Dental comes in three forms:

Indemnity An indemnity dental plan has NO associated network of providers. Employees go to any dentist they desire.
PPO Preferred Provider Organization. A PPO dental plan incorporates a network of dentists. Employees receive higher benefits if they are treated by a dentist in the network.
DHMO Dental Health Maintenance Organization. Employees must use a dentist in the network to receive a benefit. Generally, employees pay only a co-pay when they receive service.

Dental plans may have the following  elements:

Deductible The deductible applies to the first dollars of dental expense paid in a calendar year by an employee. Some Carriers do not require deductibles on  Preventive procedures.

Co-pay An employee may pay a co-pay at the dentist’s office at the time of dental care.
Co-insurance Once the deductible has been paid by the employee, the insurance company pays a portion of the balance of the dental expenses. Co-insurance levels may be different for in-network expenses and out-of-network expenses.
Calendar Year Maximum The calendar year maximum is the maximum benefit that will be paid by the insurance company to each insured person.

The benefits of a dental plan depend upon the work that is done. Dental work is divided into three categories:

Preventive Examples of Preventive dental procedures include:

Basic

• Examination
• Cleaning
• X-rays
• Fluoride treatment

Major Examples of Major dental procedures include:

Orthodontics

• Periodontal surgery
• Endodontics (Root canal therapy)
• Complex oral surgery
• Crowns
• Bridges
• Dentures

Dental insurers generally require employers to pay between 75% and 50% of the employee cost and 0% of the dependent cost.  The also require 75% of the eligible employees to be enrolled.  They may require some dependent participation.