Absolutely, the use of diluted Chlorhexidine mouthwash with water in the morning routine of oral care can be safe and helpful. The usual concentration is 0.12% and it can be used once or twice per day. This mouthwash is good for inflammation of gums, plaque as well as bacteria in the mouth. To get the best outcome, do not swallow and follow directions cautiously.

It can be a hard time for one to have teeth that are not in shape. However, braces are a good treatment for this problem. Crooked teeth may be a cause of issues while eating and brushing. Braces are like small assistants who help move your teeth into a more appropriate position. 

In my opinion the advice given by your doctor isn't wrong and opinion from multiple doctors can lead to confusion or chaos, but if you see deterioration in your state then you can reach out again.

The short answer is “no” but the long answer is “sort of.”  Here’s why:

The earliest stage of tooth decay or a cavity is demineralized enamel. The outer layer of enamel becomes weak and soft, due to acids and plaque biofilm coming into contact with it on an extended basis.

Fortunately, demineralized enamel can — to an extent — be remineralized before a physical cavity (hole) ruptures through the surface.

What are some ways to help this happen?

• Improved hygiene and plaque removal on an everyday basis
• Protective dental sealants over deep grooves and fissures, which are someof the most cavity-prone surfaces
• Drinking fluoridated tap water throughout the day
• Supplementation with a prescription strength fluoride or mouthrinse, providedby your dentist
• Use of everyday oral hygiene products that contain fluoride
• Eating more fresh fruits and vegetables, sharp cheddar cheese, and fewerprocessed carbohydrates
• Eliminating acidic beverages and those that contain natural or artificial-sweeteners

The types of cells that make up your teeth do not re-grow or repair themselves after the tooth is fully developed.

Once a tooth has a physical cavity (opening or hole) inside of it, there is no feasible way to help the enamel grow back on your own. Instead, the cavity will gradually worsen, due to the bacterial infection inside of the tooth structure.

Ideally, you would want to treat the cavity as soon as it’s diagnosed and while it’s as small as possible. When you do, your dentist can place a minimally invasive filling and preserve as much healthy tooth structure as possible.

But untreated cavities will expand to the point that they require larger fillings. Or worse, they will reach into the nerve chamber and create an abscess. What could have initially been treated with a modest restoration now becomes a situation requiring a root canal and a crown

It is normal for swelling to occur after wisdom teeth removal. This is a part of the healing. But if the swelling is severe, your sister should see her dentist or an oral surgeon for a review.