Stephan Studer

Osteoradionecrosis of the mandible: Minimized risk profile following intensity-modulated radiation therapy (IMRT)

Background and Purpose:Osteoradionecrosis (ON) of the mandible is a serious late complication of high-dose radiation therapy for tumors of the oropharynx and oral cavity. After doses between 60 and 72 Gy using standard fractionation, an incidence of ON between 5% and 15% is reported in a review from 1989, whereas in more recent publications using moderately accelerated or hyperfractionated irradiation and doses between 69 and 81 Gy, the incidence of ON is between < 1% and ~ 6%. Intensity-modulated radiation therapy (IMRT) is expected to translate into a further important reduction of ON. The aim of this descriptive study was to assess absolute and relative bone volumes exposed to high IMRT doses, related to observed bone tolerance.Patients and Methods:Between December 2001 and November 2004, 73 of 123 patients treated with IMRT were identified as subgroup “at risk” for ON (> 60 Gy for oropharyngeal or oral cavity cancer). 21/73 patients were treated in a postoperative setting, 52 patients underwent primary definitive irradiation. In 56 patients concomitant cisplatin-based chemotherapy was applied. Mean follow-up time was 22 months (12–46 months). Oral cavity including the mandible bone outside the planning target volume was contoured and dose-volume constraints were defined in order to spare bone tissue. Dose-volume histograms were obtained from contoured mandible in each patient and were analyzed and related to clinical mandible bone tolerance.Results:Using IMRT with doses between 60 and 75 Gy (mean 67 Gy), on average 7.8, 4.8, 0.9, and 0.3 cm3 were exposed to doses > 60, 65, 70, and 75 Gy, respectively. These values are substantially lower than when using three-dimensional conformal radiotherapy. The difference has been approximately quantified by comparison with a historic series. Additional ON risk factors of the patients were also analyzed. Only one grade 3 ON of the lingual horizontal branch, treated with lingual decortication, was observed.Conclusion:Using IMRT, only very small partial volumes of the mandibular bone are exposed to high radiation doses. This is expected to translate into a further reduction of ON and improved osseointegration of dental implants.Hintergrund und Ziel:Die Osteoradionekrose (ON) des Unterkiefers ist eine schwerwiegende Komplikation kurativer normofraktionierter Radiotherapie von Oropharynx- und Mundhöhlenkarzinomen. Nach Dosen zwischen 60 und 72 Gy besteht gemäß den Angaben einer Übersicht aus dem Jahr 1989 eine ON-Inzidenz von 5–15%, während laut neueren Arbeiten über leicht akzelerierte oder hyperfraktionierte Behandlungsschemata mit Dosen von 69–81 Gy die ON-Inzidenz zwischen < 1% und ca. 6% beträgt. Intensitätsmodulierte Radiotherapie (IMRT) dürfte die ON-Rate weiter reduzieren. Ziel dieser deskriptiven Arbeit war, absolute und relative Knochenvolumina mit hoher Dosisexposition zu evaluieren und in Beziehung zur beobachteten Knochentoleranz der eigenen Patienten nach IMRT-Behandlung zu setzen.Patienten und Methodik:Zwischen Dezember 2001 und November 2004 wurden an der eigenen Klinik 123 Patienten mit Tumoren der Kopf-Hals-Region mit IMRT behandelt; hiervon waren 73 einer Untergruppe von Patienten mit Risiko für ON zuzurechnen (Karzinome des Oropharynx oder der Mundhöhle und Herddosen > 60 Gy). 21 Patienten wurden postoperativ, 52 primär kurativ bestrahlt; 56 erhielten eine simultane cisplatinbasierte Chemotherapie. Die mittlere Beobachtungszeit betrug 22 Monate (12–46 Monate). Die Mundhöhle inkl. Kieferknochen außerhalb des Planungszielvolumens wurde konturiert, und Dosis-Volumen-Bedingungen zur Organschonung wurden festgelegt. Retrospektiv wurde für jeden Patienten das gesamte Kieferknochenvolumen konturiert, und die Dosis-Volumen-Histogramme wurden im Hinblick auf die klinische Knochentoleranz ausgewertet.Ergebnisse:Durch IMRT in Dosen zwischen 60 und 75 Gy (Mittelwert 67 Gy) wurden im Mittel 7,8, 4,8, 0,9 und 0,3 cm3 einer Dosis von > 60, 65, 70 und 75 Gy ausgesetzt (Tabelle 1 und Abbildung 1). Diese Werte sind deutlich kleiner als nach konventioneller Bestrahlung. Der Unterschied wurde im Vergleich mit einer historischen Serie näherungsweise quantifiziert (Abbildung 3). Zusätzliche Risikofaktoren der eigenen Patienten wurden analysiert (Abbildung 2). Nur ein ON-Ereignis (Grad 3) im Bereich des lingualen Horizontalasts der Mandibula wurde beobachtet und erfolgreich mit einer lingualen Dekortikation behandelt.Schlussfolgerung:Mittels IMRT werden nur sehr kleine Knochenvolumina hohen Bestrahlungsdosen ausgesetzt. Durch diese Knochenschonung werden eine weitere Reduktion des ON-Risikos und eine höhere Erfolgsrate rekonstruktiver Zahnimplantate (Tabelle 2) erwartet.

Osteoradionecrosis of the Mandible

Background and Purpose:Osteoradionecrosis (ON) of the mandible is a serious late complication of high-dose radiation therapy for tumors of the oropharynx and oral cavity. After doses between 60 and 72 Gy using standard fractionation, an incidence of ON between 5% and 15% is reported in a review from 1989, whereas in more recent publications using moderately accelerated or hyperfractionated irradiation and doses between 69 and 81 Gy, the incidence of ON is between < 1% and ~ 6%. Intensity-modulated radiation therapy (IMRT) is expected to translate into a further important reduction of ON. The aim of this descriptive study was to assess absolute and relative bone volumes exposed to high IMRT doses, related to observed bone tolerance.Patients and Methods:Between December 2001 and November 2004, 73 of 123 patients treated with IMRT were identified as subgroup “at risk” for ON (> 60 Gy for oropharyngeal or oral cavity cancer). 21/73 patients were treated in a postoperative setting, 52 patients underwent primary definitive irradiation. In 56 patients concomitant cisplatin-based chemotherapy was applied. Mean follow-up time was 22 months (12–46 months). Oral cavity including the mandible bone outside the planning target volume was contoured and dose-volume constraints were defined in order to spare bone tissue. Dose-volume histograms were obtained from contoured mandible in each patient and were analyzed and related to clinical mandible bone tolerance.Results:Using IMRT with doses between 60 and 75 Gy (mean 67 Gy), on average 7.8, 4.8, 0.9, and 0.3 cm3 were exposed to doses > 60, 65, 70, and 75 Gy, respectively. These values are substantially lower than when using three-dimensional conformal radiotherapy. The difference has been approximately quantified by comparison with a historic series. Additional ON risk factors of the patients were also analyzed. Only one grade 3 ON of the lingual horizontal branch, treated with lingual decortication, was observed.Conclusion:Using IMRT, only very small partial volumes of the mandibular bone are exposed to high radiation doses. This is expected to translate into a further reduction of ON and improved osseointegration of dental implants.Hintergrund und Ziel:Die Osteoradionekrose (ON) des Unterkiefers ist eine schwerwiegende Komplikation kurativer normofraktionierter Radiotherapie von Oropharynx- und Mundhöhlenkarzinomen. Nach Dosen zwischen 60 und 72 Gy besteht gemäß den Angaben einer Übersicht aus dem Jahr 1989 eine ON-Inzidenz von 5–15%, während laut neueren Arbeiten über leicht akzelerierte oder hyperfraktionierte Behandlungsschemata mit Dosen von 69–81 Gy die ON-Inzidenz zwischen < 1% und ca. 6% beträgt. Intensitätsmodulierte Radiotherapie (IMRT) dürfte die ON-Rate weiter reduzieren. Ziel dieser deskriptiven Arbeit war, absolute und relative Knochenvolumina mit hoher Dosisexposition zu evaluieren und in Beziehung zur beobachteten Knochentoleranz der eigenen Patienten nach IMRT-Behandlung zu setzen.Patienten und Methodik:Zwischen Dezember 2001 und November 2004 wurden an der eigenen Klinik 123 Patienten mit Tumoren der Kopf-Hals-Region mit IMRT behandelt; hiervon waren 73 einer Untergruppe von Patienten mit Risiko für ON zuzurechnen (Karzinome des Oropharynx oder der Mundhöhle und Herddosen > 60 Gy). 21 Patienten wurden postoperativ, 52 primär kurativ bestrahlt; 56 erhielten eine simultane cisplatinbasierte Chemotherapie. Die mittlere Beobachtungszeit betrug 22 Monate (12–46 Monate). Die Mundhöhle inkl. Kieferknochen außerhalb des Planungszielvolumens wurde konturiert, und Dosis-Volumen-Bedingungen zur Organschonung wurden festgelegt. Retrospektiv wurde für jeden Patienten das gesamte Kieferknochenvolumen konturiert, und die Dosis-Volumen-Histogramme wurden im Hinblick auf die klinische Knochentoleranz ausgewertet.Ergebnisse:Durch IMRT in Dosen zwischen 60 und 75 Gy (Mittelwert 67 Gy) wurden im Mittel 7,8, 4,8, 0,9 und 0,3 cm3 einer Dosis von > 60, 65, 70 und 75 Gy ausgesetzt (Tabelle 1 und Abbildung 1). Diese Werte sind deutlich kleiner als nach konventioneller Bestrahlung. Der Unterschied wurde im Vergleich mit einer historischen Serie näherungsweise quantifiziert (Abbildung 3). Zusätzliche Risikofaktoren der eigenen Patienten wurden analysiert (Abbildung 2). Nur ein ON-Ereignis (Grad 3) im Bereich des lingualen Horizontalasts der Mandibula wurde beobachtet und erfolgreich mit einer lingualen Dekortikation behandelt.Schlussfolgerung:Mittels IMRT werden nur sehr kleine Knochenvolumina hohen Bestrahlungsdosen ausgesetzt. Durch diese Knochenschonung werden eine weitere Reduktion des ON-Risikos und eine höhere Erfolgsrate rekonstruktiver Zahnimplantate (Tabelle 2) erwartet.

Soft tissue correction of a single-tooth pontic space: a comparative quantitative volume assessment.

STATEMENT OF PROBLEM Various augmentation procedures are recommended for the correction of localized alveolar ridge defects. However, no study has quantitatively evaluated the results of these procedures to date. PURPOSE This study compared 2 soft tissue augmentation surgeries commonly used to alter contours of single-tooth pontic space by quantifying 3-dimensional volume changes with the optical projection Moiré method at 1 and 3.5 months after surgery. MATERIAL AND METHODS Twenty-four patients required surgery. Each patient had a localized alveolar ridge defect, corresponding to a mesial-distal width of 1 single tooth. The defect of 12 patients was corrected with a subepithelial connective tissue graft; the remaining 12 patients were treated by receiving a free full-thickness gingival graft, which included epithelium and connective tissue with fatty tissue. Six unoperated defects of 6 patients formed the control group. For each defect, an impression was made before treatment, at 1 and 3.5 months after surgery to measure the volume changes on the dental casts with a validated projection Moiré system. Volume change was assessed relative to the preoperative dimension at the buccal and crestal aspects of the single-tooth pontic space. RESULTS At 3.5 months postsurgery, mean volumetric gain for the connective tissue group with 159 mm(3) (SD +/- 80) was significantly greater (P =.027) than for free full-thickness gingival graft group with 104 mm(3) (SD +/- 31). CONCLUSION The applied projection Moiré method proved its applicability in assessing 3-dimensional volume changes of pontic spaces with a single-tooth width. Volumetric assessment after 1 and 3.5 months revealed significantly greater volume gain with the subepithelial connective tissue graft in comparison to the free full-thickness gingival graft.

Is mandibular reconstruction using vascularized fibula flaps and dental implants a reasonable treatment

PURPOSE this study retrospectively analyzed the rate of screwed implant insertion and risk factors in patients undergoing mandibular reconstruction with microsurgical revascularized fibula flaps. METHODS This study retrospectively analyzed all patients with microvascularized fibula grafts between 1997 and 2005. Collected data included general data and risk factors (e.g., smoking, alcohol use), and irradiation was the main predictor variable. The number of patients rehabilitated with dental implants and the implant success rate were evaluated, possible influencing factors were identified, and the results were compared with previously published data. RESULTS The sample included 33 patients (17 men, 16 women; mean age: 52 years); 76% were smokers, 42% drank alcohol regularly, and 73% had undergone mandible irradiation. Twenty-three patients received 140 screw-retained implants for dental rehabilitation. Twenty-three implants were lost. Overall 1- and 5-year implant survival rates were 94% and 83%, respectively. Implant survival rates were 86% in non-irradiated mandibular bone, 86% in non-irradiated grafted fibular bone, 82% in irradiated mandibular bone, and 38% in irradiated grafted fibular bone. CONCLUSION This study showed that the use of dental implants in patients with fibula flaps is an appropriate and successful option for dental rehabilitation, even in those with risk factors such as smoking, alcohol use, and irradiation. Implant placement in irradiated grafted bone seems to be a high-risk procedure.

Ridge augmentation with soft tissue procedures in aesthetic dentistry: first clinical results measured with a new kind of moire technique

The oral health of the Swiss population was significantly improved by the successful prevention of dental caries and periodontitis. Along with the healthy dentition the demand for aesthetic dentistry is increasing. Removable partial dentures are becoming less accepted. Therefore, to substitute lost teeth by permanent fixed partial prosthesis (bridges), the often deformed alveolar ridge has to be operated, either to improve the aesthetic appearance or to make it possible to restore the missing teeth by a fixed cemented bridge. The aim of this paper is (1) to evaluate whether the moire technique is an appropriate and handy method, and (2) to validate the precision of the new method. The measuring system consisted of a moire projector with an integrated phase shift device and a moire viewer with a CCD video camera, connected to a frame grabber in a personal computer. a highly versatile software was allowed to control the system as well as to grab the moire images using the four-phase shift technique in order to compute the phase image of the actual object. The new technique was validated with one solid test object measured by a 3D coordination, high precision measuring machine.

Ridge augmentation with soft tissue procedures in aesthetic dentistry: pre- and postoperative volume measurements with a new kind of moire technique

The aim of this paper was to measure the volume differences of operated alveolar ridge defects before and until 3 months post-surgically. Ten patients with ten localized alveolar ridge defects were operated on. Five alveolar ridge defects were corrected by using the full thickness onlay graft technique and the other five defects were operated by the subepithelial connective tissue graft technique. A strict standardized operation protocol was followed and all alveolar ridge defects were operated on by the same dental surgeon. Before as well as 1, 2, and 3 months after surgery the corrected defect was photographed and an impression was made by using an A-silicon material to produce a gypsum-cast model. The form of all these cast models was then measured using the moire technique. The three months result of ten cases shows that the form of the operated alveolar ridge defects, which were corrected by the subepithelial connective tissue graft technique are more stable compared to those which were operated on by the full thickness onlay graft technique. Localized alveolar ridge defects using the latter method does not show a form stability after 3 months post-surgically.