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Tri-factorial Classification for Osteotome Sinus Floor Elevation Retrospective Analysis.

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Tri-factorial Classification System for Osteotome Sinus Floor Elevation ( OSFE) 
Based on an Observational Retrospective Analysis of 926 Implants Followed up to 10 years.

French D, 1  ) Nadji N, 1)   Larjava H,1)   Liu S 2)                            1) Department of Oral Health Sciences, University of British Columbia, Vancouver BC, Canada           2) Department of Mathematics and Statistics, Mount Royal University, Calgary, AB, Canada

Introduction

Residual bone height (RBH) has typically been used to classify OSFE sites.  Early classifications  used 4 groups ( ≥10 mm), (7-10 mm) ,(5-6 mm) ,(≤ 4mm) with the typical  threshold  for OSFE procedure being >5mm. (ref 1,  ref 2)

Shorter and micro-rough implants make older classification divisions less valid.  Since 8mm implants  have comparable success a 10-12mm (ref 3)  the >7mm division is not meaningful.  Furthermore, the ≤4mm category  used to restrict  sites to lateral window sinus elevation but these can now be treated with OSFE using 6mm implants.

In addition  to RBH  we propose two other factors that can affect  the OFSE procedure.

  • The “contour” of the sinus floor can facilitate or complicate the OSFE procedure.  For example a concave floor (figure 2b) may facilitate a sinus left as compared to a flat sinus floor.
  •   The “tenting” effect of multiple adjacent OSFE sites  that may facilitate the lift.

Objective:

To propose a classification system for osteotome mediated sinus elevation (OSFE) using a  tri-factorial analysis  utilizes a modified division for RBH and introduces divisions for sinus contour, and sinus membrane tenting.  This paper then evaluate this in an observational retrospective study of implants placed using the OSFE procedure. 

Materials and Methods:

926 implants were placed using OSFE with no added bone material in 541 patients (279 females, 262 males).

Exclusion criteria were patients with RBH <2 mm at the edentulous site for multiple implants and RBH < 4 mm for single site implants or was classified as ASA status 3 or above.

Inclusion criteria all maxillary posterior mature edentulous sites <12 mm RBH.  In cases with edentulous maxillary posterior sextants where RBH was between 2 and 5 mm and when multiple teeth were missing, patients were given the option of short splinted 6 or 8 mm implants using OMSE ( Figures 2 and 4) or longer implants placed following a lateral window sinus elevation.

Trifactorial Classification divisions as follows:

 -       RBH =  High (RBH > 6mm), Mid (RBH = 4.1-6 mm) or  Low (RBH = 2-4 mm)

-       Contour =  flat, concave, angle  or  septa

-       Tenting =   Yes  (if multi-site adjacent  OFSE)  or    No  ( if single site OFSE)      

A descriptive analysis of OFSE sites relative to  RBH, contour and tenting  was performed and then site characteristics were evaluated for interaction between each other.  Subsequently, an evaluation of site characteristics relative to implant failure was performed.  Chi square test was utilized to evaluate the associations between every two site characteristics and then evaluated for failure rates of different levels in each site characteristics.

 

Results:   

Implant survival rates

Of the 926 implants only 12 failed for 5 year survival rate of 98.3% and 10-year survival rate of 97%. Six implants failed before loading , six failed after loading

Site characteristic distributions: 

-       There was a significant association between site characteristics;  RBH and contour, RBH and tenting, as well as contour and tenting. 

-       majority of sites were flat or concave in all RBH groups but the prevalence of flat sites increased as the RBH  reduced .

-       Significantly more angle and concave forms were in high RBH.

-       Even amounts of multiple and single sites overall (N = 494 and 434 )

-       concave and septa locations tended to be single sites.

-       flat or angle sites tended to be multiple sites.  

The number of sites treated with multiple OSFE increased in lower RBH sites compared to single OSFE sites, such that in the Low RBH group, the vast majority were multiple OSFE sites. 

Tri-factorial classification & failure:

RBH was a significant predictor of failure with rates as follows:     Low RBH = 5.1%, Mid RBH = 1.5% and High RBH= 0.4%. ( P-Value = 0.000).

Sinus contour revealed a trend to higher failure rates in flat sites at 1.9% compared to 1% for concave and 0%-1% for the septa and angle groups, respectively .

Sinus tenting (single versus multiple adjacent sites)  revealed a trend to lower failure for adjacent OSFE at 0.8% compared to 1.8% for the single sites

Relative to failure neither contour or tenting achieved statistical significance however, the power of the study was limited by low numbers of failures.

 

Conclusion

The Osteotome Tri-Factorial Classification System as proposed revealed significant relationships between each two site characteristics. 

There was a significant relationship between RBH and implant failure. 

Sinus contour and tenting revealed trends relative to implant failure, but due to low numbers of failures these were not statistically significant.

The tri-factor analysis may assist planning OFSE and may allow better comparison of future OFSE studies.

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