No abstract

Although 3D-printing is common in dentistry, the technique does not produce the required quality for all target applications. Resin type, printing resolution, positioning, alignment, target structure, and the type and number of support structures may influence the surface roughness of printed objects, and this study investigates the effects of these variables. A stereolithographic data record was generated from a master model. Twelve printing processes were executed with a stereolithography Desktop 3D Printer, including models aligned across and parallel to the printer front as well as solid and hollow models. Three layer thicknesses were used, and in half of all processes, the models were inclined at 15°. For comparison, eight gypsum models and milled polyurethane models were manufactured. The mean roughness index of each model was determined with a perthometer. Surface roughness values were approximately 0.65 µm (master), 0.87–4.44 µm (printed), 2.32–2.57 µm (milled), 1.72–1.86 µm (cast plaster/alginate casting), and 0.98–1.03 µm (cast plaster/polyether casting). The layer height and type and number of support structures influenced the surface roughness of printed models (p ≤ 0.05), but positioning, structure, and alignment did not.

IntroductionTo identify potential risk factors for the development of jaw osteoradionecrosis (ORN) after 3D-conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) among patients with newly diagnosed head and neck cancer.Material and methodsThis study included 776 patients who underwent 3D-CRT or IMRT for head and neck cancer at the Department of Radiotherapy at the University Hospital Halle-Wittenberg between 2003 and 2013. Sex, dental status prior to radiotherapy, tumor site, bone surgery during tumor resection, concomitant chemotherapy, and the development of advanced ORN were documented for each patient. ORN was classified as grade 3, 4, or 5 according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer classification or grade 3 or 4 according to the late effects in normal tissues/subjective, objective, management, and analytic scale. The cumulative incidence of ORN was estimated. Cox regression analysis was used to identify prognostic risk factors for the development of ORN.ResultsFifty-one patients developed advanced ORN (relative frequency 6.6 %, cumulative incidence 12.4 %). The highest risk was found in patients who had undergone primary bone surgery during tumor resection (hazard ratio [HR] = 5.87; 95 % confidence interval [CI]: 3.09–11.19) and in patients with tumors located in the oral cavity (HR = 4.69; 95 % CI: 1.33–16.52). Sex, dentition (dentulous vs. edentulous), and chemotherapy had no clinically relevant influence.Discussion and conclusionIn contrast to most previous studies, we noted a low cumulative incidence of advanced ORN. Patients with tumors located in the oral cavity and those who undergo bone surgery during tumor resection prior to RT may be considered a high-risk group for the development of ORN.

The presented directly fabricated chairside attachment system represents RFs superior to existing attachment systems after artificial aging.

Telescopic crowns with additional retention elements were more resistant to wearing than double crowns without additional retention elements. An additional clinical benefit might be the quick and easy possibility of enhancing retention.

Parotid gland sparing resulting in a dose below 20 Gy reduces radiation damage on dental hard tissues, and therefore, the dose may act as a predictor for the damage to be expected.

Removable implant-anchored dentures have become an established treatment concept especially for older, multimorbid patients. This study investigates the retention force (RF) of two different attachment systems. A total of 96 specimens (n = 8 for each condition) were fabricated and RF was measured under different conditions: fatigue (10,000 cycles dislodging), thermal undulation (5/55 °C, 5000 cycles) and implant-angulation (0°, 5°, 10°, 15°, 20°). The Novaloc system ((N), 0° and 15° abutments, yellow matrix (Y)) was compared to the Locator system ((L), pink (P) and orange (O)). Initial RFs (8.57 ± 0.99 N (NY), 19.39 ± 8.10 N (LP), 8.8 ± 5.28 N (LO)) were reduced by ageing simulation (26% (NY), 66% (LP), 89% (LO); p < 0.001). After thermocycling, Novaloc’s RFs decreased by 33% (p < 0.001) while the Locators’ RFs increased by 34% (LP: p = 0.002, LO: p = 0.148). In contrast to LP, the RFs of Novaloc abutments and LOs predominantly showed no clinically relevant dependence on implant angulation. Ageing processes tended to result in lower RFs at higher implant angulation. Thus, the Novaloc attachment system offers an alternative to Locator attachments. It is characterized by a comparatively continuous RF-curve over the entire wearing period. Future clinical studies have to be conducted to verify the in vitro demonstrated advantages of the Novaloc system.

Prosthetic treatment in head and neck cancer patients do not lead to the same improvement in OHRQoL as found in the normal population. This might be taken into account especially if extensive dental treatment is intended.