Spontaneous early exposure of submerged implants: II. Histopathology and histomorphometry of non-perforated mucosa covering submerged implants

BACKGROUND: Spontaneous early exposure is a complication that could account for significant interference during the early healing phase of dental implants. Spontaneous perforations of the mucosa covering implants have been classified according to the degree of implant exposure from 0 (no perforation) to IV (complete exposure). In this study, the characteristics of the epithelium and connective tissue of clinically non-perforated mucosa over submerged implants are histologically and histomorphometrically evaluated. METHODS: Ten randomly selected tissue disks of intact (Class [Cl]-0) mucosa covering submerged implants were removed using a biopsy punch. Identical mucosal punch specimens were obtained from edentulous sites treated by non-submerged (1-stage) implants for use as controls. Specimens were histopathologically examined. The epithelial width and inflammatory infiltrate adjacent to the epithelium were histomorphometrically measured and the data statistically analyzed. RESULTS: Non-perforated mucosa covering the submerged implants (Cl-0) was characterized by an inflammatory fibro-epithelial hyperplasia. In 70% of Cl-0 hematoxylin and eosin-stained sections, there was mineralized material in the connective tissue, mostly sequestra. The epithelial width was 1.5 times higher (0.553 +/- 0.187 mm) when compared to controls (0.345 +/- 0.129 mm; P <0.0001). Concomitantly, the chronic inflammatory infiltrate was almost double in Cl-0 specimens (1,411 +/- 617 cell/mm2) when compared to controls (833 +/- 275 cells/mm2; P<0.001). A positive correlation between the linear combination of the epithelial width and the linear combination of the inflammatory cell concentration was found in both groups: Cl-0: r = 0.669, P= 0.0001; control: r = 0.541, P= 0.005. CONCLUSIONS: Different factors may result in the formation of spontaneous early perforation, most of which are associated with mechanical trauma to the mucosa or tension in the tissue flaps covering the implants. Bone debris produced during the osteotomy could act as an additional predisposing factor; these are sequestrated and accompanied by chronic inflammatory cell infiltration as well as epithelial-covering reaction. Since this study focused only on specimens from intact mucosa, until further investigation of this phenomenon in spontaneously perforated sites is conducted, no conclusions on the role of these histopathological findings can be made.     

Spontaneous early exposure of submerged implants: I. Classification and clinical observations

BACKGROUND: It is believed that during the osseointegration phase of submerged dental implants, complete mucosal coverage and isolation of the implant from the oral cavity avoids trauma and infection and establishes favorable conditions for osseointegration. Spontaneous early exposure is one of the complications that could adversely affect osseointegration of implants. METHODS: This study clinically classifies spontaneous early exposure and describes and analyzes this complication in a group of 148 patients treated with 372 submerged implants: 216 (58%) in the mandible and 156 (42%) in the maxilla. Edentulous sites were exposed by mid-crestal incisions and full thickness gingival flaps. Incisions were closed in an attempt to achieve complete closure and healing by primary intention. Measurements were taken to avoid mechanical trauma to the mucosa over the implants. Patients were followed up weekly and examined to identify early exposures. Perforations were classified according to the degree of exposure from 0 (no perforations) to 4 (complete exposure). RESULTS: Of the implants 51 (13.7%) presented spontaneous early exposure, (13%) in the mandible and 23 (14.7%) in the maxilla. Class 2 perforation was the most frequent, followed by Class 3, Class 1 and Class 4. Inflammation at the mucosal orifices of the perforations was minimal, but no objective index (bleeding, probing) was taken in order to avoid morphological changes of the lesions that were biopsied for histological examination. CONCLUSIONS: 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, damage to the peri-implant mucosa, and possible peri-implant loss.     

Spontaneous early exposure of submerged endosseous implants resulting in crestal bone loss: a clinical evaluation between stage I and stage II surgery

Spontaneous early exposure of submerged implants during the osseointegration healing phase may be a harmful factor that results in early crestal bone loss around the implants. The objective of this study was to assess the effect of spontaneous early exposure on crestal bone loss around submerged implants, with special attention given to the relationship between the degree of exposure and the amount of peri-implant bone loss. Crestal bone level relative to the shoulder of the implant was measured at the time of placement and at the time of exposure 4 to 5 months later. During the period between stage I and stage II surgery, implant sites were observed, and each implant site in which spontaneous early exposure was detected was recorded. Perforations were classified according to the degree of implant exposure from Class 0 (no perforation) to Class IV (complete exposure). Measurements from 206 implants in 64 patients produced 85 groups valid for statistical comparison; each of these contained at least 2 lesions of different types. There was a statistically significant difference between bone loss associated with intact mucosa (Class 0) and Class I, Class II, and Class III lesions, and between Class I and II lesions. There were no significant differences between Class I and III and between Class II and III. In Class II and III lesions, there was more bone loss associated with the buccal aspect of the implants. Of the 115 perforated sites, 10 were associated with bone loss exceeding 2 mm, 2 presented 3 to 4 mm bone loss, 1 showed more than 4 mm, and 1 displayed more than 5 mm. In view of the clinical implications that spontaneous early exposure may have on the success of osseointegration, prematurely partially exposed implants should be exposed as soon as possible after the perforation is observed.     

Spontaneous early exposure and marginal bone loss around conventionally and early‐placed submerged implants: a double‐blind study

Purpose: The aim of this retrospective study was to compare the frequency of spontaneous early exposure of cover screws and marginal bone resorption in conventionally and early‐placed submerged implants before second‐stage surgery. Materials and methods: A total of 103 Nobel Biocare Branemark implants were conventionally (Group 1), or early‐placed (Group 2) in 46 consecutive patients following the two‐stage surgical protocol. Patients in both groups received oral hygiene training in self‐performed plaque control measures, including exposure of cover screws during healing. Spontaneous cover screw exposure (CSE) of each implant was recorded for both groups and scored from Class 0 (no perforation) to Class 4 (complete exposure). Plaque index scores were recorded and marginal bone‐level (MBL) changes were measured in radiographs before second‐stage surgery in a blind manner. Results: MBL in Group 2 was higher than Group 1 in patients with or without interim prosthesis (P<0.05). The use of interim prosthesis did not increase MBL in Group 1, but led to higher MBL in Group 2. The percentage of non‐exposed implants in Group 1 was higher than Group 2 (P=0.007, odds ratio=7). Group 1 implants had 11.5 times greater plaque index score 0 than those in Group 2 (P=0.031, odds ratio=11.5). The differences between MBL with regard to CSE scores 0 and 1–4 was significant for both sides in Group 2 and the mesial side in Group 1 (P<0.05). The difference between MBL with regard to plaque index scores 1–3 was similar in both groups (P>0.05). Conclusions: There is a direct relation between spontaneous early cover screw perforations with early crestal bone loss. Early‐placed implants experienced more spontaneous perforations and associated bone loss in comparison with conventionally placed submerged implants. The use of interim dentures may lead to more CSE and consequent MBL in the early‐placement protocol. To cite this article:
Çehreli MC, Kökat AM, Uysal S, Akca K. Spontaneous early exposure and marginal bone loss around conventionally and early‐placed submerged implants: a double‐blind study.
Clin. Oral Impl. Res. 21 , 2010; 1327–1333.
doi: 10.1111/j.1600‐0501.2009.01952.x     

Diagnoses,clinical classification,and proposed treatment of spontaneous early exposure of submerged implants

Spontaneous early exposure of implants can become a serious complication during the initial healing phase. These early perforations and partial exposure of the coverscrews are a foci for plaque accumulation which, if left untreated, may result in inflammation, damage to the periimplant mucosa, and possible bone loss. Sometimes, these exposures are so small so as not to be clinically visible. This article presents methods of diagnoses of perforated mucosa around submerged implants. In addition, an easy-to-use classification of the spontaneous early exposure is proposed. Treatment modalities to prevent or intercept mucositis during the initial healing phase, when early exposures occur, are suggested.     

Demineralized perforated bone implants in craniofacial surgery.

Between July 1990 and September 1991, demineralized perforated allogeneic bone implants (Pacific Coast Tissue Bank, Los Angeles, CA) were placed in 72 patients. Because many patients received more than one implant, a total of 248 implants were used in 80 procedures. The technology of processing demineralized bone implants is described in detail. All patients were operated on by one surgeon (K.E.S.) at the Humana Craniofacial Institute in Dallas, Texas. Forty-one patients had craniofacial deformities, 16 had secondary deformities following cleft lip and palate repair, 8 had bony defects following removal of tumors, and 10 had various skeletal deformities following trauma. Of the 72 patients, 6 had two surgical procedures during which additional implants were inserted. Implants placed in the cranial vault and the maxillary complex, including alveolar grafts, were inlay grafts, whereas implants placed in the orbital, nasal, paranasal, temporal, and malar areas were onlay grafts used for contouring, augmentation, or both. Complications were limited to delayed wound healing in 6 patients. According to our observations, demineralized perforated bone implants represent an encouraging alternative to autogenous bone grafting. Further clinical and experimental studies are necessary to obtain more information about this material.     

Light-microscopic evaluation of the dimensions of peri-implant mucosa around immediately loaded and submerged titanium implants in monkeys

Background: Immediate loading of dental implants is a successful treatment concept. The importance of healthy peri-implant soft tissues for the long-term success of dental implants has been widely recognized. The aim of this study was to evaluate the peri-implant soft tissues around immediately loaded and submerged implants in monkeys. Methods: A total of 48 implants were inserted in six Macaca fascicularis monkeys. For 24 implants (test implants), the prosthetic abutments were inserted immediately, and a custom-made metal superstructure was cemented after 3 days; the other 24 implants were left unloaded (control implants). Block sections of bone segments containing the implants were retrieved 9 months after surgical placement. A histomorphometric measurement of sulcular epithelium (SE), junctional epithelium (JE), and connective tissue (CT) contact percentage of the soft tissues around test and control implants was carried out. Results: In some specimens, the peri-implant epithelium was very similar to a pocket epithelium, whereas in others it was possible to observe an SE and a long junctional-like epithelium with a moderate amount of inflammatory cells. The supracrestal peri-implant CT was dense and organized in collagen fibrous bundles in an annular pattern around the implant. No statistically significant differences were present in the dimensions of SE, JE, and CT in test and control implants (P >0.05). Conclusion: Immediate loading did not produce changes in the dimensions of the peri-implant soft tissues.     

The sequential failure of osseointegrated submerged implants

This report presents a case of sequential failure of nonrestored implants that were osseointegrated and submerged for 3 years. The suspected causes of failure were investigated and analyzed. These included anatomic, physiologic, traumatic, and pathogenic factors. The findings of this report compliment other literature and contribute to the comprehensive classification of implant failure based on osseointegration criteria.     

Healing and osseointegration of submerged microtextured oral implants

The success of dental implants is primarily dependent upon the degree of osseointegration or bone-to-implant contact (BIC), possibly facilitated by a roughened implant surface. This study was performed to histologically evaluate the nature of osseointegration and bone healing of submerged microtextured implants in eight dogs. Three months following tooth extraction in the posterior mandibulae, three microtextured submerged implants were placed in each quadrant. Block biopsies were harvested at 4 and 16 weeks (four dogs each) following surgery, and histologic preparation was performed. Histomorphometric analysis demonstrated that % BIC value increased marginally from 40% at 4 weeks to 48% at 16 weeks, without a statistically significant difference. The first bone-to-implant contact (f-BIC) at 16 weeks was significantly lower than the 4-week f-BIC (0.81 mm vs. 0.56 mm). In conclusion, this study found minimal change in BIC over time (from 4 to 16 weeks) in unloaded microtextured implants, while the mean f-BIC value significantly increased during this same observation period.     

A protocol for maintaining or increasing the width of masticatory mucosa around submerged implants: a 1-year prospective study on 53 patients

Masticatory mucosa around implants may be useful to enhance esthetics and/or plaque control. This study proposes simplified guidelines for maintaining or obtaining a minimal amount of masticatory mucosa around submerged implants in cases of partial edentulism, and for keeping the need for additional surgery to a minimum. Free gingival grafts were used in the mandibular arch when the width of buccal masticatory mucosa was less than 2 mm. The width of masticatory mucosa expected to be available for attachment to the bone surface buccal to implants was estimated by measuring the distance between the emergence of the implant from bone and the mucogingival junction. When this distance was 3 mm or less, the use of an apically positioned flap for implant exposure was preferred over gingivectomy. The amount of masticatory mucosa buccal to implants was measured 2 weeks, 6 months, and 12 months after implant exposure. In no case was the width of masticatory mucosa less than 2 mm at 1 year. Therefore, this protocol is recommended for the treatment of cases where the presence of an adequate amount of masticatory mucosa is necessary to ensure a satisfying appearance or is useful for facilitating oral hygiene.     

Managing congenitally missing lateral incisors. Part III: single-tooth implants

Three treatment options exist for the replacement of congenitally missing lateral incisors. They include canine substitution, a tooth-supported restoration, and a single-tooth implant. Selecting the appropriate treatment option depends on the malocclusion, anterior relationship, specific space requirements, and condition of the adjacent teeth. The ideal treatment is the most conservative option that satisfies individual esthetic and functional requirements.
Today, the single-tooth implant has become one of the most common treatment alternatives for the replacement of missing teeth. This article closely examines the many interdisciplinary issues that arise when treatment planning the placement of single-tooth implants in patients with congenitally missing lateral incisors. The specific criteria that must be evaluated illustrate the importance of an interdisciplinary treatment approach to achieve optimal esthetics and long-term predictability. This is the final article of a three-part series discussing the three treatment alternatives for replacing congenitally missing lateral incisors.     

Clinical outcome of submerged vs. non-submerged implants placed in fresh extraction sockets

Aim: The aim of this study was to compare the clinical outcome of submerged vs. non-submerged tapered implants placed into fresh extraction sockets.
Materials and methods: A prospective, controlled, multicenter, randomized, clinical trial has been performed in two centers in Rome and Torino (Italy). Thirty healthy patients were recruited according to the following inclusion criteria: need for an immediate post extraction implant, ages between 18 and 70, horizontal defect depth <2 mm, smokers <10 cigarettes/day and absence of any circumstance or condition that could represent contraindications to implant surgery. The patients were randomly allocated to submerged or non-submerged treatment groups immediately after flap elevation and tooth extraction. Submerged implants were exposed 8 weeks after the first surgery; all implants were loaded with provisional restorations 12 weeks after the first surgery and with definitive restoration 12 weeks thereafter. Clinical and radiographic parameters were evaluated at baseline, at implant loading and at the 1-year follow-up visit.
Results: The results showed statistically significant differences between the two groups in the mean value of keratinized tissue (KT) height after surgery that was significantly reduced for submerged implants when compared with transmucosal implants (mean reduction of KT at year follow-up: T group 0.2 mm, S group 1.3 mm; P =0.007).
Conclusion: Similar outcomes were found for submerged and non-submerged implants placed in fresh extraction sockets with a horizontal peri-implant defect smaller than 2 mm, except for a reduction of KT in the submerged group. Either with a submerged or a non-submerged procedure, 1 mm of mean soft tissue recession is seen after 1 year when compared with the pre-extraction situation.     

Tissue reaction to submerged ceramic tooth root implants. An experimental study in monkeys.

Tooth root replica implants made from alumina ceramic material of solid structure coated with a porous layer, were used as dental implants in monkeys. The porous coating was 1/2 mm thick and had pore sizes within 50--200 microns range, with a 30% degrees of porosity. Tne implants were inserted into prepared sockets in the mandible of 5 Cercopithecus monkeys. After submerged implantation periods varying from 5 to 15 weeks, a perforating steel post was introduced through the covering gingiva into the artificial root canal of the implants. The animals were sacrificed after 6 weeks, 2, 3 and 4 months. Three out of the total number of 10 implants were lost. The remaining 7 specimens were retrieved for histologic and microradiographic examination. Fibrous and mineralized tissue ingrowth of the porous layer of the implants was found. No adverse reactions of the adjacent bone were demonstrable. The implants became anchored to the host and no epithelial downgrowth along the ceramic was found.     

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).     

Clinical and radiographical features of submerged and nonsubmerged titanium implants

A clinical and radiographical study was performed to evaluate whether initial submergence of titanium fixtures is an obligate treatment measure for the establishment of proper bone anchorage when implants a.m. Brånemark are used. The sample was comprised of 11 subjects with edentulous mandibles. A split‐mouth design was employed; in the right mandibular quadrant a traditional 2‐step procedure for fixture installation and abutment connection was utilized, while in the left quadrant a 1‐step procedure was carried out, i.e., fixtures were placed and abutments were connected in one and the same session. Three to 4 months after fixture installation, fixed bridgeworks were fabricated and rigidly connected to the implants. Clinical examinations (including probing pocket depth, bleeding on probing and implant stability test) were performed after 12 and 18 months. Radiographs were taken following insertion of the bridges and at the 12‐ and 18‐month re‐examinations. The probing pocket depth, the bleeding on probing, the implant stability and the radiographic determinations were similar for the 2 groups of treatment alternatives. This indicates that titanium fixtures a.m. Brinemark can be properly anchored (osseointegrated) in mandibular bone and successfully used for bridge retention also when a 1‐step procedure is used for implant installation.     

Long-term evaluation of submerged and nonsubmerged ITI solid-screw titanium implants: a 10-year life table analysis of 468 implants

PURPOSE: Submerged and nonsubmerged ITI solid-screw titanium implants were followed retrospectively from 1989 to 1993 and prospectively from 1994 on to analyze long-term prognosis in partially and fully edentulous patients. MATERIAL AND METHODS: A total of 468 implants were consecutively inserted in 191 patients from 1989 to 1998. Two hundred twenty-eight successfully integrated fixed-restoration implants and 238 with removable restorations were restored following a healing period of 4 to 6 months (9 months in sinus floor elevation sites). From 1994 on all implants inserted were documented annually up to 9 years. During examination the clinical status of the implants was analyzed and evaluated according to predefined criteria of success and this allowed the calculation of 10-year cumulative survival and success rates for 468 implants. RESULTS: Two implants (0.43%) did not successfully integrate during the healing period, and 8 implants (1.7%) were classified as failures during follow-up (1 late failure under load, 7 with a progressive bone loss from 1 to 3 threads). Including 68 implants in subjects who dropped out (with a dropout rate of 14.4%), the 10-year cumulative survival and success rates were 99.2% and 96.4%, respectively. DISCUSSION: Over the course of this long-term study, osseointegrated implants, once used as a last possible solution, became nearly standard in cases of single-tooth implants because of the high rate of long-term success. Life table analysis not only determines whether an implant is functioning, it also makes a statement about its clinical status according to strict success criteria. CONCLUSION: The study demonstrated that ITI solid-screw titanium implants achieved success rates above 95% in a clinical center for an observation period of up to 10 years.