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At least 559 records · Page 31Linked to original sources
PubMed1998

NADPH-diaphorase activity in nerves and Schwann cells in the periodontal ligament of rat incisor teeth.

The lingual portion of the incisor periodontal ligament demonstrated activity for nicotinamide adenosine dinucleotide phosphate (NADPH)-diaphorase. Schwann cells surrounding Ruffini-like endings coexpressed NADPH-diaphorase activity and immunoreactivity for inducible nitric oxide synthase. NADPH-diaphorase-positive nerve fibres which coexpressed immunoreactivity for neuronal nitric oxide synthase were in contact with Schwann cells surrounding Ruffini-like endings or terminated as free nerve endings. Neural NADPH-diaphorase activity could not be found in the tissues covering the labial portion of incisor tooth root. It is possible that nitric oxide in Schwann cells and nerves has functions specific to the incisor periodontal ligament.

Animals↗
PubMed1999

Differences in the pattern of lanthanum diffusion into predentine and dentine in mouse incisors and molars.

Lanthanum nitrate was either perfused intravascularly or segments of mouse tooth were immersed in a fixative solution containing the tracer. The tracer deposits were examined in young (8-day-old) and older (8-week-old) mouse incisors and molars, demineralized or undemineralized. Lanthanum passed the distal junctional complex of odontoblasts and appeared in the predentine of incisors as large electron-dense stellate aggregates, 40-70 nm in diameter, and in molars as round, 20-40 nm dots. In dentine, tracer deposits were detected at three locations. Near the predentine dentine junction, the tracer densely stained a band 0.5-2.5 microm in width, also termed metadentine; in the inner circumpulpal dentine, the staining was weaker or lacking in an area extending 5-7 microm from the predentine-dentine junction; in outer circumpulpal dentine, lateral diffusion had occurred in porosities of intertubular dentine. Lanthanum impregnated the walls of dentine tubules and a peritubular-like dentine. In contrast, the mantle dentine was never stained. These differences in the pattern of diffusion prove that lanthanum staining is age-dependent and varies between mouse incisors and molars, independently of tissue processing. Architectural properties and driving flux are involved in the transport and localization of lanthanum in predentine and dentine.

Age Factors↗
PubMed2000

Effects of neonatal injury of the inferior alveolar nerve on the development and regeneration of periodontal nerve fibers in the rat incisor.

Our previous study showed that the migration of terminal Schwann cells occurred in the periodontal ligament of the rat lower incisor following transection of the inferior alveolar nerve (IAN) in the adult animals [Y. Atsumi, K. Matsumoto, M. Sakuda, T. Maeda, K. Kurisu, S. Wakisaka, Altered distribution of Schwann cells in the periodontal ligament of the rat incisor following resection of the inferior alveolar nerve: An immunohistochemical study on S-100 proteins, Brain Res. 849 (1999) 187-195]. The aim of the present study was to investigate the effects of neonatal transection of the IAN on the regeneration of axon elements and Schwann cells in the periodontal ligament of the rat lower incisor. Following transection of IAN at post-natal day 5 (PN 5d), when the numbers of both axon elements and the terminal Schwann cells were very small, regenerating nerve fibers appeared between post-injured days 7 (PO 7d) and PO 14d, and increased in number thereafter gradually. Although the terminal morphologies of regenerated Ruffini endings became identical to those of the adult animals by PO 54d, the number of regenerated PGP 9.5-IR nerve fibers did not recover the adult levels even by PO 56d. A small number of Schwann cells migrated into the shear zone, the border between the alveolus-related part (ARP) and the tooth-related part (TRP), but did not enter into the TRP. Following transection of the IAN at PN 14d or PN 28d, when clusters of apparent terminal Schwann cells could be recognized, axon regeneration started around PO 5d. Individual axon terminals of the regenerating Ruffini endings ramified and became identical to those of the adult animals around PO 28d, but the number of regenerated Ruffini endings was smaller than that of the adult animals. Similar to the adult animals, the migration of Schwann cells into the shear zone and TRP occurred, and disappeared prior to the completion of the axonal regeneration. The present results indicate that the migration of the Schwann cells into TRP during the regeneration of the periodontal nerve fibers following nerve injury to the IAN depends on the maturation of the terminal Schwann cells of the periodontal Ruffini endings, not on post-operative time.

Age Factors↗
PubMed2002

Effects of incisor-cutting on muricidal behavior induced by olfactory bulbectomy in rats.

Muricidal behavior in rats is composed of two main components, attacking and killing performance. Since a large number of mice could be killed by rats during behavioral experiments, research has been limited in the past decade possibly because of ethical considerations. In preliminary studies, we found that the rat incisors play a key role in muricidal behavior in rats, so, in the present study, we cut off the incisors and assessed the following parameters of muricidal behavior: attack latency, first attack site, lethal attack site, attack frequency, total attack duration and mean attack duration. If after incisor-cutting (IC) rats still tried to demonstrate muricidal activity, but failed to kill the mouse, this would be an ideal model for studying the mechanisms of muricidal behavior. Since muricide can be induced in rats by olfactory bulbectomy (OBX), young adult male Wistar rats with OBX displaying muricidal behavior were tested for muricidal activity 4 h after IC, then every 24 h for 3 days. At 4 and 28 h after IC, only 9% and 36% of rats killed mice, but these values rose to 73% and 82% 52 and 76 h after IC, respectively. At 4, 28 and 52 h after IC, there was no significant difference in attack latency, first attack site, lethal attack site or mean attack duration between IC-treated rats (both killers and nonkillers) and sham-operated controls, while the attack frequency was obviously increased in IC nonkiller rats, and a significantly longer total attack duration was seen in both IC killer and nonkiller rats compared to controls. Since IC treatment increases attack frequency and prolongs the total attack duration without affecting other basic components of muricidal behavior in rats, these results suggest that the killer rats treated with IC may provide a suitable model for research on muricidal behavior.

Aggression↗
PubMed1989

A maxillary central incisor having two root canals geminated with a supernumerary tooth.

This article reports the treatment of a maxillary left central incisor geminated with a supernumerary tooth. A patient having labial swelling around the maxillary incisors was referred to this hospital for diagnosis and endodontic treatment of the maxillary left central incisor. Clinical and radiographic examinations revealed a tooth having two roots and three canals. Examination of a rubber base impression of the cleaned canals showed there was neither perforation of, nor communication with, the radicular groove in the tooth.

Child↗
PubMed1997

Periapical replacement resorption of permanent, vital, endodontically treated incisors after orthodontic movement: report of two cases.

Radiographic observations show that periapical replacement resorption (PARR) is a frequent and unpredictable sequella of orthodontic movement of permanent maxillary incisors. Only the apical root portion undergoes resorption, and it is subsequently replaced with normal bone. PARR also occurs without orthodontic tooth movement, but these resorptions differ as to type and location. PARR clearly occurs in teeth with vital pulps after orthodontic movement; however, our two cases and a review of 43 other cases indicate that endodontically treated incisors show a statistically significant lesser frequency and severity of apical resorption than untreated teeth. The role the vital pulp plays in this apical resorption is yet to be determined. A hypothetical explanation is offered suggesting that pulpal neuropeptides may be involved in PARR in both vital and endodontically treated incisors. The role calcium hydroxide plays in endodontically treated teeth is also considered.

Adolescent↗
PubMed1999

Ideal endodontic access in mandibular incisors.

Straight-line access in mandibular incisors facilitates locating and debridement of the canals. The purpose of this study was to plot where ideal access should be located in mandibular incisors to obtain straight-line access to the apical third of the root canal and to determine if a correlation exists between incisal edge wear and position of access opening. Two hundred and seventy-nine mandibular incisors were radiographed in clinical and proximal views. Straight-line access was determined by finding midpoints in the canal at two levels and extending a line connecting the points through the crown. Teeth were graded as to the condition of the incisal edge. Ideal straight-line access was determined to be at the incisal edge in 72.4% of the teeth, whereas in 27.6% of the teeth it was to the facial of the incisal edge. As the wear of the incisal edge increased, the ideal access moved from the facial toward the incisal.

Chi-Square Distribution↗
PubMed1997

Innervation of the mandibular incisors by the mental nerve.

PURPOSE: This study tested the hypothesis that some sensory innervation to the lower incisor teeth comes from reentry of the terminal branches of the mental nerve through the labial plate of the anterior mandible. PATIENTS AND METHODS: Ten cadaveric heads (20 sides) were dissected and studied to determine whether the mental nerve crossed the midline or reentered the labial plate. Using careful dissection, the most posterior branch of the nerve was exposed from its point of emergence at the mental foramen to its insertions, and any entries into the labial plate were recorded and photographed. RESULTS: Three of 20 (15%) specimens showed unequivocal evidence of nerve reentry into the labial plate. Five specimens displayed strong evidence of nerve fibers reentering the plate, but these were too fragile to be dissected through the periosteum without breaking. In 12 of 20 (60%) specimens, there were no branches identified that reentered the bone plate. Of the eight specimens showing evidence of reentry, four had substantial midline crossover. CONCLUSIONS: The finding that branches of the mental nerve may reenter the labial plate to supply the lower incisors explains the phenomenon of crossover innervation from the contralateral mental nerve and the fact that a labial infiltration injection will anesthetize the lower incisor teeth.

Anesthesia, Dental↗
PubMed2000

Orthodontic, genetic, and periodontal considerations in the treatment of impacted maxillary central incisors: A study of twins.

Treatment of twins each with one impacted maxillary central incisor and a mesiodens is described. Treatment included rapid expansion, extraction of the mesiodens, surgical exposure of the impacted central incisor, and its forced eruption. The impacted incisor was brought into functional position in one patient but was lost in the other because of insufficient root length and high mobility. Orthodontic, genetic, and periodontal considerations of these 2 cases are evaluated.

Adolescent↗
PubMed2003

Early and unusual incisor resorption due to impacted maxillary canines.

A very early and severe case of maxillary incisor resorption caused by impacted canines is reported. An estimated 50,000 cases of ectopic eruption and impaction of maxillary canines occur each year in the United States. Although incisor resorption due to ectopically positioned permanent maxillary canines can be swift, silent, and devastating, an effective protocol has been developed for early detection and management of this condition. Palpation and, if indicated, radiographic evaluation are combined with primary canine removal in selected cases. These strategies--particularly when used early--can prevent the vast majority of palatally impacted maxillary canines and the potentially devastating resorption of adjacent incisors.

Child↗
PubMed1993

Molar and incisor changes with Wilson rapid molar distalization.

The purpose of this study was to determine the magnitude and direction of maxillary and mandibular first molar and incisor changes that occur during Class II molar correction with Wilson "rapid molar distalization." Nineteen patients (13 females, 6 males) were selected from the clinic at Loma Linda University Department of Orthodontics. All patients received maxillary bimetric distalizing arches (BDA), and either a mandibular three-dimensional lingual arch, with or without a passive 0.016 x 0.016-inch utility arch, or a traditional edgewise full banded and bonded arch. The arches were activated with open coil spring and Class II intermaxillary elastics. A total of five activations were completed or until visual inspection revealed a Class I molar relation. Prestudy and poststudy lateral cephalometric radiographs were taken with molar bands cemented. Dental changes were determined, with Ricketts superimpositions. The mean change in molar relation measured at the occlusal plane was 4.1 mm. The mean maxillary molar distalization was 2.16 mm, with 7.8 degrees of tip. The rate of maxillary molar movement was 0.56 mm per month. The mean mandibular molar mesial movement was 1.38 mm. The maxillary incisors protruded a mean of 0.3 mm, and extruded a mean of 1.6 mm. Except for the edgewise sample, all mandibular molars moved mesially further than the incisors, reducing the mandibular arch length. The presence of erupted maxillary second molars did not correlate with the rate of maxillary first molar movement, magnitude of movement, or amount of tipping that occurred.

Adolescent↗
PubMed1988

The mechanics of lower incisor intrusion: experiments in nongrowing baboons.

The effects of different combinations of segmented intrusion arch wires and anchorage units on the relative vertical positions of anterior and posterior teeth in the lower arch were demonstrated in four nongrowing baboons. Forces of between 90 and 100 g were delivered by the intrusion arch wires to the four lower incisor teeth in each animal over a period of 5 months. The dental and skeletal changes occurring during that period were assessed from lateral cephalometric radiographs. Lower incisor intrusion, determined by the vertical movement of an internal reference point, was demonstrated in each of the animals. However, the actual effects of the mechanics on the relative anterior and posterior vertical tooth positions, and consequently on the height of the lower face, were found to depend largely on the magnitude of the reactive moments acting on the anchorage units. It was suggested that in general, for a given intrusive force, the further forward the center of resistance is positioned in the anchorage unit, the smaller the reactive moment will be and the more incisor intrusion one might reasonably expect to achieve during arch leveling.

Animals↗
PubMed1995

Treatment of a crowded Class II malocclusion with significant maxillary incisor protrusion.

A case report of a 10-year-old girl with a skeletal and dental Class II, Division 1 malocclusion is presented. There was marked arch length deficiency in the mandibular arch and significant maxillary incisor protrusion. The patient was treated with maxillary premolar extractions and early maxillary treatment for incisor retraction. The treatment was completed nonsurgically with full treatment later and a single mandibular incisor extraction. The Class II malocclusion and crowding were resolved with Class II molar and Class I canine relationships and a positive profile change. [This case was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board.]

Bicuspid↗
PubMed1995

Mandibular incisor uprighting identification.

An important consideration during the diagnosis and subsequent treatment of every orthodontic patient is the position of the mandibular incisors. This article proposes guidelines for posttreatment mandibular incisor position that, when used, either preserve or enhance facial balance and harmony, and explains the interrelationship of the profile line and its relationship to the tip of the nose with the ratio of posterior facial height to anterior facial height. The article offers ideas about posttreatment mandibular incisor position that will allow the clinician a better understanding of facial balance and harmony.

Adolescent↗
PubMed1997

Changes in jaw movement and jaw closing muscle activity after orthodontic correction of incisor crossbite.

The possible influences of the direction of occlusal loading delivered to the incisors in the sagittal direction during chewing on jaw movement and jaw closing muscle activity were investigated. Ten healthy children with crossbite of one or two incisors on the right side were selected. Each subject chewed a piece of chewing gum on the right side, and jaw displacements and electromyographic signals from the posterior temporalis and superficial masseter muscles on the ipsilateral side were sampled simultaneously. After orthodontic correction of the incisor crossbite relationship, identical records were taken. The inclinations of the gliding contacts for each posterior tooth in the lateral jaw excursion position were consistent before and after the treatment. The posttreatment records showed broader jaw movement patterns in the frontal view and faster jaw movement velocity in the lateral direction at a level close to the habitual maximum intercuspation position, when compared with the pretreatment records (P < 0.05). The duration of the muscle activity and the incidence of the silent periods of the masseter muscle during chewing significantly decreased after the treatment (P < 0.05). The current results give a neurophysiologic rationale for explaining the significance of orthodontic treatment in improving lowered masticatory efficiency in the way that the change in direction of the occlusal load achieved by tooth movement influences on the periodontal sensory input, which, in turn, modifies the trigeminal motor output and thus, eventually, jaw muscle activities.

Bite Force↗
PubMed1998

Directions of orthodontic tooth movements associated with external apical root resorption of the maxillary central incisor.

External apical root resorption is a multifactorial problem encountered in all disciplines of dentistry, but it is most commonly seen in cases treated orthodontically. Specific tooth movements that are most likely to exacerbate external apical root resorption are poorly understood. Purpose of the present investigation was twofold: (1) to quantify apical and incisal movements of the maxillary central incisor in the sagittal and vertical planes from cephalograms and (2) to use stepwise multivariate linear regression analyses to see which tooth movements and skeletodental relationships are most predictive of external apical root resorption. The sample consisted of 110 adolescents with similar pretreatment malocclusions (Class I crowded or bimaxillary protrusive) and treatment planned similarly (extraction of four first premolars) by experienced private practitioners. Each of three practitioners used a different orthodontic appliance; the sample was divided proportionately into cases treated with Tweed standard edgewise technique, Begg lightwire technique, and Roth-prescription straightwire technique. Lateral cephalograms were analyzed at the start, middle, and end of treatment. There was no statistical difference in average external apical root resorption between sexes or among techniques. Measures of tooth movement were highly predictive, explaining up to 90% of the variation in root resorption. Apical and incisal vertical movements and increase in incisor proclination were the strong predictors of external apical root resorption for each regression model. Incisor intrusion with increase in lingual root torque together were the strongest predictors of external apical root resorption. In contrast, distal bodily retraction, extrusion, or lingual crown tipping had no discernible effect.

Adolescent↗
PubMed1999

Postretention mandibular incisor stability after premolar serial extractions.

The purpose of this study was to evaluate the mandibular incisor alignment in serial extraction cases, using the longitudinal dental cast records of the Burlington Growth Center as a control sample. Various parameters were investigated and the statistical differences determined between the treated and untreated groups. The results were also compared with data from serial extraction groups that subsequently had orthodontic treatment. Untreated subjects and subjects treated only with serial extractions showed similar longitudinal changes. However, the extraction group that also received orthodontic treatment appeared to show more lower incisor crowding long-term. No predictors for stability of clinical significance could be determined. Mechanotherapy influences the craniofacial and dentoalveolar dimensions, which appear to cause more long-term lower incisor crowding.

Adolescent↗
PubMed1996

Double dens in dente with a central cusp and multituberculism in bilateral maxillary supernumerary central incisors: report of a case.

A case of bilateral molarized teeth in the maxillary central incisor region is reported. The bilateral central incisor teeth were extracted in a 13-year-old boy and examined radiographically and histologically. Both malformed teeth were diagnosed as double dens in dente with a central cusp and multituberculism in maxillary supernumerary central incisors.

Adolescent↗