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At least 271 records · Page 15Linked to original sources
PubMed2002

A comparison between a conventional optical method and image-analysis for measuring the unimpeded eruption rate of the rat mandibular incisor.

The impeded/unimpeded eruption rates of the rat incisor have been much studied. The most commonly used optical microscopic method, which has inherent weaknesses, was compared here with an image-analysis method to measure the eruption rate of the mandibular incisor. The study also evaluated the incisal edge as a reference point for the measurement of the unimpeded eruption rate, and the frequency of shortening the mandibular incisor. The image-analysis method was found to be a simple and reliable technique that could replace the optical method. There was no significant difference between the data from the two methods; their kappa coefficients were similar at the 0.99 level. It was concluded that shortening the incisor in the measurement of the unimpeded eruption rate should be done at least every 48 h, and that the incisal edge of the shortened incisor can be used as the reference point for that measurement.

Animals↗
PubMed2003

Three-dimensional reconstruction studies and morphometric analysis of rudimental tooth primordia in the upper incisor region of the sheep (Ovis aries, Ruminantia).

The functional dentition of the domestic sheep lacks all upper incisors and the upper canines. Nevertheless, occurrence of a dental lamina and rudimental tooth primordia had been described in the upper incisor region of the sheep. The aim of this study was to describe temporo-spatial pattern of origin and regression of these rudimental tooth primordia by light microscopy, computer-aided three-dimensional reconstruction and morphometry of the dental epithelium. Transient existence of a dental lamina in the upper incisor region of the sheep and three epithelial thickenings on its deep mesenchymal margin has been observed at day of ontogeny (DO) 48-53. They could not been identified as full-value tooth primordia, because they did not induce differentiation of tooth mesenchyme, but they could represent last remnants of functional upper incisors in early ancestors of ruminants. Additionally, a large rudimental upper canine primordium near the sutura maxilloincisiva occurred at DO43, reached early cap stage at DO52 and started to regress at DO53. Thus, our findings showed a discrepancy between the embryonic and adult dental pattern in the sheep. Similar molecular mechanisms as described for diastemal tooth rudiments in rodents could be involved during regression of rudimental tooth primordia in the upper incisor region of the sheep.

Animals↗
PubMed2003

Vibration perception thresholds of human maxillary and mandibular central incisors.

Tactile information from dental mechanoreceptors contributes to the perception of food bolus textures and the control of mastication. While numerous studies have measured the light-touch sensory thresholds of teeth, little information is available about the vibrotactile perception thresholds of teeth. This study uses an adaptive psychophysical procedure to determine thresholds of vibratory stimulation of maxillary and mandibular central incisors in 16 healthy human subjects. An electromechanical vibrator delivered labiolingual forces perpendicular to the long axis of the maxillary and mandibular incisors at 10 stimulation frequencies between 40 and 315 Hz. The median thresholds ranged between 44 and 104 mN. A linear regression analysis revealed a significant increase in the vibrotactile thresholds with increasing frequencies for stimulation of the maxillary and mandibular incisors. No significant differences were found between regression slopes of the thresholds of the maxillary and mandibular incisors. These results indicated that maxillary and mandibular incisors should be able to discriminate effectively among a variety of textures based on their ability to encode a wide range of vibration frequencies.

Adult↗
PubMed2000

The effects of local trauma to the enamel-related periodontal tissues in the eruption of the rat incisor.

The periodontal tissues related to enamel (PTE) of the rat incisor comprise a connective tissue derived from the dental follicle and the enamel organ with its successive stages of development. Localized damage to these tissues in rat lower incisors was done surgically in three ways: with an endodontic file introduced into the labial periodontal space through either (i) its basal or (ii) its incisal extremities, or (iii) by the partial removal of the mandibular lower border, at the level of the molar teeth, together with the introduction of an endodontic file into the incisal part of that space. The lesions in the molar region of the PTE produced first a variable period of retarded eruption, and, depending upon their extent or degree were followed by a cessation of the eruptive movement and, in the majority of the operated teeth, a recovery of the normal eruption rate before the end of the experiment (17 weeks after surgery). Access to the PTE through the basal portion of the socket was erratic, but when the tissues were damaged produced similar effects. Effects on eruption of lesions produced through the alveolar crest were minimal or even absent. Localized injury to the periodontal ligament of either lower or upper incisors did not produce similar effects on tooth eruption. The dental follicle and the enamel organ of teeth of limited growth when their crown is completed are similar to the PTE in the molar region of continuously growing rodent incisors. In teeth of limited growth these tissues play an essential part in the intraosseous stage of eruption. The results here suggest that the PTE may also have a role in the supraosseous stage of eruption, which is continuous in teeth such as rat incisors due to the presence of a continuously functioning odontogenic organ.

Alveolar Process↗
PubMed1981

Eruption of impacted permanent upper incisors after removal of of supernumerary teeth.

In a retrospective study of 63 patients, an attempt is made to determine in how many cases retained permanent upper incisors erupt after the removal of supernumerary teeth, and what predisposing and etiological factors are of importance. It proved that the eruption of a supernumerary tooth positively contributed to the chance of a spontaneous eruption of the permanent incisors. No relationship could be demonstrated between the age of a patient from whom supernumeraries were extracted, the number of supernumeraries, the extent of root formation, marked apical displacement and the chance of spontaneous eruption of the permanent incisors. It also proved that only in 1 out of 2 children did spontaneous eruption occur after removal of the supernumeraries. It therefore seems advisable to provide all impacted upper incisors with a cervical ligature of bracket with twined wire sling during the first operation in order to create the possibility for orthodontic traction if spontaneous eruption of the incisor does not occur, and thus to prevent a second operation for the child.

Adolescent↗
PubMed1994

Incidence and size of pretreatment overlap and posttreatment gingival embrasure space between maxillary central incisors.

Five hundred sets of orthodontic diagnostic records of patients (age 15 years +/- 3) (228 males, 272 females) whose six maxillary anterior teeth had erupted were studied. Incidence of overlapped and crowded maxillary central incisors and magnitude of that crowding were determined, also the incidence of postorthodontic open gingival embrasures (black triangles) and width of those triangular spaces between maxillary central incisors were determined. Of the 500 patients 185 (37%) had preorthodontic crowding of maxillary central incisors. Magnitude of crowding was 1.08 mm +/- 0.94, n = 185. One hundred twenty-nine of these patients were treated. Their postorthodontic records were studied. Of the 129 cases 54 (41.9%) had a black triangular gingival embrasure space between the two maxillary central incisors postorthodontically. Width of the triangular space was 0.43 mm +/- 0.32, n = 54. One third of a similar population of orthodontic patients can be expected to have crowded central incisors. Two-fifths of those can be expected to have a postorthodontic black triangle when treated similarly.

Adolescent↗
PubMed1998

Does orthodontic proclination of lower incisors in children and adolescents cause gingival recession?

In this investigation we sought to assess the effect of orthodontic proclination of lower incisors in children and adolescents with respect to the possible development of gingival recession. Ninety-eight children with a mean +/- SD start-of-treatment age of 12.8 +/- 1.4 years, treated with the Herbst appliance, were surveyed, for a total of 392 lower incisors. Lateral head films, dental casts and intraoral photographs were analyzed with respect to the degree of orthodontic proclination, crown height, and gingival recession. In all subjects, Herbst treatment resulted in varying degrees of lower-incisor proclination (mean = 8.9 degrees, range = 0.5 degrees to 19.5 degrees). In 380 of the surveyed teeth (97%), either no recession developed or preexisting recession remained unchanged during Herbst therapy. In only 12 teeth (3%) did recession develop or preexisting recession deteriorate during treatment. No interrelation was found between the amount of incisor proclination and the development of gingival recession. In conclusion, orthodontic proclination of lower incisors in children and adolescents seems not to result in gingival recession.

Adolescent↗
PubMed1999

Treatment of an impacted dilacerated maxillary central incisor.

Impacted Incisor With Dilaceration refers to a dental deformity characterized by an angulation between crown and root causing noneruption of the incisor. Surgical extraction used to be the first choice in treating the severely dilacerated incisor. In this article, a horizontally impacted and dilacerated maxillary central incisor was diagnosed radiographically. By combining two stages of the crown exposure surgery with light force orthodontic traction, the impacted dilacerated incisor was successfully moved into proper position. However, long-term monitoring of the stability and periodontal health is critical after orthodontic traction.

Anodontia↗
PubMed2003

Abfraction lesion formation in maxillary incisors, canines and premolars: a finite element study.

Abfraction lesions are angular, wedge-shaped defects found at the cervical region of teeth and are caused by mechanical overloading initiated by cuspal flexure. Clinically, these lesions are more prevalent on the labial aspect of maxillary incisors. The aim of this study was to provide a biomechanical explanation for this clinical variation. Two-dimensional plane strain finite element models of an maxillary incisor, canine and first premolar were developed and the cervical stress profiles were examined along a horizontal plane 1.1 mm above the amelo-cemental junction. The local X (horizontal) stress on the labial/buccal side was 176.4 MPa for the incisor, 57.8 MPa for the premolar, and 3.4 MPa for the canine. Similarly, the maximum labial/buccal principal stress was 181.4 MPa for the incisor, 25.2 MPa for the premolar, and 66.8 MPa for the canine. The labial/buccal stress profile in the cervical region of an maxillary incisor was always greater than that found in an maxillary canine or premolar tooth. These findings provide a biomechanical explanation for the clinical variation seen in the prevalence of cervical abfraction lesions.

Bicuspid↗
PubMed2002

The esthetic outcome of autotransplanted premolars replacing maxillary incisors.

Autotransplantation of developing premolars to replace maxillary incisors has been documented to provide physiologically sound results, but comprehensive studies of the esthetic outcome have not been made previously. In order to assess the applicability of this approach and to identify factors important for planning of treatment, 22 autotransplanted premolars reshaped to incisor morphology were compared to their natural, contralateral maxillary incisors by scoring of features considered important for esthetics (color, soft tissue appearance, tooth morphology, and position). The sum of scores for each feature was used to place the reshaped transplant in one of three categories - Match, Deviate, Mismatch. The 22 patients were asked to fill in a questionnaire which addressed the same features that were examined professionally, and the responses were categorized as either Satisfied, Acceptable, or Dissatisfied. Eleven of the 22 patients had received orthodontic treatment with fixed appliances following the transplantation. Most of the transplanted premolars matched the contralateral incisor, and the majority of patients were satisfied with the appearance of the transplant. Fourteen percentage of the transplants were categorized as Mismatch and 18% of patients reported dissatisfaction. The distribution in categories assessed professionally and by the patients was not significantly different. The color and gingival width of the transplanted tooth were scored as different from the natural incisor in about half of the bilateral comparisons. For those teeth categorized professionally as Mismatch and by patients as Dissatisfied, a potential for esthetic improvement could be identified, as allocation to these categories was primarily due to suboptimal positioning and restorative build-up of the transplant. Inter-disciplinary planning is important for successful esthetic results.

Bicuspid↗
PubMed2003

Clinical outcomes for permanent incisor luxations in a pediatric population. III. Lateral luxations.

A longitudinal outcome study was designed to identify variables that influenced tooth survival as well as pulpal and periodontal outcomes of laterally luxated permanent maxillary incisors of children and adolescents. All cases were treated between June 1988 and June 1998 in a teaching hospital clinic. Clinical and radiographic data were collected for 42 patients (26 males, 16 females) that represented 58 permanent maxillary incisors. Mean age at the time of injury was 11.4 years (range: 6.3-17.8 years). Mean follow-up time was 1460 days (range: 183-3905 days). In the entire sample (n = 58), no incisors required extraction. Survival analysis and logistic regression were used to identify variables significantly related to the survival and healing outcomes of these incisors. Pulp necrosis (PN) (40%) and pulp canal obliteration (PCO) (40%) were common healing complications. Proportional hazards (Cox) regression showed that PN develops within the first year. Logistic regression demonstrated that root development (P = 0.3, PN; P = 0.8, PCO) and extent of lateral luxation (P = 0.5, PN; P = 0.9, PCO) were not significantly related to PN and PCO. This study provides the first report of incisor survival in children and adolescents following lateral luxation injuries.

Adolescent↗
PubMed1976

The relationship between lower incisor inclination and various reference lines.

The relationship between the inclination of the lower incisors and different cranial reference lines has been studied in a group of 60 children including 35 males and 25 females between the ages of 7-12 years. Following a 3-4 year observation period, 30 of these children were reexamined to study the relationship between changes in the position of the lower incisors and various craniofacial variables brought about by growth. In analysing the results obtained, an attempt was made to distinguish between those relationships which were to a certain extent due to a topographical relationship between the variables involved and those relationships which were of a biological character. The results obtained from the first registration indicated a strong correlation between Ll-NB mm and Ll-ML degrees and Ll-NB degrees. In addition, the connection between lower incisor inclination and the basal bone relationship (ANB degrees) was found to be strongly significant. The angle ML/NL was found to be correlated only with the inclination of the lower incisors to the mandibular line. Regarding the growth changes occurring during the observation period, no significant correlation could be found between, on the one hand, changes in lower incisor orientation and, on the other hand, changes in the angle ML/NL. The absence of this relationship has been interpreted as being due to the influence of environmental factors in the form of tongue and lip function.

Adolescent↗
PubMed1977

The mandibular dental arch: Part I, lower incisor position.

The position of the lower incisor with respect to hard tissue references has been evaluated. Two samples were used for this purpose: one containing 78 patients with posttreatment records having a postretention period of at least 4 years, and the other composed of 82 normal occlusions. The results indicated: 1) There was no significant difference in relapse of lower incisor crowding between cases where the lower incisor had been moved lingually, labially, or held in the same relative position during treatment. 2) The position of the maxilla should be considered when placing the lower incisor. The APo plane adequately serves as a guide to this purpose, whereas other reference lines such as mandibular plane or facial plane do not. 3) The positions of the incisors with respect to popular cephalometric reference lines such as APo, NB, or mandibular plane were not correlated with the relapse of mandibular crowding. Therefore, other clinical guides might be more successful for determining stability.

Dental Arch↗
PubMed2002

Does the canine dental follicle cause resorption of permanent incisor roots? A computed tomographic study of erupting maxillary canines.

We performed computed tomography (CT) on 107 children and adolescents aged 9-15 years with 176 unerupted maxillary canines (152 erupting ectopically and 24 erupting normally) to determine whether there is an association between widened dental follicles of the maxillary canines and resorption of the adjacent incisors during eruption. Contiguous axial (transverse) CT scans were obtained through the maxilla in the region of the canines. The width and shape of the dental follicles were recorded, as were any contacts between the follicles and the crowns of the maxillary canines and neighboring incisors. Fifty-eight lateral incisors (38%) and 14 central incisors (9%) had some type of root resorption. The position of the maxillary canine in relation to the root of the lateral incisor varied greatly, as did the width and shape of the canine dental follicle. Follicle width ranged from 0.5 mm to 7.0 mm. The mean +/- SD width of dental follicles was, on average, larger for the ectopically positioned canines (2.9 +/- 0.8 mm) than for the normally erupting canines (2.5 +/- 0.8 mm) (P < or = .01). We found that during eruption, the follicle of the erupting maxillary canine frequently resorbed the periodontal contours of adjacent permanent teeth but not the hard tissues of the roots. We concluded that the dental follicle did not cause root resorption of permanent teeth. Resorption of neighboring permanent teeth during maxillary canine eruption was most probably an effect of the physical contacts between the erupting canine and the adjacent tooth, active pressure during eruption, and cellular activities in the tissues at the contact points, all of which are part of the eruptive mechanism. The findings also confirm an association between root resorption of deciduous canines and the dental follicles of erupting permanent canines.

Adolescent↗
PubMed2006

Severe crowding and a dilacerated maxillary central incisor in an adolescent.

This study reports the treatment of an adolescent patient with dilacerated maxillary incisor. She complained of severe crowding with a high-positioned left upper canine. Her left central incisor had been impacted and moved to proper position at the age of eight years, resulting in a severe root dilaceration. To avoid any progression of root dilacerations and resorption in the maxillary incisor, maxillary lateral expansion and molar distalization plus multibracket appliance were selected as the best nonextraction treatment plan. The maxillary expansion and molar distalization should provide adequate space for the correction of the severe crowding, and treatment with a multibracket appliance was initiated. After a 17-month treatment with a multibracket appliance, an acceptable occlusion was achieved with a Class I molar relationship. An acceptable occlusion was maintained without recurrence of the crowding and impairment of the dilacerated root in the maxillary incisor during three years of retention. It is emphasized that careful planning is required to avoid any progression of the root dilaceration and resorption through orthodontic treatment. A shortening of the period of applying orthodontic force on the dilacerated incisor and avoidance of tooth extraction will minimize the risk factors.

Adolescent↗
PubMed2002

Bilateral maxillary fused primary incisors accompanied by succedaneous supernumerary teeth: report of a case.

A rare case of fusion between maxillary primary central incisors and supplemental teeth occurring bilaterally, accompanied by succedaneous supernumerary teeth, is presented. The patient was an 8.5-year-old Japanese boy. Intraoral examination revealed fusion of left and right maxillary primary central incisors to supplemental teeth, which had labial and lingual grooves. The maxillary primary lateral incisors were present. Radiographs showed that the fused teeth had separate roots, pulp chambers and root canals. There were two impacted supernumerary teeth and eruption of the permanent maxillary central incisors was delayed. Treatment was performed and the fused primary teeth and the impacted supernumerary teeth were extracted. After 6 months observation, surgical exposure of the two crowns of the permanent maxillary central incisors was performed. The teeth began to erupt and have since been kept under observation.

Child↗
PubMed2000

A retrospective study of unerupted maxillary incisors associated with supernumerary teeth.

We retrospectively reviewed the clinical records and radiographs of 100 patients who had had supernumerary teeth removed. Their mean (SD) age was 9 years 3 months (2). The 100 patients had a total of 127 unerupted maxillary incisors associated with supernumerary teeth. The supernumerary tooth was removed without exposure of the permanent tooth more often among the 79 younger children (aged 10 years or less) (SND=3.52, P<0.01), and when the incisors were less mature (Cvek classification 1, 2, and 3) (SND=5.27, P<0.01). Of these incisors with immature roots that were treated conservatively, 60 (72%) erupted and 24 (28%) required further operation. Of the mature incisors treated conservatively, 10 (63%) required further operation. In this study, almost three-quarters of immature incisors erupted spontaneously after removal of the associated supernumerary teeth. Over half of the mature teeth required further operation. Mature teeth should be exposed with or without bonding at the time of removal of the supernumerary teeth.

Adolescent↗
PubMed2003

Incisor crown shape and crowding.

The aim of this study was to investigate correlations between the shape of mandibular incisor crowns and crowding. Study models of 50 untreated white subjects (25 men and 25 women) with varying degrees of crowding were studied. The lower incisors were sectioned and imaged at the contact point and midpoint levels, and the mesiodistal width was measured. Crowding was quantified by using both Little's irregularity index and anterior tooth size-arch length discrepancy. The ratio of the 2 mesiodistal widths was correlated with Little's irregularity index and anterior tooth size-arch length discrepancy. In the women, the ratio showed correlations of 0.52 (P =.008) and 0.55 (P =.005) for central and lateral incisors, respectively, with anterior tooth size-arch length discrepancy. No predictors of lower incisor crowding could be established from mandibular incisor crown shape in this study.

Adolescent↗