Do occlusal contact areas of maximum closing position during gum chewing and intercuspal position coincide?

Objective

Occlusal contact area (OCA) is most important during the occlusal phase when food particles are being pulverized. OCA is most easily measured statically at the maximum intercuspal position (ICP). However, the assumption of coincidence between dynamic maximum closing position (MCP) and statically determined ICP has not been previously tested. The purpose of this study is to introduce a method of quantifying OCA of all teeth during dynamic mastication to determine whether the OCA at the dynamic MCP during chewing is similar to the statically determined maximum possible OCA.

Design

Thirteen healthy females participated in this study. Morphologic tooth shape data were measured from dental models using an automatic 3D digitizer. Mandibular movement during gum chewing was recorded using an optoelectronic analysis system with 6 degrees of freedom, and ten cycles were selected for analysis. The dynamic OCA was estimated with a measurement system combining 3D tracking of mandibular movements with 3D digitization of tooth shape.

Results

The estimated mean 3D difference between the incisor position at ICP and MCP was 0.129 mm. At the dynamic MCP, the maximum OCA was 98.5% (68.42 mm²) of the maximum possible contact area in the static ICP (69.46 mm²). Both between-subject and within-subject variation were least at the dynamic MCP.

Conclusion

The maximum OCA during chewing is nearly identical to statically determined maximum possible OCA.     

Length of the occlusal glide during chewing in children with primary dentition

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.     

Length of the occlusal glide at the lower incisal point during chewing

The purpose of this study was to estimate the length of the occlusal glide during gum chewing at the lower incisal point. Mandibular excursions with occlusal contacts in 25 females with permanent dentition were recorded using an optoelectronic system that can measure mandibular movement with 6 d.f. at a sampling frequency of 100 Hz. A curved mesh diagram of incisor coordinates during maximum mandibular excursions (CMDME) was plotted. Gum chewing movement was also measured using the same system and computer software which divided the chewing movement into cycles at each maximum opening position. Each cycle was standardized at 0.1 mm intervals from the most closed position. Finally, the distance between the CMDME and each position of the incisor during a chewing cycle was calculated. Whenever, this distance was less than 0.2 mm opposing teeth were considered to be in contact. The occlusal glide was defined as the distance travelled by the lower incisal point as the mandible moved along occlusal contacts of the CMDME. The vertical coordinates at the beginning of the occlusal glide (during closing) and at the end of occlusal glide (during opening) were also calculated. The lengths of the occlusal glide pathway averaged 1.29 mm during closing and 1.55 mm during opening, a total length of 2.84 mm. Mean vertical coordinates at the beginning and end of the glide were -0.95 and -1.12 mm from intercuspal position, respectively.     

Characteristics of the gum chewing occlusal phase in children with primary dentition

Understanding of the growth and development of mandibular function is indispensable to the diagnosis of functional disturbances during childhood. The purpose of this study was to clarify the characteristics of the occlusal phase during gum chewing in children with primary dentition. Chewing motion at the working molar of 14 children with primary dentition and 28 female adults was recorded optoelectrically, and the frontal and sagittal angles of their closing and following opening strokes were measured and compared. In children the closing strokes were entered more vertically and anteriorly than in adults, and the opening strokes shifted to the non-working side in adults but moved to the working side in children. The degree of variance also differed between the two groups; the variance of the frontal angle was larger than that of sagittal angle in adults, but the opposite was true in children. These results suggested that the chewing pattern in children during the occlusal phase is distinctly different from adults and the chewing movement in children is not always less stable than in adults.     

Changes in masticatory mandibular movements in growing individuals: a six-year follow-up

The pattern of mandibular movement during chewing is influenced by several central and peripheral factors. The aim of the present study was to determine whether changes in masticatory function, characterized by mandibular velocity and displacement, occurred during individuals' normal growth. Forty-seven children, 9-15 years of age, were followed over a 6-year period. All had an Angle Class I occlusion with no obvious orthodontic problems. Oral motor function with respect to mandibular displacement, duration, and velocity was monitored 3-dimensionally with an opto-electronic method. The chewing cycle was divided into an opening, closing, and occlusal phase. Total body height was measured. During the follow-up period, all masticatory variables except the 3-dimensional opening distance showed significant changes. The total chewing cycle duration, the opening and occlusal time of the chewing cycle, and the 3-dimensional closing distance increased during the growth period, while the closing time of the chewing cycle, the 2-dimensional lateral and vertical distances and both the opening and closing velocity decreased. The children who grew proportionally most in height during the 6-year period, i.e. the youngest children in the group studied, showed a significantly larger decrease in the opening velocity. From this study it becomes evident that the variables of the chewing cycle undergo a continuous process of change during growth. This is possibly a reflection of anatomical changes, maturation of the central nervous system, and altered functional demands.     

Changes in masticatory mandibular movements in growing individuals: a six-year follow-up

The pattern of mandibular movement during chewing is influenced by several central and peripheral factors. The aim of the present study was to determine whether changes in masticatory function, characterized by mandibular velocity and displacement, occurred during individuals' normal growth. Forty-seven children, 9-15 years of age, were followed over a 6-year period. All had an Angle Class I occlusion with no obvious orthodontic problems. Oral motor function with respect to mandibular displacement, duration, and velocity was monitored 3-dimensionally with an opto-electronic method. The chewing cycle was divided into an opening, closing, and occlusal phase. Total body height was measured. During the follow-up period, all masticatory variables except the 3-dimensional opening distance showed significant changes. The total chewing cycle duration, the opening and occlusal time of the chewing cycle, and the 3-dimensional closing distance increased during the growth period, while the closing time of the chewing cycle, the 2-dimensional lateral and vertical distances and both the opening and closing velocity decreased. The children who grew proportionally most in height during the 6-year period, i.e. the youngest children in the group studied, showed a significantly larger decrease in the opening velocity. From this study it becomes evident that the variables of the chewing cycle undergo a continuous process of change during growth. This is possibly a reflection of anatomical changes, maturation of the central nervous system, and altered functional demands.     

A possible biomechanical role of occlusal cusp–fossa contact relationships

Summary Biomechanical features of occlusal contacts are important in understanding the role of the occlusion contributing to masticatory function. Cusp–fossa contact is the typical pattern of occlusion between upper and lower teeth. This includes static relations, such as that during clenching, and dynamic relations when mandibular teeth contact in function along the maxillary occlusal pathways, as during mastication. During clenching in the maximum intercuspal position (ICP), cuspal inclines may take the role of distributing the occlusal forces in multi‐directions thus preventing excessive point pressures on the individual tooth involved. During chewing movement on the functional side, the mandible moves slightly from buccal through the maximum ICP to the contralateral side. The part of the chewing cycle where occlusal contacts occur and the pathways taken by the mandible with teeth in occlusal contacts are determined by the morphology of the teeth. The degree of contact is associated with the activity of the jaw muscles. To obtain repeatable static and dynamic occlusal contact information provided by the morphology of the teeth, maximum voluntary clenching and chewing movements with maximum range are needed. In conclusion, in addition to the standard occlusal concepts of centric relation/centric occlusion and group function/cuspid protection relation, biomechanics in static and dynamic cusp–fossa relationships should be included to develop an understanding of occlusal harmony which includes no interfering or deflective contacts in functional occlusal contact.     

安氏Ⅱ^1类人群牙尖交错位的平衡与稳定性的分析

目的研究安氏Ⅱ^1类人群肌位到牙位运动过程中的动态咬合接触情况,探讨牙尖交错位的稳定性、肌位一牙位的一致性（平衡性）及其相关的牙胎形态因素。方法对60名未经过正畸治疗的安氏Ⅱ^1类受试者进行检查,采用T-ScanⅡ咬合分析系统记录并分析其肌位到牙位运动过程中的动态骀接触情况,在模型上分析牙殆形态,利用SPSS12．0对数据进行分析。结果①牙尖交错位上的骀力中心点与中线的垂直距离、左右侧殆力差值及骀接触点数目在三次重复测量中均无显著差异;②肌位牙位不调与否的两组间在上下牙弓后段宽度上存在差异;③两组间在Spee曲线深度、Spee曲线流畅性、磨牙近远中向指数等垂直向及矢状向指标上的差异没有统计学意义。结论安氏Ⅱ。类人群具有一定的牙尖交错位的稳定性;肌位牙位的一致性与牙弓后段宽度的协调性有关,而与该人群的垂直向及矢状向的牙殆形态异常无关。     

A clinical study of the functional significance of the occlusal contacts on chewing movements

The study was aimed to investigate the effects of the occlusal contacts on chewing movements according to the changes of the mandibular first molar crown surfaces in 32 young adults. The study includes three components of the experiments as the control, various types of occlusal contact defects and the excessive conditions of occlusal surface contacts on the tooth. The chewing movement consistency was tested in the control study. The effects of the occlusal contact defects to the chewing movements, i.e., a periodontal mechanoreceptive defect (sensory block), a complete defect of coronal contact, partial defects (buccal or lingual cusp and inclination) of coronal surface, were then examined. Third, the effects of the occlusal deflective interference provided for the subjected tooth to the chewing movement was examined as the experiment in the excessive condition. The results obtained were as follows: 1. The consistency of segmental single tooth chewing movements was tested in the control study and revealed highly reliable among parameters of intra-day variance, but not enough for the inter-day variance in each subject. 2. The effects of occlusal contact defects were significant to the path and the rhythm of chewing movements in a poriodontal mechanoreceptive defect, complete coronal defect, cusp and inclination defects. 3. The effects of deflective occlusal interference were significant in the parameters, such as posterior deviation during closing path and inferior deviation of occluding point, prolonged duration in the closing phase, and shortening of duration in the occluding phase. It is suggested that either the occlusal defects or the interference conditions on one side of the first mandibular molar tooth may provide some effects to the chewing movements, and that appropriate occlusal contacts for the tooth may serve to maintain stabilized the path and the rhythm during chewing movements.     

Study of gliding tooth contacts during mastication.

Tooth gliding occurs frequently both in the opening (55.9%) and closing (60.5%) chewing strokes. The average glide length was 1 mm. Good occlusions could not be distinguished from poor occlusion on the basis of frequency and length of gliding contacts. The greater the component of lateral movement during the closing stroke, the greater the probability that gliding contacts would occur.     

Effect of occlusal contact stability on the jaw closing point during tapping movements

PurposeWe studied the relationship between tapping point reproducibility and stability of occlusal contacts at maximum intercuspation.MethodsTapping movements of 12 adult volunteers who had dentition with natural teeth were recorded, and distances between the tapping point (TP) and the intercuspal position (ICP) at the incisal point were calculated. Occlusal contacts at the ICP of individual subjects were also evaluated with black-colored silicone impression material. The correlation between TP–ICP distance and occlusal contact stability was studied.ResultsTP–ICP distance exhibited negative correlations with the total number of teeth showing occlusal contact at the ICP. Standard deviations of TP–ICP distance also negatively correlated with the extension of occlusal contact area over dentition.ConclusionsThis finding indicates that occlusal contacts at the ICP affect the kinematic behavior of tapping movements. The results of this study also suggest that jaw movement data may provide useful clinical information for the evaluation of occlusal contact at ICP.     

Is the reverse cycle during chewing abnormal in children with primary dentition?

Summary  The purpose of this study was to clarify whether the reverse cycle during chewing is abnormal in children with primary dentition. Children with normal primary dentition ( N  =   23; 5·5 ± 0·8 years) and female adults ( N  = 25; 20·7 ± 1·9 years) participated in this study. Chewing movement was recorded using an opto-electronic analysis system with six degrees-of-freedom (TRI-MET, Tokyo-shizaisha; Tokyo, Japan). Each subject was given a stick of chewing gum (new TRIDENT, WARNER-LAMBERT CO., Morris Plains, NJ, USA) and instructed to chew it normally. Starting from the maximum intercuspal position, each chewing sequence was recorded over a period of 20 s. A custom computer program identified individual chewing cycles. Frontal views were used to distinguish seven types of cycle shapes according to Ahlgren (Acta Odontol Scand, 24, 1966, 1–109; Acta Odontol Scand, 25, 1967, 3–13). Multilevel statistical models evaluated differences between children and adults. In the adults, type II cycles that initially opened towards the balancing side and then moved towards the working side were the most common, and the closing pathway was lateral to the opening pathway. In the children, type V (reverse) cycles that opened towards the working side were most common, the closing pathway was medial to the opening pathway, and there was a smaller lateral component during opening and closing than in adults ( P  < 0·05). We conclude that the reverse cycle is not abnormal because normal children with primary dentition have a smaller lateral component and difficulty in controlling asymmetric muscle activity.     

Distance of the contact glide in the closing masticatory stroke during mastication of three types of food

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.     

Jaw movements'' in young adult men during chewing

Jaw movements of a selected group of subjects were studied by clinical observation, examination of wax occlusal records and mounted casts, photoelectric mandibulography, and oscilloscopic tracings. Subjects were found to have substantially consistent and reproducible patterns of jaw movement during empty and functional chewing exercises. However, the individual patterns could not be predicted from analysis of occlusal status.Mean values of (1) the chewing cycle time, (2) the pause at centric occlusion, (3) maximum opening, (4) maximum movement to the right and left of the midline, and (5) maximum jaw point velocity while opening, closing, and moving to the right and left were obtained for 22 subjects chewing a single peanut on the right and the left sides. Great diversity in chewing patterns was observed, but in general, individual subjects exhibited specific and repetitive patterns.All subjects exhibited a pause in centric occlusion at the end of a closing masticatory stroke. A substantially constant jaw point velocity was observed for most of a chewing cycle when the open-close, close-open, left-right, and right-left components of jaw movements were analyzed separately.     

Evaluation of the short-term effectiveness of education versus an occlusal splint for the treatment of myofascial pain of the jaw muscles

BackgroundThe authors conducted a clinical trial to compare the effectiveness of an education program with that of an occlusal splint in treating myofascial pain of the jaw muscles across a short period.MethodThe authors assigned 44 patients randomly to two treatment groups; 41 patients completed the study. The first group (four male, 19 female; mean [standard deviation {SD}] age, 31.4 [14.0] years) received information regarding the nature of temporomandibular disorder (TMD) and self-care measures, whereas the second group (five male, 13 female; mean [SD] age, 31.1 [8.8] years) received an occlusal splint. One of the authors evaluated each patient every three weeks during a three-month treatment period. Treatment outcomes included pain-free maximal mouth opening, spontaneous muscle pain, pain during chewing and headache.ResultsAfter three months, changes in spontaneous muscle pain differed significantly between the education and occlusal splint groups (P = .034; effect size = 0.33). Changes in pain-free maximal mouth opening did not differ significantly between groups (P = .528; effect size = 0.20). Changes of headache and pain on chewing did not differ significantly between groups (P ≥ .550, effect size ≤ 0.10).ConclusionsDuring a short period, education was slightly more effective than an occlusal splint delivered without education in reducing spontaneous muscle pain in patients with TMD. Pain-free mouth opening, headache and pain during chewing were not significantly different between the two treatments.     

Bolus size and unilateral chewing cycle kinematics

The purpose of this study was to determine how bolus size alters the human chewing cycle. This prospective within-subject design evaluated chewing cycles of 38 young adults between 20 and 38 years of age (21 males and 17 females). An optoelectric jaw tracking system was used to record movements of the chin during unilateral (right sided) chewing of four randomly ordered bolus sizes (1, 2, 4 and 8 g) of gum. Using each subject's 10 most representative cycles, multilevel statistical procedures were used to evaluate jaw kinematics. The results showed that bolus size has no consistent effect on opening, closing or total cycle duration. Cycle excursions increased significantly with increasing bolus size. With increasing bolus sizes, chewing cycle excursions along the three axes increased 52-115%. The greatest differences between bolus sizes occurred when the jaw was changing direction (i.e. passing from opening to closing and from working to balancing sides). However, the increases were proportionate and the shape of the chewing cycle was maintained. In order to maintain cycle duration while increasing excursive ranges, jaw velocities increased significantly, with the greatest differences occurring at approximately 70% of opening and 30% of closing. We conclude that humans adapt to larger bolus sizes by increasing chewing cycle perimeter and by increasing cycle speed, while maintaining cycle shape and duration.     

Occlusal interference during mastication can cause pathological tooth mobility

BACKGROUND AND OBJECTIVE: Despite little evidence regarding the relationship between tooth mobility and nonworking contact, the evaluation of occlusion is performed mainly by the detection of premature and/or nonworking contacts during tapping movements and lateral excursion. The hypothesis of this study is that occlusal contact during mastication is potentially traumatic to periodontal tissue. It clarifies the relationship between chewing patterns and the status of periodontal tissue. MATERIAL AND METHODS: Subjects included 73 adults, 20-29 years of age (39 men and 34 women), with complete sets of teeth and no history of orthodontic treatment or periodontal disease. The closing chewing patterns of each subject were classified into three groups by the Masticatory Deviation Index, which depicts the deviation from the normal chewing patterns within 5 mm from the intercuspal position. Periotest was used to diagnose teeth mobility and the values were compared among the three groups. RESULTS: The present study indicates that the chewing movements which deviated from the normal chewing movements increased the mobility of specific types of teeth. CONCLUSION: The results of this study imply a relationship between chewing movements and tooth mobility and indicate that functional evaluation of occlusion is necessary for the examination of periodontal tissue. Occlusal evaluation with border and tapping movements might be insufficient, and functional occlusal evaluation during chewing movements can be clinically useful for using to evaluate periodontal tissue.     

Stable tooth contacts in intercuspal occlusion makes for utilities of the jaw elevators during maximal voluntary clenching

Data are inconsistent concerning whether the level of the surface electromyographic (SEMG) activity of jaw‐closing muscles increases when biting forces elevated during maximal voluntary clenching (MVC). In this study, T‐Scan III system and BioEMG III system were used to record bite force, occlusal contacts and SEMG activity of the anterior temporalis (TA) and of the masseter muscles (MM) simultaneously. Recordings were obtained from 16 healthy young adult males during different conditions: (i) a fast MVC from resting position to intercuspal position (ICP); (ii) mandibular movements from ICP to protrusive or lateral edge‐to‐edge positions with teeth in contact with biting; (iii) a fast MVC in protrusive and lateral edge‐to‐edge positions. A higher level of SEMG activity was associated with a higher bite force during occluding movements (P < 0·05). However, during fast MVC from rest to ICP, the largest number of occlusal contacts was achieved and distributed more symmetrically, the highest level of biting force was obtained, but the SEMG activity of the jaw elevator muscles was reduced compared with its maximum level (P < 0·05). This phenomenon was not observed during the fast MVC in protrusive or lateral edge‐to‐edge positions. The present results that a lower SEMG activity was associated with the largest number of occlusal contacts and the highest level of bite force during centric MVC demonstrated a complex integration of jaw‐closing muscles when a stable occlusion is present.     

Gender difference in masticatory performance in dentate adults

PurposeTo clarify whether there might be a gender difference in masticatory performance in dentate adults.MethodsThirty male subjects and thirty female subjects were asked to chew gummy jelly on their habitual chewing side for 10, 15 and 20 s and the amounts of glucose extraction were measured. The changes of both glucose extraction and standardized glucose extraction from 10 to 20 s were investigated differently for males and females. The amount of glucose extraction was compared between males and females for each chewing duration. In addition, in order to confirm a gender difference in occlusal force, the maximum occlusal force was compared between males and females.ResultsFor both males and females, the amount of glucose extraction was lowest for 10-s chewing and increased significantly for 15-s and 20-s chewing. The mean standardized glucose extraction values increased in proportion with the duration of chewing. The standard deviations of the standardized glucose extraction were very small (below 0.02) for all chewing durations in both males and females. With regard to comparison of the glucose extraction between males and females, the amount of glucose extraction was significantly larger for males than for females for all chewing durations. The maximum occlusal force was significantly larger for males.ConclusionIt was suggested that it might be important to take into consideration gender-related differences while analyzing masticatory performance in dentate adults.     

Occlusal phase of gum-chewing strokes

The occlusal phase of chewing is especially interesting because food particles are being pulverized in this phase. For efficient chewing the upper and lower teeth must come together in a congruent fashion with less variation than in other phases. To examine this expectation the chewing motions of 28 women were recorded optoelectrically, and their frontal and sagittal angles of the closing and following opening strokes were measured at 3.0 mm (3-D linear distance) of opening. Closing strokes were more stable than opening strokes. The frontal angle was correlated with the sagittal angle during closing. The opening and closing sagittal angles were moderately correlated, and the opening and closing frontal angles were negatively correlated at the intersubject level. No direct association was found between the closing strokes and following opening strokes at the intra-subject level. These results suggest that closing strokes are more stable than opening strokes, resulting in efficient mastication.