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At least 235 records · Page 13Linked to original sources
PubMed1997

Effects of unilateral upper incisor extraction on facial growth of young rats.

The effects of unilateral extraction of the upper incisor (one tooth) on facial growth of young rats were studied. The remaining upper incisor showed deviation towards the opposite side, and there was regular dental wear of all the incisors. The effects were evident only in the mid-facial area. Cephalometric measurements showed significant shortening with deviation of the incisor bone on the extraction side. There was no significant disturbance of the growth of the rest of the maxilla and mandible. These results indicate that upper incisor extractions have a localized influence, leading to impairment of incisor bone growth.

Alveolar Process↗
PubMed1982

The lingual angle of incisors.

A morphologic trait, not previously registered, on the incisor lingual surface: "The lingual angle of incisors", was studied in Norwegians. The lingual angle is the angle between the floor of the lingual fossa and the dental tubercle. Measurements of the lingual angle could be performed with sufficient accuracy. Deviations from normal distribution in skewness and kurtosis values did not affect statistical testing. The general similarity of the frequency polygons for all incisors in the way they were peaked and stepped is possibly due to participation of the same factors on the genetic level in the determination of the trait. The mean lingual angles were (in degrees): I1sup = 142, I2sup equal 156, I1inf = 153 and I2inf = 154. No significant bilateral asymmetry or sex differences were found. Correlations were high for both central to central and lateral to lateral incisors in both jaws, highest for centrals in the maxilla and laterals in the mandibula. Central to lateral correlations were relatively low, especially in the upper jaw. Interjaw correlations were low, but I1sup showed a tendency to be better correlated than I2sup to lower incisors. I2sup and I1inf were the most variable incisors in each jaw. The dental tubercle probably plays an important role in determining the lingual angle. Measurements of the lingual angle give information on the profile of the lingual surface in inciso-cervical direction. Statistical analysis of a phenotypic trait may give information on factors which determine the trait.

Adolescent↗
PubMed2000

Differential expression of laminin-5 subunits during incisor and molar development in the mouse.

Rodent incisors are continuously growing teeth and enamel deposition is restricted to the labial side. In the present study, the expression of laminin-5 subunits (alpha3, beta3 and gamma2) has been analyzed by in situ hybridization in developing mouse lower incisors and compared to that reported in the molar. At the bud stage (E12), mRNAs for all subunits were detected in the whole epithelial thickening. At E14, when histogenesis had started, transcripts for alpha3 and gamma2 subunits were restricted to the outer dental epithelium (ODE), whereas the beta3 subunit was intensely expressed in the inner dental epithelium (IDE). A transient expression for alpha3 subunit was seen in the enamel knot area and disappeared at E15. Subsequently, all laminin-5 subunit genes were re-expressed in differentiating ameloblasts on the labial side. Similar patterns of transcription were observed in incisor and molar, suggesting that the differential expression of laminin-5 subunits in the IDE might be involved in the histogenesis of the IDE and ameloblast differentiation. At E16.5, cells of the IDE at the anterior extremity of the incisor and in the anterior part of the lingual IDE expressed transcripts for alpha3 and beta3 but not for gamma2 subunit. Similar expression patterns were observed in the enamel-free areas of the E18 molar. This specific expression might thus be related to cells that do not differentiate as functional ameloblasts. Throughout incisor development, intense expression for all laminin-5 subunits was restricted to the labial side of the cervical loop. The asymmetrical expression of laminin-5 might be related to incisor morphogenesis and to the differences in histogenesis and cytodifferentiation of the IDE that exist in the labial versus lingual aspect of the cervical loop.

Animals↗
PubMedDate not supplied

Simultaneous presence of a congenitally missing premolar and supernumerary incisor in the same jaw: report of case.

Supernumerary teeth and hypodontia can be regarded as opposite developmental phenomena. An eight-year-old girl presented a concomitant occurrence of a supernumerary tooth and two congenitally missing teeth. The supernumerary tooth was found in the left maxillary incisor region, while the left second premolar in the maxilla and the left lateral incisor in the mandible were congenitally missing. The supernumerary tooth showed a similar color and morphology to those of the maxilla lateral incisor, and the lateral incisor on the mesial side was diagnosed as a supernumerary tooth from dental age, eruption time, and mesiodistal crown dimension. The supernumerary incisor was guided labially to cure an anterior cross-bite, and the lateral incisor, canine, and first premolar were guided distally to compensate for the space left by the congenitally missing left second premolar.

Age Determination by Teeth↗
PubMedDate not supplied

Spectral analysis of /s/ sound with changing angulation of the maxillary central incisors.

PURPOSE: The aim of the study was to measure the influence of the maxillary central incisors free from adaptation phenomena using spectral analysis. MATERIALS AND METHODS: The maxillary dentures of 18 subjects were duplicated. The central incisors were fixed in a pivoting appliance so that their position could be changed from labial to palatal direction. A mechanical push/pull cable enabled the incisor section to be handled extraorally. Connected to the control was a sound generator producing a sinus wave whose frequency was related to the central incisor angulation. This acoustic signal was recorded on one channel of a digital tape recorder. After calibration of the unit, the denture duplicate was inserted into the subject's mouth, and the signal of the /s/ sounds subsequently produced by the subject was recorded on the second channel during alteration of the inclination angle simultaneously with the generator signal. Spectral analysis was performed using a Kay Speech-Lab 4300B. RESULTS: Labial displacement in particular produced significant changes in spectral characteristics, with the lower boundary frequency of the /s/ sound being raised and the upper boundary frequency being reduced. CONCLUSION: Maxillary incisor position influences /s/ sound production. Displacement of the maxillary incisors must be considered a cause of immediate changes in /s/ sound distortion. Therefore, denture teeth should be placed in the original tooth position as accurately as possible. Our results also indicate that neuromuscular reactions are more important for initial speech sound distortions than are aerodynamic changes in the anterior speech sound-producing areas.

Acoustics↗
PubMedDate not supplied

Assessment of dental appearance following changes in incisor angulation.

PURPOSE: This study evaluated the assessment of attractiveness of standardized changes in incisor angulation of different tooth arrangements. MATERIALS AND METHODS: Four sets of images showing the maxillary anterior teeth without lips against a black background were used for evaluation. Each set contained the original photograph, one computer-manipulated symmetric image, and four images with different standardized changes in incisor angulation (10 degrees). The judges, consisting of three groups (30 dental students, 30 medical students, 30 art students), ranked each photo set for attractiveness from 1 (most attractive) to 6 (most unattractive). RESULTS: The mean ranking (in parentheses) showed that symmetric teeth with ideal axes (2.5) and changes in the angulation of one (2.8) or both (2.5) lateral incisors were significantly more attractive than the angulation of one (4.2) or both (4.6) central incisors. There were no differences between the groups of participants. All findings were reproducible. CONCLUSION: Tooth arrangements showing central incisors with ideal axes were more attractive. Slight changes in the angulation of one or both lateral incisors did not influence attractiveness negatively.

Adult↗
PubMed2004

Esthetic restoration of infra-occluded retained primary mandibular incisors with all-ceramic crowns in adult dentition.

The prevalence of hypodontia is reported to be between 1.5% to 10% in the permanent dentition. In the anterior teeth, maxillary lateral incisors and mandibular central incisors are the most frequently involved teeth. This causes esthetic problems for the patient. Several reports have focused on restoration of retained maxillary primary anterior teeth, but none have described restoration of retained mandibular primary incisors. This clinical report describes the restoration of infra-occluded retained primary mandibular central incisors of a 17 year-old girl diagnosed with hypodontia. All-ceramic crowns made with computer-aided design/ computer-aided manufacturing technology were used to restore the teeth incisally and interproximally. Due to a relatively short root length and inadequate crown-root ratio, the primary mandibular central incisors were splinted and adjusted to distribute the protrusive force evenly across the maxillary and mandibular incisors. Functional and esthetic results were achieved.

Adolescent↗
PubMed2005

The nose shape as a predictor of maxillary central and lateral incisor width.

OBJECTIVE: One of the primary aspects of complete denture prosthodontics is determining the correct proportion for the maxillary central incisor width to the lateral incisor width. It has been suggested that the anatomy of the patient's nose is a reliable guide for deciding this ratio. The aim of this study was to test the hypothesis about the relationship between the shape of the nose and the proportion of the central incisor width (CIW) to the lateral incisor width (LIW). METHOD AND MATERIALS: The CIW and LIW from a total of 138 subjects (73 males, 65 females) were measured intraorally. The interalar width (IAW) and the width of the root of the nose (WRN) were measured on standard photographs of the subjects. Spearman's rho test was used to analyze the correlation between the proportions of the CIW to the LIW and the IAW to the WRN. The Mann-Whitney Utest was applied to test for any possible gender differences. RESULTS: The IAW, the WRN, and the nose angle (NA) were statistically significantly wider in male subjects than in female subjects. The correlation between IAW/WRN, NA, and CIW/LIW was statistically significant only in female subjects. In the general population, the only statistically significant relationship was between CIW/LIW on the left side and IAW/WRN. CONCLUSION: Within the results of the IAW, WRN, and NA measurements, we suggest that males have wider, more triangular-shaped noses than females. The proportion of IAW to WRN seems to be a reliable guide for deciding the proportion of the maxillary central incisor width to the lateral incisor.

Adult↗
PubMed2003

Maxillary incisor root forms in orthodontic patients in Nairobi, Kenya.

OBJECTIVE: To evaluate, radiographically, the root forms of maxillary incisors in a sample of patients seeking orthodontic treatment in Nairobi, Kenya. DESIGN: A retrospective study of maxillary incisor root forms based on periapical radiographs. SETTING: A private dental clinic in Nairobi, Kenya. MATERIALS AND METHODS: The study comprised 393 maxillary incisors in 100 consecutive subjects (51 boys, 49 girls) aged 9-24 years. Intra-oral periapical radiographs of the incisors were evaluated. An index was used to categorise the roots as follows: 0=normal, 1=short, 2=blunt, 3=apical bend, 4=pipette apex. RESULTS: Normal root form was recorded in 60%, short in 12.5%, blunt in 7%, apical bend in 13%, and pippete-apex in 7% of the roots. Sixty nine percent of the pippete-apex roots were in central incisors and 94% of the roots with apical bend were in lateral incisors. Seventy three percent of short roots were in females. CONCLUSION: Based on evidence from previous studies on risk of root resorption which indicates that pipette and blunt roots are the forms mostly involved in this phenomenon, the present data imply that about 14% of the roots may have been at risk of moderate to severe resorption during fixed orthodontic treatment.

Adolescent↗
PubMedDate not supplied

A retrospective assessment of zinc oxide-eugenol pulpectomies in vital maxillary primary incisors successfully restored with composite resin crowns.

PURPOSE: The purpose of this retrospective study was to evaluate, via clinical and radiographic assessments, the treatment outcome of zinc oxide-eugenol (ZOE) pulpectomies performed in vital maxillary primary incisors successfully restored with composite resin crowns. METHODS: Pulpectomized vital primary incisors were treated by a uniformed technique, filled with ZOE paste, and successfully restored with composite resin crowns. Those that remained intact and noncarious for the assessment interval were evaluated for the outcome (success or failure) based on clinical and radiographic findings and compared to: (1) the reason for treatment; (2) the canal filling extent; (3) the type of composite resin crown restoration performed; and (4) the eruption status of its succedaneous tooth. RESULTS: For 104 maxillary primary incisors meeting the inclusion criteria, failure, as judged by presence of pathologic root resorption and/or apical lucency, was determined to be 24% (25/104), for a mean duration of 18 months observation. Failures were statistically associated with the reason for treatment (higher for trauma), the extent of ZOE paste filler in the pulp canal (higher for gross overfill), and the eruption status of the associated succedaneous permanent incisor (higher for delayed eruption). CONCLUSIONS: This study determined a failure rate (24%) for pulpectomies-using ZOE paste and performed on vital primary incisors-comparable to that reported for nonvital pulpectomies. A statistically significant increase in failure rates was found for: (1) incisors treated for trauma (42%) vs those treated for dental caries (19%); and (2) grossly overfilled canals (80%) vs canals filled to the apex (0%).

Child, Preschool↗
PubMed1990

[Roentgencephalometric evaluation of inclination and the position of incisors in orthodontic malocclusions and normal occlusion].

The aims of the study were: --to determine sagittal differences in the position and inclination of incisors in defined orthodontic anomalies as compared to eugnathic occlusion; --to assess the importance of variable interrelationships for the evaluation of incisor orientation; and --to describe the distribution of compatibility of all linear and angular assessments of incisor orientation studied in relation to both jaws, direction of deviation and type of malocclusion. A sample of 436 roentgenograms taken in subjects of both sexes aged 10-18 years (180 with eugnathic occlusion and 256 with orthodontic anomalies) were analyzed. Five dentoalveolar variables were observed. Use of the 3 degrees = 1 mm principle allowed the inclination and position of incisors to be compared. The following conclusions were reached: --as compared to eugnathic subjects, dentoalveolar variables were changed in defined orthodontic malocclusions with clear differentiation according to type of anomaly; --a significant relationship was found for most variables used to assess the position and inclination of incisors; --a complete compatibility between the position and inclination was recorded in 16.7% and 15.7% of cases in the maxilla and mandible, respectively; --compatibility between the inclination and position was highest in subjects with eugnathic occlusion; and --inclination and position of incisors may be mutually independent or even contradirectional in one and the same subject, necessitating separate analytical evaluation.

Adolescent↗
PubMed1994

Incisor retraction and profile changes in adult patients.

The aims of this study were to evaluate the changes in the facial profile related to maxillary incisor retraction and to check for correlations between changes in the lip and changes in the positions of the teeth and alveolar bone during orthodontic treatment. Initial and final lateral cephalometric radiographs of 25 nongrowing Brazilian patients were selected for this study. All patients initially presented with Class I or II malocclusions and had their maxillary incisors retracted at least 2 mm during orthodontic treatment. Changes in lip position, length, and width, as well as changes in the positions of the alveolar bones and incisors, were calculated. Statistically significant differences from pretreatment to posttreatment were observed for all measurements except for upper lip length and point A. A high correlation was demonstrated between changes in the lower lip sulcus and point B and between changes in the lower lip sulcus and the mandibular incisor. Changes in the maxillary and mandibular incisors did not show a high correlation to the total lip changes, but high correlation coefficients were obtained when the changes in lip width were excluded from the total lip changes. In other words, changes in lip width tended to mask the changes in lip position caused by retraction of the maxillary incisors.

Adolescent↗
PubMed2000

Palatally displaced upper lateral incisors: relapse after orthodontic treatment and its correlation with dentoskeletal morphology.

The purpose of the present study was to determine whether the relapse tendency of the palatally positioned upper lateral incisor differs in patients treated with or without premolar extraction, and if there is any correlation between the amount of upper lateral incisor relapse and pretreatment dentoskeletal morphology or post-treatment changes. Forty-six patients with bilateral palatally displaced upper laterals who also exhibit maxillary dental constriction were separated into two groups: a premolar extraction (30 cases) group and a non-extraction (16 cases) group. All subjects had undergone orthodontic treatment with quad helix and edgewise appliances, followed by a 2-year retention period. Differences in the amount of the upper lateral incisor relapse and their correlations with the dentoskeletal morphology before and after treatment were determined on the lateral and postero-anterior cephalograms and dental casts. Results revealed that the upper lateral incisor relapse in the extraction group was significantly greater (p=0.0002) than the relapse in the non-extraction group. There was a positive correlation between incisor relapse and the distance of lateral incisor movement in both groups (r=0.539; p=0.030). Relapse in the non-extraction group was correlated with the widths of the upper dental arch (r</=-0.507, p</=0.044), with the naso-maxillary variables before treatment (r=-0.514, p=0.041), and also with changes in the upper inter-premolar and inter-molar widths during retention (r=0.514, p=0.040).

Journal Article↗
PubMed2002

[Periodontal status of mandibular incisors after pronounced orthodontic advancement during adolescence].

OBJECTIVE: To analyze whether pronounced orthodontic advancement of the mandibular incisors during Class II correction in the mixed dentition results in gingival recession. METHODS: Through mandibular superimposition of the pretreatment and posttreatment cephalograms of 67 Class II patients who were treated, 45 patients with a minimum of a 1-mm advancement of the CEJ and a minimum of a 2-mm advancement of the IE were identified.Using the same protocol in Class II patients,30 individuals who finished treatment at a similar time and age,but with no advancement of the CEJ and a maximum of 1-mm advancement of the IE were identified. A total of 30 patients with pronounced advancement and 21 patients with no advancement could meet for a follow-up examination with a mean period of 7.83 years and 9.38 years after treatment, respectively. Through measuring cephalograms,study models,as well as clinical examinations to analyze the periodontal status of mandibular incisors. RESULTS: Clinical examinations at the time of follow-up revealed no differences in the amount of recession,the width of attached gingiva,the length of supracrestal connective tissue attachment,the probing pocket depth, gingival bleeding index or visible plaque index of the mandibular incisors between the patients in the 2 groups. No differences in the number of mandibular incisors that developed recession from T1 to T2 and from T2 to T3.The increase of mandibular incisor crown height demonstrated no difference from T2 to T3 between the patients in the 2 groups. CONCLUSION: Pronounced advancement of the mandibular incisors may be performed in adolescent patients with dentoalveolar retrusion without increasing the risk of recession.

English Abstract↗
PubMed1991

[Morphological changes in the lower incisor of suckling rats induced by large dose of aspirin].

Large doses of aspirin (200 mg/kg or 400 mg/kg, s.c) caused marked hypocalcemia in suckling rats, two hours after administration. The hypocalcemic effect was more evident in two week old rats than in one week old ones. Although the mechanism of aspirin-induced hypocalcemia is not clear at this moment, the drug can be a useful tool for inducing experimental hypocalcemia in suckling rats, besides hormonal and/or nutritional controls. In this report, large doses of aspirin were administrated to new born rats, once at one week after birth, or twice at one and two weeks after birth. The morphological changes of the lower incisor were examined using computer programs which have been developed for the analysis of plane curves such as the traces of the side view of the incisor. Aspirin administration shortened the length of the lower incisor and its labial trace. The width of the incisor, especially in the middle, was also diminished by aspirin administration. These observations suggest that the drug not only induced hypocalcemia in suckling rats but also to some extent suppressed the activity of odontoblasts which produce the dentin of the incisor. Analysis of curvature variance, calculated with the labial trace of the lower incisor, also suggested that large doses of aspirin had two effects. It suppressed mineralization of the teeth through its hypocalcemic effect, and it inhibited synthesis of the collagenous matrix. The computer programs applied in this study have proved useful in determining and analyzing morphological changes of bio-materials which are difficult to measure directly.

Analysis of Variance↗
PubMed1990

[Dependence of incisor dentin mineralization on plasma calcium levels in parathyroidectomized rats].

This experiment was performed to clarify whether mineralization of incisor dentin depends upon plasma calcium (Ca) levels. Male Wistar rats (7 weeks old) were parathyroidectomized (PTXed) and given vitamin D-deficient diets containing various amounts (0.3-2%) of Ca for 2 weeks in order to maintain the plasma Ca at various levels and to examine their relationship with the mineralization of incisor dentin. Plasma Ca levels, which were lowered to about 6 mg/dl by PTX, ranged from 5.1 to 10.1 mg/dl after feeding on diets containing various amounts of Ca; the plasma Ca level in the group given 2% Ca reached the same level as that in the sham-operated group. On the other hand, plasma phosphorus (P) levels, which were increased by PTX, reduced markedly with increases in dietary Ca, leading to hypophosphatemia in the group given 2.0% Ca. In this series of experiments, the plasma Ca levels in PTXed rats seemed to be kept constant by the dietary Ca without any involvement of hormones regulating the Ca metabolism because a high correlation was found between the plasma Ca and the dietary Ca (r = 0.987). Both dry and ash weights of the upper incisor also increased with the plasma Ca levels, but with the plasma P levels it was just the opposite. The content of ash in the incisor also increased with the plasma Ca levels. Transverse sections of the lower incisors stained with hematoxylin showed a zone of remineralization of the dentin on the lingual aspect in rats with plasma Ca levels of about 6.5-7.0 mg/dl; the width of the zone was greater in groups of rats with higher plasma Ca levels. Appositional rates of dentin (y, micron/3 days) as determined by a time marking method showed a high positive correlation with the plasma Ca levels (x, mg/dl). The regression equations were as follows: y = 4.8 + 5.7x (r = 0.915, p less than 0.001) on the lingual aspect and y = 6.0 + 5.8x (r = 0.959, p less than 0.001) on the labial aspect. There were a high positive correlation and a negative correlation between appositional rates of dentin and plasma Ca: P ratios (r = 0.928) and between appositional rates of dentin and plasma P levels (r = -0.927) or the products of plasma Ca x P (r = -0.834). These results suggest that the mineralization of incisor dentin depends upon the plasma Ca levels in PTXed rats.

Animals↗
PubMed1990

[Appositional rate of incisor dentin and hematic calcium level in rats. Application of time marking method using lead acetate].

Matsumoto et al. have reported that the remineralization of rat incisor dentin following administration of various drugs depends upon the hematic calcium (hCa) level in parathyroidectomized (PTX) rats. It is known that injected lead according to a time marking method deposits at the mineralizing front in hard tissues. In the present study, we observed the alteration of the mineralizing front of the incisor dentin and examined the dependency of the dentin remineralization on the hCa level in PTX rats given 1,25 (OH)2D3. Male Wistar rats (7-8 weeks old) were used. They were fed a synthetic diet containing 0.3% Ca or 0.02% Ca (Ca-deficient) from 3 days before PTX. In order to mark the time in the incisor dentin, lead acetate was injected at 3 day intervals. Exp. I: A group of rats fed a diet containing 0.3% Ca was given a single injection (400 ng/kg) of 1,25 (OH)2D3 on the 9th day after PTX. Exp. II: four groups of rats were given daily injections of various doses (vehicle, 25, 50 and 100 ng/kg) of 1,25 (OH)2D3 from the 11th day after PTX for 13 days. The distance between the two lead-lines observed in the histological sections of the incisor was measured as an indicator of the appositional rate of dentin. In rats given a diet containing Ca below 0.3%, the hCa level was about 5 mg/dl after PTX. Mineralization of the incisor dentin was suppressed markedly, and a hematoxylin unstained zone was observed in the histological sections, indicating that the mineralizing front had been stagnant. In Exp I, a high dosage of 1,25 (OH)2D3 raised the hCa level to over 8 mg/dl within 12 hours; formation of a new mineralizing front and remineralization of the dentin were observed. In Exp. II, daily injections of 1.25 (OH)2D3 raised the hCa levels gradually and dose dependently. The hCa levels in groups of rats given 50 and 100 ng/kg of 1,25 (OH)2D3 were over 8 and 10 mg/dl respectively after the 6th day from the beginning of the drug administrations. The distance between the two lead-lines deposited in dentin also increased gradually. Therefore, the appositional rate of the incisor dentin seemed to increase in accordance with the rise in the hCa level. The correlation coefficient between the appositional rate of lingual dentin and the hCa level was estimated to be 0.922 (p less than 0.001, y = 4.4x + 19.2).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Incisor microwear, diet, and tooth use in three Amerindian populations.

Incisor microwear patterns have been shown to reflect aspects of diet and ingestive behaviors in a wide range of nonhuman primates. While some studies have suggested that anterior dental microwear might be used to infer unusual front tooth use practices in archaeological populations, quantitative work on modern human incisors has thus far been limited. In this study we examined dental microwear on the maxillary central incisors of three groups of humans: Aleutian Islanders (n = 16), Arikara from the Mobridge Site in South Dakota (n = 15), and a Late Woodland Bluff sample from Jersey County, Illinois (n = 17). High-resolution replicas were prepared and examined by scanning electron microscopy following conventional procedures. Photomicrographs were taken at consistent locations on the labial surface, and microwear was quantified using Microware 3.0 (Ungar, 1997). Statistical test results revealed significant differences among the groups in microwear feature densities, sizes, and shapes. The Aleut, Arikara, and Illinois Bluff samples showed a gradient of increasing microwear density, increasing linearity in feature shape, and decreasing feature size. These differences evidently correspond to amount of meat consumption, and apparently to degree of use of the incisors in heavy loading. No differences were observed between groups in heterogeneity of feature orientations, and no sex-related differences were found. Associations between incisor microwear on the one hand and subsistence practice and anterior tooth use on the other likely have important implications for the study of hominid paleobiology.

Fossils↗