This document discusses factors that influence osseointegration and primary stability of dental implants, including implant design characteristics, surgical technique, and loading protocols. Specifically, it covers the processes of osseointegration and how forces on implants can either promote or inhibit bone remodeling. Key implant design considerations like length, diameter, threads, coatings and surface topography are analyzed in terms of their effects on stress distribution and bone-implant contact. The importance of primary stability and factors influencing it like bone quality and surgical skill are also addressed. Loading protocols ranging from immediate to conventional loading are compared.

1. K.V.Arun

2.  Direct bone to implant contact

3. Process of Osseointegration
 Primary stability- mechanical
interlocking
 Contact osteogenesis- direct apposition
 Secondary stability- mineralized nodule
formation
(Berglundh,2003)

4. Forces acting on bone
 Favorable forces
Remodelling of bone
Woven bone formation

5.  Unfavorable forces
• excess load
 Microcracks- osteoclast activation
(Hansson &Werke, 2003)
 Insufficient remodeling-defect forms,
accumulate , coalesce, filled with fibrous tissue
(Misch 2001)
 Severe bone loss- implant failure
(Bruski, 1999)

6. Forces Acting on Bone/Implant
 Compressive forces
 Tensional forces
 Shear forces

7.  Stress= force/ surface area
 Forces may not be controlled
 Surface area?

8.  Compressive stress –beneficial
 Tensile stress - harmful
 Shear stress – most harmful

9. Primary Stability
 Implant
 Implant length
 Implant diameter
 Implant design
 Loading protocol
 Bone
 Quality, volume
 Density
 Surgical technique

10. Implant Length
 Length directly
proportional to surface
area
 Greater bone to implant
contact

11.  Longer implant- greater surface area-
greater stability
 Favorable crown/implant ratio
 Longer implants >10 mm compatible
with CSR
(Adell 1982, Lee 1995)

12.  D1 bone- bicortical stabilization
unnecessary as bone is homogeneous
 D2 , D3 bone- bone over heating
 D4 bone- apical areas too soft for local
compression stabilization

13.  Stress concentration -maximum ?

14.  Lateral stress distribution poor in short
implants

15.  Review on short implants <7mm
(Hagi D, Deporter DA)
 Threaded implants- shorter implants,
higher failure rates
 Sintered, porous implants- high success
rates >95%

16.  Short implants- 7mm or 9 mm
(Misch CE, 2005)
 Survival rate-99%
 Increase diameter, eliminate lateral
forces, splint implants.

17. Implant Diameter
 Related to surface area
 Anatomical limitations

18.  Traditionally wide implants >5mm
associated with greater failure

19. Wide Body Implants
 > 5mm in diameter
(Vanderweghe, Ackernman A, 2009)
 95.7% survival rates
 Used as rescue implants
 extraction sockets in poor primary stability
 poor bone quality

20. NDI implants
 <3.75 mm in dia
(Arisan V, Bolukbusu 2010)
 Overdenture in mandible
 94-100% survival rates
 Follow up- 1-9 years, CSR .95%
(Cho CS, Froum S)

21.  Impact of length and diameter
(Renourd F, Nisand D, 2006)
 Dense bone, textured implants, good
operator skill – short, wide, implants had
same survival rates as traditional
implants

22.  Influence of diameter and length on
early implant loss
(Olate S, Lynn MC, 2010)
 Early implant loss associated with short
implants
 Not associated with diameter

23.  Ultra short implants 5mm long, 5mm in
diameter in posterior areas
(Deporter D,2008)
 1-8 year follow up results
 Maxillary, mandibular failure rates 14.3
and 0%

27. Implant Design
 Macro design
 Body shape
 Thread
 Thread design
 Micro design
 Implant materials
 Surface morphology
 Surface coating

28. Implant Body Shape
 Cylindrical, tapered implants
 Other shapes not in use
 Tapered implant- 4 degree non parallel
30 degree maximum

29.  Tapered implants- increased
compressive forces
 Cylindrical implants- increased shear
forces
(Lemons, 1993)
 Cylindrical implants- increased failure
rates
(Misch, 2008)

30. Implant Threads
 Screw threads
 tapped
 self tapping
 Solid body press fit
 Sintered bead technology

31. Thread Geometry
 Increase bone implant contact area
○ Total vs functional surface area
 Stress distribution
 Stability

32.  Bone bridge from one thread to another
 Cusp like bone formation
 Heterogenous stress field

33.  Thread shapes available include; V-shape,
square shape, buttress and reverse buttress
shape (Boggan et al. 1999).

34.  Bone implant contact-
 increased in square threads
(Steinganga,2004)
 Density highest below threads
 Weakest- tip of threads
(Bolind,2005)

35. • Square, Buttress threads
◦ Axial load - dissipated
through compressive force.
(Bungardener, 2000)
 V shaped and reverse
buttress
◦ Axial load – dissipated
through compressive,
tensile and sheer force.
( Misch, 2005)

36.  Cancellous bone
 V shaped, broad square threads
 Significantly less stress
 Cortical bone
 No difference
(Geng 2004)
 Square thread least stress concentration
(Chun et al 2000)

37.  The face angle is
the angle between a
face of a thread and
a plane
perpendicular to the
long axis of the
implant.

38. • Face Angle
 Shear stress increased as face angle
increases
 V shaped, 30°
 Reverse buttress 15°
 V shaped, buttress
 Generates excess forces
 Defect formation
(Hansson & Werke 2003)

39. • Thread pitch refers to the
distance from the center
of the thread to the center
of the next thread,
measured parallel to the
axis of a screw (Jones
1964).
• It may be calculated by
dividing unit length by the
number of threads (Misch
et al. 2008).

40. Thread pitch
 Maximum effect on design variables
 Affects surface area
 Lower pitch- increased % BIC
 Less pitch- deceased stress
(Motoyosti, 2005)

41.  .8 mm pitch optimal for primary stability
*V shaped threads
 Shorter or longer pitch
* Unfavorable forces
 Affects cancellous more than cortical
bone

42.  Thread depth is defined as the distance
from the tip of the thread to the body of
the implant.
 Thread width is the distance in the same
axial plane between the coronal most
and the apical most part at the tip of a
single thread.

43.  Thread depth & width
 Affects implant surface area
 Deeper the thread- wider surface area of
implant
 Shallower thread- ease of placement

45.  Progressive thread design
 Greater depth apically, decrease
gradually in a coronal direction
 Increased load transfer to more flexible
cancellous bone
 Decreased cortical bone resorption

46.  Optimal thread depth - .34-.5mm
 Thread width- .18- .3 mm
 Depth more sensitive to peak stresses
(Abrahamsson, 2010)

48. Macrodesign: Summary

49. Crest module
 Traditionally smooth
 Soft tissue formation, less plaque
formation

50.  Sterile environment changes to open
oral cavity
 Thicker cortical bone- primary stability
 Increased force concentration
(Bozkoya, 2004)

51.  Microthreads in
crest module
 Insufficient data
 Postulated to reduce
crestal bone loss
(Kim 2009)

53.  Approaches to alter implant surfaces
can be classified as
 Physicochemical
 Morphologic or
 Biochemical.
(Ito et al.)

54. Surface materials
 Commercially pure titanium and Ti-6Al-
4V niobium
 Molybdenum & manganese
 Zirconia

55.  Surface energy
 Zeta potential
 Interfacial tension
 Surface charge
 Net positive or negative charge
 Surface composition
 Oxide layer

56. Physicochemical properties
 Zeta potential
○ Difference in potential between tightly bound
layers and diffuse layers
 Interfacial tension
 Wettability- property of interaction forces
between different materials and interaction
between cohesion forces within materials
(Mollers)

57.  Low wettability- low osteoblast cell
attachment and decreased collagen
production (Reddy 2000)
 Increased polar components –
increased osteoblast function

58.  Electrostatic interaction in biological
events -conducive to tissue integration.
(Baier RE et al., 1998)
 No selective cell adhesion
 Does not increase implant tissue
interface strength
(Puleo DA et al., 2006)

59. Surface Morphology
 Surface topography/morphological
characteristics.
 Chemical properties.

60. Surface Roughness
 Increased surface area of implant
adjacent to bone.
 Improved cell attachment to bone.
 Increased bone present at implant
interface.
 Increased biochemical interaction of
implant with bone.

62. • Smooth surfaces: Sa value < 0.5 μm (e.g.
polished abutment surface)
• Minimally rough surfaces: Sa value 0.5 to <
1.0 μm (e.g. turned implants)
• Moderately rough surfaces: Sa value 1.0 to
< 2.0 μm (e.g. most commonly used types)
• Rough surfaces: Sa value ≥ 2.0 μm (e.g.
plasma sprayed surfaces).
(Wennerberg and Albrektsson, 2009)

63. • Moderate roughness and roughness is
associated with implant geometry-
allowed for bone ongrowth and provided
mechanical interlocking (Berglungh et al.
2003, Franchi et al. 2005)
• Higher BIC and removal torque force
suggested enhanced secondary stability
compared to smooth and minimally
rough implants (Buser et al. 1991,
Wennerberg et al. 1996).

65. Morphology
 Based on texture
 Concave texture (mainly by additive
treatments like hydroxyapatite (HA) coating
and titanium plasma spraying)
 Convex texture (mainly by subtractive
treatment like etching and blasting)

66. Based on the orientation of surface irregularities
Isotropic surfaces: have the same topography
independent of measuring direction.
Anisotropic surfaces: have clear directionality and
differ considerably in roughness.

67. Surface coatings
 Chemical agents
 Biological agents

68. Chemical
 Al2 O3 and TiO2, with particle size
ranging from small, medium to large
(150-350 μm) grit.
 HA coating

69.  Obtain improved bone implant
attachment.
 Being osteoconductive in nature, more
bone deposition has been reported

70. Lower the corrosion rates of the same substrate
alloys.
Delamination of coating leads to failure of
implant

71. Dissolution/fracture of HA coating results in failure.

72. • Predisposes to plaque retention.
• Inflammatory reaction.
(Gross M 1999, Jansen, 1997)

73. Biological Coatings
 Cell adhesion molecules
 Biomolecules with demonstrated
osteotropic effects

74. Adhesion Molecules
 RGD sequence
 BMPR 2 peptide

75. Bioactive Proteins
 BMP
 PDGF
 TGF

76. Loading Protocol
 Immediate loading
 First longitudinal trial (Shitman,1990)
 Immediate , early loading in mandible

77. Esposito, 2009
 Immediate- within 1 week
 Early- 1 week to 2 months
 Conventional- > 2months

78.  Immediate and early can be done with
good success
* case selection
* operator skill
 Failure rates:
 early> immediate > conventional
 Primary stability- very important

79. Esposito, 2007
 Differences between immediate & early:
not clear
 More studies needed

80. Esposito, 2004
 Successful in mandible, dense bone
 Few well controlled RCT’s.

81.  Publication bias in immediately loaded
implants
(Polson, 2000)
 Trial aborted in UK due to unacceptable
failure rate

82.  Progressive loading
(Cannizaro,2003)
 Immediate provisionalisation
 Insertion torque- 40Ncm

83.  Large , multicentric trial
(Donati, Zollner, 2008)
 Insufficient information
 Risk of bias

84. Platform Switching
 Wide diameter implants-intro in late
1980s
 Fitted with standard diameter
abutments- showed no changes in
crestal bone levels around implants

85.  Concept
 Small diameter
prosthetic component
connected to larger
diameter implant
platform- creating a
90° step
(Lazzara RJ 2006)

86.  Long term studies (Wagenberg B 2010)
 advantage of platform switching in
preserving crestal bone levels.
 Recommended in anatomic sites where
minimum distance between implant and
adjacent units cannot be achieved.

87. Theories
1. Biomechanical theory
◦ Bone resorption limited by shifting stress concentration
zone away from crest and directing it along axis (Maeda
2007)
2. Placement of implant- abutment junction (IAJ) at
or below crestal bone level may cause vertical
bone resorption to reestablish biological width
(Hermann 2001).
3. Presence of inflammatory cell infiltrate at the IAJ
(Ericsson 1995) and Peri-implant microbiota.

88. Esposito- SR, 2007
 No evidence to show any implant better
than another

89. Implant survival rates
 Popelet A,Valet F
 63% DID NOT REPORT INDUSTRY
FUNDING
 66%-RISK OF BIAS

90.  Inclusion/ exclusion criteria
 Blinding
 Drop out rates not reported

91.  Survival rate significantly lower in
industry non funded studies
 Highest when funding undisclosed

92. Esposito 2004
 Bone quality, volume most important

93. TO BE CONTINUED……………………….