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PubMed2005

Managing congenitally missing lateral incisors. Part II: tooth-supported restorations.

Three treatment options exist for the replacement of congenitally missing lateral incisors: canine substitution, a tooth-supported restoration, or a single-tooth implant. Selecting the appropriate treatment option depends on the malocclusion, the anterior relationship, specific space requirements, and the condition of the adjacent teeth. The ideal treatment is the most conservative alternative that satisfies individual esthetic and functional requirements. This article closely examines the three options when replacing a missing lateral incisor with a tooth-supported restoration. These options are a resin-bonded fixed partial denture, a cantilevered fixed partial denture, and a conventional full-coverage fixed partial denture. The specific criteria that must be evaluated for each option is addressed to illustrate the importance of interdisciplinary treatment planning to achieve optimal esthetics and long-term predictability. This article is the second of a three-part series discussing the three treatment alternatives for replacing congenitally missing lateral incisors.

Anodontia↗
PubMed1991

An epidemiologic estimate of the critical period during which human maxillary central incisors are most susceptible to fluorosis.

The temporal relation between a declining fluorosis gradient and an abrupt downward shift in community drinking water fluoride concentration was evaluated through multiple correlation analysis to determine the critical time frame during which developing maxillary central incisors are most susceptible to fluoride challenge. Fluorosis data were scrutinized through a time-related series of epidemiologic "windows" or time frames of varying lengths. The placement of these time frames was in turn related to the presumed start of enamel mineralization (at birth), and ranged from zero to 60 months later. In this way, the susceptibility of developing enamel to changes in water fluoride concentration was localized. The greatest risk was associated with a four-month critical period commencing at 22 months following birth. The risk of fluorosis from exposures to a fluoride challenge acting during shorter periods was better localized than risk associated with longer exposures. We concluded (1) that human maxillary central incisors are most susceptible to fluorosis during a critical period of as little as four months' duration, commencing at 22 months of age; and (2) that for these incisors, fluoride exposure during the months prior to this period carries less risk than continued exposure for up to 36 months beyond this critical time.

Aging↗
PubMed1995

Refining the estimate of the critical period for susceptibility to enamel fluorosis in human maxillary central incisors.

PURPOSE: The purpose of this study was to determine an improved estimate of the critical period for susceptibility to fluorosis in human maxillary central incisors. METHODS: The fluorosis score, S, of the incisal (I), middle (M), and cervical (C) third divisions on the labial surface of right maxillary central incisors of subjects (a representative sample of 1,085 Hong Kong Chinese children aged 7 to 12 years surveyed in 1986) was determined according to the Chronological Fluorosis Assessment (CFA) Index. Subject data were grouped by month of birth relative to June 1978, when the designated concentration for waterborne fluoride in the community water supply was reduced from 1.0 to 0.7 mg/L. The analytical task was one of finding the correlation maximum in a system of 12 variates and adjustable parameters including the waterborne fluoride concentration, [F-], and the fluorosis score. RESULTS: The main findings were: (1) the peak correlation of S vs [F-] for the male incisal third centered at 17.5 months after birth; (2) and six months later for females; (3) the correlation of S with [F-] is maximized for S(M) following S(I) by two months, and S(C) following S(M) by a further two months for both males and females; and (4) the critical period for exposure to fluoride is of about four months' duration for each third. CONCLUSIONS: The maxillary central incisor, as a whole, appears most at risk to fluorosis from dietary fluoride between age 15 and 24 months for males and between 21 and 30 months for females.

Age Factors↗
PubMed1994

Ectopic eruption of transposed mandibular permanent lateral incisors beneath primary first molars. Case report.

Mandibular permanent lateral incisors showing bilateral transposition and ectopic eruption were seen beneath primary first molars on bitewing radiographs in a female aged 9 years. This report chronicles management of the case during the mixed dentition period. Appropriate space maintenance after extraction of mandibular primary first molars, cuspids and lateral incisors on both sides facilitated eruption and repositioning of the permanent lateral incisors without the need to sever supracrestal gingival fibres.

Child↗
PubMed2000

Restoring the vertical dimension of mandibular incisors with bonded ceramic restorations.

Mandibular incisors are difficult to restore with conventional anterior crowns due to their small axial diameters. Crown preparation risks pulp exposure and results in a thin core of dentine. An experiment was designed to determine if increasing the thickness of ceramic to restore incisal edges affects the load at the point of restoration failure. Forty-eight mandibular incisors were randomly divided into four groups. The incisal edges of the teeth in three groups were reduced so that the coronal height was 7.5 mm (Group A), 6.5 mm (Group B), and 5.5 mm (Group C). Group D was designated as the experimental control. A fifth group (Group E), independent of the random sample, was introduced to the study for discussion purposes and was characterized by each of the incisors having an intact incisal edge of enamel. Groups A, B and C were prepared in a standard fashion for ceramic veneer restorations that were constructed to restore the vertical height of each tooth to 8.5 mm. Prior to cementation, the preparation surfaces were analysed and the relative surface areas of enamel and dentine were calculated. The ceramic restorations were cemented using a resin luting agent. The teeth were then thermocycled prior to loading at 135 degrees C until failure. The mean fracture load was 305 N (SD 134 N) for Group A, 403 N (SD 101 N) for Group B, 515 N (SD 296 N) for Group C, 587 N (SD 187 N) for Group D and 395 N (SD 129 N) for Group E. As determined by analysis of variance followed by a Sheffè multiple comparison test there was a significant difference (p < or = 0.01) between Group A and Group D. There were no significant correlations of load at failure with the percentage of exposed dentine, enamel surface area, total preparation surface area, and the incisal surface area. The patterns of failure of the fractured specimens were also analysed. There were significantly (p < or = 0.05) greater fractures of the ceramic restorations when they were bonded with the minimum incisal thickness of ceramic.

Analysis of Variance↗
PubMed2004

A rare presentation of dens invaginatus in a mandibular lateral incisor occurring concurrently with bilateral maxillary dens invaginatus: case report and review of literature.

BACKGROUND: Dens Invaginatus (DI), commonly known as dens in dente, is a developmental malformation of tooth that most commonly affects permanent maxillary lateral incisor teeth. Deciduous teeth are infrequently affected. Presence of DI in mandibular permanent teeth is extremely rare. Further, the presence of DI bilaterally in the maxillary lateral incisors of the same patient is even more unusual. METHODS: In this article, an unusual case of DI affecting a mandibular lateral incisor tooth is described. This malformation was uncovered after a full mouth radiographic examination when the patient presented for dental treatment unrelated to this finding. In addition, the various radiographic appearances of DI as they present within the maxillary and mandibular teeth are described. Essential clinical considerations and treatment options are presented. A review of the pertinent literature is undertaken and a table summarizing previous published findings of mandibular DI is presented. RESULTS: A review of the literature indicates that DI in mandibular teeth is extremely rare with only 10 other cases involving 13 teeth reported previously. CONCLUSIONS: Although this is an extremely rare case, DI is an anomaly that should be familiar to all practising dentists due to the clinical implications of potential sequelae of pulpal involvement.

Dens in Dente↗
PubMed2005

Comprehensive therapy of a fusion between a mandibular lateral incisor and supernumerary tooth: case report.

The term fusion is used to define a developmental anomaly characterised by the union of two adjacent teeth. In the case reported here, clinical and radiographic examinations suggested a unilateral fusion between the mandibular left permanent incisor and a super-numerary tooth. Radiographs showed that the fused teeth had two distinct pulp chambers and canals. A diagnosis of chronic periapical abscess of the supernumerary tooth was made. Before root canal therapy, a periodontal surgical procedure was performed to section the central incisor and its fused supernumerary. Also, odontoplasty was performed on the roots, to establish an anatomy consistent with a normal central incisor. Later, the chronic apical abscess on the supernumerary tooth was instrumented chemo-mechanically, root canal filling was performed and an anterior composite resin restoration was placed. The patient was evaluated for one year after root canal therapy. The tooth was asymptomatic, not exhibiting any pathological root resorption or alveolar resorption, and the anterior composite restoration was intact. Instead of extracting the supernumerary tooth, the application of endodontic, periodontal, and restorative procedures proved to be an alternative treatment.

Child↗
PubMed1975

Incisor size and diet in anthropoids with special reference to Cercopithecidae.

In 57 species of anthropoids relative size of incisors in highly correlated with diet. Anthropoids that feed primarily on large food objects (large fruits) have larger incisors than those that feed on smaller food objects (berries or leaves). This difference reflects a need for more extensive incisal preparation of larger food objects before mastication. Extensive incisal preparation causes increased tooth wear, therefore, enlarged incisors are probably an adaptive response to increase their wear potential.

Animals↗
PubMed2000

The dentinal structure of equine incisors: a light and scanning electron-microscopic study.

This paper gives an anatomical overview of the dentinal structure in equine incisor teeth with special reference to the three-dimensional organization, the number and the diameter of the dentinal tubules. The spatial arrangement of equine dentine was examined by scanning electron microscopy of occlusal surfaces and longitudinally fractured teeth and by light microscopy of both decalcified and ground sections. The dentinal tubules of the peripherally situated primary dentine were directly continuous with those of the circumpulpal secondary dentine. The tubules had numerous side branches along their entire course and ramified into terminal branches near the dentino-enamel junction. Tubules of tertiary dentine, situated in the centre of the dental star, were few in number and not continuous with those of the surrounding secondary dentine. On non-etched incisors tubular orifices were clogged by an amorphous smear layer that covered the occlusal surface. On etched occlusal surfaces the numerical tubular density was calculated in different zones. The largest number of tubules per unit area was situated in the secondary dentine forming the dark periphery of the dental star, whereas the smallest number was present in the tertiary dentine located in the pale centre of the dental star. Dentinal tubular diameters were measured at various distances from the pulp. They were widest near the pulpal wall and narrowed progressively towards the dentino-enamel junction. Tubular widths measured on etched occlusal surfaces were considerably larger than those measured on undecalcified incisors due to the removal of intratubular dentine during the etching process.

Animals↗
PubMed1977

Effects of ionizing radiation on incisor development of the prenatal mouse.

The effects of 100 rad of X-irradiation of incisor development in CD1 mice were studied. 24 pregnant mice were irradiated on the 12th day post coitum and sacrificed from the 14th through the 20th gestational days. The 191 irradiated fetuses were smaller than those not irradiated, their crania and necks were malformed and their lower extremities were poorly developed. The developing incisors of the irradiated animals were retarded, the pulpal vessels were enlarged and the vessels walls did not maintain their structural integrity. The cells of the future pulp were necrotic, and the basement membranes appeared hyalinized. Ameloblasts and odontoblasts were abnormal in morphology and the formation of dental hard tissue was inhibited in places. Complete absence of incisor tooth germ was noted in three of the fetuses.

Animals↗
PubMed2001

Characteristics of incisor-premolar hypodontia in families.

Nonsyndromic tooth agenesis is a genetically and phenotypically heterogenous condition. It is generally assumed that different phenotypic forms are caused by different mutated genes. We analyzed inheritance and phenotype of hypodontia and dental anomalies in 214 family members in three generations of 11 probands collected for genetic linkage study on incisor-premolar hypodontia (IPH). Our analysis confirms the autosomal-dominant transmission with reduced penetrance of IPH. The prevalence of hypodontia and/or peg-shaped teeth was over 40% in first- and second-degree relatives and 18% in first cousins of the probands. Four of nine noted obligate carriers of hypodontia gene had dental anomalies, including small upper lateral incisors, ectopic canines, taurodontism, and rotated premolars. These anomalies were also observed at higher than normal frequency in relatives affected with hypodontia. We conclude that incisor-premolar hypodontia is a genetic condition with autosomal-dominant transmission and that it is associated with several other dental abnormalities.

Adolescent↗
PubMedDate not supplied

Patterns of crowding of permanent mandibular incisors before eruption.

Observation of the radiographs taken of 37 mandibles from children ten months to seven years of age showed that the unerupted, permanent mandibular central incisors were rotated in 45 of 74 jaw halves (60.8%). The type of rotation in which the mesial aspect is directed lingually was most commonly seen (44.6%). The next most common observation was of jaw halves without any rotation of the central incisor (39.2%). The type of rotation in which the central incisor's distal aspect is turned lingually was the least common observation (16.2%). The rotation seemed symmetric in 25 jaws (67.6%).

Child↗
PubMed1984

Effect of long-term administration of fluoride on the levels of EDTA-soluble protein and gamma-carboxyglutamic acid in rat incisor teeth.

EDTA-soluble material, extracted from incisor teeth of rats given 50 ppm fluoride (NaF) in drinking water ad libitum from conception to age nine wk, contained significantly higher levels of protein (P less than 0.01) and gamma-carboxyglutamic acid (P less than 0.01) than did similar material from control rats. Tooth fluoride levels indicated that the incisors were mildly fluorosed. Analysis of these data indicates that mild fluorosis of rat incisor teeth involves not only the characteristic disturbances of pigmentation and mineral structure but also some alteration of the matrix protein.

1-Carboxyglutamic Acid↗
PubMed1987

The influence of vanadate on calcium uptake in maturing enamel of the rat incisor.

The influence of vanadate, a potent inhibitor of Ca2+-ATPase and Na+-K+-ATPase, on 45Ca uptake in maturing enamel of the rat incisor was investigated by a vascular perfusion method combined with 45Ca autoradiography. The morphological integrity of the maturation-stage enamel organ was well-retained during vascular perfusion under all the experimental conditions. Distinct patterns of 45Ca labeling, comparable with those found in previous in vivo 45Ca autoradiographic studies, appeared in the maturing enamel after vascular perfusion with a standard perfusate. One mmol/L vanadate added to the standard perfusate caused a drastic decrease in 45Ca uptake in the maturing enamel, corresponding to the ruffle-ended ameloblasts, leaving narrow peaks of moderate intensity corresponding to the bands of the overlying smooth-ended ameloblasts. The in vitro labeling of exposed enamel surfaces with 45Ca revealed blackening of autoradiographic emulsion in wide bands separated by unlabeled or slightly labeled narrow ones resembling the distribution of smooth-ended ameloblasts in both control and vanadate-treated incisors. Our observations indicate that the ruffle-ended ameloblasts of the rat incisor serve as an efficient diffusion barrier to calcium ions and regulate transcellular calcium transport to the maturing enamel, at least in part, by a vanadate-sensitive mechanism.

Ameloblasts↗
PubMed1992

The occurrence of interglobular dentin in incisors of hypophosphatemic mice fed a high-calcium and high-phosphate diet.

The incisor dentin of hypophosphatemic (Hyp) mice was examined histopathologically to determine whether the multiple occurrences of interglobular dentin would be influenced by the serum phosphate level. Both normal and Hyp mice (12 weeks of age) were divided into two groups. The mice in one group were given a control diet (1.42% Ca, 1.16% P) and the other a high-calcium and high-phosphate diet (2.00% Ca, 3.00% P) for 30 days. Blood was collected from the mice every fifth day for measurement of the calcium and phosphate concentrations in serum. Both ground and decalcified cross-sections were prepared from incisors from the mandible and maxilla for microscopic examination. The levels of serum Ca and P were almost constant in normal mice, regardless of diet. On the other hand, serum P levels in Hyp mice fed the control diet were significantly lower than those in normal mice. The ten days' feeding of the high-Ca/-P diet significantly elevated the serum P level in Hyp mice, and it reached a level similar to that of the normal mice. However, histopathological examination showed no significant changes in incisor dentin of Hyp mice fed the high-Ca/-P diet, and interglobular dentin still occurred. These results suggest that the multiple formations of interglobular dentin, which is the most outstanding feature of X-linked hypophosphatemic vitamin-D-resistant rickets, are not influenced in Hyp mice by the short-time normalization of the serum phosphate level.

Animals↗
PubMed2004

Immunolocalization of enamelysin (matrix metalloproteinase-20) in the forming rat incisor.

In the rat model, we used the continuously growing incisor to study the expression pattern of matrix metalloproteinase-20 (MMP-20) during the formation of mineralized dental tissues. Casein zymography analysis of extracts of the forming part of the incisor revealed lysis bands corresponding to both the latent form at 57 kD and the active 46- and 41-kD forms, whereas omission of proteinase inhibitors during protein extraction resulted in a single band at 21 kD. A higher molecular weight form of 78 kD was also stained with MMP-20 and TIMP-2 antibodies in Western blotting, and was therefore believed to correspond to an MMP-20/TIMP-2 complex. Immunohistochemical and immunogold electron microscopic results demonstrated strong MMP-20 staining in the forming outer enamel, which diminished near the dentino-enamel junction, but dentin and predentin were unstained. A strong concentration of MMP-20 was seen in the stratum intermedium (SI), particularly at the earlier stages of enamel development. Our results confirm the presence of MMP-20 protein in ameloblasts and odontoblasts of rat incisor and show it to be localized in the same sites of the forming enamel as amelogenin. Their expression is transient in odontoblasts but persists in ameloblasts, and in both cases the expression of amelogenin preceded that of MMP-20 suggesting a developmentally controlled regulation.

Amelogenin↗
PubMed1990

Fordyce's granules of the incisor and molar gingiva in F344 rats.

Fordyce's granules were observed in the gingiva of the upper incisor and molar teeth in F344 rats. The data were based on 734 males and 722 females that were used as control and treated animals in 26-week, 65-week, and 2-year studies by the National Toxicology Program. The incidence of Fordyce's granules was markedly different when comparing sex, age, and site of the lesion. Fordyce's granules were very common in the midsagittal gingiva of the upper incisor in males and increased in incidence with age (34.2, 50, and 56.3% in 26-week, 65-week, and 2-year studies, respectively). The granules of the incisor gingiva were rare in females (0,0, and 2.8% in 26-week, 65-week, and 2-year studies, respectively). Fordyce's granules of the molar gingiva were very rare in both sexes and were found only in 9/734 (1.2%) males and in 3/722 (0.4%) females. Only three unilateral granules of the molar were grossly recognized as focal swelling of the gingiva or a white nodule with a huge cyst in the third upper molar. Histologically, Fordyce's granules were arranged as a collection of sebaceous glands unassociated with hair follicles. In addition, the granules of the molar gingiva were associated with cystically dilated ducts filled with sebum. Ultrastructurally, the sebaceous cells were characterized by varying numbers of cytoplasmic lipid droplets and occasional desmosome and hemidesmosome formation. Fordyce's granules previously reported in rats of other strains were also reviewed and compared with those in F344 rats in regard to incidence, location, and age.

Animals↗
PubMed2002

Effects of excitatory amino acid receptor antagonists on pulpal blood flow of the rat mandibular incisor.

Pulpal blood flow (PBF) changes have been monitored by laser Doppler flowmetry on rat mandibular incisors. Electrical stimulation (10 sec, 50 microA, 2 ms, 20 Hz) of one incisor induced a blood flow decrease followed by a blood flow increase. The effect of intravenous administration of antagonists of ionotropic glutamate receptors (iGluRs) and antagonists of metabotropic glutamate receptors (mGluRs) was compared with that of those obtained from animals treated with the vehicle alone. No long-term effect on basal PBF was observed, except a remaining increase of 34.5% (p < 0.05, n = 5) for ketamine (10 mg/kg), an iGluR antagonist, and of 37% (p < 0.05, n = 5) for MCPG (7.5 mg/kg), an mGluR antagonist. In animals treated with iGluR antagonists, acute changes in PBF after stimulation were not significantly different from those observed with vehicle. In animals treated with mGluR antagonists, the blood flow decrease was significantly enhanced in amplitude and duration for MCPG (7.5 mg/kg), respectively, +73% and +92% (p < 0.05, n = 5). These results suggest that Group I mGluRs participate in the regulation of the immediate pulpal blood flow decrease induced by electrical stimulation of the lower incisor in the rat.

Analysis of Variance↗