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First Molars (first + molar)
Kinds of First Molars Selected AbstractsRHYTHMIC AND IRREGULAR MOVEMENT OF THE FIRST MOLAR WHILE EATING FOODS WITH DIFFERENT TEXTURESJOURNAL OF TEXTURE STUDIES, Issue 3 2000MICHIKO TOGASHI ABSTRACT The three-dimensional movement of a tooth, any tooth, while naturally eating, was measured by an apparatus developed in our laboratory. The movement of the first molar on the usually used side is reported here. The mastication movements are divided into two parts, namely the rhythmical chewing period during which there are mastication pressure loads on the molar and the irregularly pulsated moving period in preparation for the swallowing followed by the rhythmical one during which there is no more pressure on it. The amplitudes of the up and down movements of the molar are 10,22mm for the rhythmical chewing period which are bigger than those for the irregularly moving period. The rhythmical chewing periods are distributed around 10,40 s depending on 14 kinds of food texture, and also on the size of the food, in a fairly similar manner for the participants. The period is longer for tough foods and bigger samples. The irregularly pulsated moving periods are widely distributed, 2,45s, and depend both on the food texture and on the participant. The irregular moving periods are longer for foods which scatter in the mouth or adhere to the teeth when chewing. The ingestion difficulty of the food was divided into two groups. One is where it is difficult to break down the food with the teeth and the other is where it is difficult to prepare for swallowing. [source] Reduced growth hormone receptor immunoreactivity in osteoclasts adjacent to the erupting molar in the incisor-absent (osteopetrotic) ratEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2003Anne L. Symons First molars fail to erupt in the incisor-absent (ia/ia) rat because of a defect in osteoclast function. Growth factors that regulate local bone metabolism include growth hormone (GH), insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and interleukin-1 alpha (IL- 1,). Since osteoclast function may be affected by these factors, the aim of this study was to determine the distribution of GH receptor (GHr), IGF-I, EGF and IL-1,, in osteoclasts located occlusal to the erupting first molar, in the ,eruption pathway', in normal and ia/ia rats. Sagittal sections of the first molar and adjacent bone from 3- and 9-d-old animals were examined. Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP). The TRAP-positive osteoclast cell numbers were higher in ia/ia animals at 3 and 9 days-of-age. In the ia/ia group, fewer osteoclasts were GHr- and IGF-I-positive at 3 d of age, and at 9 d of age fewer osteoclasts were GHr-positive. In the ia/ia rat, defective osteoclast function failed to resorb bone to provide an eruption pathway for the lower first molar. The expression of GHr, and to some degree IGF-I, by these osteoclasts was reduced, which may be related to their ability to differentiate and function. [source] Scanning electron micrograph analysis of hypomineralized enamel in permanent first molarsINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 4 2005B. JÄLEVIK Summary. First molars with cream- to yellow-coloured demarcated opacities of the enamel, often in combination with severe loss of substance, are common in many child populations. The aetiology is obscure. Aim and Method., The aim of this study was to study the ultrastructure of the enamel of 10 affected teeth by means of scanning electron microscopy (SEM) in order to gain a better understanding of the clinical appearance and treatment problems of this condition, and to find some clues to its aetiology. Results., The basic enamel structure with enamel rods and interrod zones was found in porous parts of the enamel, as well as in normal parts, but the packing of the hydroxylapatite crystals seemed to be looser and less well organized in the porous parts. The border between normal and hypomineralized enamel was usually distinct, and followed the direction of the rods. The preserved basic structure indicates normal function of the ameloblasts during their secretion phase, but impaired function during their maturation stage. Conclusion., Considering the poor etch profile, it seems reasonable to recommend removal of all affected enamel surrounding the cavity, if possible, and to use a glass ionomer filling with its chemical bonding to tooth substrate, when restoring first molars with remaining affected enamel. [source] The three-dimension finite element analysis of stress in posterior tooth residual root restored with postcore crownDENTAL TRAUMATOLOGY, Issue 1 2010Gang Fu Some researchers have analyzed the stress of the anterior teeth after postcore crown restoration, but the stress of the posterior teeth after such restoration has not been reported. We used three-dimension finite element methods to analyze the stress magnitude and distribution of remaining dentin in posterior tooth residual root restored with postcore crown. The binding material, loading direction, number, length and material of posts were studied. Methods:, The models of residual root of maxillary first molar restored with postcore crown were created by CT scanning, mimics software and abaqus software. Different number, length and material of posts were used in the modeling. The posts were cemented with zinc-phosphate cement or composited resin. A load of 240 N was applied to the occlusal surface in four directions and tensile, shear, and von Mises stresses were calculated. Result:, (i) The maximum stress on remaining dentin changed irregularly as the number and length of posts changed. (ii) The maximum stress on remaining dentin decreased slightly as elastic modulus of the material of posts increased. (iii) The maximum stress on bonding layer and remaining dentin was lower when bonded with resin luting agent than with zinc-phosphate cement. (iv) The maximum stress on remaining dentin increased markedly as loading angle increased. Conclusion:, The number, length, material of posts, bonding material and loading angle all have influence on the magnitude and distribution of stress. The influence of loading angle is most apparent. [source] Analysis of 154 cases of teeth with cracksDENTAL TRAUMATOLOGY, Issue 3 2006Byoung-Duck Roh Abstract,,, It is well known that cracked teeth occur most frequently in the mandibular molars with large or poor restorations, in those over 50 years of age. However, with increasing knowledge and experience with cracks of teeth, cracks appear to be found frequently in intact teeth without restorations. The aim of this study is to analyze the cases of tooth cracks in a dental hospital in a year, and to find out the characteristic features of cracks of teeth. For 1 year, each tooth that were identified as a cracked tooth was recorded and analyzed in terms of the classification of cavity and restorative material, the nature of opposing tooth, the location in the arch, the age and gender, and the clinical signs and symptoms, and treatment result. Cracked teeth were observed most frequently in the teeth with no restorations (60.4%) and with class I restorations (29.2%). The most prevalent age was in those over 40 years of age (31.2% in their 40s, 26.6% in their 50s) and the prevalence was similar in men (53.9%) and women (46.1%). Cracked teeth were found most frequently in the maxillary molars (33.8% in first molar, 23.4% in second molar) than in the mandibular molars (20.1% in first molar, 16.2% in second molar). 96.1% of the cracked teeth responded to the bite test, and 81.1% of the cracked teeth were observed in the mesiodistal direction. The prevalence of cracked tooth was highest in the intact teeth with no restoration, in maxillary molars, and in those over 40 years of age. When examining a intact maxillary posterior tooth that is sensitive to a bite and thermal change, crack in the mesiodistal direction need to be considered one of the causes. [source] Reduced growth hormone receptor immunoreactivity in osteoclasts adjacent to the erupting molar in the incisor-absent (osteopetrotic) ratEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2003Anne L. Symons First molars fail to erupt in the incisor-absent (ia/ia) rat because of a defect in osteoclast function. Growth factors that regulate local bone metabolism include growth hormone (GH), insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and interleukin-1 alpha (IL- 1,). Since osteoclast function may be affected by these factors, the aim of this study was to determine the distribution of GH receptor (GHr), IGF-I, EGF and IL-1,, in osteoclasts located occlusal to the erupting first molar, in the ,eruption pathway', in normal and ia/ia rats. Sagittal sections of the first molar and adjacent bone from 3- and 9-d-old animals were examined. Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP). The TRAP-positive osteoclast cell numbers were higher in ia/ia animals at 3 and 9 days-of-age. In the ia/ia group, fewer osteoclasts were GHr- and IGF-I-positive at 3 d of age, and at 9 d of age fewer osteoclasts were GHr-positive. In the ia/ia rat, defective osteoclast function failed to resorb bone to provide an eruption pathway for the lower first molar. The expression of GHr, and to some degree IGF-I, by these osteoclasts was reduced, which may be related to their ability to differentiate and function. [source] Factors influencing proximal dental contact strengthsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2000Christof E. Dörfer The aim of this study was to systematically measure proximal contact strength in complete natural dentitions of 30 adults (25.3±3.0 years of age), and to analyze its relationship to tooth type, tooth location, chewing effort and time of day variation. The contact strengths were measured dynamically during removal of a calibrated 0.05-mm-thick metal strip between the proximal contacts of adjacent teeth. Proximal contact strengths were lower in the maxilla (2.51±1.36 N) compared to the mandible (4.26±1.88 N). Within the jaws, the lowest proximal contact strength was measured between canine and first premolar (2.91±1.79 N) and the highest between second premolar and first molar (3.73±1.95 N). Chewing increased the proximal contact strength within the maxilla (before: 2.51±1.36 N, after: 3.02±1.45 N) but it remained unchanged in the mandible (before: 4.26±1.88 N, after: 4.22±1.85 N). The proximal contact strength increased significantly from morning (3.39±1.86 N) to noon (3.61±1.77 N), and then decreased in the afternoon (3.43±1.60 N). It was concluded that proximal contact strength can be significantly influenced by location, tooth type, chewing and time of day variation. Based on the differences in distribution due to the effect of chewing and time of day, it is speculated that proximal contact strength is a physiological entity of multifactorial origin. [source] Original article: Effect of flask closure method and post-pressing time on the upper denture base adaptationGERODONTOLOGY, Issue 3 2010Andréa F. Lira doi:10.1111/j.1741-2358.2009.00307.x Effect of flask closure method and post-pressing time on the upper denture base adaptation Objectives:, The purpose of this study was to evaluate the effect of flask-closure methods, post-pressing times and acrylic resins on denture base adaptation. Materials and methods:, The resins were flasked using a hydraulic press and closed with the traditional clamp or RS system. Conventional heat-cure resin was polymerised immediately or at 6 h post-pressing at 74°C for 9 h. Rapid cycle heat-cure resin was polymerised in boiling water for 20 min. After cooling, the bases were deflasked and the sets of cast-base transversally sectioned in the regions distal to the canine, mesial to the first molar and in the posterior palatal zone. The adaptation was measured with an optical microscope (0.0005 mm) at five reference points for each section. Data were analysed using anova and Tukey's test (, = 0.05). Results:, Traditional clamp and immediate post-pressing time improved base adaptation for conventional heat-cure resin. Both post-pressing times showed most accurate base adaptation for conventional heat-cure resin when the traditional clamp was used. Immediate post-pressing time improved base adaptation for conventional heat-cure resin and the 6-h delay in time was significant for the rapid cycle heat-cure resin. Conclusions:, Traditional clamp and immediate post-pressing time improved base adaptation for conventional heat-cure resin. [source] Critical role of NFATc1 in periapical lesionsINTERNATIONAL ENDODONTIC JOURNAL, Issue 2 2010C. Zhang Zhang C, Yang L, Peng B. Critical role of NFATc1 in periapical lesions. International Endodontic Journal, 43, 109,114, 2010. Abstract Aim, To observe NFATc1 expression in experimental periapical lesions in rats. Methodology, Apical periodontitis was induced in Wistar rats by occlusal pulp exposure in mandibular first molar teeth. After exposure, 30 rats were killed on days 0, 7, 14, 21 and 28. The jaws that contained the first molar were removed and prepared for histological examination, immunohistochemistry and enzyme histochemistry. Results, From day 0 to day 28, the areas of periapical bone loss and the number of NFATc1-positive cells increased, peaking on day 28. The number of TRAP-positive cells increased substantially from day 0 to day 14 and then gradually decreased from day 14 to day 28. Conclusions, NFATc1 was detected and possibly involved in the inflammatory response and bone resorption of periapical tissues, as well as being associated with periapical lesion pathogenesis. [source] Investigation of the root canal configuration of mandibular first molars in a Taiwan Chinese populationINTERNATIONAL ENDODONTIC JOURNAL, Issue 11 2009G. Chen Abstract Aim, To investigate the root form and canal morphology of mandibular first molar teeth in a Taiwan Chinese population. Methodology, A total of 183 mandibular first molars were collected and examined visually through a dissecting microscope after rendering the teeth transparent. The number of roots, number of canals and canal configuration were recorded. The root canal morphology was categorized and compared according to Vertucci (1984). Results, Overall 46% of the mandibular first molars had four canals and 20% had extra-distal roots (distolingual root). In addition, 97% of the specimens had two mesial canals and 46% had two distal canals. In total, 68% of teeth with two mesial canals had two separated apical foramina, and 33% of teeth with two distal canals had two apical foramina. The most common canal configurations (Vertucci, 1984) of mesial roots were type 4 (46%) and type 2 (23%). Type 1 was encountered in 54% of the distal roots. Conclusions, The frequency of the extra-distal root on the mandibular first molar was 20%, and the incidence of three canals (Vertucci's type 8 classification) with separate apical foramina at the apex of the mesial root was 6%. The three-rooted variation of the mandibular first molar appears to be a genetic characteristic of an Asiatic racial background. [source] A six-canal maxillary first molar: case reportINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2002F. Maggiore No abstract is available for this article. [source] LPS-Induced Inhibition of Osteogenesis Is TNF-, Dependent in a Murine Tooth Extraction Model,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2009Nobuyoshi Tomomatsu Abstract TNF-, is a major etiologic factor of inflammatory bone diseases such as periodontitis and rheumatoid arthritis. In addition, patients with metabolic diseases such as chronic heart disease and diabetes have significantly increased plasma levels of TNF-,. Several lines of evidence show inhibition of osteoblastogenesis by TNF-, in vitro. Therefore, bone formation and osteogenesis in these patients might be inhibited because of TNF-,. However, little is known about the inhibitory role of TNF-, in bone formation/osteogenesis in vivo. The purpose of this study was to investigate the role of TNF-, in osteogenesis using a murine tooth extraction model. Lipopolysaccharide (LPS) was injected subcutaneously into the calvariae of either wildtype (WT) or TNF-,,deficient (KO) mice. The left incisor was extracted 4 days after LPS injection. The measuring area was established as the tooth socket under the mesial root of the first molar. A significant increase in serum TNF-, levels after LPS injection was observed in WT mice. The BMD of the tooth socket was significantly decreased by LPS injection 21 days after extraction in WT but not in KO mice. Histomorphometric analysis showed a significant decrease in the mineral apposition rate after LPS injection, which appeared at an early stage in WT but not in KO mice. Injection of a peptide that blocked the TNF-, signaling pathway by preventing transmission of the NF-,B signal recovered the inhibition of osteogenesis observed after LPS injection. In conclusion, TNF-, might play a major role in LPS-induced inhibition of osteogenesis under inflammatory conditions. [source] 5-aminoisoquinolin-1(2H)-one, a water-soluble poly (ADP-ribose) polymerase (PARP) inhibitor reduces the evolution of experimental periodontitis in ratsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2007Rosanna Di Paola Abstract Background: Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischaemia-reperfusion and inflammation. Recent studies have demonstrated that PARP activation plays a crucial role in the pathogenesis of acute periodontal injury. Aim: We have investigated the effect of 5-aminoisoquinolin-1(2H)-one (5-AIQ), a water-soluble PARP inhibitor, in a rat model of periodontitis. Materials and Methods: Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day eight, the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis. Results and Conclusions: Ligation significantly induced an increased neutrophil infiltration and a positive staining for PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of 5-aminoisoquinolin-1(2H)-one (5-AIQ) (5 mg/kg daily for eight days) significantly decreased all of the parameters of inflammation as described above. This suggests that inhibition of PARP may represent a novel approach for the treatment of periodontal disease. [source] Treatment planning for replacing missing teeth in UK general dental practice: current trendsJOURNAL OF ORAL REHABILITATION, Issue 7 2010P. M. PATEL Summary, The aim of this study was to examine the confidence, barriers and attitudes towards the replacement of missing teeth by general dental practitioners (GDPs). The perceived impact of the recently introduced National Health Service (NHS) contract on the provision of prosthodontic treatments was also considered. Pre-piloted postal questionnaires were mailed to 500 GDPs in Wales. Open- and closed-ended questions were utilised to establish confidence, adequacy of training and attitudes towards treatments for replacing missing teeth. Two hundred and seventeen completed questionnaires were received (response rate = 43·4%). Many respondents described themselves as ,confident' or ,very confident' in the provision of removable partial dentures (RPDs) (acrylic = 100%, metal based = 99·5%), cantilever resin-bonded bridges (94·4%) and conventional bridgework (98·6%). GDPs were ,not confident' providing fixed-fixed resin-bonded bridges (21·1%) or implants (81·4%). Financial barriers were identified to the provision of prosthodontic treatments, including comments such as "the new [National Health Service] contract does limit the treatments available". Privately funded patients were more likely to be offered a fixed bridge or implant replacement of a missing upper first molar, whereas non-privately funded patients were more likely to be offered no treatment (P < 0·01). Most respondents reported confidence at providing more routine forms of prosthodontic care such as RPDs and bridges. It appears that funding arrangements may have an impact on treatments offered to replace missing teeth, particularly under the current NHS contract. [source] Expression of c-Fos protein in the trigeminal nuclear complex resulting from quantified force application to the rat molarJOURNAL OF ORAL REHABILITATION, Issue 11 2003M. Watanabe summary, This study was conducted to investigate the expression and distribution of c-Fos-like immunoreactive neurones (Fos-neurones), in the rat trigeminal sensory nuclear complex, produced by mechanical forces with various magnitudes and durations applied to the left upper first molar. The magnitudes of forces applied to the tooth were 25, 50 and 100 g and the duration was 2 h. A quantified force of 100 g was also applied to the upper molar for varying durations [short-time (1,2 min)], 2, 4, 8 and 12 h. Fos-neurones distributed in the bilateral superficial laminae of the subnucleus caudalis, and the ipsilateral dorsomedial part of subnucleus oralis (Sp5Odm). The number of Fos-neurones increased in the subnucleus caudalis (Sp5C) according to the force magnitude. In the Sp5C, the number of Fos-neurones exhibited maximum level, 2 or 4 h after the application. In the Sp5Odm, however, the number of Fos-neurones reached the maximum level at 8 h. These data suggest that the change in the number of nociceptive neurones in Sp5C reflect changes in encoding the magnitude of force to tooth, and that the nature of pain response to orthodontic forces might have some relation to the delayed expression of c-Fos protein in the Sp5Odm. [source] Expression of receptor activator of nuclear factor kappa B ligand relates to inflammatory bone resorption, with or without occlusal trauma, in ratsJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2007Y. Yoshinaga Background and Objective:, Receptor activator of nuclear factor kappa B ligand (RANKL) is an important factor in osteoclast differentiation, activation and survival; however, its involvement in inflammatory bone resorption, with or without occlusal trauma, is unclear. The purpose of the present study was to investigate the distribution of RANKL-expressing cells in rat periodontium during lipopolysaccharide-induced inflammation with or without occlusal trauma. Material and Methods:, Lipopolysaccharide was injected into rat gingiva of the lower left first molar to induce inflammation. In addition, the occlusal surface of the upper left first molar of rat was raised by placing a gold inlay to induce occlusal trauma in the lower left first molars. The distribution of RANKL-expressing cells was immunohistochemically observed. Results:, In the inflammatory model, many osteoclasts were observed at the apical inter-radicular septum on day 5 and they were reduced by day 10. On the other hand, in the inflammatory model with occlusal trauma, many osteoclasts were still observed on day 10. RANKL expression was similar to the changes in osteoclast number. The expression of RANKL increased in endothelial cells, inflammatory cells and periodontal ligament cells. Conclusion:, These findings clearly demonstrated that RANKL expression on endothelial cells, inflammatory cells and periodontal ligament cells is involved in inflammatory bone resorption and the expression is enhanced by traumatic occlusion. These results suggest that RANKL expression on these cells is closely involved in the increase of osteoclasts induced by occlusal trauma. [source] Different distribution of immunocompetent cells in the dentogingival junction during root formation in rat molarsJOURNAL OF PERIODONTAL RESEARCH, Issue 1 2003Hiroshi Tamura The distribution of immunocompetent cells in the dentogingival junction of rat molars during root formation was investigated by immunocytochemistry using antibodies to class II major histocompatibility complex (MHC) molecules (OX6-antibody) and monocyte/macrophage lineage cells (ED1-antibody) as well as by histochemical reaction for periodic acid,Schiff (PAS). Two portions (the junctional epithelium in the mesial gingiva of the first molar, and the interdental gingiva between the first and second molars) were selected for observations. At the eruption stage of the first molar (16,18 days after birth), OX6-positive cells, dendritic or oval in shape, were abundantly distributed in the connective tissue between the oral epithelium and tooth germ. Positive cells with slender cell processes were also found beneath the ameloblast layer. At the commencement stage of the first molar occlusion (24,28 days after birth), numerous OX6-positive cells displaying a dendritic fashion existed preferentially in the mesial gingiva, but were fewer in the interdental gingiva. In contrast, the interdental gingiva showed a denser distribution of ED1-positive cells and PAS-reactive polymorphonuclear leukocytes (PMLs) than the mesial gingiva. At the completion stage of root formation (100,120 days after birth), the OX6-immunopositive cells invaded the deeper position of the mesial gingiva with the downgrowth of the epithelium; they had a considerably higher cell density compared with those in the interdental gingiva where PAS-reactive PMLs persisted. These findings indicated that the immunocompetent cells showed a region-specific distribution and cell density by their roles in immune response. [source] Histometric evaluation of the effect of nicotine administration on periodontal breakdown: an in vivo studyJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2001Francisco H. Nociti Jr The present study investigated the effect of nicotine administration on periodontal breakdown resulting from ligature-induced periodontitis in rats. Twenty adult male Wistar rats were used. After anesthesia, a mandibular first molar was randomly assigned to receive a cotton ligature in the sulcular area while the contralateral tooth was left unligated. The animals were randomly assigned to one of the following treatments, of daily intraperitoneal injections: A , saline solution, B , 0.37 mg of nicotine/kg, C , 0.57 mg of nicotine/kg and D , 0.73 mg of nicotine/kg. Thirty days later, the animals were sacrificed and the specimens routinely processed for serial decalcified sections. Statistical analysis (ANOVA) revealed greater bone loss (p<0.05) in the ligated teeth of animals which received nicotine (groups B/C/D) than in the ligated teeth of animals which received saline solution (group A). In addition, a dose-dependent response was observed among the nicotine groups. A negative effect of nicotine was observed in the unligated teeth of the experimental groups (p<0.05). Therefore, daily administration of nicotine enhanced, in a dose-dependent manner, the effects of local factors in producing periodontal breakdown. Furthermore, the nicotine seemed to have a direct deleterious effect on the periodontal tissues. [source] RHYTHMIC AND IRREGULAR MOVEMENT OF THE FIRST MOLAR WHILE EATING FOODS WITH DIFFERENT TEXTURESJOURNAL OF TEXTURE STUDIES, Issue 3 2000MICHIKO TOGASHI ABSTRACT The three-dimensional movement of a tooth, any tooth, while naturally eating, was measured by an apparatus developed in our laboratory. The movement of the first molar on the usually used side is reported here. The mastication movements are divided into two parts, namely the rhythmical chewing period during which there are mastication pressure loads on the molar and the irregularly pulsated moving period in preparation for the swallowing followed by the rhythmical one during which there is no more pressure on it. The amplitudes of the up and down movements of the molar are 10,22mm for the rhythmical chewing period which are bigger than those for the irregularly moving period. The rhythmical chewing periods are distributed around 10,40 s depending on 14 kinds of food texture, and also on the size of the food, in a fairly similar manner for the participants. The period is longer for tough foods and bigger samples. The irregularly pulsated moving periods are widely distributed, 2,45s, and depend both on the food texture and on the participant. The irregular moving periods are longer for foods which scatter in the mouth or adhere to the teeth when chewing. The ingestion difficulty of the food was divided into two groups. One is where it is difficult to break down the food with the teeth and the other is where it is difficult to prepare for swallowing. [source] The effects of up to 240 days of tacrolimus therapy on the gingival tissues of rats , a morphological evaluationORAL DISEASES, Issue 1 2008CA Nassar Background:, Tacrolimus, an immunosuppressive drug used in organ transplantation, has been reported not to induce gingival overgrowth. However, prevalence studies are limited, and the methods used for assessing gingival overgrowth varies among studies. Objective:, The purpose of this study was to evaluate the effects of up to 240 days of tacrolimus therapy on gingival tissues of rats. Materials and methods:, Rats were treated for 60, 120, 180 and 240 days with daily subcutaneous injections of 1 mg/kg body weight of tacrolimus. After histological processing, the oral and connective tissue, volume densities of fibroblasts (Vf), collagen fibers (Vcf) and other structures (Vo) were assessed in the region of the lower first molar. Results:, After 60 and 120 days of treatment with tacrolimus, gingival overgrowth was not observed. The gingival epithelium, connective tissue, as well as the values for Vf, Vcf, and Vo were similar to those of the control rats (P > 0.05). After 180 and 240 days of the treatment, gingival overgrowth was associated with a significant increase in the gingival epithelium and connective tissue as well as an increase in the Vf and Vcf (P < 0.05). Conclusions:, Within the limits of the experimental study, it may be concluded that the deleterious side effects of tacrolimus on the gingival tissues of rats may be time-related. [source] Low-energy laser irradiation accelerates the velocity of tooth movement via stimulation of the alveolar bone remodelingORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2009T Yoshida Structured Abstract Authors,,, Yoshida T, Yamaguchi M, Utsunomiya T, Kato M, Arai Y, Kaneda T, Yamamoto H, Kasai K Introduction,,, Previously, the authors have reported the acceleration of tooth movement and osteoclastogenesis on the pressure site in an experimental tooth movement model by low-energy laser irradiation (LELI), which stimulated the RANK/RANKL system and c-fms/macrophage colony-stimulating factor system. However, the effect of LELI on osteogenesis on the tension site is not known clearly. Moreover, the temporal changes in alveolar bone during tooth movement have not been investigated as yet. Therefore, the present study was designed to examine the effects of LELI on alveolar bone remodeling during experimental tooth movement, and observe the temporal bone mineral density (BMD) using micro-computed tomography (,CT). Materials and methods,,, To induce experimental tooth movement in rats, 10 g force was applied to the upper right first molar with Nickel titanium closed-coil. Next, a gallium-aluminum-arsenide (Ga-Al-As) diode laser was used to irradiate the area around the moved tooth, and BMD and the amount of tooth movement were measured by ,CT scanning for 21 days. Histopathological examination was also performed. Results,,, The amount of tooth movement in the LELI group was significantly greater than in the non-irradiation group by the end of the experimental period. Further, compared with the non-irradiation group, the fall of BMD was less in the LELI group. Conclusion,,, These findings suggest that LELI accelerates the velocity of tooth movement via stimulation of the alveolar bone remodeling. [source] Tissue reaction to orthodontic tooth movement in different bone turnover conditionsORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 3 2003C. Verna Structured Abstract Authors , Verna C, Melsen B Objectives , To study the tissue reaction to orthodontic load in normal, high, and low bone turnover states. Design , ,Split mouth' design performing orthodontic tooth movement in 52, 6-month-old male rats with: normal (n = 19), high (n = 16), and low bone turnover (n = 17), the latter two being obtained by induction of hyperthyroidism and hypothyroidism, respectively. Performed at the Department of Orthodontics at Aarhus University. Experimental Variable , The upper left first molar was moved for 21 days. Bone markers were administered 7 and 2 days before killing. Histological sections were cut at the coronal and apical levels. Outcome Measure , Alveolar socket area, periodontal ligament width, the relative extension of alveolar wall with erosion surfaces, and the mineralizing surfaces were measured and compared in the three groups. Results , Alveolar socket, periodontal ligament width, and erosion surface were larger on the treated than on the control side in the three groups. The normal and hypothyroid groups showed a wider periodontal ligament at the bucco-distal site at the coronal level, while the hyperthyroid group showed a widening which was not spatially oriented. The normal and hyperthyroid groups showed higher erosion at the corono-mesial site. The mineralizing surfaces were larger on the treated than on the control side in the normal and hypothyroid groups, but not in the hyperthyroid group. Conclusion , In the hyperthyroid group, the widening of the periodontal ligament was not spatially oriented and the increased erosion was not accompanied by increased formation, as observed in the normal and hypothyroid groups. [source] Variations in the mechanical properties of Alouatta palliata molar enamelAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Laura A. Darnell Abstract Teeth have provided insights into many topics including primate diet, paleobiology, and evolution, due to the fact that they are largely composed of inorganic materials and may remain intact long after an animal is deceased. Previous studies have reported that the mechanical properties, chemistry, and microstructure of human enamel vary with location. This study uses nanoindentation to map out the mechanical properties of Alouatta palliata molar enamel on an axial cross-section of an unworn permanent third molar, a worn permanent first molar, and a worn deciduous first molar. Variations were then correlated with changes in microstructure and chemistry using scanning electron microscopy and electron microprobe techniques. The hardness and Young's modulus varied with location throughout the cross-sections from the occlusal surface to the dentin-enamel junction (DEJ), from the buccal to lingual sides, and also from one tooth to another. These changes in mechanical properties correlated with changes in the organic content of the tooth, which was shown to increase from ,6% near the occlusal surface to ,20% just before the DEJ. Compared to human enamel, the Alouatta enamel showed similar microstructures, chemical constituents, and magnitudes of mechanical properties, but showed less variation in hardness and Young's modulus, despite the very different diet of this species. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Brief communication: High-resolution assessment of the dental developmental pattern and characterization of tooth tissue proportions in the late Upper Paleolithic child from La Madeleine, FranceAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009Priscilla Bayle Abstract Affinities and differences in dental maturational patterns between modern humans and Neanderthals remain a matter of discussion. In particular, deciduous teeth are rare for Late Pleistocene humans, and few entire sequences have been detailed for their developmental status. Here, we report the results from the 3D virtual reconstruction and structural analysis of the deciduous lower dentition (nine teeth in situ) of the child from La Madeleine (LM4), France, the first Upper Paleolithic specimen detailed so far by means of high-resolution microtomography (,CT). With respect to the modern dental developmental standards, age at death of this individual is now more likely estimated within the interval 3,4 years. LM4 lacks the slight discrepancy between a proportionally advanced stage of mineralization of the deciduous first molar and a relatively delayed maturational level of the incisors, which is found in Neanderthals (Bayle et al.: J Hum Evol 56 [2009] 66,75). By using a Bayesian approach, we calculated the probability that its maturational sequence is found within the extant human variation as represented by a tomographic (CT) reference sample of 45 children scored according to the same protocol (Liversidge and Molleson: Am J Phys Anthropol 123 [2004] 172,180). Results show that the specific sequence of this Magdalenian individual is found three times in the comparative sample included in this study. LM4 absolute tooth size and relative dental tissue proportions are close to the modern human figures (characterized by proportionally reduced dentine volumes) and lie systematically below the values shown by the Neanderthal child from Roc de Marsal, France (OIS 5a). Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] Load transfer characteristics of unilateral distal extension removable partial dentures with polyacetal resin supporting componentsAUSTRALIAN DENTAL JOURNAL, Issue 1 2009T Jiao Abstract Background:, To photoelastically examine load transfer by unilateral distal extension removable partial dentures with supporting and retentive components made of the lower stiffness polyacetal resins. Methods:, A mandibular photoelastic model, with edentulous space distal to the right second premolar and missing the left first molar, was constructed to determine the load transmission characteristics of a unilateral distal extension base removable partial denture. Individual simulants were used for tooth structure, periodontal ligament, and alveolar bone. Three designs were fabricated: a major connector and clasps made from polyacetal resin, a metal framework as the major connector with polyacetal resin clasp and denture base, and a traditional metal framework I-bar removable partial denture. Simulated posterior bilateral and unilateral occlusal loads were applied to the removable partial dentures. Results:, Under bilateral and left side unilateral loading, the highest stress was observed adjacent to the left side posterior teeth with the polyacetal removable partial denture. The lowest stress was seen with the traditional metal framework. Unilateral loads on the right edentulous region produced similar distributed stress under the denture base with all three designs but a somewhat higher intensity with the polyacetal framework. Conclusions:, The polyacetal resin removable partial denture concentrated the highest stresses to the abutment and the bone. The traditional metal framework I-bar removable partial denture most equitably distributed force. The hybrid design that combined a metal framework and polyacetal clasp and denture base may be a viable alternative when aesthetics are of primary concern. [source] Influence of changing the chewing region on mandibular movementAUSTRALIAN DENTAL JOURNAL, Issue 1 2009K Hashii Abstract Background:, In the shortened dental arch condition, little is known of how patients adapt their jaw function during mastication to the new oral environment. This study aimed to investigate the changes in mandibular movements when the chewing region was changed from the first molar to the first premolar. Methods:, Thirty clinical residents with natural dentitions were recruited. The subjects were asked to chew a piece of beef jerky using either the first molar or the first premolar on the preferred chewing side. Three-dimensional trajectories of lower incisors and both condyles were analysed using a jaw movement tracking device with six degrees of freedom during the period between the onset and offset of electromyographic bursts from the masseter and anterior temporal muscles. Results:, The closing angle of the lower incisors for first premolar chewing was narrower in comparison with that for first molar chewing (p < 0.05). The lengths of the condylar trajectories and the maximum velocities of the condylar movement for first premolar chewing were smaller and slower, respectively, in comparison with those for first molar chewing (both sides; p < 0.01). Conclusions:, The mandibular movement during mastication might be changed to adapt the premolar chewing because of a loss of posterior occlusal supports. [source] Endodontic treatment of a mandibular first molar with three mesial canals and broken instrument removalAUSTRALIAN ENDODONTIC JOURNAL, Issue 2 2010Article first published online: 27 JUL 2010 No abstract is available for this article. [source] Endodontic treatment of a mandibular first molar with three mesial canals and broken instrument removalAUSTRALIAN ENDODONTIC JOURNAL, Issue 1 2010Farhad Faramarzi dds Abstract To succeed in any dental procedure, the clinician's awareness of the patient's dental anatomy and its variations is crucial. In endodontic therapy, obtaining full information about the root canals' variations can affect the outcome substantially. This case report presents the endodontic treatment of a mandibular first molar exhibiting three mesial root canals with 4 mm of a separated K-file in the coronal third of the mesiolingual canal on an 18-year-old female patient. This case demonstrates the importance of locating additional canals in any roots undergoing endodontic treatment and how the clinician's awareness of aberrant internal anatomy may change the treatment results. [source] The Buccofacial Wall of Maxillary Sinus: An Anatomical Consideration for Sinus AugmentationCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 2009Hun-Mu Yang DDS ABSTRACT Purpose: This study aimed to quantify the thickness of the buccofacial wall of the maxillary sinus where sinus augmentations are often performed. Materials and Methods: Fourteen sites located 15 and 20 mm superior to the anatomical cervical line (named as groups H15 and H20, respectively) and along the long axes of the mid and the interproximal of two premolars and two molars were measured from 74 Korean hemiface cadavers. Results: The buccofacial wall of the maxillary sinus was thinnest at the area between the maxillary second premolar and first molar in groups H15 and H20. The lowest mean thickness was 1.2 mm in both groups. The walls were thicker in males than in females, with statistically significant gender differences found at four and two sites on the anterior horizontal reference in groups H15 and H20, respectively. However, the thickness did not differ significantly with age or laterality. Incomplete septa were found in seven of the 74 specimens, and they were present in the area between the first and second molars in six (86%) of these cases. Conclusions: These observations indicate that anatomical characteristics of the buccofacial wall thickness of the maxillary sinus need to be considered when performing a window opening procedure for sinus augmentation. [source] Bone Reformation and Implant Integration following Maxillary Sinus Membrane Elevation: An Experimental Study in PrimatesCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2006Vinicius C Palma DDS ABSTRACT Background:, Recent clinical studies have described maxillary sinus floor augmentation by simply elevating the maxillary sinus membrane without the use of adjunctive grafting materials. Purpose:, This experimental study aimed at comparing the histologic outcomes of sinus membrane elevation and simultaneous placement of implants with and without adjunctive autogenous bone grafts. The purpose was also to investigate the role played by the implant surface in osseointegration under such circumstances. Materials and Methods:, Four tufted capuchin primates had all upper premolars and the first molar extracted bilaterally. Four months later, the animals underwent maxillary sinus membrane elevation surgery using a replaceable bone window technique. The schneiderian membrane was kept elevated by insertion of two implants (turned and oxidized, Brånemark System®, Nobel Biocare AB, Göteborg, Sweden) in both sinuses. The right sinus was left with no additional treatment, whereas the left sinus was filled with autogenous bone graft. Implant stability was assessed through resonance frequency analysis (OsstellTM, Integration Diagnostics AB, Göteborg, Sweden) at installation and at sacrifice. The pattern of bone formation in the experimental sites and related to the different implant surfaces was investigated using fluorochromes. The animals were sacrificed 6 months after the maxillary sinus floor augmentation procedure for histology and histomorphometry (bone-implant contact, bone area in threads, and bone area in rectangle). Results:, The results showed no differences between membrane-elevated and grafted sites regarding implant stability, bone-implant contacts, and bone area within and outside implant threads. The oxidized implants exhibited improved integration compared with turned ones as higher values of bone-implant contact and bone area within threads were observed. Conclusions:, The amount of augmented bone tissue in the maxillary sinus after sinus membrane elevation with or without adjunctive autogenous bone grafts does not differ after 6 months of healing. New bone is frequently deposited in contact with the schneiderian membrane in coagulum-alone sites, indicating the osteoinductive potential of the membrane. Oxidized implants show a stronger bone tissue response than turned implants in sinus floor augmentation procedures. [source] | ||||||||||||||||||||||||||||||||||