Ib Leth Nielsen

Comparison of airway space with conventional lateral headfilms and 3-dimensional reconstruction from cone-beam computed tomography

INTRODUCTION Changes in the normal pattern of nasal respiration can profoundly affect the development of the craniofacial skeleton in both humans and experimental animals. The orthodontist is often the first clinician to notice that a child is breathing primarily through the mouth, either at the initial examination or later during treatment. The lateral headfilm, part of the patients normal records, might show increased adenoid masses, suggesting that these could be part of the problem. Previous studies have, however, questioned the validity of the information from lateral headfilm. METHODS Our aim was to compare imaging information about nasopharyngeal airway size between a lateral cephalometric headfilm and a 3-dimensional cone-beam computed tomography scan in adolescent subjects. The nasopharyngeal airway area and volume were measured in 35 subjects (8 boys, 27 girls; average age, 14 years). RESULTS Volumetric measurement errors ranged from 0% to 5% compared with known physical airway phantoms used to calibrate. A moderately high (r = 0.75) correlation was found between airway area and volume; the larger the area, the larger the volume. However, there was considerable variability in the airway volumes of patients with relatively similar airways on the lateral headfilms. Nine of the 35 patients had over 25% of the potential nasopharyngeal airway volume occupied by inferior turbinate protuberances, leading to significant airway restriction in some patients. CONCLUSIONS The cone-beam 3-dimensional scan is a simple and effective method to accurately analyze the airway.

Vertical malocclusions: etiology, development, diagnosis and some aspects of treatment

Vertical malocclusions develop as a result of the interaction of many different etiological factors; one of the most important of these factors is mandibular growth. Variations in growth intensity, function of the soft tissues and the jaw musculature as well as the individual dentoalveolar development further influence the evolution of these malocclusions. This article reviews the most common etiological factors and their possible contribution to the development of vertical malocclusions with special emphasis on the role of mandibular growth in the development of open bite and deep bite. The role of the cephalometric morphological analysis in the differential diagnosis of vertical malocclusion is emphasized. Aspects of orthodontic treatment of vertical malocclusions are illustrated with individual cases.

Patterns of mandibular movements in subjects with craniomandibular disorders

Mandibular movements were evaluated for border and functional movements in 24 adult normal subjects and 26 adult patients with muscle pain associated with a craniomandibular disorder. The mandibular incisor position was tracked with an electromagnetic system in three planes by use of either a Myotronic Kinesiograph or a Siemens Sirognathograph instrument while the subject sat in an upright position. In the normal subjects, the maximum movements of the mandible in lateral, protrusive, and vertical directions were compared with the envelope of movement during speech and mastication. The range of the rest position was 1 to 5 mm in relation to the intercuspal position; the range of maximum excursion during speech was 30% to 36% of maximum opening; the vertical extent of excursion during mastication was 18% to 90% of the maximum vertical opening dependent on the bolus. Protrusive movements were straight forward, dividing the angle evenly between left and right laterotrusion. Laterotrusive movements were of equal length and similar to the length of protrusion. Twenty-six patients with muscle pain, in many instances, demonstrated asymmetry in the length of laterotrusive movements. Different pathways for moving the mandible away from the intercuspal position and returning to this position could be seen during laterotrusion. Unequal laterotrusive excursions and asymmetrical, nonparallel movement patterns for mandibular protrusion and retrusion were often observed. In contrast, the extent of the speech envelope and the envelope of mastication were similar to that of the controls.

Dental and skeletal contributions to occlusal correction in patients treated with the high-pull headgear–activator combination

The purpose of this study was to examine dental and skeletal changes in patients treated with the high-pull headgear-activator combination. A group of 40 consecutively treated subjects with a Class II molar relationship and a minimum of 5 mm overjet was used for this study. The results showed that Class II correction often was achieved by distal repositioning of the maxillary teeth (mean, 0.07 mm) and mesial repositioning of the mandibular teeth (mean, 3.3 mm) with a wide range of variation. Correlation of maxillary molar repositioning with total interarch occlusal change showed a positive relationship; however, a weak correlation suggested that other variables were contributing factors, in addition to distal upper molar positioning. The change in mandibular molar position compared with the movement of pogonion strongly suggests that forward growth of the mandible is important to the correction of the Class II malocclusion. When total molar repositioning in the upper jaw was correlated with total molar repositioning in the lower jaw, a strong inverse correlation was found, indicating that upper molar movement parallels lower molar movement.

Consistency and precision of landmark identification in three-dimensional cone beam computed tomography scans

The purpose of this study was to quantify the consistency and precision of locating three-dimensional (3D) anatomic landmarks. The hypotheses tested are that these landmarks have characteristic and variable error patterns associated with their type and location. The consistency and precision of nine orthodontists identifying 32 landmarks of 19 patients were quantified. The cone beam computed tomography (CBCT) data were acquired using a Hitachi CB MercuRay system. Prior to the study, all examiners were calibrated with respect to the definitions of the landmarks and on the use of the software program (Dolphin) for identifying the landmarks. In addition, a reference guide was provided that had the definitions and sample images of the landmarks. Data were collected in spreadsheets as x, y, and z co-ordinates and statistically analysed to determine the mean and standard deviation (SD). The mean location for a given landmark on a given patient served as the reference point. The mean of the distances from the reference point was used as the consistency, while the SD of this mean was used as a measure of precision. The error in the x, y, and z planes was calculated in order to determine the specific characteristics of each landmark. The consistency in landmark location and precision did not differ significantly among the nine examiners. Sella turcica was the most consistently (0.50 mm) and most precisely (0.23 mm) identified anatomic landmark. The most inconsistent landmark was porion-right (2.72 mm) and the most imprecise landmark was orbitale-right (1.81 mm). Due to the lack of even distribution of the errors, careful use of these landmarks for analysis purposes is needed.

Facial growth during treatment with the function regulator appliance

Facial growth was examined in ten patients who had completed one year of treatment with the function regulator 2 (FR-2) as described by Fränkel. Cephalometric headfilms taken before and one year into treatment were superimposed on stable structures in the anterior cranial base, and the qualitative changes were analyzed. The results showed that facial growth in most patients was mainly in the vertical plane, but considerable individual variations were seen. The maxilla generally became more retrognathic during treatment and showed backward rotation and posterior displacement in some patients. Marked individual variations were seen in the mandible. No indications were found that the FR-2 promoted forward growth of the mandible as used in this study (no notching of teeth and less than 5 mm of mandibular advancement). The improvement in dental occlusion observed was primarily due to changes in the vertical relationship between the jaws.

Comparison of drug‐induced sleep endoscopy and lateral cephalometry in obstructive sleep apnea

To evaluate the association between findings from drug‐induced sleep endoscopy (DISE) and lateral cephalometry in obstructive sleep apnea (OSA)

Characteristics of Jaw Growth in Cleidocranial Dysplasia

OBJECTIVE The purpose of this pilot study was to assess craniofacial morphology in young and adult individuals with cleidocranial dysplasia (CCD). DESIGN Craniofacial morphology in young individuals (primary dentition) and in young adults was compared with control data using ratios and angles obtained from lateral head films. SETTING The CCD individuals were referred to the Center for Craniofacial Anomalies for diagnostic workup and treatment recommendations. SUBJECTS The sample consisted of 14 Caucasians. The inclusion criterion for the young, prepubertal group (A) was complete primary dentition, and for the adult, postpubertal group (B), the eruption of all four first molars was required. INTERVENTIONS No treatment other than extraction or surgical removal of selected primary or supernumerary teeth was performed. RESULTS Both groups showed significantly smaller anterior upper face height compared with controls. Group B subjects demonstrated significantly smaller face height values than the controls in the A point-nasion-B point (ANB) angle, facial axis, mandibular plane angle, palatal plane/mandibular plane angle, and gonial angle. No significant differences were found between group A individuals and the controls for these measurements. The older group had shorter anterior lower face height compared with both anterior upper face height and posterior lower face height. CONCLUSIONS Whereas young CCD subjects showed relatively normal jaw proportions and morphology of the mandible, older CCD individuals tended to have short lower face height, acute gonial angle, anterior inclination of the mandible, and mandibular prognathism. These differences can be attributed to pronounced horizontal mandibular growth resulting from lack of vertical maxillary growth and impaired eruption of permanent teeth.

Response patterns of craniomandibular muscles with and without alterations in sensory feedback

1. Surface EMG recordings were made bilaterally from the anterior part of the temporal muscle, superficial masseter muscle, and the suprahyoid complex of muscles while tracking mandibular incisor movement in three planes. This was done in 20 normal subjects with 16 different responses. Some responses involved clenching whereas other responses occurred with actual mandibular movement. 2. Each muscle demonstrated a probability of recruitment dependent on the response that correlated with the intensity of recruitment. The higher the probability of recruitment, the greater the intensity of muscle activity. 3. The anterior temporal muscle demonstrated no statistically significant difference in any of the responses between the left and right muscles. The masseter muscle also demonstrated bilateral symmetry. 4. The anterior part of the temporal muscle was recruited in more than 60% of its trials (60% to 100%) in ipsilateral laterotrusion, retrusion, fast vertical raising, clenching on the ipsilateral or intercuspal position, and mastication. The temporal muscle was recruited in less than 60% of its trials in contralateral and incisor clenching, and less than 30% in contralateral laterotrusion, protrusion, and opening. 5. The superficial masseter muscle was recruited in more than 60% of its trials in protrusion, vertical raising, all clenches, and mastication. The masseter muscle was recruited less than 60% in retrusion, ipsilateral laterotrusion, and opening. 6. The suprahyoid group of muscles was recruited in more than 60% of its trials in protrusion, opening, and mastication. This group of muscles was recruited less than 60% of the time in clenching, lateral movements, and rapid vertical raising of the mandible. 7. Applying a maxillary splint to seven subjects significantly decreased the recruitment of the anterior temporal and masseter muscles during mastication. The splint also modified the use of the masseter muscle during protrusion so that it was less active, but increased its recruitment during contralateral clenching. The suprahyoid muscle group was unaffected by the maxillary splint. 8. These data support the concept that movement of the mandible from the intercuspal or rest position develops a coactivation pattern that will excite or inhibit a given muscle regardless of whether clenching with occlusal contacts or no occlusal contact is involved. 9. The data also demonstrate that the maxillary splint can alter the use of the jaw elevator muscles, predominantly in mastication.

Direct bonding on impacted teeth

In eighteen patients twenty-three impacted teeth were surgically exposed and provided with Cuspid-Pull Brackets by the direct-bonding technique. Light orthodontic traction was applied after 10 minutes. Only three brackets were lost during the experiment. The experiment showed that sufficient bonding could be established on impacted teeth without pumicing the tooth surface and that phosphoric acid in minimal amounts causes no harm to the adjacent tissues but assists in preventing bleeding from the surrounding tissues. This made it possible to obtain the necessary dryness of the exposed tooth surface. The reasons for bond failure are discussed.