to fabricate mouthguards and vacuum-formed templates. Many of the steps involved in fabricating these devices are similar and fairly simple to learn.
Mouthguards are constructed of acrylic resin or vinyl-like material that covers and protects all of the teeth in the arch. The purpose of a mouthguard is to reduce the potential for injury to the teeth and surrounding tissues. Although a mouthguard does not prevent the teeth from fracturing, it does keep the fragments from lacerating or embedding in the oral tissue. The mouthguard also reduces the risk of concussion by acting as a shock absorber. If the head is impacted, the guard cancels part of the force, reducing the risk of concussion.
The first step in fabricating a mouthguard is to draw the outline of the mouthguard on the cast with a soft lead pencil. Design the mouthguard by drawing or scribing a line around the maxillary arch in the buccal flange area to the highest point to which you want the material to extend. Normally, the mouthguard extends to the point where the soft tissue meets the attached gingiva. Next, trim the working cast as close to the outline as possible as seen in figure 8-36(A). The thickness of the cast base should not exceed 6 mm. The reason for trimming the cast as specified is to facilitate the cacuum formation and to minimize stretching and thinning of the vinyl plastic during the molding. For the same reason, drill a hole in the palate with a large pear-shaped bur. Soak the cast in water for a couple of seconds to prevent the hot thermoplastic material from adhering to the cast. Remove excess water from the cast. Place the wet cast on the perforated plate of a vacuum-forming device.
Several different types of vacuum-forming machines can be used to adapt thermoplastic material. Most machines consist of a perforated plate connected to a source vacuum, an electrical heating element, and a metal frame in which the vinyl plastic blank can be clamped. Regardless of the machine's manufacturer, the procedures used to adapt the material are basically the same. The construction procedures, in general, consist of the following steps:
1. Clamp a vinyl plastic blank in the frame, and place it in position to be heated. The molding temperature usually is estimated by the amount the sheet of vinyl plastic material "sags" as it softens (fig. 8-36(B)). Excessive heating of the material will cause the mouth protector to stretch and thin out. Sharp reproductions of the surface detail are not necessary.
2. When the material is ready, turn the vacuum on and move the frame to the molding position (fig. 8-36(C)). Hold it in this position until the vinyl plastic is completely adapted to the contours of the cast.
3. Turn off the vacuum. Release the clamp on the frame and set the cast with the mouth protector aside until it cools completely.
Trim excess material away with scissors as shown in figure 8-36(D). Heat a Bard-Parker blade and trim the outline of the mouthguard. Remove the mouthguard and reduce the borders to approximately 5-7mm. A large bur, arbor band, or finishing stone may be used to reduce the border thickness. Polish the edges with pumice, or lightly flame the mouthguard with an alcohol torch. Flaming has the benefit of clearing any cloudy areas in the material. Wash and disinfect the mouthguard, then place it in a prosthetic denture bag for delivery to the patient.
The completed mouthguard should conform to the general outline presented in figure 8-36(E). Notice that the posterior border of the maxillary mouthguard ends on the hard palate, and that the facial flanges do not restrict the movement of any frena. The posterior border may end in the rugae area to increase the patient's speech and comfort.
Provisional fixed restorations (temporaries) are usually made using some type of matrix or template. Two methods more commonly used for providing these templates are the impression method and the vacuum-forming method. Basically, the template or impression is a shell that will be filled later with tooth colored resin and seated on the prepared teeth, forming the provisional restoration. For this purpose, we will only discuss making a template using the vacuum-forming method since you are already familiar with how to make an impression.Continue Reading