Intraoral radiographs of dental implants in the edentulous mandible

Radiographs of dental implants in the edentulous mandible, which are suitable for evaluation studies, are difficult to obtain. This article describes the development of an aiming device for intraoral radiography of the crestal bone around the neck of dental implants. Error analysis of serial radiographs indicated only small deviations in reproducibility. Subsequently three methods of measurements of marginal bone level around the neck of dental implants are described, measurements with: 1. a computerized image analysis system, 2. a magnifying glass, and 3. a digital sliding gauge. The intra- and interobserver error analysis showed that determining the precise bone height on the image is responsible for a large standard deviation for each method. Measurements with a digital sliding gauge are preferable, since this method is easy to put into practice, whereas the accuracy matches the accuracy of the two other methods.     

Effect of diameter and length on stress distribution of the alveolar crest around immediate loading implants

Background: Many clinical observations have shown that immediate loading is indicated when the stabilization of the bone/implant is optimal and when the estimated loads are not excessively high. Nonetheless, more experimental studies are needed to consider the immediate loading protocol as a safe procedure. Mechanical analysis using the finite element (FE) method analysis has been employed by many authors to understand the biomechanical behavior around dental implants. Purpose: This study was to evaluate the effect of the diameter and length on the stress and strain distribution of the crestal bone around implants under immediate loading. Materials and Methods: By an ad hoc automatic mesh generator, high‐quality FE models of complete range mandible was constructed from computer tomography, with three Straumann (Straumann Institute, Waldenburg, Switzerland) implants of various sizes embedded in the anterior zone. The implant diameter ranged from 3.3 to 4.8 mm, and length ranged from 6 to 14 mm, resulting in seven designs. The implant–bone interface was simulated by nonlinear frictional contact algorithm. For each design, vertical and oblique loadings of 150 N were applied, respectively, to each implant, and stresses and strains in the surrounding cortical bone were evaluated. Results: The biomechanics analysis provided results that the oblique loading would induce significantly higher interfacial stresses and strains than the vertical loading, while the intergroup stress difference significant levels was evaluated using t‐tests method and the level of significance (.05) that was accepted for significance. Under both loadings, the maximal values were recorded in the 3.3 (diameter) × 10 (length) mm implant configuration, whose mean and peak values were both higher than that of others with significant statistical differences. The second maximal one is 4.1 × 6 mm configuration, and the minimal stresses were recorded in 4.8 × 10 mm configuration, whose strains were also near to lowest. Conclusions: Increasing the diameter and length of the implant decreased the stress and strain on the alveolar crest, and the stress and strain values notably increased under buccolingual loading as compared with vertical loading, but diameter had a more significant effect than length to relieve the crestal stress and strain concentration.     

Vertical alveolar crest bone maintenance around implants in two-stage surgery: an in situ study in dogs

The aim of this study was to evaluate in situ changes in the alveolar crest bone height around immediate implant-supported crowns in comparison to tooth-supported crowns (control) with the cervical margins located at the bone crest level, without occlusal load. In Group I, after extraction of 12 mandibular premolars from 4 adult dogs, implants from Branemark System (MK III TiU RP 4.0 x 11.5 mm) were placed to retain complete acrylic crowns. In Group II, premolars were prepared to receive complete metal crowns. Sixteen weeks after placement of the crowns (38 weeks after tooth extraction), the height of the alveolar bone crest was measured with a digital caliper. Data were analyzed statistically by the Mann-Whitney test at 5% significance level. The in situ analysis showed no statistically significant difference (p=0.880) between the implant-supported and the tooth-supported groups (1.528 + 0.459 mm and 1.570 + 0.263 mm, respectively). Based on the findings of the present study, it may be concluded that initial peri-implant bone loss may result from the remodeling process necessary to establish the biological space, similar to which occurs with tooth-supported crowns.     

Estimation of alveolar crest height using routine periapical dental radiographs

The reproducibility of estimations of the alveolar crest height based on their relationship to two other fixed points on the tooth has been analyzed in a study of 302 routine periapical radiographs of 96 endodontically treated teeth. The radiographs were made at normal recall appointments by use of the extension tube paralleling technique. The various distances between four fixed points on each tooth in any radiographic series were compared by means of a statistical model. The results indicate that, in periodontal follow-up studies, completely standardized projection of the structures onto the film is unnecessary since measurements of the crest height can be related to any suitable fixed measuring standard on the tooth.     

Cortical structure of the pig mandible after the insertion of metallic implants into alveolar bone.

The effect of tooth extraction and endosseous metallic implants on the bone structure of adult pigs was studied using both densitometric and microradiographic techniques. Similar methods were used to study the bone structure of both growing and adult pig mandibles. The use of tetracycline and ³²P-labelled phosphate in vivo indicated that the porous bone deposited periosteally is the most metabolically active bone during growth. This formation occurs over almost the entire surface of the body of the mandible throughout life but, despite an overall density increase with age, the internal structural pattern established during development, is maintained. Both tooth extraction and the introduction of metallic endosseous implants stimulated further remodelling. Despite the different responses to tooth extraction and implantation, the internal structural pattern remained constant.     

Crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged and submerged implants in the canine mandible

BACKGROUND: Today, implants are placed using both non-submerged and submerged approaches, and in 1- and 2-piece configurations. Previous work has demonstrated that peri-implant crestal bone reactions differ radiographically under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of the interface (microgap) between the implant and abutment/restoration in 2-piece configurations. The purpose of this investigation was to examine histometrically crestal bone changes around unloaded non-submerged and submerged 1- and 2-piece titanium implants in a side-by-side comparison. METHODS: A total of 59 titanium implants were randomly placed in edentulous mandibular areas of 5 foxhounds, forming 6 different implant subgroups (types A-F). In general, all implants had a relatively smooth, machined coronal portion as well as a rough, sandblasted and acid-etched (SLA) apical portion. Implant types A-C were placed in a non-submerged approach, while types D-F were inserted in a submerged fashion. Type A and B implants were 1-piece implants with the rough/smooth border (r/s) at the alveolar crest (type A) or 1.0 mm below (type B). Type C implants had an abutment placed at the time of surgery with the interface located at the bone crest level. In the submerged group, types D-F, the interface was located either at the bone crest level (type D), 1 mm above (type E), or 1 mm below (type F). Three months after implant placement, abutment connection was performed in the submerged implant groups. At 6 months, all animals were sacrificed. Non-decalcified histology was analyzed by evaluating peri-implant crestal bone levels. RESULTS: For types A and B, mean crestal bone levels were located adjacent (within 0.20 mm) to the rough/smooth border (r/s). For type C implants, the mean distance (+/- standard deviation) between the interface and the crestal bone level was 1.68 mm (+/- 0.19 mm) with an r/s border to first bone-to-implant contact (fBIC) of 0.39 mm (+/- 0.23 mm); for type D, 1.57 mm (+/- 0.22 mm) with an r/s border to fBIC of 0.28 mm (+/- 0.21 mm); for type E, 2.64 mm (+/- 0.24 mm) with an r/s border to fBIC of 0.06 mm (+/- 0.27 mm); and for type F, 1.25 mm (+/- 0.40 mm) with an r/s border to fBIC of 0.89 mm (+/- 0.41 mm). CONCLUSIONS: The location of a rough/smooth border on the surface of non-submerged 1-piece implants placed at the bone crest level or 1 mm below, respectively, determines the level of the fBIC. In all 2-piece implants, however, the location of the interface (microgap), when located at or below the alveolar crest, determines the amount of crestal bone resorption. If the same interface is located 1 mm coronal to the alveolar crest, the fBIC is located at the r/s border. These findings, as evaluated by non-decalcified histology under unloaded conditions, demonstrate that crestal bone changes occur during the early phase of healing after implant placement. Furthermore, these changes are dependent on the surface characteristics of the implant and the presence/absence as well as the location of an interface (microgap). Crestal bone changes were not dependent on the surgical technique (submerged or non-submerged).     

下颌后牙区软组织水平种植体边缘骨吸收相关因素的临床研究

目的研究下颌后牙软组织水平种植体边缘骨吸收的影响因素,为减少种植体边缘骨吸收量,提高种植体存留率提供理论依据。方法 选择76例患者行下颌后牙区软组织水平种植,共植入种植体116枚。记录患者的一般情况、种植体特征、种植体植入部位特征及修复体特征,在术后即刻、种植后3个月、修复后3个月、修复后12个月行锥形束CT检查,利用One Vlume Viewer软件测量并计算边缘骨吸收量,采用SPSS 20.0软件进行统计学分析。结果 吸烟、骨密质厚度、种植体长轴与牙冠长轴夹角、种植体局部卫生情况在各组间的差异有统计学意义（P<0.05）,患者性别、年龄、种植体长度、种植体直径、种植体系统、种植体边缘骨高度和修复体类型在各组间的差异无统计学意义（P>0.05）。结论 吸烟、骨密质较厚、种植体长轴与牙冠长轴夹角较大、种植体局部卫生差是引起种植体边缘骨吸收的危险因素,其中,局部卫生差与种植体边缘骨吸收的相关性较强。     

Advanced alveolar crest atrophy: an alternative treatment technique for maxilla and mandible

A concept of oral implantology for the treatment of advanced crest atrophy is presented: The lateral insertion technique with disk-design implants is less invasive than bone grafting. An implant case demonstrates the simultaneous surgery of an edentulous maxilla and a mandible. Implant loading zones in the anterior and posterior areas of the arch are created with disk-design implants. Their support is tricortical or multicortical. Seven to eight days after surgery, the implants are immediately loaded with fixed esthetic temporaries. After another 40 days, the definitive restorations on the implants can be fabricated. The procedure is safe and shortens chairtime.     

Soft tissue management using palatal mucosa around endosteal implants in vascularized composite grafts in the mandible.

Excessive thickness and mobility of the skin flap and lack of a vestibular sulcus in composite vascularized bone grafts for mandibular reconstruction limit the usefulness of endosteal implants to support a prosthetic device. Palatal mucosal grafts and a simple acrylic stent are an excellent means to overcome these problems. The technique is presented in this paper.     

Stress distribution around dental implants: influence of superstructure, length of implants, and height of mandible.

The stress distribution around dental implants was investigated by use of a two-dimensional model of the mandible with two implants. A vertical load of 100 N was imposed on abutments or the bar connection. The stress was calculated for a number of superstructures under different loading conditions with the help of the finite element method. The length of the implants and the height of the mandible were also varied. A model with solitary abutments showed a more uniform distribution of the stress when compared with a model with connected abutments. The largest compressive stress was also less in the model without the bar. Using shorter implants did not have a large influence on the stress around the implants. When the height of the mandible was reduced, a substantially larger stress was found in the bone around the implants because of a larger overall deformation of the lower jaw.     

Bone regeneration around implants in the canine mandible with cultured fibroblasts in polyglactin mesh

BACKGROUND: Human fibroblast-derived dermal substitute (HFDDS) is a tissue-engineered material that consists of polyglactin mesh seeded with cultured fibroblasts. Cultured fibroblasts are not as differentiated as tissue fibroblasts and retain the ability to differentiate into other cells types. HFDDS also is capable of stimulating angiogenesis and wound healing. The purpose of this study was to attempt to evaluate the effects of HFDDS on guided bone regeneration at sites with 1.5-mm peri-implant defects in the canine mandible. METHODS: Fifty sand-blasted acid-etched test implants were placed into the edentulous areas of mandibular ridges of five American foxhounds. Each site had a standardized 1.5-mm circumferential peri-implant defect in the coronal half of the implant, created by a specialized drill at the time of osteotomy. In each canine two implants received no treatment of the defects, four implants were treated with polyglactin mesh (carrier only) wrapped around the circumference of the defect wall, and four implants were treated with HFDDS placed in a similar fashion to the mesh. Implant sites healed submerged for 10 weeks, at which time sacrifice took place and sections were prepared, processed, and analyzed histomorphometrically. RESULTS: The mean distance from the top of the fixture to the first point of bone-implant contact was 2.20 mm, 2.25 mm, and 2.60 mm for the HFDDS, carrier, and control sites, respectively (P = 0.202). Overall mean percentage of bone-to-implant contact (BIC) in the defects was 32.8%, 31.0%, and 22.8% for the HFDDS, carrier, and control groups, respectively. These differences were not statistically significant, but approached statistical significance for the control group compared to HFDDS and carrier (P = 0.057). Overall mean bone fill in the defects calculated histometrically was 36.0%, 35.8%, and 33.9% for the HFDDS, carrier, and control groups, respectively. These differences were not statistically significant. Sites with dehiscence at the time of implant placement had significantly greater distance to first bone-implant contact (P = 0.002), a smaller percentage of BIC (P = 0.006), and significantly less bone fill (P = 0.006) in the defects. It was consistently found that when dehiscence occurred on the buccal side of the implant, the outcomes for all parameters measured were significantly inferior on the lingual side as well. Factorial analysis, which grouped outcomes by dehiscence categories (none, partial, or full dehiscence), revealed that with intact defects without dehiscence, HFDDS had less bone fill compared to the carrier. However, in defects with partial or full dehiscence, HFDDS had more bone fill compared to carrier sites. These differences were statistically significant (P = 0.034). CONCLUSIONS: In intact sites without dehiscence, the presence of cultured fibroblasts in 1.5-mm-wide peri-implant defects did not significantly enhance bone regeneration compared to the carrier, polyglactin mesh. However, sites with partial or full dehiscence treated with HFDDS had significantly greater bone fill compared to the carrier (P = 0.034). When dehiscence occurs during immediate implant placement on narrow ridges without the use of membranes, bone regeneration tends to be inferior on the side of the dehiscence as well as the opposite side of the implant.     

Identification of dental implants on radiographs.

In the future, dentists will more frequently encounter patients who have dental implants. To use radiographs to identify implants that were previously inserted by other dentists, dentists have to be familiar with the detailed morphology of different products and types of fixtures as well as with the principles for formation of their radiographic images. In the present study, radiographic images of ten common dental implants were analyzed. Images varied with viewing angles. The influences of surface structures, such as threads, cuts, holes, perforations, and flutes, are demonstrated.     

The effect of electrical stimulation on bone formation around hydroxyapatite implants placed on the rabbit mandible.

Nonresorbable, nonporous, particulate hydroxyapatite (HA) was implanted on the mandible in rabbits and stimulated electrically, 4 hours per day, during the first postoperative week. Stimulated and control implant sites were recovered 8 weeks postoperatively and examined histologically. The HA migrated into the mandible in the electrically treated specimens, and was routinely found in intimate association with preexisting mandibular bone. In the controls, the HA remained superior to the mandibular surface. In further studies (without electrical stimulation) in which the implant site was recovered 26 weeks postoperatively, HA was observed in the mandible; some HA particles migrated completely through the mandible and were found in the adjacent soft tissue. It was concluded that, under the conditions studied, electrical stimulation does not promote bone growth into HA, but rather produces the opposite result--it promotes more rapid movement of HA particles into the mandibular bone. The HA particle migration into the mandible observed (longer postoperative times) in the absence of electrical stimulation suggests that migration is a general property of HA particles when placed over bone under muscle.     

Influence of the size of the microgap on crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged implants in the canine mandible.

BACKGROUND: Endosseous implants can be placed according to a non-submerged or submerged approach and in 1- or 2-piece configurations. Recently, it was shown that peri-implant crestal bone changes differ significantly under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of an interface (microgap) between the implant and abutment/restoration in 2-piece configurations. Several factors may influence the resultant level of the crestal bone under these conditions, including movements between implant components and the size of the microgap (interface) between the implant and abutment. However, no data are available on the impact of possible movements between these components or the impact of the size of the microgap (interface). The purpose of this study was to histometrically evaluate crestal bone changes around unloaded, 2-piece non-submerged titanium implants with 3 different microgap (interface) dimensions and between implants with components welded together or held together by a transocclusal screw. METHODS: A total of 60 titanium implants were randomly placed in edentulous mandibular areas of 5 hounds forming 6 different implant subgroups (A through F). In general, all implants had a relatively smooth, machined suprabony portion 1 mm long, as well as a rough, sandblasted, and acid-etched (SLA) endosseous portion, all placed with their interface (microgap) 1 mm above the bone crest level and having abutments connected at the time of first-stage surgery. Implant types A, B, and C had a microgap of < 10 microns, approximately 50 microns, or approximately 100 microns between implant components as did types D, E, and F, respectively. As a major difference, however, abutments and implants of types A, B, and C were laser-welded together, not allowing for any movements between components, as opposed to types D, E, and F, where abutments and implants were held together by abutment screws. Three months after implant placement, all animals were sacrificed. Non-decalcified histology was analyzed histometrically by evaluating peri-implant crestal bone changes. RESULTS: For implants in the laser-welded group (A, B, and C), mean crestal bone levels were located at a distance from the interface (IF; microgap) to the first bone-to-implant contact (fBIC) of 1.06 +/- 0.46 mm (standard deviation) for type A, 1.28 +/- 0.47 mm for type B, and 1.17 +/- 0.51 mm for type C. All implants of the non-welded group (D, E, and F) had significantly increased amounts of crestal bone loss, with 1.72 +/- 0.49 mm for type D (P < 0.01 compared to type A), 1.71 +/- 0.43 mm for type E (P < 0.02 compared to type B), and 1.65 +/- 0.37 mm for type F (P < 0.01 compared to type C). CONCLUSIONS: These findings demonstrate, as evaluated by non-decalcified histology under unloaded conditions in the canine mandible, that crestal bone changes around 2-piece, non-submerged titanium implants are significantly influenced by possible movements between implants and abutments, but not by the size of the microgap (interface). Thus, significant crestal bone loss occurs in 2-piece implant configurations even with the smallest-sized microgaps (< 10 microns) in combination with possible movements between implant components.     

Effect of loading on the development of nerve fibers around oral implants in the dog mandible

Occlusal forces cause stress which morphologically affects the supporting tissues of implants. The aim of this study was to examine the effects of occlusal forces on the distribution of neurofilament protein (NFP)-positive nerve fibers in the tissue of peri-implant bone. The bilateral 2nd, 3rd and 4th mandibular premolars and the 1st molars were extracted from three mongrel dogs. After 4 months of healing, 4 screw-type implants were inserted in the oral cavity. Three months after insertion, the implants on the molar site were loaded by occlusal forces, while those on the premolar site were unloaded. After a further 3 months, the dogs were sacrificed, and specimens were prepared for immunohistochemical NFP-positive staining by the labeled-streptavidin-biotin method. Many NFP-positive nerve fibers were found in the tissues of the loaded site when compared with the unloaded site. These fibers were localized in both the bone marrow space and in the peri-implant fibrous tissue. They had two types of nerve endings: simple free nerve endings, and nerve endings with tree-like ramifications. The present results suggest that loading by occlusal force causes an increase in the number of NFP-positive nerve fibers, many of which have free nerve endings in the peri-implant tissue. The possible role of these NFP-positive nerve fibers is discussed.     

Testing the consistency of measurements of the distance between the cemento-enamel junction and the alveolar bone crest on bitewing radiographs

Abstract The purpose of the research described in this paper is to test the consistency of measurements of the distance between the cemento-enamel junction and the alveolar bone crest (CJ-AC) on bitewing radiographs. The present paper shows how the consistency tests were organized and which statistical analyses were used. Since the actual characteristic (CJ-AC) could not alter, the variations of the results had to be due to one more of the 5m-factors (man. material, machine, method and manipulation). To test the consistency of the measurements of CJ-AC. a pretest and an en route test were performed. Both the bitewing radiographs for the pretest and the en route test were sampled at random from the principal material. The principal material consisted of 856 sets of bitewing radiographs from persons born 1930–1949. The pretest of 40 sets of bitewing radiographs were read twice by 2 independent readers. The en route test consisted of 85 sets of bitewing radiographs which were read twice by 1 reader. Neither the results of the pretest nor the results of the en route test showed statistical or clinical differences of significance. In conclusion: the consistency of this method of measuring is satisfactory for the 2 readers.     

Plaque-induced inflammation around implants.

This article is a review of plaque-induced inflammation around dental implants. The microflora around successful implants is similar to healthy sulci, while that associated with failing implants is similar to periodontally diseased sites. Implant microflora is similar to the tooth microflora in the partially edentulous mouth. The microflora of implants in partially edentulous mouths differs from that in edentulous mouths. This seems to indicate a bacterial reservoir around the teeth and the possibility of reinfection of the implant sulcus by periodontal pathogens. The maintenance of a tooth microflora consistent with periodontal health in partially edentulous mouths may lead to maintaining an implant microflora consistent with peri-implant health. Thus, periodontal and implant maintenance are linked and neither can be overlooked.