Spinoni have a variety of problems related to the teeth and jaw structure. They are all probably polygenic and none are genetically related to the othersin other words, there is no single "bad bite" gene. The problems seen in Spinoni are as follows:
It is not recommended to breed a dog with an over, under or wry mouth. The jaw is deformed and obviously the dog is carrying defective genes. Breeding a dog with these problems is a guarantee that you are giving a significant dose of those genes to its offspring. (Rather like breeding a dog you know is dysplastic.) If an unaffected dog produces multiple affected offspring, particularly from different and unrelated mates, you should withhold that dog from further breeding. Do not repeat breedings that produce these defects. The parents and siblings (full and half) should not be bred to near relatives and should only be bred to mates from families where the fault in question is not a problem.