An investigation of the mandibular third molars in orthodontic cases.
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Adolescent↗
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Orthodontic root resorption studied by electron microscopy.
The present study supports previous findings that root resorption takes place simultaneously with and after the elimination of hyalinized tissue. The cementoid layer and the more mature periodontal collagen fibers adjacent to cementum are possible barriers preventing root resorption. The microenvironment around hyalinized tissue is favorable for the introduction of hard-tissue resorbing cells. The findings show that the elimination of hyalinized tissue leads to the removal of the cementoid and the mature collagen thus leaving a raw cemental surface without a barrier. It is therefore hypothesized that such an area is readily attacked by odontoclasts. Once resorption lacunae are established, the cementum is resorbed from the rear as an undermining process. By continued orthodontic force application the resorption process will proceed even after all hyalinized tissue is eliminated. If the orthodontic force is discontinued or falls under a certain level, the resorption lacunae are repaired.
Animals↗
Remodeling reversals in anterior parts of the human mandible and maxilla.
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Adolescent↗
Diagnosis and prevention of maxillary cuspid impaction.
Upper cuspid impaction is a serious problem that occurs with sufficient frequency to justify diagnosis and intervention as early as a dental age of 8 years. Screening consists of identifying patients who lack a normal cuspid bulge on palpation, with follow-up radiographic evaluation where indicated. Selective removal of deciduous cuspids is a suggested interceptive measure in Class I uncrowded malocclusions.
Adolescent↗
Transverse dento-skeletal relationships and third molar impaction.
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Cephalometry↗
Spatial position of mandibular third molars in monozygotic twins.
Measurement of anterior and medial inclinations of third molars from 10 to 18 years of age in monozygotic twins finds a consistent pattern of uprighting, with high correlations within twin pairs indicative of strong genetic influence.
Adolescent↗
Infraocclusion of primary molars with aplasia of the permanent successor. A longitudinal study.
Infraocclusion of deciduous molars that also lack a permanent successor is found to progress more than where a successor is present, while exfoliation is severely retarded. The aplasia is the most important factor in treatment planning and timing.
Adolescent↗
Dental development, dental age and tooth counts.
Emergence data on the 20 deciduous teeth and the first 29 permanent teeth were collected from 212 randomly selected urban Swedish children who were followed from birth to 18 years of age. The sex difference in the emergence of the deciduous teeth is less than one month, which is not statistically significant. Boys are consistently ahead of girls until the 17th deciduous tooth. From the 17th deciduous tooth on through most of the permanent dentition, girls are consistently ahead of boys. In the permanent dentition the sex difference ranges from 3 MO to 11 MO; these differences are statistically significant except for the 29th tooth. Reference data on dental age based on counts of 1-19 deciduous and 1-27 permanent teeth are tabulated and tooth emergence curves constructed. The tooth emergence curves can be used to express individual dental development in terms of standard deviation scores. Validity of dental age assessed by counts of permanent teeth is evaluated by a cross-sectional comparison with another sample of Swedish boys and girls. The mean difference between estimated age and chronological age is about one month in either sex. Precision of an individual estimate of dental development in terms of 95% confidence level (approximately equal to +/- 2 S.D.) varies from about +/- 4 months in the deciduous dentition to +/- 3 years in the permanent dentition. Assessment of dental development and dental age by means of tooth counts is a convenient and simple method, although it can only be applied at ages when emergence can be expected. It is especially useful in cross-sectional evaluations, as no serial data are required. In populations with a low incidence of caries the impact of such disturbing factors on emergence is correspondingly low, further increasing the validity of assessments of dental development based on tooth emergence.
Adolescent↗
Mandibular condyle morphology in relation to malocclusions in children.
Recent studies show that forces applied to the mandible during treatment with functional appliances and other orthodontic therapies produce changes in the TMJ. Specific malocclusions might also apply forces that can produce changes in the morphology of the TMJ. This study examined 104 orthodontic patients (44 males and 60 females) prior to treatment. The size and location of the condyle was determined on submento-vertex and tomographic films which was related to clinical findings including age, sex, malocclusion type, facial type, TMJ symptoms, tooth eruption sequence, crossbites and midline discrepancies. The medio-lateral width of the condylar head correlated positively with the patients age (p less than 0.001) and sex (p less than 0.001). Also the antero-posterior widths of the condyle were correlated with age (p less than 0.05). The condylar size in males was found to be greater than in females. Midline discrepancy significantly altered the increase in condylar size during growth. Transversel anomalies had a markedly greater influence on condylar growth compared to other characteristics of occlusion. The major change in condylar size during growth occurred in medio-lateral dimension as compared to the antero-posterior. In addition, the medio-lateral width was affected by midline discrepancy but not the antero-posterior width.
Adolescent↗
Mandibular growth and third molar impaction in extraction cases.
The position of mandibular third molars was studied in 60 patients from the pedodontic and orthodontic departments at the Federal University of Rio de Janeiro. All individuals received orthodontic treatment with an edgewise appliance following the extraction of first premolars. Examination of superimposed pretreatment and posttreatment cephalometric radiographs led to the observation that mandibular growth is directly related to the positioning of mandibular third molars. Third molar impactions were more likely to occur in cases with a predominance of vertical growth. The larger ascending ramus, the diminution in total length of the mandible and the larger mesial inclination of the crowns also seem to be indicative of third molar impaction.
Adolescent↗
Premature or delayed exfoliation of deciduous teeth and root resorption and formation.
The present cross-sectional study was based on orthopantomograms of 1245 Greek children (590 males and 655 females), whose ages ranged from 6 years 10 months to 14 years. Three orthodontic practices were the source of these orthopantomograms which were taken before the start of orthodontic treatment. The resorption process of the deciduous mandibular canine and molar roots was divided into five stages and the root formation process of their permanent successors into eight stages. The percentage distribution of the deciduous root resorption stages for each root formation stage of the corresponding permanent teeth was then recorded. Exfoliation of these three deciduous teeth occurred when the root formation of their successors had reached the R2/3, R3/4 or the beginning of the Rc stage. As far as the effect of local factors on root resorption and formation process our findings indicated that decay, pulp necrosis and pulpotomy hastened the rate of root resorption of the deciduous molars, while they did not influence the rate of root formation of the corresponding permanent teeth.
Adolescent↗
Sucking, chewing, and feeding habits and the development of crossbite: a longitudinal study of girls from birth to 3 years of age.
The prevalence of posterior crossbite among pacifier-sucking girls in Falköping, Sweden, was previously found to be 26%. The aim of this investigation was to follow the development of crossbites in pacifier suckers and to determinate the possibility of reducing the prevalence of crossbite by informing and instructing the parents about sucking habits and reducing the time the child has the pacifier in the mouth. Parents of 60 consecutively born girls belonging to St Olof's health district, Falköping, Sweden, were invited to take part in the study. All parents agreed to participate. Five interviews or examinations of each girl took place from birth until 3 years of age. Fifty-four (90%) of the 60 girls were breast-fed. The mean duration of breast-feeding was 8 months, and 67% of the girls were breast-fed for half a year or more. Forty-three children (72%) developed a pacifier-sucking habit, 6 (10%), a digit-sucking habit, and 11 (18%), no sucking habits. The mean duration of breast-feeding was longer for the nonsuckers (11 months) than for the pacifier- and digit-sucking children (5 months). Of the 39 girls who still had the pacifier habit at 3 years of age, 2 had developed a posterior crossbite. Another girl stopped the habit when a crossbite was registered at the 2 1/2-year examination. At the next appointment, the crossbite had corrected itself spontaneously. One of the 2 girls with crossbite at 3 years of age developed a prenormal occlusion with both anterior and posterior crossbites. For 12 more pacifier suckers, an interfering contact was noted with a forced guidance of the mandible and a midline shift. In all 12 cases, the interfering teeth were primary canines. We conclude that parents should be instructed to reduce the "in the mouth time" of the pacifier. The transverse occlusal relationship in pacifier-sucking children should be evaluated between 2 and 3 years of age. If interfering contacts of the primary canines exist, the parents should be instructed to reduce the pacifier-sucking time.
Breast Feeding↗
Maxillary molar intrusion with fixed appliances and mini-implant anchorage studied in three dimensions.
The intrusion of an overerupted maxillary molar using traditional orthodontic treatment is a real challenge. The aim of this study was to investigate the envelope of intrusive movements of a maxillary molar in cases using mini-implants as anchorage with partial or full-mouth fixed edgewise appliances. The cusp tips of the pretreatment and postintrusion dental casts were recorded by a three-dimensional (3D) digitizer. The 3D data of the serial dental casts were analyzed to distinguish the direction and magnitude of individual tooth movement. The mean intrusive movement of the maxillary first molars was three to four mm, with a maximum of over eight mm. For the adjacent maxillary second molars and second premolars, the amount of intrusion was two mm and 1-2 mm, respectively. This study demonstrated that significant true intrusion of maxillary molars could be obtained in a well-controlled manner by using fixed appliances with titanium mini-implants as bony anchorage.
Adolescent↗
Microvascular system of the rat incisor enamel organ. A scanning electron microscopic study of vascular corrosion casts.
The rat incisor is a commonly used model in studies of tooth eruption, amelogenesis and effects of mechanical loading on the dental and periodontal tissues. The purpose of this study was to assess the three-dimensional architecture of the microvascular bed of the rat incisor enamel organ, to describe the direction of blood flow, and to provide a histometric assessment of the vascular categories that can be statistically analyzed. Vascular corrosion casts were prepared and examined by scanning electron microscopy. The microvasculature of the labial periodontal space was arranged in three distinct layers. The inner layer in direct relation to the enamel organ consisted of a capillary network which was drained by short venules at the cemento-enamel junction. The intermediate layer consisted of arterioles oriented parallel to the long axis of the incisor mainly mid-labially, branching off smaller arterioles to the capillary network. The outer layer was formed by flattened sinusoid vessels of larger caliber. Blood supply was from the anterior superior alveolar artery branches through the arterioles into the capillary network. Drainage was postero-laterally along the cemento-enamel junction via short venules which emptied into the sinusoid vessels, finally to flow through Volkmann's canals into the alveolar bone via small venules. The findings demonstrate that the microvasculature of the rat incisor enamel organ has an exceptionally high level of physiologically-adapted structural organization.
Analysis of Variance↗
A treatment decision-making model for infraoccluded primary molars.
The objective of this paper is to clarify the literature's findings and provide guidelines for decision-making during the long-term treatment planning of infraoccluded primary molars. This paper presents a synopsis of findings concerning prevalence, aetiology, diagnostic methods, diagnostic criteria and treatment options. Treatment decisions are mainly guided by the clinical assessment of the presence or absence of succedaneous tooth, evaluation of onset, time of diagnosis, resorption rate, rate of progression of infraocclusion, risk of adverse effects over time, and predictive clinical patterns of infraoccluded primary molars. These models are a result of a comprehensive review of the literature and presents a compilation of findings in a format that is of practical use to the clinician.
Decision Making↗
Space-regaining treatment for a submerged primary molar: a case report.
The aetiology of submerged primary molars is not known and optimal treatment has still not been established. If submerged primary teeth are left untreated, the occlusal consequences are space-loss due to tipping of adjacent teeth and/or overeruption of the opposing teeth. Normally, treatment consists of extraction of the deciduous teeth or observation for normal exfoliation. Here we report a case where the submerged primary molar was extracted surgically after space-loss had been regained.
Bicuspid↗
UK National Clinical Guidelines in Paediatric Dentistry. Extraction of primary teeth -- balance and compensation.
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Child↗
The effect of fluorides and caries in primary teeth on permanent tooth emergence.
This study addressed two questions: (i) is there an effect of exposure to fluorides on the timing of emergence of permanent teeth? and (ii) can a difference in timing of tooth emergence be explained by the impact of fluorides on the caries experience of the predecessors? Data were obtained from a long-term follow-up study of the oral health condition in a sample of 4468 Flemish children. Survival analyses with log-logistic distribution were performed to calculate median emergence ages and 95% confidence intervals; four fluoride exposure parameters (fluorosis, use of systemic fluoride supplements, age at which tooth brushing started and frequency of tooth brushing) and caries experience were taken as covariates in the model. The present study indicates that the impact of any of the four fluoride exposure parameters on permanent tooth emergence was relatively minimal. Caries experience in the primary molars had a more pronounced impact on the timing of emergence of the successors than exposure to any of the four fluoride parameters.
Age Factors↗