Abnormalities in the number of teeth

Abnormalities in the number of teeth
The absence of the teeth from the arch may be due to the non-eruption of fully calcified teeth; to non-evolution of the tooth germ; to the failure of the calcification processes in the dental follicle; to injury to the developing tooth germ from traumatism or infectious processes; to the accidental removal of the permanent tooth germ by the extraction of the deciduous tooth; to the transformation of the tooth germ into an odontoma.

Whenever a calcified tooth does not erupt, it is a case of incarceration or impaction according to whether the path leading to normal position in the arch is free or obstructed. This abnormality affects the third molars, upper and lower, the upper second bicuspids, the upper laterals and upper and lower cuspids with greater frequency than other teeth. Incarceration of a permanent tooth is sometimes associated with the retention of the corresponding deciduous tooth until later in life than normal, and occasionally even throughout the life of the individual.

The influence of heredity in these abnormalities of number is well shown in the case of the upper laterals, this tooth being sometimes absent through several generations, in one or several members of the same family.
The absence of the complete dentition, both deciduous and permanent and of the permanent alone, is an extremely rare occurrence, nevertheless cases of this kind are on record in dental literature.

The absence of the permanent upper right lateral incisor is a rather frequent abnormality. The absence of a lower incisor is a rare abnormality. A lower bicuspid may be absent and when it fails to erupt it is the second more frequently than the first. The permanent first molar may be absent owing to the failure of the fully calcified tooth to erupt, its presence in the substance of the jaw being made evident with the aid of radiography. The absence of the permanent cuspids is rarely the result of the non-development of the tooth, but in most instances is due to the failure of the fully formed tooth to erupt.

Direct and indirect speech can be a source of confusion for English learners. Let's first define the terms, then look at how to talk about what someone said, and how to convert speech from direct to indirect or vice-versa.
You can answer the question What did he say? in two ways:
by repeating the words spoken (direct speech)
by reporting the words spoken (indirect or reported speech)
DIRECT SPEECH
Direct speech repeats, or quotes, the exact words spoken. When we use direct speech in writing, we place the words spoken between quotation marks (" ") and there is no change in these words. We may be reporting something that's being said NOW (for example a telephone conversation), or telling someone later about a previous conversation.
INDIRECT SPEECH
Reported or indirect speech is usually used to talk about the past, so we normally change the tense of the words spoken. We use reporting verbs like 'say', 'tell', 'ask', and we may use the word 'that' to introduce the reported words. Inverted commas are not used.