الفهرس 
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Abstract
Each vocal fold is a laminated structure consisting of a pliable vibratory layer of connective tissue, known as the lamina propria, sandwiched between a membrane (epithelium) and a muscle (vocalis muscle).
Vocal fold scarring is the greatest cause of poor voice after vocal fold injury, the superficial lamina propria is particularly prone to scarring resulting from mechanical damage due to voice abuse or to other causes.
The origins of the vocal fold scar include trauma, radiation, and surgical treatment for neoplasms, iatrogenic causes, and inflammatory response to infection or injury in the airway tissues.
Scar leads to increased effort to overcome the localized mucosal stiffness caused by the scar results in a poor voice, often with glottal insufficiency.
The voice quality may be strained, harsh, diplophonic, or dysphonic. Pathophysiologically, anatomic alterations caused by the disease or surgical injury result in loss of the normal layered structure of the vocal fold.
The ultimate goal of the bioengineering of the vocal folds is to reestablish normal vibratory characteristics to scarred vocal folds to help patients regain their normal voice.
The strategies for voice restoration include following approaches:
• The first is the use of tissue engineering methods to “grow” new vocal fold tissue.
• The second involves the creation of injectable materials to improve pliability of damaged vocal folds with replacement of portions of the scarred vocal folds with these materials.
Tissue engineering is one of the most important future methods to restore normal vibratory characteristics of scarred vocal fold. However, in vivo studies are expensive and slow, and often present difficulties for isolating and studying single processes/mechanisms, in vitro cultures are inferior to in vivo studies in many ways.
There is a cornucopia of materials that can be applied to different specific clinical situations, various forms of collagen are useful for temporary corrections of glottic insufficiency and might give lasting benefits to patients with smaller gaps, focal defects and minimal scar.
Numerous methods and materials have been used to augment paralyzed or paretic vocal folds and glottic soft tissue defects. Although successful medialization result in improved phonation time and improved airway protection due to improved cough and glottic closure, injection laryngoplasty remains popular method for treating glottic insufficiency. However there is no doubt that the ideal injectable material for vocal fold must be safe, biologically inert, stable with minimal resorption like gelatin sponge, hyaluronic acid, collagen, autologus fat, calcium hydroxlapatite and silicone.