Mandibular Translation Research Articles

Evaluation of condylar and mandibular movements on the upper airway during the use of mandibular advancement device for obstructive sleep apnea treatment.

To evaluate the temporomandibular joint (TMJ), condylar and mandibular movements in obstructive sleep apnea (OSA) patients treated with mandibular advancement device (MAD) and to identify the influence of these anatomic factors on upper airway (UA) volume and polysomnographic outcomes after treatment. Twenty OSA patients were prospectively treated with MAD. Clinical examinations, cone-beam computed tomography, and polysomnography were performed before MAD treatment and after achieving therapeutic protrusion. Polysomnographic variables and three-dimensional measurements of the TMJ, mandible, and upper airway were statistically analyzed. Condylar rotation, anterior translation, and anterior mandibular displacement were directly correlated with total UA volume, while vertical mandibular translation was inversely correlated with the volume of the inferior oropharynx. MAD treatment resulted in an increase in the volume and area of the superior oropharynx. There was no statistically significant correlation between condylar rotation and translation and polysomnographic variables. With MAD, there was a significant increase in vertical dimension, changes in condylar position (rotation and translation), and mandibular displacement. The central and medial lengths of the articular eminence were inversely correlated with condylar rotation and translation, respectively. The lateral length of the eminence was directly correlated with condylar translation, and the lateral height was directly correlated with condylar rotation and translation. Condylar and mandibular movements influenced UA volume. The articular eminence played a role in the amount of condylar rotation and translation. Individualized anatomical evaluation of the TMJ proves to be important in the therapy of OSA with MAD.

Uncommon Restoration on Nonvital Premolar with Porcelain Inlay: A Case Report with Five-year Follow-up

Introduction: In fixed prosthodontics, the old paradigm on endodontically treated teeth leads to more fragilization due to the architectural preparation needed for a full coverage crown. Endodontically treated premolars with class II defects are common in daily practice. When only one proximal surface is affected, direct adhesive restorations are the most used. The use of porcelain inlay is quite uncommon in this situation despite its advantages. Case Presentation: This article illustrates a clinical case of a 31-year-old female with healthy teeth except for the non-vital first maxillary premolar, presenting a class II mesio-occlusal cavity. The occlusion exam revealed functional anterior guidance and canine guidance on both sides during lateral mandibular translation. Based on mini-invasive dentistry principles, the decision was to restore the nonvital bicuspid with a porcelain inlay. Although scientific literature did not report restoration of the premolars with a ceramic inlay in clinical practice, this option was retained. The realization of a porcelain inlay was described step by step. A follow-up up to 5 years was done. Results: The iatrogenic tooth fragilization was avoided by a mini-invasive approach. At the end of this follow-up period, there was no complication or complaint. The patient was satisfied with the final result. Conclusion: Porcelain inlay seems to be a good option to restore the occluso-proximal cavity on nonvital premolars in a context of a favourable occlusion. Porcelain inlay is respectful of the principles of minimally invasive dentistry and allows to achieve the objectives of function, aesthetics and biocompatibility. However, clinical studies should be conducted to investigate the longevity of porcelain inlay on ETPs.

Arthroscopic Disc Suturing and Repositioning Technique for Treating Anteriorly Displaced Disc in Temporomandibular Joint Disorders: A Posterior Anchorage Technique

Several treatment modalities have been reported for patients with arthrogenous temporomandibular disorders. The most common temporomandibular disorder is internal derangement, usually accompanied by displacement of the articular disc. Most often anteriorly and medially displaced, patients may develop clicking, impaired jaw function, and pain. Articular disc repositioning has been described as an effective method to eliminate interference during mandibular translation, improving mandibular range of motion, and eliminating pain. In this article, we present a new, simple, and reproducible technique without requiring specific instruments for repositioning and suturing the articular disc with posterior anchorage fixed to the tragus cartilage. It has the advantages of a better anteroposterior vector of traction force, without adverse effects as lateralization of the articular disc and skin depression, commonly presented in other techniques.

Selecting a Virtual Articulator: An Analysis of the Factors Available with Mechanical Articulators and their Potential Need for Inclusion with Virtual Articulators.

The ever-expanding world of digital technology has produced many changes, including the availability of virtual articulators. The use of such digital technology requires an understanding of the features that have been available with different mechanical articulators. These features include such items as facebow, intercondylar distance, incisal guide table, condylar inclination, reference plane, lateral condylar inclination, immediate mandibular translation, and ability to verify a centric relation record. This paper reviews the adjustable features that have been available with different types of mechanical articulators so that clinicians can determine if these features should be included in the virtual articulators they choose to use. Regardless of whether one is utilizing a mechanical or virtual articulator, the rationale for which type of articulator to select is the same and is predicated on the needs of the patient, the occlusal philosophy of the clinician, and the required accuracy.

Mini-Anchors to Surgically Treat the Chronic Mandibular Dislocation

Evaluate the feasibility of using mini-anchors for the treatment of chronic mandibular dislocation and to identify the variables that affect the success of this approach. A retrospective cohort study evaluated 9 patients with bilateral recurrent dislocation of the mandible (18 operated joints), treated by a mandibular translation control system using the mini-anchor technique. Data was collected using a Visual Analog Scale (VAS) for subjective parameters and measurements for objective parameters prior to surgery (T1) and at the longest available follow-up (T2) with a minimum of a 12 months interval. Patients subjectively rated their facial pain/headache, jaw function, disability, temporomandibular joint (TMJ) pain and diet. Objective functional changes were determined by measuring the interincisal opening and lateral excursions at T1 and T2. Significant subjective improvements in pain and dysfunction (89 to 94%) were observed (P < .01) from T1 to T2 in all parameters. The comfortable and guarded interincisal opening without mandibular dislocation increased by 41%, the maximum interincisal opening reduced 12 mm, and lateral excursions improved by 43%. Patients with recurrent mandibular dislocations with or without disc dislocation can be treated effectively by the mini-anchor translation control system.

In vivo three-dimensional mandibular kinematics and functional point trajectories during temporomandibular activities using 3d fluoroscopy.

To measure in vivo three-dimensional kinematics of the mandible and associated end-point trajectories and to quantify their relationships during temporomandibular joint activities using 3D fluoroscopy. A novel fluoroscopy-based 3D measurement method was used to measure motions of the mandible and the associated end points (i.e. incisors and lateral poles of both condyles) during open close, lateral gliding and protrusion-retraction movements in healthy young individuals. The contributions of each of the rotational and translational components of the mandible to the end-point trajectories were quantified through experiment-based computer simulations. The mandibular rotation was found to account for 91% of the maximal mouth-opening-capacity and 73% of the maximal lateral incisor movement, while the condylar translation contributed to 99% of the anterior protrusion distance. Incisor trajectories were nearly vertical within the first 60% of the maximal opening during the open-close movement. Similar condylar downward rotation paths but with bilaterally asymmetrical ranges were used to perform basic mandibular movements of different targeted TI trajectories in three dimensions, that is, open-close, lateral-gliding and protrusion-retraction. Mandibular rotations contributed to the majority of the principal displacement components of the incisor, that is, vertical during open-close and towards the working-side-during lateral-gliding, while mandibular translation contributed mainly to the forward movement of the incisor during protrusion-retraction. Owing to the anatomical constraints, the freedom of mandibular translation is limited and mainly in the anteroposterior direction, which is considered helpful for the control and stability of the TMJ during oral activities.

Dental microwear reveals mammal-like chewing in the neoceratopsian dinosaur Leptoceratops gracilis.

Extensive oral processing of food through dental occlusion and orbital mandibular movement is often cited as a uniquely mammalian trait that contributed to their evolutionary success. Save for mandibular translation, these adaptations are not seen in extant archosaurs or lepidosaurs. In contrast, some ornithischian dinosaurs show evidence of precise dental occlusion, habitual intraoral trituration and complex jaw motion. To date, however, a robust understanding of the diversity of jaw mechanics within non-avian dinosaurs, and its comparison with other vertebrates, remains unrealized. Large dental batteries, well-developed dental wear facets, and robust jaws suggests that neoceratopsian (horned) dinosaurs were capable chewers. But, biomechanical analyses have assumed a relatively simple, scissor-like (orthal) jaw mechanism for these animals. New analyses of dental microwear, presented here, show curvilinear striations on the teeth of Leptoceratops. These features indicate a rostral to caudal orbital motion of the mandible during chewing. A rostrocaudal mandibular orbit is seen in multituberculates, haramiyid allotherians, and some rodents, and its identification in Leptoceratops gracilis is the first evidence of complex, mammal-like chewing in a ceratopsian dinosaur. The term circumpalinal is here proposed to distinguish this new style of chewing from other models of ceratopsian mastication that also involve a palinal component. This previously unrecognized complexity in dinosaurian jaw mechanics indicates that some neoceratopsian dinosaurs achieved a mammalian level of masticatory efficiency through novel adaptive solutions.

Novel approach to the study of jaw kinematics in an alloplastic TMJ reconstruction

Total alloplastic temporomandibular joint (TMJ) reconstruction is a reliable treatment modality in patients with severely diseased TMJ with good clinical behaviour. TMJ mandibular function after alloplastic reconstruction has scarcely been analysed as a biomechanical parameter and investigation has generally been limited to interincisal measurements without deeper insight into joint kinematics. Dynamic stereometry to assess condylar movements relative to the fossa was performed at the 5 year follow-up of a patient who underwent condylar resection of the right TMJ followed by total alloplastic joint reconstruction to treat pigmented villonodular synovitis. The patient could achieve wide mouth opening, but overall mandibular kinematics showed a strong deviation towards the prosthetic side due to the lack of mandibular translation caused by the absence of the lateral pterygoid attachment. Possible overloading of the joint contralateral to the TMJ prosthesis might be prevented by optimizing replacement joint design.

Comparative evaluation of the breaking strength of a simple mobile mandibular advancement splint

Mandibular advancement splints (MASs) are used to advance the mandible forward in patients with sleep-disordered breathing. The conventional rigid MAS restricts the movement of the mandible, and this immobility sometimes produces discomfort, including temporomandibular disorders. A simple method for fabricating a mobile MAS was devised, using a connector made from a polyethylene toothed belt, with the intention of making the MAS more comfortable. The experimental connector is easily constructed, inexpensive, and small enough for use as an intraoral MAS. To evaluate durability, the axial and diagonal tensile breaking strengths of the MAS, using high- or low-density polyethylene (HDPE or LDPE) lateral toothed belts, were compared with those of a conventional mobile MAS (Silensor). The values were compared by factorial analysis of variances and post hoc Scheffe's S multiple comparison intervals, with the value of statistical significance set at alpha = 0.05. In addition, the experimental LDPE connectors were clinically tested in 30 patients (23 males and 7 females aged 19-71 years) and evaluated. Compared with the Silensor, the experimental MAS exhibited sufficient breaking strength, especially when a diagonal tensile load was applied to mimic mandibular lateral translation. When examining the clinical evaluation between 3 and 4 months after insertion, no damage or failure was observed. The experimental connecting system may have clinical applications. To make the connector stronger for clinical use, HDPE should be used.

Reconstruction of the curve of Spee

AIM: The construction of a flat occlusal plane or one showing a haphazard curvature does not correspond to the concept of "best practice" in restorative dentistry. Unlike a flat reconstruction, a correct occlusal curvature allows mandibular translation without occlusal interferences in the posterior segment, Furthermore masticatory efficiency on the working side is not lost. In this way, a better distribution of the axial load and protection against T.M.J. overloading is achieved. MATERIALS AND METHODS: A simple cephalometric was used to determine the optimal radius of the circle. This curvature was transferred using a template, which was then placed in the appropriate position on the articulator; in order to facilitate the prosthetic construction of an optimised Curve of Spee. CONCLUSION: An appropriately constructed template, when fitted to an articulator may be useful to guide a clinician when designing a wax-up or prosthetic construction. This could be of benefit when constructing a surgical stent for optimum implant placement.

インプラント支持を含む固定性補綴装置によりアンテリアガイダンスを設定した症例

A 24-year-old female patient visited our dental office with esthetic complaint. Implant-supported fixed prostheses were placed on the upper right and left side canine area. The cusps of bone anchored crowns were made to contact with the lower canine cusps during mandibular translation. The patient was followed for 5 years with no surgical or prosthetic complications. Stability of the intercuspal position and reduction of lateral force are of importance when providing occlusal contacts for bone-anchored prosthesis in eccentrec relations. This case offers useful information on occlusal contact for implant-supported prostheses.

Mitek anchors for treatment of chronic mandibular dislocation.

The purpose of this study was to present a new technique for limiting mandibular translation in patients with chronic mandibular dislocation. TECHNIQUE DESIGN: This relatively simple procedure uses 2 Mitek mini bone anchors with osseointegration potential. One anchor is placed in the lateral pole of the condyle, and the other is placed in the posterior root of the zygomatic arch. Heavy suture material is threaded through the eyelet of each anchor and tightened to function as a restraining ligament. This technique has been used on 5 patients with a follow-up of 2 to 4 years, with no failures. This technique provides an effective method for the prevention of condylar dislocation while permitting some controlled translation.

Remodeling of the temporomandibular joint following mandibular distraction osteogenesis in the transverse dimension.

Transverse mandibular distraction osteogenesis involves moving the osteotomized segments of the mandible in either a varus or valgus direction. This maneuver allows for widening of the bigonial distance or for a lateral shift of an asymmetric mandibular midline. During this process, a significant amount of torque is placed on the mandibular condyles, because they act as the pivot point for the mandibular translation. Although standard linear distraction osteogenesis induces transient, reversible changes in the temporomandibular joint, it is not known what effect the varus and valgus stresses of transverse distraction have on the temporomandibular joint. We therefore designed a study to document the temporomandibular joint changes following various degrees of transverse distraction. Bilateral transverse mandibular distraction was performed on 10 adult, female mongrel dogs using an external, multiplanar mandibular distraction device. The distraction protocol was as follows: (1) complete osteotomy at the angle of the mandible, (2) 5-day latency period, (3) distraction rate of 1 mm/day, (4) rhythm of one turn per day, (5) linear activation 16 to 30 mm bilaterally, and (6) 8-week consolidation period. A variety of varus and valgus distraction vectors were applied to the mandible only after 10 mm of initial linear distraction had been achieved. Posteroanterior and lateral cephalograms were performed throughout the entire process. Pre-distraction and post-consolidation computed tomographic scans were also performed. Changes in mandibular conformation, axis of rotation, temporomandibular joint structure, and glenoid fossa changes were directly assessed by evaluating the postmortem craniofacial skeleton. The findings were compared with those of normal, age-matched mongrel dog skulls. Significant remodeling changes were observed in the temporomandibular joints of all animals involved in the study. The mandibular condyles demonstrated varying degrees of flattening and erosion at all contact points with the craniofacial skeleton. In some cases, the condyle became part of the distraction regenerate process and was hypertrophied in all dimensions. The condyles were frequently displaced out of the glenoid fossa, particularly on the side in the direction of varus distraction. When the latter occurred, a new fossa was created on the undersurface of the zygomatic arch. Varying degrees of mandibular rotation in the sagittal plane were also observed, which led to abnormal torquing of the condyles in the coronal plane, depending on whether the axis of rotation occurred primarily around the condyle or around the distraction regenerate zone.In conclusion, transverse mandibular distraction is an effective means of producing a varus or valgus shift in the gonion relative to the midsagittal plane. However, unlike linear or angular mandibular distraction, transverse distraction has a multitude of nontransient effects on the temporomandibular joint. Therefore it must be emphasized that in clinical practice, transverse distraction should be used cautiously. One must also be aware that such a maneuver in distraction can have negative effects on the temporomandibular joint.

A model of temporomandibular joint function in anthropoid primates based on condylar movements during mastication.

The hypothesis that the shape of the bony temporomandibular joint (TMJ) is functionally related to sagittal sliding of the condyle during mastication is tested, and a model of the relation of sagittal sliding to mandibular size, TMJ shape, and diet is developed. Sagittal sliding is defined as fore-aft motion of the condyle during mandibular translation and/or angular rotation. Ascending ramus height is used as a structural correlate of the distance between the condyle and the mandibular axis of rotation (CR). Cineradiographic data on sagittal sliding and gape during mastication in Ateles spp., Macaca fascicularis, Papio anubis, and Pan troglodytes in conjunction with comparative data on mandibular size and TMJ shape are used to evaluate the hypothesis. The results show that 1) linear and angular gape are highly positively correlated with sagittal sliding, 2) pure mandibular translation is rare during mastication, 3) the CR is rarely if ever located at the condyle during mastication, 4) angular gape should be standardized in interindividual comparisons of sagittal sliding, and 5) the height of the ascending ramus (and by inference the CR-to-condyle distance) is highly positively correlated with absolute sagittal sliding. Sagittal sliding relative to the length of the articular eminence was the variable used to explore the relation between TMJ shape and sliding. This variable standardized absolute sagittal sliding relative to joint size. The relative depth and orientation of the articular eminence were not correlated with relative sagittal sliding. The anteroposterior curvature of the condyle was highly negatively correlated with relative sagittal sliding. Flat condyles are associated with large amounts of relative sagittal sliding. A flat condyle increases joint contact area, which reduces joint stress. A flat condyle also increases joint congruence, and this may facilitate the combined sliding and rolling motion of the condyle when the sliding motion is relatively large. The shape of the entoglenoid process was also positively correlated with relative sagittal sliding. A relatively large entoglenoid process may help to guide sagittal sliding and prevent excessive mediolateral sliding of the condyle. The functional model makes a number of predictions about the correlations between food consistency and food object size, mandibular size, TMJ shape, and sagittal sliding of the condyle during mastication and incision.

An in vivo study of voluntary mandibular lateral translation concerning its existence, magnitude, and timing

Statement of problem. The existence of mandibular lateral translation and the approaches to its measurement and interpretation by using a pantograph are controversial. Purpose. This study evaluated the validity of using a pantograph to measure mandibular lateral translation and analyzed human pantographic tracings to determine whether they exhibited mandibular lateral translation. Material and methods. A pantograph was modified by adding 2 posterior horizontal recording tables and styli at the transverse horizontal axis. Pantographic tracings of 25 human subjects were compared with the corresponding theoretically determined values for tracings that exhibited only rotation with no translation. Differences in the tracings at 2 pantographic recording table locations, relative to the transverse horizontal axis, were also compared. Results. The character of the lateral component of 100 pantographic tracings all differed from the lateral component of theoretically determined values for pure rotation. In 64% of tracings, over 50% of the total mandibular lateral translation occurred by the first 1 mm of forward movement of the nonworking side condyle. In 94% of tracings, more than 50% of the translation had occurred in the first 3 mm of forward movement. For the pantographic system used, the amount of mandibular translation represented in the tracing was not changed by altering the posterior horizontal recording table position in the anterior-posterior direction, relative to the transverse horizontal axis. Conclusion. All subjects showed evidence of mandibular lateral translation. New definitions for timing of mandibular lateral translation are proposed. Of the tracings, 64% were classified as exhibiting early translation, 30% as intermediate, and 4% as late mandibular lateral translation. (J Prosthet Dent 1998;80:672-9.)

Artifacts in recording immediate mandibular translation: A laboratory investigation

Statement of problem. Even though immediate mandibular translation has been extensively studied and analyzed, and its clinical significance emphasized, there is controversy as to whether it actually exists or whether it is just an artifact of the pantograph. Purpose. The aim of this study was to determine whether what appears to be pantographic evidence of immediate mandibular translation can actually be an artifact and, if so, to find a method to avoid it. Material and methods. The first part of this article explains geometrically with computer vector graphics how pure rotation can produce a pantographic tracing on the horizontal plate that is identical to what would be seen for immediate mandibular translation. The second part of the article presents a technique that uses a modified pantograph that eliminates the rotational artifact and thus permits proper interpretation of true immediate mandibular translation. Results. This study shows that pure rotation about the sagittal axis mimics immediate mandibular translation on a pantographic tracing when the plates are inferior to the transverse horizontal axis, produces scribings in an opposite direction for plates in a superior position, and produces no scribing when the plates are level with it. By modifying the pantograph so the tip of the scribing pin of the horizontal plate is level with the transverse horizontal axis, true immediate mandibular translation can most easily be differentiated from rotational artifact. Conclusions and Clinical Significance. Rotation can cause artifacts that mimic immediate mandibular translation. A technique to avoid this problem is presented. This technique provides the foundation for a valid evaluation of patients to determine whether true immediate mandibular translation exists and whether it is clinically important. (J Prosthet Dent 1997;78:172-8.)

Rate of mesial translation of mandibular molars using implant-anchored mechanics.

Retromolar dental implants served as anchorage to close first molar extraction sites in five adult patients. Rates of unidirectional space closure for mandibular second molars were assessed with periapical radiographs superimposed on anatomical landmarks and retromolar anchorage implants. Regression analysis revealed that mesial displacement of the midroot area of the leading root was less variable (r = 0.97) than for other landmarks on the same teeth: crown (r = 0.83), alveolar crest (r = 0.82) or apex (r = 0.90). When mesial root movement (uprighting) was the principal feature of the initial mechanics (4 of the 5 patients), mesial movement of the apex was about 0.60 mm/mo for the first 8 months and then decreased to about 0.34 mm/mo as the trailing (distal) root of the second molar engaged the relatively dense bone formed by the leading (mesial) root. During the last year of space closure, radiolucent foci were noted 1-2 mm ahead of the distal root. These data suggest: (1) sustained orthodontic translation is a physiological manifestation of bone modeling and remodeling throughout the adjacent alveolar process, and (2) rate of mandibular molar translation is inversely related to the apparent radiographic density of the resisting alveolar bone.

Incisal bite force direction in humans and the functional significance of mammalian mandibular translation.

AbstractIncisal bite force direction was recorded and analyzed in ten human subjects using a specially designed force transducer. In all ten subjects the maxillary incisal bite force was vertically and anteriorly directed both during static biting and during biting associated with simultaneous mandibular translation and rotation. Since the resultant muscle force could not have been equal and opposite to the mandibular bite force, the mandibular condyles must have been loaded. These data demonstrate that the mandible acts as a lever during incisal biting and that there is no consistent relationship between incisal bite force direction and object size. In some individuals the bite force direction was more vertical during biting on a large transducer (30 mm high), while in other subjects it was more vertical during biting on a small transducer (10 mm high).

The growth in situ of isolated mandibular segments

M uch of the present controversy surrounding the study of mandibular growth concerns the role of condylar cartilage. It was once widely assumed that condylar growth is directly responsible for mandibular translation.“. 35-37 The condylar hypothesis was based to a considerable extent on the facile assumption that condylar cartilage serves as an epiphyseal plate. In many respects this analogy is questionable. Unlike an epiphyseal plate, the layer of condylar cartilage is a secondary addition to a pre-existing membrane bone,32, 4o has what might be called a perichondrium,2~ 3* accomplishes much of its growth by apposition, and has a distinctly different antigenic profiie.5 Despite these obvious differences, pathoses such as acromegaly, vogelgesicht, and Class III malocclusions, to name a few, make it easy to believe that some kind of discrete growth center is responsible for mandibular translation. Of late, the condylar hypothesis has been challenged by Moss and his co-workers.21-2s They argue that the translatory growth of the various bones of the craniofacial complex occurs as a result of the volumetric expansion of a variety of so-called “capsular matrices”-brain, orbital contents, “functioning” spaces, and the like. A basic feature of this provocative formulation is the claim that condylar cartilage can grow only in response to changes in mandibular position brought about by the enlargement of the “oropharyngeal functioning space.” Although the current version of Moss’ “ functional matrix hypothesis’ has achieved a considerable measure of popular support, craniofacial biologists have been able to provide little in the way of evidence for its more extreme elements. Functioning spaces are easy to talk about but hard to study. As a result, workers of all persuasions still tend to study mandibular growth from the vantage point of the condyle. As a general rule, two experimental questions are most often asked: (1) Can condylar cartilage grow in a “functionally neutral” environment? (2) Can mandibles grow in the absence of condyles? Although it has been demonstrated repeatedly that epiphyseal, synchondrosal, and septal cartilages will grow in the absence of “functional” stimulation,s* *‘-*‘* 30* 31S 41 transplantation studies involving condylar cartilage have produced equivocal results. Initially, condylar transplantation produced results that were technically suspect and, perhaps