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International Poster Journal of Dentistry and Oral Medicine
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Int Poster J Dent Oral Med 11 (2009), No. 4     15. Dec. 2009

Int Poster J Dent Oral Med 2009, Vol 11 No 4, Poster 466

Cast dental restorations modern repair possibilities

Language: English
 

Authors:
Assist. Prof. Dr. Sorin Porojan, Assoc. Prof. Dr. Liliana Sandu, Prof. Dr. Cristina Maria Bortun, Assist. Prof. Dr. Florin Topala,
"Victor Babes" University of Medicine and Pharmacy Timisoara, University School of Dentistry, Timisoara, Romania

Date/Event/Venue:
May 7-10th, 2008
The 1st International Scientific Conference of Faculty of Dentistry Jordan University of Science and Technology and 5th Annual Scientific Meeting of IADR-JOR
Amman, Jordan
 

Introduction

In classical conditions some lack of substance defects of cast restorations need their renewal, but modern techniques of dental alloys welding in protective gas shield allow correction of these defects, without repeating all of the clinical and technical stages.
 

Objectives

The aim of the study was to test microplasma welding possibilities of cast dental restorations.
 

Material and Methods

Different Ni-Cr cast restorations with defects were chosen in order to add proximal contacts, to repair casting voids and to lengthen short cast crowns (Fig. 1-3) using microplasma welder (Schütz Dental, Rosbach, Germany). As filler material a Ni-Cr wire Wiroweld NC (Bego, Bremen, Germany) was selected. The optimal welding parameters were correlated with the defect type, size, and working stage.
If these marginal discrepancies are minor and if cast the piece correctly adapts to die axial, proximal and occlusal and there are no other casting defects, they can be repaired by welding with filler material.
Nondestructive and destructive analyses tested the welding quality.

Fig. 1: Lack of substance defects on restoration Fig. 2: Undersized contact area
Fig. 3: Marginal lack of substance defect on restoration
 
Fig. 4: Filling of the material absence by welding

Results

The welding parameters were determined for each defect type. Pores and holes defects repairs (Fig. 4) were made using the following welding parameters: power step 6 and pulse delay 35 ms both for deposition and for surface fining. Undersized contact areas were corrected by welding with filler material (Fig. 5) using the parameters: power step 6 and pulse delay 30 ms for deposition and power step 7 and pulse delay 35 ms for surface fining. The used parameters for minor marginal discrepancies (short restoration) (Fig. 6) were: power step 3 and pulse delay 25 ms for wire fixing, deposition of filler material and fining.
An adequate combination of them allowed to obtain optimal repairs. These were proved by testing methods (Fig. 7-9).

Fig. 5: Rebuilding of the contact area by welding with filling material Fig. 6: Extension of the cast restoration margin by welding with filling material
Fig. 7a: Microstructure of the occlusal repair: heat affected zone Fig. 7b: Microstructure of the occlusal repair: weld area
Fig. 8a: Microstructure of the contact area build-up: heat affected zone Fig. 8b: Microstructure of the contact area build-up: weld area
Fig. 9a: Microstructure of the marginal extension: heat affected zone Fig. 9b: Microstructure of the marginal extension: weld area

Conclusions

Minor defects of cast restorations are suitable for correction, by welding with filling material and the used time is much more reduced than those needed for restoration renewal are.
 

Literature

  1. Rosenstiel S, Land M, Fujimoto J.: Contemporary fixed prosthodontics, 3rd ed., Mosby, St. Louis, 2001.
  2. Sandu L., Borţun C., Pop D., Negruţiu M.: Tehnologia restaurărilor protetice fixe unidentare, Îndreptarul de lucrări practice; Lito UMFT, 2006.
  3. Leretter M., Sinescu C., Sandu Liliana, Lakatos S.: Curs de tehnologie a protezelor fixe, vol I, Bazele tehnologiei protezelor fixe, Lito UMFT, 2002.
  4. Sandu L, Bîrdeanu V, Borţun C, Matekovits G.: A fémvázas részleges fogsorok ötvözeteinek hegesytése puzáló lézernyalábbal, A Fogtechnika - das dental labor, 2006, 1:42-4.
  5. Bertrand C, Le Petitcorps Y, Albingre L, Dupuis V.: The laser welding technique applied to non precious dental alloys procedure and results, British Dental Journal, 2001, 190(5):255-7.
  6. Burkhardt H.J.: Ein wirtschaftlicher Weg mit Erfolgschancen - Schweißen mit dem CeHa Phaser MX1, Quintessenz Zahntech, 2005, 31(2):136-42.
     

This Poster was submitted by Assist. Prof. Dr. Sorin Porojan.
 

Correspondence address:
Assist. Prof. Dr. Sorin Porojan
"Victor Babes" University of Medicine and Pharmacy Timisoara
University School of Dentistry
2 L. Blaga Str., App. 5
code 300002, Timisoara, Romania