Vertical repositioning accuracy of magnetic mounting systems on 4 articulator models.

STATEMENT OF PROBLEM: Research of the ability of a cast mounted on an articulator on maintaining the identical position of a cast mounted on an articulator after repeated repositioning is lacking, despite the possible effects this may have on the occlusion of a mounted cast. PURPOSE: The purpose of this in vitro study was to verify and compare the vertical repositioning accuracy of 4 different, commercially available articulator magnetic mounting plate systems. MATERIAL AND METHODS: Four articulators and their associated magnetic mounting plates were selected for the study. These were the Artex AR articulator (Amann Girrbach AG), the Denar Mark II articulator (Whip Mix Corp), the Kavo Protar Evo articulator (Kavo Dental GmbH), and the SAM3 articulator (SAM Präzisionstechnik GmbH). Three new magnetic mounting plates were prepared for each articulator system. The repositioning accuracy of each mounting plate was evaluated by comparing the standard deviation of the vertical distances measured between the mounting plate and a laser displacement sensor. The lower arm of the articulator was secured, and the vertical distance was measured by positioning the laser displacement sensor positioned vertically above the mounting plate. Once the vertical distance was measured, the mounting plate was detached from the articulator and reattached manually to prepare for the next measurement. This procedure was repeated 30 times for each of the 3 magnetic mounting plates. Data were analyzed by ANOVA for 2-stage nested design and the Levene test (α=.05). RESULTS: Significant differences were detected among articulator systems and between magnetic mounting plates of the same type. The standard deviations of the measurements made with the Artex AR articulator, Denar Mark II articulator, Kavo Protar Evo articulator, and SAM3 articulator were 0.0027, 0.0308, 0.0214, and 0.0215 mm, respectively. Thus, the repositioning accuracy could be ranked in the order as follows: Artex AR, Kavo Protar Evo, SAM3, and Denar Mark II. CONCLUSIONS: The position of the magnetic mounting plate after repositioning did not maintain an identical position in the vertical dimension on any of the 4 articulator models tested. The repositioning accuracy of the mounting plates showed significant differences among the articulators tested in this study.

Three-dimensional repositioning accuracy of semiadjustable articulator cast mounting systems.

STATEMENT OF PROBLEM: In spite of its importance in prosthesis precision and quality, the 3-dimensional repositioning accuracy of cast mounting systems has not been reported in detail. PURPOSE: The purpose of this study was to quantify the 3-dimensional repositioning accuracy of 6 selected cast mounting systems. Five magnetic mounting systems were compared with a conventional screw-on system. MATERIAL AND METHODS: Six systems on 3 semiadjustable articulators were evaluated: Denar Mark II with conventional screw-on mounting plates (DENSCR) and magnetic mounting system with converter plates (DENCON); Denar Mark 330 with in-built magnetic mounting system (DENMAG) and disposable mounting plates; and Artex CP with blue (ARTBLU), white (ARTWHI), and black (ARTBLA) magnetic mounting plates. Test casts with 3 high-precision ceramic ball bearings at the mandibular central incisor (Point I) and the right and left second molar (Point R; Point L) positions were mounted on 5 mounting plates (n=5) for all 6 systems. Each cast was repositioned 10 times by 4 operators in random order. Nine linear (Ix, Iy, Iz; Rx, Ry, Rz; Lx, Ly, Lz) and 3 angular (anteroposterior, mediolateral, twisting) displacements were measured with a coordinate measuring machine. The mean standard deviations of the linear and angular displacements defined repositioning accuracy. RESULTS: Anteroposterior linear repositioning accuracy ranged from 23.8 ±3.7 µm (DENCON) to 4.9 ±3.2 µm (DENSCR). Mediolateral linear repositioning accuracy ranged from 46.0 ±8.0 µm (DENCON) to 3.7 ±1.5 µm (ARTBLU), and vertical linear repositioning accuracy ranged from 7.2 ±9.6 µm (DENMAG) to 1.5 ±0.9 µm (ARTBLU). Anteroposterior angular repositioning accuracy ranged from 0.0084 ±0.0080 degrees (DENCON) to 0.0020 ±0.0006 degrees (ARTBLU), and mediolateral angular repositioning accuracy ranged from 0.0120 ±0.0111 degrees (ARTWHI) to 0.0027 ±0.0008 degrees (ARTBLU). Twisting angular repositioning accuracy ranged from 0.0419 ±0.0176 degrees (DENCON) to 0.0042 ±0.0038 degrees (ARTBLA). One-way ANOVA found significant differences (P<.05) among all systems for Iy, Ry, Lx, Ly, and twisting. CONCLUSIONS: Generally, vertical linear displacements were less likely to reach the threshold of clinical detectability compared with anteroposterior or mediolateral linear displacements. The overall repositioning accuracy of DENSCR was comparable with 4 magnetic mounting systems (DENMAG, ARTBLU, ARTWHI, ARTBLA). DENCON exhibited the worst repositioning accuracy for Iy, Ry, Lx, Ly, and twisting.

A comparison of facebow and dentofacial analyzer mountings.

AIM: This investigation compared the accuracy and reliability of one arbitrary facebow (4000 FB Pana -Mount) to the recently introduced "Dento-Facial Analyzer" (4300 FB Kois) for locating and trasferring the hinge axis to articulator. A kinematically located transverse horizontal axis provided the reference. MATERIAL AND METHODS: Fourteen subjects, 9 female and 5 male, and 3 types of facebows were utilized in this study. One orientation record was made with each of 3 instruments to mount 1 pindexed maxillary cast 3 times for each subject on the same articulator. In order to measure the distance from articulator's hinge axis to first molar bilaterally; a small nail was inserted in the stone cast in the area of the first molar on both sides. A small indentation on the hinge axis of the articlator served as the second reference point. A 6-inch/150 mm digital caliper was used for measuring the distance between these points with an accuracy of 0.03 mm and resolution of 0.01 mm. Four repeat measurements were done on both sides of each mounted cast and averaged. RESULTS: The arbitrary earbow recorded the hinge axis closer to the kinematic axis (within 4.18 mm on the right side and 3.57 mm on the left side) with smaller standard deviation compared to the Dento-Facial Analyzer (5.58 mm on the righ side and 5.72 mm on the left side). CONCLUSION: The arbitrary facebow was found to be more accurate as compared to the Dento-Facial Analyzer for reliability and accuracy and may serve better when occlusal function is a primary concern. CLINICAL IMPLICATION: The simplicity of the use of Dento-Facial Analyzer did not improve the accuracy of mounting the maxillary cast onto the articulator. As a result it should be used in the clinic cautiously.

Accuracy of two face-bow/semi-adjustable articulator systems in transferring the maxillary occlusal cant.

CONTEXT: The precision of an arbitrary face-bow in accurately transferring the orientation of the maxillary cast to the articulator has been questioned because the maxillary cast is mounted in relation to arbitrary measurements and anatomic landmarks that vary among individuals. AIM: This study was intended to evaluate the sagittal inclination of mounted maxillary casts on two semi-adjustable articulator/face-bow systems in comparison to the occlusal cant on lateral cephalograms. MATERIALS AND METHODS: Maxillary casts were mounted on the Hanau and Girrbach semi-adjustable articulators following face-bow transfer with their respective face-bows. The sagittal inclination of these casts was measured in relation to the fixed horizontal reference plane using physical measurements. Occlusal cant was measured on lateral cephalograms. SPSS software (version 11.0, Chicago, IL, USA) was used for statistical analysis. Repeated measures analysis of variance and Tukey's tests were used to evaluate the results (P < 0.05). RESULTS: Comparison of the occlusal cant on the articulators and cephalogram revealed statistically significant differences. Occlusal plane was steeper on Girrbach Artex articulator in comparison to the Hanau articulator. CONCLUSION: Within the limitations of this study, it was found that the sagittal inclination of the mounted maxillary cast achieved with Hanau articulator was closer to the cephalometric occlusal cant as compared to that of the Girrbach articulator. Among the two articulators and face-bow systems, the steepness of sagittal inclination was greater on Girrbach semi-adjustable articulator. Different face-bow/articulator systems could result in different orientation of the maxillary cast, resulting in variation in stability, cuspal inclines and cuspal heights.

Evaluation of an improved orthognathic articulator system. 2. Accuracy of occlusal wafers.

The errors produced by occlusal wafers constructed on casts of the teeth mounted on a standard articulator and an improved orthognathic articulator were investigated by carrying out simulated orthognathic surgery on plastic skulls. The wafers were used to relocate the position of the maxillae of the skulls. The vertical and horizontal displacements of the maxillae were determined from measurements of the positions of markers on the skull and teeth. Comparison of the magnitudes of the actual and intended movements showed that wafers constructed on the standard articulator had systematic prediction errors of up to 5mm, but the improved orthognathic articulator showed much smaller random errors. There was a statistically significant improvement in overall accuracy in predicting maxillary Le Fort I position with the use of the improved orthognathic articulator which the authors recommend for clinical use.

Evaluation of an improved orthognathic articulator system: 1. Accuracy of cast orientation.

A systematic study was carried out using plastic model skulls to quantify the accuracy of the transfer of face bow registration to the articulator. A standard Dentatus semi-adjustable articulator system was compared to a purpose built orthognathic articulator system by measuring the maxillary occlusal plane angles of plastic model skulls and of dental casts mounted on the two different types of articulators. There was a statistically significant difference between the two systems; the orthognathic system showed small random errors, but the standard system showed systematic errors of up to 28°.

Face bow and articulator for planning orthognathic surgery: 1 face bow.

Orthognathic surgery that involves movement of the maxilla relative to the skull is usually planned using casts mounted on an articulator. Accurate positioning of the maxilla relative to the skull is essential for reliable planning, but current methods of mounting casts on articulators are inaccurate and unreliable. We propose that the casts should be mounted using the relation between the horizontal plane and the resting head position to define the position of the skull. A photographic study of 10 subjects confirmed the reproducibility of the head position and its relation to the horizontal plane. A face bow incorporating a circular spirit level was used to transfer the relation between the horizontal and the maxillary dentition to a semiadjustable articulator. The angle between the horizontal and maxillary occlusal planes was measured from six lateral cephalograms and compared with those of casts mounted on a semiadjustable articulator using a face bow with either an orbital pointer or a spirit level. The face bow with a spirit level produced considerably more accurate results.

Accuracy of a fixed value nasion relator in facebow design.

PURPOSE: This study examined whether a fixed value nasion relator accurately locates the orbitale in a patient population. MATERIALS AND METHODS: The mean value for the vertical distance between soft tissue nasion and orbitale was determined through the analysis of cephalometric radiographs of 114 adult patients. This value was then compared to a facebow design, which uses a fixed value of 25.4 mm. RESULTS: In this study, the mean distance between the orbitale and nasion was found to be 26.8 mm. The values ranged from 15.9 to 39.4 mm with a standard deviation of 3.87 mm. CONCLUSION: The difference between the calculated mean and the 25.4 mm fixed value was less than 2.0 mm and presumed to be clinically irrelevant; however, an accumulation of design errors combined with the variation within the patient population was asserted to be clinically relevant and makes the use of a fixed value nasion relator impractical.

The lateral leeway in the habitual intercuspation: experimental studies and literature review.

The habitual intercuspation is used ubiquitous for manufacturing small dental restorations. However, a little is known on its precision. The aim of the present study was therefore to investigate the unambiguity and accuracy of the habitual occlusion in mounted plaster casts from fully dentate persons. Eighty-one fully dentate volunteers, 36 women and 45 men aged 26.8 +/- 6.2 years (18-55 years), with minor fillings and no signs or symptoms of TMD took part in the experiments. Silicone impressions were taken, poured with stone plaster and the obtained casts mounted into Dentatus ARL(R)- articulators using an individual face bow transfer. Subsequently, the models were transferred to a custom-made measuring articulator where the lateral leeway and the accuracy of the hand-held habitual intercuspation were quantified in the condylar area. Measurements were repeated seven times with the upper cast pushed either to the maximum right or the maximum left intercuspation. The hand-held habitual intercuspation of upper and lower cast proved ambiguous in 57% of pairs of casts. The average lateral leeway of the habitual intercuspation in the condylar area was 0.10 +/- 0.05 mm (0-0.51 mm; median 0.07 mm) between the maximum right and left occlusal positions. The average accuracy of three repeated measurements was 0.22 +/- 0.09 mm (0.02-1.17 mm; median 0.16 mm). Natural occlusal surfaces in a full dentition do not guarantee an unambiguous habitual intercuspation of the plaster casts. The described leeway and technical limits might be possible causes for occlusal adjustments that are sometimes necessary when inserting restorations manufactured in habitual intercuspation.

Interchangeability of two semiadjustable articulators.

PURPOSE: Interchangeability between articulators allows mounted casts to be transferred accurately from one articulator to another. The purpose of this study was to evaluate the interchangeability of 109 new, unused interchangeable articulators in the centric position. MATERIALS AND METHODS: The interchangeability of 38 unused Whip Mix model #2240 and 71 unused model #3040 semiadjustable articulators was evaluated using the Whip Mix #2245 check system as the standard. Vertical discrepancies between the check system cylinders were also measured. RESULTS: Within the standard for interchangeability established by the Whip Mix #2245 check system (< 94 microns horizontal discrepancy), 101 (93%) of 109 articulators were interchangeable (34 were model #2240 and 67 were model #3040). Overall, the amount of vertical space between the check system cylinders was < or = 52 microns in 99.4% of the model #2240 articulators and 99.7% of the #3040 articulators. CONCLUSION: New, unused Whip Mix model #2240 and #3040 articulators are potentially interchangeable in the centric position.

Assessing the interchangeability of the Hanau Wide-Vue semiadjustable articulator.

This study evaluated the ability of the Hanau Wide-Vue articulator system to be utilized as an interchangeable articulator system within a clinically acceptable range of accuracy.

[The use of the Dentatus articulator in complete denture prosthetics]. / Teljes kivehetó fogpótlás készítése Dentatus artikulátor segítségével.

The adjustable articulators and the bilaterally balanced occlusal scheme is not commonly used in Hungary, even if it is the mainly used type of occlusion in the world. The authors provide a short historical background about occlusal types then show how to use the Dentatus semi-adjustable articulator in the practice of the complete denture prosthetics: how to use the Dentatus ear-bow, and how to adjust individual values on the articulator. With the help of this procedures a bilaterally balanced occlusal scheme is designed, so the authors show the characteristics of this occlusal type. The aim of the authors is to present a view of "how to organize" occlusion for complete dentures.