Developmental Odontogenic Lesions Associated with the Crown of an Impacted Tooth: A Guide to the Distinct Histologic Features Required for Classification.

Odontogenic cysts are categorized as inflammatory and developmental. Of the developmental odontogenic cysts, the dentigerous cyst is the most common and by definition is attached to the cervical region of an unerupted tooth. The cyst envelops the crown forming a sac. However, there are other developmental cysts, and rarely, odontogenic tumors, that can have a similar clinical and radiographic presentation as dentigerous cyst, including odontogenic keratocyst, orthokeratinized odontogenic cyst and ameloblastoma, unicystic type. Understanding the key histologic differences of these cysts will aid the pathologist to correctly diagnose these lesions, ensuring appropriate clinical management.

A Rare Case of Radicular Dens Invaginatus (Dens in Dente) in a Dog.

A rare case of radicular dens invaginatus (dens in dente) was found during dental cleaning of a 5-year-old male Rottweiler dog. Radiographic examination revealed intense radiopacity, which extended from the crown to the apical root region of the affected tooth. Macroscopically, the crown of the left maxillary first molar tooth (209) had irregular and deformed buccal and lingual surfaces. Microscopic examination revealed dentine invagination in the pulp cavity in of the crown and root and pulp necrosis. Based on the gross, radiographic and histological findings, a diagnosis of radicular dens invaginatus was made.

3D evaluation of tooth crown size in unilateral cleft lip and palate patients.

AIM: The aim of this retrospective study is to evaluate and compare the 3-dimensional (3D) crown sizes of the left and right sides of upper and lower dental arches in patients with unilateral cleft lip and palate (UCLP). MATERIALS AND METHODS: Dental casts of 94 patients all in permanent dentition were included in this study. Dental casts were divided into three groups as 36 casts with unilateral left cleft lip and palate (ULCLP), 18 casts with unilateral right cleft lip and palate (URCLP), and 40 casts without cleft (control). Mesiodistal (MD), buccolingual (BL), and gingiva incisal (GI) values of each tooth were measured by scanning the dental models with a high-precision optical 3D scanner. Paired t-test and independent t-test were used for statistical analysis. RESULTS: U1 MD, U6 MD (P = 0.001) and BL (P = 0.01), L3 GI (P = 0.05) were greater in UCLP patients on the non-cleft side while U1 GI, L1 BL, L5 MD (P = 0.001), L4 MD, and BL (P = 0.01) values were found to be greater on the cleft side. Comparison of the cleft-sides and the control group showed that MD, BL, and GI dimensions of teeth on the cleft sides were generally found to be smaller, excluding the UR7 GI values for URCLP group (P = 0.05). CONCLUSION: In the measurements of teeth size, reliable and repeatable results were acquired through 3D software. Tooth size asymmetries can occur non-syndromic UCLP patients in both jaws. MD, BL, and GI dimensions of teeth are mostly found to be smaller in patients with CLP.

Reproductive life histories influence cariogenesis: Exploring sex-specific variation in dental caries and survivorship in the human past.

OBJECTIVES: Differences in dental caries prevalence between males and females is considered a reflection of diet. However, recent syntheses argue that sex-specific variation in dental caries prevalence also reflects changes in the oral cavity attributable to variation in reproductive life histories. This study explores sex-specific variation in carious lesions using a life history perspective to understand if differences in reproductive ecology influence this process. MATERIALS AND METHODS: Survival probability between 860 males and females from the Terry Collection was compared using carious lesion manifestation (absent, crown presence, root/cemento-enamel junction [CEJ] presence) and sex as covariates and age as a time series variable. A four-way multivariate analysis of variance (MANOVA) comparing carious lesion type by sex, age, and periodontal disease presence was used to evaluate interaction between these variables. RESULTS: Individuals with carious lesions have greater survivorship than those without lesions. Males and females with crown lesions do not differ in survivorship from individuals without carious lesions. Females with root/CEJ lesions are characterized by the highest survivorship. A significant interaction was found for root/CEJ carious lesions by age, sex, and periodontal disease presence. Root/CEJ lesion formation in older males was not dependent upon periodontal disease presence, though dependence between these variables characterizes postmenopausal females. CONCLUSION: Sex-specific variation in crown lesions is not associated with reproductive life histories and likely reflects diet. By contrast, root/CEJ lesions form through pathways attributable to reproductive life histories, particularly age-induced periodontal disease in females. These results suggest the formation of carious lesions is complex, and in some cases, rooted in reproductive life histories.

Arch parameters and dental discrepancy (crowding and spacing) in a sample of an Afro-Colombian population.

The aim of this study was to determine the differences in arch length, inter-canine distance, inter-premolar distance, intermolar distance and arch shape between dental discrepancies (crowding and spacing) in a sample of dental casts from the Afro-Colombian population of San Basilio de Palenque. An analytical, cross-sectional study was conducted on a convenience sample of 63 subjects aged 11 to 57years, of Afro-Colombian origin, with full dentition from first molar to first molar, without extensive caries or restorations, and excluding casts with defects due to loss. The differences between arch (upper and lower) variables were analyzed according to dental discrepancies. Plaster models digitalized with a TR1OS3 Mono scanner with exactitude (6.9 ± 0.9 pm) and precision (4.5 ± 0.9 pm) were analyzed with Orthonalyzer software. Statistical analyses were done on SPSS software (Version 20 for Windows) and Real Statistics. Spacing discrepancy of68.25% was found for upper arch and 66.66% for lower arch; crowding discrepancy of 19.04% for upper arch and 20.63% for lower arch, and an adequate ratio of 12.69% for both arches. No statistically significant difference (p>0.05) was found between arch parameters except for inter-premolar distance on the lower arch. The most frequent arch shape in the population was oval for both upper arch, with 76.19%, and lower arch, with 71.42%. Tooth size was larger in males than females but the difference was not statistically significant.

El objetivo de este estudio fue determinar las diferencias en longitud de arco, distancia intercanina, interpremolar, intermolar y la forma de arco entre discrepancias dentales (apiñamiento y espaciamiento), en una muestra de modelos dentales de la población afrocolombiana de San Basilio de Palenque. Se realizó un estudio analítico transversal, en una muestra por conveniencia de 63 sujetos con un rango de edad entre 11 y 57 años, de origen afrocolombiano, quienes tuvieron dentición completa de primer molar a primer molar, sin caries extensas, ni restauraciones; se excluyeron los modelos con defectos por el vaciado. Se analizaron las diferencias entre las variables de los maxilares (superior e inferior) con las discrepancias dentales. Se utilizaron modelos de yeso que fueron digitalizados con el escánerTR1OS3 Mono con una exactitud de (6.9 ± 0.9 pm) y una precisión de (4.5 ± 0.9 pm)y analizados con el software Orthonalyzer. Los análisis estadísticos se llevaron a cabo utilizando el software SPSS (Versión 20 para Windows) y Real Statistics. Se encontró una discrepancia de espaciamiento de un 68,25% para el arco superior y 66,66% en el arco inferior; y una discrepancia de apiñamiento en el arco superior de 19,04% e inferior de 20,63% y una relación adecuada de 12,69% para los dos arcos. No se encontraron diferencias estadísticamente significativas (p>0.05) en los parámetros de arco a excepción de la distancia interpremolar del arco inferior. La forma de arco más frecuente en la población fue ovalada tanto en el arco superior con un 76,19% como en el arco inferior con un 71,42%. En cuanto al tamaño dental, se presentó mayor tamaño en los hombres que en las mujeres, pero este no fue estadísticamente significativo.

Arch parameters and dental discrepancy (crowding and spacing) in a sample of an Afro-Colombian population / Parámetros de arco y discrepancia dental (apiñamiento y espaciamiento) en una muestra de población Afrocolombiana

The aim of this study was to determine the differences in arch length, inter-canine distance, inter-premolar distance, intermolar distance and arch shape between dental discrepancies (crowding and spacing) in a sample of dental casts from the Afro-Colombian population of San Basilio de Palenque. An analytical, cross-sectional study was conducted on a convenience sample of 63 subjects aged 11 to 57years, of Afro-Colombian origin, with full dentition from first molar to first molar, without extensive caries or restorations, and excluding casts with defects due to loss. The differences between arch (upper and lower) variables were analyzed according to dental discrepancies. Plaster models digitalized with a TR1OS3 Mono scanner with exactitude (6.9 ± 0.9 pm) and precision (4.5 ± 0.9 pm) were analyzed with Orthonalyzer software. Statistical analyses were done on SPSS software (Version 20 for Windows) and Real Statistics. Spacing discrepancy of68.25% was found for upper arch and 66.66% for lower arch; crowding discrepancy of 19.04% for upper arch and 20.63% for lower arch, and an adequate ratio of 12.69% for both arches. No statistically significant difference (p>0.05) was found between arch parameters except for inter-premolar distance on the lower arch. The most frequent arch shape in the population was oval for both upper arch, with 76.19%, and lower arch, with 71.42%. Tooth size was larger in males than females but the difference was not statistically significant.

El objetivo de este estudio fue determinar las diferencias en longitud de arco, distancia intercanina, interpremolar, intermolar y la forma de arco entre discrepancias dentales (apiñamiento y espaciamiento), en una muestra de modelos dentales de la población afrocolombiana de San Basilio de Palenque. Se realizó un estudio analítico transversal, en una muestra por conveniencia de 63 sujetos con un rango de edad entre 11 y 57 años, de origen afrocolombiano, quienes tuvieron dentición completa de primer molar a primer molar, sin caries extensas, ni restauraciones; se excluyeron los modelos con defectos por el vaciado. Se analizaron las diferencias entre las variables de los maxilares (superior e inferior) con las discrepancias dentales. Se utilizaron modelos de yeso que fueron digitalizados con el escánerTR1OS3 Mono con una exactitud de (6.9 ± 0.9 pm) y una precisión de (4.5 ± 0.9 pm)y analizados con el software Orthonalyzer. Los análisis estadísticos se llevaron a cabo utilizando el software SPSS (Versión 20 para Windows) y Real Statistics. Se encontró una discrepancia de espaciamiento de un 68,25% para el arco superior y 66,66% en el arco inferior; y una discrepancia de apiñamiento en el arco superior de 19,04% e inferior de 20,63% y una relación adecuada de 12,69% para los dos arcos. No se encontraron diferencias estadísticamente significativas (p>0.05) en los parámetros de arco a excepción de la distancia interpremolar del arco inferior. La forma de arco más frecuente en la población fue ovalada tanto en el arco superior con un 76,19% como en el arco inferior con un 71,42%. En cuanto al tamaño dental, se presentó mayor tamaño en los hombres que en las mujeres, pero este no fue estadísticamente significativo.

3-dimensional finite element analysis of the outcomes of Alexander, Gianelly, Roth and MBT bracket prescription.

The purpose of this study was to compare the effect of a 4-bracket system including Alexander, Roth, MBT (Maxillary Transverse Bioadaptation), and Gianelly on the upper anterior tooth movement in sliding mechanics with the help of a 3-Dimensional (3D) Finite Element Method. METHODS: Displacement, stress, strain, centre of rotation and resistance on the incise edge and apex of the maxillary central incisor were calculated when 100, 200, 300, 400grams of retraction force were applied. RESULTS: The amount of incise edge displacement was 2.609×10-4mm 2.682×10-4mm 2.875×10-4mm and 2.881×10-4mm in Alexander, Gianelly, Roth and MBT respectively with 100gr of retraction force. The value of apex root movement was 3.485×10-4mm 3.547×10-4mm 3.852×10-4mm and 3.864×10-4mm in Alexander, Gianelly, Roth and MBT respectively with 400g of retraction force. CONCLUSIONS: The MBT system had the maximum apex root and incisal edge movement in all 100, 200, 300, 400grams of retraction force. The Alexander system had the lowest apex and incisal edge movement in all retraction forces.

Finite Element Analysis of Stress in Maxillary Dentition during En-masse Retraction with Implant Anchorage.

The goal of this study was to investigate how the height of the archwire hook and implant anchor affect tooth movement, stress in the teeth and alveolar bone, and the center of resistance during retraction of the entire maxillary dentition using a multibracket system. Computed tomography was used to scan a dried adult human skull with normal occlusion. Three-dimensional models of the maxillary bone, teeth, brackets, archwire, hook, and implant anchor were created and used for finite element analysis. The heights of the hook and the implant anchor were set at 0, 5, or 10 mm from the archwire. Orthodontic force of 4.9 N was systematically applied between the hook and the implant anchor and differential stress distributions and tooth movements observed for each traction condition. With horizontal traction, the archwire showed deformation in the superior direction anterior to the hook and in the inferior direction posterior to the hook. Differences in traction height and direction resulted in different degrees of deformation, with biphasic movement clearly evident both in front of and behind the hook. With horizontal traction of the hook at a height of 0 mm, all the teeth moved distally, but not with any other type of traction. At a height of 5 mm or 10 mm, deformation showed an increase. The central incisor showed extrusion under all traction conditions, with the amount showing a reduction as the height of horizontal or posterosuperior traction increased. The center of resistance was located at the root of the 6 anterior teeth and entire maxillary dentition. The present results suggest that it is necessary to consider deformation of the wire and the center of resistance during en-masse retraction with implant anchorage.

Age estimation based on the volume change in the maxillary premolar crown using micro CT.

Age is often estimated using teeth because numerous external and internal changes appear due to aging. The purpose of this study was to investigate an age estimation method based on the volume ratio of the internal structure of the crown. 61 maxillary first premolars and 50 maxillary second premolars from subjects aged 20-79 years old were used. Micro CT, which can be used to analyze teeth in a non-destructive manner with high sensitivity, was employed in the present study. In consideration of individual differences among subjects, the volume ratio was calculated for the following four items: The pulp chamber was calculated separately based on the presence of enamel.In order to estimate age, regression analysis was conducted with the actual age as the dependent variable and each volume ratio as the independent variable. As a result, the highest correlation was found with PVR (E-) for each measurement item. Therefore, the regression equation using the volume change of the maxillary premolar crown as an index was as follows: Age = -12.43 × 4: PVR (E-) + 69.85. Age = -12.94 × 5: PVR (E-) + 72.54.

Tooth crown discoloration induced by endodontic sealers: a 3-year ex vivo evaluation.

OBJECTIVES: The aim of this study was to evaluate the tooth crown discoloration induced by commonly used and new-generation endodontic sealers after 1 month and 1 and 3 years. MATERIALS AND METHODS: The crowns of 60 extracted incisors were cut and the pulp chambers were cleaned. The specimens were divided randomly into four groups (n = 15 each). Pulp chambers were filled with Pulpispad in group 1, AH26 in group 2, MTA Fillapex in group 3, and EndoREZ in group 4. Specimen color was measured with a spectrophotometer before and after sealer placement. Commission International de L'Eclairage's (CIE's) lighteness (L*), red-green (a*), yellow-blue (b*) color system values and color difference (ΔE) were recorded at 1 month and 1 and 3 years. Data were analyzed using repeated-measures analysis of variance and Tukey's honestly significant difference test (α = 0.05). RESULTS: All sealers caused discoloration. At 1 month, ΔE values were significantly higher in groups 1 and 2 than in groups 3 and 4 (p < 0.05). At 1 year, ΔE values were significantly lower in group 3 than in the other groups (p < 0.05). At 3 years, ΔE values were significantly higher in group 1 than in the other groups (p < 0.05). CONCLUSIONS: All tested sealers induced varying chromatic alterations. After root canal obturation, thorough debridement of sealers from the pulp chamber is essential for the prevention of sealer-induced discoloration. CLINICAL RELEVANCE: Tooth discoloration induced by endodontic materials is a problem for clinicians and patients and may impair the esthetic of endodontically treated teeth. Therefore, evaluation of long-term discoloration effects commonly used, and new-generation endodontic sealers were purposed in this study.

Papilla-Crown Height Dimensions around Zirconium Dioxide Implants in the Esthetic Area: A 3-Year Follow-Up Study.

PURPOSE: Soft tissue interactions with ceramic dental implants have previously been shown to have favorable esthetic outcomes. This study aimed to evaluate the papilla-crown proportion around zirconia implants in a 3-year follow-up study and the correlation between the gingival biotype and changes in papillary height. MATERIALS AND METHODS: This was a prospective study of 39 patients with 40 single-gap implants (Straumann PURE Ceramic ZLA Implant). The papilla-crown proportion was assessed after 3 months, 1 year, and 3 years. In addition, correlations between the peri-implant biotypes and changes in papillary heights were evaluated. RESULTS: The papilla-crown proportion improved from 35.5% after 3 months to 41.7% after 3 years. The gingival biotype was correlated very weakly to papilla height alterations. Significant papillary fill was observed in the interdental space between 3 months and 3 years (p < 0.001). CONCLUSIONS: An ideal papilla-crown proportion of 40% around single implants was observed after 3 years. A thin or thick gingival biotype showed a very weak correlation with soft tissue alterations.

Pulp canal obliteration after traumatic injuries in permanent teeth - scientific fact or fiction?

Pulp canal obliteration (PCO) is a frequent finding associated with pulpal revascularization after luxation injuries of young permanent teeth. The underlying mechanisms of PCO are still unclear, and no experimental scientific evidence is available, except the results of a single histopathological study. The lack of sound knowledge concerning this process gives rise to controversies, including the most suitable denomination. More than a mere semantic question, the denomination is an important issue, because it reflects the nature of this process, and directly impacts the treatment plan decision. The hypothesis that accelerated dentin deposition is related to the loss of neural control over odontoblastic secretory activity is well accepted, but demands further supportive studies. PCO is seen radiographically as a rapid narrowing of pulp canal space, whereas common clinical features are yellow crown discoloration and a lower or non-response to sensibility tests. Late development of pulp necrosis and periapical disease are rare complications after PCO, rendering prophylactic endodontic intervention useless. Indeed, yellowish or gray crown discoloration may pose a challenge to clinicians, and may demand endodontic intervention to help restore aesthetics. This literature review was conducted to discuss currently available information concerning PCO after traumatic dental injuries (TDI), and was gathered according to three topics: I) physiopathology of PCO after TDI; II) frequency and predictors of pulpal healing induced by PCO; and III) clinical findings related to PCO. Review articles, original studies and case reports were included aiming to support clinical decisions during the follow-up of teeth with PCO, and highlight future research strategies.

Deformation behaviour of aged coronal dentin.

OBJECTIVE: This study aimed to identify the changes in the time-dependent deformation response of coronal dentin with ageing and its relationship with changes in chemical composition. BACKGROUND: The structural behaviour of dentin with ageing is affected by changes in the density and diameter of its dentinal tubules (ie porosity), as well as changes in chemical composition throughout the tooth. However, little is known about the time-dependent deformation behaviour of aged dentin and the importance of its hierarchical structure and variations in chemical composition. MATERIALS AND METHODS: The spherical indentation response of aged coronal dentin was analysed in the outer, middle and inner regions, and its time-dependent deformation response was modelled in terms of its microstructure and chemical composition using a model recently proposed for young dentin. RESULTS: The viscous deformation behaviour of aged dentin followed a power-law response with a decrease in the stress exponent when compared to young dentin. These results can be explained by cross-linking of the collagen present in the tissue. CONCLUSION: A decrease in the deformation ability of aged dentin was found. This behaviour could be a result of a dissolution process and reprecipitation of the minerals present in intertubular dentin into the dentinal tubules.

Prevalence of pre-eruptive intracoronal radiolucencies in Thai children and adolescents: A retrospective study.

AIM: The aim of the present study was to determine the prevalence, location, size, and tooth type of pre-eruptive intracoronal radiolucencies (PEIR) from panoramic radiographs in Thai patients. METHODS: A retrospective study of PEIR was conducted on 1599 panoramic radiographs of 629 Thai males and 970 Thai females with an age range of 4-20 years (average age: 14.0 ± 4.0 years). Each radiograph was reviewed by two calibrated examiners. The age and sex of the patients, location, size, and tooth type of the lesions were recorded. The SPSS program was used for statistical analysis. RESULTS: The PEIR were found in 0.32% of tooth samples (29/9060) and 1.63% of patients (26/1599). There was no statistical difference in the presence of PEIR between both sexes. The mandibular second molars were the most affected teeth. The lesions were mostly located at the central part of the crown. The lesion sizes were mostly limited to less than one-third of dentinal thickness. CONCLUSIONS: The present study showed that the prevalence of PEIR in Thai samples is 1.63%. This could raise dentists' awareness in reviewing unerupted teeth in panoramic radiographs. Early detection of the lesions should aid in proper treatment planning of affected teeth to prevent complications from carious invasion after tooth eruption.

Pulp canal obliteration after traumatic injuries in permanent teeth - scientific fact or fiction?

Abstract: Pulp canal obliteration (PCO) is a frequent finding associated with pulpal revascularization after luxation injuries of young permanent teeth. The underlying mechanisms of PCO are still unclear, and no experimental scientific evidence is available, except the results of a single histopathological study. The lack of sound knowledge concerning this process gives rise to controversies, including the most suitable denomination. More than a mere semantic question, the denomination is an important issue, because it reflects the nature of this process, and directly impacts the treatment plan decision. The hypothesis that accelerated dentin deposition is related to the loss of neural control over odontoblastic secretory activity is well accepted, but demands further supportive studies. PCO is seen radiographically as a rapid narrowing of pulp canal space, whereas common clinical features are yellow crown discoloration and a lower or non-response to sensibility tests. Late development of pulp necrosis and periapical disease are rare complications after PCO, rendering prophylactic endodontic intervention useless. Indeed, yellowish or gray crown discoloration may pose a challenge to clinicians, and may demand endodontic intervention to help restore aesthetics. This literature review was conducted to discuss currently available information concerning PCO after traumatic dental injuries (TDI), and was gathered according to three topics: I) physiopathology of PCO after TDI; II) frequency and predictors of pulpal healing induced by PCO; and III) clinical findings related to PCO. Review articles, original studies and case reports were included aiming to support clinical decisions during the follow-up of teeth with PCO, and highlight future research strategies.

Altered passive eruption (APE) and active secondary eruption (ASE): differential diagnosis and management.

The process of tooth eruption consists of two phases, active and passive. While the distinction is unequivocal, the mechanism is ambiguous. This article compares and contrasts altered passive eruption (APE) and active secondary eruption (ASE). Although these phases present with similar clinical manifestations, each has its own etiology, physiogenesis, and pathogenesis. Furthermore, the differential diagnosis between the two, and that between other mirroring conditions, is essential for arriving at a definite diagnosis and correct treatment strategies, which may be similar but have different consequences. This article concludes with two case studies that show the management of APE and ASE, highlighting the treatment similarities and differences that are dependent on the specific etiology.

[The influence of teeth morphology on bioelectrical activity of masticatory muscles]. / Vliianie morfologii zubov na bioélektricheskuiu aktivnost' zhevatel'nykh myshts.

The aim of the study was to reveal correlation of dental morphology and bioelectric activity of masticatory muscles. The study included 76 young adults (47.4% females and 52.6% males) divided in 3 groups according to dental morphology features: intact teeth (26 patients), dental decay in fissures with intact cusps (25 patients), pronounced dental decay with varying degree of crown destruction (25 patients). Electromyography (EMG) was used to document the bioelectric activity (BEA) of temporal and masticatory muscles. The study showed high level of correlation of destructive teeth changes with BEA of masticatory muscles. Intragroup correlation proved direct link of BEA to the number of decayed teeth. EMG activity differed significantly between groups 2 and 3. There was no statistically significant difference between groups 3 and 1 mostly because of high variability of BEA in group 3. Relative activity of temporal and masticatory muscles increased in groups 2 and 3 by 2 and 4% and 38 and 19%, correspondingly. There was no significant impact of gender or emotional status on masticatory muscles BEA.

Predicting extension of cracks to the root from the dimensions in the crown: A preliminary in vitro study.

BACKGROUND: In this study, the authors investigated whether extension of a tooth crack into the root can be predicted by the appearance of the crack in the crown in vitro. METHODS: The authors obtained 22 cracked teeth from 22 patients who underwent extraction, and they scanned the teeth using microcomputed tomography. The length and width of the crack on the occlusal surface (LOS and WOS, respectively) and the length of the crack on the proximal surface (LCPS) were measured on 3-dimensional reconstruction images. The pulp chamber roof was penetrated and removed. A crack line visible under the microscope only on the access cavity wall rather than extending to the bottom of the pulp chamber was termed a "nonroot crack." A crack seen at the bottom of the pulp chamber or root wall was termed a "root crack." The authors analyzed the data using Pearson correlation coefficients and receiver operating characteristic curves. RESULTS: There was a significant correlation between the LOS and LCPS (correlation coefficient, 0.782; P < .001) and between the WOS and LCPS (correlation coefficient, 0.651; P < .05). The LCPS increased by 1.195 millimeters for every 1-mm increase in the LOS. The area under the receiver operating characteristic curve was 0.839 (95% confidence interval, 0.659 to 1.000) for LOS and 0.760 (95% confidence interval, 0.557 to 0.964) for WOS. CONCLUSIONS: The extent of a crown crack may indicate how far the crack extends to the root. Both the LOS and WOS may be valuable for assessing whether a crack involves the root, although the LOS seems to be more useful. PRACTICAL IMPLICATIONS: The dimensions of a crack in a crown provide a helpful approach for predicting the depth of the crack and its likely prognosis.

Survival of labial inversely impacted maxillary central incisors: A retrospective cone-beam computed tomography 2-year follow-up.

INTRODUCTION: The aim of this study was to analyze the development and stability of roots and alveolar bone in orthodontically treated labial inversely impacted maxillary central incisors in a long-term follow-up by cone-beam computed tomography. Comparisons were made between the labial inversely impacted maxillary central incisors after treatment and normally erupted mature contralateral incisors. METHODS: The sample consisted of 12 participants, with a mean age of 7.80 ± 0.91 years. Cone-beam computed tomography scanning data at the completion of treatment and the long-term follow-up were available for each participant.The mean length of follow-up was 24.57 ± 4.33 months. Root length, crown height, root canal width, labial/lingual alveolar bone vertical loss, and bone thickness of the impacted and contralateral incisors were measured with the SimPlant Pro program (version 13.0; Materialise Dental, Leuven, Belgium). RESULTS: In the follow-up, the root lengths of both the labial inversely impacted dilacerated maxillary central incisors (10.99 ± 1.96 mm) and the contralateral mature maxillary central incisors (11.65 ± 1.37 mm) were significantly longer than at posttreatment (8.37 ± 1.74 mm and 9.81 ± 1.65 mm, respectively). The root canal widths of the impacted and contralateral incisors were significantly narrower during the follow-up. The size of the angle between the long axis of the crown and apical third of the root decreased significantly. The lingual alveolar bone loss of the impacted incisors was greater than that of the contralateral incisors. The labial bone thickness at the apex of the impacted incisors increased significantly during the follow-up period. CONCLUSIONS: The treated labial inversely impacted maxillary central incisors had continuous and similar growth as did the mature contralateral incisors in the follow-up period. The roots had an increase in length and a change in direction of the apex, with a relatively stable condition of the surrounding alveolar bone. Neither the labial inversely impacted maxillary central incisors nor the contralateral incisors had further alveolar bone loss.

The Influence of Force Direction on the Fracture Pattern and Fracture Resistance of Canine Teeth in Dogs.

Biomechanical studies of the elongated canine tooth of animals are few, and thus our understanding of mechanical and physical properties of animal teeth is limited. The objective of the present study was to evaluate the influence of force direction on fracture resistance and fracture pattern of canine teeth in an ex vivo dog cadaver model. Forty-five extracted canine teeth from laboratory beagle dogs were standardized by hard tissue volume and randomly distributed among 3 force direction groups. The teeth were secured within a universal testing machine and a load was applied at different directions based on testing group. The maximum force to fracture and the fracture pattern classification were recorded for each tooth. After correcting for hard tissue cross-sectional area in a multivariate analysis, no significant difference in the amount of force required for fracture was apparent between the different force direction groups. However, the influence of force direction on fracture pattern was significant. The results of this study may allow the clinician to educate clients on possible causal force directions in clinically fractured teeth and, thus, help prevent any contributing behavior in the future.