Dentitions damaged by severe periodontal disease need a comprehensive treatment plan encompassing nonsurgical and surgical periodontal therapy, as well as prosthetic rehabilitation, to restore health, function, and aesthetics.1–3 Although in last decades, the use of osseointegrated implants has shown long-term high percentages of success in treating completely and partially edentulous subjects, some limitations are still present in implant therapy.4,5 Especially, periodontally compromised patients after teeth extraction have often insufficient bone volumes to correctly position implants.6 There are several surgical methods to solve inadequate bone support problems, but these techniques involve a high biological risk, are clinically complex, take a long time, and increase the costs.7 In patients refusing such surgical procedures, an alternative treatment could be the use of a few “strategic” implants associated with the maintenance of as many teeth as possible after periodontal treatment.
There are just few trials assessing in periodontally treated and maintained patients the function of restorations supported by teeth/implants combination, according to the type of prosthodontics treatment, therefore, the present study was aimed to investigate and to compare the long term outcomes of full-arch telescopic-retained retrievable prostheses (TRPs) versus full-arch fixed prosthesis (FPs), both supported by teeth-implants, used to rehabilitate periodontal compromised dentitions after ATP, in patients refusing complex bone grafting surgical therapies.
Materials and Methods
This retrospective and clinical follow-up study comprised all periodontally compromised patients, refusing bone grafting surgical therapies, who received full-arch TRPs and full-arch FPs, both supported by teeth-implants. The patient population comprised 35 periodontally compromised patients (17 women and 18 men) with a mean age of 49.7 years (±4.8) who were selected in one Italian private dental clinic to receive supplementary implants with the aim of an extensive prosthetic support. All surgical treatments were performed by one clinician (R.G.), whereas all the prosthetic treatments were performed by another clinician (S.I.). In each patient, at least 8 abutments (teeth plus implants) per arch were obtained for the prosthetic rehabilitation. The patients were informed, and written informed consent forms were used. The declaration of Helsinki was followed.
Patients were divided into 2 groups: 18 patients in TRPs group and 17 in FPs group. In TRPs group, a total of 164 implants (BioLok; now marketed by BioHorizons, Birmingham, AL) were placed, in addition to 233 teeth. For each arch, all natural teeth in combination with the strategic implants were provided with telescopic crowns to achieve a continual design of the prosthesis (Fig. 1).
In FPs group, a total of 152 implants, including 91 BioLok implants (now marketed by BioHorizons) and 61 P1H implants (P1H s.r.l., Villanova di S. Daniele, UD, Italy), were placed in addition to 151 teeth (Fig. 2).
Exclusion criteria were presence of dental implants, alcohol and drug abuse, pregnancy, uncontrolled systemic/metabolic disorders, and no interest in participating into the study.
Pretreatment Clinical Examination
Gender, date of birth, smoking habits, medical history at the time of the initial visit, and treatment planning were obtained. At the first clinical examination, the following parameters were assessed: full mouth plaque score, full mouth bleeding score, pocket depth, number of sites with plaque, and number of sites with bleeding on probing (BOP). Tooth mobility according to Miller classification was evaluated. Moreover, subjects were radiographically monitored at baseline.
Before active periodontal therapy (APT) and 15 years later, complete sets of periapical radiographs using film holders were obtained for each patient (Fig. 3). All radiographs were viewed in a darkened room using a radiograph screen. Relative bone loss in percent was assessed at the periodontally most affected site of each tooth using a Schei ruler to the nearest 10%.8 All radiographic assessments were performed by one examiner (R.G.). Mean values of all relative bone loss assessments measured per patient were calculated to characterize an individual. In 5 patients, radiographic assessments were repeated after 14 days to assess reproducibility. In 94%, the difference between repeated measurements was ≤10%.
Evaluation of Patients' Charts
The following information was retrieved from the patients' charts:
- Tooth loss and implant failure after APT were assessed by comparison of the first and last (≥15 years later) examinations.
- Each patient was assigned a baseline diagnosis (eg, aggressive/chronic periodontitis) according to the actual classification of periodontal diseases.
- According to their self-reported smoking history, patients were categorized as current smokers, former smokers, or nonsmokers. Nonsmokers were patients who had never smoked in their lives and patients who had quit smoking at least 5 years before treatment. All other patients were classified as current or former smokers.
Active periodontal therapy
All patients received a similar periodontal treatment. If PPD was ≥5 mm with signs of inflammation like BOP, additional access flap surgery was performed. Pocket elimination surgery, osseous resection, or augmentative regenerative procedures were attempted, if needed. Furcation involvement (FI) was diagnosed clinically by probing (Nabers probe, Hu-Friedy Mfg. Co., LLC, Chicago, IL) and classified according to Hamp et al9 For teeth with advanced FI (degree II and III), furcation debridement was performed with diamond-coated sonic scaler inserts during flap surgery.10
Dental implants were placed, under local anesthesia, according to the manufacturer's instruction during or after the periodontal surgery. All implants were placed using a standardized two-stage surgical procedure, with the border of the rough surface approximating the alveolar bone crest leaving the machined neck portion in the transmucosal area. Implants that required bone augmentation were not included in the study. If necessary, an excision of soft tissue was performed to allow a close adaptation of the wound margins, submerging the implant. The number and position of implants in each patient were determined after a thorough diagnosis of the anticipated needs for the planned prosthesis and the presence of anatomical limitations. Appropriate healing screws were placed 4 to 6 months after implant installation, and abutment connection was carried out 3 to 6 months postsurgery.
Small preparation angles and almost parallel preparations of the abutment teeth were preferred to create a secure retention. The presence of long clinical crowns, as a sequel of clinical attachment loss and/or pocket elimination periodontal surgery, was favorable in terms of retention and resistance form. After final teeth preparation, impressions were obtained using screw-retained implant impression coping and a customized tray with polyether material (Impregum 3 M Espe, Seefeld, Austria). During the same appointment, a preliminary bite registration was taken. Master models were fabricated using die stone with implant analogues and a flexible gingival mask. Prosthetic margins were located supragingivally.
On the stone models, the implant abutment and prepared teeth were waxed up with primary copings with dome-shaped upper surface cast with cobalt-chromium alloy. Screwed implant abutments were individualized regarding length and parallelism. The castings were milled using a paralleling cutting device. The primary copings for the prepared teeth were designed with a wall thickness of 0.1 to 0.2 mm. A putty impression with the primary coping in place was made for the fabrication of the framework. The frameworks with secondary copings were waxed up on the refractory cast and casted in cobalt chromium alloy. The frameworks were veneered using a conventional built-up technique. The veneering porcelain (Esprident Triceram, Dentaurum, Ispringen, Germany) was fired in layers on the framework. The copings were permanently cemented onto the prepared teeth with glass-ionomer cement (Fuji I, GC, Tokyo, Japan) and screwed on the implants. Retention of the denture was finally provided by the friction between the parallel surfaces of the primary and secondary copings.
The framework was constructed using Wirobond C (Bego, Bremen, Germany), a nickel-free cobalt/chromium (Co/Cr) alloy with veneering capacity. Metal try-in/jaw registration and porcelain try-in at bisque bake stage allowed refining of the occlusion. The veneering porcelain (Esprident Triceram, Dentaurum) was fired in layers on the framework. The final bridge was cemented semipermanently using Rely X Temp NE (3M Espe).
Patients were recalled at various intervals (from 3 to 6 months), depending on the initial diagnosis and the results of the therapy, for supportive periodontal therapy (SPT). Motivation, reinstruction, instrumentation, and treatment of reinfected sites were performed as needed. Patients were placed on an individually tailored maintenance care program, including continuous evaluation of the occurrence and the risk of disease progression.
SPT encompassed the following elements for all patients at each appointment: assessment of approximal plaque index, reinstruction and remotivation to achieve effective individual plaque control, professional tooth cleaning with hand instruments, and polishing of all teeth using rubber cups and polishing paste and application of a fluoride gel. A dental status and PPD were obtained at 6 sites per tooth on a semi-annual basis. Thirty seconds after probing BOP was recorded. Sites exhibiting PPD = 4 mm and BOP as well as sites with PPD ≥5 mm were scaled subgingivally.
Data Assessment and Analyses
Complication-related data were assessed from the patient records and included biological complications (progression of periodontal disease, implant failure, and tooth extraction), restorative complications (caries and root canal infection), and prosthetic complications (de-cementation of crowns, unscrewing of abutment, screw or abutment fracture, restoration or veneering porcelain fracture, implant or tooth fracture, intrusion of abutment teeth, and restoration replacement).
Statistical analyses were performed with IBM SPSS Statistics version 19 (IBM Corp). The observation period started with the day of prosthesis insertion and ended with the day of clinical reevaluation after 15 years. Data were analyzed descriptively (mean and SDs), and groups were compared using independent-samples t test. Statistical significance level was set at P < 0.05. Cox regression was used in each group to test predictors and their possible effect on success: sex, patient age, location (maxilla and/or mandible), periodontal diagnosis, smoking habit, and mean bone loss. P < 0.05 was regarded as indicative of exploratory significant difference.
In Table 1 are reported the details of patients, teeth, abutment teeth loss, and implant failures, for TRPs group and FPs group, before APT (T0) and at the beginning (T1) and end (T2) of follow-up. In Table 2 are reported the positions of implants according to treatment groups at the beginning (T1) and end (T2) of follow-up. In Table 3 are reported the number of implants and teeth lost according to treatment groups for each arch.
In Table 4 are reported data on severe complications recorded in 2 groups.
During the 15-year observation period, 6 implant failures occurred after the delivery of TRPs (96.4% implant survival rate). In addition, 11 teeth were extracted after prosthetic treatment due to progression of the periodontal disease (2, 4, 3, and 5 teeth after 3, 5, 7, and 8 years, respectively). Further 8 teeth were extracted after, 3, 5, 7, 7, 9, 10, 11, and 12 years, respectively, 4 teeth due to endo-perio untreatable lesion, and 4 teeth due to caries (91.8% tooth survival rate). The restorations were reshaped and thereafter positioned again. Thus, 7 TRPs had to be subsequently changed (87.7% unchanged TRPs after 15 years); but all 36 complete-arch restorations remained functional (100% TRPs survival rate).
During the 15-year observation period, 5 implant failures occurred after the delivery of FDPs (96.8% implant survival rate). Two implants were removed after 4 years, 1 implant after 6 years, 2 implants after 9 years, and 1 implant after 13 years. In addition, 23 abutment teeth were extracted after prosthetic treatment (10.4%). Eleven teeth were removed due to progression of the periodontal disease (1, 3, 2, 3, and 2 teeth after 8, 10, 11, 13, and 14 years, respectively). Eight teeth were extracted after 3, 5, 7, 7, 9, 10, 11, and 12 years, respectively, due to endo-perio untreatable lesions. Further 2 teeth were removed after 6 and 8 years, and 2 teeth were removed after 7 and 12 years, respectively, due to caries/root fractures (89.8% tooth survival rate). The restorations were reshaped and thereafter positioned again. Thus, 7 FDPs had to be subsequently changed (82.5% unchanged FDPs after 15 years). Between 2 groups, no significant statistical difference of tooth loss and implant failure was found (P > 0.05). In RTPs patients, 7.9% (11/139) of teeth with bone loss of ≤50, 7.3% (6/82) of teeth with bone loss from 50 to <70%, and 16.6% (2/12) of teeth with bone loss ≥70% were extracted during SPT (T1-T2). Respective numbers for FDs patients were 15.6% (22/141), 10.2% (8/78), and 10% (1/10) of teeth. There was no significant statistical difference of tooth loss between the groups (P > 0.05, t test). At T1, 77% (27/35) of all patients presented furcation-involved molars, with 43% (15/35) of them with FI degree III. For RTPs patients, PPD (mean ± SD) for molars during SPT was 4.1 ± 0.9 mm in comparison with 4.3 ± 0.8 mm for FPs group, without significant difference between groups of patients or molars (P > 0.05). In each group, Cox regressions identified no statistically significant correlation (P > 0.05) for age, sex, and location, whereas significant difference (P < 0.05) was found for smoking, mean initial bone loss, and aggressive periodontitis as factors contributing to tooth loss and implant failures in general. No statistical differences were found for implant failures between 2 groups in relation to the implant positions (Tables 2 and 3).
Table 5 reported the frequency of interventions carried out during the 15-year follow-up for TRPs and FDs.
Recementation of primary crowns was necessary for 5 of the 36 reexamined TRPs (13.8%). Sixty percent of these prostheses (3/5) required repeated recementations. With reference to the number of abutment teeth, 34 of the reexamined 233 primary crowns (14.5%) were affected. Of these, 25.7% were repeatedly recemented. Rescrewing of abutment was necessary for 6 of the 36 reexamined TRPs (16.6%); 2 of 6 (33.3%) of these TRPs required repeated rescrewing. Reveneering was necessary for 8.3% (3/36) of the prostheses that were reevaluated, with 33.3% in need of multiple reveneering. No cracks or fractures in the framework were observed in the TRPs.
Recementation of crowns was necessary for 4 of the 34 reexamined FDPs (11.4%). Fifty percent of these prostheses (2/4) required repeated recementations. With reference to the number of abutment teeth, 26 of the reexamined 221 crowns (11.7%) were affected. Rescrewing of abutment was necessary for 5 of the 34 reexamined FPs (14.7%); 1 of 2 (50%) of these FPs required repeated rescrewing. Reveneering was necessary for 11.7% (4/34) of the prostheses that were reevaluated. No cracks or fractures in the framework were observed in the FDPs.
Dentitions damaged by severe periodontal disease often cause problems not only to the patient but also to the dentist regarding the decision if teeth with advanced bone loss can be retained and used as abutments or extracted and replaced with dental implants. The choice to maintain and treat periodontally compromised teeth is related to the prognosis assigned to these teeth. Hopeless teeth have to be extracted as part of the initial (cause-related) therapy, whereas teeth with questionable prognosis that have not responded to the initial phase of periodontal therapy, and teeth with unpredictable prognosis that, after the APT, still present an high risk, may have to be extracted following.11–19 Remaining and properly treated teeth with healthy but markedly reduced periodontal support are often mobile and need to be splinted to enhance patient comfort.20,21 Once splinted, these teeth can carry extensive fixed prostheses for a very long time with survival rates of about 90%, provided the periodontal disease is eradicated and prevented from reoccurring.12,19 Several long-term follow-up studies12,15,19 have shown that full-arch fixed bridges can be placed and successfully maintained on a minimal number of abutment teeth with greatly reduced periodontal support, provided the prosthodontic treatment is preceded by adequate periodontal therapy, and followed by a SPT. Such findings underscore the necessity of careful consideration regarding the choice to extract periodontally compromised teeth, especially in patients requiring, for a correct implants placement, complex surgical technique of bone augmentation, which present disadvantages of increased postoperative morbidity, higher treatment time and costs, and higher risks of complications. Nevertheless, because full masticatory function requires a sufficient number of occluding posterior units, possibly avoiding cantilever extensions,22,23 the use of supplemental, so-called strategic, implants could be recommended to enhance the clinical performance in this kind of patients, in which unfavorable prosthetic baseline situations with reduced number of abutment teeth are present.24–26
Results of the present study (91.9% of abutment teeth survival rate for RTPs and 89.6% for FPs) indicated that successful long-term retention of periodontally compromised abutment teeth with advanced bone loss is possible after APT if patients are enrolled in regular consequent SPT. These outcomes are in agreement with conclusions of other studies,27–29 suggesting the retention as long as possible, and even prosthetic restoration of periodontally compromised teeth (including mobile teeth), while performing STP, and to only replace teeth later on if absolutely necessary. As far as our knowledge, very few data have been published according to the concept using osseointegrated implants associated to residual teeth in periodontally treated and maintained patients.30 In contrast, several studies contraindicated the use of tooth-implant-supported restorations, due to biologic, restorative, and prosthetic reasons.31–36 However, data present in literature are contrasting because there are also several studies which indicated that there is sufficient flexibility within the implant restoration unit to allow for movement of the tooth within the socket to a degree where support is also achieved from the tooth, resulting in a more equal force distribution between the tooth and the implant.36–40 The sharing of force may be partly due to prosthesis and abutment screw flexibility, partly due to fixture movement in the bone, and partly due to the flexibility of the prosthesis. In the present study, at least 8 abutments (teeth plus implants) per arch were obtained for the RTPs and FDs. The implant survival rate (96.4% for RTPs group and 96.8% for FPs group) after 15 years of follow-up indicates that in periodontally treated and maintained patients refusing complex bone grafting surgical therapies, combined tooth-implant full-arch prosthetic rehabilitation does not increase the implant's biological and prosthetic risk. We can only speculate on the mechanism how these factors might affect implant survival rate of the present study. The integration of several abutments (teeth plus implants) might allow a more favorable distribution of loading forces, especially if the distribution of these abutments is arranged in a tangentially or cross arch linear relation to the arch. Furthermore, because abutment teeth with severely reduced but healthy periodontal tissue support still possess periodontal mechanoreceptors in the apical third of the root contributing to tactile sensitivity,41 the improved perception of teeth associated with implants supported full-arch prostheses may help to protect implants against occlusal overload. However, it is important to highlight that 100% of patients of the present study were fully compliant with STP, which has been proven as a key factor in enhancing long-term outcomes of periodontal and implant therapy.42,43 According to our results, the type of the prosthetic rehabilitation (full-arch RTPs vs full-arch FDs) did not influence the long-term outcomes, as the comparative rate of abutment teeth loss and implant failures were found with no statistically different comparing the 2 groups. However, a higher complications rate of caries, and endodontic lesions, was recorded in FDs group. A rigid construction of a one-piece casting supported by teeth and implants reduces the retrievability of the prostheses because of the cement retention on the natural tooth abutment. To overcome this limitation, according to what suggested in literature,44 we used in FDs group of patients a temporary cementation. In the other group, to allow the prosthetic retrievability, telescopic crowns were used. Results indicated that telescopic crowns on teeth and implants are a reliable alternative to the use of FDs cemented with temporary cement. TRPs provide the retrievability of prostheses, allowing at the same time the reduction of the risks of dental caries, and endodontic lesions, developed in a number of situations where loss of retention connected with the temporary cementation on the natural abutment went.
In each group of the present study, the initial periodontal diagnosis of aggressive periodontitis, the severity of the periodontal disease, and the smoking habit were identified as statistically significant factors in tooth loss and implant failure. These data are in agreement with previous studies45–47 and suggest that, due to the retrievability of RTPs which provides the option of periodontal/periimplant treatment and repair, if needed, this treatment should be preferred in smokers, in patients with aggressive periodontitis, and in cases of severe periodontal disease.
An alternative treatment could have been the extraction of all teeth, and the therapy with all-on-four concept, to avoid all the possible problem of keeping hopeless periodontally involved teeth and teeth-implants connection. A recent literature review48 on the all-on-four treatment indicated an implant survival rate for more than 24 months of 99.8%. However, only 2 studies, assessed for eligibility, reported data at 10 years of follow-up. The outcome is favorable in quality of life, when compared with the traditional 3 to 6 months during which the fixtures are protected from premature loading, requiring second surgery to expose them and connect the trans-mucosal components, and increasing the time and cost of treatment, as well as patient morbidity. However, on loading dental implants indiscriminately and immediately, there is a potential risk of unfavorable stress distribution and a negative cellular response under such high stress during early healing, when the implants are not splinted. Other relevant topics of all-on-four treatment reported in literature are related to use of sedation (via the oral or intravenous route) associated with local anesthesia and to use of guided surgery to obtain optimal insertion with adequate angle inclination. Benzodiazepines such as triazolam are contraindicated in pregnant or nursing patients, as well as in individuals who consume alcohol or are under treatment with macrolide antibiotics, certain protease inhibitors, psychotropic agents, ketoconazole, itraconazole, nefazodone, or other medications that impair oxidative metabolism mediated by the cytochrome P450A. Guided surgery has been often associated with complications, such as implant loss, prosthetic or surgical guide fractures, and low primary stability, and there is a learning curve for ensuring treatment success. Moreover, in the all-on-four treatment, prosthetic complications, such as acrylic fracture or the detachment of prosthetic parts, were frequently reported.
The choice between different therapy strategies in periodontally compromised patients leads an important question: “in these patients do implants perform better than periodontally compromised teeth?” Several important reasons justified our therapeutic choice: psychological, functional, biologic, and prognostic. Psychological issues stemming from all teeth loss should not be underestimated when a treatment plan is carried out. Each patient of the present study, during all the period of the therapy, was always wearing fixed temporary prostheses, which guaranteed him a continuous psychological, aesthetic, and functional comfort. Before each treatment section (initial preparation/caused related therapy, periodontal surgery, implant surgery, etc), the temporary fixed restoration was removed and then immediately reinserted in the patient's mouth before he was dismissed from the dental office. Retaining a number of own teeth, also with questionable/unpredictable periodontal prognosis (sometimes also with hopeless prognosis), as a foundation for a functional fixed temporary prosthesis (which will be later substitute by the definitive prostheses), can be a great source of self-confidence and improved outlook on life. Many periodontally compromised patients after teeth extractions often present insufficient bone housing for implants. Certainly, there are extraordinary methods available to solve the problems of inadequate bone support, such as sinus floor elevation and other bone augmentation procedures, but these methods carry a high biological risk and are clinically complex and time-consuming. The long-term clinical results of the present study should be compared with results obtained using advanced surgical techniques necessary to place a greater number of implants in resorbed jaws. A review of the literature conducted by Chiapasco et al7 reported that survival rates of implants placed in maxillae/mandibles reconstructed with onlay bone, in augmented maxillary sinuses, with vertical distraction osteogenesis procedures and in guided bone regeneration technique protocols were 87.1%, 95%, 95.9%, and 96%, respectively. These data, compared to those obtained in the present study, indicated that priority should be given to simpler approaches. In addition, it is also important to highlight that periimplantitis lesions at one or more implants have been found to occur in 16% to 28% of implant patients after 5 to 10 years and with higher prevalence among patients with multiple implants.49 Although it is well documented that severe periodontitis can be successfully treated, and further pathological bone destruction can be prevented, the long-term prognosis of periimplantitis treatment is as yet poorly documented. If further periodontal destruction is arrested by successful periodontal treatment, there is no obvious reason to replace a tooth with an implant even in cases with significant bone loss. In addition, although it is known that even as little as 25% to 30% remaining periodontal support seems to be sufficient in the long term to support extensive bridges,21 the capacity (prognosis) of implants with markedly reduced but healthy bone support to carry an extensive bridge is unknown.
As a retrospective analysis, the present study lacks the random allocation of patients into treatment and control groups. Another limitation lies in the fact that the distribution and number of implants, abutment teeth, and pontics varied between the patients. However, to minimize the differences, considerable effort was taken to identify 2 groups that were as similar as possible regarding, age, gender, smoking, diagnosis (aggressive/chronic periodontitis), degree of bone loss, and number of teeth at the baseline.
Within the limits of the present study, it is possible to conclude that in periodontally treated and maintained patients refusing bone grafting surgical therapies:
- Full-arch telescopic-retained retrievable prostheses and full-arch fixed prosthesis, both supported by teeth-implants combination, presented comparable and predictable long-term results of tooth loss and implant failure, if regular consequent supportive periodontal therapy is implemented
- Supplement, strategic implants, used in connection with residual abutment teeth, may enhance the clinical performance in unfavorable prosthetic baseline situations.
The authors claim to have no financial interest, either directly or indirectly, in the products or information listed in the article.
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