Home About us Contact
|
Home About us Contact | ||
|
|
||
Mandibular Movement (mandibular + movement)
Selected AbstractsCorrelations between incisor and condylar movements during lateral excursion in children with primary dentitionJOURNAL OF ORAL REHABILITATION, Issue 11 2007I. SAITOH Summary, The purpose of this study was to look for associations between lower incisor movement and working and balancing condylar movement during lateral excursion in children with primary dentition and adults with permanent dentition. Mandibular movement was recorded using a TRI-MET (an optoelectronic analysis system with six degrees-of-freedom) at a sampling frequency of 100 Hz. The movement data was transferred to a graphics workstation for analysis. Subjects were categorized by age into two groups. The primary dentition group consisted of 19 children (mean age: 5 years and 5 months, s.d.: 8·7 months), and the permanent dentition group consisted of 22 women (mean age: 20 years and 5 months, s.d.: 26·3 months). The occlusion and TMJ in both groups were normal, with no history of orthodontic treatment. Three orthogonal excursive ranges and the 3D linear distance of the incisal and balancing and working condylar points, along with inter- and intra-individual correlations between the incisor and the balancing and working condyles during lateral excursion, were estimated by using multilevel statistical models. Lateral excursion in children with primary dentition was characterized by smaller incisor excursive ranges and 3D linear distance than in adults, and stronger inter- and intra-individual correlations between incisor and balancing condylar movements than in adults. In both children and adults the lateral excursion of the incisor was a good indicator of the extent of balancing condylar movement, but not working condylar movement. [source] Distance of the contact glide in the closing masticatory stroke during mastication of three types of foodJOURNAL OF ORAL REHABILITATION, Issue 8 2009B. RILO Summary, This study was designed to characterize the distance of the contact glide in the closing masticatory stroke in healthy adult subjects, during chewing of three types of food (crustless bread, chewing gum and peanuts). Mandibular movements (masticatory movements and laterality movements with dental contact) were registered using a gnathograph (MK-6I Diagnostic System) on the right and left side during unilateral chewing of the three food types. Length of dental contact was measured in masticatory cycle, which is defined as where the terminal part of the chewing cycles could be superimposed on the pathways taken by the mandible during lateral excursions with occlusal contacts. The length of dental contact during mastication of chewing gum is 1·46 ± 1 mm, during chewing of soft bread is 1·38 ± 0·7 mm and during chewing of peanuts is 1·45 ± 0·9 mm. There is no significant difference in the lengths of dental contact during mastication of three types of foods that enable direct tooth gliding. [source] Using a Motion-Capture System to Record Dynamic Articulation for Application in CAD/CAM SoftwareJOURNAL OF PROSTHODONTICS, Issue 8 2009Oliver Röhrle PhD Abstract Purpose: One of the current limitations of computer software programs for the virtual articulation of the opposing teeth is the static nature of the intercuspal position. Currently, software programs cannot identify eccentric occlusal contacts during masticatory cyclic movements of the mandible. Materials and Methods: Chewing trajectories with six degrees of freedom (DOF) were recorded and imposed on a computer model of one subject's maxillary and mandibular teeth. The computer model was generated from a set of high-resolution ,-CT images. To obtain natural chewing trajectories with six DOF, an optoelectronic motion-capturing system (VICON MX) was used. For this purpose, a special mandibular motion-tracking appliance was developed for this subject. Results: Mandibular movements while chewing elastic and plastic food samples were recorded and reproduced with the computer model. Examples of mandibular movements at intraoral points are presented for elastic and plastic food samples. The potential of such a kinematic computer model to analyze the dynamic nature of an occlusion was demonstrated by investigating the interaction of the second molars and the direction of the biting force during a chewing cycle. Conclusions: The article described a methodology that measured mandibular movements during mastication for one subject. This produced kinematic input to 3D computer modeling for the production of a virtual dynamic articulation that is suitable for incorporation into dental CAD/CAM software. [source] The influence of age and dental status on elevator and depressor muscle activityJOURNAL OF ORAL REHABILITATION, Issue 2 2006I. Z. ALAJBEG summary, The objective of this study was to determine whether the muscle activity at various mandibular positions is affected by age and dental status. Thirty edentulous subjects (E), 20 young dentate individuals (G1) and 20 older dentate individuals (G2) participated in this study. Surface electromyographic (EMG) recordings were obtained from the anterior temporal (T), masseter (M) and depressor muscles (D). Muscle activity was recorded during maximal voluntary contraction (MVC), maximal opening (Omax) and in six different mandibular positions. One way anova and the Bonferroni tests were used to determine the differences between groups. Significant differences between the three tested groups were found at MVC and Omax for all examined muscles (P < 0·001). The differences in muscle activity in dentate subjects of different age were found in protrusion for depressor muscles (P < 0·05) and in lateral excursive positions for the working side temporal (P < 0·05) and non-working side masseter and depressor muscle (P < 0·05). There was a significant effect regarding the presence of natural teeth or complete dentures in protrusion and maximal protrusion for all muscles (P < 0·05) and in lateral excursive positions for non-working side temporal (P < 0·05) and working side masseter muscle (P < 0·05). Muscle activity at various mandibular positions depends greatly on the presence of the prosthetic appliance, as edentulous subjects had to use higher muscle activity levels (percentages of maximal EMG value) than age matched dentate subjects in order to perform same mandibular movement. Different elevator muscles were preferentially activated in the edentulous subjects when compared with dentate group in lateral excursive positions of the mandible. The pattern of relative muscle activity was not changed because of ageing. [source] Length of the occlusal glide during chewing in children with primary dentitionJOURNAL OF ORAL REHABILITATION, Issue 11 2003H. Hayasaki summary, Chewing is one of the most important functions of the mandible, but, to date, there are very few studies of this function in children. The purpose of this study was to quantify the length of the occlusal glide at the lower incisal point during gum chewing in children with primary dentition. Eleven girls with primary dentition were selected for this study. Mandibular excursions with occlusal contacts and gum chewing movement were measured using an optoelectronic system that can measure mandibular movement with six degrees-of-freedom at a sampling frequency of 100 Hz. A curved mesh diagram of incisor coordinates during mandibular excursions was established to calculate the length of the occlusal glide for each subject. The occlusal glide lengths of children were compared with previously reported results for adults. The estimated length of the occlusal glide during closing was significantly shorter in children than in adults, contrary to that during opening. This result suggests that children have a characteristic chewing pattern that differs from adults. [source] A study on the mandibular movement of anterior openbite patientsJOURNAL OF ORAL REHABILITATION, Issue 9 2000J.-Y. Koak The purpose of this study was to compare the mandibular movements of anterior openbite patients using those of normal bite (angle class I) patients, to ascertain which components of mandibular movement are different in the two groups, and to use this information for occlusal treatment. The Saphon Visi-trainer Model 3 and the Denar Pantronic were used to record mandibular movement and a Pantronic survey was performed using an arbitrary hinge axis, according to manufacturer's instructions. The subjects were 43 adults and included 28 subjects presenting with acceptable normal occlusion (angle class I) with no sign of TM dysfunction syndrome (TMD) and 15 subjects with anterior openbite with no anterior guidance. In the anterior openbite group, the average anterior and lateral condylar inclination, maximum opening and the distance between the intercuspal position with retruded contact position distance (anterior,posterior) were significantly lower than normal. The results suggest that in openbite patients the condyle inclination is flatter and the function of the TMJ is more restricted than in the mandibular movements of the normal group. It is hoped that these results will be useful for the correction of the anterior openbite condition. [source] The History of Articulators: The "Articulator Wars" Phenomenon with Some Circumstances Leading up to ItJOURNAL OF PROSTHODONTICS, Issue 4 2010Edgar N. Starcke DDS Abstract At the dawn of the 20th century, all was not well with the practice of "plate prostheses." Removable prosthodontics had been degrading for several decades and was now generally in low esteem, even though there had been many significant advances. W. E. Walker had introduced adjustable condylar guides, George Snow, the facebow, and Carl Christensen, a method for clinically measuring the condylar inclines. Nevertheless, the average practicing dentist was still using simple hinge articulators and was apathetic to the deplorable state of the artificial teeth available; however, this was all going to change dramatically when two dentists, Alfred Gysi and J. Leon Williams, working together between 1910 and 1914, presented to the profession the "Trubyte Artificial Tooth System" that embodied both a typal system for selecting anterior teeth and new posterior occlusal carvings that made possible, for the first time, the articulation of artificial teeth. This incited many of prosthetic dentistry's elite to introduce their own theories of mandibular movement and the articulators that they designed to reflect those theories. The intense debates that ensued, both in the meeting halls and in the literature, were numerous and lasted for decades. At the time, the "Articulator Wars" had both positive and negative consequences. Today, with many of the "Articulator Wars" issues remaining as part of the practice of dentistry, the "Articulator Wars" can be considered a phenomenon of enlightenment. [source] Early Designs for the Occlusal Anatomy of Posterior Denture Teeth: Part IIIJOURNAL OF PROSTHODONTICS, Issue 2 2005Robert L. Engelmeier DMD Part III of this series of articles, like Part II, reviews the pioneering efforts in the 19th century to improve the quality of artificial teeth. The focus of this article, unlike that of Part II, is specifically modifications in the design of the occlusal anatomy of the 19th century denture teeth, along with the theories of mandibular movement that inspired those modifications. This article concludes the introductory phase of this project, which seeks to unravel the confusing history of the development of (posterior) denture teeth. [source] The history of articulators: A critical history of articulators based on "geometric" theories of mandibular movement.JOURNAL OF PROSTHODONTICS, Issue 1 2003Part IV: Needles, a look at some who followed, wadsworth [source] The history of articulators: A critical review of articulators based on geometric theories of mandibular movement, part II: Rupert Hall's conical theoryJOURNAL OF PROSTHODONTICS, Issue 3 2002Edgar N. Starcke DDS [source] Temporomandibular joint sound evaluation with an electronic device and clinical evaluationORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 2 2001R. A. Tanzilli Sound analysis to diagnose internal derangement has received much attention as an alternative to radiographic examination. The purpose of this study was to compare findings with an electronic device (sonography) and clinical examination to magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ). Twenty-three symptomatic patients (46 joints) were evaluated for this study. All patients had jaw joint pain and one or more of the following findings; limitation of jaw opening, painful mandibular movement with or without clicking or crepitation. The presence or absence of joint sounds was evaluated clinically by palpation and auscultation and with sonography. If sounds were present (clicking or crepitation) on either examination the patient was considered positive for disc displacement for that examination. Two by two tables were constructed comparing sonography and clinical examination with MRI findings. The sensitivity of the sonogram was 84% and the specificity was 33% when compared with MRI findings. The sensitivity of the clinical examination was 70% and the specificity was 40% when compared with MRI findings. This study suggests that clinical and sonographic examination has a high sensitivity (low false negative examinations) but low specificity (high false positive examinations). [source] Influence of changing the chewing region on mandibular movementAUSTRALIAN DENTAL JOURNAL, Issue 1 2009K Hashii Abstract Background:, In the shortened dental arch condition, little is known of how patients adapt their jaw function during mastication to the new oral environment. This study aimed to investigate the changes in mandibular movements when the chewing region was changed from the first molar to the first premolar. Methods:, Thirty clinical residents with natural dentitions were recruited. The subjects were asked to chew a piece of beef jerky using either the first molar or the first premolar on the preferred chewing side. Three-dimensional trajectories of lower incisors and both condyles were analysed using a jaw movement tracking device with six degrees of freedom during the period between the onset and offset of electromyographic bursts from the masseter and anterior temporal muscles. Results:, The closing angle of the lower incisors for first premolar chewing was narrower in comparison with that for first molar chewing (p < 0.05). The lengths of the condylar trajectories and the maximum velocities of the condylar movement for first premolar chewing were smaller and slower, respectively, in comparison with those for first molar chewing (both sides; p < 0.01). Conclusions:, The mandibular movement during mastication might be changed to adapt the premolar chewing because of a loss of posterior occlusal supports. [source] Positional relationships between the masticatory muscles and their innervating nerves with special reference to the lateral pterygoid and the midmedial and discotemporal muscle bundles of temporalisJOURNAL OF ANATOMY, Issue 2 2000KEIICHI AKITA For an accurate assessment of jaw movement, it is crucial to understand the comprehensive formation of the masticatory muscles with special reference to the relationship to the disc of the temporomandibular joint. Detailed dissection was performed on 26 head halves of 14 Japanese cadavers in order to obtain precise anatomical information of the positional relationships between the masticatory muscles and the branches of the mandibular nerve. After complete removal of the bony elements, the midmedial muscle bundle in all specimens and the discotemporal muscle bundle in 6 specimens, derivatives of the temporalis, which insert into the disc were observed. On the anterior area of the articular capsule and the disc of the temporomandibular joint, the upper head of the lateral pterygoid, the midmedial muscle bundle of temporalis and the discotemporal bundle of temporalis were attached mediolaterally, and in 3 specimens the posterosuperior margin of the zygomaticomandibularis was attached to the anterolateral area of the disc. It is suggested that these muscles and muscle bundles contribute to various mandibular movements. Although various patterns of the positional relationships between the muscles and muscle bundles and the their innervating nerves are observed in the present study, relative positional relationships of the muscles and muscle bundles and of nerves of the mandibular nerve are consistent. A possible scheme of the developmental formation of the masticatory muscles based on the findings of the positional relationships between the muscles and the nerves is presented. [source] Evaluation of minimum interdental threshold ability in dentate female temporomandibular disorder patientsJOURNAL OF ORAL REHABILITATION, Issue 5 2010E. M. KOGAWA Summary, Minimum interdental threshold is the smallest thickness that can be detected between teeth during an occlusion and has an influence on the occlusal force and on the control of mandibular movements. The aim of this study was to assess the possible association of the signs and symptoms of temporomandibular disorders (TMD) with the ability to detect a minimum interdental threshold. Two hundred women were equally divided into four groups: asymptomatic (control), subjects with masticatory muscle pain, with articular [temporomandibular joint (TMJ)] pain and mixed (muscular and articular pain). Evaluation of the ability to detect a minimum interdental threshold was performed using aluminium foils with 0·010, 0·024, 0·030, 0·050, 0·080 and 0·094 mm of thickness in the premolar region. A total of 20 tests with each thickness for each patient were performed, starting with the thickest foil (0·094 mm) and ending with the thinnest one. The myogenic pain and articular groups presented significantly higher threshold values (0·020 and 0·022 mm, respectively), when compared to the control. Both groups reached the level of certain perceptiveness only at 0·030 mm. No significant correlation was found between minimum interdental threshold and age. These results suggest that discrimination of thicknesses can be disturbed as a consequence of TMD manifestations and not the cause of it. Clinicians should, therefore, be aware that changes on muscles and TMJ can secondarily lead to occlusion changes. The mechanisms involved in this process, however, are not well understood and warrant further investigation. [source] Reproducibility of jaw movements in patients with craniomandibular disordersJOURNAL OF ORAL REHABILITATION, Issue 11 2006M. STIESCH-SCHOLZ summary, It has never been investigated, if mandibular movements of patients with craniomandibular disorders (CMD) result in a lower reproducibility of dynamic functional parameters which are used for the individual articulator setting. The aim of the present study was to compare the reproducibility of electronically registered functional parameters in patients with CMD and in a control group. Dynamic functional parameters were recorded in 30 patients and 30 volunteers with a computerized ultrasound system (ARCUSdigma). The whole registration was performed three times during one session and three times at a second session 1 week later. The horizontal condylar inclination in the patient group gave a standard deviation of 2·17° ± 0·95°, indicating poorer reproducibility than in the volunteer group, for which the standard deviation was 1·37° ± 0·42°. The reproducibility of measurements of the Bennett angle was also poorer in the patient group than in the volunteer group, with standard deviations of 1·70° ± 0·62° and 1·22° ± 0·40°, respectively. The standard deviations calculated for determination of incisal inclination during laterotrusion was 3·02° ± 1·49° for patients and 2·30° ± 1·17° for volunteers. The standard deviations for incisal inclination during protrusion was 2·02° ± 0·95° for patients and 2·06° ± 1·82° for volunteers. The reproducibility of measurement of horizontal condylar inclination, Bennett angle and incisal inclination during laterotrusion therefore showed significantly lower reproducibility in the patient group than in the volunteer group (P < 0·05). The overall reproducibility of the measurements was nevertheless good in both groups, with standard deviations under 3·1°, so that an individual setting of an articulator seems useful even in patients with CMD. [source] Differences in chewing strategies used by edentate peopleJOURNAL OF ORAL REHABILITATION, Issue 9 2002M. R. HEATH Aim:, To examine, in detail, the different masticatory measures that contribute to individual chewing strategies of edentate people. Measures:, Variables relating to displacement and force were derived using a new three dimensional implant force transducer, a mucosal pressure transducer and measurements of mandibular movements. Materials:, Five edentate subjects with conventional upper dentures and lower dentures stabilized on two dental implants. The subjects chewed unilaterally on their preferred chewing side. Seven foods were chewed , almond, fruit pastille, chewing gum and four different meats. Analysis:, The data were analysed by separating each sequence into cycles and ,phases' of cycles for which variables were derived. Results:, As expected, the results showed greater differences between subjects than between foods. From the five subjects, four basic strategies were identified in response to the different foods: one subject primarily modulated force, one subject modulated the number of cycles, two subjects modulated force and the number of cycles and one subject showed little modulation at all. As part of these strategies many striking differences between subjects were observed, e.g. one subject showed little modulation of her ,default' chewing pattern for different foods, yet one subject modulated the number of force and manipulation cycles, the force strategy (forces increasing through sequences) and swallow thresholds. Conclusion:,People appear to develop different strategies to compensate for chewing difficulty by modulating speed, the number of cycles and/or penetration forces. [source] The effects of bolus hardness on masticatory kinematicsJOURNAL OF ORAL REHABILITATION, Issue 7 2002K. Anderson This study investigated how jaw kinematics, including cycle duration, three-dimensional (3-D) excursive ranges and velocities, and cycle shape, changed with increasing hardness of chewing gum. Twenty-six subjects (13 males and 13 females; mean age 23·6 ± 2·5 years) with Class I normal occlusion were asked to chew two brands of gum with differing hardness. Jaw motion during chewing was tracked with an Optotrak® camera at 100 Hz, and all movements were recorded as pure 3-D mandibular movements relative to Frankfort horizontal. Cycle duration did not change significantly with harder gum, but 3-D excursive ranges and velocities increased, except during the occlusal phases of the chewing. Cycle shape was similar for hard and soft gum, but the overall size of the cycle was larger with hard gum. These results suggest that greater muscular effort when chewing harder gum produces a greater acceleration of the mandible in all phases except when the harder gum slows the mandible during the occlusal phases. [source] Spaciostructural analyses of mandibular and perioral soft tissue movements during masticationJOURNAL OF ORAL REHABILITATION, Issue 10 2001K. Sakaguchi We considered that elucidation of the movements of perioral soft tissues during mastication would be useful in evaluating masticatory movements. However, evaluation of movements specific to soft tissues is difficult because movements of the surface of the lower face during mastication include movements of the muscles of facial expression and mandibular movements. The aims of this study were to elucidate the influence of mandibular movements on perioral soft tissue movements during mastication using principal component analysis (PCA) and to abstract the component of movement specific to soft tissues in order to evaluate masticatory movements from the movements of perioral soft tissues. The subjects were 10 healthy persons with complete natural dentition. The experimental food used in this study was sufficiently softened chewing gum. The results of this study showed that the movements of mandibular and perioral soft tissue were closely related in the first and third PCs; in other words, the second PC was the component of movement specific to soft tissues. Thus, elucidation of the second PC is useful for evaluation of masticatory movements from movements of perioral soft tissues. [source] A study on the mandibular movement of anterior openbite patientsJOURNAL OF ORAL REHABILITATION, Issue 9 2000J.-Y. Koak The purpose of this study was to compare the mandibular movements of anterior openbite patients using those of normal bite (angle class I) patients, to ascertain which components of mandibular movement are different in the two groups, and to use this information for occlusal treatment. The Saphon Visi-trainer Model 3 and the Denar Pantronic were used to record mandibular movement and a Pantronic survey was performed using an arbitrary hinge axis, according to manufacturer's instructions. The subjects were 43 adults and included 28 subjects presenting with acceptable normal occlusion (angle class I) with no sign of TM dysfunction syndrome (TMD) and 15 subjects with anterior openbite with no anterior guidance. In the anterior openbite group, the average anterior and lateral condylar inclination, maximum opening and the distance between the intercuspal position with retruded contact position distance (anterior,posterior) were significantly lower than normal. The results suggest that in openbite patients the condyle inclination is flatter and the function of the TMJ is more restricted than in the mandibular movements of the normal group. It is hoped that these results will be useful for the correction of the anterior openbite condition. [source] Using a Motion-Capture System to Record Dynamic Articulation for Application in CAD/CAM SoftwareJOURNAL OF PROSTHODONTICS, Issue 8 2009Oliver Röhrle PhD Abstract Purpose: One of the current limitations of computer software programs for the virtual articulation of the opposing teeth is the static nature of the intercuspal position. Currently, software programs cannot identify eccentric occlusal contacts during masticatory cyclic movements of the mandible. Materials and Methods: Chewing trajectories with six degrees of freedom (DOF) were recorded and imposed on a computer model of one subject's maxillary and mandibular teeth. The computer model was generated from a set of high-resolution ,-CT images. To obtain natural chewing trajectories with six DOF, an optoelectronic motion-capturing system (VICON MX) was used. For this purpose, a special mandibular motion-tracking appliance was developed for this subject. Results: Mandibular movements while chewing elastic and plastic food samples were recorded and reproduced with the computer model. Examples of mandibular movements at intraoral points are presented for elastic and plastic food samples. The potential of such a kinematic computer model to analyze the dynamic nature of an occlusion was demonstrated by investigating the interaction of the second molars and the direction of the biting force during a chewing cycle. Conclusions: The article described a methodology that measured mandibular movements during mastication for one subject. This produced kinematic input to 3D computer modeling for the production of a virtual dynamic articulation that is suitable for incorporation into dental CAD/CAM software. [source] INFLUENCE OF MEASUREMENT TECHNIQUE, TEST FOOD, TEETH AND MUSCLE FORCE INTERACTIONS IN MASTICATORY PERFORMANCEJOURNAL OF TEXTURE STUDIES, Issue 1 2007FLÁVIA RIQUETO GAMBARELI ABSTRACT The role of texture and flavors in mastication is evident, but it is difficult to understand the interactions among food properties, oral physiology and perception. Mastication results from rhythmic mandibular movements. The teeth and masticatory muscles together form the mechanism whereby the food particles are fragmented. Masticatory performance and efficiency are defined as the capacity to reduce natural or artificial test materials during mastication, or by counting the number of strokes required to reduce food, respectively. Foods eaten for nourishment are very different from the industrial test materials used to quantify masticatory performance, thus, divergences could arise if the chewable material can or cannot be swallowed. This study presents a synopsis of masticatory performance methods, which is also related to muscle force, number of teeth and test chewing substance diversity. PRACTICAL APPLICATIONS The attributes of food, such as appearance, flavor and texture, as well as its interaction with saliva, number of teeth and conditions of the biomechanical system, influence the chewing process. In addition, reflex control and cognition can influence food perception and breakdown in the mouth. Food acceptability and choice depend on sensory properties of the food, which are perceived during chewing and swallowing. Masticatory performance and maximal occlusal force measurement may provide essential information that could lead to an appropriate diagnosis as regards masticatory function. Masticatory efficiency and performance can be measured to determine the individual's capacity to comminute a natural or a chewable test material. A material with uniform properties that can be reliably reproduced is essential to provide an ideal test bolus for the scientific study of masticatory effectiveness. [source] Influence of changing the chewing region on mandibular movementAUSTRALIAN DENTAL JOURNAL, Issue 1 2009K Hashii Abstract Background:, In the shortened dental arch condition, little is known of how patients adapt their jaw function during mastication to the new oral environment. This study aimed to investigate the changes in mandibular movements when the chewing region was changed from the first molar to the first premolar. Methods:, Thirty clinical residents with natural dentitions were recruited. The subjects were asked to chew a piece of beef jerky using either the first molar or the first premolar on the preferred chewing side. Three-dimensional trajectories of lower incisors and both condyles were analysed using a jaw movement tracking device with six degrees of freedom during the period between the onset and offset of electromyographic bursts from the masseter and anterior temporal muscles. Results:, The closing angle of the lower incisors for first premolar chewing was narrower in comparison with that for first molar chewing (p < 0.05). The lengths of the condylar trajectories and the maximum velocities of the condylar movement for first premolar chewing were smaller and slower, respectively, in comparison with those for first molar chewing (both sides; p < 0.01). Conclusions:, The mandibular movement during mastication might be changed to adapt the premolar chewing because of a loss of posterior occlusal supports. [source] | |||||||||||||