They say that the mouth is the window to overall health.And rightly so, because signs of oral health problems can work as indicators of various health problems.

Most of us think of visiting a dentist only when we are facing major dental problems.Otherwise, we always try and ignore issues like cavity formation, bad breadth, teeth cleaning, e.t.c. Little do we realise that our laziness or reluctance to make regular dentist visits can cost us a lot more on the long run.

1.Pain in the upper molars-Sinusitis
The root cause of acute pain in the upper molars is sinusitis.When the maxillary sinus-air cavities within the cheek bones, above the upper jaw, becomes inflamed due to infection, it exerts pressure on the upper jaw.The roots of the upper molars are in close proximity with the sinus and on being pressed, they mimic pain of dental origin.

2.Tooth sensitivity-Acidity and Heatburn
Those who suffer from frequent heartburn or acid reflux invariably suffer from eroded teeth enamel.Un-healthy eating habits such as eating large meals, lying down in the back right after a meal or snacking before bed time are some factors that cause the valve at the entrance of the stomach to become loose and stomach acids to travel backwards.

3.Gingivitis and Pregnancy
Pregnancy causes hormonal changes that increase the risk of developing oral health problems like Gingivitis(A mild form of gum disease with inflammation of the gum) and Periodontitis(A serious gum infection that damage the soft tissue and bone that support the tooth).Pregnant women with these problems are four to seven times more likely to deliver prematurely-and underweight babies, than mothers with healthy gums.

4.Flat teeth-High stress
A lot of people tend to clench and grind their teeth during the day and night without being aware of it.Long term grinding of teeth makes them flat, causing jaw tenderness, fatigue of cheek muscles, headache and ear aches.Stress is one of the pivotal causes of Bruxism(It refers to excessive grinding of teeth and/or excessive clenching of jaw)

Some other signs:

5.Mouth Ulcer-Weak immune system
Usually, mouth ulcer occur when the body's immune system is weak.In very rare cases, mouth ulcers can signal a warning of mouth or throat cancer.

6.Dry mouth-Diabetes
Constant case of dry mouth, clinically known as Xerostomia, may be an early sign of diabetes.It causes the blood vessels present on the salivary glands to thicken thereby slowing down the natural flow of saliva and elimination of toxins, leaving the gums vulnerable to infections.
http://www.ynaija.com/what-your-mouth-reveals-about-your-state-of-health/
http://www.m.timesofindia.com/life-style/health-fitness/health/your-mouth-reveals-your-ailments/articleshow/20244853.cms