Abstract
Recreating a harmonious gingival contour for contiguous missing teeth in the anterior maxilla is challenging. The aim of this study was to evaluate a split pedicle roll envelope technique designed for pontics. Twelve patients presented a labial flat or concave profile at the implant and pontic sites before second-stage surgery. The contour deficiency was compensated with a palatal split pedicle flap with the implant part rolled into the labial envelope and the pontic part covering the denuded ridge. Interim restorations were screwed in to guide tissue remodelling. The labial convex profile (CPF) and facial mucosal level (FML) at the implant and pontic sites, the Jemt papilla index (PIS) in the different restorative environments, and peri-implant bone levels were recorded at baseline and at 1 week, 3 months, and 6 months postoperative. Results showed that the CPF had increased by 1.4 mm at the implant site and 1.5 mm at the pontic site at 6 months after surgery. PIS had increased by 2 at the implant–tooth/pontic–tooth sites and by 2.6 at the implant–pontic site. FML was coordinated with that of the contralateral teeth. All indices were favourable at 3 months and then remained stable. Within the limitations identified, this combined therapy can be considered as an alternative to achieve aesthetic success when contiguous maxillary anterior teeth are missing.
The treatment concept of implant dentistry has shifted from implant survival to aesthetic rehabilitation. When aesthetics is added to the criteria for success, the success rate of implant-supported prostheses drops significantly. For contiguous missing maxillary anterior teeth, aesthetics is even less predictable than with a single missing tooth, particularly regarding the maintenance of inter-implant tissue.
When the bone morphology permits implant installation, the ‘one tooth, one implant’ treatment protocol can be adopted where space allows. However, anatomical limitations, patient-centred issues, and aesthetic considerations may justify implant-supported bridges or cantilevers. Although Tarnow et al. recommend an inter-implant horizontal distance of at least 3 mm to reduce crestal bone loss, it is usually hard to meet this requirement in the anterior maxilla. In addition, the predicted inter-implant papilla height is lower than that adjacent to a natural tooth or pontic. Thus it appears advisable to circumvent this risky inter-implant dilemma by using pontics. Among the various pontic designs, the ovate pontic is recommended as an effective replication of the natural emergence profile, and long-term mucosal health can be maintained.
Adequate alveolar bone and soft tissue volume are the prerequisites for aesthetic reconstructions of either a pontic or an implant site. Many ridge augmentation techniques have been applied to condition the ridge topography. However, the grafted tissues often undergo unpredictable resorption. Therefore, re-grafting is often necessary at the second-stage surgery. It is documented that a deficiency of <3 mm in dimension can be resolved by soft tissue augmentation alone. Thus soft tissue grafting and various flap designs have been devised for contour compensation. The acquirement of soft tissue from the palate aggravates patient morbidity, and compared to pedicled grafts, free connective tissue grafts (CTG) have a higher risk of shrinkage. To circumvent these problems, Man et al. developed a palatal roll envelope technique for soft tissue reconstruction around single implants that is minimally invasive and has the potential to reduce graft shrinkage and scar formation. However, it cannot be applied to the pontic area because it might expose the alveolar bone there directly to the oral cavity.
The purpose of this study was to: (1) present a therapy consisting of a split pedicle roll envelope technique and restorative designs with ovate pontics, and (2) objectively evaluate its efficacy and predictability.
Materials and methods
Patients and study design
Twelve consecutive patients (six women and six men, mean age 34 ± 5.8 years) were included in this study. To be enrolled, the patient had to fulfil the following criteria: (1) age ≥18 years with good oral hygiene and compliance; (2) presenting at least one location with multiple adjacent maxillary anterior teeth missing; (3) presenting a flat or concave profile before the second-stage surgery, with a sufficient bone base; (4) no tobacco abuse.
A total of 19 implants were installed, including 14 Osstem GS II implants (Osstem Implant Co., Ltd, Busan, Korea) and five ITI bone level implants (Institut Straumann AG, Basel, Switzerland) between August 2012 and March 2013. Of the 12 patients, five had single-implant-supported cantilevers with the pontic situated in the position of lateral incisor and seven had three-unit implant-supported bridges. Informed consent was obtained. After healing for 3 months, the split pedicle roll envelope technique was performed at second-stage surgery. This study was designed as an observational prospective study.
Surgical procedure
Under local anaesthesia, an initial partial-thickness crestal incision was made 1–2 mm towards the palatal side, to gain a maximum amount of keratinized tissue in the labial flap, and 1–2 mm away from the adjacent teeth, to preserve the papilla. Two partial-thickness vertical incisions, 5–10 mm in length, were made on the palatal side (see the superficial incision in Fig. 1 a ). The superficial part was elevated by sharp dissection (see the dissected superficial flap and underlying connective tissue in Fig. 1 b). Then, another incision, parallel to the union of the two split palatal flaps, involving only the deeper one, further disconnected the two flaps (see the deep incision in Fig. 1 a, indicated by the blue lines). The deeper half was elevated and transformed into a wide mobile pedicled flap, which was divided into two narrow peri-implant parts and one wide pontic part with two small vertical incisions (see the divided flap in Fig. 1 c). In the case of single-implant-supported cantilevers, only one vertical incision was needed. A labial envelope was prepared. After the insertion of healing abutments, the peri-implant parts were rolled and positioned in the labial envelope to imitate the emergence profile at the implant site. The tissue rolled into the envelope further pushed the mucosa covering the pontic ridge labially, eliminating the labial concavity of the pontic site. The pontic part was then left in situ loosely to cover the denuded ridge, leaving a strip of de-epithelialized connective tissue exposed. Then on the palatal side, the dissected superficial flap was extended labially with a blood clot underneath, to provide tension-free closure over the pontic ridge. Interrupted or mattress sutures (6–0) were anchored into the exposed connective tissue and the palatal superficial flap to stabilize both of the flaps and close the wound (see the augmented labial contour and exposed connective tissue band in Fig. 1 d).
Prosthetic restoration
Immediately after suture removal, an impression was made for interim prosthesis fabrication. On the plaster cast, a composite resin crown, modelled according to the shape of the contralateral teeth, was formed onto one or two temporary abutments. The ovate pontic site was carefully prepared in such a way that the tissue surface of the acrylic pontic was a little over-contoured, which gave rise to the illusion of a natural emergence profile. Sufficient room was reserved for interproximal tissue regeneration and access for oral hygiene. After the tissue surface had been highly glazed, it was manually screwed in and adjusted until no excursive contact existed. Patients were instructed to properly use dental floss and brush their teeth. Postoperative healing was monitored and the interim restoration was adjusted 1–3 times in the next 3 months to optimize aesthetics. Although a mature status of the soft tissue was achieved by the third month, the use of the interim restorations was continued for a further 3 months to avoid tissue deformation. The peri-implant and pontic circumferential indices were then accurately transferred to assist the dental laboratories, and the definitive restoration was seated 6 months after surgery ( Fig. 2 a–c ).
Clinical evaluation
Evaluations were done at the preoperative examination (T0) as the baseline and then at follow-up visits 1 week (T1), 3 months (T2), and 6 months (T3) after surgery. The following variables were recorded at the designated time points: (1) Convex profile on the facial aspect (CPF ): CPF over-contour = 3, CPF present = 2, CPF partially present = 1, CPF absent = 0; this was measured at T0, T1, T2, and T3. (2) Facial mucosal level (FML), recorded as a positive value when located in a coronal position when compared to the contralateral tooth or restoration; this was measured at T0, T1, T2, and T3. (3) Jemt papilla index score (PIS ): no papilla = 0, less than one half the height of the papilla = 1, more than half of the height of the interproximal space = 2, papilla fills the entire proximal space = 3, hyperplastic papilla = 4; this was measured at T0, T1, T2, and T3. (4) The marginal bone level (MBL), measured at T1 and T3. (5) The proximal bone level (PBL), measured at T1 and T3. (6) The modified plaque index (mPLI): no plaque = 0, plaque recognized only by running a probe across the marginal surface of the implant restoration = 1, plaque seen with the naked eye = 2, abundance of soft matter = 3; this was measured at T0, T2, and T3.
Digital photographs were taken to record CPF, PIS, and FML. The preoperative examinations were carried out by graphically adding the imaginary contour of an optimal restoration to the preoperative photograph. The same operator performed all the measurements. The MBL and PBL were measured using sequential peri-apical radiographs with a paralleling technique ( Fig. 2 d and e). The distance from the prosthetic platform to the first bone contact was calculated at the mesial and distal sites for each implant separately, and then given as a mean value averaged to the nearest 0.1 mm. Angular differences between T1 and T3 were standardized by implant length. A value of zero was given to T1. A negative value was given when the MBL and PBL was apical to T1.
Statistical analysis
The Friedman test was applied to evaluate CPF, PIS, and FML changes. A difference was considered significant if the P -value was <0.05. If an overall significant difference existed, separate Wilcoxon signed-rank tests were added. The statistical analysis was performed using IBM SPSS Statistics for Windows, version 19.0 (IBM Corp., Armonk, NY, USA). The MBL/PBL and mPLI changes were explained descriptively.
Results
During the 6-month follow-up, no patient was lost and no implant showed loss of osseointegration. Postsurgical inconveniences were minimal and all patients showed good oral hygiene at T2 and T3, indicated by low plaque indices ( Table 1 ). The pedicled flap blended in well with the surrounding tissue. The screw of one cantilever had come loose at the 1-month recall and this was tightened manually. A minor crown fracture occurred in three interim restorations; these were mended with composite resin.
| Index | Values | Friedman test | Wilcoxon signed-rank test |
|---|---|---|---|
| CPF | |||
| Peri-implant | T0 = 0.53 ± 0.51 T1 = 2.63 ± 0.50 T2 = 1.95 ± 0.23 T3 = 1.89 ± 0.32 |
χ 2 = 52.21; df = 3 P < 0.001 |
T1–T0: Z = 4.185; P < 0.001 T2–T0: Z = 3.946; P < 0.001 T3–T0: Z = 3.963; P < 0.001 T2–T1: Z = −3.606; P < 0.001 T3–T1: Z = −3.742; P < 0.001 T3–T2: Z = −1.000; P = 0.317 |
| Pontic | T0 = 0.33 ± 0.49 T1 = 2.83 ± 0.39 T2 = 1.92 ± 0.29 T3 = 1.83 ± 0.39 |
χ 2 = 34.76; df = 3 P < 0.001 |
T1–T0: Z = 3.145; P = 0.002 T2–T0: Z = 3.153; P = 0.002 T3–T0: Z = 3.145; P = 0.002 T2–T1: Z = −3.317; P = 0.001 T3–T1: Z = −3.207; P = 0.001 T3–T2: Z = −1.000; P = 0.317 |
| PIS | |||
| Implant–tooth | T0 = 0.79 ± 0.63 T1 = 1.21 ± 0.63 T2 = 2.53 ± 0.51 T3 = 2.79 ± 0.42 |
χ 2 = 52.85; df = 3 P < 0.001 |
T1–T0: Z = 2.828; P = 0.005 T2–T0: Z = 3.912; P < 0.001 T3–T0: Z = 3.886; P < 0.001 T2–T1: Z = 4.017; P < 0.001 T3–T1: Z = 3.919; P < 0.001 T3–T2: Z = 1.667; P = 0.096 |
| Implant–pontic | T0 = 0.26 ± 0.45 T1 = 1.21 ± 0.42 T2 = 2.63 ± 0.50 T3 = 2.89 ± 0.32 |
χ 2 = 54.86; df = 3 P < 0.001 |
T1–T0: Z = 4.243; P < 0.001 T2–T0: Z = 3.923; P < 0.001 T3–T0: Z = 3.963; P < 0.001 T2–T1: Z = 3.946; P < 0.001 T3–T1: Z = 3.987; P < 0.001 T3–T2: Z = 1.890; P = 0.059 |
| Pontic–tooth | T0 = 0.80 ± 0.45 T1 = 1.40 ± 0.55 T2 = 2.60 ± 0.55 T3 = 2.80 ± 0.45 |
χ 2 = 17.11; df = 3 P = 0.001 |
T1–T0: Z = 1.890; P = 0.059 T2–T0: Z = 2.264; P = 0.024 T3–T0: Z = 2.449; P = 0.014 T2–T1: Z = 2.264; P = 0.024 T3–T1: Z = 2.232; P = 0.026 T3–T2: Z = 1.342; P = 0.180 |
| FML | |||
| Peri-implant | T0 = −0.16 ± 0.22 T1 = 1.22 ± 0.41 T2 = 0.05 ± 0.15 T3 = −0.01 ± 0.15 |
χ 2 = 41.92; df = 3 P < 0.001 |
T1–T0: Z = 3.828; P < 0.001 T2–T0: Z = 3.294; P = 0.001 T3–T0: Z = 2.614; P = 0.009 T2–T1: Z = −3.828; P < 0.001 T3–T1: Z = −3.831; P < 0.001 T3–T2: Z = −1.309; P = 0.190 |
| Pontic | T0 = −0.55 ± 0.38 T1 = 1.16 ± 0.30 T2 = 0.03 ± 0.14 T3 = −0.03 ± 0.13 |
χ 2 = 30.26; df = 3 P < 0.001 |
T1–T0: Z = 3.063; P = 0.002 T2–T0: Z = 2.950; P = 0.003 T3–T0: Z = 2.810; P = 0.005 T2–T1: Z = −3.068; P = 0.002 T3–T1: Z = −3.069; P = 0.002 T3–T2: Z = −1.273; P = 0.203 |
| mPLI | T0 = 0.42 ± 0.67 T2 = 0.33 ± 0.49 T3 = 0.25 ± 0.45 |
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