Ultra-low frequency transcutaneous electric nerve stimulation does not affect the centric relation registration.

OBJECTIVE: To evaluate the influence of ULF-TENS on the displacement of the mandibular condyle and on the repeatability of centric relation (CR) registration of three different techniques: bimanual manipulation (BM), long strip technique, and harmonic centric occlusal relationship (R.O.C.A. wires). METHODS: Twenty-five participants without temporomandibular disorder (TMD) underwent two study stages conducted via electronic position analysis: (1) three CR records were made, one for each manipulation technique; (2) the ULF-TENS was applied for 30 min, and after that the same CR records were repeated. STATISTICAL ANALYSES: Mann-Whitney, ICC, and one-tailed F test. RESULTS: The ULF-TENS did not influence the condyle total displacement, regardless of CR recording technique used (p > 0.05). BM showed an improvement in repeatability after ULF-TENS. DISCUSSION: Concerning the variance, BM showed less variation at the X-axis. Long strip technique and R.O.C.A. wires varied less at the Y-axis. Long strip technique was again less variable at the Z-axis.

The muscle engram: the reflex that limits conventional occlusal treatment.

The engram (the masticatory "muscle memory") is shown to be a conditionable reflex whose muscle conditioning lasts less than two minutes, far shorter than previously thought. This reflex, reinforced and stored in the masticatory muscles at every swallow, adjusts masticatory muscle activity to guide the lower arch unerringly into its ICP. These muscle adjustments compensate for the continually changing intemal and external factors that affect the mandible's entry into the ICP. A simple quick experiment described in this article isolates the engram, enabling the reader to see its action clearly for the first time. It is urged that every reader perform this experiment. This experiment shows how the engram, by hiding the masticatory muscles' reaction (the hit-and-slide), limits the success of the therapist in achieving occlusion-muscle compatibility. This finding has major clinical implications. It means that, as regards the muscle aspect of treating occlusion, the dentist treating occlusion conventionally is working blind, a situation the neuromuscular school of occlusal thought seeks to correct. The controversy over occlusion continues.

Evaluation of treatment for functional posterior crossbite of the deciduous dentition using Planas' direct tracks.

BACKGROUND: Functional posterior crossbites are a common finding in children with deciduous teeth and must be treated as soon as they are diagnosed in order to avoid unwanted changes in normal growth and development patterns. OBJECTIVE: This study objective was to evaluate the changes caused by Planas' direct tracks treatment on the arch dimensions of patients with functional posterior crossbite in first dentition. MATERIALS AND METHODS: The sample consisted of 20 children, 4 to 6 years old, divided into two groups, paired up according to age and gender. Group test was composed of 10 patients with functional posterior crossbite treated with PDT. Group control consisted of 10 children with normal occlusion. The evaluation criteria were intercanine and intermolar distances and Carrea's analysis (arch perimeter). All data were collected by a pre-calibrated examiner on study casts obtained at baseline and after 4 months of treatment. The statistical analysis of the data was achieved using GraphPad InStat software, version 3.05 for Windows, with the level of significance set at 0.05. For the comparison between intercanine and intermolar distances, the Tukey-Kramer Multiple Comparisons test was used. When Carrea's analysis was considered, the Mann-Whitney test was used. RESULTS: At the beginning of the study, all the evaluated criteria showed lower mean values in patients with posterior crossbites, and significant differences between test and control groups were noticed (P<0.05). After the end of follow-up period, these differences could not be verified (P>0.05). CONCLUSIONS: Within the limits of the present study, it is possible to conclude that the treatment with Planas' direct tracks was able to give back the normal dimensions of deciduous arch in patients with unilateral functional posterior crossbites, thus making it possible a better growth pattern.

Comparative study of intermaxillary relationships of manual and swallowing methods.

This study compared the mandibular displacement from three methods of centric relation record using an anterior jig associated with (A) chin point guidance, (B) swallowing (control group) and (C) bimanual manipulation. Ten patients aged 25-39 years were selected if they met the following inclusion criteria: complete dentition (up to the second molars), Angle class I and absence of signs and symptoms of temporomandibular disorders and diagnostic casts showing stability in the maximum intercuspation (MI) position. Impressions of maxillary and mandibular arches were made with an irreversible hydrocolloid impression material. Master casts of each patient were obtained, mounted on a microscope table in MI as a reference position and 5 records of each method were made per patient. The mandibular casts were then repositioned with records interposed and new measurements were obtained. The difference between the two readings allowed measuring the displacement of the mandible in the anteroposterior and lateral axes. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. There was no statistically significant differences (p>0.05) among the three methods for measuring lateral displacement (A=0.38 +/- 0.26, B=0.32 +/- 0.25 and C=0.32 +/- 0.23). For the anteroposterior displacement (A=2.76 +/- 1.43, B=2.46 +/- 1.48 and C=2.97 +/- 1.51), the swallowing method (B) differed significantly from the others (p<0.05), but no significant difference (p>0.05) was found between chin point guidance (A) and bimanual manipulation (C). In conclusion, the swallowing method produced smaller mandibular posterior displacement than the other methods.

Comparative study of intermaxillary relationships of manual and swallowing methods

This study compared the mandibular displacement from three methods of centric relation record using an anterior jig associated with (A) chin point guidance, (B) swallowing (control group) and (C) bimanual manipulation. Ten patients aged 25-39 years were selected if they met the following inclusion criteria: complete dentition (up to the second molars), Angle class I and absence of signs and symptoms of temporomandibular disorders and diagnostic casts showing stability in the maximum intercuspation (MI) position. Impressions of maxillary and mandibular arches were made with an irreversible hydrocolloid impression material. Master casts of each patient were obtained, mounted on a microscope table in MI as a reference position and 5 records of each method were made per patient. The mandibular casts were then repositioned with records interposed and new measurements were obtained. The difference between the two readings allowed measuring the displacement of the mandible in the anteroposterior and lateral axes. Data were analyzed statistically by ANOVA and Tukey's test at 5 percent significance level. There was no statistically significant differences (p>0.05) among the three methods for measuring lateral displacement (A=0.38 ± 0.26, B=0.32 ± 0.25 and C=0.32 ± 0.23). For the anteroposterior displacement (A=2.76 ± 1.43, B=2.46 ± 1.48 and C=2.97 ± 1.51), the swallowing method (B) differed significantly from the others (p<0.05), but no significant difference (p>0.05) was found between chin point guidance (A) and bimanual manipulation (C). In conclusion, the swallowing method produced smaller mandibular posterior displacement than the other methods.

Este estudo comparou o deslocamento mandibular a partir de 3 métodos de registro da relação cêntrica usando um jig anterior associado com: (A) guia da ponta do mento; (B) deglutição grupo controle (C) manipulação bimanual. As moldagens dos arcos maxilares e mandibulares foram feitas com hidrocolóide irreversível. Os modelos de estudo de cada paciente foram obtidos e montados em máxima intercuspidação como uma posição de referência no microscópio. Foram obtidos 5 registros de cada método em 10 pacientes. Os modelos mandibulares foram reposicionados com os registros interpostos e novas medidas foram obtidas. A diferença entre as duas leituras permitiu a medida do deslocamento mandibular nos eixos ântero-posterior e laterais. ANOVA não demonstrou diferença estatisticamente significativa entre os 3 métodos em relação ao registro do deslocamento lateral (A = 0,38 ± 0,26, B = 0,32 ± 0,25 e C = 0,32 ± 0,23). Quanto ao deslocamento anteroposterior, ANOVA e o teste de Tukey (a=0,05) indicaram diferença estatisticamente significante entre os três métodos (A=2,76 ± 1,43, B=2,46 ± 1,48 e C=2,97 ± 1,51). Não houve diferença estatisticamente significante entre A e C. A deglutição propiciou menor deslocamento mandibular posterior que os outros métodos.

Neuromuscular diagnosis in orthodontics: effects of TENS on the sagittal maxillo-mandibular relationship.

AIM: This study was conducted in order to assess the changes in the occlusal position of the mandible after ULF (Ultra Low Frequency)-TENS relaxing procedure in subjects in pubertal growth phase with diagnosed Angle Class II division 1 and mandibular dentoalveolar retrusion. MATERIALS AND METHODS: This study was performed on 19 patients (13 females, 6 males) with an Angle Class II division 1, aged between 10 and 15 years old (mean age 12.26, SD 1.32), characterised by mandible dentoalveolar retrusion and optimal vertical facial dimension, diagnosed by clinical and cephalometric evaluation. Diagnostic neuromuscular registrations were made for all subjects. The casts were mounted on articulator in habitual intercuspal position with a tooth-guided wax bite registration. Reference points were chosen at molar level. Subsequently the same casts were mounted in myocentric position and compared to the habitual intercuspal position, assessing the sagittal shift after TENS procedure. STATISTICS: Mean and standard deviation were calculated on the amount of shifting at the left molar reference point after TENS procedure. Analysis of variance (ANOVA), using STATA statistics package, was carried out in order to evaluate the influence of sex and age on the amount of molar shift. RESULTS: Nine subjects showed, in the sagittal plane, a forward mandibular shift in neuromuscular myocentric position compared to habitual intercuspal position. Six subjects showed no differences between habitual and myocentric position in the sagittal plane. Four individuals showed a backward mandible shift after TENS indicating worsening of the II molar class in the sagittal plane. CONCLUSION: This study suggests that TENS recorded occlusion in subjects with Class II division 1 with mandible dentoalveolar retrusion allows to visualise an unusual trend of growth. The advancements of the mandible were not taken into account. These results could offer new diagnosis and prognosis methods for Class II malocclusions.

[Efficacy of treatment with hard and soft occlusal appliance in TMD].

Temporomandibular disorders (TMD) include clinical disorders involving the masticatory muscles, the temporomandibular joints (TMJ) and the adjacent structures. TMD was recognized as a main source for pains in the orofacial area, which are not caused from dental origin, and is defined by the American Academy of Orofascial Pain (AAOP) as a sub-group within the frame of musculoskeletal disorders. The main etiology for TMD has not been found yet. The customary treatments for this disorder include treatment with occlusal splints, physiotherapy, medicaments, behavioral-cognitive treatment, hypnosis, acupuncture and surgery that should be considered only if all conservative treatments were unsuccessful. Occlusal splint is the most common and efficient treatment for TMD patients proved by many studies with a successful rate of 70-90%. The following article reviews the different opinions in the treatment of TMD with special attention to hard and soft occlusal appliances. Based upon much research, and despite the many disagreements regarding its efficacy, the hard splint is a customary application which has the most successful outcome in patients who suffer from functional disorders of the masticatory system. The stabilization splint has an important benefit for being a non-penetrating and reversible appliance. However, despite this, the dentist should evaluate the joint or muscular problem, and seriously consider the various available treatments before deciding to use the appliance as a means of treatment.

Assessment of treatment for functional posterior cross-bites in patients at the deciduous dentition phase.

The aim of this study was to clinically assess the results of treatment for functional posterior cross-bites by means of selective grinding in individuals at the deciduous dentition phase over a period of 12 months. From a total of 1,011 children examined in the 2-to-6-year age bracket, 26 with functional posterior cross-bites were selected. The sample was divided into 2 groups of 13 children each, group 1 receiving the treatment proposed and group 2 serving as the control group. Treatment was followed up by exercises designed to alter the children's muscular memory. The results showed that correction of functional posterior cross-bite was achieved for all the children treated, the correction remaining stable 12 months later. No self-correction of malocclusion occurred among the control group.

The use of a deprogramming appliance to obtain centric relation records.

The purpose of this study was to investigate the effect of an anterior flat plane deprogramming appliance (Jig) in 40 subjects for whom centric relation (CR) records were obtained before and after the use of the appliance. Incisal overbite and overjet dimensions and three-dimensional instrument condylar representation using the Panadent condylar path indicator (CPI) were recorded from maximum intercuspation and centric relation. Subjects were assessed subjectively to determine the degree of difficulty manipulating the mandible to obtain the centric relation record. The mean overbite difference from maximum intercuspation (MI) to centric relation without (CR) and with (CRJ) the appliance were statistically significant and decreased 1.58 mm and 2.23 mm, respectively. The mean overjet values from MI to CR and CRJ were statistically significant and increased .44 mm and .57 mm, respectively. Significant differences were determined on the Panadent articulator for the absolute vertical (Z) and absolute horizontal (X) values for centric relation with and without the appliance. The number of subjects who exceeded the threshold values of 2 mm for CPI recordings in either the horizontal or vertical direction was 7 (18%,) from MI to CR and 16 (40%) from MI to CRJ. The Lucia-type jig deprogramming appliance provides a centric relation record with greater displacement from MI than a centric relation record alone. This appliance may be a useful adjunct in a patient where mandibular manipulation in taking a centric relation bite registration is deemed not easy.

The traditional therapeutic paradigm: complete denture therapy.

The art and science of complete dentures for oral restoration has been espoused and debated for over a century. A tradition of clinical mentoring has passed this prosthodontic trust through time to create an educational cycle where the pupil ultimately became the tutor for yet another pupil. Today's clinical techniques and judgments are an amalgamation of these original prosthodontic philosophies. This article will bring forward some procedures for the fabrication of complete dentures for the scrutiny of their scientific bases. Scrutiny does not imply that aspects of therapy not proved in studies of rigorous scientific design are untruths. However, it is incumbent that those aspects of denture therapy regarded as "public domain" by the corpus of the profession be analyzed. It is also incumbent that possible costly or harmful aspects of denture therapy be identified. There is a paucity of "procedural research" in clinical investigations; research that involves performing an invasive or clinician-intensive procedure. This article also discusses the difficulties in performing procedural research as a means of understanding its importance, but also realizing the reasons that this type of research is not prevalent in the dental and health professional literature. The most common types of investigations used to evaluate patient acceptance and function of dentures will also be discussed.

Clinical study of location and reproducibility of three mandibular positions in relation to body posture and muscle function.

Clinical studies have confirmed the adequate reproducibility of both centric occlusion and centric relation when used as reference positions during treatment; however, the reproducibility of the neuromuscular position has been found inadequate. This study evaluated the location and reproducibility of these three mandibular positions in relation to body posture, sitting and supine, and bilateral muscle activity before and after the insertion of a flat mandibular positioning device equilibrated to balance the muscle functions, as shown by two electromyography biofeedback instruments. Intraoral recordings were made in 11 young subjects with complete natural dentition. Acrylic resin clutches that supported a screw point in the maxillary arch and painted glass in the mandibular arch were used and positioned not to interfere with the occlusion. The distances of the screw scratch from two of the edges of the painted glass were used to measure the anteroposterior and mediolateral locations with a micrometer. The reproducibility was evaluated by measuring the scratch surface by measuring the weight of the print cutouts made from photographs of the scratches taken with a stereoscope. The location and reproducibility of centric occlusion and centric relation were not affected by body posture. A more precise posterior neuromuscular position was obtained in the supine position. The insertion of a mandibular positioning device did not affect centric occlusion but gave a more precise centric relation. Neuromuscular position became as precise as centric occlusion and was located anteroposteriorly between centric occlusion and centric relation.

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.

A technique to investigate the three-dimensional kinesiology of the human temporomandibular joint.

Previous kinesiological studies of the temporomandibular joint (TMJ) were based on the motion of only one or two selected points on the mandible (such as the lower central incisor, the mandibular condyle). In the present study, a technique was developed to measure, analyze, and describe the full three-dimensional kinematic characteristics of the TMJ during any mandibular activity. The technique was based on determination of the relative position between the mandible and the temporal bone from measurement of the location of points on light-weight frames rigidly attached through splints to the maxillary and mandibular teeth. An optoelectric kinematic data acquisition system has been used to record the location of these points. The results of the study indicate the following major advantages of this technique over previously reported kinesiological methods: (1) the technique provides a full description of the motion of the mandible with respect to the temporal bone, including all the six degrees of freedom associated with this motion; (2) the description of motion in terms of joint parameters enhances interpretation of the data by clinicians; (3) the motion of any point of interest on the mandible can be easily derived from the data and; (4) the system provides only negligible interference with the natural jaw motion of the subject. It does not require head fixation, does not alter or interfere with the natural occlusion, and its light weight causes only minimal (and negligible) loading of the mandible.