Polycarbonate crowns are heat-molded acrylic resin shells that are adapted to teeth with self cured acrylic resin. They were popular in the 1970’s, however, although they were more aesthetic than stainless steel crowns the polycarbonate material was brittle and did not resist strong abrasive forces, exhibiting frequent fracture and dislodgement. With the advent of composite strip crowns they lost their popularity. In the 1990’s new manufacturing techniques made them thinner and more flexible resulting in stronger restoration and resurgence in their use.
Although polycarbonate crowns are available through a number of manufacturers the technique described here is the one recommended by PedoNatural Crowns, Valencia CA.
Advantages
They are very aesthetic, with greater durability than composite strip crowns and pre-veneered crowns.
They are not as technique sensitive as composite strip crowns as the fabricated crown is cemented with self adhesive resin cement rather than bonding.
They take about the same amount of time to place as stainless steel crowns, composite strip crowns and preveneered crowns, and less than open faced stainless steel crowns.
Disadvantages
Polycarbonate Crowns Technique
|  |
| | |
|  |
| | |
|  |
| | |
|  |
| | |
|  |
| | |
Select a crown that fits easily over the prepared tooth and has the appropriate mesial-distal dimension. If the crown does not seat without incisal interference additional tooth reduction is necessary.
|
|
Reseat the crown form onto the prepared tooth. All margins are subgingival. Check or estimate the occlusion. Adjust the margins and occlusion.
|  |
| | |
|  |
| | |
|  |
| | |
|  |
| | |
 | |  | | Pre-crimped crown | | Crimped crown |
|
| | |
| Cementation Immediately prior to cementation, thoroughly rinse the tooth with a high speed water spray. Once the tooth is clean place a 2X@ gauze over the tooth with firm pressure on the gingival tissues to control any bleeding, as necessary while the crown is being loaded with self-adhesive resin cement. Apply GC Coat Plus (GC) to the internal surface of the crown using a brush or pledget. Dry the GC Coat Plus with a gentle air flow until bone dry and then light cure for 10 seconds. Fill the crown will self adhesive resin (e.g. RelyX (3M ESPE, St. Paul, MN), SmartCem (Dentsply, York, PA) or G-Cem Automix (GC America, Alsip, IL). Use a shade labeled Translucent or Light Seat the crown fully and completely. Maintain finger pressure on the crown and light cure the buccal and lingual margins for 2-3 seconds. Remove excess cement with an explorer and floss interproximately taking great care to stabilize the crown so that the position of the crown is not disturbed while the cement is setting. Light cure the crown for 20 seconds
|
|
| Note: Photos for the polycarbonate crown technique courtesy of PedoNatural Crown. |
| |
| With all full coverage restorations parents must be advised to institute appropriate preventive health practices (elimination of sugar containing drinks, regular tooth brushing and topical fluoride application) to maximize gingival health and minimize the recurrence of caries under the restorations. |