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At least 541 records · Page 30Linked to original sources
PubMed1987

Soft-tissue profile changes resulting from retraction of maxillary incisors.

The response of the soft-tissue profile to retraction of the maxillary incisors is still a matter of controversy. The purpose of this study was to improve the clinician's ability to predict the soft-tissue profile changes caused by retraction of the maxillary incisors by quantifying the profile changes, and identifying and quantifying the contribution of the most significant factors responsible for these changes. The cephalometric records of 80 Class II, Division 1 treated female subjects and 53 untreated female subjects were digitized and analyzed by means of a stepwise multiple regression analysis. The statistical assessment of the data suggested the following conclusions: In general, growth was associated with only minimal changes in the soft-tissue profile in a period not exceeding 36 months. The three clinically significant soft-tissue changes occurring in response to orthodontic treatment that included a mean upper incisor retraction of 6.7 mm were the retraction of the upper lip, the increase in the lower lip length, and the increase in the nasolabial angle. Other soft-tissue changes, which were of little clinical significance, included the retraction of the lower lip, the reduction of the interlabial gap, the increase in the thickness of both the upper and lower lips, the increase in the soft-tissue lower facial height and the lower soft-tissue component, which is the distance between lower stomion and soft-tissue menton. The length of the upper lip did not increase with either growth or orthodontic treatment. In general, changes in the lower lip in response to orthodontic tooth movement were more predictable than those of the upper lip. The low degree of predictability associated with the upper lip response to orthodontic tooth movement may be caused by the complex anatomy and/or dynamics of the upper lip, which could not be evaluated by the presently available cephalometric techniques.

Adolescent↗
PubMed1988

Substitution of a transposed premolar for a congenitally absent lateral incisor.

The purpose of this report is to review the orthodontic treatment of a patient with bilateral transposition of maxillary canines and first premolars in addition to congenital absence of a maxillary lateral incisor. This unique combination of factors led to substitution of the maxillary left first premolar for the left lateral incisor. The occlusal fit, gingival form, and esthetic appearance of premolar/lateral incisor substitution are discussed.

Adolescent↗
PubMed1988

The effect of load duration on long-term recovery of the eruptive function in the rat incisor.

The purpose of this study was to determine the long-term recovery of the normal rate of eruption of the rat incisor following application of loads of similar magnitude but of varying duration. The daily rate of eruption of the continuously growing tooth served as indicator of the functional recovery of its periodontium. The left mandibular incisor was shortened out of occlusion in 34 experimental and 16 control rats. The experimental animals were divided into groups A, B, and C, and continuous loads (19.47 g +/- 0.42 g) were applied to the shortened incisors by means of closed-coil springs for 5, 14, and 28 days, respectively. Following removal of the springs, the daily rate of eruption was measured and calculated in all 50 animals for a period of 10 weeks. The extended impairment of eruption in the experimental animals was directly proportional to the duration of loading: at 10 weeks postloading, it was present in 18%, 67%, and 100% of the rats in groups A, B, and C, respectively. The intragroup variations in the rate of eruption of individual teeth were more pronounced following short-term loading than after prolonged load application. Short-term loading proved to be least harmful regarding recovery of eruptive function.

Animals↗
PubMed1989

Labial root torque: effect on the maxilla and incisor root apex.

This study was designed to determine the effectiveness of labial root torque on anterior nasomaxillary development. Quantification was made of the angular and linear changes in Downs' point A (representing midsagittal basal bone) and incisor point A (representing the dentoalveolar bone) and any concomitant incisor root resorption. The study was divided into two parts: part 1--to determine the anatomic configuration of the premaxillary region by use of laminagraphy on skulls, and part 2--to use the morphologic landmarks found in part 1 to assess the development of the nasomaxillary complex in maxillary retrusive patients. The clinical study involved 17 maxillary retrusive patients, aged 8.0 to 15.7 years, who had been treated for a period between 0.31 and 3.70 years with edgewise advancing mechanics. Clinical results indicate that during the first phase of orthodontic treatment with labial root torque, encompassing a 0.63-year mean treatment period, a greater rate of advancement of Downs' point A was produced when compared with normal growth. The skeletal convexity increased, whereas normal growth straightened the profile. Incisor point A advanced at a greater rate than Downs' point A, suggesting that treatment caused a larger dentoalveolar effect than the effect on midsagittal basal bone. When treatment was extended to 1.57 years, similar changes were found but at a reduced rate. Overall apical root resorption was 12.7%/year. Sex and age were not found to have any correlation to the amount of apical root loss.

Cephalometry↗
PubMed1989

The effect of cortisone on the eruption rate of root-resected incisors in the rat.

It is generally thought that the periodontal ligament plays a key--perhaps even exclusive--role in tooth eruption. The present study was designed to test the hypothesis that the fundus also may contribute to the process. To this end the effect of cortisone on the eruption rate of root-resected mandibular incisors was examined in male albino rats. Half of the animals received daily injections of cortisone; the other half were given normal saline. Impeded and unimpeded eruption rates were measured at 3-day intervals and tested for between- and among-means differences by repeated-measures analysis of variance (ANOVA). In contrast to the acceleration commonly seen in intact incisors, cortisone produced no change in the eruption rate of root-resected incisors. It was concluded therefore that the accelerative effect of cortisone is mediated by the fundus, rather than the periodontal ligament. Further, it is hypothesized that early eruption is controlled by cellular proliferation within the fundus; however, once the tooth enters the oral cavity and becomes functional, the periodontal ligament matures and becomes the dominant factor in subsequent eruption.

Alveolar Process↗
PubMed1989

Intrusion of incisors in adult patients with marginal bone loss.

Elongated and spaced incisors are common problems in patients suffering from severe periodontal disease. Thirty patients characterized by marginal bone loss and deep overbite were treated by intrusion of incisors. Three different methods for intrusion were applied: (1) J hooks and extraoral high-pull headgear, (2) utility arches, (3) intrusion bent into a loop in a 0.17 x 0.25-inch wire, and (4) base arch as described by Burstone. The intrusion was evaluated from the displacement of the apex, incision, and the center of resistance of the most prominent or elongated central incisor. Change in the marginal bone level and the amount of root resorption were evaluated on standardized intraoral radiographs. The pockets were assessed by standardized probing and the clinical crown length was measured on study casts. The results showed that the true intrusion of the center of resistance varied from 0 to 3.5 mm and was most pronounced when intrusion was performed with a base arch. The clinical crown length was generally reduced by 0.5 to 1.0 mm. The marginal bone level approached the cementoenamel junction in all but six cases. All cases demonstrated root resorption varying from 1 to 3 mm. The total amount of alveolar support--that is, the calculated area of the alveolar wall--was unaltered or increased in 19 of the 30 cases. The dependency of the results on the oral hygiene, the force distribution, and the perioral function was evaluated in relation to the individual cases. It was obvious that intrusion was best performed when (1) forces were low (5 to 15 gm per tooth) with the line of action of the force passing through or close to the center of resistance, (2) the gingiva status was healthy, and (3) no interference with perioral function was present.

Adult↗
PubMed1992

Controlled retraction of maxillary incisors.

The force characteristics inherent in the prefabricated PG retraction spring have been shown to be efficient for controlled movement of canines. In the present investigation, this spring was analyzed with regard to its applicability for controlled retraction of the maxillary incisors. A description of the required system of moments and horizontal and vertical forces, acting at both the active (alpha) and reactive (beta) units, is presented. The three-dimensional force system generated by specific modifications of the spring was registered in a bench testing device mounted with strain gauges, and the resultant data presented in a graphic. It is concluded that the PG retraction spring can be used as a module for controlled retraction of both canines and incisors. The magnitude of horizontal and vertical forces is kept within the anticipated physiologic limits and can be identified by the shape of the activated spring. Variability of the distance between the anterior and the posterior points of force attack has no significant influence on the horizontal and vertical forces produced. Only minor clinical adjustments are needed to modify the retraction spring from canine-to-incisor retraction.

Calibration↗
PubMed2003

Management of a hyperdivergent Class III malocclusion, maxillary midline diastema, and infected mandibular incisors in a young adult.

This is a case report of a 20-year-old woman with a hyperdivergent Class III malocclusion, infected mandibular incisors, maxillary midline diastema, and a mild tongue thrust. Extraction of the infected incisors and orthodontic treatment involving partial mesial movement of the remaining mandibular teeth produced a well-intercuspated Class III occlusion. After successful orthodontic treatment, a 4-unit bridge with pontics for the mandibular central incisors completed the rehabilitation and met the functional, esthetic, and occlusal treatment goals. Occlusal stability of the treatment result has been excellent in the 3-year follow-up.

Adult↗
PubMed2004

Interdisciplinary treatment including forced extrusion and reintrusion of a traumatized mandibular incisor for a patient with Class II Division 1 skeletal open bite.

A woman with Class II Division 1 long-face syndrome characteristics had a history of facial trauma, dentoalveolar fracture of her mandibular anterior teeth, and temporomandibular joint pain. The pretreatment apical radiograph showed a large area of external root resorption of the mesial surface of the mandibular left central incisor. To arrest the external root resorption, the mandibular left central incisor was extruded. During extrusion, sequential apical radiographs were taken. As the tooth moved away from the site of osteoclastic activity, resorption ceased, and repair took place on the root surface. At this time, the mandibular left central incisor was intruded, the mesial defect self-repaired, the tooth remained vital, and the periodontial ligament was intact. The biologic bases for this cessation of resorption and the repair of the tooth's surface are presented.

Adult↗
PubMed2005

The effectiveness and long-term stability of overbite correction with incisor intrusion mechanics.

BACKGROUND: Correction of deep overbite with subsequent achievement of long-term stability is difficult. The purpose of this study was to investigate the effectiveness and long-term stability of overbite correction with incisor intrusion mechanics. METHODS: The treated group consisted of 25 subjects (13 female, 12 male) with deep overbite of at least 4 mm (mean overbite, 5.9 mm). The orthodontic treatment was initiated in the late mixed or early permanent dentition, and all patients were treated nonextraction. All patients had lateral cephalometric radiographs taken at pretreatment (T1), posttreatment (T2), and postretention (T3). The treatment included cervical headgear and lever arches to intrude mainly the maxillary incisors and occasionally the mandibular incisors. Premolars were not included in the fixed appliances during the treatment. The untreated group consisted of 25 age- and sex-matched subjects from the Bolton Growth Study. RESULTS: The mechanics used were effective in overbite correction. During the posttreatment period, overbite increased by 0.7 mm. CONCLUSIONS: Although this change was statistically significant, the amount was small and is considered clinically insignificant, given the severity of the overbite pretreatment. Furthermore, a net overbite correction (T3-T1) of 3.3 mm and postretention overbite on 2.6 mm is an excellent clinical outcome.

Cephalometry↗
PubMed2005

Long-term follow-up of severely resorbed maxillary incisors after resolution of an etiologically associated impacted canine.

BACKGROUND: Resorption of maxillary incisor roots because of an impacted canine is a well-recognized phenomenon that occurs in a surprisingly high proportion of patients with impacted canines. In this retrospective study, we studied a sample of patients in whom the resorption was particularly severe. METHODS: The sample consisted of 11 patients (age, 11.8 +/- 1.2 years) with 20 severely resorbed maxillary incisors. The amount of resorption was measured at the outset (T1), when the impacted canine was distanced from the incisor root area (T2), at the completion of the orthodontic treatment (T3), and at a follow-up appointment at least 1 year posttreatment (T4). RESULTS: A 17.2% increase in the crown/root ratio occurred due to aggressive continued resorption between T1 and T2. The resorption rate reduced to an almost insignificant level, despite continued and often appreciable orthodontic movement of the resorbed teeth from T2 to T3. CONCLUSIONS: Patients with impacted canines should be screened for resorption and the impacted tooth treated as soon as possible. The resorption process can be halted and the affected tooth moved orthodontically without further risk of resorption. In the long term, with early treatment, even severely resorbed teeth do not suffer from increased mobility or discoloration and might not require splinting.

Child↗
PubMed2006

A new technique for symmetry determination in tooth morphology using image analysis: application in the diagnosis of solitary maxillary median central incisor.

OBJECTIVE: To develop a new technique for determining symmetry in tooth morphology and to evaluate this in the investigation of a patient with a solitary maxillary median central incisor (SMMCI) and a control group. DESIGN: A 9-year-old Caucasian female presented with SMMCI. Clinically the tooth appeared symmetrical. Morphology measurements of the maxillary central incisor were made using an image analysis system. Symmetry was determined by outlining the tooth from labial and axial views. These images were block filled, duplicated, flipped horizontally and then superimposed on the original image. The coincident area and perimeter of the two images from both views were measured. The method was repeated for the maxillary central incisors of 20 sets of control study models for young adult patients from which reference intervals for comparison with the SMMCI case were prepared. RESULTS: From the labial view, the area and perimeter of the two images of the SMMCI tooth were 98.85% and 98.97% coincident, respectively. From the axial view the area of the two images was 96.17% coincident, while the perimeter was 99.03% coincident. In all but one comparison for coincidence the SMMCI was above the upper limit of the reference range from the control group. CONCLUSIONS: This new technique is a valid method of assessing symmetry and is a useful clinical tool in cases of SMMCI.

Adult↗
PubMed2006

Periostin is an extracellular matrix protein required for eruption of incisors in mice.

A characteristic tooth of rodents, the incisor continuously grows throughout life by the constant formation of dentin and enamel. Continuous eruption of the incisor is accompanied with formation of shear zone, in which the periodontal ligament is remodeled. Although the shear zone plays a role in the remodeling, its molecular biological aspect is barely understood. Here, we show that periostin is essential for formation of the shear zone. Periostin-/- mice showed an eruption disturbance of incisors. Histological observation revealed that deletion of periostin led to disappearance of the shear zone. Electron microscopy revealed that the disappearance of the shear zone resulted from a failure in digestion of collagen fibers in the periostin-/- mice. Furthermore, immunohistochemical analysis using anti-periostin antibodies demonstrated the restricted localization of periostin protein in the shear zone. Periostin is an extracellular matrix protein, and immunoelectron microscopy showed a close association of periostin with collagen fibrils in vivo. These results suggest that periostin functions in the remodeling of collagen matrix in the shear zone.

Animals↗
PubMed2005

In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations.

STATEMENT OF PROBLEM: The in vitro effectiveness of a uniform circumferential ferrule has been established in the literature; however, the effect of a nonuniform circumferential ferrule height on fracture resistance is unknown. PURPOSE: This in vitro study investigated the resistance to static loading of endodontically treated teeth with uniform and nonuniform ferrule configurations. MATERIAL AND METHODS: Fifty extracted intact maxillary human central incisors were randomly assigned to 1 of 5 groups: CRN, no root canal treatment (RCT), restored with a crown; RCT/CRN, no dowel/core, restored with a crown; 2 FRL, 2-mm ferrule, cast dowel/core and crown; 0.5/2 FRL, nonuniform ferrule (2 mm buccal and lingual, 0.5 mm proximal), cast dowel/core and crown; and 0 FRL, no ferrule, cast dowel/core and crown. The teeth were prepared to standardized specifications and stored for 72 hours in 100% humidity prior to testing. Testing was conducted with a universal testing machine with the application of a static load, and the load (N) at failure was recorded. Statistical analysis was performed with a 1-way analysis of variance and the Tukey Honestly Significant Difference test (alpha=.05). The mode of fracture was noted by visual inspection for all specimens. RESULTS: There was strong evidence of group differences in mean fracture strength ( P <.0001). Following adjustment for all pairwise group comparisons, it was found that the lack of a ferrule resulted in a significantly lower mean fracture strength (0 FRL: 264.93 +/- 78.33 N) relative to all other groups. The presence of a nonuniform (0.5 to 2-mm vertical height) ferrule (0.5/2 FRL: 426.64 +/- 88.33 N) resulted in a significant decrease ( P =.0001) in mean fracture strength when compared with the uniform 2-mm vertical ferrule (2 FRL: 587.23 +/- 110.25 N), the group without RCT (CRN: 583.67 +/- 86.09 N), and the RCT-treated tooth with a crown alone (CRN/RCT: 571.04 +/- 154.86 N). The predominant mode of failure was an oblique fracture extending from the lingual margin to the facial surface just below the insertion of the tooth into the acrylic resin. CONCLUSION: The results demonstrated that central incisors restored with cast dowel/core and crowns with a 2-mm uniform ferrule were more fracture resistant compared to central incisors with nonuniform (0.5 to 2 mm) ferrule heights. Both the 2-mm ferrule and nonuniform ferrule groups were more fracture resistant than the group that lacked a ferrule.

Crowns↗
PubMed2001

Missing lateral incisors in Iron Age South-East Asians as possible indicators of dental agenesis.

The absence of lateral incisors is generally a reflection of agenesis or hypodontia, with a significant genetic basis and possibly environmental influence on the phenotypic expression. A human skeletal sample from the Iron Age cemetery of Noen U-Loke in Thailand has a very high prevalence at 79% of adults (30/38) with at least one incisor missing in either maxilla or mandible. If the cause of this high rate is genetic, it may be indicative of homogeneity, and, therefore, endogamy and probably isolation, of the population represented. Supporting agenesis as the explanation for this is the lack of space between the central incisors and canines in more than half the cases. An alternative explanation is that the teeth may have been lost during life through pathology or deliberate removal (ablation). There is no evidence in the form of remodelled lesions for pathological loss of the teeth. Although there were no significant differences between males and females in the numbers of teeth missing, there were significant differences in the patterns of loss, with males having more missing teeth on the right and females more on the left. No evidence was found in the clinical literature of agenesis involving side preference by sex, so this may indicate deliberate removal of the teeth. Males were also more likely than females to have no space for the missing teeth. Ablation of teeth has been recorded in other prehistoric South-East Asian populations but in these cases the evidence was much clearer. Agenesis seems to offer the most likely explanation for the missing teeth at Noen U-Loke and if so, indicates that a small, isolated population may develop a very high rate of hypodontia, with a side preference dependent on sex.

Anodontia↗
PubMed2001

Histomorphometric study of the periodontal vasculature during and after experimental tipping of the rat incisor.

The periodontal vasculature encircling the entire length of the rat lower incisor was studied at the time of tipping movement and 3 months later. In 12 rats (212+/-4 g b.w.), loads (0.19+/-0.016 N) were applied to the lower left incisor in a linguointrusive direction. After 2 weeks of loading, six experimental animals were killed with the loading springs in place. The springs were removed in the six remaining rats, which were killed 12 weeks later. Six additional rats with intact teeth served as control. All incisors were fixed, demineralized, embedded in glycol methacrylate and cross-sectioned perpendicular to the long axis of the tooth. The distance of each section (2 microm) from the apex was calculated. A computerized image-analysis program was used to measure the width and area of the labial and lingual periodontal ligament to establish whether the measured segments corresponded to the compressed or expanded zones. In each cross-section, the various types of blood vessels were counted and the cross-sectional area of all venous vessels was measured. The results showed that after 2 weeks of loading (1) the general trend of vascular changes was similar under pressure and tension; (2) the large-diameter vessels were unaffected by loading; (3) the mean number of terminal arterioles had decreased significantly, while the number of capillaries and postcapillary venules had increased significantly in the apical tooth part; (4) the venous blood vessel area had decreased significantly in the apical tooth part; (5) the intensity of the vascular reaction was dependent on the degree of tissue distortion; and (6) after 12 weeks' recovery the vascular changes were still present, demonstrating a rebound effect. The findings suggest that microvascular alterations following tooth loading are not directly related to the spatial effect of loading itself and are of a much longer duration than expected.

Animals↗
PubMed2002

Alveolar bone remodelling pattern of the rat incisor under different functional conditions as shown by minocycline administration.

Remodelling of the socket surrounding the continuously growing and erupting rat incisor was examined in teeth under normo, hyper and hypofunctional conditions. Cross-sections of the mandible were observed under fluorescence microscopy, where minocycline labelling evidenced bone remodelling. Animals had received minocycline (10 mg/day) during the experimental period. Control animals (from all three groups) received vehicle alone and samples from these animals were not fluorescent. Minocycline did not interfere with the eruption rates in any of the functional conditions studied. Normofunctional (impeded) incisors showed constant osteogenic activity in the alveolar bone facing the periodontal ligament in all regions of the incisor. Under hypofunctional (unimpeded) and hyperfunctional (impeded) conditions, osteogenesis in the region close to the alveolar crest was markedly increased in the mesial wall of the socket. The labial alveolar bone, facing the enamel-related periodontium, was almost entirely formed during the experimental period in all the groups, but in hyper and hypofunctional teeth the newly formed bone was thicker and contained a substantial amount formed before the experimental period. In the more apical regions of the socket no marked differences between the three functional conditions were found. The similar bone remodelling shown in hypo and hyperfunctional teeth might indicate that there are common factors causing this pattern. Consideration of possible factors appear to rule out the eruption rate, which is very different under these two functional conditions.

Animals↗
PubMed2002

Analysis of incisor pulp cell populations in Wistar rats of different ages.

Pulp cell function and viability is important for maintaining tooth vitality throughout life. However, the effects of ageing on pulpal cell populations and pulp tissue remodelling are still unclear. The aim here was to quantify age-related cell-density changes in the pulp of rat incisor teeth, using histomorphometric analysis and ANOVA. Mandibular (n=35) and maxillary (n=34) incisors were carefully extracted from 20 Wistar rats aged between 1 and 18 months, fixed and processed for light microscopy. Cell counts were performed in mature and immature regions at both labial and lingual aspects of all teeth. Odontoblast and subodontoblast cell densities were reported per mm of pulp-dentine border and core fibroblast density per mm2 pulp tissue. Irrespective of age, odontoblast and subodontoblast densities were lower in the immature than the mature regions of both maxillary and mandibular incisors (P<0.001). However, in both regions odontoblast and subodontoblast densities decreased significantly with increasing age (P<0.0001). The age-related reduction in odontoblasts was significantly greater in mature than immature regions (P<0.02) but not influenced by other variables. In contrast, the age-related reduction in subodontoblasts was significantly different between mandibular and maxillary teeth (P=0.012) but not influenced by site. Unlike odontoblasts and subodontoblasts, core fibroblasts showed small but significant increases with increasing age (P<0.0001). These age-related reductions in the density of odontoblasts and subodontoblasts may partly explain the slower rate of secondary dentine secretion and decreased pulp repair activity associated with ageing.

Aging↗