Alteration of functional loads after tongue volume reduction

Functional tooth mobility in young pigs

Mobility is a fundamental characteristic of mammalian teeth, and has been widely used to determine individual tooth prognosis. However, the direction and extent of tooth movement under functional loads are unknown. This study investigated maxillary molar mobility, alveolar bending, and periodontal space (PDL) fluid pressure during mastication and masseter muscle contraction in young pigs, along with PDL space measurements. Twelve three-month-old farm pigs were instrumented with some or all of the following: (1) ultrasonic crystals, one implanted into the pulp chamber of a deciduous maxillary molar and additional crystals glued onto its buccal and palatal alveolar plates; (2) rosette strain gauges affixed to the buccal and palatal of alveolar ridges; (3) a pressure transducer inserted into palatal alveolar bone facing the PDL. Tooth mobility, alveolar bending, and fluid pressure were simultaneously recorded during unrestrained feeding and subsequent masseter muscle stimulation. The PDL widths were measured using micro-CT. The results indicate that during the power stroke of mastication, (1) the molar displaced buccally and apically (192 ± 95 µm) regardless of the side of chewing; (2) compressive bone strain was greater on the buccal than on the palatal alveolar plate; and (3) PDL pressure increased during the power strok (3.63 ± 0.80 kPa). Masseter contraction produced similar results but with generally lower values. The PDL widths were larger than the range of tooth mobility, and showed no correlation with the mobility. Thus occlusal function causes buccal tipping and intrusion of maxillary molars with concomitant compression of the buccal alveolar plate and raised pressure within the PDL space.

Do facial morphology, posture and function change following glossectomy? A systematic review

OBJECTIVES

To systematically investigate and critically appraise the quality of the currently available literature regarding the morphological, postural, and functional changes observed in individuals following glossectomy.

MATERIALS AND METHODS

A search without restrictions in eight databases (including grey literature) and hand searching from inception until March 2018 was performed. Data on morphological, postural, and functional changes after glossectomy were reviewed. Methodological quality was evaluated using the risk of bias in nonrandomized studies of intervention tool.

RESULTS

Out of 835 initially identified unique records, only three articles following patients for 1 year after glossectomy fulfilled the selection criteria. Overall, no significant morphological, postural, and functional changes were observed. Only the distance between the dorsum and the nasal line increased and the freeway space decreased significantly.

CONCLUSIONS

Overall, no significant differences were noted in the medium term, in terms of dentofacial structures adaptation and tongue function following glossectomy. Further research is warranted in order to elucidate the consequences of the altered oral environment.

Osseous Loading by a Volume-Reduced Tongue During Muscle Contractions

PURPOSE

To investigate how tongue volume reduction affects loads on surrounding bone surfaces produced by neuromuscular stimulation of the tongue.

MATERIALS AND METHODS

Of each pair of same-gender minipig siblings, 1 received tongue reduction and 1 underwent sham surgery. Either immediately (acute, 6 pairs) or 1 month (chronic, 5 pairs) after surgery, bone surface and/or suture strains and pressures were recorded from the following locations when the hypoglossal nerve trunk, hypoglossal nerve medial branch, hypoglossal nerve lateral branch, genioglossus, and styloglossus (SG) were electrically stimulated: 1) three rosette strain gauges on the premaxillary palatal surface (premaxilla [PM]) and lingual surfaces of the mandibular alveolus at anterior (mandibular incisor [MI]) and posterior (mandibular molar [MM]) locations; 2) two single-element strain gauges over the palatal surface of the premaxillary-maxillary suture and the lingual surface of the mandibular symphysis; and 3) two pressure transducers on the palatal surface of the maxilla (palatal process) and the lingual surface of the mandibular alveolus (mandibular corpus).

RESULTS

Compared with the sham animals in the acute study, reduction animals showed significantly decreased PM and MI strains, as well as palatal process pressure. With muscle contractions, mandibular symphysis and MM strains were enhanced significantly with a more dorsal orientation. In the chronic study, reduction animals showed decreased PM and increased MM strains. On comparison of chronic versus acute studies, PM, MI, and MM strains under SG stimulation were significantly smaller whereas MM strain was significantly larger under hypoglossal nerve trunk, hypoglossal nerve lateral branch, and SG stimulations.

CONCLUSIONS

Muscle contractions from a volume-reduced tongue produce lower and higher loads in the anterior and posterior mouth, respectively. However, although the effects on reducing loads in the anterior mouth are persisting over time, compensatory load enhancement in the posterior mouth diminishes owing to surgical healing.

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.