Aim of this presentation is to review the role of the Er:YAG laser in dentistry and to give a general overview on the work done with it up to date. A look at the development and evolution of this system is given as well as a brief introduction into the basic principles of ablation at the characteristic wavelength 2.94 micrometer. The more important research reports of the different groups all over the world are summarized and the large field of applications such as cavity preparation, caries ablation, periodontology and bacterial reduction is considered.

Objective: This study was performed in order to establish that the pulpal and dentinal tissue are safe when exposed to the 2.94 micron pulsed Er:YAG laser radiation for the procedures of caries removal, cavity preparation, and etching prior to acid etching. This presentation discusses the histological results of a double-blind study comparing a pulsed Er:YAG with a standard dental drill. Methods: A double-blind histological evaluation of the pulpal and dentinal tissue changes induced by the Erbium laser and the dental drill was conducted on teeth extracted immediately following the dental procedure and at various intervals up to 1 year post-treatment. A statistical analysis was used to determine if any statistically significant clinical differences in dental tissue response could be observed between the Er:YAG laser and the standard dental drill. Conclusions: Analysis of the results indicated there were no significant differences observed between the laser and control groups in this study.

The aim of the clinical study is to evaluate Er:YAG laser ablation after two year-long clinical treatment. One hundred fifty cavities were volunteered for checking. Three restorative materials were used following manufacturer's directions. For the experiment, an Er:YAG laser drilling machine was applied. The laser delivered energy from 100 to 450 mJ, repetition rate from 1 to 4 Hz. The length of the generated pulses was 200 microseconds. During our experiments cooling of the teeth was achieved by fine water mist. The number of pulses was from 16 to 489. Caries of enamel and dentin were treated. Old insufficient fillings were also removed (not amalgam or metal alloys). The experiments followed the guidelines of the Declaration of Helsinki (1964), Tokyo (1975), Venice (1983) and Hong-Kong (1989). Clinical evaluation of fillings after 6, 12, 18 and 24 months based on ADA recommendation was used. Eight criteria were applied for the restoration control. Composite resins and glassionomers could be used as filling materials.

Objective: In Phase I, we demonstrated the safety and efficacy of the pulsed 2.94 micron Er:YAG laser for caries removal, cavity preparation and laser etching utilizing in vivo teeth scheduled for removal to quantitatively verify the safety of the product for up to one year following treatment. Phase II was a continuation of this study evaluating in vivo teeth to verify the safety and efficacy of the Er:YAG in a long-term follow-up study. Methods: We randomly divided the patients into two groups: a laser group and a control group, which employed the high speed drill. The investigators rated clinical efficacy by several criteria, evaluated pain and measured pulpal vitality up to two years following treatment. This phase consisted of 512 procedures that made up the laser group and 357 procedures that made up the control group. Conclusions: The results from this phase showed that the Er:YAG laser was able to perform as well as, if not better than, the drill in caries removal, cavity preparation, and acid etching alone. Use of the laser virtually eliminated the need for anesthesia. The Er:YAG laser is safe and efficacious for removal of caries, cavity preparation and etching prior to acid etching.

An Er:YAG laser apparatus with a contact fiberoptic delivery system has been newly developed in Japan and its clinical use was approved by the Ministry of Health and Welfare in 1995. Previous investigations using the laser apparatus and its prototype showed that the Er:YAG laser was able to effectively ablate dental hard and soft tissues without major thermal damage, and that the influence on the tooth pulp was minimal. The degree of damage to the surrounding tissues caused by the inadvertent irradiation has also been evaluated. Bactericidal effect of the Er:YAG laser has been shown. The utility and safety of the Er:YAG laser treatment for caries removal and cavity preparation, soft tissue minor surgery, and scaling have been revealed by several clinical studies. Reports describing the usefulness of the Er:YAG laser are increasing. However, further studies are required in order to clarify the advantages and limitations of the Er:YAG laser treatment and to establish a reliable procedure.

This study was performed in order to evaluate the safety of pulpal and dentinal tissue when exposed to the 2.94 micron pulsed Er:YAG laser radiation for the clinical procedures of caries removal, cavity preparation and laser etching prior to acid etching and restoration. This paper discusses the histological changes observed in dentin and pulpal tissue induced by the Erbium laser and the dental drill as performed in the clinical setting at five test sites. Carious teeth were treated in-vivo and then extracted at various periods ranging from immediately to 1 year post treatment. Following extraction, the specimens were evaluated by a double-blind histological examination of dentin and pulp tissue for comparison of results. Specimens were ranked and scored according to the absence or severity of the histopathologic changes observed and the results subjected to statistical analysis (ANOVA) to determine if significant differences existed between treatment groups (laser vs. drill) and/or procedure. Conclusions: Analysis of the results indicate that there were no significant differences attributable to method of treatment. Etching by either method resulted in no discernible change. Cavity preparation and caries removal resulted in mild to moderate changes in the tissues.

The aim of our study was to verify the efficiency of delivery systems for Er:YAG laser radiation which could be used in dentistry. The influence of increasing energy and number of pulses on a profile and depth of drilled holes was investigated. Er:YAG laser was operating in a free-running mode, generating a length of pulses 200 microsecond with a maximum energy of 500 mJ. The delivery systems investigated were an articulated arm and a fluorocarbon polymer-coated silver hollow glass waveguide. The prepared hard tissues were a sliced part of enamel, dentine and ivory. The laser radiation was directed on them by focusing optics (CaF₂ lens) together with the cooling water to ensure that the tissues will not be burned. For the evaluation of shapes, depth and profiles of the prepared cavities the metallographic microscope, x-ray microtomograph and scanning electron microscope were used. From the results it was observed that the profile and depth of the cavities prepared by the laser radiation delivered by the various systems (waveguide or articulated arm) are not the same. The laser radiation delivered by waveguide produces a larger diameter cavity with a lower depth. The holes are smoother and without side effects.

Aim of the study was to investigate the surface and subsurface structure of enamel after irradiation with an Er:YAG laser (wavelength 2.94 micrometer, pulse duration 250 - 500 microseconds, free running, beam profile close to tophead, focus diameter 600 micrometer, focus distance 13 mm, different power settings, air-water spray 2 ml/min; KAVO Key Laser 1242, Kavo Biberach, Germany). The surface of more than 40 freshly extracted wisdom teeth were irradiated using a standardized application protocol (pulse repetition rate 4 and 6 Hz, moving speed of the irradiation table 2 mm/sec and 3 mm/sec, respectively). On each surface between 3 and 5 tracks were irradiated at different laser energies (60 - 500 mJ/pulse) while each track was irradiated between one and ten times respectively. For the scanning electron microscope investigation teeth were dried in alcohol and sputtered with gold. For light microscopic examinations following laser impact, samples were fixed in formaldehyde, dried in alcohol and embedded in acrylic resin. Investigations revealed that at subsurface level cracks can not be observed even at application of highest energies. Borders of the irradiated tracks seem to be sharp while melted areas of different sizes are observed on the bottom of the tracks depending on applied energy. Small microcracks can be seen on the surface of these melted areas.

Specifics of fiber-tip ablation of hard dental tissues with mid-infrared laser radiation are investigated in vitro. Sequences of free-generated Er:YAG laser pulses are applied to fresh human dentin and enamel slices at a low repetition rate and the resulting craters inspected and measured by optical microscopy. Influence of the laser pulse fluence (up to 55 J/cm²), number of pulses in the sequence (1 to 20), and the gap between the fiber tip and the tissue surface (0 to 1.0 mm), is determined quantitatively. Additionally, the effect of the optical quality of the fiber tip on the ablation efficiency is assessed qualitatively. The results help us identify the optimum working regime for the dental fiber-tip handpieces in both tissues. Additionally, they provide new clues for understanding the process of mid-infrared ablation of hard biological tissues, especially in presence of the water spray, which interacts directly with the laser radiation.

The purpose of this study was to evaluate the suitability of Q-switched Er:YAG radiation with a pulse duration of approximately 150 ns for caries ablation in dental enamel and dentin. The rate and efficiency of ablation were determined at various laser fluences via perforation of enamel and dentin thin slabs. Peripheral thermal and acoustic damage was evaluated using optical and electron microscopy. Enamel and dentin were ablated with extremely high precision without peripheral thermal damage using these short laser pulses. However, mechanical damage resulted from stress transients produced during the ablative process which caused fracture s in dentin and enamel on the back side of the perforated tissue samples. The thickness of the layer of spallated dentin increased linearly with deposited energy consistent with proposed models. The possibility of acoustic-mechanical damage may limit the maximum single pulse energy that may be deposited when using short pulsed Er:YAG lasers for hard tissue use. This work was supported by NIH/NIDR Grant R29DE12091.

The suitability of CTE:YAG laser radiation was investigated for caries preventive laser treatments and caries ablation. Although, CTE:YAG laser radiation at 2.69 micrometer is less highly absorbed by dental hard tissues than other erbium laser wavelengths, namely 2.79 and 2.94 micrometer, it can readily be transmitted through a conventional low hydroxyl fiber with minimal loss. These studies show that reasonable ablation rates and efficiencies are obtainable with both free running (200 microseconds) and Q-switched (100 ns) laser pulses on both dentin and enamel with the application of a relatively thick layer of water to the tissue surface. The water served to remove tissue char and debris from the ablation site leaving a clean crater. However, mechanical forces produced during the energetic ablative process resulted in peripheral mechanical damage to the tissue. Surface dissolution studies on enamel indicated that CTE:YAG radiation inhibited surface dissolution by organic acid by 60 - 70% compared to unirradiated controls, albeit, at fluences an order of magnitude higher than those required for CO₂ laser radiation. This layer system may be suitable for dental hard tissue applications if mechanical damage can be mitigated. This work was supported by NIH/NIDR Grants R29DE12091 and R01DE09958.

Previous studies have shown that the status of the residual tooth surface after hard dental tissue ablation using laser irradiation may vary depending on the parameter combinations and cooling mechanisms used. The purpose of this investigation was to assess the effects of Er:YAG laser cavity preparation at different fluences on microleakage of glass ionomer and composite resin restorations. In freshly extracted clinically and radiographically healthy human anterior teeth, standardized Class V cavities were prepared using the dental drill or the Er:YAG laser (Quantronix 294). Fluences of 10 - 40J/cm² were used at a p.r.r. of 1 Hz and pulse durations of 250 microseconds under an air/water coolant spray. Thirty three teeth were included in each subgroup; 3 teeth were used for light microscopy and SEM; 15 underwent conventional restoration with glass ionomer and 15 with composite resin. After immersion in 5% methylene blue, dye penetration was measured linearly in 5 standardized locations on each of the bisected samples. Using the Pearson correlation coefficients, microleakage correlated strongly with laser fluence for glass ionomer (p equals 0.0238) and for composite resin (p equals 0.0099) restorations. Results differed significantly between the 2 restoration types (p less than 0.05). In conclusion, the parameters used during laser ablation of dental tissues must be carefully controlled to optimize clinical outcome.

This study evaluated the ablation rate in dentin and enamel of the Nd:YAG laser (1 - 2W, 10Hz) and the Er:YAG laser (1 - 2.5W, 10Hz), compared to the high-speed drill, low-speed drill and air abrasion (fine and extra-fine particle size). Subsequently, the effectiveness of caries removal and restoration in enamel of the Nd:YAG laser at the same powers and pulse repetition rate was compared to the high-speed drill, low-speed drill, and air abrasion. Enamel and dentin of 1mm thick mid-coronal sections from extracted third molars were ablated by Er:YAG laser ((lambda) equals 2.94 micrometer), Nd:YAG laser ((lambda) equals 1.06 micrometer) both with air/water spray, high-speed drill with 300 carbide bur, and low-speed drill with $1/4 round bur and air abrasions at 160 psi, with fine air abrasion at 50 micrometer and extra fine at 27 micrometer particle size. Removal (ablation) rate defined as dentin or enamel thickness divided by time required for perforation of the samples was determined for lasers, drills and air abrasion. Multifactor randomized ANOVA (p less than 0.05) considered removal rate as a function of treatment conditions. Removal Rate (micrometers per second) Enamel Dentin High-speed drill 273 +/- 47.34 493 +/- 1.73 Low-speed drill 0 42 +/- 14.25 Nd:YAG 2W 0 103 +/- 37 Er:YAG 2W 35 +/- 10 348 +/- 101 Air abrasion/fine 220 +/- 27 433 +/- 99 Air abrasion/extra fine 151 +/- 13 203 +/- 30 Er:YAG laser at 2W 10Hz ablated both enamel and dentin faster than the low-speed drill but slower than the high-speed drill, while the Nd:YAG laser at identical power and pulse rate did not ablate healthy enamel but was capable of removing dentin. To determine caries removal rate in enamel, extracted superficial carious molars (n equals 35) that included minimal explorer penetration and radiographic confirmation of caries extent were selected. Samples were randomly distributed into treatment groups: high-speed drill (HS), low-speed drill (LS), Nd:YAG laser (L), Nd:YAG with air-water spray (A/W), air abrasion fine (F) and air abrasion extra-fine (EF). The amount of time required to achieve caries removal was measured. Subsequently, the teeth were embedded in resin and cut longitudinally into 0.5mm sections with a diamond saw for inspection of caries removal. Utilizing single-factor random design ANOVA (p less than 0.05), data were analyzed and compared. All treatments successfully removed caries in enamel, with significant differences in amount of tissue removed and time of treatment. Time of removal procedure indicated L greater than A/W greater than LS greater than HS very much greater than F equals EF. Width of tissue removed (mm): HS equals 1.59 plus or minus 0.26, LS equals 0.91 plus or minus 0.38, L equals 0.60 plus or minus 0.17, A/W equals 0.54 plus or minus 0.18, EF equals 0.81 plus or minus 0.19 and F equals 0.79 plus or minus 0.15. The Nd:YAG laser was the most conservative of the treatment methods tested, followed by air abrasion, low-speed and high-speed drilling. Lasers are slower and more conservative while air abrasion is faster and more conservative than conventional dental drills.

The use of the Nd:YAG laser on the vital tooth is not without problems, since neither the dental enamel nor the healthy dentin have an absorption maximum at the range of 1064 nm wavelength. An unhindered transmission of radiation may cause a reversible or irreversible damage of the dental pulp. To stay within these physical limits it can be helpful to apply an initiator gel to the tooth surface which will absorb the laser light at the surface of the tooth. The effect of an initiator gel on the temperature change in the dental pulp chamber during laser treatment of a dentin cavity was studied in vitro. The temperature changes were recorded with a thermistor. The results shows a significant difference within the first 20 seconds of laser treatment between the group with initiator gel and the one without.

Using electronic microscope we have studied the opportunity to apply YAG:Cr,Tm-Er laser irradiation (lambda equals 2.64 micrometer) for preparation of the enamel and dentine in different modes of operation. High efficiency of enamel and dentin preparation was shown when using 50 J/sm² energy density and frequency of pulses proceeding 3-5 n. There was no damaged effects involved teeth hard tissues in our experiences.

Dental caries continues to be the most prevalent oral disease in spite of remarkable progress made during the past half- century to reduce its prevalence. Conventional procedures for caries detection are unable to detect the lesions until they are well advanced and involve about one-third of the thickness of enamel. Laboratory research on alternative caries detection methods based upon alterations in the conductance and optical properties associated with enamel demineralization has shown significant promise in recent years. Of these alternative measures, quantitative laser/light fluorescence appears to show the greatest promise for the detection of dental caries at a much earlier stage of development than is currently possible. A clinical trial was initiated in 150 children to evaluate, compare and validate several caries detection methods; in addition to the conventional diagnostic procedure, these detection methods involved quantitative light fluorescence, electrical conductivity, and direct digital radiography. Although the clinical trial is not yet complete, early results suggest the possibility for the earlier detection of dental caries with these alternative methods.

In the past ten years Partial Coherence Interferometry (PCI) and Optical Coherence Tomography (OCT) have been successfully developed for high precision biometry and tomography of biological tissues. OCT employs the partial coherence properties of a superluminescent diode and the Doppler principle yielding resolution and precision figures of the order of a few microns. Presently, the main application fields of this technique are biometry and imaging of ocular structures in vivo, as well as its clinical use in dermatology and endoscopic applications. This well established length measuring and imaging technique has now been applied to dentistry. First in vitro OCT images of the cemento (dentine) enamel junction of extracted sound and decayed human teeth have been recorded. These images distinguish dentine and enamel structures that are important for assessing enamel thickness and diagnosing caries. Individual optical A-Scans show that the penetration depth into enamel is considerably larger than into dentine. First polarization sensitive OCT recordings show localized changes of the polarization state of the light backscattered by dental material. Two-dimensional maps of the magnitude of the interference intensity and of the total phase difference between two orthogonal polarization states as a function of depth can reveal important structural information.

Infrared lasers have been investigated for the modification and ablation of dental hard tissue. Understanding the laser- tissue interaction relies on accurate determination of the optical properties of the tissue. Biological tissues absorb strongly in the infrared region of the spectrum at wavelengths resonant with vibrational absorption bands. In these regions scattering is negligible, therefore only the absorption coefficient and the reflectance are necessary to describe the laser energy deposition in the tissue. Measurement of absorption coefficients is a seemingly simple problem that presents many difficulties when a brittle material such as dental enamel is highly absorbing in the spectral region of interest. Disintegration of dental enamel ensues as a result of fracture before the sample is thin enough to allow direct transmission experiments to determine absorption coefficients at highly absorbing wavelengths (9.3 and 9.6 micrometer). Time resolved radiometric measurements combined with computer modeling of heat deposition and redistribution was used to estimate the absorption coefficient of enamel at various wavelengths in the infrared. This technique allows determination of absorption coefficients in regions not accessible to direct transmission measurements. Problems with the radiometric method and solutions to those problems are presented. The absorption coefficient at 9.6 micrometer was determined to be 5000 cm^-1 plus or minus 1000 cm^-1.

Previous studies have demonstrated that carbon dioxide (CO₂) laser treatment of dental enamel can inhibit subsequent sub-surface caries-like progression. Irradiation of dental enamel by specific wavelengths and fluences of CO₂ laser light alters the chemical composition of the crystals, decomposing the carbonate component. The present study examined the effects of fluence and number of pulses on the surface dissolution kinetics of dental enamel following laser irradiation of the surface. The initial dissolution rate of dental enamel (5 by 5 mm blocks) in pH 4.5 acetate buffer was determined after laser irradiation by a pulsed CO₂ laser at 9.3 micrometer, with a pulse duration of 100 microseconds, and 0-25 pulses per spot, with fluences of 0-8 J/cm². Maximum inhibition of dissolution occurred at fluences of 3-5 J/cm² coinciding with maximum carbonate loss, but the beneficial effect was negated at higher fluences as the surface chemistry changed. Irradiation by more than 5 pulses produced minimal further benefit.

The authors report on the effects of NSLT in the treatment of maxillofacial disorders. Further to our previous study, this paper reports the results of the use of NSLT on the treatment of several disorders of the oral and maxillofacial region. This paper presents NSLT as an effective method of treating such disorders. Two hundred and five female and 36 male patients aged between 7 and 81 years old (average 38.9 years old) suffering from disorders of the maxillofacial region were treated with 632,8,670, and 830nm diodes Lasers at the Laser Center of the Universidade Federal de Pernambuco (UFPE). The disorders included TMJ pain, Trigeminal neuralgia, muscular pain, aphatae, inflammation, tooth hypersensitivity, postoperatively, and in small haemangiomas. Most treatment consisted of a series of 12 applications (twice a week) and in 15 cases a second series was applied. Patients were treated with an average dose of 1.8 J/cm². One hundred fifty four out of 241 patients were asymptomatic at the end of the treatment, 50 improved considerably and 37 were symptomatic. These results confirm that NSLT is an effective tool and brings many benefits for the treatment of many disorders of the Maxillofacial region.

The low level power laser has been used in dental treatments aiming to improve tissue healing. An in vitro study was performed to analyze the laser influence on gingival fibroblast. A human gingival fibroblast culture (LMF) was produced in DME medium with 10% bovine fetal serum (BFS) cells (LMF) were allocated in Petri plates and cultured in different SFB concentrations (0%, 5% e 10%). After 48 hours the plates were divided in 9 groups: 3 control: 3 irradiated by 635 nm laser; and 3 irradiated by 780 nm laser. The cultured cells received 4 applications, in 12 hours intervals, with energy dosage of 2 joules for each plate, by means of a punctual technique. The growth curves showed that the growth levels were lower in low BFS concentrations. The irradiation with laser accelerated the growth rate in all groups. Additionally, the number of cells developed in low BFS concentration (5%) and irradiated was similar to the number of control cells developed in ideal conditions (10% BFS). There was no statistically significant differences between the effects of the two types of laser studied.

The subject of this work follows changes of the sIgA and albumin levels in the saliva of 48 patients treated after the extraction of their lower molars with either diode or He-Ne biostimulatory laser, using different modulatory frequencies (5 Hz, 292 Hz, 9000 Hz). The results were compared to the sIgA and albumin levels in the saliva of the control, i.e. not- treated group. For the tests radial immunodiffusion (RID) method was used (commercial RID kit of the Binding Site, Birmingham, Great Britain). Appropriately chosen laser beam modulatory frequency should influence the increase in the sIgA and albumin levels against the base level. In our study, this hypothesis was confirmed in the group treated with the frequency of 292 Hz and 9000 Hz (both diode GaAIAs, 670 nm, red, 20 mW, energy density 1.5 Jcm²) on albumin levels and 9000 Hz on sIgA levels. The changes of the levels of the watched markers versus the control group were at this frequencies (292 Hz and 9000 Hz) statistically significant. At the others used frequencies (5 Hz diode laser and 5 Hz He-Ne laser) the changes of the levels of the watched markers versus control group were statistically insignificant. The aim of this study was to contribute to the evaluation of specific modulatory frequencies (5 Hz, 292 Hz, 9000 Hz) for therapeutical use in a given pathological case of the oral cavity. We can conclude that using frequency 9000 Hz had best immunomodulatory effect.

Previous studies have demonstrated the ability of the Argon laser and conventional curing light to polymerize light- activated materials. This study was conducted to evaluate the effect of beam size on the diametral tensile strengths of a composite resin. The Argon laser (HGM Model 8) at 280 mw and 450 mw and beam size of approximately 5 mm , 8 mm, and 13 mm, with 10 second exposure were used to polymerize samples of TPH (L.D. Caulk) composite resin. The conventional curing light (the Max/L.D. Caulk) with beam sizes of 8 mm and 13 mm and 20 seconds exposure were used to polymerize Silux Plus (3M) composite resin. Twelve samples were made for each set of parameters for a total of 96 samples. The samples were stored in light-proof containers for 24 hours at room temperature and then tested on the Instron testing machine for diametral tensile strengths (MPa). Mean values were calculated for each set of data and ANOVA and Fisher PLSD were used for statistical analysis. Results indicate that in this study there was no statistical difference in diametral tensile strengths (MPa) between the beam sizes for a given power setting and light source.

Previous researches have discussed the importance of sealing the internal surface of the root canal after preparing it for posts or dowels, avoiding tubuli contamination by the oral environment. The purpose of this study was to investigate the effects of Neodymium-Yttrium-Aluminum-Garnet laser irradiation, associated or not with another materials, on the root inner walls after post space preparation. Forty single rooted endodontically treated teeth had theirs filings partially removed for prosthetics restoration, divided into 8 groups which received a coat of the following materials: group A: Copalite vanish; group B: Copalite vanish and laser; group C: Scothbond Multi-Purpose; group D: Scothbond Multi-Purpose and laser; group E: methylcianoacrilate; group F: methylcianocrilate and laser; group G: laser only; group H: control. The roots were placed in methylene blue dye and transversally cutted, then submitted to the analysis in the profile projector. So far we could observe that the Nd:Yag laser was able to enhance the sealing properties of the Scothbond Multi-Purpose.

Er;YAG and Er,Cr;YSGG Lasers that emit in the near red wave lengths cut both enamel and dentine. Dental preparations are often restored with composite resins that bond to enamel. The purpose of this investigation was to assess the shear strength of composite resin bonded to tooth structure cut by an Er,Cr;YSGG powered hydrokinetic system (HKS), (Millennium System^TM, BioLase Technology, Inc, San Clemente, CA) as compared to surfaces cut with a carbide bur. Extracted human molars devoid of caries and restorations were treated with both systems, with and without acid etching. Shear bond strengths (SBS) for composite resin adherence to these surfaces were measured and compared. There was no significant difference between bur and HKS prepared surfaces in the etched enamel group. The SBS for composite bonded to nonetched enamel was significantly higher with the HKS treatment compared with the bur cut surfaces. There were no significant differences between acid etched bur cut and non etched HKS enamel surfaces. Bonded to nonetched dentin was found to be higher for bur cut surfaces. It is concluded that the Er,Cr;YSGG hydrokinetic system produces surface characteristics that allow for adequate bonding of composite resin to both etched and nonetched enamel.

Countless researches conducted in these last years have compared the sealing capacity of various materials for retrofillings. Besides, the association of laser irradiation to traditional procedures inquires to increase the success of this kind of treatment. The purpose of this study was to evaluate the morphological changes on dentin surface and the junction between retrofilling material and apical cavity, with different materials irradiated or not with CO₂ laser, in scanning electron microscopy. The following materials were used: Group A yields Super EBA; group B yields Super EBA and CO₂ laser irradiation (Luxar System); group C yields Glass Ionomer Cement; group D yields Glass Ionomer Cement and CO₂ laser. In groups B and D the power set was 2 watts, 20 msec, with a CT3105 ceramic point, and the power density for the CO₂ laser application was 397,93 w/cm². The morphological analysis permitted to conclude that the dentin laser irradiation showed different and less intense superficial alteration when compared with retrofilling materials. In most cases, the alterations to the material surfaces showed cavities and craters. Group B presented more irregular and affected surfaces, creating blank spaces in the adjacent areas to the radicular dentinal surfaces after laser application, probably because of the carbonization.

Until now, no suitable delivery fiber existed for CO₂ laser endodontic radiation in the apical region where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, we designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal, thus favorably increasing the thermal effects. The 15 F CO₂ microprobe is a flexible, hollow, metal fiber, 300 micrometer in diameter and 20 mm in length, coupled onto a handpiece, with the following radiation parameters: wavelength -- 10.6 micrometer; pulse duration -- 50m/sec; energy per pulse 0.25 joule; energy density -- 353.7J/cm² per pulse; power on tissue -- 5 W. The study was conducted on 30 vital maxillary or mandibulary; central, lateral, or premolar teeth destined for extraction due to periodontal problems. Twenty were experimentally treated with pulsed CO₂ laser delivered by this newly developed fiber after conventional root canal preparation. Temperature measured at three points on the root surface during laser treatment did not exceed 38 degrees Celsius. Ten teeth represented the control group in which only root canal preparation was performed in the conventional method. Histological examination of the laser treated teeth showed coagulation necrosis and vacuolization of remaining pulp tissue in the root canal periphery. Primary and secondary dentin appeared normal, in all cases treated with 15 F CO₂ laser. Gramm stain and bacteriologic examination revealed complete sterilization. These results demonstrate the unique capabilities of this special microprobe in sterilization of the root canal, and no thermal damage to the surrounding tissue.

The present paper investigated the effects of two different laser beams on dentin and root canal walls. Five human intact teeth (incisors and canines), with endodontic treatment accomplished by Paiva and Antoniazzi technique, had their crowns separated from the roots using a diamond teeth. After polishing the dentin surfaces, they were irradiated with CO₂ and NdYag laser and analyzed using SEM and light microscopy. The light microscopy revealed some cicunscribed carbonized areas with some cracks of varied depths in all samples but indicated that the CO₂ laser, at power level of 5 watts, was more effective than NdYag laser at power level of 2 watts. The SEM showed formation of circular depressions with areas containing dentin fusion, melted dentin on small holes on the vitrified surfaces. From the data obtained, it was concluded that the methods analyzed are able to remove the remaining residues on the dentin layer and root canal walls. However, no complete fusion of the dentin layer occurred.

The aim of this research was to evaluate under SEM observation, the apical cut surface and retrofilling cavity prepared with Er:YAG laser and two other conventional techniques. Thirty extracted human teeth were divided into two groups of 15 teeth each. For Group 1 apicoectomy was performed using high speed handpiece and diamond burs. For Group 2 Er:YAG* laser irradiation (wavelength of 2.94 micrometer, pulse width of 250 - 500 microseconds) was used in 400 mJ of energy, frequency of 6 Hz, on focus mode under destiled water refrigeration. Each group was divided into 3 subgroups. For groups G1A and G2A, retrofilling cavity preparations were performed using low speed handpiece and burs, for groups G1B and G2B Enac technique was indicated. Groups G1C and G2C Er:YAG laser irradiation was used under same energy level previously described. All specimens were prepared for SEM observations. Pictures were taken under 30x and 600x magnification. Two different observers analyzed the smoothness and morphological appearance of those preparations. Data's were collected showing a smoothness surface, no debries or smear layer on group 2 (Laser irradiation) compared to group 1. Differences were also noted when retrofiling cavities were analyzed.

Assessment of tooth color by visual evaluation is a complex task. A number of attempts to build a reliable instrument that can measure the color of teeth have been undertaken in the last 15 years. These attempts were aimed at using conventional colorimeters designed for color measurement of oblique objects. However, the translucency of teeth strongly affected the colorimeters' readout because of the size of the measuring aperture and the geometry of the spectroscope. Here we present the results of our spectroscopic study of dental materials and human teeth that show a characteristic behavior of optical spectra collected with a fiberoptic probe. The probe consisted of 300 micrometer irradiating and 1 mm detecting fibers that were coupled to a white light source (color temperature 6500 K) and to a spectroscope. The conventional shades from Vita and Chromascop shade guides were measured with different location of the fibers. The color of the dental shades was measured by a standard spectrophotometer with two different apertures. We found that registered spectra depended on fiber position and color coordinates changed with aperture size. The influence of the fiber positioning was approved with color measurement of vital teeth. A simplified colorimetric system based on two color coordinates, lightness L*, and the difference, (a* - b*), has been proposed. Finally, we describe a novel dental color matching device based on a fiberoptic probe. The device is able to classify all dental shades from Vita, Chromascop, and Bioform shade guides and is aimed at better color matching of restorative materials to native teeth.

The purpose of this study was to determine the bactericidal effect of a CO₂ laser used in a continuous mode. Classically prepared root canals were irradiated under standardized conditions with power settings of 2, 4, and 6 Watts. The mean elimination of Enterococcus faecalis in prepared and infected root canals of extracted teeth was 98.97%, 99.51% and 99.34% respectively. Minimum elimination was 91.67% and maximum 99.696%.