The document discusses tooth preparation for crowns in different situations. It explains that tooth preparation aims to balance crown conservation and pulp health while achieving aesthetics and strength. Preparation depends on whether roots are weakened or removed. For maxillary first molars, it describes how preparation differs depending on whether the distofacial, mesiofacial, or palatal root is removed. It also discusses preparations when both facial roots are removed. For mandibular teeth, it explains that the mesial root is usually preserved and can be used as an abutment for short or long-span bridges when the distal root is removed.

1. TOOTH PREPARATION
CROWN CONFIGURATION

2. TOOTH PREPARATION
• Tooth preparation represents a balance between the conservative
crown and the healthy pulp also achieving an aesthetic and strong
crown.
• In the case of periodenatlly weakened tooth, the tooth preparation
will be different because of a removal of a root.
• Removing of a root means losing part of support for the tooth.

3. MAXILLARY FIRST MOLAR
• Distofacial: distofacial root of maxillary first molar is one of the most removed
roots, its more susceptible to frequent periodontal involvements and that’s
because of the proximity of the divergent distofacial root to the nearby
second molar
• So in the preparation process the distofacial cusp will be smaller and wont
cause any aesthetic problems because the distofacial cusp is hidden by the
mesiofacial cusp in normal tooth alignment.
• The proximal contact is restored to its normal faciolingual size. And it is very
important that the contours of the distofacial cusp apical to the contact
area have a definite concave shape This insures that crown contours will be
aligned with the root configuration in that critical area, preventing
impingement on the gingiva.

4. MAXILLARY FIRST MOLAR
• Mesiofacial root: the loss of mesiofacial root will cause a loss of a big
support for the tooth because it contains 25-36% of first molar root
area.
• The preparation for this kind of tooth tends to be more triangular
configuration because of the greater faciolingual dimension of the
root that has been removed.
• there will be a concavity gingivofacial to the proximal contact on the
mesial surface of the crown.

5. MAXILLARY FIRST MOLAR
• Palatal root: In this type of tooth the palatal surface of the preparation will
be flat, reflecting the general configuration of the remaining root stump, The
facial cusps of the preparation will be near normal faciolingually. The lingual
cusps will be small, The preparation will have a distinct concave flute on the
facial surface arising from the facial bifurcation.
• Finally there will be no lingual cusp, The presence of lingual cusps would
produce an area that would be hard to maintain hygiene in the
linguogingival segment of the crown.
• It also creates torqueing forces that could tip the tooth lingually,or cause
fracture to the tooth preparation under the crown.

6. MAXILLARY FACIAL ROOTS
• Facial roots (distal and mesial): when both roots gets removed and only
the palatal root stays, the preparation will either have an oval or circular
configuration, it depends on the root it self.
• It should be prepared in a way that occlusal forces wont be directed faciall
that comes from the mandibular teeth.

8. MANDIBULAR HEMI SECTION
• In mandibular teeth the possibilities are fewer because we only have two
roots, one will be removed and one stays and usually saving the mesial
would be more desirable if the opposing teeth did not extend very far distal
to the mandibular first molar.
• The distal root could be used as an abutment for a short span fixed partial
denture replacing the mesial root.
• Occasionally the one root may be used as the distal abutment for a longer-
span fixed partial denture, replacing an entire molar.
• this must be viewed as a high-risk prosthesis, since the remaining distal root
has slightly less than one-third of the alveolar support of the intact tooth with normal
bone.

9. MANDIBULAR HEMI SECTION
• The process of maintaining both roots of molar after the resection is
called as (bicuspidization).
• in this case it is important that they be separated from each other to
have normal gingival embrasure spaces.
• If they are not naturally separated, some measure must be taken to
accomplish it, or the crowns placed over those roots will have no
embrasure space. The result will be a proximal contact that extends
subgingivally to the marginal ridge.

10. MANDIBULAR HEMI SECTION
• We can accomplish this separation orthodontically or we have a term
called (Skyfurcation) which it may be desirable to separate the roots
of a maxillary molar without removing a root This is possible only if the
roots are long, well-supported by bone, and distinctly separate.
• The roots are cut apart and then rejoined by a "crown" that in reality is
a very short interradicular splint with concave connectors from one
root to the other. The occlusal configuration of the splint, or "crown," is
pretty much that of an ordinary molar. This procedure, in effect,
makes the furcation metal and moves it occlusally while separating
the roots This improves access to the furcation and protects a caries-
prone area

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