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.     

Clinical and radiographic evaluation of early loaded free-standing dental implants with various coatings in beagle dogs.

STATEMENT OF PROBLEM: Immediate loading of implants may be a predictable treatment alternative when cross-arch stabilization with a fixed provisional is observed. PURPOSE: This study investigated the effect of immediate masticatory loading on the stability of single-standing dental implants with 4 different surfaces. MATERIAL AND METHODS: A total of 40 solid screw implants (diameter 3.3 mm, length 8 mm) were placed in the mandibles of 4 beagle dogs. Test groups included 3 hydroxyapatite (HA) coatings of titanium plasma-sprayed (TPS) implants. Implants with TPS alone served as control. Gold crowns were inserted 2 days after implant placement and the dogs were immediately put on a hard food diet. Implants were followed for 6 months after loading. Clinical and radiographic assessments of implants were performed at time of crown insertion (baseline) and after 1, 3, and 6 months of loading. The Periotest instrument was used for mobility measurements and radiographs were obtained for evaluation of peri-implant radiolucency and measurement of crestal bone changes. RESULTS: Of 40 implants, 39 displayed no discernible mobility, corresponding to successful clinical function. Peri-implant radiolucencies were absent for all but the 1 mobile implant. The reduction in crestal bone levels adjacent to the implants between baseline and 6 months was statistically significant (P <.0001). No statistically significant differences in crestal bone level changes over time were found between the various coatings demonstrating the absence of a treatment effect initiated by the surface coatings. CONCLUSION: In this study in beagle dogs, immediate masticatory loading of single-standing dental implants did not jeopardize tissue integration, provided the implants had excellent primary stability.     

Radiographic evaluation of modern oral implants with emphasis on crestal bone level and relevance to peri‐implant health

Implant stability and maintenance of stable crestal bone level are prerequisites for the successful long‐term function of oral implants, and continuous crestal bone loss constitutes a threat to the longevity of implant–supported prosthetic constructions. The prevalence/incidence and reasons for crestal bone loss are under debate. Some authors regard infection (i.e. peri‐implantitis) as the cause for virtually all bone loss, while others see crestal bone loss as an unavoidable phenomenon following surgery and implant loading. Irrespective of the cause of continuous crestal bone loss, correct usage and scientifically sound interpretation of radiographs are of utmost importance for evaluation of oral implants. The periapical radiographic technique is currently the preferred method for evaluating implant health based on bone loss, and digital radiographs allow easy standardization of the image contrast. It is suggested that baseline radiographs should be taken at the time the transmucosal part pierces the mucosal tissues and annually thereafter. The number of unreadable radiographs should be presented in scientific publications to give insights into the quality of the radiographic examination. It is suggested that not only mean values, but also the range of bone levels, should be presented to describe the proportion of implants that show continuous crestal bone loss. In the absence of other clinical symptoms, bleeding on probing around implants seems to be a weak indicator of ongoing or future loss of crestal bone. According to recent longitudinal studies on modern implant surfaces peri‐implantitis defined as ‘infection with suppuration associated with clinically significant progressing crestal bone loss’ occurs with a prevalence of less than 5 % in implants with 10 years in function.     

软组织瓣早期裂开或穿孔对种植体颈缘部骨组织的影响

放射线性片评估种植手术后软件组织瓣早开裂或穿孔对种植体周边缘骨吸收的影响。方法：１７例种植患者,植入的３２颗两段式骨内种植体,其中１７颗出现软组织瓣早期裂开或穿孔,导致种植体早期暴露。根据种植体入当天及种植Ⅱ期手术（安装愈合基台）前的Ｘ线片（根尖片）,测量出种植体颈部边缘骨高度的变化。结果：早期暴露的种植体均产生明显吸收,近中平均１．９５ｍｍ,远中平均２．１５ｍｍ;而正常愈合种植体（非裂开）骨变化     

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.     

The effect of inter-implant distance on the height of inter-implant bone crest

BACKGROUND: The biologic width around implants has been well documented in the literature. Once an implant is uncovered, vertical bone loss of 1.5 to 2 mm is evidenced apical to the newly established implant-abutment interface. The purpose of this study was to evaluate the lateral dimension of the bone loss at the implant-abutment interface and to determine if this lateral dimension has an effect on the height of the crest of bone between adjacent implants separated by different distances. METHODS: Radiographic measurements were taken in 36 patients who had 2 adjacent implants present. Lateral bone loss was measured from the crest of bone to the implant surface. In addition, the crestal bone loss was also measured from a line drawn between the tops of the adjacent implants. The data were divided into 2 groups, based on the inter-implant distance at the implant shoulder. RESULTS: The results demonstrated that the lateral bone loss was 1.34 mm from the mesial implant shoulder and 1.40 mm from the distal implant shoulder between the adjacent implants. In addition, the crestal bone loss for implants with a greater than 3 mm distance between them was 0.45 mm, while the implants that had a distance of 3 mm or less between them had a crestal bone loss of 1.04 mm. CONCLUSIONS: This study demonstrates that there is a lateral component to the bone loss around implants in addition to the more commonly discussed vertical component. The clinical significance of this phenomenon is that the increased crestal bone loss would result in an increase in the distance between the base of the contact point of the adjacent crowns and the crest of bone. This could determine whether the papilla was present or absent between 2 implants as has previously been reported between 2 teeth. Selective utilization of implants with a smaller diameter at the implant-abutment interface may be beneficial when multiple implants are to be placed in the esthetic zone so that a minimum of 3 mm of bone can be retained between them at the implant-abutment level.     

Crestal bone loss minimized when following the crestal preparation protocol: a histomorphometric study in dogs

Initial breakdown of the implant-tissue interface generally begins at the crestal region in successfully osseointegrated implants. The purpose of this study was to evaluate the effect on crestal bone loss (CBL) around implants specially developed for immediate loading with a unique crestal drill. After 8 weeks postextraction, 6 young male mongrel dogs received 48 implants (XiVE) in the region corresponding to the 4 mandibular premolars. The implant sites were prepared according to the manufacturer's protocol with conventional standard drills. Before implant placement, the crestal drill was used in the experimental group but not in the control group. After a healing period of 12 weeks, the dogs were sedated and euthanized. Through linear measurements, from the top of the implant to the first bone-implant contact, the amount of CBL was determined. The histomorphometric results of CBL (mean +/- SEM) were 0.88 +/- 0.13 mm (range 0.0-3.0 mm) in the experimental group and 1.69 +/- 0.17 mm (range 0.0-4.2 mm) in the control group. The difference was statistically significant (P < .05) when the implants were used as the experimental units. The statistical analysis also revealed significance when the dogs were used as the experimental units (P < .05). When the median was used for analyses, the CBL was 0.44 mm for the experimental group and 1.91 mm for the control group. Crestal bone loss was minimized when the crestal preparation protocol was carefully followed by using the osseocondensating XiVE implant system.     

A 1‐Year Controlled Clinical Trial of Immediate Implants Placed in Fresh Extraction Sockets: Stability Measurements and Crestal Bone Level Changes

Purpose: The aim of this study was to measure stability and crestal bone level changes of implants placed in fresh extraction sockets in elderly patients. Methods: Thirty‐five patients who were in need of tooth extractions were recruited for this study. They received a total of 65 implants in both jaws to support fixed or removable prostheses. The teeth were carefully extracted, the implants set directly in the root socket, and resonance frequency analysis (RFA) measurements were simultaneously performed (Time 1 = T1). After a healing time of 6 to 10 weeks the measurements were repeated (Time 2 = T2). Orthograd periapical radiographs were taken when the new prostheses were fabricated and after 1 year of loaded period. The distance between the first visible bone implant contact (BIC) and the implant‐shoulder was measured and crestal bone loss was calculated (ΔBIC). Mean RFA and BIC were compared for various subgroups (p < .05). By means of a fixed effects model, the impact of the parameters gender, jaw, and prosthetic indication on RFA measurements was analyzed (p < .016). Results: The mean implant stability quotient (ISQ) values were 64.4 ± 6.7 at T1 and 64.0 ± at 8.6 T2, with a trend to higher values for male patients. The mixed model showed that only the jaw had a statistically significant impact on ISQ values, with higher values for the mandible. Mean crestal bone loss was small with 0.49 ± 0.81 mm, ranging form 0.1 to 2.4 mm. Twenty percent of the implant sites lost more than 1‐mm crestal bone. No differences were found in subgroups. Conclusions: Good primary and secondary stability of the implants was reached in both jaws. Crestal bone loss was small but may not be fully predictable for a single site. This treatment modality can be applied successfully in elderly patients and can be suggested for various prosthetic indications in both jaws.     

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.     

Radiographic evaluation of marginal bone maintenance around tissue level implant and bone level implant: a randomised controlled trial. A 1‐year follow‐up

The etiologic factors associated with crestal bone loss have not been comprehensively clarified. Several theories exist as to the reason for the observed changes in crestal bone height following implant restoration. In the 1990s, the wide‐diameter implants were commercially introduced. Initially, the implants were restored with standard‐diameter abutments because of lack of matching prosthetic components. Long‐term radiographic follow‐up of these ‘platform‐switched’ restored wide‐diameter dental implants has demonstrated a smaller‐than‐expected vertical change in the crestal bone height around these implants that is typically observed around implants restored conventionally with prosthetic components of matching diameters. The aim of this randomised controlled study was to assess radiographically marginal bone level alterations in implants restored according to the platform‐switching concept compared with traditionally restored implants. Fifty‐four subjects to participate in this randomised controlled study were selected. Two groups were assigned at random: control group (56 implants were restored with standard matching‐diameter abutments) and test group (58 implants were restored with medialised abutments). X‐ray explorations were taken for peri‐implant bone level at the minute the last cementing of the prosthesis and at 1‐year follow‐up. NHI Image was used to digitally process and manipulate the radiographic images and perform the measurements. Mean of bone loss with platform‐switching implants was ?0·01 mm, and the mean of bone loss with standard platform implant was 0·42 mm. Outcomes of this study indicated that the platform‐switching design could preserve the crestal bone levels to 1‐year follow‐up. There was a statistically significant difference in marginal bone loss.     

Retrospective clinical evaluation of tapered screw-vent implants: results after up to eight years of clinical function

Uncertainty about the causes of peri-implant bone loss and difficulties in measuring it often have resulted in omission of bone loss data from published long-term implant studies. This nonrandomized, uncontrolled, retrospective study evaluated the clinical outcomes of treatment with tapered, multithreaded implants with a special emphasis on peri-implant crestal bone status. Chart reviews were conducted of 60 patients who had been treated with 267 implants for the placement of 1 or more missing and/or unsalvageable teeth, and who met general inclusion criteria for dental implant therapy. In all cases, marginal bone changes were calculated from the cementoenamel junction (CEJ) or the implant neck to the crestal bone level with standardized radiographs taken at implant placement (baseline) and during annual follow-up. After a mean followup of 7.5 years, implant survival was 98.5% (263/267) for all implants placed, and implant success was 96.2% (253/263) for all surviving implants. No discernible bone loss was evident in 88% of surviving implants. Crestal bone loss was observed in 25% (15/60) of total study subjects and in 12% (32/263) of all surviving implants: 29 implants exhibited 1 mm of bone loss and 3 implants lost 2 mm of bone. Low-density maxillary jawbone and more extensive bone remodeling, which were required around implants immediately placed into extraction sockets, were the probable causes of observed bone loss in this study. Implants exhibited excellent long-term outcomes with little or no bone loss.     

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.     

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.     

Radiographic changes around immediately restored dental implants in periodontally susceptible patients: 1-year results

PURPOSE: There is little information available about radiographic bone changes around immediately restored implants in periodontally compromised patients. The aims of this study were to evaluate the effect of immediate restoration on radiographic bone changes and to compare radiographic changes between arches and between healed and extraction sites in periodontally susceptible patients. MATERIALS AND METHODS: Patients received periodontal treatment. "All in one" implant surgery was then performed: Hopeless teeth were extracted, debridement around remaining adjacent teeth was performed, implants were inserted guided by a surgical stent, and a prefabricated screwed provisional restoration was immediately delivered on selected implants. Periapical radiographs using a parallelism appliance were taken at implant surgery and 6 and 12 months postsurgery. The distance between the alveolar crest and the implant shoulder was measured at the mesial and distal aspect of each implant. Bone changes were compared between immediately restored, submerged, and nonrestored implants; between arches; and between healed and extraction sites. RESULTS: Nineteen patients received 74 implants. Twelve implants in 4 patients failed within the first 6 months. Mean bone changes (+/- SE) between baseline and 12 months ranged between -1.19 +/- 0.19 mm and -1.88 +/- 0.3 mm. No difference was found between restored versus nonrestored sites or between maxillary and mandibular sites. Bone loss was slightly higher in healed sites. CONCLUSIONS: First-year bone changes around immediately restored dental implants in periodontally susceptible patients were slightly higher than most reports in the literature. This indicates a potential influence of periodontal disease on the success rate of dental implants.     

Evaluation of an endosseous titanium implant with a sandblasted and acid‐etched surface in the canine mandible: radiographic results

Previous studies have demonstrated in short‐term experiments that a sandblasted and acid‐etched (SLA) titanium implant had a greater bone‐to‐implant contact than a titanium plasma‐sprayed (TPS) implant in non‐oral bone. In the present study, an SLA implant was compared radiographically to a TPS implant under unloaded and loaded conditions in the canine mandible for up to 15 months. 69 implants were placed in 6 foxhounds. Standardized radiographs were taken at baseline, preload, 3, 6, 9, and 12 months of loading. Loaded implants were restored with gold crowns similar to the natural dentition. Radiographic assessment of the bone response to the implants was carried out by measuring the distance between the implant shoulder and the most coronal bone‐to‐implant contact (DIB) and by evaluation of bone density changes using computer‐assisted densitometric image analysis (CADIA). 5 different areas‐of‐interest (AOI) were defined coronally and apically along the implant. DIB measurements revealed that SLA implants had significantly less bone height loss (0.52mm) than TPS implants (0.69mm) at the preload evaluation ( p =0.0142) as well as at 3 months of loading (0.73mm/1.06mm: p =0.0337). This difference was maintained between the implant types during the 1‐year follow‐up period. The same trend was also evident for CADIA measurements with SLA implants showing higher crestal bone density values when comparing preload to baseline data ( p =0.0890) and 3 months to baseline data ( p =0.0912). No measurable bone density changes were apparent in the apical areas of either implant. These results suggest that SLA implants are superior to TPS implants as measured radiographically in oral bone under unloaded and loaded conditions.     

A follow-up study of maxillary implants supporting an overdenture: clinical and radiographic results

PURPOSE: Studies of maxillary overdentures supported by endosseous implants often show a high implant failure rate. The aim of the present investigation was to evaluate clinically and radiographically non-submerged implants supporting an overdenture in the maxilla. MATERIALS AND METHODS: Forty-one patients were consecutively admitted for treatment. The standard procedure was to place 4 implants and to mount a U-shaped bar for overdenture connection. When the overdenture was delivered to the patients, peri-implant parameters were recorded and radiographs were taken. All patients were required to follow a maintenance care program. In the context of this study, all patients were clinically examined and the peri-implant parameters were compared. Crestal bone loss was analyzed using linear radiographic measurements. A life table analysis was applied to calculate the cumulative survival rate (CSR). RESULTS: Three implants failed in the early healing phase, and 3 patients lost 6 implants during the loading period. The 5-year CSR of all implants was 94.2%. The peri-implant parameters gave evidence of healthy soft tissues and good oral hygiene. The increases in probing depths and attachment loss were significant (P < .05). The mean marginal crestal bone loss was about 0.7 mm and was statistically significant at mesial and distal sites (P < .001). DISCUSSION: The correlation between clinical attachment loss and crestal bone loss was not significant. Pronounced marginal bone loss was found around some implants. CONCLUSION: In planned maxillary overdenture treatment, it is possible to achieve a satisfactory survival rate of the implants.     

Crestal Bone Changes at Teeth and Implants in Periodontally Healthy and Periodontally Compromised Patients. A 10‐Year Comparative Case‐Series Study

Background: Limited data exist on the longitudinal crestal bone changes around teeth compared with implants in partially edentulous patients. This study sought to compare the 10‐year radiographic crestal bone changes (bone level [BL]) around teeth and implants in periodontally compromised (PCPs) and periodontally healthy (PHPs) patients. Methods: A total of 120 patients were evaluated for the radiographic crestal BL around dental implants and adjacent teeth at time of implant crown insertion and at the 10‐year follow‐up. Sixty patients had a previous history of periodontitis (PCPs), and the remaining 60 were PHPs. In each category (PCP and PHP), two different implant systems were used. The mean BL change at the implant and at the adjacent tooth at the interproximal area was calculated by subtracting the radiographic crestal BL at the time of crown cementation from the radiographic crestal BL at the 10‐year follow‐up. Results: At 10 years after therapy, the survival rate ranged from 80% to 95% for subgroups for implants, whereas it was 100% for the adjacent teeth. In all eight different patient categories evaluated, teeth demonstrated a significantly more stable radiographic BL compared with adjacent dental implants (teeth BL, 0.44 ± 0.23 mm; implant BL, 2.28 ± 0.72 mm; P <0.05). Radiographic BL changes around teeth seemed not to be influenced by the presence or absence of advanced bone loss (≥3 mm) at the adjacent implants. Conclusions: Natural teeth yielded better long‐term results with respect to survival rate and marginal BL changes compared with dental implants. Moreover, these findings also extend to teeth with an initial reduced periodontal attachment level, provided adequate periodontal treatment and maintenance are performed. As a consequence, the decision of tooth extraction attributable to periodontal reasons in favor of a dental implant should be carefully considered in partially edentulous patients.     

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.     

AICRG, Part II: Crestal bone loss associated with the Ankylos implant: loading to 36 months

PROBLEM: The Ankylos endosseous dental implant is a new implant design that will be available in the United States in early 2004. It features an internal tapered abutment connection, a smooth polished collar without threads at the coronal part of the implant body, and a roughened surface with variable threads on the body of the implant fixture. A precise, tapered, conical abutment connection eliminates the microgap often found in 2-stage implant systems. This microgap may allow the accumulation of food debris and bacteria, as well as micromovement between the parts during clinical function, both of which can lead to a localized inflammation and crestal bone loss. PURPOSE: The purpose of this section of the study was to assess any crestal bone loss associated with this new implant. METHOD: The clinical performance of this new implant design was studied under well-controlled clinical conditions. Over 1500 implants were placed and restored. The vertical crestal bone loss was measured "directly" between the time of implant placement and uncovering, using a periodontal probe. Serial dental radiographs were taken between loading, and the 12-, 24-, and 36-month follow-up visits to determine "indirect" crestal bone loss within a specific period. RESULTS: Bone loss varied among the participating centers from less than 0.5 mm to 2.0 mm. The largest amount of bone loss occurred between the time of placement and uncovering. Following loading, the mean bone loss for all implants for a period of 3 years was about 0.2 mm/y. CONCLUSIONS: The extent of the crestal bone loss after loading was minimal for patients regardless of age, gender, prosthetic applications, bone density, and remote or crestal incisions, as well as for smokers or nonsmokers. Bone loss per year is well within the guidelines of 0.2 mm/y proposed by others.     

Prospective Clinical Trial Evaluating a New Implant System for Implant Survival,Implant Stability and Radiographic Bone Changes

Background: There are a few prospective studies reporting on new implant systems. When a new implant is brought to market, prospective trials should be carried out to determine the predictability of that system. Purpose: This prospective study evaluates implant survival, Resonance Frequency Analysis (RFA), and crestal bone level changes for a new implant system (Neoss System, Bimodal surface, Neoss Ltd, Harrogate, UK). Materials and Methods: Seventy‐six patients, 38 females (age ranging from 23 to 57 years) and 38 males (ranging in age from 17 to 85 years) received 100 Neoss implants. Patients were consecutively enrolled in the study if they were missing one or more teeth in either arch, or a single tooth was scheduled for removal and immediate implant replacement. Evaluated implants were 4, 4.5, or 5 mm wide and were 7, 9, 11, 13, or 15 mm long. A one‐stage approach was followed. At first stage and prior to healing abutment placement RFA measurements were taken. Measurements were retaken at second stage. Fifty‐one implants were placed for restoration of single missing teeth and 49 were for short span implant bridges. Results: The cumulative survival rate at 1‐ to 2‐year interval was 93%. Average initial RFA measurement for all implants was 72.06, while the average final score was 72.58. These changes were not statistically significant. Changes in RFA scores for maxillary implants were insignificant. Forty‐two paired mandibular RFA measurements were evaluated. Initial and final mean mandibular RAF measurements were 73.65 (SD 9.203) and 77.186 (SD 6.177), respectively. These changes were statistically significant (p = .02). Sixty‐four paired radiographs were available for evaluation. Between examinations, there was an average –0.6 mm of bone loss, which was statistically significant (p = .03). On average, 4.0‐mm‐wide implants lost 0.1 mm of bone when compared with 5‐mm‐wide implants. These differences were insignificant (p = .86). Bone loss was adjusted for implant length, and tooth position and there were small, but clinically insignificant changes. Five‐millimeter‐wide implants lose 0.2 mm more than 4.0‐mm‐wide implants (p = .7). Maxillary incisors lose the least amount of bone 0.152 (p = .33). Conclusions: The implants tested in this study had initially high RAF readings, indicating good primary stability. RFA readings for implants placed in the mandible improved from baseline and the changes were statistically significant. Marginal bone levels revealed clinically insignificant bone loss from implant installation to second stage. Loss of seven implants with initially high RFA readings is surprising.