Having an aesthetic smile has become very common among patients today. Recent studies have shown that people aged 18-49 want to have whiter and brighter teeth. The demand for whitening has increased by 300% in the last 5 years. New materials and equipment have been developed to meet this demand, and various whitening techniques have been developed for use at home and in clinical practice. Determination of color in dentistry; It can be divided into two categories with the help of visual and computer-aided devices. Eye color determination is the most widely used method during the construction of a indirect restoration. The evaluation of tooth color by eye is quite subjective. Physiological variables such as external light source, experience, age and human eye fatigue, color blindness cause inadequate results. Due to interpersonal detection differences during color perception, the lack of standardization in the determination of tooth color can be improved with the use of computer-aided devices such as spectroradiometer, spectrophotometer, colorimeter and with the help of film-based photographs and digital photographs. Spectrophotometric approach; the point of view is interesting, as it allows for an objective application, regardless of the practitioner's experience. The color selection made with the use of these devices provides a potential advantage over the color selection made with the eye. Because these measurements are objective, can be counted and can be obtained faster. Although widespread uses of computer aided colorimeters and spectrophotometers have been reported in dental studies, most devices are not suitable for routine clinical use. Color analysis with these computer-aided devices may cause inaccurate results especially in the evaluation of translucent objects such as teeth. Therefore, a combination using both eyes and devices should be used.

Tooth color; It is formed by the combination of enamel, dentin and pulp with different optical properties. Tooth coloring is divided into two as etiological, internal and external. External colorants can be removed simply by cleaning. Removal of intrinsic coloring is possible with chemical bleaching. In the treatment of tooth coloring, whitening is considered the least aggressive method.

Due to the increasing interest in aesthetics in recent years, patients' demands for teeth whitening have increased. Home-bleaching technique, developed by Haywood and Heymann in 1989, has been the most frequently used method until recently. In this method, the bleaching agent contains 10% hydrogen peroxide. For 2-5 weeks, whitening is performed by placing the gel in a plate by the patient every night. The advantages of this method are that it is easy to apply, low cost, use of lower rates of hydrogen peroxide, and less time spent in the clinic. However, the disadvantages are that the whitening process is not under the control of the physician, the patient does not apply the whitening gel regularly, and the procedure takes several weeks. Office-bleaching technique has been developed in order to make the bleaching process more controlled, to ensure color stability and to shorten the time. This technique, which contains a high concentration of (15-38%) hydrogen peroxide, is activated by heat or light sources. These sources include plasma arc, LED, UV lamps and laser. However, there is no consensus on the effectiveness of heat and light sources used in tooth whitening.

The light sources used during bleaching are expected to increase the effectiveness of the bleaching and shorten the processing time. Among these, plasma arc and diode lasers have a wide range of uses. Laser teeth whitening method has been applied for about 15 years and many laser devices have been recommended for this procedure. It is expected that the treatment time will decrease and the sensitivity that may occur in the teeth will decrease as a result of laser application. However, the superiority of laser bleaching compared to other methods is still controversial.

External root resorption and irritation in soft tissues can be observed during the teeth whitening, even if in a small amount. It is stated that the sensitivity of teeth after the procedure is the most common complication by some researchers, but disappears by itself after the end of the bleaching process.

The purpose of aesthetic applications in dentistry; morphological, optical and biological compatibility. Tooth color is one of the most important criteria of aesthetics. Clinically, two different methods are used in color selection. The first, visual method, includes evaluation with the naked eye. The second method is colorimeter, spectrophotometer etc. is the use of devices that measure color. During clinical applications, color selection of dental materials is done by using visual scales. Color selection by visual method is both subjective and difficult; it can also lead to inadequate results. During color selection, erroneous results may occur due to parameters such as ambient light, physician's experience and age, and eye fatigue.

Due to these existing disadvantages, systems such as spectrophotometers, colorimeters, digital color meters have been launched to assist the physician in color selection. In dentistry, spectrophotometers and colorimeters are used to overcome problems related to color selection with the eye. Although the visual method is used more in the selection of colors by clinicians, it is stated that the color measurements made by using the visual method and spectrophotometer together are quite successful.

Color is formed by the merge of wavelengths in a light beam. In order for an object to be visible, it must emit light or reflect light from a light source. From the point of view of dentistry, the property of objects to reflect the incoming light is more important. The incoming light usually consists of a mixture of various wavelengths, that is, it has a polychromatic feature. When light comes on an object, it absorbs certain wavelengths and reflects certain wavelengths. The human eye can distinguish light between wavelengths of 400-700 nμ. Nerve responses play a big role in the appearance of color. As a result of attached stimulation, the eye gets tired and the reaction of the eye decreases. Color separation is a subjective issue.

The first color specification was proposed by CIE in 1931. Although this system was developed in the following years, its principles have still not changed. CIE system uses 3 variables, X, Y and Z. These variables are based on the spectral response functions defined by the CIE observer. The CIE chromaticity diagram is also used to define the exact color. In another CIE color system, three variables are used: L *, a * and b *.

The spectrophotometer is a photometric appliance that is used to measure the transmittance, reflection and true absorption of color. They contain prisms or dispersing parts to create a continuous color line in their structure. Spectrophotometric color measurements may vary depending on the light source used and the measurement mode. Some spectrophotometers can be used according to two different measurement modes: Specular Component Included (SCI) and Excluded (SCE). Many types of standard light source are also used for color measurement of dental materials. These devices give three stimulus values x, y, z or CIE L *, a *, b *. These values can be converted into numerical values and color variables of different objects can be compared.

The aim of the study is to compare the color change caused by laser-activated and chemically activated vital whitening systems with two different evaluation methods (digital camera and spectrophotometer). In this way, a comparison of the effectiveness of both the whitening systems and the reliability of the evaluation methods will be made. It is also aimed to determine the sensitivity of the teeth that may occur during and after bleaching.

Inclusion Criteria:

1. Systemically healthy individuals
2. Non-smokers
3. Those who do not consume more than three cups of tea / coffee per day
4. No devital and / or restorated teeth in the upper anterior six teeth

Exclusion Criteria:

1. Pregnancy
2. Patient with hypersensitivity
3. Patient with crack, exposed dentin
4. Patients with dental caries
5. Patient who have gingival recession