Lateral Ridge Augmentation Using Autogenous Block Grafts and Guided Bone Regeneration: A 10-Year Prospective Case Series Study.

BACKGROUND: The use of autogenous block grafts harvested from intraoral donor sites has proven to be effective for the reconstruction of horizontal bone defects. PURPOSE: The objective of this study was to analyze implant success and the rate of block graft resorption 10 years after ridge augmentation to elucidate contributing factors influencing graft maintenance. MATERIALS AND METHODS: A staged horizontal block graft augmentation was performed in 52 implant sites exhibiting severe horizontal bone atrophy using autogenous block grafts protected by DBBM and collagen membranes. The crest width was assessed intraoperatively at surgery and at re-entry after 6 months. At the 10 year reexamination clinical and radiographic parameters were assessed using cone beam computed tomography. RESULTS: The 10-year implant success rate amounted to 98.1%, with minimal peri-implant bone loss (-0.17 mm for the maxilla, -0.09 mm for the mandible). The surface resorption rate after 10 years was 7.7% (0.38 mm). Grafts originating from the chin demonstrated significantly better graft maintenance at 10 years compared to retromolar grafts. Recipient site and age had no significant impact on graft resorption, whereas females showed more bone loss at the 10-year examination. CONCLUSIONS: Lateral ridge augmentation using autogenous block grafts and guided bone regeneration demonstrated a favorable success rate of 98.1% with minimal block graft resorption of 7.7% after 10 years. Modulating factors were origin of the graft and gender.

Osseointegration of Zirconia in the Presence of Multinucleated Giant Cells.

BACKGROUND: Current strategies to reduce medical device-associated infections propose zirconia as a potential implant material which may limit bacterial adhesion. Because multinucleated giant cells (MNGCs) have been detected on these implant surfaces, concerns have been raised regarding tissue integration. PURPOSE: The present study examined the presence of MNGCs and their subsequent effect upon tissue integration. Surface-modified implants made of yttria-stabilized (TZP) and alumina-toughened zirconia (ATZ) were compared with commercially pure titanium (Ti). MATERIALS AND METHODS: Seven miniature pigs received three implants on either side of the maxilla. After healing periods of 4 and 8 weeks, the tissue response at the implant surfaces was characterized according to three specific parameters: bone-to-implant contact (BIC), MNGC-to-implant contact (MIC), and the peri-implant bone density (BD). RESULTS: Despite being present on all tested implant surfaces, MNGCs were not associated with an inflammatory cell infiltrate or with fibrous encapsulation. MNGCs were less numerous on the Ti implants (range: 3.9-5.2%) compared with the ceramic implants (range: 17.6-30.3%, p < .0001). Even though the values of newly formed bone and pristine bone in direct contact with the implant surfaces were high at 4 weeks (tBIC: Ti = 82.3%, TZP = 64.3%, ATZ = 70%), a negative correlation was observed between the presence of MNGCs and newly formed bone at the implant surface (p < .001). Interestingly, the newly formed peri-implant bone density, defined as the percentage of new bone area inside the screw threads (nBD), was not diminished by the presence of MNGCs. CONCLUSIONS: Differences in the presence of MNGCs and the BIC parameters between Ti and the ceramic implants appear to be a local cellular phenomenon which is restricted to the implant-bone marrow interface and do not affect the peri-implant bone formation. Factors triggering MNGC differentiation and their persistence in response to biomaterial surface need to be investigated in future studies.

Numerical assessment of bone remodeling around conventionally and early loaded titanium and titanium-zirconium alloy dental implants.

The aim of this study was to investigate conventionally and early loaded titanium and titanium-zirconium alloy implants by three-dimensional finite element stress analysis. Three-dimensional model of a dental implant was created and a thread area was established as a region of interest in trabecular bone to study a localized part of the global model with a refined mesh. The peri-implant tissues around conventionally loaded (model 1) and early loaded (model 2) implants were implemented and were used to explore principal stresses, displacement values, and equivalent strains in the peri-implant region of titanium and titanium-zirconium implants under static load of 300 N with or without 30° inclination applied on top of the abutment surface. Under axial loading, principal stresses in both models were comparable for both implants and models. Under oblique loading, principal stresses around titanium-zirconium implants were slightly higher in both models. Comparable stress magnitudes were observed in both models. The displacement values and equivalent strain amplitudes around both implants and models were similar. Peri-implant bone around titanium and titanium-zirconium implants experiences similar stress magnitudes coupled with intraosseous implant displacement values under conventional loading and early loading simulations. Titanium-zirconium implants have biomechanical outcome comparable to conventional titanium implants under conventional loading and early loading.

A pilot study of joint stability at the zirconium or titanium abutment/titanium implant interface.

PURPOSE: To compare the interfaces of loaded and unloaded zirconium and titanium abutments with titanium implants using scanning electron microscopy (SEM). MATERIALS AND METHODS: Zirconium and titanium abutments (n = 5 per group; four test and one control) were torque-tightened into titanium implants secured into metal blocks, and computer-aided design/computer-assisted manufacture-based zirconium oxide copings were fabricated and cemented to the abutments with temporary resin-based cement. Specimens of each restoration were subjected to cyclic axial and lateral loading of 30 N at 2 Hz for 500,000 cycles using a servohydraulic test system; control specimens were left unloaded. Then, the abutment/implant assemblies were embedded in acrylic resin, sectioned longitudinally along the midline, and inspected under SEM with x-ray microanalysis. RESULTS: Loosening or fracture of the copings and implant components was not observed after dynamic loading in both groups. SEM and x-ray microanalysis revealed unexpected microleakage of acrylic resin at the interface. Acrylic resin in the implants tightened to the titanium abutments was limited to the cervical part, and the components displayed scratched and smashed regions, suggesting slight deformation of the implant neck. Microleakage and pooling of acrylic resin were observed approaching the screw joint in loaded implants tightened to zirconia abutments, and the amount of microleakage was greater than in the unloaded control specimens, which had a larger microgap than the titanium abutment/titanium implant interface. Loaded zirconia abutments were associated with wear, scratches, and, in one sample, chipping. CONCLUSIONS: Zirconium abutment/titanium implant interface may be susceptible to wear of the abutment coupled with deformation of the implant neck greater than that associated with the conventional titanium abutment/titanium implant interface under dynamic loading.

CAD/CAM glass ceramics for single-tooth implant crowns: a finite element analysis.

PURPOSE: To evaluate the load distribution of CAD/CAM mono-ceramic crowns supported with single-tooth implants in functional area. MATERIALS AND METHODS: A 3-dimensional numerical model of a soft tissue-level implant was constructed with cement-retained abutment to support glass ceramic machinable crown. Implant-abutment complex and the retained crown were embedded in a Ø 1.5 × 1.5 cm geometric matrix for evaluation of mechanical behavior of mono-ceramic CAD/CAM aluminosilicate and leucite glass crown materials. Laterally positioned axial load of 300 N was applied on the crowns. Resulting principal stresses in the mono-ceramic crowns were evaluated in relation to different glass ceramic materials. RESULTS: The highest compressive stresses were observed at the cervical region of the buccal aspect of the crowns and were 89.98 and 89.99 MPa, for aluminosilicate and leucite glass ceramics, respectively. The highest tensile stresses were observed at the collar of the lingual part of the crowns and were 24.54 and 25.39 MPa, respectively. CONCLUSION: Stresses induced upon 300 N static loading of CAD/CAM aluminosalicate and leucite glass ceramics are below the compressive strength of the materials. Impact loads may actuate the progress to end failure of mono-ceramic crowns supported by metallic implant abutments.

Early-loaded one-stage implants retaining mandibular overdentures by two different mechanisms: 5-year results.

PURPOSE: To compare the biologic and prosthetic outcomes of implants loaded early to retain mandibular overdentures by means of two different attachment systems. MATERIALS AND METHODS: Patients were screened according to specific inclusion/exclusion criteria and randomly allocated to treatment groups involving two-implant-supported early loaded mandibular overdentures retained by ball attachments or Locator attachments. Marginal bone loss, Plaque Index, peri-implant infection, Bleeding Index, prosthetic complications, and Kaplan-Meier survival estimates of the groups were assessed at the 5-year recall. RESULTS: Among the 29 patients (58 implants) who completed the study, one implant was lost during healing; all implants survived after prosthesis delivery. Bone loss in the ball attachment group (0.77 ± 0.05 mm) was significantly greater than that in the Locator group (0.59 ± 0.03 mm). The Plaque and Bleeding indices of both groups were comparable, and peri-implant inflammation scores in both groups were zero for all implants. The frequencies of activation of the matrix, replacement of the matrix, and denture reline in the ball attachment group were significantly higher than those observed in the Locator group. While assessments for the absence of any complication showed that the 1- and 3-year Kaplan-Meier survival probabilities of both groups were comparable, when activation of the retainer was excluded, survival probabilities of the ball attachment group were higher. CONCLUSIONS: The biologic outcomes of early loaded mandibular overdentures retained by ball attachments or Locators were comparable. Although the frequency of prosthetic complications with ball attachments was higher, this did not decrease the survival probability for the treatment.

A prospective, open-ended, single-cohort clinical trial on early loaded Titanium-zirconia alloy implants in partially edentulous patients: up-to-24-month results.

PURPOSE: To evaluate biologic and prosthetic outcomes of titanium-zirconia alloy implants supporting fixed prostheses. MATERIALS AND METHODS: A total of 52 titanium-zirconia alloy implants were placed in 23 consecutive patients with partial edentulism. All implants were subjected to an early loading protocol by means of single-unit or up-to-four-unit fixed partial prostheses and observed between 7 and 24 months. The radiographic marginal bone loss and peri-implant soft tissue scores (Plaque Index, Bleeding Index, and Calculus Index) were recorded. In addition, prosthetic complications were recorded during the period of the study. RESULTS: Early or late implant failures were not observed, resulting in 100% implant survival and success of the implants. No prosthetic complications were observed. The mean (standard deviation) of marginal bone loss for 52 implants was 0.315 mm (0.24 mm). There were no signs of excessive bone loss with or without swelling or suppuration of the peri-implant soft tissue, and the soft tissue scores indicated good soft tissue integration. CONCLUSIONS: Titanium-zirconia alloy implants supporting fixed prostheses showed optimum radiographic, clinical, and prosthetic outcomes in an up-to-24-month assessment period.

Immediate versus conventional loading of implant-supported maxillary overdentures: a finite element stress analysis.

PURPOSE: To compare biomechanical outcomes of immediately and conventionally loaded bar-retained implant-supported maxillary overdentures using finite element stress analysis. MATERIALS AND METHODS: Finite element models were created to replicate the spatial positioning of four 4.1 × 12-mm implants in the completely edentulous maxillae of four cadavers to support bar-retained overdentures with 7-mm distal extension cantilevers. To simulate the bone-implant interface of immediately loaded implants, a contact situation was defined at the interface; conventional loading was simulated by "bonding" the implants to the surrounding bone. The prostheses were loaded with 100 N in the projected molar regions bilaterally, and strain magnitudes were measured at the buccal aspect of bone. RESULTS: The amplitude of axial and lateral strains, the overall strain magnitudes, and the strain magnitudes around anterior and posterior implants in the immediate loading group were comparable to those seen in the conventional loading group, suggesting that the loading regimens created similar stress/strain fields (P > .05). CONCLUSIONS: Conventional and immediate loading of maxillary implants supporting bar-retained overdentures resulted in similar bone strains.

Low-level laser therapy vs. pulsed electromagnetic field on neonatal rat calvarial osteoblast-like cells.

To compare the effects of pulsed electromagnetic field (PEMF) and low-level laser therapy (LLLT) on osteoblast cells in a cell culture model. Fifty thousand neonatal rat calvarial osteoblast-like cells per milliliter were seeded and 0.06 mT PEMF, 0.2 mT PEMF, and LLLT at 808 nm were applied for 24 and 96 h on the cells. To evaluate cellular proliferation and differentiation, specimens were examined for DNA synthesis, alkaline phosphatase (ALP) activity, cell numbers, and viability of the cells. Morphological appearances of the cells were observed using scanning electron microcopy after 24 and 96 h of incubation. At 24 and 96 h, the control group had a higher cell proliferation than 0.06 and 0.2 mT PEMF groups (p=0.001). At 96 h, 0.2 mT PEMF group had higher cell proliferation rate than 0.06 mT PEMF and LLLT groups (p=0.001). The cell count and cell viability in 0.2 mT PEMF group were higher than the 0.06-mT PEMF and LLLT groups, although these differences were not statistically significant at 96 h (p>0.05). At 24 and 96 h, cell viability in the control group was higher than the test groups. Alkaline phosphatase levels of the groups were comparable in both time intervals (p>0.05). 0.2 mT PEMF application on osteoblast-like cells led to cell proliferation and differentiation better than 0.06 mT PEMF and LLLT at 808 nm, although a remarkable effect of both PEMF and LLLT could not be detected. The ALP activity of 0.2 and 0.06 mT PEMF and LLLT were comparable.

Efficacy of resonance frequency analysis in the diagnosis of compromised bone-implant interface.

PURPOSE: To investigate the sensitivity level of resonance frequency analysis (RFA) in the identification of contact loss at compromised bone-implant interfaces. METHODS: Twelve cylindrical acrylic experimental models housing a perpendicularly positioned dental implant were generated. Two different compromised bone-implant interfaces to simulate the loss of bone-to-implant contact were created in 8 models, whereas the resting 4 simulated the intact relationship between implant and bone. Each implant received RFA and subjected to serial sectioning to evaluate bone-acrylic interface microscopically. Implant stability quotient values were statistically compared among groups. Correlation level between the implant stability quotient values and bone-acrylic interface conditions was assessed. RESULTS: RFA was not sensitive to recognize the lack of horizontal contact (approximately 0.276 mm), but it was able be to discriminate the additional loss of approximately 0.1 mm at the bone-implant interface. CONCLUSION: RFA is not a reliable method in the assessment of the initial contact loss at bone-implant interface.

Fatigue resistance of 2 different CAD/CAM glass-ceramic materials used for single-tooth implant crowns.

PURPOSE: To evaluate the fatigue resistance of 2 different CAD/CAM in-office monoceramic materials with single-tooth implant-supported crowns in functional area. MATERIALS AND METHODS: A metal experimental model with a dental implant was designed to receive in-office CAD/CAM-generated monoceramic crowns. Laterally positioned axial dynamic loading of 300 N at 2 Hz was applied to implant-supported crowns machined from 2 different glass materials for 100,000 cycle. Failures in terms of fracture, crack formation, and chipping were macroscopically recorded and microscopically evaluated. RESULTS: Four of 10 aluminasilicate glass-ceramic crowns fractured at early loading cycles, the rest completed loading with a visible crack formation. Crack formation was recorded for 2 of 10 leucite glass-ceramic crowns. Others completed test without visible damage but fractured upon removal. DISCUSSION: Lack in chemical adhesion between titanium abutment and dental cement likely reduces the fatigue resistance of machinable glass-ceramic materials. However, relatively better fractural strength of leucite glass-ceramics could be taken into consideration. Accordingly, progress on developmental changes in filler composition of glass-ceramics may be promising. CONCLUSION: Machinable glass-ceramics do not possess sufficient fatigue resistance for single-tooth implant crowns in functional area.