Maxillary sinus floor augmentation and dental implant placement using dentin matrix protein-1 gene-modified bone marrow stromal cells mixed with deproteinized boving bone: A comparative study in beagles

ObjectiveThe aim of the study was to evaluate the effects of the combined use of dentin matrix protein-1 (DMP1) gene-modified bone marrow stromal cells (BMSCs) and Bio-Oss^® for maxillary sinus floor augmentation (MSFA) implant placement in dogs.Materials and methodsBMSCs were derived from bone marrow of six beagles and cultured. The cells were transduced with a lentiviral vector overexpressing the DMP1 gene and enhanced green fluorescent protein (EGFP) gene (Lenti-DMP1/EGFP) in test group, and with a lentiviral vector encoding EGFP gene (Lenti-EGFP) in control group. Six dogs received sinus augmentations using the bilateral approach with a simultaneous implant placement at each site respectively. At the same concentration, 2 × 10⁷ cells/ml, one sinus was grafted using a mixture of autologous DMP1/EGFP gene-modified BMSCs and Bio-Oss^® (DMP1 group), and the contralateral sinus was grafted with autologous EGFP gene-modified bMSCs and Bio-Oss^® (EGFP group). After a 3 month healing period, bone regeneration and osseointegration were evaluated using histologic and histomorphometric methods.ResultsThe bone-implant contact (BIC) and the bone area fraction in the DMP1 group (BIC: 34.67% ± 8.23%, bone area fraction: 35.16% ± 3.32%) were significantly greater compared with the EGFP group (BIC: 26.06% ± 5.16%, bone area fraction: 20.74% ± 1.63%) (P < 0.05). No significant difference between the residual bone substitute material volume (BSMV) in the DMP1 group (35.86 ± 7.35) and the EGFP group (32.16 ± 9.16) was found in our study (P > 0.05).ConclusionBMSCs modified with the DMP1 gene can be used as an adjunct to Bio-Oss^® to enhance new bone formation and the osseointegration of dental implants in MSFA of dogs.     

Bone tissue responses to glass fiber-reinforced composite implants – a histomorphometric study

Objectives: The aims of this study were to evaluate bone-to-implant contact (BIC) and the osteoconductive capacity of bioactive fiber-reinforced composite implant (FRC) in vivo .
Material and methods: Threaded sand-blasted FRC implants and threaded FRC implants with bioactive glass (BAG) were fabricated for the study. Titanium implants were used as a reference. Eighteen implants (diameter 4.1 mm, length 10 mm) were implanted in the tibia of six pigs using the press-fit technique. The animals were sacrificed after 4 and 12 weeks. Histomorphometric and scanning electron microscopic (SEM) analyses were performed to characterize BIC.
Results: In general, the highest values of BIC were measured in FRC-BAG implants, followed by FRC and Ti implants. At 4 weeks, the BIC was 33% for threaded FRC-BAG, 27% for FRC and 19% for Ti. At 12 weeks, BIC was 47% for threaded FRC-BAG, 40% for FRC and 42% for Ti. Four weeks after implantation, all the implants appeared biologically fixed by a newly formed woven bone arranged in the thin bone trabeculae filling the gap between the implant and the bone of the recipient site. Twelve weeks after implantation, the thickness of the woven bone trabeculae had increased, especially around the FRC-BAG implants.
Conclusion: Our results suggest that the FRC implant is biocompatible in bone. The biological behavior of FRC was comparable to that of Ti after 4 and 12 weeks of implantation. Furthermore, the addition of BAG to the FRC implant increased peri-implant osteogenesis and bone maturation.     

The impact of a modified cutting flute implant design on osseointegration

Information concerning the effects of the implant cutting flute design on initial stability and its influence on osseointegration in vivo is limited. This study evaluated the early effects of implants with a specific cutting flute design placed in the sheep mandible. Forty-eight dental implants with two different macro-geometries (24 with a specific cutting flute design – Blossom group; 24 with a self-tapping design – DT group) were inserted into the mandibular bodies of six sheep; the maximum insertion torque was recorded. Samples were retrieved and processed for histomorphometric analysis after 3 and 6 weeks. The mean insertion torque was lower for Blossom implants (P < 0.001). No differences in histomorphometric results were observed between the groups. At 3 weeks, P = 0.58 for bone-to-implant contact (BIC) and P = 0.52 for bone area fraction occupied (BAFO); at 6 weeks, P = 0.55 for BIC and P = 0.45 for BAFO. While no histomorphometric differences were observed, ground sections showed different healing patterns between the implants, with better peri-implant bone organization around those with the specific cutting flute design (Blossom group). Implants with the modified cutting flute design had a significantly reduced insertion torque compared to the DT implants with a traditional cutting thread, and resulted in a different healing pattern.     

Effects of a fluoride etchant and a phosphate primer on bonding of veneering composite to Ti–6Al–4V alloy for CAD/CAM restorations

PurposeTitanium abutments and superstructures are commonly veneered or covered with esthetic materials. The present investigation was carried out to evaluate the effects of an experimental surface treatment using etchant and primer on bond strength between a resin composite and Ti–6Al–4V alloy.MethodsDisk-shaped Ti–6Al–4V alloy was machine milled, the surface was air abraded with alumina, and the alloy was chemically etched with 5wt% ammonium hydrogen fluoride (F-etch) for 30 s. A phosphate primer (MDP-primer) was applied to the bonding area, and then a resin composite, with or without milled-fiber resin composite (FRC), was veneered on the specimen. Shear bond strengths were determined after thermocycling for 20,000 cycles. Bond strength data were analyzed by means of ANOVA and a multiple comparison test (α = 0.05). The surface of Ti–6Al–4V alloy was observed using a scanning electron microscope before and after the etching procedure.ResultsNo-FRC/F-etch/MDP-primer exhibited the highest bond strength (28.2 MPa), followed by No-FRC/No-etching/MDP-primer (24.2 MPa), FRC/F-etch/MDP-primer (19.9 MPa), FRC/No-etching/MDP-primer (17.8 MPa), No-FRC/No-etching/No-primer (13.6 MPa), while FRC/No-etching/No-primer (2.5 MPa) resulted in the lowest value. Microphotographs showed that numerous micro and nano pits were created on the Ti–6Al–4V alloy surface modified with F-etch.ConclusionsThe bond strength between Ti–6Al–4V alloy and the veneering resin composite was the highest when the alloy surface was modified with alumina blasting, fluoride etchant, and phosphate primer successively.     

Three-dimensional measurement of radiographic bone–implant contact lengths of zygomatic implants in zygomatic bone: a retrospective study of 66 implants in 28 patients

Zygomatic implant treatment is widely applied for severe maxillary atrophy to help rehabilitate the maxillary dentition. This retrospective study was performed to evaluate the actual radiographic bone–implant contact (rBIC) lengths of zygomatic implants. The records of 28 patients who underwent zygomatic implant surgery and subsequent follow-up examinations between August 2013 and September 2018 in the Department of Oral and Maxillofacial Surgery, Taipei Tzu Chi Hospital were reviewed. The surgeries were performed by a single surgeon using the same treatment protocol. All patients had a computed tomography scan at 1 year after the surgery. Using three-dimensional imaging software, an investigator measured the rBIC lengths of 66 implants and documented their clinical status. The implant survival rate was 100%. The mean rBIC length was significantly longer in male patients than in female patients (20.80 ± 5.88 mm versus 17.79 ± 6.34 mm; P = 0.028). The mean rBIC length of double zygomatic implants was significantly longer when compared to that of single implants (21.11 ± 6.23 mm versus 17.75 ± 5.85 mm; P = 0.027). This article is novel in reporting the exact rBIC lengths of zygomatic implants in a clinical setting. The results showed that zygomatic implants are a viable treatment modality for full-mouth rehabilitation.     

The effect of injectable calcium phosphate cement on bone anchorage of titanium implants: an experimental feasibility study in dogs

Calcium phosphate has high osteotransductive potential. The injectable form of calcium phosphate cement (ICAP) can be used as an adjunctive supportive agent for dental implants. The aim of this study was to assess the effect of an ICAP on the reverse torque resistance of titanium implants. Two implant beds (total 24) were prepared in each proximal tibia of 6 beagles. ICAP was injected into one of prepared implant beds (test) and the implant was inserted. The next implant was inserted without ICAP to serve as control. Three dogs were killed after 2 weeks and 3 after 12 weeks. Retrieved implants were subjected to reverse torque test. Results were analyzed with Student's t-test. Scanning electron microscope (SEM) was used for further evaluation. Mean torque values in 2-week healed implants were 52.48 N cm and 50.57 N cm for test and control implants, respectively (p = 0.4). 12-week healed implants showed 81.61 N cm and 76.71 N cm for test and control implants, respectively (p = 0.14). Results indicated no statistical difference between test and control implants for either healing time. SEM images of tested samples revealed close contact between the bone–ICAP–titanium surface. ICAP must be tested on further developed experimental models.     

Effects of anodized implants coated with Escherichia coli-derived rhBMP-2 in beagle dogs

This study evaluated the effects of Escherichia coli-derived rhBMP-2 (ErhBMP-2) coated onto anodized implants to stimulate bone formation, osseointegration and vertical bone growth in a vertical bone defect model. Six young adult beagle dogs were used. After a 2-month bone healing period, anodized titanium implants (8 mm in length) were placed 5.5 mm into the mandibular alveolar ridge. Eighteen implants coated with ErhBMP-2 (BMP group) and another 18 uncoated implants (control group) were installed using a randomized split-mouth design. The implant stability quotient (ISQ) values were measured. Specimens were fabricated for histometric analysis to evaluate osseointegration and bone formation. The ISQ values at 8 weeks after implant placement were significantly higher in the BMP group than in the control group (p < 0.05). Histological observations showed that the changes in bucco-lingual alveolar bone levels were higher in the BMP group than in the control group (p < 0.05). The ErhBMP-2 coated anodized implants can stimulate bone formation and increase implant stability significantly on completely healed alveolar ridges in dogs. Further studies evaluating the effects of ErhBMP-2 on osseointegration in the bone–implant interface are warranted.     

Initial bone regeneration around fenestrated implants in Beagle dogs using basic fibroblast growth factor–gelatin hydrogel complex with varying biodegradation rates

PurposeThe purpose of this study was to compare the effectiveness of fast and slow biodegradation of basic fibroblast growth factor (bFGF)–gelatin hydrogel complex on bone regeneration around fenestrated implants as a new augmentation drug delivery system.MethodsNine titanium implants (3.3 mm diameter and 10 mm length) were placed into the edentulous areas of the mandibles of three adult beagle dogs with four screws exposed at the upper buccal side. The effectiveness of bFGF–gelatin hydrogel complexes of varying degradation types used to cover implant screws without membrane were compared with 1 μg and 10 μg bFGF–98 wt% gelatin as the fast degradation type and 10 μg bFGF–95 wt% gelatin as the slow degradation type. After 4 weeks, bone regeneration around the screws was evaluated histologically and histomorphometrically.ResultsWith use of 10 μg bFGF, regenerated bone around exposed screws was clearly seen in both the fast and slow degradation type groups. In contrast, little bone formation was seen in the fast degradation-type group with 1 μg bFGF. Height of regenerated bone for the slow degradation-type complex group was significantly greater than for the fast degradation-type group with 1 μg bFGF (P < 0.05).ConclusionThese results suggest that use of slow degradation-type bFGF–gelatin hydrogel complex may accelerate bone regeneration around fenestrated implants at an early stage of bone regeneration.     

Torque-fitting and resonance frequency analyses of implants in conventional sockets versus controlled bone defects in vitro

The primary stability of implants should be high on insertion into fresh extraction sockets. Torque-fitting and resonance frequency analyses (RFA) are used to assess primary implant anchorage and stability. The torque-fitting and RFA of implants placed in conventional surgical sockets and sockets with controlled coronal bone defects was compared. The possible relation between torque-fitting and RFA was explored. Ø 3.3 mm × 12 mm implants were placed in 16 sockets finalized with Ø 2.8 mm surgical pilot drills in the right iliac crests of two fresh cadavers (control). In the test group, implants were placed into sockets prepared by Ø 2.8 mm drill followed by Ø 4.2 mm twist drills to a depth of 6 mm to create circumferential controlled coronal bone defects (50% bone loss). Primary implant stability was assessed using insertion torque values (ITV) followed by RFA. Mean ITV and RFA measurements for test groups (7.83 ± 0.91 N cm and 40.88 ± 3.57) were significantly lower than controls (14.80 ± 1 N cm and 66.31 ± 0.9) (P < 0.05). Reductions of ITV and RFA measurements in relation to bone defect were 47% and 38%. The existence of controlled bone defects eliminating contact coronally leads to decrease in torque-fitting and primary stability of implants. No relationship was observed between torque-fitting and RFA.     

Rationale for a reverse tapered body shift implant for immediate placement

Immediate implant placement holds considerable value, yet primary implant stability is often a critical factor. The aim of this study was to evaluate the stability, volumetric viability, and buccal gap size of reverse tapered body shift (RTBS) implants after immediate placement. Peak insertion torque measurements of two RTBS designs (apical 40% vs. apical 50%), relative to conventionally tapered implants, were assessed in simulated extraction sockets prepared in synthetic bone blocks. Additionally, the proximity of the RTBS implants to neighbouring teeth and anatomical structures, and the buccal gap distance were evaluated in human cadavers. The mean (± standard deviation) insertion torque was 12.00 ± 1.40 N•cm for the conventionally tapered implants (n = 50), 35.36 ± 2.74 N•cm (n = 50) for RTBS-1, and 48.20 ± 2.90 N•cm (n = 50) for RTBS-2; the difference between designs was statistically significant (P < 0.01). In total, 40 RTBS implants (20 per design) were placed in six cadaveric premaxillae. Only one locus was inappropriate for both RTBS implant designs, due to the proximity of neighbouring teeth. The average buccal gap for both implant designs was 2.8 mm (P = 0.104). The improved primary stability and increased buccal gap size with RTBS implants may enhance the feasibility of immediate placement. The study findings should be further validated in clinical trials.     

Analisi agli elementi finiti per la definizione della distribuzione degli stress meccanici negli impianti

ObjectivesTo study a spiral family implant by finite element analysis (FEA) inserted in mandible, connected with straight abutment and loaded with vertical and lateral forces.Materials and methodsThe biomechanical behaviour of 5 mm × 13 mm Ultimate dental implant (AoN Implants, Grisignano di Zocco, Vicenza, Italy), connecting screw, straight abutment subjected to static loads, in contact with mandibular bone was evaluated by FEA.ResultsStress and strain values of fixture are comparable to those obtained by analyzing different spiral implants.ConclusionsThese implants can be used in mandibular bone. However, clinical studies are needed to verify the reported results.     

Outcomes of osseointegrated implants in patients with benign and malignant pathologies of the head and neck: a 10-year single-centre study

The surgical management of head and neck pathologies involving the maxilla and mandible results in significant functional and aesthetic deficits, and ultimately reduced quality of life. Composite free flaps used for reconstruction address many of these deficits and create a foundation for the use of osseointegrated implants to support prosthetic replacement of the dentition. There are few comparative studies examining outcomes of implants in native and reconstructed bone in head and neck cancer patients. The aim of this retrospective cohort study was to compare survival rates and the effects of risk factors between implants placed in native and reconstructed bone. The Kaplan–Meier method estimated cumulative 1- and 5-year implant survival rates of 99.5% and 95% for native bone and 96% and 88% for reconstructed bone. Multivariate Cox regression found an increased risk of implant failure in reconstructed bone (hazard ratio (HR) 9.9, 95% confidence interval (CI) 3.4–29.7, P < 0.001). Subgroup analysis of the cohorts found an increased risk of failure in the reconstructed group associated with radiotherapy (HR 6.4, 95% CI 1.8–22.3, P = 0.004), current smoking (HR 23.2, 95% CI 2.7–198.6, P = 0.004), and previous smoking (HR 9.0, 95% CI 1.1–71.9, P = 0.038). There was no effect in the native bone group. Implants placed into reconstructed bone had higher rates of failure, and smoking status and radiotherapy increased the risk of implant failure.     

Comparison between flapless and open-flap implant placement: a systematic review and meta-analysis

No consensus has been reached regarding the influence of the flapless and open-flap surgical techniques on the placement of dental implants. This systematic review compared the effects of flapless implant placement and implant placement with elevation of the mucoperiosteal flap in terms of marginal bone loss, implant survival rate and complications rates. This review followed PRISMA guidelines and was registered in PROSPERO with the registration number CRD42017071475. Two independent reviewers performed a comprehensive search of the PubMed/MEDLINE, Scopus, and Cochrane Library databases for studies published until December 2017. The search identified 559 references. After a detailed review, 24 studies were assessed for eligibility. A total of 1025 patients who had received a total of 1873 dental implants were included. There were no significant differences between the flapless and open-flap surgical techniques in terms of implant survival rates (P = 0.34; risk ratio (RR): 1.36; confidence interval (CI): 0.72–2.56), marginal bone loss (P = 0.23; MD: −0.20; CI: −0.52–0.13), or complication rates (P = 0.67; RR: 1.10; CI: 0.70–1.73). The current meta-analysis showed that the implant survival rate, marginal bone levels, and complications of flapless surgery were similar to those of open-flap surgery over a mean follow-up period of 21.62 months.     

Texture analysis of cone beam computed tomography images reveals dental implant stability

The aim of this study was to characterize the alveolar bone of edentulous maxillary sites using texture analysis (TA) of cone beam computed tomography (CBCT) images and to correlate the results to the insertion torque, thus verifying whether TA is a predictive tool of final implant treatment. This study was conducted on patients who had received single implants in the maxilla (46 implants) 1 year earlier and whose torque values were properly recorded. Three cross-sections of the sites were selected on CBCT scans. Two regions of interest (ROIs) corresponding to the implant bone site and peri-implant bone were also outlined, according to virtual planning. The CBCT scans were exported to MaZda software, where the two ROIs were delimited following the previously demarcated contours. Values for the co-occurrence matrix were calculated for TA. With regard to the insertion torque value, there was a direct correlation with the contrast of the peri-implant bone (P < 0.001) and an inverse correlation with the entropy of the implant bone site (P = 0.006). A greater contrast indicates a greater torque value for insertion of the implants, and there is a possible association with a lower entropy value of the implant–bone interface.     

Retention and stress distribution in distal extension removable partial dentures with and without implant association

PurposeThe present study aimed to evaluate the retention and stress distribution of conventional (C) RPD and compare to RPD associated to implant for support (IS) and retention (IR).MethodsFrameworks were cast from cp Ti (n = 18) and Co–Cr alloy (n = 18) by plasma and injected by vacuum–pressure. Conventional RPDs were compared to implant associated RPDs using a distal implant to support (IS) or to support and retain (IR) RPD. The specimens were subjected to insertion/removal cycles simulating 5 years of use and the retention force (N) was measured or evaluated. A mixed linear model was used to analyze the data (α = 0.05). Photoelastic models were qualitatively examined for stress when an occlusal load of 15 kgf was applied over support teeth and RPD.ResultsRetention force of IR RPDs is greater than IS and C RPDs for both cp Ti and Co–Cr alloy specimens. Retention force of cp Ti RPDs increased initially and was maintained throughout 5 years of simulation test while Co–Cr RPDs presented a decrease at the beginning of the test and had their retention force maintained throughout the test. Implant placement at residual alveolar ridge decreased stress around teeth, mainly in the first premolar. Stress concentration in the IS RPD is slightly greater than in the IR RPD.ConclusionThe results suggest that implant placement at the distal extension improves retention and stress distribution of RPDs.     

Effect of implant abutment connection designs,and implant diameters on screw loosening before and after cyclic loading: In-vitro study

AimsThe purpose of this in-vitro study was to evaluate the screw loosening of two different forms of implant abutment connection designs, and two implant diameters by measuring removal torque value (RTV) before and after cyclic loading.Materials and methodsTwenty implant fixtures were divided equally into 2 groups (N = 10): group I fixture with conical hybrid connection (CH), and group II fixture with internal hex connection (IH). Each group was divided equally into two subgroups according to implant diameters: subgroup A (3.3 mm), and subgroup B (4.2 mm). Each fixture was vertically placed in the center of an acrylic resin block. The samples were fixed to the jig, and an implant abutment connected it with a 20 Ncm tightening torque. The samples were subjected to eccentric cyclic loading (at a distance of 5 mm) away from center of abutment at 100,000 cycles. A digital torque gauge was used to evaluate screw loosening by measuring RTVs in (Ncm) before and after cyclic loading. The removal torque loss ratio before and after cyclic loading and the removal torque loss ratio between before and after cyclic loading were calculated and analyzed using the SPSS statistical analysis.ResultsFor GI the initial removal torque loss ratio measurement was (14.45 ± 3.18) and decreased significantly after loading, it was (11.47 ± 3.64). For GII the initial removal torque loss ratio measurement was (20.47 ± 4.99) and increased significantly after loading, being (35.35 ± 4.26). There is no significant effect upon screw loosening for two implant diameters.ConclusionWithin the limitations of this study, the results suggested that conical hybrid connections showed a better screw stability than an internal hex connection. Therefore, the use of conical implants can be promoted as they have better screw stability compared to other systems.     

Effects of different abutment material and surgical insertion torque on the marginal adaptation of an internal conical interface: An in vitro study

PurposeTo evaluate the marginal adaptation at implant–abutment connection of an implant featuring a conical (45° taper) internal hexagonal abutment with a connection depth of 2.5 mm, comparing the performance of two identical abutments of different material (titanium grade-4 and Co-Cr-alloy).MethodsTwenty implants (3.75 mm × 15 mm) were connected to non-matching abutments (5.5 mm × 10 mm) of two different materials (titanium grade-4: n = 10; Co-Cr-alloy: n = 10). The specimens were separately embedded in epoxylite resin, inside copper cylinders, and submerged without covering the most coronal portion (5 mm) of the fixture. Five specimens per group were stressed simulating a surgical 100 Ncm insertion torque, while the others had no torque simulation. All specimens were subjected to a non-axial static load (100 N) in a universal testing machine, under an angle of 30° with respect to the implant axis. Once 100 N load was reached, low shrinkage self-curing resin was injected inside the cylinders, and load was maintained until complete resin polymerization. Specimens were cut and analyzed with optical and scanning-electron-microscope (SEM) to evaluate the marginal adaptation at the implant–abutment connection. Statistical analysis was performed using one-way ANOVA (p = 0.02).ResultsNone of the 20 samples failed. The implant–abutment connection was able to guarantee a good optical seal; SEM analysis confirmed the absence of microgaps.ConclusionsWithin the limits of this study (small sample size, limited time) the marginal adaptation of the implant–abutment connection was not affected by the abutment material nor by the application of surgical insertion torque.     

Dimensions of hard and soft tissue around adjacent,compared with single-tooth,zirconia implants

Preservation or regeneration of the papilla has always been a challenge around consecutive implants or with implants next to teeth, and many studies have evaluated the papilla’s behaviour and patterns based on surgical technique and prosthetic design, though evidence about its behaviour around zirconia implants is scarce. The aim of this study was to evaluate papilla behaviour between implants and teeth (tooth-implant group) and between consecutive implants (implant–implant group). Ninety patients with 122 zirconia implants (Straumann^® PURE Ceramic Implant) were examined at the one-year follow up. We measured the effect of the distance: first from the base of the contact point of the crowns to the contact with bone at the implant site (D1); secondly, to the contact with the bone at the neighbouring tooth or implant site (D2); and thirdly on the papillary deficit (D3). In both the tooth-implant group and the implant–implant group, D1 and D2 correlated significantly with the papillary deficit (D3), whereas D2 was the major determinant factor (Spearman’s rho = 0.60). In both groups, when D1 and D2 were <6 mm, the papilla was present every time. The papillary deficit was significantly greater in the tooth-implant group than in the implant–implant group (p = 0.048). We conclude that the ideal distance from the base of the contact point to the bone contact at the implant and to the bone contact at the adjacent tooth in both groups is <6 mm. The height of the bone on the teeth adjacent to implants has a significant impact on that of the papilla.     

Prevalence of early and late oral implant loss among smokers: a nationwide survey in Japan

A cross-sectional, nationwide survey was conducted in Japan to examine the relationship between tobacco smoking and oral diseases including implant failure. A questionnaire survey was sent to designated facilities by post, and 158 answered questions regarding implant loss. Smoking status, number of implant failures, and other related variables were collected from the participating dentists as secondary data. A total of 1966 patients who were treated with dental implants by participating dentists during the survey period were analysed. Among the total sample, 90 (5%) had early implant loss (≤12 months) and 153 (8%) had late implant loss (>12 months and ≤120 months). The number of pack-years was significantly higher in the total (early and late) implant loss group (31.2 ± 15.9) than in the group with no implant loss (26.1 ± 18.1) (P = 0.026). In the multivariate analysis, the number of implants installed, smoking, and pack-years were significant factors for total implant loss. The adjusted odds ratio for implant failure for current smokers compared with never smokers was 2.07 (95% CI 1.19–3.62) for early implant loss and 1.48 (95% CI 0.92–2.37) for late implant loss. This study reaffirms that current smoking is associated with an increased risk of early implant loss, irrespective of the duration of smoking exposure.     

The combined effects of undersized drilling and implant macrogeometry on bone healing around dental implants: an experimental study

This study investigated the effect of undersized preparations with two different implant macrogeometries. There were four experimental groups: group 1, conical implant with an undersized osteotomy of 3.2 mm; group 2, conical implant with an undersized osteotomy of 3.5 mm; group 3, cylindrical implant with an undersized osteotomy of 3.2 mm; group 4, cylindrical implant with an undersized osteotomy of 3.5 mm. Implants were placed in one side of the sheep mandible (n = 6). After 3 weeks, the same procedure was conducted on the other side; 3 weeks later, euthanasia was performed. All implants were 4 mm × 10 mm. Insertion torque was recorded for all implants during implantation. Retrieved samples were subjected to histological sectioning and histomorphometry. Implants of groups 1 and 2 presented significantly higher insertion torque than those of groups 3 and 4 (P < 0.001). No differences in bone-to-implant contact or bone area fraction occupied were observed between the groups at 3 weeks (P > 0.24, and P > 0.25, respectively), whereas significant differences were observed at 6 weeks between groups 1 and 2, and between groups 3 and 4 (P < 0.01). Undersized drilling affected the biological establishment of bone formation around both dental implant macrogeometries.