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PubMed2004

Morphogenesis of parrot jaw muscles: understanding the development of an evolutionary novelty.

Parrots have developed novel head structures in their evolutionary history. The appearance of two new muscles for strong jaw adduction is especially fascinating in developmental and evolutionary contexts. However, jaw muscle development of parrots has not been described, despite its uniqueness. This report first presents the normal developmental stages of the cockatiel (Nymphicus hollandicus), comparable to that of the chick. Next, the peculiar skeletal myogenesis in the first visceral arch of parrots is described, mainly focusing on the development of two new jaw muscles. One of the parrot-specific muscles, M. ethmomandibularis, was initially detected at Nymphicus Stage 28 (N28) as the rostral budding of M. pterygoideus. After N32, the muscle significantly elongates rostrodorsally toward the interorbital septum, following a course lateral to the palatine bone. Another parrot-specific muscle, M. pseudomasseter, was first recognized at N36. The muscle branches off from the posteromedial M. adductor mandibulae externus and grows in a dorsolateral direction, almost covering the lateral surface of the jugal bar. The upper tip of the muscle is accompanied by condensed mesenchyme, which seems to be derived from cephalic neural crest cells.

Animals↗
PubMed1986

Computer-aided modeling in the assessment of the biomechanical determinants of diverse skeletal patterns.

Aberrant functional patterns of the masticatory musculature have been alleged as a factor influencing the morphogenesis of mandibular dysplasias. These include such expressions as the hyperdivergent skeletal open bite and its counterpart, the hypodivergent skeletal deep bite. A lack of anatomic data dealing with the actual musculoskeletal orientations of these types has resulted in speculative reports on divergent anatomy and its purported effects. In this study anatomic dissections of a hyperdivergent and a hypodivergent human cadaver illustrated that skeletally dysmorphic types possess different spatial orientations of the masticatory adductors in relation to dentofacial structures. A two-dimensional analysis of static equilibrium using computer-aided modeling demonstrated that these two types produce biomechanically distinct modes of muscle action. Temporalis activity must be 40% higher in the hyperdivergent model as compared with its counterpart to produce a biting force of 500 N (112 lb). The data suggest a rationale for the weak biting forces previously reported in long-faced persons when compared with horizontally developed subjects. The direction of condylar reaction force was also found to vary from a vertical orientation in the hyperdivergent model to oblique in the hypodivergent model. "Physis-like" behavior of the condyle, which can orient axially toward loading forces, may present an explanation for the reported differences in the direction of condylar growth in dysmorphic persons. A finite element analysis pictured distinct regions of deformation and compression in a novel perspective to help evaluate the currency of accepted hypotheses of stress-induced osteogenesis. The data support previous work reporting a latent geometric interdependency existing between muscle orientation and mandibular morphology.

Adult↗
PubMed1991

Growth of the pharynx and its physiologic implications.

The bony nasopharynx increases its capacity predominantly by means of vertical development. Analogous to the facial structures is an expression of some somatotopic features that give rise to a higher and more shallow pharyngeal dimension in the dolichocephalic growth pattern. The nasopharynx's ultimate patency, however, depends on the growth and relative size of the soft tissues that line the skeletal boundaries. A decreased patency of the oropharyngeal airway can induce some postural adaptations, which secure a constant sagittal dimension at that level. However, at a certain critical point, purely nasal respiration will be turned into an oronasal breathing pattern, which in turn will elicit more compensatory mechanisms. This muscle recruitment is a possible cause of a deviant vertical craniofacial growth pattern.

Adaptation, Physiological↗
PubMed1998

Cephalometric analysis of changes in occlusal relationship.

One of the main problems in assessing the mode of action of various treatment modalities is the method of measuring the treatment change. The purpose of the present study was to develop a cephalometric method that would permit a detailed evaluation of the individual growth processes (skeletal and dental) that contribute to the overall change in occlusal relationship. The change in molar relationship was resolved in five components, i.e. translation of the maxilla, of the upper molar, of the mandible, of the lower molar, and rotation of the mandible. These movements were recorded using regional superimposition of various structures, with the aid of a computer program. Derotation of the mandible was performed to remove any confounding effects of total mandibular rotation on the interpretation of the measurements. The results show that assessment of treatment effects can be carried out by comparison of the five resulting vectors.

Cephalometry↗
PubMed1994

The influence of pharyngeal flap on facial growth. Long-term results in the patients with isolated cleft palate.

The facial growth of 22 children from 6 to 17 years of age with repaired isolated cleft palate was studied. Eleven patients had had posterior pharyngeal flap surgery at about 7 years of age and were examined one year before, and three and 10 years after, flap surgery. The other eleven patients served as matched references. The convexity of the facial profile decreased significantly in both groups. There were differences in growth between the two groups in the variables that concerned mandibular position and anterior facial height. The results indicated that the reference individuals had achieved more anterior growth rotation during the development of the face. There was no improvement in mandibular retrognathism in the flap group until the patients were 10 years of age, but the mandible then resumed the normal anterior rotation and had caught up with the reference group after puberty, to result in a facial form with no significant difference from that in adolescents with cleft palate and without pharyngeal flaps. We suggest that the influence of a pharyngeal flap on facial growth has no long term clinical importance in patients with an isolated cleft palate, but the impact of the temporary change in facial growth after pharyngoplasty should be taken into consideration when orthodontic treatment is planned.

Adolescent↗
PubMed1997

Cervical neckgear--villain or savior?

An understanding of growth and development and the effect our appliances have on a person's growth and development is necessary in the selection of the therapeutic appliances we choose to use, out of the multitude available. Timing of treatment is also important in effecting positive changes in skeletal and dental relationships. Early treatment to correct skeletal discrepancies and gain arch length can allow for an increase in nonextraction therapy. Cervical extraoral appliances, maxillary fixed expansion appliances, and mandibular labial "E" arches can be used early to effectively reduce of skeletal discrepancies and to gain arch length without the fear of rotating the mandible down and back, permanently increasing the mandibular plane angle. Case reports are presented to illustrate the beneficial changes that can occur with early treatment with these appliances.

Cephalometry↗
PubMed1993

Longitudinal study of jaw growth and prosthetic management in a patient with ectodermal dysplasia and anodontia.

A patient with hypohidrotic ectodermal dysplasia and anodontia was studied clinically and cephalometrically from 6 to 18 years of age. This case is exceptional in that the patient was a young girl. Five sets of complete dentures were fitted during this period. Periodic recall examination and adjustment maintained good oral function and aesthetics. Serial cephalometric analysis of craniofacial development revealed that growth of the maxilla was slightly reduced, but there was no detectable effect in the mandible. Three-dimensional analysis of the alveolar ridge form from serial casts showed that increase of the anteroposterior arch dimension was larger than that of the lateral arch dimension in both jaws. There was a lateral expansion in the anterior and premolar regions and a considerable height increase in the posterior tooth region of the upper alveolar ridge. Our findings support those of Sarnart et al. (1953) in showing that lack of teeth did not affect growth of the jaws.

Anodontia↗
PubMed2001

Management of a Class II deep bite malocclusion with combined straightwire appliance and bioprogressive therapy.

Development of straightwire appliances and improvement in archwire technology have simplified fixed appliance therapy in orthodontics. Although straightwire appliances are routinely used to treat most malocclusions, there are inherent limitations and it is necessary to look at the needs of each individual case rather than to simply proceed through a "cookbook" series of archwires to achieve a desired result. The Bioprogressive Therapy, although biomechanically complex, offers several advantages that can be integrated with the straightwire appliances to overcome the latter's shortcomings. This article illustrates the use of simplified Bioprogressive mechanics by means of utility arch in the treatment of a Class II deep bite malocclusion with high anchorage requirement.

Adolescent↗
PubMed1976

The reliability of head film measurements. 3. Tracing superimposition.

The superimposition of tracings from lateral skull x-ray films taken at different timepoints is an important method for assessing developmental and treatment changes through time. The usefulness of the data derived is, however, limited by the fact that the physical act of superimposing tracings is performed with some error. The magnitudes of error for superimpositions on different "planes" have not been amenable to quantitation by previously available methods. Using newly developed computer-aided techniques, we have been able to quantitate both the primary errors of tracing superimposition and the associated secondary landmark displacements for four conventionally employed anatomic reference "planes". For each reference "plane," twenty-five independent film pairs were examined independently by each of four judges. Therefore, 100 acts of tracing superimposition were available for each reference "plane." Output data are presented which appear to support the conclusion that measurement errors in tracing superimposition are a consequential factor affecting the confidence which should be placed in head film comparisons, particularly with regard to individual cases. Some consequences of this conclusion with respect to growth prediction and to the evaluation of treatment effects are considered.

Cephalometry↗
PubMed2005

[The Procuste superimpositions: its value in the study of typology and its development during Edgewise Tweed-Merrifield treatment].

By transforming all figures into the same size, the Procruste mathematical superimpositions system allows orthodontists to analyze and compare geometric shapes whose different areas and forms would otherwise have made comparison impossible. Procruste is, accordingly, particularly useful in the study of facial types. In this retrospective study we analyzed the effects exerted by both growth and Edgewise Tweed Merrifield treatment upon changes in patients' typology of three different facial types. One hundred patients with Class II dental malocclusions were divided into three groups of deep bite, normal bite, and open bite. We found no significant statistical difference in the effects of treatment and of growth on modification of "form" of the facial skeleton as seen on profile cephalograms of the three categories. Patients in all the groups showed an average anterior rotation of the mandible.

Adolescent↗
PubMed2002

Effects of maxillary protraction on craniofacial structures and upper-airway dimension.

This study was conducted to examine the effect of treatment with a maxillary protraction appliance on the development of the craniofacial structures and upper-airway dimensions. A total of 25 patients (mean age: 9.8 years) with Class III malocclusions were evaluated by the use of lateral cephalograms. A significant increase in maxillary forward growth, inhibition of mandibular forward growth, and clockwise rotation of the mandible were observed. The maxillary incisors were significantly proclined and the mandibular incisors significantly retroclined. A multiple-regression analysis revealed that maxillary growth had a significant positive effect on the superior upper-airway dimension. These findings indicate that the superior upper-airway dimension can be altered during maxillary protraction.

Cephalometry↗
PubMed1989

The effects of forceps delivery on facial growth.

Postnatal growth of the face is a composite function of genetic and environmental factors. A sudden traumatic insult due to the use of forceps at birth could have long-term effects which could detrimentally influence growth and development. This study examines the development of the skeletal and dental components of forceps vs. non-forceps-delivered patients. The association between delivery methods as related to TMJ problems, bruxism, posterior crossbites, and molar arch width differences was evaluated in 16 forceps-delivered and 29 naturally delivered patients. Results showed no statistically significant difference between delivery method and TMJ problems, posterior crossbites, bruxism, or molar arch width. It was noted that the non-forceps group had a higher incidence of posterior crossbite and narrower molar arch width. The forceps-delivered group had a higher percentage of bruxism and TMJ pain and/or noise. It was also noted that the small sample size may have influenced the statistical relationships.

Adolescent↗
PubMed1999

The influence of the muscles of facial expression on the development of the midface and the nose in cleft lip and palate patients. A reflection of functional anatomy, facial esthetics and physiology of the nose.

The further improvement of well-established techniques in primary and secondary cleft surgery requires a detailed and interdisciplinary knowledge and observation of anatomical, functional and developmental problems. An investigation into the macroscopic and microscopic anatomy of the perinasal and perioral muscles and parts of the human nasal septum, as well as into the pathomorphology of ancient skulls with untreated clefts is presented. On this basis an interpretation of clinical findings in untreated newborns compared with surgically treated CLP-patients has been undertaken. The 3D-CT, superimposing photography and coloured experimental settings of nasal airflow complete the visualisation of the anatomical and functional findings.

Adult↗
PubMed1980

Dental asymmetry and mental retardation: a comparison of subjects with mental retardation resulting from prenatal or postnatal influences.

The development of phenotypic characteristics is believed to be stabilised within certain limits of variability by processes described as canalisation or developmental homeostasis. Dental asymmetry is thought to reflect the relative success that developmental homeostasis has in countering developmental disturbances. The present study demonstrated that dental asymmetry of the permanent dentition was generally higher in non-Down retarded subjects whose mental retardation was associated with a prenatal rather than a postnatal or birth related insult. Because variations in the size and shape of teeth are generally produced during the prenatal period, the finding of increased fluctuating dental asymmetry in the group with prenatal insult supported the contention that dental asymmetry reflects the relative success that developmental homeostasis has in countering developmental disturbances.

Birth Injuries↗
PubMed1998

A longitudinal study of the development of crowded dental arch.

It is important to determine both where and when in the process of dental arch development crowding occurs. The authors investigated 81 children (boys/37, girls/44). These children were developing permanent dentition without early loss of deciduous or permanent teeth, which is considered to be one of the causes of malocclusion. Impressions were taken from subjects who had normal, spaced, or crowded permanent dental arch, and longitudinal casts made every two months from three years of age. In both the maxilla and the mandible, the transition to the crowded condition most often occurred (maxillary: 84.6%, mandibular: 64.5%) at the time of eruption. Crowding condition was also caused by the eruption of other teeth; however, this was rare. The maxillary and mandibular crowding mostly occurred (maxillary: 69.2%, mandibular: 77.4%) in the anterior teeth. It was seldom observed in the premolar and first molar regions.

Child↗
PubMed1982

["Renal dwarfism". Its impact on dental development and on maxillary growth].

Children with terminal renal failure require iterative dialysis while awaiting kidney graft, and these have to be repeated over a period of years until a suitable graft presenting histocompatibility with the receiver is found. This has a considerable growth retardation effect (-3 to -6 SD, according to the age at onset of terminal failure). Two features appear to be paradoxical in these children. 1) In spite of a high carbohydrate diet and generally poor oral hygiene, they present a low prevalence of caries, probably related to modified salivary components. The only objective finding is an increase in salivary urea levels. 2) In spite of harmonious hypotrophy, no particular encumbrance of the dental arch is observed. Alveolar growth, contemporary with dental eruption, is sufficient to compensate possible hypotrophy of maxillary bone bases.

Adolescent↗
PubMed1983

Orthopedic coordination of dentofacial development in skeletal Class II malocclusion in conjunction with edgewise therapy. Part II.

This second of two articles describes the effects of mandibular growth enhancement in a comprehensive orthopedic approach to the correction of skeletal Class II malocclusion. Clinical and experimental evidence gives support to the concept, and case histories show the clinical mode of use of the appliance system. An initial 10- to 12-month orthopedic phase is followed by a second phase of similar duration in which full edgewise therapy is used to establish a gnathologically ideal occlusion. As the essential corrections are achieved in the orthopedic phase, the second phase is much reduced in complexity and is generally confined to alignment and final detailing. This combined approach to skeletal Class II treatment offers the possibility of better harmony of dental and facial features, with continued stability through the period of facial growth.

Cephalometry↗
PubMed1991

Craniofacial growth in bone marrow transplant recipients treated with growth hormone after total body irradiation.

The effect of growth hormone (GH) treatment on craniofacial development was studied in five children exhibiting growth retardation following bone marrow transplantation. Linear and angular measurements were made on lateral radiographic cephalograms taken prior to the start of GH treatment and after an average treatment time of 1.2 yr. The results showed that the mean growth increments of mandibular length in the GH treated children, exceeded the corresponding values of the control group by 150% during the period of investigation. It is suggested that this dimensional increase in the patients was due to GH stimulation on the chondral growth process in the mandibular condyles.

Adolescent↗