Importance of occlusion aspects in the completion of orthodontic treatment

The purpose of this study was to address the therapeutic goals regarding the static and functional occlusion in the completion of orthodontic treatment. For such purpose, a study population comprising 20 female treated Class II malocclusion subjects with an initial mean age of 11 years underwent a two-phase treatment (orthopedics and orthodontics). The patients were diagnosed in centric relation and were treated according to the six keys for normal occlusion and functional occlusal parameters (centric relation, vertical dimension, lateral and anterior guidances, occlusal contacts and direction of forces applied on the teeth). After removal of fixed mechanics, retainers were installed and maintained for two years. Five years after orthodontic completion, the occlusal stability of the patients was evaluated regarding molar relationship and overjet, measured in dental casts. All subjects maintained the normal molar relationship and correct overjet achieved at the end of treatment, indicating a fair level of occlusal stability. The importance of the criteria of the ideal functional occlusion to ensure a better stability after completion orthodontic treatment will be discussed in detail in this paper. In addition, some clinical situations in which localized adjustments are indicated for occlusal refinement will be described.     

Influence of group function and canine guidance on electromyographic activity of elevator muscles

A comparative EMG study was done between two types of occlusal guidances: group function and canine guidance. The purpose was to determine which of the two occlusal schemes causes a greater reduction in muscle activity and thereby a decrease in muscle tension in eccentric mandibular positions. Full-coverage occlusal splints were made for six test subjects with normal function of the stomatognathic system. Left- and right-side integrated EMG recordings were made of the masseter and temporal muscles during static (clenching) and dynamic (lateral excursion and clenching) maximal contractions. The results showed an EMG activity reduction of the elevator muscles with group function relative to their activity in centric occlusion. A more marked reduction was observed on the mediotrusive side, mainly in the temporal muscle. With canine guidance, the reduction in elevator muscle activity is much greater, more significant, and mainly in the temporal muscle of the mediotrusive side. The clinical implications of this study suggest the use of canine guidance in laterotrusion for therapy with full-coverage occlusal splints.     

The influence of the mandibular lateral translation

There has been much controversy concerning the existence and importance of mandibular lateral translation. However, more sophisticated techniques of registration and evaluation have addressed many of these questions, and there has recently been less discussion of the topic. This report addresses the specific relationship of cuspal contacts in centric occlusion and introduces a modification in typical occlusal morphology to avoid interferences caused by the lateral translation. A specific position of the centric contacting cusps to avoid such interferences is suggested. A spatial registration of the cuspal pathways, using variable posterior and anterior guidances, is said to offer more precise cuspal placement.     

Occlusion and orthodontics.

The importance of considering the functional aspects as well as the static concepts of an occlusion was demonstrated in the case of an 11-year-old girl with postorthodontic temporomandibular joint muscle pain dysfunction. The following characteristics of an ideal occlusion were discussed as they relate to the entire masticatory system: 1. There should be no slide in centric; that is, there should be a stable jaw relationship when occlusal contact is made in centric relation closure. 2. There should be freedom in centric, that is, freedom for the mandible to move from centric relation to centric occlusion and slightly anterior to centric occlusion without interference. 3. Centric relation should be at the same contact vertical dimension as centric occlusion. 4. There should be no buccolingual thrust or impact to any tooth on closure to contact in centric relation or to centric occlusion. 5. Between centric relation and centric occlusion there should be an unrestricted glide with maintained occlusal contact. 6. Complete freedom for smooth-gliding occlusal contact movements in various excursions from both centric occlusion and centric relation. 7. Occlusal guidance should be on the working or functioning side rather than on the balancing or nonfunctioning side. 8. There should be no soft-tissue impingment from occlusal contacts. In effect, the occlusion should be related to centric relation and centric occlusion prior to, during, and at the completion of active treatment. The final occlusion should provide unhindered closure in centric relation, smooth-sliding lateral and protrusive movements, and an optimal bilateral vertical contact dimension. Orthodontic treatment must include proper occlusal adjustment procedures to obtain the goals of an ideal occlusion in most instances.     

The role of the general practitioner in restoring patients with temporomandibular joint dysfunction

Treatment of temporomandibular joint pain, resulting from occlusal dysfunction, is divided into two phases. First, occlusal splint therapy is used to eliminate the initial signs and symptoms and to achieve stability in centric relation. In the second phase of treatment the occlusion is adjusted and, if indicated, restored by means of crown and bridge procedures. Casts, properly mounted in a semi-adjustable articulator, with the lower cast mounted in centric relation, can be extremely helpful for an occlusal analysis and a diagnostic occlusal adjustment in the articulator. Each occlusal adjustment procedure in the mouth should be preceded by an initial study, occlusal analysis and occlusal adjustment on articulator mounted casts. The two main criteria for restoring the occlusion are: maximum intercuspation occurring in centric relation and disocclusion of the posterior teeth during excursive movements by means of anterior guidance. Patients with a history of temporomandibular joint pain and dysfunction usually have a limited adaptive capacity of even the smallest occlusal imperfection. In order to cope with the occlusal restoration of patients with such a low level of occlusal tolerance the final crowns and bridges should be cemented temporarily for a period of at least 3 months. A matt gold surface will be very helpful to locate undesirable occlusal contacts during temporary cementation.     

An electromyographic and roentgen cephalometric study of occlusal morphofunctional disharmony in children.

In a sample of children with dual bite and symptoms in the masticatory system, the activity of the anterior temporal and masseter muscles was studied electromyographically during clench and light tapping in the posterior occlusal contact position and centric occlusion and in protrusive bite on the incisors. The findings indicated that the optimal muscle function during maximal clench and tapping with displayed in the posterior occlusal contact position, which in the present subjects was situated, on the average, 0.5 to 1 mm. anterior to the centric jaw relation. It should therefore be recommended that, in orthodontic treatment of children with dual bite, the intercuspal position (centric occlusion) should be established in the posterior occlusal relationship. This is in accordance with the opinion of several authors who have emphasized the use of the retruded contact position (the centric jaw relation) as key reference position in orthodontic treatment and occlusal rehabilitation. These authors have further emphasized the importance of stable occlusal contacts in centric relation, centric occlusion, and the various jaw excursions in obtaining and maintaining a harmonious function between the dentition, the temporomandibular joints, and the neuromuscular system.     

Accuracy of perioperative mandibular positions in orthognathic surgery

Mandibular position is an important parameter used for the diagnosis of dentofacial deformities, as well as for orthognathic surgery planning and execution. Centric relation (anterior and superior relationship of the mandibular condyles interposed by the thinnest portion of their disks against the articular eminencies), centric occlusion (when lower teeth contact upper teeth at centric relation), and maximal intercuspation (complete interdigitation of lower and upper teeth) are not often addressed as factors that influence the results of orthognathic surgery, although these relationships are critical to ensure accuracy during the surgery. The present study assessed occlusal measurements taken before and after the induction of general anaesthesia from consecutive orthognathic surgery subjects. The variables assessed included the differences between these occlusal measurements, patient age, gender, type of deformity, and type of proposed orthognathic surgical procedure. The results demonstrated statistically significant differences for mandibular retrusion from maximal intercuspation to centric occlusion position, whereas the mandible appeared not to change significantly from centric occlusion after the induction of general anaesthesia. Patient age and the type of deformity appeared to influence the results. While in most instances centric occlusion can be adequately reproduced under general anaesthesia, for some specific orthognathic cases more accurate results might be obtained if the mandible-first sequence is used.     

The effect of changing the maxillomandibular relationship by a bite plane on the habitual mandibular opening and closing movement

The relationship between the change of afferent information from occlusal contacts and its influence on the jaw muscles was investigated. For this purpose, the following questions were posed and experimental studies designed. If the subject was given habitual occlusal contacts in centric relations with a bite plane, were the habitual mandibular closing and opening movements influenced? Second, was it easier for the subjects to accomplish regular habitual mandibular opening and closing movements, when the bite plane was inserted and removed? From the results it could be concluded that the centric occlusal contacts in centric relation were more physiological for the jaw muscles. In addition, when the new occlusal position was coincident or close to the centric relation, it was easier for the subject to study and acquire the new habitual mandibular opening and closing movement.     

COMPARATIVE EVALUATION OF THE EFFICACY OF OCCLUSAL SPLINTS FABRICATED IN CENTRIC RELATION OR MAXIMUM INTERCUSPATION IN TEMPOROMANDIBULAR DISORDERS PATIENTS

Fabrication of occlusal splints in centric relation for temporomandibular disorders (TMD) patients is arguable, since this position has been defined for asymptomatic stomatognathic system. Thus, maximum intercuspation might be employed in patients with occlusal stability, eliminating the need for interocclusal records. This study compared occlusal splints fabricated in centric relation and maximum intercuspation in muscle pain reduction of TMD patients. Twenty patients with TMD of myogenous origin and bruxism were divided into 2 groups treated with splints in maximum intercuspation (I) or centric relation (II). Clinical, electrognathographic and electromyographic examinations were performed before and 3 months after therapy. Data were analyzed by the Student''s t test. Differences at 5% level of probability were considered statistically significant. There was a remarkable reduction in pain symptomatology, without statistically significant differences (p>0.05) between the groups. There was mandibular repositioning during therapy, as demonstrated by the change in occlusal contacts on the splints. Electrognathographic examination demonstrated a significant increase in maximum left lateral movement for group I and right lateral movement for group II (p<0.05). There were no significant differences (p>0.05) in the electromyographic activities at rest after utilization of both splints. In conclusion, both occlusal splints were effective for pain control and presented similar action. The results suggest that maximum intercuspation may be used for fabrication of occlusal splints in patients with occlusal stability without large discrepancies between centric relation and maximum intercuspation. Moreover, this technique is simpler and less expensive.     

骨转换标志物对于牙槽嵴重度吸收患者咀嚼效能与两种改良牙合型全口义齿戴用的影响

目的 对骨转换标志物正常和升高的牙槽嵴重度吸收的无牙颌患者,分析两种改良牙合型（长正中牙合型、舌向集中牙合型）全口义齿的戴用与咀嚼效能的关系,以期为临床全口义齿修复中牙合型的选择提供参考。 方法 选取85例（男45例,女40例）牙槽嵴重度吸收的无牙颌患者,采用随机数字表法随机选用两种改良牙合型全口义齿（长正中牙合型全口义齿、舌向集中牙合型全口义齿）治疗方案。电化学发光免疫法测量血清中骨转换标志物——Ⅰ型前胶原N端前肽（P1NP）和Ⅰ型胶原交联C 末端肽（CTX）的水平,分为骨转换标志物正常组及升高组。义齿戴用3个月后,吸光度法测定咀嚼效能,多因素方差分析不同骨转换标志物测量值的患者不同类型改良牙合型全口义齿的戴用与咀嚼效能的关系。 结果 骨转换标志物（P1NP和CTX）正常组的患者,不同类型改良牙合型（长正中牙合型、舌向集中牙合型）全口义齿的戴用与其咀嚼效能的关系无统计学差异。而骨转换标志物（P1NP和CTX）升高组患者,不同类型改良牙合型全口义齿的戴用与其咀嚼效能的差异有统计学意义（P<0.01）,与戴用舌向集中牙合型全口义齿的患者相比,戴用长正中牙合型全口义齿的患者具有更高的咀嚼效能。 结论 骨转换标志物较高的患者,选用长正中牙合型全口义齿会得到相对更高的咀嚼效能。骨转换标志物有望成为牙槽嵴重度吸收的无牙颌患者选择戴用不同改良牙合型全口义齿时的参考指标。     

Locating the centric relation prematurity with a computerized occlusal analysis system

Locating the first tooth contact that interferes with freedom of movement in and out of centric relation has been the diagnostic and treatment objective of most occlusal therapies. The centric relation prematurity can be located by various methods, which involve operator-guided mandibular positioning combined with the patient's subjective assessment of his or her perceived first tooth contact. The method known as bimanual manipulation has been widely recognized and accepted as a predictable method of determining and verifying the centric relation position. The first occlusal contact that results when the mandible is closed on a correct centric relation axis is known as the centric relation prematurity. An alternative procedure combines bimanual manipulation with the simultaneous recording of the sequence of resultant tooth contacts using a computerized occlusal analysis system. This alternative offers a significant improvement in the precision of locating the first tooth contact. This article describes a method of identifying the first tooth contact while not relying on the patient's subjective assessment of his or her perceived occlusal feel.     

Centric relation. Its effect on occluso-muscle harmony.

The most common cause of pain in the region of the temporomandibular joint is occluso-muscle imbalance. This results most often from disharmony between the articulation of the teeth and the centric relation of the condyles. Muscle tenderness of palpation indicates that muscle is involved. An examination must then be done to determine the cause of the muscle tenderness. Before the condyle-occlusion relationship can be evaluated, an accurate centric relation must be determined and verified. The condyles are in centric relation when they are in the most superior position possible in the fossae. From that apex of force position, the condyle can travel neither forward nor backward without moving downward. This position can be located with careful bilateral manipulation and then verified if it can resist firm pressure with no tension or tenderness. Until this correct centric relation is located and verified, it is not possible to properly evaluate the occlusal relationship to the temporomandibular joints. If the occlusion is harmonized to a centric related condyle that can resist firm pressure with pressure with no discomfort, there will be no reason for the muscles to protect either the teeth or the joints. If an occlusion is adjusted to a malrelated condylar position, the occluso-muscle imbalance will be perpetuated and often intensified. Centric relation is the starting point of occlusal contact. Incline interferences in excusive movements must also be eliminated and the occlusion must be harmonized to the envelope of function for each patient. If centric relation is not properly located, occlusal interferences will remain regardless of what procedures are used to record or adjust excursive movements.     

平衡对全口义齿咀嚼效能影响的研究

目的:研究平衡对全口义齿咀嚼效能的影响。方法:采用吸光度法来测定20例全口义齿戴用者在正中选磨前、正中选磨后以及正中与非正中选磨后的咀嚼效能。结果:(1)正中选磨后的咀嚼效能明显高于选磨前的咀嚼效能(p<0.05);(2)正中与非正中选磨后的咀嚼效能略高于仅正中选磨后的咀嚼效能,但无统计学上的意义(p>0.05)。结论:(1)平衡是决定全口义齿修复效果的重要因素之一,全口义齿修复后进行系统选磨是非常必要的;(2)咀嚼效能测定可作为评价全口义齿平衡的功能性检测手段之一。     

A technique for evaluation of centric relation tooth contacts. Part II: Following use of an occlusal splint for treatment of temporomandibular joint dysfunction

The purpose of this study was to determine the effect of TMJ dysfunction on the recording of centric relation. Centric relation was recorded using an anterior occlusal stop and by bimanual manipulation. Changes in occlusal contacts were recorded before and after occlusal splint therapy in six subjects with TMJ dysfunction. The pantographic reproducibility index and clinical signs and symptoms were used to determine the presence or absence of dysfunction. Use of the anterior occlusal stop resulted in a more posterior, superior initial tooth contact position when compared with bimanual manipulation. Occlusal contact positions were less consistent in TMJ dysfunction subjects than in control subjects. Initial occlusal contacts changed toward centric relation as the dysfunction disappeared. Final occlusal contact was found on the side where clinical signs and symptoms occurred. The condyle on the affected side appeared to be repositioned posteriorly and superiorly in most instances. Occlusal splint therapy was more effective when the splint was adjusted weekly. This study indicates the need to eliminate TMJ dysfunction before recording centric relation or adjusting the occlusion. Occlusal interferences found with TMJ dysfunction are not the same as occlusal interferences found when TMJ dysfunction is absent. Abnormal features on pantographic tracings may aid in indicating the presence of occlusal interferences. Occlusal adjustment in the presence of TMJ dysfunction would result in erroneous occlusal reduction.     

Occlusal objectives in orthodontic treatment.

An attempt has been made to present a means for preventing the temporomandibular joint pain-dysfunction syndrome by treating to the terminal hinge position and using postreatment occlusal adjustment procedures. 1. Any postorthodontic patient who is not in centric relation and has occlusal interferences has the potential for temporomandibular joint pain-dysfunction syndrome symptoms to develop in the future. 2. The orthodontist should manipulate the mandible of every patient at each visit, placing the condyle in the terminal hinge position. He should close the mandible until initial tooth contact is reached and diagnose the patient's problems from this position and not from the centric occlusion position. 3. The case should be finished with the teeth in centric relation occlusion. 4. The orthodontist should equilibrate the occlusion of every completed case to eliminate the minute occlusal interferences which are always present. 5. The case treated to centric relation can be equilibrated effectively without mounting on an articulator. 6. If we have the concept of building an occlusion to fit the jaw mechanism, the temporomandibular joint pain-dysfunction syndrome can be virtually eliminated in the postorthodontic patient.     

Discussion of the effect of occlusal factor on bruxism]

Controversy has been existed on the effect of occlusal factor on bruxism. The purpose of this study is to evaluate the effect of occlusal factor on bruxism by clinical examination and photo-occlusion analysis. The patient group and control group are selected for this study. The results show that (1) the occlusal status in centric occlusion and eccentric articulation of the patient and control group has no significant difference; (2) the occlusal contact strength and distribution in centric occlusion of the patient and control group has no significant difference; (3) occlusal interferences are existed in different extent both in patient group and control group. This expresses that most of the subjects can compensate this kind of occlusal disorder without feeling any discomfort; (4) This can be concluded that occlusal factor is not an major causal factor on bruxism.     

长正中《牙合》型下颌全口义齿近中移位量的初步研究

目的 探讨无牙颌患者戴用长正中<牙合>型全口义齿3个月后下颌义齿的近中移位量能否满足患者长正中量的自然要求,从而检验长正中<牙合>型全口义齿的设计理论. 方法 为10例无牙颌患者制作长正中<牙合>型、线性<牙合>型和解剖<牙合>型3种全口义齿,采用哥特式弓描记装置测量无牙颌患者的长正中量,采用三维精密平移台测量3种<牙合>型下颌义齿的近中移位量.对比分析不同<牙合>型下颌义齿近中移位量的差异,并与患者长正中量进行对比. 结果 10例无牙颌患者的长正中量为(1.02±0.36)mm,3种<牙合>型下颌义齿的近中移位量分别为:长正中<牙合>型(1.016±0.348)mm,线性<牙合>型(1.092±0.448)mm,解剖<牙合>型(0.409±0.253)mm. 结论 长正中<牙合>型全口义齿能满足患者长正中量的自然要求,以及在患者正中关系位至肌力闭合道终点的位置之间无障碍的义齿设计要求.     

Is occlusion becoming more confusing? A plea for simplicity

It is not difficult to observe and record patient occlusal characteristics before starting simple or complex occlusal rehabilitations. If this is done, and if the subsequently placed crowns and fixed prostheses are constructed in observation of similar characteristics, clinical success usually is the result. Deviations from the suggestion to duplicate the "normal" occlusion should be made when the original natural occlusion had caused overt pathosis, or when all teeth or one arch of the teeth is being restored at one time. If this is the case, centric relation occlusion is more reproducible and easier to develop than occlusion with a shift from centric relation to centric occlusion. Peculiar requests of patients relative to occlusal positioning, or routine dependence on various devices to predetermine occlusal characteristics for rehabilitation (as is currently popular in some groups), should be considered, but they should be tempered with careful observation of preoperative occlusal characteristics.     

Influence of Protrusive Functions on Electromyographic Activity of Elevator Muscles

Several authors have studied the influence of varied centric and eccentric occlusal relationships on neuromusculature. However, the authors know of no research comparing the effects on mandibular muscle activity of different occlusal functions in protrusive guidance.

This study used an orthopedic splint to compare the influence exerted by different protrusive occlusal functions on elevator muscle activity. The paper also explains the neuromusculature involved and quantifies the activity in comparison with registration in the mandibular centric position.     

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.