Vertical Jaw Research Articles

Comparative Assessment of Various Cephalometric Parameters Used for Determining Vertical Skeletal Dysplasia.

The aim of the study is to assess and correlate the different cephalometric parameters used to determine the vertical jaw relationship. Cephalometric radiographs from 148 patients were assessed and comparison was made using all eight parameters. Statistical analysis was performed using mean, standard deviation and coefficient of variance. A correlation was found between different variables using the Pearson's correlation coefficient. In the entire sample, the basal plane angle displayed the most variable distribution, while the R angle displayed the most homogeneous distribution. There was a significant correlation found between the Jarabak ratio, Steiner's mandibular plane angle (SN-GoGn), Frankfort mandibular plane angle (FMA), R angle, and DR angle. There was a moderate to weak correlation between the Y-axis, basal plane angle, and facial height ratio with other skeletal analyses. Among angular variables DR angle, R angle, SN-GoGn and FMA can be used and among linear variables Jarabak ratio could be used reliably to assess the growth pattern. It suggested that in order to obtain an accurate evaluation of the vertical jaw relationship, a variety of measurements should be combined.

HYOID BONE POSITION AND PHARYNGEAL SPACE IN DIFFERENT VERTICAL JAW DYSPLASIAS

Background: The position of hyoid bone and pharyngeal space is affected by various factors. One of the factors is vertical malocclusion. This study aimed to evaluate the position of hyoid bone and pharyngeal space in different vertical jaw dysplasias. Methods: In total 102 lateral cephalograms of 70 females and 32 males in the age range of 15 to 25 years were selected from records of the patients who visited to the Department of Orthodontics and Dentofacial Orthopedics, UCMS College of Dental Surgery Bhairahawa, Nepal. For the vertical plane of the face, sample was divided into three groups based on Frankfort mandibular plane angle: Group 1 (n=34; normal growth pattern) group 2 (n=34; horizontal growth pattern) and group 3 (n =34; Vertical Growth Pattern). Results: The anteroposterior position of the hyoid bone was found significantly forward in horizontal grower compared with normal and vertical grower (p<0.05). There was no statistically significant difference in vertical positioning of the hyoid bone among the patients with different growth patterns. There was no statistically significant difference in the axial orientation of the hyoid bone in patients with different growth patterns. Upper pharyngeal space was significantly different in different facial skeletal patterns (p=0.019) whereas, lower pharyngeal space had no significant association. Conclusions: The position of the hyoid bone in horizontal growth pattern group was more anterior than the vertical growth pattern group. The upper pharyngeal space was found narrower in vertical growth pattern than horizontal and normal growth patterns.

Assessment of vertical jaw relationship by R angle- A cephalometric analysis

The norms of the "R" value may not be extended for other regional populations because they are based on the South Indian population group. Therefore, the goal of the current study is to determine the mean value and standard deviation for R angle in a population of North Indian suburbs for subjects with horizontal, average, and vertical growth patterns, as well as to assess its correlation with other variables used to gauge vertical discrepancy.The current cross-sectional study was carried out at the Swami Devi Dyal Dental College and Hospital, Barwala, Distt. Panchkula (Haryana), Department of Orthodontics and Dentofacial Orthopaedics, among 90 participants between the ages of 18 and 26 years having their pretreatment records. The parameters used in the study are R angle, Frankfort Mandibular Angle, Y- axis (Down’s Analysis), Facial axis, SOP, SNO, SNPP, MMA. The ratios analyzed in the study are Jarabak Ratio, Facial index, LAFH ratio, skeletal, LAFH, Soft tissue. The results of the study showed that high correlation was found between R angle and LAFH (Skeletal), Y Axis, Facial Axis, FMA, SNMP, Sum of posterior triangles (SOP), Maxillomandibular plane angle (MMA), SN to palatal plane angle (SNPP). A strong negative correlation was found between R angle and Jarabak ratio and facial index.There are many cephalometric parameters accessible, however not all of them point towards a certain pattern. In an effort to get around the difficulty of correctly and quickly identifying landmarks, the "R" angle was added.

Exploring the Validity of an Optoelectronic Integrated Cone Beam Computed Tomography Jaw Tracking System.

Jaw motion tracking functionalities of cone beam computed tomography (CBCT)-scanners can visualize, record, and analyze movements of the mandible. In this explorative study, the validity of the 4D-Jaw Motion module (4D-JM) of the ProMax 3D Mid CBCT scanner (Planmeca, Helsinki, Finland) was tested in vitro. The validity of the 4D-JM was accepted if values differed less than 0.6 mm (three voxels sizes) from the gold standard. Three dry human skulls were used. CBCT scans, the gold standard, were taken in eight jaw positions and exported as three-dimensional (3D) models. Individualized 3D-printed dental wafers ensured the correct positioning of the mandible. Jaw positions were recorded with the 4D-JM tracking device and exported as 3D models. The coordinates of six reference points for both superimposed 3D models were obtained. The differences in the x, y and z-axis and the corresponding vector differences between gold standard 3D models and 4D-JM models were calculated. For the mandible 10% and for the maxilla 90% of the vector differences fell within 0.6 mm of the gold standard. With an increasing vertical jaw opening, larger differences between the gold standard and the 4D-JM 3D models were found. The smallest differences of the mandible were observed on the x axis. In this study, the 4D-JM validity was not acceptable by the authors' predefined standards.

Skeletal and dentoalveolar effects of class II malocclusion treatment using bi-maxillary skeletal anchorage: a systematic review

BackgroundThe goal of this systematic review was to assess the available evidence regarding the skeletal and dentoalveolar effects of bi-maxillary skeletal anchorage devices (BMSADs) used in treating growing class II malocclusion patients.MethodsA comprehensive search was conducted on PubMed, Scopus, Science Direct, Web of Science, Cochrane, and LILACS up to November 2021, which was augmented by a manual search. The studies included were clinical trials (RCTs) and/or follow-up observational studies (retrospective and prospective). The outcomes of interest were the skeletal, dentoalveolar, and occlusal treatment-induced changes obtained from pre- and post-cephalometric measurements. The risks of bias of the included studies were assessed using an assessment tool from previous publications.ResultsOut of 742 screened articles, only 4 were eligible and thus included in the qualitative synthesis. They showed a moderate overall risk of bias. The results are presented as mean changes in both the study and control groups. All studies reported retrusion of the maxillary base and advancement of the mandible (meaning reduced ANB angle). Three of the included studies reported an increase in the vertical jaw relation, which was contrary to what the fourth study reported. Three studies reported an increase in the maxillary incisors’ inclination or position, while one study reported their retroclination. Proclination of the mandibular incisors happened in two studies, whereas the other two studies reported retroclination. The overjet was reduced in all included studies.ConclusionApart from the protrusive effects on the mandible, retrusive effects on the maxilla, and the consequent reduction of the overjet, BMSADs results in inconsistent skeletal and dentoalveolar effects. However, the current evidence is limited due to the variability in the biomechanics of the intermaxillary components, type of anchorage, and comparable groups in the included studies. Further RCTs with more standardized methodologies are highly encouraged.Clinical relevanceBMSADs (using miniscrews or miniplates on both jaws) induces more skeletal than dentoalveolar effects. However, this must be practiced with caution, based on the benefit to risk (surgical insertion) ratio, and the limited evidence available in hand so far.Registration The protocol for this systematic review was registered at the International Prospective Register of Systematic Reviews (PROSPERO, No.: CRD42020199601).

Changes in the occlusal function of orthognathic patients with vertical malformations after combined orthodontic surgical therapy: a prospective clinical study

The aim of this study was to assess the changes in occlusal patterns during combined surgical and orthodontic therapy in patients with vertical jaw malformations. Twenty-six orthognathic patients (18 female, eight male; median age 25 years, interquartile range 11.5 years) and 10 control patients (five female, five male; median age 29.8 years, interquartile range 13.5 years) recruited from neutral configured patients attending the Department of Orthodontics, were investigated. Based on cephalometry, the patients were grouped into vertical skeletal configurations of either open, deep, or natural bite cases. Registrations of the occlusal contacts were taken using a digital occlusal sensor immediately before surgery and at 9 months after the surgical intervention. Before the intervention, open and deep bite patients showed significantly less efficient occlusal patterns than the untreated controls regarding total tooth contact (P < 0.001), time of occlusion (P = 0.002), occlusal asymmetry (P = 0.001), anterior tooth contact (P < 0.001), and posterior tooth contact (P < 0.001). After surgery, the parameters in the deep bite patients were similar to those in the controls; however, in open bite patients, total tooth contact (P = 0.003), occlusal asymmetry (P = 0.011), and posterior tooth contact (P = 0.035) differed significantly. In conclusion, combined orthodontic and surgical correction of vertical malocclusions was found to improve occlusal function in patients with deep bite to the level of controls.

Craniofacial changes from 13 to 62 years of age.

SummaryBackgroundIn long-term studies of orthodontic, orthognathic, and prosthodontic treatments, control subjects are needed for comparison.ObjectivesTo study the craniofacial (skeletal, soft tissue, and dental) changes that occur in untreated subjects with normal occlusion between 13 and 62 years of age.Materials/MethodsThirty subjects with a Class I normal occlusion and harmonious facial profile were studied. X-ray examinations were performed at 13 (T1), 16 (T2), 31 (T3), and 62 (T4) years of age, and data were obtained from cephalograms. In total, 53 angular and linear parameters were measured using superimposition-based and conventional cephalometric methods to describe the craniofacial changes.ResultsThe jaws showed significant anterior growth from T1 to T2, and significant retrognathism from T3 to T4. The anterior face height and jaw dimensions increased significantly until T3. Significant posterior rotation of the mandible and opening of the vertical jaw relation, in addition to significant retroclination of the incisors and straightening of the facial profile, were found from T3 to T4.LimitationsGiven the small sample size at T4, it was not possible to analyse the gender dimension.Conclusions/ImplicationsCraniofacial changes continue up to the sixth decade of life. These changes are consistent, albeit to a lesser extent, with the adolescent growth patterns for most of the studied parameters, with the exceptions of incisor inclination, sagittal jaw position, vertical jaw relation and inclination, and posterior face height.

Canine Rise Method: A Conservative Approach for Worn Teeth Rehabilitation with Different Adhesive Restorative Materials

Background In this article, two cases with generalized dental wear and four cases with localized dental wear are reported. In some of the cases, the worn teeth were restored with direct composite techniques with no mock-up and articulator mounting according to the canine rise method. This method is used without any change in the intercuspation of posterior teeth without a muscle relaxation appliance. It introduces a stable occlusal condition that can alter neuromuscular reflex activity, leading to improvements in certain muscle pain disorders. It is also used to protect the teeth and supporting structures from abnormal forces that might create a further breakdown and/or tooth wear. Methods The first step of treatment in all the cases was a composite build-up for maxillary and mandibular canines to restrict and guide the horizontal and vertical jaw movements and create adequate space for restorations. The second step was the placement of direct or indirect restorations on upper and lower anterior teeth efficiently and accurately. Results This method enhanced the esthetic outcomes in a conservative approach with no reduction in tooth material or time-consuming treatments. Conclusions This technique can be suggested for the treatment of worn teeth in patients with Angle's Cl I and Cl II classifications of malocclusion based on the follow-up results. It is not applicable for the treatment of worn teeth in patients with Angle's class III because occlusion is reversed, and canine teeth do not have guidance role. Practical Implications. This method significantly reduces the overall treatment time, and additional steps are required to restore the worn-out teeth and/or occlusion using the canine rise method.

Neutral Zone: Concept and Technique Application for Managing Severely Resorbed Mandibular Ridges – A Case Report

Abstract: Full dental prosthesis rehabilitation on flat mandibular ridge has been a difficult case for clinicians for a long time. A huge resorption of mandibular ridge results in inadequate retention, and tounge muscle pressure, as well as lip and cheek muscles, causing a decrease in denture’s stability and retention. Neutral zone is a potential area or position where lips and cheek on one side, and tounge on the other side have balance pressure. We reported a 60-year-old male patient with chief complaints of difficulty in mastication, and loose upper and lower dentures. He also complained of denture moving during swallowing and speaking. In case management, the aim was to acquire optimum stability of the denture and arrangement of the mandibular teeth in full dental prosthesis guided by using the neutral zone. Preliminary impression was done by using alginate, then, horizontal and vertical jaw relation was recorded by using bite rim. Suction method impression technique was used to acquire functional impression. Lower denture teeth arrangement adapted the result of neutral zone impression. Acrylic denture was being contoured to adjust the natural anatomy of the oral cavity. In conclusion, the patient got a new full denture with maximum retention and stability while speaking as well as masticating. This article discussed about making of full dental prosthesis with pressure point on neutral zone impression technique on flat mandibular ridge caused by huge resorption.Keywords: flat mandibular ridge; denture stability; neutral zone; impression technique

Correlation between symphyseal morphology and mandibular length in class 1 malocclusion between males and females: A radiographic study

Mandibular symphysis (MS) morphology is a valuable diagnostic and treatment-planning tool in orthodontics. MS is affected by a number of factors that include neuromuscular factors, vertical jaw relationships, inclination of lower incisors and genetic factors among others. 80 lateral cephalograms (40 – males and 40 – females) were used in the study and mandibular lengths (Schwarz analysis) were measured for males and females separately. Pearson correlation coefficient showed no statistically significant correlation between symphyseal morphology and mandibular length both in males and females. The inter-examiner reliability (IER) showed Cronbach’s Alpha for mandibular length shows a value of .70 implying good agreement. The study concludes there is no correlation between mandibular length and symphysis morphology. Although sexual dimorphism exists.

Development of the Sakiika transport test: A practical screening method for patients with oral-phase dysphagia.

This study aimed to develop a simple screening test for mastication, "the Sakiika (squid jerky) transport test (STT), which evaluates the vertical jaw movement coordinated with the lateral tongue movement during stage I transport, and investigate the possibility of its clinical application. The study included 73 people with dysphagia (mean age, 78.5 ± 7.8 years; median age, 79.0 years; interquartile range, 75.0-84.0). The STT evaluated the ability of a participant to transport a piece of squid jerky placed on the midline of the tongue to the molar region. The STT score was defined as the number of vertical jaw movements occurring as the tongue transported food to the molars. A cutoff value was set by comparing the STT scores with masticatory function evaluated via a videofluoroscopic swallowing study and with food texture evaluated using the Food Intake LEVEL Scale (FILS). The STT scores counted by the two examiners had a κ coefficient of 0.79, indicating good reliability. The STT score was significantly associated with both the presence of masticatory movement ( p = 0.019) and food texture classified by FILS ( p = 0.032) at cutoff value of "3" (3 vertical movements). The STT showed 62% sensitivity and 75% specificity for masticatory movements. The STT could be a useful screening test to assess the presence or absence of food transportation to the molars for mastication in older patients with dysphagia. In addition, the STT could be useful in identifying the need to modify food texture to meet functions.

The relationship between three-dimensional craniofacial and upper airway anatomical variables and severity of obstructive sleep apnoea in adults.

The aim of this study was to evaluate the relationship between three-dimensional craniofacial and upper airway anatomical variables and severity of obstructive sleep apnoea (OSA) using cone beam computed tomography (CBCT). This was a prospective observational study, consisted of 95 adult OSA whose polysomnography and CBCT were available. Three-dimensional craniofacial and upper airway anatomical analysis were performed using 12 CBCT variables, including sagittal and vertical jaw relationships, maxillary width, the volume, length and minimum axial area of upper airway. The severity of OSA was evaluated through the apnea-hypopnea index (AHI). A hierarchical regression was performed to analyze the relationship between OSA severity and craniofacial and upper airway anatomical variables after controlling patients' demographic characteristics (gender, age, and BMI). After controlling patients' gender, age, and BMI, individual CBCT variables including MAA, V-RPA, L-RPA and Go-Me were related to AHI. The final hierarchical regression model with demographic variables in Step 1 and CBCT variables (MAA, L-RPA and Go-Me) in Step 2 indicated that CBCT variables added additional explanatory power for AHI (ΔF(3,88) = 5.176, P = 0.002). Among these variables, L-RPA and Go-Me were statistically significant (P < 0.05). The OSA severity was expressed by AHI alone. Three-dimensional craniofacial and upper airway morphology played an essential role in OSA severity. The most relevant anatomical characteristic with OSA severity were the length of retropalatal airway and mandibular body, which could be used to recognize severe OSA patients and as estimators for selecting the most appropriate treatment modality for OSA patients.

Predictability of skeletal sagittal and vertical jaw relationship with its correlation to cervical vertebral morphometry and cervical spine inclination

The cervical vertebra and its relation to maxilla and mandible is of particular interest to orthodontist due to their correlated developmental and anatomical relationship. The aim of the study is to evaluate and correlate the relationship between cervical vertebral morphology and cervical spine inclination with skeletal sagittal jaw relationship and growth pattern for an individual. Cephalogram of 30 subjects was divided in 3 groups based on ANB angle. All the craniofacial and craniocervical landmarks that are required to be analysed were recorded and it was concluded that class III patients had more posterior inclination of dens axis of CV2 but straighter spine inclination on subsequent arches. EVT/VER values indicated more enhanced curvature of vertical column in class II and class III patients. Morphological assessment of CV1SL & CV1HT revealed significantly less measurements in Class III that among class I and II subjects. CV2BL measurement in class II & III was significantly more than class. CV3Sl was significantly more in class III and CV3BL was significantly less in class II.

Transferring occlusal vertical dimension in full arch implant prosthesis: A review

The maxillo-mandibular relationship record is a critical step to establish occlusion in implant supported full mouth rehabilitation involving fixed or removable prosthesis. The definitive implant casts have been articulated by several techniques at optimum occlusal vertical dimension (OVD) in the correct centric relation (CR) in edentulous patients receiving implants. Newer methods have been discussed for transferring vertical jaw relation that have claimed to reduce chair side time, establish accurate records and increase comfort for both, the patient and the clinician. The various techniques are, stabilized record bases with occlusal rims screwed in or supported by healing abutments, plastic sprues reinforced by acrylic record base, duplicate denture, relining existing denture, use of buccal index of existing denture and use of silicone cones. Thus, a review of the various techniques available to transfer these records onto the articulator is enlisted, from which the clinician is free to choose the technique most feasible.

Dental and dentoalveolar dimensions in individuals with osteogenesis imperfecta

Objective This cross-sectional study compared tooth and dental arch dimensions of individuals with Osteogenesis imperfecta (OI) and healthy controls. Material and Methods The 37 OI patients and 37 controls were aged 10 to 74 years. Mesio-distal tooth size, dental arch dimensions, and palatal height were measured from dental models. The differences between the patient and control groups were analysed statistically with a t-test, chi-square test, and Mann–Whitney U test. Results The average mesio-distal tooth size of individuals with OI was smaller by 0.1 to 0.8 mm, corresponding to 1.4 to 7.3% of the size of the tooth. The patients and controls showed similar anterior-posterior lengths of maxillary and mandibular arches. The OI patient group exhibited increasingly wider maxillary dental arches posterior to the canines and a shallow palate. Conclusions Reduced tooth size is a developmental feature of OI and a shallow palate a characteristic possibly associated with previously documented imparity of vertical jaw development. Observed posterior widening of the dental arches may follow from altered tongue position. Smaller tooth size can be favourable from orthodontic point of view in alleviating crowding, but it might further predispose to fracturing of teeth which is a considerable risk associated with dentine abnormality. The shallow jawbones may initiate development of posterior open bite, rare in general population but relatively often encountered in OI.

Scandcleft trial of primary surgery for unilateral cleft lip and palate: Craniofacial cephalometrics at 8 years.

The Scandcleft trial is a randomized controlled trial that includes children with unilateral cleft lip and palate where registrations are standardized and therefore provides the opportunity to describe craniofacial characteristics in a very large sample of patients. The aim of this study was to describe craniofacial growth and morphology in a large study sample of 8-year-old children with unilateral cleft lip and palate (UCLP); before orthodontic treatment and before secondary alveolar bone grafting; and to compare the cephalometric values with age-matched non-cleft children from previous growth studies to identify the differences between untreated cleft- and non-cleft children. There are 429 eight-year-old UCLP patients in the Scandcleft study group. A total of 408 lateral cephalograms with a mean age of 8.1 years were analysed. Cephalometric analyses were performed digitally. The results from three previously published growth studies on non-cleft children were used for comparison. Cephalometric analyses showed a large variation in craniofacial morphology among the UCLP group. In general, they present with significant maxillary retrusion and reduced intermaxillary relationships compared to the age-matched non-cleft children. In addition, the vertical jaw relationship was decreased, mainly due to decreased maxillary inclination. The upper and lower incisors were retroclined. It can be expected that these differences will increase in significance as the children age. Results from this study provide proposed norms for the young UCLP before any orthodontic treatment and can be valuable for the clinician in future treatment planning. ISRCTN29932826.

Method and accuracy of determining the jaw position of repositioning splint with the aid of digital technique

Objective To establish the workflow of determining the jaw position of repositioning splint with the aid of digital technique, and to evaluate the accuracy of this workflow and compare the accuracy of raising different vertical dimensions in vitro. Methods A volunteer was recruited. The data of full-arch scans, cone beam computed tomography (CBCT) image and ultrasonic jaw motion tracking of the volunteer were acquired. The full-arch scans were merged with the CBCT image, which were then matched to the jaw motion tracking reference system. The jaw position of repositioning splint was determined when the anterior teeth opening was 3 mm and the condyle was in centric relation of the fossa in the sagittal plane. A digital repositioning splint was designed in the software based on virtual articulator and fabricated with additive manufacturing technique. After the splint was tried in, another CBCT image was taken and a qualitative analysis was conducted to compare the position of condyle between these two CBCT images. In the in vitro study, standard dental plaster casts with resin ball markers attached to the base were mounted onto a fully adjustable articulator in the intercuspal position. The dental casts were scanned by an extraoral scanner to establish digital models. The ultrasonic jaw motion tracking device was used to obtain simulated jaw movements on the articulator, which was repeated for three times. The digital models and data of jaw movements were merged in one coordination with the aid of bite forks. The jaw position of repositioning splint was determined by adjusting data of jaw movements, each of which was used to determine three vertical jaw positions 4 mm, 5 mm, and 6 mm with the horizontal jaw position of protrusion 2 mm. The virtual articulators with differently adjusted jaw movements were applied in designing repositioning splints, and the final repositioning splints and virtual jaw relationships were exported in STL format. Then the repositioning splints were fabricated with additive manufacturing technique and tried in plaster casts on the mechanical articulator, which were scanned and the jaw relationships on the mechanical articulator were exported later. The virtual jaw relationships and scanned jaw relationships were registered according to lower models and displacement of upper models was calculated. Ball markers were fit to acquire the coordinates of centers and absolute difference values of centers along three coordinating axes X, Y, and Z were calculated. One-way analysis of variance was conducted using SPSS 18.0 software to compare deviations of the three different vertical jaw relationships in two-side test and the significance level was 0.05. Results With the aid of multi-source data fusion and individualized jaw motion, the clinical workflow of determining jaw position of repositioning splint was preliminarily established. The designed jaw position was realized on the right and the condyle was more inferior than the designed position on the left. Both displacement of the upper models and absolute difference values of centers showed no significant differences (P>0.05) in different vertical jaw dimensions. The displacement of the upper models was (0.25±0.04) mm. The absolute difference values of centers along the three coordinating axes X, Y, and Z were respectively (0.08±0.01) mm, (0.30±0.02) mm, and (0.21±0.04) mm. Conclusion A novel method of determining the jaw position of repositioning splint with the aid of digital technique is established. It is proved to be feasible by try-in after multi-data fusion, computer-aided design and computer-aided manufacturing. As is shown in vitro, it is accurate to apply this method in adjusting jaw position. Further clinical trial will be designed to evaluate its clinical effect.

Functional Analysis of Rhythmic Jaw Movements Evoked by Electrical Stimulation of the Cortical Masticatory Area During Low Occlusal Loading in Growing Rats.

The maturation of rhythmic jaw movements (RJMs) and related neuromuscular control has rarely been studied in animals, though this process is essential for regulating the development of stomatognathic functions. Previous studies have shown that occlusal hypofunction during growth alters masticatory performance. However, little is known about patterns of cortically-induced RJMs under conditions of soft-diet feeding during development. The aim of this study is to clarify the effect of low occlusal loading on the pattern of cortically induced RJMs and related neuromuscular responses in growing rats. Sixty-four 2-week-old male albino Wistar rats were randomly divided into two groups and fed on either a normal diet (control) or soft diet (experimental) soon after weaning. At 5, 7, 9, and 11 weeks of age, electromyographic (EMG) activity was recorded from the right masseter and anterior digastric muscles along with corresponding kinematic images in RJMs during repetitive intracortical microstimulation of the left cortical masticatory area (CMA). Rats in both groups showed an increase in gape size and lateral excursion until 9 weeks of age. The vertical jaw movement speed in both groups showed no significant difference between 5 and 7 weeks of age but increased with age from 9 to 11 weeks. Compared to the control group, the average gape size and vertical speed were significantly lower in the experimental group, and the pattern and rhythm of the jaw movement cycle were similar between both groups at each recording age. EMG recordings showed no age-related significant differences in onset latency, duration, and peak-to-peak amplitude. Moreover, we found significantly longer onset latency, smaller peak-to-peak amplitude, and greater drop-off mean and median frequencies in the experimental group than in the control group, while there was no significant difference in the duration between groups. These findings indicate that a lack of enough occlusal function in infancy impedes the development of patterns of RJMs and delays the neuromuscular response from specific stimulation of the CMA.

A salamander that chews using complex, three-dimensional mandible movements.

Most non-mammal tetrapods have a hinge-like jaw operation restricted to vertical opening and closing movements. Many mammal jaw joints, by contrast, operate in more complex, three-dimensional (3D) ways, involving not only vertical but also propalinal (rostro-caudal) and transverse (lateral) movements. Data on intraoral food processing in lissamphibians and sauropsids has prompted a generally accepted view that these groups mostly swallow food unreduced, and that in those cases where lissamphibians and sauropsids chew, they mostly use simple vertical jaw movements for food processing. The exception to this generally accepted view is the occurrence of some propalinal chewing in sauropsids. We combined 3D kinematics and morphological analyses from biplanar high-speed video fluoroscopy and micro-computed tomography to determine how the paedomorphic salamander Siren intermedia treats captured food. We discovered not only that S. intermedia uses intraoral food processing but also that the elaborated morphology of its jaw joint facilitates mandibular motions in all three planes, resulting in complex 3D chewing. Thus, our data challenge the commonly held view that complex 3D chewing movements are exclusive to mammals, by suggesting that such mechanisms might have evolved early in the tetrapod evolution.

Long-term Effectiveness of Occlusal Splint Therapy Compared to Placebo in Patients with Chronic Temporomandibular Disorders.

PurposeThe aim of this study was to compare long-term effectiveness of stabilization splint (SS) with that of placebo splint (PS) in chronic TMD patients and to investigate differences in treatment outcomes based on diagnostic subgroups [disc displacement (DD)/myofascial pain (MP)].Materials and MethodsThirty-four female participants, diagnosed with chronic TMD, were classified in groups: one provided with SS and other with PS and were followed for six months. Treatment outcomes included spontaneous pain [visual analogue scale (VAS)], self-perceived quality of life (OHIP-14), pain-free maximal mouth opening (MCO), maximal mouth opening (MMO), level of perceived stress (PSS), characteristic pain intensity [graded chronic pain scale (GCPS)], and functional jaw limitation [jaw functional limitation scale (JFLS)].ResultsBaseline characteristics did not differ significantly between the two groups (p>0.05). After six months of treatment the changes in spontaneous pain and OHIP-14 scores differed significantly between treatment groups (p=0.004, p=0.02 respectively), with greater reduction in SS compared to the PS group. Pain-free maximal mouth opening did not change significantly over time, however MCO values differed significantly between the two treatment groups, with greater overall values in the SS compared to the PS group (p= 0.046), as well as between TMD subgroups, with greater overall values in MP compared to DD patients (p= 0.03). In the SS group, significant difference in JFLS categories was found between baseline and after 6 months of treatment in all except emotional and verbal expression (mastication p=0.00015; vertical jaw mobility p=0.00018). No such changes in JFLS categories were observed in the PS group.ConclusionsDuring 6-month period, SS was more effective than PS in reducing spontaneous pain and improving self-perceived quality of life and functional limitations of the lower jaw. Moreover, significantely higher values of pain-free mouth opening were observed in patients treated with stabilization splint. While placebo might be partly responsible for improving the symptoms of TMD, it seems that itcannot maintain a continual long-term positive therapeutic effect.