Initial Mouth Opening Research Articles

Influence of preoperative anatomy and functional status on outcomes after total temporomandibular joint replacement with patient-specific endoprostheses: A retrospective cohort study.

Temporomandibular joint (TMJ) replacement may be indicated for various pathological conditions, and the type of condition can affect the surgical procedure and outcomes. The causes of limited range of motion after alloplastic TMJ replacement have not been extensively studied. The present study aimed to evaluate the impact of preoperative jaw anatomy and functional status on the immediate and long-term outcomes of total TMJ replacement using a two-component patient-specific TMJ endoprosthesis. This retrospective study included 31 patients who underwent total TMJ replacement surgery between 2016 and 2020. The main outcome variable was the maximal incisal opening (MIO) after treatment. Secondary outcome variables included MIO improvement and the presence and type of postoperative complications. The primary predictive variable was the preoperative initial MIO. Secondary predictive variables included sex, age, indications for TMJ replacement, preoperative occlusion, condition of the glenoid fossa and/or condyle, shortening of the mandibular ramus, sagittal mandible position, lateral chin deviation, shape of the coronoid process, and type of surgery. The mean preoperative MIO was 13.0 ±8.0 mm, while the mean MIO 1 month after surgery was 20.6 ±5.5 mm, which was not statistically significant. However, at a later follow-up, functional parameters showed a significant improvement (p = 0.003), with a mean MIO of 32.5 ±5.0 mm 3 years after surgery. Statistical analysis indicated that the initial mouth opening is the strongest predictor of long-term functional recovery after TMJ replacement. Postoperative complications occurred in 4 cases (12.9%) following patient-specific endoprosthesis (PSE) placement. The use of PSEs for TMJ replacement has enabled the restoration of anatomical relationships in complex clinical cases and an improvement in mouth opening. The preoperative MIO was the only factor that significantly influenced long-term functional outcomes.

Captive maturation, breeding and seed production of the brackishwater ornamental fish silver moony,Monodactylus argenteus(Linnaeus, 1758)

Silver moony, Monodactylus argenteus (Linnaeus, 1758), belonging to the family Monodactylidae, has high significance in the ornamental fish industry. The present study provides the details of captive broodstock maturation, induced breeding and larval rearing of this species for the first time. Juveniles were collected from wild and raised to adults in net cages. Female with oocyte diameter =500 µm and oozing males were selected in the sex ratio of 1:2 (female: male) and induced to spawn using a single dose of LHRHa. Spontaneous spawning and fertilization were observed after 36 to 40 hr of hormonal induction. The average fertilization and hatching rates were 83.50 ± 4.37% and 70.83 ± 5.19% respectively. The incubation period was observed to be 18 to 20 hr at a temperature of 29 ± 1.8°C. Newly hatched larvae measured 1,630 ± 0.20 µm in length. Larval rearing was carried out in 500-L circular fibre reinforced plastic tanks using a green water system. Larvae were stocked at 5 L−1 in larval rearing tanks. Initial mouth opening and complete yolk absorption were observed at 48 and 96 hr post-hatching respectively. Larval feeding was done using live feeds, rotifer and Artemia nauplii. Metamorphosis began on 23 dph, and 100% larvae became juvenile on 32 dph with an average survival rate of 49.6 ± 8.73%. These findings on the development of captive seed production of silver moony would pave the way for mass scale production and reduced exploitation of wild stocks.

Conservative management of Oral Submucous Fibrosis in early and intermediate stage

Aims & objectiveTo evaluate the efficacy of combined intralesional injection of Hyaloronidase and Triamcinolone with third molar removal in early and intermediate stage (Stage II & III) of Oral Submucous Fibrosis (OSMF) for improvement in mouth opening and hypersensitivity to food. Study design48 patients in stage II & III OSMF were selected for the study. All the third molars were extracted in each patient followed by 6–8 doses of combined intralesional injection of Hyaloronidase and triamcinolone at 10days interval targeting the fibrotic bands. Mouth opening and improvement in hypersensitivity to food was noted by numerical grading. The patients were followed for one year at regular intervals. The data was expressed as mean±SD, and a probability (p) value of <0.05 was considered significant. ResultsThe initial mouth opening in Stage II patients (n=27) was 30±3.0mm and in Stage III patients (n=21) was 19±3.5mm and the increase in mouth opening at the end of treatment was 11.3±1.9mm and 10.2±2.3mm respectively. The mean improvement in hypersensitivity to food in both the groups was 2.9 and 2.2 respectively. ConclusionThere is significant improvement in grade II patients in mouth opening and hypersensitivity to food. Grade III patients show variable improvement or no improvement wherein surgery becomes the only option. Third molar extraction helps in reducing inflammation and fibrosis in the retromolar region thus easing in mouth opening. This combined approach for moderately staged OSMF can be proposed as a viable conservative modality.

Résultats fonctionnels après reconstruction de l’articulation temporo-mandibulaire par prothèse totale (2e partie)

Temporomandibular joint (TMJ) disorders are usually managed medically. But partial or total reconstruction may be indicated according to the severity and the functional impairment. We assessed the functional results after total TMJ reconstruction using the Biomet Microfixation® prosthesis (Jacksonville, FL, USA). We reviewed the files of patients having undergone reconstruction, between 2009 and 2010, with a total TMJ prosthesis. We analyzed the pre- and postoperative mouth opening, the pre- and postoperative occlusion, pre- and postoperative pain according to a simple spoken scale ranging from 0 (no pain) to 4 (severe pain). Twelve total TMJ prostheses were placed in five women and three men (mean age 49.2 years). Restriction of mouth opening was the first cause of consultation. The etiology was trauma for four patients. Three patients had preoperative malocclusion. Four patients had bilateral reconstruction. Preoperative pain ranged between 2 and 4. The average initial mouth opening was 17.8mm. There was neither infection nor any major complication. No prosthesis was removed. The mean follow-up was 18.5 months. At the end of the study, pain ranged between 0 and 2. All patients with preoperative malocclusion resumed an Angle class I postoperatively. The average postoperative mouth opening was 39.5mm. Total TMJ reconstruction with the Biomet Microfixation® prosthesis improves mouth opening and reduces pain.

Realization of Masticatory Movement by 3-Dimensional Simulation of the Temporomandibular Joint and the Masticatory Muscles

Masticatory muscles are closely involved in mastication, pronunciation, and swallowing, and it is therefore important to study the specific functions and dynamics of the mandibular and masticatory muscles. However, the shortness of muscle fibers and the diversity of movement directions make it difficult to study and simplify the dynamics of mastication. The purpose of this study was to use 3-dimensional (3D) simulation to observe the functions and movements of each of the masticatory muscles and the mandible while chewing. To simulate the masticatory movement, computed tomographic images were taken from a single Korean volunteer (30-year-old man), and skull image data were reconstructed in 3D (Mimics; Materialise, Leuven, Belgium). The 3D-reconstructed masticatory muscles were then attached to the 3D skull model. The masticatory movements were animated using Maya (Autodesk, San Rafael, CA) based on the mandibular motion path. During unilateral chewing, the mandible was found to move laterally toward the functional side by contracting the contralateral lateral pterygoid and ipsilateral temporalis muscles. During the initial mouth opening, only hinge movement was observed at the temporomandibular joint. During this period, the entire mandible rotated approximately 13 degrees toward the bicondylar horizontal plane. Continued movement of the mandible to full mouth opening occurred simultaneously with sliding and hinge movements, and the mandible rotated approximately 17 degrees toward the center of the mandibular ramus. The described approach can yield data for use in face animation and other simulation systems and for elucidating the functional components related to contraction and relaxation of muscles during mastication.

TheraBite exercises to treat trismus secondary to head and neck cancer

PurposeThe aim of this study was to evaluate the effect of TheraBite exercises on mouth opening and to analyze factors influencing this effect in a patient record evaluation.MethodsEffect of exercises with a TheraBite to treat trismus was evaluated in 69 head and neck cancer patients of two university medical centers. Mouth opening was measured as interincisal distance in millimeters. Patient, tumor, and treatment characteristics were analyzed for their relationship with change in mouth opening. Variables univariately associated (p ≤ 0.05) with change in mouth opening were entered in a logistic regression analysis as possible predictors for an increase in mouth opening of the smallest detectable difference of 5 mm or more.ResultsMean initial mouth opening was 22.0 mm (SD 6.4); mean increase in mouth opening was 5.4 mm (SD 5.7). “Chemotherapy”, “medical center”, and “time from oncological treatment to start exercises” were significantly associated with an increase in mouth opening. In the logistic regression analysis, “medical center” (β = 1.97) and “time from oncological treatment to start exercises” reduced the odds of reaching an increase in mouth opening of 5 mm or more, β = −0.11 per month.ConclusionsAfter TheraBite exercises, mouth opening increased averagely with 5.4 mm. The odds of an increase in mouth opening of 5 mm or more reduces if the time from oncological treatment to start exercises lengthens, corrected for the effect of medical center.

Morphological aspects of feeding and improvement in feeding ability in the early larval stages of red sea bream Pagrus major

: The present study examined the appearance, ossification and growth of the bones that form the oral cavity in early larval stages of laboratory reared red sea bream (Pagrus major) for 380 h after hatching. The fundamental elements of the oral cavity appeared 11 h after initial mouth opening (HAMO). Development in the red sea bream, based on the osteological development of the feeding apparatus, was divided into three phases following the first feeding (24 HAMO; mean total body length 3.3 mm). The first phase was the early sucking phase (24 to 80–100 HAMO; approximately 3.9 mm), during which the head and bones increased in size. The intensified sucking phase (to 200–220 HAMO; approximately 4.9 mm) was defined by the appearance of new structural elements and a continued enlargement of the head and bones. Finally, during the transition phase (beyond 300 HAMO; approximately 5.6 mm), larvae used grasping as well as sucking to feed, new elements appeared, ossification began, size increased and teeth were acquired. As the larvae advanced through these three phases, the ability to feed by sucking was enhanced by the appearance and growth of new bones. The developmental phases appear to be linked to the transition from endogenous to exogenous nutrition resources under laboratory rearing conditions and to diversification in the size and components of wild food organisms.

The riddle of the large loss in bite force after fast jaw-closing movements.

In unloading experiments (in which the resistance to a forceful static bite is suddenly removed), it is shown that the residual bite force (when the jaw system is arrested shortly after the unloading) is remarkably small. For example, of a 100-N initial bite force, only 18 N is left after a jaw travel distance of 5.0 mm. The present experiments were designed to study whether the magnitude of the low residual bite force is dependent on the initial bite force, the initial degree of mouth opening, and the distance of jaw travel. Furthermore, we analyzed whether the low magnitude of the residual force can be attributed to reflex events of the jaw muscles or to the force-length properties of the jaw-closing muscles. It was found that the residual forces are largely dependent on the distance of jaw travel and are barely sensitive to variations in initial mouth-opening. The relative residual forces are independent of the magnitude of the initial bite force. The maximum residual forces are on the order of 25% of the initial bite force after a jaw travel of 4.5 mm. The low values of the residual forces cannot be attributed to reflex events, because it took about 80 ms for the masseter muscles to decrease their force to a 50% level after their excitation was switched off. Furthermore, it was shown that the force-length properties of the jaw-closing muscles are not responsible for the small values of the residual forces, since over the trajectories used in the present experiments, the sarcomere lengths of the jaw-closing muscles were beyond their optimum. It is suggested that the low residual forces are brought about by (1) a non-uniform sarcomere behavior of the jaw-closing muscles when contracting, or (2) a long-lasting change in the myofilament system of the closing muscles induced by the sudden shortening of muscle fibers.

Impact Velocities of the Teeth after a Sudden Unloading at Various Initial Bite Forces, Degrees of Mouth Opening, and Distances of Travel

A potentially dangerous situation arises when an individual bites on hard and brittle food which suddenly breaks, since the impact velocity of the lower teeth onto the upper teeth after the food is broken can be high and may cause dental damage. The present experiments were designed to study the magnitude of the impact velocity after a sudden unloading at various initial bite forces, degrees of mouth opening, and distances of travel. Subjects were asked to perform a static biting task during which the resistance to the bite was suddenly removed. The upward mandible movement was arrested after a certain distance. The velocity of the lower teeth at impact was calculated just before the mandible came to a standstill in combinations of 4 different bite forces (100, 80, 60, and 40 N), 4 different initial degrees of mouth opening (33.5, 30.5, 27.5, and 24.5 mm), and 3 different distances of travel of the mandible (4.5, 3.0, and 1.5 mm). We found that the bite force rapidly declined after the unloading, resulting in a small impact velocity of the lower front teeth. This impact velocity largely depended on the magnitude of the initial bite force and the distance traveled; it was barely sensitive to variations in degree of initial mouth opening. The maximal velocity of the lower teeth was 0.43 m/s (at an initial bite force of 100 N). This maximum was reached after a distance of travel of about 4 mm in 12 ms. The data suggest that the rapid decline in bite force coupled with a limitation of impact velocity is due to the force-velocity properties of the active jaw muscles and is not caused by neural control.

Why is grouper larval rearing difficult?: an approach from the development of the feeding apparatus in early stage larvae of the grouper,Epinephelus coioides

The osteological development of elements forming the oral cavity was examined in early stage larvae of the grouper,Epinephelus coioides, from hatching to 242.5 hours after hatching. By the time of initial mouth opening, at 54 hours after hatching, the fundamental elements, composed of the trabecula, some components of the lower branchial and hyoid arches, the quadrate and symplectic-hyomandibular cartilages, maxilla and Meckel's cartilage, had appeared. No further elements were observed until 165 hours after initial mouth opening, except some components in the lower branchial arch and head region. The appearance of new elements and initial ossification of existing cartilage occurred thereafter, but all elements related to feeding either had not appeared or had not started ossifying until 188.5 hours after initial mouth opening. Based on the morphology and developmental modes of these elements, the feeding mode of grouper larvae was considered to be “sucking/grasping.” However, the appearance and ossification of elements occurred slowly, with no transitional phase from sucking to grasping modes of feeding being observed during the study; such delayed development of the feeding-related bony elements was considered to be a cause of the difficulty in rearing early stage grouper larvae.

Morphological aspects of feeding and improvement in feeding ability in early stage larvae of the milkfish,Chanos chanos

The osteological development of elements comprising the oral cavity and fins was examined in early stage larvae of laboratory-reared milkfish,Chanos chanos, from hatching to 200 hours after hatching. Fundamental elements of the oral cavity had developed by the time of initial mouth opening, 54 hours after hatching. The oral cavity was long and cylindrical, with a short, robust Meckel's cartilage, and robust quadrate and symplectic-hyomandibular cartilages. The initial ossification of existing elements and addition of new elements occurred between 120–146 hours after initial mouth opening (HAMO), whereas the cartilaginous basihyal and caudal fin-supports appeared at 37.5 and 61.5 HAMO, respectively. Based on the morphology and developmental patterns of characters examined in this study, the feeding mode of early stage larval milkfish was considered to be “straining,” with an improvement in feeding ability occurring between 120–146 HAMO.

Osteological development of the feeding apparatus in early stage larvae of the seabass,Lates calcarifer

The osteological development of the feeding apparatus was examined in early stage larvae of laboratory-reared seabass,Lates calcarifer. At initial mouth openings 40 hours after hatching, the larvae were equipped with the fundamental elements forming the oral cavity, such as the trabecular roof, the lower branchial and hyoid arches forming the floor, the quadrate and symplectic-hyomandibular cartilages making up the sides, and the maxilla and Meckel's cartilage bordering the jaws. The cleithrum appeared almost simultaneously. The mechanics of creating a negative pressure in the oral cavity, which results in a “sucking” mode of feeding, were elucidated from these elements. During a period from 50–60 to 100–110 hours after initial mouth opening (HAMO), new elements such as the premaxilla and jaw teeth appeared, and the ossification of existing elements started. The new elements apparently enabled the larvae to “grasp” food organisms, in addition to the already existing and increasing sucking ability, from 100–110 HAMO.