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At least 289 records · Page 16Linked to original sources
PubMed1986

The effect of partial denture design on abutment tooth and saddle movement.

A laboratory investigation designed to simulate the effect of loads applied to a free-end saddle partial denture was carried out. Abutment tooth and also saddle movement were monitored using a photogrammetric method. Loads applied to the denture saddle were transmitted through the occlusal rest and also the clasp components causing movement of both denture saddle and the abutment tooth. The direction of abutment tooth movement was towards the mesial, whether the occlusal rest was situated on the mesial or distal aspect of the tooth crown. It was also evident that the design of the clasp unit used affects the magnitude and direction of abutment tooth movement.

Dental Abutments↗
PubMed2000

Mesiodistal crown dimensions and tooth size discrepancy of the permanent dentition of Dominican Americans.

The purpose of the study was to establish normative data on the mesiodistal crown dimensions of Americans of Dominican background. The Bolton tooth size analysis was performed on a sample of 54 Dominican Americans. The mean, range and standard deviation were calculated for the size of the teeth, and a coefficient of variation was obtained for the tooth size ratio. A 2-sample t-test was used to test for the statistical difference between means. In general, the values obtained for the Dominican American sample closely resembled previous data available for the African American population. The tooth size ratios obtained were compared to the Bolton ratios. The overall ratio was found to be 91.3, equivalent to the Bolton overall ratio, whereas the anterior ratio was 78.1, larger than the 77.1 Bolton ratio. The frequency of tooth size discrepancy outside 2 standard deviations from the Bolton mean was also calculated. An overall tooth size discrepancy was found in 11% of our sample, and 28% of the sample presented an anterior tooth size discrepancy.

Adult↗
PubMed1990

[The influence of the home position operator's posture on the prepared abutment contour of jacket crown--the maxillary right central incisor].

The abutment teeth preparation with jacket crown for the maxillary right central incisor was prepared in Home Position. The following are the result of a study made on the influence to the prepared tooth form. The operators were five dentists who had 2-4 years clinical experiences and were made to prepare with 1.0 mm width shoulder. 1. The reduction of incisal edge was like the indication. 2. As for the subgingival reductions, the proximal surfaces were deep and the facial and lingual surfaces were shallow. 3. As for the degree of axial taper, angles of convergence were comparatively like the indication, and prepared teeth were inclined to distal direction for imaginary axis of tooth crown before operation. 4. The width of shoulder were insufficient except at the facial surface. 5. The surface roughness on axial wall was almost acceptable, but the roughness on shoulder was sufficient at facial surface, while insufficient at others. 6. As for Rough Value, smoothness of curve on finishing line was questionable. 7. Tooth preparation of maxillary anterior teeth in Home Position, compared with posterior, is fairly easy to operate under mirror view, and the method is stable and available.

Crowns↗
PubMed1993

Effect of luting media on the compressive strengths of two types of all-ceramic crown.

This study evaluated the effect of selected luting media on the compressive strength of two types of all-ceramic crown. Tooth preparation was standardized; each preparation had a shoulder width of approximately 1.2 mm, and all internal preparation angles were rounded. Hi-Ceram and Dicor all-ceramic crowns were fabricated and cemented into the preparations with zinc phosphate, glass-ionomer, or composite resin cement. Coronal compressive fracture strengths were determined, using a set of unrestored teeth as a control. There were no statistically significant differences among the mean compressive strengths of the three luting media, and there was no statistically significant difference between the mean compressive strength of Dicor and that of the natural tooth control.

Aluminum Oxide↗
PubMed1982

Allometric scaling in the dentition of primates and prediction of body weight from tooth size in fossils.

Tooth size varies exponentially with body weight in primates. Logarithmic transformation of tooth crown area and body weight yields a linear model of slope 0.67 as an isometric (geometric) baseline for study of dental allometry. This model is compared with that predicted by metabolic scaling (slope = 0.75). Tarsius and other insectivores have larger teeth for their body size than generalized primates do and they are not included in this analysis. Among generalized primates, tooth size is highly correlated with body size. Correlations of upper and lower cheek teeth with body size range from 0.90-0.97, depending on tooth position. Central cheek teeth (P44 and M11) have allometric coefficients ranging from 0.57-0.65, falling well below geometric scaling. Anterior and posterior cheek teeth scale at or above metabolic scaling. Considered individually or as a group, upper cheek teeth scale allometrically with lower coefficients than corresponding lower cheek teeth; the reverse is true for incisors. The sum of crown areas for all upper cheek teeth scales significantly below geometric scaling, while the sum of crown areas for all lower cheek teeth approximates geometric scaling. Tooth size can be used to predict the body weight of generalized fossil primates. This is illustrated for Aegyptopithecus and other Eocene, Oligocene, and miocene primates. Regressions based on tooth size in generalized primates yield reasonable estimates of body weight, but much remains to be learned about tooth size and body size scaling in more restricted systematic groups and dietary guilds.

Animals↗
PubMed1996

Heterochronic quantitative microevolution: dental divergence in aboriginal Americans.

Studies of tooth crown morphology alone have proven valuable in defining human population differentiation. We test the hypothesis that quantitative comparisons of more complex whole tooth structure may prove informative in understanding human diversity. Three disparate populations in Native American genetic history were compared: Kodiak Island Western Eskimos, Peruvian Inca Amerindians, and Southeast Asians. Enamel depth (an increasing gradient extended from Southeast Asians to the Inca) and root parameters were the most discriminating variables. The observed microevolution appears to result from variation in timing of known X-linked, Y-linked, and autosomal genes that affect either ameloblast or odontoblast differentiation. The dental traits were sexually dimorphic, the effect being more pronounced in aboriginal Americans, with male teeth having robust roots and thin enamel compared to female. Southeast Asians were isometrically related. The prominence of sexual dimorphism and the importance of sex-linked genes in the determination of the dental phenotypes suggest that sexual selection was one evolutionary force acting on early Asian populations. Subsequently, the selection appears to have been relaxed in Southeast Asians. Observed divergence of tooth shape among the populations, i.e., differences in the appropriation process of tooth primordia, was mainly the consequence of genetic drift modulating heterochronic regulators of homeotic genes.

Analysis of Variance↗
PubMed2003

Tooth-root form and function in platyrrhine seed-eaters.

Research into the functional and adaptive basis of tooth crown form has provided a useful framework for the inference of diet in extinct primates. However, our understanding of variation in tooth-root form is limited. Studies within the clinical literature emphasize the influence of tooth-root surface area on stress resistance, but it is not known if root form has diversified during primate evolution in relation to dietary specialization. This hypothesis was tested by quantifying maxillary canine and postcanine tooth-root surface areas in four platyrrhine species that differ in the material properties of their diet: Cebus apella, Cebus albifrons, Chiropotes satanas, and Pithecia pithecia. Pairwise comparisons between closely related taxa support predictions based on dietary differences. Taxa that regularly consume resistant seeds (Cebus apella and Chiropotes satanas) exhibit significantly larger relative surface area values for those teeth used in seed processing than closely related taxa that consume resistant foods less often (Cebus albifrons and Pithecia pithecia). Additionally, relative molar-root surface area appears to be greater in Pithecia than in Chiropotes, as predicted from the more folivorous diet of Pithecia. Tooth-root surface area was also found to vary along the tooth row and should therefore have a significant influence on antero-posterior bite-force gradients. The results of this study suggest a close relationship between tooth-root form and patterns of occlusal loading. Further elucidation of this relationship could improve our inferences of diet in extinct taxa, and augment research into the mechanics and evolution of feeding.

Animals↗
PubMed1979

Traction--a surgical/orthodontic procedure.

Maxillary crowding may cause failure of eruption of the canine. The teeth so displaced are directed buccally or palatally. In both cases, surgical intervention is indicated after space has been made in the arch. Palatally displaced canines are treated by surgical excision of palatal mucosa to promote eruption. Wide excision is indicated to prevent the healing process from covering the exposed tooth crown. Because of the anatomy of the buccal mucosa, however, surgical excision of the crowns of buccally displaced canine frequently results in periodontal problems. An alternative technique is therefore presented; this involves the surgical exposure of the crowns of buccally displaced teeth to allow the attachment of a wire traction hook. The crown is then recovered. The traction hook provides a point of attachment, so that orthodontic forces may be applied to the unerupted tooth to guide its eruption. The preservation of the mucosal flap ensures a normal epithelial attachment develops on the buccal surface of the tooth, and the normal gingival anatomy of the buccal mucosa is maintained. The procedure may also be used in cases where upper incisors have been prevented from erupting because of the presence of supernumerary teeth. Even after surgical removal of the supernumerary teeth, the permanent incisors often fail to erupt. In such cases, the placement of traction hooks will enable the orthodontist to bring the unerupted teeth into their correct positions in the arch.

Adolescent↗
PubMed1987

Porcelain-fused-to-metal crowns as replacements for denture teeth in removable partial denture construction.

A procedure has been described for using porcelain-fused-to-metal crowns in place of denture teeth on a removable partial denture. Improved esthetic results are achieved when replacement denture teeth are made simultaneously with, and visually match, adjacent tooth crowns. This procedure provides a superior treatment result, particularly where multiple unilateral anterior teeth are lost and a removable partial denture is indicated.

Crowns↗
PubMedDate not supplied

Stainless steel crown and pulpotomy: procedure and technique for primary molars.

The purpose of this article is to facilitate performance of the stainless steel crown and pulpotomy procedures in order to save chair time and provide a more durable and reliable final restoration for primary molars. The rationale and methods for preparing the tooth, crown selection, and placement of a stainless steel crown are included, along with alternatives for selection and technique for fabrication of more esthetic options. Medicament and tips for the pulpotomy procedure also are discussed. Information for patient education and consent regarding the procedures and their limitations is provided to complete this step-by-step guide for the clinician.

Child, Preschool↗
PubMed2006

Axial-wall inclination angle and vertical height interactions in molar full crown preparations.

OBJECTIVE: This study has been designed to evaluate the interaction of axial wall heights with inclination angles in full crown tooth preparations. The interaction of these parameters was related to the resulting preparation surface area. MATERIALS AND METHODS: A right regular pyramid was used to simulate a single mandibular molar preparation with known convergence angles and vertical heights. Various combinations of these two variables allowed the calculation of surface areas with a formula for the area of a pyramid and right triangles through trigonometric manipulations. The pyramidal model system had a 9-mm square base with vertical heights from 3- to 5-mm and single-side inclination angles from 2 to 25 degrees. The occlusal surface was a flat, square or rectangular surface and was included in the total area. RESULTS: A percentage of surface area lost or gained served as the dependent variables. The significance levels were set at 10.0% or greater magnitude of loss/gain in a surface area compared to the ideal 2 degree-level. Significant area loss was demonstrated in all alpha-level comparisons. The largest change was found in the 5-mm height grouping compared to the 3-mm height grouping, -36.6% difference between groups at the 2 degree-level. CONCLUSIONS: Axial single-side inclination angles greater than 10 degrees in 3- and 4-mm height-molars are detrimental to maximum surface area in full crown restorations. The 5-mm axial wall height with < or = 10 degree single wall has been shown to maximize the luting agent surface area between restoration and tooth structure.

Crowns↗
PubMed2003

[A study of Bolton tooth-size discrepancies of malocclusion patients].

OBJECTIVE: To analysis the sum and frequencies of Bolton tooth-size discrepancies Angle Class I, II, III malocclusion patients. METHODS: Measured each tooth crown mesial-distal size between the first molar of 439 dental plaster casts of malocclusion patients and obtained the sums of six anterior tooth-size and twelve tooth-size between the first molar of upper or lower and calculated the anterior and total tooth-size discrepancies by Bolton rate standards, then statistic analyses were done. RESULTS: Patients whose sums of anterior tooth-size discrepancy were pass 1.5 mm or less than -1.5 mm was 14.02% in Angle Class I malocclusion patients and 9.49% in Class II and 19.32% in Class III. Patients whose sums of total tooth-size discrepancy were pass 1.5 mm or less than -1.5 mm was 19.63% in Angle Class I malocclusion patients and 15.33% in Class II and 20.45% in Class III. The upper sum of anterior tooth-size of Class I malocclusion patients whose sums of anterior tooth-size discrepancies were pass 1.5 mm or less than -1.5 mm was always smaller than normal and the lower sum was always larger. The sums of anterior tooth-size discrepancy of Class I, II, III and total tooth-size discrepancy of Class I were always between 1.5 mm-2.5 mm or -2.5 mm(-)-1.5 mm. Patients whose sums of anterior tooth-size discrepancy were pass 3.5 mm or less than -3.5 mm was 2.34% in Class I malocclusion patients and 0 in class II and 0 in class III. Patients whose sums of total tooth-size discrepancy were pass 3.5 mm or less than -3.5 mm was 4.21% in Class I and 1.46% in Class II and 4.54% in Class III. CONCLUSION: Tooth-size discrepancy of malocclusion patients was not the general cause of malocclusion.

Adolescent↗
PubMed1989

Reflex responses in the digastric and tongue muscles to stimulation of intradental nerves in the cat.

Electrical stimulation of tooth pulp nerves induces the digastric jaw-opening reflex in the cat, apparently due to activation of intradental A-fibres; C-fibres do not seem to be involved. In fact, reflex responses to activation of pulpal C-fibres have not been studied. In the present experiments on anesthetized cats we recorded EMG reflex responses of the digastric and tongue muscles to stimulation of the intact tooth crown, exposed dentine, and the pulp. We used stimuli that selectively activate either A- or C-fibres of the pulp. Slow heating of the tooth and application of capsaicin into the pulp, both procedures known to excite only C-fibres in the pulp, evoked licking movements of the tongue and prolonged EMG-responses in the tongue and, less consistently, digastric muscles. Similar muscle responses were elicited by high intensity electrical current pulses applied to the tooth. At low current intensities only short-duration digastric activation (jaw-opening reflex) was induced. Similar digastric jaw-opening was also evoked by drilling and air-drying of dentine, both stimuli able to activate only intradental A-fibres. These results indicate that activation of both A- and C-type pulp nerve fibres can induce reflectory muscle activation, and further, they support the concept of afferent intradental C-fibre innervation.

Animals↗
PubMed2004

Sexual dimorphism in crown units of mandibular deciduous and permanent molars in Australian Aborigines.

Sexual differences in the crown units of mandibular molars were investigated in Australian Aborigines. The first and second deciduous molars (dm1 and dm2), and first to third permanent molars (M1, M2 and M3) were measured on dental casts using a sliding caliper. Measurements of tooth crowns included overall mesiodistal and buccolingual diameters, as well as the mesiodistal and buccolingual diameters of the trigonid and talonid. Percentage dimorphism values were greater in the talonid dimensions than the trigonid, indicating that sex differences tend to be larger in the later-developing crown units. Sex differences in mesiodistal diameters increased from dm1 to M2 but decreased for M3, the tooth that showed the least dimorphism of all the molars. This result seems to be due to the marked variability in size of the M3 between individuals.

Female↗
PubMed1999

Retention of adhesive cement on the tooth surface after crown cementation.

STATEMENT OF PROBLEM: Adhesive cements increase crown retention, but it is unknown if traces of cement remain undetected on the tooth surface after clinical removal of excess cement, which could exacerbate plaque retention. PURPOSE: This study measured the surface area, volume, mean depth, and maximum depth of a resin composite and a compomer luting cement left adherent on the tooth surface after removal of excess cement, as judged clinically. METHODS AND MATERIAL: Four groups of specimens (n = 48) were prepared for full coverage crowns: group AC bonding alloy with chamfer finish line, group G gold alloy with chamfer finish line, group PC porcelain with a chamfer finish line, and group PS porcelain with a shoulder finish line. Two profiles of the mesial and distal surfaces of the teeth were carried out: (1) tooth with crown seated but not cemented and (2) tooth with the crown cemented in place. Two cements and 2 methods of cement removal were studied. RESULTS: A 4-way analysis of variance for cement, crown type, method of removal, and tooth surface morphology showed that significantly greater volumes and mean depth, but not surface areas, of resin composite cement remained adherent than compomer cement (P<.05). Among crown types, significant differences were found for cement volume (group G>AC, G>PC, G>PS), cement surface area (group AC>PC, G>PC, G>PS), and maximum cement depth (group G>AC). There was no significant difference between the 2 methods of cement removal. Significantly larger surface areas and maximum depths of cement were retained on the anatomically grooved mesial surface of the maxillary first premolars than on the ungrooved distal surface. CONCLUSION: Subclinical cement retention occurred after crown cementation, which was influenced by cement, crown type, and tooth surface morphology but not method of cement removal.

Adhesives↗
PubMed1997

A reconsideration of the Archi 1 Neandertal mandible.

A reassessment of the early last glacial immature Neandertal mandibular corpus from Archi indicates a series of features in which it closely resembles other pre-adolescent Neandertal mandibles and contrasts with those of similarly aged recent humans. These are in the context of a re-aging of the specimen to ca. 3 years on the basis of deciduous dental eruption and attrition and permanent dental calcification. The Archi 1 mandible resembles other immature. Neandertals in having a "retreating" symphyseal profile in the context of moderate development of mental trigone features. It is relatively robust in the development of lateral and basilar corpus features and some increased symphyseal and lateral corpus thickness. And it exhibits, along with other Middle Paleolithic immature mandibles, anteriorly wide dental arcades, probably due to large developing anterior permanent tooth crowns.

Age Factors↗
PubMed2003

Identification of a novel putative signaling center, the tertiary enamel knot in the postnatal mouse molar tooth.

The final shape of the molar tooth crown is thought to be regulated by the transient epithelial signaling centers in the cusp tips, the secondary enamel knots (SEKs), which are believed to disappear after initiation of the cusp growth. We investigated the developmental fate of the signaling center using the recently characterized Slit1 enamel knot marker as a lineage tracer during morphogenesis of the first molar and crown calcification in the mouse. In situ hybridization analysis showed that after Fgf4 downregulation in the SEK, Slit1 expression persisted in the deep compartment of the knot. After the histological disappearance of the SEK, Slit1 expression was evident in a novel epithelial cell cluster, which we call the tertiary enamel knot (TEK) next to the enamel-free area (EFA)-epithelium at the cusp tips. In embryonic tooth, Slit1 was also observed in the stratum intermedium (SI) and stellate reticulum cells between the parallel SEKs correlating to the area where the inner enamel epithelium cells do not proliferate. After birth, the expression of Slit1 persisted in the SI cells of the transverse connecting lophs of the parallel cusps above the EFA-cells. These results demonstrate the presence of a novel putative signaling center, the TEK, in the calcifying tooth. Moreover, our results suggest that Slit1 signaling may be involved in the regulation of molar tooth shape by regulating epithelial cell proliferation and formation of EFA of the crown.

Amphibian Proteins↗
PubMed2001

Localization of activated caspase-3-positive and apoptotic cells in the developing tooth germ of the mouse lower first molar.

This study examined the immunohistochemical detection of activated caspase-3, and its association with apoptosis, during tooth morphogenesis of the mouse lower first molar. The distribution of cells positive for caspase-3 closely corresponded with the localization of the terminal deoxynucleotidyl transferase-mediated deoxyuridine-5'-triphosphate-biotin nick end labelling (TUNEL)-positive apoptotic cells through the developmental course of tooth germs from embryo day 12 (E12) to E19, thus showing that the apoptosis occurring in the developing odontogenic tissue was induced by the activation of the caspase family. The specific distribution pattern of apoptotic cells in the developing odontogenic epithelial tissue from the initiation (E12) of tooth germ to the completion of tooth crown morphology (E19) also suggests that apoptotic events are related not only to a deletion of functionally suspended cells, but also participate in initiation and the completion of tooth morphogenesis. Electron microscopic examination revealed that apoptotic cells were present in the primary enamel knot, and these apoptotic cells were phagocytized by neighbouring odontogenic epithelial cells, thus indicating the prompt disposal of any dead cells by epithelial cells.

Animals↗