Centric relation: A needed reference position.

PURPOSE: Centric relation (CR) is a universally recognized term and an acceptable reference position with a long history of success. The problem is that there is little consensus as to its definition or the method of recording it, and this has created an uprising to abolish it. METHODS: A review of pertinent literature related to its definition, method of recording, anatomic considerations, and long-standing principles was conducted. RESULTS: Centric relation is an established term but there are valid concerns over its definition and method of recording. There is consensus on using it as a restorative position in a patient in need of full-arch reconstruction, and there is no substantive clinical research to contradict this. If a clinician decides to use a different position, it should have a different name. CONCLUSIONS: Centric relation is a reproducible reference position that can be utilized for diagnostic and restorative dental procedures with substantial scientific evidence to support that premise. There are numerous well-documented techniques, all of which are intermaxillary, that can replicate the position. There is little scientific evidence to support a premise as to where the exact position of the condyle should be in relation to the fossa.

Centric relation: A matter of form and substance.

The recent review article by Zonnenberg, Türp and Greene 'Centric relation critically revisited - What are the clinical implications'? opens an important debate by addressing topics of central relevance in Dentistry, namely the relationship between occlusion and the condyle-to-glenoid-fossa position, and the need for diagnostic assessment and therapeutic alteration of the condylar position in orthodontic patients. Zonnenberg, Türp and Greene concluded that the mandibular condyle is correctly situated in most orthodontic patients. Thus, in their view, orthodontists can disregard this aspect during treatment, and rely on the plastic properties of the masticatory supporting structures, while aiming at finishing the cases in a good occlusal relationship. We think that this approach fails to consider that biological variation of the stomatognathic structures can also be pathological and that, as dental occlusion determines condylar relative position within the glenoid fossa, changes in the occlusion are likely to alter the original condylar-to-glenoid-fossa relation. Hence, we claim that whenever the occlusal relationship must be changed, the clinician should carefully monitor the condyle position and the mandibular function to prevent possible iatrogenic effects. To advance the discourse on the topic, we invite Zonnenberg, Türp and Greene to clarify their definition of 'average patient' and their interpretation of 'full-mouth orthodontic and orthognathic treatment', their understanding of 'biologically acceptable condylar relationship', their justification of maximum intercuspation as reference position, the extent to which they think it is safe to rely on the TMJ resilience, and finally their alternative to centric relation in the treatment of patients needing condylar repositioning.

Centric relation critically revisited-What are the clinical implications?

PURPOSE OF THE ARTICLE: Centric relation is a dental term that has undergone many alterations over the years, which in turn have led to significant clinical controversies. These continuing changes in the meaning of the term CR have not only led to confusion, but they also have resulted in a variety of unnecessary diagnostic and therapeutic procedures. Analysis of the dental literature reveals ongoing misunderstanding and disagreement regarding that term among both clinicians and academic dentists. MATERIALS AND METHODS: A search of the PubMed database was performed with the following search terms: "centric relation", "masticatory muscles", "maxillomandibular relationship" and "condylar position." Relevant literature from the past 70 years until the present day was meticulously scrutinised. RESULTS: As expected, the literature review on the topic of CR revealed a problematic pattern of changing definitions and clinical disagreements, all of which have had a significant impact on the practice of dentistry. CONCLUSION: There are semantic, conceptual and practical reasons for concluding that the term 'centric relation' is flawed. Those flaws have a significant impact on dental practice. Based on our analysis, argumentation is provided to conclude that the term 'centric relation' should be abandoned. Instead, it appears that every individual has a unique temporomandibular joint relationship which cannot be described by any singular term. In healthy dentate patients, this relationship is determined by the maximum intercuspation of the teeth and should therefore be considered as biologically acceptable.

The Relationship Between Centric Occlusion and The Maximal Intercuspal Position and Their Use as Treatment Positions for Complete Mouth Rehabilitation: Best Evidence Consensus Statement.

PURPOSE: The purpose of this Best Evidence Consensus Statement was to evaluate the existing literature relative to two focus questions: How often does centric occlusion coincide with maximal intercuspal position in dentate and partially dentate populations?; and should centric occlusion or maximal intercuspal positions be equivalent for dentate and partially dentate patients undergoing complete mouth rehabilitation? MATERIALS AND METHODS: Keywords used in the initial search were: intercuspal position, centric occlusion, centric relation, maximal intercuspal position, prosthodontic rehabilitation, and occlusion. The search was then limited to Systematic Reviews, Randomized Controlled Studies, Meta-analyses and Clinical Trials. RESULTS: The initial search strategy related to the selected search terms resulted in more than 15,000 articles. When the subsequent search was limited to Systematic Reviews, Randomized Controlled Studies, and Meta-Analysis and Clinical Trials, 313 articles were selected for further analysis. CONCLUSIONS: Review of the literature reveals that most dentate and partially dentate patients do not have coincident centric occlusion and maximal intercuspal position. There is support for coincidence between centric occlusion and maximal intercuspal position as the preferred occlusal relationship in complete mouth rehabilitations. The literature does not report conclusive evidence of adverse prosthodontic outcomes with complete rehabilitations in centric occlusion or maximal intercuspal position in a healthy population. However, there is support for an association between centric occlusion-maximal intercuspal position discrepancies and occlusal instability as well as temporomandibular joint disorders. Hence, it is concluded that partially and completely dentate patients requiring complete mouth rehabilitation should be restored in centric occlusion.

Two-dimensional versus three-dimensional Frӓnkel Manoeuvre: a reproducibility study.

BACKGROUND/OBJECTIVES: To assess intra- and inter-observer reproducibility of the evaluation of the Frӓnkel Manoeuvre (FM) on three-dimensional (3D) scans and to compare it to the assessment on two-dimensional (2D) pictures. MATERIALS/METHODS: This study included 44 individuals with a skeletal Class II malocclusion [9-16-years old mean age ± standard deviation: 13.5 ± 2.01 years]. All patients had a full Class II molar relationship, overjet ≥6 mm and point A, Nasion, point B angle (ANB) ≥5 degrees. During the FM, each patient was invited to bite in centric occlusion and then to posture the mandible forward to reach a Class I molar relationship. The FM was recorded both by a normal camera and a 3D scanner (3dMD system). Six examiners divided into two groups according to their orthodontic clinical experience (<5 and >10 years), and one gold standard in the evaluation of FM, commented twice (every 15 days) on both 2D photographs (T0 and T2) and 3D scans (T1 and T3). The intra-observer agreement and the inter-observer agreement compared to the gold standard were evaluated by computing the Cohen's K. RESULTS: The agreement between observations for each examiner ranged from 0.36 to 1 on 2D pictures (T0 versus T2), and from 0.22 to 0.69 on 3D scans (T1 versus T3). The overall agreement was 0.63 (95 per cent CI = 0.35-0.91) in 2D analysis and 0.5 (95 per cent CI = 0.35-0.64) in 3D analysis. CONCLUSIONS/IMPLICATIONS: The FM was less reproducible when performed on 3D records than on 2D pictures.

Meta-analysis of brain mechanisms of chewing and clenching movements.

Functional magnetic resonance imaging (fMRI) is widely used for investigating brain activation patterns associated with chewing and clenching movements. Whether studies consistently identify similar brain loci engaged in these movements remains unknown. We investigated the consistency with which specific brain loci were reported to be activated during teeth-occluding movements, using the activation likelihood estimation (ALE) meta-analysis. Twenty fMRI studies that used fMRI to investigate brain activation during a chewing or clenching task in healthy participants were included. Data from the selected studies were pooled, and ALE methods were used to estimate the likelihood of finding a locus associated with the movements. We found that (i) The bilateral primary motor cortex/supplementary motor area/thalamus, the right primary somatosensory cortex (S1)/secondary somatosensory cortex and the posterior cerebellum (lobule VI) have been identified as reliable loci that show consistently activation when teeth occlude. (ii) The right S1 showed a significant likelihood of activation associated with both chewing and clenching, while the left S1 showed a greater likelihood of activation in chewing than in clenching. (iii) Both younger and older participants showed a significant likelihood of activation in the cerebellum. No significant cluster was identified in the contrast analysis. The fMRI studies reliably identified the sensorimotor cortex, the thalamus and the cerebellum as brain loci associated with chewing and clenching and illustrated a differential activation pattern between chewing and clenching. These findings support the use of fMRI as a potential tool for assessing brain activation patterns related to oral sensorimotor functions in humans.

A hemispherical contact model for simplifying 3D occlusal surfaces.

STATEMENT OF PROBLEM: Currently, dental articulators can recreate mandibular movements and occlusal contacts. However, whether virtual articulators can also provide information about occluding dental surfaces, functional movements, and the mandibular condyles is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the occluding surfaces on dental casts obtained from a patient and approximate them to a hemispherical contact model. Both models were tested by digitizing the Dentatus ARL dental articulator. MATERIAL AND METHODS: A combination of photogrammetry and structure from motion methods were used to scan a Dentatus ARL articulator and representative dental casts. Using computer-aided engineering and finite element analysis, contact points and action vectors to the forces on occluding surfaces and condyles were obtained for cast and hemispherical models. This experiment was performed using centric occlusion and 3 different condylar inclinations. The Kruskal-Wallis 1-way analysis of variance on ranks test was used to allow all pairwise comparisons between condylar inclination and mechanical action vector values in each location (α=.05). RESULTS: Action vectors from the cast model and each location of the hemispherical model were calculated to show the mechanical consequences and the similarity among models. Overall, no significant differences were observed for action vectors (A20 versus A40 versus A60) at each location (dental cast/hemisphere, right condylar, and left condylar) in the analysis of dental casts and the hemisphere model (.382≤P≤.999). CONCLUSIONS: This study provided graphical information that may assist the dental professional in determining which occlusal contacts should be modified to attain condylar and balanced centric occlusion.

Symmetry of fMRI activation in the primary sensorimotor cortex during unilateral chewing.

OBJECTIVE: Functional magnetic resonance imaging (fMRI) is one of the most advanced techniques to analyze the cerebral effects on many behavior aspects of the oral system such as chewing and mastication. Studies on imaging of the cerebral representation of chewing demonstrated differential results with respect to cortical lateralization during unilateral chewing. The aim of our study is to clarify the effects of cerebral responses during unilateral chewing. MATERIAL AND METHODS: We used fMRI to compare brain activities during occlusal function in centric occlusion on natural teeth and chewing on a gum located on the right or the left teeth in 15 healthy subjects. Group data were performed by Talairach normalization and in addition by an assignment of activation maxima to individual anatomical landmarks in order to avoid possible loss of spatial preciseness of activation sites by normalization procedures. RESULTS: Evaluation of group data by Talairach normalization revealed representation sites for occlusal movements in bilateral primary (S1) and secondary (S2) somatosensory cortices, primary motor (M1) and premotor cortices, supplementary motor area (SMA) and medial cingulate gyrus, bilateral anterior cerebellar hemispheres and vermis, insula, orbitofrontal cortex, thalamus, and left pallidum. Right-sided chewing showed no differential activation to left-sided chewing, and both showed activation in areas also involved in bilateral occlusion. Both techniques, the one based on group normalization and the one based on an individual evaluation method, revealed remarkable low differences in activation maximum location in the primary motor, the primary and secondary somatosensory cortices, and the anterior cerebellar lobe. All chewing movements tested involved bilateral sensorimotor activation without a significant lateralization of activation intensities. CONCLUSION: Overall, a general lateralization of occlusion movements to the dominant side could not be verified in the present study. Chewing on the left or on the right side of teeth makes no difference for brain representation of chewing. CLINICAL RELEVANCE: The results describe the basic effects of what we can expect by evaluation of cerebral effects of chewing and mastication. Based on these results, clinical fMRI studies can be performed in different patient groups.

Self-report of temporomandibular joint clicking and psychological factors: is there an association?

The objectives of this study were to test the hypothesis that self-reported TMJ clicking sounds in adolescents are positively associated with non-specific somatic symptoms, self-perception of body image and care-seeking behaviour. A cross-sectional study was carried out in 353 young adolescents (48·4% females) recruited from community (N = 272) and orthodontic clinic (N = 81) settings. Assessments included self-reported TMJ clicking, non-specific physical symptoms, body image concerns and for the clinic sample only, the source of motivation for treatment. TMJ sounds were self-reported by 19% of the sample and were associated with higher scores for non-specific physical symptoms and body image concerns (P < 0·001). Adolescents who were self-motivated to seek orthodontic treatment had greater scores for non-specific physical symptoms, more body image concerns and tended to report TMJ sounds more often (26·3% and 7·7% respectively; P = 0·41) than those who were solely parent/family-motivated to seek treatment. Self-reported TMJ sounds in adolescents were associated with a propensity to somatisation and concerns with body image. Care-seeking adolescents have greater non-specific physical symptoms and body image concerns and tend to report more frequent TMJ sounds.

[Clinical and diagnostic rationale for the final stage of orthodontic treatment]. / Kliniko-diagnosticheskoe obosnovanie zavershaiushchego étapa ortodonticheskogo lecheniia.

The aim of the study was to improve the efficiency of the final stage of orthodontic treatment. The study included 32 patients divided into two groups of 16. Orthodontic treatment was performed using a bracket system active self-ligation straight arc technique with step adjustment anthropometric quantitative evaluation system (The ABO Model Grading System). Centric occlusion and centric relation were analyzed at baseline and after treatment by mandible position indicator MPI (Mandibular Position Indicator). The first group received treatment according to conventional protocol, in the second group braces were readjusted by indirect bonding after ABO anthropometric measurements. The efficiency of orthodontic treatment using ABO system at the late stages of adjustment in the second group was significantly higher than in the first group (p=0.002248; p=0.023431, respectively). MPI analysis in the first group in 10 (62.5%) patients showed mismatch of centric occlusion and centric relation not seen in the second group. In 3 (18.75%) patients of group 2 the difference did not exceed 0.5 mm which was considered normal. Thus, the application of ABO anthropometric system followed by readjustment of incorrectly positioned brackets by indirect bonding promotes MPI values improvement, which in turn allows getting the most accurate, and stable results of orthodontic treatment.

Incidence of temporomandibular joint clicking in adolescents with and without unilateral posterior cross-bite: a 10-year follow-up study.

Among different malocclusions, posterior cross-bite is thought to have a strong impact on the correct functioning of the masticatory system. The association between unilateral posterior cross-bite (UPCB) and temporomandibular joint (TMJ) clicking, however, remains still controversial. The aim of this study was to investigate whether the presence of UCPB during early adolescence increases the risk of reporting TMJ clicking after a long-term follow-up. A longitudinal survey design was carried out in a group of 12-year-old young adolescents, who were examined at baseline for TMJ clicking sounds and unilateral posterior cross-bite. After 10 years, 519 subjects could be reached by a telephone survey. Standardised questions were used to collect self-reported TMJ sounds and to determine whether participants had received an orthodontic treatment. Logistic regression analysis revealed a significant association between unilateral posterior cross-bite and subjectively reported TMJ clicking (odds ratio = 6·0; 95% confidence limits = 3·4-10·8; P < 0·0001). The incidence of TMJ clicking was 12%. At a ten-year follow-up, self-reports of TMJ clicking were significantly associated with the presence of UPCB at baseline, but not with the report of having received an orthodontic treatment. Within the limitation of this study, the presence of unilateral posterior cross-bite in young adolescents may increase the risk of reporting TMJ sounds at a 10-year follow-up. The provision of an orthodontic treatment, however, does not appear to reduce the risk of reporting TMJ sounds.

Reproducibility of the assessment of the Fränkel manoeuvre for the evaluation of sagittal skeletal discrepancies in Class II individuals.

OBJECTIVES: The Fränkel manoeuvre is a procedure by which the mandible of Class II individuals is postured forward in dental Class I relationship. The evaluation of the resulting facial profile provides information concerning the components determining the sagittal discrepancy. Data concerning the reproducibility of its assessment are not available. This study aimed to evaluate the intra-observer and inter-observer reproducibility of the assessment of the manoeuvre and to assess whether the amount of clinical experience affects its reproducibility. METHODS: Two lateral photographs, one in centric occlusion, and the other with the mandible postured forward (Fränkel manoeuvre) of 100 Angle Class II individuals aged between 9 and 13 years were evaluated by six orthodontists (T0). Each examiner was asked whether the facial profile worsen or not with the manoeuvre after being trained by an expert orthodontist. The test was repeated after 2 weeks interval (T1). Intra-observer and inter-observer agreement were evaluated by computing the Cohen's K. RESULTS: The agreement (K values) between observations (T0 versus T1) for each examiner ranged from 0.49 to 0.72. The overall agreement was 0.65 [95% confidence interval (CI) = 0.54-0.75]. The agreement in the group with less clinical experience was 0.61 (95% CI = 0.46-0.76), while it was 0.68 (95% CI = 0.53-0.83) in the more experienced group. The amount of clinical experience did not affect intra-observer agreement (P = 0.50). The overall agreement between the examiners and the trainer was 0.74 (95% CI = 0.65-0.83) and 0.73 (95% CI = 0.64-0.83) at T0 and T1 respectively. CONCLUSION: The assessment of the Fränkel manoeuvre is reproducible and it is not influenced by the amount of clinical experience.

Canine guidance via Biogeneric Copy: a clinical report.

The advent of computer-aided design/computer-aided manufacturing (CAD/CAM) technology in dentistry has enabled a wide range of applications. The Cerec Acquisition Center (Cerec AC, Sirona Dental Systems Inc., Charlotte, NC) allows for the construction of all-porcelain restorations, either in-office or through a remote dental laboratory. One feature of the Cerec AC is its ability to duplicate the dental morphology of an existing tooth onto a new CAD/CAM ceramic restoration designed for that tooth. This design mode capability of the Cerec AC is termed Biogeneric Copy. This function has been discussed in the literature where it has been utilized to fabricate a CAD/CAM ceramic crown to fit an existing removable partial denture (RPD).1-3 There are occasions in dentistry where the exact anatomy and position of an existing tooth, not associated with an RPD, should ideally be replicated in a definitive restoration. This case report describes such an occasion.

Canine-guide Occlusion and Group Function Occlusion are Equally Acceptable When Restoring the Dentition.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Impact of lateral occlusion schemes: A systematic review. Abduo J, Tennant M. J Prosthet Dent 2015;114(2):193-204 SOURCE OF FUNDING: Not reported TYPE OF STUDY/DESIGN: Systematic review.

[Evaluating the effectiveness of the new mouthguard design in athletes involved in power sports]. / Otsenka effektivnosti primeneniya novoi konstruktsii zubnoi shiny u sportsmenov, zanimayushchikhsya silovymi vidami sporta.

The aim of the study was to assess the effectiveness of the new mouthguard design for functional rehabilitation of dental system in athletes involved in contact power sports. The functional state of dental system was evaluated by interferential electromyography of masticatory muscles and Doppler ultrasound examination of periodontal tissues. Before mouthguard use the asynchrony of masticatory muscles was seen which was released after the mouthguard application: electromyographic activity of the left and right masticatory muscles was balanced and the decrease in biopotentials amplitude was found out. The mouthguard also caused no functional disorders in periodontal tissues.

Effect of natural mediotrusive contact on electromyographic activity of jaw and cervical muscles during chewing.

OBJECTIVE: This study evaluated the effect of a natural mediotrusive contact on the electromyographic (EMG) activity of the anterior temporalis and sternocleidomastoid muscles during chewing in healthy subjects. MATERIALS AND METHODS: The study sample included two groups of 15 subjects each (Group 1: with natural mediotrusive contact; Group 2: without natural mediotrusive contact). Bilateral surface EMG activity was recorded on anterior temporalis and sternocleidomastoid muscles during unilateral chewing of a half cookie and unilateral chewing of a piece of apple. Anterior temporalis and sternocleidomastoid muscle activity was normalized against activity recorded during maximal voluntary clenching in intercuspal position and maximal intentional isometric head-neck rotation to each side, respectively. The partial and total asymmetry indexes were also calculated. Data were analyzed using Mann-Whitney, Wilcoxon and unpaired t-test. RESULTS: EMG activity of anterior temporalis and sternocleidomastoid muscles showed no significant difference between the groups. EMG activity of anterior temporalis was similar between working and non-working sides during chewing in both groups. EMG activity of sternocleidomastoid muscle was higher in the working side than in the non-working side in Group 2 subjects. Asymmetry indexes were not significantly different between groups. CONCLUSIONS: The similar EMG pattern and asymmetry indexes observed suggest the predominance of central nervous control over peripheral inputs on anterior temporalis and sternocleidomastoid motor neuron pools.

The relationship between facial morphology and the structure of the alveolar part of the mandible in edentulous complete denture wearers. A preliminary study.

OBJECTIVE: Although the effect of involutional processes that occurs in the maxilla and mandible of edentulous subjects is obvious, the problem of factors definitely determining the direction of changes still remains unsolved. This study was aimed at determining the relationship between facial morphology and the structure of the alveolar part and the body of the mandible in edentulous complete denture wearers. MATERIALS AND METHODS: Twenty-five healthy edentulous Caucasian patients in the 70.5 ± 9 years of age group were examined. All patients underwent tele-X-ray examination with the presence of currently used dentures in the oral cavity. To assess morphological parameters of the facial skeleton, cephalograms were analyzed according to Ricketts and Mc Namara method. To assess the mandible morphology, the films were measured using the method of Tallgren. RESULTS: The period of edentulism was found to be negatively correlated with the anterior segment of the body of the mandible within its symphysis. The parameter corresponding to the location of the first lower molar showed a directly proportional correlation with G'-Sn', G'-Me', Sn'-Me', N-Ans, N-Me, Ans-Me, Co-Gn and Co-Go. Positive correlations were found between the parameters describing contour of the alveolar part of the body of the mandible and mandibular symphysis and G'-Me', Sn'-Me', N-Me, Ans-Me describing the height of the occlusal vertical dimension. CONCLUSION: The study showed a directly proportional correlation between the vertical occlusal dimension of the lower face conditioned by prosthetic rehabilitation and the height of the alveolar part in the lateral regions of the mandible.

In vitro comparison of the maxillary occlusal plane orientation obtained with five facebow systems.

STATEMENT OF PROBLEM: The sagittal and coronal orientation of the maxillary occlusal plane plays an important role in the esthetic and functional outcome of dental prostheses. The accuracy of contemporary facebow transfer systems in transferring this orientation to semiadjustable articulators has not been quantified. PURPOSE: The purpose of this in vitro investigation was to analyze the sagittal and coronal orientation of the occlusal plane with 5 different facebow transfer systems. MATERIAL AND METHODS: A phantom head containing a maxillary typodont (control) was oriented so that the Frankfort horizontal plane was horizontal. The angle between the occlusal plane of the maxillary arch of the phantom head and the Frankfort horizontal plane was measured along the sagittal and coronal planes with a digital protractor. Fifteen facebow records using each of 5 facebow transfer systems (test groups) were made on the phantom head containing the maxillary typodont. Diagnostic casts of the maxillary typodont were mounted on semi-adjustable arcon articulators from the facebow records. The same angles measured on the control were measured on the test groups. These angles were compared with the same angle measured on the maxillary arch of the phantom head (control). All measurements were made by 2 operators. RESULTS: Significant differences in the sagittal and coronal orientation of the occlusal plane were noted. Compared with the control, the Denar system had the least significant difference in the coronal orientation of the occlusal plane, while the Pana-Mount system had the least significant difference in the sagittal orientation of the occlusal plane. An intergroup comparison of the test groups showed significant differences among the groups. The Kois system showed the greatest difference in the coronal plane orientation, while the Denar system showed the greatest difference in the sagittal plane orientation. CONCLUSIONS: None of the tested facebow systems exactly replicated the sagittal and coronal orientation of the maxillary occlusal plane. Significant differences in the sagittal and coronal orientation of the occlusal plane were observed between the test groups and the control. Intergroup comparisons revealed significant differences in the sagittal and coronal orientation of the occlusal plane.

Reliability of the anterior functional device in recording the centric relations of patients with posterior tooth loss.

STATEMENT OF THE PROBLEM: The recording of centric relations (CRs) in patients with posterior tooth loss is a process that is subject to inaccuracy. A number of techniques and devices, including the anterior functional device (AFD), have been developed in the pursuit of better results. PURPOSE: The purpose of this in vivo study was to evaluate the reliability of the AFD for the recording of the CR in participants with different types of posterior tooth loss. MATERIAL AND METHODS: Two CR records were obtained (CR1, CR2), and 2 maximal intercuspal position records were obtained (MIP1, MIP2) by a single operator at intervals of 5 minutes. This study included 45 participants of both sexes aged between 18 and 65 years who were divided into 3 groups. The first group had intercalated tooth loss (n=19), the second group had distal extensions (n=11), and the third group had no tooth loss (n=15). The distance between the CR and MIP was termed the condylar displacement and was measured in millimeters in the vertical, horizontal, and transversal planes with a condylar position indicator (CPI). The condylar displacements between the CR and MIP in both stages of the study (D1 and D2) were compared with the CPI after mounting the casts on a semiadjustable articulator. Repeated-measures analyses of variance with one factor were used to compare the records for each group in each of the planes: right vertical (RV), left vertical (LV), horizontal right (HR), horizontal left (HL), and transverse (T) (α=.05). No significant differences between the records in any of the planes (RV, LV, HR, HL, or T) were observed; thus, the means of the records of each plane were used to compare the groups (the intercalated tooth loss, distal extension, and no tooth loss groups). The means of the records of the HR and HL planes were compared by ANOVA because the data were normally distributed. The means of the records of the RV, LV, and T planes were compared by using nonparametric Kruskal-Wallis tests because the data were non-normally distributed. RESULTS: No statistically significant difference (P >.05) was found between the condylar displacements for any of the studied variables in the 3 considered groups: RV (.512), LV (.690), HR (.179), HL (.494), and T (.644). CONCLUSIONS: Repeatability of the condylar displacement was observed between the CR and MIP (D1, D2), which indicates the reliability of the AFD method for recording the CR in participants with posterior tooth loss. The AFD was demonstrated to be a user-friendly tool and permitted the recording and evaluation of excursive movements with tracings.

Comparison of the accuracy of a 3-dimensional virtual method and the conventional method for transferring the maxillary cast to a virtual articulator.

STATEMENT OF PROBLEM: The currently available virtual articulators fail to locate the digitized maxillary cast at the exact position in the virtual environment. Some locate the casts on a mechanical articulator with a facebow, and this position is then digitized for the virtual environment. PURPOSE: The purpose of this study was to compare the location of the maxillary cast on an articulator by using 2 different procedures: the conventional method and a virtual method. MATERIAL AND METHODS: With the conventional procedure, the kinematic axis of the participant was determined with an axiograph. The location of the maxillary cast in reference to this axis was then physically transferred to a Panadent mechanical articulator. By a virtual procedure, the same kinematic axis and the maxillary cast were transferred directly from the participant to the Panadent virtual articulator by means of reverse engineering devices. The locations obtained with both procedures were compared in a virtual environment with an optical scanner. By calculating the deviation at every point of the occlusal surface, the results obtained with this procedure were then compared with those of the conventional method. RESULTS: The mean deviation on the occlusal surface was 0.752 mm, and the standard deviation was 0.456 mm. CONCLUSIONS: The deviation between the procedures was sufficiently small to allow the methodology for orthodontic purposes. However, the accuracy of the virtual procedure should be improved so as to extend its use to other fields, such as orthognathic surgery or dental restorations, in which the clinical technique requires an articulator.