BACKGROUND AND OBJECTIVES:The Finite Element Method (FEM) is a cornerstone of biomechanical analysis in dental implantology. However, the accuracy of FEM predictions is highly dependent on the underlying model, particularly the resolution of the input computed tomography (CT) images and the assigned material properties. A lack of standardized guidelines creates uncertainty about how these modeling choices affect outcomes, hindering the comparison of results across studies. This study aims to systematically quantify the impact of CT image resolution and material model selection on the predicted biomechanics of a bone-implant system. METHODS:Twenty-three computational models of a dental implant within a human mandible segment were developed and analyzed. The models were based on three micro-CT scan resolutions and featured two different geometric representations of cancellous bone. A range of material properties was assigned, including both homogeneous and non-homogeneous (density-based) Young's moduli. Peri-implant bone strain distribution, maximum implant stress, and displacement were evaluated. RESULTS:Principal Component Analysis demonstrated a clear segregation of models into distinct clusters, primarily driven by the geometric representation (trabecular vs. non-trabecular) and secondarily by image resolution. Low-resolution (150 µm) trabecular models predicted substantially higher strains and displacements than high-resolution (30 and 60 µm) models. Axial displacement values of the dental implant ranged from 8 to 22 µm in the 30 µm models and from 19 to 55 µm in the 150 µm models, while stresses ranged from 161 to 164 MPa and from 196 to 226 MPa, respectively. Notably, simplified non-trabecular models with non-homogeneous material properties could approximate the strain distributions of some complex trabecular models, but failed to accurately predict implant stress. CONCLUSION:There is no single "best" model; the optimal choice must be tailored to the specific research question. While high-resolution trabecular models provide the most comprehensive data, simplified non-trabecular models can be an efficient alternative for bone strain analysis. However, they are inadequate for predicting implant stress. These findings provide a crucial framework for developing standardized, application-specific modeling protocols in dental implantology.

Background:Oronasal fistula (ONF) remains a common complication following primary palatoplasty, particularly in wide clefts. The use of pedicled bilateral buccal fat pad flaps (BFPFs) has shown promise in reducing ONF incidence, but clear indication criteria are lacking. This study evaluates the efficacy of BFPF interposition in primary palatoplasty and explored the use of the palatal index (PI) as a quantitative tool for flap indication. Methods:A systematic literature review following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines identified studies reporting bilateral BFPF use during primary palatoplasty. Additionally, a retrospective cohort analysis was conducted on 139 patients undergoing primary cleft palate repair (2017-2024) at a single institution. Following a protocol revision in 2021, BFPF was selectively used based on intraoperative assessment. In the post-2021 cohort, PI and cleft width were measured to determine their association with BFPF use and ONF incidence. Results:The systematic review revealed limited studies with inconsistent reporting on cleft severity and BFPF indication. In the institutional cohort, ONF incidence dropped significantly from 15.5% (group A) to 2.5% (group B; P = 0.005). BFPFs were used in 46.9% of post-2021 cases, primarily in severe clefts (PI ≥ 0.43). PI was significantly higher in patients receiving BFPF (P < 0.001), and no ONFs occurred above the 0.43 PI threshold. Conclusions:Bilateral BFPF interposition significantly reduces ONF incidence in primary palatoplasty. The PI is a useful, objective criterion to guide its use, with a PI value of 0.43 or higher proposed as an effective threshold. These findings support incorporating BFPF into standardized protocols for primary palatoplasty.

STATEMENT OF PROBLEM:Intraoral scanning is currently becoming the standard method for imaging the maxilla in patients with cleft lip and palate. However, the reliability of intraoral scans compared with traditional conventional impression methods has not yet been sufficiently described and examined in detail in newborns with severe types of cleft lip and palate. PURPOSE:The purpose of this clinical study was to assess the reliability and agreement between intraoral scanning and traditional impression methods for maxillary measurements in newborns with unilateral and bilateral cleft lip and palate (U/BCLP). A secondary aim was to evaluate the consistency of maxillary measurements obtained with and without general anesthesia. MATERIAL AND METHODS:Six newborns with cleft lip and palate underwent 4 maxillary impression methods (silicone impression and 3-dimensional (3D) scan, with and without anesthesia). Intra- and inter-observer reliability was assessed by 3 clinicians using intraclass correlation coefficient, median absolute deviation, and median relative deviation (α=.05). RESULTS:The intraclass correlation coefficient values for both inter-observer and intra-observer reliability indicated excellent agreement (ICC>.90, P<.05) for maxillary dimension measurements. Acceptable variability was observed because of differences in reference point identification by clinicians and across data collection methods. CONCLUSIONS:When assessing the maxilla in U/BCLP patients, both intraoral scanner and traditional impression techniques showed excellent reliability and agreement in measurements, whether performed while the newborns were awake or under general anesthesia.

Background Orofacial clefts are common congenital malformations, affecting both facial aesthetics and function. Intubation in newborns with cleft lip and palate is challenging and carries a high risk of oral tissue damage. This study investigates the use of a customized protective palatal obturator (CPPO) to improve intubation safety and reduce tissue injury during cleft lip surgery.Methods A single-center, randomized neonatal sub-study was conducted, including 55 newborns who underwent cleft lip surgery. Patients were randomized into an intervention group (CPPO use) and a control group (standard intubation without CPPO). The primary aim was to evaluate the degree of oral tissue injury during intubation, its severity, and location, in both groups, secondary aims included laryngoscopy image during intubation (modified Cormack-Lehane scoring system), intubation time, and attempts, number of intubations attempts and anesthesiologic complication during intubation. This study was registered on www.clinicaltrials.gov (ClinicalTrials.gov Identifier: NCT04422847 and NCT04422964).Results No tissue damage occurred in the CPPO group, while the control group had a 21.4% incidence of tissue injury (p = .023). Secondary outcomes showed no statistically significant differences between groups for intubation time or the number of intubation attempts. Difficult intubation was less frequent in the CPPO group (40.7%) compared to the control group (50%), though this difference was not statistically significant.Conclusion The CPPO significantly reduces the risk of tissue damage during intubation in newborns undergoing cleft lip surgery, without increasing intubation time or attempts. It is particularly beneficial for severe clefts, and its use may facilitate safer airway management in these high-risk patients.

Statement of problem. Accurate implant placement is essential for the success of dental implants. This placement influences osseointegration and occlusal forces. The freehand technique, despite its cost-effectiveness and time efficiency, may result in significant angular deviations compared with guided implantation, but the effect of angular deviations on the stress-strain state of peri-implant bone is unclear. Purpose. The purpose of this finite element analysis (FEA) study was to examine the effects of angular deviations on stress-strain states in peri-implant bone. Material and methods. Computational modeling was used to investigate 4 different configurations of dental implant positions, each with 3 angles of insertion. The model was developed using computed tomography images, and typical mastication forces were considered. Strains were analyzed using the mechanostat hypothesis. Results. The location of the implant had a significant impact on bone strain intensity. An angular deviation of +/- 5 degrees from the planned inclination did not significantly affect cancellous bone strains, which primarily support the implant. However, it had a substantial effect on strains in the cortical bone near the implant. Such deviations also significantly influenced implant stresses, especially when the support from the cortical bone was uneven or poorly localized. Conclusions. In extreme situations, angular deviations can lead to overstraining the cortical bone, risking implant failure from unfavorable interaction with the implant. Accurate implant placement is essential to mitigate these risks. (J Prosthet Dent 2024;131:128.e1-e10)

Cleft lip and cleft palate are among the most common congenital defects of the head. The treatment of clefts is centralized, multidisciplinary, and involves a plastic surgeon, orthodontist, anesthesiologist, clinical speech therapist, and other specialists. While the incidence of cleft lip and cleft palate remains approximately unchanged, the approach to their treatment is evolving. Modern treatment methods increasingly include 3D printing and the associated therapeutic and educational possibilities.

Abstract Objectives This study evaluated maxillary growth and dental arch relationships at 5 and 10 years of age in patients with unilateral cleft lip and palate (UCLP) who underwent early cleft lip and palate surgery. Methods 28 patients with UCLP who underwent cleft lip surgery in neonatal age and cleft palate surgery at average age of 7 months without orthodontic treatment (intervention group) were measured for intercanine and intermolar distances and for dental arch length. These measurements were compared with those of 30 healthy participants in a control group. Dental arch relationships in the intervention group were evaluated by 5-YO index at 5 years and the GOSLON Yardstick score at 10 years of patients’ age. Results Patients in the intervention group had significantly shorter mean intercanine distance and arch length than control patients at both 5 and 10 years of age (p<.001 for all). There were no significant differences in intermolar distance at both 5 (p = .945) and 10 years (p = .105) of patients’ age. The average 5YO index increased from 2.46 to an average GOSLON 10-year score of 2.89 in intervention group. Conclusion Intercanine distance and dental arch length of patients with UCLP are significantly reduced at 5 and 10 years after early cleft lip and palate surgeries compared to the healthy population. Dental arch relationships at 5 and 10 years of patients with UCLP show comparable outcomes to those reported by other cleft centers. Clinical significance This study evaluates maxillary growth in UCLP patients 5 and 10 years of age who underwent early primary lip and palate surgery.

The purpose of this study was to investigate the effect of load-induced local mechanical strain on bone cell activity of peri-implant bone in mice. Titanium implants were placed in the maxillae of 13-week-old male C57BL/6J mice and subjected to intermittent 0.15 N, 0.3 N, or 0.6 N loads for 30 min/day for 6 days. The animals were sacrificed 2 days after the final loading. Unloaded mice were used as controls. An animal-specific three-dimensional finite element model was constructed based on morphological data retrieved from in vivo microfocus computed tomography for each mouse to calculate the mechanical strain distribution. Strain distribution images were overlaid on corresponding histological images of the same site in the same animal. The buccal cervical region of the peri-implant bone was predetermined as the region of interest (ROI). Each ROI was divided by four strain intensity levels: 0-20 mu epsilon, 20-60 mu epsilon, 60-100 mu epsilon, and 100 mu epsilon, and the bone histomorphometric parameters were analyzed by the total area of each strain range for all loaded samples. The distance between the calcified front and calcein labeling as a parameter representing the mineral apposition rate was significantly greater in the areas with strain intensity >100 mu epsilon than in the area with strain intensity <100 mu epsilon, suggesting that the bone formation activity of osteoblasts was locally enhanced by a higher mechanical strain. However, the shrunken osteocytes and the empty osteocyte lacunae were significantly lower in the highest strain area, suggesting that osteoclastogenesis was more retarded in higher strain areas than in lower strain areas. The histomorphometric parameters were not affected geometrically in the unloaded animals, suggesting that the load-induced mechanical strain caused differences in the histomorphometric parameters. Our findings support the hypothesis that bone cell activity related to bone resorption and formation is local strain-dependent on implant loading.

Patient-specific approach is gaining a wide popularity in computational simulations of biomechanical systems. Simulations (most often based on the finite element method) are to date routinely created using data from imaging devices such as computed tomography which makes the models seemingly very complex and sophisticated. However, using a computed tomography in finite element calculations does not necessarily enhance the quality or even credibility of the models as these depend on the quality of the input images. Low-resolution (medical-)CT datasets do not always offer detailed representation of trabecular bone in FE models and thus might lead to incorrect calculation of mechanical response to external loading. The effect of image resolution on mechanical simulations of bone-implant interaction has not been thoroughly studied yet. In this study, the effect of image resolution on the modeling procedure and resulting mechanical strains in bone was analyzed on the example of cranial implant. For this purpose, several finite element models of bone interacting with fixation-screws were generated using seven computed tomography datasets of a bone specimen but with different image resolutions (ranging from micro-CT resolution of 25 μm to medical-CT resolution of 1250 μm). The comparative analysis revealed that FE models created from images of low resolution (obtained from medical computed tomography) can produce biased results. There are two main reasons: 1. Medical computed tomography images do not allow generating models with complex trabecular architecture which leads to substituting of the intertrabecular pores with a fictitious mass; 2. Image gray value distribution can be distorted resulting in incorrect mechanical properties of the bone and thus in unrealistic or even completely fictitious mechanical strains. The biased results of calculated mechanical strains can lead to incorrect conclusion, especially when bone-implant interaction is investigated. The image resolution was observed not to significantly affect stresses in the fixation screw itself; however, selection of bone material representation might result in significantly different stresses in the screw.

This study investigated the effect of implant thickness and material on deformation and stress distribution within different components of cranial implant assemblies. Using the finite element method, two cranial implants, differing in size and shape, and thicknesses (1, 2, 3 and 4 mm, respectively), were simulated under three loading scenarios. The implant assembly model included the detailed geometries of the mini-plates and micro-screws and was simulated using a sub-modeling approach. Statistical assessments based on the Design of Experiment methodology and on multiple regression analysis revealed that peak stresses in the components are influenced primarily by implant thickness, while the effect of implant material is secondary. On the contrary, the implant deflection is influenced predominantly by implant material followed by implant thickness. The highest values of deformation under a 50 N load were observed in the thinnest (1 mm) Polymethyl Methacrylate implant (Small defect: 0.296 mm; Large defect: 0.390 mm). The thinnest Polymethyl Methacrylate and Polyether Ether Ketone implants also generated stresses in the implants that can potentially breach the materials' yield limit. In terms of stress distribution, the change of implant thickness had a more significant impact on the implant performance than the change of Young's modulus of the implant material. The results indicated that the stresses are concentrated in the locations of fixation; therefore, the detailed models of mini-plates and micro-screws implemented in the finite element simulation provided a better insight into the mechanical performance of the implant-skull system.

Osseointegration is paramount for the longevity of dental implants and is significantly influenced by biomechanical stimuli. The aim of the present study was to assess the micro-strain and displacement induced by loaded dental implants at different stages of osseointegration using finite element analysis (FEA). Computational models of two mandible segments with different trabecular densities were constructed using microCT data. Three different implant loading directions and two osseointegration stages were considered in the stress-strain analysis of the bone-implant assembly. The bony segments were analyzed using two approaches. The first approach was based on Mechanostat strain intervals and the second approach was based on tensile/compression yield strains. The results of this study revealed that bone surrounding dental implants is critically strained in cases when only a partial osseointegration is present and when an implant is loaded by buccolingual forces. In such cases, implants also encounter high stresses. Displacements of partially-osseointegrated implant are significantly larger than those of fully-osseointegrated implants. It can be concluded that the partial osseointegration is a potential risk in terms of implant longevity.

In this study 6 pre-operative designs for PMMA based reconstructions of cranial defects were evaluated for their mechanical robustness using finite element modeling. Clinical experience and engineering principles were employed to create multiple plan options, which were subsequently computationally analyzed for mechanically relevant parameters under 50N loads: stress, strain and deformation in various components of the assembly. The factors assessed were: defect size, location and shape. The major variable in the cranioplasty assembly design was the arrangement of the fixation plates. An additional study variable introduced was the location of the 50N load within the implant area. It was found that in smaller defects, it was simpler to design a symmetric distribution of plates and under limited variability in load location it was possible to design an optimal for expected loads. However, for very large defects with complex shapes, the variability in the load locations introduces complications to the intuitive design of the optimal assembly. The study shows that it can be beneficial to incorporate multi design computational analyses to decide upon the most optimal plan for a clinical case.

Medical grade 3D printing offers the possibility to manufacture patient-specific implants to treat cranial defects. The performance of the implant assembly depends on many factors, such as material, thickness, size and manufacturing accuracy. A significant factor in the stability and success of the assembly is the fixation method. Cranial implants are usually fixed to the skull by means of mini-plates. Biomechanical assessment of fixing the implant to the skull might be helpful not only for mini-plate design but might be beneficial also for the surgeons. In this study, four different mini-plate designs were analyzed and compared based on the stress-strain analysis of one cranial implant fixed at three locations by mini-plates. Computational simulations were done using Finite Element Method.

It is widely accepted that bones have the ability to adapt to new biomechanical environment by changing their material properties, geometry and inner architecture. Bones have also an exceptional ability to self-repair, to remove microcracks and to prevent the bone damage caused by the fatigue failure. These abilities are enabled through coupled processes of bone resorption and bone formation, the processes collectively referred to as bone remodeling. Numerous studies have shown that bone remodeling is governed by combination of mechanical stimulus (strains) and its frequency, both sensed by sensor cells (osteocytes). Through mechanotransduction, the stimulus is transmitted to actor cells (osteoclasts, osteoblasts) that actually do the bone resorption or formation. Several theories have been proposed to predict bone remodeling and several finite-element-based algorithms have been introduced. The vast majority of them uses strain energy density as the mechanical stimulus. The purpose of this paper is to investigate and discuss the applicability of also other strain-based representations of the mechanical stimulus in simulations of remodeling of bone with an initial microcrack. The need for developing more reliable models is essential for both clinicians and engineers who are interested, for instance, in prediction of bone performance when various implants are involved.

The response to the mechanical loading of bone tissue has been extensively investigated; however, precisely how much strain intensity is necessary to promote bone formation remains unclear. Combination studies utilizing histomorphometric and numerical analyses were performed using the established murine maxilla loading model to clarify the threshold of mechanical strain needed to accelerate bone formation activity. For 7 days, 191 kPa loading stimulation for 30 min/day was applied to C57BL/6J mice. Two regions of interest, the AWAY region (away from the loading site) and the NEAR region (near the loading site), were determined. The inflammatory score increased in the NEAR region, but not in the AWAY region. A strain intensity map obtained from \(\upmu \hbox {CT}\) images was superimposed onto the images of the bone formation inhibitor, sclerostin-positive cell localization. The number of sclerostin-positive cells significantly decreased after mechanical loading of more than \(150\,{\upmu }{\upvarepsilon }\) in the AWAY region, but not in the NEAR region. The mineral apposition rate, which shows the bone formation ability of osteoblasts, was accelerated at the site of surface strain intensity, namely around \(170\,{\upmu }{\upvarepsilon }\), but not at the site of lower surface strain intensity, which was around \(80\,{\upmu }{\upvarepsilon }\) in the AWAY region, thus suggesting the existence of a strain intensity threshold for promoting bone formation. Taken together, our data suggest that a threshold of mechanical strain intensity for the direct activation of osteoblast function and the reduction of sclerostin exists in a murine maxilla loading model in the non-inflammatory region.

Using porous bioceramics became recently an alternative approach to increase bone density which is a key factor for successful dental implant application. These novel biomaterials should substitute missing natural trabecular structures in terms of material strength as well as deformation characteristics. However, mechanical behavior of these materials used as bone fillers are still in question. This problem is made more difficult by the fact that bone structure itself exhibits a complex mechanical behavior which is still in question as well and, therefore, appropriate analytical criteria should to be established. The purpose of this paper is to determine typical mechanical behavior of trabecular structure of mandibular cancellous bone using computational simulations which can serve as a basis for establishing such criteria. For this purpose, four bone specimens of various bone density were μCT-scanned and high-level finite element models including detailed trabecular structure were created on their basis to analyze relevant mechanical quantities for various loadings in terms of bone density and various histomorphometric parameters.

This computational study investigates the effect of shape (defect contour curvature) and bone-implant interface (osteotomy angle) on the stress distribution within PMMA skull implants. Using finite element methodology, 15 configurations - combinations of simplified synthetic geometric shapes (circular, square, triangular, irregular) and interface angulations - were simulated under 50N static loads. Furthermore, the implant fixation devices were modelled and analysed in detail. Negative osteotomy configurations demonstrated the largest stresses in the implant (275 MPa), fixation devices (1258 MPa) and bone strains (0.04). The circular implant with zero and positive osteotomy performed well with maximum observed magnitudes of - implant stress (1.2 MPa and 1.2 MPa), fixation device stress (11.2 MPa and 2.2 MPa), bone strain (0.218e-3 and 0.750e-4). The results suggest that the preparation of defect sites is a critical procedure. Of the greatest importance is the angle at which the edges of the defect are sawed. If under an external load, the implant has no support from the interface and the stresses are transferred to the fixation devices. This can endanger their material integrity and lead to unphysiological strains in the adjacent bone, potentially compromising the bone morphology required for anchoring. These factors can ultimately weaken the stability of the entire implant assembly. (C) 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

The first aim of this study was to assess displacements and micro-strain induced on different grades of atrophic cortical and trabecular mandibular bone by axially loaded dental implants using finite element analysis (FEA). The second aim was to assess the micro-strain induced by different implant geometries and the levels of bone-to-implant contact (BIC) on the surrounding bone. Six mandibular bone segments demonstrating different grades of mandibular bone atrophy and various bone volume fractions (from 0.149 to 0.471) were imaged using a micro-CT device. The acquired bone STL models and implant (Brånemark, Straumann, Ankylos) were merged into a three-dimensional finite elements structure. The mean displacement value for all implants was 3.1±1.2 µm. Displacements were lower in the group with a strong BIC. The results indicated that the maximum strain values of cortical and cancellous bone increased with lower bone density. Strain distribution is the first and foremost dependent on the shape of bone and architecture of cancellous bone. The geometry of the implant, thread patterns, grade of bone atrophy and BIC all affect the displacement and micro-strain on the mandible bone. Preoperative finite element analysis could offer improved predictability in the long-term outlook of dental implant restorations.