A study into the variations in the labial reduction of teeth prepared to receive porcelain veneers – a comparison of three clinical techniques

Abstract

Objectives: Various techniques have been suggested to enable the operator to produce an even reduction of 0.5 mm of labial tooth enamel during preparation for a porcelain veneer. For example, in addition to the traditional free hand method, longitudinal or horizontal depth orientation grooves and the use of small round burs to produce dimples as depth guides have been suggested. However, there is no published data that compares how effective these techniques are at producing the 'ideal' veneer preparation. In this study three techniques were compared using the technique of co-ordinate metrology. Method: A single operator using the above three techniques prepared 84 extracted teeth. Impressions of the prepared and unprepared teeth were scanned using a co-ordinate measuring machine (CMM). Measurements of maximum labial reduction along the mid-labial plane were taken and analysed. Results: The study showed that among the three techniques studied the use of small round burs (D001-012), when used side on at an angle of 45°t o the tooth surface to produce dimples as depth guides, resulted in the greatest frequency of tooth reductions closer to the 'ideal' depth chosen for this study, ie within the 0.4 mm -0.6 mm range. Conclusion:The study concluded that even after using techniques designed to produce consistent preparations, a single operator still produced preparations with considerable variation from the ideal. The study showed that among the three techniques compared the use of small round burs, when used side on at an angle of 45° to the tooth surface to produce dimples as depth guides, resulted in the greatest frequency of tooth reduction closer to the 'ideal' depth chosen for this study only, ie within the 0.4 mm -0.6 mm range. It is stressed that this range may not be the ideal in all clinical situations.It is commonly accepted that, to satisfy the biologic needs of the periodontium, the technical needs of the ceramist and the aesthetic demands of the patient, some form of tooth preparation, confined within the enamel, is mandatory for veneering a tooth. 1,2,3 Such a 1* PhD Student, 2 Senior Lecturer, 3

Taper of Full-Veneer Crown Preparations by Dental Students at the University of the West Indies

“…It characterizes and defines the geometry of objects. This method has more recently been applied to human “freeform” surface measurements 17–19 . The engineering machine has been adapted by software modification to analyze human freeform surfaces, and data acquisition is achieved by use of both optical laser probes and the stylus.…”

A study of labial groove-textures of upper central incisors by Shadow Moiré technology

“…Because of aesthetics and durability, ceramic structures are widely used to replace missing teeth because of disease or trauma. Research on ceramic restoration for anterior teeth has focused primarily on clinical techniques (5, 6), veneer materials (7) and preparation design (8–10), while the final depiction of the surface morphology depends entirely on the technician’s personal experience and discretionary practice. Data of the length, width and depth of the labial grooves‐textures lack specific numerical reference; consequently, a poor resemblance between natural teeth and the prosthesis would be expected.…”

Dimensional Measurement for Dentistry

“…With surface form (shape) measurements, Co-ordinate Measuring Machines (CMMs) are more suited for the inspection of automotive parts in industry since the 1950's (Bosch, 1995). Since the late 90's, along with the development of new technology in optics and computing, numerous applications have been advanced in the fields of medicine and dentistry (Chadwick, 1989;Seymour et al 1996;Kabban, et al 2001;Zou, et al , 2009Cherukara GP et al 2002;Theocharopoulos et al, 2010;Morris et al 2011 ).…”

“…Metrology has also been used in dentistry to measure the amount of tooth wear on the surface of a tooth. Specifically in the preparation of crowns, it has been used previously to measure the width of the crown preparation margin, the angulation of the margin (Seymour et al,1996, Cherukara et al, 2002 and the taper angle formed when a tooth is prepared for a crown (Rafeek et al, 2006(Rafeek et al, , 2010.…”