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At least 127 records · Page 7Linked to original sources
PubMed2003

Crown-root shape of the permanent maxillary central incisor.

This study aimed to determine whether the lateral cephalometric crown-root shape differs among the permanent maxillary central incisor in Class I, Class II division 1, Class II division 2 and Class III malocclusions and to identify the nature of any differences. Of the 499 lateral cephalograms recorded at a university orthodontic clinic during 2001, 361 satisfied the inclusion criteria. Sixty cephalograms were selected from the four malocclusion groups and were digitized in random order. The configurations of the 10 landmarks characterizing the crown-root shape of the permanent maxillary central incisor were then optimally superimposed using Procrustes algorithms. Discriminant analysis of the principal components of shape determined the incisor shape differences between the malocclusion groups. The crown-root shape of the permanent maxillary central incisor did not differ significantly among the Class I, Class II division 1, and Class III groups (P > .05); however, the crown-root shape of the Class II division 2 permanent maxillary central incisor was significantly different (P < .001) from that of the Class 1, Class II division 1 and Class III. The shape discrimination involved axial bending of the Class II division 2 incisors. Principal components 1, 2, and 3 accounted for 63% of the Class II division 2 incisor shape variance, encompassing a shorter root, a longer crown, and axial bending of the incisor, in addition to a reduced labiopalatal thickness. These shape features could precipitate the development of a deep overbite in Class II division 2 malocclusion and may limit the amount of palatal root torque during fixed appliance therapy.

Algorithms↗
PubMed1998

No effect of lip bumper therapy on the pressure from the lower lip on the lower incisors.

The pressures from the lower lip on the lower incisors were measured at the midline between the central incisors and between the left lateral incisor and canine. The measurements were made with the lip at rest and during swallowing of water in 24 boys and 40 girls aged 9-15 years. The children were divided into four groups, two treated with a lip bumper with and without an oral shield, and two with a lingual arch with and without springs for proclination of the lower incisors. Recordings of the pressures were made before the start of the treatment, and 3 and 8 months after the use of the appliance, as well as 4 months after the removal of the lip bumper or lingual arch. The treatment with a lip bumper did not change the pressure from the lip on the lower incisors at rest. The pressure at the midline during swallowing was also unaffected by the lip bumper therapy, but the pressure between the lateral incisor and canine increased. Thus, lip bumper therapy did not lead to decreased pressure from the lip on the incisors. Proclination of the lower incisors with a lingual arch resulted in an increase of the pressure from the lip at rest. Thus, no adaptation of the lower lip to the proclination occurred. After relapse of the proclination the pressure from the lip decreased to a value no different from that before the start of the treatment.

Acrylic Resins↗
PubMed2000

The retraction of upper incisors with the PG retraction system.

The aim of this study was to evaluate the effect on the dentoalveolar structures of the application of PG springs for retraction of upper incisors and to compare the outcome with the effect of a closed coil spring retraction system. Thirty-six subjects with Angle Class I or Class II malocclusions were selected for the study. Each subject had the two upper first premolars extracted and presented a symmetrical extraction space of at least 3 mm distal to the lateral incisors after canine retraction. The subjects were divided into two groups, the PG group with 17 subjects and the coil group with 19 patients. One group had the incisors retracted by PG universal retraction springs, whereas in the other a closed coil spring system was used. The average chronological ages were 18 years 4 months for the PG group, and 18 years 7 months for the coil group. In both groups the springs were activated to produce an initial force of 150 g per side. To examine the type of movement of the anterior and posterior teeth, and the time and rate of space closure, 20 parameters were measured and evaluated statistically with Wilcoxon and Mann-Whitney U-tests. In both groups the incisor retraction was accompanied by mesial movement of the buccal segments. Distal movement of the root apex of the incisors was observed in both groups, although more pronounced in the PG group (P < 0.01). A significant incisor intrusion resulting in a decrease in overbite was found in the PG group, whereas the deep bite increased significantly in the coil spring group. The PG spring produced a three-dimensional control in the movement of the upper incisors, so that application of additional intrusive mechanics after completion of the incisor retraction became unnecessary.

Adolescent↗
PubMed1989

Emergence of the deciduous incisors in CLP children.

A longitudinal study of the time of emergence of the deciduous incisors was performed in Dutch cleft lip and/or palate (CLP) children (n = 52). A group of normal children (n = 62) served as control. Emergence dates were registered by the parents and checked regularly by one of the investigators. Mean emergence times of the deciduous upper incisors--including both the cleft-sided lateral in the distal segment and in the premaxilla--and lower incisors were studied. The lateral incisor on the cleft side situated in the distal segment was delayed 8 months in children with a cleft lip and alveolus and 13 months in cleft lip and palate children. The delay for the lateral incisor situated in the premaxilla increased by nearly 4 months in these children. The upper lateral incisors on the non-cleft side and in cleft palate children were not delayed as compared with normal children. The central lower incisors emerged one month earlier than normal when there was a palatal cleft. Presurgical orthopaedics used in these groups could have caused this acceleration. The central upper and lateral lower incisors showed no significant differences in mean emergence ages as compared with the control group, nor between the various cleft types. Sex differences were not found in any of the groups.

Age Factors↗
PubMed2005

Variability in the eruption of the permanent incisor teeth in sheep.

The incisor teeth of 176 sheep of six breeds were inspected every two to three months for a year to record the shedding of the deciduous teeth and the eruption of the permanent teeth. In all the breeds the permanent central incisors erupted at between 12 and 18 months of age. In 96 per cent of the sheep the permanent middle incisors erupted at between 18 and 26 months; and in 92 per cent the permanent lateral incisors erupted at between 24 and 36 months of age. The permanent corner teeth erupted at between 32 and 44 months in 96 per cent of the sheep. The gingival redness and swelling accompanying the eruption of a permanent tooth disappeared within two months. In 14 cases two pairs of incisors erupted during the year, in 18 cases the incisors erupted asymmetrically, and in 22 cases no incisors erupted. Rotation of one incisor was observed in five sheep and was combined with dental deviation in one.

Animals↗
PubMed1999

Effects of maternal acetazolamide treatment on body weights and incisor development of the fetal rat.

The incisor development of fetal rats on gestation day 19 was well correlated with their fetal weights. The number of odontoblasts in the mandibular incisors, an index of incisor development, increased more than that of the maxillary incisors with increase in fetal body weights. Maternal acetazolamide treatments were observed to suppress the mean fetal weight and to retard incisor development. A smaller incisor size, a thinner predentin layer, and fewer odontoblasts were characteristic of the acetazolamide group. There was also a good correlation between the fetal weights and the number of odontoblasts in the acetazolamide group. From these results, we postulated that the retarded incisor development of the fetal rats caused by the maternal acetazolamide treatment was related to their suppressed fetal weights. However, the regression coefficient of the fetal weights and the number of odontoblasts in the acetazolamide group was smaller than that of the vehicle control group. It may indicate that retarded incisor development in response to maternal acetazolamide treatment is to some extent independent of suppressed fetal weight.

Acetazolamide↗
PubMed2005

Difference in the prevalence of enamel alterations affecting central incisors of children with complete unilateral cleft lip and palate.

OBJECTIVE: To evaluate the prevalence of enamel alterations affecting the deciduous and permanent central maxillary incisors of children with complete unilateral cleft lip and palate and to verify their characteristics. DESIGN: Cross-sectional. SETTING: Hospital for Rehabilitation of Craniofacial Anomalies-University of São Paulo, Bauru, São Paulo, Brazil. PATIENTS: A sample of 90 patients attending the Hospital for Rehabilitation of Craniofacial Anomalies, presenting with complete cleft lip and palate, of both genders, ages 2 to 11 years old. METHODOLOGY: The buccal surfaces of the maxillary central incisors of patients were analyzed for observation of the presence of enamel defects, their type, number, and location. The prevalence of defects was compared between deciduous and permanent teeth and between the incisors at the cleft and noncleft sides. RESULTS: There was a higher frequency of defects among incisors on the cleft side for both deciduous and permanent dentitions compared with the noncleft side (p < .05); the permanent central incisor was more frequently affected than the deciduous. Evaluation of the types of defects for both incisors in both dentitions demonstrated a homogeneous distribution, except for a lower proportion of yellow opacity in the permanent dentition on the cleft side. In general, the most affected area in all dentitions was the incisal third. CONCLUSION: The prevalence of enamel alterations affecting incisors adjacent to the cleft was higher than for incisors on the noncleft side. This difference also was present in the permanent dentition.

Chi-Square Distribution↗
PubMedDate not supplied

[The topographical anatomy of the incisor canal].

In 254 skulls (22-70 years of age) with orthognathic intact occlusion in 66 maxillodental sawing topographic anatomy of the incisor canal has been studied by means of craniometric and statistical methods. In mature age the average length of the incisor canal and its openings possess certain statistically significant age and sex differences. The incisor canal is situated near the tops of the central incisors roots at the distance of 7.40 +/- 0.11 mm. The incisor opening, independently on the sex, is situated on the inferior surface of the palatile process of the median line at the distance of 9.81 +/- 0.21 mm from the point formed by the medial angles of the crowns of the upper central incisors. In mature age the distance between the incisor opening and the central incisors roots is 3.51 +/- 0.10 mm.

Adult↗
PubMed1989

[Occurrence of muscle contraction headache in children with abnormal incisor occlusion].

The principal result of the investigation indicates that children with abnormal incisor occlusion must be regarded as a risk group concerning muscle contraction headache (MCH). The need for orthodontic treatment of children with abnormal incisor occlusion is usually by layman regarded as being based upon psychosocial considerations. These considerations shall not be underestimated. For children as well as for grown up persons an appearance dominated by a visible abnormal incisor occlusion will be loading in contact with other people. From a professional point of view need for orthodontic treatment of children with abnormal incisor occlusion has usually been defined from the demand for stability. Grown up people with abnormal incisor relations are frequently referred to orthodontic specialists because of problems, such as migration of the incisors, extreme attrition or functional disturbances in the masticatory system. These problems are closely related to the abnormal incisor occlusion. With our present knowledge of the importance of the incisor relation for the function of the masticatory system, this condition must have high priority in the evaluation of need for orthodontic treatment of children. The treatment will, by improving the functional condition of the masticatory system and normalizing the function, have importance as prophylaxis and/or early treatment of a risk group concerning muscle contraction headache.

Child↗
PubMed1989

[Stabilized position of incisors after orthodontic treatment on reversed occlusion cases with skeletal imbalance. Application of quadrilateral analysis].

This study was made to evaluate the position of the incisors after orthodontic treatment on reversed occlusion cases with skeletal imbalance and to establish norms of the upper and lower central incisors on the quadrilateral (quadrilateral analysis) as the orthodontic treatment objectives through lateral cephalograms. The materials used for this study consisted of twenty-eight posttreatment lateral cephalograms which were taken at more than 2 years after active treatment, and twenty lateral cephalograms which were taken from young-adult females with normal occlusion. The treated samples were of twenty-eight females which were over 14 years old and had reversed occlusion with less than 2 degrees of ANB angle at first examination. These samples were divided into two groups: one consisted of 17 cases females with more than 0 degree of ANB angle and the other of 11 cases with less than 0 degree of ANB. And 11 cases which were treated with multi-bracket appliance alone were selected from the treated samples in order to examine the morphological changes during orthodontic treatment. The results were as follows: 1. In the treated sample the mean profile showed protrusion of the soft pogonion and had slightly forward position of the upper lip and the lower lip, but the outline from the subnasale to the soft pogonion coincided with that of the normal occlusion sample. 2. The ANB angle of the treated sample was smaller than that of the normal occlusion sample so that the mandible of the treated sample was prognathic. 3. The overjet of the treated sample revealed normally in spite of this skeletal disharmony because of compensation by labial inclination of the upper incisors and lingual inclination of the lower incisors. The stronger this skeletal imbalance was, the more the upper incisors inclined labially. But the Ll-Mp showed no difference between the groups which had more than 0 degree of ANB angle and that which less than 0 degree of ANB. 4. The edges of the maxillary and mandibular central incisors always were at a certain place from A'B' line not undergoing an effect of the jaw relationship, and the edge of the mandibular central incisor placed at 8 mm in front of A'B' line. 5. In the treated sample the mandibular central incisor positioned at 1 mm above the occlusal plane. 6. Occlusal plane-A'B' angles in the treated and the normal occlusion samples were revealed about 90 degrees.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

[Spacing of permanent incisors and its influence on the available space for mandibular canines and premolars].

The report analysed differences between deposal space in segments I2-M1 measured from mesioaproximal surface C to mesioaproximal surface M1, measured by Moyers's method and by predictable width of teeth crowns C, P1 and P2 established by correlation method with known value sum of lower incisors with significance of 75% at 158 subjects both sexes with mixed dentition. In regard to spacing of incisors subjects are distributed in three groups: normal spacing of incisors, crowding of incisors and the spaces between incisors. Differences among predictable widths of crowns C, P1 and P2 and desposal space in segments I2-M1 evaluated by two methods show statistically significant differences at groups with crowding of incisors and the spaces between the incisors. Moyers's method of measuring desposal space for position C, P1 and P2 in dental arch is not convenient for the effect of evaluation of premature loss of deciduous teeth from resistance zone on the loss of the space in dental arch at mentioned spacing of incisors.

Child↗
PubMed1996

Morphological characteristics of mouse incisor enamel.

Maxillary and mandibular incisors of mice aged 5 wk were sectioned and ground along various planes, acidetched and observed by scanning electron microscopy (SEM). The general design of the enamel structure resembled rat incisor enamel with an uniserial lamellar pattern of prisms in the inner enamel and incisally directed parallel prisms in the outer enamel. The centrolabial thickness of the enamel was about 60 microns in the maxillary and about 95 microns in the mandibular incisor. The angle between prism rows and enamel-dentine junction was about 70 degrees in the maxillary and about 45 degrees in the mandibular incisor, while the angle of decussation, which increased from the enamel-dentine junction towards the outer enamel, was 50-95 degrees and 30-80 degrees respectively. The angle between outer enamel prisms and enamel surface was about 12 degrees in the maxillary and 5-15 degrees in the mandibular incisor. The outer 1/2-1/3 of the outer enamel contained iron and was more acid-resistant than the rest of the enamel. The superficial 3-5 microns was prismless with a Fe/Ca ratio of about 25/75 in the maxillary and about 10/90 in the mandibular incisor. The latter concentration of iron was insufficient to give visible pigmentation to the enamel. The extreme mesial and lateral enamel was neither typical of inner nor of outer enamel. Assuming that the length of the zone of enamel secretion is half the corresponding length in the rat, it could be calculated that ameloblasts in mouse mandibular incisors produce enamel at a rate of about 6 microns per day, about half the corresponding rate in the rat. In spite of this, the mouse mandibular incisor has a relatively thick layer of enamel, since the ameloblasts spend a relatively long time in the zone of enamel secretion due to a fairly slow eruption rate.

Animals↗
PubMed2005

Velocardiofacial syndrome with single central incisor.

Three siblings and their mother are reported who all had cytogenetically proven velocardiofacial syndrome (VCFS). One boy had normal dental and craniofacial findings, except for an increased cranial base angle. His sister had only one central incisor in the maxilla. One central incisor had also been missing in the primary dentition. She had no labial frenulum present. Cephalometry showed a small maxillary unit length indicating mild maxillary hypoplasia, an increased anterior face height, steep mandibular plane angle, retruded chin, and a large cranial base angle. Dental measurements showed retroclined lower incisors and increased interincisal angle. A second sister had a cleft of the secondary palate. All permanent teeth were present with the exception of a missing central incisor in the lower jaw: the single lower central incisor was situated in the midline. Her cephalometry showed similar findings as in her sister. All three siblings required palate surgery for speech. Mother was not available for detailed dental and other oral investigations. A single maxillary central incisor has previously been reported in VCFS, but to our knowledge a single central incisor in the mandible has not been reported previously in this entity.

Abnormalities, Multiple↗
PubMed1990

Effect of occlusal functional forces on incisor socket morphology and location in the rat mandible.

The effect of functional occlusal stress on dimensional alterations of the rat incisor socket and mandible were studied from roentgenograms. In 12 rats, the lower left incisor was shortened twice weekly, whereas the lower right incisor was allowed to remain in contact with both upper incisors. Thus, the right incisors were subjected to hyperfunction, and the left ones, to hypofunction. The lower incisors of 16 rats with normal occlusal contact served as control. Following an experimental period of 3 months, the animals were killed and standardized radiographs were taken of the cleaned mandibles. Socket and mandibular dimensions were measured on magnified tracings of the roentgenograms. Socket area, its posterior length, posterior mandibular length, and gonial angle changed in the same direction under both hyper- and hypofunction. The anterior socket was relocated in opposite directions: under hyperfunction, it assumed a more inferior position, whereas in hypofunction, it moved superiorly. The angulation of the socket became significantly more acute under hyperfunction, whereas in hypofunction, this parameter remained unchanged. It is concluded that altered functional demands affect the morphology of the incisor socket and its location within the mandibular borders.

Animals↗
PubMed1986

A computerized histomorphometric study of the effects of intoxication with vitamin D3 or 1,25 (OH)2D3 on growth and dentin production of impeded and unimpeded rat incisors.

The effects of Vitamin D3 and 1,25(OH)2D3 intoxication on growth and dentinogenesis were studied in impeded and unimpeded rat incisors. Animals were intoxicated either with Vitamin D3 (2 mg/kg/day) or 1,25(OH)2D3 (400 ng/kg/day) for 19 days. Undecalcified transverse sections were obtained from all lower incisors. The outlines of all dental tissues were traced and fed into a computer which depicted the changes in all variables measured (circumference and cross-sectional area of tooth, pulp and dentin, width of dentin, CEJ [cemento-enamel junction] diameter and maximal labio-lingual diameter). Eruption rates, which had been recorded previously every 48 h, were used to compute the physiological age of each tooth site, so that only areas of similar age be compared. Growth. External dimensions of all intoxicated teeth decreased as the experiment progressed in contrast with control incisors which continued to increase in size. This effect was more pronounced in unimpeded incisors and may be due to the inhibitory influence of 1,25(OH)2D3 on cellular proliferation at the apical progenitor end. Dentinogenesis. 1,25(OH)2D3 intoxication had no significant effect on the rate of eruption and dentin formation in both impeded and unimpeded incisors. The same was true for impeded incisors intoxicated with Vitamin D3 but, both eruption and dentin production rates were impaired in Vitamin D3 unimpeded incisors.

Animals↗
PubMed2005

Pulsed Nd:YAG laser effect on eruption of rat mandibular incisors following disturbance of the enamel organ in the pulp.

We investigated the effects of pulsed neodymium:yttrium-aluminium-garnet (Nd:YAG) laser irradiation time on the eruption of 56 mandibular incisors in 28 rats. Clinically, some incisors erupted and the others did not. The incisors were irradiated at 2 W, 20 pulses/s for the period of 3 s, 5 s, 7 s, and 10 s, and the regeneration process was monitored at 20 days after laser treatment. Incisors irradiated for 3-5 s continued their eruption; five incisors irradiated for 7 s and all incisors irradiated for 10 s did not erupt. In the incisors that continued to erupt, the inner epithelial cells differentiated into ameloblast and a part of the pulp cavity was occupied by osteodentin. In the teeth in which eruption had ceased, the inner epithelium cells did not differentiate into ameloblast, and most of the pulp cavity was occupied by osteodentin. The results indicate that a relatively short time duration of pulsed Nd:YAG laser irradiation in the pulp induced the reparative process without disturbing the eruption.

Aluminum↗
PubMed1982

Soft-tissue changes associated with maxillary incisor retraction.

The nature of incisor retraction and lip adaptation is still controversial. The present study was undertaken to determine the response of upper and lower lips to maxillary and mandibular incisor movement. Cephalometric head films of thirty late-adolescent and early-adult female patients were analyzed for changes in the integumental profile with treatment. Sample selection was intended to reduce variables caused by growth and sex differences. A stepwise multiple regression analysis (forward) revealed a complex interaction between dentition, bony structures, and soft tissues of the perioral area. The lower lip was more variable than the upper lip to differences in the upper incisor movement. The upperlip at labrale superius was found to be more variable with increased retraction of the upper incisors. In the prediction equation, change of sulcus superius had a more direct relationship with retraction of labrale superius and labrale inferius than with dental movement. Pogonion and/or menton entered at statistically significant levels into four (LS, LI, SI, Stm I) of the six prediction equations, indicating that mandibular position is of paramount importance in the prediction of vertical and/or horizontal changes in the upper and lower lips. The upper lip response was related to both upper and lower incisor movement, mandibular rotation, and the lower lip. Upper incisor point position related a moderately high correlation for the prediction equation for change in labrale superius. Lower incisor movement did not correlate with change of either the upper or lower lip. The equations derived were an improvement over previous prediction methods.

Adolescent↗
PubMed1993

The effect of the consistency of the diet on eruption rates and lengths of incisor teeth in rats.

It is uncertain whether the consistency of the diet affects the eruption of rodent incisors. One study reported that harder diets made incisors shorter and erupt faster, and suggested that the faster eruption was due to the decreased length. Two other studies found no effect on eruption rates. In the present study the impeded and unimpeded eruption rates of these lower incisors were measured, using ether anaesthesia for all procedures. There were two groups of rats fed in alternate periods on standard laboratory pellets and in the intervening periods on the same material ground to a powder. In each period, one group was fed on pellets and the other on powder. The impeded eruption rate was less when the rats were fed on powder than on pellets and the rate declined with time. The unimpeded incisors were not affected by the diet, so the effects on the impeded incisor were direct effects on the tooth and not systemically mediated. The impeded incisors lengthened during the experiment and the lengthening was greater on powder than on pellets. The ratio of the change in impeded eruption rates to the increase in tooth length on changing from pellets to powder was different from the ratio for going from powder to pellets, so the effect of the diet on the impeded eruption rate was not due to the change in length of the teeth. There was a negative correlation between the decline in impeded eruption rates and the lengthening of the incisor with time, suggesting that tooth length can influence eruption rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗