The International Journal of Oral & Maxillofacial Implants, 06/2019

Purpose: To assess surface characteristics and implant stability after implantoplasty performed by two different instrument sequences regarding material loss, surface roughness, and fracture load resistance. Additionally, operators' subjective experience during instrumentation and the damage to neighboring teeth were evaluated. Materials and Methods: Titanium implants were placed in the position of both first maxillary molars in models exposing 6 mm of their surface. Implantoplasty was performed in phantom heads: Exposed surfaces were instrumented with diamonds and Arkansas stones or abrasive stones and silicone polishers. Operators reported on abrasion, gloss, effectiveness, and tactility using a visual analog scale (VAS). Residual wall thickness of implants was measured on radiographs, material abrasion using three-dimensional (3D) scans, and surface roughness by contact profilometry. Maximum bending moments were measured. Results: Residual thickness and weight loss were comparable after both treatments (0.3 ± 0.1 and 0.25 ± 0.07 mm and 0.22 ± 0.01 g, and 0.03 ± 0.01 mm and 0.02 ± 0.01 g, respectively, P > .05). Mean surface roughness was lower (P = .0001) for the group with the silicone polishers (0.4 ± 0.2 μm) compared with the group employing diamonds (0.8 ± 0.1 μm). Maximum bending moments showed neither intergroup differences nor stability loss compared with untreated implants. The stone-and-silicone polisher group showed less abrasion (4.6 ± 2.2) and higher gloss values (8.1 ± 1.4) than the diamond-and-Arkansas group (3.1 ± 1.3 and 4.1 ± 2.1, respectively). Superficial tooth injuries at proximal neighbor teeth were common (73% and 80%). Conclusion: Implantoplasty did not weaken implant stability. The use of silicone polishers revealed lower surface roughness. Regarding surface smoothness, the instrumentation sequence employing silicon carbide and Arkansas stones followed by silicone polishers seems to be superior to the combination of diamond and Arkansas stones. Keywords: dental implants, fracture, implantoplasty, peri-implantitis, resective surgery, surface roughness

Purpose: There is uncertainty in the literature on whether the presence of keratinized tissue (KT) ameliorates the state of peri-implant tissue health. A systematic review and meta-analysis was performed to synthesize evidence on the association between peri-implant keratinization, defined as adequate (≥ 2 mm) or inadequate (0 to 2 mm), and peri-implant health and stability, measured as tissue inflammation, plaque accumulation, tendency to bleeding, and probing depth (PD). Materials and Methods: This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement and was registered on PROSPERO. According to predefined inclusion criteria, full papers for potentially eligible studies resulted from electronic databases (PubMed, Cochrane, and OpenGrey) and screening of titles/abstracts. Publication bias and risk of bias in primary studies were assessed. The primary outcome was gingival inflammation, measured with Gingival Index (GI) and modified Gingival Index (mGI). Additional outcomes were plaque accumulation (mPI/PI), bleeding (bleeding on probing/modified Bleeding Index), and PD. For each outcome, a random-effects meta-analysis was performed comparing the adequate group (≥ 2 mm, KT1) and the inadequate group ( 2 mm, KT0) KT width. The mean number of implants and proportion of mandibular implants were investigated as potential causes of heterogeneity using meta-regression. Sensitivity analysis was performed excluding low-quality studies. Results: From 362 screened studies, a total of 15 papers were included in the systematic review, and 8 articles were finally included in the meta-analysis. Heterogeneity was found for all outcomes. The main analysis showed a statistically significant association between adequate KT level and a lower mGI-GI (standard mean difference [SMD] KT1 vs KT0 = -1.25, 95% CI = -2.12 to 0.37, P = .01). For plaque accumulation (SMD = -1.18, 95% CI = -2.36 to 0.00, P = .05), bleeding (SD = -1.99, 95% CI = -4.60 to 0.61, P = .13), and PD (MD = -0.06, 95% CI = -0.13 to 0.01, P = .10), no statistically significant difference was detected; however, the trend of results was in favor of the KT1 group. The sensitivity analysis supported the main analysis conclusions. Conclusion: The importance of having an adequate KT width around implants was confirmed by this review; adequate KT was significantly associated with less peri-implant inflammation evaluated qualitatively with mGI/GI. No difference was found for plaque accumulation and bleeding, but a positive trend was found favoring implants with adequate KT. Keywords: keratinized tissue, peri-implant health, systematic review

Purpose: To investigate the tensile bond strength between zirconia abutments and titanium bases, luted with two different resin composite cements, after different cleaning procedures. Materials and Methods: Zirconia abutments and titanium bases were luted with either a DMA/HEMA-based cement (n = 80; Multilink Hybrid Abutment, Ivoclar Vivadent) or a Bis-GMA/TEGDMA-based cement (n = 80; Panavia V5, Kuraray Noritake). The adhesive gap of half of the specimens was polished (n = 40 per resin composite cement). Four separate specimens underwent roughness measurements and scanning electron microscopy. The specimens were divided into four groups (n = 10 per subgroup): (1) not cleaned, (2) cleaning in an ultrasonic bath, (3) cleaning in an autoclave, and (4) treatment with low-pressure plasma. The specimens were thermocycled (20,000×, 5°C/55°C), tensile bond strength was tested, and fracture types were analyzed. Data were examined using the Kolmogorov-Smirnov test, univariate ANOVA with additional partial eta-squared (ηp 2), and the Mann-Whitney U test. The defined level of significance was adjusted by Bonferroni correction (P .003). Results: The tensile bond strength of specimens luted with the DMA/HEMA-based cement was higher than that of specimens luted with the Bis-GMA/TEGDMA-based cement. The polishing step and the cleaning procedures showed no impact on tensile bond strength results. Specimens luted with the DMA/HEMA-based cement presented more cohesive fractures, whereas specimens luted with the Bis-GMA/TEGDMA-based cement presented themselves with more fractures of the interface between the resin composite cement and zirconia abutment. Ra values showed a decline in roughness after polishing for both resin composite cements. Conclusion: As the DMA/HEMA-based cement showed higher tensile bond strength values, the usage of this resin composite cement for luting implant abutments to titanium bases can be recommended. Neither polishing nor the use of different cleaning procedures had an impact on tensile bond strength. Keywords: cleaning procedures, tensile bond strength, titanium base, zirconia abutment

Purpose: There is a lack of knowledge concerning the critical buccal bone thickness required for securing favorable functional and esthetic outcomes, conditioned to the dimensional changes after implant placement. A preclinical study was therefore carried out to identify the critical buccal bone wall thickness for minimizing bone resorption during physiologic and pathologic bone remodeling. Materials and Methods: A randomized, two-arm in vivo study in healthy beagle dogs was carried out. The first group of dogs was sacrificed 8 weeks after implant placement for histomorphometric examination of postsurgical resorption of the buccal bone wall. The second group of dogs was monitored during three ligature-induced peri-implantitis episodes and a spontaneous progression episode. Morphometric and clinical variables were defined for the study of physiologic and pathologic buccal and lingual bone loss. Results: Seventy-two implants were placed in healed mandibular ridges of 12 beagle dogs. Two groups were defined: 36 implants were placed in sites with a thin buccal bone wall ( 1.5 mm), and 36 were placed in sites with a thick buccal bone wall (≥ 1.5 mm). No implants failed during the study period. For the great majority of the histomorphometric parameters, a critical buccal bone wall thickness of at least 1.5 mm seemed to be essential for maintaining the buccal bone wall during physiologic and pathologic bone resorption. Suppuration (+) and mucosal recession (-) were more often associated with implants placed in sites with a thin buccal bone wall. Conclusion: A critical buccal bone wall thickness of 1.5 mm at implant placement is advised, since a thicker peri-implant buccal bone wall (≥ 1.5 mm) is exposed to significantly less physiologic and pathologic bone loss compared with a thinner buccal bone wall ( 1.5 mm). Keywords: alveolar bone, dental implants, diagnostic, implant stability, peri-implant mucositis, peri-implantitis

Purpose: The aim of this study was to evaluate how continuous heavy orthopedic forces affect the stability of sandblasted, large-grit, acid-etched (SLA)-surfaced miniscrew implants and surrounding bone tissue healing at three different loading periods with treatment of photobiomodulation and ozone therapy. Materials and Methods: Miniscrew implants were applied on the tibias of 9-month-old rabbits (n = 18). The animals were randomly divided into three groups: control, photobiomodulation, and ozone therapy. In all groups, miniscrew implants were loaded with 500 gf at 0, 4, and 8 weeks, respectively (G1, G2, and G3). Several biomechanical and histologic analyses were performed in different centers to measure the implant stability quotient level, bone volume, and bone-to-implant contact. Results: According to the results of the Infinite Focus Microscopy, the ozone therapy group revealed significantly higher scores than the control group and photobiomodulation group at the 4-week loading time, whereas the photobiomodulation and ozone therapy groups revealed significantly higher scores than the control group at the 8-week loading time in terms of bone volume measurements in mm3 (P .05). According to the histologic analysis, the ozone therapy and photobiomodulation groups revealed significantly higher scores than the control group at the 4-week loading time, whereas the photobiomodulation group showed the highest scores among the 8-week loading groups (P .05). Conclusion: This is the first study in the literature that reveals a better osseointegration process in miniscrew implants when treated with photobiomodulation and ozone therapy compared with control groups. Although the photobiomodulation and ozone therapy groups did not reveal significantly higher scores in immediately loaded miniscrew implants (G1), these treatments were significantly more effective when loaded after 4 or 8 weeks of osseointegration (G2 and G3). SLA-surfaced miniscrew implants are successful in the orthopedic forces (500 gf) and can be removed without complications. Keywords: biomechanics, bone screws, histomorphometric, laser, low-level light therapy, orthodontic appliance design, ozone

Purpose: Implants in the anterior region are challenging, and literature reporting outcomes of narrowdiameter implants (NDIs) in anterior sites is scarce. This systematic review summarized evidence of functional and esthetic performance of anterior single crowns supported by NDIs. Materials and Methods: Ten databases were searched to find studies evaluating anterior single crowns supported by NDIs. Risk of bias was assessed, and random-effects meta-analyses were applied to analyze mean differences in survival, success, and marginal bone level (MBL). The review was registered in the PROSPERO database (CRD42018089886). Results: Twenty-one studies meeting the screening criteria were included for qualitative analysis, and three for meta-analysis. A total of 892 NDIs, placed in 736 patients, were analyzed. Follow-up duration varied from 12 months to 14 years (mean: 40 months), and 16 failures (implant loss) were recorded. Fixed-effect meta-analysis (I2 = 0%) of survival rate revealed a risk difference of 0.02 (95% CI: -0.03 to 0.08) between NDIs and controls (regular-diameter implants), without differences between groups (P = .39). Success rates ranged from 84.2% to 100% (mean: 95.2%). Random-effects meta-analysis (I2 = 56%) of MBL indicated a mean difference of 0.02 mm (95% CI: -0.21 to 0.25), without differences between groups (P = .87). Conclusion: Single crowns supported by NDIs are a predictable treatment, since their survival rate and MBL are comparable to those supported by regular-diameter implants. Due to data shortage reporting esthetic outcomes, more studies are needed to evaluate the long-term performance of the single crowns supported by NDIs in the anterior region. Keywords: alveolar bone loss, esthetics, narrow-diameter implants, review (systematic), single implant, survival analysis

Purpose: Short implants have been considered as an alternative to regular implants even where native bone is potentially adequate. Hence, the aim of this study was to evaluate the impact of implant length on its survival. Materials and Methods: A systematic literature search of randomized controlled trials and prospective studies was performed using the PubMed (MEDLINE), EMBASE, and Cochrane databases. Metaregression analysis determined the effect of the length on the implant survival rate. Results: Sixty-six studies comprising 4,525 implants were included in the meta-regression analysis. Overall, for each additional 1 mm of length, the survival rate was increased by 0.42 percentage points (P = .056). In the maxilla, an additional 1 mm in length implied 0.68 percentage points more in the rate (P .001), while in the mandible, statistical significance was not reached. Eventually, the implant survival rate in the 3- to 5-year period was strongly affected by the length of the implants in the maxilla, since it increased by 2% for each additional 1 mm of length. Conclusion: In the presence of adequate native bone, placement of longer/regular-sized implants should be chosen over placement of short implants in the maxilla. However, in a posterior mandible, short implants offer a judicious alternative. Keywords: dental implants, implant survival, review, short implants, systematic

Purpose: To evaluate topographic changes and effectiveness of mechanical instrumentation upon machined (MA) and roughened (RG) surfaces of dental implants. Materials and Methods: The coronal one-third of seven RG and seven MA implants was coated with a mixture of cyanoacrylate and toluidine blue dye to resemble calculus. Implants were cleaned with three curettes (SS: stainless steel, PT: plastic, TI: titanium), two ultrasonic tips (UM: metal tip, UP: plastic tip), a titanium brush (TB), and an air-polishing device (AA) until visibly clean. Additionally, a simulation of 1- and 5-year supportive peri-implant therapy (SPT) was performed on 14 implants using the aforementioned instruments with 20 strokes/40 s (T1) or 100 strokes/200 s (T5). Each implant was evaluated using stereomicroscopy, atomic force microscopy, and scanning electron microscopy. Results: UM was the most effective instrument, with 0% average percentage of residual artificial calculus (RAC), followed by TB (2.89%) and UP (4.90%). SS was more effective than TI (15.43% vs 20.12% RAC, respectively), while PT failed to remove any deposit (100% RAC). AA completely removed deposits on RG surfaces but not MA surfaces (26.61% RAC). Noticeable topographic changes were observed between both implant surfaces. RG surfaces became less rough, whereas MA surfaces became rougher at both T1 and T5 with the exception of AA. Plastic- and titanium-like remnants were noted after debridement with PT, SS, and TI, respectively. Conclusion: Artificial calculus removal by mechanical instrumentation, with the exception of PT, was proven to be clinically effective. All instruments induced minor to major topographic changes upon dental implant surfaces. AA did not remarkably change MA and RG surfaces at both micrometer and nanometer levels. Findings from this study may impact the selection of instruments or devices used during SPT protocols. Keywords: maintenance, mechanical instrumentation, microtexture, peri-implant disease

Purpose: The aim of this study was to explore the surface roughness and hardness of the implant head of orthodontic mini-implants made from different alloys before and after their in vitro exposure to agents for prevention of gingivitis, mucositis, and peri-implantitis: chlorhexidine and probiotics. Materials and Methods: Three types of commercially available mini-implants were tested: 316 stainless steel, titanium Grade 5, and titanium Grade 23 (both Ti-6Al-4V alloys with the same atomic weight percentage of Ti, Al, and V, with the difference being in maximal reduction of O2 in Grade 23 to 0.13% of atomic weight). They were immersed in three experimental solutions: artificial saliva, saliva with probiotic bacteria Lactobacillus reuteri, and saliva with oral antiseptic chlorhexidine (CHX). Samples were immersed for 28 days, thermocycled, then stored in an incubator at 37°C. Surface roughness and microhardness on five samples of each of the three implant types were measured by atomic force microscopy and the Vickers method, respectively. Results: Exposure of titanium implant Grade 5 to probiotics significantly increased roughness compared with other media (P .005). Exposure to CHX significantly increased the roughness of steel implants (P .05). Neither saliva, probiotic, nor CHX altered microhardness of titanium implants significantly. In steel implants, the exposure to CHX and probiotics decreased microhardness compared with unexposed implants (P .031), but not in comparison to saliva. Conclusion: Probiotics seem to increase roughness of titanium mini-implants, while CHX seems to increase roughness of steel mini-implants. Only stainless steel implants had an altered, decreased hardness after exposure to CHX, although the same was found after their exposure to saliva. For patients undergoing orthodontic treatment with temporary anchorage units, CHX could be recommended for titanium, and probiotics for stainless steel mini-implants in oral-hygiene maintenance. Keywords: biomaterials, biomechanics, microbiology

Purpose: This study represents a systematic review of the literature to assess the effectiveness of strontiumcoated titanium surfaces on osseointegration in experimental assays with healthy, nonosteoporotic and/or nonosteopenic animals. Materials and Methods: An electronic search was conducted of the databases MEDLINE/PubMed, Wiley Library, and Web of Science through 2018, with the aim of identifying studies on the osseointegration of titanium implants modified with strontium. Results: A total of 255 papers were found, of which 11 were included in this systematic review. The primary result was the percentage of boneto- implant contact (BIC) around the titanium implants with or without a strontium-coated surface. The different techniques used to coat titanium surfaces with strontium recorded significant results in terms of the improvement in the implant's quality, as they increased its contact with the bone, bone area, and bone formation, as well as enhanced its biomechanical properties. Conclusion: Nine of 11 studies reported that titanium implants coated with strontium showed significantly higher BIC (P .001 to P .05). This coating also improved the implants' biomechanical properties. Keywords: animal model, osseointegration, strontium, surface modification, titanium implant

Purpose: New solutions need to be developed for cases in which implants that were placed years ago are now presenting prosthetic complications. A conical head screw design for a single-tooth abutment was developed to preserve the initial applied torque. The aim of this study was to assess the preload maintenance of different screw design sets (a conical head screw set and a flat head screw set) for single-tooth abutments in external hexagon implants, verifying whether reverse torque changes after mechanical loading at different crown/implant ratios and to understand if the use of the tested conical head screw set design can help clinicians solve loosening torque. Materials and Methods: Forty external hexagonal implants, 40 singletooth abutments, 20 conical head screws, and 20 flat head screws were split into four groups with different crown/implant ratios (crown/implant ratio > 1 or crown/implant ratio 1). The abutments were attached to the implants by applying a torque of 35 Ncm; the specimens were mechanically loaded for 1 million cycles, and the loosening torque was checked and recorded with a digital torque wrench. The Kruskal-Wallis test (P = .05) and Wilcoxon test were performed to assess the results. Results: In all groups, at least one specimen kept 100% of the initial applied torque before mechanical loading (t0). After mechanical loading (t1), all specimens presented torque reduction. The Kruskal-Wallis test was performed, and the flat head screw t0 group presented lower torque maintenance and a significant difference (P .05) compared with the initial applied torque and with the conical head screw t0 group. The conical head screw t0 group presented a higher torque maintenance and no significant difference (P > .05) compared with the initial applied torque. For the flat head screw, the crown/implant ratio affected the torque maintenance. For the conical head screw, the crown/implant ratio did not affect the torque maintenance (P > .05). Conclusion: The conical head screw set presented a higher maintenance of applied preload than the flat head screw set. As far as reverse torque is concerned, the crown/implant ratio affects the torque maintenance only in association with a flat head screw set. The use of the tested conical head screw set can help clinicians solve loosening torque, mainly in a situation with a crown/implant ratio > 1. Keywords: dental implantation, dental prosthesis, implant-supported, torque

Purpose: This study evaluated the effect of anodized titanium implants coated with submicron-sized poly(lactideco- glycolide) (PLGA)/recombinant human transforming growth factor-β2 (rhTGF-β2) particles via electrospray on osseointegration in an in vivo model. Materials and Methods: An experimental group of anodized titanium implants coated with submicron PLGA/rhTGF-β2 particles by electrospray was compared topographically and histomorphometrically to noncoated anodized implants. Forty-eight anodized titanium implants were inserted into the tibias of 12 New Zealand rabbits. The histomorphometric specimens were prepared after sacrificing at 3 and 6 weeks after implant placement. Bone-to-implant contact percentage (BIC%) and bone area percentage (BA%) were calculated. The surface roughness and histomorphometric values were statistically analyzed, with a P value .05 defined as statistically significant. Results: The implant surfaces showed a uniform submicron-sized coating of PLGA/rhTGF-β2 particles. There was no significant difference in surface roughness between the groups. Both BIC% and BA% of the three best consecutive threads in the experimental group (3 weeks postplacement) were significantly higher than those of the control group (P = .045 and P = .048, respectively), whereas only the BIC% of the three best consecutive threads of the experimental group (6 weeks postplacement) was higher than that of the control group (P = .033). None of the groups tested showed any statistically significant differences in these metrics along the total length of the implant. Conclusion: Within the limitations of this study, coating rhTGF-β2 on implants with the help of PLGA carriers by electrospray may have enhanced osseointegration during the early stage of implant healing period in in-vivo rabbit tibia model. Keywords: anodized implant, electrospray, osseointegration, polylactic acid-polyglycolic acid copolymer, recombinant human transforming growth factor-β2

Purpose: The aim of this animal study was to evaluate new bone formation in human dentin block grafted on rabbit calvaria according to a comparison of histologic analysis. Materials and Methods: Human teeth were prepared according to four different types of dentin blocks: group 1, demineralized and microperforated dentin block; group 2, demineralized dentin block; group 3, undemineralized and microperforated dentin block; group 4, undemineralized dentin block. These four different dentin blocks were grafted on nine rabbit calvaria, and animals were sacrificed at 2, 4, and 8 weeks after the surgical procedure for histologic evaluation. Results: In group 1, histologically, new bone formation was initiated at the interface between demineralized and microperforated dentin block and host bone and microholes at 2 weeks, and mature bone was observed at 8 weeks. In group 3, new bone formation was observed at 8 weeks in the undemineralized and microperforated dentin block bottom and microholes. The bone formation ratio of group 1 was significantly higher at 2, 4, and 8 weeks compared with groups 2, 3, and 4 (P .05). The bone formation ratio in microholes at 2 and 8 weeks in group 1 was significantly greater than in group 3 (P .05). Conclusion: New bone formation of the demineralized dentin block began more rapidly than the undemineralized dentin block, and perforated dentin block was more effective in bone formation than dentin block without microholes. Keywords: demineralization, dentin block, new bone formation, ridge augmentation, tooth block bone

Purpose: The purpose of this study was to compare the efficacies of autogenous bone ring and autologous growth factor-enriched bone graft matrix as graft materials in extraction sockets. Materials and Methods: Subjects (n = 34) requiring extraction of a single incisor or premolar in a type II socket were segregated into two groups: BR and AFG. Autogenous bone ring transplant and autologous fibrin glue with particulate bone graft (sticky bone) were used in subjects under the BR and AFG groups, respectively, for socket augmentation. After 6 months, osteotomy preparation was carried out, and implants were placed in all subjects. The efficacies of both of the procedures were compared by assessing measures of bone density, buccal/lingual plate height, implant stability quotient (ISQ) readings, and mineralized tissue volumes. Results: At 6 months, there was a highly significant gain (P ≤ .001) in the buccal (3.09 ± 1.6 mm vs 1.90 ± 0.94 mm) and lingual/palatal bone heights (3.31 ± 2.66 mm vs 1.99 ± 1.22 mm) and a significant difference in the bone density (659.6 ± 133.8 vs 552.1 ± 65.6; P = .016) in the BR group compared with the AFG group. Significant differences were observed between the two groups for ISQ values at the end of 6 months (61.60 ± 8.9 vs 45.02 ± 6.33; P = .034). Biopsy specimens from the BR group showed a highly significant increase (50.39% ± 11.96% vs 38.91% ± 12.22%; P ≤ .001) in the percentage of tissue mineralization over the AFG group. Conclusion: The autogenous bone ring procedure seemed to confer additional benefits over autologous growth factor- enriched bone graft when various parameters were compared. The sites augmented with autogenous bone ring at the end of the study period showed a sufficient gain in bone height and quality for implant placement. Keywords: alveolar process, dental implants, platelet-rich fibrin, transplants

Purpose: To treat mandibular edentulous patients by fitting immediately loaded two-implant overdentures via guided flapless surgery and evaluate their masticatory performance. Materials and Methods: Nineteen patients who presented with edentulous mandibles (mean age: 69.8 years; range: 60 to 85 years) at the Dental Hospital, Tokyo Medical and Dental University, were enrolled in this study. A newly fabricated complete denture was used as a radiographic guide. Computer planning followed the design procedure, and surgical guides were fabricated for each patient. Flapless surgery was performed using this guide, and two implants were placed in the canine positions. On the day of surgery, a removable overdenture supported by two ball attachments was fitted. Masticatory function was evaluated on the basis of masticatory performance with a color-changeable chewing gum, maximum occlusal force with an occlusal force meter, and occlusal contact area with an occlusal diagnostic system. Results: The masticatory performance significantly improved from 48 months after surgery. The maximum occlusal force significantly increased 24 months after surgery. The occlusal contact area significantly increased from 6 months after surgery. This prospective study indicated that maximum occlusal force and occlusal contact area significantly improved at a comparatively earlier period after implant surgery and were maintained for up to 5 years with the immediate loading of twoimplant overdentures with stud attachments. However, masticatory performance took more time to improve than maximum occlusal force and occlusal contact area. Conclusion: According to this 5-year prospective study, masticatory performance, maximum occlusal force, and occlusal contact area showed significant improvement after 4 to 5 years, 2 years, and 6 months postsurgery, respectively. Keywords: immediately loading, masticatory function, overdenture, prospective study, two-implant overdenture

Purpose: To evaluate initial implant stability and initial healing around newly placed dental implants in well-controlled type 2 diabetes patients. Materials and Methods: Forty patients requiring implant therapy comprising 15 nondiabetic and 25 diabetic patients were recruited for this prospective study. Implant stability quotient and bone biomarkers such as osteopontin, receptor activator of nuclear factor-kB ligand, and interleukin 8 were evaluated at baseline and 1 and 3 months using Osstell Mentor and enzyme-linked immunosorbent assay, respectively. Results: Mean implant stability quotient values showed a statistically significant difference at each interval in both of the groups except between 1 and 3 months in the diabetic group. The percentage increase in implant stability quotient values was more in the nondiabetic (14.2%) than in the diabetic group (6.03%) from 1 to 3 months. Significant variations were observed in all three bone biomarkers between baseline and 3 months at P .002 in both groups. In the diabetic group, receptor activator of nuclear factor-kB ligand showed a higher reduction from baseline to 3 months, whereas interleukin 8 showed a less significant decrease between baseline and 1 month. Changes in correlation between implant stability and bone biomarkers were noted in the initial period of healing between the two groups. Conclusion: Variations in the pattern of response of osteopontin, receptor activator of nuclear factor-kB ligand, interleukin 8, and initial implant stability are noted in well-controlled diabetic individuals. Keywords: bone, dental implant, diabetes, implant stability, resonance frequency analysis

Purpose: This prospective clinical study evaluated the influence of an interposed bone graft with inferior alveolar nerve lateralization in terms of rates of sensory disturbance, mean sensation recovery time, and survival rates for placement of osseointegrated implants. Materials and Methods: Patients with an atrophic posterior mandible were enrolled in this study and randomized into two groups: bone graft group (a bone graft was placed between the implant and inferior alveolar nerve after lateralization) and control group (implants were placed in direct contact with the inferior alveolar nerve after lateralization). Neurosensory disturbances were evaluated via questionnaire 1 week after surgery and at the end of each month during the first year after surgery. Results: Eighty-two implants were placed, with a survival rate of 97.56%. Two implants were removed due to mandibular fracture. All patients reported initial sensory disturbances arising from the surgical procedure. In the control group, the mean time for recovery from sensory disturbance was 3.95 ± 2.33 months, compared with 4.11 ± 4.68 months in the bone graft group (P = .587). Conclusion: The interposition of a bone graft between implants and the inferior alveolar nerve after lateralization did not prevent sensory disturbances and did not influence the sensation recovery time or implant survival rates. Keywords: inferior alveolar nerve, neurosensory function

Purpose: To evaluate the effect of placement of single implants in the esthetic zone of the maxilla in preserved alveolar ridges, compared with nonpreserved alveolar ridges, on the change in midlabial mucosal level, esthetics, marginal bone level, and patient satisfaction. Materials and Methods: Patients with a failing single tooth, and demonstrating a large vertical defect (≥ 5 mm) of the labial wall of the extraction socket, were pre-augmented with a mixture of autologous bone and anorganic bovine bone. A mucosal graft sealed the pocket. After 4 months, a single implant was placed in the preserved alveolar ridge (test group; n = 20). The results were compared with those from patients who had one missing tooth and were treated with placement of an implant in a nonpreserved alveolar ridge, whereby the connective tissue graft was combined with the placement of the implant (control group; n = 20). Changes in midlabial mucosal level were scored on intraoral images. Intraoral radiographs were made to assess marginal bone level changes after definitive crown placement (1 month [T1], 12 [T12] months). The pink esthetic score/white esthetic score at T12 was used to determine esthetics. Patient satisfaction was assessed before treatment (Tpre), and at T1 and T12. Results: The mean midlabial mucosal level changes were 0.07 ± 0.29 mm and -0.15 ± 0.23 mm at T1 and T12 for the control and test groups, respectively (P = .01). No significant changes were observed for the other outcome variables. Conclusion: Single implant treatment in a preserved alveolar ridge and nonpreserved alveolar ridge is accompanied by clinically nonrelevant changes in the midlabial mucosal level. Changes in marginal bone level, esthetics, and patient satisfaction were comparable between the groups. Keywords: alveolar ridge augmentation, connective tissue grafting, esthetics, single-tooth implants

Purpose: To investigate the influence of age and time since edentulism on masticatory function and quality of life related to oral health (OHRQoL) in totally edentulous patients after implant-retained mandibular overdenture (IMO) loading. Materials and Methods: The sample consisted of 33 patients categorized in two age groups (≤ 65 and > 65 years, respectively), and two time since edentulism groups ( 25 and ≥ 25 years). The masticatory function was evaluated through the masticatory performance and swallowing threshold tests before IMO loading, and 1, 3, 6, and 12 months after IMO loading. The OHRQoL was evaluated by applying the Oral Health Impact Profile (OHIP-EDENT) and Geriatric Oral Health Assessment Index (GOHAI) questionnaires, before loading and after 3, 6, and 12 months. Data were subjected to the Mann-Whitney test and Wilcoxon signed-rank test for paired samples. Results: The masticatory performance and swallowing threshold were not influenced by the age nor by time since edentulism, except 6 months after IMO loading when patients ≤ 65 years of age performed the swallowing threshold test in a significantly shorter time with a reduced number of masticatory cycles (P .05). The masticatory performance and swallowing threshold outcomes showed a gradual improvement up to 12 months, irrespective of the patient categorization. The GOHAI questionnaire scores showed that the OHRQoL was influenced by age in complete denture wearers with a difference between groups in the psychosocial and global domains. The time since edentulism was not affected by the GOHAI scores of complete denture wearers (P .05). The OHIP-EDENT questionnaire only indicated significant differences as a function of age or time since edentulism between complete denture wearers. Age was associated with significant differences in the physical pain domain outcome, while time since edentulism did not affect only the psychologic discomfort, psychologic inability, and handicap domains. Conclusion: Neither the age nor the time since edentulism influenced the masticatory function of IMO-wearing patients. However, IMO significantly improved the masticatory function in totally edentulous patients, and this is more evident for younger patients (≤ 65 years) with a shorter time since mandibular edentulism ( 25 years). The OHRQoL is only influenced by age and time since edentulism in complete denture wearers; IMO treatment eliminates these differences. Keywords: edentulism, masticatory function, overdentures, quality of life, totally edentulous patients

Purpose: To assess the pattern of bone loss in peri-implantitis in partially edentulous patients and relate patient and implant/site characteristics that may influence such patterns. Materials and Methods: In this retrospective study, the records of partially edentulous patients with dental implants were stratified according to sex, age, smoking, and diabetes. Implants were stratified according to site, number of years in function, presence of adjacent implants, diameter, bone-grafted site, and implant platform. All these variables were obtained from previous periodontal charts and radiographs. The implants were then classified into two main groups: (1) bone loss as defined by the presence of progressive marginal bone change found on radiographs at least 12 months following prosthesis placement compared to a baseline with a threshold ≥ 2 threads of bone loss; and (2) no bone loss as defined by no detected bone change or bone level change with a threshold 2 threads. The bone loss group was further divided into three subgroups according to pattern: vertical, horizontal, and combined. Descriptive analyses were applied to assess the frequency of the pattern of bone loss (horizontal, vertical, and combined). A statistical regression model was used to find if there was a significant correlation between patient/implant characteristics and the pattern of bone loss. Results: A total of 304 charts with 540 implants met the inclusion criteria. One randomly selected implant per patient through Microsoft Excel software was included in this study. Of these, 157 (51.6%) of examined charts were men and 147 (48.4%) were women. The patients' mean age was 63.9 ± 11.4 years (range: 27 to 85 years) at implant placement, and implants had been in function for 12 to 120 months (median: 37 months). The percentage of implants that had bone loss was 24.7% (75 out of 304). The pattern of bone loss was 65%, 22%, and 13% for vertical, horizontal, and combined, respectively. Implants that had been placed in surgically bone-grafted sites had increased odds of vertical bone loss with either narrow or wide implants (OR = 2.5 [P = .04] and 3.1 [P = .01], respectively). The presence of adjacent implants had significantly (P = .003) increased odds of horizontal bone loss (OR = 5.1). Conclusion: Approximately one-quarter of dental implants (24.7%) developed bone loss beyond normal physiologic remodeling. Vertical bone loss around single implants was the most common pattern (65%), particularly around implants placed in bone-grafted sites with odds ratio of 2.5 for narrow implants vs 3.1 for wide implants. In the presence of adjacent implants, the odds of horizontal bone loss was 5.1 (P = .003). Keywords: dental implant, pattern of bone loss, peri-implantitis, risk factors

Purpose: Treatment by means of implant-supported immediately loaded fixed full-arch prostheses is known to be related to biologic and technical complications. The aim of this retrospective study was to investigate the prevalence and moment of occurrence of biologic and technical complications happening in immediately loaded fixed full-arch prostheses. Materials and Methods: This study investigated patients who received treatment with immediately loaded fixed full-arch prostheses using four to six implants from 2007 to 2013. The investigation included biologic and technical complications. Complications were depicted regarding their prevalence and their first time of occurrence. Statistical analysis was performed regarding the differences of the mean complication values between the mandible and the maxilla and between technical and biologic complications. Results: The investigation included 482 immediately loaded fixed full-arch prostheses (380 patients, mean observation period: 23.5 months). In 193 arches (40%), either technical (30.9%), biologic (6.5%), or both (3.1%) types of complications occurred. Technical complications occurred significantly more often than biologic complications (P .000). The most frequent technical complication was "fracture of veneering material" (24.7%, arch level). The most frequent biologic complication was "marginal bone loss ≥ 2 mm" (16.3%, implant level). The median first advents of technical complications were after 23/26 months (implant-/prosthesisrelated) and after 3 months for biologic complications, respectively. There was no significant difference of the mean complication rates between the maxilla and the mandible (P = .409). In 99.0% of the arches with complications, the restorations could be obtained. Conclusion: Within this treatment concept, biologic and technical complications may occur over time. However, the vast majority of complications (99.0%) do not affect the overall prosthesis survival. Technical complications are assumed to occur significantly more often than biologic complications. It is suggested that not only stress and material fatigue but also function is a matter concerning this treatment option and, thus, may be a factor related to complication rates. Keywords: immediate function, immediate implants, immediate loading, immediate placement, implant

Purpose: The purpose of this study was the clinical and radiographic evaluation of four-implant-supported fixed prostheses and milled bar overdentures for rehabilitation of the edentulous mandible. Materials and Methods: Thirty-six edentulous participants received four implants in the mandible (two vertical implants in the canine/lateral incisor area and two distally inclined implants anterior to the mental foramina) using flapless surgery. The implants were loaded with the mandibular dentures on the same day after necessary modifications. Three months after implant placement, participants were randomly allocated to one of two groups: (1) the overdenture group, where participants received milled bar overdentures; or (2) the fixed group, where participants received ceramo-metal fixed prostheses. Plaque and gingival indices, pocket depth, implant stability (using Osstell device), and marginal bone resorption (using standardized intraoral radiographs) were evaluated at the time of prosthesis insertion (T0), and 6 (T6) and 12 (T12) months after insertion. Results: The implant survival rate was 100% for both groups. Plaque Index, Gingival Index, pocket depth, implant stability, and bone resorption significantly increased by time for anterior (P .001) and posterior (P .018) implants. Fixed prostheses showed significantly higher Plaque Index, Gingival Index, and pocket depth than milled bar for anterior (P .001) and posterior (P .037) implants. No significant differences in implant stability and bone resorption between groups were noted. For fixed prostheses, anterior implants showed significantly higher Plaque Index, Gingival Index, and pocket depth than posterior implants (P .001) after 12 months. However, no significant differences in implant stability and bone resorption between anterior and posterior implants were noted for both groups. Conclusion: Both fixed prostheses and milled bar prostheses could be used successfully for immediately loaded four-implant rehabilitations of the edentulous mandible, as they were associated with favorable clinical and radiographic outcomes after 1 year. However, milled bar may be more advantageous than fixed prostheses in terms of reduced plaque/ gingival indices and probing depth. Keywords: All-on-4, bone resorption, clinical, implant, milled bar, prosthesis

Purpose: To measure the volume effect on maintaining a sealing around immediately rehabilitated dental implants in a comparison between customized and conventional provisional crowns at a 3-year follow-up. Materials and Methods: A single crown supported by a dental implant was used as a rehabilitation strategy for a failing tooth. The primary predictor was the type of immediate restoration with custom or conventional provisional crowns; a secondary predictor was tooth position: incisor, canine, or premolar. In order to accurately measure the width between buccal and palatal plates at the alveolar margin in a comparison between preoperative (before tooth extraction) and postoperative (at the 3-year follow-up) radiographs, two cone beam computed tomography (CBCT) scans were three-dimensionally analyzed and superimposed. Results: Seventy-six patients, rehabilitated with single implants, were selected (31 implants belonging to the custom group and 45 to the conventional group). In patients treated with conventional restorations, a significant shrinkage (-0.6 ± 1.2 mm with P = .002) was registered. On the other hand, the bone change registered for the custom restoration group appeared negligible, with a nonsignificant and slight increase in width (+0.2 ± 0.7 mm). When the subgroups regarding the implant sites were investigated, the decrease in width was very limited for the canine tooth in the custom group (-0.3 ± 0.2 mm), whereas the shrinkage at the canine in the standard group appeared to be significantly higher (-1.5 ± 0.7 mm with P = .0001). Conclusion: An anatomically contoured provisional restoration may provide a strategy to stimulate peri-implant soft tissue healing, minimize loss of buccal bone plate at the marginal level, and maintain pristine volume in the alveolar bone better than noncustomized restorations. Keywords: CBCT, customized healing restoration, fresh socket implants, immediate loading, prosthetic procedure

Purpose: The aim of this study was to evaluate a new guided drill system (MIPS) for placement of boneanchored hearing systems (BAHS) with respect to cutting performance, generation of heat, and distortion of the bone during drilling and compare it with a conventional drill system (Ponto). Further, the role of irrigation and drilling procedure with respect to the degree of heat generation was evaluated. Materials and Methods: Compact artificial bone was subjected to each drill in the two systems (conventional vs guided) while measuring thrust force, torque, and temperature. The temperature changes, induced during different drilling procedures, were measured by thermocouples positioned 0.5 mm from the periphery of the drill tract. The degree of bone damage was evaluated histologically after drilling in bovine, compact, tibial bone. Results: The mean thrust energy was significantly lower for the drills of the guided system compared with the corresponding conventional drills. In contrast, the mean torque energy was higher using the guided system but only for the initial guide drilling step. Whereas twist drills in combination with a guided drilling approach (MIPS) generated relatively more heat, especially during a prolonged drilling sequence, it was more forgiving in the case of impaired irrigation. The histologic evaluation showed relatively more even cut surfaces and fewer microcracks in the osteotomy wall using the guided system compared with the conventional system. Conclusion: Provided the clinically recommended drilling procedure was adhered to, the absolute temperatures using either a conventional drill system or a guided drill system were below the threshold for thermally induced tissue damage. This study suggests that the guided MIPS system conveys a promising design for an efficient and still-safe osteotomy site preparation for BAHS placement. Keywords: BAHS, bone drilling, bone-anchored hearing system, bone-anchored prosthesis, drill mechanics, flapless procedure, guide, heat generation, osteotomy, surgical guide, surgical procedure

Purpose: To examine the stress values of different bone densities and to compare the tapered and cylindrical implant designs. Materials and Methods: Finite element analysis was used to apply a force of 100 N vertically and at an angle of 30 degrees to implants with a cylindrical or tapered design in D1 and D4 bones in eight separate models. The von Mises and principal stress values obtained from the models were compared, and the optimal stress values were determined and compared with the physiologic stress limit of the bone. Results: Von Mises stress was found to be lower in D1 bone densities, in vertical loading, and in implants with a tapered design. In the case of both implant designs, the von Mises and principal stress values were lower for D1 bone densities. The tapered implant was found to have higher principal stress than the cylindrical implant in both bone densities, while von Mises stress was higher in the cylindrical implant than in the tapered implant. Vertical loading was found to induce less stress than loading at a 30-degree angle. Conclusion: D4 bone density and loading at a 30-degree angle increases von Mises and principal stress more than selection of different implant designs. Keywords: bone density, cylindrical implant, finite element analysis, mandible, tapered implant

Purpose: To evaluate the biomechanical behaviors of different framework materials in implant-supported fixed mandibular prostheses using three-dimensional (3D) finite element analysis. Materials and Methods: A model of a severely resorbed edentulous mandible was obtained from a tomography database. Morse taper-connection implants and multi-unit abutments were cut with an electro-erosion machine and scanned using a 3D scanner. The implants were positioned on the model at the bone level and distributed equally to support a fixed complete prosthesis. The simulations were divided into six groups according to the framework material: titanium (Ti); cobalt-chromium (Co-Cr); zirconia (ZrO2); polyether ether ketone (PEEK); carbon fiber- reinforced polyether ether ketone (CFR-PEEK); and polymethyl methacrylate (PMMA). The resultant load applied was obtained from the masseter, temporal, lateral, and medial pterygoid muscles. The principal stresses and von Mises equivalent stresses were analyzed and compared among the framework materials, and the results were described both quantitatively and qualitatively. Results: PEEK and PMMA frameworks showed the highest total deformation values, showing decreases of von Mises stresses in the frameworks, implants, and abutments, but with a high tensile stress in the trabecular bone that achieved critical values. CFR-PEEK frameworks achieved their failure limit, whereas the ZrO2, Co-Cr, and Ti frameworks exhibited principal stresses in the bone region within physiologic limits. Conclusion: From a biomechanical point of view, the Ti, Co-Cr, and ZrO2 frameworks demonstrated the most favorable outcomes. Keywords: biomechanics, dental prosthesis, finite element analysis, implant-assisted

Purpose: The purpose of this study was to examine the biomechanics of zygomatic implants that were planned on an atrophic maxilla with five different buccal defect types and two different bone types. Materials and Methods: Three-dimensional models of zygomatic implants, human skulls, and maxillary prostheses were modeled with SolidWorks software. Ten finite element models of skulls with five different buccal defect types and two different bone types were constructed to mimic various clinical scenarios. Two bilateral zygomatic implants and two anterior dental implants were inserted into all models. The data were processed by ANSYS Workbench software. Vertical occlusal (150-N) and masseteric (300-N) loads were simulated on a modeled prosthesis. The stresses on and deformations of the bones and implants were then observed and compared. Results: Maximum von Mises stress was found in skulls modeled with a type 4 defect and D3 bone type. Minimal stress values were found in the skull model with a type 1 buccal bone defect and D2 bone type. Displacement values were correlated with stress values. Conclusion: Cortical bone anchorage and bone type of zygomatic implants positively affect their biomechanics. Alveolar crest support has an effective role in the biomechanics of zygomatic implants. Keywords: atrophic maxilla, bone type, finite element analysis, zygomatic anatomy guided approach, zygomatic implant