**2.6 Standards around the area**

Although dimensional measurements have been widely applied in dental research, for some of the measurements, such as taper angle measurement, a consensus has been demonstrated (Noonan & Goldfogel, 1991; Sato et al., 1998; Patel et al., 2005; Ayad et al., 2005; Mack, 1980; Rafeek et al., 2006, 2010). In other areas, such as tooth wear measurements (Zhou and

(Posteriors) BL mean taper MD mean taper

(Trinidad dental school) 16.8° 22.4°

(Japanese dental school) 18.8° 19.2°

(Trinidad dental school) 18.2° 14.2°

Table 2. Comparison of mean bucco-lingual (BL) and mesio-distal (MD) tapers of Clinical and Laboratory specimens with this study and studies utilising traditional methodology.

The comparisons of these data demonstrate that dental students in the Trinidad dental school have produced tapers that are comparable to dental students in many other dental schools around the world (Noonan & Goldfogel, 1991; Sato et al., 1998; Patel et al., 2005; Ayad et al., 2005; Mack, 1980). The dental students in the metrology study not only achieved mean tapers comparable to other students but also to dentists in a US study (Nordlander et

Because of the varying methods used to measure taper in the past, one must compare data with caution, however, it would appear from this work that measurements made by 3-D coordinate metrology are in close range of several studies previously undertaken. The traditional methodologies however do involve forming a two dimensional profile from the three dimensional die replica. This in itself can introduce error. This 3-D coordinate metrology is unique in that it is truly 3-D free-form surface digitisation, rather than 2-D profiling. The software is also able to use the image in a particular requested plane, therefore the taper angles can be calculated in the same plane for each of the samples. This reduces the possible error in angle calculation due to the samples being misaligned. It would be useful to measure the taper of the dies using traditional devices and then measure the taper of the same dies using CMM and compare the data to determine how closely they

Although dimensional measurements have been widely applied in dental research, for some of the measurements, such as taper angle measurement, a consensus has been demonstrated (Noonan & Goldfogel, 1991; Sato et al., 1998; Patel et al., 2005; Ayad et al., 2005; Mack, 1980; Rafeek et al., 2006, 2010). In other areas, such as tooth wear measurements (Zhou and

(US dental school) 19.5° 18.5°

(UK dental school) 14.7° 16.3°

(Posteriors) BL mean taper MD mean taper

15°-20° 14-°20°

CLINICAL SPECIMENS

Rafeek et al., 2010

Noonan & Goldfogel, 1991

Sato et al., 1998

Patel et al.,2005

 LABORATORY SPECIMENS

Rafeek et al., 2010

Ayad et al., 2005 Egyptian, US and Saudi Arabian dental schools

al., 1988).

measure up.

**2.6 Standards around the area** 

Zheng, 2008; Pintado MR et al, 2000; Mitchell and Chadwick, 1998) this has not been the case. There have been some 640 papers published in tooth wear measurement over the period of 1960 to 2007, and the measurements within these papers are wide ranging using a clinical tooth wear index, a modified index, reduced depth of tooth surface in the laboratory, reduced volume and changes in percentage of the area or volume. Moreover the accuracy of these measurements were reported by accuracy, precision, inaccuracy, error and uncertainty, which demonstrated a lack of a standard in the measurement strategy, therefore it is often difficult to compare the results directly between the laboratories and published papers. The ISO is in the process of establishing and organising a committee for the dental computer assisted design-computer assisted manufacture (CAD/CAM) and its related issues so that more formal standards and protocols may be set up to improve dimensional measurements in dentistry. However, this standard will not assist in the comparison of research data, where the inaccuracies listed above are inherent. Employment of instruments with high levels of accuracy such as the CMM as a 'norm' in this type of clinical research would enable data from different laboratories to be compared at the appropriate level and power and thus enable more meaningful conclusions to be made.
