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 Table of Contents  
ORIGINAL ARTICLE
Year : 2006  |  Volume : 6  |  Issue : 4  |  Page : 190-191

Simple intra-oral technique for prevention of breakage of teeth of a cast during its retrieval from final impression


Department of Prosthodontics including Crown and Bridge and Implantology, Yenepoya Dental College, Derlakatte, Mangalore, Karnataka; Rajiv Gandhi University of Health Sciences, Karnataka, India

Correspondence Address:
Sanath Shetty
Department of Prosthodontics including Crown and Bridge and Implantology, Yenepoya Dental College, Derlakatte, Mangalore - 575 018, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-4052.30694

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  Abstract 

One of the commonest problems experienced by a dentist is the broken teeth on the master cast, which occurs during retrieval from the impression, especially when the anterior teeth have gingival recession and open interdental spaces. This article describes a technique of preventing the breakage of cast, by adapting wax on non-critical surfaces intra-orally and thus, reinforcing the critical surfaces. This technique is simple and requires minimal chair side time.

Keywords: Cast strengthening


How to cite this article:
Shetty S, Shenoy KK, Jain S. Simple intra-oral technique for prevention of breakage of teeth of a cast during its retrieval from final impression. J Indian Prosthodont Soc 2006;6:190-1

How to cite this URL:
Shetty S, Shenoy KK, Jain S. Simple intra-oral technique for prevention of breakage of teeth of a cast during its retrieval from final impression. J Indian Prosthodont Soc [serial online] 2006 [cited 2020 Dec 2];6:190-1. Available from: https://www.j-ips.org/text.asp?2006/6/4/190/30694

Safe retrieval of a cast removable partial denture master cast from an impression, without breaking the teeth, is a challenging task. This problem is even magnified when the teeth have extensive bone loss and open interdental spaces. Variation in position of reattached stone tooth may not lie within the limit of physiologic tooth movement, even if reattached carefully. Therefore, ideally the impression procedure should be repeated and a new cast be retrieved.[1] Various techniques like use of die pins, bobby pins,[2],[3] modifying the impression before pouring cast, and so on[2],[4] have already been mentioned in the literature. However, these techniques are complicated and involve manipulation of the impression, which might lead to inaccuracies in the impression and finally in the master cast.

Identification of critical and non-critical surfaces can be helpful to prevent cast breakage.[4] A critical surface is the surface of a tooth or soft tissue that is critical in diagnosis, fabrication or wearing of the prosthesis. A non-critical surface is one that will not be used in the diagnosis or fabrication of the prosthesis.

This article describes a simple technique, which involves alteration of non-critical areas intra-orally, thereby strengthening the cast.


  Technique Top


  1. Identify critical and non-critical surfaces by analyzing the diagnostic cast.
  2. Dry the teeth with air syringe and isolate the area using cotton rolls [Figure - 1].
  3. Take carding wax (soft tooth carding wax, Kemdent) and adapt it on to the non-critical surfaces of the teeth (interdental spaces, facial surfaces, etc.) [Figure - 2].
  4. Make the impression with the desired material.
  5. Impression is observed for any remnants of wax. If present, should be removed carefully with sharp instrument.
  6. Wax in the patient's mouth can also be easily removed by any sharp instrument [Figure - 3].
  7. Cast is poured using the desired material.
  8. Final cast is analyzed for any imperfections. The resulting master cast has an increased bulk on the surfaces that are non-critical while the critical surfaces have been preserved and reinforced [Figure - 4],[Figure - 5].



  Discussion Top


Breakage of teeth on the master cast during retrieval of cast from the impression can be due to poor removal technique or improper clinical or technical use of dental materials.[5],[6] Even if these factors are taken care of, in situations where anterior teeth have recession and open interdental spaces, the chances of breakage of teeth are very high. A technique of using commonly and easily available carding wax for increasing the bulk of teeth and thus preventing breakage of teeth in the master cast has been discussed. Technique is simple and consumes minimal chair side time.

 
  References Top

1.
Sato Y, Takaki N, Tsuga K, Hosokawa R. Effect of abutment tooth reinforcement techniques on the fracture resistance of removable partial denture master casts. J Prosthodont 2001;10:22-5.  Back to cited text no. 1
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2.
Sato Y, Tsuga K. Post-impression preparation to prevent fracture to isolated abutments with extensive bone loss in master casts. J Prosthodont 1998;7:198-9.  Back to cited text no. 2
[PUBMED]    
3.
Casey DM, Crowther DS, Lauciello FR. Strengthening abutment or isolated teeth on removable partial denture master casts. J Prosthet Dent 1981;46:105-6.  Back to cited text no. 3
[PUBMED]    
4.
Moon MG, Holmes RG. Modifications of the impression to prevent cast breakage. J Prosthet Dent 1997;77:323-5.  Back to cited text no. 4
[PUBMED]  [FULLTEXT]  
5.
Rudd KD, Morrow RM, Eissman HF, et al . Dental laboratory procedures. 3rd ed. Mosby: St. Louis; 1986.  Back to cited text no. 5
    
6.
Stewart KL, Rudd KD, Kuebker WA. Clinical removable partial prosthodontics. 2nd ed. Ishiyaku: ST Louis; 2003.  Back to cited text no. 6
    


    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]



 

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