Scanning electron microscopic and immunocytochemical studies of contraction during secondary CO2 laser wound healing in rat tongue mucosa

Epithelial separation theory for post-tonsillectomy secondary hemorrhage: evidence in a mouse model and potential heparin-binding epidermal growth factor-like growth factor therapy

OBJECTIVE

To provide histological evidence to investigate a theory for post-tonsillectomy secondary hemorrhage (PTH) in a mouse model and to evaluate the potential for heparin-binding epidermal growth factor-like growth factor (HB-EGF) treatment on wound healing in this model.

METHODS

A prospective randomized single-blinded cohort study. A uniform tongue wound was created in 84 mice (day 0). Mice were randomized to HB-EGF (treatment, n = 42) or saline (control, n = 42). In treatment mice, HB-EGF 5 µg/ml was administered intramuscularly into the wound daily (days 0-14). In control mice, normal saline was administered daily. Three mice from each group were sacrificed daily through day 14 and the wounds evaluated histologically by blinded reviewers.

RESULTS

Key stages of wound healing, including keratinocyte proliferation and migration, wound contraction, epithelial separation, and neoangiogenesis, are defined with implications for post-tonsillectomy wound healing. Epithelial separation (59 vs. 100%, p = 0.003) and wound reopening (8 vs. 48%, p < 0.001) were reduced with HB-EGF. Epithelial thickness (220 vs. 30 µm, p = 0.04) was greater with HB-EGF. Wound closure (days 4-5 vs. day 6, p = 0.01) occurred earlier with HB-EGF.

CONCLUSIONS

In healing of oral keratinocytes on muscle epithelial separation secondary to muscle, contraction occurs concurrently with neoangiogenesis in the base of the wound, increasing the risk of hemorrhage. This potentially explains why post-tonsillectomy secondary hemorrhage occurs and its timing. HB-EGF-treated wounds showed greater epithelial thickness, less frequent epithelial separation and wound reopening, and earlier wound closure prior to neovascularization, suggesting that HB-EGF may be a potential preventative therapy for PTH.

LEVEL OF EVIDENCE

NA-animal studies or basic research.

Oral crest lengthening for increasing removable denture retention by means of CO2 laser

The loss of teeth and their replacement by artificial denture is associated with many problems. The denture needs a certain amount of ridge height to give it retention and a long-term function. Crest lengthening procedures are performed to provide a better anatomic environment and to create proper supporting structures for more stability and retention of the denture. The purpose of our study is to describe and evaluate the effectiveness of CO₂ laser-assisted surgery in patients treated for crest lengthening (vestibular deepening). There have been various surgical techniques described in order to restore alveolar ridge height by pushing muscles attaching of the jaws. Most of these techniques cause postoperative complications such as edemas, hemorrhage, pain, infection, slow healing, and rebound to initial position. Our clinical study describes the treatment planning and clinical steps for the crest lengthening with the use of CO₂ laser beam (6–15 Watts in noncontact, energy density range: 84.92–212.31 J/cm², focus, and continuous mode with a focal point diameter of 0.3 mm). At the end of each surgery, dentures were temporarily relined with a soft material. Patients were asked to mandatorily wear their relined denture for a minimum of 4–6 weeks and to remove it for hygienic purposes. At the end of each surgery, the deepest length of the vestibule was measured by the operator. No sutures were made and bloodless wounds healed in second intention without grafts. Results pointed out the efficiency of the procedure using CO₂ laser. At 8 weeks of post-op, the mean of crest lengthening was stable without rebound. Only a loss of 15% was noticed. To conclude, the use of CO₂ laser is an effective option for crest lengthening.

Experimental Study on the Morphological and Functional Recovery following Partial Glossectomy in Rabbits: A Comparison between CO2Laser and Electrocautery

OBJECTIVE

The aim of the present study was to evaluate and compare the morphological and functional recovery following partial glossectomy in rabbits with the CO(2) laser and electrocautery.

METHODS

Partial glossectomy with the CO(2) laser or electrocautery in rabbits was performed to investigate changes in the body weight and tongue width after surgery. The study models were classified into three groups. In group 1, the excised edges of the wound were left unsutured after partial glossectomy with the CO(2) laser. In group 2, the wound was closed after CO(2) laser surgery. In group 3, as a control group, the wound was closed after partial glossectomy with electrocautery. The specimens of the tongues obtained from the rabbit were microscopically assessed.

RESULTS

No significant differences were found in the percent change in the body weight among the three groups. There was a significant difference in the tongue width between groups 1 and 3 at each time point: 2 weeks (p < 0.05), 4 weeks (p < 0.01), and 8 weeks (p < 0.001) postoperatively. Furthermore, there was a significant difference in the tongue width between groups 2 and 3 at 8 weeks (p < 0.02) postoperatively. Histologically, the scar tissue of the wound was extensive in the control group, although it was localized in the laser group.

CONCLUSION

Postoperative dysfunction was reduced when excised edges were left unsutured after partial glossectomy with the CO(2) laser.

Assessment of the behavior of myofibroblasts on scalpel and CO(2) laser wounds: an immunohistochemical study in rats

OBJECTIVE

The aims of this study were to quantitative and statistically assess the presence of myofibroblasts on both conventional and CO(2) laser wounds.

BACKGROUND DATA

Wound contraction of both traumatic and surgical origin may reduce or limit the function of the tissue. Myofibroblasts are cells involved in the process of wound contraction, which is smaller in CO(2) laser wounds.

MATERIALS AND METHODS

Thirty-two animals (rattus norvegicus) were divided into four groups and treated using either the CO(2 )laser (groups 1 and 2) or conventional scalpel (groups 3 and 4). The animals were sacrificed eight days post-operatively (groups: 1 and 3) and 14 days after surgery (groups: 2 and 4). The specimens were routinely processed to wax and stained with alpha-smooth muscle actin (alpha SMA) and analyzed under light microscopy (40x) using a calibrated eyepiece and a graticule. Two standard areas around the wound of each slide were selected and used to count the number of myofibroblasts present.

RESULTS

The results of this study show that it is possible to determine the number of myofibroblasts present in wounds produced by the laser or the scalpel at both eight and 14 days after surgery. However the number of myofibroblasts at day eight was significantly higher than at day 14 (laser, p = 0.007 and scalpel, p = 0.001). The number of cells present in group 3 was significantly higher than in group 1 (p = 0.001). However on the 14th day there was no such difference (p = 0.072).

CONCLUSION

It is concluded that the small number of myofibroblasts at day eight after wounding with the CO(2) laser may be the reason that contraction on this wound is smaller than the one observed in conventional surgery.

Myofibroblasts in healing laser excision wounds

BACKGROUND AND OBJECTIVE

The lack of myofibroblasts, cells responsible for wound contraction, has been suggested to be the underlying factor to the clinically observed minimal contraction in CO2 laser wounds. However, the histologic background to this phenomenon in laser excisions has not been thoroughly clarified. Therefore, we analyzed the expression of myofibroblasts in healing laser excisions and control excisions made by scalpel.

STUDY DESIGN/MATERIALS AND METHODS

CO2 laser (continuous wave, 5 W) or scalpel excision wounds were created in the dorsal tongue mucosa of 144 rats. Sixteen additional rats were kept as untreated controls. Specimens from the tongues were cut at 16 different healing time points and fixed in 10% formalin. Immunohistochemical stainings with monoclonal antibodies to vimentin and to alpha-smooth muscle actin were done to determine microscopically the contractile type of myofibroblasts.

RESULTS

The maximum amount of myofibroblasts was almost three times higher in scalpel than in laser excisions. The peak value was reached at 4 days in laser and at 3 days in scalpel wounds. The increase reverted to normal levels at 14 days in laser and at 6 days in scalpel wounds, respectively.

CONCLUSION

Myofibroblasts appeared and disappeared slower in laser wounds. There were clearly fewer myofibroblasts in CO2 laser than in corresponding scalpel excisions known to heal by contraction. The lack of contractile myofibroblasts, therefore, is suggested as the reason for the minimal degree of contraction in CO2 laser excision wounds.

Lasers in plastic surgery

The laser is a relatively new tool in many branches of medicine. In particular, in the field of plastic surgery, lasers have found numerous applications. Laser light is produced by the stimulated emission of photons from the lasing medium. Lasers may be classified according to the lasing medium employed, the wavelength of the emitted light and the pulse duration. One of the main uses of lasers is in the treatment of vascular lesions such as port wine stain (PWS). The 585 nm flashlamp pumped pulsed dye laser (FPPDL) is particularly effective in this role. The principle of selective photothermolysis has allowed highly specific targeting of different tissue components. Newer lasers have been developed to treat pigmented lesions as well as primary and metastatic cutaneous malignancies. In cosmetic surgery, lasers have been developed for skin resurfacing and removal of wrinkles, tattoos and unwanted hair. There has been recent interest in the use of lasers to promote wound healing. Laser therapy is not without complications and the safety of both patient and operator must remain paramount. The future is likely to hold greater advances in this rapidly developing field.

Quantitative evaluation of intact peripheral nerve structures after utilization of CO2 laser, electrocautery, and scalpel

OBJECTIVE

This study aimed to evaluate quantitatively the integrity of nerve structures near CO2 laser incisions.

BACKGROUND DATA

There are some hypotheses that try to explain the analgesia reported after CO2 laser surgery. One of them is based upon the observation of the destruction of nerve endings after use of this technique.

METHODS

A comparative study was carried out using 25 animals (Rattus norvegicus) divided into five groups of 5 animals each. Standard incisions were carried on the dorsum of the tongue of each animal using the cautery (group 2), scalpel (group 3), CW CO2 laser (group 4), and SPS CO2 (group 5); group I served as control. The animals were killed immediately after the experiment, and specimens were taken and routinely processed to wax. Three-micrometer sections were cut and stained using S-100 protein antibody. The stained sections were analyzed under light microscopy using a calibrated graticule, and the number of intact nerves was counted in five standard areas around the incision.

RESULTS

The results of this study showed that there were no statistically significant differences in the numbers of intact peripheral nerve structures in both laser groups and other groups. No statistically significant difference was found between nonoperated and scalpel groups. The number of intact peripheral structures in cautery wounds was significantly smaller than in non-operated and scalpel wounds.

CONCLUSIONS

Therefore, it is unlikely that immediate destruction of peripheral nerve structures is the cause of post-operative analgesia following CO2 laser surgery.

Longterm comparison of soft palate scars after UPPP made by CO(2), contact Nd-YAG or combined CO (2) and Nd-YAG laser beams

C0(2) laser, contact Nd-YAG laser and Combolaser (combined CO(2) and Nd-YAG laser beam) vary distinctively in the way they interact with target tissue. To study the quality of mature scars produced by these lasers, the ultrastructure and amount of collagen in soft palate scars after 60 uvulopalatopharyngoplasty (UPPP) operations were analysed. The CO(2) laser was used in 19, contact Nd-YAG in 21 and Combolaser in 20 operations. At a clinical follow-up examination carried out, on average, 51 (range 34-74) months postoperatively, a specimen was obtained from the soft palate scar for collagen analysis. Postoperative complaints of the patients were acknowledged. No differences between the laser groups were observed concerning the gross appearance of the scars or the amount and ultrastructure of collagen. Neither the frequency nor the quality of post-operative symptoms showed any differences between the lasers. Although the initial tissue effects are different, long-term remodelling produces nearly identical soft palate scars after the use of CO(2), contact Nd-YAG and Combolaser beams.

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).