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DENTAL SCIENCE - ORIGINAL ARTICLE
Year : 2013  |  Volume : 5  |  Issue : 5  |  Page : 54-59  

Evaluation of the inclination of maxillary occlusal plane on mounted casts using a fixed value and customized nasion indicator in artex articulator: Facebow system - An in-vivo comparative study


1 Department of Prosthodontia, K.S.R. Institute of Dental Science and Research, Thiruchengode, Namakkal, Tamil Nadu, India
2 Department of Prosthodontia, Rajah Muthiah Dental College and Hospital, Chidambaram, Tamil Nadu, India
3 Department of Prosthodontia, Rajas Dental College, Kavalkinaru, Thirunelveli, Tamil Nadu, India
4 Department of Prosthodontia, Sree Balaji Dental College and Hospital, Chennai, Tamil Nadu, India
5 Department of Prosthodontia, Yogita Dental College and Hospital, Khed, Ratnagiri, Maharastra, India

Date of Submission02-May-2013
Date of Decision04-May-2013
Date of Acceptance04-May-2013
Date of Web Publication13-Jun-2013

Correspondence Address:
Manikandan Ramasamy
Department of Prosthodontia, K.S.R. Institute of Dental Science and Research, Thiruchengode, Namakkal, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0975-7406.113297

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   Abstract 

Aim: To evaluate and compare the variations in the inclination of occlusal plane of casts mounted on Artex articulator using a facebow with a fixed value and customized nasion indicator. Materials and Methods: Twenty two subjects were selected for this investigation. Two maxillary impressions were made, and casts poured. For each of the twenty two subjects, the facebow records were made with, Artex face-bow using a fixed value nasion indicator and customized nasion indicator and mounted. The angle between the occlusal plane of upper cast and the upper articulator arm was measured with a Universal bevel protractor and compared with the gold standard cephalometric value. Results: It shows that, when angle was measured between maxillary occlusal plane and upper member of the articulator, on the mounted cast using a customized nasion indicator and fixed value nasion indicator against the gold standard cephalometric value as a whole, it was found to be not significant. But, if each patient were evaluated individually, there found to be the difference in the angle. Discussion and Conclusion: Variation in occlusal plane was very minimal and close to the cephalometric value when using customized nasion indicator compared to fixed value nasion indicator on the Artex.

Keywords: Articulator, cephalometry, facebow, nasion, occlusal plane


How to cite this article:
Ramasamy M, Karthigeyan S, Giri T C, Rajendran V, Shetty A, Deivanai M. Evaluation of the inclination of maxillary occlusal plane on mounted casts using a fixed value and customized nasion indicator in artex articulator: Facebow system - An in-vivo comparative study. J Pharm Bioall Sci 2013;5, Suppl S1:54-9

How to cite this URL:
Ramasamy M, Karthigeyan S, Giri T C, Rajendran V, Shetty A, Deivanai M. Evaluation of the inclination of maxillary occlusal plane on mounted casts using a fixed value and customized nasion indicator in artex articulator: Facebow system - An in-vivo comparative study. J Pharm Bioall Sci [serial online] 2013 [cited 2022 Nov 28];5, Suppl S1:54-9. Available from: https://www.jpbsonline.org/text.asp?2013/5/5/54/113297

Accurate mounting of dental casts is achieved by transferring the tridimensional spatial relationship of the maxillary arch to an articulator, by using a face-bow. This is done by using 3 reference points. The criteria in the selection of these reference points have been ease of location, convenience, and reproducibility. Two points are located in the area of temporomandibular joints (TMJ). A third point is selected, anterior to the TMJs, to define a plane of reference, which is oriented in the articulator so that the 3-dimensional position of the upper cast is reproduced. [1],[2],[3],[4],[5]

Purpose of the study

Mounting of maxillary cast is done by choosing various anterior reference points and different techniques. [6],[7] Most commonly used anterior point of reference is Orbitale. [8] According to McCollum, [9] axis-orbitale plane is parallel to Frankfort plane, which he relates it to the upper articulator arm, that was horizontal and therefore, parallel to the Frankfort plane.[Figure 1]
Figure 1: Artex articulator with Mounting Jig

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Gonzalez and Kingery [10] in 1968, evaluated three plane of reference namely axis-orbital plane, maxillary residual ridge plane, occlusal plane for orienting maxillary casts on articulator and concluded that axis-orbital plane was the least variable. According to them, none of these planes of reference was parallel to Frankfort horizontal, rather axis-orbital plane exhibits a positive anterior tilt and the mean for the perpendicular distance from the condylar axis point to the Frankfort horizontal was 7.1 mm.

Pitchford's [11] recommended a method of mounting the maxillary casts, "Esthetics Reference Plane" by leveling the face bow with bubble level. Pitchford also stated that neither the FH nor the axis-orbitale plane is parallel to the reference horizontal in the esthetic reference position. The use of either plane as reference horizontal in facebow will place maxillary cast too low in articulator. Ercoli, et al., [12] uses the angular relationship between the occlusal plane and the condylar path to mount the maxillary cast on the articulator.

Weinberg [13] stated that if occlusal plane is not properly oriented on the articulator with any of reference planes may produce an increase or decrease of 0.2 mm of the tooth surface on the balancing side. This error occurs mainly around the second molar region.

According to Sicher Nasion −23 mm, [8] another skull landmark, the nasion, can be approximately located in the head as the deepest part of the midline depression just below the level of the eyebrows. The nasion guide, or positioner, of the Quick Mount face-bow, which is designed to be used with the Whip-Mix Articulator, fits into this depression. The center of nasion shaft is aligned with the greatest convexity of nasion indicator. This guide can be moved in and out, but not up and down, from its attachment to the face-bow crossbar.

Wilcox [14] in 2008 evaluated the accuracy of fixed value nasion relator in facebow design through analysis of cephalometric radiographs of 114 adult patients, found a mean distance of 26.8 mm distance between nasion and orbitale with the values ranged from 15.9 mm to 39.4 mm, also he concluded that a variable value nasion relator/orbitale indicator is recommended.

The changes in inclination of occlusal plane of cast mounted on Artex articulator have not been studied or compared previously. In the present study, we have compared the changes in inclination of occlusal plane, using customized nasion and fixed value nasion indicator. Artex facebow system uses nasion as anterior reference point. When the face-bow is positioned anteriorly by the nasion guide, the crossbar will be in the approximate region of orbitale, so it is orbitale and not the nasion which serves as an anterior point of reference.

A study was conducted to evaluate and compare the variations in the inclination of occlusal plane of casts mounted on Artex articulator using a facebow with a fixed value and customized nasion indicator.


   Materials and Methods Top


In the present study, Artex articulator with earpiece facebow that utilizes fixed nasion as an anterior point of reference was chosen. In Artex facebow, the crossbar is located 35 mm below the midpoint of the nasion positioned. Hence the cross bar will be too low from the orbitale and can result in changes in the inclination of occlusal plane once mounted. In the present study, Artex facebow with a fixed value nasion relator and a customized variable nasion relator was used to evaluate the effect of a customized nasion relator in facebow design, by measuring the relationship of maxillary occlusal plane (MOP) to the upper member on the articulator and the same is compared to the frankfort horizontal plane (FHP) on the cephalogram.[Figure 2]
Figure 2: Facebow with fixed nasion and customized nasion relator

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In this study, a comparison of Inclination of Occlusal Plane of cast mounted on Artex articulator using a fixed value nasion indicator and customized nasion indicator were compared with occlusal plane angle on the Cephalogram.

A customized nasion indicator is one in which it can be raised or lowered vertically to a distance of 10 mm above and below from the standard fixed value 35 mm, with readings marked on it.

Twenty two subjects, were selected for this investigation who were having Angles ideal class I relation, Two maxillary impressions were made for each subject using stock tray with alginate (Zelgan, Densply). The impression were disinfected with 2% glutaraldehyde (Korsolex, Ramen Weil) sprayed and rinsed. Dental stone was mixed in the W/P ratio 0.28-0.30 and vibrated in to the impression.

The face-bow used in this study was Artex (TK) (GIRRBACH). Artex facebow is an earpiece facebow. The external auditory meatus is the posterior reference point. This face bow has a fixed nasion indicator that is used as the anterior reference point.

For each of the twenty two subjects, the facebow records were made with, Artex face-bow using a fixed value nasion indicator and customized nasion indicator. The face bow recording was registered according to manufacturer's instruction. Each facebow was mounted on to its Artex articulator.

Cotton rolls were placed below the disposable bite fork so that the mandibular arch holds the bite fork against the maxillary arch firmly. The facebow frame was placed on the patient so that the earpiece was placed in the external auditor meatus. The earpiece was placed such that the patient did not feel the pressure. Then the nasion bar was stabilized and the nasion set-screw was turned to lock. The bite fork was attached to the facebow frame with the three dimensional universal joint with the connecting screw. The universal joint was locked in all three dimensions by turning one toggle lever.

Facebow was removed from the patient mouth with the universal joint. The universal joints containing the bite fork was detached from the facebow. The universal joint was transferred to the transfer stand of artex-facebow system, quick-setting plaster was placed between the bite fork and transfer stand for securing the bite fork. The base table with bite fork was detached from the transfer stand. It was secured and transferred to the articulator. The base table was attached to the articulator in the place of lower mounting plate. The upper cast was placed over the bite fork. The base of the cast was moistened, mounting plaster (Kalabai) was mixed to manufacturer instructions and applied to the base of the cast, the upper member of articulator was closed and the excess was removed.

All records for each subject were completed on the same day by the same operator.

Measurements

The angle between the occlusal plane of upper cast and the upper articulator arm was measured to indicate the inclination of the MOP. The upper articulator arm was horizontal and therefore parallel to the Frankfort plane. The angle between the occlusal plane and the upper articulator arm was measured with a Universal bevel protractor (MITUTOYO). This instrument was modified to suit the purpose of this study. A suitable mount for this device was constructed consisting of a flat base with a vertical extension to which the protractor's holding rod is fixed. Modified universal bevel protractor can be raised or lowered on its holding rod. It can be also fixed on the holding rod at any particular height.

The Universal bevel protractor has a calibrated dial with reading from 0° to 90° in four quadrants. There is second dial, which rotates with the main dial. The calibrated dial has a horizontal extension which is modified with a glass plate. This glass plate touches the occlusal plane. The entire device can be placed in front of the articulator on a leveled platform. When the glass plate touches the occlusal plane the second dial moves over the first dial and the readings can be seen on the first dial through a lens which is attached to the second dial indicating the inclination of the occlusal plane. [15],[16],[17],[18],[19],[20],[21],[22]

Cephalometric analysis

Cephalometric tracing were done by hand on fine acetate sheets. All tracing are done by a single person. The FHP, orbitale, and the soft tissue nasion points were identified on the photocopy of each cephalometric tracing. Linear measurements were made from orbitale to nasion at a 90 angle to FHP. The angle on the cephalogram that reproduced the angle measured clinically on the articulator was FHP to MOP. [14] The FHP is a line between the machine porion and orbitale and the MOP is between first molar mesiobuccal cusp and the incisor edge. Angle between FHP and MOP is measured using a protractor by the same individual who did the clinical study.


   Results Top


Difference in nasion to orbitale distance (DIFFNASORBIT) from the fixed value 35 mm to cephalometric value in mm and their occurrence in 22 patients was measured [Table 1]. When angle was measured between MOP and upper member of the articulator, on the mounted cast using a customized nasion indicator and fixed value nasion indicator against the gold standard cephalometric value as a whole, it was found to be not significant [Table 2].
Table 1: DIFFNASORBIT from the fixed value 35 mm to cephalometric value in mm and their occurrence in 22 patients

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Table 2: Descriptive statistics of angle measured

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However, if each patient were evaluated individually, there found to be the difference in the angle. So the 22 patients were divided into nine groups, based on the number of patients that comes under one value, when making a cephalometric difference in the distance between the fixed distances of nasion to orbitale [Table 1].

The results of the present study shows that There were no changes in the inclination occlusal plane when transferred to the articulator when using customized nasion indicator in at least 22.7% of patients [Table 3]. It was also observed that only for 9.1% of patients, there were no changes in the inclination occlusal plane when transferred to the articulator when using a fixed value nasion indicator [Table 4]. Also, the angle obtained between FHP and MOP was found to be more close to cephalometric value when using customized nasion indicator when the DIFFNASORBIT was ± 3 mm and greater [Table 5] and [Table 6]. Likewise, all 9 groups have been calculated and totally 15 tables were tabulated in this study. Even when the customized nasion indicator was used for other DIFFNASORBIT, it was found to be more close to cephalometric value when compared to a fixed value.
Table 3: DIFFCUSTCEPH and their frequency in 22 patients

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Table 4: DIFFFIXCEPH and their frequency in 22 patients

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Table 5: Based on DIFFNASORBIT of 1 mm

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Table 6: Based on DIFFNASORBIT of 3 mm

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In the present study, when using the fixed value nasion indicator, it was found to be close to the gold standard cephalometric value only when the DIFFNASORBIT was around ± 2 mm. There was not much difference in the angle and was within the acceptable limit, but not considered always superior to customized nasion indicator. It was also observed that when using customized nasion indicator, it produces less error in inclination of MOP.

Also, it was observed that the highest variation 27.3% was observed for 2° difference when using customized nasion indicator, and 3° difference for remaining when using a fixed value nasion indicators. This could be the reason for more flattening of occlusal plane when using a fixed value nasion indicators.

The results of this study showed that the Inclination of the occlusal plane was not maintained when transferred to the articulator. When compared to the angle on the cephalogram, occlusal plane was flattened by a minimum of 2°. This variation was found when using both nasion indicators, but found to be less when using customized nasion indicator.


   Discussion Top


The selection of the anterior reference point [8] on the triangular spatial plane, determines which plane in the head will become the plane of reference and this governs the horizontal plane of reference. The various anterior reference points are Orbitale, Orbitale −7, Nasion −23, Incisal edge plus articulator midpoint to articulator axis-horizontal plane distance and Ala of the nose. The orbitale with the two posterior arbitrary hinge-axis points will define the axis-orbitale plane. The criteria used in the selection of any of these reference planes are of ease of location, convenience and reproducibility.

Variations in the occlusal plane when transferred to the articulator have also been reported by previous studies. [23],[24],[25] Malley and Milosevic [23] compared the steepness of occlusal plane in three different articulators. They compared three different articulator system Wipmix, Denar and Dentatus and concluded that Whipmix which was closest to the gold standard of this study and flattened the occlusal plane by only 2°. The results of the Denar and Dentatus differed significantly from those of the cephalogram as they flattened the occlusal plane by 5° and 6.5° respectively.

Mohammed Abdullah [24] compared the steepness of occlusal plane on Whipmix and Hanau-H2 and stated that the steepness of occlusal plane of the cast when mounted on Whipmix was significantly greater than the cast mounted on Hanau-H2. Kyung-Suk Seo [1] reported that the steepness of occlusal plane angle to Frankfort plane in cast-mounted articulator is steeper than that of cephalogram. The mean difference of occlusal plane angle between cast-mounted articulator and cephalogram was 3.3°.

The limitations of a lateral cephalogram image relate to comparison of three-dimensional objects with the two-dimensional cephalograph, and any mesiolateral can't of the MOP is not seen on the lateral cephalograph. None the less, the cephalometric gold standard fundamental to this study (Frankfurt horizontal / Maxillary occlusal plane (FH/MOP)) is as reliable as many commonly accepted tracing angles.

The angle between FHP with occlusal plane (OP) in cephalogram and OP with upper member of articulator (FH) was compared. The mean angle was 8.9° which is the cephalometric gold standard for this study. The mean angles of cephalometric gold standard used by various studies were, according to Gonzalez 9°, [10] Kyung-Suk Seo 10.4°, [1] Jaime Cateno 6.1°, [25] Malley 14.6°, [19] and Ow Richard 11.2° in Chinese patients and 10.7° in Swedish patients. [20]

In Artex facebow, the crossbar is located 35 mm below the midpoint of the nasion positioned. Hence the cross bar will be too low from the orbitale. Wilkie [8] has stated that relating the maxillae to Orbitale plane will slightly lower the maxillary cast anteriorly. Hence lowering the Orbitale plane will flatten the occlusal plane on articulator. This could be the reason for flattening of the occlusal plane of the cast when mounted on Artex.

According to Wilcox [14] the fixed value of the Whipmix nasion relator as measured from the top of the horizontal bar of the facebow and the center of the nasion shaft is 25.4 mm. In his study, the mean distance between orbitale and nasion was 26.8 mm. Hence he concluded that fixed value nasion relator was thought to be impractical and a variable value nasion relator or orbitale indicator is recommended.

A customized nasion indicator was designed which can be raised or lowered vertically to a distance of 10 mm above and below from the standard fixed value 35 mm, with readings marked on it. This was based on the pilot study on103 patients, did by the same operator, in which linear measurements were made from orbitale to nasion at a 90° angle to FHP and the resulting values ranged from 26 mm to 43 mm. [Figure 3]
Figure 3: customized nasion indicator

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Previous studies have also suggested that articulators that use orbital reference will position the occlusal plane too steeply in the articulator. Fraser Walker [17],[18] used a facebow with both an orbital pointer and sprit level on Dentatus articulator. He stated that there were large significant systematic differences between the occlusal angle measured from the cephalograms and casts mounted using the orbital pointer. He concluded that the facebow with sprit level produced considerably more accurate results. [Figure 4]
Figure 4: Angle measured with universal bevel protractor on mounted maxillary cast

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Present study shows the comparison of angle between the different nasion indicators based on individual DIFFNASORBIT in mm. For certain individual differences, the number of patients under these categories were minimal and so it was not possible to compare the results. The reason for this is smaller sample size.

Limitations

Further studies are required to confirm these results, because of the

  1. Smaller sample size.
  2. Digital values are not recorded in the present study and
  3. Also, the operator error in recording the small difference in angle.
Within the limitations of this study, it can be concluded that

  1. A customized nasion indicator is of value when using Artex facebow.
  2. Variation in occlusal plane was very minimal and close to the cephalometric value when using customized nasion indicator compared to fixed value nasion indicator on the Artex.
  3. When Nasion to Orbitale distance was 35 ± 3 mm, the angular difference between FHP and MOP was very close to the gold standard cephalometric value when customized nasion indicator was used.
  4. Fixed value nasion indicator was found to be close to the gold standard cephalometric value, only when Nasion to Orbitale distance was 35 ± 2 mm but not superior to the other.


 
   References Top

1.Suk Seo K. The comparative study for occlusal plane between articulated cast model and cephalogram in orthogantihic surgery patients. J Kor Oral Maxillofac Surg 2003;29:239-44.  Back to cited text no. 1
    
2.Brandrup Wognsen T. The face-bow, its significance and application. J Prosthet Dent 1953;3:618-30.  Back to cited text no. 2
    
3.Starcke EN. The history of articulators: From facebows to the gnathograph, a brief history of early devices developed for recording condylar movement: Part II. J Prosthodont 2002;11:53-62.  Back to cited text no. 3
    
4.Thorp ER, Smith DE, Nicholls JI. Evaluation of the use of a face-bow in complete denture occlusion. J Prosthet Dent 1978;39:5-15.  Back to cited text no. 4
    
5.Stade EH, Hanson JG, Baker CL. Esthetic considerations in the use of face-bows. J Prosthet Dent 1982;48:253-6.  Back to cited text no. 5
    
6.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. 6
    
7.Piehslinger E, Bauer W, Schmiedmayer HB. Computer simulation of occlusal discrepancies resulting from different mounting techniques. J Prosthet Dent 1995;74:279-83.  Back to cited text no. 7
    
8.Wilkie ND. The anterior point of reference. J Prosthet Dent 1979;41:488-96.  Back to cited text no. 8
    
9.Chitre V. Need for an anterior point of reference in face bow transfer: The changing viewpoint. Changing concepts regarding anterior reference point. J Indian Prosthodont Soc 2006;6:112-4.  Back to cited text no. 9
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10.Gonzalez JB, Kingery RH. Evaluation of planes of reference for orienting maxillary casts on articulators. J Am Dent Assoc 1968;76:329-36.  Back to cited text no. 10
    
11.Pitchford JH. A reevaluation of the axis-orbital plane and the use of orbitale in a facebow transfer record. J Prosthet Dent 1991;66:349-55.  Back to cited text no. 11
    
12.Ercoli C, Graser GN, Tallents RH, Galindo D. Face-bow record without a third point of reference: Theoretical considerations and an alternative technique. J Prosthet Dent 1999;82:237-41.  Back to cited text no. 12
    
13.Lawrence A. Weinberg: An evaluation of the facebow mounting. J Prosthet Dent 1961;11:32-42.  Back to cited text no. 13
    
14.Wilcox CW, Sheets JL, Wilwerding TM. Accuracy of a fixed value nasion relator in facebow design. J Prosthodont 2008;17:31-4.  Back to cited text no. 14
    
15.Monteith BD. A cephalometric method to determine the angulation of the occlusal plane in edentulous patients. J Prosthet Dent 1985;54:81-7.  Back to cited text no. 15
    
16.Monteith BD. Cephalometrically programmed adjustable plane: A new concept in occlusal plane orientation for complete-denture patients. J Prosthet Dent 1985;54:388-94.  Back to cited text no. 16
    
17.Walker F, Ayoub AF, Moos KF, Barbenel J. Face bow and articulator for planning orthognathic surgery: 1 face bow. Br J Oral Maxillofac Surg 2008;46:567-72.  Back to cited text no. 17
    
18.Walker F, Ayoub AF, Moos KF, Barbenel J. Face bow and articulator for planning orthognathic surgery: 2 articulator. Br J Oral Maxillofac Surg 2008;46:573-8.  Back to cited text no. 18
    
19.O'Malley AM, Milosevic A. Comparison of three facebow/semi-adjustable articulator systems for planning orthognathic surgery. Br J Oral Maxillofac Surg 2000;38:185-90.  Back to cited text no. 19
    
20.Ow RK, Djeng SK, Ho CK. Orientation of the plane of occlusion. J Prosthet Dent 1990;64:31-6.  Back to cited text no. 20
    
21.Karkazis HC, Polyzois GL. Cephalometrically predicted occlusal plane: Implications in removable prosthodontics. J Prosthet Dent 1991;65:258-64.  Back to cited text no. 21
    
22.Ismail YH, Bowman JF. Position of the occlusal plane in natural and artificial teeth. J Prosthet Dent 1968;20:407-11.  Back to cited text no. 22
    
23.Bailey JO Jr, Nowlin TP. Evaluation of the third point of reference for mounting maxillary casts on the Hanau articulator. J Prosthet Dent 1984;51:199-201.  Back to cited text no. 23
    
24.Abdullah M A, Sherfudhin H. A comparative study of facebow transfer on hanau and whip-mix articulators. Saudi Dent J 1994;6:8-12.  Back to cited text no. 24
    
25.Gateno J, Forrest KK, Camp B. A comparison of 3 methods of face-bow transfer recording: Implications for orthognathic surgery. J Oral Maxillofac Surg 2001;59:635-40.  Back to cited text no. 25
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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