Dental Anatomy PDF

8 Teejan Lajneh Wisdom Aseel Sharaireh  MOLARS By definition: molars are the most posterior teeth at the back of mammal's mouth and are used for the grinding of food. -Three molars per quadrant in the permanent set of teeth (12 permanent molars) -Two molars p...

8 Teejan Lajneh Wisdom Aseel Sharaireh  MOLARS By definition: molars are the most posterior teeth at the back of mammal's mouth and are used for the grinding of food. -Three molars per quadrant in the permanent set of teeth (12 permanent molars) -Two molars per quadrant in the deciduous dentition (8 deciduous molars). Unique in their design than any other tooth in the oral cavity. The largest and strongest teeth in the mouth by virtue of their crown bulk size and root anchorage in bone. Virtue: ‫بفضل‬ ❖ The Largest occlusal surfaces of any teeth. ❖ Three to five major cusps. ❖ Lower permanent molars: always 2 lingual cusps. ❖ Upper permanent molars: always 2 buccal cusps. ❖ Lower molars: 2 roots. ❖ Upper molars: 3 roots. MOLARS Unprecedented/ Accessional/ nonsuccedaneous They are NOT preceded by primary teeth. Permanent molars are accessional teeth without primary predecessors. In contrast permanent incisors, canines and premolars are succedaneous )successional teeth(.  Note : Third molar has no teeth distal to it. MOLARS Functions: Aesthetic Masticator Occlusal FUNCTIONS OF MOLARS The primary functions of the teeth are for: Mastication/ Swallowing/ Speech/ Expressions /Psychologic Aesthetics/Cranio-mandibular stabilization. Masticatory -Molars are chewing teeth; they mainly crush and grind the food and they perform the major portion of the work in the mastication and comminution of food. -they slice food into particles that are small enough to be swallowed and digested in the digest tract Aesthetics Aesthetics are not restricted to the six anterior maxillary teeth and premolars. In large smiles, THE FIRST MOLAR CAN BE SEEN AND HIGHLY CONTRIBUTE TO AN AESTHETIC SMILE DESIGN. In most people, during laughing, second molars can be seen as well! Occlusal The bulky size and strong multiple roots of molars anchor these teeth firmly in the jaws, providing a stable foundation for the muscles of mastication. Bite Force The bite force generated by molars is impressive! In an average adult female, the second molars can exert a force of up to 2300 N, which is equivalent to lifting around 234.5 kg..The preservation of VERTICAL DIMENSION of the jaws also contribute to the overall FACIAL DIMENSIONs and thus the overall facial aesthetic.. Anna Hathaway You can see two molars of hers while smiling. Angelina Jolie You can see both her upper and lower molars when she smiles wide.  MAXILLARY MOLARS ❖ 6 MOLARS IN THE MAXILLA ❖ POSTERIOR TEETH ❖ 3 OR MORE CUSPS: AT LEAST 2 BUCCAL CUSPS AND ONE OR MORE LINGUAL CUSPS. ❖ 3 ROOTS: 2 BUCCAL AND 1 PALATAL ❖ POSITION: Distal to second premolars and Mesial to none! Disto-lingual cusp shrinks in size when going posteriorly to almost being missing in the 3rd molar. Bucco-lingual dimension is larger the mesio-distal dimension. OBLIQUE RIDGE: Mesio-lingual cusp to disto-buccal cusp (Exist in the maxillary molars only). 1st molar is the largest & shows the least morphological variation while 3rd molar is the smallest & shows the most morphological variation!  MAXILLARY FIRST MOLAR 4 developed functional cusps (MB/ DB/ MP/ DP) and 1 supplemental cusp called the “Cusp of Carabelli” or “Carabelli's tubercle”(on the mesio Remember that: cusps lingual cusp only) of the lingual side of Mesio lingual cusp is the largest. upper molars, are the functional cusps BUCCAL and Distal convergence! Three roots. OCCLUSAL VIEW: MESIAL MARGINAL Mesial triangular fossa It has a pit RIDGE: is longer & more - MB & ML supplementary prominent than the grooves DISTAL MARGINAL Distal triangular fossa RIDGE It has a pit - DB & DL supplementary Oblique ridge grooves Two distinct components: (by the oblique ridge) -TRIGON -Bears MB, ML & DB cusps -Tricuspate triangle -Talon (looks like a tail of a bird) - Bears DL cusp & DMR (distal marginal ridge) -Located DL to the tricuspate triangle -Well developed in 1st molar & undergoes reduction in size in 2nd & 3rd molars. Two Major Fossae: 1-Central fossa: Central pit Buccal groove Distal groove Central groove 2-Distal fossa: D pit DL groove or distal oblique groove which continues as the L groove BUCCAL VIEW: Remember: a pit is often the site of the onset of dental caries. -The mesio-buccal and disto-buccal cusps dominate the facial outline. -MB & DB cusps are of almost equal height. -Mesio-buccal is wider than disto-buccal. -Buccal developmental groove separates MB and DB cusps and terminates halfway the crown height in the BUCCAL PIT. M -Mesio-lingual cusp is the largest it can be seen from this aspect. -All three roots are visible (palatal+DB+MB). -The buccal roots present a 'plier handle' appearance with the larger and longer lingual root centered between them. -The bifurcation between the MB and DB roots starts at the end of the root trunk on the junction between Cervical & middle thirds. -Mesio-Buccal root is usually the smallest but it has a curvature and might have two canals. Clinical notes! -The bifurcation between the MB and DB roots starts at junction between Cervical & middle thirds. → CLINICAL SIGNIFICANCE: periodontal disease reaching bifurcation: prognosis -Mesio-Buccal root is usually the smallest, but it has a curvature and might have two canals. → CLINICAL SIGNIFICANCE: endodontic treatment of this tooth needs proper inspection for the second Mesio-Buccal canal (MB2). In a study: the MB2 canal was present in 80% of specimens. -Mesial contact area: 3/4 the distance from cervical D M line to mesial marginal ridge. -Distal contact areas: 3/5 the distance from cervical line to distal marginal ridge. LINGUAL VIEW Unequal sizes of the two cusps. (mesio-lingual side is more dominant, disto-lingual side is smaller) The fifth cusp of the supplemental “Cusp of Carabelli” can be seen clearly on the ML cusp. (It appears only in maxillary first molars). Disto-lingual groove separates the two lingual cusps Palatal root (largest): M - Tapered with blunt apex - Shallow vertical depression from cervical line to 2/3 of the root length.  MESIAL VIEW Trapezoidal outline: with maximum bucco-palatal dimension is at the cervix of the crown Buccal Maximum curvature: middle of cervical 3rd then outline continues straight Palatal maximum curvature: middle of middle 3rd -Palatal root is narrow & Banana-shaped it curves palatally then buccally at the apex. -Mesial contact area placed more to the buccal Mesial marginal ridge side is marked by several tubercles & supplementary grooves. -Cervical line is slightly curved towards the crown (1 mm). -Deep developmental groove on the root surface on mesio-buccal root. DISTAL VIEW: -Buccal and palatal profiles are similar to in this view to the mesial side. -Cervical line on this side is nearly straight (0 mm) -Distal contact area lies in the centre (bucco-palatally) -Distal marginal ridge rarely has tubercles, it is shorter & less prominent than mesial marginal ridge —> You can see part of the occlusal surface. -Disto-buccal root is the shortest in size. -mesio-buccal is longer, but it is thinner PULP MORPHOLOGY: In a cross sectional view at cervix: 3-4 canals with 3-4 canal orifices The shape of access cavity is triangular with head of triangle towards the mesio-palatal cusp and the base towards the buccal. In a mesio-distal cross sectional view: 2 horns, MB is higher Large Pulp chamber (it has a roof & a floor) Buccal canals are narrow while palatal canal is usually wide. In a bucco-palatal cross sectional view: Pulp chamber is wider 2 horns of equal height Pulp morphology is complicated and variant between individuals. (which makes the treatment difficult) About roots:- Largest + Longest—> palatal Shortest --> disto-buccal Longer than disto-buccal—> mesio-buccal  MAXILLARY SECOND MOLARS Similar to maxillary first molar generally but differ in the followings: The disto-buccal cusp is not as well developed as in maxillary first molar. The disto palatal cusp is smaller. The cusp of Carabelli is absent from this tooth. The roots are of the same length as 1st molar and sometimes longer The roots are slightly less divergent The crown is shorter cervico-occlusally with almost the same width buccopalatally when compared to maxillary first molar OCCLUSAL VIEW: NARROWER CROWN MESIODISTALLY WHEN COMPARED TO THE FIRST MOLAR THE DISTO-PALATAL CUSP IS SMALLER IN THE 2ND MOLAR (SMALLER TALON). DIFFERENCE IN THE SIZE OF CUSPS IS MORE EXAGGERATED: (LARGEST TO SMALLEST): MESIOPALATAL, MESIOBUCCAL, DISTOBUCCAL, AND DISTOPALATAL. MORE VARIABLE PIT/GROOVE PATTERN MORE NUMEROUS SUPPLEMENTARY GROOVE BUCCAL VIEW: Similar to the first molar. The two buccal roots are nearly parallel and they are M more straight compared to 1st molar. Both Mesial and Distal contact points tend to be centered bucco-palatally below the marginal ridges. -Molars become shorter. LINGUAL VIEW: Palatal root is narrower mesiodistally slightly distally inclined. M MESIAL VIEW: The crown is shorter than the first molar The palatal & mesio-buccal roots have less divergence and roots tend to remain within the crown profile. Buccal Maximum curvature: middle of cervical 3rd Palatal maximum curvature: middle of middle 3rd Mesial marginal ridge has less numerous tubercles compared to 1st molar. DISTAL VIEW: A greater portion of the occlusal aspect is visible from this aspect (due to the distal divergence of the molar teeth). PULP MORPHOLOGY: Similar to morphology and access cavity of maxillary first molar but the second mesio- buccal canal (MB2) is less likely to be present. MAXILLARY THRID MOLARS Maxillary (and mandibular) third molars show more developmental variation than any other permanent tooth. They are also frequently congenitally missing. Maxillary third molars vary considerably in size shape and position Some third molars resemble the adjacent second molar; others may have many cusps, small 'cusplets', and many grooves. The crown of this tooth is the smallest of the maxillary molars. OCCLUSAL VIEW: o The outline of the occlusal surface can be described as triangular or “heart-shaped”. o Difference in the size of cusps is even more exaggerated -Largest to smallest: mesiopalatal, mesiobuccal and distobuccal distopalatal is of minimal size. o Oblique ridge is barely visible o Pit/groove pattern is variable o Numerous supplementary grooves BUCCAL VIEW: -The crown: Shorter and smaller in all dimensions. - The mesial buccal cusp is larger than the distal buccal cusp. -Two buccal roots are present, they are shorter but M in commonly found fused. Roots shows a slight distal inclination. -Mesial contact point middle of crown is below the marginal ridges. Technically, the mesial surface is the only 'proximal' surface. The distal surface does not contact another tooth. LINGUAL VIEW: Either one large palatal cusp or two with poorly developed disto-palatal cusp and its poorly developed lingual groove. M Palatal root is often fused to the two buccal roots. MESIAL VIEW: ▪ The rounded or bulbous outline. ▪ Crown profile is irregular ▪ Fused roots DISTAL VIEW: ▪ A greater portion of the occlusal aspect is visible from this aspect compared with 1st & 2nd maxillary molars. PULP MORPHOLOGY: In a mesio-distal cross In a bucco-palatal In a cross sectional view at cervix the pulp looks: sectional view: cross-sectional view: Ovoid Large mesiobuccal horn Mesiobuccal and Narrow mesio-distally & small distobuccal horn palatal horns are of equal prominence  OCCLUSION! In a typical Class I occlusal relationship: Static: maximum Inter-cuspation during centric occlusion: Maxillary 1st molar is ½ tooth distal to the Mandibular 1st molar Maxillary 2nd molar is ½ tooth distal to the Mandibular 2nd molar Mesio-palatal cusp of maxillary 1st molar occludes in the central fossa of mandibular 1st molar Disto-palatal cusp of maxillary 1st molar occludes in the distal triangular fossa of mandibular 1st molar Mesio-palatal cusp of maxillary 2nd molar occludes in the central fossa of mandibular 2nd molar Disto-palatal cusp of maxillary 2nd molar Note! Lingual side of the occludes in the distal triangular fossa of upper molars (and all mandibular 2nd molar upper teeth) is the functional cusp. ‫تمت كتابة هذا الشيت صدقة جارية عن روح والدة زميلنا عمرو رائد من دفعة تيجان‬ ‫دعواتكم لها بالرحمة والمغفرة‬ ‫‪Thank you‬‬ ‫جنه جنه جنه وهللا يا وطنا‬ ‫يا وطن يا حبيب يابو تراب الطيب‬ ‫حتى نارك جنه‬ ‫حتى نارك جنه‬