Abstract
Objectives
This clinical study evaluated the long-term outcome and survival rate of all-ceramic cantilever resin-bonded fixed dental prostheses (RBFDPs) made of zirconia-ceramic with a single-retainer design to replace missing incisors. In addition, whether the reason for missing incisors has an influence on the longevity of RBFDPs was analyzed.
Materials and methods
One hundred and eight zirconia ceramic cantilever RBFDPs were provided for 87 patients. Seventy-five RBFDPs replaced maxillary incisors and 33 mandibular incisors. The restorations were subsequently categorized into 3 groups according to the reasons for missing teeth (congenitally missing, trauma and other reasons). The patients were followed up annually, and the restorations were assessed for function and aesthetics. The mean observation time of the RBFDPs was 92.2 ± 33 months.
Results
Six debondings and 1 loss of restoration were recorded. The lost restoration was removed at the patient’s request after a small chip occurred on the mesial edge of the pontic. Three of the 6 observed debondings were caused by traumatic incidents. All debonded RBFDPs were rebonded successfully with no further complications. Zirconia ceramic RBFDPs yielded a 10-year survival rate of 98.2% and a success rate of 92.0%.
Conclusions
Anterior zirconia ceramic cantilever RBFDPs provided excellent clinical longevity. The reasons for missing incisors did not influence the longevity of the cantilever RBFDPs.
1
Introduction
Missing teeth in the anterior aesthetic region represent an urgent need for dental intervention and often require an early treatment strategy that restores both the aesthetic and functional aspects of the dentition . Missing anterior teeth may be congenital or occur as a result of traumatic incidents, caries and periodontitis .
Congenital absence of teeth is one of the most common malformations in humans . In the permanent dentition, with the exclusion of third molars, the prevalence of congenitally missing teeth on different continents ranges between 0.15% and 16.2% . Maxillary lateral incisors are the most commonly affected teeth in the anterior region . They are also the most common congenitally missing teeth bilaterally .
Traumatic events are another main reason for missing incisors , whether as a direct result of an incident or as a late complication. Maxillary central incisors are most frequently affected by trauma .
The main treatment options in these situations are the autotransplantation of deciduous or permanent teeth, orthodontic space closure, resin-bonded fixed dental prostheses (RBFDPs), implants, and conventional fixed dental prostheses (FDPs) .
Cantilever resin-bonded fixed dental prostheses (RBFDPs) are considered a minimally invasive treatment approach to the replacement of single missing anterior teeth and provide excellent clinical outcomes, high survival rates and great patient satisfaction . Fiber-reinforced composite RBFPDs offer a good aesthetic outcome, but are considered short-term prostheses . Metal-ceramic RBFDPs provide a long-term and successful option when designed as single-unit cantilever prostheses . Cantilever all-ceramic RBFDPs have demonstrated clinically excellent outcomes in terms of durability, outcome, aesthetics and function, whether made from glass-infiltrated alumina ceramic or from zirconia ceramic .
Additionally, RBFDPs have many advantages. They require a simple and conservative preparation, are low in cost and are a reversible treatment option, with no risk of pulpal irritation, no need for anesthesia, and minimal risk of caries development; in addition, they are a valid option for young patients . Moreover, these restorations demonstrated a high survival rate of up to 81.8% after 18 years of clinical service .
A recent systematic review on the rehabilitation of patients with congenitally missing teeth , concluded that the best restorative replacement was with dental implants. Conventional prosthetics, including RBFDPs, was considered an inferior treatment option with lower success and survival rates. However, this systematic review included no clinical studies using cantilever RBFDPs despite cantilever RBFDPs demonstrating excellent success and survival rates in such situations .
To the authors’ best knowledge, no studies have evaluated the influence of the cause of the missing teeth on the clinical performance of cantilever all-ceramic RBFDPs . The purpose of this clinical study was to determine the long-term success and survival rates of cantilever zirconia ceramic RBFDPs replacing incisor teeth. Additionally, the study was designed to determine whether the reasons for missing incisors would influence these rates. The null hypotheses of this study were that the success and survival rates of cantilever zirconia ceramic RBFDPs would not be influenced by the reasons for missing incisors.
2
Materials and methods
This retrospective clinical evaluation was approved by the ethics committee of the Christian-Albrechts University at Kiel, Germany. Between October 2001 and December 2013, 87 patients with missing incisors and an indication for RBFDPs received 108 anterior cantilever RBFDPs made from zirconia ceramic. The patients were selected based on the following inclusion criteria:
- 1.
Patients with 1 or 2 missing incisors.
- 2.
Abutment teeth were caries-free or had minor defects that could be covered by the retainer wing. The available bonding area on sound enamel had to be at least 30 mm 2 .
- 3.
Abutment teeth without periodontitis.
- 4.
Edentulous space width corresponded to the size of the missing tooth.
- 5.
Appropriate occlusion that allowed the application of a retainer wing with a thickness of at least 0.7 mm.
- 6.
Retention phase of at least 3 months after active orthodontic treatment.
- 7.
Patient commitment to attend annual recall appointments.
Patients were informed about the treatment modality and possible treatment alternatives and signed an informed consent form. The patients were 61% female and 39% male with the youngest patient being 13 years old and the oldest being 78, with a mean age of 32 ±20 years.
The preparation of the abutment was minimally invasive, limited to the enamel and was carried out as described previously . The preparation of the retainer consisted of a thin lingual veneer design, a fine incisal finishing shoulder and a fine cervical chamfer. The finish line in the proximal area did not extend farther than the proximal contact. A small box of approximately 2 × 2 × 0.5 mm was prepared proximally. Additionally, a pinhole was created on the cingulum, and finally all sharp edges and surfaces were carefully smoothed. A schematic drawing of the preparation design is depicted in Fig. 1 .
Impressions were taken and then poured with die stone. Restorations were designed using CAD/CAM technology, milled out of presintered zirconia ceramic blocks, and then densely sintered and manually veneered. The minimum thickness for the retainer wing was 0.7 mm. The minimum zirconia ceramic dimensions of the proximal connector were 2 mm (horizontally) × 3 mm (vertically). During the final clinical try-in appointment, marginal adaptation, fit, aesthetics, proximal contacts and static and dynamic occlusion were all carefully examined.
Prior to insertion, the bonding surfaces of the restorations were air-abraded with 50-μm alumina particles (0.25 MPa blasting pressure until the year 2009 and thereafter 0.1 MPa pressure) and then cleansed ultrasonically in 99% isopropanol. Rubber dam was used for isolation, and the enamel was etched with 37% phosphoric acid for 30s, and then the restorations were adhesively bonded using 1 of 2 adhesive luting systems (Panavia 21 TC, Kuraray, or Multilink Automix after application of Metal/Zirconia Primer, Ivoclar-Vivadent). An oral view of 2 cantilever zirconia ceramic RBFDPs is shown in Fig. 2 .
Fifty-nine patients received 1 cantilever RBFDP, 21 patients each received 2 cantilever RBFDPs, while 7 patients missing both maxillary lateral incisors received cantilever RBFDPs splinted at the midline by connecting their retainer wings to maintain the orthodontic closure of a midline diastema. The number and distribution of replaced missing teeth are shown in detail in Table 1 .
| Pontic location | Maxilla | Mandible | Total |
|---|---|---|---|
| Central incisors | 13 | 26 | 39 |
| Lateral incisors | 69 a | 7 | 76 |
| Total | 82 | 33 | 115 |
a In the maxilla, seven restorations replaced both missing lateral incisors.
Patients were recalled at least annually to examine and assess the restorations both functionally and aesthetically. Patients who could not attend a clinical examination for any reason were contacted by telephone and interviewed about the status of their RBFDP. Patients were categorized according to the reason for the missing tooth into 3 categories: congenitally missing ( G1 ), traumatic incidents ( G2 ) and other reasons ( G3 ), including periodontitis, caries and orthodontic treatment. One patient (1 restoration) was excluded from this analysis as the reason for the missing tooth was unknown. The RBFDPs replaced teeth that were congenitally missing in 59.6% of the cases, missing because of traumatic incidents in 13.2% and for other reasons in 27.2%. Table 2 specifies the number of teeth and the cause of missing teeth.
| Cause for missing teeth | Number of missing teeth | Percentage% |
|---|---|---|
| Congenitally missing (G1) | 68 | 59.6 |
| Traumatic incidents (G2) | 15 | 13.2 |
| Other reasons (G3) | 31 | 27.2 |
| Total | 114 | 100 |
The data were collected, coded, tabulated and input to a PC using Statistical Package for Social Science (SPSS 20.0 for Windows, SPSS Inc, Chicago, IL, USA). Using the Kaplan-Meier method, the success and survival rates of the restorations were analyzed considering 2 failure criteria: debonding for success and loss of the restoration for survival rates. The Log-Rank test was used to compare the survival rates of groups for these 2 criteria.
2
Materials and methods
This retrospective clinical evaluation was approved by the ethics committee of the Christian-Albrechts University at Kiel, Germany. Between October 2001 and December 2013, 87 patients with missing incisors and an indication for RBFDPs received 108 anterior cantilever RBFDPs made from zirconia ceramic. The patients were selected based on the following inclusion criteria:
- 1.
Patients with 1 or 2 missing incisors.
- 2.
Abutment teeth were caries-free or had minor defects that could be covered by the retainer wing. The available bonding area on sound enamel had to be at least 30 mm 2 .
- 3.
Abutment teeth without periodontitis.
- 4.
Edentulous space width corresponded to the size of the missing tooth.
- 5.
Appropriate occlusion that allowed the application of a retainer wing with a thickness of at least 0.7 mm.
- 6.
Retention phase of at least 3 months after active orthodontic treatment.
- 7.
Patient commitment to attend annual recall appointments.
Patients were informed about the treatment modality and possible treatment alternatives and signed an informed consent form. The patients were 61% female and 39% male with the youngest patient being 13 years old and the oldest being 78, with a mean age of 32 ±20 years.
The preparation of the abutment was minimally invasive, limited to the enamel and was carried out as described previously . The preparation of the retainer consisted of a thin lingual veneer design, a fine incisal finishing shoulder and a fine cervical chamfer. The finish line in the proximal area did not extend farther than the proximal contact. A small box of approximately 2 × 2 × 0.5 mm was prepared proximally. Additionally, a pinhole was created on the cingulum, and finally all sharp edges and surfaces were carefully smoothed. A schematic drawing of the preparation design is depicted in Fig. 1 .
