DEVELOPMENT OF
DENTITION
&
OCCLUSION
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing dental education

www.indiandentalacademy.com

www.indiandentalacademy.com
Role of occlusion in maintaining
aesthetics and function of dentofacial
complex:
Term occlusion is derived from Latin word...
Occlusion is an anatomic and physiologic complex
present when the opposing teeth are in contact.
It consists of positional...
The development of dentition is closely
associated with the morphology & growth
of the face & the way in which the
functio...
Why 2 sets of teeth?
The possession of 2 sets of teeth in
mammals imparts the advantage of
equipping the young in a short ...
The deciduous or temporary dentition is
gradually shed & followed by a permanent
or succedaneous dentition . This is a
mec...
Factors that cause the resorption of
deciduous dentition:
The physiologic process resulting in the
elimination of the deci...
Cells responsible - odontoclasts.
Histochemically characteristic
feature - alkaline phosphatase.
Alk phosphatase activity ...
found - on surfaces of roots in relation to
advancing permanent teeth. Also found in
root canals & pulp chambers of resorb...
Sequence of events in resorption of
dental lamina:
pressure

If succesional
tooth germ
is missing , shedding
of deciduous ...
Experimental removal of permanent tooth
germ delays but not prevents shedding of
deciduous teeth
Forces of mastication app...
Stages of dental
development
The first local changes occurring in
tooth development occurs as early as
the 6th week of pre...
Individual tooth formation proceeds by
means of mitotic activity ,particularly in the
inner enamel epithelium , until the
...
It has become evident that developmental
regulatory genes have been conserved to a
great degree during evolution & that si...
S.M are released from oral ectoderm & they bind
to the receptor on ectomesenchymal cells &
activate the transcription fact...
Path of eruption of permanent
dentition:
The word eruption refers to cutting of the
tooth through the gum.( in Latin erump...
As their deciduous predecessors erupt they
move to a more apical position & occupy
their own bony crypts.
Premolars begin ...
The permanent molars which have no
deciduous predecessors also move
considerably from the site of their initial
differenti...
Mandibular molars develop with their occlusal
surfaces inclined mesially & only become upright
as room becomes available ....
The neuromuscular & osseous
movements influencing the
eruption of teeth:
Pre-emergent eruption
Post-emergent eruption
juve...
Pre emergent eruption:
Labial or buccal drift
Eruptive movement begins soon after root begins
to form
Processes necessary ...
Rate of bone resorption & the rate of
tooth eruption are not controlled
physiologically by the same
mechanism.
Ex : expts ...
Mechanism of eruption:
Cross linking of collagen fibers
contribute to elasticity of periodontal
ligament.
Contractions & r...
Other possibilities:
Localized variations in BP
Forces delivered from contraction
of fibroblasts.
Alterations in the extra...
Post emergent eruption:
Once tooth emerges into oral
cavity it continues till it
approaches the occlusal level & is
subjec...
Juvenile occlusal equilibrium:
Phase of very slow eruption
Rate of eruption parallels rate of jaw
growth.
Disturbance in c...
Adult occlusal equilibrium
When pubertal growth spurt ends , a final
phase in tooth eruption called the adult
occlusal equ...
If its antagonist is lost at any age , a tooth
can again erupt at more rapidly ,
demonstrating that eruption mechanism
rem...
If severe occlusal wear occurs – cannot be
compensated by eruption hence lower facial
height decreases.
In few cases any w...
Neonatal line:
Despite the physical adaptations
that facilitate it, birth is a traumatic
process.
For a short period growt...
Such an interruption in growth
produces a physical effect in skeletal
tissues that are forming at that time,
because the o...
Natal tooth:
First primary teeth do not erupt until
approximately 6 months of age.
The natal tooth may be a supernumerary
...
Eruption of primary teeth:
Development of incisors & canines
precedes that of the structures that contain
them – this expl...
As synchondrosis in the mandible calcifies
at about 6 months of age , the potency for
transversal growth in the lower jaw ...
The first vertical support associated
with interdigitation – the interlocking of
maxillary & mandibular posterior teeth
oc...
In most instances , the large palatal
cusp of the maxillary 1st molar arrives
with its cone shape with in the crater
forme...
 A required movement of the teeth will
be involved will be derived more from a
displacement of the maxilla than of the
ma...
There after the relation between the two
dental arches will stabilize in the transverse
& sagittal direction.
The deciduou...
Mandibular teeth occlude slightly lingual
with the maxillary ones. The terminal plane
of deciduous dentition will be flush...
First transitional period:
Emergence of 1st permanent molar & the
transition of the incisors.
The anteroposterior relation...
If the crown dimensions of the max & mand
deciduous second molars are same , the sagittal
relation between corresponding M...
If the mand 2nd deciduous molar is
considerably larger than the maxillary one
then the distal surfaces will lie in one pla...
Early mesial shift
In pts with spaced primary dentition & st terminal
plane relationship of molars , the permanent
molars ...
Late mesial shift:
In pts with closed primary dentition & st terminal
plane the permanent max &mand 1st molars
emerge into...
Incisor liability:(Warren Mayne 1969)
Mesiodistal width of permanent incisors are
more compared to deciduous incisors.
Thi...
Safety valve mechanism:
During the period of permanent incisor eruption
notable amounts of intercanine arch width
developm...
According to Moorrees ( J dent res 1965) the
average increase in the mandibular dentition of
boys & girls is approximately...
A small opening in the bony alveolar
process is present on the lingual aspect of
each deciduous incisor in the upper & low...
The opening of the gubernacular canal on
the oral side increases in size with the
approach of the associated permanent too...
Inter transitional period:
The inter transitional period presents itself
in a growing child as a rather stable phase
with ...
Root formation of the already emerged
incisors & molars continues. The roots of
permanent canines, premolars, & 2nd molars...
Between the 4 permanent incisors & right &
left first permanent molars , the deciduous
canines & & 1st & 2nd deciduous mol...
Ugly duckling stage:( 9 - 12 yrs)
During the eruption of permanent canines,
the crowns of permanent canines hit the
roots ...
In mandible the incisors are less
labially inclined than in the maxilla. A
diastema is seldom present between the
mandibul...
Second transitional period:
At approximately 10 yrs of age the 1st
deciduous tooth in the post region usually a
mand canin...
During formation maxillary canine & 1st
premolar are in close proximity of with
each other& overlap vertically. The alread...
A comparable M concavity is absent or
present only in reduced form at the maxillary
2nd premolar whose crown morphology
st...
Variations may occur in the sequence of
emergence with a restriction that as a rule
the 1st PM precedes the permanent cani...
During the replacement of deciduous
canines & molars by premolars, leeway
space is utilized.
The deciduous 1st & 2nd molar...
Abnormalities in dental arches
The most frequently occuring abnormality
in the dental arches is a discrepancy
between the ...
Deviation in the number of teeth in the
deciduous dentition is rare.they are regularly
encountered in the permanent dentit...
Supernumerary teeth can be encountered
in the dental arches & particularly in the
mand & max incisor region.
most frequent...
Anomalies in size
MD width is more in males compared to
females & it is more pronounced in
permanent teeth.
Anomalies are ...
Anomalies in shape:
Peg shaped lateral
Cingulum quite prominent
Sharp marginal ridges (particularly
Japanese)
Extra lingua...
Developmental defects like
amelogenesis imperfecrta,
hypoplasia, gemination, dens in
dente, odontomas, fusion,
congenital ...
Diastema:
Midline diastema & presence of fibrous
tissue attachment provides excellent
chicken & egg routine for controvers...
Heavy occlusion against the
lingual surface of the maxillary
incisors, habits such as thumb
sucking, tongue thrusting, lip...
Premature loss of deciduous teeth
Primary teeth are organs of mastication,
space savers, maintain opposing teeth at
occlus...
If primary second molar exfoliates early _ 2 nd
PM is blocked out.
If maxillary molar drifts mesially, the
mesiobuccal cus...
Prolonged retention & abnormal
resorption of deciduous tooth:
Dentist should maintain the tooth
shedding timetable at abou...
Hypo thyroidism – delayed developmental
pattern, prolonged retention of deciduous
teeth
Increased gonadotropic harmone – d...
Retained root fragments of
deciduous tooth:
Deflect permanent tooth
Prevent proper contact between permanent
teeth
Serve a...
Delayed eruption of permanent
teeth:
Endocrine disorders – hypothyroidism
Congenital absence
Supernumerary tooth
Deciduous...
Bony crypt occasionally forms in
line of eruption of permanent
teeth .
A check of timetable in other
segments should be ma...
Abnormal eruptive path
Secondary manifestation of primary
disturbance.
A blow is a possible
Early ortho intervention of cl...
Coronal cyst
3rd molars are impacted due to
abnormal path of eruption
Ectopic eruption.
Sign of arch length deficiency
ind...
Ankylosis :
6 – 12 years
May be due to injury
Part of PL is perforated & bony bridge is
formed joining the laminadura & ce...
Dental caries:
Premature loss of teeth both primary &
secondary
Abnormal axial inclination
Over eruption
Bone loss
Not onl...
Improper dental restorations:
Over extended proximal restorations
cause irregular mandibular incisors .
Tight contact caus...
www.indiandentalacademy.com
Leader in continuing dental education

www.indiandentalacademy.com
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Development of dentition & occlusion /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

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Development of dentition & occlusion /certified fixed orthodontic courses by Indian dental academy

  1. 1. DEVELOPMENT OF DENTITION & OCCLUSION www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3. Role of occlusion in maintaining aesthetics and function of dentofacial complex: Term occlusion is derived from Latin word occlusio defined as the relationship between all the components of the masticatory system in the normal function dysfunction and parafunction www.indiandentalacademy.com
  4. 4. Occlusion is an anatomic and physiologic complex present when the opposing teeth are in contact. It consists of positional relations , the stresses directed to the supporting structures their resistance to the stresses , the form and arrangement of the teeth , the influencing parts of the components of the TMJ & the neuromuscular mechanism responsible for mandibular movements. www.indiandentalacademy.com
  5. 5. The development of dentition is closely associated with the morphology & growth of the face & the way in which the functions of the orofacial region are exercised. The size of the two jaws , their anteroposterior relationship , the vertical dimension as well as the changes occurring during growth in these components play an essential role in the development of the dentition www.indiandentalacademy.com
  6. 6. Why 2 sets of teeth? The possession of 2 sets of teeth in mammals imparts the advantage of equipping the young in a short time , with the teeth capable of cutting crushing & grinding , while the much larger , more durable & slowly formed permanent teeth are being constructed & erupted. www.indiandentalacademy.com
  7. 7. The deciduous or temporary dentition is gradually shed & followed by a permanent or succedaneous dentition . This is a mechanism that adjusts the size of dental battery to the growing face and jaws. Since teeth once formed cannot increase in size a second dentition consisting of larger & more teeth is required for the larger jaws of the adult www.indiandentalacademy.com
  8. 8. Factors that cause the resorption of deciduous dentition: The physiologic process resulting in the elimination of the deciduous dentition is called shedding or exfoliation. The pressure generated by the growing and erupting permanent tooth dictates the pattern of deciduous tooth resorption. www.indiandentalacademy.com
  9. 9. Cells responsible - odontoclasts. Histochemically characteristic feature - alkaline phosphatase. Alk phosphatase activity occurs with in the vacuoles. www.indiandentalacademy.com
  10. 10. found - on surfaces of roots in relation to advancing permanent teeth. Also found in root canals & pulp chambers of resorbing teeth lying against the predentin origin - same as osteoclasts.( monocytes circulating in the blood originally gives rise to all the different tissue macrophages.) www.indiandentalacademy.com
  11. 11. Sequence of events in resorption of dental lamina: pressure If succesional tooth germ is missing , shedding of deciduous teeth is delayed Followed by extracellular dissolution of organic matrix osteoclast Alk phosphatase activity www.indiandentalacademy.com Initial removal of mineral
  12. 12. Experimental removal of permanent tooth germ delays but not prevents shedding of deciduous teeth Forces of mastication applied to the deciduous teeth are capable of initiating the resorption. As the individual grows , the muscles of mastication increase in size & exert forces on the deciduous teeth greater than its periodontal ligament can with stand. This leads to trauma to the ligament & the initiation of resorption www.indiandentalacademy.com
  13. 13. Stages of dental development The first local changes occurring in tooth development occurs as early as the 6th week of prenatal life. The oral epithelium in the upper & lower jaw thickens , forming the dental lamina from which local buds arise at each point where a tooth will form. www.indiandentalacademy.com
  14. 14. Individual tooth formation proceeds by means of mitotic activity ,particularly in the inner enamel epithelium , until the ameloblasts & odontoblasts are differentiated. The stages of dental development are bud stage, cap stage, bell stage The tooth is an example of typical vertebrate organ starting as an epithelial bud & undergoing complex morphogenesis , www.indiandentalacademy.com
  15. 15. It has become evident that developmental regulatory genes have been conserved to a great degree during evolution & that similar gene network s regulate the development of teeth as of other vertebrate organs. 5 families of signaling molecules are found to be responsible for tooth development. They are BMP ( bone morphogenic protein) TNF alpha Hedge hog www.indiandentalacademy.com WnT
  16. 16. S.M are released from oral ectoderm & they bind to the receptor on ectomesenchymal cells & activate the transcription factors . They enter the nucleus & regulate the expression of genes. The homeobox genes are Msx – 1 & Pax – 9. They again act on oral epithelium & these are responsible for invagination of oral epithelium & development of tooth buds. From cap stage onwards www.indiandentalacademy.com
  17. 17. Path of eruption of permanent dentition: The word eruption refers to cutting of the tooth through the gum.( in Latin erumpere means “to break out”.) permanent incisors & canines first develop lingual to the deciduous tooth germs at the level of their occlusal surfaces & in the same bony crypt. www.indiandentalacademy.com
  18. 18. As their deciduous predecessors erupt they move to a more apical position & occupy their own bony crypts. Premolars begin their development lingual to the predecessors at the level of their occlusal surfaces & in the same bony crypt. They also shift so that they are eventually situated in their own crypts beneath the divergent roots of the deciduous molars. www.indiandentalacademy.com
  19. 19. The permanent molars which have no deciduous predecessors also move considerably from the site of their initial differentiation. For ex the upper permanent molars which develop in the tuberosity of the maxilla , at first have their occlusal surfaces facing distally & swing around only when the maxilla has grown sufficiently to provide the necessary space. www.indiandentalacademy.com
  20. 20. Mandibular molars develop with their occlusal surfaces inclined mesially & only become upright as room becomes available . All these movements are related to jaw growth and may be considered as movements positioning the tooth & its crypts with in the jaws preparatory to tooth eruption www.indiandentalacademy.com
  21. 21. The neuromuscular & osseous movements influencing the eruption of teeth: Pre-emergent eruption Post-emergent eruption juvenile occlusal equilibrium adult occlusal equilibrium. www.indiandentalacademy.com
  22. 22. Pre emergent eruption: Labial or buccal drift Eruptive movement begins soon after root begins to form Processes necessary for pre-emergent eruption resorption of bone & primary tooth overlying the crown of erupting tooth. eruption mechanism. Ex: cleidocranial dysplasia. www.indiandentalacademy.com
  23. 23. Rate of bone resorption & the rate of tooth eruption are not controlled physiologically by the same mechanism. Ex : expts on dog & child Follicle of erupting tooth signals bone resorption Nature of signal – unknown . www.indiandentalacademy.com
  24. 24. Mechanism of eruption: Cross linking of collagen fibers contribute to elasticity of periodontal ligament. Contractions & relaxations of these fibers leads eruption force. Proved by animal expts. www.indiandentalacademy.com
  25. 25. Other possibilities: Localized variations in BP Forces delivered from contraction of fibroblasts. Alterations in the extra cellular ground substances of the PL similar to those that occur in thixotropic gels. www.indiandentalacademy.com
  26. 26. Post emergent eruption: Once tooth emerges into oral cavity it continues till it approaches the occlusal level & is subjected to the forces of mastication. Post emergent spurt. www.indiandentalacademy.com
  27. 27. Juvenile occlusal equilibrium: Phase of very slow eruption Rate of eruption parallels rate of jaw growth. Disturbance in coordination between these two leads to orthodontic problems. Since the rate of eruption parallels the rate of jaw growth pubertal spurt in eruption of teeth accompanies the spurt in jaw growth. www.indiandentalacademy.com
  28. 28. Adult occlusal equilibrium When pubertal growth spurt ends , a final phase in tooth eruption called the adult occlusal equilibrium is achieved. During adult life , teeth continue to erupt at a n extremely slow rate. www.indiandentalacademy.com
  29. 29. If its antagonist is lost at any age , a tooth can again erupt at more rapidly , demonstrating that eruption mechanism remains active and capable of producing significant tooth movement even late in life. Occlusal wear of teeth is compensated by eruption of teeth. www.indiandentalacademy.com
  30. 30. If severe occlusal wear occurs – cannot be compensated by eruption hence lower facial height decreases. In few cases any wear of teeth is compensated by additional eruption & facial height remains constant or even increases slightly in 4th 5th & 6th decades of life www.indiandentalacademy.com
  31. 31. Neonatal line: Despite the physical adaptations that facilitate it, birth is a traumatic process. For a short period growth ceases & there may be a small decrease in weight during first 7 – 10 days of life. www.indiandentalacademy.com
  32. 32. Such an interruption in growth produces a physical effect in skeletal tissues that are forming at that time, because the orderly sequence of calcification is disturbed – noticeable line across bones & teeth that are forming at that time. www.indiandentalacademy.com
  33. 33. Natal tooth: First primary teeth do not erupt until approximately 6 months of age. The natal tooth may be a supernumerary one formed by an aberration in the development of the dental lamina, but usually is merely a very early but otherwise normal central incisor. www.indiandentalacademy.com
  34. 34. Eruption of primary teeth: Development of incisors & canines precedes that of the structures that contain them – this explains the overlapping of incisors & canines before birth. This extra space needed is provided by the jaw growth after birth in first 6- 8 months after birth. The extensive early transverse development of both jaws can be realized mainly because of the presence of suture in the median plane of the maxilla & of a synchondrosis in the mandible. www.indiandentalacademy.com
  35. 35. As synchondrosis in the mandible calcifies at about 6 months of age , the potency for transversal growth in the lower jaw is eliminated . In contrast with the situation of the mandible maxilla maintains its rapid median growth potency. Maxillary median suture remains until the development of the two dental arches become coordinated. www.indiandentalacademy.com
  36. 36. The first vertical support associated with interdigitation – the interlocking of maxillary & mandibular posterior teeth occurs when the first deciduous molar attains contact. As rule , those teeth are not centered over each other in such a position that no transverse or sagittal translation will be required to reach correct interdigitation. www.indiandentalacademy.com
  37. 37. In most instances , the large palatal cusp of the maxillary 1st molar arrives with its cone shape with in the crater formed by the occlusal anatomy of the mandibular one. The crater will function as a funnel by which both teeth are directed towards each other in the proper position. www.indiandentalacademy.com
  38. 38.  A required movement of the teeth will be involved will be derived more from a displacement of the maxilla than of the mandibular molar as the structures in the mandible favor such a movement less than those in the maxilla.  The occlusion in the posterior region is established when the deciduous 1st molars have settled. www.indiandentalacademy.com
  39. 39. There after the relation between the two dental arches will stabilize in the transverse & sagittal direction. The deciduous dentition is complete after all the 2nd deciduous molars have attained occlusion, usually at around 2.5 years of age. Diastemata is present between all teeth particularly in the anterior region. www.indiandentalacademy.com
  40. 40. Mandibular teeth occlude slightly lingual with the maxillary ones. The terminal plane of deciduous dentition will be flush. Little changes take place in the deciduous dentition from 2.5 to 5 years. Superiorly & lingually to the deciduous teeth the formation of their successors continues in the maxilla. The permanent molars are formed posterior to the dental arches. www.indiandentalacademy.com
  41. 41. First transitional period: Emergence of 1st permanent molar & the transition of the incisors. The anteroposterior relation between the two opposing molars after emergence depends on their positions previously occupied with in the jaws, the sagittal relation between the mandible & maxilla & the ratio of mesiodistal crown dimensions of the mandibular & maxillary deciduous 2 nd molars www.indiandentalacademy.com
  42. 42. If the crown dimensions of the max & mand deciduous second molars are same , the sagittal relation between corresponding M & D surfaces will be similar. A mesial shoulder will be present anteriorly at the mesial surfaces & posteriorly at the D surfaces of the teeth. The terminal plane will have a M step. Baume (journal of dental research, 1950 ) classified the relationships of primary teeth into straight terminal plane, mesial step & distal step. www.indiandentalacademy.com
  43. 43. If the mand 2nd deciduous molar is considerably larger than the maxillary one then the distal surfaces will lie in one plane. Under these occlusal conditions a flush terminal plane is present. One month or more may pass between the emergence of corresponding left & right incisors in one jaw. www.indiandentalacademy.com
  44. 44. Early mesial shift In pts with spaced primary dentition & st terminal plane relationship of molars , the permanent molars will erupt at around 6 yrs of age & move the primary molars mesially , close the space distal to the primary canines, convert the st terminal plane to mesial step , reduce the arch length in mand dentition & allow the permanent molars to emerge in class I relationship. www.indiandentalacademy.com
  45. 45. Late mesial shift: In pts with closed primary dentition & st terminal plane the permanent max &mand 1st molars emerge into a cusp to cusp relationship as no space exists. At approximately 11 yrs the primary mand 2nd molars are exfoliated & the permanent mand 1st molars migrate mesially into the excess lee- way space provided by the diffs in the mesiodistal dimensions of the primary second molars & the permanent second premolar teeth. Again this reduces arch length ,converts the st terminal plane into a mesial step & provides for a class I relationship of 1st molars. It has been referred to www.indiandentalacademy.com as the late mesial shift.
  46. 46. Incisor liability:(Warren Mayne 1969) Mesiodistal width of permanent incisors are more compared to deciduous incisors. This space is gained by the labial & distal movement of canines thus enhancing the intercanine distance(secondary spacing). The incisor liability is about 1.6 mm on each side. www.indiandentalacademy.com
  47. 47. Safety valve mechanism: During the period of permanent incisor eruption notable amounts of intercanine arch width development occur in both the max & mand dentition. In mand the increase occurs between 6 &9 years for boys & between 6&8 yrs for girls. In maxilla it increases longer to 16 yrs in boys & 12 yrs in girls. This is called safety valve mechanism. www.indiandentalacademy.com
  48. 48. According to Moorrees ( J dent res 1965) the average increase in the mandibular dentition of boys & girls is approximately 3mm ,in maxilla it is approximately 4.5 mm. according to Mayne ( current orthodontic concepts & techniques 1969) permanent incisors erupt labial to the deciduous incisors.Baume estimated that the permanent incisors are 2.2 mm forward of primary incisors in maxilla & 1.3 mm in the mandible. www.indiandentalacademy.com
  49. 49. A small opening in the bony alveolar process is present on the lingual aspect of each deciduous incisor in the upper & lower jaws. This opening forms the oral aspect of gubernacular canal which runs to the crypt of the successor. Gubernacular canal contains the gubernacular cord which which consists of epithelium of the dental lamina. The epithelium dissolves & a C.T strand remains ,which subsequently disintegrates further www.indiandentalacademy.com
  50. 50. The opening of the gubernacular canal on the oral side increases in size with the approach of the associated permanent tooth. The gubernacular canal probably plays a role in the guidance of the direction of eruption of incisors through the bone & in the determination of the spot of emergence. www.indiandentalacademy.com
  51. 51. Inter transitional period: The inter transitional period presents itself in a growing child as a rather stable phase with little changes in the dentition.when only the intraoral picture is considered. However with in the jaws resorption of the deciduous roots & reduction in the cervically surrounding bone takes place. www.indiandentalacademy.com
  52. 52. Root formation of the already emerged incisors & molars continues. The roots of permanent canines, premolars, & 2nd molars gradually increase in length. The space needed for that purpose is is provided by the concomitantly increase in height of the alveolar processes in both jaws. In the inter transitional period the mandible & maxillary dental arches consists of sets of deciduous & permanent teeth. www.indiandentalacademy.com
  53. 53. Between the 4 permanent incisors & right & left first permanent molars , the deciduous canines & & 1st & 2nd deciduous molars are located on each side of the dental arch. Maxillary incisors are labially inclined . A central diastema is present. Frequently no contact exists between centrals & laterals. Like wise a diastema is often present in the maxillary dental arch mesial to the deciduous canine. www.indiandentalacademy.com
  54. 54. Ugly duckling stage:( 9 - 12 yrs) During the eruption of permanent canines, the crowns of permanent canines hit the roots of lateral incisors leading to their distal tipping . It is a self correcting anomaly. Once the permanent canine erupts, the diastema will be closed as the erupting canines apply a mesial force on the incisors. www.indiandentalacademy.com
  55. 55. In mandible the incisors are less labially inclined than in the maxilla. A diastema is seldom present between the mandibular central incisors. All incisor crowns are usually in contact with each other & laterals touch the deciduous canines. www.indiandentalacademy.com
  56. 56. Second transitional period: At approximately 10 yrs of age the 1st deciduous tooth in the post region usually a mand canine sheds. This happens more than 1.5 years after the maxillary LI has emerged & about 1 yr after it has reached the level of the occlusal plane. www.indiandentalacademy.com
  57. 57. During formation maxillary canine & 1st premolar are in close proximity of with each other& overlap vertically. The already calcified distal corner of the permanent canine is directly adjacent to the forming mesial cervical region of the 1st PM. Accordingly max 1st PM shows a concavity on the M surface at the cementoenamel junction.(fossa canina). The premolar erupts first. www.indiandentalacademy.com
  58. 58. A comparable M concavity is absent or present only in reduced form at the maxillary 2nd premolar whose crown morphology strongly resembles that of the maxillary 1 st premolar. Sequence of emergence of posterior permanent teeth in mandible – canine,1st PM, 2nd PM. Maxilla – 1st PM,2nd PM,canine. www.indiandentalacademy.com
  59. 59. Variations may occur in the sequence of emergence with a restriction that as a rule the 1st PM precedes the permanent canine in eruption. In majority of cases the 2nd permanent molar emerges after all the deciduous teeth have been lost& replaced. The transition in lower jaw usually runs ahead of that in the upper www.indiandentalacademy.com
  60. 60. During the replacement of deciduous canines & molars by premolars, leeway space is utilized. The deciduous 1st & 2nd molars are wider in mesiodistal dimension compared to premolars. This leeway space is around 2.5 mm in upper arch & 1.5 mm in lower arch. www.indiandentalacademy.com
  61. 61. Abnormalities in dental arches The most frequently occuring abnormality in the dental arches is a discrepancy between the needed & the available dental arch perimeter. Concerning the individual teeth , abnormalities in size shape number & position. www.indiandentalacademy.com
  62. 62. Deviation in the number of teeth in the deciduous dentition is rare.they are regularly encountered in the permanent dentition. Agenensis occurs quite often. The sequence of diminishing frequency in agenesis is 3rd molars , max lateral incisor, mand 2nd PM, mand incisor, max 2nd PM. www.indiandentalacademy.com
  63. 63. Supernumerary teeth can be encountered in the dental arches & particularly in the mand & max incisor region. most frequently a supernumerary tooth occurs between two max central incisors. May form at any time before birth or at 10 –12 years of age. Most commonly found in maxilla. www.indiandentalacademy.com
  64. 64. Anomalies in size MD width is more in males compared to females & it is more pronounced in permanent teeth. Anomalies are more common in mand 2nd PM region. One or more teeth fuse with neighbouring teeth. www.indiandentalacademy.com
  65. 65. Anomalies in shape: Peg shaped lateral Cingulum quite prominent Sharp marginal ridges (particularly Japanese) Extra lingual cusp on mand 2nd PM www.indiandentalacademy.com
  66. 66. Developmental defects like amelogenesis imperfecrta, hypoplasia, gemination, dens in dente, odontomas, fusion, congenital syphilitic aberrations such as hutchinsons incisors & mulberry molars www.indiandentalacademy.com
  67. 67. Diastema: Midline diastema & presence of fibrous tissue attachment provides excellent chicken & egg routine for controversy. Faustin weber noted the following as causative factors. They are Microdontia, Macrognathia, Supernumerary teeth(mesiodens), peg shaped lateral, missing laterals. www.indiandentalacademy.com
  68. 68. Heavy occlusion against the lingual surface of the maxillary incisors, habits such as thumb sucking, tongue thrusting, lip biting, lip sucking, midline cysts. www.indiandentalacademy.com
  69. 69. Premature loss of deciduous teeth Primary teeth are organs of mastication, space savers, maintain opposing teeth at occlusal level. When there is generalized lack of space, primary canines exfoliate faster to give space for erupting incisors. This is often a clue for guided extraction of deciduous teeth & possible removal of 1st PM. www.indiandentalacademy.com
  70. 70. If primary second molar exfoliates early _ 2 nd PM is blocked out. If maxillary molar drifts mesially, the mesiobuccal cusp rotates lingually. If mandibular molar drifts rotation is less but it tips mesially. Permanent 1st molar is lost in many children due to caries. It leads to shortening of arch length on that side ,tipping of contiguous teeth, over eruption of opposing teeth, periodontal implications www.indiandentalacademy.com
  71. 71. Prolonged retention & abnormal resorption of deciduous tooth: Dentist should maintain the tooth shedding timetable at about the same level for each of the 4 buccal segments. If dental developmental age is abnormally advanced or retarded a check into endocrine history should be made. www.indiandentalacademy.com
  72. 72. Hypo thyroidism – delayed developmental pattern, prolonged retention of deciduous teeth Increased gonadotropic harmone – dental dev markedly accelerated because maturation occurs early ,crowding is mandatory. Cortisone & other steroids are frequently used in treatment of a variety of general diseases.dental dev pattern may become abnormal. Hence medication may be the ultimate cause. www.indiandentalacademy.com
  73. 73. Retained root fragments of deciduous tooth: Deflect permanent tooth Prevent proper contact between permanent teeth Serve as foci for cysts ocassionally Rupture of periodontal membrane at one or more points establishing a bony bridge between tooth and lamina dura preventing normal eruption www.indiandentalacademy.com
  74. 74. Delayed eruption of permanent teeth: Endocrine disorders – hypothyroidism Congenital absence Supernumerary tooth Deciduous root Mucosal barrier – if erupting force is not vigorous , the mucosa can effectively stop the erupting tooth for a considerable period of time www.indiandentalacademy.com
  75. 75. Bony crypt occasionally forms in line of eruption of permanent teeth . A check of timetable in other segments should be made before deciding to curette bone barrier. www.indiandentalacademy.com
  76. 76. Abnormal eruptive path Secondary manifestation of primary disturbance. A blow is a possible Early ortho intervention of class II cases trying to move maxillary dentition back can cause maxillary 2nd molar to erupt in cross bite or can impact 3rd molar. www.indiandentalacademy.com
  77. 77. Coronal cyst 3rd molars are impacted due to abnormal path of eruption Ectopic eruption. Sign of arch length deficiency indicate the need of surgical or guided extraction. www.indiandentalacademy.com
  78. 78. Ankylosis : 6 – 12 years May be due to injury Part of PL is perforated & bony bridge is formed joining the laminadura & cementum Accidents or trauma Endocrine conditions Congenital conditions like cleidocranial dysostosis www.indiandentalacademy.com
  79. 79. Dental caries: Premature loss of teeth both primary & secondary Abnormal axial inclination Over eruption Bone loss Not only to prevent infection & loss of teeth but to maintain integrity of dental arches www.indiandentalacademy.com
  80. 80. Improper dental restorations: Over extended proximal restorations cause irregular mandibular incisors . Tight contact causes elongation of tooth being restored or approximating teeth. Loose contact permits easy packing of food in the interdental area leading to caries. www.indiandentalacademy.com
  81. 81. www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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