Five-Year Study of Implant Placement in Regenerated Bone and Rehabilitation With Telescopic Crown Retained Dentures: A Case Report

Telescopic crowns are widely used on natural teeth to support dentures and allow easy access around the abutment for oral hygiene, as well as easy handling of the overdenture.1–4 However, limited data are available on the use of telescopic crowns on implants. Compared with the use of fixed implant–supported dentures, this treatment modality may improve esthetics and oral hygiene access, reduce the need for implants, and provide sufficient denture support in cases where single abutments have failed. Furthermore, the high retention obtained with telescopic crowns leads to good mastication and phonetics. We previously reported the use of telescopic crowns as attachments for implant-supported restorations.5 

Alveolar ridge resorption following tooth extraction is a frequently observed phenomenon that can impair dental implant placement. The advent of guided bone regeneration (GBR) using barrier membranes has provided clinicians with a new method to potentially modify extraction socket healing.6 Current methods used to prevent ridge resorption include the use of particulate autografts, allografts, alloplasts, xenografts, and resorbable or nonresorbable membranes manufactured from various materials. For instance, a high-density polytetrafluoroethylene (dPTFE) membrane designed specifically for use in socket grafting and that does not require primary closure has been successfully used in animal and clinical investigations.7–10 

In the following case report, the results of a 5-year full-mouth rehabilitation are presented. Implants were placed in areas of regenerated bone and subsequently were loaded using telescopic crowns as attachments for implant-supported overdentures.

A 41-year-old man was referred to the private office of one of the authors (G.G.Z.) for implant treatment in September 2003. His main concern was pain and tooth mobility. The patient had avoided dental treatment for the previous 20 years owing to dental phobia. Advanced chronic periodontitis was diagnosed, and the prognosis for the remaining dentition was poor, with the exception of tooth No. 22. In contrast to the rest of the teeth, No. 22 had grade 1 mobility and a mean pocket depth of 4.5 mm. Radiologically, the bone loss in No. 22 was less than one-third of the root length without vertical bone defects (Figure 1). For these reasons, the patient was scheduled to keep this tooth.

The nonsalvageable teeth were extracted, and during surgery, tooth No. 22 was treated by access flap surgery (AFS). Socket preservation was performed according to Hoffmann et al10 using nonresorbable dPTFE membranes (Cytoplast, Regentex GBR-200, Oraltronics, Bremen, Germany) without the use of any soft or hard tissue grafts. Two provisional implants (IPI, Immediate Provisional Implants, Nobel Biocare, Cologne, Germany) were placed in areas No. 26 and 29 to support the temporary restoration. The membrane covering the temporary implant site was pierced with a scalpel at the implant shoulder, and a healing cap was used to fix the membrane in place. Interim dentures were made available 1 day after the surgery. Eight months after surgery, 11 implants (screw cylinder, SLA, Ø4.1 mm PLUS, length 10 mm, Straumann, Waldenburg, Switzerland) were placed (maxilla, N  =  6, Nos. 5, 6, 7, 10, 11, and 12; mandible, N  =  5, Nos. 27, 28, 30, 21, and 19) (Figure 2).

Four months after implant placement, the provisional implants were removed and the definitive implants were loaded. The maxilla and the mandible were restored with telescopic crown–retained removable dentures (Figures 3 and 4). Gold customizable abutments were used (SynOcta RN 048.642, Straumann, Waldenburg, Switzerland) to fabricate the gold implant abutments (Portadur P4, Au 68.50%, Wieland Dental Technik, Pforzheim, Germany; Figure 5A and B). After casting, the customized gold implant abutments were grinded and polished, and served as primary telescopes (Figure 5C). As secondary telescopes, electroformed pure gold copings with a thickness of 0.25 mm were fabricated (AGC Galvanogold, Au >99.9%, Wieland Dental Technik; Figure 5D and E).11,12 For supraconstruction castings, a CoCrMo alloy was used (Ankatit Laser, Ankatit-Anka Guss, Waldaschaff, Germany).

The electroformed gold copings were fixed in the implant supraconstructions using a self-curing compomer cement (AGC Cem, Wieland Dental Technik, Pforzheim, Germany; Figure 5F through H). For supraconstruction veneering, we used a lightly cured indirect ceramic polymer (Solidex, Shofu Dental, Ratingen, Germany) and composite artificial teeth (Veracia, Shofu Dental, Ratingen, Germany) (Figure 3C through F, Figure 5I).

The patient was prescribed an analgesic (diclofenac 100 mg, once daily for 4 days), a systemic antibiotic (clindamycin 600 mg, once daily for 6 days), and a 0.1% chlorhexidine digluconate rinse (chlorhexamed fluid, twice daily). The patient was instructed to start these medications 1 day before undergoing extractions and/or implant surgery.

The surgical sutures were left in for 1 week. The membranes were left partially exposed and were removed after a healing period of 4 weeks. After surgery, the patient was enrolled in a maintenance program consisting of semiannual follow-up appointments. At the follow-up visits, oral hygiene instructions were given, and debridement was performed followed by polishing. The first maintenance visit, which was used as the baseline examination (BSL), was performed 3 months after placement of the supraconstruction. The BOP, PI,13 and PAL values were recorded on the 4 surfaces of natural tooth No. 22 and of the implants. The PAL was estimated using a periodontal probe (UNC 15, Hu-Friedy, Leimen, Germany) as the distance (in millimeters) between the deepest point of the peri-implant pocket and the smooth neck section of the implants; the implant shoulder was considered as the reference point. Measurements at BSL and at 1, 2, 3, and 5 years after loading are reported.

A total of 11 implants, placed 8 months after tooth extraction and socket preservation, were observed over 5 years. Implants were loaded 4 months after placement using telescopic crowns as attachments for the implant-supported overdentures. All implants remained functional throughout the 5-year observation period.

Because of the small number of implants, a statistical analysis of the clinical measurements could not be performed. However, no major changes in the BOP or PI values were found among the 5 examinations (BSL, 5 years; range, 2%–4% for both parameters). Compared with BSL (mean  =  0.5 mm), PAL outcomes on the 11 dental implants showed deterioration of 1.5 mm during the observation period (1 mm at 1 year and 1.5 mm at 3 years; Figure 6). Between the first and second years, as well as between the third, fourth, and fifth years, no changes in PAL outcomes were observed. Furthermore, PAL outcomes of natural tooth No. 22 were stable (range, 1–1.5 mm) during the 5-year observation period.

Here we report the 5-year observation of a 41-year-old patient receiving 11 implants in his mandible and maxillae. These implants, which were restored using telescopic crown–supported dentures, remained in function over the 5-year period. Radiographic evaluation revealed stable bone levels for all implants, and no changes in the BOP or PI (range, 2%–4% for both parameters) were observed. PAL deteriorated by 1.5 mm during the first 3 years, with no subsequent changes.

Telescopic crowns have been used successfully for several decades to connect dentures to natural teeth and/or implants. The telescopic crown concept ensures maximally favorable masticatory force transmission, which always takes place axial to the abutments. Retention occurs through the force of friction.14 Regarding the use of telescopic crowns with implant-supported overdentures, only limited data are available; however, the results so far indicate that this treatment modality can lead to predictable long-term treatment outcomes.5,14–16 Patient removability of the secondary structure facilitates abutment hygiene, making the telescopic crown system more acceptable from a periodontal perspective.5,17 

The clinical and radiographic 5-year follow-up results reported here reveal stable bone crest levels for all implants. This is in agreement with a previous study, in which a different prosthetic protocol was used.18 Bone loss following tooth extraction may impair the future possibility of placing implants. Various techniques to preserve bone volume at extraction sites have been described. In the present study, a dPTFE membrane alone, without the addition of any graft material, was used. This resulted in sufficient preservation of bone volume to allow for implant placement. The surgical protocol for this approach, as well as clinical and histologic findings, was published previously.10 Increasing evidence suggests that the bone regenerated beneath nonresorbable dPTFE membranes has a similar load-bearing capacity as pristine nonregenerated bone, and that good osseointegration can be expected when implants are placed in the augmented bone.18 

In conclusion, our results demonstrate that all 11 implants were integrated successfully by the time of the 5-year examination time point, with a survival rate of 100%. These results are consistent with a previous 5-year study on the same type of implants in nonregenerated bone.19 

The authors report no conflicts of interest related to this study. The authors thank Mrs Ulrike Schulz, Dipl-Math, MediStat, Kronshagen, Germany, for statistical consulting, and Mr Jochen Rebbe, Chief Dental Technician, Dentalstudio Herrmann, Duesseldorf, Germany, for his help with technical work.