Mucosal adhesion phenomenon after maxillary sinus floor elevation: A preclinical study.

AIM: To describe the histological events that occur after maxillary sinus floor elevation when the elevated and undetached sinus mucosa are in close proximity or in contact with each other. MATERIALS AND METHODS: From 76 rabbits, 152 elevated maxillary sinuses were analyzed histologically. Sites without adhesions were classified as "No proximity," whereas the adhesion stages were divided into "Proximity," "Fusion," and "Synechia stages." The width of the pseudostratified columnar epithelium and the distance between the two layers of the elevated and undetached sinus mucosae were measured at various standardized positions. RESULTS: Thirty-one sites presenting with adhesions were found. Twelve sites were in the proximity stage," presenting cilia of the two epithelial layers that were shortened and interlinked within the mucous context. Hyperactivity of the goblet cells was also observed. In the other cases, the hyperplastic epithelium showed attempts to reach the contralateral mucosa. The 15 "fusion stage" sites presented regions with epithelial cells of the two mucosal layers that penetrated each other. Four sites presented "synechiae stages," represented by bridges of connective tissue connecting the two lamina propria. CONCLUSIONS: Close proximity or tight contact between the elevated and undetached mucosa adhering to the bone walls might occur after maxillary sinus floor elevation. This induced hyperplasia of the epithelial cells and adhesion of the two layers until synechiae formation.

Evaluation and comparison of histologic changes and implant survival in extraction sites immediately grafted with two different xenografts: A randomized clinical pilot study.

OBJECTIVES: The purpose of this prospective, single-center randomized pilot study was to histologically evaluate and compare vital bone development in premolar and molar-extraction sites grafted with two different bovine-derived xenografts. The secondary outcome of interest was implant survival in the grafted sites. MATERIALS AND METHODS: Adult patients in need of at least two tooth extractions were enrolled. A paired design was used; each patient received at least one of each type of graft at different sites. Each extraction site was randomized to one of two xenograft treatment groups. A resorbable membrane was always placed, and primary intention soft tissue closure was achieved. Four months later, implants were placed and a trephine drill was used to remove bone cores for histologic and histomorphometric analysis. RESULTS: Sixteen patients with 40 extraction sites were enrolled; 20 sites were grafted with one type of xenograft and 20 with another. Mean patient age was 53.5 years, and 65% of patients were male. Evaluation of bone core samples taken from grafted sites showed no significant difference in the mean value of percentage of new bone formation between the different grafted sites (33.4% and 32.4%, p = .76). Cumulative implant survival was 97.5% at the 24-month follow-up visit. CONCLUSION: Within the limitations of this pilot study, no statistically significant differences in new bone growth between sites grafted with two different types of xenograft were found. Both graft materials promoted the formation of new bone and provided osseous support for implant placement after socket grafting.

Biological and mechanical complications of angulated abutments connected to fixed dental prostheses: A systematic review with meta-analysis.

OBJECTIVES: To evaluate the biological and mechanical complications of angulated abutments on full-arch and partial jaw rehabilitations with a follow-up for at least 1 year. METHODS: Electronic search was carried out in MEDLINE, EMBASE and Web of Science. Studies published between January 2000 and January 2019 were included. The quality of the included studies was assessed. The data extraction was focused on implant loss, marginal bone loss and mechanical complications, and meta-analyses were performed for marginal bone loss, mechanical complications and implant failure. RESULTS: Nine studies, three prospective and six retrospective cohort studies were included. They reported on 797 patients that received 4127 implants. The total number of abutments was 4079 of which 1673 were angulated, and 2406 were straight. All abutments were prefabricated. Angulated abutments were associated with increased implant failure rates (two studies; RR = 7.30; 95% CI = 2.79-19.08) and an effect that was both statistically significant (P < .001) and clinically relevant. Three studies reported differentiated data for mechanical and technical complications at 1 year of follow-up, being mostly related to the retention screw while screw fracture. Angulated abutments were associated with a statistically significant increase in MBL 1 year after insertion compared to straight abutments (three studies; MD = 0.08 mm; 95% CI = 0.01-0.14 mm; P = .02), which might be, however, clinically negligible. CONCLUSIONS: The prosthetic complications such as screw loosening and abutment loosening were frequent. After 1 year of follow-up, implants supporting angulated abutments yielded significantly more marginal bone loss than those supporting straight abutments.

Sinus Floor Elevation and Antrostomy Healing: A Histomorphometric Clinical Study in Humans.

OBJECTIVES: To compare the histomorphometric outcomes of biopsies collected from the antrostomy and from the alveolar crest of the maxillary sinus after a sinus-lift procedure. MATERIAL AND METHODS: In 12 volunteers, sinus floor elevation was performed using collagenated corticocancellous porcine bone. Nine months after the surgery, 2 biopsies, 1 from the alveolar crest and 1 from the antrostomy, were collected for histological analysis. RESULTS: Biopsies from 11 patients were available for histological analyses (n = 11). At the alveolar crest sites, the percentage of mineralized bone was 40.1 ± 14.1%, of bone marrow was 40.1 ± 18.0%, and of the xenograft was 14.7 ± 15.2%. Small amounts of soft tissue were found. At the antrostomy sites, the percentages of mineralized bone, bone marrow, and xenograft were 26.0 ± 10.8%, 23.4 ± 17.0%, and 28.2 ± 15.7%, respectively. Soft tissue was represented by 19.7 ± 19.4%. CONCLUSION: Higher amounts of mineralized bone and bone marrow were found in the alveolar crest compared with the antrostomy.

Long-term follow-up of single crowns supported by short, moderately rough implants-A prospective 10-year cohort study.

OBJECTIVES: To evaluate prospectively the clinical and radiographic outcomes after ten years of short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region. MATERIAL AND METHODS: Forty 6 mm modified sandblasted large-grit acid-etched (mod-SLA), soft tissue level implants were installed in the distal segments of 35 consecutive patients. After 6 weeks of healing, abutments were tightened, and single porcelain-fused-to-metal crowns were cemented. Implant survival, marginal bone loss, and clinical crown/implant ratio were evaluated at various time intervals up to 10 years after loading. RESULTS: Two out of the 40 implants were lost before loading, one implant was lost after 7 years because of peri-implantitis. One patient with two implants died and was excluded from analysis. Two patients did not come at the 10-year follow-up and were considered as drop out (2 implants). The survival rate was 91.7% (n = 36). Thirty-three implants were available for marginal bone loss evaluation. A mean marginal bone loss after 10 years of function was 0.8 ± 0.7 mm. Between 5 and 10 years, the loss was 0.2 ± 0.4 mm. No technical complications were registered during the 10-year period. The clinical crown/implant ratio increased with time from 1.6 at the delivery of the prosthesis to 2.0 after 10 years of loading with no increase between 5 and 10 years. CONCLUSION: Short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region and loaded after 6-7 weeks maintained full function for at least 10 years with low marginal bone resorption.

Biological and technical complications of tilted implants in comparison with straight implants supporting fixed dental prostheses. A systematic review and meta-analysis.

OBJECTIVES: To evaluate the implant failure, marginal bone loss (MBL), and other biological or technical complications of restorations supported by tilted and straight implants after at least 3 years in function. METHODS: Electronic and manual searches were performed in MEDLINE, Embase, Web of Science, and OpenGrey to identify clinical studies published up to December 2017. After duplicate study selection and data extraction, the risk of bias was assessed with the ROBINS-I tool. Random-effects meta-analyses of relative risks (RRs) or mean differences (MD) and their 95% confidence intervals (CIs) were performed, followed by subgroup/sensitivity analyses and application of the GRADE approach. RESULTS: A total of 17 nonrandomized studies (eight prospective/nine retrospective) were included. The number of implants of the overall systematic review was 7,568 implants placed in 1,849 patients supporting either full-arch or partial implant prostheses. No difference in the failure of tilted and straight implants was seen (eight studies; 4,436 implants; RR = 0.95; 95% CI = 0.70 to 1.28; p = 0.74), with the quality of evidence being very low due to bias and imprecision. Likewise, no difference in MBL was seen between tilted and straight implants (16 studies; 5,293 implants; MD = 0.03 mm; 95% CI = -0.03 to 0.10 mm; p = 0.32), with the quality of evidence being very low due to bias and inconsistency. Contradictory results regarding implant survival were found from prospective and retrospective studies, which could indicate bias from the latter. CONCLUSIONS: Within the limitations of the present systematic review, no effect of implant inclination on implant survival or peri-implant bone loss was found.

Hard and soft tissue changes around implants activated using plasma of argon: A histomorphometric study in dog.

OBJECTIVE: To histologically assess the hard and soft tissue changes after insertion of cleaned and activated titanium implants using plasma of argon. MATERIALS AND METHODS: Eight dogs were included in this study. The mandibular premolars and first molars were extracted. For each hemi-mandible, four implants, 7 mm long and 3.3 mm of diameter, with a ZirTi surface were used. The surface of two implants was randomly treated with argon plasma (test), while the other two implants were left untreated (control). After 1 month, the same procedure was performed in the contralateral hemi-mandible. The amount of old bone, new bone, overall value of old bone plus new bone, and soft tissue was histologically evaluated. RESULTS: After 1 month of healing, high percentages of new bone in close contact with the implant surface were found at both the treated (60.1% ± 15.6%; 95% CI 56.5%-78.0%) and untreated (57.2% ± 13.1%; 95% CI 49.3%-67.5%) implants. Low percentages of old bone were found at this stage of healing, at both the treated (4.4% ± 3.0%; 95% CI 1.2%-5.4%) and untreated (3.4% ± 3.1%; 95% CI 0.6%-4.9%) implants. Not statistically significant differences were found between groups (p > .05). After 2 months of healing, treated implants presented a significantly higher (p = .012) new bone formation (72.5% ± 12.4%; 95% CI 69.6%-86.8%) compared to untreated sites (64.7% ± 17.3%; 95% CI 59.4%-83.3%). Controversially, no difference (p = .270) in terms of old bone was present between treated (3.1% ± 1.7%, 95% CI 1.8%-4.2%) and untreated implants (3.8% ± 1.9%, 95% CI 3.2%-5.8%). Significant differences (p = .018) in terms of total mineralized bone were found between treated (75.6% ± 13.0%, 95% CI 73.3%-91.3%) and untreated implants (68.4% ± 16.8%; 95% CI 64.2%-87.6%). CONCLUSIONS: Implants treated using plasma of argon was demonstrated to reach a higher bone-to-implant contact when compared to untreated implants.

Reposition of the bone plate over the antrostomy in maxillary sinus augmentation: A histomorphometric study in rabbits.

OBJECTIVE: To test if repositioning the bony plate secured with a cyanoacrylate over the antrostomy in maxillary sinus augmentation was superior to covering the antrostomy with a collagen membrane in terms of the bone augmentation area and the bone density. MATERIAL AND METHODS: After the exposure of the nasal bone in eighteen rabbits, a rectangular access window was prepared with a sonic instrument, and the bony plate was removed. A bilateral sinus mucosa elevation was performed, and the space was filled with a resorbable xenograft. On the test side, the bone plate was repositioned over the antrostomy and fixed with a cyanoacrylate. On the control side, a collagen membrane was placed over the opening. Per group, six animals were sacrificed after 2, 4, and 8 weeks of healing, respectively. Histological ground sections were prepared. RESULTS: The augmented area after elevation decreased between 2 and 8 weeks from 9.4 ± 1.8 to 4.8 ± 2.8 mm2 at the test and from 9.5 ± 2.6 and 5.1 ± 1.6 mm2 at the control sites. Small amounts of new bone were seen after 2 weeks in both groups (~1.6%-2.5%) forming from the bony sinus walls. New bone density increased over time in both groups reaching ~ 10%-11% and ~ 23%-25% after 4 and 8 weeks, respectively. No statistically significant differences were found. Small residual defects were present both at the test sites in the margin of the bone plate, and at the control sites in the center of the antrostomy. CONCLUSIONS: The bone healing in the elevated sinus space was similar irrespective of the coverage of the antrostomy. After 8 weeks, the bone plate repositioned on the antrostomy was incorporated while at the control sites the healing was still incomplete. Residual defects were still present in both groups.

Biomechanical aspects: Summary and consensus statements of group 4. The 5th EAO Consensus Conference 2018.

OBJECTIVES: The aim of the present publication was to report on the EAO Workshop group-4 discussions and consensus statements on the five reviews previously prepared. These reviews provided the scientific evidence on the effect of crown-to-implant ratio, on reconstructions with cantilevers in fully and partially edentulous patients, on biological and technical complications of tilted in comparison with straight implants, and on the effects of osseointegrated implants functioning in a residual dentition. MATERIAL AND METHODS: The group discussed, evaluated, corrected where deemed appropriate, and made recommendations to the authors regarding the following five reviews submitted: (a) Is there an effect of crown-to-implant ratio on implant treatment outcomes?; (b) Implant-supported cantilevered fixed dental rehabilitations in fully edentulous patients; (c) and in partially edentulous patients; (d) Biological and technical complications of tilted implants in comparison with straight implants supporting fixed dental prostheses; (e) What are the adverse effects of osseointegrated implants functioning among natural teeth of a residual dentition? Based on the five manuscripts and the discussion among the group as well as the plenum members, the major findings were summarized, consensus statements were formulated, clinical recommendations were proposed, and areas of future research were identified. RESULTS: Crown-to-implant ratios ranging from 0.9 to 2.2 did not influence the occurrence of biological or technical complications also in single-tooth restorations. Reconstructions with cantilevers for the rehabilitation of fully and partially edentulous jaws showed high implant and reconstruction survival rates. In contrast, the rate of complications-in particular associated with veneering material-was high during the observation period of 5-10 years. The data reported were primarily derived from studies with high risk of bias. The data for single-implant reconstructions were small. There was no evidence that distally tilted implants were associated with higher failure rates and increased amounts of marginal bone loss. The data supporting these findings, however, were at high risk of bias and frequently incompletely reported. Frequent positional changes occurred between the natural teeth and the implant-supported restorations. These changes were more pronounced in younger individuals, and even though they were reduced with age, they still occurred in adult patients. Even though these changes were frequent, potential implications for the patient are unclear. CONCLUSIONS: The use of single-tooth restorations with crown-to-implant ratio in between 0.9 and 2.2 may be considered a viable treatment option. Multiunit reconstructions with cantilevers are a viable treatment option in fully and partially edentulous patients. Clinicians and patients should be aware, however, that complications are frequent and primarily related to resin material used for veneering. There is some evidence that tilting an implant does affect stability of the implant and the surrounding bone. Treatment options to tilted implants should carefully be considered, as the effect on soft tissues and on prosthesis behavior is poorly reported for tilted implants. Positional changes in the dentition in relation to implant-supported restorations occur frequently. The patient should be informed about the possible need for a treatment related to these changes in the long term.

Use of Combination of Allografts and Xenografts for Alveolar Ridge Preservation Procedures: A Clinical and Histological Case Series.

AIM: To perform a clinical and histomorphometric evaluation of a combination of allograft and xenograft for alveolar ridge preservation (ARP) procedures. METHODS: Seven consecutive cases in need of nonmolar tooth extraction and posterior implant placement were treated by ARP, using a combination of a cortico-trabecular allograft and a mineralized xenograft. All sites received a minimally traumatic tooth extraction, bone graft, collagen membrane placement, and flap closure as possible. Healing time was 4 months for the majority of cases. After tooth removal and just before implant installation, clinical measurements were taken; after the healing time, bone biopsies were taken. RESULTS: All sites healed uneventfully. Bone dimensional changes were small; a mid-buccal vertical bone gain of 1.0 mm (SD, 3.2 mm) and a horizontal bone reduction of 1.6 mm (1.6) were recorded. Histomorphometric analysis showed large variability in percentages of new bone (mean 22.3% [17.3], range: 1.8%-35.2%) and a considerable amount of residual bone graft material (mean 33.2% [13.2], range: 5.5%-45.8%). CONCLUSION: Favorable clinical results were observed after the use of the combined bone graft, although a large variability in tissue proportions was present at 4-month healing time, especially for new mature bone.

Influence of the Presence of Alveolar Mucosa at Implants: A Histological Study in Humans.

OBJECTIVE: To evaluate the influence of the presence or absence of keratinized mucosa on hard and soft tissues around implants. MATERIAL AND METHODS: Sixteen volunteers with edentulous regions in the distal aspect of the mandible participated in the study. In each patient, 2 solid titanium screw-shaped devices, 3.5 mm in diameter and 5 mm long, were installed. The incision of the mucosa was performed in such a way to allow that, after the suture of the flaps, only the alveolar mucosa surround the test sites and the keratinized mucosa surround the control implants. After 3 months of healing, biopsies were retrieved and ground sections were prepared for histological analysis. RESULTS: Eighteen biopsies from 9 patients were collected for analysis. Both buccal bone resorption and most coronal level of osseointegration were higher at the test sites compared with the control sites, the difference between the 2 sites being 0.2 and 0.5 mm, respectively. The difference in the coronal level of osseointegration between the test and control sites was statistically significant. Mineralized bone-to-implant contact was 70.6% ± 10.9% at the test sites and 71.5% ± 9.2% at the control sites. CONCLUSIONS: The presence of alveolar mucosa at implants resulted in a more apical position of the coronal level of osseointegration in respect of the implant margin compared with the presence of keratinized mucosa.

Immediate loading at single crowns and 2-unit bridges supported by implants installed in a healed alveolar bony ridge or immediately after tooth extraction. An experimental study in dogs.

To evaluate presumptive differences in osseointegration at implants installed in healed sites or extraction sockets, supporting either crowns or bridges that were functionally loaded or left unloaded. In six dogs, the mesial roots of the first mandibular molars were treated endodontically. Bilaterally, the teeth were hemisected, and the distal roots extracted. First and second mandibular premolars were extracted as well. After 3 months, the mandibular third and fourth distal roots were extracted after endodontic treatment of the mesial roots. Four implants were installed bilaterally, two in the healed sites corresponding to the second premolar and first molar regions, and two into the extraction sockets. Cobalt-chrome single crowns were prepared and installed in the two most anterior implants, and bridges at the two most posterior implants, bilaterally. A 3-unit bridge was applied to the premolars in the upper jaw only at the loaded sites. All prostheses had a flat occlusal surface and contacts in centric occlusion only at the loaded sites. Three months later, biopsies were retrieved for histological analysis. Higher levels of osseointegration and bone density were observed at the unloaded sites, both at implants installed in healed and post-extraction sites. However, only at implants installed in the post-extraction sites and supporting single crowns, the difference in bone-to-Implant contact was statistically significant. In implant installation immediately following extraction or delayed after three months, osseointegration and bone density were not affected by occlusal contact schemes.

Influence of the Buccal Bone Crest Width on Peri-Implant Hard and Soft Tissues Dimensions: A Histomorphometric Study in Humans.

OBJECTIVE: To histologically evaluate hard and soft tissues adaptation at screw-shaped devices installed at recipient sites in the distal segments of the alveolar edentulous ridge prepared with a buccal bone width of 1 or 2 mm. MATERIAL AND METHODS: Sixteen volunteers received 2 nonsubmerged titanium implants each; after 3 months, biopsies were obtained and processed for histology. The distances between implant shoulder (IS), top of the bony crest (C), coronal level of osseointegration (B), peri-implant mucosa (PM), and apical extension of the junctional epithelium (aJE) were measured. RESULTS: There were no significant statistically differences between test and control sites regarding IS-C, IS-B, PM-IS, PM-B, PM-aJE, aJE-B measurements. The horizontal bone resorption 1 mm below IS was 0.3 ± 0.3 and 1.0 ± 0.7 mm at the test and control sites, respectively. This difference was statistically significant. CONCLUSIONS: Similar hard and soft tissues dimensions were observed in both groups. However, a higher horizontal bone resorption was seen at the control sites. Nonsubmerged implant installation should be performed when a 1 mm buccal bony crest width is present so as to limit the horizontal bone resorption.

Dynamics of osseointegration in various human and animal models - a comparative analysis.

OBJECTIVE: To investigate the sequential events of osseointegration in various model situations. MATERIAL AND METHODS: A series of eight recent sequential studies on the early phases of osseointegration performed in various species analyzing new bone apposition and parent bone resorption at the implant surfaces have been studied. One human, six dog and one rabbit studies were analyzed for old and new bone percentages, assessed at least at 4 periods of the early osseointegration. Data on new and old parent bone in contact with the implant surfaces were collected. The interception point of the two proportions of new and old bone was calculated in terms of osseointegration (y; %) and period of the interceptions (x; days). RESULTS: It has been shown that the interception point of old and new bone proportions was strongly influenced by the choice of the model adopted (human, dog, rabbit), by the density of the surrounding bone (cortical, spongy, trabecular) and by the implant geometry. Implant surface configuration, time of implantation and load influenced the interception point to a lesser degree. The fastest rate of osseointegration was observed in the rabbit model followed by the dog model. The slowest osseointegration rate was seen in humans. Osseointegration was documented best in spongiosa bone when compared to cortical bone. The moderately rough surfaces gave rise to faster osseointegration than did the turned implant surfaces. CONCLUSIONS: The interception points may provide information on efficacy of early osseointegration. The slope of the line (m) is related to the efficacy of bone appositions.

Healing at implants placed in bone of different morphology: an experimental study in dogs.

OBJECTIVE: To study osseointegration at implants installed using a standard bed preparation in sites of different bone morphology. MATERIAL AND METHODS: In six Labrador dogs, all mandibular premolars and first molars were extracted. After 4 months of healing, flaps were elevated, and two recipient sites were prepared in each side of the mandible, one in the second premolar and the other in the molar regions. Bone morphology and final insertion torque were evaluated. Healing abutments were applied, and the flaps were sutured to allow a non-submerged healing. After 4 months, the animals were sacrificed and ground sections were obtained for histomorphometric analyses. RESULTS: At the premolar sites, bone morphology Class 2 and at the molar regions Class 3 or 4 were identified. The final insertion torque was 50-55 Ncm at the premolar and 30-35 Ncm at the molar sites. Mean osseointegration in percentage reached 61.5 ± 11.5% and 63.3 ± 10.1% at the premolar and molar sites, respectively. Mineralized bone density evaluated from the implant surface up to a distance of about 0.6 mm lateral to the implant surface was 63.0 ± 7.4% and 65.4 ± 17.7% at the premolar and molar sites, respectively. CONCLUSIONS: Similar implant bed preparations performed at premolar and molar sites with different bone morphology, yielding insertion torque values of about 30-35 and 50-55 Ncm, respectively, did not affect osseointegration after 4 months at non-submerged implants.

Morphometric evaluation of the early stages of healing at cortical and marrow compartments at titanium implants: an experimental study in the dog.

OBJECTIVE: To study the early sequential stages of tissue composition in the cortical and marrow compartments of the alveolar bone crest at implants with a moderately rough surface. MATERIALS AND METHODS: Three month after tooth extraction in 12 Labrador dogs, full-thickness flaps were elevated in the edentulous region of the right side of the mandible and one implant was installed. The flaps were sutured to allow a fully submerged healing. The timing of the installations in the left side of the mandible and of sacrifices were scheduled in such a way to obtained biopsies representing the healing after 5, 10, 20, and 30 days. Ground sections (n = 6 per each healing period) were prepared, and the percentages of osteoid/new bone, old bone, new soft tissues (provisional matrix and primitive marrow), mature bone marrow, vessels, and other tissues (bone debris/particles and clot) were evaluated laterally to the implant surface up to a distance of about 0.4 mm from it. RESULTS: Osteoid/new bone was found after 5 days at percentages of 10.8 ± 4.3% at the marrow and 0.6 ± 0.6% at the cortical compartments. After 30 days, these percentages increased up to 56.4 ± 4.0% and 23.3 ± 6.1%, respectively. Old parent bone was resorbed between 5 and 30 days from 28.7 ± 10.9% to 14.9 ± 3.4% at the marrow (~48% of resorption) and from 81.2 ± 9.4% to 67.6 ± 5.6% at the cortical (~17% of resorption) compartments. All differences were statistically significant. CONCLUSION: Bone apposition to an implant surface followed a significantly different pattern in the compact and the marrow compartments around the implants. While in the compact compartments, bone apposition had to develop through the BMUs following resorption, it developed in very dense layers through an early apposition in the marrow compartments.

Marginal healing using Polyetheretherketone as healing abutments: an experimental study in dogs.

OBJECTIVE: To evaluate the marginal soft and hard tissue healing at titanium and Polyetheretherketone (PEEK) healing implant abutments over a 4-month period. MATERIAL AND METHODS: In six Labrador dogs, all mandibular premolars and first molars were extracted. After 4 months of healing, flaps were elevated, and two implants were installed at each side of the mandible, one in the premolar and the other in the molar regions. Four different types of healing abutments were positioned on the top of each implant: (i) titanium (Ti); (ii) PEEK material bonded to a base made of titanium (Ti-P), randomly positioned in the premolar region; (iii) PEEK, pristine (P); and (iv) PEEK, roughened (P-R), randomly positioned in the molar region. The flaps were sutured to allow a non-submerged healing, and after 4 months, the animals were sacrificed and ground sections obtained for histological evaluation. RESULTS: A higher resorption of the buccal bone crest was observed at the PEEK bonded to a base made of titanium abutments (1.0 ± 0.3 mm) compared to those made of titanium (0.3 ± 0.4 mm). However, similar dimensions of the peri-implant mucosa and similar locations of the soft tissues in relation to the implant shoulder were observed. No statistically significant differences were seen in the outcomes when the pristine PEEK was compared with the roughened PEEK abutments. The mean apical extension of the junctional epithelium did not exceed the implant shoulder at any of the abutment types used. CONCLUSIONS: The coronal level of the hard and soft tissues allows the conclusion that the use of PEEK as healing abutments may be indicated.

6-mm-long implants loaded with fiber-reinforced composite resin-bonded fixed prostheses (FRCRBFDPs). A 5-year prospective study.

AIM: To evaluate the clinical and radiographic outcomes and the survival rates of fiber-reinforced composite resin-bonded fixed prostheses (FRCRBFDPs) placed in the posterior area supported by two short (6 mm) implants. MATERIALS AND METHODS: Twenty consecutive patients received 40 SLActive 6-mm-long implants with a diameter of 4.1 mm (n = 29) or 4.8 mm (n = 11). Insertion torques and RFA (Resonance Frequency Analysis) were measured at implant installation. The prosthetic rehabilitation was performed after 8 weeks from insertion with a screw-retained two- or three-unit fixed dental prosthesis fabricated of FRCRBFDPs. Implant survival rates and marginal bone levels were evaluated at various time intervals until 5 years after loading. RESULTS: Two of 20 patients lost four implants supporting two FRCRBFDPs between the second and the third year of follow-up (cumulative survival rate: 90% after 5 years). Four patients suffered a fracture of the prosthetic reconstruction, and the success rate of the rehabilitation was 70% after 5 years. A mean marginal bone loss of 0.30 ± 0.34 mm was found after 5 years of function at the remaining implants. CONCLUSION: The survival of short implants was 90% owing to two bridges losses in the maxilla. However, the success rate of FRCRBFDPs over 5 years was only at 70%.

Healing at implants installed concurrently to maxillary sinus floor elevation with Bio-Oss® or autologous bone grafts. A histo-morphometric study in rabbits.

OBJECTIVE: To compare the healing at elevated sinus floors augmented either with deproteinized bovine bone mineral (DBBM) or autologous bone grafts and followed by immediate implant installation. MATERIAL AND METHODS: Twelve albino New Zealand rabbits were used. Incisions were performed along the midline of the nasal dorsum. The nasal bone was exposed. A circular bony widow with a diameter of 3 mm was prepared bilaterally, and the sinus mucosa was detached. Autologous bone (AB) grafts were collected from the tibia. Similar amounts of AB or DBBM granules were placed below the sinus mucosa. An implant with a moderately rough surface was installed into the elevated sinus bilaterally. The animals were sacrificed after 7 (n = 6) or 40 days (n = 6). RESULTS: The dimensions of the elevated sinus space at the DBBM sites were maintained, while at the AB sites, a loss of 2/3 was observed between 7 and 40 days of healing. The implants showed similar degrees of osseointegration after 7 (7.1 ± 1.7%; 9.9 ± 4.5%) and 40 days (37.8 ± 15%; 36.0 ± 11.4%) at the DBBM and AB sites, respectively. Similar amounts of newly formed mineralized bone were found in the elevated space after 7 days at the DBBM (7.8 ± 6.6%) and AB (7.2 ± 6.0%) sites while, after 40 days, a higher percentage of bone was found at AB (56.7 ± 8.8%) compared to DBBM (40.3 ± 7.5%) sites. CONCLUSIONS: Both Bio-Oss® granules and autologous bone grafts contributed to the healing at implants installed immediately in elevated sinus sites in rabbits. Bio-Oss® maintained the dimensions, while autologous bone sites lost 2/3 of the volume between the two periods of observation.

Sequential morphometric evaluation at UnicCa® and SLActive® implant surfaces. An experimental study in the dog.

AIM: To study sequential osseointegration around implants with nano-technologically modified surfaces at different periods of healing. MATERIALS AND METHODS: After 3 months, two different implant systems with different nano-technologically modified surfaces were randomly installed in the edentulous molar regions of the mandible of 12 dogs. One surface was acid-etched surface, and subsequently modified with calcium ions (UnicCa® ), while the other was a hydrophilic sandblasted with large grit and acid-etched (SLActive® ) surface. The implants were fully submerged, and biopsies were obtained representing the healing after 1, 2, 4 and 8 weeks (n = 6 per period). A morphometric evaluation of densities of new soft tissues (provisional matrix and immature bone marrow), new and old bone, mature bone marrow, vessels and other tissues (bone debris/particles and clot) was performed in the spongiosa compartment of the sites of implantation. RESULTS: After 1 week of healing, the soft tissues, mainly composed of provisional matrix, were present at 41.5 ± 23.9% and 30.1 ± 20.0% at the UnicCa® and SLActive surfaces, respectively. These percentages were >40% at both surfaces after 2 weeks of healing, presenting greater amount of immature bone marrow. Subsequently, these percentages decreased up to disappear after 8 weeks of healing. New bone increased progressively between 1 and 8 weeks of healing from 8.2 ± 3.0% to 77.1 ± 6.4% and from 6.8 ± 2.8% to 67.9 ± 6.8% at the UnicCa® and SLActive® , respectively. Old bone decreased progressively over time. CONCLUSIONS: The patterns of healing at highly hydrophilic surfaces occurred through the early formation of a provisional matrix followed by the formation of new bone and marrow at various stages of maturation. The healing was similar to those described in different animal models, anatomical sites and surgical procedures.