Evaluation of Alterations That May Occur on Root Surfaces after Root Planing Procedures with a Scanning Electron Microscope

Abstract

Background: The aim of root debridement procedures in non-surgical periodontal treatment is the elimination of etiologic factors that cause periodontal disease, as well as the removal of cement affected by the disease. However, root debridement procedures for the treatment of periodontal diseases produce root surface irregularities that can adversely affect the healing of periodontal tissues. The objective of the present study is to evaluate the surface texture of a root after instrumentation, including an ultrasonic instrument, a Gracey curette, or a double Gracey curette. Methods: A total of 26 single-rooted teeth were used in this study; two specimens were used as controls, and the remaining 24 specimens were equally divided into three groups. Specimens from each group were then subjected to root planing using one of the following instruments: (1) an ultrasonic instrument; (2) a Gracey curette; or (3) a double Gracey curette. The control group was treated with no instrumentation. The extracted teeth were analyzed under a scanning electron microscope and graded in terms of the “roughness and loss of tooth substance index” and the “exposed dentin tubule index.” The SPSS (Statistical Package for Social Sciences) V.21 program was used to conduct a statistical analysis of the data obtained in this study. While evaluating the data, in addition to descriptive statistical methods (mean and standard deviation), a one-way analysis of variance (one-way ANOVA) was carried out to compare the quantitative data and evaluate normally distributed parameters between groups, while a post hoc multiple comparison test was carried out for subgroup comparisons. Results: There was no statistically significant difference between the roughness and material loss on the root surfaces in the samples treated with the ultrasonic instrument or the Gracey curette, and no exposed dentine tubules were observed. Meanwhile, it was observed that the double Gracey curette caused more roughness and material loss on the root surface, and exposed dentine tubules were observed in some samples. The time required for treatment using a double Gracey curette was significantly shorter than that required with the Gracey curette and ultrasonic instruments. Conclusions: The double Gracey curettes produced a relatively rougher root surface than the Gracey curettes or the ultrasonic instrument.

1. Introduction

The instrumentation used for the root surface is an important part of non-surgical periodontal therapy; in particular, the removal of accumulated material from the root and root planing are essential for the treatment of periodontal disease [1]. The purpose of root surface roughening is to prevent the formation of plaque deposits and to provide a biocompatible root surface for the adhesion of periodontal fibroblasts. Therefore, the use of an ultrasonic hand instrument is important, as it can impact clinical outcomes such as clinical attachment loss, pocket depth, and bleeding upon probing [2].

Ample evidence has indicated that plaque and calculus are the principal etiological agents of periodontal disease [3]. Roughened root surface accumulation favors bacterial attachment and causes increased biofilm formation [4]. The calculus increases the colonization of subgingival microbes [5]. Scaling and root planing aim to eliminate these factors through mechanically debriding the diseased root surface.

In a previous study, as bacterial endotoxins were tightly bound to root surfaces, aggressive root planing was carried out [6]. Current evidence suggests that there is weak adherence of bacterial endotoxins to the root surface; thus, aggressive root planing and the intentional removal of the infected cementum and root surface are not necessary for the healing of periodontal tissues. Increased exposure of the dentinal tubules causes sensitivity [7]. Numerous studies have been conducted to determine which instruments lead to lower levels of root roughness [8]. While some believe that ultrasonic instruments are better at removing plaque and biofilm, others claim that hand instruments—such as curettes—are more effective [9]. The aim of periodontal treatment is to provide effective debridement and protect the root structure. Increased roughness leads to higher bacterial adhesion and biofilm formation [10], and, according to Bollen et al., an increase in surface roughness affects plaque and biofilm formation [11].

Numerous studies have compared hand instruments with power-driven instruments and lasers to assess the resulting root surface roughness [12,13]. These studies have produced variable and inconclusive results [14,15] and, at present, there is no universally accepted method for root planing and scaling.

It has been documented that hand- and power-driven instruments may cause some gouging and the removal of tooth substance. Tooth substance loss is also affected by the shape and design of the instrument. Matheus Andre Muller investigated the effect of different Gracey curettes on the roughness of the root surfaces and found that the quality of the curette’s cutting surface affected the homogeneity of the root surface [16].

No research comparing conventional hand instruments (such as the Gracey curette) with contemporary hand instruments (such as the double Gracey curette) has been conducted to date. This trial was carried out in this study due to the limited and inconsistent evidence regarding the effectiveness of modified versions of curettes with respect to the root surface. The objective of this study was to compare and evaluate the effects of an ultrasonic instrument, a Gracey curette, and a double Gracey curette in terms of root surface roughness and exposed dentin tubules using scanning electron microscopy (SEM). Additionally, the total working times of these two different curette designs are compared.

2. Methods

The teeth selected for the study were extracted from patients who had reported to the outpatient department of periodontology at the Istanbul University Faculty of Dentistry. Teeth that had undergone root canal treatment, any periapical lesion, caries, or a history of scaling and root planing in the previous 6 months were excluded from the study. This study was found to be ethically appropriate, with the article numbered 48,317 issued by the Istanbul University Faculty of Dentistry.

A total of 26 single-rooted human teeth were used in this study, which were extracted due to severe chronic periodontitis having a hopeless prognosis with a bone loss of >70% and grade III mobility. The teeth were washed with distilled water, treated with a 2% sodium hypochlorite solution, and then stored in normal saline until further study.

2.1. Description of Test Instruments

The study used the following curettes and ultrasonic scalers for root instrumentation.

Ultrasonic instruments (Dentsply Cavitron 30K tip, Charlotte, NC, USA) were used for root instrumentation. Unidirectional strokes were given on the proximal surface along the long axis of the teeth.

Gracey 5/6 and 7/8 curettes (American Eagle Instruments, Missoula, MT, USA) were used for instrumentation.

Double Gracey curettes (American Eagle Instruments, Missoula, MT, USA) were used for instrumentation.

Double Gracey Anterior: The Double Gracey™ Anterior combines the Gracey 1–2 curette for all anterior surfaces with the Gracey 7–8 for all buccal and oral surfaces of premolars and molars.

Double Gracey Posterior: The Double Gracey™ Posterior combines the Gracey 11–12 mesial with the Gracey 13–14 distal curette.

2.2. Sample Size Calculation

To determine the required number of samples, exemplary studies on the subject were consulted. Based on the significance of statistical evaluations, the minimum number of samples required to create this difference was determined to be 24. As such, a total of 26 samples were included in the study, including 2 control samples. The power of the study was determined to be 80%, with Type 1 error being 5% and Type 2 error being 20%. The number of samples in the control group was determined according to previous studies. A control group was considered for a comparison of SEM photographs between the instrumented test samples and the non-instrumented control samples. In this way, visual differences between surfaces with and without instrumentation could be evaluated more easily.

2.3. Specimen Preparation

Two randomly selected teeth from the 26 single-root teeth formed the control group, while the remaining 24 teeth formed the study group. The 24 teeth in the study group were divided into 3 groups with 8 teeth each, with equal numbers of central, lateral, canine, and premolar teeth in each group. In the study groups, the type of periodontal instrument to be used was determined randomly using the coin toss method. A single operator performed subgingival instrumentation in vitro using the ultrasonic scaler, Gracey curette, or double Gracey curette. Instrumentation was not performed in the control group, which was titled group 1. The second group included teeth that were instrumented with the ultrasonic scaler. The third group of teeth was instrumented with the Gracey curette, while in the fourth group, the double Gracey curette was used (

Table 1. Allocation of samples and treatment assignments.

	No. of Samples (26)	Group Titles	Treatment Provided
Control	2	1	No Treatment
Ultrasonic	8	2	Ultrasonic Scaling
Gracey	8	3	Gracey Curette Scaling
Double Gracey	8	4	Double Gracey Curette Scaling

). Scaling and root planing were performed until a smooth and hard surface was detected by the operator using an explorer.

Instrumentation was performed in vitro by a single operator trained in periodontology with extensive experience, calibrated using a modified pen grasp technique for holding the curettes [17]. The angle between the cutting edge of the curette and the teeth was between 45 and 90 degrees, and a good finger rest was used to allow for natural wrist–forearm motion. The length of time was measured with a stopwatch from the start until the root surface appeared smooth upon visual inspection and examination with an explorer. After root planing, under effective water cooling, a first cut was made approximately 1 mm apical to the cemento-enamel border, a second cut was made 3 mm coronal to the root tip, and a third cut was made along the long axis of the tooth, using diamond-separated burs. Only one of the two surfaces obtained was used as an example in the study.

2.4. Preparation of Root Specimens for Scanning Electron Microscopy

After instrumentation, the samples were fixed in Formaldehyde (4%). All specimens were kept for 10 min in a graded series of ethanol (50%, 70%, 85%, and 96% ethanol) for dehydration [18]. The samples were then treated with nitrogen gas for 20–30 s to completely remove the water trapped inside. They were mounted on plates containing aluminum plates, each with carbon tape. Before SEM examination, insulating samples were coated using an Au–Pd sputtering device to obtain conductive properties and increase the clarity of the images.

2.5. Scanning Electron Microscope Analysis

The micrographs were assessed by two examiners blinded to the treatment groups. Four SEM photographs with different standardized magnifications were taken for each specimen, which were later assessed according to the ”roughness and loss of tooth substance index” [18] and the self-developed “exposed dentinal tubules index.” The “roughness and loss of tooth substance index” [18] and ”exposed dentinal tubules index” were analyzed taking the magnifications (×500, ×1000, ×2000, and ×5000) into consideration.

Roughness and loss of tooth substance index [18]:

0.

A smooth and even root surface was found without marks from instrumentation and with no loss of tooth substance

1.

Slightly roughened and corrugated local areas confined to the cementum were found.

2.

Definitely corrugated local areas were found where cementum may be completely removed, although most of the cementum was still present.

3.

A considerable loss of tooth substance was found, with instrumentation marks in the dentin. The cementum was completely removed in large areas, or it had a considerable number of lesions from the instrumentation.

Exposed dentinal tubules index:

• There are no exposed dentinal tubules.
• There are exposed dentinal tubules.

2.6. Statistical Analysis

In this study, the SPSS (Statistical Package for Social Sciences) V.21 program was used for the statistical analysis of the results. Besides descriptive statistical evaluation, differences between groups were assessed through a one-way analysis of variance (one-way ANOVA) for parameters showing a normal distribution among the groups; furthermore, a post hoc multiple comparisons test was also used. The results were interpreted through Bonferroni correction and evaluated in terms of the 95% confidence interval at a significance level of p < 0.05.

3. Results

SEM images showing the roughness of the root surface, the loss of root material, and the presence of exposed dentinal tubules are presented below.

3.1. Evaluation of Scanning Electron Microscopy Images

In the control group images, an uneven surface structure of the root cementum and calculus was observed on the root surface (Figure 1). In group 2, a hard, clean root surface was observed (Figure 2). In group 2, traces of the ultrasonic vibrating tip were observed on the root surface (Figure 3). In group 3, several scratch marks (train tracks) from the curette blades were observed on the root surface (Figure 4). In group 4, the removal of the root cementum was observed at selected sites on the root surface (Figure 5).

3.2. Evaluation of Root Surface Roughness

The mean roughness and loss of tooth substance index scores for groups 2, 3, and 4 were 0.68, 0.93, and 1.57, respectively (

Table 2. Descriptive statistics of the roughness and loss of tooth substance index values for control and study groups (group 3 and group 4, p < 0.05 and p < 0.01, respectively).

	N	Minimum	Maximum	Mean	p
Group 1	2	0	0	0	0
Group 2	8	0	1	0.68	0.37
Group 3	8	0.5	1	0.93	0.17
Group 4	8	1	2	1.57	0.44

). The roughness and material loss index values were similar in groups 2 and 3, and no significant difference was observed between these two groups (p = 0.92). No significant difference was observed between group 1 and group 2 (p = 0.1). However, statistically significant differences were observed when group 1 was compared with groups 3 and 4 (p < 0.05 and p < 0.01, respectively). The roughness and material loss index values were higher in group 4 when compared to all the other study groups (Table 2).

3.3. Evaluation of Exposed Dentinal Tubules

No significant difference was observed between the study groups in terms of the exposure of dentinal tubules (p = 0.14); however, exposed dentinal tubules were observed on the root surfaces of the group 4 (double Gracey) samples (

Table 3. Descriptive statistics of dentinal tubule monitoring values.

	N	Minimum	Maximum	Mean	(Ss)
Group 1	2	1	1	1	0
Group 2	8	1	1	1	0
Group 3	8	1	1	1	0
Group 4	8	1	2	1.14	0.24

, Figure 6).

3.4. Evaluation of the Treatment Duration

The time required for treatment using a double Gracey curette was significantly shorter than that with the ultrasonic instrument and the Gracey curette. The mean treatment duration for groups 2, 3, and 4 was 53.5, 54.13, and 35.75 s, respectively (

Table 4. Descriptive statistics of periodontal instrument usage times of the groups (* p< 0.01).

	N	Minimum	Maximum	Mean	Standard Deviation
Group 2	8	40 s	60 s	53.5 s	6.65
Group 3	8	46 s	65 s	54.13 s	6.68
Group 4	8	24 s	48 s	35.75 * s	8.32

). The difference between the treatment durations for groups 3 and 4 was statistically significant (p < 0.01).

4. Discussion

In the present study, scaling and root planing were evaluated through an in vitro study, as this facilitated the selection of a comparable test surface and permitted the standardization of the experimental procedures [18].

Previous studies using older tip designs have shown that ultrasonic instruments have a greater potential to produce root surface damage than curettes [19,20]; however, in more recent studies, ultrasonic instruments could produce root surfaces as smooth as or smoother than those produced with curettes [21,22]. Current evidence suggests that ultrasonic instruments used at medium power may do less damage to the root surface than curettes [23]. In this study, it was observed that the root surface roughness produced with the ultrasonic scaler and Gracey curette was similar.

It has been established that there is no difference in bleeding upon probing, periodontal pocket depth, or clinical attachment levels when using ultrasonic or hand instruments [24], although a significant difference in root roughness has been reported when manual and ultrasonic instruments were used [16]. Regarding hand instruments, to the best of our knowledge, there have been no studies comparing the effects of debridement on the root structure using separate hand instruments, such as Gracey and double Gracey curettes. In this study, the effects of these different curettes and an ultrasonic scaler on the root surface ultramorphology were examined.

Matthew Andre conducted another study to compare the effects of different brands of Gracey curettes (no. 5/6), including carbon steel and stainless steel curettes, on the resulting root roughness and topography. He suggested that the quality of the cutting edge of the curette leads to a difference in the topography of the root surface. His study showed that stainless steel millennium provided the most homogeneous root surface [16]. In our study, in terms of smoothness, the Gracey curettes produced a smoother root surface compared to the double Gracey curettes, consistent with the study mentioned above.

Based on the results of the current study—which had an in vitro design involving SEM—we found that the double Gracey curettes produced greater root roughness than the Gracey curettes. These results were in accordance with the study of C. Landy, who compared a long-shank, short-blade curette against the conventional Gracey curette variant (Curvette Sub-0) in vitro using a profilometer. His results verified that the test curette (Curvette-0) caused greater root roughness [25].

In the present study, all the test groups (i.e., ultrasonic instrument and Gracey and double Gracey curettes) presented gouging and cracks of varying sizes on the root surfaces. The root surfaces also exhibited deep scratches after root instrumentation. These results are consistent with many other studies that have reported the presence of cracks and gouging when using hand instruments [25,26,27].

Similarly, a recent clinical trial that evaluated clinical outcomes and post-treatment hypersensitivity using Gracey curettes, ultrasound, and diamond burs revealed that Gracey curettes and ultrasound improved clinical performance in terms of attachment levels when compared to diamond burs [28]. In this study, no exposed dentinal tubules were found when using Gracey curettes or ultrasonic scrapers; however, exposed dentinal tubules were observed when using double Gracey curettes. Therefore, root sensitivity is expected to be higher when double Gracey curettes are used compared to ultrasonic and Gracey curettes. The results of this study are limited to single-rooted teeth only. In the future, more studies are required to assess the ultramorphology of root surfaces, as there have been few studies and inconsistent results. Different methodologies and techniques may be used for determination. More rigorous studies must be conducted due to the paucity of research on double Gracey curettes. The positive and negative aspects of double Gracey curettes have been seen in clinical use: with double Gracey curettes, the time spent at the bedside is shorter, and less hand and wrist fatigue is experienced by the physician. The negative aspect is that the exposed dentinal tubules resulted in insensitivity on the root surface.

5. Conclusions

The ultrasonic scaler and Gracey curettes produced a relatively smoother root surface when compared to the double Gracey curettes. There was no difference between the ultrasonic scaler and Gracey curettes in terms of root roughness and exposed dentinal tubules. Meanwhile, exposed dentinal tubules were observed when the double Gracey curettes were used. However, with the double Gracey curettes, the time taken for treatment was shorter, given that there was no need to change or rotate the instrument. Further studies in this line of work are required in order to determine the impact of these new curettes on the root morphology.