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Int Poster J Dent Oral Med 5 (2003), No. 1     15. Mar. 2003

Int Poster J Dent Oral Med 2003, Vol 5 No 01, Poster 168

Immediate Bridge Restored Implants Under Functional Loading

- A Study in Mini-Pigs -

Language: English

Authors: Jörg Neugebauer1, U. Thams2, F. San Roman2, H. Steveling3, J. E. Zöller1
1Medical Center University to Cologne Clinic and Teaching Hospital for Dental Surgery and for Oral-, Maxillo and Plastic Facial Surgery, Germany
2University Complutens Madrid, Spain
3University Heidelberg, Germany

Date/Event/Venue:
March 14-16, 2002
17th Annual Meeting Academy of Osseointegration
Dallas/Texas

Poster Award
1st Prize for Best Poster

 

Introduction

The immediate loading of dental implants in partially edentulous patients has not been widely investigated. Following the experience of the treatment of the anterior mandible (Ledermann 1979, Ledermann 1988), immediate loading requires pre-conditions such as immobilization of the implants with a superstructure and shortened surgical and prosthetic treatments (Brunski 1993). The preparation of the receptor site in the mandible is accomplished with drills. In soft bone, improvement of the bone quality can be achieved by BoneCondensing (Fürst 1999). This technique can also be used to perform minor sinus-lift procedures. Adaptation of the receptor site by "under-sizing" the osteotomy relatively to the implant is another option to help achieve primary stability (Schmidinger 1999). An animal study on mini pigs was performed to evaluate the clinical success and bone reaction during the course of osseointegration for implants in the mandible and maxilla.

 

Material and Methods

The premolars and the first molar were removed. After three months, implant placement and prosthetic temporization was performed for 61 XiVE® implants (FRIADENT GmbH, Mannheim, Germany). 27 implants were placed in the maxilla and 34 in the mandible. The preparation in the mandible was performed with drills. The preparation in the maxilla was performed by BoneCondensing technique to increase the local bone quantity and quality with an internal sinus-lift. The special thread design with a lower thread profile in the crestal portion allows a differentiated implant site preparation with the final crestal drill. Based on the bone quality, internal condensation by the implant is used to improve the final insertion torque. 49 implants were stabilized with prefabricated caps and glass fiber ribbons. The bridges were cemented onto the abutments at the end of surgery and controlled until the animals were sacrificed. Markers for the histological staining were given according the protocol of Becker et al. (1992).

 

Summary

Immediate loading of dental implants in the partially edentulous patient has not been investigated widely. Immediate loading requires immobilization of the implants by the superstructure (Ledermann, Brunski). An animal study was performed to evaluate the clinical success and the bone metabolism during the course of osseointegration on 12 implant borne bridges. Three months after tooth extraction implant insertion and prosthetic treatment was performed.
29 implants out of 62 had an insertion torque (IIT) above 35 Ncm. The average insertion torque of the implants per bridge (BIT) were determined. If the BIT was higher than 35 Ncm the bridges were successful after 4 months of loading. The histomorphometric finding of loaded and unloaded implants shows no significant difference. The procedure with prefabricated auxiliary parts allows fabricating a bridge reconstruction during one appointment as a predictable procedure if the parameters for success were considered.

 

Clinical Procedure Step-by-Step

Prior to the extraction of the teeth an impression was made to fabricate a surgical stent for the implant placement and for the fabrication of the provisional bridge. The implant sites were prepared with standard drills in the mandible. The depth of the crestal preparation was reduced in soft bone to create a tighter fit of the implant (internal condensation of the bone). The implants were placed with a hand piece at 15rpm.


Situation after suturing: The implant mount called a TempBase stays in place as a temporary abutment. Complete wound closure was double checked to avoid contact of the temporary resin with the fresh wound. The TempBases were reseated if the flats on the abutments were not placed in a straight line. The prefabricated TempBase caps were seated on the abutments for a stable reinforcement with fiber ribbon, a straight line is optimal.


Light-cured fiber material was utilized to connect the caps. Contamination for the fibers with saliva or blood during the placement of the fiber core must be prevented. Additional resin is applied to stabilize the fibers and increase the mechanical stability. The resin should be placed in thin layers to avoid tension in the superstructure during shrinkage of the material.


The template is double checked before the auto-polymerizing resin is applied. During polymerization, irrigation fluid is utilized to protect the soft tissue from the high temperature of the resin as it sets. After final polymerization the superstructure is removed. Voids are filled-in with resin and the bridge is finished and polished. The bridge is cemented onto the TempBase abutments.


Histological Findings

Toluidin blue staining of loaded implant. Good BIC, initial resorption until first rough surface. Toluidin blue staining of un-loaded implant. Complete BIC even at smooth collar of the implant.


Toluidin blue staining of unloaded implant illustrates close bone-to-implant contact at the apical threads. The bone between the threads shows large marrow spaces.


Toludin blue staining of loaded implant with newly formed osteozyt between the apical threads. Alizarin staining shows time of reossification.
Unloaded implant in flourochrome microscopy shows active remodeling around the crestal threads after internal condensation. Fluorochrome microscopy of the apical region of a loaded implant. Strongest cell activity is shown after eight weeks with Allzarin-marker.


Histomorphic Analysis

The histomorphometric analysis was performed for the mandibular implants for statistical reasons. The following definitions were used:

bone-to-implant contact = length of the bone surface border in direct contact with the implant/complete implant surface.

interthread bone density = area of bone inside the threads/complete area inside the threads.

Surrounding the implant, up to a lateral extent of two mm peri-implant bone density = bone volume/tissue volume (McMillan et al. 2000).

A 2-way analysis of variance was used, with implant placement technique as first factor and animal identity as the second factor to compensate any influence by the study design (Kolmogorov-Smirnov-Test and Levene's Test). There was no significant difference (P-value <= .05) for the bone to implant contact, the interthread and the peri-implant bone density for the loaded and unloaded implants detected.

 

Results

Due to the adaptation of the receptor site preparation based on the bone quality, utilizing cortical drills in the mandible and bone condensing instruments in the maxilla, 92% of all implants were placed with an insertion torque (IIT) above 25 Ncm. The mean value of the insertion torque per bridge (BIT) was evaluated. If the BIT was less than 35 Ncm the bridges were not stable and the implants were lost after a few weeks prior to the first recall. In the mandible, of the directly loaded implants (N=27) two failures occurred (92.6% success). The control implants in the mandible had a 100% success rate (N=7).
Three out of 22 directly loaded implants in the maxilla were stable after three months (13.6% rate). Two out of 5 control implants in the maxilla were stable (40% success rate).

IIT / BIT     Maxilla     Mandible    
15 - 20 Ncm 4 (4) implants   -  
25 - 30 Ncm 15 (12) implants 5 (5) bridges 4 (0) implants  
35 - 45 Ncm 3 (3) implants 1 (0) bridges - 2 (0) bridges
50 and over Ncm 3 (2) implants   23 (2) implants 4 (0) bridges
Torque analysis loaded implants (failures)


RFA-Value     Minimum   Median    Maximum   Mean    N    
Maxilla 67 76 80 75.2 5
Mandible 42 77 88 75.4 34
RFA-Analysis

There was no difference between loaded and unloaded implants regarding the RFA Resonance Frequency Analysis - values visible after three months of implant placement (Rasmusson 1998).

 

Discussion

Primary stability is a pre-condition for immediate implant placement. Internal condensation has been used to improve primary stability. In the maxilla additional bone condensing was used to gain additional length into the sinus. With these techniques, BIT values between 25 and 45 Ncm were reached in the maxilla.
In the mandible the BIT values were between 35 Ncm and more than 50 Ncm.
Bridges with a BIT below 35 Ncm failed. Bridges with BIT above 35 Ncm were successful in the animal model. The control implants were placed next to the immediate loaded implants, losing the immediate loaded implants also damaged these implant sockets. The control implants in the mandible showed complete osseointegration. Histological observation and histomorphometric analysis showed no difference in bone contact for loaded and unloaded implants in successfully osseointegrated implants.
RFA-analysis showed no difference between mandible and maxilla. Also, there was no visible difference between loaded and unloaded implants.
The reduction of the occlusal contacts in the maxilla, to avoid maximal load was much more difficult than in the mandible due to the anatomy of the animal model.
In general this procedure, utilizing pre-fabricated components, allows the fabrication of a provisional bridge in one appointment for immediate loading. The histomorphometric evaluation demonstrates that immediate loaded implants shows no difference to unloaded implants four month after implant placement if the primary stability of the bridge was suitable for initial loading.

Positive parameters

  • BIT greater than 35 Ncm
  • Implant stabilization by resin superstructure

Negative parameters

  • BIT less than 30 Ncm
  • Internal sinus lift for gaining vertical bone height
  • Limited reduction of horizontal load during the first weeks of initial loading

 

Literature

  • Becker, J. Meissner, T. Neukam, F.W. Knöfler, W. Graf, H.-L. / Reichart, P.: Tierexperimentelle Untersuchungen zur Einheilung von ANOF-beschichteten Titanimplantaten, 1991
  • Brunski JB. Avoid pitfalls overloading and micromotions of intraosseous implants (interview). Dent Implantol Update, 1993; 4(10):77-81
  • Fürst, U., Klug, D., Neugebauer, J.: Sinusbodenelevation mit dem FRIALIT-2 BoneCondenser, ZWR, 1999; 108: 506-510
  • Ledermann P.D.: Die neue Ledermann-Schraube Quintessenz 1988, 5, 1-17
  • Ledermann PD. Stegprothetische Versorgung des zahnlosen Unterkiefers mit Hilfe von plasma-beschichteten Titanschraubenimplantaten. Dtsch. Zahnärztl. Z. 1979; 34:907-911.
  • Rasmusson, L., Meredith, N., Kahnberg, K.-E., Sennerby, L.: Stability assessments and histology of titanium implants placed simultaneously with autogenous onlay in the rabbit tibia, Int. J. Oral Maxillofac. Surg. 1998;27: 229-235
  • Schmidinger, S., Uhl, F.: Sinus Elevation, is there a need for spezial implants? Posterpresentation EAO- Annual Meeting Cophenhagen April 16-17,1999
  • McMillan PJ, Riggs ML, Bogle GC, Crigger M. Variables that influence the relationship between osseointegration and bone adjacent to an implant. Int J Oral Maxillofac Implants 2000;15:654-661

 

This Poster was submitted by Dr. Jörg Neugebauer.

Correspondence address:
Dr. Jörg Neugebauer
Medical Center University to Cologne
Clinic and Teaching Hospital for Dental Surgery and
for Oral-, Maxillo and Plastic Facial Surgery
Kerpener Strasse 32
D-50937 Cologne
Germany