One of the long-standing problems in dentistry is premature breakage or perforation of crowns. When a porcelain crown is broken (Fig.1), it is necessary to replace it immediately because its existing cracks and pressure will continuously lead to further fractures. Moreover, the broken pieces of porcelain can be swallowed and scratch the intestinal walls. The perforated crown (Fig.2) may allow dental decay to develop into the dentin under the crown, and that may require root canal treatment or the extraction of the tooth.
Crown preparations are hindered by the limited space in the mouth and small size of the coronal portion of the tooth. Excessive reduction of tooth structure causes hypersensitivity and can diminish retention, leading to a crown that recurrently falls off its abutment.
In contrast, if the tooth structure was not reduced enough, the crown will likely break prematurely because it has been made too thin, wearing off rapidly and leading to perforation.
Ceramic is the most popular dental material for crowns for its aesthetics, however, the breakage of the porcelain crown has been the most common problem. This is caused by insuffcient occlusal reduction leading to the fabricated ceramic crown being too thin. Therefore, it is essential to prepare teeth precisely with enough occlusal clearance.
There are a few devices to guide the occlusal reduction of teeth for crowns, but all of them are ineffcient or inaccurate. Their flat designs ignore the cuspal wave reduction, guiding users to cut flat abutments that ignore the tooth anatomy. This creates hypersensitivity because the tips of the pulpal horns are left too close to the prepared flat cut or are exposed. Because of this lack of reliability with the existing devices, many dentists use their own naked eye to guess the occlusal clearance, which leads to liability for miscalculations that cause financial burden for doctors and patients.
This problem inspired me to invent an accurate and reliable device to measure, monitor, and confirm the required occlusal clearance. Through years of research and experiments, I have developed PrepSure, Crown Prep Guide, which is designed to satisfy every requirement for ensuring accurate crown preparations.
• PrepSure guides the crown preparation properly with optimal reduction for occlusal clearance, preventing under- or over-reduction and following the cuspal waves for improved retention (Fig.3)
• PrepSure is designed with 3 diameters of the functional tips for all common crown materials:
1.0 mm for mono-layered solid zirconia materials and metallic materials, 1.5 mm for bi-layered materials, and 2.0 mm for ceramic and CAD/CAM ceramic materials.
• PrepSure is used to glide through on the mesial half of the tooth with its Mesial Tip and the distal half of the tooth with its Distal Tip to detect high spots and avoid unnecessary over reduction. (Fig.4)
PrepSure’s unique design is the solution for this long-standing crown preparation problem, providing excellent patient experiences and leading to a win-win for patients and dentists, alike.