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Table of Contents   
ORIGINAL ARTICLE  
Year : 2012  |  Volume : 23  |  Issue : 1  |  Page : 2-6
Single step approach to make diagnostic impressions of both the arches and face bow transfer: A novel technique


1 Department of Prosthodontics, Saraswati Dhanwantri Dental College, Parbhani, Maharashtra, India
2 Department of Prosthodontics, Vishnu Dental College, Bhimavaram, Andhra Pradesh, India

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Date of Submission09-Jul-2010
Date of Decision03-Dec-2010
Date of Acceptance21-Jan-2012
Date of Web Publication26-Jul-2012
 

   Abstract 

Context: Mounting the maxillary and mandibular dentulous casts for Diagnostic purpose requires many steps (including making maxillary and mandibular impressions, face-bow transfer, and bite registration) or many appointments. A simple new technique of doing all of this together without compromising on the accuracy can save time over the conventional mounting procedure.
Aim: To compare the accuracy of a new technique of a single-step diagnostic mounting procedure with that of the conventional diagnostic mounting procedure.
Materials and Methods: Ten dentulous patients with the full complement of teeth and without any history of temporomandibular disorder and orthodontic treatment were selected for this study. A detachable metal triple tray to replace the fork part of the face bow fork that further could be attached to face bow was fabricated. Dual-arch impressions and face-bow transfer were made in these subjects using this modified triple tray. These mountings were compared with the ones done with the conventional mounting procedure. Five linear measurements (using stable reference points on the articulator and the cast) were made and the values obtained by both the methods were compared.
Statistical Analysis: The Student's 't' test for statistical analysis was used in this study.
Results: The measurement values obtained by the single-step method were almost similar to the ones obtained by the conventional method. The various mean measurements for the single step and conventional methods were 37.7 ± 6.8 and 38.5 ± 6.5 mm; 70.0 ± 4.4 and 70.1 ± 4.2 mm; 57.0 ± 4.9 and 57.3 ± 4.2 mm; 71.3 ± 4.5 and 71.0 ± 4.6 mm; and 58.7 ± 2.5 and 58.3 ± 2.3 mm; respectively. The differences between the values obtained by the conventional and single-step methods were not statistically significant.
Conclusion: The single-step procedure of diagnostic mounting can be used as an alternative to the conventional method, without compromising the quality of mounting.

Keywords: Diagnostic mounting, dual-arch impression, face-bow transfer, triple tray, dual arch tray

How to cite this article:
Komuravelli AK, Suresh Sajjan M C. Single step approach to make diagnostic impressions of both the arches and face bow transfer: A novel technique. Indian J Dent Res 2012;23:2-6

How to cite this URL:
Komuravelli AK, Suresh Sajjan M C. Single step approach to make diagnostic impressions of both the arches and face bow transfer: A novel technique. Indian J Dent Res [serial online] 2012 [cited 2014 Jul 29];23:2-6. Available from: http://www.ijdr.in/text.asp?2012/23/1/2/99028
Maxillary and mandibular diagnostic casts should be articulated in approximately the same relationship to the temporomandibular joints as exists in the patient. This articulation permits the static and dynamic relationships of the teeth to be examined without interferences from protective neuromuscular reflexes; also, unencumbered views from all directions reveal aspects of the occlusion not always easily detectable in the oral cavity. [1],[2]

Articulated diagnostic casts permit a detailed analysis of the occlusal plane, the occlusion, soft tissue contours, vestibular morphology and frenal attachments, bony contours, crown length and morphology, tooth alignment and paths of insertion, available pontic space, existing restorations, and esthetic factors. [3] Diagnostic procedures can be performed for formulating a better diagnosis and treatment plan; tooth preparations can be rehearsed on the casts, and diagnostic waxing procedures will allow evaluation of the eventual outcome of the proposed treatment. [2]

Conventionally, mounting of the diagnostic casts to an anatomical articulator involves several steps, including making the maxillary and mandibular impressions, face-bow transfer, and bite registration; these are recorded separately in different appointments and the diagnostic mounting is completed. Combining some or all of these steps would be advantageous by reducing the number of appointments.

The objective of this study was to design a single-step technique and to compare the accuracy of the new technique with that of the conventional technique. In this new single-step procedure, impression making, face-bow transfer, and bite registration would be done simultaneously. Such a technique would help save time, increase patient comfort, and reduce the number of appointments. The null hypothesis was that this new technique would not have any difference compared to that of conventional technique in accurate mounting of the casts.


   Materials and Methods Top


Triple tray assembly for the new technique

A modified bite fork was designed, with the tines (the 'U'-shaped part) of the bite fork replaced by a metallic triple tray. The triple tray was attached to the stem (the 'L'-shaped part) with an antirotation and locking mechanism. This assembly could be dismantled so as to provide ease and convenience while pouring the dual impression [Figure 1].
Figure 1: Parts of the triple tray assembly

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Technique for single-step diagnostic mounting procedure

  • The triple tray was tried out in the patient to check for the fit of the tray.
  • Hydrocolloid impression material was loaded in the triple tray on both the sides.
  • The tray was placed in the mouth so that the midline of the tray coincided with the dental midline. The subject was asked to occlude the teeth in maximum intercuspation.
  • After the Impression material is set, the bite-fork stem was made to slide into the transfer clamp assembly. The frame of the spring-bow was oriented in position so that the earpieces were guided into the external auditory meatus. The face-bow orientation record was carried out as usual [Figure 2].
  • Figure 2: Face-bow transfer recorded

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  • After completing the orientation of the face-bow, the frame was separated from the transfer clamp assembly. Then, the transfer clamp assembly along with the stem was separated from the triple tray, leaving the triple tray with the impression in the mouth. Care was taken not to disturb the assembly.
  • The dual-arch impression was removed from mouth. First, the mandibular impression was poured using dental stone. After the initial set of the stone, the maxillary impression was poured in dental stone.
  • Without separating the casts, the triple tray was reoriented to the transfer clamp assembly and the total face-bow assembly was transferred to the articulator.
  • Maxillary and mandibular casts were mounted to the articulator, with the triple tray in position.


Ten dentulous subjects with the full complement of teeth and without history of temporomandibular disorder and orthodontic treatment were selected for the study. The subjects were aged 20-35 years. A medium-sized triple tray was fabricated and the subjects were selected accordingly. The tray design (triple tray) includes with a 'U'-shaped frame and a piece of fabric mesh. The mesh connects the sides of the tray in the bucco-lingual dimension and allows holding the alginate on both sides to make maxillary and mandibular impressions together.

Irreversible hydrocolloid alginate impression material (Imprint® , Dental Products of India Ltd.) was used for making impressions in the present study as it is the most commonly preferred material for making diagnostic impression. Hanau™ spring-bow (Waterpik Technologies Inc., Fort Collins, CO, USA) was used to transfer the impression to the articulator (Hanau Wide-Vue™ Arcon articulator; Waterpik Technologies, Inc. Fort Collins, CO, USA) [Figure 2]. Dental stone (Goldstone™; Asian Chemicals, Rajkot, Gujarat, India) was used to pour both the impressions, and dental plaster (White Gold ; Asian Chemicals, Rajkot, Gujarat, India) was used for mounting of the casts to the articulator.

Face-bow transfer for both the single-step method and the conventional method was done in all the 10 subjects and the casts were mounted onto the articulator separately using extra pairs of mounting rings [Figure 3].
Figure 3: Face-bow attached to Hanau Wide-Vue™ articulator, with maxillary mounting done

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A total of 20 mountings (10 for each method) were done. In order to evaluate three-dimensional positions and to draw comparisons between the single-step procedure and the conventional procedure, five reference points were selected on the articulator. One point was on the incisal rod, one on the wing of the lower member of the articulator, and the remaining three on the lower member of the articulator [Figure 4].
Figure 4: Anteroposterior, lateral, right and left vertical, and anterior vertical measurements

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Cusp tips (distobuccal cusp of maxillary second molar on both sides) were selected as measuring points on the casts. The mesioincisal point angle of the central incisor was selected anteriorly. A total of three reference points were marked on the casts. Five measurements (one anteroposterior, one lateral, and three vertical) were used to evaluate the 3-dimensional orientation of maxillary cast in the articulator. A digital caliper with a precision of 0.01 mm was used for the measurement. The measurements were recorded for all the mountings. The three vertical measurements together indicated any variation of the occlusal plane of the casts mounted by both the procedures.


   Results Top


The mean value of each measurement for both the single-step and the conventional methods are presented in [Table 1]. The paired 't' test was used for analysis, and the probability values were calculated to determine the significance of differences between groups. The measurement values obtained by the single-step method were almost similar to the ones obtained by conventional method. The mean antero-posterior, vertical (left, anterior, right) and lateral measurements for the single step and conventional methods were 37.7 ± 6.8 and 38.5 ± 6.5 mm; 70.0 ± 4.4 and 70.1 ± 4.2 mm; 57.0 ± 4.9 and 57.3 ± 4.2 mm; 71.3 ± 4.5 and 71.0 ± 4.6 mm; and 58.7 ± 2.5 and 58.3 ± 2.3; respectively.
Table 1: The mean value of each measurement for both single-step and conventional methods

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The probability values show that the differences between the values obtained by the conventional and single-step methods were not significant. Significant difference in values was found only in the anteroposterior measurements; however, clinically, this difference was not significant.

A graph [Graph 1] was plotted to establish the relationship between the single-step method and the conventional method. The values were plotted using the prediction equation:

Single-step method: -1.73 + 1.03 (conventional method)

Conventional method: 2.16 + 0.96 (single-step method).



Actual single-step procedure values deviate only slightly from the predicted values. This indicates the reasonable accuracy of the single-step procedure of diagnostic mounting.


   Discussion Top


Diagnostic casts are mounted on the articulator in order to simulate the movements of the mandible. Incongruity between orientation of the maxillary cast on the articulator and the orientation of the maxilla to the patient's transverse horizontal axis can result in occlusal discrepancies because of deviations in the arc of closure. To avoid these variations, face-bow transfer was advocated. A study demonstrated that earpiece face-bow transfer produced an error of similar magnitude to that of kinematic face-bow instrument in orienting maxillary cast to the articulator. [4],[5] Thus the earpiece face-bow was found to be a consistent method of articulating the maxillary cast.

Zanetti and Ribas introduced an impression procedure that permitted the mounting of the maxillary impression along with the cast to the articulator. [6] A transfer tray was used to transfer the patient's maxillary impression to the articulator in a single-step procedure. The authors concluded that this procedure saved time and materials when compared to conventional procedures for mounting casts in an articulator. The study however did not compare this procedure with the conventional procedure.

A metal dual-arch tray was used in the present study. Although some studies have reported poor accuracy with the use of dual-arch trays, [7] the majority of the studies show that impressions made using metal dual-arch trays were comparable in accuracy to conventional trays in producing casts. [8],[9]

The present investigation combines the various steps performed to mount the diagnostic casts in the conventional procedure. The maxillary and mandibular impressions and the face-bow transfer are made in a single step. The difficulty faced when using the dual-arch mounting is in pouring the impressions without disturbing the face-bow transfer. In this study, the face-bow fork was replaced with the dual-arch tray, which was modified so that a joint was created between the triple tray and bite fork stem, with an antirotational groove. This favored pouring of impressions separately from the face-bow record. This study on 10 individuals shows that the values obtained with the single-step procedure and the conventional procedure are similar, indicating that both procedures have comparable accuracy. The mean anteroposterior value of the single-step procedure (37.7 ± 6.8 mm) deviated slightly from that of the conventional procedure (38.5 ± 6.5 mm) (P<.05); the difference was significant statistically but not clinically. The exact reason for deviation in the anteroposterior value could not be logically attributed; however, a combination of the following reasons can be hypothesized:

  • The combined discrepancies in the vertical and lateral values could in turn lead to some discrepancy in the anteroposterior direction.
  • A joint was provided at the junction of triple tray and stem so that it can be dissembled and reassembled during the procedure. Any minor discrepancy could also add up to the error.
  • This study was a conducted on 10 subjects. A study on a larger sample would give more accurate results.


The single-step procedure of mounting the diagnostic casts proved to be better than the conventional procedure. The single-step procedure was time saving and as accurate as the conventional procedure. Reduction in the number of appointments improved patient comfort, and the mounting procedures were simplified and consistent.

Further studies should be done to examine the advantages of the use of this type of face-bow with dual-arch tray in the field of fixed partial denture fabrication after the tooth preparation is done.


   Conclusion Top


Within the limitations of this study, the following conclusions were drawn:

The single step procedure of triple tray with face-bow transfer can be used as an alternative to the conventional procedure for mounting the diagnostic casts to the articulator without affecting the orientation relation.

  • The single-step procedure combining maxillary and mandibular impressions and face-bow transfer was shown to be an accurate procedure for diagnostic mounting.
  • The single-step procedure for mounting the casts will save chairside time for the dentist.
  • The number of appointments for the patient and the discomfort caused to the patient due to longer procedures can be reduced.
  • The procedure will reduce error-inducing variables by eliminating several steps necessary with the conventional procedures for mounting casts in an articulator.


 
   References Top

1.Articulation of casts. In: Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE, Editors. Fundamentals in fixed prosthodontics. 3 rd ed. Carol Stream: Quintessence; 1997. p. 47-72.  Back to cited text no. 1
    
2.History, Examination, Diagnosis and Prognosis. In: Rosensteil, Land, Fugimoto, Editor. Contemporary fixed partial dentures. 3 rd ed. Missouri: Mosby; 1995. p. 3-45.  Back to cited text no. 2
    
3.Malone WF, Koth DL. Tylman's Theory and practice of fixed prosthodontics. 8 th ed.  Back to cited text no. 3
    
4.Bowley JF, Michaels GC. Reliability of a face-bow transfer procedure. J Prosthet Dent 1992;67:491-8.  Back to cited text no. 4
    
5.Choi DG, Bowley JF, Marx DB, Lee S. Reliability of an ear-bow arbitrary face-bow transfer instrument. J Prosthet Dent 1999;82:150-6.  Back to cited text no. 5
[PUBMED]    
6.Zanetti AL, Ribas R. A new method to simplify and increase the precision of maxillary cast mounting procedures in fully adjustable or semiadjustable articulators. J Prosthet Dent 1997;77:219-24.  Back to cited text no. 6
[PUBMED]    
7.Breeding LC, Dixon DL. Accuracy of casts generated from dual-arch impressions. J Prosthet Dent 2000;84:403-7.  Back to cited text no. 7
[PUBMED]    
8.Larson TD, Nielsen MA, Brackett WW. The accuracy of dual-arch impressions: A pilot study. J Prosthet Dent 2002;87:625-7.  Back to cited text no. 8
[PUBMED]    
9.Davis RD, Schwartz RS. Dual-arch and custom tray impression accuracy. Am J Dent 1991;4:89-92.  Back to cited text no. 9
[PUBMED]    

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Correspondence Address:
Anil Kumar Komuravelli
Department of Prosthodontics, Saraswati Dhanwantri Dental College, Parbhani, Maharashtra
India
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DOI: 10.4103/0970-9290.99028

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