Cephalometric and electromyographic study of patients of East African ethnicity with and without anterior open bite.

INTRODUCTION: A review of the literature showed that there are disturbances of muscle activity and tongue function in patients with anterior open bite (AOB). However, most studies have had white subjects, even though open bite is more prevalent in black populations. In this pilot study, we examined jaw muscle activity and tongue pressure in East African black subjects. METHODS: Ten subjects (4 boys, 6 girls; ages, 10.1-13.2 years) were recruited. A cephalometric comparison of subjects with and without AOB was performed. Surface electrodes were placed on the bilateral anterior temporalis, superficial masseter, superior orbicularis oris, and anterior digastric muscles. Electromyograms were recorded at rest, maximal voluntary clenching, chewing, and swallowing. Tongue pressure during rest and swallowing, and maximal bite force were also measured. RESULTS: There was no statistically significant difference between the 2 groups in cephalometric measures (except in amount of open bite and overbite) and maximum bite force. During chewing, both groups showed similar coordinated activity patterns in the muscles, but the AOB subjects tended to show more electromyographic activity in the muscles of the balancing side. During clenching, the AOB subjects exhibited lower electromyographic activity compared with the controls. AOB subjects also had greater anterior tongue pressure during swallowing. Data from tongue pressure at rest were inconclusive. CONCLUSIONS: East African blacks appear to have neuromuscular and skeletal predispositions to AOB, but their vertical incisor relationships are variable. Factors in addition to those investigated might be involved.

Morphologic and histologic outcomes of tongue reduction surgery in an animal model.

OBJECTIVE: To describe the effect of anterior tongue reduction surgery on tongue size, morphology, and histology. DESIGN: Prospective experiment. MATERIALS: Twenty-two 12-week-old Yucatan minipigs. METHODS: Six sibling pairs had tongue reduction (Group B) or sham surgery (Group A), and underwent euthanasia the day of surgery. Five sibling pairs had tongue reduction (Group D) or sham surgery (Group C), and were raised for four weeks. Data collected included changes in tongue morphology, histology, and animal response to surgery. RESULTS: All animals tolerated surgery and maintained their weight. Tongue size was uniformly reduced in all animals as compared to sham surgery. Tongue reduction was stable long term in Group D. All animals had normal wound healing and neurovascular structure preservation. Fibrosis occurred at the repair site. CONCLUSION: Midline tongue reduction resulted in uniform tongue reduction in all dimensions and volume, without damaging neurovascular structures. Localized fibrosis is a sequela of healing.

Functional loads of the tongue and consequences of volume reduction.

PURPOSE: This study was conducted to evaluate functional loads of the tongue on its surrounding bones and investigate how tongue volume reduction affects these loads. MATERIALS AND METHODS: Masticatory bone strains and pressures on facial bones directly contacted by the tongue were measured in 12 (6 sibling pairs) 12-week-old Yucatan miniature pigs. One of each sibling pair underwent surgery to reduce the tongue volume by 23% to 25% (reduction group); the other underwent identical tongue incisions without tissue removal (sham group). Rosette strain gauges were bonded to the palatal surface of premaxilla (PM), the lingual surface of mandibular alveolar bones between the second and third decidious incisors (MI), and below the third decidious molar (MM). Single-element stain gauges were placed across the palatal surface of the premaxillary stuture (PMS) and the lingual surface of the mandibular symphysis (MSP). Pressure tranducers were placed on the hard palatal surface of the maxillary (PAL) and the lingual surface of the mandible (MAN) posterior to the deciduous canine. Animals were allowed to feed unrestrainedly after surgery and device placement. Data from bone strain, pressure, and electromyographic (EMG) activity of bilateral masseter muscles were recorded during natural mastication (pig chow). RESULTS: In the sham animals, the principal bone surface strains were less than 100 microepsilon in all measures. The principal strains were greater compressive than tensile strains at the PM and greater tensile than compressive strains at the MI and MM. Tensile strains were significantly greater at the MM than at the PM (P < .01). Strains were tensile at the PMS and compressive at the MSP, with significantly higher magnitude (> 100 microepsilon) at the PMS (P < .05). Pressures ranged from 2.12 to 8.04 kPa, with higher readings at the MSP compared with the PAL (P < .05). Tongue volume reduction did not affect strain polarity at any site but did diminish principal strain magnitudes significantly at the MI (P < .05). At the PM and MI, the principal tensile orientation was significantly altered from the lateroanterior to the lateroposterior direction (P < .05 to .001). Strains at the MM and MSP showed little change. Compared with the sham animals, tensile strain at the PMS and pressures at the PAL and MAN were decreased by > or = 50% (P < .01). CONCLUSIONS: These results suggest that 1) the tongue produces greater functional loads (strains and pressures) on mandibular lingual surfaces than on maxillary/premaxillary palatal surfaces; 2) tongue volume reduction decreases these loads, specifically those in the anterior mouth; and 3) masticatory loads produced by the tongue on the lingual mandibular and palatal maxillary/premaxillary surfaces are much smaller than those produced by masticatory muscles on the dorsal surfaces of these bones and temporomandibular joint structures.

Roles of intrinsic and extrinsic tongue muscles in feeding: electromyographic study in pigs.

The performance of tongue muscles in various feeding behaviours is not well defined. This study was undertaken to examine the role of the intrinsic and extrinsic tongue muscles during natural drinking, food ingestion and chewing. Ten 12-week-old Yucatan miniature pigs (5 in each gender) were used. Under anesthesia, fine-wire electrodes were inserted into three intrinsic (verticalis and transversus [V/T]; superior and inferior longitudinalis [SL and IL]) and two extrinsic (genioglossus [GG] and styloglossus [SG]) tongue muscles and two jaw muscles (masseter [MA] and anterior digastricus [DI]). Electromyogram (EMG) and jaw movement were recorded and synchronized when pigs were drinking water, ingesting and chewing food freely. Chewing frequency (CF), onset of activation, burst duration and integrated activity (IEMG) were assessed quantitatively, and EMG activities during drinking and ingestion were examined qualitatively. Results indicate that during chewing, the V/T and GG had one phase of activity starting at early jaw opening, and the V/T activity lasted through late of jaw closing. The SL, IL and SG had double phases with the first starting at jaw opening and the second at late jaw closing phases. The three intrinsic tongue muscles and the SG were active during 35-48% of the chewing cycle. IEMG values of the SL, IL and SG of both sides were significantly greater compared to the other muscles (p<0.05-0.01). Both the SL and the IL showed significantly higher activities in the contralateral than ipsilateral sides (p<0.05). The timing sequences of both extrinsic and intrinsic muscles were similar between ingestion and chewing, but amplitudes of the GG and IL were greatly enhanced and those of the MA and SL were reduced during ingestion. The simultaneous activation of the MA, GG and V/T were seen during drinking, along with major activity in the GG and V/T. These results suggested that the majority of activity in the intrinsic and extrinsic tongue muscles occurred during jaw opening and the occlusal phases of chewing. The activity of the GG and IL played a major role during ingestion, whereas simultaneous activation of jaw, extrinsic and intrinsic tongue muscles and major activity in the GG and V/T occurred during drinking.

Tongue deformation, jaw movement and muscle activity during mastication in pigs.

This study was undertaken to address the lack of information about tongue functional deformation in relation to jaw movement and muscle activity. Dimensional changes in tongue anterior and base widths, body length and base thickness were measured using six ultrasonic crystals implanted into the tongue in eight Yucatan minipigs. Jaw movements were captured on videotape and digitized, and electromyography (EMG) of tongue intrinsic (verticalis/transversus [V/T], superior and inferior longitudinalis [SL, IL]), extrinsic (genioglossus and styloglossus [GG, SG) and jaw (masseter and digastricus [MA, DI]) muscles were recorded. Signals from these three sources were synchronized. Tongue dimensions showed stereotyped and rhythmic changes during chewing cycles, with the largest changes in the body length and base thickness of the contralateral (non-working) side. The anterior tongue widened during jaw opening while the tongue base widened and thickened during jaw closing. The body lengthening accompanied base widening and ended at early power stroke, while base thickening lasted through most of the power stroke. Significant associations were found between changes of anterior width, body length and base thickness and integrated EMGs of VT, SL, SG, GG, MA and DI, but not IL. Thus, majority of tongue dimensional expansions occur during jaw closing. Intrinsic tongue muscle activities are not correlated more with tongue dimensional changes than are extrinsic tongue and jaw muscle activities.

Internal Kinematics of the Volume-Reduced Tongue: A Longitudinal Microsonometric Study.

This study examined tongue internal kinematics during feeding over time after its volume reduction. Six ultrasonic crystals were implanted into the tongue to record distance changes in anterior width (AW), bilateral lengths (LENG), posterior thicknesses (THICK), and posterior dorsal (PDW) and ventral (PVW) widths in five sibling pairs of Yucatan minipigs (N = 10). In each pair, one received tongue volume reduction surgery (reduction), and the other had the identical incisions without tissue removal (sham). Functional deformation of the tongue from preimplanted ultrasonic crystals was recorded during natural feeding 1 day before, 7-8, 13-15, and 28-30 days after the surgery. The results revealed that feeding behavior and tongue functional deformation were unchanged over time in the sham pigs. However, at Days 7-8, more frequent and longer ingestion episodes were seen in the reduction as compared with the sham. Moreover, deformational changes in AW and LENG decreased, whereas those in THICK, PDW, and PVW increased significantly (P < 0.001). At Days 13-15, the reduced deformational changes in LENG (P < 0.01) slightly restored, and the increased deformation in THICK (P > 0.05), PDW (P < 0.01), and PVW (P < 0.05) diminished. At Days 28-30, the restoration of AW and LENG continued (P < 0.01-0.05), but previously enhanced deformations in THICK, PDW, and PVW were no longer significantly different from the baseline (P > 0.05). These results suggest that the tongue volume reduction has significant and persistent impacts on feeding behaviors and tongue internal kinematics, and the restoring capacity of internal kinematics in the anterior tongue is limited and incomplete over time.

A digital atlas of ion channel expression patterns in the two-week-old rat brain.

The approximately 350 ion channels encoded by the mammalian genome are a main pillar of the nervous system. We have determined the expression pattern of 320 channels in the two-week-old (P14) rat brain by means of non-radioactive robotic in situ hybridization. Optimized methods were developed and implemented to generate stringently coronal brain sections. The use of standardized methods permits a direct comparison of expression patterns across the entire ion channel expression pattern data set and facilitates recognizing ion channel co-expression. All expression data are made publically available at the Genepaint.org database. Inwardly rectifying potassium channels (Kir, encoded by the Kcnj genes) regulate a broad spectrum of physiological processes. Kcnj channel expression patterns generated in the present study were fitted with a deformable subdivision mesh atlas produced for the P14 rat brain. This co-registration, when combined with numerical quantification of expression strengths, allowed for semi-quantitative automated annotation of expression patterns as well as comparisons among and between Kcnj subfamilies. The expression patterns of Kcnj channel were also cross validated against previously published expression patterns of Kcnj channel genes.

Internal kinematics of the tongue following volume reduction.

This study was undertaken to determine the functional consequences following tongue volume reduction on tongue internal kinematics during mastication and neuromuscular stimulation in a pig model. Six ultrasonic-crystals were implanted into the tongue body in a wedge-shaped configuration which allows recording distance changes in the bilateral length (LENG) and posterior thickness (THICK), as well as anterior (AW), posterior dorsal (PDW), and ventral (PVW) widths in 12 Yucatan-minipigs. Six animals received a uniform mid-sagittal tongue volume reduction surgery (reduction), and the other six had identical incisions without tissue removal (sham). The initial-distances among each crystal-pairs were recorded before, and immediately after surgery to calculate the dimensional losses. Referring to the initial-distance there were 3-66% and 1-4% tongue dimensional losses by the reduction and sham surgeries, respectively. The largest deformation in sham animals during mastication was in AW, significantly larger than LENG, PDW, PVW, and THICK (P < 0.01-0.001). In reduction animals, however, these deformational changes significantly diminished and enhanced in the anterior and posterior tongue, respectively (P < 0.05-0.001). In both groups, neuromuscular stimulation produced deformational ranges that were 2-4 times smaller than those occurred during chewing. Furthermore, reduction animals showed significantly decreased ranges of deformation in PVW, LENG, and THICK (P < 0.05-0.01). These results indicate that tongue volume reduction alters the tongue internal kinematics, and the dimensional losses in the anterior tongue caused by volume reduction can be compensated by increased deformations in the posterior tongue during mastication. This compensatory effect, however, diminishes during stimulation of the hypoglossal nerve and individual tongue muscles.

Effects of tongue volume reduction on craniofacial growth: A longitudinal study on orofacial skeletons and dental arches.

The interaction between tongue size/volume and craniofacial skeletal growth is essential for understanding the mechanism of specific types of malocclusion and objectively measuring outcomes of various surgical and/or orthodontic treatments. Currently available information on this interaction is limited. This study was designed to examine how tongue body volume reduction affects craniofacial skeleton and dental arch formation during the rapid growth period in five 12-week-old Yucatan minipig sibling pairs. One of each pair received a standardized reduction glossectomy to reduce tongue volume by 15-17% (reduction group), and the other had the reduction glossectomy incisions without tissue removal (sham group). Before surgery, five stainless steel screws were implanted into standardized craniofacial skeletal locations. A series of cephalograms, lateral and axial, were obtained longitudinally at 1 week preoperative, and 2 and 4 weeks postoperative. These images were traced using superimposition, and linear and angular variables were measured digitally. Upon euthanasia, direct osteometric measurements were obtained from harvested skulls. Five en-bloc bone pieces were further cut for bone mineral examination by dual photon/energy X-ray absorptiometry (DEXA). The results indicate that: (1) while daily food consumption and weekly body weight were not significantly affected, tongue volume reduction showed an overall negative effect on the linear expansion of craniofacial skeletons; (2) premaxilla and mandibular symphysis lengths, and anterior dental arch width were significantly less in reduction than sham animals at 2 and/or 4 weeks after the surgery; (3) both premaxilla/maxilla and mandible bone mineral density and content were lower in reduction than sham animals, significantly lower in anterior mandible; (4) craniofacial skeletal and dental arch size were significantly smaller in reduction than sham animals, being most significant in the mandibular anterior length and ramus height, the anterior dental arch and midface width. These results suggest that reducing tongue body volume in young animals slows craniofacial skeletal growth and anterior dental arch expansion during rapid growth. The mandible, in particular its symphysis portion, and the anterior dental arch width are most affected. These effects may in part contribute to the decrease of functional loads in the anterior mouth by a volume-reduced tongue.

Internal kinematics of the tongue during feeding in pigs.

Six ultrasonic crystals (Ø2 mm) were implanted into the tongue body to form a wedge-shaped configuration in six 12-week-old Yucatan minipigs. These crystals allow recording of the distance changes in bilateral lengths (RL/LL) and base thicknesses (RT/LT), and anterior (AW) and posterior (dorsal and ventral, PDW and PVW) widths during natural feeding. Results indicated that changes in all measured dimensions were stereotypical with considerable regularity. The greatest dimensional changes during chewing were seen in the AW (33.3%), significantly larger than those in other dimensions (P < 0.05-0.001). During ingestion, change in all widths and thicknesses reduced significantly compared with those during chewing (P < 0.05), but changes in the lengths (RL/LL) were significantly larger than those during chewing (P < 0.01). During drinking, overall dimensional changes reduced and amplitudes were symmetrically distributed in all dimensions. The timing analysis indicated that, during chewing, the reversal of dimensional decrease to increase in the PVW occurred first, followed by those of PDW, AW, RT/LT, and RL/LL (P < 0.05). During ingestion, the AW started widening first. Time sequence of these reversals during drinking was similar to that during chewing, but RT/LT thickening was behind RL/LL lengthening. These results suggested that during natural feeding, regional tongue deformations are rhythmic and stereotypical similar to jaw movement. The reversals of expansion-contraction of various dimensions are not synchronous, but occur in a sequential manner in timing. Tongue internal deformations are task-specific in both timing and amplitude. The dimensional expansions-contractions are dominant in the transverse and sagittal planes during chewing and ingestion, respectively, but are smaller and more symmetrically distributed across various dimensions during drinking.