Final answer:
For a 7-year-old with a large carious exposure on a vital permanent first molar with no periapical involvement, a pulpotomy followed by placement of calcium hydroxide and sealing the tooth is the ideal treatment.
Step-by-step explanation:
A large carious exposure on a permanent first molar in a 7-year-old patient requires careful consideration in treatment, especially given that there is no periapical involvement and the tooth is vital. The best treatment in this case would be to perform a pulpotomy. This procedure involves removing the diseased pulp tissue from the crown portion of the tooth while leaving the healthy pulp within the roots. After the pulpotomy, a medicament such as calcium hydroxide is placed to encourage healing, and then the tooth is sealed, often with a dental material like zinc-oxide and eugenol.
Capping the exposure with calcium hydroxide and placing zinc-oxide and eugenol is another potential treatment and could be considered in cases of very minor exposure; however, in the case of a large exposure, a pulpotomy is generally the preferred course of action. A pulpectomy, which fully removes the pulp from the crown and root, might be considered if the tooth were non-vital, but as the tooth is stated to be vital, it is unnecessary and too aggressive. Likewise, extraction of the tooth should be considered only as a last resort when other treatments are not viable or have failed, given the importance of maintaining primary teeth for the developing dentition.