Accuracy of a Predetermined Transverse Horizontal Mandibular Axis Point

used to orient the mandibular cast.4, 5 However, theaxis of rotation belongs to the moveable mandible andnot to the fixed cranial base, and many rotational cen-ters are possible.

The transverse horizontal mandibular axis as a rota-tion center, its location, and its transfer to a suitablearticulator have been controversial topics for manyyears.6 Interest in these subjects crosses many dentalspecialties and embraces both diagnosis and treat-ment.7-14 Arbitrary axis points determined fromanatomical landmarks are popular due to their ease ofuse compared to the trial-and-error method of locat-ing the kinematic axis. It has been demonstratedmathematically that location of an arbitrary axis point± 5 mm anterior-posterior to the kinematic axis willresult in negligible error (0.2 mm) on the nonworkingside when a 3-mm–thick centric relation record is

Accuracy of a predetermined transverse horizontal mandibular axis point

William W. Nagy, DDS,a Thomas J. Smithy, DMD, MSD,b and Carl G. Wirth, DDSc

School of Dentistry, Marquette University, Milwaukee, Wisc.

Statement of problem. The transverse horizontal mandibular axis point may be located most preciselyby a kinematic process. However, an anatomical method of locating the axis is also an acceptable tech-nique, and an easily determined point that is consistently close to the kinematic axis would simplifytransfer of the arc of rotation from the patient to the articulator. Purpose. This in vivo study compared the location of an anatomically predetermined hinge axis pointwith the determined kinematic axis. Material and methods. Forty subjects (27 males, 13 females; 23 to 47 years of age) with functionallyacceptable occlusion and no detectable clinical signs of temporomandibular disorders participated in thestudy. The earpiece alignment flags on a mechanical SAM Axiograph III combination flag/face-bow wereused to locate the right and left predetermined hinge axis points, 10 mm anterior to the earpiece. Theright and left kinematic center of rotation was located as described by Lauritzen and confirmed with thePC Axiotron electronic Axiograph to within 0.25 mm. All points were transferred to 1 mm2 grid paperon the subject’s skin. The distance between each predetermined and kinematic point was measured ±0.25 mm. Wilcoxon and Mann-Whitney tests were used to examine differences between the left andright axis points and potential significant differences between genders at a significance level of P<.05. Thenumber of occurrences and the distance of the predetermined axis points from the kinematic axis alsowere described.Results. The mean distance between points was 1.1 mm on the right (range 0.0 to 3.0 mm), 1.2 mmon the left (range 0.0 to 3.0 mm), and 1.1 mm for all 80 points (±0.63). More than 96% of the predeter-mined points were within 2 mm of the kinematic axis, and 67% were within 1 mm. There was nosignificant difference between the right and left points and no significant differences based on gender.Conclusion. Within the limitations of this study, the results suggest that the predetermined axis point iswell within the clinical norm for estimated location of the transverse horizontal mandibular axis. (J Prosthet Dent 2002;87:387-94.)

Accurate articulation and mounting of stone castshave long been a challenge and a difficult procedure indentistry because of the many variables that can lead toerrors.1 The maxillary cast must be related to the cra-nial base utilizing 3 points of reference, and themandibular cast must be physiologically related to themaxillary cast at a repeatable reference position.2 Aface-bow is commonly used to orient the maxillary castto the axis orbital reference plane since it is the leastvariable,3 and a centric relation interocclusal record is

APRIL 2002 THE JOURNAL OF PROSTHETIC DENTISTRY 387

CLINICAL IMPLICATIONS

The results of this study suggest that the predetermined axis point located with an ear-piece face-bow, when combined with coordinated articulator reference points, canprovide a quick and accurate transfer of the maxillary cast/transverse horizontalmandibular axis relationship.

An abstract (#764) of the pilot research was presented at the 27thannual session of the American Association for Dental Researchin Minneapolis, Minn., March 1998.

aAssociate Professor and Director, Graduate Prosthodontics.bAssistant Professor, Division of Prosthodontics.cAdjunct Associate Professor, Division of Prosthodontics.

used.15 Preston,16 however, indicated that a superior-inferior error will produce a greater error than acomparable anterior-posterior error. While the kine-matic axis is preferable11 and can usually be locatedwithin 1 mm of accuracy, it is technique sensitive andrequires good visual acuity.16-18

The search continues for an easily located anatomicaxis point that consistently falls within the 5 mm radiusguidelines. Many studies have evaluated the deviationof arbitrary points to that of the kinematic center.19-27

Most recognize the inconsistencies in locating soft tis-sue landmarks and their individual variability and thefact that a significant percentage of points do not fall

THE JOURNAL OF PROSTHETIC DENTISTRY NAGY, SMITHY, AND WIRTH

388 VOLUME 87 NUMBER 4

within the 5 mm radius of the kinematic axis.Schallhorn22 reported 95% correlation and Walker19

only 20% correlation with the use of common estimat-ed points. Most points fall within the 50% to 75%range.28

The ear face-bow that makes use of the externalauditory meatus and nasion was one attempt to solvethe problem of identifying anatomically determinedarbitrary axis points. This system became widely pop-ular after the introduction of the QuickMountface-bow (Whip Mix Corp, Louisville, Ky.) in the early1960s.23 Ricketts24 has reported that variations in earanatomy may contribute to earbow error.

Several studies have evaluated earpiece-type face-bows and their relationship to the kinematic axis andother estimated points.8,21,23,25-27,29 The Bergströmpoint is a common denominator to earpiece face-bowsand has long been considered one of the most accuratearbitrary points. Bergström29,30 made use of an arbi-trary axis located automatically by his face-bow 10 mmanterior to the center of a 1-cm spherical insert for theexternal auditory meatus and 7 mm below theFrankfort horizontal plane. The face-bow requiredonly orientation to the left orbitale. His articulator axiswas positioned 10 mm anterior to the point of attach-ment for the face-bow and 7 mm below Frankfortplane; the face-bow and articulator worked in combi-nation. Beck29 reported that the point for 12 subjectswas 4.1 mm from the kinematic axis and the mostaccurate of the points tested.

Lauritzen et al21 used a Richey condyle marker inthe external auditory meatus and marked a line witha ruler from the top of the marker to the outer can-thus of the eye. The condyle marker was rotated tomake an intersecting line 13 mm from the anteriorside of the earpiece. The Lauritzen method21 wasused to determine the kinematic axis points. Theauthors found that only 33% of the kinematic pointswere within a 5-mm radius of the arbitrary points inthe 50-subject study.

Teteruck et al23 used an early version (forward-fac-ing earpieces) of the QuickMount face-bow (WhipMix Corp). The nasion relater positioned the anteriorcrossbar in the region of orbitale (nasion minus 23 mm).31 The Lauritzen method also was used tolocate the kinematic axis points. Fifty-six percent of theearbow points were within 6 mm of the kinematic axisin their 40-subject study. If the earbow mounting holewas repositioned, 75% would have been within 6 mmof the kinematic point. Current earbows have therepositioned mounting holes.

Palik et al25 evaluated the Hanau 159-4 earpieceface-bow (Waterpik Technologies, Ft Collins, Colo.).An orbital pointer positioned on the infraorbital fora-men was used as the anterior reference. Maxillary castswere mounted for 18 subjects on a Hanau 158-3

Table I. Distribution of predetermined axis points

Distance from kinematic axis

Subject Age Gender R point (mm) L point (mm)

1 37 M 1.0 1.52 27 F 1.5 1.53 47 F 1.0 1.04 31 M 2.0 3.05 33 M 2.0 2.06 30 M 1.0 1.57 26 M 1.0 1.08 27 M 3.0 1.09 26 M 1.0 010 30 M 1.0 1.011 32 F 1.0 0.512 29 M 1.5 1.513 26 M 1.0 2.014 25 M 1.0 1.515 31 M 2.0 1.016 41 F 1.0 1.017 35 F 1.5 2.018 27 M 1.0 1.019 28 M 0.5 1.020 30 M 1.0 1.021 30 M 0.5 1.522 25 M 1.0 0.523 25 F 0 1.524 28 M 0.5 0.525 32 F 0.5 0.526 28 F 1.0 1.027 26 F 1.0 1.028 25 F 1.5 1.529 37 F 0 1.030 23 M 2.0 3.031 25 M 1.0 1.032 38 F 2.0 1.533 31 M 0.5 2.034 28 F 0.5 0.535 27 M 1.5 1.036 25 M 1.0 0.537 26 M 1.0 0.538 26 M 0.5 0.539 36 M 0 0.540 23 M 1.0 1.0

articulator (Waterpik Technologies) with use of theinfraorbital flag (orbitale minus 7). The Lauritzenmethod was used to locate the kinematic axis with aHanau 135-6 face-bow (Waterpik Technologies). Theearbow was repeated 4 times for each subject and thepoints marked on disks located lateral to each articula-tor condylar element. Fifty percent of the arbitrarypoints were within a 5-mm radius of the kinematicaxis. However, 89% were within a 6-mm radius. Theauthors concluded that this earpiece face-bow methodwas not statistically repeatable.

Three other studies8,26,27 investigated earpiece-typeface-bows but did not directly measure distance of anarbitrary point from the kinematic axis. It is interestingto note, however, that one study27 showed that directpalpation of the opening and closing axis of the

NAGY, SMITHY, AND WIRTH THE JOURNAL OF PROSTHETIC DENTISTRY

APRIL 2002 389

mandible (Dawson method) located an axis point 0 to4 mm from the kinematic axis for 120 subjects.

The Axiograph III (SAM Präzisionstechnik GmbH,München, Germany) uses the nasion and 2 externalauditory meatus alignment devices to position the hingeaxis alignment pins 10 mm anterior to the earpiece onthe axis orbital plane. The point is called the predeter-mined hinge axis. When verified by kinematicdetermination, the styli were most often on the kinemat-ic axis or very close. This in vivo clinical study comparedthe location of an anatomically predetermined hinge axispoint with the determined kinematic axis.

MATERIAL AND METHODS

Forty faculty, staff, students, and patients at theMarquette University School of Dentistry volunteered

Fig. 1. Diagram of SAM Axiograph III shows maxillary flag/face-bow combination andmandibular recording bow. Lower bow is attached to mandibular teeth with tray clutch andimpression plaster. Earpiece alignment flags with blue hygienic earpiece caps and axis align-ment pins and nasion relator position predetermined points. Axis alignment tubes on lowerbow align bow and writing stylus colinear to flags. (Reproduced from SAM AxiographIII/Axiomatic Procedures Manual with permission)

for the study after giving informed consent. All sub-jects had intact natural or restored dentitions throughthe first molar, no masticatory muscle or temporo-mandibular pain on palpation, no pain on movementof the mandible, and no limitation of range of motion.Twenty-seven males (age 23 to 37) and 13 females(age 25 to 47) participated (Table I).

The Axiograph III flagbow and lower recordingbow were positioned on the subjects according to theprocedure manual and verified by 2 authors (W.N. andT.S.) (Figs. 1 and 2). The tray clutch was fixed to themandibular teeth with impression plaster (Snow White2; SDS Kerr, Romulus, Mich.) and attached to thelower recording bow with a nontorsion clamp.

The 2 upper flagbow sidearms were positionedequally from the side of the subject’s head and parallelto the mid-sagittal plane with the anterior crossrod

parallel to the frontal plane. The earpiece alignmentflags with blue hygienic earpiece caps position the holein the earpiece in close proximity to the anatomic pori-on, and the nasion relator determines the anteriorreference position. The axis alignment pins on the ear-piece flag allow a predetermined axis point position 10 mm anterior to the hole in the earpiece on the axisorbital plane (Figs. 3 through 5). The predeterminedpoint is automatically and mechanically determined bythe upper bow and not influenced by mandibularmovement.

The lower recording bow was considered properlypositioned when the axis alignment tubes were able toslide on and off the alignment pins, essentially friction-free, when the mandible was in centric relation. Thereference alignment gauge ensured colinearity of theupper flagbow assembly; the axis alignment tubes andnontorsion clamp ensured colinear positioning of themandibular writing styli (Fig. 5).

The right and left alignment flags were replacedwith a custom flag with a machined sleeve replacingthe axis alignment pin (Fig. 6). The sleeve allowed co-linear positioning of a marking stylus to transfer thepredetermined axis point to a 1 mm2 grid adhesive-backed graph paper (SAM Präzisionstechnik GmbH)affixed to the skin anterior to the external auditorymeatus (Fig. 7). The earpieces were removed fromthese flags to prevent unwanted skin tension on thegraph paper. This predetermined axis point wasmarked in red on the graph paper (Fig. 8).

The right and left custom flags were then replacedwith the standard recording flags and covered withself-sticking note paper (Post It; 3M, St Paul, Minn.),and the mandibular writing styli were lightly posi-tioned against the note paper. The right and lefttransverse horizontal mandibular hinge axis pointswere determined according to Lauritzen andBodner.21 The predetermined points were covered by



Fig. 3. Earpiece alignment flags with axis alignment pin andremovable blue hygienic earpiece cap.

Fig. 4. Right earpiece alignment flag in position on subject.

Fig. 2. Left lateral diagram of Axiograph III in position onsubject. (Reproduced from SAM Axiograph III/AxiomaticProcedures Manual with permission)

the recording flags and not visible during axis deter-mination.

The right and left standard recording flags werereplaced with the XZ digitizer recording plates and theY optical recording assembly of the PC Axiotron elec-tronic Axiograph (SAM Präzisionstechnik GmbH),and the hinge position was verified or refined to with-in 0.25 mm. The on-line center of rotation program

allowed the centric relation reference position to bemarked and the styli adjusted until the screen cursorrotated within a magnified circle representing a 0.25-mm-diameter circle at the recording plate. Thedigitizer plates were removed, and this determined axiswas marked in black on the graph paper (Fig. 8). Alldetermined axis verifications were performed by a sin-gle investigator (W.N.).


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Fig. 5. Superior horizontal diagram shows relationship of earpiece to external auditory me-atus, axis alignment pins, and axis alignment tubes. Note colinearity of maxillary andmandibular bows. (Reproduced from SAM Axiograph III/Axiomatic Procedures Manual withpermission)

Fig. 6. Custom earpiece alignment flags with machinedsleeve and marking pin. Earpiece has been removed to pre-vent skin tension on grid paper.

Fig. 7. Right custom earpiece alignment flag and adhesivegrid paper. Pin is being inserted to mark predeterminedpoint.

The graph papers were labeled left and right,removed from the subject’s face, and affixed to a datasheet that listed the subject’s gender and age. Anobservation was made as to whether the anteriorAxiograph crossbar was parallel to the interpupillaryline. The distance between the predetermined (red)and determined (black) points, center to center, wasmeasured with original magnification × 3 (OptiVisor;Donegan Optical Co, Kansas City, Mo.) with a dividerand stainless steel ruler (No 311-ME; General Tools,New York, N.Y.) to the nearest 0.25 mm. No attemptwas made to determine directional variance from thekinematic axis point.

Eighty points (40 right and 40 left) were recordedand measured, and Wilcoxon and Mann-Whitney testswere used to examine differences between the left andright points and to determine whether significant gen-der differences existed. Levels of P<.05 were deemedstatistically significant. The number of occurrences anddistance of the predetermined points from the kine-matic axis also were described.

RESULTS

The distribution of predetermined axis points anddistance from the determined (kinematic) axis are list-ed in Tables I and II. All points were within a 5-mmradius, with 4 of the points coincidental with thedetermined axis. The anterior flagbow crossbar was

also parallel to the interpupillary line in all 40 sub-jects.

The mean distance between the predetermined andthe determined points for all 80 axis points was 1.1 ± 0.63 mm, with a mean distance of 1.1 ± 0.62mm for the right and 1.2 ± 0.64 mm for the left. Therange for both right and left was 0.0 to 3.0 mm.Overall, 96.2% of the points were within 2 mm of thekinematic axis and 67.5% were within 1 mm. AWilcoxon test indicated no significant differencebetween the left and right points, and the Mann-Whitney test indicated no significant differences basedon gender (P<.05).

DISCUSSION

Accurately mounted casts should look like thepatient, with a correct midline, anterior incisal plane,and relationship to the reference horizon. The face-bow transfer of the maxillary cast ideally should bereproducible with clinically acceptable accuracy frommounting to mounting. This has been a difficult task,however, because of the lack of an anatomically recog-nizable reference position. The protocol forapplication of each point also has been skewed withtime.

The Axiograph III system uses 2 mandibularrecording styli in colinear alignment and rectolinearwith the upper maxillary flag/face-bow recordingplates. The flag/face-bow automatically positions the2 lower recording styli on a colinear predeterminedhinge axis reference point. The upper flagbow usesfixed cranial reference points and planes and was rigid-ly attached and fixed to each subject. The subject’shead was positioned in the headrest to prevent acci-dental and unwanted movement. Unique to thisdevice is the fact that the predetermined point isrecorded by the fixed upper flagbow and is not influ-enced by mandibular movement. It is a selected point.

The Axiotron’s center of rotation program providesfor location of the kinematic axis beyond visual acuity,minimizing the limitations of a manual trial-and-errormethod.16-18 This electronic device uses industry-stan-dard miniature XZ-axis digitizing recording platesalong with a Y-axis optical recorder stylus in contactwith the digitizing plate. This combination outputsXYZ data to a pixel dot computer screen with directon-line visualization in 3 planes. The mandible is posi-tioned to a centric relation reference position and theinstrument zeroed before axis determination. Dataregistration are input every 4 milliseconds with anaccuracy of 0.02 mm. The screen magnification (a cir-cle) is approximately 8-1 when a 0.25 mm circle isrepresented at the recording plate. The kinematic axiswas considered verified when the cursor would“rotate” in both the sagittal and horizontal plane cir-cles.



Fig. 8. One-mm2 grid paper from left side of subject 6.Predetermined point is marked in red and determined pointin black. Distance between points is 1.5 mm.


APRIL 2002 393

The predetermined point lies 10 mm anterior to thecenter hole of the earpiece on the axis orbital plane andis most closely associated with the Bergstöm point.30

In their analysis of data points, Palik et al25 indicatedthat 92% of the kinematic points were posterior to theearbow point, suggesting that the arbitrary axis pointshould be less than 13 mm from the external auditorymeatus. The observation was confirmed by the presentstudy. The angled shape of the 1-cm-diameter bluehygienic earpiece cap appeared to position the hole inthe earpiece against the cartilaginous porion describedby Sicher32 and very close to the anthropologic pori-on, a skull landmark. The patient determines the actualposition in the external auditory meatus by holdingthe earpiece and inserting it lightly until the hearing isjust blocked. The earpiece is positioned superiorly andthen medially until hearing is open again. Too deep aposition on one side can turn the horizontal plane inrelation to the sagittal plane of mounted casts. Theanterior reference point is nasion minus 25 mm andvery close to the anthropologic orbitale in the generalCaucasian population. The axis orbital plane is notalways parallel to the esthetic reference horizontal,33

and the results may not be true for all populations.Further studies are ongoing and will address these dif-ferences.

The predetermined point appeared to be mostclosely associated with the kinematic axis for this sub-ject population (96.2% within 2 mm). No attempt wasmade to determine directional variation from the kine-matic axis due to the proximity of the points and thedifficulty of transferring an accurate axis orbital planeline to the grid paper. However, it was observed thatthe points were evenly distributed around the kine-matic axis, with a slightly greater number in theposterior-inferior quadrant.

This study did not evaluate cast mounting or repro-ducibility of the face-bow transfer. However, clinicalexperience indicates that maxillary casts mounted withthe anatomic face-bow are more accurately related tothe sagittal, frontal, and horizontal esthetic referenceplanes. Preliminary research also indicates that castmounting with this face-bow is highly reproducible.

The clinician is faced with a difficult choice in pick-ing a face-bow and matching it to an articulator thattruly represents the intended reference plane and theanatomical axis points. Face-bow mounting jigs mayhave no relation to the intended third reference point

and can cause serious problems with maxillary cast ori-entation.7 Much confusion still exists regarding thedaily task of dental cast orientation and mounting inan articulator. There is no question that protocolsneed to be developed to standardize the procedureand that the face-bow and articulator reference pointsmust be coordinated.

A predetermined axis point that falls within 1 to 2 mm of the determined hinge axis is more thanacceptable for clinical use and may make determina-tion of the kinematic axis unnecessary. A new 2-mmclinical norm should be considered.

CONCLUSIONS

Within the limitations of this study, the predeter-mined axis point was well within the 5-mm clinicalnorm for estimated location of the transverse horizon-tal mandibular axis for the population studied.

REFERENCES

1. Wirth CG. Interocclusal centric relation records for articulator mountedcasts. Dent Clin North Am 1971;15:627-40.

2. Piehslinger E, Celar A, Celar R, Jager W, Slavicek R. Reproducibility ofthe condylar reference position. J Orofac Pain 1993;7:68-75.

3. Gonzales JB, Kingery RH. Evaluation of planes of reference for orientingmaxillary casts on articulators. J Am Dent Assoc 1968;76:329-36.

4. Wood GN. Centric relation and the treatment position in rehabilitatingocclusions: a physiologic approach. Part I: Developing an optimummandibular posture. J Prosthet Dent 1988;59:647-51.

5. Wood GN. Centric relation and the treatment position in rehabilitatingocclusions: a physiologic approach. Part II: The treatment position. JProsthet Dent 1988;60:15-8.

6. Winstanley RB. The hinge-axis: a review of the literature. J Oral Rehabil1985;12:135-59.

7. Ellis E 3rd, Tharanon W, Gambrell K. Accuracy of face-bow transfer:effect on surgical prediction and postsurgical result. J Oral MaxillofacSurg 1992;50:562-7.

8. Wood DP, Korne PH. Estimated and true hinge axis: a comparison ofcondylar displacements. Angle Orthod 1992;62:167-75; discussion 176.

9. Tuppy F, Celar RM, Celar AG, Piehslinger E, Jager W. The reproducibilityof condylar hinge axis positions in patients, by different operators, usingthe electronic mandibular position indicator. J Orofac Pain 1994;8:315-20.

10. Morneburg T, Pröschel PA. Differences between traces of adjacentcondylar points and their impact on clinical evaluation of condylemotion. Int J Prosthodont 1998;11:317-24.

11. Yatabe M, Zwijnenburg A, Megens CC, Naeije M. The kinematic center:a reference point for condylar movements. J Dent Res 1995;74:1644-8.

12. Yatabe M, Zwijnenburg A, Megens CC, Naeije M. Movements of themandibular condyle kinematic center during jaw opening and closing. JDent Res 1997;76:714-9.

13. Ferrario VF, Sforza C, Miani A Jr, Serrao G, Tartaglia G. Open-close move-ments in the human temporomandibular joint: does a pure rotationaround the intercondylar hinge axis exist? J Oral Rehabil 1996;23:401-8.

14. Kinderdnecht KE, Wong GK, Billy EJ, Li SH. The effect of a deprogram-mer on the position of the terminal transverse horizontal axis of themandible. J Prosthet Dent 1992;68:123-31.

Table II. Number of occurrences and distance of predetermined axis points from the kinematic axis

Distance 0 mm 0.5 mm 1.0 mm 1.5 mm 2.0 mm 2.5 mm 3.0 mm

Number 4% 16% 34 14. 9. 0% 3.Percentage 2% 20% 42.5% 17.5% 11.25% 0% 3.75%

15. Weinberg LA. An evaluation of the face-bow mounting. J Prosthet Dent1961;11:32-42.

16. Preston JD. A reassessment of the mandibular transverse horizontal axistheory. J Prosthet Dent 1979;41:605-13.

17. Fox SS. The significance of errors in hinge axis location. J Am Dent Assoc1967;74:1268-72.

18. Beard CC, Clayton JA. Studies on the validity of the terminal hinge axis.J Prosthet Dent 1981;46:185-91.

19. Walker PM. Discrepancies between arbitrary and true hinge axes. JProsthet Dent 1980;43:279-85.

20. Simpson JW, Hesby RA, Pfeifer DL, Pelleu GB Jr. Arbitrary mandibularhinge axis locations. J Prosthet Dent 1984;51:819-22.

21. Lauritzen AG, Bodner GH. Variations in location of arbitrary and truehinge axis points. J Prosthet Dent 1961;11:224-9.

22. Schallhorn RG. A study of the arbitrary center and the kinematic centerof rotation for face-bow mountings. J Prosthet Dent 1957;7:162-9.

23. Teteruck WR, Lundeen HC. The accuracy of an ear face-bow. J ProsthetDent 1966;16:1039-46.

24. Ricketts RM. Perspectives in the clinical application of cephalometrics.The first fifty years. Angle Orthod 1981;51:115-50.

25. Palik JF, Nelson DR, White JT. Accuracy of an earpiece face-bow. JProsthet Dent 1985;53:800-4.

26. Goska JR, Christensen LV. Comparison of cast positions by using fourface-bows. J Prosthet Dent 1988;59:42-4.

27. Razek A. Clinical evaluation of methods used in locating the mandibu-lar hinge axis. J Prosthet Dent 1981;46:369-73.

28. Abdal-Hadi L. The hinge axis: evaluation of current arbitrary determi-naºtion methods and a proposal for a new recording method. J ProsthetDent 1989;62:463-7.

29. Beck HO. A clinical evaluation of the arcon concept of articulation. JProsthet Dent 1959;9:409-21.

30. Bergström G. On the reproduction of dental articulation by means ofarticulators, a kinematic investigation. Acta Odontol Scand 1950;9(suppl4):125-41.

31. Wilkie ND. The anterior point of reference. J Prosthet Dent 1979;41:488-96.

32. DuBrul EL. Sicher and DeBrul’s oral anatomy. 8th ed. St. Louis: IshiyakuEuroAmerica; 1988. p. 60-4.

33. Pitchford JH. A reevaluation of the axis-orbital plane and the use oforbitale in a facebow transfer record. J Prosthet Dent 1991;66:349-55.

Reprint requests to:DR WILLIAM W. NAGY

DIRECTOR, GRADUATE PROSTHODONTICS

MARQUETTE UNIVERSITY SCHOOL OF DENTISTRY

MILWAUKEE, WI 53233FAX: (414)288-6516E-MAIL: [email protected]

Copyright © 2002 by The Editorial Council of The Journal of ProstheticDentistry.

0022-3913/2002/$35.00 + 0. 10/1/122960

doi:10.1067/mpr.2002.122960



Bone and soft tissue integration to titanium implants withdifferent surface topography: an experimental study in thedogAbrahamsson I, Zitzmann NU, Berglundh T, Wennerberg A,Lindhe J. Int J Oral Maxillofac Implants 2001;16:323-32.

Purpose. In an effort to improve implant prognosis when bone quality or quantity is unfavorable,implant surface modifications have been considered. This study was designed to evaluate the hardand soft tissue formed adjacent to endosseous implants with 2 different surface configurations.Material and methods. Mandibular premolar teeth were removed from 5 beagle dogs. After 3months of healing 4 self-tapping standard implants (SI) and 4 Osseotite implants (OI) were placed.Abutments were connected 3 months after implant placement. Block biopsies were obtained 6months after abutment connection. Two implants of each type were prepared for histometricanalysis from each animal. Ground sections were used to determine bone-to-implant contact in dif-ferent zones along the implants.Results. Peri-implant soft tissue and marginal bone level were similar for both implant types. Thepercentage of bone-to-implant contact was significantly greater for OI (72.0% to 76.7%) than forSI (56.1% to 58.1%) surfaces. Bone density values were similar for both implant surfaces.Conclusions. This study corroborates the findings of previous reports that showed higher levelsof bone-to-implant contact adjacent to the roughened surface of the Osseotite implant. 40References. —SE Eckert

Noteworthy Abstractsof theCurrent Literature

Accuracy of a Predetermined Transverse Horizontal Mandibular Axis Point

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