FINISHING & POLISHING OF COMPLETE DENTURE
Surface roughness and gloss: Surface roughness (Ra): is a measure of irregularity of the finished and polished surface and is measured in micrometers. A smooth surface (Ra less than 0.2 micrometers) is desirable to reduce retention of bacteria and to have a shiny appearance. Gloss: is a measure of the reflection of light from a surface. An ideal restorative material would have high gloss after polishing and would retain its gloss during function in the mouth.Finishing and Polishing
Materials used for finishing and polishing of complete denture The materials used are abrasives and polishing agents. Abrasives: are generally harder than the object being polished, they are hard coarse abrasives used primarily for development of desired contours of a restoration and for removal of gross irregularities on the surface. Polishing agents: are often softer than the object being polished, they used to smooth surfaces roughened typically by finishing abrasives.
The efficiency of abrasive depends on: The speed at which it is used: The higher speed, the greater is the frequency per unit of time the particle contacts the surface. The particles hardness: As the hardness of abrasive particles increase, the rate of abrasion is increased. The particles size: The Larger particles cause deeper scratches in the material and wear away the surface at a faster rate. The pressure applied: A heavy pressure being applied by the abrasive causes deeper scratches and more rapid removal of material.
Materials of Polishing Arkansas stone: It contains micro crystalline quartiz; it is dense, hard and uniformly textured. Tungsten carbide: It is effective in removing rough edges from acrylic resin dentures. Sand: Commonly used in the form of sand paper of various grades for preparing dentures for polishing. Pumice: It is the commonest substance used for polishing acrylic resin. Whiting or precipitated chalk: It is used as a final polishing agent for acrylic resin.
Finishing: Is the process of removal any excess of acrylic (and stone) form the denture that result from press the flask during packing. We remove the excess by the use of finishing machine. We remove the stone from inner surface of denture by sharp knife or lacrone. The bubbles that present around the teeth can be removed by small round bur and without touch teeth.
Finishing and Polishing
Finishing and Polishing
We use the acrylic bur to remove any excess from the outer surface and the border of the denture just only remove the excess, otherwise it results in shortage of denture border. We use the little finger in order to determine any sharpness. We use the stone bur in order to remove any roughness that create after using of acrylic bur. If we desire to make stippling (not made during waxing), we can make it by using a conical ciliated bur. By using sand paper, we can obtain the finishing of the denture to be ready for polishing.Polishing: it is a procedure by which we can obtain a shiny, glossy surface of the denture . Every restoration that is placed in the mouth must be highly polished. This is necessary for three reasons: Improve esthetic of the patient. For the comfort of the patient. To prevent food debris, saliva and plug from adhering on the polish surfaces of the denture.
Finishing and Polishing
Polishing is done by polishing machine with the use of pumice. The pumice must be wet to minimize generation of heat. Over heating affects the appearance of the denture and may cause warpage to occur.
Finishing and Polishing
The polishing is done by pressing the denture against the wheel of the polishing machine. A wet muslin buffing wheel is used to polish the borders, lateral and palatal surfaces of the denture. The next stage in polishing is the use of Tripoli: this material is applied to a dry muslin buffing wheel.
Final polish is placed on the denture with a high shiny material.(for e.g Whiting). When final polishing is completed, all traces of polishing agents must be washed off and rinsed with water.
Notes Resin teeth must be covered or protected during polishing with pumice, other wise teeth appear yellow because of loss of outer labial enamel shade. Gingival crevices should be polished with a brush wheel and an abundance of wet pumice. The denture is stored in water until the delivery of the dentures to the patient.