Oncological Outcome of Node-Positive Oral Squamous Cell Carcinomas Treated With Selective and Comprehensive Neck Dissection.

Selective neck dissection (SND) is the treatment of choice in patients with oral squamous cell carcinomas (OSCCs) and clinically node-negative necks (cN0). The treatment of patients with positive-staged necks (cN+) includes SND as well as comprehensive neck dissection (CND). The clear benefit of one or the other remains under debate. We aim to address this lack of clarity by analysing patients with OSCC staged with clinically node-positive necks, treated with either CND or SND using a level-by-level approach. This retrospective study included patients diagnosed with OSCC with clinically (cN+) and pathologically (pN+) positive cervical lymph nodes (LNs) with clear neck level categorization during the years 2010-2019. In total, 74 patients were analysed. Cox regression analysis found no significance for the type of ND being an independent risk factor, neither for overall survival (OS) nor for disease-free survival (DFS). Regional recurrence of CND cases (5.77%) was comparable to SND cases (9.09%). For OS, extracapsular spread (ECS) and male sex were identified as independent risk factors with poorer outcome. pT-stage and ECS were found to be independent risk factors for DFS. The results of this study suggest that both CND and SND may be viable treatment options for certain patients with OSCC pN+.

Volumetric evaluation of osteotomy gap following mandibular bilateral sagittal split osteotomy using a novel semi-automated approach: a pilot study.

OBJECTIVES: To establish an analysis pipeline for the volumetric evaluation of the osteotomy site after bilateral sagittal split osteotomy (BSSO). PATIENTS AND METHODS: Cone-beam computed tomography (CBCT) was performed before, directly after BSSO, and 6-12 months after surgery. Image segmentations of each osteotomy gap data set were performed manually by four physicians and were compared to a semi-automatic segmentation approach. RESULTS: Five patients with a total of ten osteotomy gaps were included. The mean interclass correlation coefficient (ICC) of individual patients was 0.782 and the standard deviation 0.080 when using the manual segmentation approach. However, the mean ICC of the evaluation of anatomical sites and time points separately was 0.214, suggesting a large range of deviation within the manual segmentation of each rater. The standard deviation was 0.355, further highlighting the extent of the variation. In contrast, the semi-automatic approach had a mean ICC of 0.491 and a standard deviation of 0.365, which suggests a relatively higher agreement among the operators compared to the manual segmentation approach. Furthermore, the volume of the osteotomy gap in the semi-automatic approach showed the same tendency in every site as the manual segmentation approach, but with less deviation. CONCLUSION: The semi-automatic approach developed in the present study proved to be valid as a standardised method with high repeatability. Such image analysis methods could help to quantify the progression of bone healing after BSSO and beyond, eventually facilitating the earlier identification of patients with retarded healing.

Frizzleds act as dynamic pharmacological entities.

The Frizzled family of transmembrane receptors (FZD1-10) belongs to the class F of G protein-coupled receptors (GPCRs). FZDs bind to and are activated by Wingless/Int1 (WNT) proteins. The WNT/FZD signaling system regulates crucial aspects of developmental biology and stem-cell regulation. Dysregulation of WNT/FZD communication can lead to developmental defects and diseases such as cancer and fibrosis. Recent insight into the activation mechanisms of FZDs has underlined that protein dynamics and conserved microswitches are essential for FZD-mediated information flow and build the basis for targeting these receptors pharmacologically. In this review, we summarize recent advances in our understanding of FZD activation, and how novel concepts merge and collide with existing dogmas in the field.

Resection status and margin control in intraoperative frozen sectioning analysis of oral squamous cell carcinoma.

PURPOSE: Intraoperative frozen section analysis (IFSA) is a well-established procedure for determining the intraoperative soft tissue resection status in patients with oral squamous cell carcinoma (OSCC). Margin status is a major predictor of the patient´s outcome, histologically free margins of ≥ 5 mm are demanded. This study evaluates the accuracy of IFSA, the impact of margin status and the impact of intraoperative margin revision on disease-free survival (DFS) and overall survival (OS). METHODS: This retrospective study included 213 patients with OSCC. IFSA results were compared with definitive histopathological reports, Kaplan-Meier analysis was performed. Cut-off values were calculated for resection margins considering known risk factors. RESULTS: IFSA showed positive margins in 8 cases (3.8%). Kaplan-Meier analysis revealed no significant differences for OS or DFS if R0-status was achieved by initial resection or immediate re-resection. Final histopathological evaluation revealed false-positive IFSA in 3/8 cases (37.5%) and false-negative IFSA in 1/205 cases (0.5%). Sensitivity was 83.3% and specificity was 98.6%. Analysis of optimal cut-off values showed no general need for larger resection margins in patients with risk factors. Cut-off values were slightly higher for patients with the risk factor alcohol consumption (7 mm for OS and DFS) or pN + ECS- disease (7 mm for DFS). Optimal cut-off values for tumour-margin-distance were around 6 mm. CONCLUSION: IFSA provides a valuable assessment method for intraoperative soft tissue resection margins. Risk factors seemingly do not significantly influence the extent of tumour resection.

Quantifying bone healing after mandibular displacement in orthognathic surgery.

Impaired bony healing following bilateral sagittal split osteotomy (BSSO) is a major unmet medical need for affected patients, and rare occurrences can hinder the identification of underlying risk factors. We hypothesised that osseous union following BSSO can be quantified using volumetric analysis, and we aimed to identify the risk factors for impaired bone healing. The percentage change in bony volume was measured in orthognathic patients following BSSO using two consecutive postoperative cone-beam computed tomography scans. Patients' characteristics and treatment parameters were documented, and correlation and regression analyses of these variables performed. Thirty-six patients (23 men and 13 women) with a mean (SD) age of 33.28 (11.86) years were included. The gap site (lingual versus buccal) (p < 0.01) had a significant impact on the change in volume. Age (p = 0.06) showed a trend towards significance. Initial width of the osteotomy gap, sex, and indication for surgery did not influence osseous healing. Increased age at surgery and the side of the buccal osteotomy are independent risk factors for impaired osseous healing following BSSO.

Diagnostic pitfalls in pediatric orbital entrapment fractures.

Prompt diagnosis and management of orbital entrapment fractures in the pediatric patient have been advocated. This retrospective study analyzed a cohort of orbital entrapment fractures in pediatric patients with regard to diagnostic pitfalls, treatment and outcomes in a Level I trauma center in Germany. Based on medical records and radiological imaging, patients under the age of 18 years who presented with orbital fractures during 2009-2021 were analyzed. Overall, 125 patients presented with orbital fractures, of whom 29 patients (23.2%) had orbital entrapment fractures. The majority of patients presented with monocle hematoma (n = 23), diplopia (n = 20), and/or restricted extraocular eye movement (n = 14). While all patients with orbital entrapment fractures underwent three-dimensional imaging, 10 radiological reports (34.5%) did not include findings on orbital entrapment fractures. All patients underwent surgical exploration in less than 24 h. In 12 patients, clinical symptoms such as diplopia and restricted ocular elevation were documented upon postoperative evaluation before discharge. Considering the significant proportion of orbital entrapment fractures that are not noted on radiological imaging, prompt clinical examination should be initiated in pediatric patients at risk for orbital fractures. Urgent surgical intervention should be recommended in entrapment fractures.

Recommended Tool Compounds: Application of YM-254890 and FR900359 to Interrogate Gαq/11-Mediated Signaling Pathways.

The macrocyclic depsipeptides YM-254890 (YM) and FR900359 (FR) are natural products, which inhibit heterotrimeric Gαq/11 proteins with high potency and outstanding selectivity. Historically, pharmacological modulation of Gα proteins was only achieved by treatment with pertussis toxin and cholera toxin, whose application can be tedious and is restricted to the inhibition of Gαi/o proteins and activation of Gαs proteins, respectively. The breakthrough discovery and characterization of YM and FR rendered the closely related Gαq, Gα11, and Gα14 proteins amenable to pharmacological inhibition, and since then, both compounds have become widely used in molecular pharmacology and were also proven to be efficacious in animal models of disease. In the past years, both YM and FR were thoroughly characterized and have substantially contributed to an improved understanding of Gαq/11 signaling on a molecular and cellular level. Yet, the possibilities to interrogate Gαq/11 signaling in complex systems have only been exploited in a very limited number of studies, whose promising initial results warrant further application of YM and FR in basic and translational research. As both compounds have become commercially available as of late, this review focuses on their application in cell-based assays and in vivo systems, highlighting their qualities as tool compounds and providing instructions for their use.

The risk of osteomyelitis after mandibular fracture is doubled in men versus women: analysis of 300,000 patients.

Postoperative complications following mandibular fracture treatment vary from local wound infections to severe conditions including osteomyelitis and impaired fracture healing. Several risk factors have been associated with the development healing disorders, including fracture localisation, treatment modality and substance abuse. However, limited research on the sex-specific influence of these complications exists. A total of about 300,000 female and male patients with mandibular fractures were examined in two cohorts. After matching for confounders (age, nicotine and alcohol dependence, malnutrition, overweight, anaemia, diabetes, osteoporosis and vitamin D deficiency), two cohorts were compared with propensity-score-matched patients according to outcomes (osteomyelitis, pseudoarthrosis and disruption of the wound) within 1 year after fracture. There were significant differences between female and male patients regarding the occurrence of osteomyelitis (odds ratio [OR] [95% confidence interval]: 0.621 [0.563; 0.686]) and disruption of the wound (OR [95% confidence interval]: 0.703 [0.632; 0.782]). Surprisingly, matching for the expected confounders did not change the results substantially. Sex plays a dominant role in determining the risk stratification for postoperative osteomyelitis and disruption of the wound, after accounting for other potential confounding factors. Additional research is needed to understand the underlying mechanisms and to develop sex-specific strategies to prevent these complications.

Impact of the adjacent bone on pseudarthrosis in mandibular reconstruction with fibula free flaps.

BACKGROUND: Mechanical and morphological factors have both been described to influence the rate of pseudarthrosis in mandibular reconstruction. By minimizing mechanical confounders, the present study aims to evaluate the impact of bone origin at the intersegmental gap on osseous union. METHODS: Patients were screened retrospectively for undergoing multi-segment fibula free flap reconstruction of the mandible including the anterior part of the mandible and osteosynthesis using patient-specific 3D-printed titanium reconstruction plates. Percentage changes in bone volume and width at the bone interface between the fibula/fibula and fibula/mandible at the anterior intersegmental gaps within the same patient were determined using cone-beam computed tomography (CBCT). Additionally, representative samples of the intersegmental zones were assessed histologically and using micro-computed tomography (µCT). RESULTS: The bone interface (p = 0.223) did not significantly impact the change in bone volume at the intersegmental gap. Radiotherapy (p < 0.001), time between CBCT scans (p = 0.006) and wound healing disorders (p = 0.005) were independent risk factors for osseous non-union. Preliminary analysis of the microstructure of the intersegmental bone did not indicate morphological differences between fibula-fibula and fibula-mandible intersegmental bones. CONCLUSIONS: The bone interface at the intersegmental gap in mandibular reconstruction did not influence long-term bone healing significantly. Mechanical and clinical properties seem to be more relevant for surgical success.

Oncologic Outcome in Advanced Oral Squamous Cell Carcinoma After Refusal of Recommended Adjuvant Therapy.

Importance: Clinicians may be confronted with patients refusing recommended adjuvant therapy (AT) after the primary resection of an advanced oral squamous cell carcinoma (OSCC). However, for this tumor entity, data are lacking regarding the oncological outcomes and associated factors after refusal of AT. Objective: To evaluate the difference in survival and disease recurrence for patients with and without recommended AT after resection of advanced OSCC. Design, Setting, and Participants: In this single-center retrospective matched cohort study, patients with advanced OSCC who refused recommended AT between January 2010 and December 2021 were matched 1:1 according to Union for International Cancer Control tumor staging with patients who completed AT. Exposures: Patients with advanced OSCC who refused or completed recommended AT between 2010 and 2021. Main Outcomes and Measures: The primary outcome of this study was the comparison of overall survival (OS) and recurrence-free survival (RFS) between the 2 study groups. Results: A total of 82 patients (mean [SD] age at time of surgery, 68.0 [11.3] years; 38 [46.3%] female, 44 [53.7%] male) with and without AT (41 per study group) were included in the analysis. Patients refusing AT developed more frequent disease recurrence than patients who completed AT (61.0% vs 26.8%; difference, 34.2%; odds ratio, 4.26; 95% CI, 1.68-10.84). In addition, patients who refused AT presented with lower 2-year OS (72.7% vs 88.6%; difference, 15.9%; 95% CI, 8.6%-40.6%) and much lower 2-year RFS (39.1% vs 74.2%; difference, 35.1%; 95% CI, 0.2%-70.5%). In the patient cohort who rejected AT, a worse OS was associated with female sex (48.6% vs 90.5%; difference, 41.9%; 95% CI, 0.6%-84.4%), pT1-2 category (57.1% vs 92.3%; difference, 35.2%; 95% CI, 3.3%-73.6%), and pN1 or higher category (61.2% vs 82.6%; difference, 21.4%; 95% CI, 14.1%-56.8%). Lower RFS was associated with female sex (37.9% vs 90.9%; difference, 53.0%; 95% CI, 8.0%-97.9%), advanced T category (pT3-4, 35.3% vs 80.0%; difference, 44.7%; 95% CI, 6.4%-95.3%), lymph node yield of 20 or greater (31.4% vs 80.6%; difference, 49.2%; 95% CI, 4.9%-93.4%), and lymph node ratio of less than 4.6% (36.6% vs 84.4%; difference, 47.8%; 95% CI, 1.8%-93.1%). Conclusions and Relevance: In this cohort study of patients with advanced OSCC, refusal of AT was associated with worse oncological outcomes. The prevalence of disease recurrence during follow-up was 34% higher in patients who refused AT than in patients who completed AT. The results from this study may assist clinicians in guiding patients who are considering refusal of or withdrawal from AT.

Patient-specific 3D-printed mini-versus reconstruction plates for free flap fixation at the mandible: Retrospective study of clinical outcomes and complication rates.

This study aimed to compare the clinical outcomes and complication rates of patient-specific 3D-printed mini- and reconstruction plates for free flap fixation in mandibular reconstruction. A retrospective monocentric study was carried out between April 2017 and December 2021 to analyze patients undergoing immediate mandibular reconstruction using fibula free flaps and osteosynthesis using patient-specific 3D-printed implants. Eighty-three patients with a mean age of 63.6 years were included. The mean follow-up period was 18.5 months. Patient-specific 3D-printed plates were designed as reconstruction plates (38 patients), miniplates (21 patients) or a combination of reconstruction- and miniplates (24 patients). With miniplates, plate removal was performed significantly more often via an intraoral approach (p < 0.001) and in an outpatient setting (p = 0.002). Univariate analysis showed a higher fistula rate with reconstruction plates (p = 0.037). Multivariate analysis showed no significant differences in complications. Case-control matching demonstrated significantly lower rates of fistula (p = 0.017) and non-union (p = 0.029) in the combined group. This retrospective study shows a tendency towards reduced complication rates with patient-specific 3D-printed miniplates in comparison to patient-specific 3D-printed reconstruction plates for immediate mandibular reconstruction with fibula free flaps.

Pediatric Maxillofacial Trauma: Insights into Diagnosis and Treatment of Mandibular Fractures in Pediatric Patients.

Aim: To assess the diagnostic and therapeutic approaches in pediatric mandibular fractures with regards to fracture pattern and localization. Patients and methods: This retrospective study included patients under the age of 17 years that presented to the Department of Oral and Maxillofacial Surgery at Charité-Universitätsmedizin Berlin with mandibular fractures over an 11-year long period (2010-2020). Medical records were analyzed for age, gender, injury mechanism, clinical presentation, imaging modalities, fracture pattern, and fracture management. Statistical analyses included descriptive statistics, normality testing, and Mann-Whitney U tests. Results: A total of 91 pediatric patients (23 females and 68 males) presented with mandibular fractures. The majority of mandibular fractures occurred in patients aged 13-16 years (67.0%, n = 61). The main causes were activities of daily life (34.1%), followed by assault (25.3%). Malocclusion and pain upon mandibular joint compression were documented in 72.5% and 51.7% of patients, respectively. The most frequently applied radiological diagnostic tool was a panoramic X-ray (49.5%). The main fracture patterns were single (42.9%) and double fractures (48.4%). An age-adapted surgical approach using open reduction and internal fixation (ORIF) was the most frequent management (61.5%). A conservative approach was favored in cases of condylar head fractures. Resorbable plates were used in eight cases of ORIF (8.8%). Conclusion: Treatment regimens should be carefully selected based on the unique anatomy of the pediatric patient with regards to centers of growth and dentition phase, to restore stomatognathic function and to maintain adequate skeletal growth and eruption of teeth. Clinical significance: This study illustrates the challenges of mandibular fracture management in the pediatric patient. How to cite this article: Hofmann E, Koerdt S, Heiland M, et al. Pediatric Maxillofacial Trauma: Insights into Diagnosis and Treatment of Mandibular Fractures in Pediatric Patients. Int J Clin Pediatr Dent 2023;16(3):499-509.

Sentinel lymph node biopsy in recurrent or secondary oral squamous cell carcinoma after previous neck dissection.

OBJECTIVES: The aim of this retrospective study was to evaluate the potential of sentinel lymph node biopsy (SLNB) in patients with recurrent or a secondary oral squamous cell carcinoma (OSCC) without clinical signs of lymph node metastases (cN0), who were previously treated with a surgical approach. PATIENTS AND METHODS: Retrospective analysis of all patients with cN0 recurrent or secondary OSCC, who were treated using SLNB after previous neck dissection. Endpoints were sentinel lymph node (SLN) detection rate, negative predictive value (NPV) and sensitivity. RESULTS: A total of 17 patients with a mean age of 68.6 years were included. SLN were detected in 15 of 17 cases (detection rate: 88.2%). In seven patients (41.2%), a bilateral or contralateral lymph drainage of a unilateral carcinoma was found. Two patients (11.8%) demonstrated a positive SLN upon pathohistological analysis, which led to an upstaging. In one case, a non-SLN was positive, which is considered a false-negative result. The mean follow-up for all patients with histologically negative SLN including the patients without a detected SLN was 11.8 months (range: 0-31 months). Of these, one patient developed (isolated) neck recurrence after 12 months resulting in an overall NPV of 86.7% and a sensitivity of 50.0% for the SLNB as a neck staging procedure. CONCLUSION: SLNB can improve the staging of patients with recurrent or secondary OSCC, who present with a history of a previous neck dissection. Further studies are required to demonstrate the oncological benefit of SLNB in this patient cohort.

Crystal structure of adenosine A2A receptor in complex with clinical candidate Etrumadenant reveals unprecedented antagonist interaction.

The Gs protein-coupled adenosine A2A receptor (A2AAR) represents an emerging drug target for cancer immunotherapy. The clinical candidate Etrumadenant was developed as an A2AAR antagonist with ancillary blockade of the A2BAR subtype. It constitutes a unique chemotype featuring a poly-substituted 2-amino-4-phenyl-6-triazolylpyrimidine core structure. Herein, we report two crystal structures of the A2AAR in complex with Etrumadenant, obtained with differently thermostabilized A2AAR constructs. This led to the discovery of an unprecedented interaction, a hydrogen bond of T883.36 with the cyano group of Etrumadenant. T883.36 is mutated in most A2AAR constructs used for crystallization, which has prevented the discovery of its interactions. In-vitro characterization of Etrumadenant indicated low selectivity versus the A1AR subtype, which can be rationalized by the structural data. These results will facilitate the future design of AR antagonists with desired selectivity. Moreover, they highlight the advantages of the employed A2AAR crystallization construct that is devoid of ligand binding site mutations.

Structure-affinity and structure-residence time relationships of macrocyclic Gαq protein inhibitors.

The macrocyclic depsipeptides YM-254890 (YM) and FR900359 (FR) are potent inhibitors of Gαq/11 proteins. They are important pharmacological tools and have potential as therapeutic drugs. The hydrogenated, tritium-labeled YM and FR derivatives display largely different residence times despite similar structures. In the present study we established a competition-association binding assay to determine the dissociation kinetics of unlabeled Gq protein inhibitors. Structure-affinity and structure-residence time relationships were analyzed. Small structural modifications had a large impact on residence time. YM and FR exhibited 4- to 10-fold higher residence times than their hydrogenated derivatives. While FR showed pseudo-irreversible binding, YM displayed much faster dissociation from its target. The isopropyl anchor present in FR and some derivatives was essential for slow dissociation. These data provide a basis for future drug design toward modulating residence times of macrocyclic Gq protein inhibitors, which has been recognized as a crucial determinant for therapeutic outcome.

Management of the Contralateral Neck in Unilateral Node-Positive Oral Squamous Cell Carcinoma.

INTRODUCTION: In lateralized oral squamous cell carcinoma (OSCC) with ipsilateral cervical lymph node metastasis (CLNM), the surgical management of the unsuspicious contralateral neck remains a matter of debate. The aim of this study was to analyze this cohort and to compare the outcomes of patients with and without contralateral elective neck dissection (END). MATERIAL AND METHODS: A retrospective analysis of patients with lateralized OSCC, ipsilateral CLNM (pN+) and contralateral cN0-stage was performed. Patients were divided into two groups according to the surgical management of the contralateral neck: I: END; and II: no END performed. Adjuvant radiotherapy was applied bilaterally in both groups according to individual risk. RESULTS: A total of 65 patients (group I: 16 (24.6%); group II: 49 (75.4%)) with a median follow-up of 28 months were included. Initially, there was no case of contralateral CLNM after surgery. During follow-up, 6 (9.2%) patients presented with recurrent CLNM. In 5 of these cases (7.7%), the contralateral neck (group I: 3/16 (18.8%); group II: 2/49 (4.1%)) was affected. Increased ipsilateral lymph node ratio was associated with contralateral CLNM (p = 0.07). END of the contralateral side showed no significant benefit regarding OS (p = 0.59) and RFS (p = 0.19). CONCLUSIONS: Overall, the risk for occult contralateral CLNM in patients with lateralized OSCC ipsilateral CLNM is low. Our data suggest that END should not be performed routinely in this cohort. Risk-adapted radiotherapy of the contralateral neck alone seems to be sufficient from the oncological point of view.

Clinical and Technical Validation of Novel Bite Force Measuring Device for Functional Analysis after Mandibular Reconstruction.

Bite force measuring devices that are generally suitable for edentulous patients or patients undergoing mandibular reconstruction are missing. This study assesses the validity of a new bite force measuring device (prototype of loadpad®, novel GmbH) and evaluates its feasibility in patients after segmental mandibular resection. Accuracy and reproducibility were analyzed with two different protocols using a universal testing machine (Z010 AllroundLine, Zwick/Roell, Ulm, Germany). Four groups were tested to evaluate the impact of silicone layers around the sensor: no silicone ("pure"), 2.0 mm soft silicone ("2-soft"), 7.0 mm soft silicone ("7-soft") and 2.0 mm hard silicone ("2-hard"). Thereafter, the device was tested in 10 patients prospectively who underwent mandibular reconstruction using a fibula free flap. Average relative deviations of the measured force in relation to the applied load reached 0.77% ("7-soft") to 5.28% ("2-hard"). Repeated measurements in "2-soft" revealed a mean relative deviation of 2.5% until an applied load of 600 N. Maximum bite force decreased postoperatively by 51.8% to a maximum mean bite force of 131.5 N. The novel device guarantees a high accuracy and degree of reproducibility. Furthermore, it offers new opportunities to quantify perioperative oral function after reconstructive surgery of the mandible also in edentulous patients.

Treatment options for critical size defects - Comparison of different materials in a calvaria split model in sheep.

Bone defects of the craniofacial skeleton are often associated with aesthetic and functional impairment as well as loss of protection to intra- and extracranial structures. Solid titanium plates and individually adapted bone cements have been the materials of choice, but may lead to foreign-body reactions and insufficient osseointegration. In contrast, porous scaffolds are thought to exhibit osteoconductive properties to support bone ingrowth. Here, we analyse in critical size defects of the calvaria in sheep whether different bone replacement materials may overcome those remaining challenges. In a critical size defect model, bilateral 20 × 20 × 5-mm craniectomies were performed on either side of the sagittal sinus in 24 adult female blackheaded sheep. Bony defects were randomised to one of five different bone replacement materials (BRMs): titanium scaffold, biodegradable poly(d,l-lactic acid) calcium carbonate scaffold (PDLLA/CC), polyethylene 1 (0.71 mm mean pore size) or 2 (0.515 mm mean pore size) scaffolds and polymethyl methacrylate (PMMA)-based bone cement block. Empty controls (n = 3) served as references. To evaluate bone growth over time, three different fluorochromes were administered at different time points. At 3, 6 and 12 months after surgery, animals were sacrificed and the BRMs and surrounding bone analysed by micro-CT and histomorphometry. The empty control group verified that the calvaria defect in this study was a reliable critical size defect model. Bone formation in vivo was detectable in all BRMs after 12 months by micro-CT and histomorphometric analysis, except for the non-porous PMMA group. A maximum of bone formation was detected in the 12-months group for titanium and PDLLA/CC. Bone formation in PDLLA/CC starts to increase rapidly between 6 and 12 months, as the BRM resorbs over time. Contact between bone and BRM influenced bone formation inside the BRM. Empty controls exhibited bone formation solely at the periphery. Overall, porous BRMs offered bone integration to different extent over 12 months in the tested calvaria defect model. Titanium and PDLLA/CC scaffolds showed remarkable osseointegration properties by micro-CT and histomorphometric analysis. PDLLA/CC scaffolds degraded over time without major residues. Pore size influenced bone ingrowth in polyethylene, emphasising the importance of porous scaffold structure.