Can damage be done during a dental injection?

Yes, the dentist can damage the nerve fiber which can lead to electric shock-like sensations in the lower jaw. You can also get an infection from the numerous bacteria that live in the oral cavity. By breaking the skin, the bacteria can enter the blood stream. One example is subacute bacterial endocarditis caused by the gram-positive bacteria called streptococcus viridans. This can lead to permanent damage to the heart valves (most commonly the mitral/bicuspid valve).