There is no overtime exemption for employees of dentists. Virtually all California employers are required to pay time and a half for working more than 8 hours but less than 12 hours a day or in the event no hours are worked over 8 any workday in the workweek then all hours worked over 40 in a workweek. Employees who work more than 12 hours in a work day are entitled to 2 times their regular rate.
Medical professionals are only exempt under CA state law if they certified nurse midwives, certified nurse anesthetists and or certified nurse practioners who engage in duties relevant to their respective certification issued pursuant to the Business and Professions Code. Further the exemptions applies to physicians, dentists and surgeons. The daily overtime requirements do not apply to ambulance drivers and attendants.
That being said, any employer can have an agreement with its employees not to pay overtime over 8 hours a day as long as they don't exceed 10 hours a day and all employees voted to except the alternative by 2/3 majority.
Health Care Industry
This same alternative workweek applies to your wife as an employee in the health care industry except the dentist can work his employees as many as 10 hours a day not to exceed 12, without paying overtime but only to the extent the same approval process listed above is followed, i.e. 2/3 of the staff at the dentist office would have to approve not receiving overtime in excess of 8 hours worked.
Lastly, there is no requirement to provide an employee handbook but Federal Law does require a summary plan description of all benefits offered pursuant to ERISA and under a qualified cafeteria plan.