Scanning electron microscope analysis of working ends of standard and modified Gracey curettes.

Context: Gracey curettes are the most frequently used manual instruments in periodontal treatments. Aim: This study aimed to evaluate morphology of working ends of standard and modified Gracey curettes no. 1-2. Materials and
Methods: Using scanning electron microscopy, four batches of unused standard curettes from seven manufacturers and modified curettes from 6 manufacturers were investigated for blade length, blade width, blade thickness, toe morphology, surface roughness, and cutting-edge morphology.
Results: Working ends of the standard Gracey curettes were longer than the modified ones, with mean lengths of 5.65 ± 0.68 and 4.42 ± 0.82 mm, respectively. However, both standard and modified Gracey curettes had comparable widths and thicknesses, with the mean width of 0.86 mm and the mean thickness of 0.71 mm. Most samples had acceptably symmetrical toes, except those from three manufacturers which had unacceptable toes with angulations. Moreover, only two manufacturers produced curettes with smooth blades on all their surfaces. In addition, sharp or functional wire edges were seen in cutting edges of curettes from three manufacturers. Conclusions: Working ends of standard and modified Gracey curettes could have different morphological features if they were from different manufacturers or different batches. It is suggested that dentists or dental hygienists make a purchase decision based on their knowledge on morphology of a good curette in relation to its intended use in dental practice, rather than their familiarity or the curette's price. Furthermore, the curette needs to be examined using a widely available magnifying device when possible. Copyright:

INTRODUCTION

Scaling and root planing are two of the most crucial steps for periodontal treatments, aiming for creating biologically acceptable root surfaces, relieving inflammation, decreasing periodontal pocket depths, and increasing attachment levels of periodontal tissue.[1] In these key steps, curettes are the most useful and the most commonly used manual instruments,[23] which have been listed as a factor that has a great influence on the success of root planing.[1]

Gracey curettes are a set of 14 instruments (#1–#14), which are specifically designed for different anatomical dentition areas, thereby providing the best conformity to root anatomy.[4] Each curette is composed of a handle, a shank, and a working end, which on its both sides has cutting edges that meet each other at a curved toe.[23] In contrast to universal curettes, Gracey curettes have their blades uniquely angled approximately 60°–70° to their lower shanks, which is the most efficient angulation for subgingival scaling and root planing.[4] Other features that distinguish a Gracey curette from a universal curette include the use of only one cutting edge and the offset blade that curves upwardly and laterally.[5]

To further improve the efficiency of curettes in particular situations, some modifications have been applied for Gracey curettes.[4] For example, Gracey curettes with extended shanks (e.g., After Five® curettes: Hu-Friedy® and Gracey +3 Deep pocket curettes: American Eagle®) have terminal shanks that are 3 mm longer than standard ones, enabling them to extend into periodontal pockets deeper than 5 mm.[4] Another noteworthy example is mini-bladed curettes (e.g., Mini Five curettes: Hu-Friedy® and Gracey +3 Access curettes: American Eagle®), which have been designed to have blades half the length of standard curettes, making them suitable for deep, narrow pockets or difficult root morphologies.[4] Mini Five curettes have been shown to cause trauma, as determined by loss of the relative attachment level after scaling and planing, to a level comparable to that the standard Gracey curettes did.[6]

Many studies have correlated the morphology of Gracey curettes with their efficiency in periodontal treatments. Working edge widths have been linked to efficient scaling, reduced trauma to the surrounding tissues, and increased ability to approach furcation areas.[789] Furthermore, sharpness of cutting edges has been associated with an increase in tactile sensitivity, patient's comfort, and operator's confidence, with a decrease in the needed amount of lateral pressure that results in the operator's fatigue and strain.[10] In addition, blades of both standard and mini-bladed curettes #5–6 have been demonstrated to have greater widths than some molar furcation entrances, resulting in inadequate instrumentation in these narrow areas.[11]

Gracey curettes produced by many companies are widely available with a wide range of prices. Even though they might look like each other, their cutting-end morphology might be microscopically different, and this therefore needs to be considered when choosing between different models. A preliminary study was performed to investigate the working ends of 3 standard Gracey curettes #1–2 from 3 different companies. Although their working end morphology was similar when examined by the unaided eye, it was apparently different when examined using surgical microscopy at × 20 magnification [Figure 1]. This study therefore aimed to further demonstrate the working-end morphology of standard and modified Gracey curettes #1–2, including blade length, blade width, blade thickness, toe morphology, surface roughness, and cutting-edge morphology, utilizing a scanning electron microscope (SEM).

Figure 1

These photographs are the working ends of standard Gracey curettes #1–2 manufactured by three different companies, captured using a surgical microscopy at ×20 magnification.

MATERIALS AND METHODS

Altogether, seven models of standard Gracey curettes and six models of modified Gracey curettes from different manufacturers were available on the market in Thailand. To achieve reproducible data, four batches of each commercially available model, thus a total of 28 standard Gracey curettes and 24 modified Gracey curettes, were obtained. All these samples were cut at 1 cm proximal to the faces of the blades. Each sample was labeled with two color codes, indicating the manufacturer (A to H) and the batch number for the same manufacturer (numbers 1–4). Images were taken with a JSM-6610LV SEM (JEOL Ltd., Tokyo, Japan) and analyzed with an SEM control user interface program (version 2.04; JEOL Ltd., Tokyo, Japan).

Samples were placed at two positions in relation to the faces of their blades for visualizing front and side views of the blades. A front view was used for determining blade length (from the blade's distal end and to the top of the flat surface, ×16) [Figure 2a], blade width (1 mm, 2 mm, and 3 mm from the blade's distal end, ×25) [Figure 2b], surface roughness (1 mm from the blade's end, ×350) [Figure 2c], and toe morphology or symmetry (×50) [Figure 2d]. A side view was used for determining blade thickness (1 mm, 2 mm, and 3 mm from the blade's distal end, ×16) [Figure 2e] and cutting-edge morphology (1 mm, 2 mm, and 3 mm from the blade's distal end, ×350) [Figure 2f].

Figure 2

These images demonstrate different microscopic views for measurements and examination of working ends of Gracey curettes. Front views are used for examining blade lengths (a); blade widths (b); surface roughness (c); and toe morphology (d), whereas side views are used for determining blade thickness (e) and cutting-edge morphology (f)

Quantitative data, including blade lengths, widths, and thicknesses, were calculated for each Gracey curette type and recorded as means ± standard deviation. The surface of cutting edges was classified according to roughness as a smooth surface [Figure 3a], a rough surface level 1 (irregularity ≤10 μm) [Figure 3b], and a rough surface level 2 (irregularity >10 μm) [Figure 3c]. The toe was classified according to its symmetry as an acceptable and symmetrical toe [Figure 3d], an acceptable but asymmetrical toe [Figure 3e], and an unacceptable toe (for any curette with an angulated toe) [Figure 3f]. The cutting edge was classified according to morphology as a sharp edge (when the blade's face and the lateral surface meet each other at a linear line) [Figure 3g], a functional wire edge (when there is a projection perpendicular to the edge) [Figure 3h], a nonfunctional wire edge (when there is a projection parallel to the edge) [Figure 3i], a narrow bevel edge (with a bevel of ≤15 μm) [Figure 3j], a wide bevel edge (with a bevel of >15 μm) [Figure 3k], and an irregular edge (when the edge is too irregular to be identified) [Figure 3l].[1213]

Figure 3

These images demonstrate appearance of each category of surface roughness (a-c); toe morphology (d-f); and cutting-edge morphology (g-l)

RESULTS

Four batches of unused standard and modified Gracey curettes from 7 to 6 manufacturers were labeled with color codes and examined for working-end morphology using a SEM. The working ends were firstly measured for their dimensions, including lengths, widths, and thicknesses. Measuring from the blade's distal end to the top of the flat surface, standard and modified Gracey curettes were 5.65 ± 0.68 mm and 4.42 ± 0.82 mm long, respectively [Table 1]. Two manufacturers (E and F) produced curettes with comparable blade lengths in both types of Gracey curettes, whereas a manufacturer (C) produced modified curettes with blades half the lengths of those of standard curettes [Table 1 and Figure 4a]. Blade widths and thicknesses, both measured at 1 mm, 2 mm, and 3 mm from the distal end, of the standard Gracey curettes were shown to be comparable to those of the modified ones, with the mean width of 0.86 mm [Table 2 and Figure 4b] and mean thickness of 0.71 mm [Table 3 and Figure 4c].

Table 1

Blade lengths of standard and modified Gracey curettes from seven manufacturers demonstrated as mean±standard deviation

Manufacturers	Mean±SD
	Standard Gracey curettes	Modified Gracey curettes
A	6.29±0.26	4.81±0.06
B	4.91±0.28	3.70±0.10
C	6.25±0.15	3.46±0.10
D	5.74±0.56	4.33±0.14
E	5.93±0.46	5.86±0.46
F	4.58±0.22	4.38±0.17
G	5.86±0.23	-
Average	5.65±0.68	4.42±0.82

SD – Standard deviation

Figure 4

These bar graphs show measurements of blade lengths (a); blade widths (b); and blade thicknesses (c), presented as mean values ± standard deviations

Table 2

Blade widths of standard and modified Gracey curettes from seven manufacturers demonstrated as mean±standard deviation

Manufacturers	Mean±SD
	Standard Gracey curettes	Modified Gracey curettes
A	0.89±0.06	0.74±0.05
B	0.98±0.03	1.09±0.01
C	0.86±0.04	0.83±0.04
D	0.77±0.07	0.83±0.05
E	0.86±0.02	0.83±0.03
F	0.78±0.05	0.81±0.14
G	0.87±0.03	-
Average	0.86±0.80	0.86±0.02

SD – Standard deviation

Table 3

Blade thicknesses of standard and modified Gracey curettes from seven manufacturers demonstrated as mean±standard deviation

Manufacturers	Mean±SD
	Standard Gracey curettes	Modified Gracey curettes
A	0.65±0.04	0.69±0.14
B	0.69±0.04	0.64±0.05
C	0.68±0.05	0.68±0.02
D	0.73±0.10	0.76±0.03
E	0.71±0.04	0.73±0.09
F	0.77±0.04	0.78±0.05
G	0.72±0.02	-
Average	0.71±0.06	0.71±0.08

SD – Standard deviation

The surface of cutting edges was visualized, dividing them into three categories: smooth, rough – level 1 (irregularity ≤10 μm), and rough – level 2 (irregularity >10 μm) [Figure 3a-c]. All the curettes from manufacturers E and F had smooth surfaces, whereas only 50% of the curettes from manufacturers A and D and none of the curettes from manufacturers B and C had smooth surfaces [Figure 5a]. Level 2 roughness was detected on as much as 62.5% of the surfaces of the curettes from manufacturer C [Figure 5a].

Figure 5

These bar graphs with stacked columns show percentages of each classification of surface roughness (a); toe morphology (b); and cutting-edge morphology (c)

According to the symmetricalness, the toe was classified as acceptable and symmetrical, acceptable but asymmetrical, and unacceptable with angulation [Figure 3d-f]. Most curettes had acceptable but asymmetrical toes, with 37.5% of those from manufacturer E impressively having symmetrical toes [Figure 5b]. However, as much as 50%, 25%, and 75% of the curettes from manufacturers A, C, and D were shown to have unacceptably asymmetrical toes, respectively [Figure 5b].

Cutting-edge morphology was examined and classified into a sharp edge, a functional wire edge (when there is a projection perpendicular to the edge), a nonfunctional wire edge (when there is a projection parallel to the edge), a narrow bevel edge (with a bevel of ≤15 μm), a wide bevel edge (with a bevel of >15 μm), and an irregular edge (when the edge is too irregular to be identified) [Figure 3g-l]. Proper cutting edges should be either sharp or functional. Surprisingly, these desirable cutting edges were seen in 70.84%, 75%, and 83.3% of curettes from manufacturers D, E, and F, respectively, and were not seen in any curettes from the other manufacturers [Figure 5c].

DISCUSSION

Treatment of narrow and deep periodontal pockets requires the use of curettes with the working-end length less than the width of dental roots to prevent inadvertent curettage. One study reported medial–lateral dental root widths of 6.4 mm, 4.7 mm, and 5.6 mm at the cementoenamel junction and 5.5 mm, 4.3 mm, and 4.6 mm at 2 mm below the cementoenamel junction for central incisors, lateral incisors, and canines, respectively.[14] Given the lengths of 4.58–6.29 mm and 3.46–5.86 mm for the tested standard and modified Gracey curettes reported in this study, some had excess blade lengths for incisors and canines at both the cementoenamel junction and 2 mm below, except only central incisors at the cementoenamel junction.

The working-end width is another important factor given that this portion of the curette is used for cleaning the furcation, which is narrow and difficult to approach. The mean width of the working end of all the tested standard and modified Gracey curettes was 0.86 mm, ranging from 0.74 to 1.09 mm, with no statistically significant difference between batches or manufacturers. Furcation entrance dimensions of molar teeth have been reported to be less than 0.75 mm in approximately 50% of all first molar entrances in Chinese[15] and up to 37.5% of all mandibular molar entrances in Jordanians.[16] This confirms the suggestion that using a Gracey curette alone may not be adequate for treatment of some teeth and the use of other instruments, such as ultrasonic devices, should be taken into consideration.[11]

The flat surface of the working end was shown to have different degrees of roughness/smoothness both between batches and between manufacturers. This variability may result from manufacturing processes or types of metals used and needs further investigations. Most examined curettes had acceptable toe morphology with either symmetrical or asymmetrical appearances. However, a proportion of curettes from three manufacturers were shown to have unacceptable toe morphology with angulation, which might cause unnecessary tissue damage during root planing or scaling.

Given that fineness of the cutting edge is an indispensable property required for appropriate use of a curette with minimal tissue damage to the root surface, it was also investigated in our study. A good unused cutting edge is expected to have a precise angle of the blade's face and the lateral surface, which is seen as a linear line between the surfaces, without an undesired wire edge. The wire edge refers to a nonsupported metal projection from the cutting edge. It can be defined as functional if the projection is perpendicular to the edge and parallel to the scaling contact area and as non-functional if the projection is parallel to the edge and perpendicular to the scaling contact area.[1213] Signs of poorer quality of the cutting edge include presence of a third surface or a bevel and total disappearance of the edge resulting from excessive irregularities of the edge.[1213] Interestingly, many of the curettes tested in our study, although unused, were demonstrated to have bevel cutting edges, signifying bluntness. Moreover, noncutting edges of some curettes were surprisingly shown to be sharp or wire edges, signifying sharpness, thereby imparting a risk of tissue damage when in contact with periodontal pockets.

Much variation in cutting edge morphology both between different models from the same manufacturers and between different manufacturers needs to be seriously considered. However, it could be difficult to choose appropriate curette models for treatments provided that the model names or codes might not well-labeled, or detailed information might not be readily available. The ignorance and misunderstanding can adversely affect the purchase decision. For example, the Gracey curettes designed for deep periodontal pockets ought to be suitable for scaling and root planing in a pocket narrower and deeper than 5 mm. The working end should therefore be especially small for this purpose. However, only one manufacturer tested in this study was seen to have a modified curette model with a terminal shank 3 mm longer and a working end 50% shorter than those of the standard curette model, which is likely to be safe for deep and narrow pockets. On the contrary, all the other manufacturers included in this study produced modified Gracey curette models that have working edges only slightly shorter than corresponding standard models. In addition, some curettes were seen to have small material defects when visualized using a microscope and these could be the weak points prone to be broken while being used.

CONCLUSIONS

It is highly recommended that dentists or dental hygienists ought to study detailed information of the Gracey curette when making a purchase decision, which should not be based on familiarity or competitive price. Furthermore, it is advised that the curette is examined using a common magnifying device that can easily be bought in the market, such as a ×1–5 magnifying glass, a × 10–30 jewelry loupe, a × 2.5–6 dental loupe, or a × 20 surgical microscope. This easy step might substantially reduce unnecessary complications such as breakage of the instrument during root planing.

Clinical relevance

Our study demonstrated that working ends of standard and modified Gracey curettes could have different morphological features if they were from different manufacturers or batches. Many Gracey curettes that were tested had unfavorable working-end morphological features. To ensure that a good curette is selected when making a purchase decision, examination of the cutting edge by a dentist or a dental hygienist is advised. This could easily be performed using a commonly used magnifying device that can be bought in the market.

Financial support and sponsorship

This study is financially supported by Faculty of Dentistry, Mahidol University.

Conflicts of interest

There are no conflicts of interest.