Mandibular Stability Research Articles

Fabrication technique for a custom face mask for the treatment of obstructive sleep apnea

The development of the positive airway pressure custom mask (TAP-PAP CM) has changed the treatment of obstructive sleep apnea. The TAP-PAP CM is used in continuous positive airway pressure therapy (CPAP) and is fabricated from the impression of the face. This mask is then connected to a post screwed into the mechanism of the TAP3 (Thornton Anterior Positioner) oral appliance. This strapless CPAP face mask features an efficient and stable CPAP interface with mandibular stabilization (Hybrid Therapy). A technique with a 2-stage polyvinyl siloxane face impression is described that offers improvements over the established single-stage face impression. This 2-stage impression technique eliminates problems inherent in the single-stage face impression, including voids, compressed tissue, inadequate borders, and a rushed experience due to the setting time of the single stage. The result is a custom mask with an improved seal to the CPAP device.

Comparison of mandibular stability after SSRO with surgery-first approach versus conventional ortho-first approach

Methods: Postoperative mandibular stability in the surgery-first (SF) approach and ortho-first (OF) approach in orthognathic surgery was retrospectively assessed using the lateral cephalo X-P in 38 patients with skeletal Angle Class III malocclusion who underwent sagittal split ramus osteotomy (SSRO). Results: The postoperative mandibular relapse of the two groups observed from T1 (2 weeks after the surgery) to T2 (for the OF group, a year after surgery; for the SF group, the day orthodontic treatment was completed) was compared. The mean (SD) horizontal relapse at pogonion was 0.86 (0.92) mm in the forward direction in the SF group and 0.90 (1.09) mm in the forward direction in the OF group. No significant difference was found in the amount of horizontal movement between the two groups. On the other hand, the mean (SD) vertical relapse at pogonion was 1.59 (2.91) mm in the downward direction in the SF group and 0.14 (1.30) mm in the upward direction in the OF group, showing a significant difference in the amount of movement between the two groups. The degree of completion of the occlusion at T2 in the SF group was compared with that in the OF group by measuring OB, OJ, L1-occlusal plane angle, and interincisal angle. No significant difference was found between the two groups and the post-treatment occlusion was clinically favourable. Conclusion: Although the SF approach has several advantages for patients, the method of operation and fixation should be selected carefully to maintain postoperative mandibular stability.

Intraoral Vertical Ramus Osteotomy Results in Good Long-Term Mandibular Stability in Patients With Mandibular Prognathism and Anterior Open Bite

Few studies have evaluated the outcomes of intraoral vertical ramus osteotomy (IVRO) for the correction of skeletal Class III malocclusion with an anterior open bite and the potential for postoperative relapse. Therefore, this study evaluated the stability of outcomes of IVRO for mandibular prognathism with and without an anterior open bite. This retrospective cohort study included consecutive patients with skeletal Class III malocclusion with (AOB group) and without (NAOB group) an anterior open bite who underwent IVRO at Yonsei Dental Hospital (Seoul, Korea). Lateral cephalograms were analyzed for predictor (open bite, yes or no) and outcome (horizontal and vertical relapse in the mandible) variables before and 7 days, 1 year, and 2 years after surgery. Other variables included the patients' demographic characteristics. Data were analyzed using independent t tests, repeated measures analysis of variance, Pearson correlation coefficients, and multiple linear regression analysis. The 2 groups (n = 15 each) were matched for baseline demographic characteristics. During the 2-year postoperative period, anterior and superior mandibular movements were observed in the NAOB group, whereas posterior and superior movements were observed in the AOB group. However, there were no meaningful intergroup differences in horizontal and vertical relapses of the mandible at all time points, although the amount of postoperative inferior relapse increased with a decrease in the amount of initial overbite. IVRO for the correction of skeletal Class III malocclusion resulted in good postoperative stability over time, regardless of the presence of a preoperative open bite, although the amount of postoperative inferior relapse showed a weak negative correlation with the initial overbite. Thus, IVRO can be a clinically acceptable treatment for skeletal Class III malocclusion with an anterior open bite.

Biomechanical Effects of Masticatory Muscles on Human Mandible After Reconstructed Mandibulectomy Tumor.

This study aimed to analyze and compare the stress distribution on the condylar process. This study was also designed to determine the effect of closing and opening muscle groups of the jaw on mandibular stability after mandibular tumor osteotomy reconstruction by three-dimensional finite element analysis. Three-dimensional reconstructed mandibles were used and divided into 2 groups: (1) 6 patients with normal mandible and (2) 6 mandibular tumor patients who underwent osteotomy reconstruction. Computed tomography scans of normal and reconstructed mandibular tumor osteotomy patients were obtained. Three-dimensional models were reconstructed using Simpleware 5.0 software. Boundary constraint and load conditions were applied. The solution process was run, and the actions of closing and opening muscle groups were simulated and calculated using finite element analysis software. Statistical software was used for analysis of the condylar stress distribution. A significant difference was observed in stress distributions on the anterior condyle of the healthy volunteers and the reconstructed mandibular tumor osteotomy patients, who were subjected to tumor osteotomy surgery in the opening muscle groups (P < 0.05). By contrast, no significant difference was observed in the posterior condyle of the opening muscle group and the closing muscle group (P > 0.05). Muscular imbalance in postoperative mandibular tumor reconstruction was changed in patients. We adjusted the force of the mandible closing muscle intraoperatively to achieve muscle balance. Therefore, poor swallowing, failure to retain saliva, speech impairment, and esthetic disfigurement were repaired and/or resolved.

Comparison between two techniques for registering mandibular position in patients with hemifacial microsomia of the Federico Gomez Children’s Hospital

To determine the true position of the mandible is one of the most important aspects of orthodontic-surgical diagnosis. It provides information about the skeletal discrepancy between the maxilla and mandible even in patients with conditions other than a normal pattern of mandibular stability. In patients with hemifacial microsomia it is difficult to determine the true position of the mandible, since due to their condition, they present structural alterations that hinder record taking. The purpose of this study was to assess two techniques for recording mandibular position (power centric technique and the gothic arch technique) to determine the most effective method to provide greater accuracy in the record taking process. Eight patients with hemifacial microsomia, ages between 13 and 17, four female (50%) and four male (50%) were assessed. A total of 16 semi-adjustable articulator mountings were conducted using both techniques. Changes in the overjet, vertical discrepancy and between dental midlines were monitored. The results showed that there were significant sagittal, vertical and transverse differences with the gothic arch technique.

Comparación de dos técnicas para el registro de posición mandibular en pacientes con microsomía hemifacial del Hospital Infantil de México «Federico Gómez»

To determine the true position of the mandible is one of the most important aspects of orthodontic-surgical diagnosis. It provides information about the skeletal discrepancy between the maxilla and mandible even in patients with conditions other than a normal pattern of mandibular stability. In patients with hemifacial microsomia it is difficult to determine the true position of the mandible, since due to their condition, they present structural alterations that hinder record taking. The purpose of this study was to assess two techniques for recording mandibular position (power centric technique and the gothic arch technique) to determine the most effective method to provide greater accuracy in the record taking process. Eight patients with hemifacial microsomia, ages between 13 and 17, four female (50%) and four male (50%) were assessed. A total of 16 semi-adjustable articulator mountings were conducted using both techniques. Changes in the overjet, vertical discrepancy and between dental midlines were monitored. The results showed that there were significant sagittal, vertical and transverse differences with the gothic arch technique.

Prothetische vervanging van afwezige gebitselementen. Indicaties voor vaste en uitneembare prothetische constructies

Prosthetic replacement of missing teeth aims to improve health. This can be achieved by improving the patient's well-being and quality of life and by restoring the biological balance in terms ofocclusal and mandibular stability in the occlusal and the orofacial system. In occlusal systems with a complete anterior region and 'satisfactory' premolar and molar regions, prosthetic replacement of missing teeth is not indicated generally. In case ofa restricted number of missing teeth in the anterior region and/or a not 'satisfactory' premolar region, fixed dental prostheses may be indicated. In case of an incomplete anterior region and no 'satisfactory'premolar as well as molar regions, removable dental prostheses are usually indicated. These guidelines are presented in the absence of sufficient scientific evidence. Therefore, in clinical decision making, the question whether prosthetic replacement of missing teeth is sensible, and if so, by which type of dental prosthesis, can only be answered after a dialogue with mutual respect between care provider and patient.

Association between prosthetic factors and temporomandibular disorders in complete denture wearers

The purpose of this study was to investigate the prevalence of temporomandibular disorders (TMD) in denture wearers and the association between prosthetic factors and this condition. There is no consensus about the relationship between prosthetic factors and TMD among denture wearers. The sample was composed of 92 patients wearing both maxillary and mandibular complete dentures. The Research Diagnostic Criteria for TMD (RDC/TMD) were adopted for patient examination. Objective evaluation of denture quality was determined by analysis of retention and stability of mandibular denture, interocclusal distance, articulation and occlusion. Association between denture quality and TMD diagnosis was analysed using chi-square and Fisher's exact tests. 37.4% of the patients presented TMD. Denture quality was not significantly associated with the presence of TMD: mandibular retention (p = 0.466); mandibular stability (p = 0.466); interocclusal distance (p = 0.328); centric relation (p = 0.175); and balanced occlusion (p = 0.56). Within the scope of this case-controlled cross-sectional study, no robust association between prosthetic factors and TMD was found.

Kronen en bruggen in relatie tot het occlusiesysteem

Occlusion concepts based on functional aspects offer more solid ground in the diagnostic process and in the treatment of (reduced) dentitions than morphologically and mechanically oriented occlusion concepts. Nevertheless, for occlusal reconstruction morphologically oriented guidelines are necessary. These guidelines are based on the border movements and positions of the mandible in the orofacial system, and on the location and modelling of the occlusal contacts in the occlusal system. The modelling of single- and multi-unit fixed dental prostheses must harmonize with the occlusal system. Moreover, an important feature is the relation of the anterior teeth which enables mutually protected occlusion. Characteristics of a healthy orofacial and occlusal system are: absence of pathology, perceived sufficient oral functions, variability inform and function, and adaptive capacity. When designing single- or multiunit fixed dental prostheses, a pragmatic starting point is to maintain the existing occlusion and the existing speech pattern unless arguments can be provided for alterations. The occlusal design should aim at optimizing oral functions, such as mandibular and occlusal stability.

Analysis of occlusal contact and guidance pattern during maximal intercuspal position and protrusive movement

Purpose: The importance of occlusal contacts of the natural dentition for durability of teeth, mandibular stabilization, and restorative dentistry is well known. The purpose of this study is to analyze the occlusal contact and guidance pattern of Koreans by evaluating the static occlusion on maximal intercuspal position and measuring dynamic occlusion during straight protrusion. Materials and methods: The occlusal contacts at maximal interincisal position and the occlusal guidance pattern during straight protrusion of 29 subjects were recorded with shimstock foil (Whaledent, Langenau, Germany), T-Scan III (Tekscan Inc., Boston, MA, USA), polyvinylsiloxane registration material (Genie Bite, Sultan Healthcare, Hackensack, NJ, USA) and compared. Occlusal registration procedures were repeated 3 times. The position was fixed to an upright position and the head position was fixed with the Frankfurt horizontal plane paralleling the horizontal plane. Fisher's Exact Test (R-General Public License, ver. 2.14.1) and Pearson's Test were used to assess the significance level of the differences between the experimental groups (α=.05). Results: When using shimstock foil, T-Scan III system, and polyvinylsiloxane registration material, most of the patients showed contact on anterior, premolar, and molar teeth during maximal intercuspal position. Approximately 51% of maximal intercuspal position showed anterior contact using shimstock foil. When examining the protrusive movement using shimstock foil and T-Scan III system, guidance pattern with the central incisor was the most common. Conclusion: During maximal intercuspal position, there were cases in which not all of the teeth showed occlusal contact. During mandibular protrusive movements, one or more maxillary central incisors frequently joined in straight protrusion and the posterior teeth were disoccluded. Therefore, the anterior teeth protect the posterior teeth, and vice versa. Thus, mutually protected occlusion should be applied when reconstructing occlusion. (J Korean Acad Prosthodont 2013;51:199207)

Kronen en bruggen - functies en typen

A single fixed prosthesis replaces parts of a tooth. However, a single fixed prosthesis may also be implant supported and in such a case it replaces in combination with the oral implant an entire tooth. A multi-teeth fixed prosthesis replaces 1 or more teeth using pontics and can be fixed on teeth, oral implants, or both. Materials applied are metal, metal fused with porcelain, and ceramic. After indicating a fixed prosthesis, the intended function is determining the appropriate type. Intended functions of single fixed prosthesis are: improvement of aesthetics, limitation of tooth fracture, acting as an abutment tooth for a removable metal frame partial denture, and splinting of mobile teeth. In addition, single fixed prostheses may be characterized by the number of replaced tooth surfaces and by the peripheral extension of the tooth preparation. The intended functions of a multi-teeth fixed prosthesis are improvement of aesthetics, chewing function, and occlusal as well as mandibular stability. Specific types of fixed prosthesis are used as temporary restorations and in case of evaluating preliminary treatments preceding a final treatment.

Effects of the closing and opening muscle groups on jaw condyle biomechanics after prominent mandibular angle osteotomy

ObjectivesThe aim of this study was to determine the effect of closing and opening muscle groups of the jaw on mandibular stability after prominent mandibular angle osteotomy, through three-dimensional finite element analysis (FEA). Materials and methodsSix patients with prominent mandibular angles, without malocclusion, were selected as finite element models of preoperative and postoperative prominent mandibular angle surgery. Computed tomographic (CT) scans were undertaken of the patients before and after surgery and three-dimensional images reconstructed using Simpleware software. The images were imported into an FEA software. Boundary-constrained and load conditions were applied. The solution process was run, and actions of closing and opening muscle groups were simulated and calculated. ResultsThe Von Mises stresses on the condyle position after the operation were higher than those before the operation. A significant difference was found between the stress distributions in the condyle position between prominent mandibular angle patients and mandibular angle ostectomy patients (P < 0.05). ConclusionsAfter osteotomy, the variation in force exerted by the closing and opening muscle groups of the jaw is one of the major factors affecting mandibular stability. FEA is a promising strategy in pre-surgical planning for improving surgical success and reducing complications.

Traitements orthodontiques en une ou deux phases : comparaisons

The optimal timing for starting an orthodontic treatment is discussed by many authors. This is even more difficult that there are different therapeutic approaches. In case of Class II, division 1 malocclusion, one approach consists of realising an early treatment during mixed dentition, then a surveillance phase and finally an alignment phase during adolescent dentition. The other approach consists of waiting for adolescent dentition to treat. We made a study with 65 subjects with Class II, division 1 malocclusion: 33 were treated in one phase during adolescent dentition and 32 were treated in two phases, beginning in mixed dentition. In both groups the patients had the same age at the beginning of treatment and were treated with Distal Active Concept. Correction of offset bases bone, increase of the diagonal mandibular and over-jet stability are significantly better in the group treated in two phases. We guess that the functions estimated progressively more and more surely in this new environment.

Tongue support of complete dentures in the elderly

This study aimed to evaluate the tongue’s role in supporting maxillary denture retention (MDR), in providing additional stabilization for the mandibular denture, and the tongue’s relationship with the oral health-related well being in elderly complete denture patients. Four hundred elderly individuals, 263 males and 137 females, were enrolled in this study. All were older than 65 years, and wore complete dentures. Intraoral examinations were performed in accordance with the 10 criteria embedded in the Functional Assessment of Dentures (FAD). Participants also received personal interviews and completed the Oral Health Impact Profile-14 (OHIP-14) questionnaire. The associations between MDR (tongue support) with the mean OHIP-14 sum scores and FAD categories were analyzed using the t test or analysis of variance (ANOVA). Combinations of MDR (tongue support), MDR (resistance to vertical pull), and mandibular denture stability (anterior–posterior movement) were also assessed with the remaining FAD criteria and OHIP-14 domain scores. Individuals with adequate MDR (tongue support) were significantly associated with denture articulation, denture occlusion, MDR (resistance to vertical pull), maxillary denture stability (pronounced rocking), and mandibular denture stability (anterior–posterior movement). When individuals with adequate MDR (tongue support) were analyzed in conjunction with adequate MDR (resistance to vertical pull) and adequate mandibular denture stability (anterior–posterior movement), significant associations were observed with the mean OHIP-14 sum score and three individual OHIP-14 domains: functional limitation, physical pain, and physical disability (p ＜ 0.05). The mean OHIP-14 sum score was lower among individuals with both adequate MDR (tongue support) and inadequate MDR (resistance to vertical pull) than among participants with both inadequate MDR (tongue support) and inadequate MDR (resistance to vertical pull). MDR (tongue support) demonstrated significant differences from denture occlusion, denture articulation, MDR (resistance to vertical pull), maxillary denture stability (pronounced rocking), and mandibular denture stability (anterior–posterior movement). MDR (tongue support), in conjunction with both adequate MDR (resistance to vertical pull) and adequate mandibular stability (anterior–posterior movement), were significantly associated with the individuals’ oral health-related well being.

Myostabilized centric relation

Intercuspation position (ICP) constitutes the occlusal reference position of the mandible while centric relation (CR) represents the articular reference position. The concept of CR depicts a key component in routine dental clinical practice due to the need for a mandibular position determined not to be dental. But a consensus on this particular topic has still not been achieved even after nearly a century of discussions with scientific and clinical arguments. A remarkable number of dental schools, restrained in their own certainty are struggling with the concept of a non-dental determined reference position, even now after many generations and decades of scientific stress. Unproductive quarrels dominate the development and consequently, a lack of reciprocal expansion of knowledge can be observed. In addition, misunderstandings bring up walls of virtual disagreements. Without pretending to have a universal knowledge, a reconnecting concept on this particular subject can be formulated, based on elementary logic and simple principles of anatomy, physiology and biomechanics. The objective of this tutorial paper is to compose and present such a concept on the basis of the scientific literature and as a synthesis of research data. The practitioner controls the homogeneity of the simple rotational character by digital perception. The absence of muscle tension (vertical oscillations) and of translation (sagittal oscillations) is an indicator for homogeneity. The patient himself gently activates his own closing movement and by doing so the correct coaptation of the condyle and disc along the articular tubercle is established. The occipital support, the light mandibular stabilization by chin control, the information of the patient before and during the procedure, the repetition of the exercise and the peripheral information through the engrammation of the localization of premature contact are parameters which facilitate the achievement of CR.

Mandibular Reconstruction Using Extraoral Trifocal Bone Transport: Report of a Case Using a New Device

A newly designed mandibular stabilization and transport distraction system is an extraoral assembly of a half-elliptical rod, with movable clamp attachments that serves the dual purpose of stabilization and transport distraction osteogenesis of mandibular segmental defects. The rod is threaded and made of stainless steel, and it conforms to the shape of the human mandible. Mandibular stabilization and bone transport are accomplished with the help of different assemblies that are attached onto this rod. There are 3 different assemblies having separate functions but achieving the same goals of mandibular stabilization and bone transport. All the assemblies have a common base unit that moves on threads of the curved rod in a graduated manner, controlled by a spanner. One full turn of 360° moves the assembly by a distance of 1 mm. The first assembly is the stabilization assembly, which helps in the rigid fixation of the frame to the mandible by use of at least 2 clamp units on either side of the midline. It helps in stabilization of the mandibular segments in an anatomic position. The bone transport assembly consists of 1 or 2 moveable clamp assemblies that are fixed at 1 end to the transport disc of the mandible, while the base unit assembly glides and engages on the threads of the distraction rod. This allows bone regeneration and laying down of new bone in the natural position along the path of movement of the transport disc in a curvilinear manner. This system allows mandibular regenera-

The influence of the closing and opening muscle groups of jaw condyle biomechanics after mandible bilateral sagittal split ramus osteotomy

ObjectiveTo investigate the influence of the closing and opening muscle groups of the jaw on mandibular stability after mandibular bilateral sagittal split ramus osteotomy (BSSRO). Materials and methodsTo establish finite element models of four conditions (the normal mandible, preoperative mandibular prognathism, postoperative (BSSRO) mandibular prognathism, and mandibular prognathism following virtual BSSRO), we imported Digital Imaging and Communications in Medicine (DICOM) data into three-dimensional reconstruction software. Finite element analysis software and statistical software were used for analysis of the condylar stress distribution as a function of condylar position during the actions of jaw closing and jaw opening muscle groups. ResultsThe stress distribution of the normal mandibular bilateral condyle was statistically different from the normal mandibular condyle, indicating that bilateral structures are asymmetrical. There was a significant difference in stress distributions with condyle position between healthy control patients and patients prior to mandibular prognathism surgery (P<0.05). There was no significant difference in stress distributions between the normal mandible and the mandible following virtual surgery or real mandibular prognathism surgery. Additionally, there was no significant difference at 6months after mandibular prognathism surgery (P>0.05). ConclusionsBilateral structures of the normal mandible were asymmetrical. After mandibular bilateral sagittal split ramus osteotomy, variation of the force arms of closing and opening muscle groups of the jaw was one of the major factors influencing mandibular stability. Virtual surgery is a promising strategy for preoperative planning to improve surgical success and reduce complications.

Treatment of oblique crown fractures in maxillary premolars using adhesive tooth fragment reattachment: 19 years of follow up

This report presents an oblique crown fracture in the maxillary right premolars of an adolescent because of fall, which was treated using adhesive tooth fragment reattachment. The impact of the mandible base to the floor caused minor fractures in multiple teeth, severe fracture of teeth 14 and 15, and condylar fractures. The fragments of teeth 43, 45, 46, and 16 were lost at the site of accident. The condylar fractures were managed with a non-surgical conservative approach combining mandibular immobilization and stabilization of temporomandibular joints with maxillomandibular fixation using acrylic splints. After 3 months, the interocclusal splints were removed, and the patient was referred for dental care. Teeth 14 and 15 presented complicated oblique crown fractures causing separation of the buccal and palatal fragments, which were in place, attached to the gingival tissue. Tooth 15 presented chronic hyperplastic pulpits. The fragments were banded for stabilization during the endodontic treatment, and the bands served as matrix for adhesive tooth fragment reattachment. The other fractured teeth received direct composite resin restorations. After 8 years, tooth 16 developed pulp necrosis and was treated endodontically and restored with composite resin. Clinical and radiographic examination 19 years after trauma showed a good adaptation of the tooth fragment/composite resin restoration, good periodontal health, no signs of root resorption, and intact lamina dura.

Residents' journal review

Traditionally, surgical treatment requires presurgical orthodontics to decompensate the malocclusion, orthognathic surgery to correct the skeletal discrepancy, and postsurgical orthodontics for finishing. This retrospective study examined the effect of presurgical orthodontics on treatment outcome regarding facial esthetics, occlusion, stability, and efficiency in skeletal Class III open-bite patients. Thirty-three patients were selected and divided into 2 groups: 13 received presurgical orthodontics, and 20 did not receive presurgical orthodontics. There were no significant differences between the groups in terms of the initial peer assessment rating (PAR) scores and cephalometric measurements. The results demonstrated no significant differences in facial convexity, facial height, upper or lower lip to E-plane, nasolabial angle, overbite, or PAR score at orthodontic debonding. The group with no presurgical orthodontics displayed a significantly larger overjets than did the presurgical orthodontics group (3.0 ± 1.2 vs 2.2 ±1.1 mm). Both values were within normal limits, and the difference was not clinically significant. No difference was found between the groups in maxillary stability in the vertical or horizontal plane. There was a statistically significant difference in mandibular stability vertically: in the group with no presurgical orthodontics, the mandible moved superiorly. However, this is a favorable direction in a patient with a Class III open bite, because it deepened the bite and is most likely due to the removal of dental interferences during the postsurgical orthodontics. The presurgical orthodontics group had a significantly longer treatment time (512 ± 103 vs 342 ± 127 days). Although further randomized and prospective trials are indicated, this study illustrates that reduced treatment time in the surgery-first approach might alleviate patient burnout without significant clinical differences in esthetics, occlusion, and stability.

Het opstellen van een behandelplan voor een frameprothese

When considering prosthetic replacement of absent teeth, a treatment plan is necessary. In evaluating whether replacement of teeth is sensible, the causes and consequences of tooth loss must be considered. This concerns information about problems having to do with the patient, potential complications, purely prosthodontic problems, and specific problems. The patient-related problems require collecting data through patient history as well as a clinical and radiologic examination. Complications are risk-factors which negatively influence the prognosis of general health or of a treatment. Potential complications should be eliminated as much as possible through a preliminary treatment. Purely prosthodontic problems are conditions in the area of absence of several teeth or parts of them, and in the area of occlusal and mandibular stability and articulation. Specific problems may be related to inadequate interocclusal space and the quality of the abutment teeth. A cast metal frame removable partial denture may be a relatively inexpensive and minimally treatment alternative for an expensive and complicated treatment with 1 or more fixed partial dentures.