One Piece CAD/CAM Abutment for Screw-Retained Single-Tooth Restorations: A 5-Year Prospective Cohort Study.

BACKGROUND: The use of ceramic-coated patient-specific CAD/CAM titanium abutments represents a therapeutic option for the rehabilitation of single tooth. The utilization of highly customized abutments enables the accurate three-dimensional positioning of the prosthetic emergence. This study evaluates the clinical performance of implant-prosthetic rehabilitations carried out using ceramic-coated CAD/CAM titanium abutments. MATERIALS AND METHODS: Thirty implants were placed in thirty patients and rehabilitated with thirty single crowns attached to CAD/CAM titanium abutments. A conventional procedure was applied, with implant placement after post-extraction socket healing and prosthetic restoration after implant healing. Implants of lengths ranging from 6-15 mm and widths of 3.6, 4.2, and 4.8 mm were used in this study. At the time of prosthesis delivery (T0), after two years (T1), and after five years (T2), plaque (PI) and bleeding (BoP) indices, probing depths (PPD), marginal bone levels (MBL), and PES/WES were evaluated for each implant. RESULTS: No patient dropped out of the study during the follow-up period. All thirty implants were clinically successful at five years post-prosthesis delivery (survival rate: 100%) and showed no signs of peri-implant infection. Peri-implant soft tissues were in good health (BoP at T2: 0% in 73% of patients; 25% in 13% of patients; 50% in 10% of patients; and 75% in 3% of patients). The mean PPD was 2.05±0.56 mm at T0, 1.992±0.6 mm at T1, and 1.867±0.439 mm at T2. The mean MBL at T0 was 0.413±0.440 mm, at T1 was 0.306±0.388 mm, and at T2 was 0.263±0.368 mm. The mean PES, WES, and PES/WES indices, 7.43±1.04, 7.57±0.82, and 15.00±1.17, respectively, indicate good integration of soft tissues, satisfactory aesthetics, and an overall positive outcome. CONCLUSIONS: The success rates, maintenance of marginal bone levels, and periodontal and aesthetic indices suggest the validity of implant-prosthetic rehabilitations with CAD/CAM abutments in cases of single crowns.

Clinical outcomes of implant- versus abutment-level connection in screw-retained fixed dental prostheses: A 5-year randomized controlled trial.

AIM: The aim of the study was to evaluate the 5 years clinical outcomes associated with implant-level connection (IL) versus abutment-level connection (AL) for implants with an internal conical connection (ICC) supporting a screw-retained fixed partial denture. MATERIALS AND METHODS: Fifty patients with 119 implants were randomly allocated to either the AL or IL group. Radiographic (Marginal bone loss) and clinical outcomes (Bleeding on Probing, probing pocket depth, plaque accumulation, incidence of peri-implantitis and peri-implant mucositis as well as prosthetic complications) were collected and compared at 1, 2, 3, and 5 years. A linear mixed model was used to evaluate the differences between groups. RESULTS: Five years after treatment, the MBL change was not significantly different between the groups at any point. The MBL was 0.23 ± 0.64 mm (AL) and 0.23 ± 0.29 mm (IL). The bleeding on Probing was 44% (AL) and 45% (IL) (p = .89). The mean probing depth was 2.91 ± 1.01 mm (AL) and 3.51 ± 0.67 mm (IL). This difference between the groups was statistically significant but clinical insignificant. Presence of plaque was slightly higher (p = .06) in the IL group (34.4%) compared with the AL group (26.3%). The overall technical, biological, and prosthetic complication rates were similar between groups. None of the implants developed peri-implantitis during the entire follow-up period. CONCLUSION: The results of this clinical trial indicated that all clinical and radiographical parameters were clinically comparable between the study groups.

Fully digital workflow for implant-supported fixed restorations consisting of a titanium primary structure and a zirconia secondary structure.

PURPOSE: To describe a fully digital workflow for an implant-supported fixed hybrid restoration that involves a double CAD/CAM structure and to highlight the benefits of this type of restoration. MATERIALS AND METHODS: Using a fully digital workflow, starting from intraoral scans, the necessary steps for producing the final hybrid prosthesis are described. The prosthesis consists of a titanium primary structure and a zirconia secondary structure that is cemented onto the primary structure in the laboratory. A clinical case is presented to illustrate the steps required for prosthetic rehabilitation. RESULTS: This technique enables the fabrication of clinically valid and passive prostheses using a fully digital workflow. CONCLUSION: In just three clinical sessions, a fully digital workflow makes it possible to produce robust implant-supported fixed hybrid prostheses, comprising a titanium primary structure and an outer secondary structure made of zirconia. This procedure can be applied to a wide range of cases from simple to extended, including full-arch restorations.

Effect of Drilling Preparation on Immediately Loaded Implants: An In Vivo Study in Sheep.

PURPOSE: To determine the biologic and biomechanical effects of two implant drilling protocols on the cortical bone around implants subjected to immediate loading. MATERIALS AND METHODS: A total of 48 implants were inserted into the mandibles of six sheep following one of two drilling protocols: undersized preparation (US; n = 24) and nonundersized preparation (NUS; n = 24). Immediately after implant insertion, an abutment was placed on each implant and 36 implants were subjected to 10 sessions of dynamic vertical loads (1,500 cycles, 1 Hz) of 25 N or 50 N. Insertion torque value (ITV) was recorded at implant installation. Resonance frequency analysis (RFA) was measured at implant insertion and at each loading session. Fluorochrome was administered at day 17, and the animals were euthanized after 5 weeks. The removal torque values (RTVs) were measured, and samples underwent histomorphometric, µCT (microcomputed tomography), and fluorescence image acquisition analyses. The bone volume density (BV/TV), bone-to-implant contact (BIC), bone area fraction occupancy (BAFO), and fluorochrome stained bone surface (MS) were calculated. A linear mixed model analysis was performed, and Pearson paired correlation was calculated. RESULTS: Five implants from the NUS group failed, with a mean ITV of 8.8 Ncm and an RFA value of 57. The mean ITVs for US group and NUS group were 80.5 (± 14) Ncm and 45.9 (± 25) Ncm, respectively (P < .001). No differences were noted in the RFA values from the time of implant insertion until the end of the study. No differences in RTV, BV/TV, BAFO, or MS were observed between the groups. Intense new bone formation took place in the NUS group implants that were subjected to load. CONCLUSIONS: Undersized preparation of cortical bone ensured a greater BIC compared to a nonundersized preparation. Moreover, this study demonstrated that immediate loading did not interfere with the osseointegration process, but loading induced intense new bone formation in the NUS group. It is not recommended to immediately load the implants when the clinically perceived primary stability is lower than an ITV of 10 Ncm and an RFA value of 60. Int J Oral Maxillofac Implants 2023;38:607-618. doi: 10.11607/jomi.9949.

A Prospective Clinical Assessment of BioHorizons Tissue-Level Implants.

This investigation was designed to evaluate crestal bone stability and soft tissue maintenance to Laser-Lok tapered tissue-level implants. Twelve patients presenting with an edentulous site adequate for the placement of two implants were recruited from four dental offices (2 to 4 patients per office). Each patient received two Laser-Lok tissue-level implants placed with a 3-mm interimplant distance according to a surgical stent. The implants were placed so that the Laser-Lok zone sat at the junction between hard and soft tissues. A total of 24 implants were placed, and all achieved satisfactory crestal bone stability and soft tissue maintenance 1 year after receiving the final prosthetic restoration.

Impact of salivary contamination during implant placement with different surface characteristics in native and augmented bone: An in vivo study in sheep calvaria model.

OBJECTIVES: The aim of this study was to evaluate whether salivary contamination during placement of implants with different surface characteristics affects osseointegration in native and in augmented bone areas. MATERIALS AND METHODS: Forty eight implants with machined surface (MS) and 48 implants with moderately rough surface (RS) were tested in the calvaria of 12 sheep. At the first surgery, 64 bony critical defects were randomly created and were subsequently augmented with two materials (autogenous or bovine bone). After 5 weeks of graft healing, 8 implants were placed per sheep, in native bone and in the centre of the augmented defects. Forty eight implants were soaked with saliva before placement (contaminated group [CG]), while 48 implants were not (non-contaminated group [NCG]). Five weeks after implant placement, bone-to-implant contact (BIC) and bone material area fraction occupancy (BMAFO) were calculated histomorphometrically. RESULTS: Saliva contamination showed a significant negative effect (p = .000) on BIC, especially in augmented areas. RS showed significant positive effect on BIC, compared to MS (p = .000), while there were no significant differences for different bone conditions (p = .103). For BMAFO, the contamination showed a significantly negative affect (p = .000), while there were no significant differences for surface characteristics (p = .322) and for bone condition (p = .538). CONCLUSION: Saliva contamination during dental implant placement has a negative effect on osseointegration in augmented areas. Moderately rough surface has a possible advantage in the aspect of initial bone to implant contact. However, it seems to be advisable to avoid saliva contamination especially for implants placed in augmented bone areas.

Use of 6-mm Short Implants in Japanese Patients: Clinical, Radiologic, and Patient Satisfaction Results in a Retrospective Study with a 2-Year Follow-up.

Implant therapy for tooth loss in the molar area is challenging due to the anatomical limitations, requiring bone augmentation procedures that are associated with high surgical complexity and long postsurgical recovery. Recently, many studies have demonstrated the usefulness of short implants. However, few studies have been performed in Japanese patients to evaluate peri-implant bone changes, changes in peri-implant epithelial tissue, and patient satisfaction. The present study included 16 patients (5 men, 11 women; mean age: 60 years) who received 26 short (6-mm) implants. Changes in peri-implant bone and epithelial tissue were measured radiographically at superstructure loading and after 2 years. Peri-implant pocket probing depth was measured at the epithelial tissue and compared at both time points. Patient satisfaction was graded using the Oral Health Impact Profile (OHIP-14) before treatment and at follow-up. The mean mesial and distal bone levels were -0.05 mm and 0.37 mm at loading, respectively, and were 0.33 mm and 0.53 mm after 2 years, respectively. Significant peri-implant bone formation for mesial and distal bone levels at both time points were determined by Wilcoxon signed-rank test. Mean probing depth increased slightly, from 3.03 mm at loading to 3.33 mm after 2 years, but no significant difference was found. The OHIP-14 found that patient satisfaction levels increased after 2 years. Using 6-mm short implants in sites with insufficient bone levels can be a highly beneficial treatment option for patients, as it avoids the need for bone augmentation. However, more long-term and detailed studies on the clinical outcomes for these implants are required.

The use of implant-level connection in screw-retained fixed partial dentures: A 3-year randomised clinical trial.

OBJECTIVES: This randomised controlled trial compares the 3-year outcomes, that is, marginal bone-level (MBL) changes and clinical parameters, between an abutment-level (AL) and implant-level (IL) connection for implants with an internal conical connection (ICC) supporting a screw-retained fixed partial denture. MATERIAL AND METHODS: Fifty patients with 119 implants were randomly allocated to either the AL or IL group. Radiographic and clinical examinations were performed after one, two, and 3 years. A linear mixed model was used to evaluate the differences between groups. RESULTS: The MBL change was not significantly different between the groups at any point. The MBL was 0.12 ± 0.31 mm (AL) and 0.23 ± 0.26 mm (IL) after 1 year; 0.15 ± 0.34 mm (AL) and 0.17 ± 0.22 mm (IL) after 2 years; 0.18 ± 0.39 mm (AL) and 0.15 ± 0.21 mm (IL) after 3 years. The bleeding on probing was 43.44 ± 39.24% (AL) and 58.19 ± 41.20% (IL) after 1 year; 35.78 ± 39.22% (AL) and 50.43 ± 41.49% (IL) after 2 years; 51.27 ± 44.63% (AL) and 49.57 ± 37.31% (IL) after 3 years and was significantly different (p = .025) between 1 and 2 years. The probing depth showed a significant difference at each time point while the plaque was not significant between the groups. The overall technical, biological and prosthetic complication rates were 5.04%, 3.36%, and 16.00%, respectively. CONCLUSIONS: The MBL change was similar in the groups. The slight differences in the soft tissue complications between the groups are likely not of clinical relevance. An IL connection is considered to be a valid alternative to an AL set-up in ICC implants.

Impact of a Hydrophilic Dental Implant Surface on Osseointegration: Biomechanical Results in Rabbit.

This study aimed to evaluate the effect of surface hydrophilicity on the biomechanical aspects of osseointegration of dental implants in the tibia and femur of rabbits. Forty-eight mature female New Zealand White rabbits were included, and 96 commercially pure, Grade 4, titanium dental implants (control group), and 96 implants of same macro geometry with the hydrophilic surface (test group) were used in this study. One osteotomy was performed in each tibia and femur on both sides of the rabbit, and four implants were placed in each rabbit. Control and test groups were randomly allocated on the left and right sides. During surgery, insertion torque (ITQ) value of the complete implant placement was recorded. After healing periods of 0, 2, 4, and 8 weeks after surgery, implant stability quotient (ISQ) value, and removal torque (RTQ) values were measured. No statistical difference was observed for ITQ, for ISQ and for RTQ between the control group and test group in tibia/femur for all time periods. The effect of hydrophilic properties on moderately roughened surfaces has no impact in terms of biomechanical outcomes (ISQ values and RTQ values) after a healing period of 2 to 8 weeks in rabbit tibias /femurs.

Fixed full-arch maxillary prostheses supported by four versus six implants with a titanium CAD/CAM milled framework: 3-year multicentre RCT.

OBJECTIVES: This RCT compares marginal bone level (MBL) change and the clinical parameters after a 3-year function in maxillary implant-supported fixed complete dentures (FCDs) treated with four-implants (4-I) or six-implants (6-I). MATERIAL AND METHOD: Three centres treated 56 patients with 280 implants allocated to the 4-I or 6-I group. Radiographic and clinical examinations were performed. The primary outcome was to investigate MBL change between the groups. RESULTS: Implant survival rates were 100% and 99% in the 4-I and 6-I groups, respectively. Considering the clustering effects, the MBL change was not significantly different between the groups over the 3-year follow-up. The MBL in the 4-I group was 0.30 ± 0.50 mm at baseline, 0.24 ± 0.31 mm at 1 year and 0.24 ± 0.38 mm at 3 years. In the 6-I group, MBL was 0.14 ± 0.32 mm at baseline, 0.16 ± 0.35 mm at 1 year and 0.12 ± 0.26 mm at 3 years. There was a statistically significant difference between the groups at BL and 3Y. No significant differences between the groups were reported for clinical parameters at each time point as well as in between the visits. The technical and biological complications rates were 1.6% and 6.0%, respectively. Prosthetic complications affected 25 FCDs (47.2%). CONCLUSION: Marginal bone level change revealed a stable condition in the 3-year period in the two groups. Few technical and biological complications occurred apart from the chipping/fracture of the prosthetic teeth. Four-implant is a feasible solution if the rehabilitation is oriented towards the most cost-effective treatment and towards avoiding bone augmentation procedures. Clinicians have to consider the potential required visits for prosthetic maintenance.

In silico multi-scale analysis of remodeling peri-implant cortical bone: a comparison of two types of bone structures following an undersized and non-undersized technique.

PURPOSE: The aim of this multi-scale in silico study was to evaluate the influence of resorption cavities on the mechanical properties and load distribution in cortical bone after implant placement with two different drilling protocols. MATERIAL AND METHODS: Two different micro-scale bone structures were assessed: cortical bone models with cavities (test) and without cavities (control) were designed from µCT data. In a macro-scale model, representing a mandibular ridge, oblique load of 150 N was applied on the implant-abutment. Maximum principal stress/strain, and shear stress/strain were calculated in the macro- and micro-scale models. RESULTS: Test presented anisotropic material properties. In tests, significantly greater maximum values of Maximum principal stress/strain were calculated in micro-scale model. These values were located at the implant neck area in the macro-scale model and in the proximity of cavities in the micro-scale model respectively. Greater values of shear stress/strain were found in the test along the mandibular horizontal plane. CONCLUSIONS: Cortical bone with resorption cavities following undersized drilling showed an impaired load distribution compared with bone without cavities. Subsequently, stress/strain distribution suggests that this bone model is more prone to microdamage, thus delaying the healing process.

CAD/CAM Implant Abutments: Peri-implant Hard and Soft Tissue Response with Up to 4 Years of Follow-up- A Retrospective Cohort Study Evaluation.

This retrospective study evaluated hard and soft tissue response and reported mechanical and technical complications around computer-aided design/computer-assisted manufactured (CAD/CAM) abutments. A total of 123 patients restored with titanium, gold-hue titanium, and zirconia CAD/CAM abutments were included (N = 291). Each patient was followed up for at least 2 years. Clinical and radiographic parameters were assessed annually and complications were recorded. No implant or reconstruction failures were reported. One fracture of a zirconia abutment occurred. The prosthetic survival rate after 4 years of function for restorations and abutments was 100% and 99.66%, respectively. No significant differences in biologic and radiographic indices were found. The bleeding on probing index was positive at 42% of implant sites, and it had no significant correlation with the overall change in marginal bone level (0.02 mm) of bone gain. The short-term survival of CAD/CAM abutments was reliable, no matter of the material used for manufacturing.

Intraosseous Temperature Change during Installation of Dental Implants with Two Different Surfaces and Different Drilling Protocols: An In Vivo Study in Sheep.

BACKGROUND: The intraosseous temperature during implant installation has never been evaluated in an in vivo controlled setup. The aims were to investigate the influence of a drilling protocol and implant surface on the intraosseous temperature during implant installation, to evaluate the influence of temperature increase on osseointegration and to calculate the heat distribution in cortical bone. METHODS: Forty Brånemark implants were installed into the metatarsal bone of Finnish Dorset crossbred sheep according to two different drilling protocols (undersized/non-undersized) and two surfaces (moderately rough/turned). The intraosseous temperature was recorded, and Finite Element Model (FEM) was generated to understand the thermal behavior. Non-decalcified histology was carried out after five weeks of healing. The following osseointegration parameters were calculated: Bone-to-implant contact (BIC), Bone Area Fraction Occupancy (BAFO), and Bone Area Fraction Occupancy up to 1.5 mm (BA1.5). A multiple regression model was used to identify the influencing variables on the histomorphometric parameters. RESULTS: The temperature was affected by the drilling protocol, while no influence was demonstrated by the implant surface. BIC was positively influenced by the undersized drilling protocol and rough surface, BAFO was negatively influenced by the temperature rise, and BA1.5 was negatively influenced by the undersized drilling protocol. FEM showed that the temperature at the implant interface might exceed the limit for bone necrosis. CONCLUSION: The intraosseous temperature is greatly increased by an undersized drilling protocol but not from the implant surface. The temperature increase negatively affects the bone healing in the proximity of the implant. The undersized drilling protocol for Brånemark implant systems increases the amount of bone at the interface, but it negatively impacts the bone far from the implant.

Effect of Misfit at Implant-Level Framework and Supporting Bone on Internal Connection Implants: Mechanical and Finite Element Analysis.

PURPOSE: To evaluate the effect of misfit at implant-level fixed partial dentures (ILFPDs) and marginal bone support on the generation of implant cracks. MATERIALS AND METHODS: This in vitro study included a mechanical fatigue test and finite element analysis. A mechanical cycling loading test was performed using 16 experimental models, each consisting of two parallel implants subdivided into four groups based on the misfit and the supporting bone condition. The framework, firmly seated at implants, was dynamically loaded vertically with a force of 1,600/160 N and 15 Hz for 1 × 106 cycles. Optical microscope, scanning electron microscope (SEM), and computed tomography three-dimensional (CT-3D) analyses were performed to detect impairments. Finite element models, representing the setups in the mechanical fatigue test, were used to represent the fatigue life. RESULTS: None of the mechanical components presented distortion or fracture at the macroscopic level during the test. In a microscopy evaluation, the fatigue test revealed scratches visible in the inner part of the conical portion of the implants regardless of the groups. SEM and CT-3D analysis revealed one implant from the misfit/no bone loss group with a microfracture in the inner part of the conical interface. The simulated effective stress levels in the coronal body were higher in the misfit groups compared with the no misfit groups. The misfit groups presented effective stress levels, above 375 MPa, that penetrated the entire wall thickness. The no bone loss group presented an effective stress level above 375 MPa along its axial direction. In the no misfit group, the area presenting effective stress levels above 375 MPa in the conical connection was larger for the bone loss group compared with the no bone loss group. CONCLUSION: This study confirmed that implant fracture is an unlikely adverse event. A clear pattern of effective distribution greater than fatigue limit stresses could be noticed when the misfit was present. The dynamic load simulation demonstrated that the crack is more likely to occur when implants are fully supported by marginal bone compared with a bone loss scenario. Within the limitations of this study, it is speculated that marginal bone loss might follow the appearance of an undetected crack. Further research is needed to develop safe clinical protocols with regard to ILFPD.

Patient satisfaction and clinical outcomes in implant-supported overdentures retained by milled bars: Two-year follow-up.

OBJECTIVES: This observational clinical study evaluated the patient satisfaction and the clinical outcomes of edentulous arches rehabilitated with overdentures retained by CAD-CAM milled titanium bars. MATERIALS AND METHODS: Edentulous patients were treated with a full-arch removable overdenture anchored on two milled bars based on a friction retention system. Patient satisfaction was tested using the validated Oral Health Impact Profile (OHIP-14) questionnaire at the pre- and post-treatment visits, up to two years after prosthesis delivery (possible score range: 0-56. Best: 0). The prosthodontist satisfaction was also assessed through a designed questionnaire (best possible range 0-4. Best:0). Radiographic and clinical examinations were performed at baseline and after 2 years of function. Implant and prostheses complications were recorded. RESULTS: Forty (25 mandible) edentulous patients, mean age 69 ± 9.5 (SD) (52% males, 10% smokers), were treated with a total of 185 implants. The mean difference between pre- and post-treatment OHIP-14 score was 20.6 ± 8.0 (P < 0.0001) showing a high level of satisfaction for aesthetics, functional and psychological outcomes. This perception was not influenced by patient's age or gender. The clinicians' mean score was 3.4 ± 4.0. There was a marginal bone level (MBL) gain of 0.02 ± 0.22 mm between the two time points. Minor complications were reported in five patients. CONCLUSIONS: This procedure may lead to satisfaction regarding aesthetics and mastication function. One of the most relevant aspects is the versatility, which allows selection of the most suitable treatment option according to patient needs. The prosthodontist satisfaction questionnaire showed that this procedure met the clinical expectations.

Implant vs abutment level connection in implant supported screw-retained fixed partial dentures with cobalt-chrome framework: 1-year interim results of a randomized clinical study.

BACKGROUND: Screw-retained fixed partial dentures (FPD) have shown a lower incidence of biologic complications and an easier retrievability compared with cemented FPD. PURPOSE: To compare the marginal bone loss at conical connection implant restored with a screw retained cobalt-chrome FPD in an implant-level (IL) or an abutment-level (AL) setup. MATERIALS AND METHODS: Patients with at least two adjacent missing teeth were randomly allocated to be restored with IL or AL FPD. Periapical radiographs and clinical examination were taken at implant placement, prosthetic connection, 6 and 12 months to evaluate marginal bone loss (MBL), and soft tissue conditions. Complications were used to calculate prognostic indexes. RESULTS: Fifty patients were treated with 50 FPD supported by 119 implants. The difference of MBL between the IL and AL groups was statistically significant (P = 0.003). At 1 year, MBL was 0.086 ± 0.313 mm and 0.005 ± 0.222 mm in the IL and AL groups, respectively. The presence of BoP increased with time in IL, whereas it decreased in AL group (P < 0.001). A minor complication was encounted in one FPD. CONCLUSIONS: A low grade of MBL was present after 1 year. IL showed greater amount of MBL and soft tissue inflammation indexes than AL. In FPD, AL may be a safer procedure than IL setup in order to preserve a healthy periimplant tissue.

Clinical Evidence of OsseoSpeed EV Implants: A Retrospective Study and Characterization of the Newly Introduced System.

This retrospective study sought to compare a new implant (Astra Tech OsseoSpeed EV) with its predecessor (Astra Tech OsseoSpeed TX) by scanning electron microscopy and interferometry. Radiographic data from 19 patients who underwent implant restoration with EV (n = 49) with a median follow-up of 16 months were evaluated for mean bone level (MBL) changes from delivery of the definitive prosthesis. EV and TX did not differ in surface roughness, and both systems had a tight seal at the implant-abutment interface. The median MBL change of the EV was -0.02 mm mesiodistally after a median follow-up period of 16 months. Greater maintenance of MBL was found in the screw-retained restorations (n = 17) compared to cemented (0.35 ± 0.33 mm and -0.38 ± 0.76 mm, respectively; P = .03). The data suggest that EV shows minimal levels of bone loss and high implant survival.

Influence of different drilling preparation on cortical bone: A biomechanical, histological, and micro-CT study on sheep.

OBJECTIVE: The aim of this study was to investigate the extent of cortical bone remodeling between two different drilling protocols by means of histomorphometric, µ-CT, and biomechanical analyses. MATERIAL AND METHODS: A total of 48 implants were inserted into the mandible of six sheep following two drilling protocols: Group A (Test, n = 24), undersized preparation; Group B (Control, n = 24), non-undersized preparation. The animals were euthanatized to obtain 5 and 10 weeks of implantation time. Removal torque (RTQ) was measured on 12 implants of each group and the peri-implant bone was µ-CT scanned. Bone volume density (BV/TV) was calculated in pre-determined cylindrical volumes, up to 1.5 mm from implant surface. Non-decalcified histology was prepared on the remaining 12 implants from each group, where total bone-to-implant contact (totBIC) and newly-formed BIC (newBIC) was measured. Bone Area Fraction Occupancy (BAFO) was determined in pre-determined areas up to 1.5 mm from implant surface. Paired sample t test or Wilcoxon signed-rank test was used to investigate differences between the groups. RESULTS: Group A presented significantly increased RTQ value at 5 weeks, while no difference was observed at 10 weeks. Group B presented increased BV/TV value at 5 weeks. Both groups showed comparable values for totBIC at both time-points. However, Group A presented significantly lower newBIC at 5 weeks. Higher BAFO was observed in Group B at 5 weeks. CONCLUSIONS: Implants inserted into undersized sites has an increased biomechanical performance, but provoked major remodeling of the cortical bone during the early healing period compared to non-undersized preparations. After 10 weeks, no difference was observed.

Bone loss at implants and teeth in the same inter-proximal unit: A radiographic study.

OBJECTIVE: This study was performed to determine whether the distance between an implant and a tooth present in an inter-proximal unit influenced the amount of marginal bone loss that occurred at the two facing (adjacent) surfaces. MATERIALS AND METHODS: One hundred and eighty patients with a total of 278 inter-proximal units were included. Radiographs of implants that also included adjacent (facing) natural tooth/teeth were digitalized, and various linear measurements were performed using a software program. The marginal bone level and the bone level change that had occurred during a mean of 5.8 years were assessed as well as distance between the implant and the adjacent tooth/teeth. RESULTS: The mean amount of additional marginal bone loss that took place during the observation period was about 0.4 mm at both implants and adjacent tooth surfaces. The horizontal distance between an implant and the facing tooth did not influence the amount of marginal bone loss that had occurred. In most inter-proximal units, more advanced bone loss (>1 mm, >2 mm) had ensued either at the implant or at the facing tooth surface. Advanced additional bone loss occurred at both the implant and the tooth in only about 3% of the examined subjects. CONCLUSION: Bone loss at implants and teeth appears to be a site-specific phenomenon and not dependent on the inter-proximal distance.