Professional orthodontists follow a series of strict principles when developing extraction plans. The primary principle is the concept of conservative treatment—"avoid extraction whenever possible." Only after comprehensively evaluating the patient's condition through various diagnostic tools such as dental model measurements and cephalometric analysis will the orthodontist decide whether extraction is necessary. This cautious approach reflects the "minimally invasive" treatment philosophy of modern orthodontics.
 

Patients with poor periodontal health are usually more suited to non-extraction approaches. Periodontal patients have limited alveolar bone height, restricting tooth movement distance, making arch expansion or interproximal reduction (IPR) safer non-extraction methods. Additionally, in periodontal orthodontics, IPR not only gains space but also changes the contact points between adjacent teeth into contact surfaces, which helps stabilize loose teeth and reduces the likelihood of tooth loss. For patients with insufficient facial fullness or concave facial profiles, tooth extraction should also be carefully considered, as it may further exacerbate facial concavity and affect aesthetics. In these cases, non-extraction orthodontics can better maintain or improve facial contours.

Modern orthodontics offers various space-gaining techniques for non-extraction treatment, enabling many cases that traditionally required extraction to retain all teeth. These techniques have distinct characteristics and are suitable for different clinical situations. Orthodontists will select the most appropriate method or combine multiple techniques based on the patient's specific conditions.
 

• Arch expansion is one of the most traditional non-extraction methods, creating additional space by increasing the width and length of the dental arch. Research shows that for every 1mm increase in intermolar width, approximately 0.7mm of space can be gained within the dental arch. Arch expansion is particularly suitable for cases with narrow dental arches, such as crowding or posterior crossbite caused by maxillary constriction. Traditional expansion devices like rapid palatal expanders (RPE) can effectively open the midpalatal suture, especially in growing patients. For adult patients, slow expansion or surgically assisted expansion is more commonly used. The advantage of arch expansion lies in its complete non-invasiveness, but adult patients may face relapse risks requiring long-term retention.
  
   

• Interproximal reduction (IPR), also known as enamel stripping, is another commonly used non-extraction technique that gains space by slightly reducing the interproximal enamel (typically 0.2-0.5mm per side). This method is particularly suitable for alleviating mild crowding and improving "black triangles" (triangular gaps formed when gingival papillae cannot fully fill the space between adjacent teeth). Moderate IPR within safe limits (≤0.3mm for upper front teeth, ≤0.2mm for lower front teeth, ≤0.5mm for premolars, and ≤0.6mm for molars) does not increase caries risk. Instead, it can change the contact points between teeth into contact surfaces, enhancing tooth stability. The advantages of IPR include simplicity and shorter treatment time, but it is only applicable for limited space requirements.
  
  
  
  Distalization of molars is a non-extraction method that has become increasingly popular in recent years with the development of clear aligner technology. This technique creates alignment space for front teeth by moving molars distally, making it especially suitable for borderline cases. When patients have sufficient bone mass in the third molar (wisdom tooth) area, extracting wisdom teeth and distalizing molars can avoid extracting other functional teeth. This technique requires good patient cooperation and highly precise appliance design. Clear aligners, with their ability to move multiple teeth simultaneously, demonstrate unique advantages in this technique. The main limitation of molar distalization is the need for adequate distal bone support and typically longer treatment times.