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 Table of Contents  
CASE REPORT
Year : 2017  |  Volume : 6  |  Issue : 1  |  Page : 48-53

Maxillary arch rehabilitation using implant-supported computer-assisted design-computer-assisted manufacturing-milled titanium framework


1 Department of Prosthodontics, MGM Dental College and Hospital, Navi Mumbai, Maharashtra, India
2 Department of Dental and Prosthetic Surgery, Tata Memorial Hospital, Mumbai, Maharashtra, India
3 Department of Conservative Dentistry, Saraswati Dhanwantari Dental College, Parbhani, Maharashtra, India

Date of Web Publication2-May-2017

Correspondence Address:
Sandeep Vivek Gurav
Department of Dental and Prosthetic Surgery, Tata Memorial Hospital, Dr. E. Borges Marg, Parel, Mumbai - 400 012, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jdas.jdas_52_16

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  Abstract 


Esthetic and functional rehabilitation of completely edentulous maxillary arch with fixed implant supported prosthesis is a challenging task. Newer technologies such as computer assisted design computer assisted manufacturing (CAD CAM) and cone beam conventional tomography play an important role in achieving predictable results. Full mouth porcelain fused to metal (PFM) individual crowns on CAD CAM milled titanium framework provides positive esthetic and functional outcome. This is a case report of rehabilitation of partially edentulous maxillary arch patient. Staged rehabilitation of this patient was planned. In the first stage, root canal treatment of key abutment teeth was done, nonsalvageable teeth were removed, and immediate interim overdenture was provided. In the second stage, five Nobel Biocare dental implants were placed. After integration impressions were made, CAD CAM milled titanium bar was fabricated. Individual PFM crowns were made and cemented. This method gives better esthetic compared to acrylic fused to metal hybrid prosthesis with the advantage of retrievability just like screw retained prosthesis. Hence, this technique is good for rehabilitation of patients with high esthetic demands.

Keywords: Computer-assisted design-computer-assisted manufacturing, dental implants, hybrid denture, porcelain-fused-to-metal crowns


How to cite this article:
Khanna TS, Gurav SV, Ghogare PH. Maxillary arch rehabilitation using implant-supported computer-assisted design-computer-assisted manufacturing-milled titanium framework. J Dent Allied Sci 2017;6:48-53

How to cite this URL:
Khanna TS, Gurav SV, Ghogare PH. Maxillary arch rehabilitation using implant-supported computer-assisted design-computer-assisted manufacturing-milled titanium framework. J Dent Allied Sci [serial online] 2017 [cited 2019 Oct 21];6:48-53. Available from: http://www.jdas.in/text.asp?2017/6/1/48/205448




  Introduction Top


The rehabilitation of maxillary arch is often challenging as compared to the mandibular arch because of high esthetic demands, type and density of bone, limited availability of bone due to the presence of sinus floor and nasal floor,[1] and anatomy of the maxillary arch which makes proper implant angulations difficult, especially in the anterior region.[1]

The angulations of implants in the anterior maxilla sometimes make the rehabilitation tricky and influence the prosthesis selection. The choice of material of final prosthesis also plays an important role in satisfactory and long-term outcome.

Various methods of full-mouth rehabilitation with osseointegrated implants have been discussed. Implant-retained removable overdenture, implant-supported cement-retained bridge, and hybrid denture to name a few.[2],[3],[4] Each of these methods has their advantages and disadvantages. Implant-supported fixed rigid bridge with cementable prosthesis provides excellent esthetics since the screw access channels are not visible on the labial side. Hybrid denture allows easy retrievability of the prosthesis.

Baig et al.[5] described a technique of metal-ceramic implant-supported fixed prostheses with milled titanium frameworks and individual cementable crowns. This technique has advantages of retrievability as in screw-retained prosthesis and esthetics as in cement-retained bridges. This article discusses stepwise fabrication of such prosthesis prepared for maxillary arch rehabilitation.


  Methodology Top


A partially edentulous, male patient aged 54 years reported to our dental office to get his missing teeth replaced. His chief desire was fixed teeth which would be esthetic and comfortable. Patient at no time wanted to be without teeth. Intraoral examination showed the presence of five teeth in maxillary arch (11, 12, 23, 24, and 25) [Figure 1]. These teeth were firm but three teeth (11, 24, and 25) displayed gingival recession along with root surface caries. The patient wore a maxillary removable partial denture to replace missing teeth which he was not happy about. Mandibular arch showed a porcelain-fused-to-metal (PFM)-fixed partial denture (FPD) in the right posterior region (44, 45, 46, and 47) and missing teeth in the left posterior region (34, 35, 37, and 38). Mandibular anterior teeth were firm and had no pathology. Medical history revealed patient to be diabetic and patient was under medication for the same. The patient was also a known smoker. The patient had no other relevant medical problems.
Figure 1: Preoperative intraoral view

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After a thorough clinical and radiographic examination, it was decided to extract maxillary teeth and fabricate a full-arch fixed implant-supported bridge for the maxillary arch and implant-supported bridge to replace missing teeth in the lower arch. Since the patient was esthetically demanding and socially active, he did not want edentulous phase; hence, it was decided to fabricate maxillary tooth supported immediate overdenture which will also act a diagnostic stent for cone beam conventional tomography (CBCT) as well as a temporary denture during the healing phase of osseointegration. The patient agreed with the treatment plan and informed consent was taken for the same.

A tooth supported overdenture was fabricated for the maxillary arch by retaining 12, 23. Ball abutments radicular posts (EDS AccessPost ™ Overdenture) were attached to these teeth after intentional root canal treatment. Extraction of remaining maxillary teeth was done and the housing was picked up in the denture. Radiopaque markers were placed in denture at prospective implant positions to convert the denture into a radiographic stent. The patient was sent for CBCT with the denture stent. After reading the CBCT, five prospective implant sites were identified and implants sizes were decided. The patient was evaluated and necessary blood investigations were carried out before the implant placement. The patient was also counseled for smoking cessation program before implant placement.

Implant surgical phase

Following all the sterilization protocols, standard open flap surgery was performed under local anesthesia and five dental implants (Replace Select, Nobel Biocare, Zürich, Switzerland) were placed in the maxillary arch. Sutures were removed after 7 days. During the integration phase, regular oral hygiene assessment was done. At this stage, patient decided for conventional FPDs for the mandibular arch. Hence, the missing 34, 35 were replaced with PFM FPD using conventional technique. Furthermore, existing FPD on the right side was replaced with a new one.

In this case, delayed loading protocol given by Branemark was followed. The prosthetic phase was delayed for 6 months for osseointegration during which the patient wore the maxillary tooth-supported overdenture relined with tissue conditioner (Viscogel, Dentsply, York, PA, USA) to avoid masticatory load on integrating implants. The second stage surgery was performed to expose the submerged implants. Cover screws were replaced with healing abutments (Nobel Biocare, Zürich, Switzerland). After around 10 days, open-tray impression of the maxillary arch was made with open-tray transfer copings (Nobel Biocare, Zürich, Switzerland) using polyvinylsiloxane elastomeric impression material (Aquasil Ultra, Dentsply, York, PA, USA). The transfer copings were splinted with autopolymerizing resin (GC Pattern Resin, GC Corp, Tokyo, Japan) before the impression was taken [Figure 2]. The impression was sent to the laboratory. In the laboratory, master cast was poured in type IV dental stone with implant replicas (NobRpl, Nobel Biocare, Zürich, Switzerland). On the master cast, a verification jig was made with autopolymerizing pattern resin (GC Pattern Resin; GC Co, Alsip, IL) and this was checked in patients' mouth for passivity [Figure 3]. This step reassured the precise recording of implant positions. In a subsequent appointment, a face-bow record and an interocclusal record (Occlufast Rock, Zhermack Co, Italy) were made. Master casts were mounted on a semi-adjustable articulator (Artex Articulator System; Girrbach Dental GmbH, Pforzheim, Germany). Denture acrylic teeth (Pala Premium Line; Heraeus Kulzer GmbH, Hanau, Germany) were used to try-in the esthetic and functional positioning of teeth, and patient's approval was taken.
Figure 2: Impression making with open tray technique

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Figure 3: Verification jig for titanium milling

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Nonengaging plastic abutments then were attached to the implant replicas on the master cast. Index of buccal and occlusal surfaces of trail denture was done [Figure 4]. A resin framework template was fabricated according to the contour of the trail denture with individual abutment preparations to accommodate the corresponding individual ceramic crowns [Figure 5] and [Figure 6]. Reduction in the abutment component of the framework allowed for optimal crown thickness. This pattern was scanned (NobelProcera optical scanner; Nobel Biocare), and computer-assisted design (CAD) designed. A titanium screw-retained bar was manufactured after computer-assisted manufacturing (CAM) processing.
Figure 4: Index of trial denture

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Figure 5: Cutback resin pattern

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Figure 6: Resin template ready for scan

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Framework try-in was done to check for passivity of fit [Figure 7] and [Figure 8]. The fit was found satisfactory, and sufficient clearance ensured for porcelain-fused-to-ceramic crown fabrication [Figure 9]. Frameworks were veneered with gingival pink porcelain to resemble soft tissue in gingival areas. Metal-ceramic cement-retained crowns then were fabricated by the conventional method on abutment component of the framework [Figure 10].
Figure 7: Milled titanium framework - trial

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Figure 8: Orthopantomogram showing passive fitting of titanium-milled framework

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Figure 9: Space for metal ceramic crown

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Figure 10: Individual porcelain-fused-to-metal crowns

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The screw-retained framework was secured to the implants at 35 Ncm torque. The screw access holes were sealed with gutta-percha and composite resin. The PFM crowns were tried on the titanium framework individually and also together to check for the contact points in between adjacent crowns. Occlusal adjustments were done to achieve mutually protected occlusion. PFM crowns were polished, glazed, and cemented over the framework individually using zinc polycarboxylate cement. The implant prosthesis restored lost function and provided the necessary esthetics [Figure 11] and [Figure 12].
Figure 11: Final prosthesis - intraoral view

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Figure 12: Postoperative view showing esthetic

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The importance of maintaining hygiene was reinforced and use of water jet (Waterpik, Waterpik Corporation, UK) was suggested. A 2 mm thick, soft night guard was given to avoid any oblique forces due to parafunctional habits. Follow-up checkups were done and necessary occlusal adjustments were done in follow-up appointments. Patient was emphasized on need of regular follow-ups.


  Discussion Top


Meeting patient's high esthetic demands through a maxillary full-arch implant-supported rehabilitation depends on the achievement of several biological and mechanical goals.[6],[7] Conventional immediate dentures help eliminate edentulous phase, thus avoiding problems in patients social life. In this case, immediate overdenture was planned as patient desired well-retentive denture. Moreover, overdenture also provides added advantage of restored proprioception, resulting in good masticatory efficiency and better centric positioning of mandible.

Fixed rehabilitation of completely edentulous situations can be achieved with the use of a screw-retained implant hybrid prosthesis, conventional screw-retained metal-ceramic prosthesis, cemented metal-ceramic prosthesis, and cemented hybrids.[2],[3],[4] Screw-retained implant fixed prostheses have been advocated traditionally because of their ease of retrievability, benefit of splinting, and low profile retention. Hybrid screw-retained prostheses additionally compensate for lost tissues in moderately to severely resorbed alveolar ridges. However, lack of passive fit of the cast framework and distortion of the framework upon porcelain firing remain problem areas. In severe ridge resorption, off-axial implant positioning may result in the labial or buccal emergence of the access screw channel, thus compromising esthetics and preventing ideal occlusal morphology.[1],[7]

The final prosthetic design and material are also influenced by opposing dentition. In this case, the patient had natural mandibular anterior teeth, and posterior teeth were rehabilitated with PFM bridges. Cross-linked resin teeth of conventional hybrid denture would have shown significant wear and repeated fractures in weak resin-metal interface.

The choice of materials used in such rehabilitations plays an important role in the final outcome. Porcelain veneering over gold alloys or zirconium oxide frameworks has set the standard for the materials of choice in such cases.[8]

Full-arch fixed implant-supported bridge which consisted of cast framework and denture teeth and gingival acrylic resin had limitations which varied from wearing off the acrylic teeth, discoloration to misfit of the cast framework which jeopardized the long-term survival of implants. This case report presents with the use of stronger material in the form of PFM crowns which would maintain the esthetics as well as the vertical dimension.

Porcelain-veneered single crowns and fixed dental prostheses are well known for fulfilling esthetics, biocompatibility, color stability, and resistance to wear.[9]

Various methods have been tried to avoid esthetic and functional failure in cases of single edentulous arch opposing natural dentition. One way is to use a compatible material section between maxillary and mandibular arches, by combining of a maxillary ceramic prosthesis with a mandibular metal-acrylic prosthesis in full-arch rehabilitations. This reduces the overall stiffness of the prosthetic elements as a whole, dramatically reducing mechanical complications.[10] Protecting the restorations with an occlusal splint “night-guard” is another method typically used to protect restorations, particularly when parafunctional habits are present. It may also lessen the odds of porcelain chipping.[11]

Implant-retained fixed prosthesis with cementable abutment was also viable treatment option. These treatment options have the advantages of passively fitting frameworks and better esthetics. Custom abutment options can compensate for malaligned implants, thus improving esthetics.[12],[13] However, retrievability, repair and maintenance, choice of cement, and excess cement in the sulcus remain areas of concern. The lack of resilience due to the absence of a periodontal ligament in implant-supported restorations demands the use of highly sophisticated materials when trying to overcome fatigue resistance due to occlusal loading. In a complex biomechanical system, where implants, abutments, frameworks, screws, and esthetic veneering materials share masticatory stress conduction, porcelain is the material most commonly prone to failure with immediate esthetic consequences.[10],[13],[14]

Another method address the mechanical failure of porcelain is to design individual full-contour crowns to be cemented on a titanium alloy screw-retained bar.[15] The benefit of this concept is based on the ability to remove and repair (or even replace) an individual fractured crown without the need to remove the entire structure,[16],[17] which in turn allows a lower cost.

A study involving 108 patients on the outcome of metal-ceramic implant-supported fixed prostheses with milled titanium frameworks and all ceramic crowns suggested that the cumulative survival rates for the implant-supported fixed prostheses were 92.4% for the individual Procera alumina crowns cemented onto a CAD/CAM-fabricated titanium framework with pink ceramic at 10 years and 100% for the individual Procera zirconia crowns cemented onto a CAD/CAM-fabricated titanium framework with pink acrylic resin that replicated the missing gingival tissues at 5 years (overall 96%).[16]

Poorly controlled diabetes negatively affects implant osseointegration; however, under optimal serum glycemic control, osseointegration can successfully occur in patients with diabetes.[18]

The patient was heavy smoker. Bain [19] in 1993 was the first to evaluate the influence of smoking on the failure rate of dental implants. They compared the results between dental implants placed in smokers versus those placed in nonsmokers. The overall failure rate of 5.92% was found to be consistent with other studies; however, when patients were subdivided into smokers and nonsmokers, it was found that a significantly greater percentage of failures occurred in smokers (11.28%) than in nonsmokers (4.76%) (P < 0.001). The findings of this study, for the first time, identified smoking as a major factor in implant failure. Subsequently, a few other studies also implicated smoking as a leading cause of implant failure.[20],[21],[22],[23]

The patient was counseled and smoking cessation program by Bain [19] was followed.

Two-stage implant procedure with delayed loading protocol given by Brain mark was followed as patient was diabetic and smoker; hence, the chances of implant failure were more.

Parafunctional habits such as bruxism produce significant amount of oblique pressure on implant–bone interface. Bruxism patients are prone for prosthetic failures such as abutment screw loosening and porcelain chipping. This patient was edentulous in maxillary arch and gave no history of parafunctional habits; still occlusal guard made up of 2 mm thick vacuum formed soft acrylic was provided as a precaution till he gets adjusted to new all porcelain surface occlusion.


  Result Top


Individual ceramic crowns on CAD-CAM milled framework has provided excellent esthetic results. This method gives better esthetic compared to acrylic fused to metal hybrid prosthesis.


  Conclusion Top


Implant-supported fixed prosthesis proves to be viable treatment option for completely edentulous patients. Use of CAD-CAM technology for milling of titanium bar gives passive fitting, screw-retained retrievable prosthesis, and individual metal-ceramic crowns provides unmatched esthetics. In patients with high esthetic demands and opposing natural or porcelain teeth, this treatment protocol proves satisfactory.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
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Kinsel RP, Lin D. Retrospective analysis of porcelain failures of metal ceramic crowns and fixed partial dentures supported by 729 implants in 152 patients: Patient-specific and implant-specific predictors of ceramic failure. J Prosthet Dent 2009;101:388-94.  Back to cited text no. 13
    
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Lambert PM, Morris HF, Ochi S. The influence of smoking on 3-year clinical success of osseointegrated dental implants. Ann Periodontol 2000;5:79-89.  Back to cited text no. 23
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]



 

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