Precision of Simultaneous Guided Dental Implantation in Microvascular Fibular Flap Reconstructions With and Without Additional Guiding Splints.

PURPOSE: Dental rehabilitation in patients receiving free flap reconstructive surgery on the mandible or maxilla is an important part of bringing patients back to normality in both a physical and psychological way. It is therefore important to be able to do this in the fastest way possible. Virtual preplanned reconstructions of jaws with implants placed simultaneously are a good way to expedite this process and have the advantage of allowing true backward planning to achieve bone placement where it prosthetically needs to be. Thus, the precise transfer of the virtually preplanned implant position to the intraoperative situation is crucial for prosthetic rehabilitation. PATIENTS AND METHODS: We compared a control group of patients (4 patients with 15 implants) with preplanned fibular reconstructions of the mandible with implants incorporated in the planning and a trial group of patients (4 patients with 13 implants) with an additional intraoperative splint for the verification of the implants' angulation. The preoperative planning and postoperative computed tomography scans were compared. RESULTS: The average positioning error at bone level was 0.9 mm in the trial group and 1.3 mm in the control group. The average angulation error in the buccolingual plane was 2.9° in the trial group and 5.5° in the control group; axially, the difference was 6.3° in the trial group and 4.1° in the control group. CONCLUSIONS: The use of digitally backward-planned fibula cutting guides with direct dental implant positioning is feasible, and the precision found is comparable with that of standard splint-guided implant placement in the general population. Although the axial angulation error has more to do with anatomic variance and positioning of the bony cutting guide, the trial population clearly profited from the additional splint in the important buccolingual angulation. Overall, we showed a high level of precision over all implants in both groups.

Risk profile for osteoradionecrosis of the mandible in the IMRT era.

BACKGROUND: The risk for osteoradionecrosis (ORN) of the mandible is positively related to bone volume exposed to > ~ 60 Gy. We hypothesized that in combined treatment, surgery may also be a risk factor. PATIENTS AND METHODS: The impact of mandibular surgery on ORN in locally disease-free IMRT cohorts was retrospectively analyzed. RESULTS: Between October 2002 and October 2013, 531 of 715 patients with oral cavity cancer (OCC), mesopharyngeal cancer (MC), or salivary gland tumor were treated with the mandible bone exposed to ~ > 60 Gy (mean follow-up, 38 months; 7-143 months). Of the 531 patients, 36 developed ORN (7 %; 1.5 % with grade 3-4). The ORN rate in definitive IMRT MC (16/227) and in postoperative IMRT OCC patients with no mandibular surgery (3/46) was 7 % each; in OCC patients with mandibular surgery the rate was 29 % (15/60, p = 0.002). Marginal or periosteal bone resection was found to be a high risk factor (39 %, vs. 7 % followed by segmental or no resection, p < 0.0001). CONCLUSION: Marginal or periosteal bone resection of the mandible was identified as the highest ORN risk factor in our IMRT cohort.

Risk-adapted dental care prior to intensity-modulated radiotherapy (IMRT).

BACKGROUND: At the Clinic for Radiation Oncology at the Zurich University Hospital (UniversitätsSpital Zürich [USZ]), head-and-neck tumor (HNT) patients have been treated with intensity-modulated radiotherapy (IMRT) since 01/2002 (n 〉 800). This method causes less damage to normal tissues adjacent to the tumor, and thus it was possible in the head/neck region to markedly reduce the rate of osteoradionecrosis (ORN), in addition to reducing the rate of severe xerostomia. Based on these results, risk-adapted dental care (RaDC) was adopted by our clinic as the standard mode of pre-IMRT dental treatment. The guidelines as formulated by Grötz et al. were respected. ORN prophylaxis is one of the most important goals of pre-radiotherapy dental care, and the ORN rate is a measurable parameter for the efficacy of dental care, given a certain radiation technique. The aim of the present study was therefore to evaluate the efficacy of RaDC as reflected by the ORN rate of our IMRT patients. MATERIALS AND METHODS: IN August 2006, RaDC was clinically implemented and has been used for all HNT patients prior to IMRT since then. Before that (01/2002-07/2006), dental restorations were performed according to the usual procedure. RESULTS: The rate of grade-2 ORN was similar in the conventionally treated and RaDC groups (2% and 1%, resp.); grade-3 ORN had not occurred by the time the analysis was conducted. As expected, fewer extractions were performed in the RaDC cohort (no extractions in 47% of the RaDC/IMRT cohort vs. 27% in the IMRT cohort receiving conventional dental care). CONCLUSION: After considerably less invasive dental treatment, no higher-grade ORN occurred and no ORN-related jaw resections were required. Based on the present data, risk-adapted minimally invasive dental care is recommended before IMRT.

Clinical outcomes of tooth-supported leucite-reinforced glass-ceramic crowns after a follow-up time of 13-15 years.

OBJECTIVES: The aim of this retrospective clinical study was to investigate the survival rate, technical and biologic complications of leucite-reinforced glass-ceramic crowns after a follow-up time of 13-15 years. MATERIAL AND METHODS: Fifty-three patients with 131 crowns were invited to the follow-up visit. The reconstructions were re-examined clinically and radiographically using the modified USPHS criteria and periodontal parameters of probing pocket depth (PPD), plaque index (PI), sulcus bleeding index (SBI). Patient satisfaction and post-operative sensitivity of the abutment teeth were evaluated with a questionnaire. The overall survival rate and the Kaplan-Meier survival estimate were calculated both on crown and patient level. Technical and biological complications were reported descriptively on crown level. The p-value <0.05 was considered statistically significant. RESULTS: Thirty-eight patients (12 men, 26 women) with 93 crowns were examined. The overall survival rate of all the crowns was 79.6% after a mean observation period of 14.4 ± 1.2 years. Most of the failures occurred after 11.1 years. The most common clinical failures were inacceptable ceramic fractures or chippings, which occurred in 5 out of 93 crowns (5.4%) and periodontitis, seen in 4 out of 93 teeth (4.3%). The most frequent technical complications were related to occlusal wear. Biological complications were not common. CONCLUSIONS: Leucite-reinforced glass-ceramic crowns showed a high survival rate of 79.6% after an observation period of 13-15 years. Ceramic fractures and periodontitis accounted for the majority of clinical failures. CLINICAL SIGNIFICANCE: Leucite-reinforced glass-ceramic crowns can be considered a safe and predictable treatment choice for restoring both anterior and posterior teeth.

Long-term outcomes of all-ceramic inlays and onlays after a mean observation time of 11 years.

OBJECTIVES: Long-term retrospective evaluation of the survival rate and the technical and biologic outcomes of all-ceramic inlays and onlays in premolars and molars. METHOD AND MATERIALS: Fifty-four patients treated as part of a prospective clinical trial and having received 157 inlays and 27 onlays made out of a leucite-reinforced glass-ceramic (IPS Empress) in premolars and molars, were invited to the present follow-up examination. The survival of the restorations was evaluated. The biologic outcomes were assessed by measuring the pocket probing depth (PPD), the Plaque Index (PI), and the Sulcus Bleeding Index (SBI). The technical behavior was evaluated using modified US Public Health Service criteria (modUSPHS). Finally, patient satisfaction was recorded with a questionnaire. Data of patients and restored teeth were analyzed descriptively, and continuous variables were given in mean values and standard deviations. For the analysis of the restoration survival over time, the Kaplan-Meier survival estimate was calculated. The level of statistical significance was set at P < .05. RESULTS: Thirty-six patients (20 women, 16 men; mean age 50.9 years) with 132 restorations, 107 inlays and 25 onlays, were examined after a mean observation time of 11.2 ± 4.3 years. The overall 11-year survival rate of the 132 restorations was 80.3%. Inlays exhibited an 11-year survival rate of 80.4% and onlays of 80.0%. Twenty-two technical complications occurred. Ceramic fractures (10.6%) and chipping (2.3%) were the most frequent complications. Six biologic complications occurred (4.5%). CONCLUSION: Glass-ceramic inlays and onlays presented favorable long-term clinical survival and success rates. Technical complications were predominant, and biologic problems remained rare. More clinical long-term data are needed.

[Recommendations for dental care prior to intensity-modulated radiotherapy (IMRT). Adaptation of the University Hospital Zurich (USZ) guidelines]. / Empfehlung für die Zahnsanierung vor intensitäts-modulierter Radiotherapie (IMRT). UniversitätsSpital Zürich (USZ)-Richtlinien-Anpassung.

This article is aimed to inform about the recently performed adjustments of the established standard procedures for pre-radiotherapeutic dental care (GROTZ 2003; Shaw et al. 2000) on intensity modulated radiation therapy (IMRT) at the Department of Radiation Oncology, University Hospital Zurich (USZ). The adjustments described base on prospectively assessed results and clinical observations of more than 300 head and neck cancer patients treated with definitive or postoperative IMRT at the own institution. In order to explain the clinical differences between conventional radiation techniques and IMRT, a brief introduction section addresses characteristics of IMRT delivery, optimization of normal tissue sparing, and resulting improved normal tissue tolerance (Fig. 1a-c). In conclusion, careful adjustments of pre-treatment dental care as proposed (Tab. I) are recommended for IMRT patients. This requires close case-related interdisciplinary cooperation between the referring radiation oncologist and the dentist or dental care centre, respectively. The depicted sketches (Fig. 2) are thought to get completed by the radiation oncologist, in order to inform the dentist about topographic risk areas/levels for radiation-induced late effects.

Survival rate of zygomatic implants in atrophic or partially resected maxillae prior to functional loading: a retrospective clinical report.

PURPOSE: The purpose of this article was to evaluate the survival rate of 34 remote anchorage implants placed in 18 patients from placement to uncovering, prior to any prosthetic loading. MATERIALS AND METHODS: A total of 18 patients (9 women and 9 men with a mean age of 63 years) who required rehabilitation with a fixed prosthesis because of severely atrophic maxillae (including 1 patient who had undergone primary and secondary cleft lip and palate repair), traumatic maxillary bone loss, and maxillectomy procedures received 1 or 2 zygomatic implants and 2 to 4 standard maxillary dental implants. The survival rate of the 34 zygomatic implants from placement to uncovering was investigated. Aspects of the placement technique or postoperative complications related to surgical procedures likely to affect the implant failure rate were detected and critically discussed. RESULTS: Osseointegration was evaluated using the reverse torque test and percussion after uncovering. Only 1 patient (5.6%) sustained postoperative clinical complications during the evaluation period which resulted in the loss of both zygomatic implants (5.9%). CONCLUSION: Although the handling of this anchorage implant system is somewhat complex, and the design has certain shortcomings, it might be an alternative to more extensive bone augmentation procedures. However, rehabilitation of partially or completely edentulous patients with fixed implant-supported prosthesis is only feasible when 2 to 4 standard implants are placed in the anterior maxilla and splinted with the zygomatic implants.

Repositioning accuracy of fractionated stereotactic irradiation: assessment of isocentre alignment for different dental fixations by using sequential CT scanning.

BACKGROUND AND PURPOSE: To quantify the accuracy and reproducibility of patient repositioning in fractionated stereotactic conformal radiotherapy (SCRT) using dental fixations in conjunction with a stereotactic head mask. PATIENTS AND METHODS: One hundred and fourteen verification CT scans were performed on 57 patients in order to check set-up alignment. The first scan was done immediately after the first treatment. Twelve patients were checked for alignment accuracy with weekly CT scans over a period of 3-6 weeks, all others had 1-2 scans. Two different dental fixations were used in combination with a non-invasive mask system: an upper jaw support (35 patients) and a customised bite-block (17 patients). Five patients were treated with no additional fixation. Co-registration to the planning CT was used to assess alignment of the isocentre to the reference markers. Additionally, the intra-operator variability of image co-registration was assessed. RESULTS: There was a significant improvement of the overall alignment in using the bite-block instead of the upper jaw support (P<0.001). The mean deviation was for the bite-block 2.2+/-1.1 mm (1 SD), for the upper jaw support 3.3+/-1.8 mm and 3.7+/-2.8 mm for the mask alone. Overall isocentre deviations independent of the method of fixation were 2.8 mm (1.7 mm, 1 SD). Displacements in CC direction were significantly less for the bite-block compared to the upper jaw support (P=0.03). The addition of an upper jaw support significantly reduced lateral rotations compared to the mask system alone (P=0.03). The intra-operator variability of image co-registration was 1.59+/-0.49 mm (1 SD). CONCLUSION: The reproducibility of patient positioning using a re-locatable head mask system combined with a bite-block is within the reported range for similar devices and is preferable to a simple upper jaw support. In order to further reduce the margin for the planning target volume an intra-oral dental fixation is recommended.

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.

A new optical method to evaluate three-dimensional volume changes of alveolar contours: a methodological in vitro study.

OBJECTIVES: The aim of this study was to evaluate the reproducibility and the accuracy of volumetric measurements of specimens imitating localized alveolar ridge defects using an optical three-dimensional (3D) system. MATERIAL AND METHODS: Eight pairs of specimens (five with a cuboid and three with a geometrically complex form) were used for the measurements. Each of them imitated a pre-operative ridge defect and a corresponding surgically corrected post-operative situation. The true volume differences between two corresponding specimens were either assessed by a mechanical 3D coordinate measuring machine or by computer calculation (controls). For the test measurements, an optical 3D system with a newly developed software for volume measurements was utilized. The volumes of the specimen pairs were captured and the data digitized. The volume differences between the simulated pre- and post-operative situations were calculated by subtracting the two values obtained. The accuracy of the optical 3D system was assessed comparing the test and the control values. The difference between these values described the systematic error of the test method. The reproducibility was evaluated by calculating the coefficients of variation of repeated test volume measurements. Descriptive statistics were applied. RESULTS: The accuracy of the optical 3D system was very high with differences between test and control measurements never exceeding 1.5%. The systematic error of the test measurements was consistently below 2.5 mm3. The reproducibility of the measurements showed very low coefficients of variation ranging from 0.05% to 0.5%, indicating excellent reproducibility. CONCLUSIONS: The tested optical 3D system showed excellent accuracy and high reproducibility for measuring volume differences between specimens imitating localized alveolar ridge defects before and after augmentation procedures.

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 cm(3) 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.

Experimental zirconia abutments for implant-supported single-tooth restorations in esthetically demanding regions: 4-year results of a prospective clinical study.

PURPOSE: This prospective clinical study evaluated an experimental implant abutment made of densely sintered zirconia with respect to peri-implant hard and soft tissue reaction as well as fracture resistance over time. MATERIALS AND METHODS: Twenty-seven consecutively treated patients with 54 single-tooth implants were included. Zirconia abutment ingots were individually shaped and set on the implants with gold screws. All-ceramic (Empress I) crowns were cemented using a composite cement. At the 1- and 4-year examinations, reconstructions were evaluated for technical problems (fracture of abutment or crown, loosening of abutment screw). Modified Plaque and simplified Gingival Indices were recorded at implants and neighboring teeth, and peri-implant bone levels were radiographically determined. RESULTS: All but 1 of the 27 patients with 53 restorations could be evaluated at 1 year, and 36 restorations in 18 patients were evaluated 4 years after abutment and crown insertion. The median observation period for the reconstructions was 49.2 months. No abutment fractures occurred. Abutment screw loosening was reported for 2 restorations at 8 months and 27 months, respectively. Mean Plaque Index was 0.4 (SD 0.6) at abutments and 0.5 (SD 0.6) at teeth; mean Gingival Index was 0.7 (SD 0.5) at abutments and 0.9 (SD 0.5) at teeth. Mean marginal bone loss measured 1.2 mm (SD 0.5) after 4 years of functional loading. CONCLUSION: Zirconia abutments offered sufficient stability to support implant-supported single-tooth reconstructions in anterior and premolar regions. The soft and hard tissue reaction toward zirconia was favorable.