This document discusses single tooth defects in the posterior quadrants and their restoration. It compares fixed dental prostheses to implants, noting that implants are generally preferred when adjacent teeth are healthy or nearly so. For endodontically treated teeth, a fixed restoration is preferred if sufficient tooth structure remains and occlusion and parafunction are minimal. Considerations for implant placement include anatomic factors, timing of placement, and prosthodontic issues like abutment selection and cement versus screw retention. The goal is to restore function while avoiding complications like fracture, overload, and peri-implantitis.

1. Single tooth defects in the posterior
quadrants
John Beumer III DDS, MS
Robert Faulkner DDS
Division of Advanced Prosthodontics, UCLA
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2. Single tooth defects – Posterior quadrants
Fixed dental prostheses
Delivery 15 year follow-up

3. Fixed vs Implant
Implant is preferred when:
l Adjacent natural teeth are virgin or nearly virgin
l The long term prognosis of the abutments is
questionable due to previous endondotic treatment or
periodontal compromise
Fixed is preferred
l Maxillary 1st molar defects -
l Pneumatization of the maxillary sinus
l Higher failure rates

4. Restoration of endodonticallly treated teeth
vs Implant crown
Endo is preferred (given a successful endodontic
treatment outcome)
l Reasonable volume of tooth structure remains
l Occlusion is ideal
l Parafunctional activity is minimal
Courtesy Dr. C. Goodacre

5. Mandible
Anatomic issues
l Buccal-lingual dimension.
l Thickness of the buccal plate
(immediate load)
l The lingual concavity
l Inferior alveolar nerve
l Mental nerve
Courtesy Dr. N. Barakat

6. Mandible
Anatomic issues
l Buccal-lingual dimension.
l Thickness of the buccal
plate (immediate load)
l The lingual concavity
l Inferior alveolar nerve
l Mental nerve
These structures are best appreciated with CT scans
Courtesy Dr. N. Barakat

7. COURTESY DR N. GEHA
Anterior loop of the mental nerve
Courtesy Dr. N. Barakat

8. Anatomic issues
• Buccal-lingual
dimension.
• Thickness of the buccal
plate (immediate load)
• Maxillary sinus
Maxilla

9. Site enhancement
l Most commonly necessary in the
maxillary premolar region

10. Timing for implant placement
Immediate vs delayed vs staged
Immediate placement - placing the implant at the same time as extraction of the tooth
ª Delayed placement - placement of the implant 2-3 months following extraction.
ª Staged placement - placement of the implant 4-6 months after tooth extraction in
order to allow for bone healing of the extraction site.

11. The intent of these strategies is to minimize bone resorption,
particularly on the facial surfaces of the implant.
ª However, following tooth removal, resorption of labial and lingual
bone occurs regardless of whether an implant is placed into the
extraction site, whether placement of the implant is delayed for 2-3
months, or whether the socket is augmented with bone substitutes.
ª Two hypotheses for resorption
ª Bone resorption is secondary to the contraction of the mucosal tissues
secondary to expression of the WIT genes (Suwanwela, et al, 2011)
ª Compromise of the blood supply to the facial bone following extraction
(DeRouk et al, 2008)
Timing for implant placement
Immediate vs delayed vs staged implant placement

12. Immediate implant placement
ª Tooth fracture, defects with no infection and
intact labial plates
ª Sufficient bone apical to the tooth socket to
insure adequate primary stabilization
ª Patients with significant bone loss are poor candidates. Those presenting with
loss of labial bone with extended biologic width requiring bone augmentation are
best treated with a staged technique
ª Patients presenting with periodontal or peri-apical infections are poor candidates
for immediate placement primarily because of the compromised blood supply
associated with the potential implant site. They are best treated with “staged
implant placement.”

13. Immediate placement
ª Tooth fracture, defects with no infection and
intact labial plates
ª Sufficient bone apical to the tooth socket to
insure adequate primary stabilization
ª Immediate placement helps retain the levels of the interdental papilla, but will not
preserve the bone on the labial side of the implant (Araugo et al, 2005; Botticelli et
al, 2006; Araujo and Lindhe, 2009).
ª If immediate placement is considered, there should be sufficient bone apical to
the tooth socket order to insure adequate primary stabilization of the implant.

14. Delayed implant placement
l Delayed placement - placement of the implant 2-3
months following extraction.

15. Site enhancement
ª Socket augmentation
ª Treatment of fresh extraction sockets with intact
buccal and lingual bone walls.
ª Ridge preservation
ª Augmenting edentulous sites that are insufficient
for implant placement.
ª Ridge reconstruction

16. Ridge preservation
Defined as treatment of fresh extraction sockets with deficient
bone walls in order to maintain ridge contours.
When successful, these procedures
permit placement of implants in ideal
position and angulation. There is no
evidence to indicate which particular
approach might be the most
efficacious (Chen and Buser, 2009).
Courtesy Dr. Krill

17. Site requirements and implant selection
Premolars
Bone volumes necessary
l Implant diameters 4.0-4.5 mm
l There should be sufficient volume of buccal-lingually
and mesial-distally to encompass the implant with at
least 2 mm of bone on each side
l 7 mm of mesial-distal space required
l Implant lengths
l Mandible – 8-10mm
l Maxilla – 10-12 mm
Beware of the use of excessively wide implants in the premolar region.
When the bone is excessively thin on the buccal side of the implant there is
risk of loss of gthe facial plate and apical migration of bone and soft tissue.
10 year follow-up

18. Site requirements and implant selection
Molars
Bone volumes necessary
l Implant diameters 5-6 mm
l Two implants, 4 mm in
diameter are preferred
when the mesial – distal
space permits
l Preferred in extension areas
l Implant lengths
l Mandible – 8-10mm
l Maxilla – 10-12 mm

19. Solitary implants restoring single molars
Avoid the use of 4mm implants - Cantilever effect
When the food bolus is applied to the marginal ridge (B), the restoration
is easily tipped because the crown is supported by such a narrow
platform.
Result: Cantilever forces lead to screw loosening, implant fracture
and overload the bone anchoring the implant.

20. Immediate loading
Generally discouraged in the posterior
quadrants
Immediate placement into
extraction sites
Generally discouraged in the molaer sites
Possible in premolar sites

21. Selection of implants
External hex vs internal interlocking
l Internal interlocking is preferred but
both have been used successfully
Tapered implants
l In extraction sites

22. l Semi-guided or fully guided site preparation
using surgical drill guides is preferred
Surgical placement

23. Prosthodontic Issues - Single tooth defects
Posterior quadrants
ª Internal connections are favored as opposed the
external hex
ª Custom abutments must be designed with
appropriate resistance and retention form if cement
retention is planned
ª Avoid ridge laps
ª Occlusal surfaces
ª Metal vs ceramic
ª Screw retention preferred over cement retention
ª Occlusion is centric only contact
ª Lingualized or buccalized

24. l Internal connections
are favored as opposed
the external hex
although external hex
designs have been
used effectively,
especially in premolar
sites
External hex vs internal connections

25. Custom abutments
CAD-CAM vs Hand Milled
l Hand milled when retention is with cross
linking scews
l CAD-CAM when cement retention is used

26. Abutment materials
l Titanium
l Metal ceramic
l Zirconia
l Not recommended
because of the risk of
fracture

27. Custom abutments
Retention and resistance form
l 3 degree taper
l Add grooves for additional resistance form

28. Custom abutments
Retention and resistance form
l Note the groove
l Important even for crowns
retained with cross linking screws

29. l Hygiene becomes problematic
Avoid ridge laps

30. Maxillary premolars
l Ridge lapping
is discouraged
except in the
esthetic zone

31. Smooth emergence profiles preferred

32. Occlusal materials
Metal vs ceramic
Laminated porcelain occlusal surfaces
are at risk for chipping and fracture

33. Avoid buccal and lingual cantilevers
The occlusal table must be narrowed to
avoid buccal and lingual cantilevers. Molars
should be no wider than premolars as
shown in these two examples.

34. Occlusion
Centric only contact
(during clenching)

35. Occlusion contacts
l Occlusal adjustment
l Two thicknesses of mylar should pass through the implant contact
when the natural teeth hold one thickness

36. Proximal contacts
Proximal adjustments
Two thicknesses of mylar

37. Premolar Sites
4 mm diameter
implants are ideal
for premolar sites
Occlusion should
be centric only
contact
This 1st premolar
site was restored
with a 4 mm implant
fixture and a UCLA
abutment

38. Premolar Sites
This mandibular 1st premolar site was restored
with a 4 mm implant fixture and a conical abutment

39. Single Tooth Restorations Distal
Extension Defects

40. Distal Extension Defects
ª Two implants are recommended
when restoring a single molar in an
edentulous extension area.
ª Note the access for a proxy brush

41. Restoration of single molar sites
Custom abutment Lingual set screw
In this patient, two 4 mm diameter implant were used to
restore the first molar. The width of the occlusal table was
limited to the width of the
natural premolar,
thereby eliminating any
possible buccal or
lingual cantilevers.

42. Restoration of single molar sites
Note:
Hygiene access for proxy brush
Note width of occlusal table

43. Restoration of single molar sites - Solutions
In this patient a wide diameter implant was used to
restore the first molar.
When there is insufficient space for two
implants, a wide diameter implant is preferred

44. Cement vs screw retention
l Screw retention preferred
l Cement retention

45. Problem - Insufficient interocclusal space to design
an abutment with appropriate resistance and retention
form.
Solution – Screw retention
l Another advantage is with screw retention the
emergence profile of the crown is improved
Courtesy G. Perri
Lack of interocclusal space

46. Challenges of cementation
Platform reduction (platform switching)
l If the cement becomes impacted below the margin, its
removal is problematic
l Access is extremely difficult if not impossible without
laying a soft tissue flap
Courtesy Dr. G. Perri

47. Challenges of cementation
l How will you remove the cement if it becomes
impacted beneath the margins of this implant
crown?
l More than likely, you will not given the severity
of the undercut associated with the custom
abutment.
l Therefore, under these circumstances it is
advisable to place the margins supra-gingival.

48. Avoid the use of preformed non-
preparable abutments
Issues of concern
v Position of the cement margin
in relation to the gingival
margin
v Particularly significant in the
anterior region
v Impaction of cement into the
gingival sulcus is highly likely
v Difficulty in seating the crown
because of hydraulic pressure

49. Avoid the use of preformed non-
preparable abutments

50. l Cementing crowns
with platform
reduction
l Cement the crown
extra-orally
Cement retention with platform reduction

51. Complications
l Implant fracture
l Implant overload
l Recurrent screw loosening
l Subgingival cement accumulation leading
to peri-implantitis and loss of the implant

52. The combination of a small diameter implant,
restoring a large mesial – distal space leads
to either screw loosening, implant fracture or
resorption of bone anchoring the implant.

53. Fracture
Implant fractured after 30 months of function
Solitary implants restoring single molars
Cantilever effect

54. Solitary implants restoring single molars
Cantilever effect
Fracture
l Implant fractured after 18 months of function

55. Single tooth restorations in the molar
region – Cantilever effect
This implant was too short and too narrow to
withstand occlusal loads and bone loss caused by
the resorptive remodeling response led to its loss.
4 mm
diameter
implant
Mesial cantilever

56. Subgingival cement accumulation and implant loss

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