Biological outcome of implant restorations in the treatment of partial edentulism: A longitudinal clinical evaluation (n

1
Biological outcome of implant restorations in the
treatment of partial edentulism A longitudinal
clinical evaluation (n 0263 IADR).Naert I.,
Koutsikakis G., Duyck J., Quirynen M., Jacobs
R., van Steenberghe D. Dept. of
Prosthetic Dent. K.U.LeuvenDept. of
Periodontology K.U.Leuven
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Introduction

• Long-term serviceability of implants in
  partially edentulous patients, before accepting
  them as a reliable alternative to traditional
  prosthodontic treatment, should be evidence
  based.
• Only Lekholm et al., 1999 reports after 10 years
  based on life table analysis and considering
  implant interdependency.
• Should one use subsequent single implant crowns
  or fixed partial prostheses to restore?

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Introduction

• Many reports relate univariate assessments and
  fail to consider
• confounding,
• interacting and
• clustering effects (Hutton et al, 1995)
• This study, based on a large series of
  consecutive installed implants, takes into
  account correct statistical analysis as suggested
  by Bryant (1998) and Esposito (1998).

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Aim

• To investigate the long-term predictability of
  implants and their restorations in the treatment
  of partial edentulism and to compare single
  restorations with fixed partial prostheses.
• Hypothesisthe latter do not influence the
  outcome for implant success 

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Materials Methods

• Patients Implants
• All partially edentulous patients with single,
  tooth-connected and free-standing FPP installled
  between 1982-98, were investigated.
• 660 patients 248 males, mean age 52 y. (20-79)
  
• 810 FPRs (235 single, 166 tooth-connected, 409
  free-standing)
• 1.956 (Brånemark System) implants

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Materials Methods

• Patients Implants
• For 170 implant sites, membranes (Gortex?) or
  autologous bone or xenon grafts (Bio-Oss ?) were
  used
• to cover the dehiscences or,
• to fill the voids between implants and extraction
  sockets or,
• to augment the alveolar crest.

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Distribution of Implants with regard to Length,
Thread profile and Ø
Profile
Implant length (mm)
Mk2
Selft
Stand.
18-20
15
13
11.5-12
10
8-8.5
6-7
540
524
827
56
454
537
15
719
58
110
13
Conical
1891
Regular Ø (3.75 and 4 mm)
52
Wide Ø (5 mm)
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Materials Methods

• Surgery
• Two-stage surgery.
• 5 (lower) and 6.8 m. (upper jaw) later
  abutmentconnection.
• Prosthetics

FPP
FPP
single
single
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Materials Methods

• Recall schedule
• Half yearly to yearly
• Observation time
• from implant install. till 16.5 y. (mean 5.5
  y.)
• Study closure June 1999.
• 73 patients dropped out. Their data were used
  till their last control visit.

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Patient, implant and FPP dropout

• Patients Implants Prostheses
• Deceased 6 (0.9) 31 (1.6) 14 (1.6)
• Other reasons67 (10.1) 173 (8.8) 88 (10.4)
• Total 73 (11) 204 (10.4) 102 (12)
• 7 unable to come, 8 had moved abroad, 13 had
  moved to unknown address, 36 did not respond at
  all, 3 were unwilling to come.

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Materials Methods

• Criteria for failed implants
• radiolucency on peri-apical RX
• mobility before or at prosthesis install., or
  when on RX some doubt, FPP was removed
• pain/infection leading to removal
• fractured implants
• Criteria for failed F.P.Restorations
• when the FPR could not remain in function as a
  consequence of implant loss, without adding
  supplementary implants (Naert et al, 1992).

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Statistics

• Shared frailty model (Hougaard, 2000) was used
  to estimate the lifetimes of implants and
  prostheses.(which is a Cox proportional hazards
  model with a patient-specific random effect
  added, the latter takes into account dependency
  between implants in the same patient. Shared
  means that all implants of a patient share the
  same common risk)

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Statistics

• As failure time, the timepoint halfway the
  previous and last control (where the failure
  occurred) was chosen.
• A multiple version of the Cox regression is used
  to take into account possible confounding
  variables. Because of the explorative character
  of the study, no corrections for multiple testing
  were made.

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Results Implants

• Although the latest censoring time was gt16 y.,
  the last implant event occurred at interval
  8.5-9.Cum. Survival Rate (Cutler Ederer,
  1958) of implants from implant installation on
  after 9 years is 91

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Estimation of survival of all implants in upper
and lower jaw
1.00
0.95
Survival Function
0.90
Last event 8.9 yearEstimated survival
91.4(Shared Frailty Model)
0.85
0.80
0
5
10
15
Years
16
- Single crowns FPP- Upper jaw Lower jaw-
Anterior Posterior- Ant. upper Post. Lower,
etc.. - Gender, age, thread profile did not have
any sign. effect
Hazard rates Implants(Multiple Cox regression)
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Estimation of implant survival in freestanding
and tooth-connected implants in upper and lower
jaw
1.00
P0.03
0.95
Survival Function
0.90
Last event 7.3 y.Estimated survival 97.2
0.85
Last event 8.6 y.Estimated survival 93.6
0.80
Years
0
5
10
15
18
Estimation of implant survival for lt10, 10-13,
?15 mm implants
1.00
0.95
Survival Function
0.90
Plt0.001
0.85
0.80
0
5
10
15
Years
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Estimation of implant survival for non- and
grafted/membrane implants
1.00
0.95
Survival Function
0.90
Plt0.001
0.85
0.80
0
5
10
15
Years
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Results FPP

• Although the longest follow-up time was 16 y.,
  the last prosthetic event occurred at interval
  8.5-9 y.Cum. Survival Rate (Cutler Ederer,
  1958) of prostheses from installation on after 9
  years is 93

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Estimation of survival for all (single,
freestanding and tooth-connected) restorations
1.00
0.95
Survival Function
0.90
0.85
Last event 8.6 y.Estimated survival 95.8
0.80
Years
0
5
10
15
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- Upper jaw Lower jaw- The less implants per
FPP, the higher the hazard rate- The higher the
number of prostheses, the higher the hazard rate
Hazard rates Prostheses (Multiple Cox
regression)
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Non-inferiority analysis for implants and
restorations in single and (freestanding) fixed
partial restorations

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Discussion

• All partially edentulous patients who could
  benefit from ISR were enrolled.
• 2.7 implants failed before loading.
• 115 implants did not acquire or lost
  osseointegration, only 17 implants did fracture.

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Discussion

• Although life table analyses have their own
  value, they are descriptive only, as they do not
  take into account implant interdependency
  (Herrmann et al., 1999) and do not correct for
  confounding variables (Hutton et al., 1995)
• Predicted estimations of survival based on a
  shared frailty Cox proportional hazard model do.

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Discussion

• FPP with 1, 2 to 3 and gt3 implants/prosthesis had
  survival times of 91, 97 and 97.6 respectively.
• In 37 single tooth replacements to restore 2, 3
  and 4 missing teeth (in 13, 1 and 2 patients)
  only one implant failed.

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Discussion
Single crowns or FPP?
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Discussion

• Single Free-standing FPP (for implants as well
  as for prostheses).
• However, the estimated upper limit of 5.87
  questioned this option.
• Further research is needed to confirm this.

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Conclusion

• Estimated CSR for implants and FPR are 91.4 and
  95.8 respectively after 16 years.
• Free-standing implants present higher survival
  rates (97.2) compared to tooth-connected ones
  (93.6), (after loading) at 15 years.
• Single restorations seem a promising option for
  the FPP.