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PubMed2005

Orthodontic extrusion of an extensively broken down anterior tooth: a clinical report.

A predictable esthetic restoration is not limited to the restored teeth; it has to include the gingival unit and its interface with the teeth involved. Failure to deliver restorations that maintain gingival health jeopardizes the success of any restorative procedure and creates potential for periodontal problems. Perforations, fractures, root resorption, or caries in the cervical area of the tooth, especially in the anterior part of the mouth, present many challenges to the clinician. Failure to place the crown margins on sound tooth material may violate the biologic width and should be considered a restorative failure. Orthodontic root extrusion or forced eruption is a well-documented clinical method for altering the relation between a nonrestorable tooth and its attachment apparatus, elevating sound tooth material from within the alveolar socket. It has some advantages over surgical crown lengthening, which is less conservative considering the sacrifice of supporting bone and the negative change in the length of the clinical crowns of both the tooth and its neighbors. This article presents a case of a maxillary right lateral incisor, extensively broken down following trauma, treated with orthodontic extrusion combined with gingival fiberotomy, without a need for a corrective surgical procedure.

Adult↗

PubMed2006

[Experimental study of the dental follicle's function in tooth root development].

OBJECTIVE: To study role of dental follicle in tooth root development. METHODS: Sixteen mandibular first molar dental germs from eight five-day postnatal Balb/c mice were divided into two groups randomly. Dental follicle of germs in one group was undetached and that of another group was removed. Subsequently, each of the germs was separately transplanted to back-muscles of adult nude mice. At seventh and fourteenth day after transplanting, the germs were collected, fixed, demineralized, dehydrated, and embedded in wax in sequence. Serial sections of 5 microm thick were made following the routine methods, stained with haematoxylin-eosin dying solution, and observed under a light microscope. RESULTS: All implantations were located in the back-muscles with abundant capillary vasculature. Under microscope, although all tooth germs could further develop after grafting, tooth germs without dental follicle developed slowly with small size and low calcification compared to those with dental follicle. Although position of Hertwig's epithelial root sheath of all germs seemed no changing, roots of the group with dental follicle could further develop and the roots develop toward the apical direction; this tendency couldn't be seen in the germs of another group. Inflammatory cells could be seen in and out of the pulp cavity of the two groups at 7th day after grafting, while no obvious inflammatory cell was observed at 14th day after grafting. CONCLUSION: Dental follicle play an important role in tooth root development. It probably can lead tooth root to develop in normal direction.

Animals↗

PubMed1990

Tooth wear and some factors influencing its severity.

Tooth wear has been studied in a dentally attending population, aged 46-85 years. The level of tooth wear was recorded for 100 persons using the tooth wear index of Smith and Knight. Aetiology was assessed using a history/questionnaire/examination. Erosion/attrition were postulated in 98 persons while abrasion was present in 82. All demonstrated some tooth wear and in 6.93% of 7,822 surfaces this was defined as pathological according to the threshold levels associated with the index. 84 persons had pathological wear on some surfaces but this was predominately cervical, only 12 persons showing pathological wear on the occlusal/incisal surfaces. Occlusal contact area was measured using imprints in soft opaque wax, transmitted light and a charge-coupled linear scanning array. The array is moved at 90 degrees to its axis by a linear translator to produce an image consisting of 1,600 lines, each of 2,048 pixels. This image is converted to hard copy using a DEC DDP 11/23 computer which will also give area measurements. Occlusal contact area ranged from 3.16 to 194.40 sq mm with a mean of 59.23 sq mm. Tooth wear is a significant clinical problem in this population. Wear on the occlusal/incisal surfaces is more common in older age groups and in males but could not be related to occlusal contact area or denture status by the methods used.

Aged↗

PubMed1997

Wear now? An update on the etiology of tooth wear.

Tooth wear is an ever-increasing problem, and younger patients are particularly at risk. The problem is likely to continue as patients' demands and expectations rise and as more natural teeth are retained into old age. The etiology of tooth wear is reviewed, with emphasis on those factors that appear to be major contributors to the problem at the moment. The clinical appearance of tooth wear is also discussed. It would appear that erosive factors are a significant cause of tooth wear. The prominence of acidic damage of tooth tissue is probably a reflection of society's concern with healthy eating and appearance.

Humans↗

PubMed1987

Postcanine tooth size in female primates.

The results of many allometric studies of postcanine tooth size in mammals have not corresponded to expectations of tooth size based on energy requirements and dental function. The purpose of this study is to investigate the relationship between postcanine occlusal surface area, body size, and the metabolic demands of pregnancy and lactation in female primates. Tooth and body sizes from 38 primate species were taken from the literature to test two hypotheses: 1) females should have relatively larger teeth than males in order to masticate additional food for the energetic costs of reproduction; 2) taxa with the largest neonatal size (a measure of average metabolic costs of pregnancy and lactation) should have females with a greater degree of relative dental enlargement. The results show that relatively large female teeth are not found consistently in primate species. Females have less occlusal surface area than expected on the basis of the male tooth and body size regression in 21% of the species, and there is no correlation between relative female tooth size and relative newborn size across higher primate taxa. The degree of female dental enlargement is most closely related to degree of sexual dimorphism in body weight. The correlation between degree of body weight dimorphism and relatively larger postcanine teeth in females than in males is 0.87 in the 38 species. Species that are monomorphic in weight tend to be monomorphic in tooth size even though females apparently require more food than males.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2003

Developmentally regulated expression of Netrin-1 and -3 in the embryonic mouse molar tooth germ.

The Netrins form a small, conserved family of laminin-related signaling proteins regulating axon guidance in the developing nervous system. Here, we analyzed the roles of Netrin-1 and -3 in trigeminal axon guidance to the first lower molar of the embryonic mouse. Netrin-1 showed a restricted epithelial expression domain buccal to the tooth germ, toward which the pioneer tooth axons initially appear to navigate. Later, before birth, transcripts were colocalized with nerve fibers around the bell stage tooth germ. Analysis of Netrin-1-deficient mice, however, did not reveal any obvious disturbances in the axon growth or pattern of tooth innervation. In contrast, Netrin-3 showed a prominent, distinct expression in the axon pathway and target field mesenchyme around the tooth. Hence, it is possible that Netrin-3 may regulate pioneer axon growth toward and within the embryonic tooth target field.

Animals↗

PubMed1990

Influence of colchicine on the addition of a sugar to the enamel protein in secretory ameloblasts of cultured germs of rat molar tooth by 3H-galactose radioautography.

The influence of colchicine on the addition of 3H-galactose to the enamel protein in secretory ameloblasts of cultured germs of rat molar tooth was investigated by light- and electron-microscopic radioautography. In tooth germs cultured without colchicine, the reaction products of 3H-galactose were observed over Golgi cisternae at early chase times and then localized over the enamel with time. In tooth germs cultured with colchicine, the silver grains were seen over the Golgi cisternae, condensing granules and accumulated secretory granules. Some grains also appeared with time over the pale granular material precipitated in the intercellular space with colchicine treatment. In quantitative analysis with light microscopic radioautography, values of silver grain counts over the unit area (100 microns2) on ameloblasts and enamel of colchicine-treated tooth germs were significantly lower at both 0 min and 30 min chase after 30 min pulse than those of control tooth germs, respectively. This finding indicates that colchicine diminished the incorporation of 3H-galactose into the secretory ameloblast of cultured tooth germs. It is suggested that colchicine decreases the activity of the Golgi apparatus with regard to the addition of sugar to the synthesizing glycoprotein in the secretory ameloblast.

Ameloblasts↗

PubMed1990

Histochemical demonstration of neural carbonic anhydrase activity within the mandibular molar and incisor tooth pulps of the rat.

Carbonic anhydrase (CA) activity was enzyme histochemically assessed in: (1) neuronal cell bodies in the rat trigeminal ganglion that were retrogradely labeled with FITC-WGA from the mandibular molar and incisor tooth pulps; (2) cell bodies retrogradely labeled with HRP-WGA from the mandibular molar tooth pulp; and (3) nerve fibers within the decalcified mandibular molar and incisor tooth pulps. The cell size spectrum of the FITC-WGA-labeled neurons was similar for both molar and incisor tooth pulps with about 90% being medium or large (greater than or equal to 300 microns2 in cross-sectional area). About 30% of the FITC-WGA-labeled cell bodies exhibited CA activity for both tooth pulps. The HRP-WGA-labeled cells also showed CA activity. In the molar root pulp, finely myelinated nerve fibers exhibited CA activity. Histochemical reaction products were distributed in the axoplasm and the cytoplasmic pocket of Schwann cell inside the compact myelin. In the incisor pulp, CA-reactive unmyelinated axons coexisted with non-reactive axons within the same Schwann units. The Schwann cell cytoplasm directly surrounding reactive axons also exhibited histochemical stainability. In the light of known distribution of CA in the peripheral nervous system, the present data suggest that the rat molar and incisor tooth pulps receive substantial innervation of large myelinated primary afferent fibers. The finely myelinated and unmyelinated axons, that have been repeatedly shown to predominate the intrapulpal nerve fibers, are considered to represent intrapulpal, terminal and preterminal specialization of otherwise large myelinated nerve fibers.

Animals↗

PubMed1986

Tooth pulp-evoked jaw-opening reflex in the cat: evidence for central facilitation induced by noxious discharge in the intradental nerve fibers.

The tooth pulp-evoked jaw-opening reflex was studied in the barbiturate-anesthetized cat. At liminal intensity of the stimulus, a stable short-latency response was obtained in the digastricus and in the tongue. At a higher stimulus intensity, there occasionally appeared to be a prolonged discharge of variable duration in the digastricus, and a second period of activity in the tongue after a silent period. The threshold intensity for these late discharges was supraliminal for the intradental A-fibers and subliminal for intradental C-fibers. Noxious conditioning stimulation of a tooth led to a temporary decrease of the threshold for the jaw-opening reflex elicited from a contralateral or adjacent tooth; only conditioning stimulation at an intensity producing a marked arousal reaction was effective in this respect. Infiltration of the tooth apex with epinephrine produced a local elevation of the threshold for the tooth pulp-evoked jaw-opening reflex. Distant noxious conditioning stimulation (tail pinch) did not influence the jaw-opening threshold. The results indicated that based on some central mechanisms, conditioning noxious stimulation of a tooth can produce a facilitation of the jaw-opening reflex.

Animals↗

PubMed1994

Tooth stiffness with composite veneers: a strain gauge and finite element evaluation.

OBJECTIVES: This study was conducted to determine the impact of composite veneer procedures on the functional properties of incisors. METHODS: Ten extracted human maxillary central incisors were mounted in pairs in a nylon ring. One strain gauge was bonded along the long axis of each tooth on the center of the lingual surface. Each pair formed half of a Wheatstone bridge circuit and was wired to eliminate all but the voltage resulting from experimentally applied procedures. The teeth were ramp-loaded to 50 N near the incisal edge on the lingual surface. Loading was performed on the unaltered teeth, teeth with preparations and restored teeth. Two-dimensional finite element (FE) models were generated to evaluate each test condition. Relative stiffness, compared with the unaltered tooth, was calculated from measurements with the strain gauge steps and from the FE models. RESULTS: A relative stiffness value of unity represents recovery of stiffness to the level of the unaltered tooth. Both methods of evaluation demonstrated a decrease in mean relative stiffness with each subsequent reduction in tooth structure. The composite restoration increased its mean relative stiffness compared to its corresponding preparation but never to the level of the unaltered tooth. Across all procedures, the two-dimensional FE model correlated well in both direction and magnitude with the experimental strain gauge method (R = 0.83). SIGNIFICANCE: A resin composite veneer does not restore the stiffness to the level of an unaltered tooth.

Analysis of Variance↗

PubMed1982

Cortical responses evoked by tooth pulp stimulation in the cat. Surface and intracortical responses.

In lightly chloralose-anaesthetized cats selective stimulation of tooth pulp afferents elicited responses in coronal, anterior suprasylvian and adjacent cortical gyri. In the lateral part of coronal gyrus the potentials evoked from the contralateral canine tooth pulps were initially positive. Such responses from the upper and lower teeth had different cortical distribution suggesting a topographical organization. In the regions adjacent to those with initially positive responses stimulation of the same tooth pulp evoked initially negative potentials. Stimulation of ipsilateral tooth pulp afferents elicited almost exclusively initially negative potentials with a similar distribution as the responses of contralateral teeth but with longer latency. Laminar analysis showed that the region with initial positivity in the response to stimulation of the tooth pulp coincided with an intracortical negative focal potential of maximum amplitude mainly in lamina IV. In areas with initially negative responses the maximum of the focal potential following tooth pulp stimulation was obtained in superficial cortical layers. It is postulated that the projection system underlying the initially positive cortical responses has a topographically arranged cortical projection terminating mainly in lamina IV. The projection system eliciting the initially negative potentials, has a widespread cortical distribution and produces excitation predominantly in the superficial laminae.

Afferent Pathways↗

PubMed2006

Evaluation of the biomechanical behavior of maxillary central incisors restored by means of endocrowns compared to a natural tooth: a 3D static linear finite elements analysis.

OBJECTIVE: The present study aimed at evaluating different restoring configurations of a crownless maxillary central incisor, in order to compare the biomechanical behavior of the restored tooth with that of a sound tooth. MATERIALS AND METHODS: A 3D FE model of a maxillary central incisor is presented. An arbitrary static force of 10 N was applied with an angulation of 125 degrees to the tooth longitudinal axis at level of the palatal surface of the crown. Different material configurations were tested: composite, syntered alumina, feldspathic ceramic endocrowns and glass post resorations with syntered alumina and feldspathic ceramic crown. RESULTS: High modulus materials used for the restoration strongly alter the natural biomechanical behavior of the tooth. Critical areas of high stress concentration are the restoration-cement-dentin interface both in the root canal and on the buccal and lingual aspects of the tooth-restoration interface. Materials with mechanical properties underposable to that of dentin or enamel improve the biomechanical behavior of the restored tooth reducing the areas of high stress concentration. SIGNIFICANCE: The use of endocrown restorations present the advantage of reducing the interfaces of the restorative system. The choice of the restorative materials should be carefully evaluated. Materials with mechanical properties similar to those of sound teeth improve the reliability of the restoartive system.

Aluminum Oxide↗

PubMed2005

Influence of tooth resection in piglets on welfare and performance.

In six commercial pig farms, we compared the effects of two methods of tooth resection (tooth clipping with pliers and tooth grinding with a rotating grindstone) on teeth themselves, on skin lesions of piglets and of sow udders as well as on litter growth and survival. An intact group was included for control. Treatments were balanced within herds with sows assigned to one of the three experimental treatments. Observations were from 107 sows and their litters (n = 35 or 36 litters/group) at farrowing (day 0) and approximately 8, 15 and 27 days later. Tooth resection was done within 24 h of birth after cross-fostering. Data concerning sows' lesions were analyzed on a farm basis and those concerning piglets' mortality, growth and skin lesions were analyzed on a litter basis. Frequency and severity of udder lesions differed between treatments at farrowing and on day 8; differences depended on the location of the teats (front, median or rear). Litter size and liveweight of piglets on day 0 (11.9+/-0.1 pigs, 1.51+/-0.03 kg) and on day 27 (10.8+/-0.1 pigs, 8.08+/-0.10 kg) were similar in the three groups (mean+/-S.E.M., n = 107). Skin lesions on piglets were more frequent and/or severe in intact than in clipped piglets on days 8 and 27, whereas ground piglets had intermediate results. Because the length of the teeth was similar after clipping and grinding (P > 0.1), tooth shortening itself does not explain the differences between treatments. Overall, tooth resection had very little effect on sow mammary injuries and litter performance. It might reduce skin damage to piglets (especially, when it is performed by clipping) but teeth are severely injured.

Animals↗

PubMed1997

Conditions for excitatory or inhibitory masseteric reflexes elicited by tooth pressure in man.

The reflex responses evoked by slowly rising pressure "push' stimuli to an upper lateral incisor tooth in human masseter muscle were studied. Factors such as the preload (the static force applied to the tooth by the stimulus probe before the start of the push stimulus) and the shape of the stimulus wave affected the outcome of the reflex response. When the stimulating probe did not apply preload to the tooth before the push stimulus took place, the force profile exhibited a large fast component as the probe took up the 'slack' in the periodontium. The fast component in the force profile was found to be responsible for inducing the inhibitory reflex (sole inhibitory reflex). When preload was applied, the size of the fast component in the force profile was reduced and the change in force rate became slower and smoother. This slower stimulus profile induced the sole excitatory reflex significantly more often (58% vs 21%) and the sole inhibitory reflex significantly less often (15% vs 52%) than in the experiments that used no preload. The shape of the stimulus wave that drove the stimulus probe was also of importance. Provided that a 0.5-N preload was applied to the tooth, the smoothest stimulus wave induced the sole excitatory reflex most often. Fitting a rubber attachment to the up of the probe made the push-force profile even smoother and thence more successful in inducing the sole excitatory reflex. Furthermore, the rubber tip reduced the possibility of the probe slipping off the tooth due to small and unavoidable movements of the participant's head. It is concluded that the periodontal mechanoreceptors can induce both excitatory and inhibitory reflexes on the jaw closers. The excitatory reflex becomes dominant when a smooth force is applied with preload. The inhibitory reflex becomes dominant when fast-force changes are applied on the tooth and/or no preload is used.

Adult↗

PubMed2001

Temporal and spatial distribution of Fos protein in the parabrachial nucleus neurons during experimental tooth movement of the rat molar.

The present study was undertaken to reveal spatio-temporal changes in the distribution of Fos-like immunoreactive (-IR) neurons in the parabrachial nucleus (PBN), one of the important relay nuclei for processing autonomic and somatosensory information from the oro-facial regions, following the induction of experimental tooth movement in rat upper molars. The experimental tooth movement was induced by the insertion of elastic rubber between the first and second upper molars. In normal animals, the PBN contained a smaller number of Fos-IR neurons. Following experimental tooth movement, the Fos-IR neurons increased in number significantly on both the ipsilateral and contralateral PBN, reaching a maximum at 4 h (about 10 times that of normal animals), and then decreased gradually. However, a significant number of Fos-IR neurons remained at 24 h post-operation. Remarkable side-by-side differences in the number of Fos-IR neurons were recognized at 1 to 4 h following the experimental tooth movement. Their number returned to normal (basal) levels at 5 days post. All subnuclei of PBN showed similar temporal changes in the number of Fos-IR neurons, this being particularly apparent in lateral PBN. Administrations of morphine (3 and 10 mg/kg, i.p.) drastically reduced the induction of Fos-IR neurons in all subnuclei of both the ipsilateral and contralateral PBN in a dose-dependent manner, and its effect was antagonized by pretreatment with naloxone (2 mg/kg, i.p.). The reduction of Fos-IR neurons by morphine pretreatment suggests that the appearance of Fos-IR neurons in the PBN may be partly due to the noxious stimulation and/or stress arising from tooth movement. The bilateral expression of Fos-IR neurons in the PBN indicates that the experimental tooth movement causes the activation of PBN neurons for the processing of somatosensory as well as autonomic information. The prolonged expression of Fos-IR neurons in all the subnuclei of bilateral PBN reflects clinical features of the transient discomfort and/or abnormal sensations, which many patients often complain about during orthodontic treatment.

Afferent Pathways↗

PubMed1987

Tooth loss among Nigerians: causes and pattern of mortality.

A study was carried out to elucidate the causes and pattern of loss of permanent teeth among Nigerians. A total of 3,163 dental extractions were carried out on 2,100 patients thus giving a ratio of 1.5 extractions per patient. The investigation revealed two major causes of tooth loss, i.e. periodontal disease (46.4%) and dental caries (43.9%). Other important aetiologic factors were trauma (4.5%), tooth impaction (2.4%) and orthodontic problem (1.6%). There was evidence to confirm fears by previous researchers that dental caries as a major cause of tooth mortality was increasing fast and could soon become the most important cause of tooth loss if not controlled. The study further showed that tooth mortality among Nigerians could be minimized if appropriate steps were taken immediately to control periodontal disease and dental caries, both of which constitute approximately 90% of all the causes of tooth loss.

Adolescent↗

PubMed1981

Function of the mandibular tooth comb in living and extinct mammals.

Among the most interesting mammalian dental specialization is the mandibular 'tooth comb' or 'tooth scraper' that evolved independently in certain primates and other mammals. Its occurrence is most widely known in lemurs and lorises, where it is comprised of the long, slender, procumbent incisors (one or two pairs) and incisiform canines (Fig. 1). In non-primates to canines are not incorporated into the comb. Some tree shrews (Tupaiidae) possess a tooth comb consisting of the four central incisors, and some early Tertiary arctocyonid condylarths had a similar structure composed of all six lower incisors. The extant flying lemurs (Dermoptera: Cynocephalus) also have a dental 'comb' but it is very different from the ones already mentioned, consisting of two pairs of pectinate incisors, each tooth modified into a comb with as many as 15 tines. This condition, although sometimes said to be similar to that in lemurs, is unique to Cynocephalus. One of the principal functions of the tooth comb in primates is to comb the fur, and we present here indirect evidence that condylarths used this structure in the same way, millions of years before tooth combs evolved in prosimians. We also show that the comb-like incisors of Cynocephalus, contrary to popular belief, probably do not function to comb the fur.

Animals↗

PubMed2003

Bolton anterior tooth size discrepancies among different malocclusion groups.

Orthodontic treatment comprises different phases with unique characteristics and challenges. The orthodontic "finishing" phase is recognized for the multitude of details necessary to achieve an excellent result. In some cases, the finishing phase is very difficult, requiring the production of complicated biomechanical forces to reach a satisfactory orthodontic solution. A high percentage of these finishing-phase difficulties arise because of tooth size imbalances that could have been detected and considered during initial diagnosis and treatment planning. The present study aimed to investigate the correlation between anterior tooth size discrepancies and Angle's Class I, II, and III malocclusions, as well as their prevalence in the Brazilian population from Belo Horizonte. We assessed the mesiodistal width of six anterior teeth in 300 patients, who were selected randomly. These patients were allocated to three groups according to their malocclusion. A chi-square test was performed to statistically compare the prevalence of anterior tooth size discrepancies among the three malocclusion groups and two genders. Analysis of variance was used to compare the mean Bolton anterior tooth size ratios as a function of Angle classification and gender. Statistical differences were determined at the 95% confidence level (P < .05). The important conclusions of our study are as follows: (1) Individuals with Angle Class I and Class III malocclusions show significantly greater prevalence of tooth size discrepancies than do individuals with Class II malocclusions; and (2) Mean anterior tooth size discrepancy for Angle Class III subjects was significantly greater than for Class I and Class II subjects.

Analysis of Variance↗