Adjacent Implants Research Articles

Investigation of Coupling Effect for Adjacent Orthopedic Implants on MRI Radio-Frequency Heating

This paper investigates the mechanism of radio-frequency (RF) heating that occurs when two adjacent orthopedic implants are present together under magnetic resonance imaging (MRI) at 1.5 Tesla and 3.0 Tesla. When a patient has multiple implants close to each other, interactions between the implants may increase RF heating. Typical generic interlocking plate and antibiotic nail implants are adopted as examples. To analyze the effect of adjacent implants, the amplitude and direction of incident and scattering vector electric fields at the hot spot position are calculated and extracted using numerical simulation based on Huygens principle. It is shown that a strong coupling effect occurs due to the existence of both the incident field and a strong scattering field. Huygens principle can be used to obtain the first and second order scattering fields generated between implants. If the first- and second-order electric field terms are summed within a certain region, the RF-induced heating of this dual-implant system increases.

Comparison of stress distribution around splinted and nonsplinted implants with different crown height space in posterior mandible: A finite element analysis study.

The purpose of this finite element analysis (FEA) study was to analyze the stress distribution on prosthetic components of splinted and nonsplinted prostheses, bone, and implants with different crown height space (CHS). Mandibular posterior segment was modeled with no resorption at the second premolar site and various amounts of resorption (0, 3, 6, and 9mm) at the first molar site. Two adjacent implants (Straumann bone level implants, 4.1 mm×8mm) were placed; at the second premolar site, the crown height was 8mm and at the first molar site, the crown height varied (8, 11, 14, and 17mm), depending on the amount of resorption. Both splinted and nonsplinted crowns were designed. Vertical and oblique loads of 400 N were applied to the crowns. von Mises stress was used to evaluate the stress distribution in the implant complex and maximum principal stress was used to evaluate the stress in the bone. When oblique forces were applied, the highest von Mises stresses were observed for nonsplinted crowns in the 17mm CHS group. The maximum principal and minimum principal stresses observed in bone under oblique loading increased with increased CHS for nonsplinted restorations. Crown height affected the amount of stress in bone and implant components. When the crown height difference between two adjacent implants increases, splinting may be crucial.

Effect of cut-out rescanning protocol on the accuracy of digital impressions in convergent implants positioned at varying depths: An in vitro study

BackgroundThis study aimed to assess the effect of the "cut-out rescan" strategy on the accuracy of intraoral digital scans from 25° convergent implants positioned at two distinct depths. Material and methodsTwo customized models were fabricated, each designated to receive two posterior converged implant fixtures: one at a depth of 1 mm and the other at a depth of 4 mm. Initially, the models were scanned as reference casts using a lab scanner. The test group was involved in scanning the 1-mm and 4-mm implant models using an intraoral scanner in the following order: (1) scanning the 1-mm (T1; n = 10) and (2) 4-mm (T4; n = 10) implant groups with scan bodies connected to both fixtures in each model; (3) cut-out rescan (COR) in the 1-mm (COR1; n = 10) and (4) 4-mm (COR4; n = 10) models, leading to 40 digital files in standard tessellation language format. The mean absolute deviation (MAD), in terms of trueness and precision, between the experimental and control scans was assessed through the alignment of their respective datasets using three-dimensional analysis software. Two-way analysis of variance (ANOVA) and Levene's tests were used to analyze the data. ResultsThe COR4 group exhibited the highest MAD, indicative of both trueness and precision (Mean ±SD: 55.659 ±34.802). In contrast, the T1 group demonstrated the lowest MAD (Mean ±SD: 43.225 ±19.237). However, the ANOVA analysis showed no significant influence of depth (P = 0.506) or type of scan (P = 0.442) on the MAD. Precision also did not differ significantly across groups (P = 0.071). ConclusionsThe cut-out rescan approach demonstrated an accuracy comparable to that of the one-time scan method. Clinical significanceDigital intraoral scanning provides clinicians with a range of tools to navigate challenging conditions in which conventional methods may prove difficult, such as cases involving angled adjacent implants. In these scenarios, the cut-out rescan tool serves as a valuable resource, aiding clinicians in overcoming the challenges associated with impression-making owing to the convergence of placed implants.

Immediate Implants in Fibulas: Does the Implant to Fibula Osteotomy Distance Impact Early Implant Failure?

BackgroundWhen placing dental implants in the free fibula flap, the osteotomy cut edge poses a unique challenge in that an optimal distance has not yet been established. PurposeThe study aimed to measure the association between implant-to-fibula osteotomy edge distance and early implant failure in patients who received free fibula flap reconstruction with immediate implants. Study DesignA retrospective cohort study was designed and implemented. The study population was composed of patients who underwent free fibula flap transfer with immediate dental implant placement for the treatment of benign or malignant conditions of the head and neck from 2015 to 2022 at John Peter Smith Hospital. Subjects were excluded if the implant was in the middle of the free flap bordered by adjacent implants, was >10mm from the osteotomy edge, or had insertional torque values of ≤30 Ncm. Predictor VariablePrimary predictor variable was the implant distance in millimeters from the fibula osteotomy edge. Outcome VariablePrimary outcome variable was early implant failure, defined as implant exfoliation noted by the patient or failure due to implant movement or pain necessitating explantation within 6 months of placement. CovariatesThe covariates were age, sex, diabetes diagnosis, American Society of Anesthesiologists classification, smoking status, history of head and neck radiation, pathology treated, and if postoperative radiation treatment was received. AnalysesA generalized estimating equations (GEE) model was used to assess the relation between the primary predictor and outcome. A p-value of <0.05 was considered statistically significant. ResultsThe sample was composed of 48 subjects who had 130 implants placed, with early failures occurring in 5 implants (3.9%) in 3 subjects. The mean age of the sample was 49 years (SD 20) and 29 (60%) were male. The mean implant distances for early failures and non-failures were 3.5 mm (SD 1.04) and 4.3 mm (SD 1.5), respectively. There was a statistically significant relation between implant distance and early implant failure (P = .005, OR 0.6, 95% CI 0.39 to 0.85). ConclusionsThis study found that shorter distances between the implant and the edge of the fibula osteotomy are associated with early implant failure.

In vitro Evaluation of Implant Impression Techniques and Elastomeric Materials: A Comparative Dimensional Accuracy Study

Abstract Context: Dimensional precision in implant impression. Aims: The purpose of this study was to comparatively evaluate the dimensional accuracy of two implant impression techniques with two different variants of vinyl polysiloxane impression material. Material and Methods: The edentulous mandible reference model was fabricated in clear resin. In the anterior region of the mandibular ridge, three dummy implants were placed in a spread-out configuration. Impressions were made using two elastomeric impression materials and two impression techniques using customised impression trays. Finished casts were then divided into four groups having four samples each. The mean centre-to-centre distances between adjacent analogues (in sample casts) and between adjacent implants (in the control cast) were measured with the help of a profile projector. Statistical Analysis Used: Data were analysed using Student’s t-test. Results: The open-tray technique showed more accurate results with a combination of medium body and light body, whereas in the closed tray technique, mono-phase vinyl polysiloxane appeared to be a better option. Amongst all, mono-phase with closed tray provided statistically significant results. P &lt; 0.05 in Group C and other group’s P ≥ 0.05. Conclusions: Within the limitations of this study, both implant impression techniques appeared to be equally accurate depending on clinical conditions, temperature and time of the procedure. However, mono-phase impression material with closed tray provided statistically significant results.

Post sterilization of intraoral scan body and the effect it has on the axes and distances between three adjacent implants: in-vitro study

BackgroundThe purpose of this pilot in-vitro study was to assess the effect of sterilization on the intra-implant axis, inter-implant axis, intra-implant distance and inter-implant distance of three implants in a straight line by using laboratory scanner (LBS) versus intra-oral scanner (IOS) with intra-oral scan bodies (ISB). Methods: A printed 3D model with three internal hex analogs in the positions 15#,16#,17# was used. Zirkonzhan (ZZ) intra-oral scan body (ISB), two-piece titanium was used. The ZZ ISBs were scanned by 7 Series dental wings (LBS) and 30 times by Primescan (IOS) pre sterilization and 30 times post sterilization. For each scan (pre and post) stereolithography (STL) file was created and a comparison between all the scans pre sterilization and post sterilization were superimposed on the laboratory scan by using a 3D analyzing software. A Kolmogorov-Smirnov test performed followed by Wilcoxon Signed Ranks tests. (p < 0.05) Results: Post sterilization of the ZZ ISB, the mean errors were significantly increased for the inter-implant distances (p < 0.0005), intra-implant distances 1,2,3 (p < 0.0005), intra-implant axis 1,3 (p < 0.0005) and inter-implant axes 13,23 (p < 0.05). In contrast, the mean errors for intra-implant axis 2 (p < 0.0005) and inter-implant axis 12 (p < 0.0005) were significantly reduced. Conclusions: ZZ ISB showed changes in all four parameters after sterilization. The middle ISB had the largest changes in mean error regarding all four parameters. Sterilization process may affect the three-dimensional (3D) structure of the ZZ ISB after three cycles. There is a lack in the literature in this field and there is a need for further studies to explore the effect of sterilization (multiple cycles) on different ISBs and for creating an approved guidelines regarding the amount of sterilization for each ISB in the industry.

Marginal Bone Loss in Posterior Implants Placed at Different Levels and Different Prosthetic Designs: A Retrospective Study With a Minimum of 1-Year Follow-Up.

Various factors influence marginal bone loss after implant placement. This study explored the association between marginal bone loss and posterior implants positioned at different bone levels. Computer records and radiographs of patients with at least 2 adjacent implants were retrieved. Cases were categorized into nonsplinted prosthesis and splinted prosthesis groups. Radiographic measurements were conducted at the time of abutment placement (T0), 1-3 years follow-up (T1), and the last visit (T2), measuring the vertical distance between adjacent implants. Multilevel linear regression models using generalized estimating equations were employed, with a significance level set at 5% (α = 0.05). Fifty-six patient records were included, comprising 120 implants: 84 nonsplinted (70%) and 36 splinted (30%). In the nonsplinted group, marginal bone loss progression significantly depended on crestal height differences. For the mesial sides of posterior implants, marginal bone loss measured 1.0 ± 0.6 mm from T0 to T1, 2.4 ± 1.1 mm from T1 to T2, and 3.4 ± 1.2 mm from T0 to T2. Similarly, the distal sides of the most anteriorly placed implant exhibited marginal bone loss of 1.0 ± 0.7 mm from T0 to T1, 2.4 ± 1.0 mm from T1 to T2, and 3.5 ± 1.2 mm from T0 to T2. Nonsplinted implants demonstrated a higher progression of marginal bone loss. This study suggests that nonsplinted implants may lead to a more pronounced progression of marginal bone loss, particularly concerning crestal height differences, underscoring the need for further research.

Application of '10 Keys' Checklist and Partial Extraction Techniques to Optimize Esthetic Outcome for Adjacent Implants in the Esthetic Zone.

Placing immediate implants in the esthetic zone area poses significant challenges. Implants should be placed with consideration to hard and soft tissue management to optimize long term implant and cosmetic success. In this case report, two maxillary central incisors were extracted in two different time points, separated by 5 years because of horizontal root fractures. Implants were placed according to immediate single-tooth guidelines, using two different surgical and loading approaches, as risk assessment factors changed in the time between first immediate placement (#8) and second immediate placement (#9). These techniques included Partial Extraction Therapy (PET), the use of allograft and growth factors, connective tissue graft (CTG), platelet rich fibrin (PRF) and immediate and conventional loading. These were grouped as the '10 keys', a checklist used to pursue long term success. After 6-year and 1-year follow-up, radiographic and clinical results were satisfactory.

Proposal regarding potential causes related to certain complications with dental implants and adjacent natural teeth: Physics applied to prosthodontics.

Complications can and do occur with implants and their restorations with causes having been proposed for some single implant complications but not for others. A review of pertinent literature was conducted. A PubMed search of vibration, movement, and dentistry had 175 citations, while stress waves, movement, and dentistry had zero citations as did stress waves, movement. This paper discusses the physics of vibration, elastic and inelastic collision, and stress waves as potentially causative factors related to clinical complications. Multiple potential causes for interproximal contact loss have been presented, but it has not been fully understood. Likewise, theories have been suggested regarding the intrusion of natural teeth when they are connected to an implant as part of a fixed partial denture as well as intrusion when a tooth is located between adjacent implants, but the process of intrusion, and resultant extrusion, is not fully understood. A third complication with single implants and their crowns is abutment screw loosening with several of the clinical characteristics having been discussed but without determining the underlying process(es). Interproximal contact loss, natural tooth intrusion, and abutment screw loosening are common complications that occur with implant retained restorations. Occlusion is a significant confounding variable. The hypothesis is that vibration, or possibly stress waves, generated from occlusal impact forces on implant crowns and transmitted to adjacent teeth, are the causative factors in these events. Since occlusion appears to play a role in these complications, it is recommended that occlusal contacts provide centralized stability on implant crowns and not be located on any inclined surfaces that transmit lateral forces that could be transmitted to an adjacent tooth and cause interproximal contact loss or intrusion. The intensity, form, and location of proximal contacts between a natural tooth located between adjacent single implant crowns seem to play a role in the intrusion of the natural tooth. Currently, there is a lack of information about the underlying mechanisms related to these occurrences and research is needed to define any confounding variables.

Advances in Surgical Template Design in Dental Implantology

Background: Expansion of three-dimensional (3D) printing technology and improvements in planning software have led to increased accuracy and precision in dental implant positioning and new applications for surgical templates in implantology. The objective of this report is to demonstrate the application of locally printed surgical templates in various dental implant surgeries and site development procedures. Methods: Nine patients were referred to the Department of Periodontics, Army Postgraduate Dental School, Postgraduate Dental College, Fort Eisenhower, GA, USA, for replacement of missing or hopeless teeth using dental implants. All surgeries were planned virtually and completed using customized surgical templates produced within the local facility. The presented cases demonstrate use of surgical templates to simplify surgery across a wide spectrum of clinical scenarios—placement of multiple adjacent implants, immediate implant placement, immediate provisionalization, sinus elevation in dentate and edentulous patients, removal of a retained root fragment in conjunction with implant surgery, alveoloplasty to increase interarch distance, and fully guided implant surgery. Results: In the presented dental implant surgeries, use of locally produced surgical templates permitted transfer of the planned implant positions to the patients with high reliability. Use of surgical templates in sinus elevation procedures ensured augmentation in the appropriate positions and simplified intraoperative management of complex anatomy. Conclusions: Specialized surgical templates have the potential to reduce the duration of surgery, limit patient morbidity, enhance communication among clinicians, and simplify the restorative phase of therapy. Accessibility to new technology has allowed implant surgeons to move beyond the era of accurate implant placement into a period characterized by creative solutions to clinical problems.

Radiographic evaluation of marginal bone levels around implants supporting splinted fixed bridges: A retrospective study on 412 implants.

The effect of the implant position within the prosthesis on bone remodeling is scarcely documented so far. Thus, the aim of the present study was to investigate whether central implants may suffer higher peri-implant marginal bone levels (MBL) compared to laterals in case of fixed splinted bridges supported by ≥ three implants. Partially edentulous subjects rehabilitated with at least one fixed bridge supported by ≥ three dental implants were enrolled. MBL was assessed radiographically by means of intraoral radiographs acquired with phosphor plates and imported in a dedicated software. MBL was calculated as the distance between the implant platform level and the most coronal visible bone-to-implant contact. A three-level linear mixed effects model was used for investigating the fixed effect of patient-, prosthesis-, and implant-level variables on the MBL. Overall, 90 patients rehabilitated with 130 splinted fixed bridges supported by 412 implants were included. The median follow-up was 136 months. The mean peri-implant MBL resulted statistically significantly higher at central implants if compared to lateral implants (p < .01). The estimated MBL averages for central and external implants were 1.68 and 1.18 mm, respectively. The prosthesis-level variables suggested that a cement-retained bridge was prone to a significant 0.82 mm higher MBL than a screw-retained one. Implant surface showed an association with MBL changes, although less pronounced than implant retention. In case of ≥3 adjacent implants supporting splinted bridges, central implants were more predisposed to MBL compared to laterals. At the prosthesis level, implants supporting cement-retained bridges were statistically more susceptible to MBL compared to screw-retained ones. Surface characteristics can also influence MBL stability at the implant level.

The effects of anatomical location and distance from dental implants on the quality and quantity of metal artifacts in cone beam computed tomography scans: a cross-sectional study

BackgroundArtifacts in cone beam computed tomography (CBCT) images can cause disruptions in diagnosis and treatment. Multiple factors influence the artifacts, including the quality and technology of devices, positions, patient-related factors, device settings, and bone density. Besides, anatomical area and distance from the implant affect the artifacts. This study aimed to investigate the effects of anatomical location and distance from the implant on the quality and quantity of artifacts.MethodsA total of 200 CBCT images of patients with titanium implants and prostheses in the anterior and posterior regions of the maxilla and mandible were evaluated in this study. Four areas were assessed for each implant in three apical, middle, and cervical regions with distances of 3 mm, 4 mm, and 5 mm from the implant. Besides, the impact of adjacent implants on the artifacts was investigated. An ANOVA test with post hoc Bonferroni correction was used to analyze variable differences between subgroups.ResultsThe differences were statistically significant, except for the difference between the posterior areas of the upper and lower jaws. A comparison of different areas revealed that most artifacts were related to the anterior maxilla, followed by anterior mandibular regions. The results of covariance analysis indicated that region and location had independent effects on the amount of artifacts.ConclusionsArtifacts are more frequent in the anterior region compared to the posterior site. They are also more frequent in the maxilla than the mandible and cervical areas close to the implant than the middle and apical regions.

Biofilm accumulation on complete arch subperiosteal implant-supported prostheses: Effect of pontic type

Statement of problemComplete arch subperiosteal implant-supported prostheses present challenges in terms of effective cleaning, leading to the accumulation of biofilm on their intaglio surfaces. The association between different intaglio surface morphologies and biofilm accumulation on complete arch subperiosteal implant-supported prostheses is unclear. PurposeThe purpose of this in vitro study was to investigate the correlation between the intaglio surface of complete arch subperiosteal implant-supported prostheses and biofilm accumulation. Material and methodsSixty-eight complete arch subperiosteal implant-supported prostheses were fabricated with varying interimplant distances and pontic morphologies. Four different types of pontic morphologies were included: saddle, flat, scalloped, and ovate. To simulate biofilm accumulation, a green aerosol was sprayed onto the intaglio surface. Dental floss was used to clean the colored spray from the intaglio surface. The intaglio surfaces of prostheses were then scanned with an intraoral scanner. The biofilm areas were identified and calculated by using a 3-dimensional macroscopical quantification method. The distances between adjacent implants and transmucosal height were measured. The correlation between interimplant distances and biofilm areas, and the correlation between the biofilm areas and transmucosal height, were analyzed using the Spearman test. Furthermore, a generalized estimating equation (GEE) was employed to examine the relationship between pontic morphology and biofilm area, adjusting for location, cantilever, implant distance, and transmucosal height (α=.05). ResultsA significant correlation was found between the biofilm area and transmucosal height (correlation coefficient=0.208, P<.001). A significant increase in biofilm accumulation was observed in the saddle group compared with the 3 groups in GEE Models I and II. ConclusionsFlat pontics and ovate pontics have significantly lower biofilm retention. Moreover, transmucosal height plays a significant role in biofilm accumulation in the pontic area.

The effect of splinting crowns on multiple adjacent implants: a retrospective study

Purpose: The purpose of this study was to retrospectively evaluate the effects of splinting implant crowns against nonsplinted crowns on the failures and complications of multiple adjacent implants. Material and methods: A retrospective chart review was conducted of all registered implant patients treated at the University of Minnesota School of Dentistry from 1988 to 2018. A total of 2738 implants within 1171 sections of 890 patients were examined retrospectively using an inclusion criteria of (1) two or more adjacent implants (section) present and (2) implants were restored by splinted crowns (Splinted group) or nonsplinted (individual) crowns (Nonsplinted group). Results: An average follow-up interval was significantly longer (p &lt; 0.0001) for Splinted (median 5.52 [IQR 1.97, 9.67] years) compared to Nonsplinted (3.76 [1.49, 6.54] years). Splinted group’s Hazard ratio (HR) for implant failure was 0.67 (95% CI 0.35–1.31, p = 0.24) relative to Nonsplinted, and estimated 5- and 10-year failures rates were 2.5 (1.3–3.7) vs. 3.0 (1.9–4.0)% and 8.7 (6.1–11.3) vs. 8.6 (5.7–11.3)%, respectively. Splinted group’s HR for total complication relative to Nonsplinted was 0.98 (95% CI 0.71–1.36, p = 0.92) and estimated 5- and 10-year complication rates were 24.7 (21.7-27.5) vs. 23.7 (21.1-26.3)% and 38.1 (34.2-41.7) vs. 42.1 (37.2-46.6)%, respectively. Three most common complications (Splinted/Nonsplinted, 10-year estimates) were crown decementation/dislodgement (20.8/13.0%), peri-implantitis (12.2/13.1%), and screw loosening (5.9/12.8%), while 3 failure causes (5-year estimates) were peri-implantitis (1.8/1.3%), implant fracture/metal collar flowering (0.3/1.1%), and soft tissue encapsulation (0.1/0.2%). When 380 Lifecore implants with higher failure rates (8.4% in 7.2 years) were excluded, the implant failure HR became lower 0.46 (0.22–0.99, p = 0.05) indicating significantly lower implant failure risk in Splinted compared to Nonsplinted, while the total complication HR did not change much 0.95 (0.64–1.40, p = 0.79). When compared per section, Splinted total complication HR went down to 0.75 (0.55–1.02, p = 0.07), indicating lower risk for complication in Splinted sections compared to Nonsplinted sections. Conclusion: The trends of implant therapy of multiple adjacent implants have changed over the last three decades. The effects of splinting crowns of multiple adjacent implants were not significant in reducing implant failures or total complications. However, when the Lifecore implants mainly used in Splinted group during earlier phase (1988 – 2003) were excluded, the Splinted group showed significantly lower implant failure risk than Nonsplined group.

Splinting or Nonsplinting Adjacent Implants? A Retrospective Study Up to 15 Years: Part I-Biologic and Mechanical Complication Analysis.

To analyze the biologic and mechanical complications of splinted and nonsplinted implant restorations. A total of 423 patients (n = implants: 888) were included in the study. Biologic and mechanical complications that occurred for 15 years were analyzed using the multivariable Cox regression model, and the significant effect of the splinting of prostheses and other risk factors were evaluated. Biologic complications occurred in 38.7% of implants: 26.4% of nonsplinted implants (NS) and 45.4% of splinted implants (SP). Mechanical complications occurred in 49.2% of implants: 59.3% NS and 43.9% SP. Implants splinted with both mesial and distal adjacent implants (SP-mid) had the highest risk of peri-implant diseases. As the number of implants splinted increased, the risk of mechanical complications decreased. Long crown lengths increased the risk of both biologic and mechanical complications. Splinted implants had a higher risk of biologic complications and lower risk of mechanical complications. The implant splinted to both adjacent implants (SP-mid) had the highest risk of biologic complications. The greater the number of implants splinted, the lower the risk of mechanical complications. Long crown lengths increased the risk of both biologic and mechanical complications. Int J Oral Maxillofac Implants 2023;38:435-442. doi: 10.11607/jomi.10053.

Evaluation of the dislodgement force of splinted restorations with engaging conical abutments over multiple nonparallel implants (in-vitro study)

BackgroundSplinted multiunit cement-retained restorations with screw access channels over engaging abutments are viable implant prosthetic options. However, information regarding the maximum degree of divergence between multiple implants is lacking. The purpose of this in vitro study was to determine the maximum degree of divergence between 2 adjacent implants with conical connections that allows insertion and removal of splinted restorations with engaging preparable abutments or titanium base abutments.MethodsTwo implants were aligned in a stone base, one straight and the other at an angle ranging from 0 to 20 degrees. The implants represented an implant system that had an internal conical connection and a hexed abutment engaging the base of the connection. Two straight preparable engaging cement retained abutments were screwed onto the implants and splinted together using acrylic resin. A total of 11 angles were tested, with 7 specimens for every angle. Evaluation of dislodging force was performed by pulling out the splinted abutments after unscrewing them. This was performed subjectively by 3 blinded investigators who applied a tactile pulling force. A scale of 0–10 was used to estimate the pulling force. Objectively the dislodging force was measured in Newtons using a universal testing machine. A statistical correlation was made between the subjective and objective dislodging force values using Spearman’s rank correlation coefficient.ResultsThe mean subjective values increased gradually from 0 to 16 degrees. A sudden rise was noticed at 18 degrees (9.71 ± 0.23) and, at 20 degrees, the investigators were not able to remove the splinted abutments from the implants. The mean objective dislodgement force values increased gradually from 0 to16 degrees and abruptly from 16 degrees (13.57 ± 0.45 N) to 18 degrees (25.40 ± 0.66 N) and 20 degrees (35.22 ± 0.64). The correlation between the subjective and the objective evaluations assessed using the Spearman’s rank correlation coefficient was 0.98 indicating a statistically significant correlation (P < .001). As the objective dislodging force increased, the subjective dislodgement difficulty increased.ConclusionsSplinting cement retained restorations with screw access channels on engaging abutments is possible when multiple implants with conical connections having an internal flare angle of 8 degrees are used, with implant divergence of up to 16 degrees.

Six-month stability following extensive alveolar bone augmentation by sausage technique

BackgroundResorption of alveolar bone is a common sequela of tooth loss and presents a clinical problem, especially in the esthetic zone. When ridge resorption occurs, adequate bone augmentation is essential to obtain satisfactory esthetic results. The purpose of this study was to determine the increase and retention rate of bone height or width in patients who received extensive bone augmentation and to analyze factors affecting its prognosis and stability.MethodsThis study was performed on patients who received extensive bone augmentation by sausage technique at the Department of Oral and Maxillofacial Surgery at Ewha Womans University Mok-dong Hospital from January 1, 2018, to February 28, 2022. CBCT images were taken before and 6 months after surgery to compare the amount of increase in bone height or width at the graft site. They were measured using reliable points such as adjacent implants or cephalometric landmarks, inferior alveolar nerve canals as reference points.ResultsA total of 8 patients underwent extensive bone grafting during the given period (mean age was 53.75 years, 2 males and 6 females). Four patients received horizontal augmentation, and 4 received vertical augmentation. When divided by surgical site, 4 patients are in maxilla and 4 in mandible. The average amount of increase in bone width or bone height was 5.38 mm, and the retention rate was about 79.9% after 6 months. The retention rate of horizontal augmentation was 88.8%, which was higher than that of vertical augmentation, which was 74.5%. The maxillary area accounted for 92.2%, and the amount of bone resorption was lower than that of the mandibular area, which was 72.6%. The average stitch out period was about 2.4 weeks, and postoperative dehiscence was observed about 37.5% of the total, more frequently in the mandible (50.0%) than in the maxilla (25.0%).ConclusionIn conclusion, extensive bone augmentation achieved significant horizontal or vertical bone height or width increase, and the retention rate after 6 months was also high. In addition, surgery in the maxillary region showed a more successful bone augmentation than in the mandible, with a higher maintenance rate and fewer cases of dehiscence.

Evaluation the Scanning Accuracy of Blue-Light Laboratory Scanners in Complete Edentulous Maxilla with Multiple Implants with Titanium Scan Bodies

To evaluate the accuracy of complete arch scanning with multiple implant titanium scan bodies using laboratory scanners. A master model of an edentulous maxillary arch with 6 implants was fabricated. Titanium scan bodies were inserted into the model. Three laboratory scanners were used: D2000 (3Shape), Vinyl High Resolution (Smart Optics), and inEos X5 (Dentsply Sirona). The master model was consecutively scanned ten times using dental laboratory scanners (LS) without detaching and repositioning the scan bodies. Linear and angular accuracy between adjacent implants was measured using inspection software (Control X, Geomagic). The accuracy of the complete arch scans was calculated. Implant regions were defined as; parallel (R1: #24-26 and #16-14), angled (R2: #22-24 and #14-12), angled to occlusal plane (R3: #12-22), and cross-arch (R4: #16-26). The effect of LS and implant region on accuracy was compared using two-Way ANOVA (α=0.05). Significant greater linear distortion was noted in R4 (61.2±17.9µm) compared to R1 (23.4±15.5µm) and R2 (26±17.7µm) (p&lt;0.01). Greater linear distortions were noted in R4 with D2000 (0.07±0.016 degrees) and Vinyl High Resolution (0.067±0.02 degrees) than inEos X5 (0.032±0.021 degrees) (p&gt;0.05). Greater mean linear precisions were noted in R1 (9±8µm) and R3 (9.3±8.3µm) than R4 (12.6±10.3µm) (p&lt;0.05). The highest linear precision was noted in D2000 (7.2±7.6µm) (p&lt;0.05). The angular precision of D2000 (0.02±0.015 degrees) was the highest (p&lt;0.01). The angular precision of R4 (0.036±0.018 degrees) was the lowest (p&lt;0.01). This study revealed that the trueness was affected by the implant region and the precision was affected by both LS and implant region.

Inter-implant distance and buccal bone thickness for a novel implant design: a preclinical study

ObjectivesThis study assessed bone height between novel tapered implants at different inter-implant thread peak (TP) distances, and the impact of TP distance from outer buccal bone (BB) on marginal bone levels (MBL).Materials and MethodsFully tapered implants with 0.5-mm thread depth and TP diameter 1 mm wider than the shoulder diameter were placed in healed ridges of minipigs. On one side, four implants were placed with inter-implant TP distances of 1, 2, or 3 mm corresponding to inter-implant implant shoulder distances of 2, 3, and 4 mm respectively. Three implants were placed on the other side with TP distances to outer BB of > 1 mm, 0.5–1 mm, or < 0.5 mm. After 12 weeks, (a) first bone-to-implant contact (fBIC), total BIC, bone area-to-total area (BATA), and coronal bone height between implants (Bi ½ max) for inter-implant distance, and (b) fBIC, BIC, and perpendicular crest to implant shoulder (pCIS) for BB were evaluated.ResultsNo significant differences in bone healing and inter-implant bone height were noted for any of the TP distances. BB resorption was significant when TP distance to outer BB was < 0.5 mm. However, fBIC was lowest with TP to outer BB of 1.75 mm.ConclusionsInter-implant bone height between adjacent implants can be maintained even at an inter-implant TP distance as low as 1 mm. A minimum TP to outer BB distance of 0.75 mm is required for predictable maintenance of MBL.Clinical relevanceInter-implant distance and BB thickness are clinically relevant and require preclinical research to clarify concepts.

Implant placement with an autonomous dental implant robot: A clinical report

Ideal implant placement is the basis for long-term implant survival and satisfactory restoration outcomes. Static and dynamic computer-assisted guidance have been used to improve the accuracy of implant placement, but both have shortcomings that robots can overcome. This clinical report describes the use of an autonomous implant robot to complete the placement of 2 adjacent implants with immediate postoperative restoration.