Abstract
Background: The aim of the present study was to compare the effectiveness of an Er:YAG laser to that of ultrasonic scaling for non-surgical periodontal treatment.

Methods: Twenty patients with moderate to advanced periodontal disease were randomly treated in a split-mouth design with a single episode of subgingival debridement using either an Er:YAG laser device (160 mJ/pulse, 10 Hz) combined with a calculus detection system with fluorescence induced by 655 nm InGaAsP diode laser radiation (ERL), or an ultrasonic instrument (UI). Clinical assessments of full-mouth plaque score (FMPS), bleeding on probing (BOP), probing depth (PD), gingival recession (GR), and clinical attachment level (CAL) were made at baseline and at 3 and 6 months following therapy.

Results: No differences in any of the investigated parameters were observed at baseline between the two groups. The mean value of BOP decreased in the ERL group from 40% at baseline to 17% after 6 months (P <0.0001) and in the UI group from 46% at baseline to 15% after 6 months (P <0.0001). The sites treated with ERL demonstrated mean CAL gain of 1.48 ± 0.73 mm (P <0.001) and of 1.11 ± 0.59 mm (P <0.001) at 3 and 6 months, respectively. The sites treated with UI demonstrated mean CAL gain of 1.53 ± 0.67 mm (P <0.001) and of 1.11 ± 0.46 mm (P <0.001) at 3 and 6 months, respectively. No statistically significant differences were observed between the groups (P >0.05).

Conclusion: Within the limits of the present study, it can be concluded that both therapies led to significant improvements of the investigated clinical parameters. J Periodontol 2004;75:966-973.

KEY WORDS

Comparison studies; lasers/therapeutic use; periodontal diseases/therapy; scaling.

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Periodontitis is an inflammatory disease caused by opportunistic bacteria residing in the oral cavity, leading to a loss of the supporting tissues of the teeth (i.e., periodontal ligament and alveolar bone).1 According to the cause-related concept of periodontal therapy, a major objective of treatment is to create a biologically acceptable root surface by eliminating the bacterial biofilm.1 Traditionally, root surface debridement is performed with hand instruments such as Gracey curets.

More recently, power-driven instruments, including sonic and ultrasonic scalers, have been proposed to provide better access to deep probing sites and to increase the efficiency of subgingival instrumentation. Numerous studies have reported on the comparative clinical outcome of sonic and ultrasonic versus manual instrumentation.2-5 Power driven instruments have been shown to be superior in the treatment of Class II and Class III furcations when used by experienced operators.6 Furthermore, studies indicate that manual instrumentation generally takes longer to achieve the same clinical results as sonic and ultrasonic scalers.7,8

Nevertheless, a drawback of power-driven instruments is the formation of pathogenic bacterial aerosols.9 In recent years, different laser systems such as the CO2 (carbon-dioxide), the Nd:YAG (neodymium-doped: yttrium, aluminum and garnet), the diode and the Er:YAG laser (erbium-doped: yttrium, aluminum and garnet) have been proposed as an alternative or adjunctive treatment to conventional, mechanical therapy in periodontics.10-12 Several studies have reported negative effects of the Nd:YAG and CO2 lasers when used directly on root surfaces due to carbonization and melting effects.13-15 Trylovich et al.16 reported that the Nd:YAG laser alters the biocompatibility of the cementum surface so as to make it unfavorable for fibroblast attachment. Moreover, Fourier transformed infrared spectroscopy revealed reductions in the intensity of the Amide II band, suggesting that Nd:YAG laser irradiation denatures surface proteins. Additional contamination with denaturation side products such as ammonium further decreased cell attachment.17

In contrast, the Er:YAG laser has been reported to be the most effective laser for periodontal treatment. The results from previous studies demonstrated its excellent ability to effectively ablate dental hard tissue and calculus without producing major thermal side effects (e.g., charring or fusion) to the root surface.10-12 The Er:YAG laser irradiation also failed to alter the intensity of Amide peaks I, II, or III, indicating that the chemical structure of the root surface was not changed.18,19

Furthermore, several studies have reported antimicrobial effects against periodontopathic bacteria and the removal of lipopolysaccharides by Er:YAG laser radiation.20-23 However, histological and SEM examination showed that the Er:YAG laser ablated not only the calculus, but also the superficial portion of the underlying cementum, and left a root surface similar to an acid etched appearance with a scale like texture.10-12,24 The results from controlled clinical trials and case report studies have indicated that non-surgical periodontal treatment with an Er:YAG laser leads to significant gain of clinical attachment, even over a 2-year period.25-29 However, these investigations demonstrated no benefit or only slightly improved treatment outcomes compared to conventional scaling and root planing. In order to avoid any damages to the root surface, a subgingival calculus detection system with fluorescence induced by 655 nm InGaAsP diode laser radiation has been recently included in an Er:YAG laser. Preliminary in vitro results have shown that 655 nm diode laser radiation induces significantly stronger fluorescence in subgingival calculus than in cementum, suggesting that calculus removal may be selectively performed.30 So far, the clinical relevance of this system remains questionable.

As mentioned above, ultrasonic instrumentation has become nowadays an essential part of the armamentarium for non-surgical periodontal treatment. However, until now, no published data have been available concerning the clinical outcomes following treatment with an Er:YAG laser when compared to ultrasonic instrumentation. Therefore, the aim of the present study was to compare the effectiveness of an Er:YAG laser combined with a calculus detection system with fluorescence induced by 655 nm InGaAsP diode laser radiation to that of ultrasonic scaling for non-surgical periodontal treatment.

MATERIALS AND METHODS

Patient Population

Twenty periodontal patients, ages 29 to 62 years (mean age 51 years), were included in the study. The study was in accordance with the Helsinki Declaration of 1975, as revised in 1983 and all participants signed informed consent forms. The patient selection criteria were: 1) no periodontal treatment within the last 12 months; 2) no systemic diseases which could influence the outcome of the therapy; 3) not pregnant; 4) no use of antibiotics for the 6 months prior to treatment; and 5) good oral hygiene.

Study Design

The study used a split-mouth design. Only pockets exhibiting a probing depth of >4 mm were instrumented. All quadrants were randomly treated with a single episode of subgingival debridement using either an Er:YAG laser device (single-rooted teeth, N = 407 sites; multirooted teeth, N = 269 sites), or an ultrasonic instrument (single-rooted teeth, N = 383 sites; multirooted teeth, N = 247 sites). In all cases treatment was performed within 24 hours. The distribution of the two treatment modalities was equally divided between the right and left sides.

Oral Hygiene Program

For 4 weeks before treatment, all patients were enrolled in a hygiene program and received oral hygiene instructions during two to four appointments as well as supragingival professional tooth cleaning according to individual needs. A supragingival professional tooth cleaning and reinforcement of oral hygiene was performed at baseline as well as 2, 4, 6, 8, 10, 12, 16, 20, and 24 weeks after treatment.

Treatment

The treatment was performed under local anesthesia. An Er:YAG laser device|| (ERL) (wave length 2.94 μm) combined with a calculus detection system with fluorescence induced by 655 nm InGaAsP diode laser radiation was selected for laser treatment using an energy level of 160 mJ/pulse and a repetition rate of 10 Hz26-29 with water irrigation according to the manufacturer’s instructions. Fiber tips of 0.5 × 1.65 (136 mJ/pulse at the tip) and 0.5 × 1.1 mm (114 mJ/pulse at the tip) were chosen by the operator according to the situation. The treatment was performed from coronal to apical in parallel paths with an inclination of the fiber tip of 15 to 20 degrees31 to the root surface. An exciting laser radiation was delivered by an InGaAsP diode laser as red light at a wavelength of 655 nm. The diode laser beam was delivered onto the root surface with the above mentioned periodontal handpiece and the prismatically cut glass fiber tip. The mode of detection of fluorescence has been previously described.32 For treatment of the control group, an ultrasonic scaler¶ (UI) with straight and curved metal tips# was used under water irrigation according to the manufacturer’s instructions. The instrumentation for both laser and ultrasonic instrumentation was performed until the operator felt that the root surfaces were adequately debrided and planed. The amount of time needed in both groups was, on average, 5 minutes for single-rooted teeth and 9 minutes for multirooted teeth. All treatments were performed by the same experienced operator.

Clinical Measurements

After the 4-week pretreatment phase (baseline) and 3 and 6 months after the last treatment, the following clinical parameters were measured by one calibrated periodontist who was not involved in providing treatment: plaque index (PI),33 probing depth (PD) as measured from the gingival margin to the bottom of the probeable sulcus, gingival recession (GR) as measured from the cemento-enamel junction (CEJ) to the gingival margin, and clinical attachment level (CAL) as measured from the CEJ to the bottom of the probeable sulcus. Bleeding on probing (BOP) was assessed simultaneously with the pocket measurements, and the presence or absence of bleeding up to 30 seconds after probing was recorded. The measurements were made at six aspects per tooth: mesio-vestibular (mv), mid-vestibular (v), disto-vestibular (dv), mesio-oral (mo), mid-oral (o) and disto-oral (do) using a manual periodontal probe.**

Statistical Analysis

After completing the examination 24 weeks after treatment, the statistical evaluations were conducted using a computer program.†† Summary statistics were calculated for baseline as well as 3- and 6-month measurements. The net difference between each pair of measurements was then calculated (baseline–3 and baseline–6 months) in both groups. Statistical analysis within groups was performed using analysis of covariance (ANCOVA) and Scheffé’s test of multiple comparisons for repeated measures with measurement time and subject included in the model to account for the split-mouth design. Comparisons between groups at the different time points were performed using the unpaired t test. All statistical procedures were based on a level of significance of 5% (P <0.05). Primary outcome variable was CAL, and post-hoc power analysis‡‡ suggested that a significant difference of 1 mm between groups would have been detected with a probability of 75%.

Intraexaminer Reliability

Five patients, each presenting with two pairs of contralateral teeth (single and multirooted) with probing depths >6 mm on at least one aspect of each tooth, were used to assess intraexaminer reliability. The examiner evaluated the patients on two separate occasions, 48 hours apart. Reliability was accepted if measurements at baseline and at 48 hours were similar to the millimeter at >90% level.

RESULTS

Clinical Measurements

The postoperative healing was uneventful in all cases. No complications such as abscesses or infections were observed throughout the study period. At the baseline examination, there were no statistically significant differences in any of the investigated parameters (Table 1, Figure 1 and Figure 2). At 3 and 6 months BOP improved statistically significantly compared to baseline, but no statistically significant differences were found between the two groups (Table 2 and Table 3). In both groups, the CAL improved significantly compared to baseline (P <0.001). However, no statistically significant difference was observed between the two groups (Table 2 and Table 3). The effect of ERL and UI at different initial PD is shown in Figure 3 and Figure 4. Initially deeper pockets (>5 mm) showed the greatest changes in the PD, GR, and CAL. Moderately deep pockets (4 to 5 mm) showed more moderate improvements (Figure 3 and Figure 4). In particular, sites where PD was initially deep showed more GR, more CAL gain, and deeper residual PD at the 3- and 6-month examination than sites with initial moderate PD. At 6 months, the ERL group showed at initially moderately deep sites a mean CAL gain of 0.6 ± 0.4 mm and of 1.8 ± 1.7 mm at initially deep sites. At 6 months the UI group displayed a mean CAL gain of 0.6 ± 0.5 mm at initially moderate sites, and of 1.9 ± 1.7 mm at initially deep sites. No statistically significant difference was observed between the two groups.

DISCUSSION

The results of the present study indicate that non-surgical periodontal treatment with both ERL and UI may lead to clinically and statistically PD reduction and CAL gain. The fact that all pockets treated in this study healed uneventfully suggests that both treatment modalities were well tolerated. However, no statistical or clinical differences in any of the investigated parameters were observed between treatment modalities.

It should be pointed out that the sample size of this study was relatively small, and does not allow for definitive conclusions to be drawn. These data may serve as a basis to design a clinical trial aimed at showing statistical equivalence between the treatment modalities.34

When interpreting the present results, it should be noted that in both groups initially deeper pockets (>5 mm) showed the greatest CAL gain. Furthermore, the greatest change in the PD, GR, and CAL were observed 3 months post-treatment with even further improvements up to 6 months. In this context it is important to point to the results of previous studies which have shown that most changes in probing depth reduction and gain in clinical attachment occur within 1 to 3 months following non-surgical therapy, although healing of the periodontium may occur over the following 9 to 12 months.3,35,36 In the present study, the ERL group showed at initially moderately deep sites a mean CAL gain of 0.6 ± 0.4 mm, and of 1.8 ± 1.7 mm at initially deep sites 6 months postoperatively. At 6 months the UI group displayed at initially moderately deep sites a mean CAL gain of 0.6 ± 0.5 mm, and of 1.9 ± 1.7 mm at initially deep sites. The finding that non-surgical periodontal treatment with either an Er:YAG laser and an ultrasonic scaler may result in statistically significant improvements in PD and CAL compared to baseline is in agreement with previously reported data.2,3,25,27-29,37,38

Unfortunately, most clinical studies have not evaluated attachment level changes. Torfason et al.2 reported in a controlled study a mean PD decrease of 1.7 mm (baseline PD: 5.0 mm) 2 months after ultrasonic instrumentation. There was no statistically significant difference between ultrasonic and hand instrumentation. Badersten et al.3 reported a mean PD decrease of 1.3 mm after 13 months for both ultrasonic and hand instrumentation (baseline PD: 4.2 mm) and Loos et al.37 reported a mean PD increase of 0.5 mm for initially shallow sites (<3.5 mm), 1.2 mm for moderately deep pockets (4 to 6.5 mm), and 2.3 mm for deep pockets (>7 mm) with a mean CAL gain of 0.6 mm 24 months postoperatively. One month postoperatively, Boretti et al.38 reported a mean PD decrease of 1.82 mm and a mean CAL gain of 1.14 mm for ultrasonic scaling. In a clinical study evaluating the clinical efficiency of an Er:YAG laser for soft tissue surgery and scaling, Watanabe et al.25 reported a mean PD reduction of 3.0 mm after 1 month (baseline PD: 5.6 mm). Following non-surgical periodontal treatment with an Er:YAG laser in a controlled clinical study, Schwarz et al.27,29 reported a mean PD decrease of 2.0 mm with a mean CAL gain of 1.9 mm after 6 months and a mean PD decrease of 1.6 mm with a mean CAL gain of 1.4 mm after 24 months (baseline PD: 4.9 mm). These results were statistically significant compared to baseline. This is in accordance with the results of ERL and UI treated sites in the present study. Another important factor that influences the outcome of non-surgical periodontal treatment is the removal of subgingival calculus and the detoxification of the root surface.3,39,40 Several studies have demonstrated that ultrasonic instrumentation achieves equal or superior treatment outcomes when compared with hand instruments.2,4,5,7 However, the effectiveness of Er:YAG laser scaling, as well as its effect on the root surface, has not yet been evaluated thoroughly. Aoki et al.24 reported on the effectiveness of Er:YAG laser scaling in comparison to ultrasonic scaling in vitro. This laser provided calculus removal on a level equivalent to that provided by an ultrasonic scaler. However, the efficiency of laser scaling was lower than that of the ultrasonic device.

As mentioned above, histological and scanning electronic microscope examination showed that the Er:YAG laser ablated not only the calculus, but also the superficial portion of the underlying cementum, and that the instrumented root surface had characteristic microstructures.10-12,24 Although this microstructured root surface showed no cracks or thermal effects like melting after CO2- or Nd:YAG laser irradiation,11 some authors have suggested additional treatment to remove the superficially changed layer of the lased root surface using root planing via hand instruments.13,16 In this context it is important to mention the results of a previous clinical study which showed that the combined treatment Er:YAG laser and scaling and root planing did not seem to additionally improve the outcome of the therapy compared to laser treatment alone.28 In contrast, studies evaluating root surface alterations produced by ultrasonic instruments suggest that this treatment modality does less damage to the root surface than hand instruments.7,41

In the present study, an Er:YAG laser device was used in combination with a subgingival calculus detection system with fluorescence induced by 655 nm diode laser radiation. To the best of our knowledge, there is only one study available reporting that 655 nm InGaAsP diode laser radiation induces significantly stronger fluorescence in subgingival calculus than in cementum.30 It was assumed that bacteria derived byproducts, such as porphyrin which is released by the periodontopathogenic Porphyromonas sp., may be responsible for the strong fluorescence of subgingival calculus.30,42 It should be noted that the present study was not designed to evaluate the clinical efficiency of this mechanism. However, based on the clinical results, especially in comparison to the above referenced studies, it may be suggested that this system did not seem to additionally improve the outcome of non-surgical periodontal treatment. Further studies are needed in order to clarify this issue. Within the limits of the present study, it may be concluded that both therapies led to significant improvements of the investigated clinical parameters.

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* Department of Conservative Dentistry and Periodontology, Johannes Gutenberg University, Mainz, Germany.
† Department of Oral Surgery, Heinrich Heine University, Düsseldorf, Germany.
‡ Department of Oral Surgery and Implantology, Johann Wolfgang Goethe University of Frankfurt, Dental School (Carolinum), Frankfurt, Germany.
§ Department of Conservative Dentistry and Periodontology, Albert-Ludwigs-University, Freiburg, Germany.
|| KEY3, KaVo, Biberach, Germany.
¶ Cavitron Select, Dentsply, Konstanz, Germany.
# FSI Slimline, Dentsply.
** PCP 12, Hu-Friedy Co., Chicago, IL.
†† SPSS version 10.0, SPSS Inc., Chicago, IL.
‡‡ G*Power Analysis Window 2.0, Edgar Erdfelder, Department of Psychology, University of Bonn, Bonn, Germany.

Correspondence: Dr. Anton Sculean, Department of Conservative Dentistry and Periodontology, Johannes Gutenberg University, Augustusplatz 2, D-55131 Mainz, Germany. E-mail: [email=”anton.sculean@gmx.de.”]anton.sculean@gmx.de.[/email]

Accepted for publication November 14, 2003.

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