A 30 year old female  patient complains of decayed teeth. Intraoral examination reveals occlusal caries with 46. Dentist decides to restore the tooth with composite restoration. What will be the C factor for this tooth?

**Core Concept**
The C-factor, also known as the contour factor, is a critical parameter in dental restorative procedures. It refers to the ratio of the bonded surface area to the unbonded surface area of the restoration. The C-factor affects the shrinkage stress and polymerization shrinkage of the restorative material, particularly in composite restorations.

**Why the Correct Answer is Right**
In the case of an occlusal caries restoration, the C-factor is high because the restoration is in contact with two opposing surfaces of the tooth. This is due to the fact that the composite restoration is placed in a cavity preparation, where it comes into contact with the tooth structure on both the mesial and distal aspects. As the composite material shrinks during polymerization, the high C-factor increases the stress on the restoration, potentially leading to microleakage, marginal breakdown, or even restoration failure. The high C-factor in this scenario necessitates careful consideration of the restoration material's properties and the use of techniques to minimize shrinkage stress.

**Why Each Wrong Option is Incorrect**
**Option A:** A C-factor of 1 is incorrect because it implies a 50:50 ratio of bonded to unbonded surface area, which is not applicable in this scenario. The C-factor in this case is higher due to the occlusal restoration.

**Option B:** A C-factor of 0.5 is incorrect because it implies a 50:50 ratio of bonded to unbonded surface area, which is not applicable in this scenario. The C-factor in this case is higher due to the occlusal restoration.

**Option D:** A C-factor of 2 is incorrect because it implies a higher ratio of bonded to unbonded surface area, which is not applicable in this scenario. However, in some cases, a C-factor of 2 can occur when a restoration is in contact with only one surface of the tooth.

**Clinical Pearl / High-Yield Fact**
A high C-factor in composite restorations can lead to increased polymerization shrinkage stress, which may result in marginal breakdown, microleakage, or restoration failure. To minimize these issues, dentists can use techniques such as incremental layering, using a flowable composite as a liner, or employing a restorative material with a lower shrinkage stress.

**Correct Answer: C.**