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Late lower incisor crowdingSeminarDept of Orthodontics UiTM30/3/2015Group COutlinesDefinitionIntroductionEtiologyThird molar and late lower labial crowding: literature reviewManagement of late lower labial crowdingConclusionReferences

Definition Late crowding of the mandibular incisors beginning between the ages of 17 and mid-twenties and progressing throughout adult life(Sakuda et al 1976)

IntroductionCrowding of the mandibular incisors is one of the most common problems encountered in the permanent dentition and is one of the most likely things to relapse after orthodontic treatment.(Cobournes Handbook of orthodontics)because of its high prevalence, late mandibular incisor crowding is considered a normal part of the aging process.(American Association of Orthodontics 1999)Approximately two-thirds of adolescents with good alignment and normal occlusions will develop incisor irregularity by early adulthood(sinclair et al 1983)The aetiology of late lower incisor crowding is recognized as beingmultifactorial(Laura mitchells Introduction to Orthodontics,)Etiology of late lower incisor crowdingMandibular growth rotations;When mandibular growth outpaces maxillary growth, forces from the maxillary arch and labial soft tissues cause uprighting, or lingual movement of lower incisorsThis results in crowding by forcing the incisors to occupy a smaller arch perimeter.

American Association of Orthodontic, Orthodontic Dialog vol 11 no. 1, Spring 1999

Cont..2. Anterior component of occlusal forcescan either be physiological or pathological (high bite, parafuntional habits)3. Physiologic mesial drift the teeth are gradually displaced mesially and causing the crowding of lower incisors4. Soft tissue maturationhyoid bone and tongue descend with age, relative to surrounding structures, causing imbalance between lip and tongue and resulting in crowding( Bench et al,. 1952 )

Cont..5. Degenerative periodontal changes allowing teeth to drift under light pressures

6. Change in diet and lack of interproximal wearDiet influence the teeth interproximal wear, less interproximal wear lead to more crowding.7. Tooth size and shape 8. Third molar eruption?

LITERATURE REVIEWSMandibular third molar and late lower incisor crowdingStudies relating 3rd molar to late lower incisor crowding Bergstorm and Jensen (1961)presence of 3rd molar may influence the development of dental arch, but they do not justify on the prophylactic removal of 3rd molars.Vego (1962)greater degree of crowding in the group presence of mandibular 3rd molar.He suggested there are multiple factors involve the crowding- not only the third molarsShanley (1962)Study on comparison in bilaterally impacted, erupted and congenitally absent 3rd molar.He found no significant differences and concluded that 3rd molar have little influence only.Selmer-Olsens (1970)Suggested people with unilateral congenital absence of third molar will have less crowding on quadrant without 3rd molar, and crowding on quadrant with presence of 3rd molar.

Cont..Schwarze (1975)He compared between group with 3rd molar germectomy and non-extraction group.Significant lower incisor crowding in non-extraction group.Lindqvist and Thilander (1982)They found 0.16mm less crowding in group with 3rd molar removal.They concluded that extraction could be recommended in severe crowding malocclusion.Richardson ME (1989)Study was done on subjects with intact lower arches and bilateral 3rd molars presence.Showed increase in crowding as 4mm and only 16% did not show the crowding.She considered 3rd molars as one of the causes of lower late incisors crowding.

Cont..Southard et. al. (1991)Their hypothesis was that the mesial force exerted by unerupted 3rd molar increases the lower late incisor crowding.However they cant detect the pressure, and concluded that pressure from 3rd molar is insignificantVander Schoot et. al (1997)Study done on subjects with 3rd molar erupted, impacted, extracted and congenitally missing.They concluded that no relationship exists between crowding and the presence or absence of 3rd molars.Harradine et al (1998)They done study to evaluate the effect of extraction 3rd molars and late lower incisor crowding.They concluded that the removal of 3rd molar to reduce or prevent late crowding could not be justified.

Cont..Gavazzi M et al (2014)193 orthodontists and oral surgeon were asked to express their opinion on the relation between upper and lower third molar eruption and anterior crowding.The majority of both groups of clinicians do not consider their preventive extraction useful in order to prevent anterior crowding.Management of Late lower incisor crowdingThe decision to treat mandibular incisor crowding depends largely on the severity of crowding and the complexity of other components of the patients malocclusionIn the presence of significant malocclusion, incisor crowding is best managed as part of a comprehensive orthodontic treatment plan. However, if a patient has Class I dental relationships and good maxillary alignment, limited treatment may be appropriate.

(American Association of Orthodontic, Orthodontic Dialog vol 11 no. 1, Spring 1999)Cont..Accept and monitor Esthetically acceptable, able to maintain good oral hygiene.Removable appliancelimited to tipping and rotational movementin cases of mild crowding where space can be required by enamel strippingClinical Problem Solving in Orthodontics and Paediatric DentistryBy Declan Millett

Cont..Fixed appliancesIn cases of moderate to severe crowding where bodily movement is required.Extraction is usually required to provide space.Extraction of lower incisors can be done in treating late lower incisor crowding but it is not advisable as it can compromised the esthetics.

retainerPreferably using the fixed bonded retainer

ConclusionThe causes of late lower labial crowding is multifactorial.Removal of symptomless lower third molars has been advocated in the past in order to prevent lower labial segment crowding.It is likely that third molar have an effect upon mandibular arch crowding but this effect is one component of a multifactorial condition and prophylactic third molar extraction is unlikely to remove the problem (Richardson, 2002). The National Institute for Health and Clinical Excellence (NICE) in the UK has recommended that prophylactic removal of pathology- free impacted third molars, which includes removal to prevent occlusal changes in the incisor regions, be discontinued.Handbook of Orthodontics by by Martyn T Cobourne

ReferencesAn introduction to orthodontics 4th edition by laura mitchellHandbook of Orthodontics by by Martyn T CobourneClinical Problem Solving in Orthodontics and Paediatric Dentistry By Declan MillettSakuda M., Kuroda Y., Wad K., Matsumoto M. Changes in crowding of teeth during adolescence and their relation to the growth of the facial skeleton.Trans Eur Orthod Soc.1976:93104.Sinclair, P.M., Little, R.M.:Maturation of untreated normalocclusions. Am. J. Orthod. Dentofac.Orthop. 1983;83:114-123.Sumitra, Arundi : Third Molars and Late Mandibular Incisor Crowding A Review, J Ind Orthod Soc 2005American Association of Orthodontic, Orthodontic Dialog vol 11 no. 1, Spring 1999Sumitra, Arundi : Third Molars and Late Mandibular Incisor Crowding A Review, J Ind Orthod Soc 2005