibles These implants are inserted in the jawbone, and penetrate the whole jaw -> anchoring at the bottom of the chin by means of a pressure plate Disadvantage: general anaesthesia owing to the extraoral surgical approach for placement -> longer hospitalisation; bone degradation around the posts Materials: CoCr-alloys, CP Ti and gold 595

21 Dental implants - Types Subperiostal implants: These implants are inserted between the top of the jawbone (onthe-bone) and the gum Long-time behaviour: the implants have to be replaced after some years (in most of the patients) 5 years upper jaw, 10 years lower jaw Cause: chronic inflammation around the implant posts and loosening over time Inflammation -> bone degradation + support removal by surgery -> crater shaped damage of the jaw -> afterwards problems with removable denture 596

22 Dental implant - Types Endosteal (endosseous) implants: The implants are completely integrated in the jaw (feel and function like natural teeth) proper conditions of material selection, design and use -> Osseointegration = bone tissue grows around the implant and provides anchorage most frequent dental implants today Blade, disc, cylinder or screw implants from titanium or metal alloys with ceramic coating, ceramics 597

23 Osseintegration (J.B. Park, Bioceramics, 2008) 598

24 Endosteal Implant Types Lower jaw without teeth and applied blade implant Screw and cylinder implants (Ti) disc implant osseosource.com/dental-implants Customised ZrO 2 dental implant in comparison with a conventional implant. Dental Tribune Austrian Edition, 12/2008, pp Dateien/BioImplantSurgeryVideos.htm 599

25 Implant Components 600

26 Implantation 2 steps 1. Anchorage of the implant in the jaw followed by a healing phase ( 4 month lower jaw, 6 month upper jaw) 2. Application of the superstructure system: crown, bridge, denture 601

27 Implant solutions 602