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The arrested development of a permanent tooth as a sequela to a periradicular infection in a primary predecessor is a rare occurrence. A case is presented where temporary arrest of root development occurred in a premolar of a child with hypodontia and extensive caries. The aetiology, management and outcome are discussed.

Objectives: To explore the relationship between mandibular dental maturation and the pattern of jaw innervation., Setting and Sample Population: The sample included 365 panoramic radiographs taken in the period 1965-1969 in a Danish municipality., Design: For assessing dental maturity, the seven left mandibular teeth (M2, M1, P2, P1, C, I2, I1) were given a dental maturity score according to a method introduced by Demirjian. Spearman correlation coefficients between the maturity score of an index tooth (one of each teeth) and the maturity score of the 6 other teeth was calculated and illustrated., Results: All the correlation coefficients were larger than 0.5 indicating a rather high level of association between the development of mandibular teeth in the same individual. Thus, associations between the pattern of dental maturation and jaw innervation were not obvious., Conclusion: When the correlation between the dental maturity stages was analysed, no significant relation was found between dental maturation and jaw innervation in the mandible. This is interesting considering the results presented in a recent study, which showed that the clinical observed tooth eruption was closely related to the pattern of jaw innervation. Those authors suggested that the factors influencing the eruption might be associated with jaw innervation. In our study, the stepwise dental maturation process, however, is not equally associated with jaw innervation.

Delayed odontogenesis of a lower second premolar is presented in a case treated without extraction and focuses on the 7-year follow-up of the delayed tooth bud. The follow-up was initiated when the crown formation was diagnosed and was finished when the tooth erupted completely into the orthodontically provided space, which enabled the orthodontic leveling and alignment of the delayed premolar. The long follow-up indicates that delayed tooth buds may develop completely and normally.

In the early developmental stage of the mandibular second premolar (MnP2), it is not unusual to find the tooth extremely angulated to the lower border of the mandible, as seen in the panoramic roentgenogram. On eruption, the tooth, in most cases, is close to being upright. However, impaction or other types of malocclusions due to its ectopic eruption are not rare. This study follows the angular changes of the MnP2 during development. Two hundred two panoramic roentgenograms of 101 patients were retrospectively analyzed. All patients had two sequential films with a minimal time interval of nine months. Each MnP2 was traced, and its developmental stage as well as its angulation to the lower border of the mandible was registered. We found that normally more MnP2 are distally (56.5%) than mesially (25%) inclined. There is a statistically significant difference in the inclination of the teeth during their development from stage D to stage F (D = 75.17 degrees +/- 15.25 degrees, E = 79.35 degrees +/- 12.18 degrees, F = 83.38 degrees +/- 10.79 degrees). The average amount of total angular change rate of the MnP2s from stage D to stage G is 0.09 +/- 0.25 degrees/mo, and the absolute angular change rate is 0.19 +/- 0.25 degrees/mo.

The survival rate of replanted and autotransplanted teeth is mainly affected by the reaction of the pulp. Pulpal necrosis can cause periapical inflammation and inflammatory root resorption. The purpose of this study is to learn more about the pulpal changes in autotransplanted immature teeth whose pulp tissue was removed before transplantation. The experimental material consisted of 16 single-rooted teeth with open apices, from a beagle dog (3 months of age). At day 0, 4 teeth were extracted, the pulpal tissues were removed, and the teeth were then transplanted to their contralateral side. The same procedure was carried out on days 9, 16, and 23, each time for 4 single-rooted teeth. Longitudinal paraffin sections were made for histologic investigation. The results showed that, after 7 days, 2 of the 4 teeth had an ingrowth of new tissue over one fourth of their length. After 14 days, all 4 teeth had ingrowth (> or =one fourth of the pulp chamber). At the 21-day observation, more than half of the pulp chambers of all teeth were filled, and, after 30 days, there was total ingrowth in 3 of the 4 teeth. This new tissue consisted of well-organized and well-vascularized connective tissue.

This study focused on five unusual cases with anomalous eruptions of the maxillary second premolars that related to late development of the germs. In four cases, the affected premolars erupted between the ages of 12y3m and 14y6m. In one case, which was suspected to include bilateral anomalies, the eruption of the premolar was excessively late, continuing up to 17y8m old. It was surmised that the degree of tooth formation in the contralateral side might help to predict approximately at what age the late premolars will erupt.

We have studied the correlation between the level of D-aspartic acid in dentin and the period of dentin formation in different types of teeth from the same individual. Except for the third molar, it is generally agreed that the formation of permanent dentin follows the pattern of growth, occurring earliest in the first molar and last in the second molar. In middle-aged individuals, racemization among the different types of teeth was highest in the first molar, corresponding to the earliest period of dentin formation. In elderly individuals, however, racemization tended to be highest in the second molar, in which dentin is formed last during growth. It is assumed that this may be due to the higher ambient temperature of the second molars, which are located deeper in the oral cavity. Thus, these results suggest that in elderly individuals racemization in teeth that have been situated deep in the oral cavity for a long time is more influenced by the environment than by the period of tooth formation.

Aim: The aims of this study were to: (i) investigate the effects of Ledermix paste as an intracanal medicament on discolouration of immature teeth, (ii) examine whether the discolouring effects were related to the method of application, (iii) examine the effects of sunlight upon discolouration of immature teeth and (iv) compare the degree of discolouration between mature and immature teeth., Methodology: The root canals of 45 immature extracted human teeth were prepared and filled with either Ledermix paste, calcium hydroxide [Ca(OH)2], or saline. In group 1, Ledermix paste was only placed apical to the cemento-enamel junction (CEJ) whilst in groups 2 and 3, the paste filled the entire pulp chamber and the root canals. In group 4, Ca(OH)2 paste and in group 5, saline (control) were allowed to fill the pulp chamber and the root canals. Group 3 teeth were kept in the dark and the other groups were exposed to daylight for 12 weeks., Results: After 12 weeks, sunlight exposure had caused dark grey-brown staining in the Ledermix groups but this did not occur when the teeth were kept in the dark. More severe staining was noted when Ledermix paste filled the pulp chamber than when the paste was restricted to below the CEJ and when teeth were exposed to sunlight. When compared to the results of a similar study using mature teeth, the results were similar but the immature teeth were more severely stained than the mature teeth. The Ca(OH)2 paste caused an increase in lightness and yellowness in immature teeth., Conclusion: It was concluded that Ledermix paste may cause discolouration of immature teeth. Such effects can be minimized if placement of the paste is restricted to below the gingival margin. Clinicians should ensure that Ledermix paste is not left on the walls of access cavities, especially in immature teeth.

Tomes' granular layer is the hypomineralized area of radicular dentin, but knowledge concerning it is limited. The present study was designed to investigate the structural characteristics of Tomes' granular layer in the dog's teeth by confocal microscopy. Permanent premolars of four beagles, two at 7 months and the other two at 14 months of age, were used for observation. During premolar root formation, the 7-month-old dogs were injected with calcein and alizarin red S for vital staining of dentin, and ground sections of the teeth were prepared. Both ground and decalcified-paraffin sections were made from the teeth of the 14-month-old dogs and stained with basic fuchsin or with hematoxylin and eosin. All sections were examined by fluorescence and confocal microscopy. In the ground sections, granules of Tomes' layer and dentinal tubules were stained with basic fuchsin and with calcein. The granules of Tomes' layer stained with calcein were seen only near the labeling lines by calcein. The granules of Tomes' layer appeared as bright spots in cross sections, and as lines in longitudinal sections. When the sections were cut tangentially through the surface of dentin, the granules of Tomes' layer showed a reticular structure. Most of the dentinal tubules were seen to pass between the granules and terminated in the dentin-cementum junction. Looped tubules were not found in this area. In the paraffin sections stained with hematoxylin and eosin, extracellular matrix of dentin showed fluorescence of various intensities and dentinal tubules appeared dark. At the surface of the radicular dentin, the granules of Tomes' layer appeared as fluorescent fibers running parallel to the surface of dentin in the longitudinal sections. The fibers appeared as bright spots in the cross sections and as a mesh in the tangential sections. In the periodontal ligament, collagen fibers showed intense fluorescence, whereas most cells were negative. From these results we conclude that Tomes' granular layer of dog's teeth may be the collagen fiber bundles that remained uncalcified or hypocalcified within the radicular dentin.

A new technique was developed making it possible to visualize changes that take place after premolar transplantation. Three sequential radiographs from a series of standardized control examinations were digitized and registered to the first radiograph in the series using subtraction technique. The digitized radiographs were then transformed into monochromatic images: red, blue, and green. After correction of gray level and contrast, the three radiographs were superimposed. All details that were common in the radiographs were then displayed in black-and-white. Details that were different appeared in color. Red and blue combines into magenta, blue and green into cyan, and green and red into yellow. A procedure was developed to create color-coded radiographs according to the above. The procedure was applied to cases that had been treated by premolar transplantation. The color coding offers the possibility to identify any radiographic changes that take place over time, eg, growth, apposition or resorption of bone, and progression or regression of pathological processes.

Three hundred and sixty rhesus macaque specimens at the Caribbean Primate Research Center were examined for evidence of linear enamel hypoplasia (LEH). A previously unreported intertooth pattern in LEH was observed. Defects occur preferentially on the sectorial premolar of both males and females. Relative to other teeth, the sectorial premolar exhibits more prominent defects and is more likely to exhibit multiple defects. This pattern is unlike the human intertooth LEH pattern and unlike patterns previously reported for monkeys and apes. These observations are discussed in the context of factors thought to influence the intertooth distribution of LEH in humans and in nonhuman primates. The authors reject crown height, the timing of crown development, and the duration of crown formation as factors contributing to the observed pattern and favor an explanation involving enamel thickness, perikymata spacing, and/or prism orientation.

Equine practitioners should be knowledgeable of dental anatomy and development to enhance their skill of age estimation of horses. The permanent teeth of horses are continually undergoing changes in shape and appearance. These changes may be used to suggest a reasonable age range for a horse.

This study describes dental development within the ferret, Mustela putorius, through study of the form of the carnassial teeth and the upper first molar at progressive growth stages. Primordial teeth were serially sectioned in sagittal and transverse planes and three-dimensional reconstructions of tooth primordia were generated using MacReco software. Regional growth of the crown and asynchronous maturation of the dental tissues were observed in each tooth. The upper carnassial blade develops early and the tooth increases in length rapidly. Lingual growth of the upper carnassial is less pronounced and the protocone and its surrounding region mature late. The lower carnassial blade develops early and the talonid is late to mature. Development of the upper first molar differs from carnassial development in the early emphasis upon transverse growth and reduced lengthwise expansion. The early development of the carnassial blades in the ferret is shared with other carnivores, and may reflect the functional significance of this feature. Later stages of tooth ontogeny differ among carnivoran taxa and the specialized morphology of ferret teeth results from an apparently truncated period of late tooth ontogeny. This suggests that carnivoran species may share a common path of early development that specifies the ontogeny of homologous tooth features and that in later stages developmental differences result in species-specific tooth forms.

The amount of sclerotic root dentine increases with age, proceeding from the apex towards the crown. There are obvious optical changes in the tissue, which becomes translucent (dentine is normally opaque). Therefore, the sclerosis of root dentine could be a reliable indicator of age in anthropological studies of human remains. We studied the histological aspects of sclerotic dentine in longitudinal thin sections (70-140 microns) of undecalcified premolars, cut in the bucco-lingual plane. To quantify the sclerosis and to construct a reference standard, we sectioned 85 premolars from subjects of known age (70 from odontological extractions and 15 from a university collection). Another 10 teeth from medieval subjects were studied to assess the applicability of the method to ancient skeletal collections. The technique consists of embedding the tooth in a polyester resin (cold method), sectioning it with a diamond blade microtome. Qualitative analysis was performed with polarized light microscopy and measurements were made with a quote 2D x,y viewer and on digital images. The sclerotic root dentine was quantified with both linear and surface area parameters in order to assess the correlation with age. The quality of the sections was sufficient for the clear discernment and quantification of the sclerotic dentine. Indeed, the technique allowed us to obtain good results with a considerable saving of time and money compared with other dental histological techniques. The best correlation with age was obtained from the surface area parameter, particularly after exclusion of the cementum and pulp chamber. To produce comparable data from similar studies, we advise the use of cold resins, as used here, and digital computerized analyzers because of their accuracy, precision and quickness. The qualitative analysis of the ancient teeth indications that this dental aging techniques can be applied to both recent and ancient dental tissues.

One-hundred-and-eighteen premolars transplanted at a stage with 3/4 to 4/4 root development with an open apical foramen were followed using a standardized clinical and radiographic technique for signs of periodontal ligament healing, root development, and tooth eruption. Root growth was unimpeded in 26 per cent, impaired in 55 per cent, and arrested in 19 per cent. Eruption of transplants occurred at the time of periodontal and alveolar healing, and before any significant root growth. Furthermore, autotransplanted premolars created growth of the alveolar process along with the eruption process.

In order to explore the bony changes in the mandibular body during prefunctional intraosseous eruption of premolars, 18 dogs aged from 8 to 16 wk at the beginning of experimental period, were given two intraperitoneal injections of oxytetracycline (50 mg/kg and 35 mg/kg 2 wk later) and 2 wk later a final injection of Alizarin red S (70 mg/kg). Microradiographic and fluorescent light microscopy studies showed that changes of the alveolar bony crypt walls were influenced by the growing dental germs which they surrounded. The cervical volumetric reduction, which indicates the end of crown formation, induced the apposition of lamellar and then woven bone on the adjacent alveolar walls. Furthermore, with occlusal displacement of the dental crown, the space below the tooth was immediately filled with woven bone trabeculae and chondroid tissue. The same phenomenon was observed at the level of the alveolar base, when the speed of tooth eruption was greater than that of root growth. During premolar development, the changes in the dental germ produces accommodating changes in the adjacent alveolar bone walls, and mandibular transversal growth has the same characteristics as that of a growing diaphysis.

Although orthodontic repositioning of impacted teeth is widely used, the treatment has its limitations. Autotransplantation or intra-alveolar surgical repositioning of teeth is an alternative therapy that may be used in selected cases of desperate impactions, when orthodontic extrusion is unsuccessful or when orthodontic treatment is rejected by the patient. A case report is presented to stress both the indications and limitations of a modified technique of intra-alveolar surgical uprighting of impacted teeth.

New optical technology now allows for precise observation of erupting human premolars. Continuous overnight tracking of an erupting tooth with a video microscope system shows that eruption occurs almost exclusively during the early evening. During the day, slight intrusion is likely to occur. When Moiré magnification is used to provide extremely high resolution (0.05 micrometer), slight movements of the erupting tooth in concert with the arterial pulse can be observed, and a previously unknown cyclic movement with a period of 20 to 50 seconds is seen consistently. Rhythms in skeletal growth and tooth eruption suggest that treatment to influence jaw growth and move teeth may be most effective at specific times of the day.

Such observation was made possible by transmitting the image of a mobile ceramic ruling on the erupting maxillary second premolar to a video-microscope via a coaxial fibreoptic cable. The cable was inserted into a reference bar secured to the adjacent first molar and first premolar. The image of the ruling was superimposed with the image from a surveillance camera focused on the patient and continuously recorded on video-tape along with the participant's blood pressure, pulse rate, electromyographic activity and occlusal contact sounds. Overnight data from 12 individuals clearly revealed a circadian rhythm in eruption during the prefunctional spurt. On average, the maxillary second premolar erupted 41 microns during an 11-h overnight observation, with almost all the eruption occurring in the late evening from 8 p.m. to 1 a.m. After 1 a.m., eruption typically ceased, with a tendency for intrusion to occur until 7 a.m. Sleep increased the rate of eruption during the late evening, but did not influence the eruption rate during the early morning. Haemodynamic changes, including blood pressure and pulse rate, did not have a significant impact on the rhythm of eruption. The observed eruption rhythm is most probably caused by changing hormone levels and their effect on the periodontal ligament. The late-evening eruption of human premolars coincides with the late-evening secretion of growth hormone and thyroid hormone typically found in humans.

Background: Cementum continues to be the least-known mineralized tissue. Although recent advances in the field of molecular biology have contributed to an understanding of the involvement of molecular factors in cementum formation during development and regeneration, cementogenesis on a cell biological basis is still poorly understood. Virtually nothing is known about cementoblast origin, differentiation, and the cell dynamics during normal development, repair, and regeneration. This review describes the recent findings of cementogenesis on roots of human premolars and opposes them to those of teeth from other mammals, particularly the rodent molar., Methods: Using light and electron microscopy, light microscopic radioautography, and various measurements, a comprehensive insight into the development and repair of cementum during and after root formation and tooth eruption has been achieved for human premolars., Results: Cementum is a highly responsive mineralized tissue. This biological activity is necessary for root integrity and for bringing and maintaining the tooth in its proper position. With regard to cementum formation and periodontal fiber attachment, considerable species-particularities exist that are mainly based on differences in growth rates and tooth sizes. Since root development and initial cementogenesis last on the average 5-7 years in human premolars, cementum formation in these teeth is characterized by along-lasting phase of prefunctional development, with occurs independent of principal periodontal fiber attachment to the root and which may take 5 years or more. The first molar of the rat, however, is in functional occlusion 3 1/2 weeks after the onset of root formation. Since initial cementum formation and periodontal fiber attachment to the root occur almost at the same time in this tooth, the distinction between cells associated with one or the other process is very difficult to achieve, and cementogenesis cannot be described independent of periodontal fiber attachment to the root. Therefore, the determination of cementoblast origin in the rodent molar may be intricate., Conclusions: Taking into account these species differences, the current description on the origin and differentiation of cementoblasts is inconsistent and the description of cementogenesis is still incomplete. This review calls into question the currently held concept of cementogenesis and offers a possible alternative.

A video microscope system, which can resolve tooth movements to 1 to 2 microns, was used to monitor the eruption of 17 human maxillary second premolars in the prefunctional phase. Eruptive movement was detected by the change in position of an optical ruling on the erupting tooth relative to a reference ruling on the occluding adjacent teeth. Eruption was observed as the teeth erupted toward the occlusal plane over approximately a 41-hour period, from late Friday afternoon until Sunday noon. Half hourly observations were made during a 6 to 8-hour continuous laboratory session, which was during the day (9 AM to 5 PM) for nine of the subjects, and during the evening (5 to 11 PM) for eight. A similar pattern of eruption was seen for all subjects. The tooth intruded from before to after dinner on the first day, erupted significantly overnight, ceased eruption and approximately maintained its position during the next day, and erupted again during the second night. On the average, a slight intrusion was observed during the day, and statistically significant intrusion was associated with breakfast and dinner. Eruption occurred during the evening observation period, and the rate of evening eruption was significantly greater in children who were supine and relaxed than those who were upright and active. The 24-hour eruption rate was slower for teeth that were within 1.5 mm of the occlusal plane. The circadian eruption rhythm may be related to fluctuations of hormonal levels that affect metabolic activities within the periodontal ligament. It is also possible that a transient reduction in pressures by the cheeks, lips, and tongue during periods of rest allows eruption to occur then.

On the basis of 147 panoramic radiographs of 49 patients, this study investigated the influence of the premature loss of deciduous teeth on the formation of their permanent successors at the time of their eruption. Furthermore the study investigated the eruptive movement of the successor teeth at the time of eruption. In addition to detecting the accelerated emergence of still immature successor premolars, the study also determined that the extraction ot the deciduous molars before the age of eight years delayed the eruption of the permanent successors given the absence of an infected deciduous tooth with abscess formation. In relation to the eruptive movement of the permanent molars due to the premature loss of the second deciduous molar, the study ascertained a mesial movement of the first permanent molars and an accelerated eruption of the second permanent molars.

The present study describes the dynamic process of both acellular extrinsic (AEFC) and acellular/cellular intrinsic fiber cementum (AIFC/CIFC) matrix production on growing human teeth. Selected erupting maxillary and mandibular premolars with roots grown to about 70%-95% of their final length were placed in organ culture immediately following extraction. Twelve teeth for short-time labeling were pulse-incubated for 15 min in medium containing 3H-proline and chased for various times in order to follow the migration and secretion of the tracer. Eight teeth for long-time incubation were labeled continuously for 5 h before being chased for 1-8 days in order to label cementum matrix accumulation. After decalcification in ethylene diaminetetraacetic acid (EDTA), their roots were subdivided into about 20 slices each. Epon-embedded sections were prepared for light- and electron-microscopic as well as autoradiographic examination. During CIFC-formation, cementoblasts revealed high intracytoplasmic silver grain concentrations within the first hour after 3H-proline administration. The release of the tracer occurred between 60 to 120 min after administration. After 2 h, cementoblasts and the cementum matrix appeared to be labeled about equally. After 5 h, most of the labeled proteins appeared to be localized in the cementoid. Silver grains increased in number over the cementum matrix from 5-24 h. Very high intracellular grain concentrations within very large cementoblasts corresponded to regions of rapid cementum formation. Tracer-halos around entrapped cells lend support to a multipolar mode of matrix production during CIFC-initiation. The fate of the tracer during the development of early AEFC-matrix was less clear. However, fibroblasts revealed dense intracytoplasmic grain accumulations within the first hour after 3H-proline administration. Thereafter, the tracer localization was vague. This indistinct grain localization reflected the particular mode of AEFC-matrix production characterized by addition of new fibril segments to pre-existing fibers of a collagenous fringe.

The present study describes for the first time the changes of both AEFC thickness and the numerical density of collagen fibers inserting into AEFC at specified levels and sites of human premolars at different stages of development. The investigation was based on 45 premolars (25 maxillary, 20 mandibular; 25 first and 20 second), extracted from adolescents and young adults. All teeth were free of disease and presented with roots developed from 30-100% of their final length. They were prefixed in Karnovsky's fixative, decalcified in EDTA and subdivided into about 14 slices each, cut from mesial and distal root surfaces, vertical to and along the root axis. The slices were postfixed in OsO4, embedded in Epon and cut for light-microscopic study. AEFC thickness (4086 measurements) and the density of the collagenous fiber fringe (454 counts) inserting in AEFC were measured at 1, 3, 5 and 7 mm apical to the cementoenamel junction. The data obtained showed: AEFC thickness increased with age and varied between 0 and 57.5 microns. Between 9 and 17 years, cervical AEFC thickness increased in maxillary first premolars from an average of 5 to 30 microns, and in mandibular second premolars from 6 to 20 microns, i.e., AEFC grew at approximately the same rate as later in life. Depending on the differences in tooth development, AEFC on maxillary first premolars became thicker than that on mandibular second premolars. Due to the corono-apically decreasing gradient of AEFC development, its increase in mid-root regions lagged behind that in cervical regions of all teeth in people younger than about 14 yr.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study describes the formative process of the initiation of cellular intrinsic fiber cementum (CIFC) in still growing human teeth. From 29 premolars and molars with incomplete roots developed to 60-90% of their final length, 8 premolars (with roots formed to three quarters of their final length) were selected for electron-microscopic investigation. All teeth were clinically intact and prefixed in Karnovsky's fixative immediately after extraction. Most of them were decalcified in ethylene diaminetetraacetic acid (EDTA), and the apical part of the roots was divided axially into mesial and distal portions that were subdivided in about 5 slices each. Following osmication and embedding in Epon, these blocks were cut for light- and electron-microscopic examination. In addition, 5 teeth with incomplete roots were freed from organic material and processed for scanning electron microscopy. It was found that CIFC-initiation commenced very close to the advancing root edge and resulted in a rapid cementum thickening. Thereafter, appositional growth continued on the already established cementum surface. Large, basophilic and rough endoplasmic reticulum-rich cementoblasts, some of which became cementocytes, were responsible for both fast and slow CIFC-formation. The CIFC-matrix was free of Sharpey's fibers and composed of more or less organized intrinsic collagen fibrils, in part fibril bundles, that ran roughly parallel to the root surface. Initially, the cementum fibrils intermingled with those of the dentinal collagen fibrils, which were not yet mineralized. This boundary subsequently underwent calcification. The development of collagen fibril bundles and their extracellular arrangement were associated with cytoplasmic processes probably involved in fibril formation and fibril assembly. Many cementoblasts contained intracytoplasmic, membrane-bounded collagen fibrils, which probably were related to fibril formation rather than degradation.

Delayed development of a bicuspid in the right premolar region of the mandible was observed radiographically in a 16-year-old male patient following surgical removal of a developing odontome. Whilst odontomes are commonly associated with a failure of eruption of permanent teeth, this case was unusual in that there was both failure and marked delay of adjacent permanent tooth germ development, suggesting that the odontome was associated with a regional disturbance of odontogenic tissues in the neonatal period.

Investigation was done with the purpose of establishing frequency of eruption and calcification of P2 and M2 and to perform a longitudinal analysis of certain types, observing the changes during growth, character of these changes and their durability. Analysis was done on 354 orthopantomographic radiographs of orthodontic patients from Nis, aged 7 to 12 years. Eruption phase was determined on the bases of vertical relation to M1 Development phase was determined with the help of a table with 11 developmental phases. Depending on tooth in predominance, patients were divided into three groups: P2M2, (P2M2) and M2P2. All three types of eruption and calcification were recorded. (P2M2) eruption is dominant in maxilla, while M2 has some advantage in mandible. In calcification of both jaws, type P2M2 is predominant in both sexes. In later age, eruption shows changes of type-in 31% to 39% of cases, but this percentage is lower in calcification-from 22% to 25%. Relation of P2 and M2 in eruption is not permanent and changes with growth: in maxilla, P2 has synchronous position in relation to M2 until 8 years of age, to gain advantage in later years; in mandible, P2 has lower position until 10 years of age, to start quicker growth in eleventh year so that in 42% of cases it erupts before M2. In development phase, P2 has advantage in both jaws. P2M2 type shows least changes with age. Other two types change into type P2M2 in 40% of cases. Once set sequence of eruption and calcification cannot be a reliable indicator of later growth since considerable changes were observed in most patients.

Postnatal development of the teeth of German Landrace and Göttingen Miniature pigs was studied by measuring the areas of each tooth visible on lateral radiographs of the mandibles. It was concluded that the appearance of the teeth at each stage, and the relation of their growth to that of the rest of the masticatory apparatus, relates mainly to postnatal changes in the relative location of the jaw pivot.

The purpose of this study is to observe and compare growth and development in the dental arch, the alveolar process, and the palate in reference to dental age, which is based on tooth emergence, and chronological age. Subjects consisted of serial dental casts taken at two-month intervals from 40 children (20 males and 20 females) with normal occlusion in permanent dentition. In terms of dental age, observations were made for a total of two years, one year before and one year after the tooth emergence of first premolar and second premolar. In terms of chronological age, observations were made for a total of two years, one year before and one year after the average age of tooth emergence of first premolars and second premolars in this sample of children. Results and Conclusions. Comparisons between growth changes in the dental arch, the alveolar process, and the palate on dental and chronological age showed some regions in which growth patterns were similar and others in which growth patterns were different. The differences between both growth patterns from two ages were classified into two groups according to the tooth which caused the difference: those produced by the tooth used as a standard for dental age and those produced by teeth other than that used as a dental-age standard. 1) Differences resulting from the influence of the tooth used as a dental-age standard In regions of the tooth used as a dental-age standard, differences occurred in growth patterns on both kinds of age in practically all measured items. In regions adjacent to that of the tooth used as a dental-age standard, the differences were observed in growth patterns of the alveolar process and the palate but not in those of the dental arch. The differences were the most pronounced in the regions of dental-age-standard teeth than in the adjacent regions. The majority of the differences caused by teeth used as standards for dental age were thought to have been the results from the influence of eruption. No growth-pattern differences were observable in regions more than two teeth away from the tooth used as a dental-age standard. 2) Differences resulting from the influences of teeth other than that used as a dental-age standard Using the emergence time of a certain tooth as a dental-age standard, the emergence times of other teeth lead to be come together in some degree.(ABSTRACT TRUNCATED AT 400 WORDS)

Dental developmental status of the permanent canines, premolars and second molars were studied in one hundred and two twelve-year-old Southern Chinese girls born and brought up in Hong Kong. Eruption of these teeth were defined as gingival emergence during the clinical examination while the root development was assessed from orthopantomographs. Root resorption pattern of the primary canines and molars were also studied with the aid of the orthopantomographs. Two-thirds of girls presented with permanent dentition stage. The root resorption patterns of the primary teeth were different from their order of exfoliation. The mandibular permanent teeth were in advanced in both eruption and root development than the corresponding maxillary teeth, except the first premolars.

The development and eruption of the mandibular cheek teeth of Cebus albifrons is described from a longitudinal series of whole body radiographs. Males are generally ahead of females in both development and eruption times. The dental development and eruption in C. albifrons is intermediate between the smaller New World primates and the larger catarrhines.

The thickness of the predentin layer was studied at three different levels of developing human premolars. The results demonstrate that at the growing end next to the apex, where dentinogenesis is most active, predentin exhibits its greatest thickness (mean value 40.4 micron). However, at the coronal region, where primary dentin has been completely formed, predentin width is reduced to a mean value of 14.8 micron. Changes in the calcospheritic configuration of the mineralization front were established for each of the predentin levels studied. A comparative analysis of these calcospheritic changes and the morphology of fluorescent tetracycline lines detected in ground sections of premolars was established. Fluorescent lines observed at the coronal circumpulpal dentin showed large calcospheritic forms beneath the mantle dentin. However, lines found near the dentin-pulp border showed small calcospherites. It is concluded that the thickness of the predentin layer and the mineralization front configuration vary as a function of dentinogenic activity during development of human premolars.

Radiographs were taken of both the right and left sets of maxillary teeth in 23 Friesian cattle of known age. The stage of development of each permanent tooth was ascertained and the degree of root resorption in the deciduous premolars was noted. All stages in individuals were later than for those of the mandibular cheek teeth except in the case of the first permanent premolar. As with mandibular cheek tooth development stages of formation occurred within certain age limits.

A total of 302 White and 904 Black children six, nine and 12 years of age were studied for the eruption of their permanent teeth. Differences between the two ethnic groups were not large, but the Black subjects were generally more precocious at the beginning of the process (especially the girls, both in the upper and lower incisors). At nine and 12 years of age, however, these dissimilarities disappear. The latter do not seem to be related to distinct rates of extraction or agenesis of deciduous teeth. No significant differences were observed in the degree of asymmetry present in the permanent dentition of the White and Black individuals studied.

Radiographic analysis of mandibular fragments of the Oligocene primates Apidium phiomense and Parapithecus grangeri provides sequences of postincisor development and eruption. Although retaining the premolar eruption sequence (P2 leads to P4 leads to P3), the parapithecids possessed the derived feature of delayed canine appearance which, with other characters of cranial and postcranial morphology, aligns them with Anthropoidea and not Prosimii or platyrrhines.

The development of premolar tooth germs in dogs, particularly their rotation and crowding, was examined on radiographs, dissected specimens of tooth germs, serial sections stained by Masson-Goldner's technique and reconstructed models. The materials used were the mandibles of 32 puppies from birth to 6 months, and the species was a highly pedigreed Shiba Inu which has no crowding of the premolars in the mature stage. The results obtained are as follows. (1) Rotations and crowdings of premolars, similar to those in brachygnathus dogs and wolves raised in captivity, were observed during ontogenesis of dolichocephalic dogs, whose adult state exhibits no crowding of teeth. (2) The type of rotation was B (the mesial portion is rotated buccally) for the second and third premolars and L (the mesial portion lingually) for the fourth premolar. (3) The rotations of the premolars did not coincide with those of their deciduous predecessors. (4) These rotations appeared in the bud and cap stages of premolars, before the formation of roots of deciduous molars. The premolars developed crowding at 5 months when they increased in dimension.

Permanent maxillary canine teeth (C1) are appreciably larger in males than in females in most nonhominid Anthropoidea. Mandibular canines (C1) and mandibular first premolars (P3), against which C1 are sharpened in honing behavior, reflect commensurate sexual dimorphism. These three teeth constitute the canine dental complex. The canine complex crown metrics of seven mature genetically female rhesus Macaques, androgenized by prenatal exposure to testosterone propionate, were compared with a control sample (N = 12) for evidence of masculinization. The C1 and C1 were measured for clinical crown lengths (L) and mesiodistal and buccolingual widths. The functionally significant and highly dimorphic honing dimensions (HD), which approximate the honing surfaces of P3, were noted. In t-test comparisons, the C1 L and P3 HD in androgenized monkeys were significantly larger than those of the control group (P less than 0.05). Identical results were obtained with White's nonparametric ranking technique. Standardized lateral skull radiographs showing earlier dental formative stages were available for five of the seven animals, and these were compared with radiographs of control skulls. The developing C1 were longer and wider than in the controls. This was not reflected in the crown metrics of mature animals because of marked dental attrition. We concluded that androgens can masculinize the female rhesus canine complex, if given during critical periods of prenatal development. We hypothesize that genes encoding the male canine complex are normally activated by endogenous fetal androgens during such critical periods.

Using a light microscope, the authors compared 484 longitudinal ground sections of human premolars from a region where the drinking water contains 1.0 p.p.m. of fluorine withe 777 preparations from a region where the drinking water contains 0.35 p.p.m. of fluorine. Water fluoridation of fluorine supply during tooth development does not lead to a statistical significant change in the occurrence of interglobular dentine areas. Additional analyses justify at best the suspicion that teeth (and in particular female teeth) which developed under the influence of fluorine show a greater variability as to the occurrence of interglobular dentine areas.