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PubMed1979

Cytochemical studies of ameloblasts and the surface layer of enamel of the rat incisor at the maturation stage.

In order to elucidate the cytochemical properties of the membranous structure between enamel and ameloblasts of the rat incisor at the maturation stage, chromic phosphotungstic acid (Cr-PTA) and periodic acid-silver methenamine (PA-silver) techniques for electron microscopy were employed in combination with a digestion test with hyaluronidase, neuraminidase, collagenase or trypsin. Also, acid phosphatase activity of ameloblasts at the maturation stage was examined with a modified GOMORI's metal salt method. An intensely Cr-PTA reactive band approximately 0.1 micron thick appeared along the surface layer of enamel at the transitional stage, and at the very beginning of the maturation stage another intensely Cr-PTA reactive band which was seen by uran-lead stain to be a delicate electron-dense membranous structure appeared as well between enamel and ameloblasts. A lot of cytoplasmic small vesicles or tubular structures, both intensely reactive to Cr-PTA, were observed near the apical membranes of the overlying ameloblasts indicating that those organelles must have been responsible for the secretion of the latter band. Acid phosphatase activity was clearly demonstrated at Cr-PTA reactive large vesicles in the cytoplasm of those cells. The PA-silver staining technique manifested a band heavily deposited with silver grains along the surface layer of enamel, i.e., where the former band existed, but showed no particular reaction at the latter, the band-like layer between enamel and ameloblasts. Hyaluronidase or neuraminidase treatment remarkably decreased the Cr-PTA reaction of the latter band. Trypsin or collagenase treatment, on the other hand, not only eliminated the Cr-PTA reaction but digested the band itself. These results suggest that the membranous structure between enamel and ameloblasts of a rat incisor is not so-called enamel cuticle but a basal lamina produced by overlying ameloblasts and that the basal lamina contains collagenous components even though it lies on enamel.

Ameloblasts↗
PubMed2002

Reposition of intruded permanent incisor by a combination of surgical and orthodontic approach: a case report.

This report presents a case of a completely intrusive luxation of an immature permanent central incisor in a 7 years 9 months-old girl. Because there are severe intrusive trauma and cortical alveolar bone fracture, it was impossible to reposition with orthodontic or surgical method alone. The intruded tooth was repositioned to healthy alveolar bone level by using surgical extrusion and stabilization with sutures and periodontal pack. After healing of adjacent bone, the intruded maxillary central incisor erupted orthodontically by removable orthodontic appliance. It was moved from a high position to level of adjacent tooth in about 7 months. A radiograph was taken 6 months after ceasing forced eruption, which demonstrated minor root resorption, but the alveolar bone height had increased.

Alveolar Process↗
PubMed2004

Pulpectomies in primary incisors using three delivery systems: an in vitro study.

This in vitro study assessed the quality of pulpectomies in primary incisors using three filling systems: syringe with plastic needle syringe with metal needle, and lentulo spiral. Preoperative radiographs of sixty extracted primary incisors were taken, canals were prepared and obturated Postoperative radiographs taken in two directions were evaluated by two independent evaluators blinded to the technique used. Filling quality was determined by analyzing radiopacity, presence of voids and amount of material in the canal After statistical analysis, this study showed that NaviTip system offered a more desirable filling quality than lentulo and Vitapex syringe techniques

Alloys↗
PubMed2005

Maxillary incisor palatal erosion: no correlation with dietary variables?

The objectives of the study were to examine a relationship between tooth erosion affecting the palatal aspects of permanent maxillary central incisors with dietary, behavioral and medical variables. The methods included, 251 schoolchildren aged 11 to 13 years were recruited to participate. Each subject had dental impressions of the palatal aspects of both upper central incisors recorded at baseline, 9 and 18 months intervals. From these, electroconductive replicas were fabricated, mapped and compared using a surface matching technique. At the end of the study all participants underwent a structured interview that sought to assay the level of potential erosive dietary, behavioral and medical risk factors. Correlation analyses of the responses given in the final structured interview with the degrees of palatal tooth substance loss (both previous and measured) were under taken. The results showed: (1) The degree of previous erosion did not predict the level of measured ongoing erosion. (2) Brushing the teeth more frequently with fluoridated toothpaste correlated significantly with lower levels of ongoing erosion (P = 0 011). It was concluded that: (1) Evidence of previous palatal erosion did not predict future erosion. (2) The application of topical fluoride as a by-product of tooth brushing may provide an element of protection against palatal erosion. (3) In view of the lack of correlation between exposure to potential risk factors and the level of ongoing palatal tooth surface loss in this study, other factors (such as an individual's susceptibility and salivary buffering power) may well be more important predictors. The clinical relevance included: Preventive advice to patients with dental erosion should not only include the use of topical fluoride, in the form of toothpaste, but recognize individual susceptibility to this condition.

Adolescent↗
PubMed2005

A case of an unerupted maxillary central incisor for indirect trauma localized horizontally on the anterior nasal spine.

The present paper emphasizes the importance of early diagnosis of retarded eruption because of trauma and the plan for the surgical management of impacted teeth. The permanent incisor was localized horizontally on the nasal spine and the roots seemed to be in a retarded stage of formation beside of contralateral tooth. The treatment plan consisted in the valuation of the necessity of space to move the impacted incisor in the normal position and the biomechanical approach for the anchorage.

Child↗
PubMed1986

The prevalence, location and conformation of palato-radicular grooves in maxillary incisors.

Palato-radicular grooves in maxillary lateral incisors have been implicated as an initiating factor in localized gingivitis and periodontitis. Focal loss of periodontal attachment associated with these grooves, some of which may extend to the apical third of the root, could result in a hopeless prognosis for tooth retention. There is disagreement as to the prevalence of this anomaly. As well, little is known about the shape, location and length of the defect. This study examined 3168 extracted maxillary lateral and central incisors. Of these teeth 4.6% had a palato-radicular groove. About half of the grooves terminated on the root and 58% of these extended more than 5 mm from the cementoenamel junction. A poorly described deformity, displacement of the cementoenamel junction, occurred in 38% of the grooves which crossed that structure. Although an extension of enamel in the groove has been suggested as a possible factor in the progression of localized periodontal disease, its presence was rarely observed.

Dental Cementum↗
PubMed1986

Periodontal adaptation following extensive extrusion and rotation of a horizontally impacted maxillary central incisor. A case report.

This report reviews the literature concerning the periodontal considerations involved in nonextraction management of impacted teeth. Further, it describes the clinical and radiographic features of periodontal tissue response to an 18-mm extrusion and 160 degree simultaneous rotation of a horizontally impacted maxillary central incisor in a 22-year-old female patient. Following surgical exposure of the unerupted incisor, an elastic thread traction was used to orthodontically move the tooth to the line of occlusion. Posttreatment evaluation of the periodontal and gingival response to a tooth movement of this complexity and magnitude was very favorable from the esthetic and functional aspects.

Adult↗
PubMed2006

[Interdental papilla reconstruction with prosthodontic treatment of maxillary central incisor: case report].

PATIENT: A 20-year-old female whose chief complaint was esthetic disturbance of a crown placed on the maxillary left central incisor. DISCUSSION: The interdental papilla was reconstructed only by the prosthodontic treatment of maxillary left central incisor. This case suggests that the proximal and subgingival contours of provisional crown is very important to the reconstruction of interdental papilla, and also suggests that the transmission of the information regarding the configuration of a provisional crown to the lab side is very important. CONCLUSION: This case shows that the emergence profile of a single crown, especially of its proximal aspect, is important to reconstruct the interdental papilla.

Crowns↗
PubMed1989

Effects of various culture conditions on matrix formative functions of rat incisor odontoblasts in a pulp-dentin slice culture system.

An attempt to develop a new pulp-dentin slice culture system was carried out using thin slices of rat incisors in order to obtain a better culture method which will be useful for studies of the physiological function of odontoblasts including the mechanism of dentiogenesis. The thin slices of incisors were prepared from mandibles of 4-5-day-old rats, using original equipment that was developed in the present study. They were incubated under stationary and rocking culture conditions with two oxygen tensions (50 and 95%). The hyperbaric condition (30% O2, 2 atm) was also tested. Histological observations, [3H]-proline uptake examination and [3H]-proline autoradiography were carried out in order to estimate the matrix formative ability of odontoblasts. The results showed that the pulp-dentin slice culture system successfully preserved the viability and the matrix formative function of odontoblasts. The rocking culture was more favorable than the stationary culture to maintain the cell viability. The higher oxygen tension improved the matrix formative function of odontoblasts. Satisfactory results were obtained from the rocking culture (95% O2) and the hyperbaric stationary culture (30% O2, 2 atm). These results suggest that a large amount of oxygen may be required for maintaining the functions of odontoblasts in this new pulp-dentin slice culture system.

Animals↗
PubMed1999

Supernumerary teeth with eumorphism in the lower incisor region: a report of five cases and a review of the literature.

Five cases of supernumerary teeth with eumorphism in the lower incisor region of the permanent dentition are reported. The patients were two males and three females. One (a 31-year-old woman) of them had bilateral supernumerary teeth. The review of the English language literature yielded only one such bilateral supernumerary teeth in the lower incisor region of the permanent dentition was reported.

Adolescent↗
PubMedDate not supplied

Analysis of dentinal stress distribution of maxillary central incisors subjected to various post-and-core applications.

This study evaluated the stress distribution on an endodontically treated maxillary central incisor restored with different post-and-core systems by using a three-dimensional finite element analysis model. Seven three-dimensional finite element models were created. Each model contained cortical bone, cancelous bone, periodontal ligament, 3 mm apical root canal filling, post-and-core and all-ceramic crowns. Two different pre-fabricated zirconia ceramic post systems, a glass fiber-reinforced post system and a titanium post system were modeled. As a control, an all-ceramic crown on an endodontically treated maxillary central incisor without a post-and-core was modeled. Each model received a 45 degrees oblique occlusal load at a constant intensity of 100 N. In each model, the ratio of Von Mises stress distribution was compared. The greatest stresses were observed in the coronal third of the roots on facial surfaces. The ratio of Von Mises stress distribution in dentin for the zirconia ceramic post (CosmoPost) and ceramic core (Cosmo Ingot), zirconia ceramic post (CosmoPost) and composite core (Tetric Ceram), glass fiber-reinforced post (FRC Postec) and composite core (Tetric Ceram), titanium post (Er post) and composite core (Tetric Ceram), zirconia ceramic post (Cerapost) and ceramic core (Cosmo Ingot), zirconia ceramic post (Cerapost) and composite core (Tetric Ceram) and the control group were 0.886, 0.889, 0.988, 0.924, 0.889, 0.893 and 1, respectively. The stress concentrations in dentin created by two different zirconia ceramic post systems were nearly the same. The zirconia ceramic post systems created slightly less stress concentration in dentin than the glass fiber-reinforced and titanium posts.

Bite Force↗
PubMed2002

A study of the ultrastructure and staining characteristics of the 'dental star' of equine incisors.

The objective of this study was to examine the diameter, extent, orientation and contents of dentinal tubules in order to validate the hypothesis of pigment penetration into the dental star of equine incisival occlusal surfaces. The time of appearance and the configuration of the dental star on the incisival occlusal surface are macroscopically visible features that, along with other more reliable parameters, are used for the determination of horses' age. Although dental stars are an integral part of the equine incisor occlusive surface, the exact nature and microstructure of the dental star are poorly documented. Therefore, equine incisor dentine was examined macroscopically and by scanning electron microscopy to elucidate numerical density, diameter and 3-dimensional organisation of the dentinal tubules in the dental star. The dental star is surrounded by primary dentine and consists of a central core of tertiary dentine, an intermediate ring of pale secondary dentine and a peripheral rim of darker, yellowish-brown secondary dentine. The central core of tertiary dentine contains relatively few dentinal tubules (<8000/mm2) that have small diameters (mean +/- s.d. 1.67 +/- 034 microm) and are arranged in an irregular pattern. The surrounding pale ring of secondary dentine comprises manifestly more and wider tubules that lie almost parallel to the occlusal surface. The dark peripheral rim of the dental star contains high numbers of tubules (28,000-58,000/mm2) that have wide luminal diameters (mean +/- s.d. 3.09 +/- 0.31 microm) and open perpendicular to the occlusal surface. In contrast, the primary dentine surrounding the dental star is made up by a lower number of dentinal tubules (<25,000/mm2). The tubules of primary dentine, which are initially mean +/- s.d. 5.15 +/- 0.80 microm wide, are narrowed by circumferential deposits of peritubular dentine and are obliquely exposed at the occlusal surface. From these observations, it was concluded that the regional differences in numerical density, diameter and spatial orientation of the dentinal tubules may influence the penetration of food pigments into the equine occlusal surface and result in the particular staining of the dental star.

Age Determination by Teeth↗
PubMed1978

Incisal overjet and traumatic injuries to upper permanent incisors. A retrospective study.

The relationships between traumatic injuries to upper incisors and incisal overjet were studied in a sample of 1445 orthodontically untreated children aged 7 to 16 years. Traumatic injuries of the hard dental tissues and exarticulations of teeth were recorded. The frequently of injuries was 14.2% in children with normal overjet (0--3 mm), 28.4% in children with increased overjet (3.1-6mm), and 38.6% in children with extreme overjet (greater than 6 mm). The severity of injuries was also greater in children with extreme overjet than in children with overjet ranging from 0 to 6 mm. Furthermore, the range of injuries increased in relation to the overjet. Two or more injured incisors were found in 19.2% of the children with normal overjet, in 22.2% of the children with increased overjet, and in 46.7% of those with extreme overjet.

Adolescent↗
PubMed1979

Influences of axial load and blood pressure on the position of the rabbit's incisor tooth.

Changes in the axial position of the left upper incisor in response to loading by 5-20 g were measured with ultrasonic technique in anesthetized rabbits. The time-response of the load-induced intrusion described a biphasic curve, with a steep initial part followed by a slower part. Maximum amplitudes after 20 s increased with increasing loads. A rise in arterial blood pressure (aortic balloon inflation) resulted in extrusion, while i.v. injection of noradrenaline or papaverine caused intrusion and extrusion, respectively. The responses to loading and changes in blood pressure were largely unaffected by transection of the root, but the effects of pressure changes were severely diminished by local infiltration of the periodontium with noradrenaline. Participation of periodontal blood vessels in the damping of load-induced intrusion was excluded by the finding of roughly equal intrusion curves at low, normal and high blood pressure and up to 38 h after death. We conclude that the resting position of the rabbit's incisor is greatly influenced by arterial blood pressure, via the periodontal vessels. The intrusion in response to loading by up to 20 g is resisted by periodontal fibers only, the blood vessels or the pulpal and periapical tissues and pressure taking no part.

Animals↗
PubMed1985

Immediate and delayed effects of repeated doxorubicin injections on rat incisor mesenchymal cells.

Effects of multiple injections of the cytotoxic drug doxorubicin hydrochloride (Adriamycin) on incisor mesenchymal cells were studied by light microscopy. Rats were killed 1 day after two and three injections, and 1 day and 5 days after four injections. Doses of 5 and 10 mg/kg were used and given on consecutive days. Necrotic alterations expanded in preodontoblast and basal pulp regions when the total dose was increased and finally embraced the entire progenitive part of the incisor. The necrotic area became encapsulated by cellular predentin produced by differentiated pulp cells to prevent further tissue damage, and commencing regeneration was observed after 5 days. When the total dose was split up, the cytotoxicity of doxorubicin increased.

Ameloblasts↗
PubMed1989

Dentin and osteodentin matrix formation in apicoectomized replanted incisors in cats.

The reestablishment and rate of osteodentin and dentin matrix formation in 27 apicoectomized replanted and 20 control incisors in cats were studied after Procion H8-BS vital staining. In control teeth the pattern of matrix formation differed in the various pulpal zones, with a higher rate of matrix formed toward apical areas, most dominantly in maxillary incisors. Osteodentin formation could be traced after a lag period of more than 10 days after replantation. Thirty and 60 days postoperatively osteodentin matrix was found in the total pulpal length in 83% and 73% of the teeth, respectively. A common finding was a tubular osteodentin matrix in the pulpal apical third in the replanted teeth. Tubular osteodentin matrix was, however, present most incisally in some teeth 60 days postoperatively. Internal resorption corresponding to outer cervical lesions dominated the pulpal reactions in the maxillary replanted teeth after 60 days. It is concluded that under the present experimental conditions the pulp tissue possesses a high healing potential and that the osteodentin formation reflects the pulpal healing pattern after replantation traumas. The results also indicate that successful pulpal healing depends on unexposed dentinal tubules.

Animals↗
PubMed1989

A search for the osteogenic factor in dentin. Rat incisor dentin contains a factor stimulating rat muscle cells in vitro to incorporate sulfate into an altered proteoglycan.

Demineralized dentin matrix has the capacity to induce bone formation via a chondrogenic pathway when implanted into muscle, in a fashion entirely analogous to bone matrix implants. In this work we have attempted to isolate, from rat incisor dentin, the matrix factor responsible for initiating osteogenesis. Rat incisor dentin was demineralized with EDTA plus 4.0 M guanidine. HCl. The proteins in the extracts were collected and, after a CaCl2 precipitation step, fractionated on Sephacryl S-200 in 6.0 M guanidine. HCl. The primary assay for activity was the incorporation of 35S-sulfate into proteoglycan in cultures of the fibroblast-like outgrowth cells from explants of neonatal rat muscle. Two Sephacryl S-200 fractions showed enhanced sulfate incorporating activity, but only one showed enhanced incorporation without a concomitant increase in cell number. In the presence of this fraction, the cell cultures produced a larger amount of a new small proteoglycan, as compared to controls, and a significant amount of a much larger proteoglycan. The active fraction had proteins in the Mr range from 8,000 to 15,000 as the major components. These data suggest that the fraction identified may contain the factors responsible for initiating the osteogenic response to dentin matrix upon its implantation in muscle in vivo.

Animals↗