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Year : 2019  |  Volume : 30  |  Issue : 5  |  Page : 772-776
Evaluation of surface integrity of root end cavities prepared using conventional and piezoelectric devices: A scanning electron microscopy study

Department of Conservative Dentistry and Endodontics, A B Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India

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Date of Submission17-Mar-2018
Date of Decision25-Jun-2018
Date of Acceptance24-Sep-2018
Date of Web Publication18-Dec-2019


Introduction: An array of factors control the success of endodontic surgery. One of them is the technique used to prepare the root end cavities which is conventionally being done with burs. In past decades, ultrasonic instruments have been introduced for the same. Studies comparing these instruments on root surface integrity are scarce. Thus, an in-vitro Scanning Electron Microscopy study was designed to evaluate the surface integrity of root end cavities prepared using conventional and piezoelectric devices. Methodology: Twelve single-rooted human intact mandibular premolar teeth were endodontically treated and included in the study. They were divided into two groups. In the first group, 3 mm root-end cavities were prepared using conventional retro preparation burs and in the second group, 3 mm root-end cavities were prepared using piezoelectric retro-tips. The specimens were coded for blind evaluation and analysed under scanning electron microscope at 100x, 500x and 1000x magnification for smear layer and debris. Gutmann's scoring criteria was followed to score the specimens. Statistical analysis was carried out using Shapiro Wilk test and the independent sample t-test was used to check mean differences between variables. Results: It was noted that significant statistical differences existed in mean debris and smear layer scores (p<0.001) between the two groups. In the piezoelectric group, significantly lower debris layer and smear layer was found, compared to the conventional bur group. Conclusion: Root-end cavities prepared using piezo retrotips produced cleaner, well-centered and more conservative surface with minimal debris & smear layer, compared to root-end cavities prepared using conventional burs.

Keywords: Piezo retro tip, root end preparation, ultrasonic preparation

How to cite this article:
Hegde MN, Honap MN, Narayanan S. Evaluation of surface integrity of root end cavities prepared using conventional and piezoelectric devices: A scanning electron microscopy study. Indian J Dent Res 2019;30:772-6

How to cite this URL:
Hegde MN, Honap MN, Narayanan S. Evaluation of surface integrity of root end cavities prepared using conventional and piezoelectric devices: A scanning electron microscopy study. Indian J Dent Res [serial online] 2019 [cited 2022 Oct 7];30:772-6. Available from:

   Introduction Top

Multitude of factors control the outcome of surgical endodontic treatment and success of retrograde filling material. One of them is the technique used to prepare the retrograde cavity. Conventionally, burs were the instruments used to prepare root-end cavities. But, in today's era of modern dentistry, piezoelectric devices show us a novel approach to do the same with the added advantage of selective cutting of mineralized tissue and sparing the soft tissue in a surgical field.

Ultrasonic instruments have been used in dentistry since 1950s. Because of better visualization, operative convenience, and precise cutting ability, ultrasonic instruments became popular.

The introduction of ultrasonics in endodontic surgery has many advantages over traditional handpieces, such as the long axis of the tooth can be followed preserving the canal morphology,[1] apical cavities may be shaped easily, safely, and with greater precision in respect to those obtained using conventional handpieces.[2]

A better-shaped root-end cavity, more central and smaller than that produced by air-driven handpieces and burs, may reduce the risk of root perforation.[3]

Despite the excellent results obtained with ultrasonic tips, some studies have shown drawbacks associated with this technique, such as dentinal cracks on the resected surface after preparation.[4],[5],[6],[7],[8],[9] However, thesein vitro studies had limitations, such as the stress exerted during tooth extraction and the risk of inappropriate storage or handling could cause alterations in the dentin.[8]

The recent introduction of piezoelectric instruments vibrating in the ultrasonic frequency range represents an important advancement.[10],[11]

Bone-tissue management and root-end cavity preparation can be performed with piezosurgery reducing the risk of damage to soft tissues. Piezosurgery is a bone-cutting modality with rapidly increasing indications in different surgical fields, including endodontic surgery.[12] Although such instruments can also be used to prepare root-end cavities, limited information is available on the effect of piezosurgery on dentin. The introduction of piezoelectric devices using various tips for different maxillofacial surgeries including endodontic surgeries prompted the present investigation. In the presentin vitro study, surface integrity of the retrograde cavities prepared using a piezoelectric device and conventional method was analyzed.

   Methodology Top

The study was conducted at the Department of Conservative Dentistry and Endodontics, AB Shetty Memorial Institute of Dental Sciences, Mangalore.

Teeth collection and disinfection

Twelve single rooted mandibular premolar teeth with completely formed apices were collected. Specimens were autoclaved according to Occupational Safety and Health Administration (OSHA) guidelines, 2004. Specimens were decoronated at the cemento-enamel junction using a diamond disk. Preoperative radiographs were taken to check root canal anatomy and access cavities were prepared using small round bur.

Preparation of teeth to receive endodontic fillings

Working length was standardized as 12 mm for all teeth and canals were prepared using Crown down technique using 3% sodium hypochlorite and saline as irrigating solutions. Canals were obturated with gutta percha and zinc oxide eugenol sealer. Teeth were then stored in saline for one week and apex resected at 90° to the long axis of the root, removing 3 mm of the apex. The prepared specimens were then randomly divided into two experimental groups of six teeth each. This was calculated based on study parameters, such as mean, group 1 = 1.225; mean, group 2 = 2.62; alpha (probability of type I error) = 0.05; beta (probability of type II error); and power = 0.8, which suggested a minimum sample size of two in each group (groups I and II). Thus, the sample size was selected as six in each group (three times more than minimum sample size required).

  1. Group I: Six teeth; 3 mm root-end cavities were prepared using piezo retrotips on Piezo Surgery Touch unit
  2. Group II: Six teeth; 3 mm root-end cavities were prepared using conventional root-end preparation burs on an Impact Air 45 airotor handpiece.

The specimens were then dehydrated in ascending ethanol: water series (30%, 50%, 70%, 90%, 100%) dried in open air. After drying, the specimens were sputter-coated with gold. The specimens were analyzed under scanning electron microscope [Karl Zeiss, OPMI]. The specimens were coded for blind evaluation.

Photomicrograph evaluation

Specimen viewing and evaluation were done by two examiners at magnifications of 100× for assessment of the superficial debris layer, and 500× and 1,000× for assessment of the remaining smear layer. These levels of viewing were chosen because they showed best the detail required to make an accurate evaluation, while still maintaining as large a field as possible.

As the specimens were scanned, the examiners independently scored each area. Scoring criteria given by Gutmann was used to score the photomicrographs[13] [Table 1] and [Table 2].
Table 1: Superficial debris

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Table 2: Smear layer

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Statistical analysis

Descriptive and analytical statistics were done. The normality of data was analyzed by the Shapiro–Wilk test. As the data followed normal distribution, parametric tests were used to analyze the data and the independent sample t-test was used to check mean differences between variables.

Software: SPSS (Statistical Package for Social Sciences) Version 24.0 (IBM Corporation, Chicago, USA).

   Results Top

Superficial debris (100×)

Greater amounts of superficial debris were present with bur preparation techniques compared with ultrasonic preparation [Photomicrograph 1] and [Photomicrograph 2].

Superficial smear layer (500× and 1,000×)

Most specimens demonstrated a clean dentinal surface with patent tubules in group I. [Photomicrograph 3].

Group II had no SSD among its levels, with all levels demonstrating a heavy smear layer covering over 75% [by definition in [Table 2] of the specimen with no tubule orifices visible. Also evidenced was the cutting or gouging of the root canal walls with the conventional bur tip, which created an irregular layered effect, with concentric rings of the bur head [Photomicrograph 4].

The mean debris and smear scores were compared between the two groups. It was found that statistical significant differences existed in mean debris and smear scores (P < 0.001) between the two groups.

Mean debris score [100×

] of group I (1.41 ± 0.37) was significantly (P < 0.001) lower than the group II score (3.16 ± 0.60). The smear layer formation was studied at 500× and 1,000× magnification [Figure 1] and [Table 3]. At 500×, the mean smear score of group I (1.41 ± 0.49) was significantly (P < 0.001) lower than the group II score (3.25 ± 0.68) [Figure 1] and [Table 3]. At 1,000×, the mean smear score of group I (1.75 ± 0.41) was also significantly (P < 0.001) lower than the group II score (3.50 ± 0.44) [Figure 1] and [Table 3].
Figure 1: Comparative bar graph of debris and smear layer scores of the two groups

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Table 3: Comparison of mean debris and smear scores between the two groups

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   Discussion Top

In this study in an attempt to avoid tooth damage, vital teeth were obtained by atraumatic extraction. In the preoperative analysis, teeth were observed under stereomicroscope to exclude any roots that had cracks or marginal chipping.

To mimic thein vivo procedure, roots were resected 3 mm from the apex with the help of a micromotor handpiece having diamond cutting bur. There is no consensus on how much of the root must be resected to satisfy biological principles. De Deus[14] showed that a large number of apical ramifications and lateral canals exist at least 3 mm from the root end. Thus, root-end amputations of < 3 mm may not remove all lateral canals and apical ramifications, increasing the risk of reinfection and eventual failure.[15]

The traditional technique uses a bevel angle of 45–60 degrees to facilitate access and visibility when using large surgical instruments. The modern technique uses a shallow bevel angle of 0–10 degrees to expose fewer dentinal tubules.[15] Minimization of the bevel angle during root resection is one of the most important developments in endodontic microsurgery.[16] Therefore, in our study, the bevel angle was kept at zero degrees.

In conventional bur group, root-end cavities were prepared using diamond cutting round bur mounted on Impact Air 45 handpiece. Impact Air handpiece prevents air emphysema by rear-venting the air in the clinical scenario.

In piezoelectric group, root-end cavities were prepared using ER2 piezo retrotip mounted on piezoelectric handpiece of PiezoTouch, Mektron, following the manufacturer's instructions in “Endo Retro” mode of the unit.

Piezosurgery uses a low-frequency modulated ultrasonic insert that produces micro vibrations in the range of 60–200 μm/sec and leads to safe and precise bony incision without damaging underlying vital structures like nerves, mucosa, and vessels.

It overcomes technical difficulties such as visibility by producing bloodless field during surgery and removes debris simultaneously through internal irrigation mechanism.[17]

In modern endodontic surgeries as well, conventional burs have resulted in a bony window that is ultimately much smaller in size than the donor surgical site due to their dimensions and the cutting action, whereas while using piezotomes, the size and shape of the elevated window correspond to the donor site precisely, making re-approximation easier. The inserts made for the piezoelectric devices are narrower than both the carbide bur and micro-saws used in oral surgery, and therefore, piezotomes have been preferred over surgical burs over time.[18]

According to a study done by Gutmann et al.[13] there were no significant differences at all levels of root-end preparations made with the ultrasonic retrotip and conventional burs for either superficial debris or smear layer.

According to a study by Khabbaz et al., it was stated that ultrasonic tips produced cleaner, well-centered, and more conservative root-end cavities than the rotary instruments with a slow-speed handpiece.[19]

A Brazilian company (Clorovale Diamantes Ind e Com Ltd Epp, Sao Jose dos Campos, SP, Brazil) developed chemical vapor deposition (CVD)-coated diamond tips adaptable for use with conventional ultrasound devices and marketed under the brand name CV Dentus System.[20]

Bernardes et al.[21] compared an ultrasonic CVD-coated tip with high- and low-speed carbide burs for apicoectomy, evaluating resection time and analyzing root-end surfaces using scanning electron microscopy. They concluded that ultrasonic root-end resection using the CVD-coated tip took longer and resulted in rougher surfaces than carbide burs at both high and low speeds.

The results in this study showed that the use of piezo retrotips produced significantly better surface integrity of the root-end cavities compared with conventional burs. This may be due to the precise linear vibration motion of piezo retrotips, selective and effective mineralized tissue cutting, less traumatic stress, and in-built irrigation source that removes debris instantaneously.

On the contrary, in air-driven handpieces, the amount of cutting is directly proportional to the amount of force applied at the surgical site that might have resulted in more debris generation in conventional method of root end cavity preparation.

Endodontic surgery outcomes have improved in the recent years because of the adaptation of microsurgical instruments, which permit a better management of the root end preparations.[22],[23] With the advent of piezoelectric devices that provide effective and precise results and the use of microsurgical instruments as adjunct aids, we can achieve much more successful endodontic outcomes.

   Conclusion Top

Considering the limitations of the study, root-end cavity prepared using piezo retrotips produced cleaner, well-centered, and more conservative surface with minimal debris and smear layer, compared with root-end cavities prepared using conventional burs. Hence, this shows us a novel approach toward root end cavity preparations. To our knowledge, only one study[24] has investigated the effect of piezosurgery on the integrity of root apices after root-end cavity preparation. Further studies are necessary to determine the long-term success rate of this novel technique.


We are grateful to Board of Research in Nuclear Sciences for funding this study under the project titled “Effect of Radiation on the biomechanical behaviour of teeth and radioprotective effects of remineralising agents on enamel.” We are also thankful to Nitte (deemed-to-be University) for providing the platform for the research work.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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Hirsch V, Kohli MR, Kim S. Apicoectomy of maxillary anterior teeth through a piezoelectric bony-window osteotomy: Two case reports introducing a new technique to preserve cortical bone. Restor Dent Endod 2016;41:310-5.  Back to cited text no. 18
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Bernardes RA, de Souza Junior JV, Duarte MA, de Moraes IG, Bramante CM. Ultrasonic chemical vapor deposition-coated tip versus high- and low-speed carbide burs for apicoectomy: Time required for resection and scanning electron microscopy analysis of the root-end surfaces. J Endod 2009;35:265-8.  Back to cited text no. 21
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Correspondence Address:
Dr. Sreenath Narayanan
Department of Conservative Dentistry and Endodontics, A B Shetty Memorial Institute of Dental Sciences, Mangalore - 575 018, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijdr.IJDR_237_18

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  [Table 1], [Table 2], [Table 3]


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