Craniofacial height in relation to cross-sectional maxillary and mandibular morphology.

BACKGROUND: In order to gain a better understanding of how growth of the alveolar bone is linked to the vertical development of the face, the purpose of this study was to investigate if there is an association between the cross-sectional morphology of the maxillary and mandibular bodies with the craniofacial height, using images from cone beam computed tomography (CBCT). METHODS: From 450 pre-treatment CBCT scans, 180 were selected to be included in the study. Lateral head images were generated from the CBCT scans and were used to categorise subjects into three groups based on their vertical craniofacial height. Cross-sectional images from CBCT volumes were reformatted of the maxillary and mandibular bodies at five locations in the maxilla and five in the mandible. Each image was measured at one height and two width measurements. Statistical analysis performed was the one-way analysis of variance with a Tukey post hoc test. A significance level of 5% was used in all comparisons. RESULTS: Patients with large vertical craniofacial height had a significantly higher cross-sectional area both in the maxilla and in the mandible. In the same group, the cross-sectional area was significantly thinner in the mandible compared with the other two groups, especially in the anterior region. CONCLUSIONS: This study further highlights the close relationship between craniofacial height and alveolar bone dimensions and contributes with important knowledge for planning and follow-up of comprehensive dental- and orthodontic treatments.

Immunohistochemical localization of epithelial rests of Malassez in human periodontal membrane.

The aim of the present study was to describe the localization and extension of epithelial rests of Malassez (ERM) in the periodontal membrane (PDM) in normal human third molars. The material consisted of 24 normally developed human third molars surgically removed from patients with an age range from 15 to 27 years (six females and six males). The root lengths were developed from close to half-length to complete apex closure. The extracted teeth were fixed in 10 per cent neutral-buffered formalin, decalcified in ethylene diamine tetra acetic acid EDTA, paraffin embedded and cut sagittaly in 5 microm serial sections. Immunohistochemistry was performed using polyclonal rabbit anti-bovine cytokeratin (wide-spectrum screening, WSS) and the EnVision+ dual link system. The results were based on the visual comparison of WSS in the tissue sections using a light microscope. It was demonstrated that the ERM cells were distributed in the PDM in a network-shaped manner along the root surface and in the furcation region. The distribution of ERM was more prominent in teeth with incomplete root formation. The ectodermal tissue layer might influence not only the morphology of the tooth but also tooth eruption. The reaction of this epithelial layer in connection with ankylosis and orthodontic tooth movement may be of future interest.

Primary retention of first permanent mandibular molars in 29 subjects.

This study consisted of two parts: the first part describes the aetiology behind primary retention of first permanent mandibular molars by comparing the affected molar region with the contralateral region, and the second the follow-up of the retained molars. The material comprised dental pantomograms from 29 patients (17 males and 12 females; aged 6 years 2 months to 12 years 5 months) which were sent by Danish public dental clinics to the Department of Orthodontics at Copenhagen Dental School for treatment guidance (Part 1). Questionnaires were later sent to the dentists for follow-up information regarding the affected teeth (Part 2). Part 1-aetiological evaluation: From each radiograph, the number and location of the molars, maturity of individual molars, and deviations from normal morphology were recorded. The findings showed that, in an affected region, disruption of normal dental development and eruption had occurred, causing a delay in dental maturity as well as arrested eruption of the first molar. Part 2-follow-up of eruption: Completed questionnaires and radiographs were returned for 25 subjects. In 10, eruption had occurred, six after surgical removal of mucosa covering the retained first molar. In eight patients the molar had been removed while in seven the observation time from first diagnosis was too short to evaluate eruption. The results indicate that retained first permanent mandibular molars have the ability to erupt and suggest that a unilaterally retained first permanent mandibular molar may represent a temporary delay in eruption rather than permanent failure.

Association between ectopic eruption of maxillary canines and first molars.

The purpose of this study was to elucidate a possible association between ectopic first molar eruption causing root resorption on the distal root of the primary maxillary second molar, and ectopic canine eruption causing root resorption on the permanent maxillary incisors. The subjects consisted of 30 patients, 22 females and eight males in the age range 8.3-15.0 years in whom root resorption of the permanent maxillary lateral and/or central incisor caused by the erupting permanent canine was diagnosed, and clinical and/or radiographic information concerning maxillary first molar eruption existed. It was found that of the 30 patients, seven (23.3 per cent) also had pathological root resorption of the second primary molar caused by ectopic molar eruption. It is suggested that patients with ectopic maxillary first molar eruption leading to pathological root resorption of the maxillary second primary molar are followed closely during the period of premolar and canine eruption, as the ectopic first molar could be an early warning of an increased risk of ectopic canine eruption leading to root resorption of the maxillary permanent incisors.

Unilateral primary or secondary retention of permanent teeth, and dental malformations.

The purpose of the present investigation was to describe the dentition in subjects with local primary or secondary unilateral retention of two or more permanent teeth, and to elucidate the aetiology by comparing the regions of retention with the innervation pattern of the jaws. The material comprised radiographic dental orthopantomograms (OTP) from 12 patients with an age range of 6-18 years (six females and six males). The locations of retention and the dental morphology in the affected regions were analysed. Comparison with contralateral teeth was undertaken and the innervation pattern of the affected field was considered. Varying degrees of dental root malformation were found to be associated with primary and secondary retention. More pronounced root malformations were observed in subjects with several affected teeth. A connection between unilateral retained permanent teeth and temporary or permanent disruption of the nerve supply to the affected region is suggested.

Midline skeletodental morphology in holoprosencephaly.

OBJECTIVE: The purpose of the present study was to analyze histologically the midline structures in a human fetus with holoprosencephaly and a single median maxillary central incisor. METHODS: A human male fetus, CRL 137 mm, postconceptional age 18 weeks, with a diagnosis of holoprosencephaly, the cebocephalic type (one nostril), and alobar brain development, was investigated. After radiography, the cranial midline structures were examined histologically. RESULTS: The histological examination revealed partial absence of the intermaxillary suture (in the region anterior to the central incisor), absence of the internasal suture, and partial absence of the metopic suture (caudal part). A single midline nasal bone was observed instead of two bilateral nasal bones, and a midline maxillary central incisor was found instead of two bilateral incisors. A short nasal septum, absence of crista galli, and partial absence of cartilaginous tissue anterior to the sella turcica in the region of the presphenoid bone were recorded. CONCLUSIONS: The study shows that in the affected fetus, there were malformations of midline structures anterior to the sella turcica comprising suture development and cartilage development.

Transverse displacement of the proximal segment after bilateral sagittal osteotomy.

PURPOSE: The aim of the present investigation was to evaluate the transverse displacement of the proximal segment and ramus rotation after a bilateral sagittal osteotomy (BSO) with rigid internal fixation (RIF) using bicortical LAG screws. PATIENTS AND METHODS: We conducted a retrospective review of 37 patients (14 males and 23 females, age range of 14 to 55 years) who underwent a mandibular advancement with BSO and RIF. Posteroanterior and lateral cephalometric radiographs were obtained 1 to 8 weeks before and 1 to 4 weeks after surgery. The transverse displacement and angulation of the proximal segments after surgery were measured on posteroanterior radiographs, using the best-fit method. The amount of mandibular advancement was compared with the amount of transverse displacement of the proximal segments. RESULTS: In the 1 to 4-week postoperative period after a BSO, 36 of 37 subjects showed an increased transverse intergonion distance (5.6 mm) (P <.0001) and 35 of 37 patients showed an increased transverse interramus width (3.3 mm) (P <.0001). No correlation was found between mandibular advancement and transverse displacement of the proximal segment. CONCLUSIONS: The study results indicate that transverse displacements of the proximal segments occur with BSO and RIF. The clinical impact on temporomandibular joint symptomatology or surgical relapse with such displacement was not assessed in the study. Future studies that address these issues may help to determine whether there is an association between proximal segment displacement and surgical relapse, temporomandibular dysfunction, or both.