Prospective Evaluation of 2,549 Morse Taper Connection Implants: 1‐ to 6‐Year Data

Background: The aim of this study is to evaluate the implant survival, the implant–crown success, and the prosthetic complications of 2,549 Morse taper interference–fit connection implants. Methods: A total of 2,549 Morse taper connection implants were inserted in 893 patients from January 2003 until December 2008. At each annual recall, clinical, radiographic, and prosthetic parameters were assessed. The implant–crown success criteria included the absence of pain, suppuration, and clinical mobility; an average distance between the implant shoulder and the first visible bone contact <2 mm from initial surgery; and the absence of prosthetic complications at the implant–abutment interface. Prosthetic restorations were fixed partial prostheses (462 units); fixed full‐arch prostheses (60 units); single crowns (531 units); and overdentures (93 units). Results: The cumulative implant survival rate was 98.23% (97.25% maxilla, 99.05% mandible). The implant–crown success was 92.49%. A few prosthetic complications at implant–abutment interface were reported (0.37%). After 6 years, distance between the implant shoulder and the first visible bone contact was 1.10 mm (± 0.30 mm). Conclusion: The use of Morse taper connection implants represents a successful procedure for the rehabilitation of partially and completely edentulous arches.     

Morse taper connection implants supporting "planned" maxillary and mandibular bar-retained overdentures: a 5-year prospective multicenter study

Objectives: In contrast to the excellent long‐term outcomes described for implant‐supported mandibular overdentures, less favorable long‐term survival and success rates have been reported for maxillary implants supporting overdentures. The aim of this study was to evaluate the treatment outcome of “planned” bar‐retained maxillary and mandibular overdentures supported by Morse taper connection implants, investigating implant survival, peri‐implant tissue health, marginal bone resorption and prosthetic complications. Material and methods: Over a 2‐year period, 60 patients were enrolled in this study, in four different clinical centers. The overdentures (maxilla 38, mandible 34) were planned with support from four implants anchored on a bar. A total of 288 Morse taper connection implants (Leone Implant System^®) were inserted (152 maxilla, 136 mandible). Implants were evaluated 5 years after insertion. Success criteria included the absence of pain, suppuration or clinical mobility, the distance between implant shoulder and first crestal bone–implant contact (DIB) <2 mm and no exudate history. Results: The overall 5‐year implant survival rate was 98% (maxilla 97.4%, mandible 98.6%), with 282 implants still in function. Among these surviving implants, 278 (98.6%) were classified in the success group. At the 5‐year examination, the mean DIB was 0.7 mm (±0.53). Few prosthetic complications were reported. Conclusions: With “planned” bar‐retained maxillary and mandibular overdentures supported by Morse taper connection implants, satisfactory survival and success rate can be achieved. To cite this article:
Mangano C, Mangano F, Shibli JA, Ricci M, Sammons R, Figliuzzi M. Morse taper connection implants supporting “planned” maxillary and mandibular bar‐retained overdentures: a 5‐year prospective multicenter study.
Clin. Oral Impl. Res. 22 , 2011; 1117–1124
doi: 10.1111/j.1600‐0501.2010.02079.x     

The Bacterial Sealing Capacity of Morse Taper Implant–Abutment Systems in Vitro

Background: The use of Morse taper systems in dental implantology has been associated widely with a more precise adaptation between implants and their respective abutments. This may lead to an increase in the stability of the implant system and may also prevent microbial invasion through the implant–abutment interface. The aim of this study was to investigate in vitro the ability of four commercially available Morse taper system units to impede bacterial penetration through their implant–abutment interfaces. Methods: Abutments were screwed onto the implants, and the units were subsequently immersed in Streptococcus sanguinis bacterial broth (1 × 10⁸ colony forming units/mL) for 48 hours. The units were examined by scanning electron microscopy (SEM) under three conditions: 1) with the implant–abutment components assembled as units to investigate for both the existence of microgaps and the presence of bacteria; 2) with the implants and abutments separated for examination of internal surfaces; and 3) with the implant–abutment components again assembled as units to measure any microgaps detected. The mean size of the microgaps in each unit was determined by measuring, under SEM, their width in four equidistant points. Results: Microgaps were detected in all units with no significant differences in dimension (Kruskal‐Wallis test, P >0.05). Within all units, the presence of bacteria was also observed. Conclusion: The seals provided by the interfaces of the commercially available Morse taper implant–abutment units tested were not sufficiently small to shield the implant from bacterial penetration.     

Vertical ridge augmentation of the atrophic posterior mandible with interpositional bloc grafts: bone from the iliac crest vs. bovine anorganic bone. Clinical and histological results up to one year after loading from a randomized-controlled clinical trial

Objectives: To compare two different techniques for vertical bone augmentation of the posterior mandible: bone blocs from the iliac crest vs. anorganic bovine bone blocs used as inlays.
Materials and methods: Ten partially edentulous patients having 5–7 mm of residual crestal height above the mandibular canal had their posterior mandibles randomly allocated to both interventions. After 4 months implants were inserted, and after 4 months, provisional prostheses were placed. Definitive prostheses were delivered after 4 months. Histomorphometry of samples trephined at implant placement, prosthesis and implant failures, any complication after loading and peri-implant marginal bone-level changes were assessed by masked assessors. All patients were followed up to 1 year after loading.
Results: Four months after bone augmentation, there was statistically significant more residual graft (between 10% and 13%) in the Bio-Oss group. There were no statistically significant differences in failures and complications. Two implants could not be placed in one patient augmented with autogenous bone because the graft failed whereas one implant and its prosthesis of the Bio-Oss group failed after loading. After implant loading only one complication (peri-implantitis) occurred at one implant of the autogenous bone group. In 16 months (from implant placement to 1 year after loading), both groups lost statistically significant amounts of peri-implant marginal bone: 0.82 mm in the autogenous bone group and 0.59 mm in the Bio-Oss group; however, there were no statistically significant differences between the groups.
Conclusions: Both procedures achieved good results, but the use of bovine blocs was less invasive and may be preferable than harvesting bone from the iliac crest.     

Influences of internal tapered abutment designs on bone stresses around a dental implant: three-dimensional finite element method with statistical evaluation

Background: The aim of this study is to determine the effects of various designs of internal tapered abutment joints on the stress induced in peri‐implant crestal bone by using the three‐dimensional finite element method and statistical analyses. Methods: Thirty‐six models with various internal tapered abutment–implant interface designs including different abutment diameters (3.0, 3.5, and 4.0 mm), connection depths (4, 6, and 8 mm), and tapers (2°, 4°, 6°, and 8°) were constructed. A force of 170 N was applied to the top surface of the abutment either vertically or 45° obliquely. The maximum von Mises bone‐stress values in the crestal bone surrounding the implant were statistically analyzed using analysis of variance. In addition, patterns of bone stress around the implant were examined. Results: The results demonstrate that a smaller abutment diameter and a longer abutment connection significantly reduced the bone stresses (P <0.0001) in vertical and oblique loading conditions. Moreover, when the tapered abutment–implant interfaced connection was more parallel, bone stresses under vertical loading were less (P = 0.0002), whereas the abutment taper did not show significant effects on bone stresses under oblique loading (P = 0.83). Bone stresses were mainly influenced by the abutment diameter, followed by the abutment connection depth and the abutment taper. Conclusion: For an internal tapered abutment design, it was suggested that a narrower and deeper abutment–implant interface produced the biomechanical advantage of reducing the stress concentration in the crestal region around an implant.     

A retrospective radiographic analysis of bone loss following placement of TiO2 grit-blasted implants in the posterior maxilla and mandible

PURPOSE: Cortical bone is a determinant of implant esthetics and may contribute to the biomechanical integrity of the implant-supported prosthesis. Historically, approximately 1.0 to 1.5 mm of bone loss has occurred immediately following second-stage surgery and implant loading. Recent consideration of implant design suggests that surface topography may affect crestal bone responses at the implant interface. The aim of this retrospective study of 102 implants in 48 subjects supporting posterior fixed partial dentures was to radiographically define the behavior of crestal bone at TiO2 grit-blasted implants following surgical placement and subsequent loading in the posterior maxilla and mandible. MATERIALS AND METHODS: The crestal bone position relative to the implant reference point (junction of the crestal bevel with the TiO2 grit-blasted surface) was evaluated at implant placement, at abutment placement, and 6 to 36 months following restoration, with an average recall period of 2.3 years. The implant position and dimension were recorded. A single investigator using 7x magnification assessed all radiographs. RESULTS: Crestal bone loss from the time of implant placement up to 36 months following restoration ranged from 0.0 to 2.1 mm. Of the 102 implants, 14 implants showed greater than 1.0 mm of crestal bone loss. They were not clustered at any particular tooth position. Eighty of the implants showed less than 0.5 mm of radiographically measured bone loss. Mean crestal bone loss was 0.36 mm (+/- 0.6 mm). Averages of 0.57 and 0.24 mm loss were shown for 3.5- and 4.0-mm-diameter implants, respectively (P < .051). Bone gain was seen at several 4.0-mm-diameter implants. DISCUSSION: This retrospective evaluation indicates that the radiographically measured bone loss may be expected to be less than 1 mm following placement and loading of TiO2 grit-blasted implants. The close approximation of bone with the implant/abutment interface suggests the attenuation of any microgap-induced bone loss. Additional reasons for crestal bone maintenance may include factors attributed to implant surface roughness and loading along a tapered implant/abutment interface. CONCLUSIONS: Several clinical advantages for maintaining crestal bone at implants supporting posterior prostheses can be identified.     

Influence of repeated screw tightening on bacterial leakage along the implant–abutment interface

Objectives: Bacterial penetration along the implant–abutment interface as a consequence of abutment screw loosening has been reported in a number of recent studies. The aim of this in vitro study was to investigate the influence of repeated tightening of the abutment screw on leakage of Streptococcus mutans along the interface between implants and pre-machined abutments.
Materials and methods: Twenty pre-machined abutments with a plastic sleeve were used. The abutment screws were tightened to 32 N cm in group 1 ( n =10 – control) and to 32 N cm, loosened and re-tightened with the same torque twice in group 2 ( n =10). The assemblies were completely immersed in 5 ml of Tryptic Soy Broth medium inoculated with S. mutans and incubated for 14 days. After this period, contamination of the implant internal threaded chamber was evaluated using the DNA Checkerboard method.
Results: Microorganisms were found on the internal surfaces of both groups evaluated. However, bacterial counts in group 2 were significantly higher than that in the control group ( P <0.05).
Conclusion: These results suggest that bacterial leakage between implants and abutments occurs even under unloaded conditions and at a higher intensity when the abutment screw is tightened and loosened repeatedly.     

Influence of interimplant distances and placement depth on peri‐implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs

Objectives: The aim of this study was to histomorphometrically evaluate the influence of interimplant distances (ID) and implant placement depth on bone remodeling around contiguous Morse cone connection implants with ‘platform‐shifting’ in a dog model. Material and methods: Bilateral mandibular premolars of six dogs were extracted, and after 12 weeks, each dog received 8 implants, four placed 1.5 mm subcrestally (SCL) on one side of the mandible and four placed equicrestally (ECL) on the other side, alternating the ID of 2 and 3 mm. The experimental groups were SCL with IDs of 2 mm (2 SCL) and 3 mm (3 SCL) and ECL with IDs of 2 mm (2 ECL) and 3 mm (3 ECL). Metallic crowns were immediately installed. After 8 weeks, the animals were euthanized and histomorphometric analyses were performed to compare bone remodeling in the groups. Results: The SCL groups' indices of crestal bone resorption were significantly lower than those of ECL groups. In addition, the vertical bone resorption around the implants was also numerically inferior in the SCL groups, but without statistical significance. No differences were obtained between the different IDs. All the groups presented similar good levels of bone‐to‐implant contact and histological bone density. Conclusion: The subcrestal placement of contiguous Morse cone connection implants with ‘platform shifting’ was more efficient in preserving the interimplant crestal bone. The IDs of 2 and 3 mm did not affect the bone remodeling significantly under the present conditions. To cite this article:
Barros RRM, Novaes AB Jr., Muglia VA, Iezzi G, Piattelli A. Influence of interimplant distances and placement depth on peri‐implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs.
Clin. Oral Impl. Res. 21 , 2010; 371–378.
doi: 10.1111/j.1600‐0501.2009.01860.x     

Equicrestal and subcrestal dental implants: a histologic and histomorphometric evaluation of nine retrieved human implants

Background: Stability of peri‐implant crestal bone plays a relevant role relative to the presence or absence of interdental papilla. Several factors can contribute to the crestal bone resorption observed around two‐piece implants, such as the presence of a microgap at the level of the implant–abutment junction, the type of connection between implant and prosthetic components, the implant positioning relative to the alveolar crest, and the interimplant distance. Subcrestal positioning of dental implants has been proposed to decrease the risk of exposure of the metal of the top of the implant or of the abutment margin, and to get enough space in a vertical dimension to create a harmoniously esthetic emergence profile. Methods: The present retrospective histologic study was performed to evaluate dental implants retrieved from human jaws that had been inserted in an equicrestal or subcrestal position. A total of nine implants were evaluated: five of these had been inserted in an equicrestal position, whereas the other four had been positioned subcrestally (1 to 3 mm). Results: In all subcrestally placed implants, preexisting and newly formed bone was found over the implant shoulder. In the equicrestal implants, crestal bone resorption (0.5 to 1.5 mm) was present around all implants. Conclusion: The subcrestal position of the implants resulted in bone located above the implant shoulder.     

Osseotite implant: 3-year prospective multicenter evaluation

Purpose : This prospective multicenter study evaluates the cumulative success rate of the Osseotite® implant after 3 years of prosthetic loading.
Materials and Methods : A total of 413 Osseotite® implants (Implant Innovations®) were placed in 142 patients (completely or partially edentulous) in five dental offices exclusively devoted to implants. The average age of the patients was 58.3 years. Of the 413 implants, 191 were placed in the maxilla and 222 in the mandible; 271 (65.6%) were posterior implants and 142 (34.4%) were anterior implants. Clinical and radiographic evaluations were made after completion of the prosthetic restoration, after 6 months of loading, at 1 year, and at 3 years.
Results : A cumulative success rate of 95.3% was obtained after 3 years of prosthetic loading. The success rate was similar in both arches: 95.1% in the maxilla and 96.8% in the mandible. Early failures (before prosthetic loading) were greater (n = 12) than late failures (n = 2). After 3 years of prosthetic loading, the marginal bone level of 385 (93.2%) implants were evaluated radiographically. Bone level was at the first thread for 91.4% of the implants. A slightly increased loss was observed around 26 implants (6.7%). Including survival implants, the cumulative implant success rate after 3 years was 96%. A success rate of 98.4% was obtained with 187 short implants (8, 5 and 10 mm) reported in this multicenter evaluation.
Conclusion : This multicenter evaluation demonstrates excellent predictability for Osseotite implants.     

Osteotome sinus floor elevation technique without grafting material: 3-year results of a prospective pilot study

Objective: In a prospective pilot study, short≤10 mm ITI-SLA implants were placed in the resorbed posterior maxilla by means of an osteotome sinus floor elevation (OSFE) procedure without grafting material. This paper presents 3-year data assessing bone-level changes around implants.
Material and methods: Twenty-five implants were placed in 17 patients to rehabilitate 16 molar and nine premolar sites. The mean residual bone height (RBH) was 5.4 ± 2.3 mm. A healing period of 3–4 months was allowed before abutment tightening. Most implants (21/25) were 10 mm long, and the others were 8 and 6 mm long. At the 3-year control, endo-sinus bone gain, implant length protruding into the sinus and crestal bone loss (CBL) were measured on periapical radiographs.
Results: All implants fulfilled the survival criteria. Despite the absence of grafting material, implants were embedded into newly formed bone tissue. All implants gained endo-sinus bone; the mean gained bone was 3.1 ± 1.5 mm. The residual protrusion length decreased from 4.9 ± 2.1 to 1.8 ± 2.1 mm. CBL was 0.9 ± 0.8 mm.
Conclusions: This study confirms that the OSFE procedure without grafting material is sufficient to create bone beyond the natural limit of the sinus. On the mid-term of 3 years, the technique was found to be predictable in the posterior maxilla when the RBH is limited. Implants gained endo-sinus bone despite the lack of grafting material. Bone gain was still improving over the first-year control. No shrinkage of the augmented area was observed.     

Multiple single-tooth implant restorations in the posterior jaws: maintenance of marginal bone levels with reference to the implant-abutment microgap

PURPOSE: The purpose of this study was to measure marginal bone loss from the implant-abutment microgap to the bone crest between multiple freestanding implants functionally loaded for up to 7.5 years in the posterior jaws. MATERIALS AND METHODS: Patients consecutively treated for the replacement of missing posterior teeth were included in the study. Using the implant-abutment interface, which was placed level with the crestal bone as a reference point, standardized follow-up radiographs were obtained to evaluate marginal bone loss. Results were subject to statistical analysis using the Wilcoxon rank sum test and the Wilcoxon signed rank test at the 95% confidence level. Additionally, soft tissue and prosthetic complications were recorded. RESULTS: One hundred seventy-three implants in 54 patients were evaluated. Implants were in function for a mean of 37 months (range, 21 to 91 months). One implant failed, for a survival rate of 99.4%. Overall mean marginal bone loss was 0.65 mm (range, 0.0 to 4.8 mm). For the 80 maxillary and 93 mandibular implants, mean marginal bone loss was 0.56 mm and 0.70 mm, respectively. The frequency of bone loss > or = 1.0 mm was 25.0% in the maxilla and 36.0% in the mandible; 23.1% of maxillary implants and 16.7% of mandibular implants demonstrated no bone loss. No significant differences were observed between men and women or between smokers and nonsmokers. The difference between mesial and distal bone levels was statistically significant (P < .001), with respective means of 0.53 mm and 0.76 mm. Recorded prosthetic complications included cementation failure (17.7%), porcelain fracture (7.2%), and abutment screw loosening (2.2%). CONCLUSIONS: Multiple single-tooth implants placed in the posterior jaws perform extremely well. Furthermore, it is possible to retain bone close to the implant-abutment microgap with certain implant designs.     

Mechanical complications of dental implants

Adverse occlusal forces can result in mechanical complications of implant components. While unacceptably high incidences of mechanical failures have been reported for the two-stage external hex screw-type implant systems, the standard-diameter ITI solid-screw implant does not seem to be vulnerable to these problems. The 8 degrees Morse taper has eliminated abutment screw loosening and fracture. The incidence of prosthetic screw loosening has been minimized by the 45 degrees bevel on the implant shoulder and by the 1.5 mm vertical abutment walls. The design of the standard-diameter solid-screw ITI implant and the material used in its fabrication (cold worked type IV cp titanium) have eliminated fixture fracture. However, because there have been some reported instances of fractures involving reduced-diameter and hollow implants, these designs should be used with caution.     

Corone singole su impianti ottenuti per fabbricazione diretta tramite laser. Studio prospettico e multicentrico con follow-up a un anno

Objectives

This prospective study evaluated the survival rate and the implant-crown success of single-tooth titanium dental implants produced with direct laser metal forming (DLMF) after 1-year of functional loading.

Materials and methods

110 maxillary (N = 65) and mandibular (n = 45) implants (TixOs^®, Leader Novaxa, Milan, Italy) were placed in 82 patients (44 males, 38 females; age range 26-67 years) in 7 different clinical centers. The prosthetic restorations included 110 single crowns (SCs) (32 anterior, 78 posterior). The scheduled 1-year follow-up examination focused on several clinical, radiographic, and prosthetic parameters. Implant success was defined as the absence of pain, sensitivity, suppuration, and exudation; absence of clinically detectable implant mobility; absence of peri-implant radiolucency; distance between the implant shoulder and the first visible bone contact (DIB) < 1.5 mm; absence of prosthetic complications at the implant abutment interface.

Results

After 1-year of functional loading, the overall implant survival rate was 99.1% (98.4% maxilla, 100% mandible). The mean DIB was 0.60 mm (± 0.32). All but 3 of the 109 surviving implants fulfilled the implant-crown success criteria (implant-crown success 97.2%).

Conclusions

Titanium dental implants produced with DLMF seem to represent a valid treatment option for single-tooth restorations in the maxilla and in the mandible. Further studies are needed to evaluate the long-term performance of these implants.     

临床平台转移技术在上颌后牙区种植中的应用

目的：评价临床平台转移技术在上颌后牙区种植的效果。方法：选择60例上颌后牙种植患者随机分实验与对照组,共植入141枚种植体,植体肩部与牙槽嵴平齐。实验组30例选用小于植体直径的愈合基台（0.7mm）与种植体相连,重建种植区的结合上皮,上部结构（基台）精细研磨,重建无缝隙冠龈连接,精度贵金属烤瓷修复。对照组选用与植体直径相同的愈合基台与种植体相连,常规修复。分别于种植修复后3、6、12月测量上颌后牙种植体周围边缘骨高度和评价软组织情况。结果：实验组种植体周围边缘骨高度变化明显小于对照组（p〈0.01）,两组软组织情况变化不明显（p〉0.05）。结论：临床平台转移技术可保持种植体周围边缘骨高度,其远期效果可期。     

A five-year life-table analysis on wide neck ITI implants with prosthetic evaluation and radiographic analysis: results from a private practice

This paper reports a 5-year life-table analysis on wide neck (WN) ITI implants placed in a private practice. In 212 patients, 263 implants were placed in the posterior region; 97% rehabilitated the molar area. Implants in the mandible and in the maxilla were 61.2% and 38.8%, respectively; the mean implant length was 9.7 and 8.9 mm, respectively. Eighty-nine percent sites had both vestibular and buccal bone lamellae > or =1 mm, 9.1% had one of them <1 mm and 1.9% had both lamellae <1 mm. Sinus perforation during surgery occurred in 52% of the maxillary implants. Prosthetic information was available for 249 implants; implants were involved in 157 single crowns (SC) and 80 fixed partial dentures (FPD). Radiographic analysis was performed on 102 implants that reached the 2-year control, and crestal bone loss (CBL) was measured. Results showed that five implants failed; the 5-year cumulative survival rate was 97.89%. The 1-year survival rate based on 259 implants was 98.8% and the 2-year survival rate based on 174 implants was 97.7%. In this 5-year timeframe, 94.3% of the SCs and 96.2% of the FPDs were free of complication. The mean CBL at the mesial and distal sides was 0.71 and 0.60 mm, respectively; bone losses >1 and >2 mm were recorded for 29.7% and 2.5% of the sides, respectively. This mid-term study showed that the WN ITI implants were highly predictable in private practice and that prosthetic complication in the molar area was an infrequent event.     

Effect of surface topography of screw-shaped titanium implants in humans on clinical and radiographic parameters: a 12-year prospective study

Objectives: Although implants with a roughened surface are widely used today, little is known about the long-term effect of a roughened surface compared with the conventional machined surface on clinical and radiographic parameters. The purpose of this study is to investigate the long-term differences between moderately rough (tioblasted) titanium implants and minimally rough machined/turned surfaces with respect to marginal bone resorption and the peri-implant soft tissues in the same patient.
Material and methods: In 20 fully edentulous patients, with severely resorbed mandibles, a total of 80 Astra Tech dental implants were placed in the mandible to support a bar construction with a full overdenture. In each patient two minimally rough-surfaced (turned) and two moderately rough-surfaced (tioblast) implants were placed alternately. Clinical evaluation was carried out at base line (prosthetic installation), 6 months, 1, 2, 3, 4, 5 and 12 years. Radiographic evaluation using standardized individual filmholders was carried out at base line (prosthetic installation), 6 months, 1, 5 and 12 years.
Results: In two patients, during the abutment surgery, one turned implant showed insufficient osseointegration and was replaced. One implant showed an abutment fracture after 9 years and was kept as a sleeper. From base line up to 12 years, no implant was lost. No significant differences were found between both implant surfaces concerning the clinical parameters such as plaque, calculus, bleeding and probing pocket depth. The mean (SD) marginal bone changes up to 12 years varied between –0.11 and +0.01 mm for the turned and −0.2 and +0.01 mm for the tioblast implants. No significant difference in marginal bone loss was found between both implant surfaces.
Conclusion: We conclude that after 12 years of follow-up, no differences could be found between the turned and the tioblasted implants, both for soft and for hard tissue parameters.     

Bacterial colonization of the implant-abutment interface using an in vitro dynamic loading model

Background: Previously, we demonstrated that the geometry of the fixture–abutment interface influences the risk of bacterial invasion into the internal part of the implant, although the contribution of loading on this invasion was not evaluated. The aim of the present study is to use an in vitro dynamic‐loading model to assess the potential risk for invasion of oral microorganisms into the fixture–abutment interface microgap of dental implants with different fixture–abutment connection characteristics. Methods: Twenty‐eight implants were divided into two groups (n = 14 per group) based on their microgap dynamics. Group 1 was comprised of fixtures with internal Morse‐taper connection that connected to standard abutments. Group 2 was comprised of implants with a four‐groove conical internal connection that connected to multibase abutments. The specimens were immersed in a bacterial solution of Escherichia coli and loaded with 500,000 cycles of 15 N in a wear simulator. After disconnection of fixtures and abutments, microbial samples were taken from the threaded portion of the abutment, plated, and cultured under appropriate conditions. The difference between loosening and tightening torque value was also measured. Results: One of the 14 samples in Group 1 and 12 of the 14 of samples in Group 2 developed multiple colony forming units for E. coli. Implants in Group 1 exhibited an increase in torque value in contrast to implants in Group 2, which exhibited a decrease. Conclusion: This study indicates that differences in implant design may affect the potential risk for invasion of oral microorganisms into the fixture–abutment interface microgap under dynamic‐loading conditions.     

Clinical Outcomes of an Osteotome Technique and Simultaneous Placement of Neoss Implants in the Posterior Maxilla

Background: Insufficient bone volume often hamper placement of dental implants in the posterior maxilla. Purpose: The aim of the present clinical study was to evaluate retrospectively the clinical outcome of implant placement in the resorbed posterior maxilla using an osteotome technique without adding any grafting material. Materials and Methods: Twenty patients with 5 to 9 mm of residual alveolar bone height in the posterior maxilla received twenty‐nine implants (Neoss Ltd., Harrogate, UK) using an osteotomy technique without bone grafts. Intraoral radiographs were taken before and after implant placement, at the time of loading and after 11 to 32 months of loading (mean 16.4 months), to evaluate bone formation below the sinus membrane and marginal bone loss. Implant stability measurements (Osstell^TM, Gothenburg, Sweden) were performed after implant installation and at abutment connection 5 months later. All implants were installed with the prosthetic platform level with the bone crest. Results: No implant was lost giving a survival rate of 100% after a mean follow‐up time of 16.4 months. The average vertical bone height was 7.2 ± 1.5 mm at placement and 10.0 ± 1.0 mm after 11 to 32 months. The average increase of 2.8 ± 1.1 mm was statistically significant. There was a statistically significant improvement in implant stability from 70.7 ± 9.2 implant stability quotient (ISQ) at placement to 76.7 ± 5.7 ISQ at abutment connection, 5 months later. The mean marginal bone loss amounted to 0.7 ± 0.3 mm after 11 to 32 months of loading. Conclusion: It is concluded that the osteotome technique evaluated resulted in predictable intrasinus bone formation, firm implant stability, and good clinical outcomes as no implants were lost and minimal marginal bone loss was observed.