138,559 research outputs found
Tooth-whitening activity of a novel home-bleaching system utilising thermal diffusion : a multifactorial simultaneous evaluation of efficacy at cervical, body and incisal tooth sites
No full textIntroduction The ability of a thermal diffusion system (TDS) to promote the tooth-whitening actions of a bleaching gel/bleaching activator combination product (containing a final hydrogen peroxide (H2O2) content of 10.0% (w/v)) towards discoloured 'smile-zone' teeth was examined.
Methods Fifty teeth in 15 participants aged 18-62 years were investigated. The CIE tooth shade parameters L*, a* and b*, together with Vitapan shade scores (VSSs), were simultaneously recorded at three separate tooth areas (cervical, body and incisal sites) with a novel spectrophotometric monitoring system before treatment, and also at 14 days after completion of a 10-day treatment period in which the product was applied 'at-home' (twice daily).
Results The tooth-whitening treatment administered gave rise to extremely significant increases in L*, and decreases in the a* and b* shade parameters for each of the tooth areas investigated (p <10−10). Post-treatment mean decreases in the VSS values were 8.26, 9.70 and 9.14 for the cervical, body and incisal areas respectively (p <10−8 in each case). Mean ΔE values determined post-treatment were also very highly significant for each tooth region examined (p <10−10 in each case).
Conclusions The tooth-whitening system tested exerted extremely powerful bleaching actions in all tooth areas investigated. The order of tooth-whitening effectiveness was body > incisal > cervical for Δb* and ΔE, and incisal > body > cervical for Δa* and ΔL*, and this may reflect the TDS's ability to promote the penetration of H2O2 to intrinsic stain sites
Comparison of Tooth Size Discrepancy of Three Main Ethnics in Malaysia with Bolton's Ratio
No full textThe objective of this study was to investigate the applicability of Bolton's ratios in orthodontic population of Malaysian main ethnics; Malay, Chinese and Indians. Ninety convenient samples consisting of 30 pre-orthodontic study casts from each ethnic that fits the inclusion criteria were selected. The greatest mesiodistal widths of each tooth from six to six for overall ratio and three to three for anterior ratio were measured using a digital callipers linked to Hamilton Arch Tooth System software to the nearest 0.01mm. Means of the ratios were calculated using Bolton analysis. One sample t-test statistic analysis was carried out to compare the means with Bolton values of anterior ratio and overall ratio and one-way ANOVA was used to analyze comparison between ethnic groups of the anterior ratio and the overall ratio with the level of statistical significance set at p < 0.05. However, there were no significant differences when comparing Bolton values with Chinese and Indian anterior and overall ratios. The Bolton standards could be applied to Malaysian Chinese, Indians and Malay's female. Subsequently, a specific standard should be used for the Malays orthodontic population.Article URL : http://www.ukm.my/jsm/pdf_files/SM-PDF-41-2-2012/17%20Aida%20Nur%20Ashikin.pd
Gastroesophageal reflux disease and tooth erosion
No full textThe increasing prevalence of gastroesophageal reflux disease (GERD) in children and adults, and of “silent refluxers” in particular, increases the responsibility of dentists to be alert to this potentially severe condition when observing unexplained instances of tooth erosion. Although gastroesophageal reflux is a normal physiologic occurrence, excessive gastric and duodenal regurgitation combined with a decrease in normal protective mechanisms, including an adequate production of saliva, may result in many esophageal and extraesophageal adverse conditions. Sleep-related GERD is particularly insidious as the supine position enhances the proximal migration of gastric contents, and normal saliva production is much reduced. Gastric acid will displace saliva easily from tooth surfaces, and proteolytic pepsin will remove protective dental pellicle. Though increasing evidence of associations between GERD and tooth erosion has been shown in both animal and human studies, relatively few clinical studies have been carried out under controlled trial conditions. Suspicion of an endogenous source of acid being associated with observed tooth erosion requires medical referral and management of the patient as the primary method for its prevention and control.Sarbin Ranjitkar, John A. Kaidonis, and Roger J. Smale
Tooth formation in Sudanese children
No full textPhDThe aim of this study was to describe the average age of permanent mandibular tooth
formation in two groups of Sudanese children using a cross-sectional design following
STROBE guidelines. The Northern groups are of Arab origin whilst the Western groups
are predominantly Fur of African origin (Darfur). North Sudanese sample (844 males,
802 females) consisted of equally distributed, randomly selected healthy university
students and school children, whilst the West Sudanese (848 males, 401 females)
consisted of a convenience sample attending religious schools in camps for the internally
displaced. Panoramic radiographs (2-23 years), with known date of birth were taken.
Height and weight were also measured. Developing permanent mandibular teeth were
staged from radiographs (Moorrees et al., 1963). The mean age of attainments were
calculated using logistic regression and comparisons carried out on 331 tooth stages to
determine gender and ethnic differences. Results showed that mean age of attainment of
teeth was not significantly different between the genders within each ethnic group
(p>0.05) for 135 out of 155 stage comparisons. The mean age of attainment of teeth was
not significantly different between same sex groups in 113 out of 174 stage comparisons
(p>0.05). The canine was more advanced in females compared to males while the
reverse was true for some crown and root stages of third molars. Growth indicators
showed that all groups are undernourished (z-scores =< -2). Severe malnutrition had
minimal effect on tooth formation of M1 and M2 (p>0.05) in Northern females. The
prevalence of hypodontia (excluding third molars) was 0.7% in the Western group and
2.6% in the Northern group. The pattern of hypodontia differed between groups.
In conclusion, the within group variation for most tooth stages is considerable while the
differences between groups are small. The study represents the first radiographic
investigation of permanent tooth formation in Africa
Development of a device to simulate tooth mobility
No full textObjectives: The testing of new materials under simulation of oral conditions is essential in medicine. For simulation of fracture strength different simulation devices are used for test set-up. The results of these in vitro tests differ because there is no standardization of tooth mobility in simulation devices. The aim of this study is to develop a simulation device that depicts the tooth mobility curve as accurately as possible and creates reproducible and scalable mobility curves. Materials and methods: With the aid of published literature and with the help of dentists, average forms of tooth classes were generated. Based on these tooth data, different abutment tooth shapes and different simulation devices were designed with a CAD system and were generated with a Rapid Prototyping system. Then, for all simulation devices the displacement curves were created with a universal testing machine and compared with the tooth mobility curve. With this new information, an improved adapted simulation device was constructed. Results: A simulations device that is able to simulate the mobility curve of natural teeth with high accuracy and where mobility is reproducible and scalable was developed
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Finite element modelling and load share analysis for involute worm gears with localised tooth contact
No full textA new approach has been developed by the authors to estimate the load share of worm gear drives, and to calculate the instantaneous tooth meshing stiffness and loaded transmission errors. In the approach, the finite element (FE) modelling is based on the modified tooth geometry, which ensures that the worm gear teeth are in localized contact. The geometric modelling method for involute worm gears allows the tooth elastic deformation and tooth root stresses of worm gear drives under different load conditions to be investigated. On the basis of finite element analysis, the instantaneous meshing stiffness and loaded transmission errors are obtained and the load share is predicted. In comparison with existing methods, this approach applies loaded tooth contact analysis and provides more accurate load capacity rating of worm gear drives
Trewenack, Reginald W. L.
No full textIndex cards recording information relating to Second World War service of Tooth staff. Cards generally include personal details (including addresses and marital status) and military service details (including service numbers, dates of service, postings and notes on any correspondene with family)
Kerr, L. T. J.
No full textIndex cards recording information relating to Second World War service of Tooth staff. Cards generally include personal details (including addresses and marital status) and military service details (including service numbers, dates of service, postings and notes on any correspondene with family)
Measurement of tooth size and shape in subjects with hypodontia and a control group using a new image analysis technique.
No full textThe literature referred to here provided information concerning the epidemiology of hypodontia and
its association with other developmental anomalies. Current research with the major developments in molecular biology has focused on the genetic component of the aetiology mainly on animals. Limited information has been gained
from human studies concerning the morphology of different teeth in hypodontia. The present research is both methodological and investigative in nature.
The aims of this study were to measure crown morphology of the permanent dentitions for hypodontia subjects divided
according to severity of hypodontia into mild, moderate and severe groups and a control group, and then to compare the measurements of groups. All subjects were of white Caucasian origin and were unrelated. The study groups were balanced for size (N = 40), gender (N = 20) and age. The effect of both severity of hypodontia and gender were examined. The total study population was N= 161.
A new measurement system using image analysis and new measurement index for tooth taper were developed,
validated and then utilised in the main study. The image analysis technique and tooth taper measurement were validated against the classical manual measurements and subjective scoring respectively. The errors of measurements were assessed by duplicate measurements to determine the intra- and inter-observer reproducibility. It was found that measurements for all study variables were repeatable without systematic error and with small method error. Comprehensive measurements (N = 15) were obtained from both the buccal and occlusal views for
the following dimensions of tooth crowns: The principal mesiodistal (MDb and MDo) and buccolingual (BL), proportional mesiodistal (MD25, MD50 and MD75) and
buccolingual (BLm and BLd), occlusogingival
(OG), perimeter (Pb and Po), area (Ab and Ao) and the distance between MDb and occlusal level (Db) and between MDo and buccal border of tooth crown
(Do). A number of indices (N = 5) to evaluate
tooth crown morphology were also calculated: Tooth
taper determination index (MD50/MD75), crown indices
of buccal morphology (CIBMI and CIBM2 i.
e. MDb/OG and Db/OG respectively) and crown indices of occlusal morphology
(CIOMI and CIOM2 i. e. MDo/BL and Do/BL
respectively). Two-way analysis of variance
followed by multi-comparison
tests with Bonferroni
adjustment
for
the significance
levels were employed
in
the main study.
The
results of the main study revealed significant differences between hypodontia groups
and control subjects
for
the following measurement variables: MDb, Db, OG, Pb, Ab,
MD25, MD50, MD75, tooth taper, CIBM2, MDo, Do, BL, Ao, Po, BLm and BLd.
Hypodontia subjects demonstrated
significantly smaller measurement values
than controls
except Db, tooth taper and CIBM2. The
severity of hypodontia affected
the degree of
difference in
tooth morphology;
for many variables
the more severe the hypodontia the
greater the difference from
controls. There were only a
few
significant
differences between
hypodontia
and control groups
for
the variables CIBM1, CIOM1 and CIOM2.
Gender differences (within groups)
indicated
that males
tend to show
larger measurements
than females
although
few findings
reached statistical significance.
The symmetry of right and
left measurements
(MDb and tooth taper), the number of cusps
in
the premolar and molar teeth and the intermaxillary
ratios were
investigated. The
findings
suggest that asymmetry
in bilateral measurements appeared to be increased in
hypodontia
subjects. Descriptive data also suggest that all the intermaxillary
ratios
tend to
be larger in hypodontia than the control group. There was a tendency for the reduction
in
the number of cusps
for hypodontia
subjects than controls. Again, these
findings were
related to severity of hypodontia.
Thus,
variation
in tooth morphology
in patients with hypodontia was clearly established.
The differences were related to the severity of the condition. However, there were also
variations
in
the measurements between individuals with hypodontia
of the same severity
group. A possible explanation
is the multifactorial aetiology of the condition.
In certain
groups, especially with severe hypodontia,
the small numbers of some tooth types which
developed may also have influenced the results
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