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

To Assess the Efficacy of Various Disinfection and Hemostasis Procedures in Providing Postoperative Pain Relief Following Pulpotomy in Cases of Symptomatic Irreversible Pulpitis

AIM

The purpose of this study is to assess the efficacy of various disinfection and hemostasis procedures in providing postoperative pain relief following pulpotomy in cases of symptomatic irreversible pulpitis.

MATERIALS AND METHODS

The data from a cohort of 50 patients who received treatment with sodium hypochlorite (NaOCl) and another cohort of 50 patients who received treatment with potassium titanyl phosphate (KTP) laser were subjected to analysis. The patients were provided a questionnaire to evaluate pain levels before and after surgery. The patients documented their levels of postoperative pain at specific time intervals, including the sixth hour, first day, second day, third day, and eighth day. This was done using a 100 mm visual analog pain scale, where a marking of 0 mm indicated no pain and a marking of 100 mm indicated the highest level of pain, reflecting the severity of the pain experienced.

RESULTS

The pain score of group B was significantly lower than that of group A on the first day. While no notable disparity was detected among the groups during the remaining postoperative periods, it is worth noting that the KTP laser exhibited comparatively lower pain scores. In both groups, the initial pain score before surgery was found to be significantly higher than the pain scores recorded at all subsequent time intervals after surgery. Within group A, it was observed that the pain score during the sixth hour after the surgical procedure was notably greater compared to the pain scores recorded during all other time intervals following the operation. In group B, the pain score at the sixth hour exhibited a statistically significant increase compared to the pain scores observed on the third day and eighth day.

CONCLUSION

The KTP laser group exhibited a lower postoperative pain score in comparison to the NaOCl group. The utilization of KTP laser-assisted pulpotomy demonstrated enhanced efficacy in alleviating pain among individuals diagnosed with symptomatic irreversible pulpitis.

Histological evaluation of mouse tongue incisions after Er:YAG laser surgery with different pulse energies versus after conventional scalpel surgery

PURPOSE

To identify the surgical instrument that allows for optimal healing of tongue incisions.

METHODS

An Er:YAG laser was compared with different pulse energies to a conventional scalpel for the incision of mouse tongue tissues. Mice were sacrificed through cervical dislocation at 24, 48, and 72 h postoperatively, followed by extraction of their tongues for incision experiments. The healing of the incisions and expression of inflammation- and pain-related factors in the tongues were compared between the surgical procedure groups.

RESULTS

In laser-treated mice, tongue incisions healed the fastest when the laser output energy was 60 MJ per pulse. Macrophage chemotaxis toward the incisional area was triggered on the first postoperative day for the 60-MJ group, while the time for macrophage chemotaxis to the surgical area was later in the 80-MJ group. Tumor necrosis factor-alpha expression increased and then decreased in the 80-MJ group; however, it gradually decreased in the 60-MJ and conventional scalpel groups. Prostaglandin E2 expression increased and then decreased in the 80-MJ and conventional scalpel groups but gradually decreased in the 60-MJ group. The expression of transforming growth factor beta 1 gradually decreased in the 60-MJ and 80-MJ groups but gradually increased in the conventional scalpel group.

CONCLUSION

Compared with surgical procedures using conventional scalpels, those using an Er:YAG laser with appropriate pulse energies can inhibit inflammation in the incisional area and promote incision healing. The use of an Er:YAG laser with appropriate pulse energies can alleviate intraoperative and postoperative pain in the incisional area.

KTP 532 Laser Assisted Surgery for Oral Cavity Malignancy-A Retrospective Study

Aims and Objective

To determine the effectiveness of KTP 532 in surgically treating early and early advanced oral malignancy with no surgical reconstruction of primary site.

Materials and methods

It is a retrospective study of 67 cases operated between 2000 to 2013 including T1, T2 and Early T3 cases, approved by ethical committee. All the cases underwent Laser assisted excision of tumour with or without Neck Dissection or Adjuvant Radiotherapy. Age of the cases varied from 20 to 80 years with mean age of 49 years. 47 cases were males and 20 were females. 26 cases in the study had neck nodes clinically whereas 41 cases had N0 status. Neck dissection was done (SOND or MRND) in 61 cases. In 6 cases (N0) no neck dissection was done.

Results

61 cases had no loco-regional residual disease on their last follow up. Six cases had loco-regional recurrence within 6 months and salvage surgery was done. The overall mean survival was 81 months (92, 82 and 71 months in Stage I, II,III respectively). 3 year disease free survival rate was 91% as calculated using Kaplan- Meier Scale. In all these cases tumour was excised with KTP 532 laser and no reconstruction was done. Wound was allowed to heal with secondary intention.

Conclusion

Laser assisted excision of oral malignancy is an alternative to conventional treatment with more precision, less morbidity, shorter hospital stay and better functional outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-022-03214-x.

Evaluation of postoperative pain relief after pulpotomy using different procedures for disinfection and hemostasis in symptomatic irreversible pulpitis

Aim

This study aimed to evaluate postoperative pain scores after sodium hypochlorite (NaOCl) and KTP laser pulpotomies in the permanent teeth with symptomatic irreversible pulpitis retrospectively. Materials and Methods: This study is based on the records of patients treated with pulpotomy using sodium hypochlorite or KTP laser for disinfection and hemostasis at the Department of Endodontics. Sixty patients' molar teeth were treated with either NaOCl or KTP laser. Sodium hypochlorite was used on 31 teeth, and KTP laser was used on another 29 teeth, for disinfection and hemostasis. Initial bleeding control was obtained with saline. 2.5% NaOCl or KTP laser was applied to complete hemostasis. Calcium hydroxide was then placed on the chamber floor to cover the canal orifices. The permanent restoration was completed with composite resin. Pre and postoperative pain scores were recorded with a visual analog scale. The evaluation was performed on the 6^th, 24^th, 48^th, 72^nd hours, and 7^th days depending on the severity of the pain. Results: There was no significant difference between the groups in terms of demographic data and preoperative pain scores (P > 0.05). The postoperative pain score in the KTP laser group was significantly lower at the 24^th hour than in the NaOCl group (P < 0.05). No significant difference was found between the groups at other evaluated time intervals (P > 0.05). The greatest pain score was recorded at the 6^th hour in both groups.

Conclusion

Although the level of pain decreased significantly in both groups in the postoperative period, KTP laser-assisted pulpotomy provided better pain control, especially at the 24^th hour.

Efficacy of Potassium Titanyl Phosphate Laser and Sodium Hypochlorite on Postoperative Pain Intensity Following Pulpotomy in Teeth with Symptomatic Irreversible Pulpitis: A Randomized Clinical Trial

Introduction: This study evaluated the postoperative pain intensity in permanent teeth with symptomatic irreversible pulpitis treated by pulpotomy using physiological saline, sodium hypochlorite (NaOCl), or the potassium titanyl phosphate (KTP) laser. Materials and methods: Ninety patients diagnosed with symptomatic irreversible pulpitis in permanent molars were randomly divided into three groups according to the pulpotomy procedures. Preoperative pain levels were recorded. Complete hemostasis was achieved with physiological saline (control group), NaOCl, or the KTP laser after initial bleeding control. Patients were asked to mark their pain level on the visual pain scale at 6, 24, 48, and 72 h and 7 and 30 days depending on the severity of pain. The permanent restoration was completed after 7 days. Data were statistically analyzed using Kruskal-Wallis, Mann-Whitney U, Friedman, and Bonferroni tests at a significance level of p < 0.05. Results: According to the present study, the statistical difference between the groups in terms of preoperative pain and percussion pain levels was insignificant (p > 0.05). There was no significant difference between groups in terms of demographic data (p > 0.05). The postoperative pain level of the KTP laser group was significantly lower at 6 h compared with the saline group (p < 0.05). There was no significant difference between groups in terms of the postoperative pain level at other time intervals (p > 0.05). The highest pain scores were observed in all groups at 6 h (p < 0.05). Conclusions: The KTP laser can be preferred primarily for reducing postoperative pain in pulpotomy treatments. The KTP laser or NaOCl-assisted pulpotomy can be an effective treatment for pain reduction in permanent teeth with symptomatic irreversible pulpitis. This report is registered at clinicaltrials.gov (ID: NCT05424796).

Fractional treatment of rosacea by LBO 532 nm laser with “one shot” procedure: A preliminary study

Rosacea is a chronic skin disease prevalently affecting the center of the face. The permanent erythema of skin face represents its typical sign. Further common features are face flushing, telangiectasias, and inflammatory presence of oedema, papules and pustules. The aim of this study was to investigate the use of LBO 532nm laser in the treatment of this disease. Ten subjects of both sex and middle age affected by rosacea in erithemato/teleangectatic stage were treated by a LBO 532nm laser single session. Discomfort evaluation during and after the treatment, one session results as well as incidence of the side effects were evaluated, with 6 months follow up. Positive results were obtained after only one session in total safety with minimal patients discomfort and without undesired effects during treatment. The study confirmed International literature data suggesting the use of laser and light devices as elective treatment of this disease. IPL, dye lasers and 532nm laser are the devices more used and the last seems to represent the gold standard for 1,2,3 phototypes. This clinical trial, with the limitations due to the small number of patients, indicated that “one session LBO 532nm laser treatment” represents an interesting and innovative approach in the therapy of the erythemato/telangectatic rosacea.

Use of laser in oral frenectomies: a case report series

The aim of these case report series concerns the use of laser technology in oral frenectomies, by discussing different methods as well as comparing different laser wavelengths and underlining the role of photobiomodulation in the healing process.

Laser as a promising non-invasive technique to treat oral submucous fibrosis: A systematic review of the literature

Background

Oral submucous fibrosis (OSMF) is one of the common oral potentially malignant disorders that can result in severe morbidity. Depending upon the stage of disease, multiple management therapies exist which include medicinal and surgical approaches. Although the surgical approach is preferred in severe conditions, numerous studies have reported its post-surgical deteriorating outcomes including increased fibrotic changes. To reduce these post-surgical complications, Light amplification by stimulated emission of radiation (Laser) has been introduced and studied as a non-invasive technique to treat oral submucous fibrosis. However, there exists a lack of knowledge about ‘which laser shows a better post-treatment outcome’. Accordingly, this review aims to answer this question.

Materials and methods

A systematic review of the published literature was performed using an electronic search in PubMed/Medline, Science Direct, Web of Science, Embase, J- STAGE, Google Scholar, and Scopus databases, from 1952 till 2019 using keywords like, ‘Oral submucous fibrosis’, ‘Treatment’, ‘Laser’, ‘Trismus’, ‘ Fibrosis’, ‘Surgical’, ‘Non-invasive’, and ‘Postoperative results’.

Results

The search strategy revealed 20 relevant published studies in which laser had been used to treat 250 patients of OSMF. Effective results were found without any complications in all the cases after follow up.

Conclusion

Observing the current literature, it can be concluded that laser might be used as a potential non-invasive approach in the management of OSMF, however, large scale studies are required to investigate the efficacy and other effects of this technology.

Use of Blue and Blue-Violet Lasers in Dentistry: A Narrative Review

Introduction: Blue and blue-violet diode lasers (450 and 405 nm) seem to represent an interesting approach for several clinical treatments today. The aim of this narrative review is to describe and comment on the literature regarding the utilization of blue and blue-violet lasers in dentistry. Methods: A search for "blue laser AND dentistry" was conducted using the PubMed database, and all the papers referring to this topic, ranging from 1990 to April 2020, were analyzed in the review. All the original in vivo and in vitro studies using 450 nm or 405 nm lasers were included in this study. All the articles on the LED light, laser wavelengths other than 405 and 450 nm and using lasers in specialties other than dentistry, as well as case reports, guideline papers and reviews were excluded. Results: From a total of 519 results, 47 articles met the inclusion criteria and were divided into 8 groups based on their fields of application: disinfection (10), photobiomodulation (PBM) (4), bleaching (1), resin curing (20), surgery (7), periodontics (1), endodontics (1) and orthodontics (3). Conclusion: Blue and blue-violet diode lasers may represent new and effective devices to be used in a large number of applications in dentistry, even if further studies will be necessary to fully clarify the potentialities of these laser wavelengths.

Comparison of diode laser - Oral tissue interaction to different wavelengths. In vitro study of porcine periodontal pockets and oral mucosa

Background

The aim of this in vitro study was to evaluate the effect of diode lasers at different wavelengths and power settings in handmade incisions in periodontal pockets and in oral mucosa of porcine tissue considering thermal damage, necrosis and the affected area of the soft tissue.

Material and Methods

Combining the following laser wavelengths, 445nm, 532nm (KTP), 810nm, 980nm, 1064nm and 1470nm, and a power range from 0.5W to 2.0W in a continuous wave mode (CW), we made handmade incisions in porcine periodontal pockets and oral mucosa. After histological processing, we measured the area of ​​lost tissue, the area of ​​thermal damage and the area of ​​necrosis. Then, we performed ANOVA to evaluate the difference between groups and two-way ANOVA to identify the influence of the laser-type variables and the power on the results.

Results

We applied an ANOVA test to evaluate the results, where statistical analysis showed clear differences between the 1470nm and 810nm laser groups that refer to thermal damage and necrosis in the periodontal pocket surface. Regarding the oral mucosa surface, the 1064nm laser showed differences in the analysis of lost tissue. According to the applied power, all the variables we studied (lost tissue area, area of thermal damage and necrosis) showed higher values when using a power of 2.0W instead of 0.5W.

Conclusions

According to our results, the 810nm diode laser for oral soft-tissue biopsy using power ranges between 0.5W and 2W would be the best choice to avoid thermal damage in peri-incisional margins.

Key words:Laser surgery, soft tissue, diode laser, KTP laser, thermal damage, necrosis.

Prospective study of the 532 nm laser (KTP) versus diode laser 980 nm in the resection of hyperplastic lesions of the oral cavity

Background

The aim of this study is to evaluate the resection of hyperplastic lesions on the buccal mucosa comparing the 532nm laser (KTP), versus diode 980nm laser, considering pain, scarring, inflammation and drug consumption that occurred postoperatively with each lasers.

Material and Methods

A prospective study of consecutive series of 20 patients in two groups that presents hyperplastic lesions on the buccal mucosa. The choice of the KTP laser or diode 980nm laser for the surgery was made randomly. The power used was 1.5W in both groups in a continuous wave mode with a 320 μm optical fiber. Parameters of pain, scarring, inflammation and consumption of drugs were recorded by a Numerical Rating Scale and evaluated postoperatively. These recordings were made the day of the surgery, 24 hours after, 14 and 28 days after.

Results

Pain and inflammation was light - moderate. The consumption of paracetamol was somewhat higher in the diode 980nm laser versus the KTP laser after 24 hours, although data was not statistically significant; significant differences were found after 28 days in regards to pain (p = 0.023) and inflammation (p = 0.023), but always in the absence parameter so we find no pain in both lasers. Scarring in the two types of laser showed no differences along the visits, with not detected scar retractable.

Conclusions

Although there is a slight histological difference regarding the KTP laser in the oral soft tissues for clinical use, both wavelengths are very suitable for excision of oral fibroma.

Key words:Laser surgery, Laser therapy, oral surgery, soft tissue, 980 nm diode laser, 532 nm KTP laser.

450 nm Blue Laser and Oral Surgery: Preliminary ex vivo Study

INTRODUCTION

Dental diode lasers were started to be used at the end of the 1990s and were shown to possess several important characteristics, such as small size and low cost, as well as the advantage of optic fibers delivering system. Although only two wavelengths (810 and 980 nm) had been the most used dental diode lasers, a wavelength emitting in the blue portion of the spectrum has recently been proposed.

AIM

The aim of this ex vivo study was to compare the effectiveness of five different fiber-delivered laser wavelengths (450, 532, 808, 1064, and 1340 nm) in the oral soft tissue ablation.

MATERIALS AND METHODS

Specimens were surgically collected from the dorsal surface of four bovine tongues and, while deep thermal increase was measured by two thermocouples at 0.5 and 2 mm depth, surface temperature was recorded by an infrared thermometer. Subsequently, specimens were fixed in 10% buffered formalin solution, cut into slices, and embedded in paraffin blocks, and a pathologist made a morphological analysis by optic microscope assigning a score based on the quality of the cut and tissue damage.

RESULTS

The analysis showed the best quality of the cut and the lowest temperature increase on the specimens obtained with the shortest laser wavelength (450 nm).

CONCLUSION

Even considering this as preliminary study, the use of 450 nm blue diode laser in oral surgery may be suggested to the clinician in their daily practice.

CLINICAL SIGNIFICANCE

This study opens a new perspective in oral surgery. Blue diode laser has demonstrated a good quality of the cut with a low energy causing a minimal thermal damage to the tissue, promising a better comfort to patients.

450 nm diode laser: A new help in oral surgery

AIM

To describe the performance of 450 nm diode laser in oral surgery procedures.

METHODS

The case described consisted of the removal of a lower lip fibroma through a blue diode laser (λ = 450 nm).

RESULTS

The efficacy of this device, even at very low power (1W, CW), allows us to obtain very high intra and postoperative comfort for the patient, even with just topical anaesthesia and without needing suture. The healing process was completed in one week and, during the follow-up, the patient did not report any problems, pain or discomfort even without the consumption of any kind of drugs, such as painkillers and antibiotics. The histological examination performed by the pathologist showed a large area of fibrous connective tissue with some portions of epithelium-connective detachments and a regular incision with very scanty areas of carbonization.

CONCLUSION

The 450 nm diode laser proved of being very efficient in the oral soft tissue surgical procedures, with no side effects for the patients.

Four different diode lasers comparison on soft tissues surgery: a preliminary ex vivo study

Objectives: The introduction of diode lasers in dentistry had several advantages, principally consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibbers. Up today only the wavelengths around 810 and 980 nm were the most utilized in oral surgery but recently more different lasers had been proposed. The aim of this study was to compare the efficacy of four diode laser wavelengths (810, 980, 1470 and 1950 nm) for the ablation of soft tissues. Material and methods: Specimens were surgically collected from the dorsal surface of four bovine tongues and irradiated by four different diode wavelengths. Thermal increase was measured by two thermocouples, the first at a depth of 0.5 mm, and the second at a depth of 2 mm. Initial and final surface temperatures were recorded by IR thermometer. Epithelial changes, connective tissue modifications, presence of vascular modification and incision morphology were histologically evaluated by two blind pathologists. Results: The time necessary to perform the excision varied between 271 seconds (808 nm, 2W) and 112 seconds (1950 nm, 4W). Temperature increase superficial level varied from 16.3° (980 nm, 4W) and 9.2° (1950 nm, 2 W). The most significant deep temperature increase was recorded by 980 nm, 4 W (17.3°) and the lowest by 1950 nm, 2 W (9.7°). The width of epithelial tissue injuries varied between 74 pm from 1950 nm diode laser at 2 W to 540 pm for 1470 nm diode laser at 4 W. Conclusion: The quality of incision was better and the width of overall tissue injuries was minor in the specimens obtained with higher wavelength (1950 nm) at lower power (2W).

Different laser wavelengths comparison in the second-stage implant surgery: an ex vivo study

The implant surgery consists of two distinct techniques, the transmucosal, also known as "one-stage" and the "two-stage" technique. Lasers represent a possible aid in implant dentistry, especially in the two-stage technique and its main characteristics are represented by a decreased trauma to bone and soft tissues, a reduction of pain as well as a reduction of the risk of postoperative infections. The aim of this study was to analyze in an animal model the thermal elevation induced by four different laser wavelengths (diode, Nd:YAG, Er:YAG, KTP) during the implant uncovering. Four pig jaws were used to carry out this study. Five implants were placed in each anatomical specimen for a total of 20 fixtures. Four wavelengths (532, 810, 1,064 and 2,940 nm) were used to uncover the implants. Two thermocouples were used to measure temperature changes during laser irradiation at bone level, peri-implant tissues and on the fixture surface The thermocouples were connected with two probes of 1.5 mm in diameter, in order to simultaneously recording two temperature variations. Surface temperature was also checked during all procedures with a thermal camera (Thermovision A 800, Flyr Systems, Stockolm, Sweden) connected to a PC. The mean temperatures of each specimen (five fixtures) were calculated (TM1, mean temperature at the beginning; TM2, mean peak temperature). Furthermore, a record of the temperature at 1 min after the end of the surgical procedure was taken (mean: TM3). All the recorded values were statistically evaluated by one-way analysis of variance (ANOVA). The thermocouples recorded a lower increase in temperature for Er:YAG and KTP laser; Nd:YAG and diode laser produced similar increases characterized by higher values. The thermo-camera pointed out the lower increase for Er:YAG and higher for diode laser. KTP laser resulted faster in uncovering implants and diode laser was the one that needed more time. This ex vivo study showed that laser utilization with the recommended parameters gives no risks of dangerous thermal elevation to the tissues and implants.

Aesthetic earlobe remodeling: my personal experience with an LBO laser at 532 nm

Since 1960, when Maiman built the first laser equipment, this technology has gone through a continuous development and an increasing utilization in several fields. Nowadays many pathologies find a less traumatic solution in laser technology. Laser can be either used to treat lesions with a high bleeding risk such as hemangioma and lymphangioma or in patients with coagulation diseases or hypertension, taking advantage of its capability to coagulate. Moreover healing and scarring are improved by the laser's effect of biostimulation and inhibition of bacterial growth, this leading to a greater comfort for the patient. The tissue vaporization and the dimension of the damaged area depend on several factors, those related to the laser used, such as wavelength, power, emission mode (continued or pulsed mode) and the power density, and those concerning to the treated tissue, like color and consistency. In this Study, we used an Lithium Borate, (LBO), laser, instead of scalpel for earlobe reduction in a 35-year-old male patient with pending lobule. LBO laser works through a solid active medium emitting a visible green light. A diode laser, with a wavelength of 810 nm, stimulates a crystal of Nd:YAG, which has a wavelength of 1064 nm. Then a crystal of LBO doubles the vibration frequency of the photons, leading to a final wavelength of 532 nm.

Comparison of two different laser wavelengths' dental bleaching results by photo-Fenton reaction: in vitro study

The purpose of this study was to perform a preliminary in vitro test on the possible use of two different laser wavelengths, 405 and 532 nm, to improve the dental bleaching results. To perform the test, the degradation of a dye, rhodamine B, under the effects of hydrogen peroxide was used. One hundred and twenty vials were divided into four groups of 30 samples each and, while three of them were irradiated with different wavelengths, 365 nm (reference), 405 nm and 532 nm, the fourth was the non-irradiated control group. Each of the four groups was further divided into three subgroups of 10 cuvettes (n = 10) each. The three subgroups included a group with a rhodamine (RH) solution, a rhodamine and hydrogen peroxide (RH + HP) solution and a rhodamine plus hydrogen peroxide and ferrous gluconate (RH + FR) solution. When hydrogen peroxide was present, only UVA irradiation was able to produce significant results, whereas when the photo-Fenton reaction occurred, all the three wavelengths were able to produce a significant degradation of rhodamine B, with better results for longer wavelengths in comparison with short wavelengths. Within the limitations of this in vitro study, the light of the two laser devices, even remaining less effective than UV activation, showed its ability to improve the performance of bleaching agents based on Fenton photocatalysis, whereas when used in combination with hydrogen peroxide only, the 405-nm laser displayed a small effect and the 532-nm laser produced no effects.

Application of laser in oral surgery

In this review collected from the literature on usage of laser in oral minor surgery based on a Medline search in the time period between the years: 2008 and 2013, the most current evidence on laser-assisted oral minor surgery is going to be surveyed.

Dental ablation with 1064 nm, 500 ps, Diode pumped solid state laser: A preliminary study

BACKGROUND

The Er:YAG laser in conservative dentistry is. good alternative to conventional instruments. Though several studies show the advantages of these devices, some drawbacks and unsolved problems are still present, such as the cost of the device and the large dimensions of the equipment.

PURPOSE

In the present study, the effectiveness of dental surface ablation with a picosecond infrared diode-pumped solid-state (DPSS) laser was investigated. In vitro tests on extracted human teeth were carried out, with assessment of the ablation quality in the tooth and thermal increase inside the pulp chamber.

MATERIALS AND METHODS

A solid-state picosecond laser was used for the experiments. The samples were exposed to laser energy at 1064 nm at a frequency of 30 kHz and a 500 ps pulse width. The target teeth were cooled during exposures. The internal temperature of the pulp chamber was monitored with. thermocouple.

RESULTS

Optical microscope images showed effective ablation with the absence of carbonisation and micro-cracks. The cooling maintained the temperature rise in the pulp chamber below the permitted 5.5°C.

DISCUSSION

The main problem with the use of lasers in dentistry when teeth are the target is the heat generated in the pulp chamber of the target teeth. With lasers operating in the femtosecond mode, a better management of the internal temperature is possible, but is offset by the high cost of such devices. With the ps domain system used in the present study together with cooling using chilled water, effective and clean ablation could be achieved with a controlled thermal effect in the pulp chamber.

CONCLUSIONS

In this preliminary study with a picosecond domain DPSS laser using water cooling for the target, effective hard tissue ablation was achieved keeping the thermal increase in the pulp within the permitted range. The results suggest that this system could be used in clinical practice with appropriate modifications.

Laser-assisted surgery with different wavelengths: a preliminary ex vivo study on thermal increase and histological evaluation

Since the introduction of laser in clinical practice, different wavelengths have been used for oral surgery on the basis of the different characteristics and affinities of each one. The aim of this study was a comparison of different laser wavelengths in relation to both thermal increase and "histological quality" in a model of soft tissue surgery procedures. Thermal evaluation was realized, during laser-assisted surgery excision performed on a bovine tongue, by a thermal camera device to evaluate thermal increase on the surface of the sample and with four thermocouples to evaluate thermal increase on the depth of the specimen; temperature was recorded before starting surgical procedure and at the peak of every excision. The quality of excision, in terms of tissue damage and regularity, was realized by two blind examiners on the basis of established criteria. The highest superficial thermal increase was recorded for Superpulse 5-W CO2 laser, the lowest one for Er:YAG laser. The highest in depth thermal increase was recorded for 5 W Diode laser, the lowest one for Er:YAG laser. The best quality of incision was obtained with a 3-W CO2 laser and 3-W diode laser; epithelial, stromal, and vascular damages were evaluated with different degrees for all the used wavelengths with the best result, in terms of "tissue respect," for Er:YAG laser. In all the surgical procedures performed, thermal increase was evaluated until the end of the procedure; at remaining tissue level, thermal decrease was evaluable in the few seconds after surgery. The Er:YAG laser was the device with a lower influence on thermal increase; CO2 and diode lasers revealed a good histological quality. Further studies may be necessary to test the reliability of laser devices for the excision of all the types of specimens needing histological evaluation and diagnosis.

Analysis of shade, temperature and hydrogen peroxide concentration during dental bleaching: in vitro study with the KTP and diode lasers

Many dental bleaching techniques are now available, several of them using a laser source. However, the literature on the exact role of coherent light in the biochemical reaction of the whitening process is very discordant. The aims of this in vitro study were: (1) to compare two different laser sources, a KTP laser with a wavelength of 532 nm and a diode laser with a wavelength of 808 nm, during dental bleaching, and (2) to investigate the relationships among changes in gel temperature, tooth shade and hydrogen peroxide (HP) concentration during laser irradiation. Altogether, 116 bovine teeth were bleached using a 30% HP gel, some of them with gel only and others with gel plus one of the two lasers (532 or 808 nm) at two different powers (2 and 4 W). The KTP laser produced a significant shade variation with a minimal temperature increase. The diode laser led to a higher temperature increase with a greater reduction in HP concentration, but the change in shade was only statistically significant with a power of 4 W. At a power of 2 W, the KTP laser caused a greater change in shade than the diode laser. No significant correlations were found among temperature, HP concentration and shade variation. The KTP laser appears to provide better results with less dangerous thermal increases than the diode laser. This might call into question most of the literature affirming that the action of laser bleaching is by increasing the gel temperature and, consequently, the speed of the redox reaction. Further study is required to investigate the correlations between the parameters investigated and efficacy of the bleaching process.