Surgery is one of the established modes of initial definitive treatment for a majority of oral cancers. Invasion of bony or cartilaginous structures by advanced upper aero-digestive tract cancer has been considered an indication for primary surgery on the basis of historic experience of poor responsiveness to radiation therapy [1]. The mandible is a key structure both in the pathology of intra-oral tumours and their surgical management. It bars easy surgical access to the oral cavity, yet maintaining its integrity is vital for function and cosmesis. Management of tumours that involve or abut the mandible requires specific understanding of the pattern of spread and routes of tumour invasion into the mandible. This facilitates the employment of mandibular sparing approaches like marginal mandibulectomy and mandibulotomy, as opposed to segmental or hemimandibulectomy which causes severe functional problems, as the mandibular continuity is lost. Accurate preoperative assessment that combines clinical examination and imaging along with the understanding of the pattern of spread and routes of invasion is essential in deciding the appropriate level and extent of mandibular resection in oral squamous cell carcinoma. Studies have shown that local control rates achieved with marginal mandibulectomy are comparable with that of segmental mandibulectomy. In carefully selected patients, marginal mandibulectomy is an oncologically safe procedure to achieve good local control and provides a better quality of life. This article aims to review the mechanism of spread, evaluation and prognosis of mandibular invasion, various techniques and role of mandibular conservation in oral squamous cell carcinoma.

To evaluate decalcified freeze dried allograft or hydroxyapatite and a combination of both as bone autograft substitutes in the healing of osseous jaw defects.

24 patients participated in the study which involved the filling of osseous defects in the maxilla/mandible with decalcified freeze dried bone allograft (DFDBA) or hydroxyapatite (HA) or a combined graft composed of these two in equal proportions.

Bone formation occurred as early as 4 weeks in the DFDBA and combination groups and 12 weeks in the HA group which was verified by radiographs, Dentascans (DentaScan® Software Program, General Electric, USA) and bone scintigraphy.

Both these materials can be used as bone graft substitutes in smaller defects although their suitability in large defects is yet to be studied.

The aim of the study was to compare image quality of two different systems based on cone-beam computed tomography (CBCT).

Primary and secondary reconstructions were performed from data sets of the Siremobil Iso-C(3D) (Siemens Medical Solutions, Erlangen, Germany) and the NewTom 9000 (NIM s.r.l., Verona, Italy) using a dried human skull. Using defined anatomical structures, image quality was analysed by 10 examiners using a ranking scale.

Regarding image quality there was no statistically significant difference between the two systems compared.

The preliminary results show, that imaging of the facial skeleton using the Siremobil Iso-C(3D) can be performed with a quality comparable to the NewTom 9000.

The purpose of this study was to compare three-dimensional (3D) imaging of the facial skeleton using an isocentric mobile C-arm system vs CT.

A dried human skull was scanned using a Siremobil Iso-C3D and a multi-detector CT (SOMATOM Volume Zoom; Siemens Medical Solutions, Erlangen, Germany) to compare reconstructed data sets. For each group of scans a standard protocol and a high resolution protocol were used. Image quality was analysed using six anatomical and six virtual structures in the primary reconstructed axial images of both data sets of the Siremobil Iso-C3D compared with CT. A receiver operating characteristic (ROC) study was performed with six examiners.

The original categorical response data revealed no significant differences in sensitivity and specificity (P < 0.05). However, image quality of the reconstructed images of the Siremobil Iso-C3D was inferior to the CT images, with metal artefacts having a more prominent negative effect.

The Siremobil Iso-C3D produces 3D images of the facial skeleton suitable for imaging osseous structures. No significant differences were found in sensitivity or specificity between the two methods. Metal objects degrade the image from the Iso-C method to a greater extent than those from CT.

This study compares the image accuracy of computerized tomography (CT) with that of plain film radiography (PFR) in analyzing the 3-dimensional shape of impacted teeth suspected of being malformed. Eighteen patients with 22 malformed teeth were studied by PFR and CT. Crown shape, root shape, crown/root relationship, and tooth inclination and structure were assessed by PFR and CT. CT was found to be superior to PFR in showing the multiplanar shape of tooth crown and root, crown/root relationship, and tooth inclination (P <.001). No difference was found in the representation of tooth structures. The findings demonstrate that CT imaging is useful to diagnose and plan treatment for patients with unerupted and malformed teeth.

The accuracy of clinical examination, peroperative periosteal stripping and imaging techniques in predicting tumour invasion of the mandible in oral cancer so far reported have been compared according to their specificity and sensitivity. Clinical examination alone was not shown to be accurate, but periosteal stripping at the time of resection was extremely accurate although so far only one study has investigated it. No single imaging technique will accurately predict the invasion of tumour into the mandible, but a combination of an orthopantomogram and bone scintigraphy is recommended in early invasion. Magnetic resonance imaging is more sensitive than computed tomography and therefore may be more useful if mandibular invasion requires consideration. The decision to resect the mandible as part of the management of oral cancer should be taken on the evidence of clinical examination, periosteal stripping and at least two imaging techniques that complement each other in terms of specificity and sensitivity.

To study the accuracy of single positron emission computed tomography (SPECT) scanning and compare its results to clinical examination, Panorex, and computed tomography (CT) scanning with respect to determining mandibular invasion by oral cavity and oropharyngeal cancer, and to define the role of SPECT scanning in the preoperative assessment of oromandibular cancer.

Prospective study of 38 patients who underwent technetium 99m SPECT scanning as part of their preoperative clinical assessment for cancer at risk of invading the mandible. All patients underwent partial or segmental mandibulectomy as part of their surgical management.

A data protocol was used to tabulate patient demographics, tumor characteristics and results of preoperative tests as patients were enrolled into the study. Following surgical treatment, these data were correlated with histopathological findings. Detailed analysis was performed to assess the tabulated data.

The SPECT scanning demonstrated an 87% overall accuracy in predicting bone invasion compared with 71% for clinical examination, CT scanning, and Panorex x-rays. The SPECT scanning was significantly more sensitive (95%) than either CT scans (55%) or Panorex x-rays (50%). Notably SPECT scanning demonstrated a considerable improvement in specificity (72%) compared with conventional radionuclide scanning. Although not as specific as CT scanning or plain films, SPECT scanning was significantly more effective in ruling out disease than was clinical examination.

Preoperative SPECT scanning used in combination with clinical examination, CT scanning, and Panorex x-rays to assess patients at risk for mandible involvement by oral cavity cancer can improve the accuracy of predicting bone invasion and help in appropriate treatment planning so as to safely reduce the proportion of disease-free jaws resected.

The purpose of this study was to evaluate the detectability of bone destruction of maxillary cancer with magnetic resonance imaging (MRI) using 14 cases of squamous cell carcinoma of the upper jaw. The detectability of bone destruction including the degree of spread to adjacent soft tissues was evaluated and compared to that of clinical examination, computed tomography (CT) and conventional X-ray films. MRI could show bone destruction of each bony part almost equally with CT, but differentiation among simple bone defects, bone expansion and bone destruction was difficult on MRI. The pattern of bone destruction of alveolus that could be detected on conventional X-ray examinations, could not be assessed on either CT or MRI. Soft tissue infiltration of the tumour was more clearly detected on MRI compared with CT and conventional X-ray films.

Assessing the adequacy of the surgical resection during composite resection of carcinoma is limited by the ability to evaluate the bone margins. The standard pathologic evaluation of bone is by decalcification.

A method of analysis was devised based on histologically proven methods of cortical invasion and subsequent spread. Frozen-section analysis of cancellous bone was investigated as a rapid method of evaluating adequacy of the mandibular resection. This report is an update of previously published results and includes an increase in the sample size as well as the analysis of additional pathology. Subjects consisted of 66 patients undergoing full thickness mandibular resection with 30 cases of histologically proven mandibular invasion qualifying for evaluation. Results on frozen section were then compared to the permanent section analysis on the cancellous bone and to the decalcified specimen.

Complete correlation was found between frozen and permanent section results. Frozen section analysis was able to correctly predict adequacy of resection in 60 of 61 margins.

Based on these results, the oncologic surgeon can evaluate bone margins at the time of the resection and adjust the amount of excision required to eradicate the disease.

We used a retrospective analysis of charts, imaging studies, and histologic findings when available in 17 patients with cancer of the oral cavity to define the value of DentaCT or multiplanar reformation software in assessing bony involvement by malignant tumors of the oral cavity. From two academic tertiary-referral medical centers, the 17 patients had a mean age of 63 years and suspected maxillary (2) or mandibular (15) invasion. All patients had conventional computed tomography scanning and multiplanar reformation scans with several additional imaging studies obtained. Two patients demonstrated no bony involvement by imaging and histologic studies. Twelve of the remaining 15 patients had surgically documented bony involvement also correctly detected by DentaCT. DentaCT was found to be a valuable tool in defining extent of bony invasion by tumor. Although not compared to other imaging modalities, our experience supports the use of DentaCT where available for this purpose.

Evaluating surgical margins during composite resection of carcinoma is limited by analysis of the bone margins. The standard pathologic evaluation of bone is by decalcification. A method of analysis was devised based on histologically proven methods of cortical invasion and subsequent spread. Frozen section analysis (FSA) of the cancellous bone was investigated as a rapid method of evaluating adequacy of the mandibular resection. Subjects consisted of 29 patients undergoing full-thickness mandibular resection, with 16 cases of histologically proven mandibular invasion qualifying for evaluation. Results of FSA were then compared to the permanent section analysis of the cancellous bone and to the decalcified specimen. Complete correlation was found between frozen and permanent section results. Frozen section analysis was able to correctly predict adequacy of resection in 32 (97%) of 33 margins.

The introduction of spiral computed tomography (CT) has been a major advance in CT scanning, particularly considering the reduction in acquisition time and improvements in 2-dimensional (2D) and 3D reconstructions. 314 out of 1262 CT examinations of the midface and jaws executed from September 1993 to September 1994 were performed in the spiral mode. Our experience is critically reviewed and a guideline for the use of spiral CT scanning of the midface and jaws for various diagnostic purposes is established: Complex midface fractures require axial spiral CT scanning with secondary coronal reconstructions Because of the long processing time 3D reconstructions are reserved for planning surgical repair of craniofacial malformations. Dental CT scans with calculation of panoramic images provide important information prior to dental implant surgery and repair of alveolar clefts.