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At least 145 records · Page 8Linked to original sources
PubMed1994

Variation in enamel thickness and cusp area within human maxillary molars and its bearing on scaling techniques used for studies of enamel thickness between species.

Thirty-nine unworn maxillary molars (M1 = 18, M2 = 12, M3 = 9), representing 37 individuals of a Slavic population, were sectioned through the mesial cusps in a plane perpendicular to the cervical margin of the crown. Whether the range of variation in enamel cross-sectional area between individuals corresponds to the range of variation found between teeth within a species was investigated. Total tooth crown area, as determined by planimetry, was used as a scaling factor on the basis that a biologically meaningful scaling procedure should take into account both enamel thickness and total tooth crown area, rather than the size of the dentine-enamel junction. Uni- and multivariate statistics revealed that the enamel cross-sectional area of second and third molars is absolutely and relatively larger than it is in first upper molars and that it scales close to isometry with tooth crown area. Conversely, first maxillary molars, with their relatively and absolutely thinner enamel, exhibit positive allometry between enamel and tooth crown area. These patterns were retained even when differences in overall tooth size were adjusted for. Hence, the notion that there exists a 'species-specific' amount of enamel over the tooth crown must be reconsidered, and one should refrain from pooling different tooth types for taxonomic purposes. At least two scaling factors are needed to describe human maxillary molars alone. However, this increase in enamel cross-sectional area from anterior to posterior is not unexpected if one bears in mind that posterior teeth occupy a more advantageous position relative to the chewing muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Austria↗
PubMed2005

Evaluation of soft tissue around single-tooth implant crowns: the pink esthetic score.

AIM: In this study, the reproducibility of a newly developed pink esthetic score (PES) for evaluating soft tissue around single-tooth implant crowns was assessed. The effect of observer specialization was another point of interest. MATERIAL AND METHODS: Twenty observers (five prosthodontists, five oral surgeons, five orthodontists and five dental students) were given photographs of 30 single-tooth implant crowns. Seven variables were evaluated vs. a natural reference tooth: mesial papilla, distal papilla, soft-tissue level, soft-tissue contour, alveolar process deficiency, soft-tissue color and texture. Using a 0-1-2 scoring system, 0 being the lowest, 2 being the highest value, the maximum achievable PES was 14. Each observer was requested to make two assessments at an interval of 4 weeks. At the second assessment, the photographs were scored in the reverse order. RESULTS: The mean PES of evaluations at the first assessment (n=600) was 9.46 (+/-3.81 SD), and 9.24 (+/-3.8 SD) at the second one. The difference between these two means was not significant statistically (P=0.6379). Implant-related mean PES for single-tooth implants varied from 2.28 to 13.8, with standard deviations between 0.46 and 3.51. Very poor and very esthetic restorations showed the smallest standard deviations. The mean total PES was 10.6 for the prosthodontists, 9.2 for the oral surgeons, 9.9 for the dental students and 7.6 for the orthodontists. CONCLUSIONS: The PES reproducibly evaluates peri-implant soft tissue around single-tooth implants. Thus, an objective outcome of different surgical or prosthodontic protocols can be assessed. Orthodontists were clearly more critical than the other observers.

Adult↗
PubMed2002

A stent fabricated on a selectively colored stereolithographic model for placement of orthodontic mini-implants.

The purpose of this report is to present a new method for placing orthodontic mini-implants using a stent fabricated on a selectively colored stereolithographic model. A stent was fabricated that incorporated a guide groove drilled in accordance with the planned direction of the mini-implant. Tooth crowns, gingiva, tooth roots, and the maxillary sinuses were clearly identified in the stereolithographic model. As a result, the stent could be fabricated while taking into account the anatomic characteristics of both the bone interior and the dental surface. A stent fabricated on the selectively colored stereolithographic model is suggested to be a promising device for guiding placement of orthodontic mini-implants adjacent to the tooth roots and the maxillary sinuses.

Color↗
PubMed2001

[Color measurements of 1,944 anterior teeth of people in southwest of China-discreption].

OBJECTIVE: To study the color distribution space of natural anterior tooth crowns of people in southwest China and effects of sex and age on tooth color. METHODS: The subjects studied consisted of 162 persons aged from 20 to 73 years and born in southwest China. A total of 1,944 healthy anterior teeth were measured in-vivo with a fiber-optical spectrophotometry system. RESULTS: Statistical analysis showed that the color distribution space of Chinese tooth crowns was wide. The value of L* varied from 42.383 to 67.428, the value of a* from -4.750 to 1.371, the value of b* from 1.88 to 20.268, the value of x from 0.298 to 0.393, the value of y from 0.332 to 0.392, and the value of Y from 19.383 to 34.025. The color difference between the upper and lower limits of 95% confidence was 31.667 CIE delta E units. The difference in colorimetry between male and female was not significant. The results showed that in three sections of teeth (incisal, middle and cervical) the values of L* and a* were negatively related to age (r < 0, P < 0.01); the value of b* was positively related to age just at the cervical and middle sites of teeth (r > 0, P < 0.01) and was not related to age at the incisal site of teeth (P > 0.05). CONCLUSION: The color distribution space of Chinese anterior tooth crowns is wide. There is no difference in the anterior tooth color between male and female subjects. The values of L* and a* and negatively related to age except the value of b*.

Adult↗
PubMed2006

Root growth in the permanent teeth of 45,X/46,XX females.

Studies on individuals with sex chromosome anomalies have provided proof of a direct differential promoting effect of the X and Y chromosome genes on tooth crown growth. 45,X/46,XX females are one subgroup of Turner patients who have both normal XX and one X sex chromosome cell lines. Their permanent tooth crown size is reduced, which is mainly due to thin enamel. 45,X females likewise show reduced crown size and enamel thickness, and their root size is reduced. By contrast, the lengths of the roots in 47,XYY males or males with an extra Y chromosome and 46,XY females or females with a male sex chromosome constitution are increased. The aim of the present study was to investigate permanent tooth root lengths in 45,X/46,XX females to obtain additional information on their dental growth. The study group consisted of 15 45,X/46,XX females, mean age 23.4 years; 10 female relatives, mean age 24.5 years; and 47 population control females, mean age 29.8 years, from the Kvantti research project. Root length measurements were made from panoramic radiographs on both sides of the jaw using a sliding digital calliper. The results showed that permanent tooth root lengths in 45,X/46,XX females were, in most cases, significantly shorter than those of the population controls or relatives. It is apparent that a reduced tooth crown size in 45,X/46,XX females is followed by reduced root growth. This begins 3 years after birth and continues to at least 14 years of age. It is suggested that the reduction in crown and root growth in 45,X/4,XX females is due to a deficiency in the amount of dental growth-promoting genes on the sex chromosomes.

Adolescent↗
PubMed1996

Using crowns to prevent tooth fracture.

Placing crowns to prevent tooth fracture is thought to be a common but infrequently documented treatment procedure. Two studies are described that provide information about dentists' use of crowns to prevent tooth fracture. North Carolina general dentists indicated that 44% of the crowns they placed were for the principal reason of fracture prevention. However, when groups of dentists examined the same patients, there was little agreement about which teeth should be crowned due to risk of fracture. These results suggest that the placing of crowns to prevent fracture merits a careful determination of effectiveness and appropriateness.

Age Factors↗
PubMedDate not supplied

Enamel thickness and the topography of the enamel-dentine junction in South African Plio-Pleistocene hominids with special reference to the Carabelli trait.

This study explores the internal morphology of early hominid teeth using high-resolution computed tomography. Data on Carabelli feature size, enamel thickness, and the topography of the enamel-dentine junction are considered together in order to examine the relationship among these variables in the maxillary molars of gracile and robust australopithecines from South Africa. In particular, one aim is to investigate the degree to which Carabelli feature size influences enamel thickness in the plane of the mesial cusps. The results demonstrate that maxillary molars attributed to Australopithecus africanus from Sterkfontein, Taung and Makapansgat possess larger Carabelli features and thinner enamel along the lingual wall of the protocone than do specimens attributed to Paranthropus robustus from Swartkrans and Kromdraai. Distinct differences in the position of the Carabelli feature at the level of both the enamel-dentine junction and tooth crown surface between early hominid species may help explain the observed disparity in enamel thickness at that region of the tooth crown as well as offer clues to the functional role of Carabelli's cusp. As the size and position of the Carabelli feature affects the linear thickness of enamel at this one particular region of the tooth crown, future comparative studies focusing on taxa that possess moderate to strong development of the Carabelli complex should use the linear thickness of enamel taken close to the protoconal dentine horn or at the maximum projection of the Carabelli's cusp.

Animals↗
PubMed2003

Insights from stable light isotopes on enamel defects and weaning in Pliocene herbivores.

A high prevalence of enamel hypoplasia in several herbivores from the early Pliocene Langebaanweg locality, South Africa, indicates general systemic stress during the growing years of life. The presence of several linear enamel hypoplasias per tooth crown in many teeth further suggest that these stress events may be episodic. The delta18O values along tooth crowns of mandibular second molars of Sivatherium hendeyi (Artiodactyla, Giraffidae) were used to investigate the cause of the stress events in this tooth type. Results show that weaning in this fossil giraffid occurred at a similar ontogenetic age to that in extant giraffes, and that the observed enamel hypoplasia towards the base of this tooth type manifested post-weaning. Further, high-resolution oxygen isotope analyses across S. hendeyi third molars suggest that the entire development of defective tooth crowns occurred under conditions of increased aridity in which the cool, rainy part of the seasonal cycle was missing. The high prevalence of this defect in many herbivores suggests that climatic conditions were not favourable. This study reiterates the value of stable isotope analyses in determining both the behaviour of fossil animals and the environmental conditions that prevailed during tooth development.

Animals↗
PubMed2004

Genetic analysis of crown size in the first molars using SMXA recombinant inbred mouse strains.

Tooth crown size may be determined by both genetic and environmental factors. The aim of this study was to identify quantitative trait loci (QTLs) affecting dental crown size and determine whether there is genetic independence between upper and lower teeth, using SMXA recombinant inbred strains of mice. Mesiodistal and buccolingual crown diameters (MD and BL, respectively) of the upper and lower first molars (M(1) and M(1), respectively) were measured. For each trait, mean values of substrains showed a continuous spectrum of distribution. Genome-wide scan detected QTLs exceeding suggestive threshold levels for MD of M(1) (chromosomes 7, 13, and 17), BL of M(1) (chromosomes 8 and 13), MD of M(1) (chromosomes 7 and 13), and BL of M(1) (chromosomes 3 and 15). These findings suggest that tooth crown size is controlled by multiple genes, and that there is some independence of genetic control between M(1) and M(1).

Animals↗
PubMedDate not supplied

A 4-year prospective study to assess peri-implant hard and soft tissues adjacent to titanium versus gold-alloy abutments in cemented single implant crowns.

PURPOSE: The purpose of this prospective clinical study was to compare titanium and gold-alloy abutments when used with cemented, implant-supported single-tooth crowns. For 4 years following prosthodontic rehabilitation, these abutments were evaluated with respect to peri-implant marginal bone levels and peri-implant soft tissue parameters. MATERIALS AND METHODS: During the years 1998 to 2000, 20 patients were selected from a patient population receiving treatment in the Implantology Department at the University of Padova, Italy. They all presented with single-tooth bilateral edentulous sites in the premolar/molar region with adequate bone width, similar bone height on each side, and an occlusal scheme that allowed for the establishment of identical occlusal cusp/fossa contacts on each side. Each subject received two identical implants (one in each edentulous site). One was randomly selected to be restored with a titanium abutment and a cemented implant-supported single-tooth crown, and the other was restored with a gold-alloy abutment and a cemented implant-supported single tooth crown. Data on peri-implant marginal bone levels and soft tissue parameters were collected for 4 years after abutment and crown insertion placement and analyzed to determine whether there was a significant (p< .001) difference with respect to the type of abutments (titanium vs. gold alloy) used. RESULTS: All subjects completed the study. All 40 implants survived, resulting in a cumulative implant success rate of 100%. Statistical analysis revealed no significant differences between the two groups with respect to peri-implant marginal bone levels and soft tissue parameters. CONCLUSIONS: Within the limitations of this study, the results indicate that there was no evidence of different response with the peri-implant marginal bone and soft tissue when titanium or gold-alloy abutments were used in conjunction with the cemented, single-tooth implant restorations provided for this limited patient population. There was no evidence of different behavior of peri-implant marginal bone and of peri-implant soft tissue when titanium abutments or gold-alloy abutments were used for cemented single-tooth implant restorations in this limited patient population.

Bone Resorption↗
PubMed1990

[Prediction of length and width of upper central incisor tooth in multivariate face information].

The possibility of accurately estimating a tooth crown length and width from measured distance of various face points was examined by using Multiple Correlation Analysis. The multiple correlation coefficient between a tooth crown length and the face point was 0.3137 and the residual standard error was 0.820; that between a tooth crown width and the face point was 0.3917 and its standard error was 0.467, obtained by substituted sample data for multiple regression equation.

Analysis of Variance↗
PubMed1988

The cracked tooth syndrome--crown root vertical fracture.

A case of an incomplete tooth fracture followed by a complete fracture was presented. The difficulty of diagnosing this condition was discussed as well as the possible histological explanation of the symptoms experienced by the patient. It once again points out to practising dentists, that whilst deep pockets can give rise to severe periodontal pain, intense and excruciating pain should be investigated with the cracked tooth in mind.

Cracked Tooth Syndrome↗
PubMed1986

A single-appointment technique for reuse of a crown after tooth fracture.

A single-appointment technique for the reuse of an existing crown, the margins of which are intact after tooth fracture, has been presented. Composite resin used in conjunction with a dentin bonding agent serves as a core and cement sealer. Para Posts or TMS pins and undercut areas in tooth structure are used for retention.

Adhesives↗
PubMed2005

John N. Crouse--crusader and mitigator.

During the last part of the nineteenth century, John N. Crouse fought hard to defeat the process patents of the International Tooth Crown Company. Prior to that time he engaged in a lucrative dental practice, was a President of the American Dental Association and was a highly respected dentist in Chicago. In the midst of his fight against the International Tooth Crown Company, Crouse organized a dental supply business and a dental journal. After the defeat of the Tooth Crown Company's patents, in an interesting turn of events, Crouse appeared to form an alliance with a party who formed another threat to the dental profession by foisting his patents on it. This article traces the life of a noteworthy man who could rightly be placed among the most important figures in American dentistry.

Dental Prosthesis↗
PubMed2006

Optimizing resin cement removal around esthetic crown margins.

OBJECTIVE: To quantify luting cement at the crown-tooth interface of esthetic crowns fabricated using four different techniques and two methods of excess cement removal. MATERIAL AND METHODS: Four methods of crown fabrication were used: the feldspathic porcelain and platinum foil technique, the feldspathic porcelain and refractory die technique, the resin composite crown and CAD/CAM technique, and the feldspathic porcelain crown and CAD/CAM technique. Half of the cemented crowns were allocated to Group A: removal of excess cement by flicking-off with a plastic instrument 3 min after initial polymerization, or Group B: removal of excess cement using a wiping action with cotton pellets. Morphologic measurements, using non-destructive digital profilometry, were made of the volume of excess cement (mm(3)), mean maximum and mean depth of excess cement (microm), and surface area of excess cement (mm(2)). RESULTS: ANOVA and Duncan post-hoc tests revealed no statistical differences (p<0.05) between the four types of crown fabrication with respect to volume and mean depth of retained luting cement. There was a significantly greater volume, mean depth, and mean maximum depth of luting cement retained using the "flick off" method compared to the cotton pellet "wiping" method for excess cement removal, but no statistical differences in mean surface area between the two methods. CONCLUSIONS: Following removal of excess luting cement, as judged clinically, using two methods, subclinical amounts of cement remained adherent to the tooth surface of all specimens at the crown-tooth interface.

Analysis of Variance↗