Lasers in the limelight: what will the future bring?

Postoperative discomfort after Nd:YAG laser and conventional frenectomy: comparison of both genders

BACKGROUND

Evidence has suggested that males and females experience and report feeling pain differently. The aim of this study was to determine the postoperative perception levels of both females and males after neodymium-doped yttrium aluminum garnet (Nd:YAG) laser frenectomy and conventional frenectomy, and to compare the perceptions between genders.

METHODS

Eighty-nine patients requiring frenectomy were randomly assigned to have treatment with either the conventional frenectomy or with the Nd:YAG laser. Postoperative discomfort (pain, chewing, talking) was recorded using a visual analog scale (VAS) on the operation day and postoperative days 1, 3, 7 and 10.

RESULTS

According to the female VAS scores of the pain, chewing and speaking discomfort were statistically higher in the conventional group than those of the laser group on the operation day, and on the first and third postoperative days. Pain discomfort in males was statistically higher in the conventional group than those of the laser group on the operation day. Speaking discomfort in males was statistically higher in the conventional group than those of the laser group on the operation day and the first postoperative day.

CONCLUSIONS

The present study indicated that Nd:YAG laser treatment used for frenectomies provides better postoperative comfort for each gender, especially in females in terms of pain, chewing and speaking than the conventional procedure up to the seventh postoperative day. According to our results, Nd:YAG laser may provide a safe, bloodless, painless surgery and an impressive alternative for frenectomy operations.

Evaluation of pain levels after Nd: YAG laser and scalpel incisions: an experimental study in rats

BACKGROUND

Postoperative pain is a recognized sequel of periodontal surgery. The pain experience has been shown to peak in the first 24 hours following the procedure, and to decrease rapidly in subsequent days. The aim of the present study was to evaluate the pain levels following scalpel- and laser-incision of rat hind paws.

METHODS

The study was carried out on 10 albino Wistar male rats. Rats were randomly assigned to two groups: Group I (n = 5, laser surgery), or Group II (n = 5, conventional surgery with scalpel). For measuring mechanical hyperalgesia, the nociceptive threshold of the hind paw after mechanical stimulation was quantified using a Basile algesimeter. The measurements were done before the surgery and on the postoperative 1(st), 2(nd), 3(rd), and 7(th) days.

RESULTS

While the pain levels of the groups were similar before the surgical procedures, the laser-applied rats had significantly fewer nociceptive thresholds of the hind paw after mechanical stimulation compared with the scalpel-incised rats on the postoperative 1(st), 2(nd), 3(rd), and 7(th) days. Functional complications were not observed in the laser groups at three days after the surgery.

CONCLUSION

The results suggested that, for soft tissue surgery, Nd: YAG lasers have often led to shorter operative times, less pain, and fewer postoperative adverse events.

Ultraviolet and laser radiation safety

Both ultraviolet radiation and laser radiation occupy pmt of the Spectrum designated "optical radiation". Thus, measurement techniques are similar and the same organs (eyes and skin) are at risk from accidental exposure. However, the equipment used to produce ultraviolet and laser radiation differs substantially and the harm caused by each type of radiation is also different. Another significant difference arises from the fact that ultraviolet radiation is natural with associated general population exposure. Consequently, the present article reviews the current status of both ultraviolet and laser radiation with the material divided into two sections where each hazard is considered separately.

Atomic analysis and knoop hardness measurement of the cavity floor prepared by Er,Cr:YSGG laser irradiation in vitro

In the present study, the compositional changes and knoop hardness of the cavity floor prepared by Er,Cr:YSGG laser irradiation was compared with that of the conventional bur cavity. Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and knoop hardness test. Statistical analyses were performed using the Mann-Whitney U-test; a value of P < 0.01 was considered significant. Surface characteristics of the prepared cavities were also investigated by light microscopy and scanning electron microscopy (SEM). The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavity floor but no significant differences were found between the Ca/P ratio and knoop hardness number of laser and bur cavities. The SEM observation revealed that the lased cavity surface was irregular and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed. Er,Cr:YSGG laser device is considered as one of the most effective and safe devices for cavity preparation because of its many advantages. This includes easy delivery system, minimal thermal damage to the surrounding tissues, minimal thermal-induced changes of dental hard tissue compositions, and favourable surface characteristic.

Morphological and microleakage studies of the cavities prepared by Er:YAG laser irradiation in primary teeth

OBJECTIVE

The purposes of this study were to investigate cavity surfaces morphologically, and compare microleakage at cavities prepared by Er:YAG laser after composite resin restoration versus conventional mechanical treatment in human primary teeth in vitro.

BACKGROUND DATA

There have been few reports on microleakage at cavities prepared by Er:YAG laser irradiation.

MATERIALS AND METHODS

A total of 30 cavities (class V) in human primary teeth were used. Half of the cavities were prepared by an Er:YAG laser system at 300 mJ pulse energy and 4 Hz, and the other half were prepared with a high-speed diamond bur. Five cavities from each group were investigated by scanning electron microscopy (SEM) and histopathological examination. Remaining cavities were filled with a composite resin without an acid-etching technique and then subjected to microleakage test in 0.6% rhodamine B solution under thermocycling.

RESULTS

Microleakage (score: 2.45 +/- 1.07) at cavities prepared by laser was significantly less than that by bur (score: 1.30 +/- 0.95; p < 0.05). SEM observation showed that, compared with the relatively flat appearance of cavities prepared by bur, cavity margins prepared by laser were irregular but there was almost no smear layer at the cavity walls.

CONCLUSION

It can be concluded that cavity surfaces prepared by Er:YAG laser are irregular, but microleakage at cavities prepared by the laser after filling with composite resin is better than that by mechanical bur using the dye penetration method.

Analysis of surface roughness of enamel and dentin after Er,Cr:YSGG laser irradiation

OBJECTIVE

The purpose of this investigation was to compare the surface roughness of enamel and dentin following the Er,Cr:YSGG laser irradiation and acid etching.

BACKGROUND DATA

Laser-roughened enamel or dentin surfaces have been expected to enhance restorative materials bond strength.

MATERIALS AND METHODS

Er,Cr:YSGG laser irradiation was performed in one half of each polished enamel or dentin sample at 3 W (33.9 J/cm2, with air 70% and water 20%,) pulse energy for 6 sec. Then the other half was treated with 37% phosphoric acid for 30 sec. Surface roughness and morphological studies were performed.

RESULTS

It was found that surface roughness was significantly increased with the laser system. Scanning electron microscopy analysis showed that irradiated surface produces a rough surface that was completely lacking of a smear layer; there was also no cracking of enamel or dentin.

CONCLUSION

Er,Cr:YSGG laser irradiation could provide an effective and alternative method to the acid etch technique.

A comparison of the morphological changes after Nd-YAG and CO2 laser irradiation of dentin surfaces

The purpose of this study was to compare the morphological changes after Nd-YAG and CO2 laser irradiation on dentin surfaces with or without the smear layer. Eighty-one 3-mm-thick dentin specimens collected from the middle third of molar crowns were used. The dentin surfaces were ground to #320, #400, and #600 grit in series to create a smear layer. Half of the specimens were treated with 14% EDTA for 2 min to remove the smear layers. The lasers were applied on each specimen perpendicularly with 1-mm focus distance to the dentin surface for 4 s. The parameters for the Nd-YAG laser were 50 mJ, 100 mJ, and 150 mJ at 10 pps, 20 pps, and 30 pps, and for the CO2 laser were 2 W, 3 W, and 4 W at 5 ms x 20 pps, 10 ms x 10 pps, 20 ms x 20 pps, 50 ms x 2 pps, 100 ms x 2 pps, and 200 ms x 2 pps. The results showed that the Nd-YAG laser caused crater and melting of the dentin surface, especially in dentin specimens with smear layers. The CO2 laser produced extensive cracking lines on dentin surfaces with a smear layer, whereas surface erosion and crater formation were found on specimens without a smear layer. In conclusion, both the laser types and smear layer have a significant influence on the morphological changes of dentin surfaces irradiated by lasers.

Nd:YAG laser effects on the microleakage of composite resin restorations

OBJECTIVE

This study evaluated microleakage of composite restorations submitted to marginal treatment with Nd:YAG laser and surface sealant.

BACKGROUND DATA

Previous studies have demonstrated that Nd:YAG-lased enamel melted and became recrystallized with a morphologic appearance similar to lava, and has been used clinically in the sealing of enamel pits and fissures.

METHODS

Class V cavities in enamel of human premolars were restored with composite resin (Z100, 3M) and randomly divided in six groups: G1, control; G2, surface sealant marginal treatment; G3 to G6, were treated with pulsed Nd:YAG laser (1.064 microm) marginal treatment, contact fiberoptic (300 microm), air cooling, for 30 seconds, powers of 1.2-2 W, repetition rates of 20-30 Hz, energies of 40-100 mJ. Teeth were impermeabilized, immersed in a rhodamine dye, sectioned, and evaluated under stereomicroscope microscopy with scores.

RESULTS

There were significant differences between marginal treatments; there were no differences between groups 1, 2, and 4, and 3,5, and 6; lower values of microleakage were at groups 3, 5, and 6 (Kruskal-Wallis,p = 0.05).

CONCLUSION

Nd:YAG laser showed improved marginal sealing and decreased microleakage of composite resins restorations.

Caries resistance in enamel by laser irradiation and topical fluoride treatment

PURPOSE

The purpose of this in vitro study was to compare caries resistance of sound human enamel following argon laser (AL) irradiation, as well as, combinations of topical fluoride foams and AL irradiation.

METHODS AND MATERIALS

Thirty extracted human teeth were sectioned into four buccal windows and assigned to one of the following treatment groups: (1) no treatment/control; (2) low fluence (11.5 J/cm2) AL irradiation for 10 seconds; (3) 1.23% APF foam for 4 minutes followed by low fluence AL irradiation; (4) 2.0% NaF foam for 4 minutes followed by low fluence AL irradiation. Caries-like lesions were created by submerging the teeth in ten Cate solution (pH 4.5). Following a 96-hour exposure period, 100 microns longitudinal sections were prepared for polarized light evaluation. Visilog 5.1.1. image analysis software was used to obtain quantitative lesion depths. The Scheffe F-test was used to compare the lesion depths for each of the four treatment groups.

RESULTS

Lesion depths were: 16.1 +/- 6 microns for control; 13.7 +/- 4 microns for AL irradiation alone; 12.1 +/- 4.3 microns for 1.23% APF foam before AL irradiation; and 11.4 +/- 5.9 microns for 2.0% NaF foam before AL irradiation. Significant difference (p < 0.05) was found between the control group and the 2.0% NaF foam before AL irradiation group. AL irradiation alone reduced lesion depth by 15% compared with the control lesion. When AL irradiation was combined with 1.23% APF foam treatment, lesion depth decreased by 25% compared with control lesions, and by 29% when combined with 2.0% NaF foam.

CONCLUSION

Combining AL irradiation and 2.0% NaF foam treatment significantly enhances the resistance of sound enamel to an in vitro cariogenic challenge.

In vivo caries-like lesion prevention with argon laser: pilot study

OBJECTIVE

This clinical pilot study was conducted to investigate the effectiveness of argon laser irradiation to reduce demineralization or loss of tooth structure in vivo.

SUMMARY BACKGROUND DATA

In vitro research previously demonstrated the ability of argon laser irradiation to reduce demineralization or loss of tooth structure.

METHODS

Using the Ogaard model of producing demineralization, the experimental teeth were irradiated with argon laser of 250 mW (producing approximately 12 J/cm2) prior to banding. Polarized light evaluation of the sectioned, extracted teeth was used to determine the amount of demineralization.

RESULTS

Results showed a 29.1% reduction in demineralization in the experimental teeth as compared to the bilateral control teeth.

CONCLUSION

Low-power argon laser irradiation significantly reduced demineralization clinically.

The effect of pulpotomy using CO2 and Nd:YAG lasers on dental pulp tissue

The histological response of the dental pulp after laser irradiation was studied. After pulpotomy was performed in the premolar and molar teeth of dogs, the exposed pulp tissue at the root canal opening was lased using either a CO2 or Nd:YAG laser. The laser parameters were 2 W, 10 ms, 5 times per second for 1, 2 and 3 s for CO2 laser and 2 W, 20 pulses per second for 1, 2 and 3 s for the Nd:YAG laser. Observations were made 30 and 45 days after treatment. The results revealed that laser irradiation caused carbonization, necrosis, infiltration of inflammation cells, oedema and haemorrhage in the pulp tissue. Under the conditions of this experiment, there was little histological evidence of repair to the treated pulp with a newly formed dentine barrier, which was in contrast to the control samples treated with a calcium hydroxide-containing cement (Dycal).

Free autogenous soft tissue graft with the argon laser

A sufficient amount of dense keratinized connective tissue attached to bone and the cervical area of the tooth is required for functional masticatory mucosa. Periodontal plastic surgery has furnished numerous reconstructive and regenerative techniques to correct the mucogingival defect. Laser technology has provided the ability for tissue fusion and incisions with better visual and mechanical access, decreased intraoperative time, improved hemostasis, and less postoperative discomfort. This article describes a technique for incisions and tissue fusion for gingival grafts with an argon laser.