Guided placement of zygomatic implants in head and neck cancer patients: implant survival and patient outcomes at 1-3 years of follow-up

Zygomatic implants (ZI) are a valuable option for supporting an obturator prosthesis after maxillary resection. This study was performed to assess the clinical outcomes of a digitally validated guided technique for ZI placement, followed by immediate prosthetic obturation. The primary objective was to evaluate implant survival, while the secondary objective was to assess patient-reported quality of life post-rehabilitation. Twelve patients treated for head and neck cancer received a total of 36 ZI after ablative surgery. The mean duration of ZI follow-up was 30.1 months. The survival rate of ZI placed in non-irradiated patients was 100%, while it was 85% in irradiated patients. Patient-reported outcomes were evaluated using the Liverpool Oral Rehabilitation Questionnaire (LORQv3) and the University of Washington Quality of Life Questionnaire (UW-QOL v4). Most patients reported satisfactory outcomes in the oral function domain of the LORQv3 (mean score 17.7 ± 4.5; possible range 12-48, with lower scores indicating better outcomes). Regarding the UW-QOL v4, the swallowing and chewing domains had the highest scores (mean 97.5 ± 8.7 and 95.8 ± 14.4, respectively; maximum possible score of 100). In conclusion, this treatment approach improves function and quality of life after maxillary ablative surgery. However, irradiated patients showed a noticeable trend of higher implant failure, and this was influenced by tumour position and size impacting the radiation dose to the zygomatic bone.

Planned dose of intensity modulated proton beam therapy versus volumetric modulated arch therapy to tooth-bearing regions

BACKGROUND

Intensity modulated proton beam therapy (IMPT) for head and neck cancer offers dosimetric benefits for the organs at risk when compared to photon-based volumetric modulated arch therapy (VMAT). However, limited data exists about the potential benefits of IMPT for tooth-bearing regions. The aim of this study was to compare the IMPT and VMAT radiation dosimetrics of the tooth-bearing regions in head and neck cancer patients. Also, we aimed to identify prognostic factors for a cumulative radiation dose of ≥40 Gy on the tooth-bearing areas, which is considered the threshold dose for prophylactic dental extractions.

METHODS

A total of 121 head and neck cancer patients were included in this retrospective analysis of prospectively collected data. We compared the average Dmean values of IMPT versus VMAT of multiple tooth-bearing regions in the same patients. Multivariate logistic regression analysis was performed for receiving a cumulative radiation dose of ≥40 Gy to the tooth-bearing regions (primary endpoint) in both VMAT and IMPT.

RESULTS

A lower Dmean was seen after applying IMPT to the tooth-bearing tumour regions (p < 0.001). Regarding VMAT, oral cavity tumours, T3-T4 tumours, molar regions in the mandible, and regions ipsilateral to the tumour were risk factors for receiving a cumulative radiation dose of ≥40 Gy.

CONCLUSIONS

IMPT significantly reduces the radiation dose to the tooth-bearing regions.

Immediate implant-retained prosthetic obturation after maxillectomy based on zygomatic implant placement by 3D-guided surgery: a cadaver study

Background

The aim of this study was to introduce a complete 3D workflow for immediate implant retained prosthetic rehabilitation following maxillectomy in cancer surgery. The workflow consists of a 3D virtual surgical planning for tumor resection, zygomatic implant placement, and for an implant-retained prosthetic-obturator to fit the planned outcome situation for immediate loading.

Materials and methods

In this study, 3D virtual surgical planning and resection of the maxilla, followed by guided placement of 10 zygomatic implants, using custom cutting and drill/placement-guides, was performed on 5 fresh frozen human cadavers. A preoperatively digitally designed and printed obturator prosthesis was placed and connected to the zygomatic implants. The accuracy of the implant positioning was obtained using 3D deviation analysis by merging the pre- and post-operative CT scan datasets.

Results

The preoperatively designed and manufactured obturator prostheses matched accurately the per-operative implant positions. All five obturators could be placed and fixated for immediate loading. The mean prosthetic point deviation on the cadavers was 1.03 ± 0.85 mm; the mean entry point deviation was 1.20 ± 0.62 mm; and the 3D angle deviation was 2.97 ± 1.44°.

Conclusions

It is possible to 3D plan and accurately execute the ablative surgery, placement of zygomatic implants, and immediate placement of an implant-retained obturator prosthesis with 3D virtual surgical planning.The next step is to apply the workflow in the operating room in patients planned for maxillectomy.

Incidental findings during the diagnostic work-up in the head and neck cancer pathway: Effects on treatment delay and survival

OBJECTIVES

As a result of the increasing number of diagnostic scans, incidental findings (IFs) are more frequently encountered during oncological work-up in patients with head and neck squamous cell carcinomas (HNSCC). IFs are unintentional discoveries found on diagnostic imaging. Relevant IFs implicate clinical consequences, resulting in delay in oncologic treatment initiation, which is associated with unfavorable outcomes. This study is the first to investigate the incidence and nature of IFs over the years and establish the effect of relevant IFs on delay.

MATERIAL AND METHODS

This retrospective study compared two time periods (2010-2011 and 2016-2017), described associations between relevant IFs and delay in carepathway interval (days between first visit and treatment initiation) and assessed the effect of relevant IFs on overall two-year survival.

RESULTS

In total, 592 patients were included. At least one IF was found in 61.5% of the patients, most frequently on chest-CT. In 128 patients (21.6%) a relevant IF was identified, resulting for the majority in radiologist recommendations (e.g. additional scanning). Presence of a relevant IF was an independent significant factor associated with delay in treatment initiation. The risk of dying was higher for patients with a relevant IF, although not significant in the multivariable model (HR: 1.46, p = 0.079).

CONCLUSION

In diagnostic work-up for HNSCC patients, relevant IFs are frequently encountered. As the frequency of additional imaging rises over the years, the number of IFs increased simultaneously. These relevant IFs yield clinical implications and this study described that relevant IFs result in significant delay in treatment initiation.

Augmented Reality Visualization for Image-Guided Surgery: A Validation Study Using a Three-Dimensional Printed Phantom

BACKGROUND

Oral and maxillofacial surgery currently relies on virtual surgery planning based on image data (CT, MRI). Three-dimensional (3D) visualizations are typically used to plan and predict the outcome of complex surgical procedures. To translate the virtual surgical plan to the operating room, it is either converted into physical 3D-printed guides or directly translated using real-time navigation systems.

PURPOSE

This study aims to improve the translation of the virtual surgery plan to a surgical procedure, such as oncologic or trauma surgery, in terms of accuracy and speed. Here we report an augmented reality visualization technique for image-guided surgery. It describes how surgeons can visualize and interact with the virtual surgery plan and navigation data while in the operating room. The user friendliness and usability is objectified by a formal user study that compared our augmented reality assisted technique to the gold standard setup of a perioperative navigation system (Brainlab). Moreover, accuracy of typical navigation tasks as reaching landmarks and following trajectories is compared.

RESULTS

Overall completion time of navigation tasks was 1.71 times faster using augmented reality (P = .034). Accuracy improved significantly using augmented reality (P < .001), for reaching physical landmarks a less strong correlation was found (P = .087). Although the participants were relatively unfamiliar with VR/AR (rated 2.25/5) and gesture-based interaction (rated 2/5), they reported that navigation tasks become easier to perform using augmented reality (difficulty Brainlab rated 3.25/5, HoloLens 2.4/5).

CONCLUSION

The proposed workflow can be used in a wide range of image-guided surgery procedures as an addition to existing verified image guidance systems. Results of this user study imply that our technique enables typical navigation tasks to be performed faster and more accurately compared to the current gold standard. In addition, qualitative feedback on our augmented reality assisted technique was more positive compared to the standard setup.?>.

Accuracy of fit analysis of the patient-specific Groningen temporomandibular joint prosthesis

Total joint replacement (TJR) with a prosthesis can be indicated for patients with severe temporomandibular joint (TMJ) dysfunction. Surgical accuracy is necessary for correct translation of the preoperatively predicted functional outcome, wear, and biomechanical behaviour of the patient-specific TMJ-TJR prosthesis. This study describes the first clinical applications of the patient-specific TMJ-TJR prosthesis according to the Groningen principles (G-TMJ-TJR), which was developed and validated in a prior human cadaver test study. The aim of this study was to validate the accuracy of placement of the patient-specific G-TMJ-TJR in the clinical setting. It was hypothesized that a virtual surgical plan (VSP) combined with guided placement of the patient-specific G-TMJ-TJR would be performed as predictably and accurately as in the prior cadaver series. All patients who received a VSP-based patient-specific G-TMJ-TJR between December 2017 and March 2020 were included in this study. The accuracy analysis was based on postoperative cone beam computed tomography (CBCT) data. All 11 prostheses could be inserted using routine pre-auricular and retromandibular surgical approaches. Analysis of the VSPs and postoperative CBCTs showed an average three-dimensional deviation of 1.07mm (standard deviation 0.46mm, range 0.33-1.91mm) for all of the fossa and mandibular components. The patient-specific G-TMJ-TJR can be applied predictably and accurately in a clinical setting.

Exploiting metabolic acidosis in solid cancers using a tumor-agnostic pH-activatable nanoprobe for fluorescence-guided surgery

Cancer cell metabolism leads to a uniquely acidic microenvironment in solid tumors, but exploiting the labile extracellular pH differences between cancer and normal tissues for clinical use has been challenging. Here we describe the clinical translation of ONM-100, a nanoparticle-based fluorescent imaging agent. This is comprised of an ultra-pH sensitive amphiphilic polymer, conjugated with indocyanine green, which rapidly and irreversibly dissociates to fluoresce in the acidic extracellular tumor microenvironment due to the mechanism of nanoscale macromolecular cooperativity. Primary outcomes were safety, pharmacokinetics and imaging feasilibity of ONM-100. Secondary outcomes were to determine a range of safe doses of ONM-100 for intra-operative imaging using commonly used fluorescence camera systems. In this study (Netherlands National Trial Register #7085), we report that ONM-100 was well tolerated, and four solid tumor types could be visualized both in- and ex vivo in thirty subjects. ONM-100 enables detection of tumor-positive resection margins in 9/9 subjects and four additional otherwise missed occult lesions. Consequently, this pH-activatable optical imaging agent may be clinically beneficial in differentiating previously unexploitable narrow physiologic differences.

It is well known that the pH of tumor tissue is lower than that of the corresponding normal adjacent tissue. Here, the authors report a clinical trial of a pH activatable nanoparticle for imaging tumours.

Quantitative 3D measurements of tibial plateau fractures

Fracture gap and step-off measurements on 2DCT-slices probably underestimate the complex multi-directional features of tibial plateau fractures. Our aim was to develop a quantitative 3D-CT (Q3DCT) fracture analysis of these injuries. CT-based 3D models were created for 10 patients with a tibial plateau fracture. Several 3D measures (gap area, articular surface involvement, 3D displacement) were developed and tested. Gaps and step-offs were measured in 2D and 3D. All measurements were repeated by six observers and the reproducibility was determined by intra-class correlation coefficients. Q3DCT measurements demonstrated a median gap of 5.3 mm, step-off of 5.2 mm, gap area of 235 mm², articular surface involvement of 33% and 3D displacement of 6.1 mm. The inter-rater reliability was higher in the Q3DCT than in the 2DCT measurements for both the gap (0.96 vs. 0.81) and step-off (0.63 vs. 0.32). Q3DCT measurements showed excellent reliability (ICC of 0.94 for gap area, 1 for articular surface involvement and 0.99 for 3D displacement). Q3DCT fracture analysis of tibial plateau fractures is feasible and shows excellent reliability. 3D measurements could be used together with the current classification systems to quantify the true extent of these complex multi-directional fractures in a standardized way.

Multi-modality 3D mandibular resection planning in head and neck cancer using CT and MRI data fusion: A clinical series

OBJECTIVES

3D virtual surgical planning (VSP) and guided surgery has been proven to be an effective tool for resection and reconstruction of the mandible. Currently, most widely used 3D VSP approaches to mandibular resection do not include detailed tumour information in the VSP. This manuscript presents a strategy where the aim was to incorporate tumour visualisation into the 3D virtual plan. Three-dimensional VSP of the mandibular resections was based on the fusion of CT and MRI data which was subsequently applied in clinical practice.

METHODS

All patients diagnosed with oral squamous cell carcinoma between 2014 and 2017 at the University Medical Centre Groningen were included. The tumour was delineated on the MRI data, after which this dataset was fused with the CT bone data in order to construct a 3D bone and tumour model for virtual resection planning. Guided resections were performed and post-operative evaluation quantified the accuracy of the resection. The histopathological findings and patient and tumour characteristics were compared to those of a historical cohort (2009-2014) of conventional mandibular continuity resections.

RESULTS

Twenty-four patients were included in the cohort. The average deviation from planned resection was found to be 2.2 mm. Histopathologic analysis confirmed all resection planes (bone) were tumour free, compared to 96.4% in the historic cohort.

CONCLUSION

MRI-CT base tumour visualisation and 3D resection planning is a safe and accurate method for oncologic resection of the mandible. It is an improvement on the current methods reported for 3D resection planning based solely on CT data.

The design, production and clinical application of 3D patient-specific implants with drilling guides for acetabular surgery

An innovative procedure for the development of 3D patient-specific implants with drilling guides for acetabular fracture surgery is presented. By using CT data and 3D surgical planning software, a virtual model of the fractured pelvis was created. During this process the fracture was virtually reduced. Based on the reduced fracture model, patient-specific titanium plates including polyamide drilling guides were designed, 3D printed and milled for intra-operative use. One of the advantages of this procedure is that the personalised plates could be tailored to both the shape of the pelvis and the type of fracture. The optimal screw directions and sizes were predetermined in the 3D model. The virtual plan was translated towards the surgical procedure by using the surgical guides and patient-specific osteosynthesis. Besides the description of the newly developed multi-disciplinary workflow, a clinical case example is presented to demonstrate that this technique is feasible and promising for the operative treatment of complex acetabular fractures.

Predictive value of the Groningen Frailty Indicator for treatment outcomes in elderly patients after head and neck, or skin cancer surgery in a retrospective cohort

OBJECTIVES

Careful selection of patients eligible for extensive head and neck cancer surgery is extremely important. A reliable predictor for postoperative outcomes in the vulnerable elderly population is not yet available. The concept of frailty describes a clinical state of increased vulnerability and can be assessed using frailty tests, such as the Groningen Frailty Indicator. In the current study, the influence of Groningen Frailty Indicator-measured frailty on clinical outcome was investigated in elderly patients surgically treated for head and neck cancer.

DESIGN

Retrospective, explorative cohort study.

SETTING

Tertiary referral centre.

PARTICIPANTS

A total of 90 patients of 65 years and older receiving surgical treatment for head and neck cancer with different primary sites.

MAIN OUTCOME MEASURES

The influence of frailty (Groningen Frailty Indicator) on postoperative complications (Clavien-Dindo classification), subjective postoperative experience of both patient and surgeon and survival were analysed.

RESULTS

A total of 36 patients were considered as frail (40%). Postoperative complications could not be predicted by frailty status. However, the Groningen Frailty Indicator dimension 'health problems' was a significant predictor for postoperative complications (P = 0.020). Unlike age and comorbidity, frailty was associated with a poor subjective patients' experience of the postoperative recovery (P < 0.01). Although not statistically significant, survival analysis showed a worse 5-year overall survival in the frail group (33%) versus the non-frail group (74%).

CONCLUSIONS

Analysis of frailty could identify elderly patients who might suffer more than expected during the postoperative period after head and neck cancer surgery. In this study, frailty was not identified as a new predictor of complications after head and neck cancer surgery.

Detection of HPV-associated oropharyngeal tumours in a 16-year cohort: more than meets the eye

BACKGROUND

Accurate assessment of the prevalence of the human papilloma virus (HPV) in oropharyngeal tumours (OpSCC) is important because HPV-positive OpSCC are consistently associated with an improved overall survival. Recently, an algorithm has become available that reliably detects clinically relevant HPV in tumour tissue, however, no complete cohorts have been tested. The aim was to determine the prevalence of active high-risk HPV infection in a complete cohort of OpSCC collected over a 16-year period.

METHODS

Using a triple algorithm of p16 immunohistochemistry, HPV-BRISH and HPV-PCR, we assessed the prevalence of active HPV infection in all OpSCC diagnosed in our hospital from 1997 to 2012 (n=193) and a random selection of 200 oral tumours (OSCC).

RESULTS

Forty-seven OpSCC (24%) were HPVGP PCR-positive; 42 cases were HPV16+, 1 HPV18+, 3 HPV33+ and 1 HPV35+. Brightfield in situ hybridisation did not identify additional HPV-positive cases. Human papilloma virus-associated tumour proportion increased from 13% (1997-2004) to 30% (2005-2012). Human papilloma virus-positivity was an independent predictor for longer disease-specific survival (HR=0.22; 95%CI:0.10-0.47). Only one OSCC was HPV+.

CONCLUSIONS

In our cohort, the incidence of HPV-associated OpSCC is low but increasing rapidly. The strict detection algorithm, analysis of disease-specific survival and the complete cohort, including palliatively treated patients, may influence the reported prevalence and prognostic value of HPV in OpSCC.

mTHPC mediated photodynamic therapy (PDT) of squamous cell carcinoma in the head and neck: a systematic review

OBJECTIVE

Photodynamic therapy (PDT) is used in curative and palliative treatment of head and neck squamous cell carcinoma (HNSCC). To evaluate available evidence on the use of mTHPC (Foscan®) mediated PDT, we conducted a review of the literature.

MATERIALS AND METHODS

A systematic review was performed by searching seven bibliographic databases on database specific mesh terms and free text words in the categories; "head and neck neoplasms", "Photodynamic Therapy" and "Foscan". Papers identified were assessed on several criteria by two independent reviewers.

RESULTS

The search identified 566 unique papers. Twelve studies were included for our review. Six studies reported PDT with curative intent and six studies reported PDT with palliative intent, of which three studies used interstitial PDT. The studies did not compare PDT to other treatments and none exceeded level 3 using the Oxford levels of evidence. Pooling of data (n=301) was possible for four of the six studies with curative intent. T1 tumors showed higher complete response rates compared to T2 (86% vs 63%). PDT with palliative intent was predominantly used in patients unsuitable for further conventional treatment. After PDT, substantial tumor response and increase in quality of life was observed. Complications of PDT were mostly related to non-compliance to light restriction guidelines.

CONCLUSION

The studies on mTHPC mediated PDT for HNSCC are not sufficient for adequate assessment of the efficacy for curative intent. To assess efficacy of PDT with curative intent, high quality comparative, randomized studies are needed. Palliative treatment with PDT seems to increase the quality of life in otherwise untreatable patients.

Non-invasive measurement of the microvascular properties of non-dysplastic and dysplastic oral leukoplakias by use of optical spectroscopy

Differential Path-length Spectroscopy (DPS) was used to non-invasively determine the optical properties of oral leukoplakias in vivo. DPS yields information on microvascular parameters such as the mucosal blood content, the microvascular blood oxygenation and the average micro-vessel diameter as well as on tissue morphological parameters such as the scattering slope and scattering amplitude. DPS measurements were made on non-dysplastic and dysplastic oral leukoplakias using a novel fiber-optic probe, and were correlated to the histological outcome of biopsies taken from the same location. Our data show borderline significant increases in mucosal blood content in dysplastic lesions compared to non-dysplastic lesions, with no changes in microvascular oxygen saturation and light scattering signatures. These results suggest that dysplastic and non-dysplastic leukoplakias may be discriminated non-invasively in vivo through differences in their microvascular properties, if they can be reproducibly quantified in the presence of a variable thickness keratin layer that optically shields the mucosal layer.

[Two unusual ulcers in one patient]

A 39-year-old Antillean woman was referred by her family doctor to an oral and maxillofacial surgeon because of an unusual and painful ulcer in the buccal region of the first left mandibular molar. Earlier that day, she was diagnosed as HIV-positive. The ulcer was diagnosed as an atypical necrotising ulcerating periodontitis. Antibiotics were subscribed and after removal of the first left mandibular molar, the ulcer healed. After several weeks, the patient was referred by her internist because of another ulcer at the lateral border of the tongue. This ulcer was diagnosed as an eosinophilic ulcer and was healing slowly. Both ulcer types are seen rarely and are strongly related to immunodeficiency diseases.

[Bisphosphonate-associated osteonecrosis of the jaws. 3. Two case reports]

The cases presented show that bisphosphonate-induced osteonecrosis of the jaw is difficult to treat. Recently, a classification of bisphosphonate-induced osteonecrosis of the jaw based on clinical appearance was published. On the basis of this classification the seriousness of the osteonecrosis can be evaluated and a method of treatment determined. The common opinion is that treatment should be as conservative as possible. This means that treatment should have as its objective the prevention of the spread of the disease by means of antibiotics and disinfectant mouthwash. Sharp bony edges may be trimmed. Extensive surgical treatment should be reserved for those rare cases in which the osteonecrosis is progressive.

Non-invasive measurement of the morphology and physiology of oral mucosa by use of optical spectroscopy

Differential path-length spectroscopy (DPS) was used to non-invasively determine the superficial optical properties of oral mucosa in vivo. DPS yields information on physiological parameters such as the mucosal blood content, the microvascular blood oxygenation and the average micro-vessel diameter as well as on morphological parameters such as the scattering slope and scattering amplitude. DPS measurements were made on normal and cancerous oral mucosa using a novel fiber-optic probe, and were correlated to the histological outcome of punch biopsies taken from the same location. Our data shows that the mucosa of oral squamous cell carcinoma is characterised by a significant decrease in microvascular oxygenation and increase in mucosal blood content compared to normal oral mucosa as well as a significant decrease in scattering amplitude and increase in scattering slope.

[Osteonecrosis of the jawbone as a side effect of intravenous treatment with bisphosphonates]

A 69-year-old man was given 4 mg of zoledronic acid intravenously monthly for 2 years because of multiple myeloma. Six months after his lower teeth had been extracted, a piece of jawbone became exposed in that area, accompanied by pain. The diagnosis 'osteonecrosis of the jawbone due to bisphosphonates' was made. The treatment consisted of local debridement, primary closure of the wound, and administration of an oral antibiotic and a disinfectant mouthwash. Necrosis of the jawbone during the use of bisphosphonates usually develops after surgery in the oral cavity, such as a tooth extraction. During intravenous treatment with bisphosphonates, jawbone necrosis occurs in 4-10% of the patients, depending on the agent used and the length of time administered. The prevalence is significantly lower during oral therapy. It would seem advisable to search for dentogenic foci before starting treatment with intravenous bisphosphonates. A source of inflammation in the gingiva, teeth or jawbone can then be eliminated in time, while the bone still has its normal capacity for regeneration. During treatment with bisphosphonates, optimal oral hygiene, regular dental check-ups and care, and, in toothless patients, a well-fitting dental prosthesis are important. Stopping the treatment with bisphosphonates after osteonecrosis has developed does not appear to be useful.

[Osteonecrosis of the jaws: a secondary effect of bisphosphonates]

When treated with intravenous bisphosphonates to prevent bone resorption, 4-10% of the patients may develop osteonecrosis of the jaws a side effect. The osteonecrosis is usually preceded by an invasive dental procedure such as the removal of a tooth. Treatment of the osteonecrosis should be conservative using aseptic mouth rinses, oral antibiotics and small debridement. It seems advisable to have a dental check-up before starting using intravenous bisphosphonates, since a potential dental infections can be treated before the bone healing capacity is reduced by the bisphosphonates.

[Spontaneous loss of sensibility of the lower lip]

A young African male was referred after the spontaneous loss of sensibility to the left of the lower lip. Anaesthesia of the left lower alveolar nerve could be confirmed. X-rays did not reveal any signs of pathology in the left mandible while clinically the gingival was tender on palpation. He was known to have sickle cell anemia. Differential diagnosis included a sickle cell mediated osteomyelitis due to infarction of the microvasculature. The diagnostic work up included additional PET scans to confirm the clinical diagnosis. The pathogenesis of sickle cell anemia and its importance to the dentist is discussed.

[Diagnostic considerations concerning a case of an unusual gingivitis]

A young woman presented a severe gingivitis that wouldn't respond to antibiotics prescribed by her general practitioner. Thorough clinical examination showed atypical gingival inflammation. In such unusual cases a careful anamnesis is essential in determining appropriate continued diagnostic procedures. Eventually, acute myeloid leukaemia was diagnosed. Since the diagnosis of gingival disease primarily lies with the dentist, it is important to be able to consider any unusual aspects of gingivitis within a dental office.

The status of in vivo autofluorescence spectroscopy and imaging for oral oncology

Autofluorescence spectroscopy and imaging have been studied for the early detection and classification of (pre)malignancies of the oral mucosa. In the present review we will give an overview of the literature on autofluorescence imaging and spectroscopy for various clinical questions. From the studies performed so far we hope to conclude whether autofluorescence spectroscopy and imaging are helpful in the diagnosis of lesions of the oral mucosa, and if this is the case: for which clinical questions they are suitable. A strong emphasis is put on in vivo human studies of the oral mucosa.

Autofluorescence and Raman microspectroscopy of tissue sections of oral lesions

Autofluorescence spectroscopy and Raman spectroscopy have been suggested for lesion diagnostics. We investigate the information contained in autofluorescence and Raman spectra recorded from oral tissue slices of various lesion types. Thirty-seven human oral mucosa lesions were biopsied and freeze-dried. Complete autofluorescence images and spectra were recorded from 20 microm sections. Raman spectra were acquired from the same positions for 12 of the sections. Cluster analysis was applied to find any relationship between spectral shape and lesion type or cell layer. Autofluorescence images showed high intensities for keratin layers and connective tissue, but hardly any for the epithelium. Autofluorescence spectra were centered around 520 nm and did not show specific spectral features. No clustering with regard to lesion type or cell layer was observed. Raman spectra allowed for reliable classification into cell layers, but differences between lesion types were not significant in this study. Autofluorescence spectra of freeze-dried oral mucosa sections did not contain useful information. A more comprehensive study is required for Raman spectra.

[Lasers in dentistry 8. Use of lasers in oral and maxillofacial surgery]

Since the 1970's lasers are used in oral and maxillofacial surgery. The effect of a laser on tissue is determined by the wavelength of the laserlight and the tissue specific absorbtion. Lasers are used for evaporation, excision and coagulation of tissue. The CO2-laser, the Nd:YAG-laser and the Argonlaser are used for these purposes. Light and laserlight are used for the diagnosis of mucosal lesions. By using different excitation wavelength autofluorescence of lesions can be detected and analysed. An artificial neural network can be used to analyse these data. Photodynamic Therapy (PDT) is a cancer therapy based on the more or less specific absorption of a drug in tumour, that can be activated with light of a specific wavelength. Activation of this drug causes tumour destruction due to the formation of oxyginradicals. PDT is limited by the penetration of the activating light and is therefore only suitable for the treatment of superficial tumours.