Altered Tongue Research Articles

Short Lingual Frenulum as a Risk Factor for Cerebral Vasculopathies

Introduction: Tongue is the first functioning organ in the embryonic era. Its developmental alterations can result in malfunctions with damage in distant districts. Craniocervical anatomy suggests that tongue dysfunction may be involved in the damage to the arteriovenous encephalic flow. Objective: To evaluate the possible relationship between short frenulum and cerebral vasal problems. Method: We conducted an epidemiological research comparing the presence of vascular problems in families where the visited subject had short frenulum (which is a genetically transmitted pathology) and families where the visited subject did not have abnormality of the frenulum. Results: The presence of short tongue frenulum was correlated with the presence of episodes of vascular damage in about 80% of cases, while in families not affected by this tongue alteration the percentage of damage was between 10 and 13%. Conclusions: The enormous influence that the presence of an altered tongue frenulum seems to have on the future possibility of developing vascular problems should induce a more careful assessment of the presence of an incorrect-sized frenulum.

Moderate-to-severe obstructive sleep apnea syndrome is associated with altered tongue motion during wakefulness.

Impairment of genioglossus control is a frequent "non-anatomical" cause of obstructive sleep apnea syndrome (OSAS) in non- or mildly obese patients. Although wake-related compensatory mechanisms prevent the occurrence of obstructive events, the genioglossus control is often impaired during wakefulness. We hypothesized that the lingual motion would be altered during wakefulness in this population in patients with moderate-to-severe OSAS. We included non- or mildly obese participants with suspected OSAS. They underwent a Bucco-Linguo-Facial Motor Skills assessment using the MBLF ("Motricité Bucco-Linguo-Faciale"), which includes an evaluation of 13 movements of the tongue. This was followed by a night-attended polysomnography. We compared patients with moderate-to-severe OSAS (apnea-hypopnea index (AHI) ≥ 15/h; n = 15) to patients without or with mild OSAS (AHI < 15/h; n = 24). MBLF total and "tongue" sub-scores were lower in patients with moderate-to-severe OSAS: total z-score - 0.78 [- 1.31; 0.103] versus 0.20 [- 0.26; 0.31], p = 0.0011; "tongue" z-sub-score (- 0.63 [- 1.83; 0.41] versus 0.35 [0.26; 0.48], p = 0.014). There was a significant age-adjusted correlation between the "tongue" sub-score and AHI. The logistic regression model for the prediction of moderate-to-severe OSAS gave area under the curve ratio of 88.2% for MBLF score plus age. Myofunctional activity of the tongue is impaired during wakefulness in non- or mildly obese patients with moderate-to-severe OSAS. This study supports the lingual myofunctional assessment using the MBLF in screening of moderate-to-severe OSAS. This simple tool could help clinicians to select patients with suspected moderate-to-severe OSAS for polysomnography.

Management of MACROGLOSSIA: Case Series and Suggested Algorithm

Idiopathic macroglossia is a rare entity of true tongue enlargement without an underlying etiology. There are only a few case reports on the diagnosis and management of idiopathic macroglossia. This study's purpose was to present a series of patients with idiopathic macroglossia and suggest a treatment algorithm. This was a retrospective case series of a cohort of patients with macroglossia who were treated by the Oral and Maxillofacial Surgery service at the University of Texas Health Science Center at Houston (UTHealth)and Emory University. The patient's medical comorbidities, history of present illness, clinical presentation, radiographic findings, and disease management were studied. The outcome variables include normalization of the tongue size, dependence on parenteral nutrition, and tolerating tracheostomy decannulation. Five patients with a mean age of 45years were included in the study. All of the patients (n=5, 100%) in our cohort developed macroglossia following prolonged oral intubation, with 3.5weeks being the average length of intubation. All patients presented with difficulty feeding orally and breathing. The average tongue dimension was 12.20 x 6.25cm. All tongue enlargements were located in the anterior 2/3 of the tongue, and all patients had displaced anterior dentition. In addition, 60% of the patients (n=3) experienced altered tongue sensation (pain and/or decreased taste). These patients were surgically managed with tracheostomy and percutaneous endoscopic gastrostomy (PEG) tube placement followed by partial glossectomy (n=5, 100%). We defined successful outcomes as 1) modifying the tongue to a functional, nonprotruding form, 2) tracheostomy decannulation and 3) PEG tube removal. Tracheostomy decannulation and PEG tube removal were achieved in 80% of the patients (n=4). In this patient cohort, we were unable to identify the cause of the pathology based on existing clinical data. When the etiology is unclear or irreversible, management should involve tracheostomy and surgical feeding access for the initial stabilization, followed by modified glossectomy to improve form, function, and cosmesis thereby improving the overall quality of life.

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.

Association between malocclusion, tongue position and speech distortion in mixed-dentition schoolchildren: an epidemiological study.

Background Malocclusions are highly prevalent in childhood and adolescence, being considered a public health problem worldwide, in addition to be considered an important predictor in the tongue position and speech disorders.Objective Evaluate the association of malocclusions with tongue position and speech distortion in mixed-dentition schoolchildren from the south of Brazil.Methodology This cross-sectional study was performed using a database of an epidemiological survey realized in the southern of Brazil, in 2015, for evaluating the dental and myofunctional condition of the mixed-dentition from 7-13 years’ schoolchildren. The outcome variables were tongue position and speech distortion, evaluated by a trained and calibrated examiner. Characteristics regarding sociodemographic and oral health measures (Angle’s classification of the malocclusion, overjet, overbite, posterior crossbite and respiratory mode) were also assessed. Poisson regression models with adjusted robust variance were used to evaluate the association among predictors variables in the outcomes. Results are presented as prevalence ratio (PR) and 95% confidence interval (95% CI).Results A total of 547 children were evaluated. Schoolchildren who presented anterior open bite (PR 2.36 95%CI 1.59-3.49) and having oral/oral-nasal breathing (RP 2.51 95%CI 1.70-3.71) are more likely to have altered position of the tongue. Both deep bite and being male represent protection factors for the abnormal tongue position. Regarding speech distortion, deep overbite presents a protective relationship to speech distortion (PR 0.41; 95%CI 0.24-0.71), whereas schoolchildren with posterior crossbite were more likely to present this problem (PR 1.77; 95%CI 1.09-2.88).Conclusion Anterior open bite and posterior crossbite were the malocclusions related to speech distortion and/or altered tongue position. Oral/oral-nasal breathing was also related to myofunctional changes. Deep bite malocclusion was a protective factor for both speech problems and altered tongue position when compared to a normal overbite.

Association between dysphagia and tongue strength in patients with amyotrophic lateral sclerosis

IntroductionAmyotrophic lateral sclerosis is the most common motor neuron disease in adults despite it being rare. It is a neurodegenerative disease in which dysphagia is a common and debilitating symptom. Dysphagia can be assessed by complementary exams, such as fiberoptic endoscopic evaluation of swallowing and the tongue strength test, as this is one of the main muscles involved in swallowing. ObjectiveTo compare the results of tongue strength and endurance measured by the Iowa oral performance instrument with the findings of the fiberoptic endoscopic evaluation of swallowing examination in patients affected by amyotrophic lateral sclerosis. MethodsCross-sectional study, carried out in a tertiary hospital specialized in treatment and rehabilitation. Twenty-five patients diagnosed with amyotrophic lateral sclerosis underwent dysphagia questionnaires, fiberoptic endoscopic evaluation of swallowing examination and tongue strength and resistance test with the Iowa oral performance instrument to assess the presence of dysphagia. ResultsForty-eight percent of the sample had dysphagia at the fiberoptic endoscopic evaluation of swallowing and 76% had an altered tongue strength test. Ninety percent of patients with dysphagia had an average tongue pressure lower than 34.2KPa. The tongue strength test showed sensitivity of 91.67% and specificity of 38.46% and accuracy of 64%. There was a statistically significant relationship between tongue strength and dysphagia and between tongue resistance and dysphagia. ConclusionTongue strength tests, such as the Iowa oral performance instrument, proved to be effective in assessing dysphagia. This result should encourage further research to facilitate the early diagnosis of dysphagia.

Functional characterization of extrinsic tongue muscles in the Pink1-/- rat model of Parkinson disease.

Parkinson disease (PD) is associated with speech and swallowing difficulties likely due to pathology in widespread brain and nervous system regions. In post-mortem studies of PD, pathology has been reported in pharyngeal and laryngeal nerves and muscles. However, it is unknown whether PD is associated with neuromuscular changes in the tongue. Prior work in a rat model of PD (Pink1-/-) showed oromotor and swallowing deficits in the premanifest stage which suggested sensorimotor impairments of these functions. The present study tested the hypothesis that Pink1-/- rats show altered tongue function coinciding with neuromuscular differences within tongue muscles compared to wildtype (WT). Male Pink1-/- and WT rats underwent behavioral tongue function assays at 4 and 6 months of age (n = 7-8 rats per group), which are time points early in the disease. At 6 months, genioglossus (GG) and styloglossus (SG) muscles were analyzed for myosin heavy chain isoforms (MyHC), α-synuclein levels, myofiber size, centrally nucleated myofibers, and neuromuscular junction (NMJ) innervation. Pink1-/- showed greater tongue press force variability, and greater tongue press forces and rates as compared to WT. Additionally, Pink1-/- showed relative increases of MyHC 2a in SG, but typical MyHC profiles in GG. Western blots revealed Pink1-/- had more α-synuclein protein than WT in GG, but not in SG. There were no differences between Pink1-/- and WT in myofiber size, centrally-nucleated myofibers, or NMJ innervation. α-synuclein protein was observed in nerves, NMJ, and vessels in both genotypes. Findings at these early disease stages suggest small changes or no changes in several peripheral biological measures, and intact motor innervation of tongue muscles. Future work should evaluate these measures at later disease stages to determine when robust pathological peripheral change contributes to functional change, and what CNS deficits cause behavioral changes. Understanding how PD affects central and peripheral mechanisms will help determine therapy targets for speech and swallowing disorders.

Atypical swallowing behind an unusual case report of anterior open bite and an anterior midline Diastema

Atypical swallowing is a my functional problem consisting of an altered tongue position during the act of swallowing, connection with the presence of malocclusions such as anterior open bite made it a topic of strong interest and discussion in science.Anterior open bite is considered a malocclusion that still defies correction, especially in terms of stability, midline Diastema create an unpleasant appearance for individuals, sometimes it may lead to phonetic problems, particularly in cases with wide space. This article describes a clinical rare case of a severe anterior open bite and an unusual midline Diastema which resulted from an atypical swallowing and shows the importance to set up an early my functional rehabilitation procedure to correct the oral habit and to prevent such malocclusion with consequences on aesthetics and self-confidence.

Surgical techniques for the removal of mandibular wisdom teeth.

Surgical techniques for the removal of mandibular wisdom teeth.

The influence of tongue mobility on children's performance in computer games that depend on lingual movements

Alteration in tongue mobility requires rehabilitation work through oral motor exercises. These exercises can be integrated with computer games to increase the patient's motivation during treatment. To investigate the influence of tongue mobility on children's motor performance in a computer game reliant on lingual movements. A cross-sectional descriptive observational study was carried out with 16 children with altered tongue mobility and 16 children with normal tongue mobility. The subjects were between 8 and 12years of age. They underwent a clinical evaluation of the tongue and performed an activity using an intra-oral joystick controlled by the tongue to play a simple computer game. The game consisted of targets appearing on the screen that the participants had to reach by moving the joystick control rod. Afterward, the participants answered a feedback questionnaire. Motor performance in the game, measured by the number of reached targets and by the time to reach the targets, was compared between groups and across directions of tongue movement and order of appearance of the targets. The group with altered tongue mobility presented a higher time to reach the target in the downward direction and in the first and last 12 targets and a lower number of targets reached in the left direction, upward direction, and in the first 12 targets than the control group. The direction of the movement influenced tongue performance in both groups. Children with altered tongue mobility exhibited a worse performance than those with normal tongue mobility.

Orofacial muscles activity in children with swallowing dysfunction and removable functional appliances.

Swallowing dysfunction is a frequent disorder among children and refers to an altered tongue posture and abnormal tongue movement during swallowing. Removable functional appliance is one of the treatments applied by dentistry to correct this disorder. The aim of this study was to evaluate any differences on orofacial muscles activity in children with swallowing dysfunction with and without removable functional appliances. 68 children were eligible for the study and divided into the orthodontic group (OG) and the no-orthodontic group (NO-OG). Both groups performed a dental occlusion-class evaluation, a swallowing function test and a myoscan analysis in order to measure perioral forces (i.e. tongue extension force, lip pressure, masseter contraction force). Our results showed a significant difference (P=0.02) between OG and NO-OG for the tongue extension force, whereas no significant differences (P>0.05) were found for the other parameters. Our findings suggest that children with swallowing dysfunction and removable functional appliance show orofacial muscles activity within the range of reference values (except for the lip pressure). However, we hypothesize that orthodontic treatment can achieve more effective results with integration of myofunctional therapy.

Lingual frenuloplasty with myofunctional therapy: Exploring safety and efficacy in 348 cases.

BackgroundAnkyloglossia is a condition of altered tongue mobility due to the presence of restrictive tissue between the undersurface of the tongue and the floor of mouth. Potential implications of restricted tongue mobility (such as mouth breathing, snoring, dental clenching, and myofascial tension) remain underappreciated due to limited peer‐reviewed evidence. Here, we explore the safety and efficacy of lingual frenuloplasty and myofunctional therapy for the treatment of these conditions in a large and diverse cohort of patients with restricted tongue mobility.MethodsFour hundred twenty consecutive patients (ages 29 months to 79 years) treated with myofunctional therapy and lingual frenuloplasty for indications of mouth breathing, snoring, dental clenching, and/or myofascial tension were surveyed. All procedures were performed by a single surgeon using a scissors and suture technique. Safety and efficacy was assessed >2 months postoperatively by means of patient‐reported outcome measures.ResultsIn all, 348 surveys (83% response rate) were completed showing 91% satisfaction rate and 87% rate of improvement in quality of life through amelioration of mouth breathing (78.4%), snoring (72.9%), clenching (91.0%), and/or myofascial tension (77.5%). Minor complications occurred in <5% of cases including complaints of prolonged pain or bleeding, temporary numbness of the tongue‐tip, salivary gland issues, minor wound infection or inflammation, and need for revision to excise scar tissue. There were no major complications.ConclusionLingual frenuloplasty with myofunctional therapy is safe and potentially effective for the treatment of mouth breathing, snoring, clenching, and myofascial tension in appropriately selected patient candidates. Further studies with objective measures are merited.Level of Evidence3

Craniofacial structure alterations of foetuses from folic acid deficient pregnant mice

IntroductionCraniofacial development in mammals is a complex process that involves a coordinated series of molecular and morphogenetic events. Folic acid (FA) deficiency has historically been associated with congenital spinal cord malformations, but the effect that a maternal diet deficient in FA has on the development of other structures has been poorly explored. In the present study, the objective was to describe and quantify the alterations of craniofacial structures presented in mouse foetuses from dams fed a FA deficient (FAD) diet compared with controls that were given a regular maternal diet. Material and methodsE17 mouse foetuses were removed from dams that were fed with a control diet or with a FAD diet for several weeks. Foetuses with maternal FAD diets were selected for the study when they showed an altered tongue or mandible. Histological sections were used to quantify the dimensions of the head, tongue, mandibular bone and masseter muscle areas using ImageJ software. The muscles of the tongue, suprahyoid muscles, lingual septum, submandibular ducts, and lingual arteries were also analysed. ResultsThe heads of malformed foetuses were smaller than the heads of the controls, and they showed different types of malformations: microglossia with micrognathia (some of which were combined with cleft palate) and aglossia with either micrognathia or agnathia. Lingual and suprahyoid muscles were affected in different forms and degrees. We also found alterations in the lingual arteries and in the ducts of the submandibular glands. Summarised we can state that pharyngeal arches-derived structures were affected, and the main malformations observed corroborate the vulnerability of cranial neural crest cells to FA deficiency. ConclusionThe present study reveals alterations in the development of craniofacial structures in FAD foetuses. This study provides a new focus for the role of FA during embryological development.

Palatal morphology changes in post-stroke patients measured by geometric morphometrics.

This study aimed to describe longitudinal palatal shape changes in post-stroke patients when compared to a sample of healthy subjects through linear measurements and geometric morphometrics. The 3D palatal scanned models of seven stroke patients having a 1-year post-stroke follow-up were matched with seven control subjects of the same age group (range 50-87 years). Intercanine, intermolar distances and palatal height were measured. 3D images were also analysed through geometric morphometrics to assess changes in the shape of the palate from T0 to T1 (1 year after the stroke). Principal component analysis was used to describe shape morphology changes, and visual colour maps were used to qualitatively assess differences between T0 and T1. No changes were detected nor in linear measures neither in palatal shape in healthy subjects from T0 to T1. The palates of stroke patients showed no linear differences either. However, when visualising shape changes through colour maps, the lateral aspects of the palatal vault were slightly narrower in T1, with respect to T0 in stroke patients. This may be attributed to altered tongue function following the stroke.

Tongue fat infiltration in obese versus lean Zucker rats.

Obesity is the most important risk factor for obstructive sleep apnea (OSA), and the effects of obesity may be mediated by tongue fat. Our objective was to examine the effects of obesity on upper airway structures in obese (OBZ) and non-obese (NBZ) Zucker rats. Animal study. Academic Medical Center. OBZ (638.2 ± 39 g; 14.9 ± 1.1 w) and age-matched NBZ Zucker (442.6 ± 37 g, 15.1 ± 1.5 w) rats. TONGUE FAT AND VOLUME AND WERE ASSESSED USING: in vivo magnetic resonance spectroscopy (MRS), magnetic resonance imaging including Dixon imaging for tongue fat volume, ex vivo biochemistry (fat quantification; triglyceride (mg)/tissue (g), and histology (Oil Red O stain). MRS: overall OBZ tongue fat/water ratio was 2.9 times greater than NBZ (P < 0.002) with the anterior OBZ tongue up to 3.3 times greater than NBZ (P < 0.002). Biochemistry: Triglyceride (TG) in the tongue was 4.4 times greater in OBZ versus NBZ (P < 0.0006). TG was greater in OBZ tongue (3.57 ± 1.7 mg/g) than OBZ masseter muscle (0.28 ± 0.1; P < 0.0001) but tongue and masseter TG were not different in NBZ rats (0.82 ± 0.3 versus 0.28 ± 0.1 mg/g, P = 0.67). Dixon fat volume was significantly increased in OBZ (56 ± 15 mm3) versus NBZ (34 ± 5 mm3, P < 0.004). Histology demonstrated a greater degree of intracellular muscle fat and extramuscular fat infiltration in OBZ versus NBZ rats. Genetically obese rats had a large degree of fat infiltration in the tongue compared to both skeletal muscle and tongue tissues of the non-obese age-matched littermates. The significant fat increase and sequestration in the obese tongue may play a role in altered tongue neuromuscular function, tongue stiffness or metabolic function.

Impact of lingual plates on the interocclusal free way space: a pilot study

Palatal augmentation prostheses are commonly used in the treatment for dysphagia. By lowering the palatal contours, the tongue contact is increased and thus the bolus propulsion facilitated. However, the unfavourable weight of such appliances may be avoided when using lingual plates. Hence, the aim of this study is to investigate the effect of two different types of lingual plates on the vertical dimension in rest position. Eleven healthy dentate subjects with an average age of 35.5 years (26-60 years) volunteered in this pilot study. The vertical overbites were measured on plaster models. Two different designs of the experimental lingual plates were tested in this pilot study (P-type & D-type). The inter-occlusal freeway space was measured using the electromagnetic K7 jaw-tracking system (Myotronics, U.S.A.), while the subjects were seated in an upright position. They were asked to close from rest position into maximum intercuspation for about 2 s. Recordings were performed without the plates and subsequently with each of the two plate designs in situ. All recordings were performed three times and the second closing movement of each recording was used for the analysis. After averaging the repetitions without experimental lingual plates, with P-type and D-type plates, the differences were analysed using a Kruskall-Wallis test. The results showed no significantly increased freeway space while using both types of lingual plates. Hence, it can be concluded that any altered tongue pressure during swallowing with lingual plates is not related to an increase in vertical dimension.

Tonsillectomy may cause altered tongue sensation in adult patients

To determine the frequency of altered tongue sensation following tonsillectomy, and its relationship to different surgical techniques. Case-control study. District general hospital. One hundred and four consecutive adults undergoing tonsillectomy, and 43 control patients. Altered tongue sensation. Twenty-eight of 100 patients described altered tongue sensation post-tonsillectomy. No patients in the control group experienced altered tongue sensation. There was a difference in rates of altered sensation between tonsillectomy patient groups undergoing bipolar diathermy and 'cold steel' techniques (p < 0.019). Three months after surgery, 22/23 contactable patients reported complete recovery of tongue sensation. One patient experienced tongue paraesthesia persisting until one year post-tonsillectomy. Tonsillectomy resulted in altered tongue sensation in 28 per cent of our study group. Bipolar diathermy dissection was significantly more likely to cause altered sensation than cold steel dissection. Ninety-six per cent of these disturbances resolved by three months, all by one year. Possible alteration of tongue sensation should be discussed whilst obtaining consent for tonsillectomy.

Alterations in Contractile Properties of Tongue Muscles in Old Rats

Fatigue and weakness are well-known signs of aging that are related to sarcopenia, or loss of skeletal muscle mass, organization, and strength. Sarcopenia may affect swallowing. The tongue plays a vital role in swallowing, but there is limited knowledge regarding age-related changes in lingual muscle contractile properties. Our purpose was to determine whether alterations in tongue force, temporal features of tongue muscle contraction, and fatigability are manifested as a function of aging in old rats. We evaluated tongue muscle contractile properties in young and old Fischer 344/Brown Norway rats. Contractions were elicited via bilateral electrical stimulation of the hypoglossal nerves. Maximum tongue forces and fatigability were not significantly altered in old animals, but aging was associated with significantly longer twitch contraction time and longer half-decay recovery time intervals (p < .01). The results indicated that old animals generated sufficient maximum tongue forces, but were slower in achieving these forces than young animals. These findings are consistent with reports of altered temporal parameters of tongue actions during swallowing in humans, and suggest that a disruption in the timing of muscle contraction onset and recovery may contribute to the altered tongue kinetics observed with aging.

Cortical Adaptation following Partial Glossectomy with Primary Closure: Implications for Reconstruction of the Oral Tongue

The considerable variability in functional outcomes for speech and swallowing with different reconstruction techniques following partial glossectomy may reflect the ability of patients to adapt to altered tongue structure. The purpose of this study was to determine mechanisms of cortical adaptation in swallowing to partial glossectomy reconstructed with primary closure. Four patients treated with partial glossectomy and primary closure underwent functional magnetic resonance imaging at a mean of 6 months after operation, and the data were compared to those from 8 healthy controls. Statistically significant increases in activity occurred predominately in the parietal cortices and the cerebellum. The volume of the resection was most highly correlated with activity in the premotor and parietal cortices and cerebellum. The adaptive changes in the cortex following partial glossectomy with primary closure reflect adaptation to the biomechanics of tongue movement during swallowing, and not altered sensation in the tongue.

The significance of late developmental crowding to early treatment planning for incisor crowding

Incisor crowding has traditionally been attributed to discrepancies in either tooth-jaw size or interarch tooth-size ratios. Such concepts have led orthodontists to develop mixed and permanent dentition space and interarch tooth-size analyses to assist in the diagnosis of crowded dentitions. Treatment plans have emphasized the removal of 4 premolars in an attempt to stabilize the dentition. Although individuals with large teeth may tend to have more incisor crowding, several factors other than tooth size may contribute to incisor crowding, for example, altered resting or functional activity in the facial and masticatory muscles. Thus, changes in occlusion, incisor crowding-spacing, lower anterior face height, and mandibular and maxillary retrognathism or prognathism have all been induced in primates through the application of a single chronically acting, environmental impact, such as either altered tongue posture or oral respiration.1-4 In addition, similar changes have been shown in human beings that were partially reversible after removal of the environmental impact.5,6 Thus, adverse neuromuscular changes, such as chronic mouth open breathing, have been associated with narrowing of both arches and lingual inclination of the incisor teeth and crowded dentitions.1,7-10 These dentoalveolar and skeletal changes were partially or fully reversible without orthodontic therapy after removal of the chronic input8,10 It follows that judicious orthodontic expansion procedures might be warranted to assist recovery in such cases after removal of the neuromuscular insult. We are indebted to the University of Washington for their documentation of late developmental crowding up to age 40 in orthodontically untreated as well as treated individuals. Study of untreated individuals at the University of Toronto shows that this phenomenon continues to at least age 70. Such crowding seen during the teen and adult years cannot be called tooth-jaw size discrepancy and must be neuromuscular in nature. Strong evidence supports the view that many of the crowdings we see during the mixed dentition are also neuromuscular or developmental. In a previous study9 of the relationship between mandibular incisor crowding and nasal mucosal swelling, cephalometric and dental cast variables from 30 male and 20 female children (8 to 13 years old) with chronic nasal mucosal swelling were compared with matched controls. These controls were orthodontically untreated and had no history of airway obstruction. The nasal mucosal swelling was confirmed with active posterior rhinomanometry and a headout volume-displacement plethysmograph. The subjects with nasal mucosal swelling had significantly (P < .001) more mandibular incisor crowding aDepartment of Orthodontics, University of Toronto. Reprint requests to: Donald G. Woodside, CM, DDS, MSc(D), PhD(hc), Department of Orthodontics, University of Orthodontics, 124 Edward Street, Toronto, Ontario, Canada M5G 1G6. Copyright © 2000 by the American Association of Orthodontists. 0889-5406/2000/$12.00 + 0 8/1/106117 doi.10.1067/mod.2000.106117 The significance of late developmental crowding to early treatment planning for incisor crowding