Before you settle on a teeth-whitening product, consider these pointers:

• Lemon juice is a natural tooth whitener and, used daily, is an effective alternative to chemical whiteners.
  
• As people get older, their teeth's dentin gradually takes on a yellowish hue.
  
• The antibiotic tetracycline can gray children's teeth if taken during their early years.
  
• Most whitening toothpastes just remove the surface stains that mask your teeth's intrinsic hue.
  
• Lasers and other light sources are sometimes used with gels, but whether light helps remains controversial.
  
• Thin veneers made of porcelain bonded to existing teeth are another whitening option.

Product information:
(All prices are approximate and subject to change.)

• Gosmile, $75, 877-8-SMILES (764-537), www.gosmile.com
  
• Natural White Pro, $25, 877-777-2743, www.naturalwhite.com
  
• Crest Night Effects, $15, www.crest.com
  
• Crest Whitestrips, $35, www.crest.com
  
• Colgate Simply White Night, $14, 800-468-6502, www.colgate.com