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PubMed1998

Histologic observations on 230 retrieved dental implants: 8 years' experience (1989-1996).

The histologic examination of dental implants retrieved from humans is important to establish the causal determinants of implant failure, and to compare and validate the results obtained from animal studies. This study presents a retrospective review of the histologic features of 230 implants retrieved in an 8-year period (1989-1996). All the implants were treated to obtain thin (20 to 30 microm) ground sections. The majority of implants were retrieved because of mobility (n=56), peri-implantitis (n=54), or fractures (n=90). Peri-implantitis occurred more frequently before (n=44) than after (n=10) abutment connection. A dense fibrous connective tissue with no inflammatory cells was present at the interface in the implants retrieved for mobility; bone was found only in the most apical part. In many of these implants epithelial cells were present. The main histologic features of peri-implantitis consisted of the presence of a bone sequestrum near the implant, many bacteria present on the implant surface, and an inflammatory infiltrate (macrophages, lymphocytes, and plasma-cells) nearby. Histology showed that in the implants removed for fracture, there was a very high percentage (80 to 100%) of peri-implant bone.

Animals↗
PubMed1999

Single tooth replacement of missing molars: a retrospective study of 78 implants.

As experience with osseointegrated implants has grown, greater use has been made of placement in the posterior jaw. The aim of this study is to present the survival rate of 78 osseointegrated single implants, inserted in the molar area and to evaluate the prosthetic rehabilitation on these teeth. This retrospective study presents findings of 55 consecutive patients with 78 restored single osseointegrated implants in the molar area. The patients went through a clinical and radiological evaluation. The same maxillofacial surgeon inserted all implants. Three of the implants were inserted into the maxilla and 75 into the mandible; 4 of the 78 implants were immediate implants. The cumulative survival rate after one year was 93.6%. Follow-up was up to 80 months, with an average of 27 months. Out of all the implants, 6 failed (7. 7%): 5 failed in the surgical stage, and 1 after prosthetic loading. The main implant failures were among the titanium screw implants. Prosthetic complications occurred in 11 cases (14%), which included loosening of the abutment and/or the crown (9 cases), fracture of the abutment (1 case), and porcelain fracture (1 case). No incident of implant fracture occurred. Within the limits of this study, replacement of a single molar by a single implant is a valid and successful surgical treatment modality, with a high survival rate.

Adult↗
PubMed2001

Fluids and microbial penetration in the internal part of cement-retained versus screw-retained implant-abutment connections.

BACKGROUND: It has been recently observed that in implants with screw-retained abutments, in in vitro as well as in vivo conditions, bacteria can penetrate inside the internal cavity of the implant as a consequence of leakage at the implant-abutment interface. An alternative to screw-retained abutments is represented by implants that can receive cemented abutments. In this case, the abutment goes through a transmucosal friction implant extension (collar) and is cemented inside the internal hexagonal portion of the implant. The aim of the present research was to compare fluids and bacterial penetration in 2 different implant systems, one with cement-retained abutments (CRA) and the other with screw-retained abutments (SRA). METHODS: Twelve CRA dental implants and 12 SRA implants were used in this study. The research was done in 3 steps: scanning electron microscopic (SEM) analysis, fluid penetration analysis, and bacterial penetration analysis. RESULTS: 1) Under SEM it was possible to observe in the SRA implants a mean 2 to 7 micron gap between implant and abutment, while in the CRA implants, the gap was 7 micron. In the latter group, however, the gap was always completely filled by the fixation cement. All the spaces between abutment and implant were filled by the cement. 2) With SRA implants, it was possible to observe the presence of toluidine blue at the level of the fixture-abutment interface and the internal threads; the absorbent paper was stained in all cases. With CRA implants, the absorbent paper inside the hollow portion of the implants was never stained by toluidine blue. No penetration of toluidine blue was observed at the implant-abutment interface and inside the hollow portion of the implants. 3) In all the SRA implant assemblies, bacterial penetration was observed at the implant-abutment interface. No bacteria were detected in the hollow portion of the CRA implants. CONCLUSION: On the basis of the results obtained in the present study using 2 different implant systems, we conclude that CRA implants offer better results relating to fluid and bacterial permeability compared to SRA implants.

Cementation↗
PubMed2002

Influence of the size of the microgap on crestal bone levels in non-submerged dental implants: a radiographic study in the canine mandible.

BACKGROUND: Accumulating evidence suggests that alveolar crestal bone resorption occurs as a result of the microgap that is present between the implant-abutment interface in dental implants. The objective of this longitudinal radiographic study was to determine whether the size of the interface or the microgap between the implant and abutment influences the amount of crestal bone loss in unloaded non-submerged implants. METHODS: Sixty titanium implants having sandblasted with large grit, acid-etched (SLA) endosseous surfaces were placed in edentulous mandibular areas of 5 American fox hounds. Implant groups A, B, and C had a microgap between the implant-abutment connection of <10 microm, 50 microm, or 100 microm, respectively, as did groups D, E, and F, respectively. Abutments were either welded (1 -piece) in groups A, B, and C or non-welded (2-piece screwed) in D, E, and F. All abutment interfaces were placed 1 mm above the alveolar crest. Radiographic assessment was undertaken to evaluate peri-implant crestal bone levels at baseline and at 1, 2, and 3 months after implant placement whereupon all animals were sacrificed. RESULTS: The size of the microgap at the abutment/implant interface had no significant effect upon crestal bone loss. At 1 month, most implants developed crestal bone loss compared with baseline levels. However, during this early healing period, the non-welded group (D, E, and F) showed significantly greater crestal bone loss from baseline to one month (P <0.04) and 2 months (P < 0.02) compared with the welded group (A, B, and C). No significant differences were observed between these 2 groups at 3 months (P > 0.70). CONCLUSIONS: Crestal bone loss was an early manifestation of wound healing occurring after 1 month of implant placement. However, the size of the microgap at the implant-abutment interface had no significant effect upon crestal bone resorption. Thus, 2-piece non-welded implants showed significantly greater crestal bone loss compared with 1-piece welded implants after 1 and 2 months suggesting that the stability of the implant/abutment interface may have an important early role to play in determining crestal bone levels. At 3 months, this influence followed a similar trend but was not observed to be statistically significant. This finding implies that implant configurations incorporating interfaces will be associated with biological changes regardless of interface size and that mobility between components may have an early influence on wound healing around the implant.

Alveolar Bone Loss↗
PubMed2002

The single-tooth implant: a viable alternative for single-tooth replacement.

BACKGROUND: The use of dental implants for single-tooth replacement cases introduces a challenge to the performance of these restorations. Clinical data suggest that single-tooth implant restorations do not benefit from lateral support from the surrounding dentition as do bridged implants, and that these restorations are subjected to greater masticatory forces. Therefore, single-tooth implants are exposed to an increased risk of failure. This prospective clinical trial was designed to evaluate the cumulative success rate of dual acid-etched single-tooth replacement implants in two clinical centers. METHODS: The study protocol included 59 patients between 19 and 73 years. Implants were evaluated for mobility, infection, and crestal bone loss from 30.9 to 60 months. RESULTS: Seventy-one (71) implants were placed in 59 patients, 20 male and 39 female. Forty-seven (47) were placed in the maxilla and 24 in the mandible. The percentages of anterior and posterior implants were 45.1% and 54.9%, respectively. A total of 13 (18.4%) implants were placed in soft, poor quality (Type IV) bone. Beginning 1 month post-implant placement, cases were followed for 30.9 to 60 months with a mean follow-up of 45.9 months. One implant failed (peri-implant infection) yielding an overall success rate of 98.6%. CONCLUSIONS: This success rate for single-tooth replacement dual acid-etched implants compares favorably with bridged implants and with success rates of other single-tooth implant studies. Dual acid-etched implants performed well even under conditions of poor quality bone, where concomitant bone augmentation was performed, and when used for immediate replacement of extracted teeth.

Acid Etching, Dental↗
PubMed2004

Immediate implants supporting single crown restoration: a 4-year prospective study.

BACKGROUND: The placement of implants at the time of tooth extraction has several clinical advantages, such as preservation of the alveolar ridge width and height and reduction of the restorative treatment time. The aim of this study was to evaluate the cumulative success rate of dental implants placed in fresh extraction sockets with and without guided bone regeneration (GBR) used to support a single crown restoration. All of the patients were preselected as candidates for implants. METHODS: Ninety-five patients aged 20 to 68 years with 163 implants were included. All patients were partially edentulous and participated in a personally tailored recall schedule. The follow-up period was 48 months. Patients underwent a clinical and radiographic evaluation annually. RESULTS: The 4-year cumulative success rate was 97%. Five of the 163 implants failed, two during the initial healing time, which were considered early failures and three a year after prosthetic rehabilitation, which were considered late failures. No failure of prosthetic rehabilitation was observed. CONCLUSIONS: Implants placed into fresh extraction sockets with or without regenerative procedures and used to support single crown prosthesis showed a very high cumulative success rate (97%) in a 4-year prospective study. Several observations should be made: 1) all the patients were preselected as candidates for implants and were following a strict oral hygiene regimen; 2) all efforts were made to reduce the number of cases requiring GBR procedures; 3) all the implants had an acid etched/sandblasted implant surface; and 4) all the prosthetic restorations were single crowns.

Adult↗
PubMed2004

Effects of implant thread geometry on percentage of osseointegration and resistance to reverse torque in the tibia of rabbits.

BACKGROUND: Dental implant thread geometry has been proposed as a potential factor affecting implant stability and the percentage of osseointegration. Therefore, the aim of this prospective, randomized, parallel arm study was to evaluate the effects of dental implant thread design on the quality and percent of osseointegration and resistance to reverse torque in the tibia of rabbits. METHODS: Seventy-two custom-made, screw-shaped, commercially pure titanium implants (3.25 mm diameter x 7 mm length) were placed in the tibiae of 12 white New Zealand rabbits. Each tibia received three implants of varying thread shapes: one with a V-shaped, one with a reverse buttress, and one with a square thread design. The rabbits were sacrificed following an uneventful healing period of 12 weeks. Implants in the right tibiae underwent histologic and histomorphometric assessments of the bone-to-implant contact (BIC) and the radiographic density of surrounding bone, while implants in the left tibiae were used for reverse-torque testing. Differences between the three thread designs were examined using analysis of variance (ANOVA). RESULTS: Data showed that the square thread design implants had significantly more BIC and greater reverse-torque measurements compared to the V-shaped and reverse buttress thread designs, while no differences were found in radiographic bone density assessments. CONCLUSION: These results indicate that the square thread design may be more effective for use in endosseous dental implant systems.

Analysis of Variance↗
PubMed2005

Resonance frequency analysis of one-stage dental implant stability during the osseointegration period.

BACKGROUND: Currently, there is no available clinical tool to evaluate the amount of osseointegration and stability around dental implants. It has been recently suggested that changes in the stiffness of an implant in bone during healing may be monitored by using resonance frequency analysis (RFA). The aim of this study was to determine whether RFA can be integrated into the routine clinical evaluation of initial healing of dental implants. METHODS: Thirty-one patients (18 female and 13 male; mean age of 51.7 years) were included into this study. A total of 122 implants and three different, but comparable, implant designs were evaluated by using RFA. The specific transducer for each implant system was used. ISQ (implant stability quotient) readings were obtained for each implant at the time of surgery, 3 and 6 weeks postoperatively, and at the time of loading (3 or 6 months following surgery). Data were analyzed for different healing times, various anatomical locations, implant length, and type. Average time in function was 12 months. RESULTS: Two implants failed during healing. Implant stability was higher on the mandible compared to the maxilla for each implant system studied (Mann-Whitney test, P <0.01). ISQ readings decreased significantly at 3 and 6 weeks post-surgery compared to readings obtained at surgery (Wilcoxon matched pairs sign-rank tests, P <0.01). A recovery to the initial ISQ levels was noted at the time of implant loading. The possible effects of different types and lengths of implants to ISQ readings were examined. CONCLUSIONS: Results of this study support the need for a clinical tool to evaluate dental implant stability prior to loading, especially for implants placed in the maxilla. It appears that implant stability is weakest at 3 to 6 weeks in one-stage non-loaded dental implants. ISQ readings can be used to determine different healing phases and the stability of dental implants. However, it is difficult to define a general standardized range of ISQ readings for successful implant integration for various implant systems. Thus, RFA values/ISQ levels should be calibrated for each implant system separately. Further studies are needed to compare the early changes seen in immediately loaded dental implants and to determine whether there is any time in which the total recovery in ISQ levels may occur.

Dental Implantation, Endosseous↗
PubMed2005

Progression of experimental chronic peri-implantitis in dogs: clinical and radiographic evaluation.

BACKGROUND: The aim of this study was to evaluate the progression of experimental peri-implantitis in dogs using implants with different surface coatings. METHODS: Thirty-six dental implants with four different surface coatings, commercially pure titanium (cpTi), titanium plasma sprayed (TPS), hydroxyapatite (HA), and acid-etched (AE), were placed in six mongrel dogs. Five months after implantation, peri-implantitis was induced by cotton ligatures to facilitate plaque accumulation for 60 days. After 60 days, the ligatures were removed and supragingival plaque control was initiated for 12 months. Probing depth (PD), clinical attachment level (CAL), vertical bone level (VBL), horizontal bone level (HBL), and mobility were obtained at baseline, and 20, 40, 60 (acute phase), and 425 days (chronic phase) after ligature removal. RESULTS: PD and CAL changed around all implant surfaces after ligature placement (P<0.0001). However, the means of PD and CAL were not statistically significant among the different surfaces (P>0.05). The range of CAL variation, calculated between baseline and 60 days (acute phase) and between 60 and 425 days (chronic phase), decreased (P<0.05). Bone loss increased during the entire experiment (P<0.0001). The HA surface showed the greatest bone loss measurement (5.06+/- 0.38 mm) and the TPS showed the smallest bone loss (4.27+/- 0.62 mm). However, statistical significance was not assessed for different coatings (P>0.05). CONCLUSIONS: The clinical data at the initial phase showed rapid and severe peri-implant tissue breakdown. However, removal of ligatures did not convert the acute destructive peri-implant phase to a non-aggressive lesion and the progression of peri-implantitis was observed at chronic phase. The experimental peri-implantitis in dogs may be a useful model to evaluate the progression of peri-implantitis.

Acid Etching, Dental↗
PubMed2006

Peri-implant bone organization under immediate loading state. Circularly polarized light analyses: a minipig study.

BACKGROUND: Immediate loading of dental implants is currently one of the most examined topics in implant dentistry. Using screw implants with a microstructured surface and bone-quality-adapted insertion procedures, osseointegration is achieved when implants are initially stable and when splinted with the superstructure. Despite reported success, there is a shortage of information relating to remodeling and peri-implant bone formation with immediately loaded implants. METHODS: Four to six immediately loaded and unloaded dental implants with a microstructured surface were placed in the mandible and the maxilla in seven minipigs. A total of 85 implants were placed. After a 4-month healing period, all implants were retrieved. Histomorphometry was performed using a light microscope in transmitted polarized light connected to a high-resolution video camera interfaced to a monitor and personal computer. This optical system was associated with a digitizing pad and a histomorphometry software package with image capturing capabilities. RESULTS: Implants showed osseointegration if the average insertion torque of the implants within one bridge was >35 Ncm. If the primary stability of the bridge was <35 Ncm, all implants in the quadrant were lost after 4 months. The multivariate discriminant analysis showed the highest correlation for implant stability by bridge insertion torque (BIT), localization (mandible or maxilla), and implant insertion torque (IIT) as success parameters. The loaded implants displayed collagen fibers, which were oriented in a more transverse way. In addition, a higher quantity of secondary osteons was present. In comparison, the unloaded implants had collagen fibers with a more parallel orientation, and a higher quantity of marrow spaces was present. CONCLUSIONS: When observed after 4 months, immediately loaded implants showed a higher degree of bone formation and remodeling in comparison to unloaded implants. Immediately loaded implants also demonstrated a prevalence of transversely oriented collagen fibers in the peri-implant bone. In this animal model, an average insertion torque of the implants within one bridge>35 Ncm was associated with the most successful implants.

Animals↗
PubMed2006

Effects of sinus membrane perforations on the success of dental implants placed in the augmented sinus.

BACKGROUND: Maxillary sinus lifting procedure enables clinicians to place implant-supported prostheses even in cases with very limited vertical bone height of the maxillary sinus. The aim of this study was to evaluate the implant success with regard to effects of the sinus membrane perforations that occurred during sinus lifting surgery. METHODS: The study group consisted of 91 patients (29 females and 54 males) with edentulous posterior maxilla. Implant placement combined with sinus lifting surgery was performed, and 259 implants were inserted. Sinus membrane perforations were detected in 12 sinus sites. After proper treatment of perforations, 26 implants were placed into perforated sinus areas. Baseline panaromic radiographs were taken before the beginning of prosthetic treatment. Panaromic radiographs taken at the last recall were used for evaluation and compared to the baseline panaromic radiographs using image analysis software to reveal the peri-implant resorption rate for the implants placed in perforated and non-perforated sinus area. The modified sulcus bleeding index and plaque index were used for the assessment of soft tissue conditions. RESULTS: Eleven implants were lost during the follow-up period, resulting in an overall survival rate of 95.9%. Two failures occurred in the group with sinus perforations. There was no statistically significant difference regarding peri-implant bone resorption (P = 0.778) and soft tissue conditions for implants placed into perforated-augmented sinus areas and augmented sinus areas. CONCLUSION: Within the limits of this study, perforation of the sinus membrane did not compromise the osseointegration process or the success of dental implants placed in the augmented maxillary sinus.

Adult↗
PubMed2006

A retrospective evaluation of 1,387 single-tooth implants: a 6-year follow-up.

BACKGROUND: The aim of this study was to evaluate the overall survival rate and factors that affect the clinical outcome of 1,387 consecutively placed implant-supported single restorations up to 6 years. METHODS: During 6 years (1999 to 2005), 1,387 implants were placed in 1,215 subjects (1,073 males and 142 females) who required single-tooth replacements. The average time from implant placement was 2.7 +/- 3.27 years. Implants were mostly placed in the maxillary premolar area (39.5%) followed by the anterior maxillary area (28.7%). Implant survival and location, need for bone augmentation, and implant dimensions were recorded and analyzed. RESULTS: Failed implants totaled 96, resulting in an overall survival rate of 93.1%. The vast majority of failures (94.8%) occurred during the first year following implant placement. Bone augmentation was performed in 9.7% of the implants with a 92.5% survival rate, similar to the survival rate of non-augmented areas (93.1%; P = 0.79). The average implant length was 13.3 mm, ranging from 8 to 16 mm. Longer implants (> or =11 mm) showed similar survival rates as implants <11 mm (93.2% versus 90.2%, respectively; P = 0.4). Implant width ranged between 3.25 to 5 mm (mean 3.9), with no effect on implant survival (P = 0.43). There was a significant difference in implant survival according to the anatomic zone of implant placement (P = 0.0075). The maxillary premolar area showed the highest survival rate (96.2%). CONCLUSION: Implant-supported single-tooth replacement is a predictable procedure with good survival rates up to 6 years.

Adult↗
PubMed1992

The corrosion behavior of Nd2Fe14B and SmCo5 magnets.

Rare earth magnets have corrosive problems associated with their use in prostheses in various fields including orthodontics. The purpose of this study is to investigate the corrosion behavior of an Nd2Fe14B magnet and a SmCo5 magnet in an oral environment. The relations among the attractive force changes, the released elements, the weight changes and the anodic polarization measurements of the magnets were examined under immersions in 1% NaCl, 1% lactic acid, 0.05% HCl, 0.1% Na2S and Greenwood's artificial saliva at 37 degrees C for forty-two days. The results showed that the rare earth magnets underwent high corrosive assaults and large attractive force reductions by the immersions in 1% lactic acid and 0.05% HCl. The problem of corrosion of the magnets could be overcome by sealing them within laser-welded stainless steel capsules.

Corrosion↗
PubMed2004

Bond strength of permanent cements in cementing cast to crown different core build-up materials.

The purpose of this laboratory investigation was to evaluate the bond strength of permanent cement (Duo-cement Kit, Meron, Durelon) to commonly used core build-up materials (President, Dyract AP, Ionofil, Vitremer). Sixty specimens (five of each product) were fabricated as a canine core build- up. Full crown castings were made to fit each core specimen. Full crown castings were cemented to core samples and stored at 37 degrees C and 100% humidity for 10 days. After storage, the bond strength was measured with a Haunsfield tensometer in tensile mode at a crosshead speed of 5 mm/min. Statistical evaluation was performed with univariate analysis of variance (P<0.001). The cement types affected the bond strength of full crown castings to core materials (F: 14.80; P<0.001). The interaction between the cement and core materials was significant (F: 3.69; P<0.01). According to the Duncan's test it was found that the values of Duo-cement were statistically different from the other cements.

Analysis of Variance↗
PubMed2005

Effect of heat history on the corrosion of ferritic stainless steels used for dental magnetic attachments.

This study investigated the effect of heat history on the corrosion of keepers used for dental magnetic attachments. Ferritic stainless steels of SUS 444 and 447J1 were prepared with heat treatments in the temperature range of 550-850 degrees C for 1-5 hours. The stainless steels were electrochemically and metallurgically examined by anodic polarization curves in a 0.9% NaCl solution and by microstructural observation using an electron probe microanalyzer with WDS. Heating both kinds of stainless steel at 650-750 degrees C for two hours or more led to the deterioration of their corrosion resistance. For example, there was evidence of a reduction in the breakdown potentials and an increase in the current densities of the anodic polarization curves. These phenomena were attributed mainly to the precipitation of the sigma (FeCr) or chi (Fe18Cr6Mo5) phase, which sometimes resulted in intergranular corrosion. When dental alloys are cast in investment molds embedding the keepers, the heat time required for thermal expansion of the molds should be kept under one hour.

Chromium↗
PubMed2005

Effect of acidic primers on bonding three magnetic steel alloys with tri-n-butylborane initiated methacrylic resin.

The purpose of this study was to evaluate the effect of acidic primers on bonding magnetic steel alloys. Three alloys (XM27, 447J1, and AUM20) were primed with one of the following materials: Acryl Bond, Estenia Opaque Primer, Eye Sight Opaque Primer, M. L. Primer, or Super-Bond liquid. The specimens were bonded with a tri-n-butylborane initiated resin, and bond strength was determined both before and after thermocycling in water. Unprimed specimen was considered as the control. Average bond strength varied from 0 to 45.3 MPa for the XM27 alloy, 0.3 to 43.6 MPa for the 447J1 alloy, and 0.5 to 41.1 MPa for the AUM20 alloy. Of the five primers, Estenia Opaque Primer exhibited better adhesive performance than the other materials regardless of the type of steel alloy. It can be concluded that the use of the Estenia Opaque Primer, which contains an adhesive monomer (10-methacryloyloxydecyl dihydrogen phosphate; MDP), is recommended for bonding the three magnetic steel alloys with TBB-initiated resin.

Acid Etching, Dental↗
PubMed2006

Effect of resin coating on adhesion of composite crown restoration.

The purpose of this study was to evaluate the effect of a resin coating technique on the microtensile bond strength (microTBS) of resin cement to dentin in composite crown restorations. Crown preparations were done on human molars. A resin coating material, Hybrid Bond, was immediately applied to the prepared dentin and light-cured, while the tooth without resin coating acted as the control. An impression of the resin-coated tooth was taken, and a composite crown fabricated on the working cast. The composite crown was then bonded with a resin cement, Chemiace II. MicroTBSs were measured at a crosshead speed of 1 mm/min, and the resin-coated group yielded significantly higher microTBSs than the non-coated group (p < 0.05). In terms of microTBS values between the axial and occlusal surfaces, no regional differences in resin-dentin bond strength were detected (p < 0.05). It was concluded that resin coating with Hybrid Bond significantly improved the microTBS of resin cement to dentin in composite crown restorations.

Analysis of Variance↗
PubMed1993

[Clinical evaluation of hydroxyapatite-coated titanium artificial tooth root].

The present study was aimed at evaluating the clinical usefulness of a new type of dental implant, one piece-type artificial root made of a titanic core coated with HAp by plasma-spray coating. A total of 227 artificial roots were implanted in 78 healthy subjects (44 females, 34 males) ranging in age from 17 to 74 years. Each of them was examined on several given occasions by both radiography and a method used in periodontal disease screening. Prognostic observation lasted up to 4 years and 3 months. No implants were rejected in 77 subjects, although marked mobility of the implants resulted in their withdrawal in 1 subject (2 implants). They were functioning favorably during the study period, affording great satisfaction to the subjects. No side effects were found in any of the subjects excluding one case of oral lichen planus in which the presence of a direct cause-effect relation remained unclear. From the above results, we conclude that this new type of artificial root is of extremely high clinical use.

Adolescent↗