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PubMed1993

The relationship of crowding to the eruptive position of the lower permanent incisors.

The aim of this study was to examine the positions of newly erupted lower permanent incisors and their relationship to crowding. Forty-one crowded and 37 uncrowded dental casts of children in the early mixed dentition were examined by means of digitization using a reflex microscope. Two aspects of alignment were considered: rotation and labio-lingual displacement. Rotations of the incisors were defined as deviations from 'ideal' predicted angles. Displacement of the incisors was measured as the distance between the most labial and most lingually placed incisors. The study showed an increase in rotations amongst the crowded sample. The result of the investigation of the relationship between crowding and displacement was inconclusive. There would appear to be significant differences between the positions of newly erupted crowded and uncrowded incisors. Crowding, however, was not the only factor causing irregularity.

Child↗
PubMed2004

Gonadotropin releasing hormone-1 expression in incisors of mice.

GnRH-1 is a decapeptide hormone that regulates gonadal maturation and fertility. In brain, GnRH-1 is secreted by neurons residing mainly in the preoptic/hypothalamic area. These neurons arise from cells in the nasal placode during embryonic development. GnRH-1 mRNA and peptide in the nonhypothalamic region have been described, suggesting other functions of GnRH-1. This paper describes for the first time the expression of GnRH-1 in developing incisors in mice. At embryonic day (E) 12.5, GnRH-1 mRNA and peptide were localized in cells in oral and dental epithelia. At postnatal day (P) 6, before incisor eruption, GnRH-1 was expressed in cells in dental epithelial-derived structures that include the papillary layer, outer dental epithelium, stellate reticulum, stratum intermedium, and enamel-secreting ameloblast cell layer. GnRH-1 expression correlated with cell maturity, becoming stronger in cells farther away from the proliferative zone. From E12.5 through P6, GnRH-1 expression was not detected in neural crest-derived dental mesenchyme or in mesenchyme-derived structures that include dental papilla, dental follicle, and dentin-secreting odontoblast. In addition, GnRH-1 expression was not detected in molars, indicating that expression of GnRH-1 is differentially regulated in incisor vs. molars, with only the former exhibiting continuous growth in this species. In homozygous hypogonadal mice at P1, GnRH-1 peptide expression was not detected, yet incisors were present. However, morphological changes in cells between dental follicle and ameloblast cell layer were noted. Taken together, our results indicate that GnRH-1 expression, although not essential for initiation and formation of incisors, may be important in maturation and/or maintenance of these placodally derived structures.

Animals↗
PubMed2005

The clinical significance and management of apical accessory canals in maxillary central incisors.

BACKGROUND: The maxillary central incisor is considered to be the least difficult subject for a clinical endodontic experience. However, the internal anatomy of maxillary central incisors can present a number of variations, including multiple accessory canals. CASE DESCRIPTION: This article highlights the clinical significance and management of accessory canals located in the apical one-third of maxillary central incisors. The authors present two case reports in which failure to detect the accessory canals led to root canal failure and subsequent surgical intervention. Another two case reports present the serendipitous discovery and nonsurgical management of accessory canals during the initial treatment of maxillary incisors. CONCLUSIONS AND CLINICAL IMPLICATIONS: It is important for the clinician to be able to detect the signs suggesting the presence of accessory canals in maxillary central incisors. Failure to do so may lead to a less-than-optimal endodontic treatment outcome.

Adult↗
PubMed2000

Radiographic determination of the position of the maxillary lateral incisor in the cleft alveolus and parameters for assessing its habilitation prospects.

OBJECTIVE: Develop patient selection criteria and guidelines for the diagnostic work-up for early secondary alveolar bone graft designed to accommodate a lateral incisor in the cleft. DESIGN: A literature review with clinical examples. INTERVENTIONS: For the majority of cleft lip and palate (CLP) patients, the timing of the secondary alveolar bone graft procedure is devised to accommodate the eruption of the maxillary canine. However, when the lateral incisor is present in the cleft area, a decision may be made to perform early grafting in order to salvage an additional tooth. Appropriate case selection for this intervention is the key for successful dental habilitation in the cleft area. RESULTS AND CONCLUSIONS: Attempts to maintain the lateral incisor are recommended only if the tooth contributes to the comprehensive orthodontic and restorative patient care and when the presence of a lateral incisor with adequate size, shape, and proper position may be demonstrated. For optimal decision making, the position, form, and periodontal ligament support of the lateral incisor should be assessed. Evaluation of these parameters is based chiefly on radiographic imaging. Occlusal projections and traditional tomography may augment the information available from periapical and panoramic radiographs. However, each of these has benefits and drawbacks that require consideration.

Alveolar Process↗
PubMed2000

Combined bone grafting and delayed closure of the hard palate in patients with unilateral cleft lip and palate: facilitation of lateral incisor eruption and evaluation of indicators for timing of the procedure.

OBJECTIVE: To compare outcomes of bone grafting performed before eruption of the lateral incisor to outcomes of grafting performed before eruption of the canine and to evaluate the long-term results of bone grafting combined with delayed closure of the hard palate during mixed dentition. DESIGN: Seventy consecutive patients (52 men and 18 women) with complete unilateral cleft lip and palate were studied. All patients underwent bone grafting with simultaneous closure of the cleft in the hard palate at the stage of mixed dentition. The velum had been repaired in infancy. Mean age for the bone grafting procedure was 8.4 years. Bone grafting was performed to facilitate eruption of the lateral incisor in 43 (61%) of the patients and to facilitate eruption of the canine in the remaining 27 (39%) patients. Intraoral radiographs were used to evaluate the morphologic characteristics of the cleft and the stage of eruption of the permanent lateral incisor and canine before bone grafting. Mean follow-up time was 4.0 years (range, 1-10.1 years). RESULTS: The mean time for the surgery, which included bone grafting and repair of the residual cleft in the hard palate, was 109 minutes, and the mean amount of bleeding was 121 ml. The rate of dehiscence in the flap covering the alveolar bone graft was 14%, and the rate of total failure of bone grafting was 3%. An oronasal fistula developed in the hard palate of 13% of patients, but the fistula was of sufficient size to serve as an indication for reoperation in only 6%. The postoperative alveolar bony height in the cleft area was more than 75% of the normal height in 94% of patients. Closure of the cleft space in the dental arch was performed or planned to be achieved orthodontically in 91% of patients. When bone grafting was performed to facilitate eruption of the lateral incisor, the cleft space was closed orthodontically in 100% of patients. The optimal indicator for timing of the bone grafting procedure from an orthodontic point of view was when the permanent lateral incisor or the canine close to the cleft was covered by a thin shell of bone (i.e., 7-9 years of age).

Alveolar Ridge Augmentation↗
PubMed1987

Sensory innervation of the periodontal ligament in the incisor and molar of the monkey, Macaca fuscata. An immunohistochemical study for neurofilament protein and glia-specific S-100 protein.

Nervous elements in the periodontal ligament of the monkey, Macaca fuscata were investigated by means of immunohistochemistry for neurofilament protein (NFP) and S-100 protein. Thick nerve bundles with NFP-immunoreactivity entered the periodontal ligament through slits at the bottom of the alveolar socket, whereas thinner bundles, also NFP-immunoreactive, penetrated the ligament from the lateral wall of the alveolar socket. The NFP-immunopositive nerve fibers were densely distributed around the root apex in both incisors and molars. In the upper incisors, another dense distribution of NFP-positive nerves was found in the apical half of the lingual periodontal ligament and in the coronal half of the labial periodontal ligament. The periodontal nerve fibers in the incisors ramified in a dendritic fashion, terminating as free nerve endings within the periodontal ligament. Immunostaining for S-100 protein demonstrated the Schwann sheaths of nerves which showed the same distribution pattern as that of the NFP-immunopositive fibers in the periodontal ligament of the incisors. In molars, immunostaining for NFP and S-100 showed that nerves were numerous in the apical region of the periodontal ligament. However, NFP-immunopositive nerves were fewer than the S-100-positive nervous elements in the apical region in molars. This discrepancy suggests the presence of NFP-immunonegative nerves. Immunostaining for S-100 is thus useful for demonstration of neural elements in the periodontal ligament of molars. The S-100-immunoreactive neural elements in the periodontal ligament were more numerous in incisors than in molars. In addition to the free nerve endings, a small population of coiled nerve endings was observed in the periodontal ligament of molars. Most of the nerve fibers and cell bodies in the trigeminal ganglion showed NFP-immunoreactivity, whereas all in the mesencephalic nucleus of the trigeminal nerve were negative in NFP-reaction. This finding suggests that the periodontal ligament of molars receives a dual innervation from the trigeminal ganglion and mesencephalic nucleus.

Animals↗
PubMed1990

Relationships between tooth eruption, occlusion and alveolar bone resorption: histochemical and cytological studies of bone remodeling on rat incisor alveolar bone facing the enamel after root resection.

The labial side of rat incisor alveolar bone facing the enamel is continuously resorbed as the result of compressive force produced by the occlusion and eruption of incisors. In order to clarify the relationship between this mechanical compressive force and the bone cells involved in bone remodeling, we examined morphological changes occurring in the alveolar bone once the compressive force was eliminated by the removal of the proliferative odontogenic base (root resection according to Berkovitz and Thomas, 1969). After root resection, the incisor migrated halfway along the socket. On the crestal part where incisor still existed, active osteoclasts were prominent on the bone surface, and flattened mononuclear cells lay close upon active osteoclasts. Sinusoidal blood vessels or capillaries were observed at short distances from the bone surface. On the basal part where socket was vacant, osteoblasts lined up on the newly formed bone, and the osteogenic cell layer lay on the osteoblasts. Between the two parts, which correspond to the reversal phase proposed by Baron (1977), osteoblastic cells with developed cell organelles increased in number and the distance between blood vessels and bone surface increased. Osteoclasts reduced their activities, and osteoblastic cells often wedged themselves between the osteoclasts and bone surface. These findings indicate that the elimination of compressive force mediated by incisors leads to the activation of osteoblastic cells and inactivation of osteoclasts, which results in a conversion from bone resorption to bone formation. Thus, osteoblastic cells may play an important role in controlling osteoclastic activity in conversion from bone resorption to bone formation, partly by a direct effect and partly by controlling the access of blood vessels to the bone surface.

Acid Phosphatase↗
PubMed1999

Successful treatment of pulpal-periodontal combined lesion in a birooted maxillary lateral incisor with concomitant palato-radicular groove. A case report.

Palato-radicular groove (PRG) is a common developmental anomaly of maxillary incisors, whereas PRG associated with a birooted maxillary incisor is relatively infrequent. The clinical significance of PRG is related to the incidence of localized periodontitis with or without pulpal pathosis, depending on the depth, extent, and complexity of the groove. Successful treatments of PRG in single-rooted incisors have been reported in the literature. However, treatment of PRG in birooted incisors has often been ineffective. This case report describes a pulpal-periodontal combined lesion occurring on a birooted maxillary left lateral incisor with concomitant PRG in a 13-year-old boy which was successfully treated by conventional endodontic therapy in combination with periodontal treatment including accessory root resection, radiculoplasty and bone grafting. Seven-year follow-up is included in this report. The basis of a successful result is accurate diagnosis and elimination of inflammatory irritants and contributory factors. Awareness of the existence of this abnormality by the clinician is important.

Adolescent↗
PubMed2007

The third-order angle and the maxillary incisor's inclination to the NA line.

OBJECTIVE: To evaluate the relationship between the angular measurement data (incisor's long axis to NA line) and the third-order angle (TA) according to Andrews' description. MATERIALS AND METHODS: The materials in the study included the lateral radiographs and corresponding dental casts of 32 males and 35 females between 10 and 25 years of age, regardless of their skeletal and dental relationships. All subjects were white and none had undergone orthodontic therapy. Using lateral radiographs, upper and lower incisor angulations were assessed in reference to the NA line. These data were compared with third-order angles derived from direct dental cast measurements, which were performed using an incisor inclination recording appliance. RESULTS: The third-order angle measurements recorded from the dental casts were a mean of 16.2 degrees (SD = 5.3 degrees) smaller than the axial inclination according to the NA line. In this sample, there was a range of 42.7 degrees for the TA variable (mean = 5.6 degrees, SD = 9.73 degrees) and 47 degrees for the 1NA/deg variable (mean = 21.7 degrees, SD = 8.67 degrees). A highly significant correlation existed (r = 0.84) between Andrews' angle and the inclination estimated in reference to the NA line. CONCLUSION: Incisor inclination can be better estimated by recognizing the relationship between the torque angle and the axial inclination referred to the NA line. Third-order measurements using dental casts can offer a simple way to get an objective and rapid vision of the incisor's inclination.

Adolescent↗
PubMed1980

Development of deciduous mandibular incisors related to developmental stages in the mandible.

On the basis of morphological and histochemical studies of 71 human mandibles from the former half of prenatal life, five stages (D I to D V) in the development of the deciduous mandibular incisors are described. These stages are related partly to general parameters of fetal development, such as M age (menstrual age), CRL (crown-rump length), CNO (composite number of ossified bones in hand and foot) and partly to stages in the skeletal development of the symphysis menti (SM I to SM V). The investigation revealed close relationship between the development of the deciduous mandibular incisors and the skeletal development of the deciduous mandibular incisors and the skeletal development of the mandible in the region of the incisors. No such relationship was found between the development of the deciduous mandibular incisors and general parameters of fetal development.

Fetus↗
PubMedDate not supplied

Sequelae and prognosis of intruded primary incisors: a retrospective study.

PURPOSE: This study was designed to assess the sequelae and prognosis of intruded primary incisors. METHODS: Of 196 children who visited the emergency clinic due to intrusion of 310 maxillary primary incisors, 110 children (172 teeth) were available for follow-up examination (study group). Eighty-six children (138 teeth) did not show for the follow-up examination (non-respondents group). Male/female ratio was 1.7:1. Age range of children at time of injury was 12-72 months (mean 28). Follow-up time ranged between 0 and 59 months (mean 27). RESULTS: Fifty-seven percent of all teeth were completely intruded. In 80%, the root was pushed labially. All but two ankylosed teeth re-erupted, and 37% of these re-erupted into an ectopic position. Completely intruded incisors re-erupted into an ectopic position in a higher percentage (45%) than partially intruded teeth (30%). Fifty-two percent of the teeth presented pulp canal obliteration (PCO). Sixty-four percent of the completely intruded incisors presented PCO compared to 40% of partially intruded teeth. Arrest of dentin apposition was found in 15% of the teeth, and was not affected by the degree of intrusion. Twenty-three teeth were extracted shortly after the injury due to suspect of contact with the developing permanent successor (19 teeth) and severe caries (4 teeth). Sixty-eight percent of the intruded teeth survived more than 36 months after the injury. Twenty-three percent were extracted due to periodontal breakdown and 5% due to repeated trauma. Antibiotic therapy did not have any effect on the survival rate. CONCLUSION: The majority of intruded primary incisors may re-erupt and survive with no complications after more than 36 months post trauma even in cases of complete intrusion and fracture of the labial bone plate.

Age Distribution↗
PubMed1999

Survey of incisor trauma in second grade students of central Taiwan.

BACKGROUND: The purpose of this study was to investigate the prevalence and related factors of incisor trauma among 1200 second grade students in Taichung City, Taiwan. METHODS: The study population consisted of 1200 second grade students, 645 boys (53.8%) and 555 girls (46.3%), at four elementary schools in Taichung City, Taiwan. This survey was composed of two parts: (1) a questionnaire of dental traumatic history, and (2) a clinical examination of each subject to record any clinical evidence of traumatic dental injury on permanent incisors. RESULTS: The questionnaires indicated that 16.5% of the children had a positive history of dental trauma. The male to female ratio of a prior dental trauma was 1.4:1. The maxilla (78.2%) was affected more frequently than the mandible. Most of the injuries had occurred at home (63.7%). Clinical examinations disclosed that 3% of the subjects, 43 teeth in 37 children, had clinical signs and symptoms of dental trauma. Maxillary central incisors (77%) were the teeth most often affected. The most common type of crown injury was enamel fracture (67%). CONCLUSION: The prevalence of a history of dental trauma and clinical findings of incisor injury in this study was lower than that in previous reports. Home and school were the settings where dental injury was most likely to occur. Clinical signs and symptoms of dental trauma were found in 3% of the subjects. Maxillary incisors were the most commonly affected teeth, and 67% of these cases involved enamel fracture.

Age Factors↗
PubMed1999

Soft tissue changes associated with incisor decompensation prior to orthognathic surgery.

A retrospective cephalometric study employing angular and linear measurements was undertaken to examine soft tissue changes associated with incisor decompensation prior to orthognathic surgery. Subjects were divided into 3 groups based on the presenting malocclusion, and radiographs for each subject were traced and subsequently digitized. The results showed that incisor decompensation was achieved more markedly in Class II division 2 and Class III patients. In Class II division 1 subjects, changes in the mandibular incisor inclination were contrary to what was anticipated. The soft tissue change/dental change ratio following incisor decompensation showed that the soft tissues were least affected in the Class II division 2 group. This may be due to the increased tone of the soft tissues in this group, which resisted the effects of the incisor change. Alternatively, it may indicate that the soft tissue "drape" is not in close approximation to the dentition and therefore dental changes are not transmitted to the soft tissues.

Cephalometry↗
PubMed2002

[Repair and revision 8. Relapse of lower incisors: retreatment?].

Research into the long-term stability of orthodontic treatment at the University of Nijmegen (the Netherlands) until 10 years after retention has shown that nearly 50% of the total relapse takes place the first two years after retention. After that period certain stability is reached except for the lower front teeth. Ten years after the retention phase their position is even worse than at the start of treatment. The changes in lower front teeth alignment are the result of relapse, but also of normal physiological changes during ageing of the dentition. Therefore it is questionable whether late mandibular incisor irregularity should be (re)treated. Relapse of mandibular incisor alignment shortly after debonding can be restored by tightly tying the rotated incisor(s) to the C-C bar with a steel ligature, by using a spring-retainer or by rebonding of brackets to the lower front teeth. After correction of the incisor position the C-C bar should be bonded to all lower front teeth. (Re)treatment of mandibular incisor irregularity at an older age asks for more complicated treatment mechanics.

Humans↗
PubMed2002

Lower incisor changes on basal bone and in relation to the lower face: combined growth and treatment effects in the late mixed-dentition.

This study was designed to determine and compare the ranges of combined growth and late mixed-dentition treatment changes in the positions of the lower incisors, either on basal bone or in relation to the APog line. While there was considerable individual variation, movements of the lower incisors in relation to APog were found to be related more to changes in the angulation of the APog line itself, than to the movements of the incisors on the basal bone. In individual cases in which considerable forward movement had occurred at pogonion and in which deep anterior overbites had been reduced, it was often found that the lower incisors had moved forward considerably in relation to the APog line without necessarily having moved forward at all on the underlying basal bone. It was concluded therefore that, in such cases, lower incisor movements on basal bone may actually occur in the opposite direction to those in relation to the APog line because of the complex interaction of changes occurring in the vertical and horizontal positions of both point A and pogonion. In these cases, it seems possible for the lower dentoalveolus to be passively carried forward with growth of the underlying basal bone, once any deep overbite has been reduced.

Analysis of Variance↗
PubMed2003

[Replacement of deciduous incisors in children: psychological aspects].

The absence of the temporary incisors could be to a genetic illness or to some multiple premature extractions. These extractions are the aftermaths of the carious lesions or some traumatisms underwent by the temporary incisors. Beyond measure the loss of the space, the premature loss some temporary incisors very often assign the relational development of the child and disturb its psychological development and the aesthetic function. Across some cases clinics, the authors show that the replacement of the temporary incisors is the therapeutic ideal solution. Indeed, the child prosthesis, replacing the temporary absent incisors, solves the psychological, aesthetic and relational problems of the child.

Anodontia↗
PubMed2006

Damage to incisors after nonmyeloablative total body irradiation may complicate NOD/SCID models of hemopoietic stem cell transplantation.

Immunocompromised murine xenotransplantation models have become an important tool to study stem cell biology. One of the most common recipient strains used is the NOD/SCID mouse, which offers sufficient longevity to quantify moderate levels of engraftment. During pilot experiments, we noted incisor abnormalities 5 to 6 wk after nonmyeloablative doses of irradiation. Here we report a detailed examination of this phenomenon and propose possible explanations and management strategies. A total of 15 NOD/SCID mice received 3 Gy total body irradiation (TBI) and were monitored over 9 wk. A control group of 15 mice were treated in exactly the same way as the study mice except that they did not receive irradiation. A total of 9 TBI mice developed incisor abnormalities between days 40 and 50 after irradiation, resulting in rapid weight loss. No mice in the control group developed incisor abnormalities, however 3 were euthanized prematurely due to the development of thymic lymphoma. Upon development of incisor abnormalities and weight loss, 2 mice in the TBI group had their teeth trimmed and received soft food. Both mice made a rapid recovery and survived for the remainder of the study. The development of incisor abnormalities occurred in 2 substrains, and alterations in antibiotic use and supplementation of the vitamin content of feeds did not prevent the abnormalities. Investigators working with this model should be aware of this complication and modify protocols appropriately.

Animals↗
PubMedDate not supplied

Correlation between maxillary central incisor form and face form in 4 racial groups.

OBJECTIVES: The purpose of this study was to evaluate the correlation between central incisor form and face form in 4 racial groups and to investigate if there was agreement among experts in categorizing the central incisor forms. METHOD AND MATERIALS: A total of 160 subjects (40 whites, 40 mulattos, 40 blacks, and 40 Asians) ranging from 18 to 33 years of age were selected. Digital photographic records were made, 1 full-face and 1 intraoral view of the maxillary right central incisor. The outline tracings of the tooth and face images were obtained using Adobe Photoshop 5.0 software. The outline tracings were printed in distinct transparencies, and 3 prosthodontists determined if there was correspondence between the tooth and the face forms by superimposition of the transparencies. If there was disagreement among the prosthodontists' evaluations, the prevalent decision was considered. The experts also classified the central incisor forms into square, ovoid, tapering, or combination at 2 different sessions. At the first session, no instructions were given. At the second session, the prosthodontists were instructed to follow Williams' method of classification. RESULTS: A correspondence between tooth and face forms was found in 23.75% of all cases. Agreement on the tooth form classifications among the prosthodontists occurred in 30.62% of all cases at the first session and 24.37% at the second session. CONCLUSION: There is not a highly defined correlation between central incisor form and face form in any racial group studied. In addition, the experts were not in fair agreement in categorizing tooth forms.

Adolescent↗