*Edited by M. Nageeb Rashed*

Organic pollutants cause several environmental problems if discharged to air or water body. The occurrence of organic pollutants in the ecosystem, their risk and removal methods are very important issues .This book deals with several aspects of organic pollutants, especially in the light of organic pollutants monitoring, risk assessment as well as the practical application of different techniques for removing it from the environment. The book is divided into three sections contains 9 chapters. The first section explains monitoring of organic pollutants in soil and water. The second section discusse its risk to human, soil and plants. The third section focuse on the different treatment process for the removal of organic pollutants.

ISBN 978-953-51-0948-8

Organic Pollutants - Monitoring, Risk and Treatment

Photo by aga7ta / iStock


*2.3. Educational Policy, Social Stratification, and Educational Uplift*

Nations' policies on education and economic development routinely make assumptions about social structure and the capacity of families to acquire cultural capital for college. In Europe, higher education offers postsecondary pathways for the working class that are no longer evident in the US. These divergent policy pathways may rest on different assumptions about social class as nations progress from empires to the breakdown of the neoliberal consensus. The shift to using debt as the low-cost mechanism for expanding access raises issues about cultural and social class differences across nations.


**3. Laser applications in periodontology**

#### **3.1 Soft tissue surgical applications**

Lasers such as diode, CO2,Nd:YAG, Er:YAG, and Er,Cr:YSGG are being extensively used in periodontal treatments including gingival soft tissue procedures such as gingivoplasty, gingivectomy, frenectomy, benign tumors or epulis elimination [30], irradiation of aphthous ulcers, gingival depigmentation, coagulation of free graft donor sites, second-stage exposure of dental implants [13], and crown lengthening procedures [30]. This diversity of laser use is due to its superior properties over conventional scalpel procedures which include bacteremia reduction, ease of soft tissue ablation, hemostasis [30], slight wound contraction and slight scarring, immediate sterilization, edema reduction, mechanical trauma reduction, no or little operative and postoperative pain [13, 31, 32], improved patient acceptance [13], more rapid healing, little need for suturing, much easier technique, and necessitating no topical anesthesia [33].

The penetration depth of lasers differs, and therefore their performance differs, and lasers possibly cause a hazardous effect on the underlying tissues by thermal injury. Laser light is absorbed in the superficial layers in Er:YAG,CO2 and Er,Cr:YSGG lasers, and hence it has the advantage of being simple and rapidly vaporized from soft tissues, while other type of laser such as diode lasers and deeply penetrating Nd:YAG associate with more thermal influences, which consequently lead to formation of thick coagulation zone on the treated surface [21, 29, 30] and hence used similar to electrosurgical procedures [30]. Finkbeiner [34] has suggested the usefulness of argon laser in soft tissue welding and soldering compared to conventional tissue closure method. Epithelial exclusion using CO2 laser had been suggested to retard its downward growth, and studies have shown effective removal of epithelium from gingival tissues without damaging the underlying connective tissues [35, 36].

#### **3.2 Removal of the pocket epithelium**

Lasers are also used for soft tissue periodontal applications. The Nd:YAG was the first laser wavelength to be compared to the scalpel for treating periodontal

pockets [16] and controlling bacteremia and gingival bleeding [16, 18]. The probing pocket depth and bleeding index scores were reduced using the pulsed Nd:YAG laser. Furthermore, clinical evaluation of soft tissue biopsies taken from human subjects using the Nd:YAG laser versus a curette presented a complete removal of the epithelium of the pocket after use of the pulsed Nd:YAG laser compared to the curette [15]. Similar effects presented in pig jaws (in vitro) after the use of a 980 nm diode laser with 2–4 W power settings and continuous wave compared to the conventional curette [37]. There are advantages in the postsurgical outcomes with the removal of pocket epithelium. A recent clinical study in India showed that the modified Widman flap with removal of the pocket epithelium was more effective in reducing mean probing depth than access flap with intrasulcular incision. It showed greater gain of clinical attachment and demonstrated less gingival recession [38]. When deep periodontal pockets are present, removal of the pocket epithelium using a fiber-optic glass laser offers benefits. With or without flap elevation and a conventional periodontal access flap procedure, the pocket epithelium will be removed from the inner and the outer part of the pocket. Depending on how the patient heals, the epithelium can later be ablated every 7–10 days from the outer part of the pocket, usually under the use of topical anesthesia, in order to control apical migration. This can result in long-term, stable connective tissue attachment, without gingival recession. The principle underlying this approach is guided tissue regeneration; it has been called "laser-assisted guided tissue regeneration" [39]. This approach should be evaluated in different prospective clinical studies involving many patients and following exactly the same protocol in order to establish that it is a technological improvement that should be incorporated routinely in daily practice. Both clinical case series and clinical research have shown the potential of this application using the CO2 laser, since the noncontact handpiece is able to ablate tissues very quickly, controlling the epithelial cell proliferation and further apical migration of a long junctional epithelium. Israel et al. [20] were able to demonstrate histologically the effects of this de-epithelialization technique in humans. The technique involves using the CO2 laser to remove (ablate) the inner part of flap after conventional periodontal flap elevation and then using the same method in the outer part of the flap to achieve epithelial retardation. Case series in patients with generalized advanced periodontal disease have shown that the laser de-epithelialization technique leads to good results without the need for multiple membrane therapy [40, 41].

## **3.3 Laser root conditioning**

The use of CO2 lasers to decontaminate root surfaces has been investigated, providing more information about the exact power settings and parameters required to avoid root damage. Barone et al. [42] showed that a defocused, pulsed CO2 laser is able to create smooth and clean root surfaces compared to a focused, continuous wave; the latter leads to melting and root surface damage. Later studies using the same parameters for CO2 lasers reported root conditioning with a better fibroblastic activity, cellular proliferation, and greater fibroblast attachment [43]. Different clinical case reports have demonstrated these advantages of CO2 laser de-epithelialization [44]. This technique has also been used in clinical studies and has shown that coronal flap advancement in conjunction with CO2 laser root conditioning leads to improvements in clinical parameters and long-term tissue stability after 15 years, compared to the modified Widman periodontal flap procedure [45]. The authors concluded that this laser technique seemed to have greater effects and should be used in treating deep periodontal pockets (more than 7 mm deep).

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*Laser Applications in Periodontology*

**3.4 Bacterial reduction**

*DOI: http://dx.doi.org/10.5772/intechopen.88046*

A laser application that has been especially promoted in the past is for the reduction of bacteria in pockets, due to the high absorption of specific laser wavelengths by the chromophores. Initially, the use of an Nd:YAG laser was shown to reduce the load of *Porphyromonas gingivalis* and *Prevotella intermedia* [46]. A study by Assaf et al. [47] is of special interest. Using a diode laser in conjunction with ultrasonic scaling for treatment of gingivitis, they were able to show a significantly lower incidence of bacteremia in the diode + ultrasonic group (36%) than the ultrasonic only group (68%). They suggested that diode lasers should be used to prevent bacteremia, especially in immunocompromised patients. Using a 980 nm diode laser to reduce periodonto-pathogenic bacteria in patients with aggressive periodontitis has also been investigated. Kamma et al. [48] confirmed that it was possible to reduce the total bacterial load in pockets without the use of any systemic antibiotic therapy. Clinical case series with 10 patients using in the same patient (in a randomized protocol) SRP in conjunction with 980 nm diode laser, SRP and an Nd:YAG laser, and SRP with photodynamic therapy (PDT) showed that the PDT was able to reduce significantly the bacteria in the pockets and provide a predictable clinical outcome for 3 months. In contrast to that, the use of Nd:YAG laser was not very beneficial and was similar to the control (SRP) group [49]. Due to the bacteria reduction and the reduced bleeding on probing provided by the PDT, the PDT was recommended

for periodontal patients especially for the maintenance appointments.

In the previous years the important role of laser in dental implant treatment has been discussed widely [50]. Because of the lack of comparable test and control sites, it is difficult nowadays to know if lasers, with their different types, can be used to treat peri-implantitis using randomized clinical trials [51]. Removal of peri-implant soft tissues and bacterial reduction, uses of laser in second-stage surgery [52], and decontamination of failing implants [53] are the most important applications for lasers in implant dentistry. However there are a lot of limitations of using laser in implant dentistry including the serious alarms about the overheating of the implant and the concern about the melting of the implant surface [54, 55], as well as the fears regarding missing of the re-osseointegration after peri-implantitis treatment with lasers. In recent years a lot of reviews have concentrated on these limitations and gave additional facts about re-stabilization and re-osseointegration of the implants subsequent to the laser decontamination of the implant surface [56]. Deppe et al. [57] showed that CO2 laser decontamination of the surface of implants placed in dogs allowed new bone to grow and be in contact with the implant surface (re-osseointegration). In vitro studies of osteoblasts have confirmed these effects for CO2 and Er,Cr:YSGG lasers [58]. Previous clinical case series were able to demonstrate new bone fill and long-term success of failing implants that were decontaminated with a CO2 laser [59, 60]. The main advantage of using CO2 laser irradiation on implant surfaces is that this wavelength does not pose the risk of overheating [61], unlike other wavelengths, such as that of diode, Nd:YAG, and Er:YAG lasers [62, 63]. A significant increase of the implant surface temperature has been demonstrated when irradiating implant surfaces with a diode laser in vitro for more than 10 s [62–64]. It is possible that authors have presented unsuccessful and nonpredictable clinical results from their studies because of overheating resulting from inconsistent power settings [65]. Limited facts available regarding laserassisted decontamination of implant surfaces, with a limited number of included

**3.5 Laser applications in implant dentistry**