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PubMed1989

Differences in tooth wear as an indicator of changes in jaw movement in the guinea pig Cavia porcellus.

Patterns of tooth wear have frequently been used to make inferences about jaw movements and tooth use in modern and extinct mammals. However, there has been relatively little experimental work to define the limits of usefulness of tooth wear studies. In the present study, electrolytic lesions in the left trigeminal motor nucleus of five guinea pigs resulted in significant changes of jaw movement. Scanning electron microscopy revealed significant differences in tooth wear between the lesion and non-lesion sides of these animals. Control animals showed no significant differences in tooth wear between right and left sides. The differences in tooth wear in the experimental animals were readily interpretable in terms of the induced changes in jaw movement.

Animals↗

PubMed1989

A preliminary study of the effects of tooth guidance on working-side condylar movement.

Clinical observations have indicated that lateral working-side tooth contacts can produce a posterior shift of the working-side condyle, resulting in pain in the temporomandibular joint. This study examined the influence of lateral retrusive and lateral protrusive tooth guidance on the movements of working condyles of the lateral pole. Four patients with lateral retrusive natural tooth contacts and four patients with lateral protrusive natural tooth contacts were studied. Movement of the lateral pole of the working condyle was recorded under the following conditions: (1) natural teeth in contact, (2) wearing of a mandibular acrylic resin splint that created lateral protrusive or lateral retrusive tooth guidance, and (3) a central bearing screw and bearing plate separating the teeth. The results indicated that the condition of the patient's temporomandibular joints was a crucial factor in consistency of condylar tracings. Condylar tracings from patients with temporomandibular joint condyle-disk lacking coordination were inconsistent and unreproducible. Consistent, reproducible tracings for patients without condyle-disk disorders indicated that lateral retrusive guidance can cause a more posterior pathway of the lateral pole of the working condyle than lateral protrusive guidance. Future studies are necessary to establish the relationship between lateral tooth guidance and temporomandibular disorders.

Adult↗

PubMed1976

Charcot-Marie-Tooth disease associated with "essential tremor": Report of 7 cases and a review of the literature.

A study of 7 cases of Charcot-Marie-Tooth disease associated with a dyskinesia resembling benign essential tremor is presented. In 4 patients, the family history strongly suggested an autosomal mode of transmission, 2 cases were sporadic without an established genetic pattern and 1 was probably recessive. The distal parts of the upper and lower limbs showed imparied muscle strength with slight or no atrophy in 4 patients and conspicuous weakness and wasting in another 2. One patient was a chairbound. Although essential tremor and the tremor seen in these patients are clinically (phenotypically) similar it seems possible that they result from two different genotypes. Further, it seems that cases with Charcot-Marie-Tooth disease and "essential tremor" are not the result of the association of two separate dominant characteristics which are generally inherited as mendelian dominant traits. In spite of the diversity of the clinical manifestations of the peripheral neuropathy, the semiologically different types of essential tremor and the electrophysiological data, it is concluded that patients who develop a peripheral neuropathy on a familial basis and who exhibit clinical features of similar character, suffer from a common type of pathological disorder. Stress is laid upon the fact that Friedreich's ataxia and Charcot-Marie-Tooth disease share many clinical features. It is suggested that when Friedreich's ataxia and Charcot-Marie-Tooth disease seem to be present in the same individual and/or alternate in different members of the same family, the process is likely to be one of Charcot-Marie-Tooth disease. The value of the type of inheritance, natural history, clinical examination and electrophysiological data in differentiating Charcot-Marie-Tooth disease (with or without essential tremor) from other degenerative disorders is analyzed.

Adolescent↗

PubMed1975

Relations between tooth positions and focal troughs of panoramic machines.

A comparison of the established focal troughs of three panoramic machines with positions of the teeth in the dental arches of 240 patients. The patients, divided into twelve cells, were selected on the basis of race, sex, age, number of teeth, and occlusion. Occlusal registrations were made in fast-set acrylic. Tooth centers were identified and, with the midline-incisal point as a reference point, various composite drawings of tooth positions of patients were made. The total composite of all teeth revealed the striking similarity of the arches. Superimposition on the focal troughs showed that the focal trough of the Panorex easily encompassed all tooth positions. The focal trough of the Orthopantomograph encompassed all tooth positions, although tooth centers lie on the edges of the trough. The focal trough of the GE-3000 with profile index 10 extended so far buccally that many teeth are positioned lingual to the trough. The focal trough of the GE-3000, when reduced uniformly to profile index 7.5, encompasses all tooth positions although some positions fall quite near the borders of the trough.

Adolescent↗

PubMed1981

Tooth eruption depends on bone resorption: experimental evidence from osteopetrotic (ia) rats.

Resorption of alveolar bone around erupting teeth is known to be independent of tooth eruption. However, the failure of tooth eruption and reduction in bone resorption in the osteopetrotic rat mutation, incisors absent (ia), suggest that tooth eruption depends upon bone resorption. This hypothesis was tested by determining the effects of neonatal restoration of bone resorption in ia rats on eruption of first molars. Newborn ia rats were treated with irradiation and spleen cells and tooth eruption and bone resorption were examined 30 days later. In 24 treated ia rats at least two molars erupted in every rat and all four molars erupted in 14. In 24 untreated ia littermates, no molars erupted in 21, one molar erupted in two and two molars erupted in one rat. All molars erupted in 38 untreated normal littermates. Alveolar bone overlying unerupted first molars in untreated ia rats was not present in treated mutant littermates. Neonatally treated ia rats had osteoclasts with ruffled borders and no skeletal sclerosis by 30 days. Within 48 hours after treatment two types of osteoclasts could be found in treated rats. One type resembled those found in untreated ia littermates and the other those found in normal rats. These data suggest that failure of tooth eruption in ia rats is directly related to the reduction in bone resorption and that alveolar bone resorption is required for tooth eruption.

Animals↗

PubMed1997

Development of a novel system for assessing tooth and restoration wear.

OBJECTIVES: This investigation sought to develop a mapping apparatus for use in the assessment of both tooth and restoration wear. METHODS: A computer controlled mapping device, capable of scanning a suitably prepared electroconductive tooth replica by means of an electrical feedback mechanism, was constructed and its accuracy assessed by measuring the thicknesses of four engineers' slip gauges 12 times each. The reproducibility of three potential methods of rendering a die stone replica electroconductive was also investigated. Finally, tooth replicas were surface profiled and compared empirically with the originals using a commercial surface mapping program. RESULTS: The overall mean accuracy of the mean thicknesses of the slip gauges was 4.4 (2.8) microns. Surface deposition of either nickel spray or gold leaf, upon a ready formed replica, did not give a reproducible thickness. Precoating silicone impressions with nickel spray prior to replica production overcame this problem. On an empirical basis the instrument yielded accurate digital terrain models of tooth replicas. CONCLUSIONS: A surface mapping device has been developed which is both accurate and reproducible. A satisfactory electroconductive surface may be produced upon a tooth replica by precoating a silicone impression with nickel spray before casting the replica. The technique should prove invaluable for monitoring both tooth and restoration wear but further work is necessary to examine how such an approach will perform clinically.

Dental Impression Materials↗

PubMed1992

The effect of acetylsalicylic acid on orthodontic tooth movement in the guinea pig.

This study examined the influence of acetylsalicylic acid an inhibitor of prostaglandin synthesis, on orthodontic tooth movement induced with light spring forces in the guinea pig. The animal model was shown to permit reliable and accurate recording of tooth movement up to 28 days. Tooth movement was found to be highly correlated with spring forces, indicating that the model provided a sensitive test of the effect of aspirin on tooth movement. Aspirin was administered orally at the rate of 65 mg/kg per day in three divided doses and was found to effectively inhibit prostaglandin synthesis at the level of the bronchioles. However, aspirin did not appear to significantly affect tooth movement. Thus prostaglandins may not be the only mediators of the bone resorption associated with tooth movement induced by light orthodontic forces under these experimental conditions.

Analysis of Variance↗

PubMed2006

Factors affecting tooth loss among rural Khon Kaen adults: analysis of two data sets.

BACKGROUND: Tooth loss is an oral health problem affecting Thai people and people of other nations as well. Not much of epidemiologic evidence concerning factors affecting tooth loss among Thai people has been reported although severity of tooth loss among Thai people has never been decreased. METHODS: This study employed two existing data sets to evaluate the role of health behaviors such as tobacco smoking and betel quid chewing (a common habit prevalent among rural Thai females), together with other factors in relation to tooth loss among rural Thai people. The study population in the first (phase I) and second (phase II) data sets included 1484 and 3471 male and female adults residing in rural areas of Khon Kaen province, Thailand during 1990-1991 and 1992-1994, respectively. The data were obtained through oral examination and interview. Employing descriptive, bivariate, and multivariable Poisson regression, key risk indicators of tooth loss were identified for both data sets. RESULTS: The findings from final multivariable Poisson regression models were consistent in that tobacco smoking, betel quid chewing, age, dental caries (defined as decayed plus filled teeth) and periodontitis were significantly related to tooth loss among these rural populations. CONCLUSION: Therefore, preventive programs aiming at discouraging Thai people from smoking tobacco and/or chewing betel quid should be established so that healthy natural teeth can be maintained.

Adult↗

PubMed2004

Developmental toxicity of dioxin to mouse embryonic teeth in vitro: arrest of tooth morphogenesis involves stimulation of apoptotic program in the dental epithelium.

Previous studies have shown that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can arrest molar tooth development in rats after in utero and lactational exposure, and that the sensitive stage is temporally restricted. To define the stage in which TCDD is able to arrest tooth development and the cellular background of the effect, mouse embryonic molar tooth explants including various early developmental stages from initiation to late cap stage were exposed to TCDD in organ culture. TCDD did not inhibit morphogenesis of the first molar teeth including the early bud-staged E12 first molars, but the teeth were smaller than in control cultures. Accordingly, the second molars underwent morphogenesis in the presence of TCDD when explanted at E15 when they were at the bud stage. TCDD arrested their development when explanted at E14 when they had not yet reached the early bud stage. Immunohistochemical localization of incorporated bromodeoxyuridine in cultured E14 teeth showed that TCDD did not affect cell proliferation. Localization of apoptosis by terminal deoxynucleotidyl transferase (TdT)-mediated nick end labeling (TUNEL) method revealed that TCDD enhanced apoptosis of dental epithelial cells, especially in the dental lamina of both the first and second molars, and in the inner dental epithelium at the cusp tips of the first molars. Thus, TCDD can arrest tooth development in vitro if the exposure starts at the initiation stage, whereas exposure at later stages leads to smaller tooth size and deformation of cuspal morphology. TCDD interferes with tooth development by stimulating apoptosis in those cells of the dental epithelium, which are predetermined to undergo apoptosis during normal development.

Animals↗

PubMed2002

The influence of parathyroid hormone-related protein (PTHrP) on tooth-germ development and osteoclastogenesis in alveolar bone of PTHrP-knock out and wild-type mice in vitro.

In a previous study, it was shown that tooth germs of neonatal homozygous parathyroid hormone-related protein (PTHrP)-knockout mice are penetrated or compressed by the surrounding alveolar bone, suggesting an important role for PTHrP in the formation and activation of osteoclasts around growing tooth germs. In order to elucidate the role of PTHrP during the development of the tooth germ and related structures, mandibular explants containing cap stage tooth germs of embryonic day 14, homozygous mice were here cultured with or without surrounding alveolar bone. There was no difference in the number of tartrate-resistant acid phosphatase-positive multinucleated osteoclastic cells around the first molars of homozygous and wild-type mice. After 10 days of culture, osteoclastic cells were rarely present in explants from homozygous mice and penetration of alveolar bone into the dental papilla was observed. The decline in osteoclast number was partly restored by the addition of PTHrP to the culture. Tooth germs of both wild-type and homozygous mice cultured without alveolar bone developed well, with no apparent structural abnormality; dentine formation was evident after 10 days. These data suggest that PTHrP is not required for the development of the tooth germ proper but is indispensable in promoting the osteoclast formation required to accommodate that development.

Acid Phosphatase↗

PubMed2003

Three-dimensional reconstruction studies and morphometric analysis of rudimental tooth primordia in the upper incisor region of the sheep (Ovis aries, Ruminantia).

The functional dentition of the domestic sheep lacks all upper incisors and the upper canines. Nevertheless, occurrence of a dental lamina and rudimental tooth primordia had been described in the upper incisor region of the sheep. The aim of this study was to describe temporo-spatial pattern of origin and regression of these rudimental tooth primordia by light microscopy, computer-aided three-dimensional reconstruction and morphometry of the dental epithelium. Transient existence of a dental lamina in the upper incisor region of the sheep and three epithelial thickenings on its deep mesenchymal margin has been observed at day of ontogeny (DO) 48-53. They could not been identified as full-value tooth primordia, because they did not induce differentiation of tooth mesenchyme, but they could represent last remnants of functional upper incisors in early ancestors of ruminants. Additionally, a large rudimental upper canine primordium near the sutura maxilloincisiva occurred at DO43, reached early cap stage at DO52 and started to regress at DO53. Thus, our findings showed a discrepancy between the embryonic and adult dental pattern in the sheep. Similar molecular mechanisms as described for diastemal tooth rudiments in rodents could be involved during regression of rudimental tooth primordia in the upper incisor region of the sheep.

Animals↗

PubMed1998

Development and cell fate in interspecific (Mus musculus/Mus caroli) orthotopic transplants of mouse molar tooth germs detected by in situ hybridization.

Interpretation of results from previous tooth germ transplantation studies is limited by the inability to distinguish between donor and host cells unequivocally. Furthermore, ectopic transplantation sites have generally been used and the relevance of this to tooth development in situ is uncertain. The aim here was to determine cell fate in orthotopic tooth germ transplants using an interspecific mouse marker system. Mandibular first molar tooth germs were dissected from Mus musculus (CD1) and Mus caroli mice (age range 15-19 day embryo) and transplanted interspecifically into the alveolar crypt of extirpated first mandibular molars in neonatal M. musculus (CD1) and M. caroli hosts. Grafts were recovered at intervals up to 4 weeks postoperatively. Paraffin wax-embedded sections were examined using routine histological techniques and in situ hybridization with a biotinylated DNA probe (pmSat5) specific for M. musculus, to distinguish between donor and host cells. Development of M. musculus tooth germs in M. caroli mandibles and vice versa was similar and transplants progressed to incipient root formation. Vascularization of transplants was chimaeric, being donor-derived in the pulp and host-derived more peripherally. The investing soft tissues comprised a mixture of donor and host cells, predominantly donor. Donor cells were also found in the soft tissue of intertrabecular spaces in the surrounding bone, but alveolar osteocytes were almost entirely host-derived. Long-term survival of grafts was limited and few donor cells were present after 2 weeks. This study provides an unequivocal demonstration of the origin of all cells present in transplanted tooth germs.

Animals↗

PubMed2002

A novel method for the three-dimensional (3-D) analysis of orthodontic tooth movement-calculation of rotation about and translation along the finite helical axis.

The purpose of this study was to establish a novel method for evaluating orthodontic tooth movement in three-dimensional (3-D) space. The present system consisted of the following procedures at a given treatment period: (1) 3-D tooth positions were measured with a 3-D surface-scanning system using a slit laser beam; (2) the 3-D shape data were registered automatically at the maxillary first molars, and the coordinate systems were normalized; (3) the rotation matrix and translation vector were calculated from the automatic registration of the two position data for a given tooth; (4) the finite helical axes of teeth were calculated as the locus of zero rotational displacement; and (5) tooth movement was presented as rotation about and translation along the finite helical axis. To test this system, a male patient (age 22 yr 2 months) with Angle Class III malocclusion and moderate crowding of the anterior teeth, who had been treated using a standard multi-bracket appliance, was used as a model case in this study. Impressions for a dental cast model were taken at five phases; immediately before and after application of the appliance, and 10 days, 1 month and 2 months after beginning treatment. The results demonstrated that the present analytical method can more simply describe the movement of a given tooth by rotation about and translation along the finite helical axis, and provides quantitative visual 3-D information on complicated tooth movement during orthodontic treatment.

Adult↗

PubMed1995

Twelve-month results of a clinical wear study of three artificial tooth materials.

This study compared in vivo wear of a new artificial tooth material with that of existing artificial tooth materials. Artificial tooth wear was determined by measuring height changes of selected points on contacting tooth surfaces in patients with complete dentures during a 12-month period. These results are part of an ongoing 3-year clinical study. A total of 67 patients were randomized to one of three treatment groups in this double-blind study. Group 1 received dentures with existing artificial tooth materials. Group 2 received dentures that contained teeth with the new experimental material. Group 3 received dentures with Bioform IPN resin teeth (Dentsply International Inc., York, Pa). A computerized coordinate measuring machine and computer-controlled X-Y positioning stages were used for this study. Tooth wear was determined by measuring vertical heights of contacting points from baseline points at each of two time intervals. The calculation of wear was made by comparing the differences in height at the beginning of the experiment with those measured at each time interval. A repeated measures analysis of variance (ANOVA) was used to test the difference in mean wear among the three groups from baseline to 6 months and from 6 to 12 months. Group differences in total wear at 12 months were also tested. The ANOVA results revealed no statistically significant differences in the wear among the three types of denture teeth at the 6- or 12-month time intervals or at 12 months (p > 0.05). The average total wear value at 12 months was 90 microns. Group 1 averaged 102 microns of wear, group 2 averaged 88 microns of wear, and group 3 averaged 76 microns of wear.

Acrylic Resins↗

PubMed1998

Clinical wear study of three commercially available artificial tooth materials: thirty-six month results.

STATEMENT OF PROBLEM: Excessive wear of artificial resin teeth has been a concern to both the patient and the dentist because of unfavorable associated sequelae. The search for a more wear resistant resin tooth material resulted in the development of modified resin teeth that displayed acceptable wear resistance. PURPOSE: This study compared clinical wear of a new modified resin tooth material with two other commercially available modified resin materials over a period of 36 months. Differences in wear by gender, cuspal anatomy, arch, individual tooth type, and chewing side preference were also evaluated. MATERIAL AND METHODS: A total of 67 patients were randomized into one of three treatment groups in this double-blind study; group 1, Ivoclar-Vivodent and Orthotyp; group 2, Dentsply-Trublend SLM; and group 3, Dentsply-Bioblend IPN. Tooth wear was determined by measuring vertical heights of contacting points at baseline and 36 months with a computerized coordinate measuring machine and computer-controlled positioning stages. Measurements were completed at 36 months for 55 patients who remained in the study. RESULTS: Repeated measures analysis of variance revealed no significant difference in total wear by gender or tooth material at 36 months. There was also no significant difference by chewing side preference or cuspal anatomy. However, there was a significant difference in individual tooth wear (canine, premolar, molar) and by arch. CONCLUSION: New modified resin teeth have displayed clinically acceptable wear resistance for most patients.

Acrylic Resins↗

PubMed1999

Influence of patient age on the nature of tooth fracture.

STATEMENT OF PROBLEM: There is much controversy in the literature relating the incidence of tooth fracture to patient age. The nature (complete or incomplete) of fracture is one aspect that is frequently reported; however, the results highlight relative differences with respect to age and the inadequacy of the statistic used for analysis. PURPOSE: This study: (1) reviewed the existing literature on the relationship of patient age and nature of tooth fracture, (2) investigated the nature of tooth fractures among attendees of an emergency clinic, and (3) assessed any relationship between nature of fracture and patient age. MATERIAL AND METHOD: From the existing literature, 6 studies were suitable for combined analysis. The study was conducted among subjects attending the Student Emergency Dental Service in the University Dental Hospital of Manchester over a 2-year period, 1995-97. Each study subject had a fractured tooth and was examined by 1 of the authors and data were recorded. RESULTS: Combined analysis showed that the age of patients with incomplete fractures was higher than those with complete fractures (P <.05). A total of 229 patients exhibited complete (n = 263) or incomplete (n = 8) fractures of 271 teeth. Age range of 18 to 47 years demonstrated a skewed distribution with a median of 21 years. There was a statistically significant difference in age distribution between the 2 natures of tooth fracture (P <.05) with incomplete fractures associated with older ages. CONCLUSION: Incomplete tooth fractures are uncommon in students attending an emergency clinic. Complete fractures may occur at any age, while it appears that incomplete fractures are associated with older age groups.

Adolescent↗

PubMed2003

Characterization of glycosaminoglycans during tooth development and mineralization in the axolotl, Ambystoma mexicanum.

Glycosaminoglycans (GAGs) involved in the formation of the teeth of Ambystoma mexicanum were located and characterized with the cuprolinic blue (CB) staining method and transmission electron microscopy (TEM). Glycosaminoglycan-cuprolinic blue precipitates (GAGCB) were found in different compartments of the mineralizing tissue. Various populations of elongated GAGCB could be discriminated both according to their size and their preferential distribution in the extracellular matrix (ECM). GAGCB populations that differ in their composition could be attributed not only to the compartments of the ECM but also to different zones and to different tooth types (early-larval and transformed). Larger precipitates were only observed within the dentine matrix of the shaft of the early-larval tooth. The composition of the populations differed significantly between the regions of the transformed tooth: pedicel, shaft and dividing zone. In later stages of tooth formation, small-sized GAGCBs were seen as intracellular deposits in the ameloblasts. It is concluded that the composition of GAGCB populations seems to play a role in the mineralization processes during tooth development in A. mexicanum and influence qualitative characteristics of the mineral in different tooth types and zones, and it is suggested that GAGs might be resorbed by the enamel epithelium during the late phase of enamel formation.

Ambystoma mexicanum↗

PubMed2001

Ultrastructure and composition of basement membranes in the tooth.

The tooth, the hardest organ in the body, is known to be formed through highly elaborate, unique processes of differentiation and development. Basement membranes play critical roles in fundamentally important biological processes such as growth and differentiation, and for better understanding of the mechanism of development and maintenance of the tooth, specializations of tooth basement membranes are reviewed in detail in relation to their roles. The basement membrane at such diverse locations in the tooth as the inner enamel epithelium, maturation-stage ameloblasts, and junctional epithelium at the dentogingival border are specialized in their own highly unique ways for anchoring, firm binding, or mediation in the transport of substances. Thus, the role of basement membranes in the developing and mature tooth is manifold and for these roles individual basement membranes are specialized in their own specific ways which are rare or not seen in nondental tissues, and these specializations are essential for successful development and maintenance of the tooth.

Animals↗