**Core Concept:**
Gypsum bonded investment is a dental material used to create a cast for a dental restoration. It consists of gypsum powder and water mixed together to form a plaster-like material that is used to make impressions of teeth in preparation for fabricating a crown, bridge, or other dental prosthesis. This process involves heating the investment to set the gypsum and solidify the impression.

**Why the Correct Answer is Right:**
The correct answer is **D** because heating gypsum bonded investment over 110°C can lead to several issues. At temperatures above 110°C, the gypsum starts to decompose, releasing water vapor and carbon dioxide. This can cause the investment to shrink, resulting in a distorted cast and a poor fit of the restoration. Additionally, overheating can cause the gypsum to lose its setting properties, making it difficult to set properly and impairing the precision and accuracy of the cast.

**Why Each Wrong Option is Incorrect:**
A. Heating over 120°C is incorrect because this temperature range is too high, leading to the issues mentioned above.
B. Heating over 90°C is incorrect because this temperature range is too low, resulting in an incomplete set of gypsum and a poor quality cast.
C. Heating over 100°C is incorrect because this temperature range is too high, causing the same issues as heating over 120°C.

**Clinical Pearl:**
When working with gypsum bonded investment, it is essential to heat the investment within the recommended temperature range of 90-110°C. Overheating can lead to a distorted cast and poor restoration fit, while underheating can result in an incomplete set and unsatisfactory cast quality. It is crucial to maintain accuracy and precision in dental treatment, and understanding the proper heating process for gypsum bonded investment is a fundamental aspect of this.