Trauma to teeth can lead to displacement and fall of teeth. If natural teeth can be saved, then better save them. For your missing tooth #9, you can get dental implants. Bone grafting may also be required if bone resorption has occurred. If tooth #10 can be saved with endodontic therapy, then better save the natural tooth. If tooth #10 deteriorates later and needs to be removed, then  it can be extracted and can be replaced with dental implants. If tooth number #8 is cracked, then it can be treated. If there is crack line on cervical portion of tooth or in case of vertical crack line, tooth needs to be removed. Otherwise cracked tooth can be saved. If cracked tooth can’t be saved, then it can be removed and can be replaced with dental implants. Aesthetics will not be compromised with dental implants. Dental implants are best option for replacement of missing teeth. If natural teeth can be saved, then it is always better to save natural biologic tooth rather than getting dental implants. For more info on dental implants, visit……   http://www.identalhub.com/article_how-the-implants-are-placed-172.aspx