24/24 (7) Chemistry HL IA (N21) – Hydrogen peroxide on removing Coffee Stains

1.0 Introduction

1.1 Research Question:

What is the effect of increasing concentrations (0.0% 3.0%, 6.0%, 9.0%, 12.0%, 15.0%) of hydrogen peroxide (H2O2) on the oxidation of coffee stains on bovine teeth, measured by light intensity reflected off of the tooth using a spectrometer?

1.2 Introduction:

Many coffee enthusiasts like myself need a coffee in the morning to start the day. Besides all the great benefits we get from coffee, it is widely known and accepted that it causes external discolouration on the tooth’s enamel despite the regular brushing and exceptional oral hygiene. Hence, there has been a greater demand for teeth whitening products (Basel, 2019). The whitening mechanism is derived from the addition of hydrogen peroxide. However, as different products contain varying concentrations of hydrogen peroxide, I wanted to experimentally investigate their whitening potentials.

1.3 Background Knowledge:

Coffee is composed of a variety of compounds including chlorogenic acid (C16H18O9) and polyphenols also known as tannins which are responsible for causing discolouration in teeth (Pratomo, Triaminingsih & Indrani, 2019). Tannins are a class of astringents which enhance the ability of chromogens (a compound containing chromophores) to bind to the enamel. Chromogens contain a compound called chromophores which are responsible for the absorption of visible light radiations. In coffee, chromogens appear in the form of chlorogenic acid and as this pigment molecule absorbs light in the visible range, it reflects the complementary colour, which is typically recognised by the eyes as yellow or brown (Pratomo, Triaminingsih & Indrani, 2019).

There are two types of teeth stains: extrinsic and intrinsic. Extrinsic stains describe a superficial type of discoloration caused by the accumulation of chromogens on the surface of the tooth, or the enamel (Alali, 2020). These stains often occur when the teeth are frequently exposed to coffee, tea, wine, soft drinks, certain medications or tobacco products (Alali, 2020). However, over time, they can penetrate through enamel pores and become intrinsic stains. Intrinsic stains refer to discolouration caused deeper within the tooth’s anatomy, usually the hard layer underneath the enamel called dentin (Alali, 2020). These stains can be caused from a multitude of factors such as genetics, trauma, infection or exposure to certain substances. In this investigation, coffee stains were studied as a form of an extrinsic stain on the tooth experienced abundantly around the world…