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TITLE

Effects of root surface debridement using Er:YAG Laser versus ultrasonic scaling - a SEM study

RUNNING TITLE

Laser versus ultrasonic debridement



KEYWORDS

Er:YAG laser, Scanning Electron Microscope, periodontology



AUTHORS

Seyed Reza Miremadi, Jan Cosyn, David Schaubroeck, Niklaus P. Lang, Roeland De Moor, Hugo De Bruyn


AFFILIATIONS AND INSTITUTIONS

Seyed Reza Miremadi1, Jan Cosyn1, David Schaubroeck2, Niklaus P. Lang3, Roeland J.G. De Moor4, Hugo De Bruyn1,5



1 Department of Periodontology, Faculty of Dentistry, Ghent University, Ghent, Belgium

2 Department of ELIS, Center for Microsystems Technology, imec,  
University of Ghent, Ghent, Belgium

3 Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR

4 Department of Restorative Dentistry and Endodontology, Ghent Dental Photonics Research Cluster, Faculty of Dentistry, Ghent University, Ghent, Belgium

5 Department of Prosthodontics, Faculty of Dentistry, Malmö University, Sweden
CONTACT ADDRESS CORRESPONDING AUTHOR

Seyed Reza Miremadi

Department of Periodontology, Dental School, Faculty of Medicine and Health Sciences, University of Ghent. De Pintelaan 185, Block P8, Ghent 9000, Belgium

Tel. +32 9 3324018 Fax. +32 9 3323851

Email : resa.miremdi@ugent.be

CONFLICT OF INTEREST AND SOURCE OF FUNDING STATEMENT

The authors declare that they have no conflict of interests. The study was completely financed by the department of periodontology of university hospital of Ghent, Belgium (Tel. +32 9 3324017). All materials and instruments used in this study were property of the university hospital of Ghent, Belgium and university of Ghent, Belgium.

Abstract

Objective : Despite promising results of Er:YAG laser in periodontal debridement, to date there is no consensus about the ideal settings for clinical use. This experimental clinical trial aimed to determine the effects of debridement using Er:YAG laser and to compare with ultrasonic treatment.

Materials and Methods : 64 teeth, were divided into two in vivo and in vitro subgroups. Each tooth received ultrasonic treatment on one side and Er:YAG laser debridement at either 60 , 100, 160 or 250mJ/pulse and at 10Hz on the other side on a random basis. All samples were morphologically analyzed afterwards under scanning electron microscope for surface changes and dentinal tubules exposure. Treatment duration(d) was also recorded.

Results : Laser debridement produced an irregular, rough and flaky surface free of carbonization or meltdown while ultrasound produced a relatively smoother surface. The number of exposed dentinal tubules (n) followed an energy-dependent trend. The number of exposed tubules among the in vivo laser groups was: n60mJ=n100mJvivo condition. Within the in vitro laser groups, dentinal tubules exposure was: n60mJin vitro laser treatments at 100, 160 and 250mJ led to significantly more dentinal denudation than ultrasound. Treatment duration (d) for the in vivo groups was: d60mJ>d100mJ>dUltrasound=d160mJ>d250mJ (p≤0.046), while for the in vitro groups it was: d60mJ>d100mJ=dUltrasound=d160mJ>d250mJ (p≤0.046).

Conclusions : Due to excessive treatment duration and surface damage, Er:YAG laser debridement at 60 and 250mJ/pulse, respectively, is not appropriate for clinical use. Although laser debridement at 100 and 160 mJ/pulse seems more suitable for clinical application, compared to ultrasound the former is more time-consuming and the latter is more aggressive. Using a feedback device or lower pulse energies are recommended when using laser in closed field.

Clinical Relevance

Scientific rationale for study: Excessive removal of intact tooth substance is a possible consequence of treatment when using Er:YAG laser for root surface debridement. The ideal pulse energy of erbium lasers for this purpose is to date a matter of debate.

principal findings: Laser debridement at pulse energies higher than 100mJ can be too aggressive, while not always yielding better treatment or time-efficiency.

Practical implications: 100mJ/pulse seems to be more suitable for periodontal treatment in closed field. Using higher energies without a calculus detection system cannot be encouraged.

Introduction

The root surfaces of periodontal pockets are contaminated and coated with a biofilm. This biofilm may be calcified as calculus and harbors great numbers of bacteria and bacterial toxins(1). Periodontal treatment aims at the elimination of the living microorganisms present in the non-calcified and possibly also on the calcified biofilm(2). Complete elimination of such microorganisms by mechanical means appears however to be difficult (3).

From a clinical point of view, the volume of dental calculus has to be minimized, providing the basis for optimal plaque control and hence, substantially delaying the re-colonization of the root surfaces that have been debrided as well. The efficiency of calculus removal may be influenced by numerous factors such as the extent of periodontal disease, anatomic factors, the experience and skills of the operator and the instruments used(4, 5). Hand instruments, sonic and ultrasonic scalers and ablative laser therapy may be used for removal of calculus and plaque. Hand instruments and sonic or ultrasonic scalers produce similar periodontal healing outcomes(6).

The Er:YAG laser is one of the mostly studied lasers in periodontics. Its wavelength lies near the highest peak of absorption by water, minimizing the thermal side effects with appropriate power settings. Ablation is possible without producing a smear layer(7) and both smear layer and endotoxins can be removed from root surface (8, 9). Fibroblasts show enhanced adhesion and proliferation on laser-treated root surfaces(10, 11). Moreover, several studies have reported promising outcomes for both clinical and microbiological aspects showing reduction in pocket depth and inflammation (12-14). However, Er:YAG laser therapy should only be applied as a mono-therapy, since adjunctive use of Er:YAG laser after scaling and root planing failed to show any additional benefits(15, 16).

Overall, there is a lack of a fixed set of parameters for Erbium laser applications in periodontal debridement. Hence, it is difficult to draw a definitive conclusion on the actual value of laser debridement in periodontics. Moreover, there are some contradictory findings among the studies, where the same laser settings lead to different outcomes (17-20). Presently, it is already clear that higher energies of a laser may perform the debridement more effectively, but in the same token, may remove bigger increments of the underlying tooth structure(17, 21, 22). Several studies have quantified the amount of ablation following laser application on the root surface(21, 23). In this regard different outcome variables such as the crater depths and dentinal tubules denudation have been utilized by some studies(17, 22).

To date and to our knowledge, only Herrero and coworkers(22) used the latter outcome variable in order to compare the root substance removal by different laser settings. In addition, treatment duration has not sufficiently been investigated in most studies. This may ultimately influence patient discomfort. Moreover, most studies were performed either in vivo or in vitro. Taking the obvious differences of the two conditions into account leads to a discrepancy between results.

Therefore, the aims of the present study were:

1) to investigate the morphologic effects of different laser settings versus ultrasonic scaling at the ultrastructural level,

2) to compare the exposure of dentinal tubules corresponding to tooth substance removal by different laser settings and ultrasonic scaling.

3) to compare the treatment duration of laser debridement using different settings with each other and to ultrasound.

Since the laser energy at 160mJ/p has been widely applied in clinical studies and favorable outcomes have been reported (13, 16, 19, 24), the research hypothesis of the present randomized controlled trial was that there is no difference in the number of exposed dentinal tubules following Er:YAG laser debridement at 160mJ/p or lower energy levels compared to ultrasonic scaling.

Material and Methods

The study was conducted in accordance with the Helsinki declaration of 1975 as revised in 2008 and the protocol was approved by the ethical committee of the University Hospital of Ghent (study no. EC/2008/522). Prior to inclusion into the study, all patients received detailed oral and written information and a written consent was obtained from all enrolled individuals before the commencement of the trial.



Study design

This experimental clinical study included a total of 64 teeth, heavily affected by periodontal disease and planned to be extracted during the course of routine periodontal treatment. The teeth had: (a) advanced periodontitis, (b) exhibited bone loss of at least two-thirds of the root length, (c) similar probing depth on the buccal and lingual surfaces, (d) radiographic evidence of subgingival calculus and (e) absence of decay or restorations adjacent to the CEJ.

Teeth were assigned to either an in vitro or an in vivo treatment group of 32 teeth each. Each group was subdivided in four subgroups of 8 teeth, which underwent subgingival ultrasonic scaling and root planing on either buccal or lingual side, and subgingival laser debridement with Er:YAG laser with one of the four settings on the opposite side.

In the in vivo group, the patients underwent the laser and ultrasonic treatment followed by tooth extraction. Freshly extracted human teeth assigned to the in vitro treatment group were stored in sterile saline solution (NaCl 0.9% at 37°C), and the actual treatment was carried out within a maximum of 3 days after extraction.

The enrollment of samples into treatment groups was randomly performed for all groups by means of a computer-generated list using simple randomization by a study member who was not clinically involved in the study (J.C). All treatments were performed by the same operator (S.R.M) at the specialist clinic of the department of periodontology of the university of Ghent, Belgium. The study flowchart is presented in figure 1.

Laser and ultrasonic treatment

In vivo group:

An Er:YAG laser (λ=2.94 µm) with a R14 Er:YAG handpiece and a chisel tip of 0.5mm x 1.5mm (AT Fidelis, Fotona, Ljubljana, Slovenia) were selected for laser debridement. Samples were irradiated at energy levels of either 60mJ/pulse, 100mJ/pulse, 160mJ/pulse or 250mJ/pulse (effective energy density: 6.7 J/cm2 per pulse, 12.0 J/cm2 per pulse, 18.7 J/cm2 per pulse and 30.7 J/cm2 per pulse respectively), and a repetition rate of 10 Hz with water irrigation and air cooling according to the instructions given by the manufacturer (70% water, 30% air). Laser application was performed using the handpiece (R14 Er:YAG Handpiece [R14-C], Fotona, Ljubljana, Slovenia) attached to a chisel tip (fiber optic tip of 0.5 x 1.5 mm). The fiber tip was moved from coronal to apical in parallel paths with an inclination of approximately 20°-25° in relation to the long axis of the root. The opposite side was treated with an ultrasonic scaler using the two available tips (1-S and 10Z, Satelec P5 Newtron ®, Acteon group, Bilbao, Spain). The endpoint of both treatments was achieving a hard, smooth, clinically calculus-free root surface as determined by tactile sensation with a pocket probe. No time limits were imposed for the treatments and the treatment duration was recorded in minutes.

The teeth were carefully extracted immediately after the treatment and placed under cold running tap water for about 1 min to remove blood and loosely adherent debris and then placed in a container with 10% buffered formalin solution at 37°C.

In vitro group :

Following laser and ultrasonic debridement of the extracted teeth outside the mouth, the samples were placed in a container with 10% buffered formalin solution at 37°C.


SEM analysis

Tooth specimens were dehydrated in ethanol / water mixtures. Step by step, the ethanol concentration of these mixtures was increased from 60, 70, 80, 96 to 100%. Specimens were kept for 24h in each of the ethanol solutions mentioned. Finally, the specimens were dried for 48h in a desiccator prior to analysis.

Scanning electron microscope (SEM) analysis is performed in a JEOL JSM-5600 (Jeol, Tokyo, Japan) with progressive magnifications (25x, 100x, 750x, 1500x, 3000x). The apparatus was used in the secondary electron mode (SEI). Prior to analysis, all samples were coated with a thin gold layer (roughly 25 nm) via plasma magnetron sputter coating. Acceleration voltages between 10 and 15 keV were applied.

For each treated site, two images of 1500x magnification (corresponding to two rectangular zones of ~0.048mm2 each, placed in the center of hypothetical midline with 1mm and 3mm distance to CEJ) were used to measure the number of exposed dentinal tubules. Following this, a mean for these two numbers was calculated, which represented the mean number of exposed dentinal tubules per site. This phase was performed twice with 48 hours in between. The dentinal tubules denudation measurements yielded an intra-examiner reproducibility of 96.2%. The morphologic changes and the number of exposed dentinal tubules were considered as primary outcome variables, whereas treatment duration was secondary.


Statistical analysis

SPSS 17.0 statistical software (SPSS, Inc., Chicago, IL, USA) licensed to the University of Ghent, Belgium was used for statistical analysis. Mean values and standard deviations for the number of exposed dentinal tubules and treatment duration were calculated for laser- and ultrasonically treated areas.

Differences between ultrasonic and the laser debrided groups (intra-group) were evaluated by Wilcoxon Signed Ranks Test. Values of p<0.05 were accepted as statistically significant. Comparison between different laser settings was performed by the Kruskall-Wallis test and the Mann-Whitney Test. After the Bonferroni correction, p<0.003 was the criterion for significance.

Results

Patients were recruited to the study between October 2009 till January 2010. For the in vivo group, 19 patients (mean age: 53.6, ranging from 41 to 74) with untreated advanced chronic periodontitis contributed a total of 32 teeth consisting of 3 incisors, 4 canines, 12 premolars and 13 mandibular molars. Probing pocket depths ranged from 6 to 11mm (mean: 7.7mm ± 2.6mm).

For the in vitro group, 32 freshly extracted teeth obtained from 21 patients (mean age: 54.1, ranging from 45 to 70) were used. These teeth were consisting of 4 incisors, 5 canines, 10 premolars and 13 mandibular molars. Probing pocket depths ranged from 7 to 11mm (mean 7.9mm ± 2.2mm). In both in vivo and in vitro groups, there were no significant differences between the sides undergoing ultrasonic and laser treatment in terms of mean pocket depth (p≥0.44).

Morphology

Calculus removal was mostly complete with partial or complete removal of subjacent cementum that, in the latter case, was accompanied with exposure of dentinal tubules. However, under SEM, various surface alterations were observed. Ultrasonic scalers produced a relatively smooth and homogenous surface (Figure 2) while in all laser-treated samples, root surfaces were irregular, rough and flaky, free of carbonization or meltdown or any other visible thermal changes. They showed large ablated defects, with a tendency to get deeper with increasing energies (Figure 3). Sporadically, areas containing remaining calculus were found on the treated regions and particularly on the apical end of very deep pockets. Moreover, the apical parts of samples which were not treated, showed cementum, tiny soft tissue remnants and often remnants of calculus. The apical and lateral borders of the treated surfaces were well-defined in form of a step which tended to be relatively deep and increasing in depth with increasing laser energies. The traces of the chisel tip were clearly visible in the laser-treated groups and sometimes, untreated areas between these traces were observed. The morphology of laser-treated surfaces is shown in the figures 4 and 5 (A-D). In comparison with laser-treated sites, surfaces treated ultrasonically were more regular and smoother and without any other surface alterations as shown in figures 4 to 5 (E). Exposures of dentinal tubules were rarely observed. Small particles of remaining calculus were scarcely spotted on treated surfaces. The borders of treated surfaces were less pronounced and were mostly gradual.



Exposure of dentinal tubules

In general, the number of exposed tubules increased with higher levels of energy, and in vitro samples tended to show more exposed tubules than in vivo samples. The mean number of exposed dentinal tubules per two areas of ~0.048mm2 ranged between 3.12 and 19.75 for the in vivo laser-treated group and 3.50 and 48.87 for the in vitro laser-treated group.

For in vivo ultrasonic scaling, the number of exposed dentinal tubules ranged from 3 to 5 and from 2.62 to 3.50 for the in vitro specimens. Intra-group comparisons within in vivo groups showed statistically significant differences between the two higher pulse energies of laser (160mJ and 250mJ) and the ultrasonically treated group regarding exposed dentinal tubules (p=0.011 and p=0.012, respectively).

Also, in vitro laser treatment at 100, 160 and 250mJ showed statistically significant differences with ultrasonically treated surfaces (p=0.012). This is documented in Table 1. Inter-group comparisons between in vivo laser groups revealed that 60mJ and 100mJ lasers produced significantly less exposures of dentinal tubules than 160mJ and 250mJ (p<0.001), and 160mJ lead to significantly less exposures than 250mJ (p=0.001).

The same comparisons within in vitro laser-treated groups, showed that each laser subgroup had a significantly less number of exposed tubules than the next higher pulse energy. Furthermore, performing inter-group comparison of each in vivo laser setting with its in vitro counterpart, 100mJ, 160mJ and 250mJ laser treatment showed significant differences (p<0.001, p=0.010 and p<0.001, respectively).

(HERE APPROXIMATELY TABLE 1 PLEASE)



Treatment duration

The mean duration of laser treatment in vivo ranged between 0.62 and 3.12 minutes while for the in vitro group, it was between 0.87 and 1.87 minutes. The duration ranged between 1 and 1.50 minutes for in vivo ultrasonic treatment and between 1 and 1.37 minutes for in vitro ultrasonic treatment. Intra-group comparisons within the in vivo groups showed statistically significant differences between laser treatment at 60mJ, 100mJ, 250mJ and ultrasonic scaling (p=0.011, 0.046 and 0.034, respectively). In the in vitro group, there were statistically significant differences between the two laser-treated groups of 60mJ and 250mJ and ultrasonic scaling (p=0.008 and 0.046, respectively). Inter-group comparisons between in vivo laser-treated groups, showed that 60mJ laser treatment took significantly more time than other settings. The same comparisons for in vitro laser-treated groups showed significant differences between 60mJ laser and 160mJ and 250mJ (p=0.002 and p=0.001 respectively). These results are summarized in Table 2.

(HERE APPROXIMATELY TABLE 2 PLEASE)

Discussion

In the current trial, each subgroup consisted of 8 teeth. This was a feasible sample size based on a somewhat similar study (22), as the studies investigating the dentinal tubules exposure as a measure for dentin denudation were very scarce.

The results of the present study revealed that Er:YAG was highly effective for hard tissue ablation. The rough and irregular surface, free of carbonization and melting, produced with all laser settings, is in line with the morphological findings in several other studies(17, 22, 24, 25). It appears that the use of Er:YAG laser under water irrigation with all the confounding factors involved in clinical applications even at a high energy of 250mJ/pulse does not cause thermal effects such as carbonization, melting and re-solidification.

Despite the general acceptance of surface roughening by laser treatment there is a range of diverse factors affecting the surface morphology such as application time and tip angulation(26). This renders the interpretation of the morphologic data difficult. In the present study, calculus was effectively ablated along with partial or complete ablation of the underlying cementum in all samples. Several other studies applying Er:YAG laser at 40-160mJ and 10Hz (22, 27, 28), reported similar calculus removal efficiency of laser and ultrasonic debridement.

There is controversy on the ideal settings of laser parameters to perform effective calculus removal while keeping the ablation of intact tooth substance to a minimum. The laser debridement at 60-160mJ/pulse, is effective in calculus removal as indicated in the present as well as other studies (23, 29, 30). However, these settings appear to ablate intact underlying tooth structures as well.

On the other hand in the present study, 250mJ/pulse laser was chosen to evaluate the effects of laser treatment with an extremely high pulse energy. Calculus removal and root substance ablation had both a similar threshold that was at approximately 37mJ/pulse. Hence, selective calculus removal without ablating cementum in clinical practice appears to be impossible (31).

Using lower pulse energies may help to limit the ablation of root cementum. Aoki and coworkers(23) removed the calculus effectively from root surface at 30mJ/pulse. Using energies of up to 120mJ/pulse, tooth substance ablation was generally observed within the cementum. Yet in another study, 100 and 120mJ/pulse laser treatment removed calculus efficiently, but lead to increased loss of cementum and dentin(17). Though, reducing the energy may reduce the efficacy and increase the treatment duration.

In our study, the number of exposed dentinal tubules followed an energy-dependent trend. This resulted in significantly more exposed dentinal tubules by in vivo laser use at 160 and 250mJ/pulse and in vitro laser use at 100,160 and 250mJ/pulse than noticed after ultrasonic treatment.

This trend was also generally noted when comparing laser energies with each other. However, the differences did not always reach statistical significance. Furthermore, the differences between the results of laser energies were more pronounced under in vitro condition. This energy-dependent pattern of ablation was observed in several studies(21, 22, 32). Nevertheless, the amount of substance removal differed extensively between reports. Some studies performed selective calculus removal with energies up to 100mJ/pulse observing only slight superficial changes. With higher energies of 120-180mJ/pulse, the ablation occurred totally within cementum (21, 30). Moreover, one study using laser treatment at 160mJ/pulse and 15Hz, achieved more dentin denudation following manual scaling(33). Nonetheless, several other studies reported complete local cementum removal following laser debridement at 80-160mJ/pulse (17, 22, 32).

Data regarding quantitative assessment of substance removal by laser are controversial. In one study utilizing laser energies of 80-150mJ/pulse, average substance removals of 174.38 (± 16.13) µm – 501.85 (± 111.01) µm and 37.78 (± 14.03) µm – 484.44 (± 80.63) µm were observed for teeth with and without calculus, respectively(21). Another study, using laser energies of 120mJ/pulse and 160mJ/pulse, reported maximum crater defect depths of 77.1 (± 42.8) µm which were within the range of ultrasonic and hand instruments(17, 34-36).

In other trials, laser at 10–120mJ/pulse, 120mJ/pulse and 40mJ/pulse were used, and a cementum ablation of 40–136 µm, 100 µm and 15–30 µm was reported, respectively(23, 28, 31). Similar to the outcomes of the present study, one study utilized 120, 140 and 160mJ/pulse lasers and observed more exposed dentinal tubules after laser debridement than after ultrasonic treatment in an energy dependent manner. However, statistically significant differences were only found for 160mJ/pulse laser (22). Such differences are partly due to the factors affecting cementum thickness such as age, periodontal condition, previous periodontal treatments and probably functional stimuli(37, 38). Furthermore, the differences may have been related to treatment conditions, such as treating in vivo or in vitro and tip angulation(26).

The amount of substance removal following conventional treatments is, to date, a matter of controversy, ranging from 12 to 410 µm among different studies (17, 39, 40). Another confounding factor is the amount of pristine cementum deposited ranging between 5 and 800 μm in molar teeth(39). This, in turn, means that one root debridement may lead to various outcomes in different teeth or various regions on one tooth, particularly causing more or less denudation of dentinal tubules. Considering the results of this and previous studies, it may be concluded that higher energies of laser than around 160mJ are probably ablating more substance than known for that of ultrasonic debridement.

Comparing in vivo laser settings with their in vitro counterparts, all in vivo laser treatments removed less cementum than in vitro. However, only at 100 and 250mJ/pulse a statistically significant difference was observed. This may be interpreted as more effective selective calculus removal under in vivo conditions. This postulate was confirmed by Schwarz and coworkers who utilized laser at 120, 140, 160 and 180mJ/pulse. They found more surface defects under in vitro than under in vivo condition(30). This more selective calculus removal under in vivo conditions, may be due to better heat diffusion within the pocket. Considering that the in vitro samples showed less selective calculus removal, extrapolating in vitro results to in vivo situations and drawing clinical conclusions from in vitro data is obviously doubtful.

The same energy dependent pattern was present when analyzing treatment duration. Within the in vivo groups, 60 and 100mJ/pulse laser took significantly more time than ultrasonic debridement, while for the in vitro group only 60mJ/pulse laser was significantly slower than ultrasonic treatment. In both in vivo and in vitro groups, 250mJ/pulse laser was significantly faster than ultrasonic debridement. Studies by Schwarz and coworkers(16, 41) presented the treatment duration using laser at 120-180mJ/pulse as 9 minutes treating 4 sides of single-rooted teeth under in vivo and in vitro conditions. The same group required 5-10 minutes for treating single- and multi-rooted teeth using either laser at 160mJ/pulse and 10Hz or ultrasonic debridement. In other studies using the same laser parameters, the treatment took 5-6.5 minutes for single-rooted and 9-11 minutes for multi-rooted teeth(19, 42). The ultrasonic treatment took 4-8.2 minutes for single-rooted teeth and 9-14.6 minutes for multi-rooted teeth in the same studies. Comparing the treatment durations of 100-160mJ/pulse laser in our study with outcomes of previous studies, the durations were in the same range. The intergroup comparisons of different in vivo laser treatment groups with each other, showed that 60mJ/pulse laser treatment took significantly more time than the other laser groups.

According to the outcome of the present study, a 60mJ/pulse laser was not significantly less aggressive than 100mJ/pulse, simply because the process required more time. Hence, it seems that this setting is impractical for clinical use. Generally, laser irradiation took more time in vivo than in vitro. This may partly be related to the difficulties associated with using a chisel attached to the arm of the laser machine and the form and thickness of the chisel which renders complete treatment of interproximal areas more demanding than ultrasonic debridement. For the same reason, the current trial focused mostly on the buccal and lingual aspects of teeth.

Recent studies have used a wide range of pulse energies for root surface debridement. While in some trials lower pulse energies around 30-50mJ/pulse (43, 44) have been utilized, others used relatively higher pulse energies like 100-160mJ/pulse (45-47). However, our observations suggest that erbium laser at pulse energies higher than 100mJ without a calculus detection system may be too aggressive for root surface debridement.

Although an efficient treatment outcome is dependent on biofilm and calculus removal, while preserving as much non-infected tooth substance as possible, there is to date no consensus about the necessary amount of cementum removal in order to achieve periodontal healing(40, 48). Excessive removal of intact tooth substance may lead to denudation of dentinal tubules which means various painful stimuli may cause sudden fluid shifts in such tubules and elicit a painful sensation and patient’s discomfort (49, 50). Moreover, studies have demonstrated that sensitive teeth have an increased number of dentinal tubules with greater diameters (51-53). However, it is not possible to precisely predict the consequences of excessive tooth substance removal, as root sensitivity remains a subjective experience.

The results of the current trial should be interpreted with caution, as the sample size was relatively small. Moreover, due to variability of cementum thickness, analyzing more areas along the root for dentinal tubules exposure might be recommended for future studies.



Conclusion

According to the results of this study, laser debridement at 160 mJ/pulse or higher was more aggressive than ultrasonic treatment. Hence, clinical application of laser debridement at 100mJ/pulse may be considered safe as it was significantly less aggressive than 160mJ and higher pulse energies, although as time-efficient as 160mJ/pulse. Using higher pulse energies without a calculus detection system can not be recommended for root surface debridement.



Acknowledgements

The authors would like to thank Dr. Maarten Meire for his contribution to this study and the colleagues in the department of Periodontology of the University of Ghent. The authors declare no conflict of interest.



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Tables

Table 1 : Intra-group and inter-group comparisons of the difference in number of exposed dentinal tubules by laser and ultrasonic scaler using uni-variate analysis

 

Table 2 : Intra-group and inter-group comparisons of the treatment duration by laser and ultrasonic scaler





Figure legends

Figure 1: The study flowchart (US: ultrasonic debridement)

Figure 2 : SEM micrographs of samples treated in vivo using ultrasonic scaler. The right image is a magnification of the area within the red rectangle. (Magnifications: x100 left image, x500 right image)

Figure 3 : SEM micrographs of samples treated in vivo using laser at: (A) and (B) 60mJ, (C) and (D) 100mJ, (E) and (F) 160mJ, (G) and (H) 250mJ. Images on the right are magnification of the areas within the red rectangles on the left side. (Magnifications: (A) x75, (B) x170, (C) x35, (D) x150, (E) x40, (F) x300, (G) x25, (H) x300)

Figure 4 : SEM micrographs of samples treated in vivo using laser or ultrasonic scaler : (A) laser at 60mJ, (B) laser at 100 mJ, (C) laser at 160mJ, (D) laser at 250mJ, (E) ultrasonic. (Magnification : x 1500)

Figure 5 : SEM micrographs of samples treated in vitro using laser or ultrasonic scaler : (A) laser at 60mJ, (B) laser at 100 mJ, (C) laser at 160mJ, (D) laser at 250mJ, (E) ultrasonic. (Magnification : x 1500)



 

 

 


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