Leaf Gauge Research Articles

The influence of the leaf gauge and anterior jig on jaw muscle electromyography and condylar head displacement: a pilot study

A leaf gauge and an anterior jig may be used to assist the recording of a reproducible jaw position for restorative and prosthodontic treatment. This study investigated possible condylar displacement using an opto-electronic jaw-tracking device and a leaf gauge or anterior jig. The effect of a leaf gauge and anterior jig on jaw muscle electromyography was also examined. Five healthy adults without symptoms of temporomandibular disorders were selected. Condylar displacement during clenching were recorded simultaneously with electromyographic activity of superior and inferior heads of the lateral pterygoid, anterior and posterior temporalis, masseter, and suprahyoid muscles. Subjects were trained to bite at maximum and half-maximum bite-force using an anterior jig incorporating a force transducer. No consistent condylar displacement was observed in x, y and z axes between different bite-forces although there was a trend towards superior displacement. Comparison of maximum intercuspal clench and maximum clench on a leaf gauge and an anterior jig produced significant decrease in anterior temporalis activity (p < 0.05), whilst an anterior jig with maximum clench significantly decreased posterior temporalis muscle activity. Within the limits of this pilot study, no consistent change in condylar position was identified with these appliances.

The effect of different condylar positions on masticatory muscle electromyographic activity in humans

Objectives. The purpose of this study was to determine a condylar position that permitted the greatest total temporalis and masseter muscle activity in maximum static clench. Study Design. Twenty normal adults, 9 women and 11 men, were evaluated to determine masseter and temporalis activity in maximum static clench with mandibular condyles in different therapeutic positions. Bimanually manipulated, leaf gauge, centric occlusion, and neuromuscular condylar positions were studied. Results. When mandibular condyles were placed anteroinferiorly in a neuromuscular position, total masticatory muscle recruitment was the greatest. In a bimanually manipulated or a leaf gauge position, mandibular condyles were positioned superoposteriorly, producing the least amount of muscle recruitment. Conclusions. The result of any therapeutic position should be an improvement in muscle function. With respect to balance and activation, a neuromuscular condylar position proved to be the position capable of recruiting the greatest motor unit activity when compared with a bimanually manipulated position, a leaf gauge position, and a neuromuscular position.

An evaluation of condyle position in centric relation obtained by manipulation of the mandible with and without leaf gauge deprogramming

Centric relation records of 19 dental students were obtained with leaf gauges and by mandibular manipulation. The condyle/fossa relationships were subsequently evaluated with enhanced sagittal cephalometry. Both clinical methods of obtaining centric relation revealed considerable variation of the condyle location within the glenoid fossa. Only 10% of the patients showed a condyle position “upward and forward” in the fossa with the leaf gauge method. In the mandibular manipulation technique of obtaining centric relation, 10% of the patients showed an “upward and rearward” position of the condyle. (Am J Orthod Dentofac Orthop 1997;111:34-7.)

The effect of orthodontic treatment on centric discrepancy.

The purpose of this study is to investigate the effects of orthodontic treatment on centric discrepancy. Thirty-six orthodontic patients who had been treated with an edgewise appliance were selected for this study while 30 persons who had no history of orthodontic treatment were used as a control group. After recording centric relation using a leaf gauge, centric prematurity, and centric slide were compared using a SAM2 articulator and mandibular position indicator. Results indicated that the number of subjects with one prematurity was significantly greater in the control group (86.7%); however, the number of subjects with two or more prematurities was greater in the orthodontic treatment group (41.6%). The orthodontic treatment group showed more bilateral prematurities. There were no differences between the two groups with regard to the teeth involved in centric prematurities. Just considering the anatomic portion of teeth, centric prematurities were significantly associated with the buccal incline of the maxillary palatal cusp. There were no significant differences in the amount or direction of centric slide between the orthodontic and control groups. This study indicates that orthodontic treatment does not generally result in an increase in centric discrepancy.

Leaf Gauge Technique

Leaf Gauge Technique

アンテリア・ジグによる中心位誘導についての考察

Among the various methods (including the method using Lucia's jig) for guiding the mandible to centric relation, locating centric relation with a leaf gauge has been assumed to be the optimum way.In this paper, the virtue of the Lusia's jig which has been improved by DR Lusia in 1985 is discussed in comparison with the old one. The improvement was to add a ledge on the upper part of the lingual side of the jig to where the incisal edge of the lower incisor contacted and in which the surface of the ledge was made in parallel to the occlusal plane.One of demerits of the old Lucia's jig was that the patient was apt to bite anteriorly due to lack of vertical stop for the lower incisor, causing the condyles to displace anteriorly. On the contrary, another demerit of it was that, in some cases, the incisal edge of the lower incisor was apt to slide along the lingual surface of the jig in supero-posterior direction and then the mandible was forced to retrude and the condyles were pressed backwards.In the improved version of Lucia's jig, the above mensioned demerits were cancelled by placing a vertical stop (a ledge) . In addition, an merit was added that the incisal edge of the lower incisor can move freely back and forth or left and right in small area on the surface of the ledge.The method of locating centric relation with a leaf gauge has the same demerits as the old Lucia's anterior jig had. Therefore, it is concluded that the method using an improved Lucia's jig is superior than the method using a leaf gauge.

Ｌｅａｆ ｇａｕｇｅ法応用の効果発現のメカニズムに関する筋電図学的研究

A leaf gauge is a device that can be used to correct the mandibular position. However, a rationale for the treatment of abnormal muscle activities by the use of the leaf gauge is unclear.The aim of this study was to investigate a rationale for the physiological effect of deprogramming of abnormal jaw masticatory muscle activity after creation of this abnormal activity by the use of experimental occlusal interference during brief maximum clenching in the intercuspal position.Six normally dentate dental students were selected as the subjects. Surface electromyograms from the bilateral masseter, bilateral anterior and posterior temporalis muscles were used.In addition, two other aspects, occlusal surface contact and mandibular position deviation during brief maximum clenching, were studied.Four eleven-session experiments were carried out for a period of 14 days each. The sessions included before and after application of an occlusal interference, the interference period and removal of the interference, and subsequent observation of interference effects was carried out.The leaf gauge was used during each session with four distinct conditions, which were two leaf gauge thicknesses of 4 mm and 16 mm for each experiment and application of eachleaf gauge for 15 and 10-minute periods.It was found that separation of posterior teeth occurred one or two days after interference, the application of a leaf gauge in an attempt to correct the imposed abnormality of muscle balance. In addition, it was found that the mandibular position was repositioned the horizontally. The occlusal contact point surface has become larger in order to become normal.Two factors contributing to the reprogramming of muscle activities were found to be the thickness of the leaf gauge and the length of time of application.

The effect of four jaw relations on electromyographic activity in human masticatory muscles

Significant differences were found in the electromyographic (EMG) activation between the masseter and temporalis muscles for the leaf gauge (LG), manually manipulated (CR) and neuromuscular (NM) bite positions during maximal static clench. The LG position consistently demonstrated the lowest EMG activity, while the NM position displayed the highest degree of muscle activity. Similarly, the ratio of the masseter/temporalis EMG activity during maximal clench was lower for the LG and CR positions and highest for the NM position. These data indicate that the NM position produced the greatest total muscle recruitment, with more masseter involvement during maximal clench, and enabled the subjects to generate greater clenching forces in the NM position as compared to the LG and CR positions.

リーフ・ゲージを用いた咬頭嵌合位における咬合面間距離の計測

リーフ・ゲージを用いた咬頭嵌合位における咬合面間距離の計測

側方運動における臼歯離開の実験的解析

The amounts of disocclusion on working side during lateral movement were measured under the condition without canine teeth by removing anterior segment from the study model mounted on a semi-adjustable articulator. The leaf gauge was used for the measurement. The average amount of disoclusion for molars was 0.16±0.16mm, which is about 40% of the value under the condition with canine teeth.Comparing this result with the data obtained on nonworking side, it was shown that the difference between the amounts of disocclusion with and without canine teeth is almost equal over all molar teeth arrangement including both working and nonworking sides. This fact shows the increment of the angle of hinge rotation of the mandible affects almost uniformly bucco-linqually and mesio-distally during lateral movement. This result confirms the prospect based upon Hobo and Takayama's theory of the mandibular movement.

筋電図を用いたリーフ・ゲージ法の分析

筋電図を用いたリーフ・ゲージ法の分析

Occlusal adjustment as treatment for tenderness in the muscles of mastication in category 1 patients

When a lateral pterygoid muscle is more tender to palpation than the other muscles of mastication, and a stress test is positive, an occlusal cause should be suspected. Patients with lateral pterygoid tenderness are divided into three categories according to two criteria: the position of the condyles in their glenoid fossae and the degree of dysfunction in the articulation. Only patients in category 1, those with a centered condylar position and without dysfunction, are discussed in this article. Occlusal adjustment is executed on the basis of information gathered from radiographs of the temporomandibular joint, diagnostic casts, and leaf gauge measurements of unequal bilateral occlusal contact. The amount of tooth structure requiring removal can be determined by using leaf gauges of differing thicknesses. Occlusal adjustments are performed without mandibular manipulation until the tenderness of the lateral pterygoid muscle is relieved.

An electrognathographic study of aspects of ‘deprogramming’ of human jaw muscles

Three-dimensional electrognathography of an incisor point was used to detect peripheral correlates of deprogramming of the jaw elevator muscles. Putative deprogramming was attempted through the clinically recommended use of a leaf gauge, placed for 10-15 min between the maxillary and mandibular anterior teeth and disoccluding the posterior teeth by about 2 mm. Studied mandibular displacements were those that occurred during voluntary elevation of the mandible from the postural to the intercuspal position. Use of the leaf gauge did not affect the displacement patterns. Within a freeway space of about 0.2 mm3, the incisor point moved about 2 mm vertically, about 1 mm sagittally, and about 0.2 mm laterally.

Suggested modifications for the leaf wafer system

The Woelfel leaf wafer system provides an easy and accurate way to register centric relation position, which is important in dental practice. This article suggests the following modifications of the system that should enhance the accuracy and convenience of the technique: (1) custom deform wafer before deprogramming or tripodizing the mandible, (2) mark position of leaf gauge at wafer slot, (3) secure leaf gauge to wafer with cyanoacrylate glue, and (4) write pertinent information on paper leaf gauge.

An electromyographic study of aspects of ‘deprogramming’ of human jaw muscles

Surface electromyograms from the right and left masseter and anterior temporalis muscles were used to detect peripheral correlates of deprogramming, also known as programming and reprogramming, of jaw elevator muscles. Putative deprogramming was attempted through the clinically recommended use of a leaf gauge, placed for 15 min between the maxillary and mandibular anterior teeth and disoccluding the posterior teeth by about 2 mm. Studied contractile activities were those of postural activity (subconscious, semi-isometric, minimal activity) and intercuspal teeth clenching (conscious, isometric, maximal activity). Use of the leaf gauge did not affect normalized postural activity (about 4%), the duration (about 900 ms) and static work efforts of clenching (about 1200 microV.s), the time to peak mean voltage of clenching (about 400 ms), and the peak mean voltage of clenching (about 300 microV). Activity and asymmetry indices showed that the studied motor innervation patterns were not changed by the leaf gauge.

Simple application of anterior jig or leaf gauge in routine clinical practice

Utilization of either of the two described methods by dentists is recommended as a simple means to routinely record or provide centric relation closures. The leaf gauge (1 to 6 mm thick) can be made from plastic or x-ray film or it can be purchased. The anterior acrylic resin jig can be made in a few minutes directly in the mouth by the dentist or an assistant or by a technician using mounted casts. Both methods avoid adaptive mandibular closure patterns and dentist-guided jaw closure as well as other commonly unrecognized errors in assessing occlusal contacts.

New device for accurately recording centric relation

A new system for recording jaw relations has been described. It is easy to learn to use correctly, is pleasant to the patient while assisting the patient's neuromusculature into the desired retruded closure at the specific vertical dimension preselected by the dentist, and its uses minimal amounts of recording media. Duplicate records can be quickly made for verification, various recording media may be used, improved stability during mounting is obtained, and the method is applicable in most dentulous and partially edentulous situations. Two elements are used, a dental arch-shaped, partially performed, thin, waterproof wafer and a disposable paper leaf gauge. The paper leaf gauge is narrower and more solid than the plastic leaf gauge and thus forms a better anterior leg of the tripod with the two condyles on patient-guided terminal hinge closures. The leaf gauge of preselected thickness is inserted into a slot in the wafer that has been deformed exactly like the occlusal plane by a previous centric occlusion closure. The system is quick, economical, and less complex than most methods presently used. Even so, it accurately reproduced six check-bites on one patient according to comparisons on the Veri-check instrument (Denar Corp., Anaheim, Calif.).

Leaf gauge with consecutively numbered leaves

Leaf gauge with consecutively numbered leaves

A technique for the serial extraction treatment of Class II and deep-bite malocclusion

2. The Myo-Monitor technique was the least repeatable or most variable technique for recording maxillomandibular relationship. 3. There was no significant difference in repeatability between the bilateral manipulation technique and the leaf gauge technique for taking maxillomandibular records. 4. There was a large significant difference in repeatability between the bilateral manipulation technique and the Myo-Monitor technique for taking maxillomandibular records.

Centric relation: A comparison of muscle-determined position and operator guidance

Fifteen subjects were used to determine direction and magnitudes of shifts in condylar position when interocclusal records were made by biting hard or easy on a leaf gauge or wax. Electromyographic recordings were made of the temporal and masseter muscles during interocclusal registrations to determine which muscles were most active in seating the condyle when the leaf gauge was used. Results indicated no significant difference in condylar position superoinferiorly between registrations. Biting hard on a leaf gauge caused a significantly more posterior position of the condyle. When this technique is used for obtaining interocclusal registrations, the temporal muscles are more active than the masseters.