An evaluation of the effects of an Nd:YAG laser on subgingival calculus, dentine and cementum. An in vitro study

Short-term results of the combined application of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and erbium-doped yttrium aluminum garnet (Er:YAG) laser in the treatment of periodontal disease: a randomized controlled trial

Objectives

Nd:YAG and Er:YAG lasers have been previously used as an adjunct in periodontal therapy. The aim of this single-blinded randomized controlled clinical trial was to evaluate the efficacy of a combined application of Nd:YAG and Er:YAG laser irradiation in periodontal treatment.

Materials and methods

Twenty-two patients with at least one site of ≥ 6 mm periodontal probing depth (PPD) after mechanical debridement with curettes and sonic instruments at periodontal reevaluation were included in the study. Patients were randomly allocated at a 1:1 ratio to either a combined Nd:YAG/Er:YAG laser therapy (test group) or a “turned off” laser therapy (control group). The Nd:YAG laser was used for periodontal pocket deepithelialization and to stabilize the resulting blood clot. The Er:YAG laser was primarily used for root surface modification. PPD (mm), clinical attachment level (CAL, mm), and bleeding on probing (BOP, +/−) at the site of laser treatment were evaluated at baseline and 2 months after treatment.

Results

The mean improvements from baseline to 2-month follow-up for PPD were significantly better in the laser group (2.05 ± 0.82 mm) compared to the control group (0.64 ± 0.90 mm; p = 0.001). Likewise, the gain in CAL was significantly better in the laser group (1.50 ± 1.10 mm) than in the control group (0.55 ± 1.01mm; p = 0.046).

Conclusions

The combined application of Nd:YAG and Er:YAG laser irradiation as an adjunct to conventional non-surgical therapy showed a significant beneficial effect on periodontal treatment results.

Clinical relevance

Combined Nd:YAG and Er:YAG laser irradiation could be a useful procedure additionally to conventional non-surgical periodontal therapy to improve periodontal treatment results.

Clinical trial registration

ISRCTN registry #ISRCTN32132076

Image-Guided Ablation of Dental Calculus From Root Surfaces Using a DPSS Er:YAG Laser

BACKGROUND AND OBJECTIVES

Recent studies have demonstrated that near-infrared (IR) imaging can be used to acquire high-contrast images of root caries and calculus on the root surfaces of extracted teeth at wavelengths longer than 1450 nm. The purpose of this study was to determine if image-guided laser ablation can be used to selectively remove calculus from tooth surfaces with minimal damage to the underlying sound cementum and dentin.

MATERIALS AND METHODS

In this study, sequential near-IR images at 1500-1700 nm were used to guide a diode-pumped (DPSS) Er:YAG laser for the removal of calculus from the root surfaces of 10 extracted teeth. The selectivity of removal was assessed using digital microscopy, optical coherence tomography, and surface profilometry.

RESULTS

Calculus was removed rapidly with minimal damage to the underlying sound cementum and dentin. Image-guided ablation achieved high-selectivity, the mean volume of calculus removal was more than 27 times higher than the mean loss of cementum.

CONCLUSIONS

We have demonstrated that near-IR image-guided laser ablation can be used for the selective removal of calculus from root surfaces ex vivo. Additionally, we have demonstrated that a diode-pumped solid-state Er:YAG laser is well suited for selective removal. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Selective removal of dental calculus with a diode-pumped Er:YAG laser

Selective removal of dental calculus with high precision is best accomplished using lasers operating at high pulse repetition rates focused to a small spot size to limit damage to sound tissues. Conventional flash-lamp pumped Er:YAG lasers are poorly suited for this purpose, but new diode-pumped solid state (DPSS) Er:YAG lasers have become available operating at high pulse repetition rates. The purpose of this study was to determine if image-guided laser ablation can be used to selectively remove calculus from tooth surfaces with minimal damage to the underlying sound cementum and dentin. A DPSS Er:YAG laser system was used to selectively remove calculus from ten extracted teeth using sequential SWIR images at 1500-1750-nm. The selectivity of removal was assessed using digital microscopy and optical coherence tomography. Calculus was removed with minimal damage to the underlying sound cementum and dentin.

Effect of Er: YAG or Nd:YAG Laser Exposure on Fluorosed and Non-Fluorosed Root Surfaces: An In Vitro Study

BACKGROUND AND AIMS

Fluorosis affects tooth mineralization. The therapeutic benefit provided by lasers on fluorosed and non fluorosed cementum requires studying and comparing. The aim of this study was to evaluate and compare the root surface changes following Er:YAG or Nd:YAG laser irradiation on periodontally healthy fluorosed versus non-fluorosed teeth by scanning electron microscopy (SEM).

MATERIALS AND METHODS

A total of 76 periodontally healthy fluorosed (FH) and non-fluorosed (NFH) teeth specimens were included in this study. In one group, the experimental root specimens were irradiated using Er:YAG or with Nd:YAG laser in the other. A SEM evaluation was performed to assess the laser induced ultra structural changes in the root surface followed by statistical analysis using Fisher's exact test.

RESULTS

It was observed that both FH and NFH groups were similarly affected by Nd:YAG or Er:YAG laser. However, the former caused more surface changes than the latter on melting of surface (p=0.12 for FH and p=0.08 for NFH), and Er:YAG laser caused more smear layer formation (p=0.51 for FH and p=0.16 for NFH).

CONCLUSION

RESULTS suggest that undesirable morphological changes were observed almost similarly in FH and NFH groups using Er:YAG or Nd:YAG laser. Hence further in-vitro studies at lower energy settings followed by clinical trials are required in this aspect.

Use of carbon dioxide laser in oral soft tissue procedures

Lasers have been introduced in dentistry as an alternative to conventional knife surgery. The advantage to the operator includes a clean dry field that enhances visibility and reduces the procedure time. The patient benefits by minimal postoperative pain and swelling. The paper discusses use of carbon dioxide laser in five conditions commonly encountered in oral cavity.

Detection, removal and prevention of calculus: Literature Review

Dental plaque is considered to be a major etiological factor in the development of periodontal disease. Accordingly, the elimination of supra- and sub-gingival plaque and calculus is the cornerstone of periodontal therapy. Dental calculus is mineralized plaque; because it is porous, it can absorb various toxic products that can damage the periodontal tissues. Hence, calculus should be accurately detected and thoroughly removed for adequate periodontal therapy. Many techniques have been used to identify and remove calculus deposits present on the root surface. The purpose of this review was to compile the various methods and their advantages for the detection and removal of calculus.

Immunohistochemical characterization of periodontal wound healing following nonsurgical treatment with fluorescence controlled Er:YAG laser radiation in dogs

BACKGROUND AND OBJECTIVE

The aim of the present study was to immunohistochemically characterize periodontal wound healing following nonsurgical treatment with fluorescence controlled Er:YAG laser radiation in dogs.

STUDY DESIGN/MATERIALS AND METHODS

Five beagle dogs suffering from naturally occurring chronic periodontitis were randomly allocated in a split-mouth design to nonsurgical periodontal treatment using either (a) an Er:YAG laser at 10.2, 12.8, 15.4, 18, and 20.4 J/cm2 (ERL1-5), or (b) an ultrasonic device (VUS) serving as control. The animals were sacrificed after 3 months. Histomorphometrical (e.g. inflammatory cell infiltrate, surface changes, cementum formation), and immunohistochemical parameters (collagen type I, CD68, matrix metalloproteinase (MMP)-8) were assessed.

RESULTS

Inflammatory cell infiltrates of different extent were commonly observed in all treatment groups. However, histomorphometrical analysis revealed new cementum formation with inserting collagen type I fibers along the instrumented root surfaces in most specimens of both ERL (ERL2: 31+/-81 to ERL5: 595+/-575 microm) and VUS (50+/- 215 microm) groups. This was associated with pronounced CD68 and weak MMP-8 antigen reactivity.

CONCLUSION

Within the limits of the present study, it was concluded that both treatment procedures (i) were effective in controlling inflammatory cell infiltrates, and (ii) may support the formation of a new connective tissue attachment.

Lasers and soft tissue: periodontal therapy

Periodontology exists as a major specialty within clinical dentistry that has developed through the extensive research carried out into all parameters pertaining to a 'best practice' approach. With the advent of surgical lasers into clinical dentistry, considerable interest has been shown in the possible benefits that might be derived from the adjunctive effects of bacterial control and haemostasis that are associated with laser use. Despite the number of publications on the subject, there is still controversy over the use of lasers in periodontology. The following paper will outline the procedures that have been advocated for laser use and provide a review of the literature.

Lasers in periodontics: a review of the literature

BACKGROUND

Despite the large number of publications, there is still controversy among clinicians regarding the application of dental lasers to the treatment of chronic periodontitis. The purpose of this review is to analyze the peer-reviewed research literature to determine the state of the science concerning the application of lasers to common oral soft tissue problems, root surface detoxification, and the treatment of chronic periodontitis.

METHODS

A comprehensive computer-based search combined the following databases into one search: Medline, Current Contents, and the Cumulated Index of Nursing and Allied Health. This search also used key words. In addition, hand searches were done for several journals not cataloged in the databases, and the reference lists from published articles were checked. All articles were considered individually to eliminate non-peer-reviewed articles, those dealing with commercial laser technology, and those considered by the author to be purely opinion articles, leaving 278 possible articles.

RESULTS

There is a considerable conflict in results for both laboratory studies and clinical trials, even when using the same laser wavelength. A meaningful comparison between various clinical studies or between laser and conventional therapy is difficult at best and likely impossible at the present. Reasons for this dilemma are several, such as different laser wavelengths; wide variations in laser parameters; insufficient reporting of parameters that, in turn, does not allow calculation of energy density; differences in experimental design, lack of proper controls, and differences in severity of disease and treatment protocols; and measurement of different clinical endpoints.

CONCLUSIONS

Based on this review of the literature, there is a great need to develop an evidence-based approach to the use of lasers for the treatment of chronic periodontitis. Simply put, there is insufficient evidence to suggest that any specific wavelength of laser is superior to the traditional modalities of therapy. Current evidence does suggest that use of the Nd:YAG or Er:YAG wavelengths for treatment of chronic periodontitis may be equivalent to scaling and root planing (SRP) with respect to reduction in probing depth and subgingival bacterial populations. However, if gain in clinical attachment level is considered the gold standard for non-surgical periodontal therapy, then the evidence supporting laser-mediated periodontal treatment over traditional therapy is minimal at best. Lastly, there is limited evidence suggesting that lasers used in an adjunctive capacity to SRP may provide some additional benefit.

Er:YAG laser scaling of diseased root surfaces: a histologic study

BACKGROUND

The aim of the present study was to observe the effects of an erbium-doped:yttrium, aluminum, and garnet (Er:YAG) laser when used to treat periodontally involved root surfaces.

METHODS

Forty teeth affected by severe periodontal disease and scheduled for extraction were divided into two groups: in group A (control), 20 teeth were treated by hand instrumentation, and in group B (test), 20 teeth were treated by Er:YAG laser.

RESULTS

In group A (teeth treated by curets), the root cementum layer was completely removed, but many deep scratches on the dentin layer were also observed. In group B, the laser-treated root surfaces, there was no cracking or carbonization, and the bacterial flora was completely eliminated, leaving a rough and uniform surface.

CONCLUSION

Results of the present study showed that clinical use of an Er:YAG laser in vivo achieves plaque and calculus removal, providing a rough surface morphology.

Er:YAG Laser in Defocused Mode for Scaling of Periodontally Involved Root Surfaces: An In Vitro Pilot Study

BACKGROUND

The Er:YAG laser may be used on periodontally involved teeth in combination with conventional periodontal therapy in order to improve the efficacy of root instrumentation. The aim of this study was to compare the effect of hand instrumentation on root surfaces of periodontally involved teeth with Er:YAG laser application.

METHODS

Thirty freshly extracted, non-carious, single-rooted, periodontally diseased human teeth from adult humans with advanced periodontal disease were used in this study. The teeth were divided into three groups of 10 specimens each. Group A was treated with scaling and root planing (SRP) with curets only (control). In group B, the root surfaces were scaled with curets and then lased with an Er:YAG laser (wavelength 2.94 microm). A handpiece with a water spray was used in non-contact mode (defocused) at a distance of 1 cm from root surface. Laser parameters were set at energy of 100 to 200 mJ/pulse, with 10 Hz of frequency. In group C, the root surfaces were lased only with power settings 250 to 300 mJ/pulse and 10 Hz frequency. An epon-araldite plastic embedding technique was used for light microscopic investigation.

RESULTS

Histologic findings showed significant differences between the test and control sites. In control sites, after hand instrumentation, the surface was smooth, without a cementum layer, and the dentin layer presented opened tubules. Defects on the dentin layer were also present along root surfaces. In the test sites (B, C) root surfaces revealed no thermal damage; no cracking or tissue carbonization were observed. The superficial layers of lased surfaces appeared smooth and melted without alterations.

CONCLUSION

Based on these findings, it appears that it may be feasible to use the Er:YAG laser for root instrumentation without prior root planing if the proper parameters are followed.

Clinical efficacy of semiconductor laser application as an adjunct to conventional scaling and root planing

BACKGROUND AND OBJECTIVES

The aim of the in vitro study was to examine the clinical efficacy of semiconductor laser periodontal pocket irradiation as an adjunct to conventional scaling and root planing.

MATERIALS AND METHODS

Twenty-two healthy patients with a need of periodontal treatment (15 women, 7 men, mean age 45.0 +/- 10.8 years) with at least four teeth in all quadrants, were included. All of them underwent a conventional periodontal treatment including scaling and root planing. Using a split mouth design, two randomly chosen quadrants (one upper and the corresponding lower one) were subsequently treated with an 809 nm GaAlAs laser operated at a power output of 1.0 Watt using a 0.6 mm optical fiber. The teeth in the control quadrants were rinsed with saline. The clinical outcome was evaluated by means of plaque index (PI), gingival index (GI), bleeding on probing (BOP), sulcus fluid flow rate (SFFR), Periotest (PT), probing pocket depth (PPD), and clinical attachment loss (CAL) at baseline and at 3 months after treatment. A total of 492 teeth in both groups were evaluated and differences between the laser and the control teeth were analyzed using the Wilcoxon test (P < 0.05).

RESULTS

Teeth treated with the laser revealed a significantly higher reduction in tooth mobility, pocket depth, and clinical attachment loss. Twelve percent of the teeth in the laser group showed an attachment gain of 3 mm or more, compared to 7% in the control group. An attachment gain of 2-3 mm was found in 24% of the teeth in the laser group and 18% in the control group. No significant group differences, however, could be detected for the plaque index, gingival index, bleeding on probing, and the sulcus fluid flow rate.

CONCLUSIONS

The higher reduction in tooth mobility and probing depths is probably not predominantly related to bacterial reduction in the periodontal pockets but to the de-epithelization of the periodontal pockets leading to an enhanced connective tissue attachment. The application of the diode laser in the treatment of inflammatory periodontitis at the irradiation parameters described above is a safe clinical procedure and can be recommended as an adjunct to conventional scaling and root planing.

Lasers in surgical periodontics and oral medicine

Surgical lasers rapidly are becoming part of the periodontal armamentarium. This article discusses the different lasers that are suitable for use on the soft tissues of the periodontium. Various laser-assisted periodontal surgical procedures and laser treatment of diseases of the oral mucosa are discussed.

In vitro effect of laser irradiation on cementum-bound endotoxin isolated from periodontally diseased roots

BACKGROUND

In a previous study, we evaluated the in vivo effects of an Nd:YAG laser on periodontal disease by measuring crevicular interleukin (IL)-1beta levels before and after laser application. It was found that laser therapy was less effective than traditional scaling and root planing. These results might be due to incomplete removal of microbial residues and cementum-bound endotoxin on root surfaces by the laser. In this study, we explored the in vitro effectiveness of an Nd:YAG laser for the elimination of cementum-bound endotoxin by measuring IL-1beta changes in stimulated monocytes.

METHODS

Fresh human monocytes were harvested from adults without periodontitis and grown in RPMI 1640 medium. Diseased cementum particles were collected and prepared from teeth with untreated periodontitis and were irradiated with 5 levels of laser energy. Cementum particles were subjected to endotoxin testing by a limulus amebocyte lysate (LAL) assay and then were incubated with cultured monocytes. Production of IL-1beta in stimulated monocytes was measured by enzyme-linked immunosorbent assay and quantified by spectrophotometry.

RESULTS

The endotoxin unit (EU) of diseased cementum was 18.4 EU/mg, which seemed to be remarkably lower than that of common periodontal pathogens including Porphyromonas gingivalis (381) at 15,300 EU/mg/ml, Prevotella intermedia (ATCC 25611) at 227 EU/mg/ml, and Fusobacterium nucleatum (ATCC 25586) at 1,987 EU/mg/ml. Monocytes subjected to stimulation by diseased cementum particles without laser irradiation produced 124 to 145 pg/ml IL-1beta, 9- to 18-fold higher than that of unstimulated monocytes (7.07 to 15.95 pg/ml). Diseased cementum particles after irradiation with various energy levels of the Nd:YAG laser could still stimulate monocytes to secrete 89 to 129 pg/ml IL-1beta. No statistically significant difference was found in the production of IL-1beta induced by diseased-bound cementum with or without laser irradiation.

CONCLUSIONS

The Nd:YAG laser varying from 50 mJ, 10 pps to 150 mJ, 20 pps, for 2 minutes, did not seem to be effective in destroying diseased cementum endotoxin.

Laser palliation of oral manifestations of human immunodeficiency virus infection

BACKGROUND

The author describes the use of lasers to palliate the oral manifestations of the human immunodeficiency virus, or HIV, infection. He discusses the advantages to both patients and dentists, but he does not address the use of lasers as a modality to treat or cure HIV infection.

CASE DESCRIPTION

Many oral manifestations of HIV infection can be used as markers for degree of immunosuppression. These manifestations may be treated with antibiotics, analgesics and antineoplastics, which may interact and interfere with antiviral agents used to treat the disease and possibly may exacerbate it. The author describes laser palliation of the oral manifestations of three HIV-positive patients.

CLINICAL IMPLICATIONS

Dentists will see more patients living longer with HIV as the disease becomes more treatable. Lasers have been shown to be effective instruments in palliation of oral manifestations of HIV infection.

Er:YAG laser scaling of diseased root surfaces

BACKGROUND

The removal of calculus and plaque is an essential component of a therapeutic approach to control periodontal disease. Er:YAG laser scaling was recently introduced as an alternative to conventional scaling procedures. In this histological study, the effects of laser instrumentation of diseased root surfaces are compared to mechanical removal of plaque and calculus with ultrasonic instruments and scalers.

METHODS

Areas of subgingival calculus were identified on 40 freshly extracted human teeth. Each of these areas was randomly divided into 2 equal parts. The control site was treated either with scaling and root planing or with an ultrasonic instrument. The test site was cleaned using an Er:YAG laser according to the manufacturer's instructions. The end point of debridement was the inability to mechanically or visibly detect any remaining calculus. After pre- and postsurgical photographs and impressions for scanning electronic microscopic investigation, a plastic embedding technique was used to cut the undecalcified roots into 15 microm thick sections.

RESULTS

Clinically and histologically, scaling resulted in complete debridement at all samples, producing a smooth root surface. At the test sites, laser scaling was accompanied by an increased removal of tissue and roughened surfaces.

CONCLUSIONS

Laser scaling results in an increased loss of cementum and dentin, which should be taken into account in clinical situations.

Effect of diode laser irradiation on root surfaces in vitro

OBJECTIVE

The objective of this study was to evaluate possible morphological alterations of root surfaces after GaAlAs-diode laser (809 nm) irradiation under standardized in vitro conditions.

MATERIALS AND METHODS

Root specimens obtained from extracted periodontally diseased teeth were scaled and root planed with curettes followed by air-powder abrasive treatment prior to lasing. The variable parameters were power output (0.5-2.5 W) and exposure time (10-30 sec per specimen). Additionally, the effect of a saline solution and a human blood film on the root surface was investigated. The root segments were analyzed by means of a reflected light microscope. Photographs before and after irradiation were taken and evaluated. The scale of carbonization was quantified using a grid laid over the photographs. Specimens with distinct morphological changes were analyzed with a scanning electron microscope.

RESULTS

Lasing dry specimens and specimens moistened with saline resulted in no detectable alterations, irrespective of irradiation time and power output applied. Depending on different settings, irradiation caused severe damages to the root surface when segments were covered by a thin blood film. Irradiation at a power output of 1 Watt and below had barely any negative effect on the root surface, whereas lasing at 1.5, 2.0, and 2.5 Watt resulted in partial or total carbonizations of the root samples. The angle of irradiation had a significant effect on the scale of the root surface damage (Mann-Whitney U test,p < 0.05).

CONCLUSION

The diode laser may cause damage to periodontal hard tissues if irradiation parameters are not adequate.

Morphology, chemical structure and diffusion processes of root surface after Er:YAG and Nd:YAG laser irradiation

OBJECTIVES

The aim of this in vitro study was to evaluate the effects of Er:YAG and Nd:YAG lasers on morphology, chemical structure and diffusion processes of the root surface.

MATERIAL AND METHODS

60 root samples were irradiated for 1 min each either with 60 mJ/p, 80 mJ/p and 100 mJ/p using Er:YAG laser or with 0.5W, 1.0W and 1.5W using Nd:YAG laser. Scanning electron microscopy (SEM) was used to determine the morphology, infrared (IR) spectroscopy to assess the alterations in chemical structure and one dimensional electron paramagnetic resonance imaging (1-D EPRI) was used to estimate the diffusion coefficients in dental root samples.

RESULTS

Er:YAG laser treatment resulted in deep crater formation with exposed dentin. Morphological alterations of root surface after Nd:YAG laser irradiation included cracks, crater formation, meltdown of the root mineral and resolidified porous globules formation. Er:YAG laser failed to alter the intensity of Amide peaks I, II or III. In contrast, treatment with Nd:YAG laser, using the highest power setting of 1.5W, reduced the intensity of Amide peak II and III in comparison to the control. The diffusion coefficients were increased significantly in all Er:YAG and Nd:YAG treated root samples.

CONCLUSION

This study demonstrated that Er:YAG laser influences only on morphology and diffusion processes of root surfaces, while Nd:YAG laser also alters the chemical structure of root proteins.

Effect of diode laser irradiation on the attachment rate of periodontal ligament cells: an in vitro study

BACKGROUND

The present study is part of a basic research program investigating the cellular effects of an 810 nm GaAlAs-diode laser on human periodontal tissues. The aim of the investigation was to evaluate the effects of laser treatment of root surface specimens on the attachment of periodontal ligament (PDL) cells in vitro.

METHODS

Root specimens were prepared from periodontally diseased teeth. PDL cells were obtained from human third molar ligaments. Cells were cultured under simple, standardized, and reproducible experimental conditions. One hundred fifty root specimens were scaled and root planed with curets followed by air-powder abrasive treatment; 75 were then lased and 75 served as controls. The irradiation time was 20 seconds at a power output of 1 W. The root segments were placed into culture dishes, covered with a solution of PDL cells, and incubated for 72 hours. The specimens were then washed with phosphate buffer to remove cells not attached to the surface, and the adherent cells were stained with methylene blue. Cells were counted using a reflected light microscope and the cell density per mm2 was calculated.

RESULTS

The analysis of 150 specimens revealed no significant differences between the groups (P = 0.347, Wilcoxon test). The cell numbers, however, were slightly higher on laser specimens. The mean was 66 cells/mm2 in the laser group and 63.7 cells/mm2 in the control group.

CONCLUSIONS

The application of the diode laser at the parameters used did not have a substantially positive effect on the new attachment of PDL cells on the tooth specimens. It remains to be investigated whether the difference detected is really clinically relevant.

Effect of diode laser irradiation on the survival rate of gingival fibroblast cell cultures

BACKGROUND AND OBJECTIVE

The present study is part of a basic research program investigating the cellular effects of the GaAlAs-diode laser with a wavelength of 810 nm on human periodontal tissues. The aim of the investigation was to evaluate the effects of the laser treatment on the survival rate of human gingival fibroblasts (HGF) in monolayer cell culture at different power settings and durations.

STUDY DESIGN/MATERIALS AND METHODS

HGF were obtained from a human gingival connective tissue explant. Cells were cultured on 24-well tissue culture plates. One hundred and thirty multi well cell cultures were laser treated. The variable parameters were power output (0.5-2.5 W) and exposure time (60-240 seconds per well). The cultures were analyzed by means of trypan blue staining, and the cell numbers counted under a light microscope. Photographs before and after irradiation were taken and evaluated.

RESULTS

Depending on different settings, the laser irradiation caused significant (P < 0.05, t-test) reductions of cell numbers. Exposure time was more relevant to this phenomenon than the power output. Linear regression analysis revealed no unambiguous correlation between power output and cell death, when exposure time was kept constant.

CONCLUSIONS

When used for periodontal pocket decontamination, the laser beam may cause damage to collateral periodontal tissues, if the power setting and the duration of the treatment are not adequate. Further investigation, especially with regard to the effects on hard tissue and microorganisms, are needed to give a secure recommendation for irradiation parameters at pocket decontamination.

The effect of working tip angulation on root substance removal using Er:YAG laser radiation: an in vitro study

OBJECTIVES

The present investigation attempted to determine the amount of cementum and/or dentin removal with Er:YAG laser radiation, dependent on the angulation of a specially-developed application tip.

MATERIAL AND METHODS

Subject of the study were 150 extracted incisors, canines, premolars, and molars. Source of laser radiation was an Er:YAG laser device emitting pulsed infrared radiation at a wavelength of 2.94 microm with a pulse duration of 250 micros and a pulse repetition rate of 10 pps. The samples of the 3 study groups were irradiated with 380 laser pulses at radiation energies of 60 mJ (group A), 100 mJ (group B), or 180 mJ (group C). In each group, 10 samples were treated at working tip angulations of 15 degrees , 30 degrees , 45 degrees , 60 degrees , and 90 degrees. The substance removal was determined 3-dimensionally using a newly developed laser scanning system (100,000 surface points per sample, accuracy 5 microm) and a special image-analysing software (Match 3D). Statistical analysis was completed with ANOVA followed by multiple comparisons using the Scheffé-test and with linear regression analysis according to Pearson-Bravais (p < 0.05).

RESULTS

Strong dependence of substance removal, both determined as maximum depth of the defects (0.5% quantil) as well as defect volume, on the angulation of the working tip was shown. At 60 mJ, the depth of the defects was 41.39 (+/- 32.55) microm at an angulation of 15 degrees and that at 90 degrees was 181.39 (+/- 74.42) microm (R2= 0.921). For the radiation energy at 100 mJ, the depth of the defects ranged from 51.96 (+/- 26.86) microm at 15 degrees to 306.64 (+/- 62.44) microm at 90 degrees (R2 = 0.983). Choosing radiation energies at 180 mJ, the depth of the defects ranged from 64.73 (+/- 27.73) microm at 15 degrees to 639.89 (+/- 47.28) microm at 90 degrees , on average (R2 = 0.853).

CONCLUSIONS

The results of the present study provide clear evidence that besides the physical radiation parameters, also the parameters of clinical handling, in particular the angulation of the application tip, has a strong influence on the amount of root substance removal using Er:YAG laser radiation.

The effect of Nd:YAG pulse duration on dentine crater depth

OBJECTIVES

The effect of alteration of laser parameters on laser-dentine interaction, in particular the effect of pulse duration, has not been well documented. The aim of this in vitro study was to determine the effect on dentine crater depth of Nd:YAG laser pulse duration, and total delivered energy, dentine site and the presence or absence of dye.

METHODS

Ninety-six sound third molars were extracted and sectioned transversely to provide 192 upper and lower cut surfaces. The upper surfaces were painted with a layer of dye (IR5) suitable for absorption at 1064 nm. The specimens were divided into 16 sub-groups and exposed to two Nd:YAG lasers; one of pulse duration 7 ms and the second of pulse duration 35 ps. Both lasers operated in a non-contact mode (spot diameter 165 microm) with repetition rates of 10.5 and 10 Hz, respectively. Four total energies (2.28, 2.64, 3.6, 4.2 J) were delivered to eight dyed and eight undyed sub-groups. Eight outer and five inner sites were irradiated on each specimen. Dentine crater depth was measured five times using a Reflex Microscope and a three-dimensional centre of gravity derived. An upper and lower specimen were taken from each sub-group and viewed under a SEM.

RESULTS

ANOVA and multiple regression analysis were applied and the following factors were found to have a statistically significant effect on crater depth (p<0.0001): total delivered energy, pulse duration and inner/outer location.

CONCLUSIONS

Increasing energy and pulse duration produced deeper craters. Similarly inner dentine sites produced deeper crater depths. Only craters produced at the ms pulse duration were carbonised. It would appear that laser-dentine interaction has a non-thermal component at picosecond pulse duration.

Root substance removal with Er:YAG laser radiation at different parameters using a new delivery system

BACKGROUND

The recently introduced Er:YAG laser radiation appears to be a promising alternative in treating dental hard tissue due to its thermo-mechanical ablation properties and the lack of thermal side effects. The present in vitro study attempted to evaluate the use of Er:YAG laser radiation in combination with a specially developed delivery system in removing calculus from root surfaces.

METHODS

Fifty extracted anterior teeth, premolars and molars, were divided into 2 groups of 25 each with (group A) and without (group B) subgingival calculus. Source of radiation was an Er:YAG laser device with a wavelength of 2.94 microm, in the infrared optical spectrum, a pulse duration of 250 ns, and a pulse repetition rate of 15 pps. In each group, 6 teeth were irradiated with 300 laser pulses either at 60 mJ, 80 mJ, 100 mJ, or 150 mJ. The samples were continually moved linearly using a computer numeric controlled device. The volumetric evaluation of root substance removal was performed with a 3-dimensional laser scanning system (100,000 surface points per sample, accuracy: 5 microm) and special image analyzing software. A scanning electron microscopic (SEM) observation was performed to assess the laser induced ultrastructural changes on the root surfaces. Statistical analysis was carried out with ANOVA followed by the Scheff*e test and with regression analysis according to Pearson-Bravais at a level of significance of 5% (P <0.05).

RESULTS

The linear measurement of substance removal on calculus samples (group A) revealed average depths between 174.38 (+/-16.13) microm and 501.85 (+/-111.01) microm. Defect depths on the teeth without calculus (group B) ranged from 37.78 (+/-14.03) microm to 484.44 (+/-80.63) microm. The SEM observation of laser-treated root surfaces revealed no signs of thermal damage; e.g., melting, fusion, or cracking.

CONCLUSIONS

The results of the present study showed that a substance removal with Er:YAG laser radiation at lower energy densities is comparable, in effect, to that after conventional root surface instrumentation with curets. The results seem to indicate that calculus removal can be selectively done using lower radiation energies. Considering the favorable results of the SEM investigation, the use of the Er:YAG laser in periodontal therapy may be possible in the future.

Comparison of Nd:YAG laser versus scaling and root planing in periodontal therapy

BACKGROUND

The Nd:YAG laser has recently been used in the treatment of periodontal disease. However, although a clinical reduction of probing depth and gingival inflammation to this new approach has been reported, it has not been fully evaluated. Interleukin-1 beta (IL- 1beta), a potent stimulator of bone resorption, has been identified in gingival crevicular fluid (GCF), which is closely associated with periodontal destruction. The aim of this study was to compare the effects of Nd:YAG laser treatment versus scaling/root planing (SRP) treatment on crevicular IL-1beta levels in 52 sampled sites obtained from 8 periodontitis patients.

METHODS

One or 2 periodontitis-affected sites with a 4 to 6 mm probing depth and horizontal bone loss from 3 adjacent single-root teeth in each of 4 separate quadrants were selected from patients for clinical documentation and IL-1beta assay. Sampling site(s) from each diseased quadrant was randomly assigned to one of the following groups: 1) subgingival laser treatment (20 pps, 150 mJ) only; 2) SRP only; 3) laser treatment first, followed by SRP 6 weeks later; or 4) SRP first, followed by laser therapy 6 weeks later. The GCF was collected and the amount of IL-1beta was assayed by enzyme-linked immunosorbent assay (ELISA). Clinical parameters and GCF were measured at baseline and biweekly after therapy for 12 weeks.

RESULTS

An obvious clinical improvement (marked decrease in the number of diseased sites with gingival index > or =2) and reduction of crevicular IL- 1beta were found in all groups. The level of IL- 1beta was significantly lower in the SRP group (P = 0.035) than in the laser therapy group for the duration of the 12 weeks. The laser combined SRP therapy group showed a further reduction of IL- 1beta (6 to 12 weeks after treatment) than either laser therapy alone or SRP combined laser therapy.

CONCLUSIONS

Our data suggest that laser therapy appeared to be less effective than traditional SRP treatment. Of the 4 treatment modalities, inclusion of SRP was found to have a superior IL- 1beta response, when compared to other therapies without it. In addition, no additional benefit was found when laser treatment was used secondary to traditional SRP therapy.

Dental calculus: recent insights into occurrence, formation, prevention, removal and oral health effects of supragingival and subgingival deposits

Dental calculus, both supra- and subgingival occurs in the majority of adults worldwide. Dental calculus is calcified dental plaque, composed primarily of calcium phosphate mineral salts deposited between and within remnants of formerly viable microorganisms. A viable dental plaque covers mineralized calculus deposits. Levels of calculus and location of formation are population specific and are affected by oral hygiene habits, access to professional care, diet, age, ethnic origin, time since last dental cleaning, systemic disease and the use of prescription medications. In populations that practice regular oral hygiene and with access to regular professional care, supragingival dental calculus formation is restricted to tooth surfaces adjacent to the salivary ducts. Levels of supragingival calculus in these populations is minor and the calculus has little if any impact on oral-health. Subgingival calculus formation in these populations occurs coincident with periodontal disease (although the calculus itself appears to have little impact on attachment loss), the latter being correlated with dental plaque. In populations that do not practice regular hygiene and that do not have access to professional care, supragingival calculus occurs throughout the dentition and the extent of calculus formation can be extreme. In these populations, supragingival calculus is associated with the promotion of gingival recession. Subgingival calculus, in "low hygiene" populations, is extensive and is directly correlated with enhanced periodontal attachment loss. Despite extensive research, a complete understanding of the etiologic significance of subgingival calculus to periodontal disease remains elusive, due to inability to clearly differentiate effects of calculus versus "plaque on calculus". As a result, we are not entirely sure whether subgingival calculus is the cause or result of periodontal inflammation. Research suggests that subgingival calculus, at a minimum, may expand the radius of plaque induced periodontal injury. Removal of subgingival plaque and calculus remains the cornerstone of periodontal therapy. Calculus formation is the result of petrification of dental plaque biofilm, with mineral ions provided by bathing saliva or crevicular fluids. Supragingival calculus formation can be controlled by chemical mineralization inhibitors, applied in toothpastes or mouthrinses. These agents act to delay plaque calcification, keeping deposits in an amorphous non-hardened state to facilitate removal with regular hygiene. Clinical efficacy for these agents is typically assessed as the reduction in tartar area coverage on the teeth between dental cleaning. Research shows that topically applied mineralization inhibitors can also influence adhesion and hardness of calculus deposits on the tooth surface, facilitating removal. Future research in calculus may include the development of improved supragingival tartar control formulations, the development of treatments for the prevention of subgingival calculus formation, the development of improved methods for root detoxification and debridement and the development and application of sensitive diagnostic methods to assess subgingival debridement efficacy.

Determination of energy density threshold for laser ablation of bacteria. An in vitro study

The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.