Editing Human tooth (section)

===Environmental===

==== Alteration during tooth development ====
Tooth abnormalities caused by environmental factors during tooth development have long-lasting effects. Enamel and dentin do not regenerate after they mineralize initially. [[Enamel hypoplasia]] is a condition in which the amount of enamel formed is inadequate.<ref>{{harvnb|Ash|2003|page=31}}</ref> This results either in pits and grooves in areas of the tooth or in widespread absence of enamel. Diffuse opacities of enamel does not affect the amount of enamel but changes its appearance. Affected enamel has a different translucency than the rest of the tooth. Demarcated opacities of enamel have sharp boundaries where the translucency decreases and manifest a white, cream, yellow, or brown color. All these may be caused by nutritional factors,<ref name=KanchanMachado2015>{{cite journal|vauthors= Kanchan T, Machado M, Rao A, Krishan K, Garg AK|title=Enamel hypoplasia and its role in identification of individuals: A review of literature|date=Apr 2015|journal=Indian J Dent|volume=6|issue=2|pages=99–102|doi=10.4103/0975-962X.155887|pmid=26097340|pmc=4455163|type=Revisión |doi-access=free }}</ref> an [[exanthem]]atous disease ([[chicken pox]], [[congenital syphilis]]),<ref name=KanchanMachado2015 /><ref name="neville51">{{harvnb|Neville|2002|page= 51}}</ref> undiagnosed and untreated [[coeliac disease|celiac disease]],<ref name=NIH>[http://celiac.nih.gov/PDF/Dental_Enamel_Defects_508.pdf Dental Enamel Defects and Celiac Disease] {{Webarchive|url=https://web.archive.org/web/20160305124250/http://celiac.nih.gov/PDF/Dental_Enamel_Defects_508.pdf |date=2016-03-05 }} National Institute of Health (NIH)</ref><ref name=FerrazCampos2012>{{cite journal|vauthors=Ferraz EG, Campos Ede J, Sarmento VA, Silva LR|title=The oral manifestations of celiac disease: information for the pediatric dentist|date=2012|journal=Pediatr Dent|volume=34|issue=7|pages=485–8|pmid=23265166|type=Review}}</ref><ref name=GiucaCei2010>{{cite journal|vauthors=Giuca MR, Cei G, Gigli F, Gandini P|title=Oral signs in the diagnosis of celiac disease: review of the literature|date=2010|journal=Minerva Stomatol|volume=59|issue=1–2|pages=33–43|pmid=20212408|type=Review}}</ref> [[hypocalcaemia|hypocalcemia]], [[dental fluorosis]], [[birth injury]], [[preterm birth]], [[infection]] or trauma from a [[deciduous teeth|deciduous tooth]].<ref name=KanchanMachado2015 /> Dental fluorosis is a condition which results from ingesting excessive amounts of [[fluoride]] and leads to teeth which are spotted, yellow, brown, black or sometimes pitted. In most cases, the enamel defects caused by celiac disease, which may be the only manifestation of this disease in the absence of any other symptoms or signs, are not recognized and mistakenly attributed to other causes, such as fluorosis.<ref name=NIH /> Enamel hypoplasia resulting from [[syphilis]] is frequently referred to as [[Hutchinson's teeth]], which is considered one part of [[Hutchinson's triad]].<ref>[http://www.mayoclinic.com/health/syphilis/DS00374/DSECTION=6 Syphilis: Complications], Mayo Clinic.</ref> [[Turner's hypoplasia]] is a portion of missing or diminished enamel on a permanent tooth usually from a prior infection of a nearby primary tooth. Hypoplasia may also result from [[antineoplastic]] therapy.

====Destruction after development====
Tooth destruction from processes other than [[dental caries]] is considered a normal physiologic process but may become severe enough to become a pathologic condition. [[Attrition (dental)|Attrition]] is the loss of tooth structure by mechanical forces from opposing teeth.<ref>"[http://www.adha.org/CE_courses/course9/loss_of_structure.htm Loss of Tooth Structure] {{Webarchive|url=https://web.archive.org/web/20121227091702/http://www.adha.org/CE_courses/course9/loss_of_structure.htm |date=2012-12-27 }}", American Dental Hygiene Association.</ref> Attrition initially affects the enamel and, if unchecked, may proceed to the underlying dentin. [[Abrasion (dental)|Abrasion]] is the loss of tooth structure by mechanical forces from a foreign element.<ref>"[https://web.archive.org/web/20100801114913/http://dentistry.umkc.edu/practition/assets/AbnormalitiesofTeeth.pdf Abnormalities of Teeth]", University of Missouri-Kansas City School of Dentistry.</ref> If this force begins at the cementoenamel junction, then progression of tooth loss can be rapid since enamel is very thin in this region of the tooth. A common source of this type of tooth wear is excessive force when using a toothbrush. [[Erosion (dental)|Erosion]] is the loss of tooth structure due to chemical dissolution by acids not of bacterial origin.<ref>{{cite journal|url=http://www.agd.org/library/2003/aug/200308_yip.pdf |pmid=15055615 |year=2003 |last1=Yip |first1=KH |last2=Smales |first2=RJ |last3=Kaidonis |first3=JA |title=The diagnosis and control of extrinsic acid erosion of tooth substance |volume=51 |issue=4 |pages=350–3; quiz 354 |journal=General Dentistry |url-status=dead |archive-url=https://web.archive.org/web/20060907094153/http://www.agd.org/library/2003/aug/200308_yip.pdf |archive-date=September 7, 2006 }}</ref> Signs of tooth destruction from erosion is a common characteristic in the mouths of people with [[bulimia]] since [[vomiting]] results in exposure of the teeth to gastric acids. Another important source of erosive acids are from frequent sucking of [[lemon juice]]. [[Abfraction]] is the loss of tooth structure from flexural forces. As teeth flex under [[pressure]], the arrangement of teeth touching each other, known as [[occlusion (dentistry)|occlusion]], causes [[Tension (mechanics)|tension]] on one side of the tooth and [[compression (physical)|compression]] on the other side of the tooth. This is believed to cause V-shaped depressions on the side under tension and C-shaped depressions on the side under compression. When tooth destruction occurs at the roots of teeth, the process is referred to as [[internal resorption]], when caused by cells within the pulp, or [[external resorption]], when caused by cells in the periodontal ligament.

====Discoloration====
{{Main|Tooth discoloration}}
[[File:Tired teeth.jpg|thumb|Discolored teeth]]
Discoloration of teeth may result from bacteria stains, tobacco, tea, coffee, foods with an abundance of [[chlorophyll]], restorative materials, and medications.<ref name="neville63">{{harvnb|Neville|2002|page= 63}}</ref> Stains from bacteria may cause colors varying from green to black to orange. Green stains also result from foods with chlorophyll or excessive exposure to copper or nickel. Amalgam, a common dental restorative material, may turn adjacent areas of teeth black or gray. Long term use of [[chlorhexidine]], a mouthwash, may encourage extrinsic stain formation near the gingiva on teeth. This is usually easy for a hygienist to remove. Systemic disorders also can cause tooth discoloration. [[Congenital erythropoietic porphyria]] causes [[porphyrin]]s to be deposited in teeth, causing a red-brown coloration. Blue discoloration may occur with [[alkaptonuria]] and rarely with [[Parkinson's disease]]. [[Erythroblastosis fetalis]] and [[biliary atresia]] are diseases which may cause teeth to appear green from the deposition of [[biliverdin]]. Also, trauma may change a tooth to a pink, yellow, or dark gray color. Pink and red discolorations are also associated in patients with [[leprosy|lepromatous leprosy]]. Some medications, such as [[tetracycline]] antibiotics, may become incorporated into the structure of a tooth, causing intrinsic staining of the teeth.

====Alteration of eruption====
Tooth eruption may be altered by some environmental factors. When eruption is prematurely stopped, the tooth is said to be [[Wisdom teeth#Impaction|impacted]]. The most common cause of tooth impaction is lack of space in the mouth for the tooth.<ref name="neville66">{{harvnb|Neville|2002|page=66}}</ref> Other causes may be [[tumor]]s, [[cyst]]s, trauma, and thickened bone or soft tissue. [[Tooth ankylosis]] occurs when the tooth has already erupted into the mouth but the cementum or dentin has fused with the alveolar bone. This may cause a person to retain their primary tooth instead of having it replaced by a permanent one.

A technique for altering the natural progression of eruption is employed by [[orthodontist]]s who wish to delay or speed up the eruption of certain teeth for reasons of space maintenance or otherwise preventing crowding and/or spacing. If a primary tooth is extracted before its succeeding permanent tooth's root reaches {{frac|1|3}} of its total growth, the eruption of the permanent tooth will be delayed. Conversely, if the roots of the permanent tooth are more than {{frac|2|3}} complete, the eruption of the permanent tooth will be accelerated. Between {{frac|1|3}} and {{frac|2|3}}, it is unknown exactly what will occur to the speed of eruption.