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Comparison of cast positions by using four face-bows
DOS SANTOS
10. Ash MM, Ramjford SP. An introduction to functional occlusion. Philadelphia: WB Saunders, 1982;21-34. 11. Lundeen HC, Shryock EF, Gibbs CH. An evaluation of mandibular border movements: their character and significance. J PROSTHET DENT 1978;40:442-52. 12. Hobo S, Shillingburg HT Jr, Whitsett LD. Articulator selection for restorative dentistry. J PR~~THET DENT 1976;36:35-
AND
ASH
Reprint requests to: DR. JOSE Dos SANTOS, JR. UNIVERSW OF MICHIGAN SCHOOL OF DENTISTRY ANN ARBOR, MI 48109-1078
43.
Comparison of cast positions by using four face-bows J. R. Goska, D.D.S.,* and L. V. Christensen, D.D.S.** Marquette
University,
School of Dentistry,
Milwaukee,
Wis.
T
he face-bow is commonly used for mounting maxillary casts on articulators. Although different face-bow configurations have been studied for accuracy and ability to orient casts on the articulator,‘-4 three-dimensional comparisons between casts mounted with various facebows have not been made. This study compared the positions of maxillary right and left first molar teeth by using four different face-bows (Hanau Kinematic Facebow, Hanau Facia-bow, Hanau 159 Earbow, Hanau Twirl-bow, Teledyne Hanau, Buffalo, N.Y.).
MATERIAL
AND METHODS
Four face-bow transfers were performed on each of 10 dental students (5 women and 5 men in the age range of 22 to 28 years). All of the students were healthy with no signs or symptoms from the mandibular locomotor system. A maxillary cast was obtained from each subject from an irreversible hydrocolloid impression. All four face-bow recordings were made according to the manufacturer’s instructions, using a point 43 mm superior to the mesial corner of the incisal edge of the maxillary right central incisor as the third point of reference. Each of the face-bow recordings was mounted on the same Hanau H2 articulator (Teledyne Hanau). When all 40 mountings were completed, minute points on the mesiobuccal cusp tips of the maxillary first molar teeth were marked on the maxillary casts. Each face-bow mounting and its respective maxillary cast was transferred to and fixed in a movable jig on the contour meter (Fig. l).’ The
*Assistant Professor, Department of Removable Prosthodontics. **Former Resident, Department of Removable Prosthodontics.
42
Fig. 1. Contour meter for determining position of maxillary right and left first molars along X, Y, and Z axes. Knobs X and Y control movements of mounting jig along respective X and Y axes. Z dial measures position of molars along Z axis. M, Mounted maxillary cast transferred to contour meter.
movable jig allowed sliding measurements along the X and Y axes. The Z axis was measured from a fixed point perpendicular to the plane of the X-Y axes. Use of the contour meter was identical to that described by Ryge and Fairhurst. The marked points on the maxillary first molars were recorded in the X-Y-Z coordinate system. The kinematically determined hinge-axis mounting was chosen as an arbitrary baseline. The variables, in millimeters, were deviations along the X, Y, and Z axes obtained by comparing the marked
JANUARY
1988
VOLUME
59
NUMBER
1
CAST POSITIONS
WITH
FOUR FACE-BOWS
Table III. Summary of nested ANOVA
Table I. Mean deviations
(in millimeters) from hinge-axis baseline, as measured in 10 human subjects by three face-bows along X, Y, and Z axes of maxillary right and left first molars ___-
Source of variation
Face-bow 159-Bow
Total Among all subgroups Groups Subgroups Error
SS
DF
605.07 12.45
59 5
6.36 6.09 592.62
2 3 54
MS
F
P
3.18 2.03 10.97
1.57 0.19
>0.25 >0.25
f
SD
x
SD
f
SD
3 14
I..62 I. .59
1.01 1.16
2.56 2.65
2.71 2.74
2.19 2.10
1.60 1.40
For key to symbols see Table II.
3 14
3.13 3.67
3.10 3.22
3.15 4.04
4.06 3.96
2.65 3.01
2.33 2.87
Table IV. Summary of nested ANOVA Z-axis data
3 14
4.01 2.99
2.16 2.20
3.82 1.89
1.29 1.22
1.61 1.15
0.80 0.76
Source of variation
left first
Total Among all subgroups Groups Subgroups Error
Axis X axis No. No. Y axis: No. No. 2 axis: No. No.
Facia-Bow
Twirl-Bow
No. 3 = Maxillary molar.
right first molar, No. 14 = maxillary
Table II. Summary of nested ANOVA
of
X-axis data Source of variation Total Among all subgroups Groups Subgroups Error
SS
DF
196.79 72.08
59 5
47.25 24.83 124.71
2 3 54
of
MS
F
P
23.63 8.28 2.31
2.85 3.58
>O.lO <0.025
For key to symbols see Table II. SS
DF
205.91 10.17
59 5
10.08 0.09 195.74
2 3 54
MS
5.04 0.03 3.62
F
168 0.01
P
0.25
SS = Sum of squares; DF = degrees of freedom; MS = mean square; F =f-ratio; P = significance level.
teeth on the cast mounted with the kinematic face-bow with those same marks when the cast was mounted with each of the other three face-bows. Each deviation was derived from two different sources, the markings on the right and left maxillary first molars. Nested, or hierarchical, analyses of variance (ANOVA) were applied, and all significance levels equal to or below the 0.05 level were accepted as significant (ia 5.05).
RESULTS Table I lists mean deviations from the hinge-axis baseline as measured at the two different sources and by the three different face-bow mountings. Table II is a summary of the ANOVA of data pertaining to the X axis. No significant difference was found among measurement sources, right and left maxillary first molars, affecting deviations from the baseline (p > .25), but a significant difference was found in deviations from the baseline related to the three different face-bows
THE JOURNAL
of
Y-axis data
(SF PROSTHETIC
DENTISTRY
(i6 < .OOl). ANOVA of Y-axis data is summarized in Table III. The analysis showed no significant differences pertaining to measurement sources or types of face-bows (p > .25). Table IV is a summary of ANOVA of Z-axis data. Measurement sources, right and left maxillary first molars, significantly affected deviations from the hinge-axis baseline (p < .025); however, no significant difference was found in deviations from the baseline related to the three different face-bows cp > .lO).
DISCUSSION For the comparison between the three different facebows, a kinematically determined hinge-axis baseline was chosen arbitrarily. Although it is not a naturally occurring axis, it is widely used as a reference axis for mounting of casts on an articulator.6s7 Table I shows that deviations between the hinge-axis baseline and the three face-bow mountings along the X, Y, and Z axes range from approximately 1.5 to 4 mm. The deviations show no consistency as a result of using a particular face-bow. In regard to earpiece face-bows this might have been the result of naturally occurring variations in ear anatomy, whereas the earpieces of the individual bows are uniform in size and shape. In addition, the Facia-bow device uses a standardized skin point as the rotational axis, and a “true” axis is not determined. These factors may contribute to the widely
43
COSKA
scattered deviations from the hinge-axis baseline. No face-bow appeared to be superior to another (Tables II through IV). SUMMARY The positions that the maxillary right and left first molars occupy when a maxillary cast is mounted in the three-dimensional space of a semiadjustable articulator (Hanau H2) were studied. Mountings were made by using four face-bows, the Hanau Kinematic Face-bow, the Hanau Facia-bow, the Hanau 159 Earpiece Facebow, and the Hanau Twirl Earpiece Face-bow. A kinematically determined hinge-axis was used arbitrarily as the baseline for comparisons among the three other bows. Deviations from the baseline were measured along the X, Y, and Z axes by using a contour meter (Fig. 1). The deviations showed great variability (Table I), and because maxillary casts are mounted in relation to anatomic landmarks that differ from subject to subject, it was not possible to establish clinical superiority of one face-bow over another.
44
AND
CHRISTENSEN
REFERENCES Logan JG. Indispensability of the face-bow and the effect of a short radius in full and partial denture construction. Dent Dig 1926;32:537-42. 2. McCollum BB. Fundamentals involved in prescribing restorative dental remedies. Dent Items Interest 1939;61:522-35. 3. Teteruck WR, Lundeen HC. The accuracy of an ear face-bow. J PROSTHET DENT 1966;16:1039-46. 4. Palik JF, Nelson DR, White JT. Accuracy of an earpiece face-bow. J PR~~THETDENT 1985;53:800-4. 5. Ryge G, Fairhurst CW. The contour meter: an apparatus for comparison of mucosal surface contour of impressions, models, and dentures.J PR~~THETDENT 1959;9:6?6-82. 6. Christensen LV, Slabbert JCG. The concept of the sagittal condylar guidance: biological fact or fallacy? J Oral Rehabil 1978;5:1-7. 7. Mohamed SE, Christensen LV. Mandibular reference positions. J Oral Rehabil 1985;12:355-67. 1.
Reprint requests to: DR.JOHN R.GOSA 831 W. GOLFRD.
LIBERTYVILLE,IL60048
JANUARY
1988
VOLUME
59
NUMBER
1
10. Ash MM, Ramjford SP. An introduction to functional occlusion. Philadelphia: WB Saunders, 1982;21-34. 11. Lundeen HC, Shryock EF, Gibbs CH. An evaluation of mandibular border movements: their character and significance. J PROSTHET DENT 1978;40:442-52. 12. Hobo S, Shillingburg HT Jr, Whitsett LD. Articulator selection for restorative dentistry. J PR~~THET DENT 1976;36:35-
AND
ASH
Reprint requests to: DR. JOSE Dos SANTOS, JR. UNIVERSW OF MICHIGAN SCHOOL OF DENTISTRY ANN ARBOR, MI 48109-1078
43.
Comparison of cast positions by using four face-bows J. R. Goska, D.D.S.,* and L. V. Christensen, D.D.S.** Marquette
University,
School of Dentistry,
Milwaukee,
Wis.
T
he face-bow is commonly used for mounting maxillary casts on articulators. Although different face-bow configurations have been studied for accuracy and ability to orient casts on the articulator,‘-4 three-dimensional comparisons between casts mounted with various facebows have not been made. This study compared the positions of maxillary right and left first molar teeth by using four different face-bows (Hanau Kinematic Facebow, Hanau Facia-bow, Hanau 159 Earbow, Hanau Twirl-bow, Teledyne Hanau, Buffalo, N.Y.).
MATERIAL
AND METHODS
Four face-bow transfers were performed on each of 10 dental students (5 women and 5 men in the age range of 22 to 28 years). All of the students were healthy with no signs or symptoms from the mandibular locomotor system. A maxillary cast was obtained from each subject from an irreversible hydrocolloid impression. All four face-bow recordings were made according to the manufacturer’s instructions, using a point 43 mm superior to the mesial corner of the incisal edge of the maxillary right central incisor as the third point of reference. Each of the face-bow recordings was mounted on the same Hanau H2 articulator (Teledyne Hanau). When all 40 mountings were completed, minute points on the mesiobuccal cusp tips of the maxillary first molar teeth were marked on the maxillary casts. Each face-bow mounting and its respective maxillary cast was transferred to and fixed in a movable jig on the contour meter (Fig. l).’ The
*Assistant Professor, Department of Removable Prosthodontics. **Former Resident, Department of Removable Prosthodontics.
42
Fig. 1. Contour meter for determining position of maxillary right and left first molars along X, Y, and Z axes. Knobs X and Y control movements of mounting jig along respective X and Y axes. Z dial measures position of molars along Z axis. M, Mounted maxillary cast transferred to contour meter.
movable jig allowed sliding measurements along the X and Y axes. The Z axis was measured from a fixed point perpendicular to the plane of the X-Y axes. Use of the contour meter was identical to that described by Ryge and Fairhurst. The marked points on the maxillary first molars were recorded in the X-Y-Z coordinate system. The kinematically determined hinge-axis mounting was chosen as an arbitrary baseline. The variables, in millimeters, were deviations along the X, Y, and Z axes obtained by comparing the marked
JANUARY
1988
VOLUME
59
NUMBER
1
CAST POSITIONS
WITH
FOUR FACE-BOWS
Table III. Summary of nested ANOVA
Table I. Mean deviations
(in millimeters) from hinge-axis baseline, as measured in 10 human subjects by three face-bows along X, Y, and Z axes of maxillary right and left first molars ___-
Source of variation
Face-bow 159-Bow
Total Among all subgroups Groups Subgroups Error
SS
DF
605.07 12.45
59 5
6.36 6.09 592.62
2 3 54
MS
F
P
3.18 2.03 10.97
1.57 0.19
>0.25 >0.25
f
SD
x
SD
f
SD
3 14
I..62 I. .59
1.01 1.16
2.56 2.65
2.71 2.74
2.19 2.10
1.60 1.40
For key to symbols see Table II.
3 14
3.13 3.67
3.10 3.22
3.15 4.04
4.06 3.96
2.65 3.01
2.33 2.87
Table IV. Summary of nested ANOVA Z-axis data
3 14
4.01 2.99
2.16 2.20
3.82 1.89
1.29 1.22
1.61 1.15
0.80 0.76
Source of variation
left first
Total Among all subgroups Groups Subgroups Error
Axis X axis No. No. Y axis: No. No. 2 axis: No. No.
Facia-Bow
Twirl-Bow
No. 3 = Maxillary molar.
right first molar, No. 14 = maxillary
Table II. Summary of nested ANOVA
of
X-axis data Source of variation Total Among all subgroups Groups Subgroups Error
SS
DF
196.79 72.08
59 5
47.25 24.83 124.71
2 3 54
of
MS
F
P
23.63 8.28 2.31
2.85 3.58
>O.lO <0.025
For key to symbols see Table II. SS
DF
205.91 10.17
59 5
10.08 0.09 195.74
2 3 54
MS
5.04 0.03 3.62
F
168 0.01
P
SS = Sum of squares; DF = degrees of freedom; MS = mean square; F =f-ratio; P = significance level.
teeth on the cast mounted with the kinematic face-bow with those same marks when the cast was mounted with each of the other three face-bows. Each deviation was derived from two different sources, the markings on the right and left maxillary first molars. Nested, or hierarchical, analyses of variance (ANOVA) were applied, and all significance levels equal to or below the 0.05 level were accepted as significant (ia 5.05).
RESULTS Table I lists mean deviations from the hinge-axis baseline as measured at the two different sources and by the three different face-bow mountings. Table II is a summary of the ANOVA of data pertaining to the X axis. No significant difference was found among measurement sources, right and left maxillary first molars, affecting deviations from the baseline (p > .25), but a significant difference was found in deviations from the baseline related to the three different face-bows
THE JOURNAL
of
Y-axis data
(SF PROSTHETIC
DENTISTRY
(i6 < .OOl). ANOVA of Y-axis data is summarized in Table III. The analysis showed no significant differences pertaining to measurement sources or types of face-bows (p > .25). Table IV is a summary of ANOVA of Z-axis data. Measurement sources, right and left maxillary first molars, significantly affected deviations from the hinge-axis baseline (p < .025); however, no significant difference was found in deviations from the baseline related to the three different face-bows cp > .lO).
DISCUSSION For the comparison between the three different facebows, a kinematically determined hinge-axis baseline was chosen arbitrarily. Although it is not a naturally occurring axis, it is widely used as a reference axis for mounting of casts on an articulator.6s7 Table I shows that deviations between the hinge-axis baseline and the three face-bow mountings along the X, Y, and Z axes range from approximately 1.5 to 4 mm. The deviations show no consistency as a result of using a particular face-bow. In regard to earpiece face-bows this might have been the result of naturally occurring variations in ear anatomy, whereas the earpieces of the individual bows are uniform in size and shape. In addition, the Facia-bow device uses a standardized skin point as the rotational axis, and a “true” axis is not determined. These factors may contribute to the widely
43
COSKA
scattered deviations from the hinge-axis baseline. No face-bow appeared to be superior to another (Tables II through IV). SUMMARY The positions that the maxillary right and left first molars occupy when a maxillary cast is mounted in the three-dimensional space of a semiadjustable articulator (Hanau H2) were studied. Mountings were made by using four face-bows, the Hanau Kinematic Face-bow, the Hanau Facia-bow, the Hanau 159 Earpiece Facebow, and the Hanau Twirl Earpiece Face-bow. A kinematically determined hinge-axis was used arbitrarily as the baseline for comparisons among the three other bows. Deviations from the baseline were measured along the X, Y, and Z axes by using a contour meter (Fig. 1). The deviations showed great variability (Table I), and because maxillary casts are mounted in relation to anatomic landmarks that differ from subject to subject, it was not possible to establish clinical superiority of one face-bow over another.
44
AND
CHRISTENSEN
REFERENCES Logan JG. Indispensability of the face-bow and the effect of a short radius in full and partial denture construction. Dent Dig 1926;32:537-42. 2. McCollum BB. Fundamentals involved in prescribing restorative dental remedies. Dent Items Interest 1939;61:522-35. 3. Teteruck WR, Lundeen HC. The accuracy of an ear face-bow. J PROSTHET DENT 1966;16:1039-46. 4. Palik JF, Nelson DR, White JT. Accuracy of an earpiece face-bow. J PR~~THETDENT 1985;53:800-4. 5. Ryge G, Fairhurst CW. The contour meter: an apparatus for comparison of mucosal surface contour of impressions, models, and dentures.J PR~~THETDENT 1959;9:6?6-82. 6. Christensen LV, Slabbert JCG. The concept of the sagittal condylar guidance: biological fact or fallacy? J Oral Rehabil 1978;5:1-7. 7. Mohamed SE, Christensen LV. Mandibular reference positions. J Oral Rehabil 1985;12:355-67. 1.
Reprint requests to: DR.JOHN R.GOSA 831 W. GOLFRD.
LIBERTYVILLE,IL60048
JANUARY
1988
VOLUME
59
NUMBER
1