Why did my tooth break after a root canal?

The two pictures above is a radiograph showing a root canal that was finished and an intraoral photo of the tooth that cracked.  When a tooth has had a root canal procedure completed, it is important to have a post inserted in the canal of the tooth, a core buildup and a crown placed on the tooth.  Otherwise fracture of the tooth can occur.

The intraloral picture indicates not only did the tooth fracture to the gumline, it also has recurrent decay (cavity) forming.

There's this white spot in my mouth but it doesn't hurt.

This patient came in for an exam after not being to the dentist for over 5 years.  He noticed this white spot on his gums by the lower teeth.  It did not hurt at all but he wanted to know what it was.  If you notice he also has cavities (as indicated by the brown spots) and a missing tooth.

This area was biopsied and came back from the lab as Mild Epithelial Dysplasia.  He was advised to stop alcohol intake and tobacco use.  These altered epithelial lesions have an increased likelihood of progressing to squamous cell carcinoma.  Please note that this white spot could only be identified through a biopsy.  This means the white area was surgically removed and sent to a pathology laboratory for analysis.

Why does my dental crown have a black line by the gumline?

So you are looking into your mouth and you notice a black line at the base of your dental crown by the gum line.  What is it?  Basically it could be one of two things: 1) it could be a cavity forming or 2) your gums are receding and the margin of your dental crown which is made of metal is showing.

There are a few types of dental crowns.  Two types are shown in the picture.  The one on the left is an all ceramic crown.  The one on the left is a porcelain fused to metal ( PFM crown).  A PFM crown has a metal substructure and then porcelain baked over it so it looks like a tooth.

The only solution if you don't like the black line showing is to have a new crown fabricated, preferably an all ceramic crown that does not have a metal substructure.  There is also another type of PFM crown that is called a Captek crown in which the metal substructure is gold.  So instead of a black line you will see a yellow line which blends in much better.  Captek crowns tend to be more expensive because gold is expensive.

Why does my tongue look black after using this mouthrinse?

Sometimes medical professionals will prescribe a mouth rinse called Peridex ( 12% chlorhexidine gluconate).  It's a mouth rinse that reduces bacteria in your mouth.  It is an oral rinse used to treat gingivitis (gum disease), a condition in which the gums become red and swollen.   Peridex is used to control gum bleeding caused by gingivitis.  It is used usually twice a day after you brush your teeth. 
This oral rinse can discolor teeth and your tongue after using it for a long period of time.  The good news is that it goes away once you stop taking it.  The picture above is an actual case that we saw here at the practice.

I have this white sore in my mouth. What is it and what do I do about it?

So you see this in your mouth one day and it hurts a lot.  Especially when you drink orange juice or eat a pizza.  It's usually a small shallow sore inside your mouth (on the gums or inside lips/cheek) that may have redness around the edges.  It's usually caused by stress or trauma and goes away in 1 to 2 weeks.  It's a canker sore or aphthous ulcer.  It's mostly a minor nuisance.  You can use an anesthetic like over the counter Anbesol or use mouthwash like Listerine.  There are other remedies you can use that will require a visit to a medical professional.

"Ulcers with similar clinical features but rarely resolving spontaneously with age may be associated with systemic conditions such as Behçet syndrome, auto-inflammatory syndromes, gastrointestinal disease, or immune defects such as HIV/AIDS. ^{[1]"   http://emedicine.medscape.com/article/867080-overview}