Clinical evaluation of overdenture restorations supported by osseointegrated titanium implants: a retrospective study

This paper reports the results of using osseointegrated titanium implants as abutments for overdenture restorations in the mandibles of 62 edentulous patients. All of these patients were edentulous for several years and required complete dentures. Six months after prosthodontic treatment, two implants (ITI, Straumann) were placed with consideration of the denture base and morphologic aspects of the mandibular residual ridge. The retention devices consisted of a bar connector or single ball-shaped precision attachments. Three or four implants splinted with a bar were placed in a control group of 11 patients. Attached keratinized gingiva (greater than or equal to 2 mm) surrounded approximately 48% of the buccal and 55% of the lingual implant sites. Evaluation after periods of 6 to 66 months postoperatively revealed good clinical results with five patients lost to recall in 1989. Two implants were lost after overdenture insertion. The findings suggest that two implants may adequately serve as retention for a mandibular complete denture and that attached gingiva surrounding the implants does not seem to be prerequisite for healthy function.     

A longitudinal microbiological study on osseointegrated titanium implants in partially edentulotis patients

The aim was to longitudinally follow the colonization of putative periodontal pathogens on titanium implants in partially edentulous patients. Nineteen individuals, who were partially edentulous and were on the waiting‐list to be treated with titanium fixtures, were included in the study. They were treated for periodontal disease with oral hygiene instructions and supra‐ and subgingival debridement and were left for maintenance. Full‐mouth recordings of each patient were performed at baseline, including attachment level and probing pocket depth. Bleeding was provoked and visible plaque were registered. Subgingival samples were taken for examination of Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans . Bridge connection was completed 1 month after abutment connection. The bone level was registered on radiographs. The patients were followed with clinical registrations and subgingival samples at 6, 12, 24 and 36 months. No significant changes in pocket depth, attachment level, bleeding on probing or plaque score occurred during the experimental period. The number of individuals positive at teeth and abutments for the various bacterial species reached approximately similar levels at 6 months. No significant changes over time were seen. Comparison between bone height. seen on radiographs, at abutments after 2, 12 and 36 months gave only 3 sites with bone loss of > 0.5 mm. All these sites were found in one patient and were accompanied by P. intermedia .     

Randomized-controlled clinical trial of customized zirconia and titanium implant abutments for single-tooth implants in canine and posterior regions: 3-year results

Objectives: The aim was to test whether or not zirconia abutments exhibit the same survival and technical/biological outcome as titanium abutments. Material and methods: Twenty‐two patients receiving 40 single‐tooth implants in canine and posterior regions were included. The implant sites were randomly assigned to 20 zirconia and 20 titanium abutments. All‐ceramic and metal–ceramic crowns were fabricated. At baseline, 6, 12 and 36 months, the reconstructions were examined for technical and biological problems. Probing pocket depth (PPD), plaque control record (PCR) and bleeding on probing (BOP) were assessed at abutments (test) and analogous contralateral teeth (control). Standardized radiographs of the implants were made and the bone level (BL) was measured referring to the implant shoulder on mesial (mBL) and distal sides (dBL). The difference of color (ΔE) of the peri‐implant mucosa and the gingiva of control teeth was assessed with a spectrophotometer. The data were statistically analyzed with Mann–Whitney Rank and Student's unpaired t‐tests. Results: Eighteen patients with 18 zirconia and 10 titanium abutments were examined at a mean follow‐up of 36 months (range 31.5–53.3 months). No fracture of an abutment or loss of a reconstruction was found. Hence, both exhibited 100% survival. At two metal–ceramic crowns supported by titanium abutments chipping of the veneering ceramic occurred. No difference of the biological outcome of zirconia and titanium abutments was observed: PPD ( 3.2 ± 1 mm, mPPD_Ti 3.4 ± 0.5 mm), PCR ( 0.1 ± 0.2, mPCR_Ti 0.1 ± 0.2) and BOP ( 0.4 ± 0.4, mBOP_Ti 0.2 ± 0.3). Furthermore, the BL was similar at implants supporting zirconia and titanium abutments ( 1.7 ± 1, 1.6 ± 1; mBL_Ti 2 ± 1, dBL_Ti 2.1 ± 1). Both, zirconia and titanium abutments induced a similar amount of discoloration of the mucosa compared with the gingiva at natural teeth ( 9.3 ± 3.8, ΔE_Ti 6.8 ± 3.8). Conclusions: At 3 years, zirconia and titanium abutments exhibited same survival and technical, biological and esthetical outcomes.     

The three-dimensional finite element analysis of fixed bridge restoration supported by the combination of teeth and osseointegrated implants

This study investigated the designs of osseointegrated prostheses in cases of free-end partial edentulism using comparative stress interpreted with the three-dimensional finite element method. Three free-end fixed osseointegrated prostheses models with various connection designs (i.e., rigidly connected to an abutment tooth and an implant, rigidly connected to an implant and two abutment teeth, and rigidly connected to an implant and three abutment teeth) were studied. The stress values of the three models loaded with vertical, buccolingual, and linguobuccal directions at 30 degrees angled to vertical axis forces were analyzed. When the fixed partial denture was connected to the three natural abutment teeth and an implant, the lowest levels of stress in the bone were noted.     

Putative periodontal and teeth in pathogens on titanium implants and teeth in experimental gingivitis and periodontitis in beagle dogs

The microflora around titanium implants and teeth in 4 beagle dogs was analyzed in order to follow the longitudinal development from healthy conditions to experimental gingivitis and periodontitis. A 2-month plaque control program was performed to establish healthy conditions on titanium implants and control teeth (baseline, day 0). Subgingival bacterial samples and radiographs were obtained. The plaque control was ceased and all measurements were repeated on day 21 (gingivitis). A new period of plaque control was initiated to re-establish healthy conditions (day 49). A cotton ligature was placed subgingivally around the implants and the control teeth to induce tissue breakdown. The ligatures were removed on day 91. The study was completed with registrations on day 121 (periodontitis). No significant microbiological difference was found between titanium implants and teeth in healthy conditions and in gingivitis and periodontitis. The mean total viable count increased 10 times on implants as well as on teeth. Streptococci were dominating at baseline: 40.2% on implants and 60.6% on teeth and decreased in gingivitis to 11.7% and 5.4%. When periodontitis had developed, the proportion of streptococci was < 1%. At baseline few Porphyromonas gingivalis and Prevotella intermedia were detected. They increased at gingivitis to 37.4% and 21.0%; when periodontitis developed, they comprised about 25.0%. Microbial colonization and establishment on titanium implants with healthy gingiva, experimental gingivitis and periodontitis follow the same pattern as on teeth.     

骨水平Xive种植体系统用于前牙美学修复的临床研究

目的:美学效果是种植修复追求的目标之一,相比功能方面的修复成功而言,实现美学方面的修复成功要更为困难,通常需要较为复杂的手术处理。本研究采用一种微创手术模式和简化的修复治疗程序,在前牙区植入骨水平种植体,评价其美学效果。方法:16例前牙缺失患者纳入本研究。所有患者经过全面检查,并做美学风险评估。采用不翻瓣加骨膨胀手术方法植入Xi ve骨水平种植体,术后连接基台,制作树脂牙冠即刻完成临时修复。四个月后更换为烤瓷牙冠完成恒久修复。观察种植体周硬软组织的变化,并对最终美学修复效果做临床评价。结果:16例患者所植入的22枚种植体在平均观察期8.3个月(5-24个月)无松动脱落。所有患者对修复结果都高度满意。种植修复的白色美学效果,受制于技工制作水平显得不太理想,而粉红色美学效果与患者组织条件有关,但与术前比较,种植体区硬软组织均有明显改善。结论:种植即刻暂时修复体,既可以满足患者美观需要,又对软组织实施了诱导成形。不翻瓣加骨膨胀手术方法,有利于增加种植体区硬软组织量,减少骨吸收,避免牙龈退缩,并避免牙龈组织的瘢痕形成,有利于获得较好的健康的软组织美学,其远期效果还有待继续观察。     

The condition of the soft tissues at tooth and fixture abutments supporting fixed bridges A microbiological and histological study.

In 10 partially edentulous patients provided with fixed bridgework supported by the combination of tooth and titanium fixture abutments, the condition of the soft tissues surrounding the abutments was examined. Sampling of supra- and subgingival plaque was performed from both teeth and fixtures. The samples were analyzed regarding the total bacterial counts, the relative distribution of bacterial morphotypes and the cultivable microflora. From each patient, soft tissue biopsies were obtained from 1 tooth and 1 fixture abutment, and the specimens were analyzed for the presence and extension of inflammatory cell infiltrates. The microbiological examination showed that the distribution of bacterial morphotypes in the supra- and subgingival plaque both at teeth and fixtures were similar, irrespective of localization and type of abutment. Nonmotile rods dominated the microflora, whereas spirochetes were either not detected or occurred in very low proportions. From the histological analysis, it was found that a majority of the soft tissue biopsies (75-80%) from both tooth and fixture sites contained only very small inflammatory cell infiltrates.     

A systematic review of single-tooth restorations supported by implants

OBJECTIVES: To make an inventory of clinical studies on single-tooth restorations supported by implants using a systematic review procedure and to aggregate overall survival results. DATA SOURCES: Papers referring to single-tooth implants were located by a MEDLINE search 1990 to April 1998. Three hundred and twenty references were found, and they were subjected to a systematic review procedure. STUDY SELECTION: A three-step inclusion/exclusion procedure was applied to identify papers that represented: good scientific practice (GSP), reported results of all patients, implants and crowns for more than 2years, and had sufficient data to generate life-table analyses. The outcomes were 'implant failure' and 'crown completion'. Nine studies survived. These data showed an overall mean GSP of 0.37 with a predicted 4year implant survival of 97% (n=459), and an uncomplicated crown maintenance of 83% (n=240). CONCLUSION: Single-tooth implants show an acceptable short-term survival of 4years, but crown complications are common.     

Targis高嵌体修复无髓后牙缺损的观察

目的：考察Targis瓷聚体作高嵌体修复无髓后牙缺损的临床效果。方法：对47例患者的53个经完善根管治疗术的后牙缺损，采用Targis高嵌体修复。根据改良的USPHS修复体评价标准，分别于修复后1、2,3年对Targis高嵌体进行随访复查。结果：Targis高嵌体的颜色协调性、边缘适合性和边缘着色在观察期内无明显改变，也未见继发龋和余留牙体的折裂，其累计成功率为94．3％。结论：Targis瓷聚体用于无髓后牙缺损的高嵌体修复效果良好，为牙体缺损的美观修复提供了新的选择，但其远期效果有待进一步观察。     

Randomized controlled clinical trial of customized zirconia and titanium implant abutments for canine and posterior single-tooth implant reconstructions: preliminary results at 1 year of function

Objectives: The aim of this study was to test whether or not customized zirconia abutments exhibit the same survival rates in canine and posterior regions as titanium abutments, and to compare the esthetic result of the two abutment types. Material and methods: Twenty‐two patients with 40 implants in posterior regions were included and the implant sites were randomly assigned to 20 customized zirconia and 20 customized titanium abutments. All‐ceramic (AC) and metal–ceramic (MC) crowns were fabricated. In all except two cases, the crowns were cemented on the abutments using resin or glass‐ionomer cements. Two zirconia reconstructions were screw retained. At baseline, 6 and 12 months, the reconstructions were examined for technical and biological problems. Probing pocket depth (PPD), plaque (Pl) and bleeding on probing (BOP) were assessed and compared with natural control teeth. Furthermore, the difference of color (ΔE) of the peri‐implant mucosa and the gingiva of control teeth was evaluated by means of a spectrophotometer (Spectroshade). The data were analyzed with Student's unpaired t‐test, ANOVA and regression analyses. Results: Twenty patients with 19 zirconia and 12 titanium abutments were examined at a mean follow‐up of 12.6±2.7 months. The survival rate for reconstructions and abutments was 100%. No technical or biological problems were found at the test and control sites. Two chippings (16.7%) occurred at crowns supported by titanium abutments. No difference was found regarding PPD (meanPPD_ZrO2 3.4±0.7 mm, mPPD_Ti 3.3±0.6 mm), Pl (mPl_ZrO2 0.2±0.3, mPl_Ti 0.1±1.8) and BOP (mBOP_ZrO2 60±30%, mBOP_Ti 30±40%) between the two groups. Both crowns on zirconia and titanium abutments induced a similar amount of discoloration of the soft tissue compared with the gingiva at natural teeth (ΔE_ZrO2 8.1±3.9, ΔE_Ti 7.8±4.3). Conclusions: At 1 year, zirconia abutments exhibited the same survival and a similar esthetic outcome as titanium abutments.     

Evaluation of stability of titanium and hydroxyapatite-coated osseointegrated dental implants: a pilot study

An endosseous implant is described as osseointegrated when it is immobile in function. Objective measures of stability testing have been described. The Periotest is a commercially available device that is used for this purpose. This study was designed to measure stability of endosseous implants placed in the mandible. Implants were placed in the mandibular canine or first premolar area to support an overdenture prosthesis. Stability was evaluated through the use of a Periotest device at the time of implant placement and following one year of functional loading. Implant designs were either a screw-shaped titanium alloy or a hydroxyapatite-coated cylinder. A total of 54 implants were placed, 37 were titanium screw-shaped implants, while the remaining 17 were hydroxyapatite cylinders. Initial measurements of stability showed no difference due to implant type. Following one year of functional loading, titanium screw-shaped implants were more stable than hydroxyapatite implants (P < 0.05). The difference in implant rigidity following a period of functional loading may be an indication of a difference in osseointegration between the two implants used in this study.     

The soft tissue barrier at implants and teeth

In the present animal experiment. analyses and comparisons were made between the structure and composition of clinically healthy supraalveolar soft tissues adjacent to implants and teeth. 5 beagle dogs were used. The right mandibular premolar region was selected in each dog for placement of titanium implants. while the left mandibular premolar region served as control. Extractions of the mandibular premolars were performed. healing allowed, following which titanium fixtures were installed in the edentolous premolar region. Abutment connection was carried out 3 months later. After another 2 months of healing. plaque control was initiated and maintained for 8 weeks. At the end of the plaque control period. clinical examinations were performed and biopsies harvested from the implant site and the contralateral premolar tooth region. Following fixation and decalcification, all tissue samples were embedded in EPON and examined by histometric and morphometric means. The result from the analyses demonstrated that the peri‐implant mucosa which formed at titanium implants following abutment connection had many features in common with gingival tissue at teeth. Thus, like the gingiva. the peri‐implant mucosa established a cuff‐like barrier which adhered to the surface of the titanium abutment. Further. both the gingiva and the peri-implant mucosa had a well‐keratinized oral epithelium which was continuous with a junctional epithelium that faced the enamel or the titanium surface. In the periimplant mucosa. the collagen fibers appeared to commence at the marginal bone and were parallel with the abutment surface. All gingival and peri‐implant units examined were free from infiltrates of inflammatory cells. It was suggested that under the conditions of study. both types of soft tissues. gingiva and peri‐implant mucosa. have a proper potential to prevent subgingival I plaque formation.     

Histological and biomechanical evaluation of phosphorylcholine-coated titanium implants

Objective: Compounds considered for drug delivery from oral implant surfaces in support of local bone formation might themselves influence osseointegration. Phosphorylcholine (PC) polymers have been shown to enhance the biocompatibility of medical devices and to serve as drug delivery systems. The objective of this study was to evaluate local bone formation and osseointegration at PC and positively charged PC (PC+)‐coated endosseous implants in an established rabbit model. Material and Methods: Sixteen adult female New Zealand White rabbits were used. Eight animals received PC‐coated and control titanium porous oxide surface implants placed in the left and right distal femural condyle (trabecular bone) and proximal tibial metaphysis (cortical bone) using aseptic routines. The remaining eight animals similarly received PC+ and control implants. One implant was placed in each femural condyle and two implants in each tibial metaphysis. Experimental and control implants were alternated between the left and right hind legs. Fascia and skin were closed in layers. The animals were euthanized following a 6‐week healing interval for biomechanical (removal torque) and histometric analyses. Results: Peri‐implant bone density was considerably greater at tibial compared with femoral sites within as well as immediately outside the implant threads. However, there were no significant differences in bone density among PC, PC+, and control implants. Nevertheless, bone–implant contact was significantly lower at PC compared with PC+ and control implants in cortical bone (p<0.05). Numerical differences in trabecular bone did not reach statistical significance. The removal torque evaluation revealed significantly lower values for PC compared with PC+ and control sites (p<0.05). Conclusion: The histometric and biomechanical analyses suggest that PC coating may influence biological processes and ultimately osseointegration of endosseous implants. Apparently, incorporation of cationic charges may reverse or compensate for this scenario. Nevertheless, both PC coatings exhibited clinically acceptable osseointegration. In perspective, PC technology appears to be a viable candidate delivery system for agents in support of local bone formation at endosseous implant surfaces.     

Implants in partially edentulous patients. A longitudinal study of bridges supported by both implants and natural teeth

The aim of the study was to compare the outcome of bridges supported by implants with bridges supported by a combination of implants and natural teeth abutments. The study comprised 23 patients with Applegate Kennedy Class I dentition in the mandible and a full upper denture. Implants ad modum Brånemark were inserted in the posterior areas of both mandibular quadrants. On one side, a bridge supported by 2 implants was constructed (Type I) and on the other side, a bridge supported by 1 tooth (mostly the canine or first premolar) and 1 implant was made (Type II). A total of 46 bridges were made and during the 3-year follow-up period, 4 Type I and 2 Type II bridges were lost. 8 out of 69 implants were lost during the 3-year follow-up, resulting in an implant survival rate of 88.4%. Marginal bone loss, one of several parameters, was evaluated on standardized intraoral radiographs. This was performed during the 1st and 2nd year of function and the total mean bone loss from loading was 0.46 mm and 0.56 mm, respectively. The bone loss during the 2nd year of function was significantly less, adjacent to implants supporting Type II bridges, than adjacent to implants supporting Type I bridges. Summarily, no disadvantages of combining of teeth and implants in the same bridge were found in this study. On the contrary, the slightly lower marginal bone loss adjacent to implants in Type II bridges may indicate that the bone reactions could be more favorable when bridges 1 are connected to both implants and teeth.     

Long-term follow-up of osseointegrated titanium implants using clinical, radiographic and microbiological parameters

Abstract: The aim of this study was to longitudinally follow up osseointegrated titanium implants in partially dentate patients by clinical, radiographic and microbiological parameters in order to evaluate possible changes in the peri‐implant health over time. Fifteen individuals treated with titanium implants, ad modum Brånemark, and followed for ten years were included in the study. Before implant placement ten years previously, the individuals had been treated for advanced periodontal disease and thereafter been included in a maintenance care program. The survival rate of the implants after ten years was 94.7%. The bone loss was 1.7 mm when using the abutment‐fixture junction as a reference point. Of the individuals, 50% were positive for plaque at the implants. Bleeding on sulcus probing was present at 61% of the implant surfaces. Ten years previously, the individuals had been carriers of putative periodontal pathogens, such as Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, Capnocytophaga spp. and Campylobacter rectus, and were also carriers of these species at the current examination. The results of the present study suggest that the presence of these putative periodontal pathogens at implants may not be associated with an impaired implant treatment. These species are most likely part of the normal resident microbiota of most individuals and may therefore be found at random at both stable and progressing peri‐implant sites.     

A comparative study of gold UCLA-type and CAD/CAM titanium implant abutments

PURPOSE

The aim of this study was to evaluate the interface accuracy of computer-assisted designed and manufactured (CAD/CAM) titanium abutments and implant fixture compared to gold-cast UCLA abutments.

MATERIALS AND METHODS

An external connection implant system (Mark III, n=10) and an internal connection implant system (Replace Select, n=10) were used, 5 of each group were connected to milled titanium abutment and the rest were connected to the gold-cast UCLA abutments. The implant fixture and abutment were tightened to torque of 35 Ncm using a digital torque gauge, and initial detorque values were measured 10 minutes after tightening. To mimic the mastication, a cyclic loading was applied at 14 Hz for one million cycles, with the stress amplitude range being within 0 N to 100 N. After the cyclic loading, detorque values were measured again. The fixture-abutment gaps were measured under a microscope and recorded with an accuracy of ±0.1 µm at 50 points.

RESULTS

Initial detorque values of milled abutment were significantly higher than those of cast abutment (P<.05). Detorque values after one million dynamic cyclic loadings were not significantly different (P>.05). After cyclic loading, detorque values of cast abutment increased, but those of milled abutment decreased (P<.05). There was no significant difference of gap dimension between the milled abutment group and the cast abutment group after cyclic loading.

CONCLUSION

In conclusion, CAD/CAM milled titanium abutment can be fabricated with sufficient accuracy to permit screw joint stability between abutment and fixture comparable to that of the traditional gold cast UCLA abutment.     

Clinical experiences of CNC-milled titanium frameworks supported by implants in the edentulous jaw: 1-year prospective study

Background: A new type of titanium framework has been introduced, but so far no clinical reports have been made in this treatment modality. Purpose: The aim of this study was to report the clinical performance of implant‐supported prostheses with computer numeric controlled (CNC)‐milled titanium frameworks in the edentulous jaw and to compare the results with prostheses provided with conventional cast frameworks during the first year of function. Material and Methods: A consecutive group of 65 patients with 67 prostheses were provided with CNC‐milled titanium frameworks in 23 upper and 44 lower jaws. During the same period, 61 consecutive patients were treated on a routine basis with 31 upper and 31 lower conventional gold alloy casting prostheses. Clinical and radiographic 1‐year data were collected for both the test and control groups. Results: A total of 14 of 729 inserted implants were lost during the follow‐up period (1.9%). All prostheses were functioning after 1 year except a conventional prosthesis with a cast framework, which was replaced by an implant‐supported over‐denture due to implant loss. The 1‐year cumulative survival rate (CSR) was 100% and 97.8% for CNC prostheses and implants, respectively. The corresponding CSR for the control group was 98.3% and 98.3%, respectively. Few problems were reported in both groups, and the clinical and the radiologic performances were similar for both groups. No mechanical complications except some resin veneer fractures (n = 6) were observed. The mean marginal bone loss for the test group during the first year in function was 0.4 mm (SD = 0.35) and 0.4 mm (SD = 0.33) in the upper and lower jaws, respectively. A similar pattern of bone reaction was also observed in the control group. Conclusion: CNC‐milled titanium frameworks can be used as an alternative to conventional castings in the edentulous jaw, presenting similar clinical and radiologic performances as conventional cast frameworks during the first year of function.