Effects of different types of intraoral scanners and scanning ranges on the precision of digital implant impressions in edentulous maxilla: An in vitro study.

OBJECTIVE: This study aimed to evaluate the precision of digital implant impressions in comparison with conventional impressions and assess the impact of the scanning range on precision. MATERIALS AND METHODS: An edentulous maxilla model with six implants was scanned with four intraoral scanners (IOSs) and a dental laboratory scanner five times each, and stereolithography (STL) data were generated. A conventional silicone impression was made, and a model was fabricated, which was scanned using the laboratory scanner. This procedure was also repeated five times. Nine different ranges of interest (ROIs) were defined, and the average discrepancies of the measurement points between each pair of STL images out of five for each ROI were calculated. The effects of "impression method" and "ROI" on precision, as evaluated by the averaged discrepancy, were tested by two-way analysis of variance (p < .05). RESULTS: The effects of "impression methods" and "ROI" and their interactions were statistically significant. The discrepancies in the scanned datasets of the dental laboratory scanner were significantly lower than those in the other impression methods. The discrepancies of the IOSs were comparable with those of the laboratory scanner when the ROI was limited, however; the discrepancies deteriorated when the ROI expanded across the arch, while those of the laboratory scanner remained stable irrespective of the ROI. CONCLUSIONS: Within the limitation of this in vitro study, digital implant impressions by IOSs may show clinically acceptable precision when the scan range is limited, such as in 3-unit superstructure supported by two implants.

Capability of new bone formation with a mixture of hydroxyapatite and beta-tricalcium phosphate granules.

OBJECTIVES: The aim of this experimental study was to test a mixture of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) granules inserted in cranial defects in rabbits, by the evaluation of the hard tissues volume, new bone formation, and residual graft after 4 and 8 weeks. MATERIAL AND METHODS: Two defects of 8 mm diameter were created at the calvarial bone of 24 Japanese white rabbits for a total of 48 defects. Four groups were created: defects filled with a mixture of HA and beta-TCP granules (test A), defects filled with HA alone (test B), defects filled with beta-TCP (test C), and empty defects (control). Hard tissues volume (remaining graft + new bone) was evaluated by µ-CT and new bone (NB) and remaining graft (RG) percentages were evaluated by histomorphometry. The animals were sacrificed at 4 or 8 weeks postoperatively. RESULTS: The test groups A, B, and C showed a significant higher total volume compared with controls at 4 and 8 weeks (P < 0.05). Regarding the percentages of NB and RG at 4 and 8 weeks, no significant differences were detected (P > 0.05). When comparing 4 and 8 weeks, test group A showed a significant increase in new bone formation. At both 4 and 8 weeks, no group showed significant differences in NB (P > 0.05). At 8 weeks, test group B had more RG than test group A. CONCLUSIONS: The novel mixture could maintain the volume of the grafted area compared with that with intervention, and in a similar way compared with HA.

Risk Factors for Early Implant Failure and Selection of Bone Grafting Materials for Various Bone Augmentation Procedures: A Narrative Review.

Implant therapy is now an established treatment with high long-term success and survival rates. However, early implant failure, which occurs within one year of superstructure placement, occurs at a higher rate than late failure, which is represented by peri-implantitis caused by bacterial infection. Furthermore, various risk factors for early failure have been reported, including patient-related factors, such as systemic diseases, smoking, and bone quality and quantity, as well as surgery-related factors, such as surgeons' skill, osteogenesis technique, and selection of graft material, and implant-related factors, such as initial implant fixation and implant length diameter. Due to the wide variety of relevant factors reported, it is difficult to identify the cause of the problem. The purpose of this review is to discuss the risk factors associated with various types of bone augmentation which have a close causal relationship with early implant failure, and to determine the optimal bone grafting material for bone augmentation procedures to avoid early implant failure.

A Comprehensive Clinical Review of Maxillary Sinus Floor Elevation in Patients with Well-Defined Faintly Radiopaque Lesions in the Antrum.

Well-defined, faintly radiopaque lesions are occasionally observed in the antrum of the maxillary sinus in asymptomatic patients during maxillary sinus floor elevation. These lesions are treated as antral pseudocysts (AP) based on the clinical diagnosis in some cases, and maxillary sinus floor elevation is performed without enucleating these lesions. However, further surgery is required after implant placement if the lesion is a mucocele, odontogenic cyst, or tumour. This comprehensive clinical review aimed to identify an appropriate approach for maxillary sinus floor elevation in patients with well-defined, faintly radiopaque lesions in the antrum based on our clinical experience.

Association between the treatment choice of implant-supported fixed partial dentures and oral health-related quality of life in patients with a shortened dental arch: A preliminary observational study.

Background/purpose: In cases of missing posterior teeth, treatment modalities based on the shortened dental arch (SDA) concept may be a viable alternative. However, the association between oral health-related quality of life (OHRQoL) and patients' treatment decisions remains unclear. This study aimed to investigate the association between OHRQoL and the decision to be treated with implant-supported fixed partial dentures (IFPDs) or take a wait-and-see approach in patients with an SDA missing a single second molar and to clarify the impact of IFPD treatment on the OHRQoL. Materials and methods: The Oral Health Impact Profile (OHIP) questionnaire was administered twice (pre- and post-treatment) and once to 41 patients with a unilateral SDA missing a single second molar who chose IFPD treatment (IFPD group, n = 22) and the wait-and-see approach (no treatment group, n = 19), respectively. Logistic regression analysis was performed with IFPD treatment choice as the objective variable and the four OHIP dimension scores, age, and sex as covariates. The pre- and post-treatment values of the OHIP summary and four-dimension scores were compared using a paired t-test. Results: The IFPD treatment choice was significantly associated with sex (male), higher Oral Function dimension scores, and lower Psychosocial Impact dimension scores (all P < 0.05). The OHIP summary and four-dimension scores were significantly lower following IFPD treatment (all P < 0.05). Conclusion: IFPD treatment for a single missing second molar may be clinically beneficial for improving the OHRQoL of patients with an SDA who experience a decline in masticatory function.

A Study of the Associated Risk Factors for Early Failure and the Effect of Photofunctionalisation in Full-Arch Immediate Loading Treatment Based on the All-on-Four Concept.

Early implant failure occurring within 1 year after implantation has been attributed to various factors. Particularly, early failure can lead to challenges in maintaining a full-arch prosthetic device, necessitating prompt intervention, including reoperation. This study aimed to retrospectively examine implant- and patient-related factors and the effects of photofunctionalisation associated with early failure in patients who underwent treatment using the all-on-four concept in both the maxilla and mandible. We conducted this retrospective study comprising 561 patients with 2364 implants who underwent implant-supported immediate loading with fixed full-arch rehabilitation using the all-on-four concept. We aimed to assess the survival rate within 1 year after implantation and determine the risk factors influencing early failure. The 1-year survival rates after implantation were 97.1% (patient level) and 98.9% (implant level) for the maxilla and 98.5% (patient level) and 99.6% (implant level) for the mandible. There was a significant difference in the implant-level survival rates between the maxilla and mandible, with a lower rate in the maxilla (p = 0.043). The risk factors associated with early implant failure according to the all-on-four concept included the maxilla (implant level) and smoking (patient level). We could not find a significant effect of photofunctionalisation on early failure (p = 0.25) following this treatment protocol.

Effects of implant surface mechanical instrumentation methods on peri-implantitis: An in vitro study using a circumferential bone defect model.

Background/purpose: Although several mechanical and chemical debridement techniques have been reported for the management of peri-implantitis, there is no consensus on the most effective method at present. This in vitro study aimed to examine the effects of different mechanical instrumentation techniques on the debridement of hard calcified materials, which are present on the implant surface, as well as the effect of the defect morphology. Materials and methods: From a total of 15 implants, five each were assigned to one of three decontamination groups (Rotary titanium brush [Ti], tricalcium phosphate air powder abrasive treatment [Air], and titanium ultrasonic scaler [US] groups); the exposed hydroxyapatite (HA)-coated portion was divided into three 1-mm sections (coronal, middle, and apical). The residual-HA of each portion was measured using a digital microscope. Results: The overall percentage of residual HA coating was significantly lower in the US group than in the Ti or Air groups (p < 0.01). The percentage of residual HA in the coronal portion was significantly lower in the Ti and US groups than in the Air group (p < 0.05 and p < 0.01, respectively). The percentage of residual HA in the middle portion was significantly lower in the US group than in the Air group (p < 0.01). The percentage of residual HA in the apical portion was significantly lower in the Ti group than in the Air or US groups (p < 0.01). Conclusion: Ti and US were more effective for shallow defects, whereas US was more effective for deeper defects.

Trueness and precision of digital implant impressions by intraoral scanners: a literature review.

BACKGROUND: With the development of intraoral scanners, their trueness and precision have been evaluated in various studies. Through these studies, the amount of accuracy that can be expected from intraoral scanners has gradually been disclosed, at the same time, it was difficult to integrate the results of individual studies due to differences in evaluation methods between studies. The purpose of this article was to review the currently available evidence, summarise what is currently known about IOS, analyse the evaluation methods of each study, and list points to note when interpreting the results. MAIN TEXT: Most of the studies were conducted in vitro. The accuracy is evaluated in situations such as single missing teeth, partially edentulous ridges with multiple missing teeth, and fully edentulous jaws. To evaluate the accuracy, direct measurement of distance or angle by coordinate measuring machines and calculation of surface deviation by superimposing surface data were predominantly performed. The influence of parameters such as the number of implants, distance between implants, angle between implants, and experience of the operator was evaluated. Many studies have shown that trueness tends to decrease as the distance between the implants and the scan range increases. It was agreed that the implant angle did not affect either trueness or precision. Regarding other factors, the results varied among studies. Therefore, the effects of these parameters are not clear. CONCLUSIONS: Heterogeneity in the research methodology was prevalent among the studies considered in this review. Therefore, we cannot make a decisive statement regarding the trueness and precision of digital implant impressions by IOSs. So far, the comparison of the numerical values of error between studies has yet to elucidate any clear answers, despite small methodological differences.

Effect of assistive devices on the precision of digital impressions for implants placed in edentulous maxilla: an in vitro study.

PURPOSE: To examine the effect of assistive devices on the precision of digital impression for multiple implants placed in the edentulous maxilla. METHODS: A reference model representing an edentulous maxilla with four implants was developed. The digital impression group included three settings: Type 0, without an assistive device; Type 1, with an assistive device connecting only neighboring implants; and Type 2, with an assistive device connecting not only neighboring implants but also the two posterior implants, with perpendicular branches from this bar towards the anterior implants. Digital impressions were made five times for each type using three intraoral scanners (IOSs). For conventional method, silicone impressions and verification jigs were prepared; fabricated plaster models were scanned using a laboratory scanner/industrial 3D scanner. In analysis 1, two-way ANOVA analyzed the effect of IOSs and assistive devices on the precision of digital impressions. In analysis 2, one-way ANOVA compared the silicone impressions, the verification jigs, and the most precise group of digital impressions from analysis 1. RESULTS: In analysis 1, the IOS and assistive device type (F = 25.22, p < .0001) effects and the interaction between these two factors (F = 5.64, p = .0005) were statistically significant. In analysis 2, CON, VJ, and digital impression with Type 2 devices (most precise devices in analysis 1) were compared; better precision was obtained by digital impression with Type 2 device than by CON and VJ (F = 30.08, p < .0001). CONCLUSIONS: For implants placed in an edentulous maxilla, digital impressions with assistive devices can provide better precision compared to silicone impressions and verification jigs.

Variations in vertical mucosal thickness at edentulous ridge according to site and gender measured by cone-beam computed tomography.

BACKGROUND: The vertical thickness of the peri-implant mucosa is associated with the amount of post treatment marginal bone loss. However, the variations in mucosal thickness at the different edentulous sites have been sparsely documented. The purpose of the study was to conduct a survey of the frequency distribution of variations in mucosal thickness at the different sites of the edentulous alveolar ridge and to compare them according to gender. Our study included 125 partially edentulous patients having a total of 296 implant sites. Cone-beam computed tomography (CBCT) scans were obtained by placing a diagnostic template with a radiopaque crown indicator on the ridge to determine the mucosal thickness at the crest of the alveolar ridge. RESULTS: The mucosal thickness was 3.0±1.3 mm in the maxilla, which was significantly greater than the mucosal thickness of 2.0±1.0 mm in the mandible (p<0.001). In both the maxilla and the mandible, the mucosa was the thickest in the anterior region, followed by the premolar and molar regions. Sites were further classified into two groups based on whether the mucosal thickness was greater than 2 mm. In the mandible, more than half of the sites showed a mucosal thickness of 2 mm or less. CONCLUSIONS: Although this study was a limited preoperative study, the vertical mucosal thickness at the edentulous ridge differed between the maxillary and mandibular regions. The majority of sites in the mandibular molar region had a mucosal thickness of less than 2 mm. Practitioners might be able to develop an optimal dental implant treatment plan for long-term biologic and esthetic stability by considering these factors.

Comparison of immediate and conventional loading protocols with respect to marginal bone loss around implants supporting mandibular overdentures: A systematic review and meta-analysis.

PURPOSE: To compare marginal bone level changes (MBLCs) of immediately- and conventionally-loaded implants supporting a mandibular implant overdenture (IOD). MATERIALS AND METHODS: Both electronic (MEDLINE, PubMed, and The Cochrane Library) and manual searches were conducted for all relevant studies published from 1 January 2000 to 1 November, 2017. Randomized controlled trials (RCTs) and prospective studies with a minimum follow-up of 12 months were selected. Studies which utilized implants narrower than 3 mm were excluded from analysis. RESULTS: Four studies met the criteria, with two evaluating horizontal bone loss. There were 70 patients in the test group (immediate loading) and 60 in the control group (conventional loading). Follow-up lasted 6-36 months, with MBLCs being interpreted from standardized periapical x-rays, panoramics or cone beam computed tomography. Each patient was given 2-3 implants.After 6 and 12 months, the differences in MBLCs were 0.04 mm (95% CI: -0.21, 0.29) and 0. 00 mm (95% CI: -0.35, 0.36) respectively. Subgroup analysis of RCTs with 2 implants revealed group differences in MBLCs as 0.13 mm (95% CI: -0.22, 0.48) and that in horizontal bone loss as 0.04 mm (95% CI: -0.02, 0.10). No statistically significant differences were identified (p > 0.05). CONCLUSION: The MBLCs of immediately-loaded implants for mandibular IODs seems comparable to those of conventional loading.

Influence of Bisphosphonates on Implant Failure Rates and Characteristics of Postmenopausal Woman Mandibular Jawbone.

Rehabilitation of oral function using dental implants is clinically effective and highly predictable. Both bone quantity and quality at the implant site affect the success of the procedure. However, the effect of bisphosphonate (BP) use on mandibular bone quality has not been well documented. The purpose of this retrospective cohort study was to evaluate the bone mineral density (BMD) and cortical thickness of the mandible, as well as the influence of BP use on early implant failure. Twenty-five female patients (≥60 years of age) were selected from among 93 candidates with partially edentulous posterior mandibles. Eleven patients had received BP therapy using alendronate (BP group), and 14 patients had received alternate therapy (non-BP group). Cortical and trabecular BMD was measured using quantitative computed tomography. Cortical thickness was measured using computed tomography. The BMDs and cortical thicknesses of the two groups were compared. The results were as follows: (1) Cortical BMD was significantly higher in the BP group, (2) trabecular BMD was not affected by BP use, and (3) Cortical thickness was affected by the duration of BP use. These results indicate that BP use affects the quality and quantity of the cortical bone in the partially edentulous posterior mandible of patients with osteoporosis, which should be considered prior to treatment with dental implants in patients taking BPs.

A randomized, 12-month controlled trial to evaluate non-inferiority of early compared to conventional loading of modSLA implants in single tooth gaps.

BACKGROUND: The aim of the study was to evaluate whether early loading of implants with a chemically modified sandblasted, large-grit, acid-etched (SLA) (SLActive®) surface was non-inferior to conventional loading in terms of change in crestal bone level. METHODS: This was a randomized, controlled, multicenter study. Patients requiring single-tooth rehabilitation in the posterior maxilla or mandible received implants and were randomized to receive a provisional restoration in occlusal load after 25 ± 3 days (early loading) or after 13 ± 1 weeks (conventional loading). The primary endpoint was change in crestal bone level between implant placement (baseline) and 6 months. Secondary endpoints included change in crestal bone level between baseline and 12 months, implant survival and success rates, and patient satisfaction. RESULTS: Of the 84 patients enrolled, 78 received implants and were randomized onto the early loading (41 patients) and conventional loading (37 patients) groups. The mean change in crestal bone level between baseline and 6 months was 0.56 ± 0.58 and 0.51 ± 0.62 mm for early and conventional loading, respectively; at 12 months, the mean change was 0.76 ± 0.60 and 0.73 ± 0.77 mm, respectively. Implant survival and success at 12 months were 100 % for both groups. Patient satisfaction was similar between the groups, except that more patients in the early loading group were satisfied or highly satisfied with the time taken for fitting. CONCLUSION: The study demonstrated that early implant loading was non-inferior to conventional implant loading in terms of crestal bone level change in a Japanese patient population in short follow-up period and single tooth gaps in molar regions.

The Maxillary Sinus Floor Elevation Using a Poly-L-Lactic Acid Device to Create Space Without Bone Graft: Case Series Study of Five Patients.

Maxillary sinus floor elevation using autologous or alloplastic bone grafting is often performed for implant treatment of maxillary molars; however, issues related to the donor site and complications such as infection have been reported. We performed maxillary sinus floor elevation using poly-L-lactic acid (PLLA) as a space-making material in patients with an insufficient bone mass (<3 mm) for simultaneous implantation between the alveolar crest and floor of the maxillary sinus and evaluated the newly formed bone. Conventional antrostomy of the maxillary sinus from the lateral wall was performed, and PLLA was placed on the floor of the maxillary sinus after elevating the sinus membrane. Six months after surgery, the bone mass and density were measured using quantitative computed tomography, and histological evaluation was performed. No complications were recorded. Radiological findings showed a bone-like radiopaque appearance, and histological examination revealed new bone formation in all patients. In cases with insufficient bone mass prior to simultaneous implant placement, this method of maxillary sinus augmentation allows for sufficient bone augmentation without bone grafting.

The effectiveness of optical coherence tomography for evaluating peri-implant tissue: A pilot study.

PURPOSE: Optical coherence tomography (OCT) has been investigated as a novel diagnostic imaging tool. The utilisation of this equipment has been evaluated through several studies in the field of dentistry. The aim of this preliminary study was to determine through basic experiments the effectiveness of OCT in implant dentistry. MATERIALS AND METHODS: To assess detection ability, we captured OCT images of implants in each of the following situations: (1) implants covered with mucosae of various thicknesses that were harvested from the mandibles of pigs; (2) implants installed in the mandibles of pigs; and (3) implants with abutments and crowns fixed with temporary cement. The OCT images were captured before cementation, after cementation, and after removing the excess submucosal cement. RESULTS: If the thickness of the mucosa covering the implant body was less than 1 mm, the images of the implants were clearly detected by OCT. In the implants were installed in pigs' mandibles, it was difficult to capture clear images of the implant and alveolar bone in most of the samples. Remnants of excess cement around the implants were visible in most samples that had a mucosa thickness of less than 3 mm. CONCLUSION: Currently, OCT imaging of implants is limited. Cement remnants at the submucosal area can be detected in some cases, which can be helpful in preventing peri-implant diseases. Still, though there are some restrictions to its application, OCT could have potential as an effective diagnostic instrument in the field of implant dentistry as well.