COMPOSITE TECHNIQUE SMILE DESIGN COMPANIES/MATERIALS MATERIAL SCIENCE
PORCELAIN REPAIR
Composite is bonded to porcelain to repair fractures of crowns, onlays, bridges or veneers. Forces onto composite causes intracomposite fracture or debonding depending on force intensity, duration, frequency and direction. Composite accepts compressive force well but fractures easily from shear and tensile forces. Preparation design that creates flat areas and mechanical locks supports composite and bonding interfaces to limit adverse effects.
Fractured porcelain surfaces are prepared with diamond burs to increase surface area. Sandblasting with a micro etcher and aluminum oxide powder can be used to further roughen and energize surfaces. A 10% gel of hydrofluoric acid is placed for one minute to dissolve and etch porcelain. The hydrofluoric acid is rinsed thoroughly with water leaving a delicate etched porcelain surface. The surface must not be wiped over with materials such as cotton or gauze or the etched surface will be destroyed. Silane is applied to the surface and left for one minute. Excess silane is removed with a gentile stream of oil free air. Hydrofluoric acid is extremely potent so isolation to avoid tissue contact is important.
Bonding resin is added and thinned with a gentile stream of air. Composite is added and cured. Large areas required layering techniques to minimize shrinkage. Replication of lost porcelain often requires layering opaquer or opaque composite under translucent outer layers.
In the case below, a patient would not wear their nightguard. Fracture occurred on the lateral incisors and the left central incisor. Repair with composite bonds to porcelain and tooth structure on the central incisor. Hydrofluoric acid is used on porcelain and phosphoric acid is used on tooth structure. Hydrofluoric acid is extremely potent and must be kept off gingival tissues, skin, eyes and the like.
COMPOSITE TECHNIQUE SMILE DESIGN COMPANIES/MATERIALS MATERIAL SCIENCE