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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 10  |  Issue : 2  |  Page : 67-76

Scanning electron microscope evaluation of morphological changes in dental hard tissue after root resection in apicoectomy by erbium, chromium:yttrium-scandium-gallium-garnet laser and #702 TC Bur: Part II


Department of Conservative Dentistry and Endodonics, Dr. R Ahmed Dental College and Hospital, Kolkata, West Bengal, India

Date of Web Publication29-Dec-2016

Correspondence Address:
Prashant Dadasaheb Babar
Department of Conservative Dentistry and Endodontics, Dr. R. Ahmed Dental College and Hospital, 142/A, A.J.C. Bose Road, Kolkata - 700 014, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2321-1385.197019

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  Abstract 

Context: In Part I of this in vitro SEM study, we have discussed the effect of root resection tools on root end in terms of Cemental damage, Dentin Surface texture and Dentinal Cracks. This part (Part II) will focus on effect of root resection tools on root end in terms of Debris, smear layer, Dentinal tubules, Intertubular Dentin and Root Dentin - Gutta percha interface. Aims: To compare surface characteristics and morphological changes in erbium, chromium:yttrium-scandium-gallium-garnet (Er;Cr:YSGG) laser and bur-resected root ends in apicoectomy. Settings and Design: 5 W, 20 Hz, 50% air, 100% water, 300 mJ. Subjects and Methods: Forty freshly extracted human central incisors treated endodontically. Gutta-percha (GP) obturated teeth were resected apically 3 mm with 0° bevel. Twenty samples were resected with #702 TC Bur while the rest half were resected with Er,Cr:YSGG laser with 600 µm sapphire tip. All the samples were examined for debris, smear layer dentinal tubules, intertubular dentin and interface of GP, and root dentin on resected root surface under surgical operating microscope at ×16. Then, samples were fixed, dehydrated, and gold sputtered for observation under scanning electron microscope (SEM). Statistical Analysis Used: Data obtained were subjected to statistical analysis using Chi-square/Fischer exact test whenever required. Results: SEM observation revealed the absence of debris and smear layer with clean cut surface and patent dentinal tubules with exposed intertubular collagen, less gap (mean 9.95 µm), and least damage to apical adaptation of GP to root dentin walls in Er,Cr:YSGG-laser-resected root surface; while bur-resected samples revealed irregular, rugged root surface covered with debris, smear layer clogged dentinal tubules more gap (mean 20.98 µm) and damage to interface at GP, and root dentin walls. Conclusions: Er,Cr:YSGG-lased root surface provides better surface morphology, more conducive surface for regeneration of periodontium as compared to bur root resection.

Keywords: #702 TC Bur, collagen, dentinal tubules, erbium, chromium:yttrium-scandium-gallium-garnet laser, morphological change, scanning electron microscope, smear layer


How to cite this article:
Babar PD, Adhikari HD. Scanning electron microscope evaluation of morphological changes in dental hard tissue after root resection in apicoectomy by erbium, chromium:yttrium-scandium-gallium-garnet laser and #702 TC Bur: Part II. J Dent Lasers 2016;10:67-76

How to cite this URL:
Babar PD, Adhikari HD. Scanning electron microscope evaluation of morphological changes in dental hard tissue after root resection in apicoectomy by erbium, chromium:yttrium-scandium-gallium-garnet laser and #702 TC Bur: Part II. J Dent Lasers [serial online] 2016 [cited 2017 Sep 20];10:67-76. Available from: http://www.jdentlasers.org/text.asp?2016/10/2/67/197019


  Introduction Top


During the last 20 years, endodontics has seen a dramatic shift in the application of periradicular surgery. [1] Periradicular surgery is indicated [2],[3] in cases of failure of nonsurgical retreatment for at least two times and when a biopsy is necessary. Surgical options should be considered only when better results cannot be achieved by nonsurgical treatment.

With the advent of more refined techniques and more biologically acceptable retrofilling materials, [4],[5],[6],[7],[8] more favorable postoperative prognosis has been observed, as well as due to improved generation of periradicular tissues. The resection by different types of burs has been practiced. The #702 TC Bur is used by most of the operators as it produces smoother surface at cut root end among the various burs. [9] In addition, the high-speed burs along with laser irradiation have been used for apical root resection [4],[10] because of its proven antibacterial and biostimulating effects.

Recently, erbium lasers have gained popularity in this field because of so many advantages. The first attempt to use a laser in endodontic surgery was performed by Dr. Weichman at the University of Southern California; he used CO 2 laser. [11] CO 2 laser produces scars due to thermal damage causing delayed healing. Hence, CO 2 laser use is abandoned nowadays. [12] All erbium lasers share a common characteristic, of an affinity of their wavelengths to be highly absorbed by water, hydroxyapatite, and collagen. [13] The mechanism of dentin removal by this laser is called a "thermo-mechanical process", in which the emitted laser light is absorbed by water within hydroxyapatite [14] and then explosion takes place due to water vaporization causing separation of crystals.

Erbium, chromium:yttrium-scandium-gallium-garnet (Er, Cr:YSGG) pulsed laser with wavelength of 2.78 μm has been found to be useful in endodontic surgery for root-end resection, root-end cavity preparation, hemostasis, and sterilization of the root apex and surrounding tissue. [15],[16]

Compared to bur resection, laser resection has many advantages. Laser apicoectomized root end not only exhibits smoother and crackles surface [17] with less cemental damage (discussed in part I) but also provides dentin surface free of debris and smear layer, with patent dentinal tubules having exposed intertubular collagen. [18],[19] There is the absence of charring carbonization or any sort of thermal damage. [20],[21] All these contribute in achieving healing by regeneration at the root end. In addition, it also been seen that laser resection provides less damage to obturated gutta-percha (GP) and exhibits less gap at the GP-dentin interface. [17]

Purpose of study

Keeping in this view, the present in vitro study was designed to evaluate the morphological changes (such as debris, smear layer, dentinal tubules, surface of root end GP, interface of root dentin wall, and GP) in #702 TC Bur and Er,Cr:YSGG laser-resected root ends in apicoectomized teeth under surgical operating microscope (SOM) and scanning electron microscope (SEM).


  Subjects and Methods Top


Forty human central incisors of average size, freshly extracted for periodontal cause were selected. Informed consent was obtained from the patients, and Institutional Ethical Committee and Review Board, Dr. R Ahmed Dental College and Hospital, gave ethical clearance for this study. Teeth were stored in normal saline after cleaning. Sample exclusion criteria were incompletely formed apex, resorbed roots, evidence of crack and fracture, calcified canals, and canal curvature.

Endodontic treatment was undertaken, GP obturated teeth were decoronated so that the length of samples remains fixed at 10 mm required for SOM observation. Apical 3 mm was then resected with 0° bevel. [22],[23],[24] Twenty samples were resected with #702 TC Bur while rest 20 were resected with Er,Cr:YSGG laser with parameters 5 W, 20 Hz, 50% air, 100% water, 300 mJ output energy with 600 μm sapphire tip.

All the 40 samples were examined under SOM at ×16. Then, the samples were fixed with Karnovsky's fixative, dehydrated in ascending series of 25%, 50%, 75%, and 100% ethanol, dried with critical point dryer using liquid CO 2 and sputter coated with gold ion sputter device for observation under SEM at different magnifications. Data obtained after SOM and SEM observation were subjected to statistical analysis using Chi-square/Fischer exact test and Kruskal-Wallis test whenever required. For statistical analysis, data were entered into a Microsoft Excel spreadsheet and then analyzed by analysed by Epi Info software, SPSS 10.0.1 and GraphPad Prism version 5 (GraphPad Software, Inc. 7825 Fay Avenue, Suite 230 La Jolla, CA 92037 USA). The median and the interquartile range have been stated for numerical variables that are not normally distributed. Student's independent sample's t-test was applied to compare normally distributed numerical variables between groups; unpaired proportions were compared by Chi-square test or Fischer's exact test, as appropriate. Once a t value is determined, a P value can be found using a table of values from Student's t-test distribution. If the calculated P value is below the threshold chosen for statistical significance (usually the 0.10, the 0.05, or 0.01 level), then the null hypothesis is rejected in the favor of the alternative hypothesis.

The objective of the present study was to compare, the surface characteristics of root ends (such as debris, smear layer, dentinal tubules, surface of root end GP, interface of root dentin wall and GP) resected with #702 TC bur and Er,Cr:YSGG laser by light microscopy and scanning electron microscopy.


  Results Top


Debris

Under SOM, in bur root resection, no debris was detected in 12 (60%) samples [Figure 1], rest 8 samples showed debris [Figure 2] while in laser root resection, no debris was detected in all 20 samples [Figure 3]a and b]. The difference between both the groups is statistically significant [P ≤ 0.001, [Table 1] and Graph 1].
Figure 1: Surgical operating microscope (16) - Bur-resected sample - no debris evident

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Figure 2: Surgical operating microscope (16) - Bur-resected sample - debris evident (arrows)

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Figure 3: (a and b) Surgical operating microscope (16) - Laser-resected sample - no debris evident on dentinal surface

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Table 1: Evaluation of debris


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Under SEM, in bur root resection, debris was detected in all 20 samples [Figure 4]a-c while in laser root resection showed no debris in 14 (70%) samples [Figure 5]a-c out of 20 samples. The difference between both the groups is statistically significant [P < 0.001, [Table 1] and Graph 2].
Figure 4: Scanning electron microscope microphotographs of bur-resected samples (a and b) low magnification debris seen (×25, ×50) (c) high magnification debris seen (×800)

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Figure 5: Scanning electron microscope microphotographs lased samples (a) low magnification no debris (×25), (b and c) high magnification no/negligible debris (×1520, ×2800)

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Smear layer

Under SOM, smear layer could not be detected in both bur and laser samples. Under SEM, in bur root resection smear layer was seen in all 20 samples [Figure 6]a and b while in laser root resection 14 (70%) samples [Figure 6]c and d] did not show any smear layer and in other 6 samples smear layer was seen at some places. The difference between both the groups is statistically significant [P < 0.001, [Table 2] and Graph 3].
Figure 6: Scanning electron microscope images under high magnification. (a and b) Bur root resection shows smear layer (×10,000, ×15,000) (c and d) laser root resection shows clean cut surface no or very less smear layer (×2000, ×5000)

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Table 2: Evaluation of smear layer


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Dentinal tubules

Under SOM, dentinal tubules could not be detected in both bur and laser groups. Under SEM, bur root resection showed open dentinal tubules only in 1 (5%) sample while rest 19 samples showed closed dentinal tubules [Figure 7]a and b. Laser root resection revealed open dentinal tubules in 16 (80%) samples [Figure 8]a and b out of 20 samples. At high magnification [Figure 9]a-c, exposed intertubular collagen is revealed due to evaporation of hydroxyapatite crystals. The difference between both the groups is statistically significant [P < 0.001, [Table 3] and Graph 4].
Figure 7: (a and b) Scanning electron microscope images of bur-resected samples reveals smear layer clogged dentinal tubules in 95% samples (×1600, ×1500)

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Figure 8: (a-2500 and b-1000) Scanning electron microscope images of laser-resected samples reveals no smear layer, patent dentinal tubules in 80% samples

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Figure 9: Scanning electron microscope images at high magnification showing (a) scaly appearance, (arrow) due to unequal ablation of dentin (×3000) (b) open dentinal tubules, whitish appearance (arrow) of peritubular dentin (×3000). (c) Protruding peritubular dentin and exposed collagen (arrow) (×12,000)

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Table 3: Evaluation of dentinal tubules


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Gutta-percha

Bubbling of gutta-percha

Bubbling is microglobular appearance of GP at cut root end. Bubbling of GP is probably the result of thermal effect of laser irradiation. [25]

Under SOM, bubbling of GP could not be detected in both bur and laser groups.

Under SEM, in bur root resection, bubbling of GP was not seen in all 20 samples [Figure 10]a while in 9 (45%) laser cut samples, bubbling of GP was observed [Figure 10]b and c. The difference between both the groups is statistically significant [P < 0.001, [Table 4] and Graph 5].
Figure 10: Scanning electron microscope images (a) bur root resection shows no bubbling of gutta-percha (×150), (b and c) laser root resction shows bubbling (arrows) (×400, ×360)

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Table 4: Evaluation of gutta-percha bubbling


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Smearing of gutta-percha

Smearing is drawing out of obturated GP in very thin sections. Under SOM, in bur-resected samples, no smearing of GP was detected in 6 (30%) samples [Figure 11]a while in rest of 14 samples, GP seems to be smeared out [Figure 11]b and c. In laser root resection, no smearing of GP was detected in 18 (90%) samples [Figure 12]a and b out of 20 samples. The difference between both the groups is statistically significant [P = 0.0001, [Table 5] and Graph 6].
Figure 11: Surgical operating microscope (16) - Bur resection (a) no smearing of gutta-percha, (b and c) smeared out gutta-percha seen (arrows)

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Figure 12: (a and b) Surgical operating microscope (×16) - Laser resction no smearing of gutta-percha seen

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Table 5: Evaluation of smearing out of gutta-percha


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Under SEM, in bur root resection, all 20 samples showed smearing of GP [Figure 13]a-c while in laser root resection, no smearing of GP was detected in 14 (70%) samples [Figure 14]a and b out of 20 samples. The difference between both the groups is statistically significant [P < 0.001, [Table 5] and Graph 7].
Figure 13: (a-c) Scanning electron microscope bur resection shows smearing (arrows) of gutta-percha (×100, ×150, ×100)

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Figure 14: (a and b) Scanning electron microscope laser resection shows absence of smeared out gutta-percha (×100)

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Interface between gutta-percha and root dentin walls (gap - in micrometer)

Under SOM, no gap between GP and root canal walls could be detected in both bur and laser root resection. Under SEM, in bur root resection, gap between GP and root canal walls was seen in 15 (75%) samples [Figure 15] out of 20 samples. In laser root resection, no gap was observed between GP and root canal walls in 9 (45%) samples [Figure 16]a while 11 (55%) samples showing gap which less in dimension compared to bur resection [Figure 16]b-d. The difference between both groups is statistically not significant [P = 0.1848, [Table 6] and Graph 8]. It is also seen that damage to apical adaptation is less in laser-resected samples.
Figure 15: (a-d) Scanning electron microscope microphotographs. Interface between root dentin and gutta-percha of bur-resected samples showing varying extent of gap and damage to apical adaptation to gutta-percha (a) Gap seen (×150) (b) 44.10 μm (×800) (c) 33.55 μm (×500), (d) 41.17 μm (×800)

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Figure 16: Scanning electron microscope microphotographs - Laser root-resected samples showing very less gap at interface between root dentin wall and gutta-percha and no or less damage to apical adaptation to gutta-percha (a) no gap (×400), (b) 10.34 μm (×2000), (c) 18.78 μm (×1000), and (d) 5.10 μm (×2000)

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Table 6: Evaluation of gap between root canal and gutta-percha


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However, mean gap measured in bur group was 20.9853 ± 12.8579 μm (with maximum - 44.1000, minimum - 4.2700) and in laser group was 9.9555 ± 4.6661 μm (with maximum - 18.7800, minimum - 4.2300). The difference between both the groups is statistically significant [P = 0.0124, [Table 7] and Graph 9].
Table 7: Comparison of gap (μm) between gutta-percha and dentin walls in two groups of 20 samples each


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  Discussion Top


This paper investigates the effect of dentin ablation by Er,Cr:YSGG laser. Comparing with the conventional methods, the major characteristics of dentin surfaces irradiated by Er,Cr:YSGG laser is devoid of debris, smear layer, and the opening of dentinal tubules. Water spray used along with Er,Cr:YSGG laser not only prevents temperature rise but also increases ablation depths. [26] Hence, the use of Er,Cr:YSGG laser irradiation should be accompanied by water spray to prevent charring and carbonization of tooth tissue which is followed in this study.

The microroughness observed in samples may be explained by heterogeneity of dentin tissue. Dentin is formed by mix of tubular, peritubular, and intertubular tissue holding different concentrations of water, thus leading to an unequal ablation. With the application of high-power settings (5.0 W, 20 Hz, 50% air, and 100% water, 300 mJ output energy), the ablation of intertubular dentin is more evident than that of peritubular dentin. Due to more depletion of intertubular dentin, peritubular dentin appears to be protruded. This reveals that Er,Cr:YSGG laser is also absorbed by the protein and lipid in collagen fiber. [27] Peritubular dentin is rich in Ca and P and less of water which also leads to unequal ablation. [26]

This study also confirms the findings of the previous studies; the laser irradiated dentin was free of smear layer and orifices of dentinal tubules were opened [Table 8]. [29],[30]
Table 8: Overall comparison between laser and bur-resected samples


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Overall scaly, microirregular and microretentive surface along with the exposure of collagen and clean surface seen in SEM is favorable for creation of conducive microenvironment for better tissue regeneration. [30],[31],[32],[33],[34] It is well known that, in vitro, cultured connective tissue cells well grow on collagen substrate and cultured fibroblasts will form oriented systems more readily in relation to demineralized root surface than to those have not been demineralized. [35] Collagen has been shown to be chemotactic in vitro for fibroblasts. [36] Furthermore, fibronectin which is also chemotactic for fibroblasts and is present in plasma, therefore shed into the wound, bind to great affinity with collagen of demineralized root surface. [37] Type I collagen have been demonstrated on fibroblasts, and these may play a role in effecting the attachment of gingival and periodontal fibroblasts to collagen exposed by demineralized root surfaces. [38],[39] All of these factors suggest that demineralization of root surface promotes migration to and attachment of fibroblasts to that site during wound healing in vivo.[34] This is in accordance with studies that evaluated the adhesion of fibroblasts [40] and blood elements [41] on root surfaces irradiated with Er,Cr:YSGG laser showed that irradiated surfaces present a biocompatibility.

Laser resection also exhibits less smeared out GP or overlapping of GP, with less gap between this and dentin than what is seen in bur resection [Table 8]. Hence, there is less damage to apical adaptation of GP with root canal walls. This may indicate to have a second thought for the procedure of retrofilling in laser resection of root in very selected cases.


  Conclusions Top


In laser root resection compared to bur root resection:

  • There is less debris
  • The smear layer is more effectively removed
  • Dentinal tubules are seen open
  • There is exposure of collagen of both peritubular and intertubular dentin
  • Collagen of intertubular dentin is more ablated, so scaly appearance of the surface is observed with protruding peritubular dentin
  • Less gap between GP and root canal walls
  • There is less distortion to GP as chances of smearing and overlapping of GP
  • On dentin is less
  • Feature of bubbling over cut end of GP in some samples is seen at higher magnification.
Bur-prepared dentin was covered with debris and smear layer. The dentinal debris clogged the dentinal tubules.

However, more detailed investigations are required to highlight the clinical benefits of this laser.

Acknowledgment

I would like to thank the Department of Sophisticated Analytical Instrument Facility, Bose Institute, Kolkata, for providing technical and instrumental support; and Dr. Sakshi Jain, Final year PG Trainee, Department of Conservative Dentistry and Endodontics of Dr. R. Ahmed Dental College and Hospital, Kolkata, for technical help to carry out this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]



 

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  In this article
Abstract
Introduction
Subjects and Methods
Results
Discussion
Conclusions
References
Article Figures
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