In a paper published in 2007, clinical limitations of clear aligners, especially Invisalign were presented [1]. In this paper, the authors outlined some malocclusions that he outlined as not candidates for clear aligners treatment. These conditions are 1) crowding and spacing over 5 mm; 2) skeletal anterior-posterior discrepancies of more than 2 mm (as measured by discrepancies in cuspid relationships); 3) centric-relation and centric-occlusion discrepancies; 4) severely rotated teeth (more than 20 degrees); 5) open bites (anterior and posterior) that need to be closed; 6) extrusion of teeth; 7) severely tipped teeth (more than 45 degrees); 8) teeth with short clinical crowns; and 9) arches with multiple missing teeth. Although these conditions might have been difficult to treat in 2007 not all of them are not candidates for clear aligners.

You can see in this book that some difficult cases like severe apical base discrepancies (skeletal Class II and class III) are treated successfully in this book. Also, severely tipped teeth (Case 4 in class II chapter) is treated within a year. Also, cases with centric-relation and centric-occlusion discrepancies can be treat- ed now with clear aligners (Facial asymmetric, Chapter 10 of this book). Although, there are no open bite cases presented in this book but there have been many reports in the literature about effective treatment of open bite cases with clear aligners [2^–7].

In recent presentation at Invisalign Summit for orthodontists in November 2012, it was declared to all attendees that any orthodontic case can be treated by clear aligners. In this book chapter, two cases are presented highlighting the limitations of clear aligners.

Fig. (11.1))
The top above intraoral photos revealed fair oral hygiene starting in June 2011. Progress photos (bottom raw) show severe hypo-mineralization after a one year treatment and hypertrophic gingival growth.

Case 1

This twelve-year old male presented in June 2011 with a chief complain that he had moderate to minimum crowded upper and lower teeth that required them to be treated. The patient presented initially with fair oral hygiene that was instructed to improve during the course of treatment. After one year of Invisalign wear, the patient developed a severe hypocalcification (Fig. 11.1). The dentist was in a position to stop the treatment until remineralization occurs. After discussion with the patient, parents and the dentist, the patient continued to wear the clear aligners and was instructed to us the clear aligners as fluoride. Clinical follow up revealed partial remineralization however not fully recovered.

This could be attributed to the fact that clear aligners may be working as microbial/plaque incubator if the patient does not maintain excellent oral hygiene. Part of this problem is that some patients cannot clean the aligners from inside as they are supposed to. Clear instructions to the patients to make sure that they should keep the aligners clear that the patients can see through them. If the aligners start to be cloudy, it is not advisable to use them until the patient cleans them thoroughly.

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