Effects of immediate loading directionality on the mechanical sensing protein PIEZO1 expression and early-stage healing process of peri-implant bone.

BACKGROUND: The reduced treatment time of dental implants with immediate loading protocol is an appealing solution for dentists and patients. However, there remains a significant risk of early peri-implant bone response following the placement of immediately loaded implants, and limited information is available regarding loading directions and the associated in vivo characteristics of peri-implant bone during the early stages. This study aimed to investigate the effects of immediate loading directionality on the expression of mechanical sensing protein PIEZO1 and the healing process of peri-implant bone in the early stage. METHODS: Thirty-two implants were inserted into the goat iliac crest models with 10 N static lateral immediate loading applied, followed by histological, histomorphological, immunohistochemical, X-ray microscopy and energy dispersive X-ray spectroscopy evaluations conducted after 10 days. RESULTS: From evaluations at the cellular, tissue, and organ levels, it was observed that the expression of mechanical sensing protein PIEZO1 in peri-implant bone was significantly higher in the compressive side compared to the tensile side. This finding coincided with trends observed in interfacial bone extracellular matrix (ECM) contact percentage, bone mass, and new bone formation. CONCLUSIONS: This study provides a novel insight into the immediate loading directionality as a potential influence factor for dental implant treatments by demonstrating differential effects on the mechanical sensing protein PIEZO1 expression and related early-stage healing processes of peri-implant bone. Immediate loading directions serve as potential therapeutic influence factors for peri-implant bone during its early healing stage.

Sonography in the diagnosis of peri-implant bone defects: An in vitro study on native human mandibles.

AIM: The aim of this study on native human cadavers was to compare clinical, sonographic, and radiological measurements of fenestrations, dehiscences, and 3-wall bone defects on implants. MATERIALS AND METHODS: The examination was carried out on five human mandibles. After the insertion of 27 implants, dehiscences (n = 14), fenestrations (n = 7) and 3-wall bone defects (n = 6) were prepared in a standardized manner. The direct measurement of the bone defects was carried out with a periodontal probe and the radiological examination was carried out using digital volume tomography (DVT). The ultrasound examination (US) was performed using a clinical 24-MHz US imaging probe. Means and standard deviations of the direct, US, and DVT measurements were calculated. Measurements were statistically compared using the Pearson correlation coefficient and Bland-Altman analysis. RESULTS: Bone defects were on average 3.22 ± 1.58 mm per direct measurement, 2.90 ± 1.47 mm using US, and 2.99 ± 1.52 mm per DVT assessment. Pairwise correlations of these measurements were R = .94 (p < .0001) between direct and US, R = .95 (p < .0001) between DVT and US, and R = .96 (p < .0001) between direct and DVT. The mean differences of the measurements (and 95% CI) between direct and US was 0.41 (-0.47 to 1.29), US and DVT 0.33 (-0.30 to 0.97), and direct and DVT 0.28 (-0.50 to 1.07). CONCLUSION: All peri-implant bone defects could be identified and sonographically measured. US measurements showed a strong correlation with direct and DVT measurements. The sonographic measurement accuracy was highest for dehiscences, followed by fenestrations and 3-wall bone defects.

Immediately versus early placed bone-level-tapered implants supporting all-ceramic crowns on titanium base abutments: 1-year radiographic and pink esthetic outcomes of a multicenter pilot RCT.

OBJECTIVES: Aim of this study was to assess survival rates, radiographic, and pink esthetic outcomes of a bone-level-tapered (BLT) implant following immediate or early implant placement. MATERIALS AND METHODS: Patients in need of tooth extraction and one implant in the anterior or premolar area were recruited in five centers. Patients were randomly assigned to the immediate or early placement protocol. Implants were restored with all-ceramic crowns cemented to titanium-base-abutments. Radiographic bone levels, implant stability quotient (ISQ), and pink esthetic outcomes were assessed. Data were analyzed descriptively. Level of significance was set at 0.05. Differences between groups were tested using Wilcoxon-signed-rank and Mann-Whitney-U test as nonparametric tests. RESULTS: A total of 60 patients received 60 BLT implants (Institut Straumann). At 12-months, 59 implants (98.3%) were osseointegrated. The mean distance from implant shoulder to first bone-to-implant contact was 0.15 ± 0.59 mm without significant differences between the groups. Median ISQ values increased from 75.5 to 78.5. A mean buccal recession of 0.1 ± 0.70 mm occurred with no difference between groups. The mean papilla height gain in both groups was 0.5 ± 1.47 mm mesially and 0.4 ± 1.36 mm distally. CONCLUSIONS: After 1 year, immediately and early placed BLT implants exhibit similar bone level changes, ISQ values, and pink esthetic outcomes. CLINICAL SIGNIFICANCE: The present research contributes to the knowledge on clinical outcomes of immediately and early placed BLT implants restored with buccally microveneered ceramic single crowns out of two different ceramic materials. The research shows that similar esthetic and radiographic outcomes can be reached by means of immediate implant placement compared to the conventional early placement protocol. The improvement of esthetic soft-tissue parameters over time was shown for both implant placement protocols.

Effect of different implant positions for two implant-retained mandibular overdenture: a retrospective 5-years radiographic evaluation of the circumferential peri-implant bone loss and posterior ridge resorptive changes.

BACKGROUND: Studies did not recommend which position for implant overdenture poses the lowest biomechanical risk and the least chance of peri-implant bone loss and ridge resorption for those who might need a mandibular two-implant overdenture. The study objectives were to investigate the impact of implant position, in lateral incisors or canine positions, on peri-implant bone loss and posterior ridge resorption. METHODS: Fifty patients with mandibular two-implants were recalled and divided according to the implant position into two groups (group L: implants in lateral incisor positions and group C: implants in canine positions). The circumferential peri-implant bone level and posterior ridge resorption were assessed at implant insertion (T0), one year later (T1), and five years later (T5) using the follow-up CBCT. Data were analyzed using the Statistical Package of Social Science (SPSS) program. A Mann-Whitney test was used to compare two different groups. Paired groups were compared using the Wilcoxon signed-rank test. The threshold of significance is fixed at a 5% level (p-value). RESULTS: Significant differences in the vertical bone loss between groups appeared at (T5 - T1) (Mann Whitney test, (P = 0.01)) and at (T5 - T0) (Mann Whitney test, (P = 0.005)), and a significant difference in horizontal bone loss between groups was found at (T1 - T0) (Mann Whitney test, (P = 0.041)) and (T5 - T1) (Mann Whitney test, (P = 0.041)). Also, there were significant differences over the evaluation period between groups at certain points along the ridge at M1 (Mann Whitney test, (P = 0.021)), M3 (Mann Whitney test, (P = 0.008)), and M4 (Mann Whitney test, (P = 0.015)). CONCLUSIONS: According to the findings of this clinical study, the placement of implants in the lateral incisor position for two implant-retained overdentures is a viable choice. In comparison to the canine position, the lateral incisor position demonstrated superior peri-implant responses, which could potentially enhance the longevity of the implants. Furthermore, the placement of implants in the lateral incisor position can promote a more even distribution of stress and help mitigate posterior ridge resorption. Conversely, implants in the canine position may cause a seesaw effect and result in greater posterior ridge resorption. CLINICAL TRIAL REGISTRY NUMBER: (NCT06055842) (13/03/2024).

Influence of crestal and sub-crestal implant position on development of peri-implant diseases: a 5-year retrospective analysis.

OBJECTIVES: The aim of the present study was to evaluate the influence of crestal and subcrestal implant position on development of peri-implant diseases. MATERIALS AND METHODS: The study was designed as a retrospective clinical and radiographic analysis. Implant-supported fixed dental prostheses were allocated in two groups: with the shoulder (i) placed in sub-crestal level and (ii) placed at bone level. For each patient, the following clinical variables were assessed: FMPS, FMBS, PlI, BOP, and PD. After prothesis delivery, an intraoral radiograph was obtained; this exam was performed also at 5 years of observation period. RESULTS: No statistically significant difference was found in terms of FMPS and FMBS at baseline and after 5 years follow-up (P < 0.05). A statistically significant difference was assessed between PD of control group and test group (P = 0.042). Patient-based analysis showed a 25.6% of peri-implant mucositis and 32.6% of peri-implantitis for implants placed with the shoulder in crestal position, while for implants inserted in sub-crestal position the percentage of peri-implant-mucositis and peri-implantitis were 19%; no statistically significant difference was found between groups after 5 years (P < 0.05). CONCLUSIONS: Within the limitation of the present study, the clinical and radiographic outcomes showed that the percentage of peri-implant mucositis and peri-implantitis was not statistically significant for both groups after 5 years follow-up. CLINICAL RELEVANCE: The outcomes of present study clinically demonstrated that a deep position of implant shoulder did not provide any benefits. On the contrary, it may be considered a possible risk indicator for implant diseases.

Radiographic peri-implant bone loss after a function time up to 15 years.

OBJECTIVE: The aim was to assess the degree of radiographic peri-implant bone loss over a follow-up period up to 15 years. In addition, another aim was to identify risk indicators for peri-implant bone loss and for moderate-severe peri-implantitis at patient- and implant level. MATERIALS AND METHODS: This is a cross-sectional clinical and radiological study of 147 patients with a total of 425 implants in combination with data collected retrospectively for baseline variables. To calculate the peri-implant bone loss (primary outcome variable), the radiographic bone level measurements from baseline were compared to the radiographic bone level measurements at the final radiographic measurement. Multilevel analyses were adopted with peri-implant bone loss and peri-implantitis as outcome variables. RESULTS: The mean follow-up time was 12.5 years (range 10-15) and the mean age of the patients was 63 years (range 29-83). The mean peri-implant bone loss was 0.94 mm (S.D. 1.3). The prevalence of moderate-severe peri-implantitis at patient level was 17% and 8.9% at implant level. The peri-implant bone loss was significantly more pronounced in healthy implants if moderate-severe peri-implantitis was present in at least one implant within the same patient. The presence of moderate-severe peri-implantitis was significantly associated with general periodontitis Stages III or IV at follow-up and smoking. CONCLUSION: The presence of moderate-severe peri-implantitis at patient level was found to be a risk indicator of peri-implant bone loss in healthy implants, while smoking and general periodontitis Stages III and IV were risk indicators of moderate-severe peri-implantitis.

Peri-implant radiographic bone level and associated factors in Spain.

OBJECTIVES: To evaluate radiographic bone level (RxBL) at dental implants and its associated factors in Spain. MATERIAL AND METHODS: This cross-sectional study was performed by a network of sentinel dentists from regions of Spain. RxBL was defined as the distance from the implant shoulder to the first clearly visible contact between the implant surface and the bone. Radiographic measurements were performed by two trained and experienced periodontists. Implant and patient data were also collected. Descriptive, bivariate, discriminative and multivariate analyses were done. RESULTS: A total of 49 sentinel dentists provided data 275 patients. Mean RxBL from 474 implants (5-13 years) was 1.87 mm (range: 0.00-13.17 mm). Statistically significant associations between RxBL and clinical output variables (bleeding on probing, oedema, plaque, probing depth, suppuration, keratinized tissue) were found. In the multiple regression analysis, statistically significant associations for RxBL were found for smoking habit, implant diameter, years of follow-up and type of prosthesis (p < 0.01). CONCLUSIONS: Peri-implant RxBL ranged from 0 to 13.17 mm. It was significantly associated with clinical output variables and with some potentially predictor variables, at patient- (smoking >10 cigarettes/day) and implant- (diameter, years of follow-up, Toronto bridge) levels.

What is the influence of implant surface characteristics and/or implant material on the incidence and progression of peri-implantitis? A systematic literature review.

OBJECTIVES: To answer the focused question, 'In animals or patients with dental implants, does implant surface characteristics and/or implant material have an effect on incidence and progression of peri-implantitis?' MATERIAL AND METHODS: Pre-clinical in vivo experiments on experimental peri-implantitis and clinical trials with any aim and design, and ≥5 years follow-up, where the effect of ≥2 different type of implant material and/or surface characteristics on peri-implantitis incidence or severity, and/or progression, implant survival or losses due to peri-implantitis, and/or marginal bone levels/loss was assessed. RESULTS: Meta-analyses based on data of pre-clinical experiments, using the ligature induced peri-implantitis model in the dog, indicated that after the spontaneous progression phase implants with a modified surface showed significantly greater radiographic bone loss (effect size 0.44 mm; 95%CI 0.10-0.79; p = .012; 8 publications) and area of infiltrated connective tissue (effect size 0.75 mm2 ; 95%CI 0.15-1.34; p = .014; 5 publications) compared to non-modified surfaces. However, in 9 out of the 18 included experiments, reported in 25 publications, no significant differences were shown among the different implant surface types assessed. Clinical and/or radiographic data from 7605 patients with 26,188 implants, reported in 31 publications (20 RCTs, 3 CTs, 4 prospective cohort, and 4 retrospective studies; 12 with follow-up ≥10 years), overall did not show significant differences in the incidence of peri-implantitis, when this was reported or could be inferred, among the various implant surfaces. In general, high survival rates (90-100%) up to 30 years and no clinically relevant differences in marginal bone loss/levels, merely compatible with crestal remodelling, were presented for the various implant types. CONCLUSION: Pre-clinical in vivo experiments indicate that surface characteristics of modified implants may have a significant negative impact on peri-implantitis progression, while clinical studies do not support the notion that there is a difference in peri-implantitis incidence among the various types of implant surfaces. No assumptions can be made regarding the possible impact of implant material on incidence and/or peri-implantitis progression due to limited information.

Early Bone Healing on Hydroxyapatite-Coated and Chemically-Modified Hydrophilic Implant Surfaces in an Ovine Model.

Implant topography affects early peri-implant bone healing by changing the osteoconduction rate in the surrounding biological environment. Implant surfaces have been designed to promote faster and stronger bone formation for rapid and stable prosthesis loading. Early peri-implant bone healing has been observed with a sandblasted, acid-etched implant that was chemically modified to be hydrophilic (cmSLA). The present study investigates whether early peri-implant bone healing extends to a rough surface implant with a high crystalline hydroxyapatite surface (TSV MP-1 HA). Three implants were randomly placed in porous trabecular bone within both medial femoral condyles of 10 sheep. Early peri-implant bone stability was measured at 3- and 6-weeks healing time following implant insertion. Results indicated a similar implant stability quotient between the implants at insertion and over time. The significant increase over time of reverse torque values with respect to insertion torque (p < 0.001) did not differ between the implants. However, the bone-to-implant contact of TSV MP-1 HA was significantly higher than that of cmSLA implants at 6 weeks (p < 0.01). These data validate previous findings of a hydrophilic implant surface and extend the observation of early osseointegration to a rough surface implant in porous trabecular bone.

Comparison of Corrosion Products From Implant and Various Gold-Based Abutment Couplings: The Effect of Gold Plating.

This study compared titanium (Ti), palladium (Pd), platinum (Pt), and gold (Au) ion release following induced accelerated tribocorrosion from three Au alloy abutment groups coupled with Ti implants over time; investigated contacting surface structural changes; and explored the effect of Au plating. Three abutment groups, G (n = 8, GoldAdapt, Nobel Biocare), N (n = 8, cast UCLA, Biomet3i), and P (n = 8, cast UCLA, Biomet3i, Au plated), coupled with implants (Nobel Biocare), immersed in 1% lactic acid, were cyclically loaded. Ions released (ppb) at T1, T2, and T3, simulating 3, 5, and 12 months of function, respectively, were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and compared. Surface degradation and fretted particle composition after T3 were evaluated with scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). ICP-MS data were nonparametric, expressed as medians and interquartile ranges. SEM/EDX showed pitting, crevice corrosion, and fretted particles on the components. Released ion concentrations in all groups across time significantly decreased for Pd (P < .001, median range: 1.70-0.09), Pt (P = .021, 0.55-0.00), and Au (P < .001, 1.01-0.00) and increased for Ti (P = .018, 2.49-5.84). Total Ti release was greater than other ions combined for G (P = .012, 9.86-2.30) and N (P < .001, 13.59-5.70) but not for P (P = .141, 8.21-3.53). Total Ti release did not differ between groups (P = .36) but was less variable across group P. On average, total ion release was 13.77 ppb (interquartile range 8.91-26.03 ppb) across the 12-month simulation. Tribocorrosion of Ti implants coupled with Au abutments in a simulated environment was evidenced by fretted particles, pitting, and crevice corrosion of the coupling surfaces and release of ions. More Ti was released compared with Pd, Pt, and Au and continued to increase with time. Abutment composition influenced ion release. Au-plated abutments appeared to subdue variation in and minimize high-concentration spikes of titanium.

Influence of abutment disconnection on peri-implant marginal bone loss: A randomized clinical trial.

OBJECTIVES: To evaluate the influence of abutment disconnections and reconnections on peri-implant marginal bone loss. MATERIAL AND METHODS: Twenty-four participants received single-unit implants and were randomly assigned into one of the two groups: the definitive abutment group (DEF), in which the definitive abutments were connected at the same time as the implant was inserted; and as a control, the healing abutment group (HEA), in which the healing abutments were disconnected and reconnected three times, at 8, 10, and 12 weeks after surgery. Peri-implant marginal bone level was measured through radiographic follow-up performed immediately after the surgery (baseline), at 8 weeks and after 6, 12, and 24 months. Implant stability and peri-implant health were assessed by resonance frequency analysis and peri-implant probing, respectively. RESULTS: At the end of 2 years, the mean bone level was -0.18 ± 0.12 mm for the DEF group and -0.13 ± 0.13 mm for the HEA group, resulting in a cumulative bone loss of -0.61 ± 0.10 mm and -0.81 ± 0.15 mm, respectively, with no statistical difference between groups. Bone level changes showed statistically significant differences only between 0 and 2 months (DEF: -0.70 ± 0.12 mm; HEA: -0.36 ± 0.10 mm) and between 2 and 6 months (DEF: -0.11 ± 0.11 mm; HEA: -0.65 ± 0.14 mm). No differences were observed between the groups for implant stability, probing depth, and bleeding on probing. CONCLUSION: Immediate connection of the prosthetic abutments did not reduce bone loss in comparison with three disconnections of the healing abutments.

Peri-implant bone alterations under the influence of abutment screw preload stress. A preclinical vivo study.

OBJECTIVES: The study purpose was to examine peri-implant bone alternations around osseointegrated implants caused solely by abutment screw preload stress using different tightening torque values. MATERIALS AND METHODS: Twenty 20- to 22-week-old Japanese white rabbits received two implants each in right and left femurs. Implants were randomly assigned to one of three tightening torque groups or the control (Cont) group. After 8 weeks, 35 Ncm torque was delivered to abutment screws in the recommended torque (RT) group (n = 16). Other screws received 70 Ncm torque as the high torque (HT) group (n = 16). Temporary tightening (TT) groups (n = 8) received only 70 Ncm torque without preload stress as screws were untightened immediately. Cont group (n = 40) remained in situ. Animals were euthanized at 4, 6, 8, and 10 weeks after torque application. Micro-CT images were then taken, and undecalcified ground sections were stained with toluidine blue. RESULTS: Cross-sections of cortical bone showed remodeling activities adjacent to the implant in all groups. While bone marrow spaces appearance was relatively small in Cont and TT groups, RT and HT groups showed large bone marrow spaces and extensive remodeling activity. Bone-to-implant contact was significantly less in RT and HT groups compared with Cont and TT groups at different time points (p Ë‚ .05). Furthermore, RT and HT groups showed significantly less bone volume and area (p Ë‚ .05). CONCLUSION: Results suggested that preload stress without any occlusal loading might negatively affect peri-implant bone stability and initiate bone remodeling. This could alter bone mechanical properties, subsequently influencing long-term implant success.

Clinical and radiographic assessment of circular versus triangular cross-section neck Implants in the posterior maxilla: A 1-year randomized controlled trial.

OBJECTIVES: Implants with a triangular neck were recently introduced to limit peri-implant bone loss. The primary objective of this randomized controlled trial was to compare peri-implant bone changes of circular versus triangular cross-section neck implants 1 year after loading. The secondary objectives were to assess buccal hard tissue thickness changes, Pink Esthetic Score (PES), and patient satisfaction. MATERIAL AND METHODS: Thirty four patients requiring replacement of the single, intercalated missing tooth of healed site for at least 4 months in the posterior maxilla were randomized into 2 groups according to the type of implant. Immediately after surgery and 1 year after final restoration, a cone beam CT (CBCT) was performed to assess proximal bone remodeling and buccal bone thickness. Peri-implant soft tissue health, PES, and patient-reported outcome measures (PROMs) were recorded. RESULTS: No implant loss occurred within the follow-up period. The mean ± SD peri-implant proximal bone loss 1 year after loading was 0.22 ± 0.30 mm for triangular and 0.42 ± 0.67 mm for circular implants necks (p = .25). Peri-implant bone loss exceeding 2 mm was observed in a single implant in the circular neck group. Buccal bone thickness remained stable and did not differ different between the 2 groups. The peri-implant soft tissue health, PES, and patient satisfaction were also comparable. CONCLUSIONS: Within the limitations of the present study, patient clinical and radiographic outcomes did not differ between triangular and circular cross-section neck implants in the posterior maxilla.

A cohort study on short mini-implants for mandibular overdentures compared to those of standard length.

OBJECTIVES: To assess peri-implant bone level, survival and success rates of short (6 or 8 mm long) one-piece mini-implants (MDIs) in edentulous patients with extremely resorbed alveolar ridge (interforaminal height <10 mm) rehabilitated with mandibular implant overdentures and to compare them with patients having standard length MDIs in 1-year prospective clinical study. MATERIAL AND METHODS: The Short MDI group consisted of 28 participants with interforaminal height ≤10 mm. Implants being, both, short and slim (short MDIs: 6 or 8 mm long, 2 or 2.5 mm wide) were inserted. The Standard-MDI group included 35 participants (interforaminal height >13 mm) who received standard length MDIs (10-14 mm long, 2 or 2.5 mm wide). Primary outcomes were assessments of MDI peri-implant bone level, survival and success rates; secondary outcomes were assessments of peri-implant tissue, oral hygiene, and prosthodontic maintenance. RESULTS: The Short MDI group had mean marginal bone loss (MBL) of 0.26 ± 0.35 mm, 6.4% of failure, and 92.6% of, both, success and survival rates. The Standard-MDI group had mean MBL of 0.34 ± 0.40 mm, 5% of failure, 95% of survival, and 94.3% success. There were no significant differences in MBL (p = .420), survival (p = .414), and success (p = .571) between the groups. The Short MDI group had significantly less plaque (p = .001) and bleeding on probing (p < .001). CONCLUSION: Within the limitations of this study, short MDIs (6 or 8 mm long) in extremely atrophied mandibles (interforaminal height <10 mm) showed good clinical results in the first year of function.

Non-surgical therapeutic outcomes of peri-implantitis: 12-month results.

OBJECTIVES: To assess the clinical and radiographic outcomes of implants treated by means of non-surgical debridement with systemic antibiotic therapy. MATERIALS AND METHODS: A prospective case series study evaluating the 12-month clinical and radiographic outcomes of peri-implantitis lesions treated with ultrasonic scaler debridement, a glycine air abrasive, and metronidazole followed by supportive maintenance. Clinical and radiographic variables and success criteria were defined a priori. RESULTS: Overall, 21 patients were included. One implant failed during the study period (implant survival rate 95.24%). Substantial changes occurred at 12 months in all the clinical and radiographic variables, reaching strong statistical significance in the majority of them. According to the success criteria applied, 40.90% of the peri-implantitis were arrested and resolved, while 59.1% presented with at least one probed site with bleeding on probing (BoP). Moreover, 95.45% exhibited peri-implant pocket depth (PPD) < 5 mm at the end of the study. None of the implants presented with progressive bone loss. CONCLUSION: Non-surgical therapy of peri-implantitis is effective to arrest progressive bone loss, reduce PPD and suppuration, and achieve radiographic bone fill in the majority of cases. Nevertheless, it failed to be completely efficacious in the achievement of successful therapeutic outcomes as BoP remained frequently present. CLINICAL RELEVANCE: Non-surgical therapy achieved significant clinical and radiological improvements.

Influence of crown-implant ratio on implant success rate of ultra-short dental implants: results of a 8- to 10-year retrospective study.

OBJECTIVES: The use of short implants has been suggested in recent years as an option for facilitating prosthetic restoration in resorbed jawbones. The aim of the present study was to determine how implant success rate is affected in the long term when ultra-short implants are rehabilitated with fixed restorations, resulting in a crown to implant (C/I) ratio of more than 3:1. MATERIALS AND METHODS: The study was conducted as an analysis on all patients operated from December 2005 to November 2007 with ultra-short dental implants. All implants were sintered porous-surfaced (SPS) with a length of 5 mm and a diameter of 5 mm (5 × 5 mm) and were restored with a single crown or a fixed dental prosthesis (FDP). Data collected included implant positioning site, crestal bone levels (CBL), and clinical and anatomical C/I ratios, and pre-established success criteria were used to evaluate the success rate of the implants. Statistical analysis was used to determine any significant differences or correlations (p = 0.05). RESULTS: Forty-one patients completed the follow-up and were eligible for this retrospective study on a total of 50 ultra-short SPS implants. The mean follow-up was 9.5 years (range 8.3 to 10.2 years). Three of the 50 implants failed because they were lost due to peri-implantitis, while all the other 47 met the pre-established success criteria giving an overall implant success rate of 94%. During the follow-up period, the mean peri-implant bone loss (PBL) was 0.41 + 0.36 mm. CONCLUSIONS: This study shows that ultra-short SPS implants can prove a reliable solution for prosthetic restoration in patients with severe alveolar bone atrophy. In selected patients with a sufficient bone width, ultra-short implants with a resulting C/I ratio of more than 3:1 presented no contraindications. CLINICAL RELEVANCE: In selected cases, ultra-short implants may represent an alternative to bone augmentation procedures and a long-term predictable solution.

Research on implants and osseointegration.

Osseointegration was originally defined as a direct structural and functional connection between ordered living bone and the surface of a load-carrying implant. It is now said that an implant is regarded as osseointegrated when there is no progressive relative movement between the implant and the bone with which it is in direct contact. Although the term osseointegration was initially used with reference to titanium metallic implants, the concept is currently applied to all biomaterials that have the ability to osseointegrate. Biomaterials are closely related to the mechanism of osseointegration; these materials are designed to be implanted or incorporated into the living system with the aims to substitute for, or regenerate, tissues and tissue functions. Objective evaluation of the properties of the different biomaterials and of the factors that influence bone repair in general, and at the bone tissue-implant interface, is essential to the clinical success of an implant. The Biomaterials Laboratory of the Oral Pathology Department of the School of Dentistry at the University of Buenos Aires is devoted to the study and research of the properties and biological effects of biomaterials for dental implants and bone substitutes. This paper summarizes the research work resulting from over 25 years' experience in this field. It includes studies conducted at our laboratory on the local and systemic factors affecting the peri-implant bone healing process, using experimental models developed by our research team. The results of our research on corrosion, focusing on dental implants, as well as our experience in the evaluation of failed dental implants and bone biopsies obtained following maxillary sinus floor augmentation with bone substitutes, are also reported. Research on biomaterials and their interaction with the biological system is a continuing challenge in biomedicine, which aims to achieve optimal biocompatibility and thus contribute to patient health.

Macrophage polarization in aseptic bone resorption around dental implants induced by Ti particles in a murine model.

BACKGROUND AND OBJECTIVES: Titanium particles/ions detected in peri-implant tissues have been considered as a potential etiologic factor for crestal bone loss around oral implants. However, the definite impact of titanium wear particles on the health of surrounding structures remains undetermined. The purpose of this study was to investigate the effects of titanium particles-induced foreign body reaction on peri-implant bone level and the related mechanism by using clodronate liposomes to deplete macrophages. MATERIAL AND METHODS: Sprague Dawley rats with custom-made titanium screw implanted in bilateral maxillary first molar area for 4 weeks to obtain osseointegration were randomly divided into four groups. Twenty microgram titanium particles were introduced into the peri-implant tissue to induce aseptic foreign body reaction, and macrophages were depleted by the local injection of 100 µL clodronate liposome immediately and re-injection every 3 days until the sacrifice of the rats (Ti + LipClod group). Titanium-injected rats also treated with phosphate buffer solution (Ti + PBS) or empty liposome (Ti + Lip) as well as rats injected with PBS alone (Control) were included as controls. Eight weeks later, animals were sacrificed and samples containing implants were collected. Half of the samples were analyzed radiologically to measure bone level change, and macrophage markers (CD68, CCR7, CD163) was also characterized by immunofluorescence to evaluate macrophage number, density, and phenotype distribution (CCR7+M1/CD163+M2). The rest of the samples were used to determine the relative mRNA expression levels of TNF-α, IL-1ß, IL-6, and RANKL with real-time PCR analysis. RESULTS: No obvious bacterial contamination was found in all titanium-injected areas, and the implant survival rate was 100% with no implant loss. Compared with Ti + PBS and Ti + Lip group, macrophage density (1.64 ± 0.86%) infiltrated into peri-implant tissue and bone loss (0.17 ± 0.03 mm) around implant decreased significantly in the Ti + LipClod group. Immunofluorescence analysis showed that more macrophage infiltrated into peri-implant tissue in the Ti + PBS and Ti + Lip groups, predominantly with M1 phenotype. In contrast, the macrophage density was lower and M2 phenotype was dominant in the Control group, while macrophages density was significantly reduced and the M1 type macrophages were slightly more than M2 type in the Ti + LipClod group. Accordingly, TNF-α, IL-1ß, IL6, and RANKL mRNA expression increased significantly in the Ti + PBS and Ti + Lip groups compared with Control and Ti + LipClod groups. CONCLUSIONS: Titanium particles had a negative effect on peri-implant tissue by activating macrophages which induced an M1 macrophage phenotype promoting local secretion of inflammatory cytokines. It was found that clodronate liposome treatment attenuated the severity of inflammation and bone loss by depletion of macrophages. Therefore, the present study revealed the marked impact of macrophage polarization with respect to peri-implant bone loss caused by titanium particles.

A 10-year retrospective comparative human study on screw-retained versus cemented dental implant abutments.

The aim of this 10-year retrospective study was to evaluate the long-term reliability, survival rate and mechanical and biological complications of single-crown implant rehabilitations with two different types of fixture-abutment connections: screw-retained abutments (SRAs) with internal hexagonal connection, and cemented retained abutments (CRAs). A total of 300 single implant-supported crowns were analysed, which had been inserted between 2004 and 2007. Patients were classified according to two groups: the SRA group (n = 150) and the CRA group (n = 150). The primary outcome was marginal bone loss (MBL) on peri-apical radiographs. Bleeding on probing (BOP) and probing depth (PD) were also evaluated. Moreover, prosthetic complications were recorded. Analysis of variance (ANOVA) was used to evaluate the differences between the groups. The overall implant failure rate was 4.2%. The overall positive BOP index was 81.9% of the sites under investigation, as 83.4% for SRA and 80.4% for CRA. Moreover, >5 mm PD demonstrated a rate of 21.0% for CRA, and 13.8% for SRA. The primary outcome of mean MBL was 2.09±1.07 mm for SRA and 1.54±1.20 mm for CRA. Analysis of variance of MBL showed statistical significance for the difference between these two groups (P less than 0.001). For the mechanical aspects, an overall 12.5% of complications occurred. No implant or abutment fractures were recorded. Although complications occurred, the results from this 10-year retrospective study show that these two methods have positive long-term follow-up. With MBL significantly greater for the SRA group than the CRA group, the clinical use of CRA is encouraged in terms of the lower bone resorption rate.

Osseointegration of titanium dental implant under fluoride exposure in rabbits: Micro-CT and histomorphometry study.

OBJECTIVE: This study aims to investigate the influence of fluoride exposure on implant osseointegration. METHODS: A total of 24 male New Zealand white rabbits were randomly divided into the control group and the fluoride exposure group. Rabbits in the control group were fed with tap water, while those in the fluoride exposure group were given 200 mg/L sodium fluoride solution. After 2-month feeding, implants were inserted into the extraction socket immediately after extraction of rabbit mandibular anterior teeth. Four rabbits in each group were sacrificed to collect the implants samples at 1, 2, and 3 months post-implantation, respectively. Radiographic and histomorphometry examinations were performed to evaluate the condition of implant osseointegration. RESULTS: Bone volume around the implants increased in a time-dependent manner in both groups. Micro-CT images illustrated that the bone mineral density (BMD) in the fluoride exposure group was significantly lower than that in the control group after implantation for 2 and 3 months. The bone-implant contact ratio (BIC) in the fluoride exposure group was much lower than that of the control group at 3 months post-implantation according to histomorphometry examination. CONCLUSIONS: In rabbit animal model, high fluoride exposure affected the quality of bone surrounding the implant and significantly reduced bone integration of the implant, especially in the late stage of osseointegration.