Lasers in dentistry

Restoration Integrity in Primary Teeth Prepared Using Erbium/Yttrium-Aluminum-Garnet Laser: A Randomized Split-Mouth Clinical Study

The most frequently used and universally accepted technique for removing caries is mechanical ablation of decayed tissues by rotating drills. New minimally invasive strategies, such as the use of lasers to perform highly controlled tissue ablation, have been introduced in dental practice. The aim of this study was to assess and compare treatment with a 2940 nm erbium/yttrium-aluminum-garnet (Er:YAG) laser versus a conventional rotary treatment during cavity preparation in children with regard to restoration integrity. In a randomized, controlled, blinded trial using a split-mouth design, 40 (9-12-year-old) children with 80 carious primary molars were included. The cavity in one quadrant was randomized to be treated conventionally using a bur, while the cavity in the other quadrant was prepared using an Er:YAG laser. At the one-year follow-up, clinical examinations were conducted to assess the integrity of the restorations according to the Ryge criteria. The data were analyzed using SPSS version 22 (IBM Inc., Chicago, IL, USA). The average age of the participants was 9.4 ± 1.29 years. Males accounted for 51.4% of the participants. The Ryge criteria showed clinical success of restorations, and there was no discernible difference between the conventional and laser intervention techniques. Over one year, no statistically significant differences in the clinical integrity based on the Ryge criteria were found following class I cavity preparation in primary teeth with either procedure.

Blue Laser for Polymerization of Bulk-Fill Composites: Influence on Polymerization Kinetics

The objective of this study was to compare the polymerization kinetics of bulk-fill resin composites cured with a LED-curing device and a diode laser (449 nm). Three bulk-fill composites were light-cured with constant radiation exposure at 10 J/cm² by varying radiant exitance and curing time. The following three light-curing protocols were used: (I) 3300 mW/cm² for 3 s; (II) 2000 mW/cm² for 5 s; and (III) 1000 mW/cm² for 10 s. The degree of conversion (DC) was monitored in real time at a data acquisition rate of 2 spectra/s over a 5-min period and again after seven days using Fourier transform infrared spectroscopy. DC amounted to 30.9-61.7% at 4-mm depth after 5 min. DC values of two sculptable composites were significantly higher with the laser, regardless of the curing protocol used, but not for the flowable composite. The maximum polymerization rate (2.0-22.1%/s) was less affected by the type of curing device for one of the composites, while the other two composites achieved significantly higher values when cured with the laser. Laser curing generally increased the DC and the maximum polymerization rate while it shortened the onset of the maximum reaction rate. New handheld laser devices with adjustable power have the potential to be used as a photopolymerization light source for new generations of bulk-fill composites.

Dental laser training and education in postgraduate periodontics programs in North America

INTRODUCTION

The application of various lasers to treat periodontal and peri-implant diseases is gaining momentum. While laser-related dental research is ongoing, it is important to determine if current periodontal training programs are keeping pace with these new treatment modalities and actively incorporating them into their training.

MATERIALS AND METHODS

An electronic survey was created to evaluate the extent to which lasers are currently being used in North American periodontal programs. A brief explanation of the study and a link to the 15-question survey was emailed to 61 periodontal program directors requesting participation in the survey. The data regarding the prevalence of laser training in all the programs, which types of laser devices are used, and which surgical procedures are performed were collected and analyzed.

RESULTS

The response rate was 49.1% (n = 30). Among those responding to the survey, 76.7% (n = 23) of these programs reported providing clinical training in lasers, with the diode laser being the most frequently used (65.2%), followed by carbon dioxide (39.1%), neodymium-doped yttrium aluminum garnet (26.1%), and erbium:yttrium aluminum garnet lasers (26.1%). Two major reasons for not utilizing lasers as part of regular patient care were cost and lack of evidence to support laser efficacy. Three out of seven programs that do not currently use lasers plan to provide laser training in the future. Over half (56.7%) of program directors did not think that lasers would become the standard of periodontal/implant care within the next 10 years, while 20% of them believed that they would.

CONCLUSIONS

Laser training and education in postgraduate periodontal programs is still limited, and the majority of periodontal residents are not exposed to many types of laser devices.

Effect of Er,Cr:YSGG laser on the surface of composite restoratives during in-office tooth bleaching

The aim of this in vitro study was to investigate the effect of Er,Cr:YSGG laser on the surface roughness and microhardness of various composite restoratives during in-office tooth bleaching. Five highly viscous composite restoratives and three flowable composite restoratives were investigated. Thirty cylindrical specimens of each material were made using Teflon molds. The specimens of each composite were randomly divided into three groups (n = 10). Group 1 specimens did not receive bleaching treatment, group 2 received a conventional in-office bleaching treatment, and group 3 received a laser-assisted in-office bleaching treatment using an Er,Cr:YSGG laser. Two-way ANOVA was used to determine significant interactions between materials and bleaching methods. One-way ANOVA and Tukey's post hoc test were used to compare the mean surface microhardness and roughness between materials for each treatment group (a = 0.05). Τhere were no significant differences in surface microhardness between the two bleached experimental groups for all the tested composites (p > 0.05). The reduction of surface microhardness after bleaching procedures ranged from 0.72 to 16.93 % for the specimens received conventional treatment and from 1.30 to 11.51 % for those received laser-assisted treatment. Moreover, there were no significant differences in Ra values between the experimental groups (p > 0.05) in all cases. The increase of surface roughness after the bleaching treatments was negligible and was between 0.43 and 4.78 %. The use of Er,Cr:YSGG laser during in-office tooth bleaching treatment did not affect the surface microhardness and roughness of the tested composite restorative materials.

Comparative evaluation of surface topography of tooth prepared using erbium, chromium: Yttrium, scandium, gallium, garnet laser and bur and its clinical implications

Background:

Erbium, chromium: Yttrium, scandium, gallium, garnet (Er, Cr: YSGG) laser has been successfully used in the ablation of dental hard and soft tissues. It has been reported that this system is also useful for preparing tooth surfaces and etching, but no consensus exist in the literature regarding the advantage of lasers over conventional tooth preparation technique.

Materials and Methods:

Labial surfaces of 25 extracted human maxillary central incisors were divided into two halves. Right half was prepared with diamond bur and left half with Er, Cr; YSGG laser and a reduction of 0.3–0.5 mm was carried out. Topography of prepared surfaces of five teeth were examined under scanning electron microscope (SEM). The remaining samples were divided into 4 groups of 10 specimens each based on the surface treatment received: One group was acid etched and other was nonetched. Composite resin cylinders were bonded on prepared surfaces and shear bond strength was assessed using a universal testing machine.

Results:

The SEM observation revealed that the laser prepared surfaces were clean, highly irregular and devoid of a smear layer. Bur prepared surfaces were relatively smooth but covered with smear layer.

Highest bond strength was shown by laser prepared acid etched group, followed by bur prepared the acid etched group. The bur prepared nonacid etched group showed least bond strength.

Conclusions:

Er, Cr: YSGG laser can be used for preparing tooth and bond strength value achieved by laser preparation alone without surface treatment procedure lies in the range of clinical acceptability.

Laser teeth bleaching: evaluation of eventual side effects on enamel and the pulp and the efficiency in vitro and in vivo

Light and heat increase the reactivity of hydrogen peroxide. There is no evidence that light activation (power bleaching with high-intensity light) results in a more effective bleaching with a longer lasting effect with high concentrated hydrogen peroxide bleaching gels. Laser light differs from conventional light as it requires a laser-target interaction. The interaction takes place in the first instance in the bleaching gel. The second interaction has to be induced in the tooth, more specifically in the dentine. There is evidence that interaction exists with the bleaching gel: photothermal, photocatalytical, and photochemical interactions are described. The reactivity of the gel is increased by adding photocatalyst of photosensitizers. Direct and effective photobleaching, that is, a direct interaction with the colour molecules in the dentine, however, is only possible with the argon (488 and 415 nm) and KTP laser (532 nm). A number of risks have been described such as heat generation. Nd:YAG and especially high power diode lasers present a risk with intrapulpal temperature elevation up to 22°C. Hypersensitivity is regularly encountered, being it of temporary occurrence except for a number of diode wavelengths and the Nd:YAG. The tooth surface remains intact after laser bleaching. At present, KTP laser is the most efficient dental bleaching wavelength.

Effect of Er:YAG laser on debonding strength of laminate veneers

Objective:

The purpose of this study was to evaluate the debonding strength of laminate veneers after using erbium-doped: yttrium aluminium garnet (Er:YAG) laser.

Materials and Methods:

A total of 60 bovine mandibular incisor teeth were divided into two groups (n = 30). Cylindrical specimens (0.7 mm × 5 mm) were fabricated from Empress II ceramic. Then, they were cemented to incisors using dual-cured resin cement (Variolink II). In the first group, no laser application was performed. The Er:YAG laser was applied on each laminate veneer at the test group for 9 s by using the scanning method. Shear force to remove the laminate veneers were applied with universal testing machine at a crosshead speed of 1 mm/min.

Results:

Results of this study exhibited significant differences between the control (27.28 ± 2.24 MPa) and test group (3.44 ± 0.69 MPa) (P < 0.05).

Conclusion:

This study shows that application of Er:YAG laser decreased the bond strength of laminate veneers.

Morphological changes produced by acid dissolution in Er:YAG laser irradiated dental enamel

Several scientific reports have shown the effects of Er:YAG laser irradiation on enamel morphology. However, there is lack of information regarding the morphological alterations produced by the acid attack on the irradiated surfaces. The aim of this study was to evaluate the morphological changes produced by acid dissolution in Er:YAG laser irradiated dental enamel. Forty-eight enamel samples were divided into four groups (n = 12). GI (control); Groups II, III, and IV were irradiated with Er:YAG at 100 mJ (12.7 J/cm(2) ), 200 mJ (25.5 J/cm(2) ), and 300 mJ (38.2 J/cm(2) ), respectively, at 10 Hz without water irrigation. Enamel morphology was evaluated before-irradiation, after-irradiation, and after-acid dissolution, by scanning electron microscopy (SEM). Sample coating was avoided and SEM analysis was performed in a low-vacuum mode. To facilitate the location of the assessment area, a reference point was marked. Morphological changes produced by acid dissolution of irradiated enamel were observed, specifically on laser-induced undesired effects. These morphological changes were from mild to severe, depending on the presence of after-irradiation undesired effects.

Chemical changes associated with increased acid resistance of Er:YAG laser irradiated enamel

BACKGROUND

An increase in the acid resistance of dental enamel, as well as morphological and structural changes produced by Er:YAG laser irradiation, has been reported.

PURPOSE

To evaluate the chemical changes associated with acid resistance of enamel treated with Er:YAG laser. Methods. Forty-eight enamel samples were divided into 4 groups (n = 12). Group I (control); Groups II, III, and IV were irradiated with Er:YAG at 100 mJ (12.7 J/cm(2)), 200 mJ (25.5 J/cm(2)), and 300 mJ (38.2 J/cm(2)), respectively.

RESULTS

There were significant differences in composition of irradiated groups (with the exception of chlorine) and in the amount of calcium released.

CONCLUSIONS

Chemical changes associated with an increase in acid resistance of enamel treated with Er:YAG laser showed a clear postirradiation pattern characterized by a decrease in C at.% and an increase in O, P, and Ca at.% and no changes in Cl at.%. An increased Ca/P ratio after Er:YAG laser irradiation was associated with the use of higher laser energy densities. Chemical changes produced by acid dissolution showed a similar trend among experimental groups. Stable or increased Ca/P ratio after acid dissolution was observed in the irradiated groups, with reduction of Ca released into the acid solution.

Factors involved in dental surgery fires: a review of the literature

Surgical fires are well-characterized, readily preventable, potentially devastating operating room catastrophes that continue to occur from 20 to 100 times per year or, by one estimate, up to 600 times per year in US operating rooms, sometimes with fatal results. The most significant risk factors for surgical fires involve (a) the use of an ignition source, such as laser or electrocautery equipment, in or around an oxygen-enriched environment in the head, neck, and upper torso area and (b) the concurrent delivery of supplemental oxygen, especially via nasal cannula. Nonetheless, while these 2 conditions occur very commonly in dental surgery, especially in pediatric dental surgery where sedation and anesthesia are regularly indicated, there is a general absence of documented dental surgical fires in the literature. Barring the possibility of underreporting for fear of litigation, this may suggest that there is another mechanism or mechanisms present in dental or pediatric dental surgery that mitigates this worst-case risk of surgical fires. Some possible explanations for this include: greater fire safety awareness by dental practitioners, incidental ventilation of oxygen-enriched environments in patient oral cavities due to breathing, or suction used by dental practitioners during procedures. This review of the literature provides a background to suggest that the practice of using intraoral suction in conjunction with the use of supplemental oxygen during dental procedures may alter the conditions needed for the initiation of intraoral fires. To date, there appear to be no published studies describing the ability of intraoral suctioning devices to alter the ambient oxygen concentration in an intraoral environment. In vivo models that would allow examination of intraoral suction on the ambient oxygen concentration in a simulated intraoral environment may then provide a valuable foundation for evaluating the safety of current clinical dental surgical practices, particularly in regard to the treatment of children.

Labial frenectomy with Nd:YAG laser and conventional surgery: a comparative study

Labial frenulums are sagittal fibrous folds of oral mucosa with a periosteal insertion that extend from the lips to the alveolar or gingival mucosa. Occasionally, they assume inadequate size or location and may lead to functional and esthetic limitations. The aim of the present study was to compare pre-, trans-, and postsurgical clinical parameters of labial frenectomies performed with conventional surgery and neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Forty individuals were assessed as a convenience sample and were divided into two groups according to the treatment: group 1 (G1), conventional surgery (n = 22), and G2, Nd:YAG laser surgery (n = 18). Clinical parameters such as frenulum insertion, location, bleeding, surgical time, suturing, preoperative fear, and postoperative discomfort/functional limitations were evaluated. All surgeries were performed by the same operator, and the level of fear, pain, and discomfort related to oral functions were assessed with a visual numeric scale. Most of the frenulums (90%) were classified as papillary or transpapillary insertion. Preoperative fear was similar between groups (p = 0.593). All G2 patients did not require suture (p < 0.001), did not bleed during the procedure (p < 0.001), and had surgical time diminished (p < 0.001). No significant statistical difference regarding pain or oral function could be observed. Three individuals (7.5%) experienced postsurgical complications. Nd:YAG laser frenectomies reduces transoperative bleeding, avoiding the need of suturing, and promotes a significant reduction of surgical time in comparison with conventional surgery. Therefore, further studies are necessary to provide a complete understanding and standardization of the technique as well as the expected clinical results.

Morphological analysis of the resin-dentin interface in cavities prepared with Er,Cr:YSGG laser or bur in primary teeth

OBJECTIVE

The purpose of this study was to analyze the resin-dentin interface in cavities prepared with laser or bur in primary teeth.

BACKGROUND DATA

Erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser was expected to be an alternative cavity preparation method, enhancing surface alterations and producing morphological changes.

METHODS

Twenty extracted primary molar teeth were divided to four groups according to one of four cavity preparation and pretreatment regimens: Er,Cr:YSGG laser (G1), Er,Cr:YSGG laser+acid-etching (G2), bur (G3), and bur+acid-etching (G4). After applying composite resin to the cavities, the teeth were sectioned. The resin-dentin interface was analyzed under scanning electron microscopy (SEM) and ion analysis was performed with SEM-energy-dispersive X-ray spectroscopy (EDX) after immersion in ammoniacal silver nitrate solution.

RESULTS

In G1 and 2, the surfaces were wavy, and in G3 and 4, the surfaces were smooth. Microcracks were seen in some of the lased cavities. In G1 and 2, dentin tubules were exposed and there was lack of a smear layer. In G3, there were gaps and a smear layer in the resin-dentin interface, but no gaps or smear layer were observed in G4. In G2, the resin tags were increased, and some resin tags were broken in cavities, which were prepared with laser (G1 and 2).

CONCLUSIONS

According to the results of this study, acid-etching was recommended after laser preparations, to have a better adhesion.

The adjunct effectiveness of diode laser gingivectomy in maintaining periodontal health during orthodontic treatment

OBJECTIVE

To evaluate the effectiveness of diode laser gingivectomy as an adjunct to nonsurgical periodontal treatment in the management of periodontal health among patients receiving fixed orthodontic appliance therapy (FOAT).

MATERIALS AND METHODS

Thirty patients undergoing FOAT with gingival enlargement were block randomized into two treatment groups. The test group received diode laser gingivectomy (940-nm diode laser, ezlase, Biolase Technology Inc) as an adjunct to nonsurgical periodontal treatment. The control group received nonsurgical periodontal treatment only. For both groups, five periodontal parameters were assessed at baseline, 1 month, 3 months, and 6 months: Plaque Index, Gingival Index, bleeding on probing, probing pocket depth, and Gingival Overgrowth Index. Intra- and intergroup variations in the periodontal parameters were determined over time.

RESULTS

Both groups showed statistically significant improvements in periodontal health over the study period (P < .05). However, significant improvements in periodontal health were evident earlier among the test group subjects (P < .05). The magnitude of improvement in periodontal health compared to baseline was greater in the test group than in the control group for Gingival Overgrowth Index at 1 month (P < .001) and 3 months (P < .05), Gingival Index at 3 months (P < .05) and 6 months (P < .05), and probing pocket depth at 1 month (P < .05).

CONCLUSIONS

Nonsurgical periodontal management with or without the adjunct use of lasers can be effective in the management of gingival health problems among patients receiving FOAT. The adjunctive use of lasers can produce an earlier and greater improvement in gingival health.

Comparison of the Er,Cr:YSGG laser with a chemical vapour deposition bur and conventional techniques for cavity preparation: a microleakage study

The aim of this study was to compare the effects of the Er,Cr:YSGG laser using chemical vapour deposition (CVD) bur cavity preparation with conventional preparation methods including a diamond bur and a carbide bur on the microleakage with two different adhesive systems. A total of 40 extracted human premolars were randomly assigned to four experimental groups according to the cavity preparation technique: group I diamond bur (Diatech); group II carbide bur (Diatech); group III Er,Cr:YSGG laser (Biolase Millennium II); and group IV CVD bur (CVDentUS). Using the different preparation techniques, Class V standardized preparations were performed on the buccal and lingual surfaces with gingival margins on the dentin and occlusal margins on the enamel. Each preparation group was randomly assigned to two subgroups (five teeth, ten preparations) according to the type of adhesive: an etch-and-rinse adhesive (Adper Single Bond), and a single-step self-etch adhesive (AdheSE One). All preparations were restored with a nanohybrid composite resin in a single increment. Following thermocycling (×500; 5-55°C), the teeth were immersed in basic fuchsin and sectioned in the orovestibular direction. Dye penetration was evaluated under a light microscope by two blinded examiners. Data were statistically analysed with the Kruskal-Wallis and Wilcoxon tests (p<0.05). There were no statistically significant differences between the preparation techniques with either of the two adhesive systems (p>0.05). Comparing the enamel and dentin leakage scores within each group, no statistically significant differences were found (p>0.05). The Er,Cr:YSGG laser cavity preparation did not differ from preparation with CVD, diamond or carbide bur in terms of microleakage with the different adhesive systems.

In Situ Study of In-office Bleaching Procedures Using Light Sources on Human Enamel Microhardness

Regardless of the light sources used, the microhardness of human dental enamel did not present significant changes 14 days after in-office bleaching.

Application of a flexible CO2 laser fiber for neurosurgery: laser-tissue interactions

Object

The CO2 laser has an excellent profile for use in neurosurgery. Its high absorption in water results in low thermal spread, sparing adjacent tissue. Use of this laser has been limited to line-of-sight applications because no solid fiber optic cables could transmit its wavelength. Flexible photonic bandgap fiber technology enables delivery of CO2 laser energy through a flexible fiber easily manipulated in a handheld device. The authors examined and compared the first use of this CO2 laser fiber to conventional methods for incising neural tissue.

Methods

Carbon dioxide laser energy was delivered in pulsed or continuous wave settings for different power settings, exposure times, and distances to cortical tissue of 6 anesthetized swine. Effects of CO2 energy on the tissue were compared with bipolar cautery using a standard pial incision technique, and with scalpel incisions without cautery. Tissue was processed for histological analysis (using H & E, silver staining, and glial fibrillary acidic protein immunohistochemistry) and scanning electron microscopy, and lesion measurements were made.

Results

Light microscopy and scanning electron microscopy revealed laser incisions of consistent shape, with central craters surrounded by limited zones of desiccated and edematous tissue. Increased laser power resulted in deeper but not significantly wider incisions. Bipolar cautery lesions showed desiccated and edematous zones but did not incise the pia, and width increased more than depth with higher power. Incisions made without using cautery produced hemorrhage but minimal adjacent tissue damage.

Conclusions

The photonic bandgap fiber CO2 laser produced reliable cortical incisions, adjustable over a range of settings, with minimal adjacent thermal tissue damage. Ease of application under the microscope suggests this laser system has reached true practicality for neurosurgery.

Evaluation of effectiveness of Er,Cr:YSGG laser for root canal disinfection: theoretical simulation of temperature elevations in root dentin

Erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) lasers are currently being investigated for disinfecting the root canal system. Prior to using laser therapy, it is important to understand the temperature distribution and to assess thermal damage to the surrounding tissue. In this study, a theoretical simulation using the Pennes bioheat equation is conducted to evaluate how heat spreads from the canal surface using an Er,Cr:YSGG laser. Results of the investigation show that some of the proposed treatment protocols for killing bacteria in the deep dentin are ineffective, even for long heating durations. Based on the simulation, an alternative treatment protocol is identified that has improved effectiveness and is less likely to introduce collateral damage to the surrounding tissue. The alternative protocol uses 350 mW laser power with repeating laser tip movement to achieve bacterial disinfection in the deep dentin (800 microm lateral from the canal surface), while avoiding thermal damage to the surrounding tissue (T<47 degrees C). The alternative treatment protocol has the potential to not only achieve bacterial disinfection of deep dentin but also shorten the treatment time, thereby minimizing potential patient discomfort during laser procedures.

Cosmetic dentistry

PURPOSE OF REVIEW

Patients seeking the expertise of facial plastic surgeons for facial aesthetic improvement may also desire or benefit from dental aesthetic procedures. This paper reviews current treatment options available in cosmetic dentistry.

RECENT FINDINGS

Many techniques exist to improve dental aesthetics in color, position, shape, size, alignment and overall smile appearance. Although orthodontic therapy is still an important modality for smile aesthetics, some simpler procedures can provide acceptable aesthetic results. Comparison of external dental bleaching techniques reveals similar long-term results for in-office and at-home bleaching; in-office treatments, however, may provide the benefit of faster results. Internal dental bleaching is an effective method for correcting nonvital teeth coloration. Enamel shaping via either direct tooth contouring or the application of resins or veneers to tooth surfaces can correct defects, asymmetries and shape or rotation problems. Veneers or crowns are also options to correct intrinsic dental stains not amenable to bleaching techniques. Treatments to refine gingival margins and borders are another proven beneficial cosmetic procedure.

SUMMARY

A myriad of techniques exist to correct a patient's particular concerns. Correction of discoloration is usually feasible as is the improvement of a patient's smile and overall dental aesthetics.

Evidence-based decision making: Guide to reading the dental materials literature

Although potential links between materials data and clinical behavior are often implied, the status of such linkage is often left obscure. This paper provides clinicians a context within which to view materials information as evidence for clinical indications and to broaden readers' appreciation for the subject. Hierarchies of both clinical and nonclinical data are presented and discussed from the point of view of their predictive potential regarding clinical performance. Excellent sources of information are identified for the clinician making treatment decisions, and perspectives are offered on the value of other published materials data.