Dogs lick each other’s teeth to get to know each other or show submissiveness.
There are many other reasons, depending on which body parts or face the dog licks.
This is normal and originates from their infant period.
During this period, they used licking to ask for food from their mother.
If it is constant or strenuous, it may state a gastrointestinal pathological condition.
Why Do Dogs Lick Each Others Teeth?
- The Origin Of Dog Licking Other Dog’s Teeth
- Most Common Causes Of Licking In Dogs
- Excessive Licking Causes
- What If Your Dog Is Licking You?
The Origin Of Dog Licking Other Dog’s Teeth
When dogs are small, they keep their eyes closed, and they hardly move.
Their only way of communication is licking and making sounds – chirping.
Their diet has limits due to the mother’s milk and later to the remains of chewed food the mother dog will provide them. 
To get food, they lick the dog’s mouth and teeth to signify hunger. 
This way of communication remains when they grow up to try food from other dogs and people.
The outcome is that they learn about what the other dog has eaten and whether there is food nearby that they can try. 
Most Common Causes Of Licking In Dogs
- Introducing Themselves
- Sensing Pheromones Production
Dogs, especially young ones, are amiable and enjoy meeting other dogs.
Licking their face or teeth, is a way of getting to know each other and saying they are coming in peace. 
After this initial introduction, the other dog may respond the same way.
Then, their friendly communication begins, and the tension subsides. 
Sensing Pheromones Production
The spectacular Jacobson’s Organ in dogs is inside the nasal cavity.
It spreads to the upper parts of the dog’s mouth near the palate bone.
The Organ of Jacobs is a receptor that is not receptive to normal and expected smells.
The nerve endings of this organ are different from the olfactory apparatus nerves. 
Nerves can receive information from molecules that are large in structure.
They do not give off any smell and are unique to each mammal.
There is a connection between nerves, the olfactory bulb, and the cerebral cortex.
Their role is information transmission, awakening mating urges, or creating specific emotions.
These two systems are separate but complement each other.
Together they create a specific relationship between dogs. 
In small puppies, it helps detect the mother’s proximity and the amount of milk and food she is carrying.
In large dogs, it can detect anger and aggression and the desire to mate with a dog of the opposite sex.
That is why the dogs approach the other dog and lick the teeth from the mouth. 
In this way, they receive information about him from three sources:
- The sense of taste
- The sense of smell (olfactory apparatus)
- Jacobson organ
Excessive Licking Causes
Excessive licking of surfaces (ELS) means licking items and surfaces for long periods.
The licking is frequent and intensive.
This behavior is an ambiguous indicator that could signal several problems.
In a study done in 2022 in Belgium, the causes of excessive licking in 100 dogs of the same breed and age got analyzed. 
Special attention got contributed to diseases of the gastrointestinal tract.
Before conducting the study, the dogs went under neurological tests.
Licking can be due to neurological issues, so these tests showed that all dogs are healthy.
Scientists found diseases in 70% of the dogs tested for gastrointestinal tract disorders. 
The most common diseases were:
- Lymphoplastic infiltrations
- Delayed gastric emptying
- Irritable Bowel Syndrome
- Chronic pancreatitis
- Gastric foreign body
- Giardiasis 
What If Your Dog Is Licking You?
When your dog licks your face and mouth, it’s usually to show you love, apologize, or ask for food.
All this is very sweet and rarely brings unwanted consequences.
But, be aware that sometimes it can have negative consequences on your health.
Zoonotic transmission of H. aphrophilus links to cases of brain abscess and endocarditis. 
The source of the infection is most likely through licking-transmitted infectious canine saliva.
P. multocida meningitis usually affects infants and kids.
The transmission is by face licking on the face of the household dog.
Pet dogs link to recurrent pharyngitis, and sore throats in family members.
This disease brings on by group A. Streptococcus.
The animals in most of these cases were asymptomatic but carried the germs in their throats. 
Humans infected by this pathogen may develop:
- Puerperal fever
- Rheumatic heart disease
- Scarlet fever
- Wound infections
Why Does My Puppy Lick My Older Dog’s Teeth?
Your puppy licks your older dog’s teeth to introduce itself.
This habit evolves from their infant behavior.
At this period they lick their female parent’s face as a sign of hunger.
In extreme cases, it may signify a certain health issue.
In which case, pet parents should seek help from a veterinary professional.