Radiographic evaluation of marginal bone levels adjacent to parallel-screw cylinder machined-neck implants and rough-surfaced microthreaded implants using digitized panoramic radiographs

Objective: The purpose of this split-mouth study was to compare macro- and microstructure implant surfaces at the marginal bone level during a stress-free healing period and under functional loading.
Material and methods: From January to February 2006, 133 implants (70 rough-surfaced microthreaded implants and 63 machined-neck implants) were inserted in the mandible of 34 patients with Kennedy Class I residual dentitions and followed until February 2008. The marginal bone level was radiographically determined, using digitized panoramic radiographs, at four time points: at implant placement (baseline level), after the healing period, after 6 months of functional loading, and at the end of follow-up.
Results: The median follow-up time was 1.9 (range: 1.9–2.1) years. The machined-neck group had a mean crestal bone loss of 0.5 mm (range: 0–2.3) after the healing period, 0.8 mm after 6 months (range: 0–2.4), and 1.1 mm (range: 0–3) at the end of follow-up. The rough-surfaced microthreaded implant group had a mean bone loss of 0.1 mm (range: −0.4–2) after the healing period, 0.4 mm (range: 0–2.1) after 6 months, and 0.5 mm (range: 0–2.1) at the end of follow-up. The two implant types showed significant differences in marginal bone levels (healing period: P =0.01; end of follow-up: P <0.01).
Conclusions: Radiographic evaluation of marginal bone levels adjacent to machined-neck or rough-surfaced microthreaded implants showed that implants with the microthreaded design caused minimal changes in crestal bone levels during healing (stress-free) and under functional loading.     

Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year

PURPOSE: To evaluate the influence of macro- and microstructure of the implant surface at the marginal bone level after functional loading. MATERIALS AND METHODS: Sixty-eight patients were randomly assigned to 1 of 3 groups. The first group received 35 implants with a machined neck (Ankylos); the second group, 34 implants with a rough-surfaced neck (Stage 1); and the third, 38 implants with a rough-surfaced neck with microthreads (Oneplant). Clinical and radiographic examinations were conducted at baseline (implant loading) and 3, 6, and 12 months postloading. Two-way repeated analysis of variance (ANOVA) was used to test the significance of marginal bone change of each tested group at baseline, 3, 6, and 12 month follow-ups and 1-way ANOVA was also used to compare the bone loss of each time interval within the same implant group (P < .05). RESULTS: At 12 months, significant differences were noted in the amount of alveolar bone loss recorded for the 3 groups (P < .05). The group with the rough-surfaced microthreaded neck had a mean crestal bone loss of 0.18 +/- 0.16 mm; the group with the rough-surfaced neck, 0.76 +/- 0.21 mm; and the group with the machined neck, 1.32 +/- 0.27 mm. In the rough-surfaced group and the rough-surfaced microthreaded group, no statistically significant changes were observed after 3 months, whereas the machined-surface group showed significant bone loss for every interval (P < .05). DISCUSSION: To minimize marginal bone loss, in addition to the use of a rough surface at the marginal bone level, a macroscopic modification such as the addition of microthreads could be recommended. A rough surface and microthreads at the implant neck not only reduce crestal bone loss but also help with early biomechanical adaptation against loading in comparison to the machined neck design. CONCLUSION: A rough surface with microthreads at the implant neck was the most effective design to maintain the marginal bone level against functional loading.     

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.     

Evaluation of peri-implant bone loss around platform-switched implants

This clinical and radiographic prospective study evaluated bone loss around two-piece implants that were restored according to the platform-switching protocol. One hundred thirty-one implants were consecutively placed in 45 patients following a nonsubmerged surgical protocol. On 75 implants, a healing abutment 1 mm narrower than the implant platform was placed at the time of surgery. On the remaining implants, a healing abutment of the same diameter as the implant was inserted. All implants were positioned at the crestal level. Clinical and radiographic examinations were performed prior to surgery, at the end of surgery, 8 weeks after implant placement, at the time of provisional prosthesis insertion, at the time of definitive prosthesis insertion, and 12 months after loading. The data collected showed that vertical bone loss for the test cases varied between 0.6 mm and 1.2 mm (mean: 0.95 +/- 0.32 mm), while for the control cases, bone loss was between 1.3 mm and 2.1 mm (mean: 1.67 +/- 0.37 mm). These data confirm the important role of the microgap between the implant and abutment in the remodeling of the peri-implant crestal bone. Platform switching seems to reduce peri-implant crestal bone resorption and increase the long-term predictability of implant therapy.     

Influence of abutment connections and plaque control on the initial healing of prematurely exposed implants: an experimental study in dogs

BACKGROUND: Spontaneous early implant exposure is believed to be harmful, resulting in early crestal bone loss around submerged implants. The purpose of this study was to examine the influence of abutment connections and plaque control on the initial healing of prematurely exposed implants in the canine mandible. METHODS: Bilateral, edentulated, flat alveolar ridges were created in the mandible of 10 mongrel dogs. After 3 months of healing, two implants were placed on each side of the mandible following a commonly used two-stage surgical protocol. Implants on each side were randomly assigned to one of two procedures: 1) connection of a cover screw to the implant and removal of the gingiva to expose the cover screw; and 2) connection of a healing abutment to the implant so that the coronal portion of the abutment remained exposed to the oral cavity. In five dogs (plaque control group), meticulous plaque control was performed. In the other five dogs (no plaque control group), plaque was allowed to accumulate. At 8 weeks post-implantation, microcomputed tomography was performed at the implantation site to measure bone height in the peri-implant bone. RESULTS: The plaque control group had greater vertical alveolar ridge height (9.7 +/- 0.5 mm) than the group without plaque control (7.4 +/- 0.7 mm; P <0.05). In the plaque control group, the average bone height was greater with the abutment-connected implant (10.1 +/- 0.5 mm) than with the partially exposed implant (9.3 +/- 0.5 mm; P <0.05). In the group without plaque control, the average bone height was greater with the partially exposed implant (8.2 +/- 0.6 mm) than with the abutment-connected implant (6.5 +/- 0.7 mm; P <0.05). CONCLUSION: These results suggest that the placement of healing abutments and meticulous plaque control may limit bone loss around submerged implants when implants are partially exposed.     

Crestal bone loss around submerged and exposed unloaded dental implants: a radiographic and microbiological descriptive study

The successful maintenance of crestal bone surrounding dental implants is imperative for long-term implant success. Crestal bone loss is reportedly related to stress. However, early perforation and partial exposure of the implant's covering device are a focus for plaque accumulation, which, if left untreated, may result in inflammation. The objective of this study was to evaluate the crestal bone levels adjacent to submerged and exposed unloaded dental implants during the initial healing phase. In addition, the microbiota around exposed implants were studied. Bilateral implants were placed in the mandible of 10 patients. In one quadrant, the implants were covered by the flap. In the other quadrant, the flap was sutured, leaving the cover screws completely exposed. Standardized periapical radiographs were obtained at implant placement and 4 months later. Radiographs were digitalized, aligned, and analyzed with a computer-assisted method. Cultures were obtained from exposed implant sites. All patients showed more crestal bone loss around exposed dental implants compared to submerged implants. Prevotella sp., Streptococcus beta-hemoliticus, and Fusobacterium sp. were the microorganisms identified in most of the sites. The exposure of the implant covering device created foci for bacterial plaque accumulation, which may have facilitated periimplant crestal bone loss. The initial healing phase follow-up may be critical for implant success.     

Platform switching minimises crestal bone loss around dental implants: truth or myth?

The aim was to assess the role of platform switching (PS) in minimising crestal bone loss around dental implants through a systematic review of the currently available clinical evidence. To address the focused question ‘Does PS minimise crestal bone loss compared with non‐platform‐switched (NPS) implants?’, PubMed/Medline and Google Scholar databases were explored from 1986 up to and including December 2013 using the following key words in different combinations: ‘bone loss’, ‘dental implant’, ‘diameter’, ‘mandible’, ‘maxilla’ and ‘platform switching’. Letters to the Editor, unpublished data, historical reviews, case reports and articles published in languages other than English were excluded. Fifteen clinical studies were included. In seven studies, PS and NPS implants were placed in both the maxilla and mandible. In 13 studies, implants were placed at crestal bone levels whereas in one study, implants were placed supracrestally. Three studies reported the bucco‐lingual (or transversal) width of the alveolar ridge which ranged between 7–8 mm. Seven studies reported that implants placed according to the PS concept did not minimise crestal bone loss as compared with NPS implants. 3D‐Implant positioning, width of alveolar ridge and control of micromotion at the implant‐abutment interface are the more critical factors that influence crestal bone levels than PS.     

Clinical and radiographic changes around dental implants inserted in different levels in relation to the crestal bone, under different restoration protocols, in the dog model

BACKGROUND: The aim of the present study was to evaluate clinical and radiographic changes that occur around dental implants inserted in different levels in relation to crestal bone under different restoration protocols. METHODS: Thirty-six implants were inserted in the edentulous mandible of six mongrel dogs. Each implant was assigned to an experimental group according to the distance from the top of the implant to the crestal bone: Bone Level (at crestal bone level), Minus 1 (1 mm below crestal bone), or Minus 2 (2 mm below crestal bone). Each hemimandible was submitted to a restoration protocol: conventional (prosthesis was installed 120 days after implant placement, including 30 days with healing cap) or immediate (prosthesis was installed 24 hours after implant placement). Fixed partial prostheses were installed bilaterally in the same day. After 90 days, clinical and radiographic parameters were evaluated. RESULTS: As long as the implants were inserted in more apical positions, the first bone-to-implant contact (fBIC) was positioned more apically (P <0.05). However, the apical positioning of the implants did not influence the ridge loss or the position of the soft tissue margin (PSTM) (P >0.05). In addition, in immediately restored sites, the PSTM was located significantly more coronally than that in conventionally restored sites (P = 0.02). CONCLUSIONS: Despite the more apical positioning of the fBIC, the height of the peri-implant soft tissues and ridge was not jeopardized. Moreover, the immediate restoration protocol was beneficial to the maintenance of the PSTM. Further studies are suggested to evaluate the significance of these results in longer healing periods.     

Performance of sintered, porous-surfaced, press-fit implants after 10 years of function in the partially edentulous posterior mandible

This article updates the results of a prospective clinical trial of press-fit, sintered, porous-surfaced dental implants placed in the posterior mandible of partially edentulous patients. Implants used had overall lengths (including transgingival collar regions) of 7 or 9 mm with designed intrabony lengths (lengths of sintered surface in contact with bone) of 6 or 8 mm. Forty-eight implants were placed in 24 patients, the majority of which replaced molar teeth, and the mean crown-to-root ratio was 1.4. Over 10 years of implant function, 2 patients with 3 implants died and 3 patients with 4 implants were lost to follow-up because of infirmity or relocation. The survival and success rates were both 95.5%. Two implants failed; the mean cumulative crestal bone loss (measured from the implant-abutment interface) for the remaining implants was 1.2 mm. Crestal bone loss was not affected by the crown-to-root ratio, prosthesis design, or whether an implant was the most distal unit in a sextant. However, there was a trend for greater crestal bone loss when implants were opposed by implants rather than by natural teeth.     

Radiographic comparisons of crestal bone levels around implants placed with low-speed drilling and standard drilling protocols: Preliminary results

BackgroundThe present study aimed to investigate the mean crestal bone loss (CBL) by placing implants using two different drilling-protocols, i.e., standard drilling with saline irrigation and low-speed drilling without saline irrigation.Material and MethodsThe patients were enrolled in the present study from a university teaching institute. Patients who fulfilled the inclusion criteria were randomly placed in two study groups: 1) control group: Standard drilling with saline irrigation and 2) test group: low-speed drilling without saline irrigation. The radiographic mean crestal bone loss (CBL) was evaluated at 3 months of follow-up before implant loading. Data analysis was performed using SPSS 20.0 (IBM product, Chicago, USA) and a p-value ≤ 0.05 was considered statistically significant.ResultsSixteen patients (10 males and 6 females) participated in the study. Thirty Camlog®-screw-line implants were placed (15 implants per study group). After 3 months of follow-up, the means CBL of implants placed with standard drilling and low-speed drilling protocols were 1.01 ± 0.49 mm and 0.74 ± 0.62 mm, respectively. No statistically significant difference could be recorded between two groups (p = 0.206).ConclusionsDental implants placed with low-speed drilling without saline irrigation exhibited a similar CBL to implants installed with the standard drilling protocol. However, further randomised clinical trials are recommended to obtain stronger evidence and a better understanding of the effect of the low-speed drilling protocol without saline irrigation on mean CBL and long-term implant survival.     

Impact of?crestal and subcrestal implant placement in peri-implant bone: A prospective comparative study

Background

To assess the influence of the crestal or subcrestal placement of implants upon peri-implant bone loss over 12 months of follow-up.

Material and Methods

Twenty-six patients with a single hopeless tooth were recruited in the Oral Surgery Unit (Valencia University, Valencia, Spain). The patients were randomized into two treatment groups: group A (implants placed at crestal level) or group B (implants placed at subcrestal level). Control visits were conducted by a trained clinician at the time of implant placement and 12 months after loading. A previously established standard protocol was used to compile general data on all patients (sex and age, implant length and diameter, and brushing frequency). Implant success rate, peri-implant bone loss and the treatment of the exposed implant surface were studied. The level of statistical significance was defined as 5% (α=0.05).

Results

Twenty-three patients (8 males and 15 females, mean age 49.8±11.6 years, range 28-75 years) were included in the final data analyses, while three were excluded. All the included subjects were nonsmokers with a brushing frequency of up to twice a day in 85.7% of the cases. The 23 implants comprised 10 crestal implants and 13 subcrestal implants. After implant placement, the mean bone position with respect to the implant platform in group A was 0.0 mm versus 2.16±0.88 mm in group B. After 12 months of follow-up, the mean bone positions were -0.06±1.11 mm and 0.95±1.50 mm, respectively - this representing a bone loss of 0.06±1.11 mm in the case of the crestal implants and of 1.22±1.06 mm in the case of the subcrestal implants (p=0.014). Four crestal implants and 5 subcrestal implants presented peri-implant bone levels below the platform, leaving a mean exposed treated surface of 1.13 mm and 0.57 mm, respectively. The implant osseointegration success rate at 12 months was 100% in both groups.

Conclusions

Within the limitations of this study, bone loss was found to be greater in the case of the subcrestal implants, though from the clinical perspective these implants presented bone levels above the implant platform after 12 months of follow-up. Key words:Immediate implants, tooth extraction, dental implants, single-tooth, crestal bone, placement level.     

Biomechanical behavior of mandibular overdenture retained by two standard implants or 2 mini implants: A 3-dimensional finite element analysis

Statement of problemMini implants (<3 mm in diameter) are being used as an alternative to standard implants for implant-retained mandibular overdentures; however, they may exhibit higher stresses at the crestal level.PurposeThe purpose of this finite element analysis study was to evaluate the biomechanical behavior (stress distribution pattern) in the mandibular overdenture, mucosa, bone, and implants when retained with 2 standard implants or 2 mini implants under unilateral or bilateral loading conditions.Material and methodsA patient with edentulous mandible and his denture was scanned with cone beam computed tomography (CBCT), and a 3D mandibular model was created in the Mimics software program by using the CBCT digital imaging and communications in medicine (DICOM) images. The model was transferred to the 3Matics software program to form a 2-mm-thick mucosal layer and to assemble the denture DICOM file. A 12-mm-long standard implant (Ø3.5 mm) and a mini dental implant (Ø2.5 mm) along with the LOCATOR male attachments (height 4 mm) were designed by using the SOLIDWORKS software program. Two standard or 2 mini implants in the canine region were embedded separately in the 3D assembled model. The base of the mandible was fixed, and vertical compressive loads of 100 N were applied unilaterally and bilaterally in the first molar region. The material properties for acrylic resin (denture), titanium (implants), mucosa (tissue), and bone (mandible) were allocated. Maximum von Mises stress and strain values were obtained and analyzed.ResultsMaximum stresses of 9.78 MPa (bilaterally) and 11.98 MPa (unilaterally) were observed in 2 mini implants as compared with 3.12 MPa (bilaterally) and 3.81 MPa (unilaterally) in 2 standard implants. The stress values in the mandible were observed to be almost double the mini implants as compared with the standard implants. The stresses in the denture were in the range of 3.21 MPa and 3.83 MPa and in the mucosa of 0.68 MPa and 0.7 MPa for 2 implants under unilateral and bilateral loading conditions. The strain values shown similar trends with both implant types under bilateral and unilateral loading.ConclusionsTwo mini implants generated an average of 68.15% more stress than standard implants. The 2 standard implant–retained overdenture showed less stress concentration in and around implants than mini implant–retained overdentures.     

Influence of a machined collar on crestal bone changes around titanium implants: a histometric study in the canine mandible

Background: It has been shown that peri‐implant crestal bone reactions are influenced by both a rough–smooth implant border in one‐piece, non‐submerged, as well as an interface (microgap [MG] between implant/abutment) in two‐piece butt‐joint, submerged and non‐submerged implants being placed at different levels in relation to the crest of the bone. According to standard surgical procedures, the rough–smooth implant border for implants with a smooth collar should be aligned with the crest of the bone exhibiting a smooth collar adjacent to peri‐implant soft tissues. No data, however, are available for implants exhibiting a sandblasted, large‐grit and acid‐etched (SLA) surface all the way to the top of a non‐submerged implant. Thus, the purpose of this study is to histometrically examine crestal bone changes around machined versus SLA‐surfaced implant collars in a side‐by‐side comparison. Methods: A total of 60 titanium implants (30 machined collars and 30 SLA collars) were randomly placed in edentulous mandibular areas of five foxhounds forming six different subgroups (implant subgroups A to F). The implants in subgroups A to C had a machined collar (control), whereas the implants in subgroups D to F were SLA‐treated all the way to the top (MG level; test). Furthermore, the MGs of the implants were placed at different levels in relation to the crest of the bone: the implants in subgroups A and E were 2 mm above the crest, in subgroups C and D 1 mm above, in subgroup B 3 mm above, and in subgroup F at the bone crest level. For all implants, abutment healing screws were connected the day of surgery. These caps were loosened and immediately retightened monthly. At 6 months, animals were sacrificed and non‐decalcified histology was analyzed by evaluating peri‐implant crestal bone levels. Results: For implants in subgroup A, the estimated mean crestal bone loss (± SD) was ?0.52 ± 0.40 mm; in subgroup B, +0.16 ± 0.40 mm (bone gain); in subgroup C, ?1.28 ± 0.21 mm; in subgroup D, ?0.43 ± 0.43 mm; in subgroup E, ?0.03 ± 0.48 mm; and in subgroup F, ?1.11 ± 0.27 mm. Mean bone loss for subgroup A was significantly greater than for subgroup E (P = 0.034) and bone loss for subgroup C was significantly greater than for subgroup D (P <0.001). Conclusions: Choosing a completely SLA‐surfaced non‐submerged implant can reduce the amount of peri‐implant crestal bone loss and reduce the distance from the MG to the first bone–implant contact around unloaded implants compared to implants with a machined collar. Furthermore, a slightly exposed SLA surface during implant placement does not seem to compromise the overall hard and soft tissue integration and, in some cases, results in coronal bone formation in this canine model.     

Impact of implant surface and grafting protocol on clinical outcomes of endosseous implants

PURPOSE: The objectives of this study were to (1) evaluate the survival of implants placed in maxillary sinuses augmented with a 70:30 mixture of autogenous bone and anorganic bovine hydroxyapatite (Bio-Oss) at 1 and 5 years, (2) observe the difference in survival rate between 1-stage and 2-stage procedures, and (3) compare the survival rate of rough-surfaced implants with that of machined implants. MATERIALS AND METHODS: A total of 30 consecutively patients (48 sinuses) with Cawood and Howell Class V and VI atrophy were evaluated. Lateral osteotomy techniques were used in all cases. Implants were placed either simultaneous with grafting (1-stage procedure) or after a delay (2-stage procedure), depending on the amount of residual bone. A 70:30 mixture of autogenous bone and anorganic bovine hydroxyapatite was used as the graft material. All patients were followed up at 1 year after prosthetic loading, while a limited group of these patients was followed up to 5 years. RESULTS: In 8 patients where the residual crestal bone under the sinus floor assessed by computed tomography was at least 4.5 mm (mean, 5.3 mm), the 1-stage procedure was used for 11 sinus elevations and 32 implants. In 22 patients where the residual crestal bone was less than 4.5 mm (mean, 2.5 mm), the 2-stage procedure was used for 37 sinus elevations and 108 implants. For the 140 implants placed, the overall survival rate was 95.7% at the healing abutment surgery, and the cumulative survival rate was 94.9% at 1 and 5 years. The type of surgical technique was significantly associated with implant failure (P < .05); implants placed using the 1-stage procedure showed a failure rate of 12.5%, while implants placed with the 2-stage procedure had a failure rate of 2.8%. No significant difference in survival rate was observed with respect to implant surface. CONCLUSIONS: A high survival rate was achieved when sinus elevation was performed with a combination of autogenous bone and anorganic bovine hydroxyapatite, even where a minimal amount of residual crestal bone was present. The survival rate was improved when implants were placed after a healing period.     

Effects of implant design on marginal bone changes around early loaded, chemically modified, sandblasted Acid-etched-surfaced implants: a histologic analysis in dogs

Background: A minimal marginal bone loss around implants during early healing has been considered acceptable. However, the preservation of the marginal bone is related to soft tissue stability and esthetics. Implant designs and surfaces were evaluated to determine their impact on the behavior of the crestal bone. The purpose of this study is to evaluate histologic marginal bone level changes around early loaded, chemically modified, sandblasted acid‐etched–surfaced implants with a machined collar (MC) or no MC (NMC). Methods: Three months after a tooth extraction, 72 sandblasted acid‐etched chemically modified implants were placed in six dogs. Thirty‐six implants had NMC, and 36 implants had a 2.8‐mm MC. All implants were loaded 21 days after placement. For histologic analyses, specimens were obtained at 3 and 12 months. Assessments of the percentage of the total bone‐to‐implant contact and linear measurements of the distance from the shoulder of the implant to the first bone‐to‐implant contact (fBIC) were performed. Based on fBIC measurements, estimates of bone loss were obtained for each implant. A mixed‐model analysis of variance was used to assess the effects of implant type and sacrifice time. Results: All implants achieved osseointegration. The mean bone gain observed around NMC early loaded implants (at 3 months: 0.13 ± 0.37 mm; at 12 months: 0.13 ± 0.44 mm) was significantly different from the mean bone loss for MC early loaded implants (at 3 months: ?0.32 ± 0.70 mm; at 12 months: ?0.79 ± 0.35 mm) at 3 months (P = 0.003) and 12 months (P <0.001). No infrabony component was present at the marginal fBIC around NMC implants in most cases. There were no statistically significant differences among the means of total bone contact for implant types. Conclusions: Chemically modified, sandblasted acid‐etched–surfaced implants with NMC presented crestal bone gain after 3 and 12 months under loading conditions in the canine mandible. The implant design and surface were determinants in the marginal bone level preservation.     

Changes in crestal bone levels for immediately loaded implants

PURPOSE: The authors' objective was to measure crestal bone level change in subjects with immediately loaded implants and to identify risk factors associated with changes in bone level. MATERIALS AND METHODS: A retrospective cohort study design was used. The sample comprised subjects who had had endosseous implants placed and immediately loaded between July 2001 and July 2003. Demographic, health status-related, anatomic, implant-specific, prosthetic, and surgical variables were examined. The primary outcome variable was change in crestal bone level over time. Appropriate uni-, bi-, and multivariate statistics were computed. RESULTS: The sample comprised 174 subjects who received 347 immediately loaded implants. The mean duration of radiographic follow-up was 6.9 +/- 4.0 months, respectively. Mean changes in radiographic bone level were -0.5 mm and -0.6 mm on the mesial and distal surfaces, respectively, after a mean of 6.9 months of radiographic follow-up. Using least squares methods, it was estimated that radiographic bone levels would be -1.0 mm and -0.8 mm on the mesial and distal surfaces, respectively, at 12 months. The multivariate model revealed that radiolucency at or adjacent to implant site was associated with an increased risk of crestal bone loss (odds ratio, 1.88; 95% CI, 1.00 to 3.60). Twelve months after placement, 92.5% of implants had had < or = 1.5 mm of crestal bone loss. DISCUSSION: The results of this study were comparable to the results of other studies comparing immediate loading to delayed loading. Further research to estimate long-term changes in crestal bone loss and to identify risk factors for bone loss with immediate loading is recommended. CONCLUSION: This study suggests that crestal bone level changes with immediately loaded implants were within the recommended range for 92.5% of the evaluated implants. The mandible showed a higher risk for crestal bone loss compared to the maxilla.     

Rehabilitation of irradiated patients with chemically modified and conventional SLA implants: five‐year follow‐up

The aim of this study is to evaluate the clinical and radiological parameters of standard SLA surface implants compared to chemically modified hydrophilic SLActive implants in irradiated patients after the initial 12‐month loading period up to 5 years. Twenty patients with a mean age of 61·1 years were treated with dental implants after ablative surgery and radio‐chemotherapy of oral cancer. All patients were non‐smokers. The placement of 102 implants (50 SLA, 52 SLActive) was performed bilaterally according to a split‐mouth design. Mean crestal bone changes were evaluated using standardised orthopantomographies and clinical parameters. Data were analysed using a Kaplan–Meier curve, Mann–Whitney U‐test and two‐factorial non‐parametric analysis. The average observation period was 60 months. The amount of bone loss at the implant shoulder of SLA implants was mesial and distal 0·7 mm. The SLActive implants displayed a bone loss of mesial 0·6 mm as well as distal 0·7 mm after 5 years. Two SLA implants were lost before loading. One patient lost five implants due to recurrence of a tumour. The overall cumulative 12‐month, 3‐year and 5‐year survival rate of SLA implants was 92%, 80% and 75·8% and of SLActive implants 94·2%, 78·8% and 74·4%, respectively. Eighteen implants were considered lost because the patients had died. Sandblasted acid‐etched implants with or without a chemically modified surface can be used in irradiated patients with a high predictability of success. Lower implant survival rates in patients with irradiated oral cancer may be associated with systemic effects rather than peri‐implantitis.     

A retrospective analysis of peri-implant tissue responses at immediate load/provisionalized microthreaded implants

PURPOSE: The aim of this retrospective study was to examine the peri-implant tissue status at immediately provisionalized anterior maxillary implants 12 to 30 months following tooth replacement. MATERIALS AND METHODS: This is a retrospective study of 43 microthreaded, TiO2 grit-blasted implants placed in healed ridges and immediate extraction sockets to restore maxillary anterior and premolar teeth in 28 patients. The cortical bone position relative to the implant reference point was evaluated at implant placement and 6 to 30 months following restoration. Radiographs were assessed using 7x magnification. The distance from the reference point to the cortical bone was measured to +/- 0.1 mm. The relationship of the peri-implant mucosa to the incisal edge of the definitive prosthesis was recorded. RESULTS: Four implants in 3 individuals failed during the first 6 weeks following placement and provisional loading. Cortical bone adaptation from the time of implant placement up to 30 months following restoration ranged from 0.0 mm to 1.5 mm (average, 0.33 +/- 0.40 mm mesially and 0.28 +/- 0.37 mm distally). The mean radiographic measurements from the interproximal crestal bone to the contact point were 4.53 +/- -0.91 mm (mesial) and 4.06 +/- 0.98. Maintenance and growth of papilla was observed in this group of immediate provisionalized single-tooth implants. Definitive abutment or abutment screw loosening was not observed. DISCUSSION: The linear clinical and radiographic measures of peri-implant tissue responses suggest that proper implant placement is followed by supracrestal biological width formation along the abutment and preservation of toothlike tissue contours. This may influence buccal peri-implant tissue dimensions. CONCLUSIONS: Generalized maintenance of crestal bone and the increased soft tissue dimension with maintenance of peri-implant papilla were identified as expected outcomes for immediate loading/provisionalization of microthreaded, TiO2 grit-blasted implants. Control of peri-implant tissues can be achieved to provide predictable and esthetic treatment for anterior tooth replacement using dental implants.     

Crestal bone changes around titanium implants. Part I: A retrospective radiographic evaluation in humans comparing two non-submerged implant designs with different machined collar lengths

BACKGROUND: Experimental studies demonstrated that peri-implant crestal hard and soft tissues are significantly influenced in their apico-coronal position by the rough/smooth implant border as well as the microgap/ interface between implant and abutment/restoration. The aim of this study was to evaluate radiographically the crestal bone level changes around two types of implants, one with a 2.8 mm smooth machined coronal length and the other with 1.8 mm collar. METHODS: In 68 patients, a total of 201 non-submerged titanium implants (101 with a 1.8 mm, 100 with a 2.8 mm long smooth coronal collar) were placed with their rough/smooth implant border at the bone crest level. From the day of surgery up until 3 years after implant placement crestal bone levels were analyzed digitally using standardized radiographs. RESULTS: Bone remodeling was most pronounced during the unloaded, initial healing phase and did not significantly differ between the two types of implants over the entire observation period (P >0.20). Crestal bone loss for implants placed in patients with poor oral hygiene was significantly higher than in patients with adequate or good plaque control (P <0.005). Furthermore, a tendency for additional crestal bone loss was detected in the group of patients who had been diagnosed with aggressive periodontitis prior to implant placement (P = 0.058). In both types of implants, sand-blasted, large grit, acid-etched (SLA) surfaced implants tended to have slightly less crestal bone loss compared to titanium plasma-sprayed (TPS) surfaced implants, but the difference was not significant (P >0.30). CONCLUSION: The implant design with the shorter smooth coronal collar had no additional bone loss and may help to reduce the risk of an exposed metal implant margin in areas of esthetic concern.     

Radiographic evaluation of marginal bone levels during healing period,adjacent to parallel‐screw cylinder implants inserted in the posterior zone of the jaws,placed with flapless surgery

Objective: The purpose of this study was to compare changes at the marginal bone level adjacent to implants placed with flapless surgery and flap surgery during a stress‐free healing period. Material and methods: Seven hundred and eighty‐five implants were placed in 417 patients with a flapless approach and 459 implants were placed in 227 patients using flap techniques. The marginal bone level was determined radiographically, using digitized panoramic radiographs, at two time points: at implant placement (baseline) and after the healing period. Results: The median follow‐up time was 0.5 years (SD, 1.2; range: 0.3–0.7). Implants placed with flapless surgery had a mean crestal bone loss of 0.5 mm (SD, 0.5; range: ?0.7–2.4) and implants placed with flap surgery had a mean bone loss of 0.5 mm (SD, 0.7; range: ?2.0–3.0) after healing. Differences in bone level changes between smokers and non‐smokers were statistically significant for the flapless group (P<0.01). Conclusions: A radiographic evaluation of marginal bone levels adjacent to implants showed comparable results for implants placed with flapless surgery and flap surgery. Appropriate case selection after virtual planning of the implant position and a sound surgical protocol is necessary for flapless surgery. Smoking habits may compromise the efficacy of flapless implant procedures. To cite this article:
Nickenig H‐J, Wichmann M, Schlegel KA, Nkenke E, Eitner S. Radiographic evaluation of marginal bone levels during healing period, adjacent to parallel‐screw cylinder implants inserted in the posterior zone of the jaws, placed with flapless surgery.
Clin. Oral Impl. Res. 21 , 2010; 1386–1393.
doi: 10.1111/j.1600‐0501.2009.01961.x