IV sedation is always optional.
Dental procedures may cause discomfort and cause a degree of anxiety. Hence dental procedurists always administer various forms of medication for relief of anxiety.
This may range from oral tablets to having medication injected intravenously. On occasion, deeper sedation may be required; this is where an anesthesiologist will be booked for the procedure. This doctor stays throughout the duration of the procedure, monitoring your oxygenation, heart rate, and blood pressure while adjusting the level of sedation medication.
I hope this helps!