SAN JOSE, Calif., US: The world’s largest clear aligner treatment provider has alerted investors to a substantial slowdown in new orthodontic appointments and adult case starts in North America. The fall in demand depressed Align Technology’s third-quarter results, and the company has warned analysts that it expects sluggish case starts to linger into the fourth quarter and to hamper its full-year results. Align Technology stock (ALGN) lost nearly one-quarter of its value after the announcement.