| Observation |
Possible Cause |
Corrective Action |
| Bubbles (voids) in hydrocolloid |
Hydrocolloid temperature too low when poured |
Temperature should be 130° -135° F. Refer to manufacturers recommendations. |
|
Air escaping from under wax-up |
Seal wax-up to cast. |
|
Air escaping from under teeth |
Seal teeth into wax-up. |
| Bubbles form under separator |
Lack of heat in cast when applying separator.
Short drying period.
Separator applied over excessive surface moisture.
|
Immediately after boil out, place the cast in a bowl of warm water for 5 minutes. Remove the case from the water and allow to dry approxi-mately 1-2 minutes. Apply a thin coat of Al-CoteŅ Separating Agent to the cast and allow to dry until a slight sheen remains. |
| Incomplete denture contour (short periphery) raised posterior palatal border, etc. |
Excess separator on cast. |
|
| Adhesion of cast to denture base resin |
Improper or incomplete application of separator |
|
| Lack of adhesion to cast |
Wax residue |
Remove wax with boiling water and detergent and rinse with clean water. |
| Resin flows very slowly into mold |
Resin mixed too long or allowed to set too long before pouring. |
Mix resin thoroughly and quickly with as little air incorporation as possible. |
|
Attempting to pour too many cases with one resin mixture. |
Most operators prefer to pour no more than two cases with each resin mix. |
|
Sprue size too small. |
Connecting or secondary sprues and/or vents should be no smaller than ¼ inch to promote free flow of resin. |
|
Thin wax-up. |
Sufficient bulk in wax-up will promote free flow of resin. "Over- waxing" may be required on occasion. |
|
Air-lock |
Pour resin slowly and continuously down a side sprue. |
| Voids in denture |
Air entrapment due to improper spruing and venting |
Sprues should be at the highest most distal point of the mold when held in the pouring position. |
|
Resin mixed and/or bench set too long |
Polymerization begins as soon as powder and liquid are combined. Mix resin quickly and thoroughly, avoiding as much as possible incorporating air into the mixture. Pour with as little delay as possible |
| Resin "flash" on teeth |
Wax film remaining on teeth when in-vested. Wax washed out at boil-out time, leaving space which filled with resin. |
Thoroughly clean teeth before investing. |
| Voids or porosity in posterior buccal flange area |
Sprue improperly positioned |
Sprue to the highest, most distal points of the mold. |
| Voids or porosity in posterior palatal area of denture |
Omission of center vent |
Center sprue (vent) is required on complete palate restorations to allow escape of air. |
| Porosity: Fine, pinhole, sub-surface |
Improper curing pro-cedures: curing temp-erature too high, in-sufficient air pressure applied too late, poured case bench set too long. Numerous small air bubbles "whipped" into resin (frothy mixture) and entrapped in the mold. |
Review resin mixing and pouring procedures. |
| Resin seems "soft" or ends of sprues seem "mushy" |
Air inhibition due to Improper resin mixing procedures, or submersion of case in water in processing pot. |
Review mixing and processing instructions. |
| Lack of retention of teeth - porcelain or plastic - in denture base |
Wax film remaining on teeth after boil-out. |
Gently scrub teeth with soft brush and detergent powder to remove all traces of wax or oil. Rinse thoroughly with clean, boiling water. |
|
Water remaining in diatorics and vent holes |
Blot teeth, both porcelain and plastic before applying bonding agent. |
|
Incorrect powder/
liquid ratio
|
Use proper powder/liquid ratio.
29 cc powder to 14 ml liquid.
|
|
Resin not flowing throughout mold, around and over teeth due to "overmixing," bench set too long, pouring too slowly, etc. |
Pour resin sooner.
Rock flask gently from side to side.
|
|
Lack of Bonding Agent |
Use Bonding Agent |
| Dull or "soft" plastic tooth surfaces |
Bonding agent ran onto tooth surface. |
Keep applications of bonding agent minimum on ridge lap area only. |
| Teeth "pop off" denture base material. |
Film of wax on teeth after boil-out. |
Review boil-out procedures: Use clean water in boil-out tank; clean teeth with soft brush and detergent powder; final rinse should be made with absolutely clean, boiling water. |
|
Insufficient application of bonding agent. |
Bonding agent may be applied to the ridge lap area of both plastic and porcelain teeth as well as to any denture base material remaining on restorations to be relined or rebased. |
