endo sheet # 4- by Maha Elrfo3

Lec.4
10-10-2010




last lec. We learn how to do access cavity for anterior teeth weather it is maxillary or mandibular
Q: what did give shape for access cavity ?
A: the cross sectional shape for chamber at level of CEJ .

our lec.
First upper premolar
internal anatomy :
• pulp chamber is wider bucco-palatally than meso-distaly .
• Usually 2 pulp horns (buccal horn is larger than palatal horn ).
• two orifices ( the palatal is the largest ).
• usually 2 canals (palatal canal is wider ).

** there are many reports concerns the NO. of root canals , one of them is vertucci's report (1984):
• 26% one single canal
• 69% two canals →(buccally & palatally)
• 5% three canals → (tow buccally & one palatally)
** if we have 2 root canals ,they are usually with same length (this is important in cleaning & shaping ).

**the root of first upper premolar is usually shorter than the root of upper canine (which is usually the longest root canal in all teeth ).

** the roots are thiner &smaller than upper canine ).

access cavity for first upper premolar :
• oval in shape
• wide bucco- lingually
• narrow mesio-distally
• during the cutting we go 2/3 or ¾ of bucca incline.
• In palatal cusp we go to ½ of palatal incline .

Note: mesial concavity at the cemento- enamel junction .this triangular area is very susceptible to perforation .so during the cavity preparation we have to be carefully centralized because if I go a little bit mesially I would perforate the mesial concavity area .

** if we have 3 orifices ,the access cavity shape will differs as follow :
• the shape will be triangle
• the base of the triangle toward buccal surface

how to start access cavity :

• starting point in central groove ,we go throw the groove perpendicular (or parallel) to occlusal surface in enamel then down to dentin (1.5mm by high speed bur ).
** note : here ,perpendicular to occlusal surface =parallel to long axis of tooth .
• Drop-in
• unroofing ( by slow speed bur )
• identify all canal orifices ,then we move to cervical dentin bulge & remove it

note :if we found single canal the access cavity will be small,but if we
found 2canals we start extending (enlarge )of access cavity bucco-lingually.
Important note :
how to know what is the shape of cavity that we should drill ?
A:usually if the tooth have two orifices ,each one located centrally in each cusp ,so if we drill centrally and we do not find the orifice this mean that the tooth have three orifices and there are two buccal orifices : one mesially and one distally .



Upper second premolar :

internal anatomy :
• two pulp horn (buccal is larger)
• pulp chamber wide bucco-lingualy than meso-distally
• usually single-wide canal
• the root(roots )is proximal to maxillary sinuses
• number of roots according to Vertucci's report :
70% single canal (in center)
25% two canals (palatal and buccal )
1% three canals ( two buccal one palatal)

note : mostly the upper first premolar has 2canal
mostly the upper second premolar has one canal

features of access cavity :
• oval in shape
• wide bucco-lingually
• narrow mesio-distally

if we have single canal ,the access cavity is small,oval & in the center of tooth
if we have 2 canals ,the access cavity will be identical to that of upper first premolar
if we have 3 canals ,the access cavity will be triangular & the base toward buccal surface


sometimes the root canal had injury for long time ,in this case some root will calcified & build dentin gradually.

Lower first premolar

lower premolar sometimes they are very difficult to clean because there


are many variations in their anatomy & if the canal did not cleaned completely the reinfection may occur .

internal anatomy of root canal
• bucco-lingually is wider than mesio-distally
• in case of two canals the buccal will be the largest
• the first third of root canal is oval then tend to be round .
• the access cavity is oval
• the most common configuration of root canal is type I , IV , V(most difficult .


How many root canals in lower first premolar?

• 74% one canal in center of bulb chamber
• 25.5% tow canals (buccle &lingual )
• 0.5% three canals
** nearly like the upper second premolar

character of access cavity :

• oval in shape
• wider bucco-lingually
• narrow mesio-distally
• we make cutting to ½ of cusp tip


how to make access cavity
• starting point is half way line of the lingual incline of the buccal cusp (not in the center because the buccle cusp is larger than lingual cusp .

*same steps as in upper premolars except we start drilling



perpendicular to enamel then we move parallel to long axis of root
because there is angle between root & crown .


note;
half way : start from the central groove


lower second premolar

internal anatomy :
• similar to lower first premolar
• bulb chamber is wider bucco-lingually
• narrow mesio-distally
• 2 bulb horns (the lingual one is larger )
• oval shape root canal along the length of root)
• no. of roots canals:

• 87.5 % single canal
• 12.5 % two canals
• 0 % three canals


how to make access cavity :

same steps in lower first premolar ,except we start cutting 1/3
from the way of lingual incline of buccle cusp because the angle
between crown & root is less than that angle in lower first
premolar .


Lec. #4
sun 10/10/2010

shadi .. it is no. 4 not 3

thx Mohammad ..