Can we predict the insertion torque using the bone density around the implant?

Feasibility analysis of bone density evaluation with Hounsfield unit value after fibula flap reconstruction of jaw defect

BACKGROUND

Implant-supported dentures have become an essential means of restoring occlusal function after jaw reconstruction. Bone mineral density (BMD) may influence the success rate of implant denture restorations. This study aimed to explore whether the Hounsfield unit (HU) value can be used to monitor the changing trend of fibular BMD after jaw reconstruction.

RESULTS

A total of 54 patients who underwent maxillar/mandibular reconstruction with a fibula flap were included in this study. There was a significant correlation between the HU value and BMD at 1 week, 3 months, and 6 months after surgery, and both were significantly correlated with follow-up time. The difference between each pair of absorption rates (DAR) was less than 10% in 66.7% and 75.9% of patients at 3 and 6 months; however, the DAR was more than 20% in 12% and 13.8% of patients at 3 and 6 months, respectively.

CONCLUSIONS

There is a significant correlation between HU value and BMD. The HU value can be used to roughly reflect the fibular BMD changing trend in a group of patients as opposed to an individual, and the HU value is not equivalent to BMD.

TRIAL REGISTRATION

ChiCTR, ChiCTR2300069661, retrospectively registered on 22 March 2023. Retrospectively registered, https://www.chictr.org.cn/showproj.html?proj=188953 .

Bone resorption after maxillary reconstruction with the vascularized free iliac flap

The aim of this study was to evaluate the resorption of the iliac bone after maxillary reconstruction with a vascularized free iliac flap. Twenty-seven patients with maxillary defects who underwent maxillary reconstruction with the vascularized free iliac flap between January 2017 and January 2021 were included. Computed tomography (CT) images taken at 1 week, approximately 6 months, and 1 year after the surgery were used for evaluation. The total iliac bone thickness and height, cortical bone thickness, and cancellous bone density were measured in the CT images. Compared with 1 week after the surgery, the total thickness and height of the iliac bone were reduced significantly 1 year after the surgery, and the cortical bone thickness and cancellous bone density were reduced significantly at 6 months and 1 year after the surgery. Compared with 6 months after the surgery, cancellous bone density was reduced significantly 1 year after the surgery. In conclusion, during the first year after maxillary reconstruction with a vascularized free iliac flap, there was significant resorption of iliac bone, including the total iliac bone thickness and height, the cortical bone thickness, and the cancellous bone density.

The Assessment of the Usefulness of Platelet-Rich Fibrin in the Healing Process Bone Resorption

The main subject of this research was the use of PRF in dental surgery aimed at preventing changes in alveolar height and width after tooth extraction. Due to the large growth factor content, it seems to be particularly useful in bone loss management starting from the simplest loss occurring after tooth extraction through loss resulting from tooth resection ending with loss caused by large bone cysts. The study was performed on 50 patients. The extraction of two maxillary or mandibular homonymous teeth was carried out in each patient, where PRF was placed in one alveolus while the other alveolus was left empty. Then, the alveoli were surgically managed with a split flap technique. On the extraction day, after 10 days, and after 6 months, the alveolar process was measured, soft tissues healing was assessed, and imaging examinations were analyzed. It was proved that the healing of soft tissues in the PRF group was better. In the PRF group after 6 months from surgery, the newly formed bone had higher grayscale values in volumetric tomography (CBCT). Moreover, the reduced atrophy of the alveolar process at the site of the extracted tooth was proved in this study.

Optimised Implant Selection Using Digital Volume Tomography (DVT) Osteodensitometry

Purpose

The density of the jaw bone has an inhomogeneous distribution and, even within partial volumes, varies more or less strongly from the size of typical implants. Consequently, the primary stability of implants using conventional techniques can only ever be determined postimplantation. The aim of the present case report is to present digital volume tomography (DVT) osteodensitometry as a procedure for assessing the primary stability preimplantation and to evaluate its benefits.

Methods

An orthopantomogram (OPT) and vertical sections, including bone density measurement, were obtained from a DVT in the course of preimplantological diagnosis. Conventional implant planning and densitometric simulation were performed on this basis.

Results

Densitometric simulation enabled assessment of the bone density at the interface to the implant body preimplantation. This procedure provides not only an overall value (averaged density) but also allocation of bone areas with different densities to the adjacent areas on the implant surface. This then allows the implant with the best possible macroscopic geometry and optimum position to be selected, with the aim of maximising primary stability. In the present case, the maximum torques during insertion confirmed the densitometric values recorded in advance.

Conclusion

DVT osteodensitometry enables selection of an implant optimised to bone density distribution. At the same time, the point at which loading occurs can already be defined at the planning stage, thanks to the predictable primary stability. A standard integration of DVT osteodensitometry in the algorithms of implant planning software thus seems desirable.

Microstructure-based numerical computational method for the insertion torque of dental implant

The bone quality has a significant effect on the insertion torque of dental implant. In most clinical studies, bone density is used as a gold standard in predicting insertion torque. By contrast, trabecular microstructure is ignored. In this study, a microstructure-based numerical computational method with high accuracy and efficiency for the insertion torque of dental implant was proposed by introducing two microscopic variables, namely, volume fraction and fabric tensor. First, two kinds of 3D microstructural solid models with same volume fraction and fabric tensor were established on the basis of the microstructural topology of six reference specimens. Second, a new numerical simulation method based on homogenous theory was used to explore the material models of these 3D microstructural solid models at the microscopic scale. Then, the anisotropic material models of specimens were developed on the basis of the mixture rule. Thereafter, a numerical simulation based on the anisotropic finite element (FE) model was carried out to acquire the insertion torque. To demonstrate the efficiency and accuracy of the simulation based on the anisotropic FE model, numerical simulations based on isotropic FE model and micro-computer tomography (micro-CT) FE models were also implemented as comparisons. Comparison of the simulated peak insertion torques of the anisotropic, isotropic, and micro-CT FE models with insertion experiments demonstrated the feasibility and potential of the proposed method. The anisotropic FE model reduced the time consumption by 91.85% and enhanced the accuracy by 11.82% compared with the micro-CT and isotropic FE models, respectively.

Insertion Torque of Variable-Thread Tapered Implants in the Posterior Maxilla: A Clinical Study

PURPOSE

Primary stability is a key factor for successful implant osseointegration, especially in poor bone quality and early/immediate loading. In the immediate loading protocol, insertion torque values (ITVs) have been suggested to be the most valid prognostic factor for osseointegration of maxillary implants. The objectives of this study were to: (1) evaluate ITVs achieved by a variable-thread tapered implant in the posterior maxilla; and (2) assess the impact of bone quality, implant dimensions, bicortical anchorage, and implant location on ITVs.

MATERIALS AND METHODS

Twenty-six adult, systemically healthy patients received 173 variable-thread tapered implants in maxillary premolar and molar healed edentulous sites with a minimum subsinus height of 8 mm. Implant sites were prepared using the bone-quality adjusted drilling sequence according to manufacturer's recommendations. Bone quality was recorded subjectively during drilling based on Misch criteria (D1-D4), and ITVs were measured with a manual torque wrench. Univariate and multivariate analyses were performed at the 0.05 significance level.

RESULTS

First and second molar sites accounted for 46.8% of all implants. D4 bone was encountered in 61.3% of the sites. Most of the implants were 4.3 mm in diameter (59.5%), and lengths of 11.5 and 13 mm were most commonly used (75.2%). Approximately half of the implants were associated with apical cortical anchorage (51.4%). The overall mean ITV was 44.5 ± 23.0 Ncm, with 65.5 ± 15.6 Ncm, 55.5 ± 19.6 Ncm, and 36.6 ± 21.7 Ncm for D2, D3, and D4 bone, respectively. Bone quality and implant location significantly affected ITVs, while implant dimensions and apical cortical anchorage did not.

CONCLUSIONS

ITVs of variable-thread implants were significantly influenced by variations in bone quality and implant position in the posterior maxilla. Despite the influence of bone quality on primary stability, the mean ITVs attained with variable-thread tapered implants in poor bone quality were within the recommended range for immediate loading.

Sinus augmentation and concomitant implant placement in low bone-density sites. A retrospective study on an undersized drilling protocol and primary stability

BACKGROUND

Recently, a torque-measuring micromotor has been shown to provide a reliable, quantitative intraoperative evaluation of bone density and implant primary stability. This may be particularly useful for determining bone quality of residual bone and consequently the most appropriate site preparation in the posterior maxilla, where bone often is of low density and quality.

PURPOSE

This work aimed to assess the medium-term success of implants placed during 1-stage sinus augmentations using an undersized drilling protocol. In case of low bone density, the relationship between residual bone height (RBH) and primary stability was also investigated.

MATERIALS AND METHODS

Clinical records of patients who underwent sinus augmentation and concomitant implant placement following a 12.5% undersized drilling protocol were retrospectively analyzed. In all patients, bone density measured intraoperatively was ≤ 0.45 g/cm³ . A minimum of 60 months of follow-up was required for inclusion.

RESULTS

Records of 106 patients who received 253 implants were reviewed. No significant difference in the implant success rate was found for patients who had less than 4 mm of RBH and those who had more.

CONCLUSIONS

Underpreparation of the implant-placement sites enabled achievement of successful implant-supported rehabilitation of the posterior maxilla even when both RBH and bone density were low.