Oral Biology Exam-1 (Quiz MCQ)

Gnarled enamel refers to the complex arrangement of rods over the cusps of teeth. This term is used to describe the twisted and interwoven pattern of enamel rods that form the outer layer of the tooth. It is a characteristic feature of the occlusal surface of molars and premolars, providing strength and resistance to wear and tear. Prismless enamel, prenatal enamel, and postnatal enamel do not specifically refer to the complex arrangement of rods over the cusps of teeth.

Dilaceration refers to the condition where the root or roots of a formed tooth are distorted. This means that the root structure is not in its normal, straight form but instead appears twisted or bent. This can occur due to trauma or developmental abnormalities during tooth formation.

The basal lamina is a thin layer of extracellular matrix that separates epithelial cells from underlying connective tissue. In this case, the correct answer is "Stratum intermedium and inner enamel epithelium" because no basal lamina is found between these two cell layers. The basal lamina is present between the outer enamel epithelium and the dental sac, as well as between the inner layer of Hertwig's sheath and the dental papilla. However, it is absent between the stratum intermedium and inner enamel epithelium.

Peritubular dentin has the highest mineral content among the given options. Dentin is a calcified tissue that makes up the majority of the tooth structure. It consists of tubules, and peritubular dentin surrounds these tubules. Peritubular dentin is highly mineralized, containing a higher concentration of hydroxyapatite crystals compared to other types of dentin. This high mineral content gives it greater hardness and resistance to decay. Therefore, peritubular dentin is the correct answer as it has the highest mineral content among the options listed.

Passive eruption refers to the natural process where the junctional epithelium, which is the tissue that attaches the gum to the tooth, migrates apically or towards the root of the tooth. This migration exposes more of the tooth's surface, resulting in an increase in the length of the clinical crown. It is a normal physiological process that occurs as a person ages. The other options mentioned, such as growth in the length of the root, deposition of bone at the fundus, and the formation of cellular cementum, are not related to passive eruption.

The inter-globular dentin is found near the amelo-dentinal junction. This junction is the area where the enamel and dentin meet in the tooth. Inter-globular dentin refers to areas of dentin where the mineralization process was incomplete, resulting in small gaps or spaces between the dentin globules. These gaps can be seen as dark spots or lines on a microscopic level. The inter-globular dentin is more commonly found near the amelo-dentinal junction because this is where the dentin formation starts during tooth development.

Ameloblasts are cells that are responsible for the formation of tooth enamel. They go through different stages during enamel formation. The stage where ameloblasts have ruffled borders is known as the maturative stage. During this stage, the ameloblasts are actively secreting enamel proteins and mineralizing the enamel matrix. The ruffled borders increase the surface area of the ameloblasts, allowing for more efficient secretion and mineralization. Therefore, the correct answer is maturative ameloblasts.

The formation of the enamel matrix between two short increments needs one day. This means that it takes one day for the enamel matrix to form between two small sections of enamel.

Tomes' fibers are most likely to be found in the dentinal tubules. Tomes' fibers are long cytoplasmic processes of odontoblasts that extend into the dentinal tubules. They are responsible for the secretion of dentin matrix and play a crucial role in dentin formation. Oxytalan fibers are found in the elastic fibers of connective tissues and are not typically present in dentinal tubules. Tomes' process refers to the secretory end of the odontoblast, which is also found in the dentinal tubules. Thick collagen fibers are not typically found in dentinal tubules.

The correct answer is "at the height of incisal edge or cusp." The stellate reticulum is a layer of cells in the enamel organ of a developing tooth. It starts to shrink at the highest point of the tooth, which is the incisal edge or cusp. This shrinkage is a part of the process of enamel formation and helps to shape the tooth's final structure.