Tooth resorption is an idiopathic destructive disease of dental hard tissues. The etiology and pathogenesis remain obscure. It has various manifestations and can be commonly classified as internal tooth resorption and external root resorption on the basis of the resorptive lesion sites. There have been many attempts to make further classification based upon the pathological manifestations in recent years. Radiographic examination is an effective tool to assist in the diagnosis. There are few systematic researches on tooth resorption worldwide, most of which are case reports. This review elaborates on the research progress of tooth resorption from aspects of pathogenesis and classification.
Humans ; Root Resorption/diagnostic imaging* ; Tooth Resorption/diagnostic imaging*

OBJECTIVE: To measure the three-dimensional morphology of the labial supraosseous gingiva (SOG) and the thickness of related labial bone in maxillary anterior teeth of periodontally healthy Han nationality youth using soft tissue indirect imaging cone-beam computed tomography (CBCT). METHODS: Twenty-five periodontally healthy subjects (11 males and 14 females) with 150 maxillary anterior teeth were involved in this study. A special impression with radiopaque material including the maxillary teeth was made, then a CBCT scan with the elastomeric matrix in position was taken for each subject. The imaging data were generated and transferred to a volumetric imaging software in which three-dimensional reconstruction was conducted and the image analyses were carried out. Measurements were made at the site of labial center of the maxillary anterior teeth. The height of the SOG, the distance between cemento-enamel junction (CEJ) and bone crest, the gingival thickness at the CEJ, and the thickness of bone 2 mm below the labial bone crest were measured and the correlation analysis between the parameters was made. All the data analyses were performed using SPSS 22.0. The data were analyzed with ANVOA and Pearson correlation tests with the significance level at α=0.05. RESULTS: The mean SOG values were (3.49±0.70) mm, (3.48±0.81) mm, and (3.54±0.67) mm for central incisors, lateral incisors and canines, respectively. There were no statistically significant differences among the different sites (P > 0.05). The mean gingival thickness values were (1.45±0.23) mm, (1.13±0.24) mm, (1.14±0.22) mm for central incisors, lateral incisors and canines, respectively. The gingival thickness of the central incisors was the largest among the maxillary anterior teeth with statistically significant difference (P < 0.05). No correlation was found between the SOG and gingival thickness among the maxillary anterior teeth (P > 0.05). CONCLUSION The gingival thickness of central incisors was the largest and the supraosseous gingival height had no correlation with gingival thickness among the periodontally healthy maxillary anterior teeth.
Adolescent ; Cone-Beam Computed Tomography ; Female ; Gingiva/diagnostic imaging* ; Humans ; Incisor/diagnostic imaging* ; Male ; Maxilla/diagnostic imaging* ; Tooth Cervix

OBJECTIVETo investigate the difference between digital periapical film and conventional film in the evaluation of tooth length and root resorption.

METHODSA standard for root resorption in vitro was developed based on 20 extracted upper central incisors. Digital periapical films and conventional periapical films were taken before and after the process of simulating root resorption at six different projection angles respectively. The tooth length and root resorption were measured on these films. The results were analyzed by paired-samples rank sum test.

RESULTSSignificant difference on tooth length measurement was found between two types of films on the same projection angle. No significant difference on the length of root resorption calculated on digital and conventional films was found.

CONCLUSIONSThe accuracy of the digital periapical film was greater than that of conventional periapical films. The conventional periapical film can still be used in the evaluation of root resorption.

Humans ; In Vitro Techniques ; Radiography, Dental, Digital ; Root Resorption ; diagnostic imaging ; Tooth Apex ; diagnostic imaging

OBJECTIVETo evaluate the effect of rapid teeth movement through reducing resistance and distraction using cone-beam computed tomography (CBCT).

METHODSThe left or right side of the mandible of 10 beagles (5 males and 5 females) was randomly selected as the control side (for the conventional distraction with a force of about 85 g) and the other side as the experimental side (subjected to reducing resistance and distraction). CBCT images were taken at 5, 10, and 15 days and also after retaining for 10 and 90 days after distraction for 15 days. The distance of teeth transportation, degree of inclination, alveolar bone density of the compressive area and root resorption were evaluated based on the CBCT images and Ez3D2009 visualization software.

RESULTSNo significant difference was found between CBCT-based measurement and direct measurement of teeth transportation distance within the mouths (P>0.05). Teeth inclination on the experimental side was slightly greater than that on the control side (P<0.05). The root resorption on the experimental side was minimal, and the bone density increased gradually along with the teeth migration. The experimental side showed a comparable newly formed alveolar bone density and similar X-ray features of the compressive area with the control side.

CONCLUSIONSCBCT three-dimensional imaging can resolve the problems of overlapping and deformation of the two-dimensional images and is especially useful for measurement of teeth inclination and alveolar bone density in the process of reducing resistance and distraction.

Animals ; Bone Density ; Cone-Beam Computed Tomography ; Dogs ; Female ; Male ; Mandible ; diagnostic imaging ; Tooth ; diagnostic imaging ; Tooth Movement Techniques ; methods

Oral teeth image segmentation plays an important role in teeth orthodontic surgery and implant surgery. As the tooth roots are often surrounded by the alveolar, the molar's structure is complex and the inner pulp chamber usually exists in tooth, it is easy to over-segment or lead to inner edges in teeth segmentation process. In order to further improve the segmentation accuracy, a segmentation algorithm based on local Gaussian distribution fitting and edge detection is proposed to solve the above problems. This algorithm combines the local pixels' variance and mean values, which improves the algorithm's robustness by incorporating the gradient information. In the experiment, the root is segmented precisely in cone beam computed tomography (CBCT) teeth images. Segmentation results by the proposed algorithm are then compared with the classical algorithms' results. The comparison results show that the proposed method can distinguish the root and alveolar around the root. In addition, the split molars can be segmented accurately and there are no inner contours around the pulp chamber.
Algorithms ; Computers ; Cone-Beam Computed Tomography ; Humans ; Image Processing, Computer-Assisted ; Normal Distribution ; Tooth ; diagnostic imaging ; Tooth Root ; diagnostic imaging

OBJECTIVETo investigate the prevalence and configuration of the isthmuses in the apical 6 mm of the mesial and distal roots of Chinese mandibular first molar by means of micro-computed tomography.

METHODSThirty-six extracted human mandibular first molars were selected. Specimens were subject to micro-CT and a slice thickness of 30 microm was obtained in the apical 6 mm of the roots examined. The number of sections showing isthmuses at each apical level was recorded. Three-dimensional images of isthmuses of mandibular first molars were reconstructed and observed.

RESULTSThe mesial roots of human mandibular first molars had a high incidence of isthmus. The isthmus incidence was greatest 4-6 mm from the apex in human mandibular first molar, with prevalence figures of 49.5%-66.1% and 17.3%-17.8% in mesial and distal roots, respectively. The chi-square test indicated a significant difference in the distribution of isthmuses between the two roots (P < 0.01).

CONCLUSIONSThe mesial roots of human mandibular first molars have a high incidence of isthmus, which may have clinical implications especially when surgical endodontics is performed on the mesial roots of mandibular molars.

Adult ; Dental Pulp Cavity ; diagnostic imaging ; Humans ; Imaging, Three-Dimensional ; Mandible ; diagnostic imaging ; Molar ; diagnostic imaging ; Root Canal Therapy ; Tooth Root ; diagnostic imaging ; X-Ray Microtomography

OBJECTIVETo evaluate the orthodontic treatment outcome in patients with impacted maxillary central incisor in the mixed dentition.

METHODSNine patients, aged 8 to 11 years, with impacted maxillary central incisor were treated orthodontically. The cone-beam CT(CBCT) was taken before treatment, after treatment and one year out of retention to evaluate the root length, root canal wall thickness, width of the apical foramen, and degree of root bending, alveolar bone height and thickness. The crown-to-root ratio was calculated. The periodontal and endodontic conditions were evaluated. The parameters of the treated incisors and contralateral ones served as controls were compared.

RESULTSNine impacted teeth were treated successfully. Throughout the treatment, the root of impacted central incisor continued to develop and the alveolar bones also continued to develop and remodel. The condition of the alveolar bone of vertically impacted teeth was better than that of horizontally impacted ones. No periodontal pocket or pulp necrosis was found after treatment. Seven patients were examined one year after treatment. No significant difference was found in root length, palatal alveolar bone level and palatal alveolar bone thickness. The control group root length was (13.07±2.15) mm, the treatment group root length was (12.06±2.00) mm. No further alveolar bone loss, gingival recession and pulp necrosis were found. The control group labial and palatal alveolar bone levels were (0.90±0.62), (0.45±0.52) mm, labial and palatal alveolar bone thickness were (0.85±0.14), (1.21±0.41) mm. The treatment group labial and palatal alveolar bone levels were (2.18±1.59) mm, (0.57±0.71) mm, labial and palatal alveolar bone thickness were (0.48±0.29), (1.43±0.31) mm.

CONCLUSIONSOrthodontic therapy for impacted maxillary central incisor in the mixed dentition could promote root development and alveolar bone remodeling. Good periodontal and endodontic conditions were achieved.

Alveolar Bone Loss ; diagnostic imaging ; Child ; Cone-Beam Computed Tomography ; Dentition, Mixed ; Gingival Recession ; diagnostic imaging ; Humans ; Incisor ; diagnostic imaging ; Maxilla ; Orthodontics ; methods ; Tooth Apex ; diagnostic imaging ; Tooth Crown ; diagnostic imaging ; Tooth Root ; diagnostic imaging ; Tooth, Impacted ; diagnostic imaging ; therapy ; Treatment Outcome

OBJECTIVETo study the alveolar bone surrounding situation and the length of the root of the maxillary labial inverted impacted incisor in mixed dentition after orthodontic treatment.

METHODSFourteen cases with maxillary labial inverted impacted incisor in mixed dentition were collected. Modified Nance arch and conventional appliance were used. Cone-bean CT (CBCT) was taken after the treatment. Simplant13.0 three-dimensional reconstruction and multi-planer reconstruction (MPR) method were used to observe the labial and lingual alveolar bone crest morphology, besides, the labial and lingual length from the alveolar bone crest to cemento-enamel junction (CEJ) of the impacted incisor and the homonym tooth after treatment, along with their root length and their labial and lingual length ratio of the root surrounded by the alveolar bone to the total root length were measured. The idependent samples t-test were used to analyze the variable differences.

RESULTSThe labial and lingual alveolar bone of fourteen cases crest of the diseased tooth after treatment presented general symmetry U shape from qualitative observation through the three-dimensional reconstruction. The labial and the lingual length of the diseased incisor from alveolar bone crest to CEJ [(2.47 ± 1.35) and (1.47 ± 0.84) mm] was significant increased than those of the homonym incisor [(1.03 ± 0.35) and (0.90 ± 0.37) mm] (P < 0.05); the length of the diseased incisor's post-treatment root [(9.82 ± 2.82) mm] was no statistically significant decreased than that of the homonym incisor root [(10.28 ± 1.38) mm, P = 0.59]; the labial and the lingual length ratio of the impacted tooth's root surrounded by the alveolar bone to the total root length [(72.83 ± 17.16)% and (85.32 ± 5.98)%] was statistically significant decrease than those of homonym teeth[(89.66 ± 3.98)% and (90.84 ± 4.61)%] (P < 0.05).

CONCLUSIONSThe diseased tooth's root had gotten enough length after the treatment. The labial and lingual alveolar bone of the maxillary labial inverted impacted incisor in mixed dentition can't offer sufficient adaptive hyperplasia after treatment, of which labial alveolar bone is more apparent, prompting careful protection when they were used.

Alveolar Process ; diagnostic imaging ; pathology ; Child ; Cone-Beam Computed Tomography ; Dentition, Mixed ; Female ; Follow-Up Studies ; Humans ; Incisor ; diagnostic imaging ; pathology ; surgery ; Male ; Maxilla ; diagnostic imaging ; pathology ; surgery ; Orthodontic Extrusion ; Tooth Root ; diagnostic imaging ; pathology ; Tooth, Impacted ; diagnostic imaging ; surgery

OBJECTIVETo investigate the characteristic of the maxillary molars with two palatal roots and its prevalence by cone-beam computered tomography.

METHODSCone-beam CT (CBCT) images of dentitions were collected retrospectively from 528 patients comprising 1957 maxillary molars. The characteristic and prevalence of maxillary molars with two palatal roots was analyzed. The tooth position, sex and unilateral and bilateral occurrence were recorded.

RESULTSThe prevalence of two palatal roots was 0.72%(14/1957). Maxillary second molar with two palatal roots was detected in 1.12%(11/979), which showed a statistically higher prevalence than maxillary first molar 0.31%(3/978). This prevalence did not differ with sex or the side(P > 0.05). The mean distance of interorifice from the mesiolpalatal canal to the distopalatal canal was (2.84 ± 0.50) mm, and the angle between two palatal roots was on average (34.6 ± 16.1) °,which were significantly greater than the mean distance of interorifice from the two buccal roots (2.15 ± 0.82) mm and the angle between the two roots was (21.3 ± 12.2) °.

CONCLUSIONSThe prevalence of maxillary second molars with two palatal roots was higher than that of the first malars. The angle between the two palatal roots brings difficulty to root canal therapy, so the consciousness of double palatal roots of maxillary molars was helpful for clinical operation.

Adolescent ; Adult ; Aged ; Cone-Beam Computed Tomography ; methods ; Dental Pulp Cavity ; diagnostic imaging ; Female ; Humans ; Male ; Maxilla ; diagnostic imaging ; Middle Aged ; Molar ; diagnostic imaging ; Prevalence ; Retrospective Studies ; Tooth Apex ; diagnostic imaging ; Tooth Root ; abnormalities ; diagnostic imaging ; Young Adult

OBJECTIVETo observe the microstructure changes of rat alveolar bone around tooth root under orthodontic force loading.

METHODSTen 10-week-old rats were included in the study. Upper first molars were moved mesially with 0.196 N of force. The alveolar bone around the root of upper first molar was scanned by a micro-computed tomography scan system (SkyScan-1076) in different period after the initiation of orthodontic force loading (on the 3rd, 7th, 14th day after force loading) and analyzed by a specially-designed software to measure the microstructure parameters of alveolar bone (bone volume fraction, bone surface to volume ratio, structure model index, trabecular thickness, trabecular separation, trabecular number).

RESULTSFrom the 7th day, bone volume fraction [(41 ± 14)%], structure model index (1.51 ± 0.52) and trabecular separation [(90 ± 30) µm] changed significantly in the compressive area compared with those [(64 ± 15)%, (0.51 ± 0.85), (56 ± 10) µm] on the 3rd day. From the 14th day, bone volume fraction [(78 ± 14)%], structure model index (0.28 ± 0.20) and trabecular separation [(29 ± 13) µm] changed significantly in the tension area compared with those [(67 ± 14)%, (0.40 ± 0.41), (48 ± 15) µm] on the 7th day. No difference on trabecular number was found between the compressive area and tension area (P > 0.05).

CONCLUSIONSThe significant resorption of the alveolar bone was observed on the 7th days in the compressive area and the deposition of the alveolar bone was observed on the 14th day in the compressive area after orthodontic force loading.

Alveolar Process ; diagnostic imaging ; ultrastructure ; Animals ; Dental Cementum ; diagnostic imaging ; Male ; Molar ; diagnostic imaging ; Rats ; Rats, Sprague-Dawley ; Root Resorption ; diagnostic imaging ; Tooth Movement Techniques ; Tooth Root ; diagnostic imaging ; ultrastructure ; X-Ray Microtomography