Denture Bases in PD -Dr.ZenaWally-23-24.pdf

Department of Prosthodontics Dr. Zena J Wally Faculty of Dentistry Prosthodontic University of Kufa...

Department of Prosthodontics Dr. Zena J Wally Faculty of Dentistry Prosthodontic University of Kufa Year 3 2023/2024 Denture Bases in Removable Partial Denture Denture base: It is that part of partial denture that supports the artificial teeth, and rest on the foundation tissues, and transfers the occlusal force to the supporting structures. Functions of denture base 1. It supports the artificial teeth and transfers forces to supporting oral structures. 2. Stimulation of the underlying tissue which will maintain the form and health of underlying tissue. 3. Prevent vertical and horizontal migration of remaining natural teeth. 4. Improve esthetics. Ideal requirements of denture base 1. Accurate tissue adaptation with minimal change in volume. 2. Thermal conductivity. 3. Sufficient strength (resist fracture or distortion under function). 4. Easily cleaned. 5. Can be relined. 6. The ability to achieve good finish. 1 7. Esthetically acceptable. 8. Light in weight. 9. Low cost. Types of denture base according to support: 1. Tooth supported partial denture base: In tooth supported prosthesis, the denture base is primarily a span between two abutments supporting teeth. The occlusal forces are transferred directly to abutment teeth through rests. The denture base and the supplied teeth serve to prevent horizontal migration of all the abutment teeth and vertical migration of teeth in opposing arch. When anterior teeth needed to be replaced the esthetic is of primary importance. When posterior teeth only to be replaced, function are of primary importance than esthetic 2. Tooth tissue borne partial denture base. In a distal extension partial denture, the denture bases must contribute to the support of the denture and improving prosthesis stability. Should be extended to provide the greatest available surface area for support and retention, without overextension or impingement on tissues. It must be made of a material that can be relined or rebased when it becomes necessary to reestablish tissue support for the distal extension base. 2 Factors (forces) affect retention 1. Adhesion. 2. Cohesion. 3. Atmospheric pressure. 4. Physiological molding of the tissue around the polished surfaces of the denture. 5. Effect of gravity on the mandibular denture. Types of the denture base according to materials 1. Resin type (acrylic denture base). Acrylic resin bases are the most common types used in removable partial dentures because of easy of fabrication and easy of attachment to metal framework. They should be routinely used in distal extension cases to allow for relining of the base to maintain mucosal support. 3 Indication 1. Distal extension ridges: Resin denture base is indicated in Cl I and Cl II because of the support of the denture by tissue and continuous bone resorption will need relining. 2. Long span ridges: In Cl III and Cl IV edentulous cases because of possibility of tissue changes underneath the denture base and there will be need for future relining. 3. In cases of immediate partial denture: because after healing period there will be need for relining. Advantages: 1. Can be easily relined. 2. Easy to fabricate, adjust, finish, polish, and repair. 3. Resin is more esthetic than metal. Disadvantages: 1. More porous than metal and therefore more difficult to clean which affect hygiene. 2. Requires more bulk for rigidity than metal. 3. Easily abraded. 4. Easily fractured. 5. poor thermal conductor. 6. dimensionally unstable. 2. Metal type denture base. It’s made of : a. Gold and platinum (but these are expensive). b. Stainless steel or chrome cobalt (more being in use nowadays). c. Titanium (used as a denture base and in implant because of its excellent properties. The metal type denture base has the ability to stimulate the underlying tissues that will maintain the integrity of the bone by preventing bone resorption. Indications: 1. Short span (tooth borne removable partial denture). 4 2. When there is no enough space for artificial teeth (Inadequate inter maxillary space) because of over eruption of opposing teeth. Advantages: 1. Cast metal bases can maintain their accuracy of form without change in the mouth and also can resist abrasion from denture cleaning. 2. Maintain healthy tissues because metal surfaces are less porous than resin surfaces and this lessens food, plaque and calculus accumulation. 3. Maintain the health of tissue by transmitting temperature through the metal base to the underlying tissue (more natural feeling). 4. Metal alloy may be cast much thinner than acrylic resin and still have adequate strength and rigidity. Disadvantages: 1. Difficult to reline, adjust, and rebase. 2. It is expensive. 3. Error that occurs in posterior palatal seal area (post dam) can’t be corrected with metal denture base, while in resin denture base repostdaming is the 4. Poor esthetic. 5 Types of artificial teeth 1. Acrylic teeth: Made of acrylic resin and it has the ability to be attached chemically to denture base. 2. Porcelain teeth: Is made of porcelain and attached to the denture base by mechanical mean. 3. Metal teeth: the teeth may be processed as part of the denture base by casting procedure this is indicated in cases of limited intermaxillary spaces. 6 Modified poly-ether-ether-ketone (PEEK): A new material in prosthodontics, comparing to the metals used in dentistry: 1. An alternative material for the fabrication of distal extension removable dental prosthesis (RDP) frameworks. 2. Can be used for patients allergic to metals, or who dislike the metallic taste, the weight, and the unpleasant metal display of the framework and retentive clasps. 3. A biocompatible, non-allergic, rigid material, with flexibility comparable to bone, high polishing and low absorption properties, low plaque affinity, and good wear resistance. 4. Can be constructed either via CAD/CAM manufacturing or via the conventional lost wax technique. 7