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Teeth

Teeth

The formation of teeth, also known as odontogenesis, is a complex process that begins in utero, around the sixth week of embryonic development. There are three stages to this process: the bud stage, the cap stage, and the bell stage.
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...

Tooth Anatomy

Tooth Anatomy

The human tooth enables us to eat a variety of foods, speak clearly, and even aid in shaping our faces. Teeth are composed of various elements that work together. Here's a detailed look at the anatomy of a human tooth.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.

Directing Effect of Substituents: ortho–para-Directing Groups

Directing Effect of Substituents: ortho–para-Directing Groups

Ortho–para directors are substituent groups attached to the benzene ring and direct the addition of an electrophile to the positions ortho or para to the substituent. All electron-donating groups are considered ortho–para directors. They donate electrons to the ring and make the ring more electron-rich. The ring is therefore susceptible to the addition of electrophiles. Substituents such as amino, hydroxy, or alkoxy, containing lone pairs on the atom adjacent to the ring, donate electrons...

ortho–para-Directing Activators: –CH3, –OH, –&NoBreak;NH2, –OCH3

ortho–para-Directing Activators: –CH₃, –OH, –⁠NH₂, –OCH₃

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...

ortho–para-Directing Deactivators: Halogens

ortho–para-Directing Deactivators: Halogens

Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...

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Updated: Jun 26, 2026

A Finite Element Approach for Locating the Center of Resistance of Maxillary Teeth

A Finite Element Approach for Locating the Center of Resistance of Maxillary Teeth

Published on: April 8, 2020

Why do dentists refer to specific orthodontists?

Jason F Hall¹, Woosung Sohn, James A McNamara

¹Department of Orthodontics and Pediatric Dentistry, The University of Michigan, Ann Arbor, Michigan, USA.

The Angle Orthodontist

|January 7, 2009

Summary

General dentists consider orthodontic treatment quality and patient satisfaction equally important for referrals. High-quality outcomes and good communication are key for orthodontic referrals.

Related Experiment Videos

Last Updated: Jun 26, 2026

A Finite Element Approach for Locating the Center of Resistance of Maxillary Teeth

A Finite Element Approach for Locating the Center of Resistance of Maxillary Teeth

Published on: April 8, 2020

Area of Science:

Dentistry
Orthodontics
Dental Practice Management

Background:

General dentists play a crucial role in referring patients for orthodontic treatment.
Understanding dentist referral motivations is essential for orthodontic practice growth.

Purpose of the Study:

To determine the relative importance of treatment outcomes and patient satisfaction in general dentist referrals to orthodontists.
To identify specific occlusal characteristics considered indicative of an outstanding orthodontic result by general dentists.

Main Methods:

A survey of 35 questions was administered to 1000 general dentists in the midwestern United States.
The study employed a random sampling method to ensure representative data collection.

Main Results:

75% of dentists rated orthodontic treatment quality and patient satisfaction as equally important for referral decisions.
The quality of the orthodontic result was deemed more critical than office location, orthodontist reputation, or treatment cost.
Canine guidance was ranked as the most important post-orthodontic occlusal characteristic, followed by Class I molar/canine relationships, even tooth contact, appropriate overjet/overbite, and absence of spacing.

Conclusions:

General dentist referral decisions are influenced by multiple interacting factors.
Orthodontic clinicians should prioritize high-quality treatment, positive patient/family interactions, and strong communication with general practitioners.