Effect of Er:YAG laser energy densities on thermally affected dentin layer: Morphological study.

BACKGROUND AND AIMS: Physical and chemical composition of dentin is subject to modification when irradiated with Er:YAG laser. Temperature rise causes water evaporation and micro-mechanical ablation of dentin. The misuse of laser parameters could affect negatively dentin collagen fibers leading to failure in bonded composite restorations. The aim of this in vitro study was to evaluate the effect of Er:YAG laser radiation at different levels of energy on the morphology of thermally affected dentin layer. MATERIALS AND METHODS: Forty-eight freshly extracted human third molars were randomly divided into six groups (n = 8). In all groups, except for the control groups, dentin was subject to irradiation with H02 handpiece Er:YAG laser in non-contact mode (SSP mode = 50 µs; 10 Hz; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min) with the following levels of energy (40, 60, 80, 100, and 120 mJ) respectively. Teeth were sliced longitudinally. Photo-ablated cavities were observed. The cavity depth and dentin fiber collagen deterioration were measured. RESULTS: Laser irradiation increased the depth of dentinal crater from 46.57 µm to 178.2 µm, when energy level increased from 40 mJ to 120 mJ. A superficial black layer, representing dentinal affected collagen fibers, was present in all groups except for control group. When comparing the thickness of the black layer, there was no significant difference between groups. It increased at 40 mJ to 28.17 µm then decreased to 15.19 µm at 60 mJ and then increased again for 80 mJ to 19.93 µm, 100 mJ to 22.87 µm and 120 mJ to 28.53 µm. Only one group (60 mJ) showed low values and significant difference as compared to the other irradiated groups, when multiple comparisons tests (ANOVA) were made using Newman-Keuls test. CONCLUSION: Dentin organic matrix presented the minimum alteration when Er:YAG laser is used specifically at an appropriate level of energy (60 mJ).

Safety Irradiation Parameters of Nd:YAP Laser Beam for Endodontic Treatments: An In Vitro Study.

Objective. Nd:YAP laser has several potentialities of clinical applications in endodontics. The aim of our study is to determine the safety range of irradiation parameters during endodontic application of Nd:YAP laser that can be used without damaging and overheating the periodontal tissue. Material and Methods. Twenty-seven caries-free single-rooted extracted human teeth were used. Crowns were sectioned to obtain 11 mm root canal length. Temperature increases at root surfaces were measured by a thermocouple during Nd:YAP laser irradiation of root canals at different energy densities. Canal irradiation was accomplished with a circular and retrograde movement from the apex until the cervical part of the canal during 10 seconds with an axial speed of 1 mm/s. Each irradiation was done in a canal irrigated continuously with 2.25% NaOCl solution. Results. Periodontal temperature increase depends on the value of energy density. Means and standard deviations of temperature increases at root surfaces were below 10°C (safe threshold level) when the average energy densities delivered per second were equal to or below 4981 J/cm(2) and 9554 J/cm(2), respectively, for irradiations using a fiber diameter of 320 µm and 200 µm. Conclusions. Within the limitations of this study and under specific irradiation conditions, Nd:YAP laser beam may be considered harmless for periodontal tissues during endodontic applications.

In vitro bactericidal effect of Nd:YAG laser on Actinomyces israelii.

A bactericidal effect has been reported by the use of near-infrared laser light on both Gram-positive and Gram-negative bacteria. The aim of this study was to evaluate the effect of Nd:YAG laser on Actinomyces israelii, filamentous bacteria causing cervicofacial actinomycosis. Experiments were realized on bacterial cells in saline suspension or streaked on Mueller-Hinton (MH) agar plates with or without India ink. Laser application was performed in Eppendorf tubes with different powers and frequencies for 40 s; bacterial suspensions were then streaked on agar plates and incubated at 35 °C in proper conditions for 5 days before colony enumeration. A reduction of colony number variable from 60.13 to 100 % for powers of 2, 4, and 6 W at 25-50 Hz of frequency was observed in comparison with growth control. For agar plates, laser application was performed with different powers at 50 Hz for 60 s. A growth inhibition was observed after 5 days of incubation on MH plates with powers of 6 W and on MH-ink plates with all applied powers. This preliminary study showed a bactericidal effect caused by Nd:YAG laser application worthy to be evaluated in further experiments in vivo.

Er:YAG Laser and Fractured Incisor Restorations: An In Vitro Study.

Introduction. The aim of this study was to analyse the effects of an Er:YAG laser on enamel and dentine in cases of dental restorations involving fractured teeth, utilizing the dental fragment. Materials and Methods. Seventy-two freshly extracted bovine incisors were fractured at the coronal level by using a hammer applied with a standardized method, and the fragment was reattached by using three different methods: Er:YAG laser, orthophosphoric acid, and laser plus acid. The different groups were evaluated by a test realized with the dynamometer to know the force required to successfully detach the reattached fragment and by a microinfiltration test by using a 0.5% methylene blue solution followed by the optic microscope observation. Results. The compression test showed only a slight difference between the three groups, without any statistical significance. The infiltration test used to evaluate the marginal seal between the fracture fragment and the tooth demonstrated that etching with Er:YAG laser alone or in combination with orthophosphoric acid gives better results than orthophosphoric acid alone, with a highly significant statistical result. Discussion. Reattaching a tooth fragment represents a clinically proven methodology, in terms of achieving resistance to detachment, and the aim of this work was to demonstrate the advantages of Er:YAG laser on this procedure. Conclusion. This "in vitro" study confirms that Er:YAG laser can be employed in dental traumatology to restore frontal teeth after coronal fracture.

Management of Root Perforations Using MTA with or without Er:YAG Laser Irradiation: An In Vitro Study.

The aim of this in vitro study is to compare the microleakage of a root perforation sealed with MTA (mineral trioxide aggregate) (group M) to that sealed with MTA following Er:YAG laser irradiation (group ML). Forty-two recently extracted human monoroot teeth were used. Two cavities were prepared on each root surface. Randomly, on each root, the exposed dentine of one cavity was irradiated prior to MTA filling using an Er:YAG laser with the following settings: 200 mJ/pulses under an air water spray, 10 Hz, pulse duration of 50 µsec, and 0.7 mm beam diameter. All cavities were then sealed with MTA. submitted to thermocycling and immersed in 2% methylene blue dye solution for 12 h. The penetration of methylene blue in the microleakage of cavity was observed and recorded. The mean value dye penetration in cavities sealed with MTA following Er:YAG laser irradiation (23.91 ± 14.63%) was lower than that of unlased cavities sealed only with MTA (25.17 ± 17.53%). No significant difference was noted. The use of an Er:YAG laser beam for dentinal conditioning prior to MTA filling of perforated roots did not decrease significantly the microleakage of MTA sealing when compared to the conventional use of MTA filling.

Laser welding and syncristallization techniques comparison: in vitro study.

Background. Laser welding was first reported in 1967 and for many years it has been used in dental laboratories with several advantages versus the conventional technique. Authors described, in previous works, the possibility of using also chair-side Nd : YAG laser device (Fotona Fidelis III, λ = 1064 nm) for welding metallic parts of prosthetic appliances directly in the dental office, extra- and also intra-orally. Syncristallisation is a soldering technique based on the creation of an electric arc between two electrodes and used to connect implants to bars intra-orally. Aim. The aim of this study was to compare two different laser welding devices with a soldering machine, all of these used in prosthetic dentistry. Material and Methods. In-lab Nd : YAG laser welding (group A = 12 samples), chair-side Nd : YAG laser welding (group B = 12 samples), and electrowelder (group C = 12 samples) were used. The tests were performed on 36 CrCoMo plates and the analysis consisted in evaluation, by microscopic observation, of the number of fissures in welded areas of groups A and B and in measurement of the welding strength in all the groups. The results were statistically analysed by means of one-way ANOVA and Tukey-Kramer multiple comparison tests. Results. The means and standard deviations for the number of fissures in welded areas were 8.12 ± 2.59 for group A and 5.20 ± 1.38 for group B. The difference was statistical significant (P = 0.0023 at the level 95%). On the other hand, the means and standard deviations for the traction tests were 1185.50 ± 288.56 N for group A, 896.41 ± 120.84 N for group B, and 283.58 ± 84.98 N for group C. The difference was statistical significant (P = 0.01 at the level 95%). Conclusion. The joint obtained by welding devices had a significant higher strength compared with that obtained by the electrowelder, and the comparison between the two laser devices used demonstrated that the chair-side Nd : YAG, even giving a lower strength to the joints, produced the lowest number of fissures in the welded area.

Low energy KTP laser in oral soft tissue surgery: A 52 patients clinical study.

OBJECTIVES: Since 1962 laser appliances have been used for soft tissues surgery of oral cavity with significant advantages compared to the traditional instruments: excellent bleeding control, possibility to avoid the use of suture, good patient compliance thanks to a decrease of intra- and post-operative discomfort and biostimulating effect. Unfortunately, the wavelengths so far used have been seen to cause, in association with an excellent ablation capacity, heat damage of the tissues that can decrease healing process and cause a greater discomfort to patients. To evaluate the laser-assisted KTP laser surgery at low power in terms of characteristics of intervention and patients compliance. STUDY DESIGN: In this study, we describe the application of a new and recently introduced in dentistry wavelength, the KTP laser (532 nm), used with low power parameter (1 Watt - CW), evaluating the time of interventions and, by a Numerical Rating Scale, the intra and postoperative pain. RESULTS: KTP laser used at low power permits to obtain good pain control during operations that were carried out with only a topic anaesthetic (EMLA, Astratech), as shown in VAS tests. Good healing with limited or absent burning areas in treated portion of tissue. CONCLUSIONS: These preliminary study allows us to affirm that KTP laser with low parameters permits to perform oral surgery with good pain control and good wound healing. A greater number of clinical cases are however necessary to confirm the result obtained.

Effect of low fluency dentin conditioning on tensile bond strength of composite bonded to Er:YAG laser-prepared dentin: a preliminary study.

Several studies in the literature have previously shown that the bond strength of a composite bonded to dentin is almost equivalent as when dentin is prepared by either bur or Er:YAG laser. The aim of this preliminary study is to assess the hypothesis that dentin conditioning at low fluency by means of Er:YAG laser can improve the value of adhesion of composites resin to dentin. Sixty surfaces of caries-free human third molars extracted for orthodontic purposes were randomly divided into five groups of 12 teeth. The bur group was the control, prepared using bur, group L was prepared using Er:YAG 200 mJ, SSP (50 µs), 20 Hz, 15 seconds of sweeping, for groups L80, L100, L120, they were prepared first, with the same parameters of the group L 200, and then they received a conditioning, which is, respectively, 15 s of irradiations at: 80 mJ (SSP, 10 Hz), 100 mJ (SSP, 10 Hz), and 120 mJ (SSP, 10 Hz). All samples were restored in a single-component adhesive system: Xenon (DENTSPLY), and ceramX (DENTSPLY) as the resin composite. The specimens were submitted to tensile bond strength test using a universal testing machine. Data were submitted to statistical analysis using ANOVA coupled to a Tukey-Kramer test at the 95% level. The mean values in MPa were 33.3 for group B, 36.73 for group L 200, 41.7 for group L80, 37.9 for group L100, and 39.1 for group L120. Our results showed that dentin conditioning at a low fluency of 12.58 J/cm(2) per pulse, with 80 mJ output energy and 50-µs pulse duration can significantly improve tensile bond strength of a composite bonded to Er:YAG laser-prepared dentine.

Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ) therapy. A critical review.

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is an area of uncovered bone in the maxillo-facial region that did not heal within 8 weeks after identification by health care provider, in a patient who was receiving or had been exposed to Bisphosphonate Therapy (BPT) without previous radiation therapy to the craniofacial region. Low-grade risk of ONJ is connected with oral BPT used in the treatment of osteopenia, osteoporosis and Paget's disease (from 0.01% to 0.04%) while higher-grade risk is associated with intravenous (IV) administration in the treatment of multiple myeloma and bone metastases (from 0.8% to 12%). The management of BRONJ currently is a dilemma. No effective treatment has yet been developed and interrupting BPT does not seem to be beneficial. Temporary suspension of BPs offers no short-term benefit, whilst long term discontinuation (if systemic conditions permit it) may be beneficial in stabilizing sites of ONJ and reducing clinical symptoms. The use of oral antimicrobial rinses in combination with oral systemic antibiotic therapy -penicillin, metronidazole, quinolones, clindamycin, doxycycline, erythromycin- is indicated for Stages I and II of Ruggiero's Staging. The role of hyperbaric oxygen therapy is still unclear but some benefits of this treatment have recently been described in association with discontinuation of BPT and conventional therapy (medical or/and surgical). Surgical treatment, in accordance to the AAOMS Position Paper, is reserved to patients affected by Stage III of BRONJ even if in the last version (2009) a superficial debridement is indicated to relieve soft tissue irritation also in the stage II (lesions being unresponsive to antibiotic treatment). Aggressive surgical treatment may occasionally results in even larger areas of exposed and painful infected bone. Surgical debridement or resection in combination with antibiotic therapy may offer long-term palliation with resolution of acute infection and pain. Mobile segments of bony sequestrum should be removed without exposing unaffected bone. If pathological fractures or complete mandibular involvement are observed, if the medical condition of the patients allows it the affected bone portion may be resected and primary bone reconstruction or revascularization graft may be carried out. Ozone therapy in the management of bone necrosis or in extractive sites during and after oral surgery in patients treated with BPs may stimulate cell proliferation and soft tissue healing. Laser applications at low intensity (Low Level Laser Therapy - LLLT) have been reported in the literature for the treatment of BRONJ. Biostimulant effects of laser improve reparative process, increase inorganic matrix of bone and osteoblast mitotic index and stimulate lymphatic and blood capillaries growth. Laser can be used for conservative surgery, whereby necrotic bone is vaporized, until healthy bone is reached. The Er:YAG laser wavelength has a high degree of affinity for water and hydroxyapatite, hence both soft and bone tissues can be easily treated. An additional advantage of the Er:YAG laser is its bactericidal and possible biostimulatory action, accelerating the healing of both soft and bone tissues, in comparison to conventional treatments. Long-term, prospective studies are required to establish the efficacy of drug holidays in reducing the risk of BRONJ for patients receiving oral BPs even if it has been suggested that BPT may be discontinued for three months before the surgical procedures and bone turnover markers (CTx, NTx, PTH, 1,25-dihydroxy vitamin D) may be checked. However it must be recognized that interindividual variability, gender, age, physical activity, and seasonal and circadian variation exist that can result in difficulty in interpreting these assays and more research is needed. Laser application (LLLT and laser surgery) nowadays appears to be a promising modality of BRONJ treatment, being safe and well tolerated, and it permits the minimally invasive treatment of early stages of the disease.

Pulp temperature increase during photo-activated disinfection (PAD) of periodontal pockets: an in vitro study.

The capacity of photo-sensitizers, used in combination with laser light to kill micro-organisms has been demonstrated in different studies. Photo-activated disinfection (PAD) has been introduced in periodontology as an aid for disinfection of periodontal pockets. The aim of this study is to verify the harm for dental vitality of the use of PAD in periodontal pockets. Root canals of 24 freshly extracted human teeth where prepared using profiles up to a size of ISO #50 and filled with thermo-conductor paste. A silicon-based false gum was made in which a periodontal pocket was created and filled with photo-sensitizer phenothiazine chloride (phenothiazine-5-ium, 3.7-bis (dimethylamino)-, chloride). The external root surface was irradiated during 60 s with a 660-nm diode laser (output power: 20 mW; power density: 0.090 W/cm(2); Energy density: 5.46 J/cm(2)) using a periodontal tip with a diameter of 1 mm and a length of 7 mm. Temperatures were recorded inside the root canal using a thermocouple. Measurements were recorded every second, starting at 10 s before lasering, during the irradiation and were continued for 150 s after the end of irradiation, and six measurements were done per tooth. An average temperature increase of 0.48 +/- 0.11 degrees C was recorded. Our results demonstrated that pulp temperature increase was lower than 3 degrees C, which is considered to be harmless for pulp injury. Regarding pulp temperature increase, the use of PAD for disinfection of periodontal pockets can be considered as a safe procedure for dental vitality.

Intra-oral laser welding: an in vitro evaluation of thermal increase.

The neodymium:yttrium-aluminium-garnet (Nd:YAG) laser is currently used in dental laboratories to weld metals on dental prostheses. Recently, the use of Nd:YAG has been suggested so that dentists themselves can repair broken fixed, removable and orthodontic prostheses by welding metals directly in the mouth. This work aimed to evaluate, through a four k-type thermocouple system on calf jaws, the thermal increase in the biological structures close to the metal parts during laser welding. We put two hemispherical metal plates onto mandibular molars and then laser welded them at three points with a four k-thermocouple system to determine the thermal rise in the pulp chamber, sulcus, root and bone. This procedure was carried out on 12 samples, and the results were processed. The highest values of thermal increase were found in the pulp chamber, 1.5 degrees C; sulcus, 0.7 degrees C; root, 0.3 degrees C; and bone, 0.3 degrees C. This study showed that thermal increases in pulp chamber, sulcus, root and bone were biologically compatible and that intra-oral laser welding, at the parameters used in this work, seems to be harmless to the biological structures close to the welding and thermally affected zones.

Effect of acid etching duration on tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet laser-prepared dentine. Preliminary study.

The purpose of this study was to compare the tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet (Er:YAG) laser-prepared dentine after different durations of acid etching. The occlusal third of 68 human third molars was removed in order to expose the dentine surface. The teeth were randomly divided into five groups: group B (control group), prepared with bur and total etch system with 15 s acid etching [37% orthophosphoric acid (H(3)PO(4))]; group L15, laser photo-ablated dentine (200 mJ) (laser irradiation conditions: pulse duration 100 micros, air-water spray, fluence 31.45 J/ cm(2), 10 Hz, non-contact hand pieces, beam spot size 0.9 mm, irradiation speed 3 mm/s, and total irradiation time 2 x 40 s); group L30, laser prepared, laser conditioned and 30 s acid etching; group L60, laser prepared, laser conditioned and 60 s acid etching; group L90, laser prepared, laser conditioned and 90 s acid etching. A plot of composite resin was bonded onto each exposed dentine and then tested for tensile bond strength. The values obtained were statistically analysed by analysis of variance (ANOVA) coupled with the Tukey-Kramer test at the 95% level. A 90 s acid etching before bonding showed the best bonding value (P < 0.05) when compared with all the other groups including the control group. There is no significance difference between other groups, nor within each group and the control group. There was a significant increase in tensile bond strength of the samples acid etched for 90 s.

[Preprosthetic surgery of the edentulous maxilla: vestibular deepening with the aid of the CO2 laser]. / Chirurgie pré-prothétique de l'édenté maxillaire complet: approfondissement vestibulaire à l'aide du laser CO2.

Vestibular deepening for maxillary edentulous patients is mainly indicated once instability cannot be reached due to important bone resorption. Vestibular deepening with CO2 super-pulsed laser enhance, in a bloodless environment, sustentation as well retention of those full dentures in good operative conditions as compared with conventional techniques.

[Use of laser Doppler flowmetry in dentistry]. / L'utilisation du laser Doppler en médecine dentaire.

An early determination of pulpal vitality is crucial with respect to a correct differential diagnosis of revascularisation or necrosis and its treatment. The use of sensibility tests (cold, heat, electrical pulp test) in combination with X-ray are commonly promoted. However these tests are arbitrary, based on sensations and therefore not always reliable. In such situation the registration of 'real' pulpal blood flow and hence pulp vitality will be more than an added value. The most studied and well documented method is laser Doppler flowmetry (LDF) as it is non invasive, direct and objective. In this article we describe blood flow, LDF and its characteristics, advantages and disadvantages of this method and the newest developments regarding LDF. Despite a low implementation of LDF in Belgium, this technique proved to belong indisputable to the basic assets of a dental clinic. A number of cases are described to demonstrate the efficacy and added value of LDF in assessing tooth vitality.

[Treatment of dentin hypersensitivity by means of the Nd:YAG laser. Preliminary clinical study]. / Traitement de l'hypersensibilité dentinaire au moyen du laser Nd:YAG. Etude clinique préliminaire.

UNLABELLED: The aim of our study is to evaluate the efficiency of the Nd:YAG laser in association with graphite for the treatment of dentinal hypersensitivity. 20 patients suffering of different degrees of this affection were involved. The treatment protocol was: cleaning and drying of the dentinal surfaces, evaluation of the level of pain using a graduated scale (after use of an air spray during 3 sec at a distance of 1 cm from the dentinal surfaces), the treated area was smeared with a graphite paste (graphite mixed to physiologic solution), then irradiated with the Nd:YAG laser until complete removal of the graphite (VSP Mode of 140 microsec, 0,25W, 10 Hz, 300 microm diameter fiber, fluence: 35.39 J/cm2), rinsing and drying followed by a second smearing with the graphite, second lasing, rinsing, drying and a new evaluation of the pain immediately after the treatment and one week later. RESULTS: The means and standard deviations of the level of pain were 7.34 +/- 0.86 before treatment, 3.24 +/- 1.18 immediately after and 2.07 +/- 0.73 one week after. No anesthetic aspect was noticed after treatment. To conclude, our result revealed significant and immediate pain reduction with respect of aesthetics and the natural aspect of the treated teeth. Our protocol is a promising alternative to the treatment of dentinal hypersensitivity.

["Power bleaching" with the KTP laser]. / "Power bleaching" au laser KTP.

The most important constituent of the bleaching process is the hydrogen peroxyde. The bleaching effect is the result of a change in the chemical structure of organic molecules in the teeth. Different bleaching techniques are described on the basis of the concentration of the hydrogen peroxyde used and on the basis of the different methods of application. It has been demonstrated that a faster change in colour can be obtained when bleaching is performed in combination with a light source i.e. power bleaching aiming for a more in depth change of colour. Different investigations have demonstrated that negative effects associated with bleaching agents are seen earlier when light sources have been used as accelerators. So, light activation may not lead to 'heating of the pulp'. Different types of laser bleaching have been described, though, not all of them will lead to the desired result. There is only one exception at present and this is the KTP-laser bleaching with the Smart Bleach gel. The specific laser-tissue interaction is the result of different activation processes of the hydrogen peroxyde in the gel: as a result of the interaction with the laser a photocatalytic effect is induced (i.e. the activation of the gel by means of light--this is also referred to as a photochemical reaction), a limited photothermal effect (light absorption may result in a certain heating of the gel). The light activated gel also has an alkaline pH, which favours the ionisation of the hydrogen peroxyde into perhydroxyl ions (these are the most reactive free radicals). It is also possible to directly cut the tetracycline molecules (a good absorption of light by the tetracycline molecules at 532 nm). This will result in better decolouration of tetracycline stained teeth. This last process is described as direct photobleaching. It also needs to be emphasized that bleaching with a laser can only be performed by a dentist who has acquired a substantial knowledge on laser-tissue interaction and laser physics, and who follows accurately the requested bleaching procedure. Furthermore, whatever the opinion might be, tooth bleaching is a medical dental procedure on biologic tissues and hence this procedure can only by dentists.

[Lasers: principles, characteristics and tissue interactions]. / Lasers: principes, caractéristiques et interaction tissulaire.

Since their appearance in 1960, lasers have been considered useful light sources for medical applications. Laser light is monochromatic, the bundle is parallel and can be directed and focussed, as a result of which very high energy densities can be achieved. Several applications in dentistry have been investigated over the past decades. This article describes the physics behind lasers, the characteristics of the laser beam and overviews the laser wavelengths currently used in dentistry. The different interactions between the laser beam and the target are explained.

[Lasers in general dental practice, an added value]. / Les lasers dans la pratique dentaire générale, une valeur ajoutée.

Laser treatment in promoting dental care is present in many areas and disciplines. Modern practice management implies also the introduction of new technology. As there is evidence of the added value for lasers in different disciplines in dentistry practitioners should not be hold back and not wait for patients demanding for this technology for dental treatment.

[Cavity preparation using an Er:YAG laser in the adult dentition]. / La préparation de cavités à l'aide du laser Er:YAG dans la denture adulte.

Many lasers (i.e., different wavelengths) are available today for clinical applications. Not all lasers are to be used for cavity preparation and removal of carious tissues. Erbiumlasers (Er:YAG and Er,Cr:YSGG) are suitable for these purposes (the wavelengths coincide with the highest absorption peaks of water and hydroxyapatite). The advantages during cavity preparation and caries removal are smear layer free cavity walls, selective and localised removal of tooth substance, a restricted need or the absence of anaesthesia, and cavity walls with a higher acid resistance resulting in a better protection against secondary decay. Possible side effects of erbium lasers with water cooling and used with respect for correct power setting are minimal and can be compared with those of rotary instruments. Erbium laser tooth preparation is now one of the options in the minimal invasive approach. The needs for acid etching has been debated for long. At present it has become clear that acid etching is mandatory to obtain a good adhesion and retention with resin composites.