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07. The Deciduous Teeth - Dentition
 

07. The Deciduous Teeth - Dentition

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    07. The Deciduous Teeth - Dentition 07. The Deciduous Teeth - Dentition Presentation Transcript

    •  Deciduous teeth are that teeth which function during childhood and then they are shed and replaced by permanent teeth. The word deciduous comes from a Latin word meaning to fall off.  There are 20 teeth in the deciduous dentition; 10 maxillary and 10 mandibular teeth.  These teeth emerge in children between the ages of 6 months and 2 years  Beginning at the age of 6 years these teeth are gradually replaced by the teeth of the permanent dentition.
    • Names: Temporary teeth, milk teeth, baby teeth. Primary teeth, all are improper terms because they means that deciduous teeth are useful for a short period only. Importance of deciduous teeth a-They need for many years from 6month to 12 years. b-They are importance during growth and development for proper arrangement of the permanent teeth and proper development of the dental arches.
    •  Eruption of the deciduous teeth Start from 6month to 2years and root completed at 3years. 18m 8m 7m 14m 24m 20m 12m 16m 6m 7m
    • Shedding of the deciduous teeth  Shedding is the process of exfoliation of the deciduous teeth.  Shedding dates:  Upper and lower central incisors at 7years.  Upper and lower lateral incisors 8y.  Lower canine and first molar 9y.  Upper molar and lower second molar at 10y.  Upper canine 11y.  Roots resorped first at the apex and continues in the direction of the crown until the entire root is resorped completely then crown is lost due to lack of support.
    • From 6m to 6y deciduous dentition. From 6y to 12y mixed dentition. Over 12 years permanent dentition. Retained deciduous tooth: Any deciduous tooth remain in the mouth of the child beyond the age of 12 years.
    •  Smaller in size than the permanent teeth.  The enamel is whiter in color and more opaque which gives the crown a lighter color than that of the permanent teeth.  The enamel of the deciduous teeth is less mineralized, more permeable and more easily worn down.  They have shorter crowns with respect to their roots.  The enamel of deciduous teeth ends suddenly at the cervical line, while in the permanent it tapers gradually towered the neck of the teeth .
    • *The crowns are more bulbous, because they are wider MD compared to their crown length. *The crown of deciduous teeth are more constricted cervically as they are narrower at their neck. *The crown of deciduous teeth have prominent cervical ridge in anterior teeth (ABC) in posterior teeth cervical ridge much more pronounced especially upper and lower D.  The crown of the deciduous teeth have more flattened and smooth no depression or perikymata on the labial surface of anterior teeth. * Cervical line in deciduous teeth is more or less straight not curved as in permanent teeth. *There is no root trunk, root divided immediately at the neck of the tooth.
    •  Roots of molars are more divergent to accommodate tooth germ of permanent successors.  Crown to root ratio is greater than permanent 1 to 2 while in permanent 1 to 1.5.  Roots are thin or slender.  The second molar roots are spread widely than the first deciduous molar.  All deciduous teeth undergo calcification before birth while only the first permanent molar show calcification at birth.  There is no mamelones on the incisal edges of anterior teeth.   The molar crown have a narrow chewing surface buccolingually. The cusps of the molars are short, the ridges are not pronounced and also the occlusal and surfaces groove and depressions not deep.
    • The pulp of deciduous teeth  Deciduous teeth have large pulp chamber, higher pulp horn, limited dentine thickness particularly in lower second molar.  The enamel of primary molars is thinner and has more consistent depth.  The enamel rods at the cevical slope occlusally instead of gingivally as in the permanent teeth.
    • Constricted neck Sharp cusp    (a) labial surface is convex ,no developmental lines, MD width greater than CI length. MI angle is sharp and DI angle is rounded. IR is straight. Root is cone shape and taper to the apex. (b) crown smaller than (a) ,CI greater than MD,2 angles are rounded. Root similar to A but longer. M slope greater than D slope, MCA and DCA at the same level about middle of the crown .Well developed long and sharp cusp .Neck more constricted . M and D outline are convex .Root is long slender tapering and inclined distally.
    • MMR DMR LF    LR 2L fossae (a) geometric outline is trapezoid. Well developed M&DMR, deep lingual fossa, highly developed cingulum may extend toward the incisal ridge to the extent that partially divides the lingual fossa into mesial and distal fossa. Root is very narrow resembling a ridge extends for its whole length. (b) smaller than (a). (c) pronounced cingulum, pronounced M&DMR ,pronounced DIC&MIC ridges ,lingual ridge well developed its continuation incisally give tubercle on cusp tip. Root is narrow lingually due to the lingual convergence.
    • Root convex with DG CL convex toward IR Greater Labiolingual (a) geometric outline is triangular . C.L is convex toward the incisal ridge. Labiolingual dimension greater in compared to the crown length especially at cervical third. Also crown appear thick labiolingually in the cervical and middle third. Root is convex and has deep DG or concavity.  (b) similar to (a).  (c) show much greater labiolingual dimension at cervical third. Root is very long. This allows maximum strength to the canine to resist force applied on it during function.
    •  (a) labiolingual greater than MD. Labial surface broad & smooth, lingual surface tapers toward the cingulum, M&D surfaces relatively broad to allow proper C.A. with adjacent teeth. IR is straight and centered labiolingually.  (b) similar to (a) but it smaller.  (c) crown appear diamond with pronounced cervical ridge, MCA&DCA and cingulum. The cusp tip is distal to the center because M slope longer than D slope.
    • D  (d) M labial surface is flat and has no DG. M&D sides tapers from C.A. to a narrow cervix. Root long and tapers to pointed apex.  (e) similar to (d) but it is larger in all dimension. IR sloped toward distal side so the distal contact area more cervically.  (f) M slope shorter than D slope.
    •    (d) lower central incisor, all elevations are well developed. Lingual fossa is flattened or slightly concave at the middle third of the crown. Crown and root is narrower than labial due to the lingual convergence. (e) lower lateral incisor, lingual fossa more concave than lower central incisor lower central incisor (d). Cingulum more developed than lower central incisor (d). IR slope downward D. (f) lower canine similar to upper deciduous canine.
    • (d) lower central incisor no lingual inclination, IR is centered over the axis of the root. Well developed cervical ridge and cingulum. Root is flat and tapers to blunt apex.  (e) lower lateral incisor lingual inclination, C.R. and cingulum less developed.  (c) lower canine similar to upper canine but C.R. and cingulum less developed. 
    • A B C A lower central incisor, incisal ridge is straight and centered labiolingually. Labial surface is flat or slightly convex. Also lingual surface is flat.  B lower lateral incisor, incisal ridge is inclined toward the distal side.  C lower canine crown appear diamond . All ridges less prominent than upper canine. The lingual ridge is raised in the incisal third & then less distinct . 
    • Mandibular lower central deciduous incisor Labial aspect Lingual aspect Mesial aspect Distal aspect
    • Mandibular lower lateral deciduous incisor labial lingual Mesial Distal
    • Mandibular lower deciduous canine Distal Labial Lingual Mesial
    • Maxillary first & second deciduous molars Maxillary first molar Maxillary second molar
    • Buccal aspects of upper deciduous molars Upper (E) Upper (D) Well developed cusps MBCR Occ. outline slightly scalloped  Upper D (a): geometric outline of the crown is trapezoid. Buccal surface is very smooth with little evidence of developmental groove  Occlusal outline has a slightly scalloped appearance with no definite cusp form.  There is mesio-buccal cervical ridge (MBCR)  3Roots are seen MBR, DBR & LR  Upper E (b):. Geometric outline of the crown is trapezoid.  Crown converge markedly from the contact area to the cervical line.  MBC equal DBC or MBC larger than DBC.  3Roots are seen MBR,DBR& LR. Roots are thicker than D  The roots of both molars are divergent ,long &slender ,no root trunk. 
    • Lingual aspects of upper deciduous molars Trapezoid outline Upper (D) Upper (E) Lingual narrower than buccal MLC DLC MMR D Tubercle of carabelli MLC DLC Crown converge lingually. MLC largest &sharpest cusps. DLC is very poorly defined small and round. MMR is prominent. DBC is larger and better developed than DLC so may be seen. D may be 3cusped type one lingual cusp with no developmental groove.  E MLC is long & well developed. DLC less developed. Tubercle of carabelli is seen related to MLC.
    • Mesial aspects of upper deciduous molars Outline form is trapezoid with the shortest of uneven sides is occlusally. Upper (D) Board& flat M B R L R M B R L R Upper (E) MBCR         D Crown is constricted at the occlusal 1/3 than cervically. Crown has pronounced cervical ridge buccally (MBCR). C.L. shows slight curvature occlusally. Roots MBR, LR . The DBR hidden by MBR. E crown is o.5 mm longer than D. B-L dimension is 1.5-2 mm longer than D . Roots are 1.5-2 mm longer than D. Cervical line almost straight line. MBR is broad & flat. LR is extend lingually beyond crown outline, It is long& slender& it is above middle 1/3 curves buccally.
    • Distal aspects of upper deciduous molars L R Poorly developed DL C    L R MBR D B R CL straight MLC Long& DBCsharp D B R DLC DBC Lingual outline is semicircular MB R Bifurcation at lower level Buccal outline is straight D Crown converge distally (narrow than mesially). Cervical ridge is not so marked as mesially. Cervical line is straight or slightly curved occlusally. E also it is narrower distally than mesially. The lingual outline appears semicircular, while the buccal outline is straight. DB&DL cusps are about the same length. Cervical outline is straight. All three roots seen from this aspect. The point of bifurcation between DB& L roots is higher towered the crown than any other aspects.
    • Occlusal aspects of upper D Rectangular with oblique ridge B MBC Rectangular Distal occlusal groove D D MBC DBC DLC Heart shape MBCR B MLC MBC M 3Supplemental groove L B DBC MB C LC L D M DBC DLC OR MLC L R M Hexagonal BC LC
    • Occlusal aspects of deciduous upper molars       D the occlusal surface is rectangular. The crown converge lingually & distally. The occlusal surface presented , CF&MTF the two fossae are connected by central developmental groove. Central pit in the central of the center fossa from it extended B groove. Mesial pit in the MTF give three grooves one buccally, one lingually & one mesial. Oblique ridge found between ML&DB cusps. If there is no oblique ridge central developmental groove extend from mesial pit & give disto-occlusal groove . Disto-occlusal groove give lingual groove between ML&DL cusps. E The occlusal surface is rhomboidal, has 4 well developed cusps & small fifth cusp. Oblique ridge between ML&DB cusps. Central fossa, MTF,DTF, BG,LG,CG. The occlusal surface resemble the occlusal surface of upper 6
    • Mandibular first deciduous molar  This teeth does not resemble any of the other teeth either deciduous or permanent .It appears strange and primitive.
    • The second deciduous molar  It resembles the first permanent molar (lower 6) but it is smaller in size.
    • Buccal aspects of lower deciduous molar        D : geometric outline is trapezoid Mesiobuccal cusp is longer than distobuccal cusp. As in upper D mesiobuccal cervical ridge is prominent (MBCR) makes the cervical line dips downward to outline this shape. There are two roots MR&DR. E: geometric outline is trapezoid, the small of uneven side cervically. 3 buccal cusps are equal in size MBC=BC=DBC. Two roots MR&DR, they are long, slender & diverge M-D at middle and apical 1/3. No root trunk. Distal outline is converge markedly to the C.L. DD DBC BC MBC E DBC MBC D MBCR M. outline is straight Long, slender& diverge roots
    • Lingual aspects of lower deciduous lower molarsroot converge MLC long&  D crown and sharp        lingually. MLC is long and sharp. DLC is well developed and rounded. MMR is well developed (regarded as third lingual cusp). E crown and root converge lingually. MLC=DLC Parts of 3 B cusps may be seen. Mesial part of the crown is longer than distal part. DLC rounded MMR D MLC DLC E
    • Mesial aspects of deciduous lower molars         Geometric outline is rhomboidal. MBC D buccal outline is flat above the MLC Flat convex of the MBCR. It is longer than lingual outline (cervical line extends D upward in B-L direction) MBCR The lingual outline extends out lingually M beyond the confines of root base. root MBC is placed over the root base. Deep Root apex is flat and almost square. DG E: MLC is longer than MBC. Compared to lower 6 the cervical ridge is prominent in lower E & it more Root apex is constricted occlusally( due to the flatting flat & almost of the buccal outline above the cervical square line to buccal cusp tip). M root is broad ,flat & blunt apex sometimes serrated apex. MLC longer MBC E Broad & flat Serrated
    • Distal aspects of lower first deciduous DMR MBC MLC molar        D: distal aspect differs from mesial aspect: 1-crown has an equal length B&L. 2-DBC&DLC are not so long and sharp as MBC&MLC. 3-DMR is less developed than MMR. 4-B outline less curved at the cervical 1/3 . 5-C.L. is straight. 6-Distal root is shorter, more rounded, taper more in its apical third. DLC DBC D root M root
    • Distal aspects of lower second DMR deciduous molar  E: distal aspect differs from distal aspect:  1- Distal surface is narrower than mesial surface MBC&MLC are seen ,also the DLC well developed.  2- DMR is shorter &at lower level than MMR.  3- Distal root tapers more at the apical third. MBC MLC BC DLC DBC D root M root
    • Occlusal aspects of lower deciduous molars Rhomboidal outline       Rectangular outline D : occlusal aspect is rhomboidal in shape. E: occlusal aspect is rectangular in shape. MD dimension at the buccal side larger than MD dimension at the lingual side so the crown converge lingually. Also the crown converge distally . DTF not so well defined as mesial fossa. DMR is not as highly developed as mesial marginal ridge.
    • Buccal Lingual Mesial Distal
    • Buccal Lingual Mesial Distal