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At least 361 records · Page 20Linked to original sources
PubMed1986

Apical root resorption of upper incisors caused by intrusive tooth movement: a radiographic study.

The purpose of the study was to investigate whether root resorption of the upper incisors occurs during intrusion of maxillary incisors. It examines the possibility of a relationship between the amount of root shortening and duration of the intrusive force. The ratio of root length before and after intrusion was compared in 20 patients. In 66 incisors with an intrusion period of 29 weeks, an intrusion of 3.6 mm was performed. The control group consisted of 15 patients who underwent no orthodontic treatment. Consequently, 58 incisors had no intrusion. The follow-up time between 2 measurements was +/- 28 weeks. The findings clearly showed root shortening after intrusion. A mean resorption of 18% of the original root length was found. In comparison, none of the control patients showed root shortening. No correlation has been found between the amount of resorption and the amount and duration of intrusion. In combination with the apical deflection of the root, the nasal floor was occasionally a limiting factor for intrusion and this may have caused root resorption.

Adolescent↗
PubMed1987

Structural changes in the dental and periodontal tissues of the rat incisor following application of orthodontic loads.

The present study deals with the morphometric changes in the loaded rat incisor and its supporting structures 3 months after load removal. The material examined was limited to that part of the tooth that is located between 8 and 20 mm from the tooth apex. Of the ten albino rats in whom laterointrusive loads (19 +/- 0.6 g) were applied to the lower left incisor for a period of 2 weeks, the rate of tooth eruption returned to normal in four animals (group A); in six rats, eruption remained grossly impaired (group B). These two groups were compared with a control group of four rats in whom the incisors were allowed to erupt normally during the 3 months of the experiment. The left mandibles were dissected and fixed; the incisors were demineralized, embedded in paraplast, and cut into transverse serial sections of 6 micron, which were used to produce a three-dimensional reconstruction of all tissue components by means of computerized histomorphometry. The parameters of pulp and dentin, and the total tooth size and shape in group A were similar to those of the control group. In group B, pulp and dentin were changed significantly, tooth size increased, and the oval shape was altered into a more rounded contour, together with a significant enlargement of the socket. Although the total PDL volumes remained similar in all three groups, the tooth/socket relation, as expressed by PDL width and PDL area at the different tooth sides and at varying distances from tooth apex, diverged from normal significantly in all teeth that had been subjected to loading.

Alveolar Process↗
PubMed1987

Two treatment approaches for missing or peg-shaped maxillary lateral incisors: a case study on identical twins.

Patients with missing or malformed maxillary lateral incisors can be successfully treated by either replacing or restoring the lateral incisor, or by positioning and reshaping the canine to simulate the lateral incisor. Identical twins were treated, one by restoring "peg laterals" to normal contours and the other by repositioning and recontouring the canines to simulate missing lateral incisors. Results of treatment would tend to indicate that considerations other than changes in facial esthetics should determine the treatment of choice.

Adolescent↗
PubMed1987

Periodontal status of mandibular incisors following excessive proclination. A study in adults with surgically treated mandibular prognathism.

The present study was undertaken to examine whether excessive proclination of mandibular incisors results in gingival retraction. In patients with surgically treated mandibular prognathism, 29 with more than 10 degrees proclination of mandibular incisors and 33 with minimal change in incisor inclination during presurgical orthodontic phase were selected. A total of 21 and 19 patients, respectively, could meet for a clinical follow-up examination including Visible Plaque Index, Gingival Bleeding Index, probing pocket depth, and length of supracrestal connective tissue attachment. Study models and intraoral color slides were also made. The mean postoperative times at this examination were 7.8 (SD 2.5) and 8.1 (SD 2.8) years, respectively. Clinical crown height was measured on the study models taken before and after appliance therapy, at the 3-year postoperative control (check) and at the follow-up examination. The number of teeth with recession was determined from the color slides taken at the same intervals; the thickness of the symphysis was measured on the cephalograms taken before treatment. The results demonstrated significantly more increase in clinical crown height and significantly more teeth developing recession both during appliance therapy and during the period from removal of appliance to the 3-year postoperative control in the patients with excessive proclination than in the patients with minimal change in incisor inclination. The correlation coefficient between width of symphysis and increase in clinical crown height in patients with excessive proclination was statistically significant. Only minimal changes were observed from 3 years postoperatively to the follow-up examination. No differences in clinical measurements were observed between the groups and bone dehiscences were not found.

Adult↗
PubMed1988

Techniques for improving orthodontic results in the treatment of missing maxillary lateral incisors. A case report with literature review.

We have presented a case report of the orthodontic treatment of a patient with congenitally missing lateral incisors and with skeletal and dental deep bite. Information was provided on methods to improve clinical orthodontic results. Different sections deal with (1) various diagnostic criteria for the best treatment approach, (2) variations in maxillary arch wire manipulation, (3) biomechanical considerations, (4) modifications of clinical crown by special procedures so that the canines resemble and function as lateral incisors, (5) functional considerations of the occlusion, and (6) details in finishing. Particular emphasis was placed on the use of a special design of closing loops for simultaneous space closure and intrusion of the anterior teeth. This article has discussed the principles of incisor and canine intrusion, and has demonstrated that the closing loops described are capable of intruding incisors with minimal side effects on the posterior teeth. It has also demonstrated how control of the mechanical variables dramatically increased the efficiency and effectiveness of intra- and extraoral forces in the treatment of malocclusion.

Adolescent↗
PubMed1992

The effect of maxillary first premolar extraction and incisor retraction on mandibular position: testing the central dogma of "functional orthodontics".

It has been argued by a vocal coterie of disaffected dentists that premolar extraction, incisor retraction, and "backward-pulling" mechanics conspire to "distalize" the condyles and, pari passu, to produce craniomandibular dysfunction. Given the gravity of this conjecture, it seemed appropriate to test the predictions it generates in a sample of patients of the type most often said to be at risk: 42 "edgewise" patients with Class II, Division 1 malocclusions, treated in conjunction with the extraction of two maxillary first premolars. Regional and anterior cranial-base cephalometric superimpositions were used to quantify the individual components of the molar and overjet corrections, to measure both at the chin and condyles the mandibular displacement seen during treatment, and to examine the extent to which this displacement is related to the correction of maxillary incisor protrusion. Although the present patients underwent marked upper incisor retraction (on average, about 5 mm), lip retraction was much less pronounced, and 70% of the sample showed a net forward displacement of mandibular basal bone. Significantly, changes in condylar position were not correlated with incisor retraction, as the "functional orthodontists" would have it, but rather with the changes in the buccal occlusion and the growth of the maxilla. Thus, 30% of the patients who showed evidence of distal displacement were generally nongrowing patients who underwent more than average anchorage loss in the mandible and less than average loss in the maxilla.(ABSTRACT TRUNCATED AT 250 WORDS)

Activator Appliances↗
PubMed1993

Maxillary incisor crown-root relationships in different angle malocclusions.

The long axis of the maxillary incisor root is not always identical to that of the crown. Instead, there is appreciable variation in the crown-root angle, generally with the crown torqued lingual to the root axis. In orthodontic cases assessed before and at the end of full-banded treatment, the crown-root angle was significantly deflected in the Class III molar relationship series, notably so in moderate to severe cases where the maxillary incisors are constrained lingual to the lower arcade. Apical root resorption was not significantly associated with the crown-root angle before or after comprehensive orthodontics. Cephalometric predictors of the amount of deflection of the crown-to-root axis were localized to intertooth relationships (overjet, interincisal angle). It is proposed that the large collum angles in Class III cases develop during tooth eruption when the maxillary incisors are trapped within the lower arch; this torques the crown of the maxillary incisor but leaves the unmineralized portion of the root free to develop as if the crown were still in its prior, more procumbent orientation.

Adolescent↗
PubMed2004

The effect of partial damage to the enamel-related periodontium combined with root resection on eruption of the rat incisor eruption.

Previous work has indicated that the enamel-related periodontium (ERP) has a role in the eruptive process of the rat lower incisor. By combining partial damage of this tissue with resection of the odontogenic organ, we examined the effect of the damage on subsequent incisor eruption. The connective tissue of the enamel-related periodontium was regenerated in less than 2 weeks, showing morphology close to normal. The injured part of the enamel organ was neither regenerated nor repaired, and a cement-like tissue, continuous with the true acellular cement, was formed on the denuded enamel. Before tooth exfoliation, the operated teeth erupted at a slower rate compared with root-resected and sham-operated incisors, probably because of the absence of a substantial part of the enamel organ due to surgical damage. As with the coronal dental follicle and the enamel organ in rat molars, the enamel-related periodontium and the enamel organ of rat incisors may have some control on their eruptive process.

Aging↗
PubMed2005

The effect of age on morphology and eruption of the lower incisors in mature rats.

OBJECTIVE: This study investigated the effect of age on tooth and periodontium morphology and on tooth eruption in the lower incisors of 28 female rats, initial age 10 weeks. DESIGN: Morphometric data of the incisors in three young mature rats (weight 199+/-2.4 g) were compared to that of three 18-week-old (weight 260+/-5 g) animals. The rate of eruption was monitored during 12 months in 11 rats with all teeth in occlusion and in 11 rats with one lower incisor kept constantly out of occlusion. RESULTS: : The incisors continued to enlarge after the animals reached maturity with the size of the teeth increasing both longitudinally and circumferentially. Tooth volume increased by 21%, while that of the periodontal ligament was enlarged by only 12%. The rate of impeded eruption declined steadily from a mean value of 542+/-49 microm/day during the first experimental month to a mean value of 443+/-25 microm/day during the concluding month (p<0.05). The eruption rate of the teeth exceeded that of attrition rate by 2.4%. The unimpeded eruption proceeded steadily throughout the experimental year, at a mean rate of 811+/-12. CONCLUSIONS: Apparently in mature rats age has no effect on the genetic potential as expressed by the unimpeded eruption. In the impeded teeth age does affect the phenotypic expression of the eruptive function governed by occlusal forces as well as by the form and size ratio of the tooth and its PDL.

Age Factors↗
PubMed2005

Effects of local injections of vasoactive drugs on eruption rate of incisor teeth in anaesthetized rats.

OBJECTIVES: Previous studies have suggested that the vasculature in the dental pulp and periodontal tissues plays an important role in producing the eruptive force in continuously erupting incisors. The aim of the present study was to investigate the effects of local injections of vasoactive drugs on regional blood flow within the socket in association with axial tooth movements to clarify the role of the local vascular system on tooth eruption. DESIGN: Twenty-two male Wistar rats, weighing 309+/-21 g (S.D.), were immobilized with halothane anaesthesia. We measured the regional blood flow within the socket using a laser Doppler flowmeter, and the axial movements of the mandibular incisor using a displacement detector. The local injections of the vasoactive drugs, adrenaline (0.001, 0.01, and 0.1 microg/kg body weight) and acetylcholine (0.05, 0.5, and 5 microg/kg), into the base of the incisor were performed by a microinjector at a rate of 1 microl/kg body weight. RESULTS: The injections of various doses of adrenaline decreased the mean regional blood flow and eruption rate dose-dependently, while those of acetylcholine increased the mean regional blood flow and eruption rate dose-dependently. The changes in the regional blood flow and eruption rate were transient. Significant correlations (p<0.001) were obtained between the maximum and minimum values in the regional blood flow and in the eruption rate following injections of various doses of adrenaline and acetylcholine. CONCLUSION: These results support the hypothesis that the eruptive force of the rat incisor is closely related to the vasculature within the socket.

Acetylcholine↗
PubMed2000

The effect of lead on the eruption rates of incisor teeth in rats.

The effects of lead on the continuously erupting rat incisors under normo-, hyper- and hypofunctional conditions were investigated. Left lower incisors of 20 rats were rendered unimpeded (hypofunctional) by cutting them out of occlusion every 2 days; the right lower incisors of these rats were considered hyperfunctional. Measurements on normally growing teeth (normofunctional) were carried out in a group of ten rats whose teeth were not cut but only marked every 2 days. On day 7 of the experiment, half of the rats from these two groups were given a single intraperitoneal injection of lead acetate (40 mg/kg), and the other half received sodium acetate (22 mg/kg). Another group of 15 rats was used to obtain blood samples for lead determination 1 h, and 10, 20, and 30 days after lead administration. Animals were killed on day 32. Hypofunctional incisors from lead-treated rats erupted more slowly than control ones (P<0.05). These results show a previously unreported toxic effect of heavy metals.

Animals↗
PubMed2003

The effects of intrusive loading on axial movements of impeded and unimpeded rat incisors: estimation of eruptive force.

Axial movements of impeded and unimpeded rat mandibular incisors were measured following application and removal of intrusive loads of 1, 2, 5, 10 and 20 mN in a stepwise order at intervals of 1h on erupting teeth. The tooth movements were recorded by a displacement detector under artificial respiration with halothane anaesthesia. The loading and unloading procedures brought about the tooth movements in two steps: an initial rapid movement immediately after application or removal of the load and a subsequent slow and gradual movement. The initial rapid intrusive or extrusive tooth movements were significantly greater in the unimpeded than in the impeded teeth at the same load. The forces to stop extrusive tooth movements, estimated from the formula of regression lines showing correlations between the intrusive loads from 0 to 5 mN and tooth movements (microm/30 min), were 4.2 mN in the impeded and 2.9 mN in the unimpeded incisors. We suggest that repeated shortenings of the rat incisor did not cause an increase in the eruptive force and that changes in the resistance of the periodontal ligament predominantly regulate the axial movement of the rat incisor.

Animals↗
PubMed1998

Adrenergic receptors and secretory responses of the rat submandibular salivary gland after periodic incisor reduction.

The lower and upper incisors of female rats were repeatedly reduced every 48 hr for 21 days. A marked enlargement of the submandibular glands was observed at the end of this period. One day after the final reduction, dose dependent curves to phenylephrine and isoproterenol were obtained in relation to salivary flow rates. Secretory responses, expressed as mg/gland, showed that the dose response curve to the alpha1-adrenomimetic drug was not modified by treatment while that for isoproterenol was shifted to the right of the control. When the responses were expressed as microg of saliva/mg of wet tissue, the dose-response curve to both agonists was shifted to the right in the incisor-reduced group. (Activation of alpha2-adrenergic receptors by clonidine did not inhibit the responses to phenylephrine in the incisor-reduced rats.) Radioligand binding assays of alpha1-, beta- and alpha2-receptors did not show differences between control and experimental glands in terms of densities (Bmax) or affinities (Kd). The lack of correlation between the decrease in alpha2- and beta-mediated responses and the radioligand bindings suggests that postreceptor mechanisms are involved in the diminished secretory responses of the rat submandibular gland after periodic reduction or amputation of incisors.

Adrenergic Agonists↗
PubMed1998

A radiographic assessment of enamel thickness in human maxillary incisors.

Crown sizes of human teeth are sexually dimorphic, with male larger than female. This holds for most human groups, though the extent of dimorphism varies among populations. It is not known whether size dimorphism is due to differences in enamel thickness, dentine differences, or some combination of the two. This study examined the pattern of variation in enamel thickness on the mesial and distal margins of the four maxillary permanent incisors. Standardized periapical radiographs of the incisors of 115 adolescent American whites were measured. Enamel was significantly thicker on the distal than the mesial margins of both the lateral and central incisors, with a mean difference of 0.1 mm. There was no sexual dimorphism in the maximum mesial or distal enamel thicknesses. In contrast, the widths of the dentine of the crowns were significantly greater in males, by an average of 6.5%. Sexual dimorphism in mesiodistal diameters of the incisors seems, then, to be due to the dentine component, which is the size attained at the end of the bell stage of tooth formation. Sex-specific correlations between enamel thickness and crown width of the dentine were low (and lower for males), indicating considerable independence between regulatory mechanisms of dentine and enamel development.

Adolescent↗
PubMed1997

Minimizing upper lip and incisor teeth paresthesias in approaches to transsphenoidal surgery.

Currently popular transsphenoidal approaches to the pituitary include sublabial, external rhinoplasty, alotomy, and transnasal techniques. The conventional sublabial approach remains the workhorse method despite postoperative lip edema, potential difficulty for denture wearers, and troublesome persistent upper lip and incisor teeth numbness. We traced the courses of the nasopalatine, infraorbital, and anterior superior alveolar nerves in 41 cadaveric half-head dissection to determine the exact contribution to upper lip and incisor teeth innervation. We then conducted a retrospective patient survey of 25 sublabial, 28 external rhinoplasty, 23 alotomy, and 12 transnasal approaches to the hypophysis to assess the incidence of upper lip and incisor teeth paresthesias lasting longer than 1 month. We conclude that rhinoplastic techniques are superior to the sublabial approach in limiting upper lip and incisor teeth numbness without compromising neurosurgical exposure for hypophysectomy.

Cadaver↗
PubMed1984

Changes in the axial inclinations of upper and lower incisors after mandibular surgery in class III cases.

Cephalometric radiographs of the position of upper and lower incisors following mandibular surgery only were undertaken in 31 cases. All cases were seen before and after treatment, and after all retention had ceased. Pre-treatment records revealed some compensation of the incisor angulation for the skeletal discrepancy, and post-operatively the upper incisors proclined further and the lower incisors remained unchanged.

Cephalometry↗
PubMed1991

Dynamics of tissue changes found after mechanical loading of the rat incisor. I. A three-dimensional longitudinal study of the morphologic aspects.

A three-dimensional morphometric method was used to evaluate progressive changes in shape and size of recovering dental and periodontal tissues after orthodontic loading. In 35 female rats weighing 212 +/- 4 gm, loads of 19.7 +/- 1.6 gm generated by closed-coil springs were applied for 2 weeks to the shortened lower left incisor. The rats were killed in groups of five at 0, 1, 3, 5, 7, 9, and 10 weeks (groups 0-w to 10-w) after the springs were removed. A group of rats with normal incisors (group C-1) and one with five incisors that had been continually shortened for 10 weeks (group C-2) served as controls for groups 0-w and 10-w, respectively. Width, area, and volume of the tooth and enamel-bordering periodontal ligament (e-PDL) and cementum-bordering PDL (c-PDL) were measured. After 2 weeks of loading (group 0-w), the volume of the compressed e-PDL had decreased by 22%, and the volume of the stretched c-PDL had increased by 72%, suggesting that bone apposition lags behind the rate of tooth movement. During the recovery period, the dental and periodontal parameters tended toward a gradual return to control (C-2) values, although at the end of 10 weeks many still lagged significantly behind the controls. Recovery was slowed by repeated reversals at different sites in the various groups. The ability of the preloaded incisor to adjust to changes in occlusal function was lastingly impaired.

Animals↗
PubMed1994

Effects of cephalometric landmark validity on incisor angulation.

An experimental cephalometric study on the accuracy of independently locating eight landmarks and the subsequent effects on the maxillary (ILs/NL) and mandibular (ILi/ML) incisor angulation was carried out on 30 dry skulls. The true location of each landmark was marked with a steel ball glued onto the skulls. Two additional steel balls were used as reference markers. A purpose-designed skullholder was made to assure a firm and reproducible positioning of the skulls in the cephalostat. Six series of cephalograms were recorded. One reference series with all the steel balls, four series each with a single steel ball marker removed, one at a time, from each jaw and one series with all the steel ball markers removed, except the reference markers. The combined method error in relocating and replacing the steel ball markers, repositioning the skulls into the skull holder, and digitizing, was low. From the first series, the true position of the palatal plane (NL), the maxillary incisor line (ILs), the mandibular plane (ML) and the mandibular incisor line (ILi) were assessed. From series 2 to 5, each of the landmarks without the steel ball markers was estimated. The accuracy of each landmark was then assessed relative to the true cephalometric plane and its perpendicular. On average, the accuracy was high for all the landmarks except posterior nasal spine (PNS), which was estimated 1.2 mm too far anteriorly (p < 0.05). The standard deviations of the accuracy of the dental and skeletal landmarks were similar, being 1.4 to 2.4 mm. The maxillary incisors were proclined 1.1 degrees (p < 0.05) by the estimates of incision superior (Is).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗