ABSTRACT
Introduction:
Histological alterations were evaluated in this study after tooth preparation with carbide burs using a traditional handpiece and Er: YAG laser.
Methods:
Tooth preparation was done on 30 intact maxillary first premolars of healthy patients. Ten maxillary first premolars were used as control, wherein no tooth preparation was done. Box-shaped tooth preparation was done on the occlusal surface of maxillary first premolars using carbide bur in the handpiece and Er: YAG laser (n = 10). After performing the recommended procedure for different groups, each tooth was extracted and 4–5 μm thick sections were prepared and stained using H and E stains. A 4–40× microscope was used to examine the morphological alterations in the odontoblasts. The Chi-square test was used to compare the outcomes.
Results:
The high-speed drill group and the control group had statistically significant differences (P = 0.05). High-speed drill and laser group differences were not statistically significant (P > 0.05)
Conclusion:
The histological findings as seen with laser tooth preparation were nearly identical to those of control or nonmanipulated teeth under light microscope, whereas disruption of odontoblastic layer was seen with high-speed drills.
KEYWORDS: Carbide bur, Er: YAG laser, high-speed handpiece, odontoblastic layer, pulp response, tooth preparation
INTRODUCTION
Tooth preparation with dental burs in high-speed handpiece causes mechanical irritation to the pulp leading to disturbance in the typical architecture of the odontoblastic cellular layer. Even though local anesthesia might lessen pain, discomfort is still caused by fears related to the needle, as well as noise and vibration from mechanical preparation. These drawbacks have prompted researchers to look into novel procedures as potential substitutes for removing tooth hard tissue.[1]
The alternative method of cavity preparation with Er: YAG laser preserves healthy dental tissues while preparing cavities due to the calcified tissue’s exceptionally effective absorption of both water and hydroxyapatite without damaging nearby tissues. Thus, this study aims to analyze the histological changes in pulp following tooth preparation with conventional carbide burs and Er: YAG laser.
MATERIALS AND METHODS
This study was conducted on 30 maxillary premolars of healthy patients from the Outpatient Department of Conservative Dentistry and Endodontics, Orthodontics and Orofacial Orthopedics, Oral and Maxillofacial Surgery, GIDSR, and Ferozepur (Punjab) after obtaining clearance from Research and Ethical Committee of the Institute. Intact maxillary first premolars which were indicated for orthodontic extraction were included in the study.
Each group of 10 teeth in the samples was divided evenly into 3 groups (n = 10).
In group 1 (control group), no tooth preparation was done.
In group 2, conservative box-shaped tooth preparation was made with carbide bur using a high-speed handpiece.
In group 3, conservative box-shaped tooth preparation was done with Er: YAG laser.
First premolars in the maxilla from either side of the mouth were divided into the appropriate groups to standardize the study. As a result, all of the patients had their right premolars prepared using an Er: YAG laser, whereas their left premolars were prepared using a carbide bur and an air rotor handpiece. Teeth were prepared for both groups without the use of anesthesia.
Using a handpiece and a no. 245 bur, box-shaped preparations were made on the occlusal surfaces of 10 maxillary left first premolars. Before starting the procedure, the teeth were isolated using a rubber dam. For all the teeth, depth for cavity preparation was retained at 1.5 mm. For all the teeth, the cavity dimensions were preserved to a standard 3 mm × 3 mm size.
Similar to this, conservative box-shaped preparations using an Er: YAG laser with a 2,940-nm wavelength and water coolant were made on the occlusal surfaces of 10 maxillary right first premolars. The non-contact laser irradiation was carried out using a focused beam under the following conditions: 1.0 mm diameter tip operating in non-contact mode, 400 mJ, 20 Hz, and 8.00 W.
The control group included 10 intact premolars wherein no tooth preparation was done.
The teeth were extracted immediately after finishing the tooth preparation in all the groups. Two millimeter of the apical end was removed to allow for easier fixative infiltration. After being submerged in 10% formalin solution for 24 h, teeth were decalcified. Light microscopy was used to analyze the morphology of the typical odontoblasts (4×, 10×, and 40× magnification).
RESULTS
The results of the present study revealed significant differences between group 1 and group 2. However, statistically insignificant differences were observed between group 1 and group 3. Statistically insignificant differences were revealed between groups 2 and 3 [Table 1].
Table 1.
Comparison of number of teeth showing intact odontoblastic layer among the groups
| Intact odontoblastic layer | Groups | P 1 | |||||
|---|---|---|---|---|---|---|---|
|
| |||||||
| Group 1 (n=10) | Group 2 (n=10) | Group 3 (n=10) | |||||
|
|
|
|
|||||
| No. | % | No. | % | No. | % | ||
| Present | 9 | 90.0 | 3 | 30.0 | 6 | 60.0 | 0.02* |
| Absent | 1 | 10.0 | 7 | 70.0 | 4 | 40.0 | |
1Chi-square test, *significant
DISCUSSION
It has been demonstrated that the pulp reacts to a variety of stimuli. When healthy, intact teeth are stimulated thermally; the dentinal fluid expands or contracts more quickly activating the hydrodynamically active intradental neurons that produce pain.[2] The cavity preparation process causes detrimental alterations in the pulp at the impacted site.[3] In direct proportion to the depth of cavity preparation, the pulp’s degree of inflammatory response likewise increases.[4,5,6] As a result, for all the teeth in this investigation, the standard depth for cavity preparation was fixed at 1.5 mm.
Pulp reaction after Er: YAG laser preparation is not very different from that after conventional treatment. There are no signs of long-term damage, so the Er: YAG laser can be regarded as a safe treatment.[7,8]
The difference between carbide bur group and control/no cavity preparation group was found to be statistically significant. The processes of the odontoblasts are mechanically damaged when the dentin is drilled, which causes the degeneration of their cells and the creation of empty spaces in their place. The handpiece’s vibration may have caused this reaction, and the thermal injury may have resulted from the water spray’s inability to sufficiently cool the cutting site.[9]
Water is the main chromophore of the Er: YAG wavelength. Rapid and extensive vaporization is the result of the free-running micropulsed emission mode. Water present in enamel and dentin is vaporized when tissue is exposed to this wavelength, resulting in explosive dislocation of the general structure. Erbium laser energy’s explosive outward action produces less thermal diffusion through the tooth structure than drilling techniques. A water spray that is coaxial with the laser helps disperse ablation products and cools the target tissue.[10]
The results of this study revealed statistically insignificant differences between traditional carbide bur using high-speed handpiece and Er: YAG laser groups where moderate pulpal response and histopathological features showing disruption of odontoblastic layer were seen with carbide bur using handpiece, whereas a mild pulpal response with an intact odontoblastic layer was seen in Er: YAG laser group. A traditional handpiece damages the odontoblastic layer by thermal injury caused by friction from the rotating bur as it removes hard tissue, whereas an Er: YAG laser employs photoablation to remove enamel and dentin while maintaining a pulp temperature that is within safe ranges. The surface dryness generated by the ablation process may be the reason of the whitish appearance seen on the enamel surfaces of the Er: YAG laser cavities.[11]
Er: YAG laser ablation works through micro-explosions and evaporations that break the target tissue, as opposed to the hard-tissue removal by high-speed handpiece.[12] At a very rapid rate, the fragments fly off the tissue’s surface. During cavity preparation, the laser does not come into direct contact with the tooth structure; rather, there is a gap of more than 10 mm between the laser generator and the tooth structure. Little heat is left in the remaining tissue as a result of the thermal energy being transferred to kinetic energy, causing little mechanical or thermal damage to the surrounding tissue. The literature also claims that the vibration caused by the lasers as well as its amplitude and frequency is substantially lower than those of traditional handpieces.[13]
CONCLUSION
Tooth preparation using conventional carbide burs in high-speed handpiece showed a moderate pulpal response and histopathological features showing disruption of the odontoblatic layer under light microscope. A mild pulpal response with normal histological features of an intact architecture of the odontoblastic layer was seen with Er: YAG laser tooth preparation.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
REFERENCES
- 1.Husein A. Applications of lasers in dentistry: A review'. Arch Orofac Sci. 2006;1:1–4. [Google Scholar]
- 2.Singh A, Velu AK. Histological changes in pulp after tooth preparation with high-speed handpieces and Er: YAG laser: A light microscopic analysis. J Oral Laser Appl. 2010;10:37–44. [Google Scholar]
- 3.Ohshima H. Ultrastructural changes in odontoblasts and pulp capillaries following cavity preparation in rat molars. Arch Histol Cytol. 1990;53:423–38. doi: 10.1679/aohc.53.423. [DOI] [PubMed] [Google Scholar]
- 4.Smith AJ, Hargreaves KM, Goodis HE. Dentin formation and repair. Quintessence Publishers. 2002:41–62. [Google Scholar]
- 5.Gronthos S, Brahim J, Li W, Fisher LW, Cherman N, Boyde A, et al. Stem cell properties of human dental pulp stem cells. J Dent Res. 2002;81:531–5. doi: 10.1177/154405910208100806. [DOI] [PubMed] [Google Scholar]
- 6.Ross MH. A Text Book and Atlas of Histology. Philadelphia: Lippincott Williams and Wilkins; 2006. [Google Scholar]
- 7.Keller U, Hibst R. Tooth pulp reaction following Er: YAG laser application. Lasers in Orthopedic, Dental and Veterinary Medicine. 1991;1424:127–33. [Google Scholar]
- 8.Miserendino L, Cozean C. Histological results following in-vivo cavity preparation with an Er: YAG laser. Lasers in dentistry. Proc SPIE. 1998;3248:46–50. [Google Scholar]
- 9.Vanderlei AD, Borges ALS, Cavalcanti BN, Rode SM. Ultrasonic versus high-speed cavity preparation: Analysis of increases in pulpal temperature and time to complete preparation. J Prosthet Dent. 2008;38:107–9. doi: 10.1016/S0022-3913(08)60158-4. [DOI] [PubMed] [Google Scholar]
- 10.Mir M, Meister J, Franzen R, Sabounchi SS, Lampert F, Gutknecht N. Influence of water- layer thickness on Er: YAG laser ablation of enamel of bovine anterior teeth. Lasers Med Sci. 2007;23:451–7. doi: 10.1007/s10103-007-0508-0. [DOI] [PubMed] [Google Scholar]
- 11.Chuah DY, Hsu CYS. Effect of Er: YAG laser and organic matrix on porosity changes in human enamel. J Dent. 2004;32:41–6. doi: 10.1016/s0300-5712(03)00138-6. [DOI] [PubMed] [Google Scholar]
- 12.Parker S. Laser-tissue Interaction. Br Dent J. 2007;202:73–81. doi: 10.1038/bdj.2007.24. [DOI] [PubMed] [Google Scholar]
- 13.Sonntag KD, Klitzman B, Burkes EJ, Hoke J, Moshonov J. Pulpal response to cavity preparation with the Er: YAG and Mark III free electron lasers. Oral Surg Oral Med Oral Pathol. 1996;81:695–702. doi: 10.1016/s1079-2104(96)80076-x. [DOI] [PubMed] [Google Scholar]
