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At least 73 records · Page 4Linked to original sources

PubMed2003

A nonlinear finite element analysis of the periodontal ligament under orthodontic tooth loading.

The stressed state of the periodontal ligament (PDL) is understood to play a critical role in the tooth movement initiated by orthodontic treatment. Finite element simulations have been used to describe PDL stresses for orthodontic loading; however, these models have predominantly assumed linear mechanical properties for the PDL. The present study sought to determine the importance of using nonlinear mechanical properties and nonuniform geometric data in computer predictions of periodontal ligament stresses and tooth movements. A 2-dimensional plane-strain finite element model of a mandibular premolar was constructed based on anatomic data of transverse sections of tooth, PDL, and bone from a 24-year-old cadaveric man. A second model was constructed of the same tooth but with a PDL of uniform thickness. Each of these was prescribed linear or nonlinear elastic mechanical properties, as obtained in our own experiments. Predictions of the maximum and minimum principal stresses and von Mises stresses in the PDL were determined for extrusive and tipping forces. The results indicated that biofidelic finite element models predicted substantially different stresses in the PDL for extrusive loading than did the uniform thickness model, suggesting that incorporation of the hourglass shape of the PDL is warranted. In addition, incorporation of nonlinear mechanical properties for the PDL resulted in dramatic increases in the stresses at the apex and cervical margin as compared with the linear models.

Adult↗

PubMed1996

Pathohistology of undecalcified primary teeth in vitamin D-resistant rickets: review and report of two cases.

The basic dental defects in vitamin D-resistant rickets seem to be manifested in dentin. Enamel is usually reported to be normal. This histologic examination showed the penetration of microorganisms through the calcified structures of the enamel layer without visible caries. The microorganisms passed through the dentinoenamel junction and invaded dentin, which was characterized by calcospherites and large amounts of interglobular dentin. Furthermore, microorganisms could be detected in dentinal tubules, which were exposed to the oral cavity when enamel was removed. However, large areas of tertiary dentin extended between such tubules and the pulp. These light microscopic results suggest that clinical manifestations, such as, pulp recrosis and periapical lesions (without carious defects) may be caused by the penetration of microorganisms through microclefts of the enamel layer as well as pathologically altered enamel microstructures of affected teeth.

Adult↗

PubMed1998

Pulpal thermal responses to an erbium,chromium: YSGG pulsed laser hydrokinetic system.

PROBLEM: Laser systems are known to raise pulpal temperatures when applied to tooth surfaces. Dental biocalcified tissues can be cut with an erbium,chromium:yttrium-scandium-gallium-garnet laser-powered hydrokinetic system. This device is effective for caries removal and cavity preparation in vitro. Pulpal monitoring of temperature changes during hard tissue cutting by a hydrokinetic system have not been reported. OBJECTIVES: This study compared the effects of hydrokinetic system, dry bur, and wet bur tooth cutting on pulpal temperature. STUDY DESIGN: In vivo thermocouple intrapulpal measurements were made on cuspid teeth in anesthetized beagle dogs. In vitro measurements were made on extracted human molar teeth preserved in high-salt solution and later rinsed in phosphate-buffered saline (pH 7.4) to simulate in vivo conditions. The hydrokinetic system was compared with conventional air-turbine-powered bur cutting. The hydrokinetic system cuts and bur preparations were randomly made on the buccal surfaces at the cervical one third of the crown and extended until exposure of the pulp was confirmed clinically. RESULTS: Pulpal temperatures associated with the hydrokinetic system either showed no change or decreased by up to 2 degrees C. Wet bur preparations resulted in a 3 degrees to 4 degrees C rise. With dry bur preparations, a 14 degrees C rise in temperature was recorded. CONCLUSIONS: Under the conditions of this study, the erbium,chromium:yttrium-scandium-gallium-garnet laser-powered hydrokinetic system, when used for cavity preparation, had no apparent adverse thermal effect as measured in the pulp space.

Aluminum Silicates↗

PubMed1999

Dental root resorption.

This article presents a review of physiologic mechanisms involved in various types of root resorption that may be encountered clinically. Included is a brief overview of suggested homeostatic mechanisms of the periodontal ligament and the role of the intermediate cementum in inhibiting root resorption. Root resorption (surface, inflammatory, and replacement) associated with traumatic injuries is discussed, with emphasis on etiology and the ability to provide treatment. The final discussion relates to other types of resorption, based on a classification of internal, cervical, and external resorption associated with periradicular pathosis and resulting from pressure in the periodontal ligament.

Humans↗

PubMed2002

Comparison of factors potentially related to the occurrence of dental erosion in high- and low-erosion groups.

Soft drink intake, method of drinking, pH variations, plaque topography, and various salivary, microbial and clinical factors were compared in Saudi men with high (n = 10, mean = 20.5 yr) and low (n = 9, mean = 20.3 yr) dental erosion. pH-measurements were carried out with a microtouch electrode at six different intraoral locations after the subjects had consumed 330 ml of regular cola-type drink in their customary manner. The results showed that higher intake of cola-type drinks was more common in the high- (253 l yr(-1)) than in the low-erosion group (140 l yr(-1)). High erosion was associated with a method of drinking whereby the drink was kept in the mouth for a longer period (71 s vs. 40 s). pH after drinking did not differ between the groups for any of the six measuring sites. Plaque accumulation on the palatal surfaces of maxillary anterior teeth and urea concentration in unstimulated saliva were lower in high-erosion subjects. Aside from these, there were no differences in salivary and microbial factors between the groups. First molar cuppings, buccal cervical defects, and mouth breathing were more common in the high- than in the low-erosion group. In summary, consumption of cola-type drink, method of drinking, amount of palatal plaque on anterior teeth, and salivary urea concentration are factors associated with dental erosion.

Adult↗

PubMed2000

Radiographic detection and assessment of the periodontal endosseous defects.

AIMS: The aim of the present study was to investigate the potential of conventional radiography in detecting and accurately imaging periodontal endosseous (or osseous) defects when compared to surgical measurements. A further objective of the study was the selection of the most successful radiographic method for the assessment of endosseous defects. METHOD: Surgical measurements, during periodontal flap surgery, and radiographic measurements, from periapical and panoramic radiographs, were obtained from 5,072 proximal surfaces of 100 patients presenting with periodontitis. RESULTS: Statistical evaluation of the surgical and radiographic measurements revealed the following. (1) The ability of the radiographs to detect periodontal osseous defects was relatively low. (2) For periapical radiography, it depended, in descending order, on the depth and buccolingual width of the defect, the number of osseous walls and the jaw location. For panoramic radiography, it depended only on buccolingual width. (3) Osseous defects of small depth and/or small buccolingual width were the most difficult to detect radiographically. (4) Periapical radiography was more successful than panoramic in detecting osseous defects, and more accurate in assessing the defect dimensions (depth, mesiodistal width). (5) The difference in the defect detection ability between the 2 radiographic methods, the accuracy of the radiographic defect dimensions assessment as well as the degree of agreement between periapical and panoramic assessment depended on defect location and dimensions. CONCLUSIONS: Periapical radiography is superior to panoramic in detecting and accurately imaging periodontal osseous destruction.

Adolescent↗

PubMed2000

Dental and periodontal status of Sjögren's syndrome.

BACKGROUND: Sjögren's syndrome (SS) is one of the most common systemic autoimmune diseases in middle-aged women. The present study had the aim to examine the dental and periodontal condition in patients with SS in comparison with disease controls and to evaluate the influence of reduced salivary flow in the periodontal tissues. METHOD: We examined 24 patients with primary or secondary SS in comparison with 27 patients who had another autoimmune disease but no signs or symptoms of SS, as well as with 29 subjects who had a subjective feeling of xerostomia or xerophthalmia without exhibiting an underlying disease. The clinical evaluation included examination of the oral mucosa, determination of missing, decayed and filled teeth, fixed or removable prosthetic appliances, plaque index, gingival index, probing pocket depth, probing attachment level, oral hygiene habits and frequency of dental visits. Statistical analysis was performed using the 2-tailed Fisher exact and Kruskal-Wallis tests. RESULTS: No significant difference was found in the dental or periodontal condition of the 3 groups. The number of teeth, feelings and distal or mesial decay lesions correlated negatively with age, while the number of fixed prosthetic appliances correlated positively. The salivary flow was statistically lower in patients with SS and exhibited a negative correlation with the number of cervical decay lesions. It was also found that SS patients had better oral hygiene habits than subjects of the control groups. CONCLUSIONS: No significant,difference could be detected concerning the dental and periodontal status of SS patients, compared with that of patients with other immune diseases as well as with that of controls who had subjective xerostomia.

Age Factors↗

PubMed2001

Human histology of new attachment after root coverage using subepithelial connective tissue graft.

BACKGROUND, AIMS: Connective tissue grafts are used successfully in periodontal therapy for root coverage. However, reports on the histologic interface between the root surface and the grafted tissue have been few in number. This report describes a case study in which a subepithelial connective tissue graft was placed in a 27-year-old female on the maxillary left side. METHODS: The graft (15 mm long, 10 mm wide, 1.5 mm thick) included palatal periosteum and was placed with the periosteal side facing the exposed bone and root surfaces. RESULTS: 15 weeks after grafting, the teeth presented with residual recessions of 1 mm, and buccal probing depths were approximately 1 mm. 14 months post-surgery, the 1st maxillary premolars on both sides were extracted for orthodontic therapy. Clinical parameters at the graft site remained as at 15 weeks. Histologic analysis of tooth #24 showed that the sulcular epithelium was keratinized; epithelium lining the dentin exhibited rete ridges projecting into the gingival connective tissue; and junctional epithelium extended over new cementum. New connective tissue attachment was also observed, including periodontal ligament. CONCLUSION: Biological width was comparable pre- and post-surgery, indicating a real gain in attachment of 3.9 mm.

Adult↗

PubMed2001

Generalized cervical root resorption associated with periodontal disease.

UNLABELLED: BACKGROUND AND DESCRIPTION OF CASE: The etiology and pathogenesis of generalized cervical root resorptions is not well understood. In the present report, a case of severe cervical root resorption involving 24 anterior and posterior teeth is presented. The lesions developed within a period of 2 years after the patient had changed to an acid-enriched diet. They extended far into the coronal dentin and were associated with gingival inflammation and crestal bone resorption. However, no generalized clinical attachment loss had occurred. Culturing of subgingival plaque revealed the presence of several putative periodontal pathogens among which Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. Treatment consisted of mechanical debridement supported by systemic antibiotics (amoxycillin plus metronidazole) and dietary advice. RESULTS: Within 1 year after the onset of treatment, all resorptive lesions had repaired by ingrowth of a radio-opaque mineralized tissue. The crestal areas showed radiological evidence of bone repair. 3 years after the onset of therapy, one premolar was extracted and examined histologically. It appeared that irregularly-shaped masses of woven bone-like tissue had invaded into the domain of the resorbed coronal dentin and were bordered by thin layers of acellular cementum. CONCLUSION: It is concluded that, in this patient, the cervical resorptions were likely the result of an osteoclastic response extending into the roots because the root-protective role of the junctional epithelium did not develop. We hypothesize that this was due to the combined effects of a periodontopathogenic microflora and a dietary confounding factor.

Acids↗

PubMed2002

Cervical tooth wear and sensitivity: erosion, softening and rehardening of dentine; effects of pH, time and ultrasonication.

BACKGROUND: Cervical dentine wear is commonly observed and may be associated with dentine hypersensitivity. Erosion is thought to play a part in both conditions but compared to enamel has been little studied in dentine. AIM: The aims of these studies in vitro were to: (i) determine the effects of citric acid on dentine at different pH values and over time; (ii) measure the depth of dentine demineralisation or softening using ultrasonication; (iii) determine whether softened dentine can be remineralised or rehardened using artificial saliva. METHODS: Groups of flat dentine specimens prepared from unerupted human third molar teeth were: (a) exposed to citric acid at pH 3.2 for periods up to 4 h with mineral water as control; (b) exposed to citric acid at pH 2.54, 3.2, 4.5, 5.5 and 6.0 for 2 h and then subjected to ultrasonication stepwise up to 480 s; (c) exposed to citric acid at pH 2.54, 3.2, and 4.5, placed into artificial saliva for 24 h and then subjected to ultrasonication as in (b). Loss of dentine was measured by profilometry, after, each phase of erosion, ultrasonication and immersion in artificial saliva. RESULTS: Depth of erosion significantly increased non-linearly with time and significantly decreased with increasing pH. Ultrasonication had minimal albeit significant effects on control specimens. Removal of softened dentine increased with ultrasonication time. Depth of softening significantly increased with increasing erosion time to 2 h, plateauing at 2 microm. Depth of softening increased to 2 microm from pH 2.54 to pH 3.2 and decreased at higher pH values thereafter. 24 h in artificial saliva provided no protection to the soften zone against ultrasonicaion. Citric acid at all pH values and exposure times removed the dentine smear layer to expose tubules. Ultrasonication did not remove the smear layer on control specimens but removed all deposits formed after exposure to artificial saliva. CONCLUSION: It is concluded that dentine is susceptible to erosion even at relatively high pH, the tubule system is readily exposed and dentine, unlike enamel, shows little propensity to remineralise.

Analysis of Variance↗

PubMed2002

Periodontal attachment level of extractions presumably performed for periodontal reasons.

BACKGROUND/AIMS: The aim of this study was to analyse the residual periodontal attachment in teeth extracted by East German dentists in order to determine a possible 'forceps level'. METHODS: Out of about 8000 extracted teeth collected from a dental waste disposal company, 500 teeth were randomly selected. After exclusion of wisdom teeth and premolars extracted for orthodontic reasons (intact teeth with attachment > 90%), coronal and root caries, fillings, pulp exposure and incomplete root fillings (based on X-rays) were registered. The periodontal ligament was stained with 1% Fuchsin Red and measured with a light microscope. RESULTS: For intact teeth (DF = 0, periodontal disease definition I), the mean periodontal attachment (50.5% +/- 16.0) was significantly lower than for teeth with carious defects or fillings (64.7% +/- 18.8. unpaired t-test: p < 0. 00 1). There was a marked increase in frequency of extractions in intact teeth below 70% periodontal attachment and 37% were extracted at attachment levels between 50 and 69%. Teeth with pulpal involvement showed significantly different frequency distributions and mean attachment values (77.9% +/- 17.8) than the remaining teeth (periodontal disease definition II; 55,2% +/- 15.5). CONCLUSIONS: A considerable number of teeth with no or minor coronal destruction were extracted at an attachment level of 50-70%, regardless of the tooth type. The threshold for 'periodontal' extractions seem to be too low and undifferentiated, which calls for an improvement in knowledge of periodontal diagnosis and treatment.

Dental Caries↗

PubMed2003

Analysis of etiologic factors and periodontal conditions involved with 309 abfractions.

OBJECTIVES: Non-carious cervical lesions (NCCL), also termed abfractions, have long been thought to be produced by excessive brushing. Nearly 20 years ago an occlusal etiology was proffered (Lee & Eagle 1984). Controversy still exists concerning these two concepts. The present work was carried out to verify the occurrence of signs of excessive brushing or occlusal disturbances associated with abfractions. MATERIAL AND METHODS: All first consultants were screened for the presence of abfractions during one trimester. NCCL were found in 61 patients who consequently received a thorough examination searching for clinical evidence of excessive brushing or occlusal disturbances. The presence of plaque, calculus, periodontitis, or mobility was also noted. Simple frequency and percentage were used to describe the occurrence of different clinical signs in association with the presence of abfractions. RESULTS: Abfractions often exist in mouths presenting plaque (40.1%), calculus (41.7%), or periodontitis (20.4%). Ulceration of the gingiva is a rare finding (1.6%). However, subgingival apical limits were frequent (32.5%). NCCL coexist almost systematically with occlusal wear facets (94.5%). Lack of canine disclusion (77.2%) was also closely associated with the presence of abfractions. Conversely, mobility was seldom found (1.9%). CONCLUSIONS: Clinical signs of excessive brushing were lacking, whereas signs of occlusal disturbance were very consistent with the presence of abfractions.

Adult↗

PubMed2003

Comparison between panoramic and intra-oral radiographs for the assessment of alveolar bone levels in a periodontal maintenance population.

BACKGROUND: Information about the agreement between intra-oral (I-O) and panoramic (OPG) radiographs is limited. AIMS: : (1) To assess the agreement between I-Os and OPGs for direct measurements of the distance between the cemento-enamel junction (CEJ) and the alveolar bone level (BL) as well as the proportional values in relation to the root length (CEJ-BL/root length), and (2) to explore the symmetry between the left- and right-side measurements. MATERIAL AND METHODS: I-Os and OPGs were studied in 292 periodontal maintenance subjects (mean age 55.5 years, SD+/-12.6) with on average 22.4 teeth (SD+/-4.1 range: 6-28). The images were measured using a PC software program. Site-based I-O and OPG values for CEJ-BL as well as CEJ-BL/root length were compared. OPG values of CEJ-BL/root length values between the left and right sides were also studied. RESULTS: A total of 11,395 linear distances (CEJ-BL plus CEJ-apex) from the I-Os and 21,462 linear distances from the OPGs were measured. The intra-class correlation coefficients (ICCs) between sets of readings of CEJ-BL varied between 0.80 and 0.89 (p<0.001), with the best agreement for tooth 22 (ICC: 0.89; 95% CI: 0.83-0.92). The ICCs for CEJ-BL/root length varied between 0.54 and 0.92. Mean differences between I-O and OPG values were in the 0.00-0.04 mm range for the CEJ-BL/root length comparisons. The maxillary anterior sextant demonstrated a 1.4 x enlargement by OPG for the CEJ-BL/root length comparisons. No distortions were observed for mandibular sextants. Left- and right-side symmetry of periodontal bone loss was demonstrated. ICC varied between 0.79 (95.00% CI: 0.71-0.84, p<0.01) and 0.53 (95.00% CI: 0.36-0.65, p< 0.01). CONCLUSIONS: I-O and OPG radiograph readings are in great agreement. Alveolar bone loss appeared to have a symmetrical distribution pattern. Hence for periodontal assessments, OPG radiographic readings may, at least in part, substitute for full-mouth periapical radiographic evaluation.

Alveolar Bone Loss↗

PubMed2000

Determination of changes on tooth-colored cervical restorations in vivo using a three-dimensional laser scanning device.

The present study aimed at the determination of changes of tooth-colored cervical restorations in vivo using an optical 3-dimensional laser scanning device. The study was performed on 197 cervical restorations placed on incisors, canines, and premolars. Four different tooth-colored restoration materials, a composite, a polyacid-modified resin composite, and two resin-modified glass ionomer cements, were used for the restoration of the lesions. For the determination of changes, images were taken at baseline and 15, 24 and 36 months after the placement of the fillings using a 3D-laser scanning device. The images were superimposed automatically, and digital subtraction was made by a specially developed image analysis software. The total substance loss on the entire filling surface at 36 months for the resin-modified glass ionomer Photac-Fil was 44 (+/-23) microm, for Fuji II LC 45 (+/-26) microm, for Dyract 71 (+/-47) microm and for Tetric 18 (+/-12) microm. Differentiating between the class of lesion, a higher wear rate was observed at 36 months on restorations which had been placed in erosion/non-carious cervical cavities (66 (+/-33) microm). In conclusion, the composite material demonstrated a distinctly lower surface wear rate over time in comparison to the resin-modified glass ionomer cements and the polyacid-modified resin composite.

Adult↗

PubMed2001

Outline and arrangement of enamel rods in human deciduous and permanent enamel. 3D-reconstructions obtained from CLSM and SEM images based on serial ground sections.

Human enamel rods were made visible continuously from the dentino-enamel junction (DEJ) up to the enamel surface. From 12 teeth (1st and 2nd dentition) enamel blocks from the cervical third were prepared with perpendicular planes, embedded in resin, and ground down in steps of 15 microm parallel to the enamel surface. Enamel rods were made visible by acid etching (35% H3PO4, 45 s), sputtered and examined in the scanning electron microscope (SEM). Prior to this, the enamel blocks were viewed under the CLSM and optical sections at distances of 2 microm were obtained, starting in the same plane as the grinding surface. The outlines of the rods were digitized and reconstructed three dimensionally. For the first time, the path of single and grouped enamel rods on their way through the entire enamel layer was depicted. 3D images obtained from confocal laser scanning microscopy (CLSM) data were similar to those gained from SEM images. Single rods did not maintain their same outline throughout their path; arcade outlines predominated close to the DEJ, while keyhole outlines prevailed at the enamel surface. Within a group of rods, neighborhood relations changed, and neighbor rods influenced their outlines mutually, including the variable extent of the tail. The interdependence between the plasticity of the rods and the ameloblasts' forms should be topics of further research.

Dental Enamel↗

PubMed2002

Internal root resorption studied by radiography, stereomicroscope, scanning electron microscope and computerized 3D reconstructive method.

AIM AND METHODOLOGY: Two cases of internal tooth resorption were examined. A mandibular premolar and a mandibular canine were studied after they were extracted using radiographs, a stereomicroscope (SM) and a scanning electron microscope (SEM). Lastly, 3D images of the sectioned teeth were obtained(3D). RESULTS: Radiographically, internal root resorption was shown as a uniform radiolucency. By SM examination, an extensive destruction of dentin was seen, while, by SEM examination, a disappearance of dentinal tubules was clear. The 3D reconstructive method revealed a circumscribed, oval-shaped defect that did not perforate the cemental layer. CONCLUSIONS: Internal root resorption is a rare remodeling process that can be studied using different experimental methods.

Bicuspid↗

PubMed2002

Healing and prognosis of teeth with intra-alveolar fractures involving the cervical part of the root.

Healing and long-term prognosis of 94 cervical root fractures were evaluated. The teeth were divided into two groups according to type of fracture: transverse fractures limited to the cervical third of the root (51 incisors) and oblique fractures involving both the cervical and middle parts of the root (43 incisors). Neither the frequency nor the type of fracture healing differed significantly between the two groups. In the material as a whole, healing of the fracture with hard tissue formation was observed in 17 teeth (18%), and healing with interposition of periodontal ligament (PDL) and, in some cases, hard tissue between the fragments in 62 teeth (66%). Fifteen teeth (16%) showed no healing and a radiolucency adjacent to the fracture. Statistical analyses revealed that incomplete root formation and a positive sensibility test at the time of injury were significantly related to both healing and hard tissue repair. The same applied to concussion or subluxation compared with dislocation of coronal fragment, as well as optimal compared with suboptimal reposition of displaced coronal fragments. The type and duration of splinting (or no splinting) appeared to be of no significance for frequency or type of healing of cervical root fractures. During the observation time (mean = 75 months), 19 (44%) of the teeth with transverse fractures and 3 (8%) of those with oblique fractures were lost after healing. In conclusion, fractures in the cervical part of the root had a healing potential and the predictive parameters identified for fractures in other parts of the root seemed to be valid for the healing of cervical root fractures. Transverse fractures appeared to have a significantly poorer long-term prognosis compared to oblique fractures, apparently due to a marked post-treatment mobility, which often led to new luxation caused by even minor impacts.

Adolescent↗

PubMed1997

Use of calcium hydroxide for apical barrier formation and healing in non-vital immature permanent teeth: a review.

OBJECTIVE: To review the use of calcium hydroxide for induction of apical barrier formation and healing in immature permanent teeth. INTRODUCTION: Pulp necrosis is a frequent complication of dental trauma in immature permanent teeth. Endodontic treatment of these teeth is often complicated. The walls of the root canals are frequently divergent and the apices immature, making debridement and obturation difficult. The aim of treatment is induction of apical healing which may be defined as apical closure through formation of mineralised tissue and repair of the periapical tissues. Calcium hydroxide is the material of choice for apical barrier formation and healing. RESULTS: The use of calcium hydroxide for apical barrier formation is successful in 74-100% of cases irrespective of the proprietary brand used. The average length of time for apical barrier formation is approximately 5 to 20 months. Control of infection and adequate cleaning of the root canal are very important for apical healing. CONCLUSIONS: While the success rate of apical barrier formation using calcium hydroxide is high, long-term follow-up of these teeth is necessary. Problems such as failure to control infection, recurrence of infection and cervical root fracture may occur. The latter is more frequent in immature luxated teeth with the least root development.

Bacterial Infections↗