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At least 433 records · Page 24Linked to original sources
PubMed2005

The nuts and bolts of hemisection treatment: managing congenitally missing mandibular second premolars.

When you treat the congenital absence of mandibular second premolars by extracting the residual deciduous second molar and closing the space, you run the risk of flattening facial fullness, especially in patients with nonextraction features--diminished facial fullness, absence of crowding, and reduced tooth size. This challenge is heightened by the increased likelihood that these features will occur in patients who have agenesis. This article describes a new approach that has been shown to minimize such a loss of anchorage. The technique is called hemisection and involves buccolingual sectioning of the second deciduous molar, followed by removal of its distal half. As necessary, the mesial half is also removed, and space closure can be completed. The advantages, philosophy, and technique are discussed in detail.

Anodontia↗
PubMed2006

Three-dimensional digital modeling and setup.

Obtaining accurate images of the craniofacial region is critical when developing an orthodontic diagnosis and treatment plan. The purpose of this article is to describe a new imaging method that provides complete 3-dimensional views of the maxilla and the mandible, and the model setup with individual anatomic roots. The method uses computed tomography technology and laser scanning; it offers high-resolution images with relatively low radiation exposure. Technical aspects of the new procedure and its possible uses for orthodontic diagnosis and treatment planning are discussed.

Cephalometry↗
PubMed2005

Developmental analysis and computer modelling of bioengineered teeth.

Here we present the developmental progression of bioengineered pig teeth from 1 to 25 weeks of development. We demonstrate that 2-25 week implants contained embryonic tooth bud- and cap-stage tooth structures consisting of dental epithelium expressing the sonic hedgehog gene and condensed dental mesenchyme. Implants harvested at 18-25 weeks also contained tooth bud-like structures, as well as mature tooth structures containing enamel, dentin and pulp tissues. Immunohistochemical analyses confirmed the expression of dentin- and enamel-specific proteins in differentiated bioengineered tooth tissues. Three-dimensional computer modelling further demonstrated a spatial organization of enamel, dentin and pulp tissues resembling that of natural teeth. We conclude that bioengineered teeth commonly exhibit morphological stages characteristic of naturally forming teeth. Furthermore, the presence of immature tooth buds at all times assayed and increased numbers of bioengineered tooth structures over time suggests that porcine dental progenitor cells maintain the ability to form teeth for at least 25 weeks.

Animals↗
PubMed2005

Biting efficiency in relation to incisal angulation.

Previous studies suggest the orientation of the incisor teeth to the path of jaw movement pronouncedly affects their efficiency of action. To test this hypothesis, upper and lower incisal portions of a study model with ideal Asian occlusion were mounted on a mechanical tester and impressed into rectangular blocks made of 15.3% w/w starch gels or Cheddar cheese. At varying angulations of attack between the long axis of the teeth (defining the orientation of the tooth crown) and force direction, the teeth were driven into the blocks for 4-6mm until fractures had grown in the foods. Both the angle of attack and the work divided by fractured area produced in the food, termed 'work to fracture', were measured. The food type (cheese or gel), incisal type (upper or lower pair) and angle of inclination were significant effects on the works to fracture. The minimal work was for angles slightly proclined to the vertical, although only angles of proclination >40 degrees were significantly higher than all other angles. Retroclination or large angles of proclination made little difference to the work done, but produced markedly off-axis cracks. It is suggested that human incisors act most efficiently at small gapes and that orthodontic corrections will thus offer definite functional benefits.

Cheese↗
PubMed2005

A randomised controlled clinical trial to compare the incidence of injury to the inferior alveolar nerve as a result of coronectomy and removal of mandibular third molars.

We randomised 128 patients who required operations on mandibular third molars and who had radiological evidence of proximity of the third molar to the canal of the inferior alveolar nerve to one of two operations: extraction [n=102], and coronectomy [n=94]. Some roots were dislodged during intended coronectomy and were therefore removed, resulting in two subgroups (successful coronectomy n=58, and failed coronectomy n=36). The mean (S.D.) follow up was 25 (13) months. Nineteen nerves were damaged (19%) after extraction, none after successful coronectomy, and three (8%) after failed coronectomy (p=0.01). The incidence of dry socket infection was similar in the three groups (10/102, 10%, 7/58, 12%, and 4/36, 11%, respectively). No root required removal or reoperation. To our knowledge this is the first clinical trial of the efficacy of coronectomy in preserving the inferior alveolar nerve. The length of follow up was about 2 years, which for the assessment of delayed eruption of the root fragments is not sufficient as this process may continue for up to 10 years. However, it seems that coronectomy reduces the incidence of injury to the inferior alveolar nerve without increasing the risk of dry socket or infection.

Adult↗
PubMed2004

Influence of substrate, shape, and thickness on microtensile specimens' structural integrity and their measured bond strengths.

OBJECTIVES: To verify whether substrate, shape, or thickness of microtensile specimens have a significant influence on their measured bond strength. METHODS: Sixty-four extracted molars provided microtensile specimens, which were prepared on enamel and dentin, in different shapes and thicknesses. The teeth were randomly divided into 16 groups (n = 4). Groups 1-8 included hourglass-shaped specimens. In Groups 1-4 specimens were prepared from enamel and in a thickness at the bonding interface of 0.5 mm x 0.5 mm, 1 mm x 1 mm, 1.5 mm x 1.5 mm, and 2 mm x 2 mm, respectively. In these same thicknesses, hourglasses were trimmed in Groups 5-8, but the specimens were prepared from dentin. Groups 9-16 included specimens obtained following the non-trimming technique. Groups 9-12 provided enamel sticks in the four evaluated thicknesses. In these same thicknesses and shape but from dentin were cut the specimens of Groups 13-16. Two specimens from each group were viewed using a scanning electron microscope. On the other ones, microtensile bond strength was measured and the values were statistically analyzed. RESULTS: Substrate, shape, and thickness of the specimens had a significant effect on their recorded bond strength (p < 0.05). Higher bond strength values were recorded by dentin versus enamel specimens and by sticks versus hourglasses. Also, bond strength decreased as specimen thickness increased. SEM analysis revealed that the trimmed specimens, especially if from enamel, often exhibited lines of fracture in the area of action of the bur. SIGNIFICANCE: It seems advisable to avoid the trimming action particularly on enamel specimens. If the hourglass shape is preferred, the cross-sectional area should not exceed 1 mm x 1 mm.

Analysis of Variance↗
PubMed2004

Relation in color of three regions of vital human incisors.

OBJECTIVES: For an adequate color reproduction, it is very valuable to quantify the color distribution in human teeth accurately. The aim of this study was to determine the color relation between three tooth segments (cervical, middle and incisal) in vital upper central incisors, using digital photography. METHODS: Digital recordings of 64 upper right central incisors were made using a standardized head-camera setup. The L*a*b* values of three regions were attained from the standardized digital images using software. RESULTS: There were statistically significant linear correlations for L* and b* between the three tooth segments (all r's > or = 0.60; p < 0.001). The correlation coefficient for a* was lower compared to L* and b* values. The L* and b* values of cervical and incisal tooth segment could be calculated from L* and b* values of middle tooth segment. SIGNIFICANCE: These results show the potency for color mapping of a whole tooth surface by extrapolation of color values of only one part of the surface.

Adult↗
PubMed2005

Anisotropic fracture in bovine root and coronal dentin.

OBJECTIVES: This purpose of this study was to address the fundamental question of how the fracture properties of dentin are related to its composite structure. METHODS: Strain concentration tests and impression-induced damage tests were designed to compare bovine root dentin with coronal dentin, and to understand the role of individual structural elements in the fracture of dentin. RESULTS: Absent in peritubular dentin, root dentin is insensitive to cracks and exhibits higher fracture resistance than coronal dentin that has a typical brittle fracture behavior along the peritubular dentin. Fracture analysis and impression damage experiments found that root dentin is highly anisotropic in fracture behavior. Cracking is predominantly controlled by the organization of collagen fibrils, with the incremental lines being the weakest planes. In coronal dentin, highly mineralized peritubular dentin that intersects with the incremental lines creates additional weak orientations that compete with the incremental lines and thus greatly decrease the degree of fracture anisotropy. SIGNIFICANCE: This study demonstrated that dentin is by no means homogeneous in terms of fracture properties. Location and orientation (especially in terms of incremental lines) should be taken into account when examining tooth failure both in laboratory and in clinical studies.

Animals↗
PubMed2006

An in vivo evaluation of bonding ability of comprehensive antibacterial adhesive system incorporating MDPB.

OBJECTIVES: This study examined the in vivo bonding ability to sound dentin of antibacterial adhesive systems incorporating an antibacterial monomer MDPB based on morphological evaluation of the resin-dentin interface. METHODS: Class V cavities were prepared on the buccal surfaces of the teeth of a beagle dog and a composite filling performed using (1) commercial self-etching system Liner Bond 2 (LB primer+LB bond), (2) experimental primer containing 5% MDPB and LB bond, (3) LB primer and experimental bonding-resin containing 2.5% MDPB, or (4) combination of experimental primer and bonding-resin. After 7 days, the tooth crown was cut and fixed in half-Karnovsky's solution, and the sectioned surface observed under scanning electron microscopy (SEM) after treatment with phosphoric acid and NaOCl. The ultrastructure of the bonding interface was also examined by transmission electron microscopy (TEM). Microtensile bond strengths (microTBS) of each group were measured using extracted teeth. RESULTS: SEM demonstrated that all groups produced a 1-2microm thick hybrid layer with funnel shaped resin tags, although the length of tags was shorter for the group in which MDPB-containing bonding-resin was used. TEM examination supported good adhesion of the comprehensive adhesive system employing MDPB-containing primer/bonding-resin, showing integrity between resin and dentin. There were no significant differences in microTBS among the four groups tested (p>0.05, ANOVA). SIGNIFICANCE: This study confirmed that the experimental antibacterial adhesive systems employing MDPB-containing primer or/and bonding-resin could produce an effective bond under in vivo conditions.

Animals↗
PubMed2005

Radiographic evaluation of teeth subjected to high temperatures: experimental study to aid identification processes.

The radiographic evaluation of dental remains represents a significant aspect in the forensic identification process, particularly after an exposure to fire. The aim of this "in vitro" study was to evaluate the radiographic features of unrestored, endodontically treated and restored teeth after exposure to an experimental range of high temperatures. Ninety human teeth were divided into two groups: (1) unrestored teeth, as a control group and (2) teeth endodontically treated (condensation technique) and restored with amalgam or composite fillings. Before testing the high temperatures, periapical radiographs of all teeth were performed. The tests of exposure to heat were carried out in an oven for six different temperatures (200, 400, 600, 800, 1000 and 1100 degrees C (392, 752, 1112, 1472, 1832, 2012 degrees F)). After each exposure, periapical radiographs of all the teeth were taken. The radiographic appearance of all the teeth before and after the thermal stresses were evaluated and the differences were recorded. The results of the radiographic examination showed that a number of significant radiographic details were conserved: the composite fillings were in place maintaining the shape till 600 degrees C (1112 degrees F), the amalgam fillings were in place maintaining the shape till 1000 degrees C (1832 degrees F) and the endodontic treatments were recognisable till 1100 degrees C (2012 degrees F).

Case-Control Studies↗
PubMed2004

The use of in situ models and QLF for the study of coronal caries.

OBJECTIVES: The purpose of the paper is to review aspects of the systems available to model the caries process in enamel. METHODS: The in situ model developed in Liverpool, and the new method of quantifying mineral loss, Quantitative Light-induced Fluorescence (QLF), are described. QLF is a powerful new diagnostic tool which can be used to measure demineralisation and remineralisation in tooth surfaces in vivo; studies to optimise, validate and use QLF in different clinical situations are described. RESULTS: Examples of the use of in situ models show that they are particularly valuable for monitoring de and remineralisation of artificial lesions in relation to product testing as alternatives to clinical trials, and present significant advances over in vitro methods. Quantification of mineral loss by Transverse Microradiography (TMR) as in the traditional Liverpool model has produced much valuable information, but the destructive nature of the method limits experimental design, and removes the system from the clinical situation. As a possible alternative, QLF has been validated and optimised. Longitudinal measures can be made on the same surface, and examples of its use are for monitoring recurrent caries and demineralisation around orthodontic brackets. CONCLUSIONS: While current in situ models provide a major advance over earlier caries models, measurement of de and remineralisation by destructive methods such as transverse microradiography limits the design of experimental investigations. QLF offers significant time saving, reduces the cost of clinical studies, and because the measurements can be carried out longitudinally in vivo, can remove the need for intra-oral appliances carrying experimental tissues.

Dental Caries↗
PubMed2005

Effect of different splinting methods and fixation periods on root development of autotransplanted immature third molars.

PURPOSE: The aim of the present study was to assess the influence of suture splinting for 1 week or rigid fixation for 4 weeks on final root length, root length increment, and mobility of autotransplanted immature third molars. PATIENTS AND METHODS: The sample consisted of 63 patients with a total of 65 transplanted immature third molars. All transplants had reached one-half (n = 29) to three-fourths (n = 36) of their expected root length. In 24 of the transplants, postoperative fixation was carried out with a rigid acid-etch composite and wire splint for 4 weeks (rigid group), and in 41 transplants, with a suture splint for 1 week (suture group). The fixation method depended on the initial stability of the transplants. All transplants were followed up clinically and radiologically for a mean period of 3.9 years. RESULTS: Transplants in the rigid group revealed a significantly lower final root length ( P = .002) and root length increment ( P = .001) than those in the suture group. The differences were found to be more pronounced in transplants at earlier developmental stages. No differences were found in transplant mobility. CONCLUSIONS: The results of the present study indicate that prolonged rigid fixation of autotransplanted immature third molars has a significantly negative influence on final root length and root length increment, especially in transplants at earlier developmental stages.

Adolescent↗
PubMed2004

Coronectomy: a technique to protect the inferior alveolar nerve.

PURPOSE: Damage to the inferior alveolar nerve when extracting lower third molars is often caused by the intimate relationship between the nerve and the roots of the teeth. The technique of coronectomy, or intentional root retention, may minimize this problem. PATIENTS AND METHODS: Forty-one patients underwent coronectomy on 50 lower third molars with follow-up of at least 6 months. The technique of coronectomy deliberately protected the lingual nerve as part of the surgical procedure. All roots were left at least 3 mm below the buccal and lingual plates of bone. All patients were radiographed preoperatively, immediately postoperatively, and after 6 months. RESULTS: There were no cases of inferior alveolar nerve-involved damage in this study of 41 patients who underwent 50 coronectomies. There was 1 case of transient lingual nerve involvement, probably from the use of the lingual retractor. One patient required subsequent removal of the roots of both lower third molars because of failure to heal, and 1 patient required subsequent removal of a root because of subsequent migration to the surface. Root migration was noted in approximately 30% of patients over a 6 month period. CONCLUSION: Coronectomy appears to be a viable technique in those cases where removal of the whole tooth might put the inferior alveolar nerve at considerable risk of damage. The technique appears to be associated with a low incidence of complications, but subsequent migration of the roots may be an issue in the long term.

Cranial Nerve Injuries↗
PubMed2005

Radiographic evaluation of the status of third molars in the Asian-Indian students.

PURPOSE: The purpose of this study is to assess the prevalence and agenesis of third molars, their impaction status, and the time and sequence of their eruption in the students of Asian-Indian population. PATIENTS AND METHODS: One hundred students with ages ranging from 17.5 to 20.0 years were randomly selected. This age group was selected because this is the age at which third molars normally begin to erupt. Students who had undergone any tooth extraction or orthodontic treatment previously were not included in the study. RESULTS: The incidence of congenital missing third molars was 11.5%, with a higher incidence in females. Of the third molars present, 31% were in mesioangular position, 42% were in the vertical position, 27% were in the distoangular position, and none were in the horizontal position. Of the 354 teeth examined, 24% of teeth were found to be erupted and 76% were in various stages of eruption. The level of eruption of third molars was 27% at A; 39%, B; and 34%, C. CONCLUSIONS: The present study showed that at the baseline (mean age, 19.3 years), 24% of third molars were erupted, 76% were in various stages of eruption, and 11.5% were congenitally missing in the Asian-Indian student population.

Adolescent↗