STAT3-IN-1

Reproduction accuracy of articulator mounting with an arbitrary face-bow vs. average values—a controlled, randomized, blinded patient simulator study

M. Oliver Ahlers1,2 • Daniel Edelhoff3 • Holger A. Jakstat4

Abstract

Objectives

The benefit from positioning the maxillary casts with the aid of face-bows has been questioned in the past. Therefore, the aim of this study was to investigate the reliability and validity of arbitrary face-bow transfers compared to a process solely based on the orientation by means of average values. For optimized validity, the study was conducted using a controlled, randomized, anonymized, and blinded patient simulator study design.

Material and methods

Thirty-eight undergraduate dental students were randomly divided into two groups; both groups were applied to both methods, in opposite sequences. Investigated methods were the transfer of casts using an arbitrary face-bow in comparison to the transfer using average values based on Bonwill’s triangle and the Balkwill angle. The Bpatient^ used in this study was a patient simulator. All casts were transferred to the same individual articulator, and all the transferred casts were made using type IV special hard stone plaster; for the attachment into the articulator, type II plaster was used. A blinded evaluation was performed based on three-dimensional measurements of three reference points.

Results

The results are presented three-dimensionally in scatterplots. Statistical analysis indicated a significantly smaller variance (Student’s t test, p < 0.05) for the transfer using a face-bow, applicable for all three reference points. Conclusions The use of an arbitrary face-bow significantly improves the transfer reliability and hence the validity. Clinical relevance To simulate the patient situation in an individual articulator correctly, casts should be transferred at least by means of an arbitrary face-bow. Keywords Jaw relation record/instrumentation . Methods, reproducibility of results, confidence intervals, analysis of variance, evidence-based dentistry . Dental occlusion, vertical dimension . Dental articulators, face-bow Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00784-018-2499-6) contains supplementary material, which is available to authorized users. * M. Oliver Ahlers [email protected] 1 Department of Prosthetic Dentistry, School of Dental and Oral Medicine, University Hospital Hamburg-Eppendorf, University of Hamburg, Hamburg, Germany 2 CMD-Centre Hamburg-Eppendorf, Falkenried 88 (CiM, Haus C), 20251 Hamburg, Germany 3 Department of Prosthetic Dentistry, University Hospital, LMU Ludwig-Maximilians-University, Munich, Germany 4 Preclinical Education and Dental Materials, Department of Prosthetic Dentistry, School of Dental and Oral Medicine, Medical Faculty, University of Leipzig, Leipzig, Germany Clinical implications Casts can be transferred into articulators either with the help of kinematic face-bows, arbitrary face-bows, or without specialized aids based on average values only [1]. Especially regarding fixed dental prostheses, the question remains unanswered, to what extent at least arbitrary face-bows are necessary to position casts in anatomically and functionally correct relationship in the articulator [2]. All transfer procedures are influ- enced by the patient situations and operator’s skills and thus potentially by operator bias. Hence evidence is required regarding the effect of the transfer proce- dure itself on reproducibility and validity without the professional experience and/or previous knowledge of the test persons. Introduction Studies on the effect kinematic and arbitrary face-bows The first studies in the accuracy of arbitrary face-bows were published by Teteruck and Lundeen [3]. Later on, Whitsett et al. published supporting information regarding the modifica- tion of semi-adjustable articulators for use with a caliper style face-bow [4]. Since then, several authors have researched the influence of a transfer of the maxillary position using arbitrary face-bows in comparison to kinematic hinge axis location, which, so far, was regarded as the Bgold standard^ [5]. The earlier study by Palik et al. determined a significant statistical difference between the arbitrary axis located with a Hanau ear-bow and the terminal hinge axis [6]. Piehslinger et al. confirmed this result using the SAM arbitrary face-bow and kinematic SAM Axiograph. The authors reported an increased variance of 5 mm in 50 to 77% of the cases [6, 7]. The authors also determined that the occlusal error, which resulted from the transfer based on the arbitrarily located hinge axis as compared to a kinematic hinge axis localization, is roughly proportional to the shift or tilting of the hinge axis in millime- ters or degrees [7]. The reproducibility of the set-up of an arbitrary face-bow itself was also experimentally investigated, as well as mount- ing the face-bow to the articulator [8, 9]. In both investiga- tions, three dentists applied an arbitrary face-bow to a single subject, and in this manner carried out a cranially oriented transfer of the jaw position to a single articulator. The position of the mounted cast was subsequently measured—in one study at three reference points [8] and in the other at four [9]—and then evaluated [8, 9]. In both studies, it was shown that the inter-individual variance of the transferred maxillary position was markedly smaller than expected according to the results of earlier studies on the variance around the kinemati- cally located hinge axis. The authors concluded that any den- tist might expect a range of ± 1.2 mm error in using this in- strument/articulator. Studies on the effect of a waiver of (arbitrary) face-bows transfers In addition to these results, three authors investigated the con- sequences of excluding the use of an arbitrary face-bow trans- fer on the casts’ occlusal relationship [10–12]. All these stud- ies confirmed the improved approximation of the simulated occlusion in the articulator following a face-bow transfer of the maxillary cast as compared to mounting the casts only based on average values only. As opposed to this, in a later pilot-study, the value and necessity of the use of a face-bow transfer for the fabrication of an occlusal appliance was questioned [13]. In that study, the three-dimensional positions of the casts in the articulator were not evaluated, nor were the resulting occlusal appliances (splints). Instead, only the number of intraoral occlusal con- tacts on the splint upon splint delivery and the time needed for chairside occlusal adjustment were recorded and did not yield clinically relevant benefits within the levels of clinical rele- vance defined in the study. Of course, this could also be due to procedural steps following after the articulator mounting. The authors acknowledged this fact to the point that they empha- sized that the results were only applicably to the confines of this study and that it was a pilot study. Unfortunately, the authors neither published a follow-up nor investigated these issues any further. Recently, a systematic review of the literature following the same perspective was published, to compare dental prostheses and occlusal splints constructed with or without face-bow transfer, to answer the question whether face-bow transfer may present better clinical results than simpler approaches. The study was based on an extensive search for randomized controlled clinical trials (RCT), following which eight RCTs were considered eligible. Based on the included literature, the authors concluded that for the construction of complete den- tures and occlusal splints, face-bow transfer is not imperative [2]. Interestingly, the authors also stated that in a search resulting in the identification of 8779 articles (sic!) they did not identify any clinical study that investigated the use of face- bows in fixed and removable dental prostheses. This stands in contrast to the earlier results cited above and to an earlier review that identified one clinical study on the effect of face- bow transfers in removable dental prostheses [14]. Nevertheless, the evidence on the effect of face-bow transfers in fixed dental prostheses on the reliability and validity and the geometrical consequences of the inherent transfer errors is insufficient [15]. Hence, the aim of the present study was to re-address the question of whether the use of an arbitrary face-bow improves the reliability and validity of the cranially orient- ed transfer of the maxillary position into an individual ar- ticulator as compared to mounting the casts without trans- fer bows. As demanded in recent literature, the setting was designed to simulate the clinical situation and at the same time offers the additional opportunity to assess reproduc- ibility and validity of measurements [2]. To create convinc- ing evidence, the test design of earlier controlled studies [7, 9] was adopted and systematically optimized by multi- ple randomizations, use of a patient simulator, and single- blinded evaluation. The null hypothesis was that no differ- ence would be found regarding three-dimensional variance between the groups where the maxillary position was transferred using an arbitrary face-bow or where the jaw position was solely oriented on the occlusion plane indica- tor and incisal guide pin, based on Bonwill’s triangle and Balkwill angle. Material and methods In this controlled randomized study, identical casts were mounted in an individual articulator, either based on the ad- aptation of an arbitrary face-bow to a single patient simulator, or without this procedure oriented only on the occlusion plane indicator and incisal guide pin. Identical casts were prepared for each trial and provided by a separate dental technician. Evaluation of the three-dimensional maxillary position was subsequently performed by a separate investigator; hence, the study was single-blinded. To further enhance the reliability of the results, non-biased test persons were selected and re- ceived standardized instructions. Materials and procedures A simulated patient (BDummy^) with a full complement of teeth served as the test object in all cases (Patient simulator G40 Cranium Denture, KaVo, Biberach, Germany). For all transfers, the dummy was continuously situated in an upright position. For recording the maxillary position, a commercially avail- able arbitrary face-bow was used (Arcus, KaVo). The supplied bite fork was adapted to the maxillary occlusion with beauty pink wax. The face-bow was used along with the manufac- turer’s instructions. Subsequently, the bite-fork and its three-dimensional sup- ports were separated from the face-bow and attached to an individual semi-adjustable articulator (Protar, KaVo). Patient simulator, face-bow, and articulator matched in dimensions. In the articulator, the bite-fork was stabilized with the aid of an acrylic block and type II mounting plaster (Artifix, AmannGirrbach, Pforzheim, Germany) to support the bite fork from below. In the following, identical maxillary casts were placed in the impressions on the bite-fork and mounted in the articulator, again using type II mounting plaster (Artifix, AmannGirrbach), which was mixed individually by the par- ticipants for their use. All maxillary casts were made by a certified dental techni- cian under identical conditions from type IV super-hard (stone) plaster (Fujirock, GC, Bad Homburg/Germany) and then randomly divided among the test persons according to lots drawn earlier prior to the test start. All instruments used were those already available in the university dental school, where the tests were conducted; they had been purchased previously during the re-equipping of the undergraduate clinical training facilities as part of a public procurement program. Test persons Thirty-eight undergraduate dental students from the University of Leipzig (Saxony, Germany) served as test persons in the study. The students were introduced for the first time to the procedures of the two methods during an extended lecture. The instruction included detailed graphic illustrations and video demonstrations of all procedures. In this way, all test persons received a uniform instruction prior to the begin- ning of the study. Up to this point, none of the test persons had any practical experience with either of the two methods being investigated during or prior to their dentistry studies. Methods and groups Following the standardized training session, a pre-generated randomization table was used to randomly divide the test per- sons into two groups (Fig. 1): The test persons of the first group transferred the jaw po- sition first using an arbitrary face-bow. Those of the second group initially transferred the jaw position oriented on the occlusion plane indicator and incisal guide pin, based on Bonwill’s triangle and the Balkwill angle. Subsequently, each test person mounted a second cast using the respective other method. In this manner, all test persons practiced both methods in succession. Standardization, anonymization, and blinding To ensure standardization, the same patient simulator and just one articulator were used in all procedures. The articulator’s accuracy was verified after each mounting process using a calibration aid fabricated by the certified dental technicians before. The measurements of all cast positions and hence of the respective transfers were carried out by only one investigator, who was blinded regarding the method used for the transfer of the respective casts. Therefore, the casts were anonymously marked with a number drawn earlier by lot. The names of the test persons, their group affiliation, the cast number, and the casts’ match to a particular test person and method were all collected in a master list. This list was maintained by the test administration and was not accessible to the evaluator. Thus, a blinded, controlled trial was per- formed. Only after all measurements were completed, this information was uncovered, and the compilation of the data for the final evaluation completed. Measurement of maxillary positions The actual evaluation of the transferred jaw position was per- formed three-dimensionally in each case by measuring the coordinates of three clearly defined reference points per cast: • Mesial contact between both maxillary central incisors; • Deepest point (fissure) of the central fossa of the maxillary right second molar; and • Deepest point (fissure) of the central fossa of the maxillary left second molar. A 3D-digitizer (Gamma Dental, Klosterneuburg, Austria) was used for the measurements (mean error < 0.01 mm). At the base of the digitizer, an identical split cast base was used, mounted in the articulator. Hence, the three-dimensional position of the base plate can be assumed identical. The digitizer was positioned manual- ly using the same workspace and illumination for all casts. For better precision, the operator used dental loupes (Zeiss). Hereby, the field of view was nearly the same for all measurements. Statistical evaluation For evaluating the readings, the variances of all three reference points in all three spatial directions were then compared for both methods. The distribution of the in- dividually measured coordinates around a statistically calculated mean was likewise compared for both methods. The review of the relevance of the deviations was carried out with the help of analysis of variance methods (Student’s t test, α-error set at 5%), as well with the calculation of the confidence intervals (Sigma Plot 13, Systat Software, San José/CA, USA). Results The data pairs for all transfers from the methods compared were first compiled in three-dimensional scatterplots for evaluation. All three-dimensional spatial coordinates of the three reference points from the transfer with the arbi- trary face-bow are shown in Fig. 2; the readings for the transfer in the control group using the transfer with a rub- ber band are shown analogously in the scatterplot in Fig. 3. The comparison of both figures indicates clearly that in the case of the face-bow transfer, the measured coordinates are comparatively closer to each other, whereas in the control group the coordinates are scattered in a wider field of dis- tribution (Fig. 2). For statistical evaluation, the distance of each measured position from the calculated mean of each group was then determined. The results of this evaluation are presented in a diagram (Fig. 4) and in a table (Table 1). The boxplots in the figure and the results in the table indicate that the readings vary for all three reference points in both groups. However, the amount of variance around the mean for all measurements after the arbitrary face-bow transfer is sig- nificantly smaller than that of the alternative method (in- cisor point p = 0.0027; right molar p = 0.019; left molar p = 0.0098). As a result, the null hypothesis had to be rejected. In addition to the calculation of the variance, the confi- dence intervals (95%) were also calculated to assess the reli- ability of the result (Fig. 5). From this, it was determined that the measurements at the incisor point showed a minor amount of overlapping in both groups, while those of both molar re- gions showed no overlapping at all between the results of both methods being investigated. Discussion Methods Evidence-based dentistry [18] emphasizes the value of ran- domized controlled trials (RCTs) [19]. For this reason, the testing design of the present study essentially followed this concept by separation of the total group of homogeneous test persons into two study groups in a randomized process at the onset of the thus randomized controlled trial. Both groups had to employ both transfer techniques, but in opposite sequences. In this way, it was ensured that no learning effect occurred resulting from the order of the individual work-steps, which supporting the arbitrary face-bow, this factor alone could have presented a serious point of criticism. Another reason is the fact that the dimensions of the patient simulator exactly matched the inner dimensions of the articulator employed in the study, which was provided by the same manufacturer. Prior to this study, only the investigation by Choi et al. relied on a dummy as test object and thus could provide information sign. P = 0.004 sign. P = 0.02 ,sign. P = 0.001 might have given a one-sided advantage to the second transfer in each group. An ideal test-design would also include a double-blind evaluation. Unfortunately, it is impossible as a rule in manual testing processes to carry out a double-blind evaluation—in contrast to pharmacological studies—because the researching test person necessarily knows how he or she has just complet- ed the preceding task. For attaining the maximum possible level of objectivity, therefore, the actual measurements in this study were carried out by an individual separated from the test persons and blinded in each case regarding the transfer meth- od whose results were being analyzed. This was ensured by the prior anonymization of the casts using number codes drawn by lots, and by the uniform appearance of the casts. In order to attain a maximum level of standardization, a patient simulator (dummy) was employed in place of the hu- man patient used in previous studies. This way, a high degree of test condition stability could be achieved. One reason for on the validity at all but this study only determined the accu- racy of an arbitrary face-bow [9]. Hence, this is the first in- vestigation that provides evidence on the validity of mounting an arbitrary face-bow in comparison to the transfer of the maxillary cast based on average values only. A standard adapted from earlier comparison studies was that all mountings were performed within a single individual articulator, which was recalibrated after each mounting. This ensured maximal reproducibility of measurements in the mounting site. Another standard adapted from earlier studies was the measurement at several three-dimensionally defined reference points [7–9]. Regarding the influence of the operators, so far, there is no external evidence on the transfer method that excludes the influ- ence of the professional experience and/or previous knowledge of the test persons. Such prior knowledge or attained skills could, for example, compensate for the deficits of the various methods. So far, two studies from the same working group investigated the reproducibility of the mounting and thus of the transfer of the maxillary position, in each case conducted by three dentists [8, 9]. In the earlier study by Bowley et al., the first author carried out the evaluations and was at the same time also the test person and hence the object of all the tests of his three co-authors. The study by Choi et al. employed a similar test design, but replaced the human patient with a dummy and allowed each of the three researchers five transfers. In both studies, the authors did neither provide information about the calibration of the researchers’ ed- ucation and on the prior experience of the researchers nor on the calibration of the clinical procedures. In contrast to all investiga- tions conducted before, in this study, undergraduate dental stu- dents were chosen who had no prior knowledge of or experience with the issue under investigation. This allowed for their uniform instruction regarding the fundamentals and the application of the two transfer techniques. In this manner, the test persons were on the one hand optimally and uniformly pre-trained; and on the other hand, they entered the study free of possible biases and/or competence-modifying prior knowledge. The method of three-dimensional evaluation of the total of 76 transfers (38 test persons × 2 methods) followed earlier studies regarding the extent to which the transferred position varies around the mean value of all transfers, because impacts of the transferred position on the occlusal relationship increase geometrically, especially with the positioning of the mandib- ular cast by means of a centric relation record [1, 7, 10–12]. Results The null hypothesis had to be rejected because of the signifi- cant difference in the reliability between both group. As the true dimensions of the patient simulator were identical to the individual articulator used for mounting, the results also prove a decisive difference in validity. Already the raw data plotted into scatterplots (Figs. 2 and 3) indicated that the three-dimensional relations vary considerably less in the transfer in the face-bow group than in the group in which the casts were mounted without using a face bow. Hence, it was no surprise that the statistical analysis of this comparison determined a significant difference (Fig. 4). As indicated in the calculation of the confidence intervals (Fig. 5 and Table 1), the extent of the difference of the spatial areas of the posterior reference points located on the molar occlusal surfaces is so distinct, that even in a repetition of the study, no other result is to be expected. For judging the measured values, their comparison of the data from this study to the data gained by the other working groups from multiple tests on a single patient is of interest. As indicated in the scatterplots depicted in Figs. 2 and 3, the variance found here with the 38 inexperienced test persons and a patient simulator corresponds exactly to the range of ± 1–2 mm in each direction reported by Choi et al. [9]. These figures are vastly superior to the variance of 5 mm reported in earlier studies [6, 7]. The results of this study describe in detail the effect of the face-bow transfer on the position of the maxillary cast in the articulator. This is relevant as the relation of the maxillary teeth to the hinge axis in the articulator and the patient is decisive for the correspondence of occlusal contacts in articulators and patients. Hence, the re- sults suggest that the correspondence of the relation in the patient to the articulator following a face-bow transfer will be essentially better. This result supports earlier publications that determined that completely excluding the use of a face- bow for transferring the maxillary position leads to a greater deviation from the subsequently simulated occlusion [11, 12]. This is especially relevant in combination with the use of unforced centric relation records due to their record height, which will have a greater effect with increasing vertical di- mension [7, 10–12, 20, 21]. For a given deviation of the arbi- trary axis, this is proportional to the resulting occlusal error [7]. If, however, studies investigate the effect of a face-bow transfer based on the effect of the subsequent prosthodontic treatments, other factors potentially shield the effect of a single procedure on the overall result. This must be considered in the evaluation of the last review on randomized clinical studies covering the effect of face-bow-transfers on splints and dentures [2]. Adding to this, in splints, the occlusion is typically flat [22–25]. Thus, on splints, only a limited number of occlusal contacts can be expected under all circumstances. This explains at first sight conflicting results from an earlier controlled clinical study on the effect of face-bow transfers on the occlusion of splints [13]. In that pilot study on patients diagnosed with bruxism, transfers with and without a face- bow (but without centric relation records) were followed by the subsequent fabrication of Michigan-type occlusion splints. The authors evaluated the benefit of using an arbitrary face- bow based on the number of occlusal contacts on the splints. As in both groups, a similar number of occlusal contacts were determined; the authors concluded that the fabrication of oc- clusal splints does not benefit from the use of an arbitrary face- bow. However, the authors also pointed out that this was only a preliminary result of a pilot study, and that for the time being, this result should be regarded as valid only for the transfer system employed and the specific situation (which did not include the effect of centric relation records). These details limit the relevance of the results as in the fabrication and adjustment of an occlusion splint, a whole chain of additional work-steps is involved which must be considered. The shrink- age parameters of the polymers used in the fabrication, for example, could cover up and/or falsify the result of the actual transfer. Also, counting an identical number of occlusal con- tacts is not equivalent to stabilizing the planned mandibular position—especially in a splint. Not without reason, the au- thors stated that their findings are not applicable for the face- bow transfer in fixed and removable partial dentures. Adding to this, the review published recently which finally identified eight randomized controlled trials on the effect of face-bows determined that so far no clinical study was available on the face-bow transfer in fixed and removable partial dentures [2]. In contrast, the study presented here uses the highest ex- perimentally realizable evidence level to prove a significant gain in accuracy and reliability through the transfer of the maxillary position using an arbitrary face-bow. Conclusions The first conclusion from this study compared to the cited literature is that the measurement values recorded using a patient simulator under the described conditions are applicable as well to Breal^ patients. The second conclusion to be drawn from the results of thisstudy is that test persons with identical level of prior experi- ence transferred maxillary casts by means of an arbitrary face- bow with significantly higher reliability and validity than by a transfer method relying only on average values based on Bonwill’s triangle and the Balkwill angle. The third conclusion arises in combination with the calcula- tions from past studies [7]. These studies established that a substantially larger transfer error is expected in combination with the use of bite registrations for unforced centric relation records, due to the increased vertical dimension required for the records. These centric relation records are indicated in a com- promised occlusal relationship of the mandibular and maxillary casts in static occlusion, and in altered movements of the indi- vidual occlusal surface elements in dynamic occlusion [10]. Therefore, it is the firm opinion of the authors of this study that the transfer of the maxillary position should be based on a face-bow transfer especially in clinical situations including the use of bite registrations in centric relation and/or later eleva- tion of the vertical dimension of occlusion. Acknowledgements The authors would like to express their heartfelt thanks to the dental students at the University of Leipzig who participated in the study as test persons, as well as to Mr. Christian Pala and Ms. Brigitte Münzner, Certified Dental Technicians at the University of Leipzig, who skillfully prepared the 152 casts. Special thanks also to Tom Kennedy, Boston, for his support in refining the manuscript as native speaker, as well as to Agnieszka Tarkowska, Hamburg, for refining and proofreading the manuscript. Compliance with ethical standards Conflict of interest The authors declare that they have no conflict of interest. Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institu- tional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent For this type of study, formal consent is not required. References 1. Ahlers MO (2000) Simulation of Occlusion. dentaConcept, Hamburg 2. Farias-Neto A, Dias AH, de Miranda BF, de Oliveira AR (2013) Face-bow transfer in prosthodontics: a systematic review of the liter- ature. J Oral Rehabil 40:686–692. https://doi.org/10.1111/joor.12081 3. Teteruck WR, Lundeen HC (1966) The accuracy of an ear face- bow. J Prosthet Dent 16:1039–1046 4. Whitsett LD, Shillingburg HT Jr, Keenan MP (1977) Modifications of a new semi-adjustable articulator for use with a caliper style ear face-bow. J Calif Dental Assoc 5:32–38 5. Hugger A, Holtkamp C, Pröschel P, Drescher D, Stüttgen U (2001) Die Reproduzierbarkeit der elektronisch ermittelten individuellen Scharnierachsenposition. [The reproducibility of an electronic hinge axis localizing method]. Dtsch Zahnärztl Z 56:383–387 6. Palik JF, Nelson DR, White JT (1985) Accuracy of an earpiece face-bow. J Prosthet Dent 53:800–804 7. Piehslinger E, Bauer W, Schmiedmayer HB (1995) Computer sim- ulation of occlusal discrepancies resulting from different mounting techniques. J Prosthet Dent 74:279–283 8. Bowley JF, Michaels GC, Lai TW, Lin PP (1992) Reliability of a facebow transfer procedure. J Prosthet Dent 67:491–498 9. Choi DG, Bowley JF, Marx DB, Lee S (1999) Reliability of an ear-bow arbitrary face-bow transfer instrument. J Prosthet Dent 82:150–156 10. Adrien P, Schouver J (1997) Methods for minimizing the errors in mandibular model mounting on an articulator. J Oral Rehabil 24: 929–935 11. Castle AL, Anthony TH (1998) Comparing vertical dimension changes with and without a face-bow transfer. Journal of Dental Technology 15:23–25 12. Morneburg TR, Pröschel PA (2011) Impact of arbitrary and mean transfer of dental casts to the articulator on centric occlusal errors. Clin Oral Investig 15:427–434. https://doi.org/10.1007/s00784- 010-0395-9 13. Shodadai SP, Türp JC, Gerds T, Strub JR (2001) Is there a benefit of using an arbitrary facebow for the fabrication of a stabilization appliance? Int J Prosthodont 14:517–522 14. Hugger A, Türp J, Pröschel P, Strub J, Stüttgen U (2001) Die Anwendung von Gesichtsbögen in der restaurativen Therapie und Funktionsdiagnostik — welches Evidenzniveau liegt vor? [The ap- plication of arbitrary face bow registration and transfer - which level of evidence exists?]. Dtsch Zahnärztl Z 56:671–675 15. Morneburg T, Hugger A, Türp J, Schmitter M, Utz K, Freesmeyer W, Rammelsberg P (2010) Wissenschaftliche Mitteilung der Deutschen Gesellschaft für Prothetische Zahnmedizin und Biomaterialien e. V. (DGPro) (vormals DGZPW): Anwendung des Gesichtsbogens beim funktionsgesunden Patienten im Rahmen restaurativer Maßnahmen [Application of face bows for restorative purposes in functionally healthy patients—scientific statement of the DGPro]. Dtsch Zahnärztl Z 65:690–694 16. Egger M, Juni P, Bartlett C, Group C (2001) Value of flow diagrams in reports of randomized controlled trials. JAMA 285:1996–1999 17. Schulz KF, Altman DG, Moher D, Group C (2010) CONSORT 2010 statement: updated guidelines for reporting parallel group randomized trials. Ann Intern Med 152:726–732. https://doi.org/ 10.7326/0003-4819-152-11-201006010-00232 18. Sackett DL, Rosenberg WM (1995) On the need for evidence-based medicine. J Public Health Med 17:330–334 19. Guyatt GH, Sackett DL, Sinclair JC, Hayward R, Cook DJ, Cook RJ (1995) Users’ guides to the medical literature. IX. A method for grading health care recommendations. Evidence-Based Medicine Working Group [published erratum appears in JAMA 1996 Apr 24;275(16):1232]. JAMA 274:1800–1804 20. Kordaß B, Rückert B, Stüttgen U (1997) Zur Länge und Lage der Interkondylarachse [Length and position of the intercondylar axis]. Dtsch Zahnärztl Z 52:1–4 21. Kordaß B, Stüttgen U (1997) Momentane Drehzentren der Unterkieferfunktion [Instantaneous centres of rotation in mandibu- lar function]. Dtsch Zahnärztl Z 52:540–545 22. Fu AS, Mehta NR, Forgione AG, Al-Badawi EA, Zawawi KH (2003) Maxillomandibular relationship in TMD patients before and after short-term flat plane bite plate therapy. Cranio 21:172–179 23. Solow RA (2013) Customized anterior guidance for occlusal de- vices: classification and rationale. J Prosthet Dent 110:259–263. https://doi.org/10.1016/s0022-3913(13)60373-x 24. Torii K, Chiwata I (2005) Relationship between habitual STAT3-IN-1 occlusal position and flat bite plane induced occlusal position in volunteers with and without temporomandibular joint sounds. Cranio 23:16– 21. https://doi.org/10.1179/crn.2005.004
25. Torii K, Chiwata I (2010) Occlusal adjustment using the bite plate- induced occlusal position as a reference position for temporoman- dibular disorders: a pilot study. Head Face Med 6:5. https://doi.org/ 10.1186/1746-160x-6-5