|Year : 2017 | Volume
| Issue : 3 | Page : 153-159
Evaluation of enamel surfaces following interproximal reduction and polishing with different methods: A scanning electron microscope study
Eenal Bhambri1, J. P. S. Kalra2, Sachin Ahuja1, Gautam Bhambri3
1 Department of Orthodontics, Surendera Dental College, Sri Ganganagar, Rajasthan, India
2 Department of Orthodontics, Guru Nanak Dev Dental College, Sunam, Punjab, India
3 Department of Oral Pathology and Microbiology, Surendera Dental College, Sri Ganganagar, Rajasthan, India
|Date of Web Publication||7-Aug-2017|
Department of Orthodontics, Surendera Dental College, H.H. Gardens, Powerhouse Road, Sri Ganganagar - 335 001, Rajasthan
Source of Support: None, Conflict of Interest: None
Background: Interproximal reduction was introduced as an alternative to tooth extraction in patients with mild-to-moderate crowding, the beneficial outcomes of interdental reduction have been well documented, but nevertheless, possible detrimental effects on enamel have also been an issue of debate. Interproximal reduction generates the formation of grooves and valleys creating plaque retentive areas, predisposing teeth to caries, and periodontal disease. Various proximal stripping techniques, it is postulated, produce varying grades of roughness of the enamel surface; it is in this area that the research in this paper was focused. Aim: The aim is to evaluate enamel surface roughness after various interproximal reduction and polishing methods. Materials and Methods: 16-blade tungsten carbide bur, diamond disc, diamond-coated metal strip, fine Sof-Lex disc, and fine diamond bur were used for interproximal reduction and polishing on extracted human premolars. The specimens were then evaluated under scanning electron microscope (SEM) and surface plots of images were made using Image J software. Statistical Analysis: The data obtained were subjected to ANOVA and posthoc multiple tests. Results: Under the SEM, all interproximal reduction protocols resulted in roughened and grooved enamel surfaces. The use of diamond-coated metal strip followed by polishing with fine Sof-Lex disc created surfaces that were reasonably smooth. Conclusions: The enamel surfaces after reduction with diamond-coated metal strip and polishing by fine Sof-Lex disc (group F) were the smoothest.
Keywords: Image J software, interproximal reduction, scanning electron microscope
|How to cite this article:|
Bhambri E, Kalra J, Ahuja S, Bhambri G. Evaluation of enamel surfaces following interproximal reduction and polishing with different methods: A scanning electron microscope study. Indian J Dent Sci 2017;9:153-9
|How to cite this URL:|
Bhambri E, Kalra J, Ahuja S, Bhambri G. Evaluation of enamel surfaces following interproximal reduction and polishing with different methods: A scanning electron microscope study. Indian J Dent Sci [serial online] 2017 [cited 2018 Feb 25];9:153-9. Available from: http://www.ijds.in/text.asp?2017/9/3/153/212389
| Introduction|| |
The extraction-nonextraction debate, ongoing for almost 100 years, has often been based more on supposition than fact. The pendulum has swung back and forth over the years between an overabundance of extraction cases and then the same with nonextraction cases. Although the percentage of patients with dished in profiles after extraction treatment was found to be very small, but elective tooth extraction is often an emotive issue for the patient. This has led this pendulum to swing back into nonextraction mode in recent years and to the increasing tendency for nonextraction therapies such as proximal stripping, lateral, anterior and posterior expansion of the dentition, molar distalization, and space regainers.
Interdental reduction, reproximation, recontouring, slenderizing, coronoplastia, and Hollywood trim are some of the various terms used to describe interproximal reduction. The various indications of interdental stripping include correction of tooth size discrepancies, creation of space to correct malocclusions, enhancement of retention and stability, simulation of stone-age man's proximal attrition, and improvement in esthetics and shape of teeth.
There have been multiple opinions on the actual amount of tooth structure to be removed, however, a general consensus existing among orthodontists is that 0.3–0.5 mm of enamel can be removed from each proximal surface without jeopardizing its health.
Various methods used for interproximal reduction are handheld or motor-driven abrasive strips, handpiece-mounted abrasive discs, chemical stripping, and air-rotor stripping. Each method has its own disadvantages as abrasive strips and discs are limited to minor enamel reduction and air-rotor stripping can create substantially more space than these methods but at the expense of enamel roughness.
The beneficial outcomes of interdental reduction have been well documented, but nevertheless, possible detrimental effects on enamel have also been an issue of debate.,, Proximal reduction generates the formation of grooves and valleys mainly in the cervical region of the teeth creating plaque retentive areas. These abraded enamel surfaces have been reported to be more prone to demineralization than intact surfaces under in vitro conditions. This has been attributed in part to the removal of the external, less soluble fluorapatite-rich enamel layer. Studies by Radlanski et al. and Crain and Sheridan  have shown that these plaque retentive areas formed lead to caries. El-Mangoury et al. has reported that proximal enamel reduction does not expose the enamel to pathological changes that could lead to caries but result in demineralization followed by remineralization within 9 months of stripping. There appears to be a dispute over the potential predisposition of stripped enamel to caries.
Polishing with finer abrasives is necessary to achieve a subsequent reduction of grooves caused by coarse abrasives. Polishing the enamel after reduction does not help achieve the same morphological characteristics as with intact enamel but various attempts have been made to achieve a smooth surface. Polishing can be done with fine grit diamond bur, Sof-Lex discs, pumice media, and use of proximal sealant after interproximal reduction. Short-term use of fluoridated dentrifice or topical gel also reduces the penetration of the lesion but not to the extent of a nontreated unabraded surface.
Various interproximal reduction techniques, it is postulated, produce varying grades of roughness of the enamel surface; it is in this area that the research in this study was focused.
Aim and objective
This study was undertaken to compare enamel surfaces following interproximal reduction and polishing with different methods with the help of scanning electron microscope (SEM).
| Materials and Methods|| |
Based on 30% CV with α = 0.05 and δ = 0.2, power of the study = 85% and 90% confidence interval, the sample size calculated was 98. Hence, 98 caries-free human maxillary premolars extracted for therapeutic reasons were included in this study. The extracted teeth were rinsed in water to remove any blood or tissue remnants and stored in deionized water  until needed. They were randomly divided into 7 groups of 14 teeth each. Each group was mounted in plaster and was aligned in an arch form with color coding for the purpose of identification. Of these 14 teeth in contact, 12 teeth provided their distal surfaces for interproximal reduction.
Each group was subjected to proximal reduction with one of the following methods [Figure 1] and [Figure 2]:
|Figure 1: Interproximal reduction with various methods; (a) use of 16-blade tungsten carbide bur (b) use of diamond disc (c) use of diamond-coated metal strip|
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|Figure 2: Polishing with various methods; (a) use of fine Sof-Lex disc (b) use of fine diamond bur|
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- Group A (White): Control group; no interproximal reduction was performed
- Group B (Black): Interproximal reduction with 16-blade tungsten carbide bur and polishing by means of fine Sof-Lex disc
- Group C (Turquoise): Interproximal reduction with 16-blade tungsten carbide bur and polishing by means of fine diamond bur
- Group D (Red): Interproximal reduction with diamond disc and polishing by means of fine Sof-Lex disc
- Group E (Green): Interproximal reduction with diamond disc and polishing by means of fine diamond bur
- Group F (Yellow): Interproximal reduction with diamond-coated metal strip and polishing by means of fine Sof-Lex disc
- Group G (Navy blue): Interproximal reduction with diamond-coated metal strip and polishing by means of fine diamond bur.
Groups B and C involved the use of the tungsten carbide bur no. H133 F (Komet) with 0.1 mm safe end tip, tapered shape, 9 mm length, and 16 blades and each bur was used on maximum 2 surfaces.
In Groups D and E, a double-sided Horico diamond disc of 15 mm diameter (Hopf, Ringleb and Co., Berlin, West Germany) was used. The disc uses diamond abrasive particles of approximately 45 μ diameter and each disc was used on a maximum of 12 surfaces.
Groups F and G involved the use of 4 mm wide, fine grit single-sided Horico diamond-coated metal strips (Hopf, Ringel and Co., Berlin, West Germany) with abrasive particles of approximately 30 μ diameter. These strips were mounted in mini stripper and each strip was used on one surface.
Further, polishing was done with 3M 13 mm Sof-Lex discs no. 4931F and fine diamond bur no. 859 F, 0.1 mm safe end tip and tapered shape (Komet) for 20 s each. A new disc with adequate water spray was used for every tooth because the surface structure of a Sof-Lex disc deteriorates rapidly.
In all groups, interproximal reduction included water cooling, similar pressure on the instruments and reduction of 0.3 mm, which was measured with the help of incremental thickness gauge [Figure 3]. Polishing time was standardized for 20 s.
|Figure 3: Use of incremental thickness gauge to measure interproximal space|
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After completion of the interproximal reduction and polishing procedures, the teeth were removed, sectioned, thoroughly rinsed with acetone, and subjected to ultrasonic cleansing in distilled water for 5 min to remove the remnants of abrasives. The specimens were then dehydrated in ascending degrees of alcohol.
After the dehydration process, samples were taken out, air-dried, and placed in a dessicator for 24 h. The dried specimens were mounted on aluminum stubs, sputter coated with gold for 2 min in a fine coat with JEOL Ion Sputter jfc-1100 Sputtering Device [Figure 4],[Figure 5],[Figure 6].
|Figure 6: Teeth coated with gold to be examined under scanning electron microscope|
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The mounted specimens were observed under SEM using model JEOL JSM-6100 operated at 20 Kv and photomicrographs were taken at center of each test surface at ×1000 magnification.
Photomicrographs were observed by five observers independently and were further converted to gray scale for application to the digital image processing software (Image J 1.43 version) Java based image processing programme developed at the National Institutes of health. Surface plots of the images were made by the software for subjective analysis of the various stripping techniques and these were then scored using a modification of the surface roughness index:
0 - Perfect surface, no peaks
1 - Satisfactory surface, fine peaks
2 - Acceptable surface, some low and some high peaks
3 - Imperfect surface, several distinct high peaks
4 - Unacceptable surface, very high peaks distributed all over the plot.
The assessment procedure of the surface plots was carried out by five-independent orthodontists who had no knowledge of which plot represented the various surface studied. To rule out interexaminer variability, means of all values were taken [Table 1].
|Table 1: Comparison of mean surface roughness values of various groups using one-way ANOVA test|
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The data thus obtained were compiled and put to one-way ANOVA and posthoc multiple statistical tests [Table 2].
|Table 2: Comparison of one group with other groups using posthoc multiple test|
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| Observations and Results|| |
Under the SEM, all interproximal reduction protocols resulted in roughened and grooved enamel surfaces.
Photomicrographs of control group (Group A) showed enamel surfaces that were not completely smooth. Small number of furrows and irregularities were distributed over the entire surface with rounded rims and interspersed with smooth areas. Heads of the enamel prisms could be seen on the surfaces [Figure 7]a.
|Figure 7: Photomicrograph (a) and surface plot (b) of respective representative of Group A|
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Interproximal reduction with tungsten carbide bur and polishing with fine Sof-Lex disc (Group B) created a small number of furrows distributed over the entire surface and interspersed with rough areas [Figure 8]a.
|Figure 8: Photomicrograph (a) and surface plot (b) of respective representative of Group B. Photomicrograph (c) and surface plot (d) of respective representative image of Group C|
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The use of fine diamond bur after reduction with tungsten carbide bur (Group C) produced deep furrows that were distributed irregularly over the entire surface and interspersed with notably rough areas [Figure 8]c.
After interproximal reduction with diamond disc and polishing with fine Sof-Lex disc (Group D), the surface appeared finely rough. Although the use of fine Sof-Lex disc appeared to reduce the rough appearance of the reduced surface, it still exhibited the underlying appearance of the stripping procedure [Figure 9]a.
|Figure 9: Photomicrograph (a) and surface plot (b) of respective representative of Group D. Photomicrograph (c) and surface plot (d) of respective representative of Group E|
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Diamond disc reduction and polishing with fine diamond bur (Group E) produced a rough surface in which furrows could be seen crossing at different depths. The surface exhibited distinct deep regular parallel grooves [Figure 9]c.
The use of diamond-coated metal strip followed by polishing with fine Sof-Lex disc (Group F) created surfaces that were reasonably smooth. The enamel surface appeared crossed by few fine and shallow furrows alternating with well-polished areas [Figure 10]a.
|Figure 10: Photomicrograph (a) and surface plot (b) of respective representative of Group F. Photomicrograph (c) and surface plot (d) of respective representative of Group G|
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Diamond-coated metal strip reduction and polishing with fine diamond bur (Group G) created many fine furrows distributed over the entire surface and interspersed with some smooth areas [Figure 10]c.
To be more closely compared, surface plots for the respective photomicrographs were made by Image J software 1.43 version [Figure 7],[Figure 8],[Figure 9],[Figure 10] and these surface plots were further scored by 5 orthodontists using the index.
Group A (control group) on comparison with Groups B, C, E, and F showed statistically significant smooth surfaces (P < 0.001**) and comparison with Groups D and G showed insignificant results in terms of smoothness [Table 2].
Groups B and C on comparison with Groups A, D, F, and G showed statistically significant rough surfaces (P < 0.01*) and comparison with Group E showed insignificant results. Groups B and C, when compared among themselves, showed significant results indicating that Sof-Lex disc is better than fine diamond bur for polishing [Table 2].
Group D on comparison with Groups B, C, and E produced statistically significant smoother surfaces and when compared with Group F produced significantly rough surfaces (P < 0.001**) [Table 2].
Group F on comparison with Groups A, B, C, D, E, and G showed statistically significant smoother surfaces (P < 0.001**). The method produced statistically significant smoother surfaces than the control group as well [Table 2].
Group G when compared with Groups B, C, and E showed statistically significant smooth surfaces (P < 0.001**) and there was no significant difference between roughness scores of Groups G, A, and D [Table 2].
| Discussion|| |
Interproximal enamel reduction, also known as interdental stripping or slenderizing is a well-known technique that is commonly applied in orthodontic treatment. Over the years, wide array of methods have been employed to reduce the enamel in a controlled manner with minimum substrate alterations. Researchers have confirmed with many studies that all these methods, in general, leave a rough surface and polishing should follow every stage of interproximal reduction.
In the present study, 0.3 mm of enamel was reduced from each proximal surface and this was ensured by the use of incremental thickness gauge as advised by Sheridan et al. Chudasama and Sheridan. Following conservative reduction and polishing with different techniques and materials, enamel surfaces were evaluated by SEM. SEM has been used by many researchers to evaluate enamel surface roughness.,,,,,
The particular advantage of the SEM in studying the enamel surface is its resolution and large depth of field, which provides an excellent means of topographic assessment.
The type of scoring (0–4) used in this study has been used very successfully by various researchers and clinicians.,,
The SEM analysis revealed that the untreated enamel surfaces have a rough uneven appearance due to the presence of the perikymata with equal proportions of crests and troughs [Figure 7]a and [Figure 7]b. The findings are consistent with the findings of Piacentini and Sfondrini, Chirla et al., Lucchese et al., and Vickers.
It was apparent from the observations of SEM that all tested enamel reduction methods altered the surface of the enamel significantly by producing furrows and grooves. Changes in enamel morphology due to interproximal reduction methods have also been reported by Piacentini and Sfondrini, Arman et al., Joseph et al., Lucchese et al., Danesh et al., and many others.
In our study, polishing with fine Sof-Lex disc after 16-blade tungsten carbide bur led to considerable smoothening of furrows but was not able to completely eliminate the furrows. SEM photomicrographs of the enamel surface after reduction with 16-bladed tungsten carbide bur and polishing with fine diamond bur introduced new grooves and thus a smooth surface could not be attained [Figure 8]a,[Figure 8]b,[Figure 8]c,[Figure 8]d. The observations resembled with the results of the study conducted by Piacentini and Sfondrini, Sheridan and Ledoux, and Chirla et al.
SEM photomicrographs of the enamel surface reduced with diamond disc and polishing with Sof-Lex discs produced the surface finely rough (mean roughness score 2.56) [Figure 9]a,[Figure 9]b,[Figure 9]c,[Figure 9]d. The use of Sof-Lex disc tried to reduce the roughness left by diamond disc but underlying appearance of the interproximal reduction procedure still remained. Finishing with fine diamond bur after reduction with diamond disc produced rough surface in which furrows crossed at different depths (mean roughness score 3.42). The findings are consistent with the findings of Piacentini and Sfondrini.
In our study, diamond-coated metal strip followed by Sof-Lex disc (Group F) produced the smoothest surface (mean roughness score 1.58) [Figure 10]a,[Figure 10]b,[Figure 10]c,[Figure 10]d. This could be attributed to the abrasive particle size of diamond-coated metal strip (30 μm). Similar results were given by Arman et al. who found out that interproximal reduction with metal strips followed by polishing with fine Sof-Lex discs produced the smoothest enamel surface.
On the whole, our results demonstrated that smoother enamel surfaces were obtained when Sof-Lex polishing discs were used after interproximal reduction. This could be due to the abrasive points of Sof-Lex discs which are less rigid, fine textured, and less porous compared to fine diamond abrasive points. These findings are in concurrence with the findings of Zhong et al. who concluded that polishing with 3 Sof-Lex discs produced surfaces smoother than untreated enamel. Piacentini and Sfondrini  and Chirla et al. too reported that with the use of Sof-Lex discs for polishing of enamel, it was possible to eliminate the furrows left by interproximal reduction methods and attain well-polished surfaces.
On comparing the SEM photomicrographs of the enamel surface reduced and polished with various methods, it was observed that diamond disc followed by fine Sof-Lex (Group D) and tungsten carbide bur followed by fine Sof-Lex (Group B) produced rough surfaces than diamond-coated metal strip followed by fine Sof-Lex discs (Group F). This can be attributed to the fact that diamond disc had more abrasive particle size (45 μm) than diamond-coated metal strip (30 μm) and tungsten carbide burs operated at high speeds produced deep scratches which could not be removed by polishing. Furthermore, the quantity and quality that was removed was controlled by manually held diamond-coated metal strips. Similar findings were reported by Piacentini and Sfondrini  who found out that it was not possible to eliminate, with normal polishing and cleaning methods, the furrows left on the enamel by diamond burs, diamond discs, and 16-blade tungsten carbide burs.
The enamel surface after the use of diamond-coated metal strip followed by fine Sof-Lex disc when compared with normal untreated enamel produced smoother surface as also reported by Zhong et al.
According to Rosenblum  and Craig et al., the main factors which affect enamel reduction are particle size of the abrasive, particle shape of the abrasive, lubrication, and the pressure of the abrasive agent against the surface being abraded or polished.
The last two factors were controlled in the study and the first two factors are controlled by the choice of the product used. The larger and more irregular shaped the abrasive particle, the coarser and deeper will be the scratches, though the quicker the surface will be reduced. In this study, it was observed that though the diamond disc reduced the proximal surface fast than diamond strip but it left the rough surface even after polishing due to large abrasive particles.
Overall, our findings demonstrated that, out of the tested methods, interproximal reduction with diamond-coated metal strips followed by polishing with Sof-Lex discs (Group F) produced the smoothest enamel surface. Although polishing with Sof-Lex disc achieved well-polished areas (smoother than untreated enamel surfaces), nevertheless, compared with intact enamel, other experimental groups had rougher surfaces with many furrows and grooves. Thus, hygiene instructions, including interproximal plaque control and prophylactic measures such as topical fluoride application, must be given after interdental stripping to prevent undesirable sequelae of the procedure.
| Conclusions|| |
From the study, following conclusions were drawn:
- The enamel surfaces after stripping with diamond-coated metal strip and polishing by fine Sof-Lex disc (Group F) were the smoothest
- Sof-Lex discs were more efficient than fine diamond burs in polishing the stripped enamel surfaces.
In conclusion, given the current emphasis on nonextraction treatment in orthodontics today, stripping is a technique that can increase space but must be performed with the best possible finishing of the interproximal enamel surface that meets the biological requirements of the oral cavity.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2]