فصلنامه لیزر در پزشکی
سال هشتم شماره 2 (پیاپی 40، تابستان 1390)

Surgical removal of impacted mandibular third molar is one of the main oral and maxiofacial surgeries. Trismus is one of the complications of surgical removal of impacted third molar that leads to problems in eating because of improper mastication and also problems in speaking and oral hygiene. The aim of this study was to evaluate the effect of Diode laser (810 nm) on trismus after surgical removal of impacted mandibular third molar.

This study was designed as controlled clinical trial and was performed on 20 patients with having 2 similar and symmetrical impacted mandibular wisdom teeth. Two teeth in each patient were removed surgically within a 2-week interval and randomly one side was selected as experimental group which was irradiated after surgery. In the experimental group, Diode laser irradiated with 810 nm wavelength and 3J intrasocket and 5J buccally and on the other side as control group it was pretended to irradiate the socket but with no actual irradiation. Trismus in the 7th day was evaluated. The results of this study were analyzed by Paired sample T-test and Wilcoxon rank test.

Post surgical trismus was significantly less in laser group compared to placebo group (P-value=0/0001).

It can be concluded that the laser with the applied parameters in this study has positive effects on reduction of post surgical side effects.

laser irradiation is a promising method for modifying and nano-structuring of the polymer surfaces. These nanostructures induced by laser irradiation can improve biocompatibility of polymers, significantly.

In this study, surface of polystyrene (PS) films were treated using ArF Excimer laser (wavelength=193 nm) at different number of pulses. The changes were characterized by atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared (ATR-FTIR), scanning electron microscopy (SEM) and contact angle measurements. L929 cell culture was used to investigate the biocompatibility of treated laser PS.

The data from ATR-FTIR spectra showed the induction process of oxygen-based functional group into laser treated PS surfaces. AFM and SEM observations demonstrated that a specific nanostructure was created on the laser-treated PS surface. Contact angle measurement indicated that water drop contact angle with one pulse laser-treated PS surface decreased and then gradually increased because of further laser pulses. The data from in vitro assays showed the significant cell attachment and growth onto laser treated samples.

Psoriasis is a skin disease which has genetical origin. In this disease, skin is covered by red plaques and silvery-white scales. PASI standard provides a method for measuring psoriasis severity by evaluating lesion area and three other parameters.. To determine the lesion area on the skin, we have developed an automatic method for segmentation of the plaques. The method isolates healthy and healed skin areas from lesion areas by an edge detection method. We customized the canny edge detection method in CIELAB color space to isolate the plaques from skin. Moreover the simulation results indicate that the proposed method is able to determine lesion areas with accuracy higher than 92 percent for 37 out of 40 cases. The advantage of this method is that it can find lesion area in noisy body, face and can remove the hair, eyes and mouth artifacts. Hence, the proposed method is superior to the previous methods and can be effectively used in automatic measuring of the lesion area in psoriasis patients.

Pulsed-dye laser (PDL) has been used with variable degrees of success in the treatment of hypertrophic scars and keloids. Some studies show that the newer scars respond better to treatment than the elder ones. Recently few studies have shown the benefits of the 585-nm PDL in improving the quality of surgical scars starting on the day of suture removal. This randomized controlled clinical trial (RCT) was designed to evaluate the effects of 585nm PDL to improve the post reduction mammoplasty surgical scars when used three weeks after surgery. Six patients with 24 linear post mammoplasty scars completed the trial. In any patient 3cm of the terminal part of the medial and lateral incisional lines were randomly allocated to be treated with PDL and the symmetrical site as control. The laser sites were treated three times on monthly intervals with 585-nm PDL which started 3 weeks after mammoplasty. The scars were evaluated by blinded examiner using the Vancouver Scar Scale (VSS) before laser sessions and 2 months after the last treatment. Two months after the last PDL session, there was significant improvement of vascularity, pliability and height of the scars in laser group (p value< 0.001), in contrast to the lesions in control group in which the improvement of vascularity (p value= 0.14), pliability (p value = 0.13) and height of the scars were not significant. The results of this RCT suggest that prophylactic 585-nm PDL irradiation is effective and safe in improving the quality and cosmetic appearance of post reduction mammoplasty incisional lines when used shortly (three weeks) after surgery.

This research analyzes the effect of platform switching design of Laser-Lok implants on the stress distribution in crestal bone of the Laser-Lok implant collar and its surrounding bone interface through Finite Element Analysis (FEA). The results are compared with control implant to show the effect of Laser-Lok implants platform switching design on the stress distribution in crestal bone. Three-dimensional modeles of the Laser-Lok implant with platform switching, the control implant (a Laser-Lok implant with same size abutment), and the mandible bone is generated for the FEA. Each implant is assembled on the mandible bone in pre-molar considering the proper boundary condition. It should be mentioned that the control implant is similar in all features to the independent implant (LL) except from the size of abutment. After meshing and considering the proper elements regarding the mastication forces and normal condition, a 100N of axial and oblique loading with angles of 15 and 45 angle is applied to the centre of the abutments of both Independent Laser-Lok implant and control implant on same condition. Under different loading conditions the independent implant has shown better results and lower stress distribution on surrounding crestal bone, comparing with control implant. Results demonstrate that the platform switching design will not only ignore the Laser-Lok fixture advantage of reducing the shear forces and bone loss but also will reduce stress concentration on the critical points of upper parts of the crestal bone. Hence transferring the stress distribution to the lower parts of the crestal bone-collar interface. It should be considered that only reducing the shear forces is not enough to decrease crestal bone loss. In this regard, excluding the biological factors should also be considered. Therefore, the platform switching design is proposed as a way to inhibit the interstitial fluid flow to surrounding tissues by creating a platform on the abutment-fixture interface and it is a biological advantages. Total results indicate that Laser-Lok implant with platform switching has not only all the advantages of control implant in reducing the shear forces on crestal bone-collar interface but also has its own advantage of reducing the crestal bone loss by eliminating the biological factor.