Morphological differences in individuals with lip competence and incompetence based on electromyographic diagnosis

Malocclusion in children with speech sound disorders and motor speech involvement: a cross-sectional clinical study in Swedish children

OBJECTIVES

The objectives of this study were to investigate the occurrence, types and severity of malocclusions in children with speech sound disorder (SSD) persisting after 6 years of age, and to compare these findings to a control group of children with typical speech development (TSD).

METHODS

In total, 105 children were included: 61 with SSD and motor speech involvement (mean age 8:5 ± 2:8 years; range 6:0-16:7 years, 14 girls and 47 boys) and 44 children with TSD (mean age 8:8 ± 1:6; range 6:0-12:2 years, 19 girls and 25 boys). Extra-oral and intra-oral examinations were performed by an orthodontist. The severity of malocclusion was scored using the IOTN-DHC Index.

RESULTS

There were differences between the SSD and TSD groups with regard to the prevalence, type, and severity of malocclusions; 61% of the children in the SSD group had a malocclusion, as compared to 29% in the TSD group. In addition, the malocclusions in the SSD group were rated as more severe. Functional posterior crossbite and habitual lateral and/or anterior shift appeared more frequently in the SSD group. Class III malocclusion, anterior open bite and scissors bite were found only in the SSD group.

CONCLUSION

Children with SSD and motor speech involvement are more likely to have a higher prevalence of and more severe malocclusions than children with TSD.

Activity Evaluation of Facial Muscles by Surface Electromyography

BACKGROUND

Surface electromyography (sEMG) is an easy, noninvasive, and reproducible way to assess spontaneous electrical activity of muscles in real time. In this study, we report data on the correlation between sEMG and mimetic muscle activity during specific tasks so as to create a case-control reference for future studies on acute, chronic, and congenital facial palsy.

METHODS

Twelve healthy participants were enrolled (6 women and 6 men) with a mean age of 42.75 (range, 26-58 years) years. sEMG signals were recorded at rest and while performing voluntary and specific tasks that elicited selective contraction of frontalis, orbicularis oculi, zygomaticus major, orbicularis oris, and platysma muscles simultaneously and bilaterally for each muscle group. Statistical analysis was performed to evaluate if there was a statistically significant difference of the average contraction values between left- and right-side data sets and between male and female participants.

RESULTS

No statistically significant difference was found between male and female participants or between the right and left sides at rest and while performing the requested tasks, even though they were not identical. No participant complained about the procedure.

CONCLUSIONS

Interindividual and intraindividual variability of the sEMG signal as well as crosstalk between muscles groups were reported downsides that we did not encounter. The absolute noninvasiveness of our procedure makes it feasible to be applied even to young children. This dataset obtained in healthy participants might also be useful in the observation of patients undergoing regeneration/reinnervation procedure following recently acquired facial palsy or mimetic muscle reconstruction for congenital/inveterate one.

Proposal for a screening questionnaire for detecting habitual mouth breathing, based on a mouth-breathing habit score

Background

When mouth breathing becomes habitual, it can cause sleep disorders and abnormal maxillofacial growth, thus early detection of habitual mouth breathing is important. We created a questionnaire for early detection of habitual mouth breathing using a score based on a spectrum of factors found to be characteristic of mouth breathers.

Methods

First, a draft 50-question questionnaire was given to 101 random dental clinic patients, classified by dental professionals into habitual mouth breathers (n = 28) and nose breathers (n = 73). The 10 questions that significantly differentiated mouth and nose breathers (p < 0.05) were identified from this questionnaire. These questions, regarding nasal obstruction, open mouth at rest, awareness of mouth breathing, gum swelling and dental staining of the front teeth, bad breath, maxillary protrusion, nasal obstruction in childhood, bottle-feeding, and history of asthma, formed the basis for a second questionnaire. This second survey was completed by another 242 participants, separately classified into mouth breathing (n = 26), suspected mouth breathing (n = 40), and nose breathing groups (n = 176).

Results

Receiver operating characteristic curve analysis of the resulting mouth breathing habit scores, representing the responses to the 10-question survey, showed moderate checklist diagnosability. Sensitivity of cut-off values was 61.5% (specificity 92.0%) for the mouth-breathing group, and 77.5% (specificity 56.3%) for the suspected mouth-breathing group.

Information was also obtained from visual assessment of maxillofacial characteristics. We found that the mouth-breathing and suspected mouth-breathing groups showed significantly high odds ratios for 7 items: discomfort while breathing and increased chin muscle tonus with lip closure, maxillary protrusion, tongue thrust, open mouth at rest, open bite, and childhood asthma. For 94.6% of the nose breathing group, ≥1 of these items applied.

Conclusions

These findings were then used together to create a sample screening form. We believe that screening of this kind can facilitate more accurate diagnosis of habitual mouth breathing and contribute to its early detection.

Comparison of EMG activity and blood flow during graded exertion in the orbicularis oris muscle of adult subjects with and without lip incompetence: a cross-sectional survey

Background/Objectives

The peri-oral muscles-including orbicularis oris-are critical in maintaining equilibrium in tooth position. Lip incompetence (LI) can thus be a factor in malocclusion. We therefore aimed to validate a technique to evaluate not only muscle activity via electromyography (EMG) but also muscle endurance and fatigue via blood flow (BF) for LI.

Subjects/Methods

Subjects were classified into increased muscle tension/lip incompetent (experimental) and normal muscle tension/lip competent (control) groups. Each subject then exerted force on a custom-made traction plate connected to a tension gauge. Using laser speckle imaging and electromyographic measurements, we characterized muscle activity and corresponding BF rates in these subjects in various states of resting, loading, and recovery.

Results

Results showed a significant difference between the experimental and control groups, notably in the rate of change in BF to the inferior orbicularis oris muscle under conditions of increasing load (graded exertion). Furthermore, the data suggested that the muscles in the control group undergo a more prolonged (and therefore presumably more complete) recovery than muscles in the experimental group. These factors of reduced BF and short recovery may combine to accelerate muscle fatigue and produce LI.

Limitations

The sample used here was controlled for malocclusion (including open bite) to eliminate this type of confounding effect.

Conclusions/Implications

From these findings, we conclude that reduced BF and inadequate recovery in the orbicularis oris muscles may be more significant than EMG activity in the assessment of LI.

Comparison of muscle activity between subjects with or without lip competence: Electromyographic activity of lips, supra- and infrahyoid muscles

AIM

This study compares the electromyographic (EMG) activity of the muscles from the lips and hyoid bone in subjects with or without lip competence.

METHODOLOGY

Two groups of 20 subjects each, with or without lip competence were studied. EMG activity of the superior orbicularis oris (SOO), inferior orbicularis oris (IOO), suprahyoid (SH) and infrahyoid (IH) muscles was recorded with the subject seated in the upright position during the following tasks: (1) at rest; (2) speaking; (3) swallowing; (4) forced deep breathing; (5) maximal voluntary clenching; and (6) chewing.

RESULTS

EMG activity was significantly higher in subjects without competent lips than with competent lips in the SOO and IOO muscles during tasks 3 and 4, SOO during task 2 and IOO during task 6. EMG activity was similar in the SOO and IOO muscles during tasks 1 and 5, SOO during task 6 and IOO during task 2. Activity of the SH and IH muscles was similar in both groups for all tasks.

CONCLUSIONS

Higher activity in subjects without competent lips implies a higher muscular effort due to the requirement of lip sealing during functional activities. Hyoid muscular activity was not modified by the presence or absence of lip competence.

Evaluation of blood flow and electromyographic activity in the perioral muscles

BACKGROUND/OBJECTIVES

Although the electromyographic (EMG) activity of the perioral muscles, including the orbicularis oris and mentalis muscles, has been described in individuals with lip incompetence during lip sealing, blood flow through these muscles remains to be elucidated. The purpose of this study was to examine the blood flow associated with EMG activity in the perioral muscles using laser speckle imaging in individuals with lip incompetence.

SUBJECTS/METHODS

Blood flow and EMG activity of the superior and inferior orbicularis oris and mentalis muscles were measured with the lips in contact (C condition) and apart (O condition) in lip incompetence (experimental) and control subjects (n = 15 in each group; mean age: 29.5 years). The change ratios of blood flow and EMG activity in the C condition versus O condition (C/O ratios) were calculated and plotted in a scattergram. The Mann-Whitney U-test, Wilcoxon signed-rank test, discriminant analysis using the Mahalanobis generalized distance, and Spearman correlation were used for statistical analysis.

RESULTS

In the experimental group, blood flow and EMG activity in all muscles were significantly greater in the C condition than in the O condition. The plots of C/O ratios in the experimental group showed a distinct and wide distribution and were significantly different than those in the control group. In both groups, a significant positive correlation was observed between blood flow and EMG activity in the mentalis muscle.

CONCLUSIONS/IMPLICATIONS

The present findings suggest that observing blood flow in the mentalis muscle is an effective and easily performed method of evaluating lip incompetence.

Microabrasion in tooth enamel discoloration defects: three cases with long-term follow-ups

Superficial irregularities and certain intrinsic stains on the dental enamel surfaces can be resolved by enamel microabrasion, however, treatment for such defects need to be confined to the outermost regions of the enamel surface. Dental bleaching and resin-based composite repair are also often useful for certain situations for tooth color corrections. This article presented and discussed the indications and limitations of enamel microabrasion treatment. Three case reports treated by enamel microabrasion were also presented after 11, 20 and 23 years of follow-ups.

Orthodontic-surgical treatment: neuromuscular evaluation in open and deep skeletal bite patients

BACKGROUND

The aim of this study was to compare electromyographic data of two groups of patients (open and deep skeletal bite) before and after surgical orthodontic treatment.

METHODS

All patients who underwent orthognathic surgery at the Department of Orthodontics (University of Milan) were subjected to periodic electromyographic evaluation of the masticatory muscles (masseter and anterior temporal muscles) and to electrokinesiographic evaluation of mandibular movements. The sample comprised 72 patients (35 open skeletal bite patients and 37 deep skeletal bite patients) at the end of craniofacial growth. The electromyographic instruments used in the study included a Freely and a K6-I electromyograph. Statistical evaluation was carried out with Student's t tests for independent samples.

RESULTS

Lots of differences between open and deep skeletal bite patients have been underlined by the analysis of the electromyographic data obtained. These results have been obtained with both electromyographic systems. Muscular activity in microvolts is higher in deep skeletal bite patients at the beginning of the treatment than in open bite ones, but during the following phases of the treatment, the two values became similar.

CONCLUSIONS

Morphologic differences between open and deep bite patients can also be demonstrated by instrumental examinations, and their correction after surgical treatment is observable on electromyographic and electrognatographic exams.

Oral habits in a group of consecutively treated orthodontic patients, using standardized video recordings for diagnosis

OBJECTIVE

To investigate the prevalence and correlation of soft tissue dysfunctions documented by standardized video recordings in a group of orthodontic patients and to evaluate orthodontic treatment changes.

SUBJECTS AND METHODS

The presence of an oral habit was evaluated from standardized pre- and post-treatment video recordings of 80 consecutive patients (30 boys and 50 girls, mean age 12.2 ± 1.7 years). Any digit-sucking habit was noted during a routine interview. Pre- and post-treatment cephalograms were traced to assess sagittal and vertical jaw and incisor relationships. Correlations and differences were tested for statistical significance using the t-test and Odds-ratio.

RESULTS

56.3% had one or more habits before treatment. The total prevalence fell during treatment. A clear correlation was found between digit sucking and atypical tongue activity. Pre-treatment cephalograms showed that patients with a habit had a larger overjet, smaller overbite, more proclined and protruded incisors, a greater ANB angle and a greater inter-maxillary angle (ML/NL) than those without a habit. Cephalometric differences between the groups after orthodontic treatment were much less pronounced. Those with an oral habit also showed a tendency for increased treatment time/number of visits.

CONCLUSIONS

Standardized video recordings improved the reliability of the recordings of the oral soft tissue dysfunctions. Their overall reduction after the end of orthodontic treatment coincided with a normalization of the sagittal skeletal and dental variables.

Lip competence in Class III patients undergoing orthognathic surgery: an electromyographic study

PURPOSE

The aim of this study was to compare the presurgical and postsurgical electromyographic (EMG) activities of the lips in patients with skeletal Class III treated with combined orthognathic surgery and contrast these data with those obtained from a control group with skeletal Class I.

PATIENTS AND METHODS

Ten patients with skeletal Class III underwent the registration of EMG activity before an orthognathic surgical procedure and 4 months after surgery. The results were compared with a control group of 11 healthy patients with skeletal Class I and clinical and EMG lip competence. EMG activity was recorded from the upper orbicularis oris and mentalis muscles during swallowing, lips in contact (LC), and lips apart (LA) using bipolar surface electrodes. The competence condition was assessed by determining the difference in the EMG activity of the mentalis muscle (LC-LA ≤0 for lip competence).

RESULTS

Patients with skeletal Class III showed greater EMG activity than the control group before and after surgery. Patients with skeletal Class III showed a significantly greater difference in LC-LA than the control group before surgery for the 2 muscles (P < .05). No significant difference was found between the skeletal Class III group after surgery and the control group for the mentalis muscle (P > .05).

CONCLUSIONS

Four months after treatment with orthognathic surgery, patients with skeletal Class III and an initial muscle activity pattern of lip incompetence different from the control group (P < .05) showed EMG values compatible with lip competence. These values were similar to the control group.

Impact of genioplasty on mandibular growth during puberty

AIM

Genioplasty has been validated for the correction of mandibular vertical excess and is generally performed at the end of the growth period, either alone or in association with other forms of osteotomy. Our aim was to assess whether genioplasty performed at an earlier age can impact mandibular growth.

METHODS

This comparative prospective study included 25 high-angle, mouth-breathing adolescents following orthodontic and ENT treatment. Subjects were divided into two groups according to their stage of puberty, either early (group 1: Tanner's stage 3, n=12) or late stage (group 2: Tanner stage 4-5, n=13). Genioplasty was performed in both groups. Cephalometric comparison was made on the overall population and for each group, before and after genioplasty (at 1, 6, 12 and 18months).

RESULTS

In the immediate postoperative period, significant variation of all the cephalometric measures was observed within each group showing reduction of the vertical dimension and sagittal augmentation. Eighteen months post-surgery, only group 1 exhibited a significant increase in SNPog. Augmentation of the SNB and anterior mandibular rotation were also significantly greater in group 1. The difference in the direction of growth of the mandible before genioplasty (18months of orthodontics) and postgenioplasty (18months of postoperative monitoring) was also significant.

CONCLUSION

Early genioplasty permits redirection of mandibular growth conducive to orthopedic correction of high angle Class II.

Electromyographic evaluation of the upper lip according to the breathing mode: a longitudinal study

The present study aimed at analyzing and comparing longitudinally the EMG (electromyographic activity) of the superior orbicularis oris muscle according to the breathing mode. The sample, 38 adolescents with Angle Class II Division 1 malocclusion with predominantly nose (PNB) or mouth (PMB) breathing, was evaluated at two different periods, with a two-year interval between them. For that purpose, a 16channel electromyography machine was employed, which was properly calibrated in a PC equipped with an analogue-digital converter, with utilization of surface, passive and bipolar electrodes. The RMS data (root mean square) were collected at rest and in 12 movements and normalized according to time and amplitude, by the peak value of EMG, in order to allow comparisons between subjects and between periods. Comparison of the muscle function of PNB and PMB subjects at period 1 (P1), period 2 (P2) and the variation between periods (Delta) did not reveal statistically significant differences between groups (p < 0.05). However, longitudinal evaluation of the muscle function in PNB and PMB subjects demonstrated different evolutions in the percentage of required EMG for accomplishment of the movements investigated. It was possible to conclude that there are differences in the percentage of electric activity of the upper lip with the growth of the subjects according to the breathing mode.

Comparação das dimensões de tecido mole entre padrões faciais distintos

OBJETIVO: o presente estudo destinou-se a comparar a morfologia tegumentar de indivíduos segundo a tipologia facial. MÉTODOS: foram utilizadas 90 telerradiografias de pacientes de ambos os sexos, de 12 a 16 anos de idade, divididas em três grupos distintos, referentes a cada padrão morfológico: mesofacial, dolicofacial e braquifacial. Os grupos foram comparados no que se refere às medidas de espessura e altura do lábio superior e inferior, além da espessura do mento mole. Ainda, foi apurada a presença de correlações entre as variáveis de tecido mole avaliadas e medidas cefalométricas de natureza dentária e esquelética. RESULTADOS E CONCLUSÕES: os lábios superiores e inferiores, assim como o mento mole, não apresentaram diferenças em relação às suas espessuras em todos os grupos morfológicos. Porém, as alturas do lábio superior e inferior foram significativamente maiores para os dolicofaciais quando esses foram comparados aos demais grupos. Braquifaciais apresentaram menor altura do lábio superior quando comparados aos mesofaciais, embora ambos não tenham se diferenciado significativamente no que se refere à altura do lábio inferior. A análise das correlações estabelecidas entre as variáveis dos tecidos moles e duros indicou evidências de um desenvolvimento vertical dos lábios superior e inferior em acompanhamento ao desenvolvimento vertical do esqueleto. O posicionamento vertical do incisivo superior se correlacionou significativamente aos mesmos parâmetros labiais, o que garantiu um nível de exposição semelhante desse elemento dentário em todos os grupos.

Distances between facial landmarks can be measured accurately with a new digital 3-dimensional video system

INTRODUCTION

The aim of this study was to investigate a new digital 3-dimensional infrared video system to determine its accuracy, precision, and validity in measuring facial distances.

METHODS

Bench experiments were performed by measuring the vertical and diagonal distances of chessboard squares of known length to determine the system's accuracy and precision. To test the system's validity, 16 healthy volunteers participated in this study. Vertical and horizontal distances of the face were measured electronically at rest, and on posed and aggressive smiles. All measurements were repeated after 8 weeks. Direct measurements of the intercanthal distance were obtained twice with calipers.

RESULTS

A minor systematic error was found in the bench experiments, with the highest absolute error of 0.227 +/- 0.39 mm. The analysis with this video system showed good reproducibility of all measured distances when the mean of 2 frames was used to compare distances. Digital measurements of the intercanthal distances showed high agreement with the clinically obtained values.

CONCLUSIONS

This digital video system can measure geometric distances in a 3-dimensional environment with high precision. Facial distances can be measured with good accuracy and precision, allowing applications in research and clinical practice.

Clinical estimation of mouth breathing

INTRODUCTION

Breathing mode was objectively determined by monitoring airflow through the mouth, measuring nasal resistance and lip-seal function, and collecting information via questionnaire on the patient's etiology and symptoms of mouth breathing.

METHODS

The expiratory airflow through the mouth was detected with a carbon dioxide sensor for 30 minutes at rest. Fifteen men and 19 women volunteers (mean age, 22.4 +/- 2.5 years) were classified as nasal breathers, complete mouth breathers, or partial mouth breathers based on the mean duration of mouth breathing. Nasal resistance, lip-sealing function, and the subjective symptoms of mouth breathing ascertained by questionnaire were statistically compared by using 1-way and 2-way analysis of variance (ANOVA) and the chi-square test in the breathing groups.

RESULTS

Nasal resistance was significantly (P <0.05) greater for the mouth breathers than for the nasal breathers, and significantly (P <0.05) greater for the partial mouth breathers than for the complete mouth breathers. There were no significant differences in the subjective responses to questions about mouth breathing among the 3 groups.

CONCLUSIONS

Detecting airflow by carbon dioxide sensor can discriminate breathing mode. Degree of nasal resistance and subjective symptoms of mouth breathing do not accurately predict breathing mode.

Gender and age differences in facial expressions

The aim of this research was to determine a reliable method for quantitatively evaluating the facial expressions of children and adults in order to assess their dependence on age and gender. This study evaluated 80 healthy subjects divided into four groups: 20 girls (mean age 10.6 years), 20 boys (mean age 10.8 years), 20 females (average age 25.6 years), and 20 males (average age 27.0 years). A video was used to record each individual executing three facial expressions: a rest pose, a lip pucker, and a posed smile. Representative video frames were chosen for each individual's expressions; they were digitized and then analysed with software that extracted a set of horizontal and vertical distances of the face. All distances measured in the posed smile and lip pucker were expressed as a percentage change from the rest pose. Statistical analysis with a two-way multivariate analysis of variance (MANOVA) was performed, with gender and age as the independent variables. It was evident that the ability to produce certain facial expressions differs between groups of individuals due to gender and age. Males had a greater upward vertical movement capacity in the studied facial expressions than females. Females had a more pronounced horizontal component in the posed smile. There was a trend from childhood to adulthood showing an increase in the percentage change in most vertical movements. This trend was present in both genders, though more pronounced in males. Using a robust quantitative method for collecting and analysing facial expressions, gender differences in adults were detected as well as differences between adults and children. The trend toward increasing vertical movements in adults compared with children suggests the possibility that the mimic musculature is developmentally regulated.

Correlation between morphology and function of the upper lip: a longitudinal evaluation

In order to evaluate the relationship between the morphology of the upper lip and muscle activity in a sample of 38 subjects (17 males and 21 females) with Angle Class II division 1 malocclusions, cephalometric and electromyographic analyses were conducted. The sample was subdivided into either predominantly nose or mouth breathers. The individuals were evaluated at two different periods, with a 2 year interval. At the first observation, the subjects were 11 years to 14 years 11 months of age and at the second observation, 13 years 4 months to 16 years 6 months of age. Height and thickness of the upper lip were measured on lateral cephalograms with the aid of a digital pachymeter. For each individual, electromyographic records were obtained of the orbicularis oris superior muscle at rest and in a series of 12 movements. The electromyographic data were normalized as a function of amplitude, for achievement of the percentage value of each movement. Pearson and Spearman correlation tests were applied. The results showed some correlation between morphology and muscle function (at a confidence level of 95 per cent). However, as the values of the correlation coefficient (r) were too low to establish associations between variables, it was concluded that the dimensions of the upper lip are not correlated with muscle activity.

[Etiological aspects of anterior open bite]

INTRODUCTION

Open bite is a multifactorial phenomenon and no single factor can account for open-bite. Etiology plays an important role in diagnosis. Heredity, unfavorable growth patterns, incorrect jaw postoure, are the characteristics of skeletal open bite.

DIGIT SUCKING

Depending on where the thumb is placed, a number of different types of dental problems can develop. Malocclusions of the late mixed or permanent dentitions, caused by thumb sucking are not self corrected and orthodontic treatment is necessary for their correction.

LYMPHATIC TISSUE

In order to produce oral respiration, the mandible is postured inferiorly with the tongue protruded and resting against the oral floor. This postural alteration induces dental and skeletal modifications similar to those caused by thumb sucking. This may cause excessive eruption of the posterior teeth, leading to an increase in the vertical dimension of the face and result in development of anterior open bite.

TONGUE THRUST

Tongue habits cause an anterior open bite or they develop secondarily to thumb sucking. In skeletal open bite the tongue habit acts as a secondary factor which helps to maintain or exacerbate the condition. Many orthodontists have had a discouraging experience of completing dental treatment, with what appeared to be good results, only to discover that the case had relapsed because the patient had a tongue thrust swallowing pattern.

CONCLUSION

Dentoalveolar or habitual open bite is caused by habits, which influence the growth and development of dentoalveolar processes and contribute to occlusal disharmonies. Prior to eruption of adult dentition, open bite related to oral habits is usually not a concern as when the habits stop, because the erupting dentition tends to improve spontaneously. Treatment is usually not necessary until permanent teeth erupt (approximately 6 years old).

Topographical Characteristics of Motor Units of the Lower Facial Musculature Revealed by Means of High-Density Surface EMG

The objective of this study was to systematically characterize motor units (MUs) of the musculature of the lower face. MU endplate positions and principal muscle fiber orientations relative to facial landmarks were identified. This was done by the analysis of motor unit action potentials (MUAPs) in the surface electromyogram. Thirteen specially trained, healthy subjects performed selective contractions of the depressor anguli oris, depressor labii inferioris, mentalis, and orbicularis oris inferior muscles. Signals were recorded using recently developed, 0.3-mm thin and flexible high-density surface electromyography (sEMG) grids (120 channels). For each subject and each muscle and for different low contraction levels, representative MUAPs ("MU fingerprints") were extracted from the raw sEMG data according to their spatiotemporal amplitude characteristics. We then topographically characterized the lower facial MUs' endplate zones and main muscle fiber orientations on the individual faces of the subjects. These topographical MU parameters were spatially warped to correct for the different sizes and shapes of the faces of individual subjects. This electrophysiological study revealed a distribution of the lower facial MU endplates in more or less restricted, distinct clusters on the muscle often with eccentric locations. The results add substantially to the basic neurophysiologic and anatomical knowledge of the complex facial muscle system. They can also be used to establish objective guidelines for placement of conventional (surface or needle) EMG electrodes as well as for clinical investigations on neuromuscular diseases affecting the facial musculature. The localized endplate positions may also indicate optimal locations for botulinum toxin injection in the face.

Assessment of open and incomplete bite correction by incisor overlap and optical density of polyvinyl siloxane bite registration

Open bite (OB) is a generalized term, which could incorporate subgroups that react differently to vertical correction. The objectives of the present study were to detect vertical treatment changes in incomplete bite (IB: inter-incisor overlap with no lower incisor contact with teeth or palate) and OB (no inter-incisor overlap) groups compared with a complete bite (CB: inter-incisor overlap with full lower incisor contact with teeth or palate) control group, to evaluate treatment response of the central and lateral incisors, and to study the vertico-sagittal interaction. Dental casts were taken at three time points, pre-treatment, post-treatment, and after one year of retention, from 54 Class II patients (22 males and 32 females with a mean age of 11 years 6 months) divided into three groups: CB (n = 21), IB (n = 18) and OB (n = 15). Measurements included incisor overlap (mm) and optical density (OD/mm2) of occlusal bite registration made of polyvinl siloxane. Both CB and IB groups demonstrated post-retention bite opening. However, bite opening in the CB group was three times greater than that in the IB group (e.g. lower lateral = -1.42 mm, 118 OD/mm2 versus -0.40 mm, 107 OD/mm2). Conversely, the OB group showed a significant (P < 0.001) bite closure (e.g. lower lateral = 1.30 mm, -377 OD/mm2). Overjet changes affected OD measurements, causing diversity in OD and millimetric measurements of the lateral incisors in the IB group. In conclusion, the OB group demonstrated a significant stable vertical correction; a post-treatment non-contact inter-incisor relationship was determined by a vertico-sagittal relapse; and full compensation of an IB was not possible.