Why do I have severe dry mouth after All-on-Four implants?

Dry mouth can be due to various reasons. I am assuming that you were wearing dentures before all on four implants and teeth. Usually denture wears causing excessive salivation more than the normal. Taking off dentures might be one reason. 
Among the more likely types to cause problems are some of the drugs used to treat depression, high blood pressure and anxiety, as well as some antihistamines, decongestants, muscle relaxants and pain medications. Also illnesses like liver diseases, stress, anxiety , depression, radiation exposure etc also can cause dry mouth. 

If possible show yourself to a physician. You can ask your local dentist for an artificial salivary substitute, common brand in India is Saleva. I am sure that will help 

 

There are certain medications or conditions that cause dry mouth. Be sure to visit your dentist and have him take a look as these teeth should feel natural. 

Dry mouth can result from various causes when undergoing an All-On-4 procedure:
- Medication: after 10 months you should not be on medication specific to the procedure itself, but be mindful that other medications can have this side effect (eg. drugs used to treat depression, anxiety, pain, allergies, and colds (antihistamines and decongestants), obesity, acne, epilepsy, hypertension (diuretics), diarrhea, nausea, psychotic disorders, urinary incontinence, asthma, etc);
- Dehydration: its important to ensure that you drink plenty of plain water throughout the day to avoid dehydration;
- Sinus issues, which may be from an allergy, or can also be from the original surgery, which cause you to breathe through your mouth;
- Certain medical conditions like Diabetes, Sjogrens Syndrome or other autoimmune conditions can cause a dry mouth;
- Menopause;
All the above are examples of causes that may not necessarily relate to the procedure itself. However, the procedure itself can also cause dry mouth when:
- the prosthesis is bulky;
- when the Occlusal Vertical Dimension is incorrect. Signs of this might be knocking of the teeth or speech difficulties. If the surgery was inadequate in providing necessary restorative space to accomodate the teeth, this may be difficult to fix;
- acrylic material is common with All-On-4, but whilst there is no clear evidence, I have seen improvement in patients with dry mouth when changing to a different material, like zirconia.