55101 Mainz, Germany 3 Institute of Medical Biometrics, Epidemiology and Medical Informatics, University of Saarland,

Transcription

1 Lasers in Surgery and Medicine 32: (2003) In Vivo and In Vitro Effects of an Er:YAG Laser, a GaAlAs Diode Laser, and Scaling and Root Planing on Periodontally Diseased Root Surfaces: A Comparative Histologic Study Frank Schwarz, 1 * Anton Sculean, PhD, MS, 2 Mohammad Berakdar, 2 Ludwig Szathmari, 2 Thomas Georg, 3 and Jürgen Becker 4 1 Department of Oral Surgery, Heinrich Heine University, Düsseldorf, Germany 2 Section of Periodontology, Department of Conservative Dentistry and Periodontology, Johannes Gutenberg-University, Mainz, Germany 3 Institute of Medical Biometrics, Epidemiology and Medical Informatics, University of Saarland, Homburg, Germany 4 Chairman of the Department of Oral Surgery, Heinrich Heine University, Düsseldorf, Germany Background and Objectives: The aim of the present histologic study was to compare the in vivo and in vitro effects of an erbium: yttrium, aluminum, and garnet (Er:YAG) laser (ERL), combined with a fluorescent calculus detection system, a diode laser (DL) and scaling and root planing (SRP) on periodontally diseased root surfaces. Study Design/Materials and Methods: Twenty-four single rooted teeth, considered for extraction due to severe periodontal destruction, were included in the study. Prior to extraction all mesial root surfaces were randomly assigned to the following treatment groups: (1) ERL combined with a calculus detection system with fluorescence induced by 655 nm InGaAsP DL radiation (160 mj/pulse and 10 pulses/second under water irrigation) (ERL), or (2) GaAlAs DL (1.8 W, pulse/pause relation 1:10), or (3) SRP using hand instruments. Immediately after extraction, all distal root surfaces were treated with the same instruments under standardized conditions. For light microscopic investigation, a plastic embedding technique was used to cut the undecalcified roots into 30 mm thick crossections. The following parameters were recorded by on blind examiner: remaining debris, root surface morphology, and thermal side effects. Results: Root surfaces instrumented with both, ERL in vivo and DL in vitro exhibited no detectable surface alterations. In contrast, ERL scaling in vitro and SRP in vivo/in vitro produced superficial microchanges in root cementum. However, irradiation with DL in vivo caused severe damages to the root surface (i.e., crater formation). There were no signs of thermal side effects in all laser treated groups. ERL provided subgingival calculus removal on a level equivalent to that provided by SRP. DL was unsuitable for calculus removal, since macroscopic inspection revealed the presence of large amounts of subgingival calculus. Conclusions: The present in vivo results showed that (i) ERL, combined with a fluorescent calculus detection system, provided a selective subgingival calculus removal on a level equivalent to that provided by SRP, and (ii) DL, using this power output, was unsuitable for calculus removal and altered the root surface in an undesirable manner. Lasers Surg. Med. 32: , ß 2003 Wiley-Liss, Inc. Key words: fluorescence; histology; laser; morphology; periodontal disease; scaling INTRODUCTION The principal objective in the treatment of periodontitis is the complete removal of all calcified and bacterial deposits from the root surfaces in order to stop disease progression [1,2]. Several treatment modalities, such as scaling and root planing (SRP), sonic and ultrasonic devices, or air abrasives have been employed with varying degrees of success in order to accomplish this goal [3 8]. One of the most documented treatments is SRP, which is accomplished using hand instruments. Numerous studies have reported beneficial results from this treatment modality in both clinical and microbial parameters [3,6,7]. However, removal of calculus using conventional hand instruments has been reported to be incomplete [1] and rather time consuming [9]. In order to improve the effectiveness and efficiency of root surface debridement, both sonic and ultrasonic scalers [5,8], and recently lasers have been used [10 14]. Among all lasers used in the field of dentistry, which include CO 2 (carbon-dioxide), the Nd:YAG laser (neodymium-doped: yttrium, aluminum, and garnet), and diode lasers (DLs), the Er:YAG laser (ERL) has been reported to be the most promising laser for periodontal *Correspondence to: Dr. med. dent. Frank Schwarz, Department of Oral Surgery, Heinrich Heine University, Westdeutsche Kieferklinik, Moorenstr. 5 D Düsseldorf, Germany. info@frank-schwarz.de Accepted 7 March 2003 Published online in Wiley InterScience ( DOI /lsm ß 2003 Wiley-Liss, Inc.

2 360 SCHWARZ ET AL. treatment. Its excellent ability to effectively ablate hard tissue and dental calculus without producing major thermal side-effects to adjacent tissue has been demonstrated in numerous studies [11,12,15 17]. Furthermore, the results from controlled clinical trials and case report studies have also indicated that non-surgical periodontal treatment with an ERL leads to significant gain of clinical attachment level [14,18 22]. This minimally invasive device may allow instrumentation of very deep and narrow pockets without leading to major trauma of the hard and soft tissues; i.e., removal of tooth substance and increase in gingival recession [14,17,22,23]. In contrast, several studies have confirmed the negative effects of the Nd:YAG and CO 2 lasers when used directly on root surfaces. These negative effects include thermal damage, such as carbonization and melting, to the root surface [24 26] which has been shown to inhibit attachment of fibroblasts and delay wound healing [27,28]. So far, there is limited information about the effects of DL radiation on the surface properties of root surfaces [29,30]. The results from a recent study showed that this laser may cause damage to periodontal hard tissues if irradiation parameters are not adequate [29]. Although periodontal treatment with an ERL offers indeed some interesting perspectives to the clinician, some questions are still present and need to be solved. One of them is the extent of the root surface damage after laser application. Histological and SEM examination showed that under in vitro conditions the ERL ablated not only the calculus, but also the superficial portion of the underlying cementum. The surface was left with an acid-etched appearance microscopically [11,12,31]. In contrast, SEM observations from a recent study showed that the clinical use of an ERL resulted in a smooth root surface morphology, even at higher energy settings [17]. However, SEM analysis may not be sufficient in order to investigate the effects of laser radiation on the subsurface layers of root cementum and dentin. In order to avoid any damages to the root surface, a subgingival calculus detection system with fluorescence induced by 655 nm InGaAsP DL radiation has been recently included in an ERL device. Preliminary in vitro results have shown that 655 nm DL radiation induces significantly stronger fluorescence in subgingival calculus than in cementum [32]. So far, there are no histologic data evaluating the in vivo effects of an Er:YAG, used with this fluorescent calculus detection system, or a DL on the surface properties of root cementum. Therefore, the purpose of the present study was to histologically determine the in vivo and in vitro effects of an ERL combined with a calculus detection system with fluorescence induced by 655 nm InGaAsP DL radiation, a GaAlAs DL and SRP on periodontally diseased root surfaces using light microscopic examination. the patients. Each tooth satisfied the following criteria: (1) probing pocket depths (>8 mm) on at least two aspects (mesio-vestibular/mesio-oral and disto-vestibular/distooral) as measured from the gingival margin to the bottom of the pocket, (2) mobility in horizontal and vertical direction, (3) no signs of carious or artificial damage on the root surface, (4) no periodontal root surface treatment within the last 12 months, and (5) no root fractures or anatomical abnormalities. Furthermore, patients suffering from systemic diseases, which could influence the outcome of the therapy, were excluded from the study. All teeth were randomly assigned to the following treatment groups: (1) ERL, (2) GaAlAs DL, or (3) SRP using hand instruments. Treatments An ERL (KEY3 1, KaVo, Biberach, Germany) device emitting a pulsed infrared radiation at a wavelength of 2.94 mm was selected for laser treatment. Laser parameters were set at 160 mj/pulse and 10 pulses/second, and pulse energy at the tip (size mm) was approximately 120 mj/pulse (19.4 J/cm 2 ) [14,18,22]. The laser beam was guided onto the root surfaces under water irrigation with a specially designed periodontal handpiece and a chiselshaped glass fiber tip (2061, KaVo). The treatment was performed from coronal to apical in parallel paths with an inclination of the fiber tip of [33] to the root surface. The exciting laser radiation was delivered by an InGaAsP DL as red light at a wavelenght of 655 nm. The DL beam was delivered onto the root surface with the above mentioned periodontal handpiece and the prismatically cut glass fibre tip (Fig. 1). The mode of detection of fluorescence has been previously described [34]. In brief, the InGaAsP DL radiation induces fluorescence in the irradiated mineralized substance. The laser radiation is guided to the angulated chisel-shaped glass fiber tip within a central fiber. Additional surrounding fibers are arranged around this central fiber that collect the fluorescent light emitted from the irradiated tissue. The fluorescent light is guided together with the reflected radiation as well as the ambient light from the surrounding fibers [32]. When the receiver no longer gets any fluorescence signals, the ERL beam is switched off. For the treatment of test group 2 a GaAlAs DL MATERIALS AND METHODS Study Design This study was conducted on 24 single rooted teeth (n ¼ 48 surfaces), considered for extraction due to severe periodontal destruction, based on informed consent of Fig. 1. Chisel-shaped application tip ( mm) for use of erbium: yttrium, aluminum, and garnet (Er:YAG) laser (ERL) radiation in periodontal treatment.

3 Er:YAG AND GaAl as DIODE LASER SCALING OF DISEASED ROOT SURFACES 361 Fig. 2. The diode laser (DL) light (810 nm) was delivered by a 600 mm contact optic fiber on the root surface. Fig. 4. Boxplots with outliners for the medians and Q1 Q3 quartiles of CD (mm) on root surfaces after instrumentation in vivo (ERL, DL, SRP). Lines below and above box plots: min, max. Fig. 3. Histometric evaluation: crater depth (CD) was measured by drawing a perpendicular line connecting the margins of the crater at the point of maximum depth (original magnification 250). (Ora-Laser-Jet 20 1, Oralia, Konstanz, Germany) with a wavelenght of 810 nm and 10,000 Hz toppulse was used. In our study, the pulse/pause relation was set at 1:10 at a power output of 1.8 W according to the instructions given by the manufacturer. The laser light was delivered by a 600 mm contact optic fiber (0.63 mj/mm 2 ) (Fig. 2). The mechanical subgingival instrumentation of test group 3 was accomplished using hand instruments (Hu-Friedy Co., Chicago, IL). All treatments were performed under local anesthesia until the mesial root surfaces were adequately debrided and planed. Immediately after instrumentation, the teeth were extracted. All root surfaces appeared unaltered by the extraction procedure. After the extraction remaining tags of the periodontal ligament were carefully removed using tweezers. After that, moistened teeth were fixed in an artificial root socket and treatment of all distal TABLE 1. Histometric Results (ERL, GaAlAs DL, SRP) Samples with craters (N) Mean number of craters/sample Mean CD (mm) Samples with exposed dentin (N) Samples with thermal side effects (N) Samples with remaining debris (N) Remaining debris as percentage of the mesial and distal root surface (N, %) In vivo group ERL (n ¼ 8) DL (n ¼ 8) SRP (n ¼ 8) In vitro group ERL (n ¼ 8) DL (n ¼ 8) SRP (n ¼ 8) ERL, erbium: yttrium, aluminum, and garnet (Er:YAG) laser; DL, diode laser; SRP, scaling and root planing; CD, crater depth.

4 362 SCHWARZ ET AL. surfaces was performed under near-clinical conditions. The end point of debridement in vitro was judged as the inability to detect subgingival calculus visually. The amount of time needed in all groups was, on average, 2 minutes per surface. Histological Examination All teeth were dehydrated in a graded alcohol series and embedded in metacrylate (Technovit 1, Kulzer Gmbh, Wehrheim Its, Germany) using a standard method [35]. After that, crossections were cut with a diamond saw at mm. The slices were ground automatically by a special machine to a thickness of 30 mm. All historical sections were stained with toluidine blue and evaluated under a light microscope (Leitz Orthoplan, Leitz, Wetzlar, Germany) by one blind and calibrated examiner. The following parameters were recorded: remaining debris (yes/no) as a percentage of the observed root surface, craters (yes/no), mean number of craters per sample, mean depth of craters, exposed dentin (yes/no), and thermal side effects (carbonization, melting, cracking) (yes/no). Each surface was viewed with a mm ocular grid subdivided into one hundred 0.1 mm squares to assess remaining debris (original magnification 25). The total number of squares, which covered each surface from the connective tissue attachment to the cemento-enamel junction were counted. Only surface areas covering more than one-half of a square were counted. Then the number of squares with calculus were counted for each surface. A percentage of squares with calculus was then calculated [36]. Intra-observer reliability was evaluated by assessing remaining debris in two specimens of each group (n ¼ 12) 10-fold. Crater depth (CD) was measured on photomicro- Fig. 5. Photomicrographs of in vivo treated root surfaces: C, cementum; CDJ, cementodentinal junction; D, dentin. a: ERL; b, hand instruments; c, d, GaAlAs DL (original magnifications: a, b: 250; c, 100; d, 400).

5 Er:YAG AND GaAl as DIODE LASER SCALING OF DISEASED ROOT SURFACES 363 graphs by drawing a perpendicular line connecting the margins of the crater at the point of maximum depth (original magnification 250) (Fig. 3) [37]. Intra-observer reliability was evaluated by measuring mean CD in two specimens of each group (n ¼ 12) 10-fold. The results were expressed as coefficient of variation. Statistical Analysis A software package (SPSS 11.0, SPSS, Inc., Chicago, IL) was used for the statistical analysis. Mean values and standard deviations for the histometric parameters were calculated. For the comparisons between groups, the unpaired t-test was used. Values of P < 0.05 were accepted as statistically significant. RESULTS Instrumentation In Vivo Intra-observer variability (measurement of CD) was between 1.9 and 3.2%. The ERL produced homogen and nearly smooth root surfaces without visible traces of the used fiber tip. Loss of cementum was generally non-existent or minimal (Table 1 and Fig. 4). Treated areas could have not been demarcated from untreated areas in respect of the surface morphology. Only the presence of calculi has given signs of the treatment borders (Fig. 5a). The histologic inspection of the root surfaces indicated that subgingival calculus was selectively removed (Fig. 5a). Histologically, no thermal damage, such as carbonization, melting, or cracking, was observed. The root surfaces treated using hand instruments generally had a smooth appearance. Some scratches, but also shallow craters caused by the curettes were occasionally observed in all specimens (Fig. 5b). Mean CD was 26.4 mm (Table 1 and Fig. 4). In contrast, DL irradiation caused severe damages to the root surface. Calculus-free areas examined histologically showed grooves and crater-like defects in all cross-sections (Fig. 5c,d). Mean CD was 62.5 mm. In six of eight samples, cementum was ablated through to the dentin (Table 1 and Fig. 5c,d). Histologically, no major thermal damage, such as carbonization, melting, or cracking, was observed. The maximum number of craters was observed in the DL group (P < 0.001), and these craters were significantly deeper than those following treatment with hand instruments (P < 0.001) (Table 1). Instrumentation In Vitro Intra-observer variability (measurement of CD) was between 1.9 and 3.2%. Histologically, no major thermal damage, such as carbonization, melting, or cracking, was observed for all treatment modalities (Table 1). Root surface instrumentation with ERL resulted in an increased removal of cementum. In one of eight samples, cementum was ablated through to the dentin. All ERL irradiated specimens exhibited numerous shallow ablation cavities with notch-edged borders and linear tracking lines caused by the fiber tip (Figs. 6 and 7a,b). Mean CD was 36.8 mm (Table 1 and Fig. 6). Comparable to instrumentation in vivo, root surfaces treated using hand instruments generally had a smooth appearance (Fig. 7c). Some scratches, but also Fig. 6. Boxplots with outliners for the medians and Q1 Q3 quartiles of CD (mm) on root surfaces after instrumentation in vitro (ERL, DL, SRP). Lines below and above box plots: min, max. shallow craters caused by the curettes were occasionally observed in all specimens. Mean CD was 24.3 mm (Table 1 and Fig. 6). In contrast, DL irradiation resulted in no detectable alterations such as crater formation, exposure of dentin, charring, or cracking on the root surface (Table 1 and Fig. 7d). The maximum number of craters was observed in the ERL group (P < 0.01), and these craters were significantly deeper than those following treatment with hand instruments (P < 0.01) (Table 1). Calculus Ablation Intra-observer variability (assessment of remaining debris) was between 2.4 and 3.7%. Clinically, the ERL provided a level of subgingival calculus removal that was similar to that provided by hand instruments (Table 1). In both groups, the histological examination occasionally revealed very tiny residual calculi on the treated root surfaces of all specimens. Calculus-free areas examined macroscopically and histologically looked fairly well cleaned. However, in vitro instrumentation was more effective than in vivo instrumentation (Table 1). In contrast, all specimens treated with the DL exhibited large amounts of subgingival calculus. These light to dark brown areas of calculus covered large areas of the root surfaces (Fig. 7c). There was no difference between in vivo and in vitro instrumentation. DISCUSSION The results of the present study have demonstrated that under in vivo conditions subgingival calculus can be

6 364 SCHWARZ ET AL. Fig. 7. Photomicrographs of in vitro treated root surfaces: C, cementum; CDJ, cementodentinal junction; D, dentin; SC, subgingival calculus. a, b: ERL; c, hand instruments; d, GaAlAs DL (original magnifications: a d: 250). removed almost completely from periodontally diseased root surfaces using both, an ERL in combination with a fluorescent calculus detection system or hand instruments. These findings are in accordance with the results from previous in vitro studies, which have shown that a pulsed ERL used with water irrigation was able to effectively remove subgingival calculus from the root surface [11,38]. This laser provided calculus removal on a level equivalent to that provided by an ultrasonic scaler [38]. The results of the present study have also shown that the subgingival calculus detection system with fluorescence induced by 655 nm InGaAsP DL radiation appears to be a valuable tool for the clinical detection of calculus, since instrumentation in vivo provided a level of subgingival calculus removal that was similar to that provided under in vitro conditions. However, in vitro instrumentation was more effective than in vivo instrumentation. This discrepancy might be explained by the fact that the intensity of fluorescence on cementum seems to be influenced by the surrounding media. The results from a recent in vitro study showed that the presence of blood or electrolytic solution considerably influenced the amount of fluorescence radiation. Nevertheless, the differential fluorescence between subgingival calculus and cementum was highly significant in air, blood, and electrolytic solution [32]. As mentioned above, elimination of all calcified deposits from periodontally involv-

7 Er:YAG AND GaAl as DIODE LASER SCALING OF DISEASED ROOT SURFACES 365 ed root surfaces is a desired goal of SRP [2]. In this context, it is important to point to the results of previous studies which have shown that complete removal of subgingival calculus may not be predictably attainable following SRP with hand instruments [1,39]. Molar teeth seemed to be more difficult to clean than single-rooted teeth [39]. In this respect, it must be pointed out that one limitation of the present study was the lack of a group consisting of multi-rooted teeth, since both, hand instruments and ultrasonic devices were relatively ineffective in removing calculus from the furcal walls [40]. Further research is needed in order to investigate the relative effectiveness of the ERL for calculus removal in molar furcations. The present results have also shown that the DL was unsuitable for calculus removal, since macroscopic inspection of the root surfaces revealed the presence of large amounts of subgingival calculus. Because no previous work on DL for calculus removal in vivo appears to have been reported, the present results cannot readily be compared with those of other studies. Furthermore, the results of the present study have also indicated that in vivo application of DL radiation for nonsurgical periodontal treatment caused severe damages to the root surface, since grooves and crater-like defects were found in all cross-sections. However, there were no signs of thermal side effects, such as carbonization or melting. In contrast, lasing moistened specimens in vitro resulted in no detectable alterations on the root surface. These findings are in accordance with the results from a previous in vitro study, which have shown that DL radiation caused severe damages to the root surface when segments were covered by a thin blood film [29]. Irradiation at a power output of 1 W and below had barely any negative effect on the root surface whereas lasing at 1.5, 2.0, and 2.5 W resulted in partial or total carbonizations of the root samples. In contrast, lasing dry specimens and specimens moistened with saline resulted in no detectable alterations, irrespective of irradiation time and power output applied. This phenomenon might be explained by the high absorption values of the laser light at 810 nm in hemoglobin and other pigments. However, in vitro instrumentation with the ERL also resulted in an increased removal of cementum. All irradiated specimens exhibited numerous shallow ablation cavities with notch-edged borders and linear tracking lines caused by the fiber tip. In contrast, in vivo instrumentation with the ERL produced homogeneous and nearly smooth root surfaces without visible traces of the used fiber tip. A loss of cementum was generally non-existent or minimal. The in vitro results are in accordance with the results of previous studies, which have shown that an ERL ablated not only the calculus, but also the superficial portion of the underlying cementum, and that the treated surface had characteristic microstructures resulting from cementum ablation [11,17,31,37,38]. However, this microstructured root surface showed no cracks or thermal effects like melting after CO 2 - and Nd:YAG-laser irradiation [31]. The results of the present study support a previous SEM investigation that reported a selective calculus removal with the ERL under in vivo conditions [17]. All root surfaces treated in vitro showed visible crater-like defects with notch-edged borders. The depth of the surface damages varied with the power applied and was localized into cementum at energy settings of mj but also reached dentine at 180 mj. Compared to that, all in vivo treated surfaces showed a homogeneous and smooth root surface morphology. The surface alterations were not related to the used energy setting. These observations, coupled with the findings that the ERL has also high antimicrobial effects against periodontopathic bacteria [10,13], probably explain, at least in part, the successful healing following non-surgical periodontal treatment as described in numerous clinical studies [14,18 22]. The achieved results also appeared to be stable over a 2-year period [22]. Although the combined treatment ERL and SRP did not seem to additionally improve the outcome of the therapy compared to laser treatment alone [18], it remains unclear to what extend this laser treated root surface is capable of supporting the new attachment of the periodontal tissues. In conclusion, within the limits of this study, the in vivo results indicate that (i) ERL, used with a new fluorescent calculus detection system, provided a selective subgingival calculus removal on a level equivalent to that provided by SRP, and (ii) DL, using this power output, was unsuitable for calculus removal and altered the root surface in an undesirable manner. REFERENCES 1. Kepic TJ, O Leary TJ, Kafrawy AH. Total calculus removal: An attainable objective? J Periodontol 1990;61: O Leary TJ. The impact of research on scaling and root planing. J Periodontol 1986;57: Badersten A, Niveus R, Egelberg J. 4-year observations of basic periodontal therapy. J Clin Periodontol 1987;14: Berkstein S, Reiff RL, McKinney JF, Killoy WJ. Supragingival root surface removal during maintenance procedures utilizing an air-powder abrasive system or hand scaling. An in vitro study. J Periodontol 1987;58: Breininger DR, O Leary TJ, Blumenshine RV. Comparative effectiveness of ultrasonic and hand scaling for the removal of subgingival plaque and calculus. J Periodontol 1987;58: Lindhe J, Westfelt E, Nyman S, Socransky SS, Haffajee AD. Long-term effect of surgical/non-surgical treatment of periodontal disease. J Clin Periodontol 1984;11: Ramfjord SP, Caffesse RG, Morrison EC, Hill RW, Kerry GJ, Appleberry EA, Nissle RR, Stults DL. 4 modalities of periodontal treatment compared over 5 years. J Clin Periodontol 1987;14: Smart GJ, Wilson M, Davies EH, Kieser JB. The assessment of ultrasonic root surface debridement by determination of residual endotoxin levels. J Clin Periodontol 1990;17: Flemmig TF, Petersilka GJ, Mehl A, Hickel R, Klaiber B. Working parameters of a magnetostrictive ultrasonic scaler influencing root substance removal in vitro. J Periodontol 1998;69: Ando Y, Aoki A, Watanabe H, Ishikawa I. Bactericidal effect of erbium:yag laser on periodontopathic bacteria. Lasers Surg Med 1996;19: Aoki A, Ando Y, Watanabe H, Ishikawa I. In vitro studies on laser scaling of subgingival calculus with an erbium:yag laser. J Periodontol 1994;65: Folwaczny M, George G, Thiele L, Mehl A, Hickel R. Root surface roughness following Er:YAG laser irradiation at different radiation energies and working tip angulations. J Clin Periodontol 2002;29:

8 366 SCHWARZ ET AL. 13. Folwaczny M, Mehl A, Aggstaller H, Hickel R. Antimicrobial effects of 2.94 micrometer Er:YAG laser radiation on root surfaces: An in vitro study. J Clin Periodontol 2002;29: Schwarz F, Sculean A, Georg T, Reich E. Periodontal treatment with an Er:YAG laser compared to scaling and root planing. A controlled clinical study. J Periodontol 2001;72: Gaspirc B, Skaleric U. Morphology, chemical structure, and diffusion processes of root surface after Er:YAG and Nd:YAG laser irradiation. J Clin Periodontol 2001;28: Sasaki KM, Aoki A, Ichinose S, Ishikawa I. Morphological analysis of cementum and root dentin after Er:YAG laser irradiation. Lasers Surg Med 2002;31: Schwarz F, Putz N, Georg T, Reich E. Effect of an Er:YAG laser on periodontally involved root surfaces: An in vivo and in vitro SEM comparison. Lasers Surg Med 2001;29: Schwarz F, Sculean A, Berakdar M, Georg T, Reich E, Becker J. Clinical evaluation of an Er:YAG laser combined with scaling and root planing for non-surgical periodontal treatment. A controlled, prospective clinical study. J Clin Periodontol 2003; Watanabe H, Ishikawa I, Suzuki M, Hasegawa K. Clinical assessments of the erbium:yag laser for soft tissue surgery and scaling. J Clin Laser Med Surg 1996;14: Jepsen S, Rühling A, König J, Dietzel K, Keller U, Albers KH. Treatment of periodontitis with a novel Er:YAG laser system. J Dent Res 2000;79:2281 (Abstract). 21. Schwarz F, Sculean A, Arweiler N, Reich E. Nicht-chirurgische Parodontalbehandlung mit einem Er:YAG Laser. Parodontologie 2000;4: Schwarz F, Sculean A, Berakdar M, Georg T, Reich E, Becker J. Periodontal treatment with an Er:YAG laser or scaling and root planing. A 2-year follow up split-mouth study. J Periodontol 2003;74: Hibst R, Keller U. Experimental studies of the application of the Er:YAG laser on dental hard substances: I. Measurement of the ablation rate. Lasers Surg Med 1989;9: Cobb CM, McCawley TK, Killoy WJ. A preliminary study on the effects of the Nd:YAG laser on root surfaces and subgingival microflora in vivo. J Periodontol 1992;63: Spencer P, Trylovich DJ, Cobb CM. Chemical characterization of lased root surfaces using Fourier transform infrared photoacoustic spectroscopy. J Periodontol 1992;63: Wilder-Smith P, Arrastia AM, Schell MJ, Liaw LH, Grill G, Berns MW. Effect of Nd:YAG laser irradiation and root planing on the root surface: Structural and thermal effects. J Periodontol 1995;66: Trylovich DJ, Cobb CM, Pippin DJ, Spencer P, Killoy WJ. The effects of the Nd:YAG laser on in vitro fibroblast attachment to endotoxin-treated root surfaces. J Periodontol 1992;63: Gopin BW, Cobb CM, Rapley JW, Killoy WJ. Histologic evaluation of soft tissue attachment to CO 2 laser-treated root surfaces: An in vivo study. Int J Periodontics Restorative Dent 1997;17: Kreisler M, Al Haj H, Daublander M, Gotz H, Duschner H, Willershausen B, D Hoedt B. Effect of diode laser irradiation on root surfaces in vitro. J Clin Laser Med Surg 2002;20: Moritz A, Schoop U, Goharkhay K, Schauer P, Doertbudak O, Wernisch J, Sperr W. Treatment of periodontal pockets with a diode laser. Lasers Surg Med 1998;22: Israel M, Cobb CM, Rossmann JA, Spencer P. The effects of CO 2, Nd:YAG, and Er:YAG lasers with and without surface coolant on tooth root surfaces. An in vitro study. J Clin Periodontol 1997;24: Folwaczny M, Heym R, Mehl A, Hickel R. Subgingival calculus detection with fluorescence induced by 655 nm InGaAsP diode laser radiation. J Periodontol 2002;73: Folwaczny M, Thiele L, Mehl A, Hickel R. The effect of working tip angulation on root substance removal using Er:YAG laser radiation: An in vitro study. J Clin Periodontol 2001;28: Lussi A, Megert B, Longbottom C, Reich E, Francescut P. Clinical performance of a laser fluorescence device for detection of occlusal caries lesions. Eur J Oral Sci 2001;109: Donath K, Breuner G. A method for the study of undecalcified bones and teeth with attached soft tissues. The Sage-Schliff (sawing and grinding) technique. J Oral Pathol 1982;11: Rabbani GM, Ash MM, Jr., Caffesse RG. The effectiveness of subgingival scaling and root planing in calculus removal. J Periodontol 1981;52: Frentzen M, Braun A, Aniol D. Er:YAG laser scaling of diseased root surfaces. J Periodontol 2002;73: Aoki A, Miura M, Akiyama F, Nakagawa N, Tanaka J, Oda S, Watanabe H, Ishikawa I. In vitro evaluation of Er:YAG laser scaling of subgingival calculus in comparison with ultrasonic scaling. J Periodontal Res 2000;35: Buchanan SA, Robertson PB. Calculus removal by scaling/ root planing with and without surgical access. J Periodontol 1987;58: Matia JI, Bissada NF, Maybury JE, Ricchetti P. Efficiency of scaling of the molar furcation area with and without surgical access. Int J Periodontics Restorative Dent 1986;6:24 35.