Laser wavelengths and oral implantology

Histological In Vivo Evaluation of Intense Pulsed Light Technology: Assessing the Safety on Oral Soft and Hard Tissues

Intense pulsed light (IPL) is used for aesthetic and therapeutic purposes. According to recent literature, utilizing IPL may boost upregulation of anti-inflammatory cytokines, and downregulation of pro-inflammatory cytokines. Concerns have been raised about potential thermal damage to the soft and hard tissues in the oral cavity. Therefore, the aim of this study was to determine the safety of using IPL of various intensities in the tissues of the oral cavity.

METHODS

Three adult pigs were included in the trial. The oral cavity was divided into four quadrants and projected with a wide range of IPL settings. Alveolar bone, buccal mucosa, and gingival tissue samples were taken immediately and after 24 h. In each animal, one quadrant of the jaw was left untreated and served as a control. All samples were processed and stained with H&E.

RESULTS

Clinical examination showed no evidence of changes in the integrity of the examined tissues. Histological examination of the different tissues did not demonstrate significant thermal damage or changes in the characterization of the cells compared to the control tissues.

CONCLUSIONS

The use of IPL in the oral cavity is safe and does not negatively affect the tissues.

Effect of Er:YAG Laser Exposure on the Amorphous Smear Layer in the Marginal Zone of the Osteotomy Site for Placement of Dental Screw Implants: A Histomorphological Study

The placement of dental screw implants typically involves the use of rotary techniques and drills to create a bone bed. This study explores the potential benefits of combining this method with an Er:YAG laser. Split osteotomies were performed on 10 jaws of euthanized domestic pigs (Sus scrofa domestica), with 12 mandibular implant osteotomies in each jaw, divided into 4 groups. In order to make a comprehensive assessment of the effect of Er:YAG lasers, histomorphological techniques were used to measure the reduction in amorphous layer thickness after Er:YAG laser treatment, both with and without the placement of dental screw implants from different manufacturers. Following bone decalcification and staining, the thickness of the amorphous layer was measured in four groups: Group A-osteotomy performed without Er:YAG laser treatment-had amorphous layer thicknesses ranging from 21.813 to 222.13 µm; Group B-osteotomy performed with Er:YAG laser treatment-had amorphous layer thicknesses ranging from 6.08 to 64.64 µm; Group C-an implant placed in the bone without laser treatment-had amorphous layer thicknesses of 5.90 to 54.52 µm; and Group D-an implant placed after bone treatment with Er:YAG laser-had amorphous layer thicknesses of 1.29 to 7.98 µm. The examination and photomicrodocumentation was performed using a LEICA DM1000 LED microscope (Germany) and LAS V 4.8 software (Leica Application Suite V4, Leica Microsystems, Germany). When comparing group A to group B and group C to D, statistically significant differences were indicated (p-value = 0.000, p < 0.05). The study demonstrates the synergistic effects and the possibility of integrating lasers into the conventional implantation protocol. By applying our own method of biomodification, the smear layer formed during rotary osteotomy can be reduced using Er:YAG lasers. This reduction leads to a narrower peri-implant space and improved bone-to-implant contact, facilitating accelerated osseointegration.

Evaluation of cutting efficiency and thermal damage during soft tissue surgery with 940 nm-diode laser: An ex vivo study

OBJECTIVES

To investigate quantitatively the cutting efficiency and the thermal effects in the surrounding soft tissues of incisions that are induced by a 940 nm-diode laser with different power settings.

MATERIALS AND METHODS

Fifty-four gingival samples were prepared from the lower jaws of freshly slaughtered German-land race pigs and were randomly divided into 9 groups (n = 6) according to the adjusted output power (1, 1.5, 2, 2.5, 3, 3.5, 4, 5 and 6 W). Five incisions were implemented for each sample using a diode laser (940 nm) in continuous wave with an initiated tip resulting in 30 incisions for each experimental group utilizing a three-dimensional computer-controlled micropositioner. The samples were prepared for histometric evaluation using a transmitted light microscope. The cutting depth and width and the thermal damage were recorded for each sample and the efficiency factor γ was calculated.

RESULTS

The highest cutting efficiency (γ_z  = 0.81 ± 0.03) exhibited the group with 5 W output power (p < 0.05), while the lowest (γ_z  = 0.45 ± 0.11) showed the 1-W group (p < 0.05). Over 3.5 W there was a rapid increase in the size of thermal damage of the incisions, especially for 6 W, which presented the largest.

CONCLUSIONS

The most effective power parameters of diode laser (940 nm) for soft tissue surgery were from 3 to 5 W. The outcomes of the current study may help to establish clinical protocols for the use of diode lasers (940 nm) in soft tissue surgery in contact mode assisting dental professionals to achieve optimal clinical results and avoid complications.

Pre-Clinical Models in Implant Dentistry: Past, Present, Future

Biomedical research seeks to generate experimental results for translation to clinical settings. In order to improve the transition from bench to bedside, researchers must draw justifiable conclusions based on data from an appropriate model. Animal testing, as a prerequisite to human clinical exposure, is performed in a range of species, from laboratory mice to larger animals (such as dogs or non-human primates). Minipigs appear to be the animal of choice for studying bone surgery around intraoral dental implants. Dog models, well-known in the field of dental implant research, tend now to be used for studies conducted under compromised oral conditions (biofilm). Regarding small animal models, research studies mostly use rodents, with interest in rabbit models declining. Mouse models remain a reference for genetic studies. On the other hand, over the last decade, scientific advances and government guidelines have led to the replacement, reduction, and refinement of the use of all animal models in dental implant research. In new development strategies, some in vivo experiments are being progressively replaced by in vitro or biomaterial approaches. In this review, we summarize the key information on the animal models currently available for dental implant research and highlight (i) the pros and cons of each type, (ii) new levels of decisional procedures regarding study objectives, and (iii) the outlook for animal research, discussing possible non-animal options.

Erbium, chromium-doped: yttrium, scandium, gallium, garnet and diode lasers in the treatment of peri-implantitis: clinical and biochemical outcomes in a randomized-controlled clinical trial

This study aims to evaluate the effects of 940 nm diode laser and 2780 nm erbium, chromium-doped: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser used in addition to mechanical therapy in the non-surgical treatment of peri-implantitis on clinical parameters and matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels in the peri-implant crevicular fluid. A total of 50 patients with peri-implantitis were randomized into three groups to receive peri-implant treatment. The control group (n = 17) only received conventional non-surgical mechanical therapy. The trial groups [(diode group (n = 16) and Er,Cr:YSGG group (n = 17)] received dental laser in addition to mechanical therapy. Gingival index (GI), plaque index (PI), bleeding on probing, probing depth (PD), MMP-9, and TIMP-1 levels were assessed at baseline (T0) and at 6 months after treatment (T1). The GI, PI, and PD significantly decreased in all groups at T1, compared to T0 (p < 0.05). The decrease in the PD was similar between the control and diode groups with Er,Cr:YSGG providing more reduction (1.16 ± 0.64 mm) than either method (p = 0.032). A significant intra-group decrease in MMP-9 level was only observed in the Er,Cr:YSGG group (p = 0.009). The decrease in TIMP-1 level from T0 to T1 was similar between the control and the diode groups (p > 0.05) and it was significantly lower than the decrease in the Er,Cr:YSGG group (p < 0.05). Addition of diode laser to non-surgical mechanical therapy does not provide any additional benefit for treatment outcomes. The Er,Cr:YSGG laser seems to be more efficient both at clinical and molecular levels. ClinicalTrials, ID: NCT04730687. Registered 13 April 2021. Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04730687.

Bacterial reduction effect of four different dental lasers on titanium surfaces in vitro

Compare the effectiveness of selected dental lasers for decontamination of machined titanium surfaces in vitro. Seventy-two sterile machined surface titanium discs were individually inoculated with strains of Streptococcus mutans (Sm), Streptococcus oralis (So), Aggregatibacter actinomycetemcomitans (Aa), or all three bacteria together (MIX) at 34.0^° C, 20.8% O₂ and 5% CO₂ for 12 h. After incubation, the discs were divided into six groups: 1) no treatment, 2) 0.12% chlorhexidine gluconate (CHX), and 3) 10,600 CO₂, 4) 810 nm diode, 5) 2780 nm Er,Cr:YSGG, 6) 1064 nm Nd:YAG laser groups. After treatment, any remaining viable bacteria were liberated from the discs via sonication, transferred onto brain heart infusion (BHI) agar plates for culturing, and colony-forming units (CFUs) were recorded. Statistical analysis was performed. There were statistically significantly differences (SSD) (p < 0.01) in bacterial reduction of discs individually inoculated with Aa between the Er,Cr:YSGG and Nd:YAG lasers. There was also a SSD (p < 0.01) lower effect with the MIX with the Er,Cr:YSGG compared with all other modalities. Bacterial reduction with the CO₂ was better (p < 0.001) than treatment with CHX or the Er,Cr:YSGG laser on killing of So. Although all modalities of treatment showed a mean of 98% or greater viable bacterial reduction, the most consistent bacterial reduction of all titanium discs was with the Nd:YAG laser (100%).

Thermal Transfer on Splinted Implants During Diode Laser Irradiation In Vitro

Objective: Laser irradiation is being used for treatment of peri-implantitis. Therefore, this study aimed to assess the heat transfer from laser irradiation on an implant-supported, metal-ceramic fixed prosthesis in vitro. Materials and methods: Two titanium implants were placed in artificial type I bone, and after abutment connection, a bridge was fabricated and cemented. A peri-implant 3-wall defect was created around one of the implants. Thermocouples were placed at coronal (T1/T2) and apical (T3/T4) positions of both implants, and the T5 thermocouple was placed in the pontic. An identical setup was created in the type IV artificial bone. Diode laser irradiation (2 W, noninitiated tips, 320-μm fiber, and noncontact) was performed for 60 sec on each experimental model. This experiment was performed separately with 810- and 980-nm lasers for pulsed and continuous modes. ΔT based on the baseline was recorded during irradiation. Statistical analysis was performed with repeated analysis of variance. Results: Across all experimental models, the recorded ΔT (°) values in T2, T4, and T5 at 10, 30, and 60 sec were significantly less than 10°C (p < 0.001) for both types of bones. For both types of bones, there was a statistically significant ΔT greater than 10°C (p < 0.001) for continuous and pulsed 980-nm irradiation and continuous 810-nm diode laser irradiation after 60 sec. For both 810- and 980-nm lasers, there was a statistically significant ΔT greater than 10°C (p < 0.001) for type I and IV bones under irradiation and only for the type I bone model under pulsed irradiation after 60 sec. Conclusions: Within the limitations of this study, 810- and 980-nm lasers on splinted implants placed in vitro may increase the temperature on adjacent splinted implants due to material conductivity and splinting. Clinicians are advised to keep the temperature lower than the critical threshold following recommended power settings to avoid excessive heat and control complications due to overheating.

First Investigation of Dual-Wavelength Lasers (2780 nm Er,Cr:YSGG and 940 nm Diode) on Implants in a Simulating Peri-Implantitis Situation Regarding Temperature Changes in an In Vitro Pocket Model

Objective: This study aimed to investigate the temperature changes and question the safe laser settings and protocols for laser-assisted peri-implantitis treatment in an in vitro environment. Materials and methods: Three types of implants (Neoss, Dentegris, and Camlog) were implanted in an artificial bone model (n = 15). The model was placed into a 37°C water bath to simulate the in vivo oral condition. Throughout the laser irradiation, K-type thermocouples were used to record the real-time temperature measurements at different anatomically important locations in the artificial bone. Results: In all of the temperature measurements, no temperature rise above the critical safe limit, that is, >47°C, was observed. Conclusions: Within the limitations of this in vitro study, the use of the dual-wavelength protocol [Er,Cr:YSGG (1 and 1.5 W, 25, 50, 75 Hz)] and the 940 nm diode (peak power 2 W, duty cycle 50%) can be considered a safe method in the treatment of peri-implantitis, regarding its thermal safety.

Clinical comparison of the use of ER,CR:YSGG and diode lasers in second stage implants surgery

OBJECTIVES

To compare the effects of diode and erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers in second-stage implant surgery applications.

METHODS

This is a cross-sectional study that was carried out on patients who received implant treatment at the Departments of Oral and Maxillofacial Surgery and Periodontology, Van Yuzuncu Yil University, Van, Turkey between January 2017 and January 2018. Implants of the patients in the first group (n=20) were exposed with 940 nm Ga-Al-As diode laser while the implants of the second group (n=20) were uncovered with 2780 nm Er,Cr:YSGG laser in the second-stage surgery. Visual analogue scale (VAS) values during day 0 and following the operation on days 1, 2, 3 intraoperative bleeding grades, number of analgesics used in the postoperative period, operation time per implant, and postoperative complications were recorded.

RESULTS

When gender, smoking, the presence of systemic disease, toothbrushing frequency, analgesic use, bleeding and complications observed at the control session were analyzed, no statistically significant relationship was found between the 2 groups. It was observed that males had statistically significant higher VAS values than females (p less than 0.05).

CONCLUSION

Since diode lasers are more economical, smaller, and can meet the clinical needs of clinicians, it is likely that these lasers may be the preferred choice of the clinicians in surgical procedures.

The Effect of Er,Cr:YSGG and Diode Laser Applications on Dental Implant Surfaces Contaminated with Acinetobacter Baumannii and Pseudomonas Aeruginosa

Treatment of peri-implantitis through several implant surface decontamination techniques have been reported, however, some of them can negatively alter the implant surface or enhance more bacterial resistance. The aim of this in vitro study was to evaluate implant surface decontamination by means of Er,Cr:YSGG and diode lasers. Fifty micro-textured (MTX) dental implants were contaminated with Acinetobacter baumannii (n = 25) and with Pseudomonas aeruginosa (n = 25). All implants were then divided into five groups for the decontamination procedure. In group I (GI), decontamination was done with an Er,Cr:YSGG laser (2780 nm), while in group II (GII) decontamination was performed using photodynamic therapy (a 650 nm diode laser). In Group III (GIII) decontamination was performed with photodynamic therapy (an 808 nm diode laser), and in group IV (GIV) decontamination was performed with 0.12% chlorhexidine. Group V (GV) was the control group with no decontamination. After decontamination, colony forming units (CFU) were counted and implants were prepared for SEM analysis. A significant difference (p < 0.001) was observed for GI compared to the other groups, and also for GIV compared to both GII and GIII. The Er,Cr:YSGG laser (GI) showed the best results in decontaminating the implant surface. Chlorhexidine (GIV), proved to be better in decontaminating the implant surface than photodynamic therapy GII and diode laser GIII. No significant difference was found between group GII and GIII. The SEM analysis showed no significant change in the implant surface topography. The results of this study suggest that the Er,Cr:YSGG laser can be considered as an effective technique for reducing bacteria contamination on implant surfaces.

Microbial Etiology and Antimicrobial Therapy of Peri-implantitis: A Comprehensive Review

Introduction:

Implants have turned out to be a well-established therapy in dental practice for the replacement of missing teeth and restoration of function.

Peri-implant disease denotes the inflammatory condition of surrounding soft and hard tissues.

Two terminologies are covered under the impression of peri-implant pathology; peri-implantitis and mucositis. Peri-implant mucositis is a reversible inflammatory process limited to soft tissues around an implant. Peri-implantitis is an inflammatory condition of hard and soft tissue around the dental implant.

Microbial Etiology:

Bacterial infections are the most common cause of peri-implantitis. It is a variable poly-microbial infection, although generally dominated by Gram-negative anaerobic bacteria Anti-infective therapy should be included in the treatment regime, while treating the peri-implant disease. Antimicrobial therapy includes local debridement, antibiotic therapy and surface decontamination of the implant.

Conclusion:

The current article gives a detailed overview of microbial etiology, antimicrobial therapy and its limitations for the treatment of peri-implant Pathology.

The effects of diode laser on Staphylococcus aureus biofilm and Escherichia coli lipopolysaccharide adherent to titanium oxide surface of dental implants. An in vitro study

Effective decontamination of biofilm and bacterial toxins from the surface of dental implants is a yet unresolved issue. This in vitro study aims at providing the experimental basis for possible use of diode laser (λ 808 nm) in the treatment of peri-implantitis. Staphylococcus aureus biofilm was grown for 48 h on titanium discs with porous surface corresponding to the bone-implant interface and then irradiated with a diode laser (λ 808 nm) in noncontact mode with airflow cooling for 1 min using a Ø 600-μm fiber. Setting parameters were 2 W (400 J/cm²) for continuous wave mode; 22 μJ, 20 kHz, 7 μs (88 J/cm²) for pulsed wave mode. Bactericidal effect was evaluated using fluorescence microscopy and counting the residual colony-forming units. Biofilm and titanium surface morphology were analyzed by scanning electron microscopy (SEM). In parallel experiments, the titanium discs were coated with Escherichia coli lipopolysaccharide (LPS), laser-irradiated and seeded with RAW 264.7 macrophages to quantify LPS-driven inflammatory cell activation by measuring the enhanced generation of nitric oxide (NO). Diode laser irradiation in both continuous and pulsed modes induced a statistically significant reduction of viable bacteria and nitrite levels. These results indicate that in addition to its bactericidal effect laser irradiation can also inhibit LPS-induced macrophage activation and thus blunt the inflammatory response. The λ 808-nm diode laser emerges as a valuable tool for decontamination/detoxification of the titanium implant surface and may be used in the treatment of peri-implantitis.

Evaluation of Temperature and Roughness Alteration of Diode Laser Irradiation of Zirconia and Titanium for Peri-Implantitis Treatment

OBJECTIVE

This study investigated the effects of diode laser (gallium, aluminium, arsenide [GaAlAs]) irradiation with decontamination parameters on the temperature and roughness of yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP), titanium (TI), and sandblasted large grit acid-etched titanium (SLA).

MATERIALS AND METHODS

Three groups (n = 10) of standardized disks with 5 mm diameter and 2 mm thickness were produced with Y-TZP obtained from computer-aided design and computer-aided manufacturing (CAD-CAM), machined TI and SLA. The diode laser single application (808 nm, 20 sec, 1 W, 50 Hz, t on = 100 ms, t off = 100 ms, energy density = 28.29 J/cm(2)) was performed in contact mode, on each disk. The temperature was measured by a thermosensor attached to a digital thermometer fixed to the opposite irradiated surface. The temperature gradient (ΔT) was calculated (ΔT = final temperature - initial temperature) for each group. The parameters Ra (in μm) and Sa (in μm(2)) were measured by white light confocal laser microscopy to express the surface roughness. Data of ΔT was statistically analyzed by one way ANOVA at the 95% confidence level and compared by Tukey post-hoc test (α = 0.05). Roughness data was analyzed by t test.

RESULTS

The diode laser irradiation presented the following results (ΔT value): Y-TZP = 10.3°C(B); TI = 38.6°C(A), and SLA = 26.7°C(A). The ΔT values ((°)C) of the titanium groups were higher than for the Y-TZP group. For both roughness parameters (Ra and Sa), data did not show statistical significant differences to "irradiation" factor (p > 0.05) to Y-TZP and SLA. The Ra results (in μm) were: Y-TZP (control) = 0.73 (0.55); Y-TZP (irradiated) = 0.45 (0.27); SLA (control) = 0.74 (0.23); and SLA (irradiated) = 0.99 (0.33). The Sa results (in μm(2)) were: Y-TZP (control) = 1.39 (1.05); Y-TZP (irradiated) = 0.73 (0.41); SLA (control) = 0.85 (0.08); and SLA (irradiated) = 1.27 (0.44).

CONCLUSIONS

Diode laser irradiation for peri-implantitis treatment increased both zirconia and TI temperature without surface roughness alterations.

Current concepts in the use of lasers in periodontal and implant dentistry

Lasers have various periodontal applications including calculus removal (Er: YAG, Er, Cr: YSGG lasers); soft tissue excision, incision and ablation; decontamination of root and implant surfaces; biostimulation; bacteria reduction; and osseous surgery. This paper reviews some of the major opportunities for using lasers in periodontal and implant specialty practices. The literature relating to the use of lasers for removal of the pocket epithelium, root conditioning, bacterial reduction and decontamination of infected implant surfaces is discussed, and a summary of the advantages and disadvantages of using lasers for periodontal treatment is provided.

Non-surgical periodontal treatment of peri-implant diseases with the adjunctive use of diode laser: preliminary clinical study

Peri-implant diseases present in two forms: peri-implant mucositis and peri-implantitis. The prevalence of peri-implant complications is significantly rising. The aim of this study was to compare conventional treatment of inflamed peri-implant tissues with conventional treatment together with diode laser application. Twenty-seven patients (age 36 to 67, 15 women and 12 men, 12 smokers and 15 non-smokers) requiring treatment for mucositis or peri-implantitis were taken into account for this preliminary study. Plaque index (PI), pocket depth (PD), and bleeding on probing (BoP) were recorded at baseline evaluation. Patients in control group (CG) received conventional non-surgical periodontal treatment. Patients in test group received conventional non-surgical periodontal treatment together with diode laser application (810 nm, 30 s, 1 W, 50 Hz, t on = 100 ms, t off = 100 ms, energy density = 24.87 J/cm(2)). Paired t test was used to evaluate the difference in repeated measurements of considered indexes at T 0 and T 1 (1 year) in both groups. A total of 606 sites were taken into account in the test group (TG) and 144 in the CG. PD mean variation in the TG was 2.66 mm ± 1.07, while mean PD variation in the CG was 0.94 ± 1.13 mm. Paired t testing of the variation in PD in CG and TG revealed a statistically significant difference between the two groups (p < 0.0001). A reduction of pathological sites from 89 % (T 0) to 14.35 % (T 1) was achieved in the TG, while reduction obtained in the CG was from 75.69 % (T 0) to 50 % (T 1); BoP scores at time T 1 had fallen below 5 % in the TG and decreased to 59.7 %, in the CG. Within the limitations of this study, diode laser seems to be an additional valuable tool for peri-implant disease treatment.

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.

Current trends in dental implants

Tooth loss is very a very common problem; therefore, the use of dental implants is also a common practice. Although research on dental implant designs, materials and techniques has increased in the past few years and is expected to expand in the future, there is still a lot of work involved in the use of better biomaterials, implant design, surface modification and functionalization of surfaces to improve the long-term outcomes of the treatment. This paper provides a brief history and evolution of dental implants. It also describes the types of implants that have been developed, and the parameters that are presently used in the design of dental implants. Finally, it describes the trends that are employed to improve dental implant surfaces, and current technologies used for the analysis and design of the implants.

Thermal effects on zirconia substrate after Er,Cr:YSGG irradiation

OBJECTIVE: The objective of the present study was to investigate the thermal effects of Er,Cr:YSGG laser irradiation (1.5W/20Hz) on yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP). MATERIAL AND METHOD: Fifteen disks of Y-TZP (AS Technology TitaniumFIX, São José dos Campos, Brazil) with 5 mm diameter and 3 mm high standardized with CAD-CAM were used. The Y-TZP disks were randomized in three groups (n=5): Y-TZP-G1 = control (no laser treatment); Y-TZP-G2 = Y-TZP + Er,Cr:YSGG laser (air-water cooling proportion 80%/25%); Y-TZP-G3 = Y-TZP + Er,Cr:YSGG laser (air-water cooling proportion 80%/0%). A thermopar (SmartMether, Novus, Porto Alegre, RS, Brazil) was attached to a digital thermometer (SmartMether, Novus, Porto Alegre, RS, Brazil) fixed to the opposite irradiated surface. The temperature gradients (ΔT) were calculated (ΔT = Final Temperature - Initial Temperature) for each group. Values were statistically analyzed by one-way ANOVA at the 95% confidence level and compared by Tukey post-hoc test (α=0.05) for each material. One sample of each group was analyzed by confocal white light microscopy. RESULT: The ANOVA test showed significant differences for the factor "laser" (p<.001). The temperature gradients (ΔT value) showed the following results: Y-TZP-G1 = 0 ºC; Y-TZP-G2 = -1.4 ºC and Y-TZP-G3 = 21.4 ºC. The ΔT values (ºC) of the non-refrigerated group were higher than the refrigerated group. The roughness value (Ra) ranged from 4.50 to -33.65 µm. CONCLUSION: The water refrigeration for Er,Cr:YSGG irradiation is essential to avoid thermal increase in the Y-TZP.

Decontamination of dental implant surface in peri-implantitis treatment: a literature review

Etiological treatment of peri-implantitis aims to reduce the bacterial load within the peri-implant pocket and decontaminate the implant surface in order to promote osseointegration. The aim of this literature review was to evaluate the efficacy of different methods of implant surface decontamination. A search was conducted using the PubMed (Medline) database, which identified 36 articles including in vivo and in vitro studies, and reviews of different decontamination systems (chemical, mechanical, laser and photodynamic therapies). There is sufficient consensus that, for the treatment of peri-implant infections, the mechanical removal of biofilm from the implant surface should be supplemented by chemical decontamination with surgical access. However, more long-term research is needed to confirm this and to establish treatment protocols responding to different implant characterics.

Decontamination of dental implant surfaces by means of photodynamic therapy

Several implant surface debridement methods have been reported for the treatment of peri-implantitis, however, some of them can damage the implant surface or promote bacterial resistance. Photodynamic therapy (PDT) is a new treatment option for peri-implantitis. The aim of this in vitro study was to analyze implant surface decontamination by means of PDT. Sixty implants were equally distributed (n = 10) into four groups and two subgroups. In group G1 there was no decontamination, while in G2 decontamination was performed with chlorhexidine. G3 (PDT − laser + dye) and G4 (laser, without dye) were divided into two subgroups each; with PDT performed for 3 min in G3a and G4a, and for 5 min in G3b and G4b. After 5 min in contact with methylene blue dye (G3), the implants were irradiated (G3 and G4) with a low-level laser (GaAlAs, 660 nm, 30 mW) for 3 or 5 min (7.2 and 12 J). After the dilutions, culture media were kept in an anaerobic atmosphere for 1 week, and then colony forming units were counted. There was a significant difference (p < 0.001) between G1 and the other groups, and between G4 in comparison with G2 and G3. Better decontamination was obtained in G2 and G3, with no statistically significant difference between them. The results of this study suggest that photodynamic therapy can be considered an efficient method for reducing bacteria on implant surfaces, whereas laser irradiation without dye was less efficient than PDT.

Temperature increase during CO(2) and Er:YAG irradiation on implant surfaces

PURPOSE

The purpose of this study was to evaluate the temperature gradient (ΔT) generated by laser irradiation of an implant surface using a carbon dioxide (CO(2)) and an Erbium:yttrium aluminium garnet (Er:YAG) laser.

MATERIALS AND METHODS

A dental implant was irradiated with a CO(2) and an Er:YAG lasers, with variable power settings. Temperature increase was measured in 2 locations of the implant surface: in the cervical area (ΔT(c)) and in the apical area (ΔT(a)).

RESULTS

The CO(2) laser showed the following results: after 60 seconds of irradiation with continuous mode, ΔT(c) was 13.9°C and ΔTa was 12.5°C. The Er:YAG laser showed the following results: after 60 seconds of irradiation with continuous mode, the temperature rise ΔT(c) was 50.6°C and ΔT(a) was 38.6°C. The CO(2) laser with continuous mode generated a temperature increase of 10°C after only 36 seconds. The Er:YAG laser with continuous mode produced a more rapid temperature increase and took only 10 seconds to reach the critical threshold.

CONCLUSIONS

The irradiation of implant surfaces with CO(2) and Er:YAG lasers may produce a temperature increase above the critical threshold (10°C) after 10 seconds of continuous irradiation.

Effect of low-level laser therapy on proliferation, differentiation, and adhesion of steroid-treated osteoblasts

There has recently been constant effort to evaluate therapies that may have a positive effect on bone regeneration. However, there are few studies in the literature on the effects of low-level laser therapy (LLLT) involving tissues treated with anabolic steroids. The present study evaluated the effects of LLLT (AsGaAl 780 nm, 3 J/cm(2), 10 mW, beam spot of 0.04 cm(2), total energy 0.12 J) on the proliferation, adhesion, and differentiation of osteoblasts cultured in the presence of nandrolone decanoate (ND). The MTT method was employed to evaluate cell proliferation and adhesion. Cell differentiation was evaluated by measuring alkaline phosphatase activity. There was a significant decrease in cell proliferation in the irradiated group treated with 50 μM ND when compared to the control group, after 48 h. After 72 h, cell proliferation was significantly greater in the control group than in the irradiated groups treated with the steroid at concentrations of 10, 25, and 50 μM. With regard to cell differentiation, alkaline phosphatase activity was significantly higher in the irradiated group treated with 50 μM ND than in the control group, irradiated non-treated group, and irradiated group treated with 25 μM ND. After 60 min of plating, the irradiated non-treated group and irradiated groups treated with the steroid at concentrations of 5, 10, and 25 μM exhibited a significant increase in cell adhesion compared to the control group. LLLT in combination with a high concentration of steroid inhibited cell proliferation, possibly by inducing cell differentiation, while irradiation combined with lower concentrations of the steroid induced an increase in cell adhesion.

Evaluation of light-emitting diode (LED-660 nm) application over primary osteoblast-like cells on titanium surfaces: an in vitro study

BACKGROUND

The goal of this study was to evaluate the behavior of neonatal rat calvarial osteoblast-like cells cultured on different implant surfaces and exposed once or three times to a 660-nm light-emitting diode (LED).

METHODS

An LED with a 660-nm wavelength was applied once or three times to cultured cells on standard and modified sandblasted acid-etched surfaces (SLA and SLActive; Straumann, Basel, Switzerland). To analyze the effect of the LED on cell proliferation, numbers, and viability, cells were cultured on titanium discs, and measurements were taken after 72 h. Cell proliferation rates were assessed using a bromodeoxyuridine immunohistochemical technique. Cell morphologies were evaluated by scanning electron microscopy (SEM).

RESULTS

Osteoblast-like cells proliferated on all tested surfaces, with differences among groups in cell counts and DNA synthesis values. The application of one LED treatment caused a significant increase in cell count in the SLActive group in comparison with the SLA group (p = 0.001), whereas the application of three LED treatments caused a significant decrease in cell count in the SLA group compared with the SLActive group (p < 0.001). After 72 h, the number of cells was highest in the SLActive group exposed once to the LED.

CONCLUSIONS

One LED application in the SLActive group resulted in significantly increased cell numbers. However, these findings were not exactly compatible with the SEM findings, which demonstrated fewer cells and weak attachments between cells and to the surface. Thus, further studies using different LED application times are needed to clarify the reason for the increased number of cells that are apparently incapable of attaching to the titanium surfaces after 72 h.

Comparative in vitro study among the effects of different laser and LED irradiation protocols and conventional chlorhexidine treatment for deactivation of bacterial lipopolysaccharide adherent to titanium surface

OBJECTIVE AND BACKGROUND

The present in vitro study was designed to evaluate and compare the efficacy of: 1) different dental laser devices used in photoablative (PA) mode, namely commercial CO(2), Er:YAG, and Nd:YAG lasers and a prototype diode laser (wavelength = 810  nm); 2) prototype low-energy laser diode or light-emitting diode (LED) (wavelength = 630  nm), used in photodynamic (PD) mode together with the photoactivated agent methylene blue; and 3) chlorhexidine, used as reference drug, to reduce the activation of macrophages by lipopolysaccharide (LPS), a major pro-inflammatory gram-negative bacterial endotoxin, adherent to titanium surface.

METHODS

RAW 264-7 macrophages were cultured on titanium discs, cut from commercial dental implants and precoated with Porphyromonas gingivalis LPS. Before cell seeding, the discs were treated or not with the noted lasers and LED in PA and PD modes, or with chlorhexidine. The release of nitric oxide (NO), assumed to be a marker of macrophage inflammatory activation, in the conditioned medium was related to cell viability, evaluated by the MTS assay and ultrastructural analysis.

RESULTS

PA laser irradiation of the LPS-coated discs with Er:YAG, Nd:YAG, CO(2,) and diode (810  nm) significantly reduced NO production, with a maximal inhibition achieved by Nd:YAG and diode (810  nm). Similar effects were also obtained by PD treatment with diode laser and LED (630  nm) and methylene blue. Notably, both treatments were superior to chlorhexidine in terms of efficiency/toxicity ratio.

CONCLUSIONS

These findings suggest that laser and LED irradiation are capable of effectively reducing the inflammatory response to LPS adherent to titanium surface, a notion that may have clinical relevance.