Initial third molar development is delayed in jaws with short distal space: An early impaction sign?

INTRODUCTION: The multifactorial aetiology of third molar (M3) impaction remains puzzling. While short retromolar jaw space is a well-established risk factor in young adults, space alone does not explain how impaction develops. Here we investigated in children and adolescents a potential new factor, delayed M3 development. We hypothesized that two important impaction correlates - lack of jaw space, and delayed M3 development - are also positively correlated with each other, and may together help suggest from early ages subsequent possible M3 impaction. MATERIAL AND METHODS: We studied 689 M3 regions on retrospective CBCT images of 179 Canadian patients aged 8-13 years, using multiple linear mixed-effects (LME) modeling to predict M3 development (using Demirjian's stages) in both upper and lower jaws based upon available distal jaw space while also accounting for age, sex, jaw, and oral quadrant. RESULTS: Lack of distal jaw space was associated with less-developed M3s in upper and lower jaws (t = 3.209, p = .001). If space availability fell below a given threshold, absence of M3 development was predicted. Upper M3s developed more than lower M3s for each additional millimetre of retro-M1 space gained. Between-sex differences were not found. CONCLUSION: Retromolar jaw space and M3 development are two positive correlates of M3 impaction that co-associate as early as childhood. Our results suggest that delayed initial M3 development merits investigation as a potential prognosticator for late M3 eruption relative to when jaw growth ceases - an outcome known to increase the likelihood of impaction.

Three-Dimensional Assessment of Crown Size and Eruption Space for Developing Third Molars: Data Collection Techniques Based on Cone-Beam Computed Tomography (CBCT).

Third molar development and eruption are two related areas of major interest in dental research into the etiology of "wisdom tooth" impaction. Third molars are not only an excellent model for studying dental development but also of fundamental clinical importance because they are very frequently impacted. Because the third molar is located in the distal-most region of the oral cavity, clinical access is relatively challenging. With the increasingly widespread use of cone-beam computed tomography (CBCT) in dentistry, studies and measurements of the third molar and its eruption area have become considerably easier to do. Here we present a novel CBCT-based measurement methodology we developed for our recent investigations that we hope will also be useful for the broader dental research community.

Effect of object location on the density measurement and Hounsfield conversion in a NewTom 3G cone beam computed tomography unit.

OBJECTIVES: The purpose of this study was to determine the effect of an object's location in a cone beam CT imaging chamber (CBCT-NewTom 3G) on its apparent density and to develop a linear conversion coefficient for Hounsfield units (HU) to material density (g cm(-3)) for the NewTom 3G Scanner. METHODS: Three cylindrical models of materials with different densities were constructed and scanned at five different locations in a NewTom 3G Volume Scanner. The average HU value for each model at each location was obtained using two different types of software. Next, five cylinders of different known densities were scanned at the exact centre of a NewTom 3G Scanner. The collected data were analysed using the same two types of software to determine a standard linear relationship between density and HU for each type of software. RESULTS: There is no statistical significance of location of an object within the CBCT scanner on determination of its density. A linear relationship between the density of an object and the HU of a scan was rho = 0.001(HU)+1.19 with an R2 value of 0.893 (where density, rho, is measured in g cm(-3)). This equation is to be used on a range between 1.42 g cm(-3) and 0.4456 g cm(-3). CONCLUSIONS: A linear relationship can be used to determine the density of materials (in the density range of bone) from the HU values of a CBCT scan. This relationship is not affected by the object's location within the scanner itself.

Density conversion factor determined using a cone-beam computed tomography unit NewTom QR-DVT 9000.

OBJECTIVE: The purpose of this study was to determine a conversion coefficient for Hounsfield Units (HU) to material density (g cm(-3)) obtained from cone-beam computed tomography (CBCT-NewTom QR-DVT 9000) data. METHODS: Six cylindrical models of materials with different densities were made and scanned using the NewTom QR-DVT 9000 Volume Scanner. The raw data were converted into DICOM format and analysed using Merge eFilm and AMIRA to determine the HU of different areas of the models. RESULTS: There was no significant difference (P = 0.846) between the HU given by each piece of software. A linear regression was performed using the density, rho (g cm(-3)), as the dependent variable in terms of the HU (H). The regression equation obtained was rho = 0.002H-0.381 with an R2 value of 0.986. The standard error of the estimation is 27.104 HU in the case of the Hounsfield Units and 0.064 g cm(-3) in the case of density. CONCLUSION: CBCT provides an effective option for determination of material density expressed as Hounsfield Units.

Radiographic features of segmental odontomaxillary dysplasia: a study of 12 cases.

The purpose of the study was to analyze the radiographic features of segmental odontomaxillary dysplasia by studying the radiographs of 12 new cases. With a standard data collection form, the radiographic characteristics were assessed by the two principal investigators who studied available radiographs of all cases. As in previously reported cases, abnormal findings in all patients were confined to the posterior segment of one maxilla. The most common findings in the cases studied were sclerosis and thickening of bony trabeculae, missing permanent premolar teeth, abnormal spacing of primary molars vertical orientation of bony trabeculae, a smaller maxillary sinus, and delayed eruption of permanent posterior teeth. Less commonly observed features were enlarged crowns, roots, and pulps of primary molars, irregular resorption of primary molar roots, mediolateral expansion of the alveolar process, splayed roots of primary molars, and an abnormal medial position of the teeth.

The occlusal radiograph revisited.

The purpose of this paper is to demonstrate occlusal radiography as an important projection for diagnostic purposes in general dental practice. There are many instances where bitewing and periapical radiographs are insufficient to demonstrate pathoses adequately. A descriptive and photographic review of the different occlusal projections and a series of illustrative cases demonstrating their diagnostic relevance is provided.

Surface disinfection of saliva-contaminated dental X-ray film packets.

A study was undertaken to determine the most effective method for the surface disinfection of saliva-contaminated dental X-ray film packets. Size 2 Kodak Poly-Soft film packets were placed in the oral cavities of patients and "sham" irradiated. After removal from the oral cavity, some of these packets were left untreated before being placed in transfer vials containing transport medium. Other packets were handled in one of three different ways before being placed in the transfer vials: 1) wiped with a piece of sterile tissue paper to remove visible saliva; 2) wiped once with a sterile piece of gauze soaked with disinfectant and then immediately wiped dry with a piece of tissue paper ("one-wipe" surface-disinfection technique); or, 3) wiped twice with a sterile piece of gauze soaked with disinfectant and allowed to air dry ("two-wipe" surface-disinfection technique). The transport medium was serially diluted and microbiological processing completed to obtain bacterial counts corresponding to the levels of bacterial contamination of the film packet surfaces. The two-wipe surface-disinfection method effectively eliminated bacterial contamination of the film packets, with all of the disinfectants tested being equally effective. The one-wipe technique, using disinfectant, appeared to be slightly less effective. Mere physical removal of the saliva from the film packet, without the use of disinfectant, was the least effective method.

Radiographic findings in a group of elderly patients at a Canadian dental school.

The panoramic and intraoral radiographs of 154 elderly dental patients aged 65 years and older were assessed at the College of Dentistry, University of Saskatchewan, Saskatoon. Thirty-seven per cent of the patients were completely edentulous, and 61% were partially edentulous. In the dentate group, 87% had evidence of at least one carious tooth, and all had radiographic evidence of alveolar bone loss. The incidence of periapical inflammatory lesions and root remnants was relatively high.

Osteomyelitis of the mandible in a patient with dysosteosclerosis. Report of a case.

Dysosteosclerosis is a rare bone dysplasia that has radiographic, histopathologic, and clinical similarities to osteopetrosis. This article reviews the dental findings reported in patients with dysosteosclerosis and presents the first reported case of osteomyelitis of the mandible in a patient with this disease. This is also the first report that demonstrates ankylosis of impacted teeth in dysosteosclerosis.

Large asymptomatic antrolith of the maxillary sinus. Report of a case.

A case of an unusually large antrolith of the maxillary sinus is presented. Because of the size of the mass, benign neoplasms were considered in the differential diagnosis. Surgery was the treatment of choice, and recurrence of the lesion is not expected.

Paradental cysts on mandibular first molars in children: report of five cases.

Five cases of paradental cyst are reported which were found to arise buccal to a mandibular first permanent molar in children under the age of 10 years. The justification for calling these lesions paradental cysts is discussed. Since the histopathological findings of this lesion are non-specific, the clinical and radiographic features are of prime importance in diagnosis when the lesion occurs in this site in patients of this age. Buccal swelling adjacent to a mandibular first molar which is partially erupted or which has a soft tissue cover is a common clinical finding. Occlusal projections generally give the best presurgical diagnostic information, demonstrating the presence of a radiolucent lesion with a periosteal bone reaction buccal to the involved tooth and displacement of the roots to the lingual. The cyst can be successfully treated by simple enucleation without disturbing the associated tooth.

Temporomandibular degenerative joint disease in children and adolescents: report of eight cases.

The prevalence of degenerative joint disease (DJD), of the temporomandibular joint (TMJ) in adolescents and its clinical and radiographic presentation has not been widely described. During a 2-year period, 174 patients with TMJ pain or dysfunction were referred to the Division of Oral Radiology, College of Dentistry, University of Saskatchewan, for radiographic evaluation. Twenty-one patients were 18 years or younger and, of these, eight were diagnosed as having DJD of one or both joints on the basis of the radiographic appearances. The clinical and radiographic features of these eight adolescent patients are described and the factors potentially associated with the development of the condition discussed. The prevalence in this study appeared to be higher than previously reported.

A study of the height of intact alveolar bone on panoramic radiographs of adult patients.

This study describes a method of estimating alveolar bone height on panoramic radiographs by using constant anatomic landmarks as reference points and calculating ratios of given distances between certain of these landmarks in dentate patients with no radiographic evidence of horizontal bone loss. Measurements were performed on four different types of panoramic radiographs. Results determined for the maxillae and mandible were constant between the different types of panoramic films. Because of differences in the measurements obtained on the right and left sides on Panorex films that have been trimmed and spliced to remove anatomic overlap in the midline areas, this type of projection may not be suitable for analysis of the maxillary alveolar bone as described in this study. The use of the mental foramen as a constant anatomic landmark for analysis of mandibular alveolar bone on panoramic radiographs may not be feasible since it appears that it may not be possible to consistently determine the exact location of the foramen. The results of the present study suggest a difference of as much as 25% among patients in the same ratio in the maxillae and as much as 12% in the same ratio in the mandible. Therefore, the results may not be of significant value as "baseline" data to estimate alveolar bone loss at a given time after tooth loss. However, this method could prove valuable in serial studies where alveolar bone height for a single patient is compared at different times before and after tooth loss.