Efficiency of three different polishing methods on enamel and cementum: A scanning electron microscope study.

BACKGROUND: Tooth polishing is an integral part of clinical dentistry. The main purpose of polishing is to smoothen the surface of the tooth and minimize the deposition of plaque to allow a healthy periodontal maintenance postscaling. Today, polishing by different methods is available to a clinician. Traditional bristle brush and rubber-cup polishing are being widely practiced and gradually getting replaced by novel air polisher. Pros and cons of each method should be weighed before its clinical applications. AIM AND
OBJECTIVES: To evaluate and compare the efficiency of three different polishing systems on enamel as well as on cementum surfaces by scanning electron microscope (SEM).
MATERIALS AND METHODS: A total of 120 samples were divided into three groups randomly - Group 1 (bristle brush), Group 2 (rubber cup), and Group 3 (air polisher) - with 20 samples each of enamel and cementum, which were subdivided into 10 control and 10 test group (subjected to polishing). The samples were analyzed by SEM at ×1000 magnification, and the data obtained were compiled and subjected to statistical analysis.
RESULTS: Polishing with bristle brush demonstrated less surface roughness and debris when compared to air polisher at P = 0.58, P = 0.03 for enamel surface and P = 0.003, P = 0.21 for cementum, respectively. The surface roughness was reduced considerably by rubber cup at P = 0.03 for enamel and P = 0.003 for cementum, compared to air polisher at P = 0.99 and P = 0.21 for enamel and cementum, respectively.
CONCLUSION: The results indicate that polishing with rubber cup was more effective and statistically significant when compared to bristle brush polishing and air polisher for the crown and root surface smoothening and debris removal.

INTRODUCTION

Polishing is defined as “the implementation of making the tooth surface smooth and lustrous” (ADHA proceedings, 1997). It is the most important measure in the treatment of periodontal diseases as it smoothens both enamel and the cementum surface of the tooth.[1] Main objective of periodontal therapy is to achieve complete periodontal health. Long term objective of periodontal treatment is maintaining the periodontal health in the long term.[23] Elimination of local etiological factors like plaque and calculus to resolve gingival inflammation is vital and it can be achieved by scaling and root planing, resulting in an uncontaminated tooth surface permitting oral hygiene maintenance during the initial or supportive periodontal therapy.[45]

Although enamel and cementum show a smooth surface clinically after debridement with the naked eye, they present with several surface irregularities that can be detected microscopically. Several studies have observed that subgingival instrumentation leads to surface roughness, resulting in a significant effect on subgingival colonization of microorganisms. A smooth enamel or cementum is less likely to accumulate plaque which can only be achieved by performing polishing after scaling or root planing.[67] There is a prevailing controversy as to polish or not to polish the tooth surface. Studies have shown that polishing removes plaque, reduces bacterial accumulation, and smoothens the tooth surface after scaling.[89101112131415] On the other hand, the beneficial effects of polishing do not justify indiscriminate use. Many dental professionals recommend selective polishing as a standard protocol at every professional maintenance appointment. Various terms like therapeutic polishing, coronal polishing, superficial polishing or selective polishing are used.

In the present-day dental practice, polishing is performed by manual as well as engine-driven devices such as porte polisher, polishing strips, rubber/prophy cup, bristle/prophy brush, air polisher, and vector system in combination with various prophylactic pastes/powders.[16] Among the various polishing methods available, rubber cup with pumice/polishing paste is the most prevalent one. Novel air-powder polishing devices are getting popular as they are innovative and capable of reaching surfaces that are inaccessible to a rotary device, although their actual efficacy in smoothing the enamel and cementum surface remains debatable.[16]

The literature review provides with evidence showing the usefulness of air polishing in contemporary practice. Air polisher is safe and effective when used by trained professionals.[17] The advantages of air polishing consist of, time efficiency, minimal operator fatigue, and effectiveness in removal of stain and plaque biofilm.[18] On the other hand, in patients with conditions affected by aerosols and sodium intake, air polisher is contraindicated and careful handling is required to avoid the soft-tissue trauma.

A large amount of information is available about finishing and polishing of the restorative materials on the tooth surface,[192021] but less attention has been given on polishing of the enamel and cementum surface, which perhaps is the most vital.

Various studies conducted so far involve a range of manual polishers such as porte polisher, polishing strips, and engine-driven polishing devices such as rubber cups, brushes attached to prophy angles, and air-powder polishers along with polishing pastes/powder; and their effects on the hard as well as the soft tissues of the oral cavity.[131417]

Limited literature available compares the efficiency of different polishing techniques on enamel and especially on cementum at the ultrastructural levels. Therefore, the present scanning electron microscope (SEM) study was undertaken to evaluate and compare the microtopography of the enamel as well as cementum surface following polishing by three different polishing systems such as bristle brush, rubber cup, and air polisher.

MATERIALS AND METHODS

A total of 60 periodontally involved human teeth were extracted, collected, and sectioned to obtain 60 enamel and 60 cementum samples. Teeth with prosthesis, fracture, showing signs of external resorption, caries, abrasion, and erosion of teeth were not included in the study.

Study design

An in vitro SEM study was conducted to evaluate and compare the microtopographic changes of the enamel and cementum surfaces subjected to polishing by three different methods such as bristle brush, rubber cup, and air-polishing device.

The extracted teeth were collected and stored at room temperature in 10% formalin. They were cleaned thoroughly to remove debris, tissue tags, and calculus from the tooth surface with the ultrasonic scaler (Woodpecker HW-113B UL3R WIS) and were stored in isotonic sodium chloride solution at room temperature.

The study was conducted in accordance with the Declaration of Helsinki[22], approved by the Institutional ethics committee (TMU/EC/403). Informed consent from the patients was obtained.

The teeth were randomly categorized into three groups having 20 teeth in each. They were further divided into two subgroups equally, serving as control and test samples. All the samples were sectioned using low speed (2500–3000 rpm) and water-cooled diamond disc attached to contra-angle handpiece along the long axis of the tooth in the mesiodistal direction.[23] The control samples were not subjected to any polishing procedure, while the test samples were polished with three different methods. After preparation of the samples, the test group samples were polished with polishing paste (slurry prepared by mixing sodium bicarbonate, which was used for air polisher with water)/or air abrasive powder for 15 s. After the polishing procedures were performed, the samples were thoroughly washed with distilled water and stored in normal saline-filled containers. The samples were equally distributed into three categories:

Group 1: 10 test samples each of enamel and cementum were polished for 15 s with bristle brush and polishing paste attached to the low-speed contra-angle handpiece in a circular motion

Group 2: 10 test samples each of enamel and cementum were polished for 15 s with rubber cup and polishing paste attached to the low-speed contra-angle handpiece in a circular motion

Group 3: 10 test samples each of enamel and cementum were polished for 15 s with air polisher using sodium bicarbonate powder.

The polishing procedure of the samples was performed by one operator (Z.C.), and the samples were analyzed with scanning electron microscopy (Carl Zeiss EV040 USA) by a trained SEM interpreter of photomicrographs at Advanced Instrumentation Research Facility (AIRF) of Jawaharlal Nehru University (JNU), New Delhi, India.

Scanning electron microscopy – Sample preparation

The samples were mounted on metal stubs and dried in a silica gel vacuum desiccator. They were sputter coated with gold and examined under SEM. The micrographs of cementum and enamel surfaces were obtained at ×1000 magnification, at 20.0 KV voltage, 25 mA current and with a eucentric sample stage.[23]

The photomicrographs were assessed on the basis of their surface conditions and judged according to the following criteria:

Roughness criteria

Enamel surface:[24]

No abrasion: Smooth normal enamel

Mild abrasion: Few micropits or prism ends (ameloblastic pits) visible between perikymata lines

Severe abrasion: Distinct perikymata lines, many prism ends and/or micropits visible on the whole surface, occasional fracturing of perikymata edge.

Root/cementum surface:[25]

Smooth surface without marks from instrumentation

Moderately smooth, but some surface pitting or tearing noted

Rough surface. Gouges, tearing, and uprooted debris present.

Both the enamel and cementum samples of the test and control groups were also evaluated on the basis of debris/plaque/smear layer presence (P) or absence (A) and were scored accordingly.

The data obtained was statistically analyzed by Fisher's exact test. P < 0.05 is considered statistically significant, with <0.001 considered highly significant and >0.05 considered as not statistically significant.

RESULTS

An in vitro study was conducted to evaluate and compare the microtopographic changes of the enamel and cementum surfaces using a bristle brush, rubber-cup, and air-polishing device by SEM under the magnification ×1000.

The overall results showed that polishing decreased the surface roughness caused by root planing along with a reduction in debris on enamel and cementum surface. Polishing with bristle brush showed less surface roughness when compared to air polisher at P = 0.58, P = 0.03 for enamel surface and P = 0.03, P = 0.21 for cementum surface, respectively. The surface roughness was reduced considerably by rubber cup as compared to air polisher at P = 0.99, P = 0.03 for enamel surface and P = 0.003, P = 0.21 for cementum surface, respectively, and was statistically significant.

SEM photomicrographs demonstrated changes in microtopography of enamel and cementum surfaces of the three groups in Figures 1–3 for surface roughness and debris before and after polishing.

Figure 1

Scanning electron microscope micrographs of the tooth surface changes caused by bristle brush. The enamel and cementum surface before (a and c) and after (b and d) treatment, respectively. Note the smear layer/debris (black arrow) and surface roughness/abrasion (white arrow) on the tooth surface. On comparison, (a) and (b) show mild abrasion and cleaner enamel surface after (b) treatment and; (c) and (d) shows a cleaner and smother cemental surface after (d) treatment

Figure 3

Scanning electron microscope micrographs of the tooth surface changes caused by air polisher. The enamel and cementum surface before (a and c) and after (b and d) treatment, respectively. Note the smear layer/debris (black arrow) and surface roughness/abrasion (white arrow) on the tooth surface. On comparison, (a) and (b) show an increase in enamel surface abrasion and debris after (b) treatment and; (c) and (d) shows a heavy smear layer with the eroded cemental surface after (d) treatment

Scanning electron microscope micrographs of the tooth surface changes caused by rubber cup. The enamel and cementum surface before (a and c) and after (b and d) treatment, respectively. Note the smear layer/debris (black arrow) and surface roughness/abrasion (white arrow) on the tooth surface. On comparison, (a) and (b) show a smoother and cleaner enamel surface after (b) treatment and; (c) and (d) shows a cleaner and smother cemental surface after (d) treatment

Tables 1 and 2 depict scores of bristle brush, rubber cup, and air-polisher group on the basis of enamel surface roughness and debris of both control and test polishing, respectively.

Table 1

Scores of enamel surface roughness of bristle brush (Group 1), rubber cup (Group 2), and air polisher (Group 3)

Table 2

Score of debris on enamel surface of bristle brush (Group 1), rubber cup (Group 2), and air polisher (Group 3)

Tables 3 and 4 illustrate control and test polishing scores of cementum surface roughness and presence of debris, respectively.

Table 3

Scores of cementum surface roughness of bristle brush (Group 1), rubber cup (Group 2), and air polisher (Group 3)

Table 4

Score of debris on cementum surface of bristle brush (Group 1), rubber cup (Group 2), and air polisher (Group 3)

Intergroup comparisons of enamel samples of a bristle brush, rubber cup, and air-polisher group are specified in Figure 4. Rubber cup demonstrates the most effective polishing system followed by bristle brush, and air polisher proves to be the least effective on the enamel surface. Figure 5 illustrates that rubber cup and bristle brushes are equally efficient polishing systems followed by air polisher in removing debris from the enamel surface.

Figure 4

Intergroup analysis of enamel surface roughness

Figure 5

Intergroup analysis of debris on the enamel surface

Figures 6 and 7 illustrate intergroup comparisons of cementum samples of a bristle brush, rubber cup, and air-polisher group, showing that rubber cup is the most efficient polishing system followed by bristle brush and air polisher on cementum in terms of reducing surface roughness and also in removing debris from the surface.

Figure 6

Intergroup analysis of the cementum surface roughness

Figure 7

Intergroup analysis of debris on the cementum surface

DISCUSSION

Routine tooth polishing is an integral part of clinical practice as it assists in the elimination of stains and/or dental plaque biofilm. The main purpose of polishing is to remove biofilm, stain, and pellicle present on the enamel and cementum surface to provide the smoothest surface possible. It has been stated that scaling and root planing alone cannot reduce the surface roughness to that extent as it could be achieved in combination with polishing.[235]

Studies have shown that scalers, curettes, and ultrasonic instruments are effective in removing subgingival plaque and calculus but does not produce a smooth tooth surface.[1526] This may influence the microbial colonization leading to an increase in dental plaque accumulation on the surface,[67] leading to the progress of periodontal disease.[6] Polishing of the tooth surface is being practiced to gain smoothness following instrumentation. There is a prevailing controversy as to polish or not to polish the tooth surface. Studies have demonstrated that polishing eliminates plaque[1011] and reduces bacterial accumulation,[10] achieving a smooth tooth surface.[12]

The present study was conducted to evaluate and compare the microtopographic changes on enamel and cementum surface subjected to polishing with three different polishing systems, i.e., bristle brush, rubber-cup, and air-polishing device by SEM under ×1000 magnification. Although polishing of crown/enamel has been studied in the past literature, there are a limited data available about polishing on root/cementum. Since the gingival recession and exposure of the root surface are commonly observed in the periodontal patient, it is mandatory to achieve a smooth surface of cementum for achieving optimum results of periodontal therapy. The present study demonstrates that rubber-cup polishing was better in gaining smoothness of cementum, which is similar to the results of a study conducted by Sylvia and Edward.[14]

Although polishing with rubber cup and paste is the most prevalent method practiced,[16] it is gradually being replaced by a novel air-powder polishing devices. It is believed to reach the surfaces that are inaccessible to a rotary device, although their actual efficacy in smoothing the enamel and cementum surfaces remains debatable.[16] The results obtained in the present study were in accordance with the studies conducted by Bailey and Phillips,[8] Kontturi-Närhi et al.,[24] Petersson et al.,[27] Han,[28] Agger et al.,[29] Castanho et al.,[30] and Sahrmann et al.,[31] demonstrating that air polisher increases the surface roughness as well as the debris on both enamel and cementum surfaces. The abrasiveness may be due to the shape of sodium bicarbonate powder particle and the high pressure of the air polisher the particles are blasted on the tooth surface. Sodium bicarbonate is a food-grade material, with a particle area of approximately 0.037496353 mm2/74 mcm and the Mohs' scale hardness number of 2.5, which is low in comparison to pumice (6–7), enamel (5–6), as well as cementum/dentin (3–4).[32] It has been shown that the shape of sodium bicarbonate particles is irregular with sharp edges,[3334] making the particles more abrasive, leading to tooth surface roughness.[8] It has been previously shown by George and Brinkmann[35] that increased pressure results in more abrasion and roughness, leading to tooth surface loss.[34] The air polisher is often used with an air setting of 80 psi, whereas the pressure applied in the case of rotary (bristle brush and rubber cup) polishing is approximately 20 psi as stated by Francis and Barnes.[36] Therefore, air-polishing device should be used with caution.

Galloway and Pashley[37] demonstrated the effects of the Prophy jet constant blast when directed at the enamel, cementum, and dentin for 5–60 s. They found that on the enamel surface there were no visible effects even after directing the spray for 60 s, but dentin and cementum surface showed substantial linear loss of structures even on an exposure for 5 s.[37] Similar results for cementum surface were seen in the present study. In contrast, studies conducted by Leknes et al.[38] and Patil et al.[39] demonstrated that polishing with air polisher reduces surface roughness as well as debris on both enamel and cementum surfaces. They observed that polishing with air polisher and rubber cup has comparable results. However, the present SEM study demonstrated that both surface roughness and debris on enamel and cementum were increased with air polisher when compared with a bristle brush or rubber cup. While assessing the effectiveness of air-polishing and rubber-cup polishing for bacterial plaque and stain removal, Braun et al. demonstrated that either method is equally effective.[40] They reported that both methods caused gingival trauma. Weaks et al.[41] have studied the efficiency of Prophy Jet® along with its effects on marginal gingiva and showed that the soft-tissue trauma was not significant. Petersilka GJ et al. have reported that exposed cementum and dentin structures are vulnerable to loss with the use of air-powder polisher.[4243] It is believed that polishing removes the outer layer of tooth enamel, which takes a period of 3 months to rebuild the fluoride-rich layer; hence, selective polishing is recommended. Various clinical and in vitro studies have been conducted on different methods of polishing using a range of polishing agents with varying results.

Tooth polishing appears to be easy, simple, and even mundane, which involves many interdependent complex issues and, if not properly performed, may cause unnecessary harm.[13] The risks versus benefits should be carefully weighed, and clinicians need to critically evaluate the effects of polishing while providing care.

The present SEM was conducted to evaluate and compare three different types of polishing methods and found that the rubber cup and bristle brush produced smoother enamel and cementum surface, with a significant reduction in debris when compared to air polishing. Results of the study indicate that although polishing with a rubber cup and bristle brush was effective, rubber cup proved to be a more efficient method of polishing than bristle brush and air polishing.

Future long-term studies should be conducted in the direction of comparing the efficiency of the various polishing agents in terms of removing debris and producing a smooth surface without any side effects or other adverse reactions causing minimal trauma to the soft tissues, considering patient's acceptance and conditions.

CONCLUSION

Regular mechanical elimination of bacterial plaque is fundamental for maintaining periodontal health. Various periodontal procedures lead to surface roughness which in turn causes the accumulation of plaque and inflammation of gingiva. Different methods of tooth polishing have been tried and tested with varying results. Although coronal polishing has been studied extensively, the efficiency of various methods of polishing on cementum needs to be considered as exposure of root is a common finding in the periodontal patient.

Based on the results of the present study, it can be concluded that polishing with rubber cup is the most effective method in producing smooth tooth surface and removal of debris from enamel and cementum when compared to polishing with a bristle brush or air polisher.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.