SEARCH · PubMed Health

Results for “Tooth”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources

PubMed1984

Transferrin is required for early tooth morphogenesis.

The role of circulating molecules during early tooth morphogenesis was studied in organ cultures of mouse embryonic molar-tooth germs. Special attention was focused on the effect of transferrin and insulin, which are necessary for the growth of most cells in culture. The requirement of serum factors for tooth morphogenesis was shown to diminish as the developmental stage advances from the bud stage in day-13 embryos to the cap stage at day 15. The day-15 teeth underwent morphogenesis and cell differentiation in unsupplemented basal culture medium, but the addition of transferrin (50 micrograms/ml) was necessary for the morphogenesis of day-14 tooth germs. We demonstrated, by using transferrin-depleted serum, that transferrin is also necessary for the morphogenesis of day-13 tooth germs. However, some still-unidentified serum components are also required for the morphogenesis of the bud-stage day-13 teeth. These factors apparently do not include insulin, since it was shown to inhibit tooth development. Analysis of the DNA content of tooth germs cultured in various culture media showed that the ability of transferrin to support tooth morphogenesis correlated with a stimulation of growth. The results support our earlier suggestions that transferrin functions as a fetal growth factor. The availability of the transferrin-containing chemically defined medium facilitates studies on the roles of other growth factors during tooth development.

Animals↗

PubMed1996

Use of the Weibull hazard model to estimate age-specific probability of permanent tooth loss.

In analysis of the probability of tooth loss with age, the exact time of tooth loss is often unknown, although it is clear whether a tooth remains or has been lost. That is, left censoring is inevitable during data sampling. This may provide a biased estimate if such data are dealt with by the product-limit method, which is a common method of survival analysis. To reduce such a bias in estimating the age-specific probability of tooth loss, we developed a survival analysis method taking left censoring into consideration. Four hundred and forty-six panoramic radiographs obtained in a daily clinical practice were used. The frequency of tooth loss with age was assumed to follow the Weibull hazard model, and a likelihood function taking left censoring into consideration was defined to estimate the probability of tooth loss. The estimate obtained from our method was compared with that from the product-limit method to examine whether the effect of left censoring was reduced. We found that the probability of tooth loss estimated by the product-limit method was biased by left-censored data, and that the bias was reduced when our method was used. A Monte Carlo simulation study, in which the true tooth loss time was given, also showed that our method provided an estimate closer to the true value. Our method is considered to be more accurate in estimating the probability of tooth loss, since it reduces the bias caused by left-censored data.

Adolescent↗

PubMed1997

Smoking, smoking cessation, and tooth loss.

Smoking is associated with an increased risk of tooth loss, but it is not known if this risk decreases significantly when individuals quit smoking. The objectives of this study were to describe the rates of tooth loss by smoking status in two populations of medically healthy men and women. Among the men, rates of tooth loss and edentulism in relation to smoking cessation were also evaluated. The subjects were drawn from a group of 584 women (aged 40 to 70) recruited from the Boston, MA, area and a separate population of 1231 male veterans (aged 21 to 75) who participated in the VA Dental Longitudinal Study in Boston. In cross-sectional baseline analyses, current cigarette smokers of either sex had significantly more missing teeth than never-smokers or former smokers. Former smokers and pipe or cigar smokers tended to have an intermediate number of missing teeth. Current male smokers had more teeth with calculus, but the differences in plaque, tooth mobility, probing depth > 2 mm, filled and decayed teeth, and bleeding on probing by smoking history were not significant. Prospective observations of 248 women (mean follow-up time = 6 +/- 2 years) and 977 men (mean = 18 +/- 7 years) indicated that individuals who continued to smoke cigarettes had 2.4-fold (men) to 3.5-fold risk (women) of tooth loss compared with non-smokers. The rates of tooth loss in men were significantly reduced after they quit smoking cigarettes but remained higher than those in non-smokers. Men who smoked cigarettes had a 4.5-fold increase in risk of edentulism, and this risk also decreased upon smoking cessation. These findings indicate that the risk of tooth loss is greater among cigarette smokers than among non-smokers. Smoking cessation significantly benefits an individual's likelihood of tooth retention, but it may take decades for the individual to return to the rate of tooth loss observed in non-smokers.

Adult↗

PubMed2003

Tooth bleaching--a critical review of the biological aspects.

Present tooth-bleaching techniques are based upon hydrogen peroxide as the active agent. It is applied directly, or produced in a chemical reaction from sodium perborate or carbamide peroxide. More than 90% immediate success has been reported for intracoronal bleaching of non-vital teeth, and in the period of 1-8 years' observation time, from 10 to 40% of the initially successfully treated teeth needed re-treatment. Cervical root resorption is a possible consequence of internal bleaching and is more frequently observed in teeth treated with the thermo-catalytic procedure. When the external tooth-bleaching technique is used, the first subjective change in tooth color may be observed after 2-4 nights of tooth bleaching, and more than 90% satisfactory results have been reported. Tooth sensitivity is a common side-effect of external tooth bleaching observed in 15%-78% of the patients, but clinical studies addressing the risk of other adverse effects are lacking. Direct contact with hydrogen peroxide induced genotoxic effects in bacteria and cultured cells, whereas the effect was reduced or abolished in the presence of metabolizing enzymes. Several tumor-promoting studies, including the hamster cheek pouch model, indicated that hydrogen peroxide might act as a promoter. Multiple exposures of hydrogen peroxide have resulted in localized effects on the gastric mucosa, decreased food consumption, reduced weight gain, and blood chemistry changes in mice and rats. Our risk assessment revealed that a sufficient safety level was not reached in certain clinical situations of external tooth bleaching, such as bleaching one tooth arch with 35% carbamide peroxide, using several applications per day of 22% carbamide peroxide, and bleaching both arches simultaneously with 22% carbamide peroxide. The recommendation is to avoid using concentrations higher than 10% carbamide peroxide when one performs external bleaching. We advocate a selective use of external tooth bleaching based on high ethical standards and professional judgment.

Animals↗

PubMed2000

BMP4 rescues a non-cell-autonomous function of Msx1 in tooth development.

The development of many organs depends on sequential epithelial-mesenchymal interactions, and the developing tooth germ provides a powerful model for elucidating the nature of these inductive tissue interactions. In Msx1-deficient mice, tooth development arrests at the bud stage when Msx1 is required for the expression of Bmp4 and Fgf3 in the dental mesenchyme (Bei, M. and Maas, R. (1998) Development 125, 4325-4333). To define the tissue requirements for Msx1 function, we performed tissue recombinations between wild-type and Msx1 mutant dental epithelium and mesenchyme. We show that through the E14.5 cap stage of tooth development, Msx1 is required in the dental mesenchyme for tooth formation. After the cap stage, however, tooth development becomes Msx1 independent, although our experiments identify a further late function of Msx1 in odontoblast and dental pulp survival. These results suggest that prior to the cap stage, the dental epithelium receives an Msx1-dependent signal from the dental mesenchyme that is necessary for tooth formation. To further test this hypothesis, Msx1 mutant tooth germs were first cultured with either BMP4 or with various FGFs for two days in vitro and then grown under the kidney capsule of syngeneic mice to permit completion of organogenesis and terminal differentiation. Previously, using an in vitro culture system, we showed that BMP4 stimulated the growth of Msx1 mutant dental epithelium (Chen, Y., Bei, M. Woo, I., Satokata, I. and Maas, R. (1996). Development 122, 3035-3044). Using the more powerful kidney capsule grafting procedure, we now show that when added to explanted Msx1-deficient tooth germs prior to grafting, BMP4 rescues Msx1 mutant tooth germs all the way to definitive stages of enamel and dentin formation. Collectively, these results establish a transient functional requirement for Msx1 in the dental mesenchyme that is almost fully supplied by BMP4 alone, and not by FGFs. In addition, they formally prove the postulated downstream relationship of BMP4 with respect to Msx1, establish the non-cell-autonomous nature of Msx1 during odontogenesis, and disclose an additional late survival function for Msx1 in odontoblasts and dental pulp.

Animals↗

PubMed2002

Incidence of tooth sensitivity after home whitening treatment.

BACKGROUND: A potential side effect of dentist-dispensed home tooth-whitening systems is tooth sensitivity. The authors conducted a randomized prospective double-blind study to determine the incidence of tooth sensitivity after home whitening treatment. METHODS: Fifty adult subjects used a gel containing 15 percent carbamide peroxide and 0.11 percent fluoride ion; an additional 50 adult subjects used a placebo gel daily for four weeks. Each subject's plaque index score, gingival recession status, caries status, current dentifrice and smoking history were recorded at baseline. The researchers evaluated sensitivity weekly by interview for four weeks. RESULTS: Fifty-four percent of subjects in both test and control groups reported mild sensitivity; 10 percent of test subjects and 2 percent of control subjects reported moderate sensitivity; 4 percent of test subjects and no control subjects reported severe sensitivity. Sensitivity decreased with time; by the second week, no severe sensitivity was reported, and by the fourth week, no moderate sensitivity was reported. The authors found a statistically significant positive correlation between reported sensitivity and gingival recession. They found no statistically significant correlations between sensitivity and any of the other recorded parameters. CONCLUSIONS: Mild tooth sensitivity can be expected in approximately one-half of patients who undergo home whitening treatment using the gel studied. Approximately 10 percent of patients may experience moderate sensitivity, and 4 percent of patients may experience severe sensitivity for one to two weeks. Patients with gingival recession appear more likely to experience tooth sensitivity during home whitening treatment. CLINICAL IMPLICATIONS: Patients considering home whitening treatment should be advised that mild tooth sensitivity is a common side effect and that severe tooth sensitivity occasionally occurs. If gingival recession is present, the probability of tooth sensitivity increases, and tooth sensitivity tends to decrease as treatment progresses.

Adult↗

PubMed2005

Periodontal disease and the incidence of tooth loss in postmenopausal women.

BACKGROUND: The role of periodontal disease as a predictor of incident tooth loss in postmenopausal women has not been determined. The aim of this cohort study was to determine the extent of the association between baseline periodontal status and incident tooth loss in a population of postmenopausal women. METHODS: The study population included 106 dentate white postmenopausal women who participated in a cross-sectional study between 1989 and 1991 who were willing and eligible to have a repeat examination after 10 to 13 years. At baseline, full-mouth assessment of periodontal status was performed clinically and radiographically. Assessment of tooth loss during follow- up was assessed clinically by a periodontist. Odds ratio (OR) and its 95% confidence interval (CI) for each periodontal variable was obtained from separate multiple logistic regression analyses adjusting for the effect of age, household income, smoking, hormone therapy, snack consumption, and number of decayed teeth. RESULTS: Sixty-one (57.5%) subjects lost at least one tooth during follow-up. Mean tooth loss per person was 1.81 +/- 2.77. After adjusting for confounders, each millimeter of alveolar bone loss at baseline increased the risk of tooth loss 3-fold (OR = 3.26; 95% CI: 1.60 to 6.64). The risk of tooth loss also increased 2.5 times for each millimeter of clinical attachment loss (OR = 2.50; 95% CI: 1.24 to 5.07). Probing depth (OR = 2.53; 95% CI: 0.98 to 6.53), gingival bleeding (OR = 1.99; 95% CI: 0.21 to 18.94), calculus (OR = 2.05; 95% CI: 0.91 to 4.61), and plaque (OR = 0.70; 95% CI: 0.13 to 3.34) were not significantly associated with incident tooth loss. CONCLUSION: Periodontal disease, especially measured by alveolar bone loss, is a strong and independent predictor for incident tooth loss in postmenopausal women.

Aged↗

PubMed1989

[Relationships between tooth loss and electromyographic activities of masticatory muscles].

For purpose of evaluating the characteristic of electromyographic activities of masticatory muscles with front or molar tooth loss, electromyographic activities of masticatory muscles and mandibular movements during tooth tapping and gum chewing were investigated in each group of tooth loss, and were compared with those of control group. The results were as follows. 1. In reference to the group with front tooth loss, 1) On tooth tapping, each S.D. of the time parameters of electromyographic activities of jaw closing muscles especially masseter and posterior temporalis was small, and that of jaw opening muscle was large. 2) On gum chewing, offset of jaw closing muscles' activities especially masseter and anterior temporalis were delayed. 3) On both tooth tapping and gum chewing, there was no difference in mandibular movements from control group. 2. In reference to the group with molar tooth loss, 1) On both tooth tapping and gum chewing, each S.D. of the time parameters of electromyographic activities of jaw closing muscles was large. 2) On tooth tapping, S.D. of opening ratio was large. 3) On gum chewing, both S.D. of chewing cycle and opening ratio were large.

Electromyography↗

PubMed2006

Factors influencing tooth shade selection for completely edentulous patients.

AIM: There is limited scientific information on the relationship between tooth shade, age, gender, and skin color in black Africans. This lack of knowledge may impact the ability of the prosthodontist to select artificial teeth for completely edentulous patients. This study explores the possibility of a relationship between tooth shade, gender, age, and skin color in a black African population. METHODS AND MATERIALS: A total of 212 individuals aged 15 to 79 years participated in this study. One investigator, calibrated for examining tooth shade, performed all examinations. A Vita-Lumin shade guide was used to examine either the maxillary right or left central incisor. One had to be sound for inclusion in the study. Tooth shades were divided into two categories according to value, and skin tones were divided into two categories (light, and dark). Chi-square analysis and Fisher's exact tests were used to analyze the data (P< 05). RESULTS: No statistically significant difference was found between tooth shade and skin color and the subjects' perception of their tooth shade. However, a statistically significant difference was found between age and tooth shade (P<.001). There was also a statistically significant difference in tooth shade between men and women. CONCLUSION: Within the limitations of this study, tooth shade value and skin color were not related. However, older adults and men are more likely to have darker teeth.

Adolescent↗

PubMed1994

The graphical analysis of tooth width discrepancy.

The standard tooth width ratio tables currently do not provide an overall indication of the final interdigitation of teeth. To provide a comprehensive analysis of inter-arch tooth width discrepancy, this study has developed a combination of cumulative percentage tooth width ratios and a method to visually determine the harmony between maxillary and mandibular tooth widths. Mesiodistal tooth widths from the first permanent molar to the corresponding first permanent molar were measured from 60 sets of pretreatment study models which were selected consecutively. Cumulative percentage ratios relating mandibular teeth to maxillary teeth were calculated utilising the mesiodistal tooth width measurements. The 13 mean cumulative percentage ratios developed in this study were plotted on graph paper showing plus and minus two standard deviations from the mean. These ratios provide a standard from which cumulative percentage ratios obtained from any new case may be compared graphically. Deviations from the mean cumulative percentage ratios are immediately recognised. No simple graphical method of assessment on the final interdigitation of anterior and posterior teeth has previously been devised. The graphical analysis of tooth width discrepancy is invaluable as an aid in localising any tooth width discrepancy and ensuring that incompatible maxillary-to-mandibular tooth widths are recognised prior to orthodontic treatment.

Humans↗

PubMed1988

Tooth size, spacing, and crowding in relation to eruption or impaction of third molars.

A study was conducted for the purpose of comparing mesiodistal tooth diameters, sum of tooth widths, and the degree of spacing or crowding in the dentitions of two groups of young adults. The subjects in the first group had complete dentitions including third molars (M3s). In the second group, all M3s had been extracted for failure to erupt. Tooth size and consequently the sum of mesiodistal tooth widths were found to be greater in the extraction group than in the group with complete dentitions. The relationship between tooth size and M3 impaction was most pronounced in female subjects. The sum of mesiodistal tooth widths is apparently one factor of importance in the cause of M3 impaction in women. The results suggest that tooth size in girls could be used at preadolescent age as one predictive variable for third molar eruption. The sexual dimorphism demonstrated regarding the relationship between tooth size and M3 impaction implies that studies in the field of M3 development and eruption should be performed on male and female subjects separately. The dental arches in the extraction group tended to be more crowded than in the group with complete dentitions. However, the differences were small and significant only as they related to the upper arches in males.

Adult↗

PubMed2001

Clinical application of computer-aided rapid prototyping for tooth transplantation.

The maintenance of healthy periodontal ligament cells in the donor tooth is one of the most important factors for successful tooth transplantation. This is achieved by minimizing the extraoral time during the surgical procedure. If a duplicate form of donor tooth could be obtained before extraction, it would be possible to precontour the recipient alveolar bone compatible with the donor tooth, and thereby reduce the extra-oral time of the donor tooth. We obtained a three-dimensional image with the real dimensions of the donor tooth from a CT Highspeed Advantage, allowing a life-sized resin model of the tooth to be fabricated. From 22 clinical cases, we achieved an average total transplantation time of 7.7 min. The average distance between the transplanted root surface and the alveolar bone from 12 available cases was 0.87 mm at the mesial cervix, 0.91 mm at the mesial apex, 0.98 mm at the distal cervix and 1.16 mm at the distal apex on the postoperative radiographs. Clinical data indicate that computer-aided rapid prototyping may be of value in minimizing the extra-oral time and possible injury to transplanted tooth during the process of autotransplantation.

Adult↗

PubMed1997

Differential expression of laminin alpha chains during murine tooth development.

Basement membranes of the developing tooth have been previously shown to contain laminins, but the nature of the laminins have not been described. We here studied the distribution of five different laminin alpha chains during tooth development. We show that both epithelial and mesenchymal cells produce laminin alpha chains. The mRNAs of three laminin alpha chains, alpha1, alpha2, and alpha4, were expressed in the tooth mesenchyme, whereas two, the alpha3 and alpha5 chain mRNAs, were found in epithelium. Drastic changes in the expression patterns of the two epithelial chains were found during development. The alpha5 mRNA was widely expressed in tooth epithelia, and the corresponding protein was evenly distributed along the tooth basement membrane throughout embryonic development. This suggests a role for alpha5 as a major laminin alpha chain in tooth basement membrane during embryonic stages. The subsequent disappearance of alpha5 and the drastic increase in alpha3A mRNA expression during terminal ameloblast differentiation and enamel secretion suggest that alpha3A acts as an important chain in the enamel matrix after degradation of tooth basement membrane. These studies show that laminin networks in tooth epithelia form as a result of epithelial-mesenchymal interactions and that the molecular composition of the laminin networks varies drastically during development of tooth.

Animals↗

PubMed2003

Analysis of tooth formation by reaggregated dental mesenchyme from mouse embryo.

Tooth morphogenesis is a well-known developmental system related to epithelial-mesenchymal interactions. In mice, the dental epithelium has the potential to induce tooth formation prior to the bud stage, whereas this potential shifts to the dental mesenchyme from the dental epithelium. The reaggregation of mesenchymal tissue leads to previous memories of individual cells being reset, which is useful for studying the predetermination of mesenchyme. Here, the mesenchyme was triturated into single cells after separation of the epithelium and the mesenchyme. These single cells were repelleted and combined with the epithelium. The reaggregated tooth was transplanted into a mice kidney capsule. In order to investigate the essential functions of both the dental epithelium and the dental mesenchyme regarding their mutual interaction, a reaggregation system was introduced using the late bud stage of the mouse first molar. Amelogenin expression was examined to confirm the cytodifferentiation in the reaggregated tooth. The results showed that a new tooth formed after reaggregating the dental mesenchyme. This tooth contained enamel, dentin, dentinal tubules and dental pulp. The inner enamel epithelium of the reaggregated tooth differentiated into ameloblasts. Immunohistochemistry for amelogenin was observed both in the ameloblasts and the enamel. However, the structure of the enamel was different from that of the normal tooth, with the thickness of the predentin becoming wider. These findings suggest that reaggregated dental mesenchyme cells can produce a tooth. The fate of dental epithelium was not affected by reaggregated dental mesenchyme, although the dental mesenchyme appears to lose the information from the dental epithelium.

Amelogenin↗

PubMed1998

Primary somatosensory cortical neuronal activity during monkey's detection of perceived change in tooth-pulp stimulus intensity.

To elucidate the functional properties of primary somatosensory cortical neurons for the perception of tooth-pulp sensation, neuronal activity was recorded from the primary somatosensory cortex (SI) in awake behaving monkeys. Monkeys were trained to detect changes in tooth-pulp stimulus intensity applied to the upper canine or incisor tooth pulp. Stimulus intensities applied to the tooth pulp were multiples of the threshold intensity for the jaw opening reflex (1.0 T) elicited by tooth-pulp stimulation. When monkeys pressed a button, baseline electrical pulses (V1: 0.5 T, 1.0 T, 2.0 T, or 3.0 T) were applied to the tooth pulp. After 4-8 s, a V2 stimulus (0.3 T, 0.5 T, 1.0 T, or 2.0 T) was added to V1. Percent escapes at V1 stimulus intensity of 0.5 T and 1.0 T were approximately 10%, 22% at 2.0 T, and 40% at 3.0 T (total of 1,997 trials). A total of 862 single units were recorded from the SI. Thirty-seven SI neurons responded to electrical stimulation of the tooth pulp (tooth-pulp-driven neurons; TPNs), 139 SI neurons responded to tactile stimulation of the lateral face area, 90 to upper lip and 99 to lower lip, 44 to tongue and 102 to periodontal membrane, whereas 351 SI neurons were not responsive to tactile stimulation of the orofacial regions. Thirty of 37 TPNs were recorded long enough to test with V1 stimuli ranging from 0.5 T to 3.0 T. Eleven of 30 TPNs linearly increased their firing frequency following increases in stimulus intensity (encoding TPNs), whereas 19 did not (nonencoding TPNs). Mean first spike latency of encoding TPNs was 24.8 +/- 1.7 ms (n = 11), that of nonencoding TPNs was 23.6 +/- 1.5 ms (n = 19), and that of unclassified TPNs was 24.7 +/- 3.7 ms (n = 7). TPNs were distributed in the areas 1-2, 3a, and 3b within the oral projection area and the transition zone between the face and oral projection areas of the SI. All of them received inputs from the intraoral structures, facial skin, or both. The firing frequency of eight encoding and nonencoding TPNs was correlated with detection latency at stimulus intensities of 0.5 and 1.0 T. On the other hand, when the baseline stimulus was increased to 2.0 T and 3.0 T, the discharge of most TPNs did not increase in firing frequency with the reduction in detection latency. These results indicate that the discharge rates of some SI TPNs are correlated with detection latency at near-noxious threshold and noxious stimulus intensities. These findings suggest that some TPNs are involved in the sensory-discriminative aspect of tooth-pulp sensation in the near-pain threshold and pain ranges.

Animals↗

PubMed1990

[Process of the tooth brushing habit formation in children. 1. Period of the start and present circumstances classified by age].

The purpose of this study was to investigate the process by which the tooth brushing habit was formed in children. The study is based on questionnaires about the habit of tooth brushing from mothers of kindergarten pupils aged from one to six years living in Nagoya and the suburbs. The results of this study were summarised as follows: 1. Period of the start: 1) The number of children who started tooth brushing before the age of one year and six months was 75.7%, and before the age of two, 88.3%. 2) The item of "Eruption of the teeth" showed the highest ratio (49.2%) regarding the motive for the start of tooth brushing. 3) The children who started tooth brushing with the motive which construction about caries prevention with mothers as the main tended to start the earliest. 4) The ratio of persons who actually brush the children's teeth were as follows, "mother brushes (51.6%)", "mother after her child (37.1%)" and "child brushes (6.8%)". 5) The number of children who started using a tooth-brush before the age of two years was 78.8%, and before the age of two years and six months, 92.5%. 2. Present circumstances classified by age: 1) The number of children whose teeth are brushed by themselves or their mothers more than once a day before they were six years old was 61.8%. 2) In all ages, the group of once or twice a day showed a high ratio for frequency of tooth brushing. 3) "mother brushes (47.4%)" for one year olds, and "mother helps her child's brushing (85.7-53.6%)" for two to five year olds, and "child brushes (64.8%)" for six years olds were the highest ratios regarding the persons who actually brush the children's teeth. 4) Co-operative attitude of the children towards their mother's help is bad for one year olds, but good above two years old. 5) Attitude of the children towards tooth brushing is negative under three years old, and positive above four years old. 6) There is little hope that children can brush well by themselves under two years old. 7) children who have experienced guidance in tooth brushing from their mothers before they were three years old numbered 84.7%, and from a dentist or dental hygienist before they were six years old numbered 49.8%.

Age Factors↗

PubMed1999

Simulation of orthodontic tooth movements. A comparison of numerical models.

Orthodontic tooth movements are based on the ability of bone to react to mechanical stresses with the apposition and resorption of alveolar bone. Currently, the underlying biophysical, biochemical, and cellular processes are the subject of numerous studies. At present, however, an analytical description of orthodontic tooth movements including all components of the processes involved seems to be impossible. It was the aim of the present study to develop a mechanics-based phenomenological model capable of describing the alveolar bone remodeling. Thus, 2 different models were developed. The first is based on the assumption that deformations of the periodontal ligament (PDL) are the key stimulus to starting orthodontic tooth movement. The second supposes that deformations of the alveolar bone are the basis of orthodontic bone remodeling. Both models were integrated into a finite element package calculating stresses, strains and deformations of tooth and tooth supporting structures and from this simulating the movement of the tooth and its alveolus through the bone. Clinically induced canine retractions in 5 patients as well as force systems were exactly measured and the tooth movements were simulated using both models. The results show that the first model allows reliable simulation of orthodontic tooth movements, whereas the second is to be rejected.

Alveolar Process↗

PubMed2006

Severe wear and tooth loss in wild ring-tailed lemurs (Lemur catta): a function of feeding ecology, dental structure, and individual life history.

The ring-tailed lemurs at Beza Mahafaly Special Reserve, Madagascar, exhibit a high frequency of severe wear and antemortem tooth loss. As part of a long-term study, we collected dental data on 83 living adult ring-tailed lemurs during 2003 and 2004. Among these individuals, 192 teeth were scored as absent. The most frequently missing tooth position is M1 (24%). As M1 is the first tooth to erupt, its high frequency of absence (primarily a result of wear) is not remarkable. However, the remaining pattern of tooth loss does not correlate with the sequence of eruption. We suggest that this pattern is a function of 1) feeding ecology, as hard, tough tamarind fruit is a key fallback food of ring-tailed lemurs living in gallery forests; 2) food processing, as tamarind fruit is primarily processed in the P3-M1 region of the mouth; and 3) tooth structure, as ring-tailed lemurs possess thin dental enamel. The incongruity between thin enamel and use of a hard, tough fallback food suggests that ring-tailed lemurs living in riverine gallery forests may rely on resources not used in the past. When comparing dental health in the same individuals (n=50) between 2003 and 2004, we found that individual tooth loss can show a rapid increase over the span of one year, increasing by as much as 20%. Despite this rapid loss, individuals are able to survive, sometimes benefiting from unintentional assistance from conspecifics, from which partially processed tamarind fruit is obtained. Although less frequent in this population, these longitudinal data also illustrate that ring-tailed lemurs lose teeth due to damage and disease, similar to other nonhuman primates. The relationship between tooth loss, feeding ecology, dental structure, and individual life history in this population has implications for interpreting behavior based on tooth loss in the hominid fossil record.

Age Factors↗