Successful Rehabilitation of Anterior Crowns with Richmond Crown: Case Series

Restoration of severely fractured/ decayed teeth requires crown restoration after endodontic therapy which is often major requisite in conservative dentistry. If there is steep incisal guidance and very less overjet then restoration of such crown is not possible with routine post and core followed by crown restoration because of very less incisal clearance. Richmond crown is advisable in such cases as it is single-unit post retained crown with porcelain facing design. Two cases have been discussed here with Richmond crown treatment modality over 2-3 years successful follow-up. Case Report Successful Rehabilitation of Anterior Crowns with Richmond Crown: Case Series Sachin Metkari1* and Manisha Metkari2 1Assistant professor, Dept. of conservative dentistry & Endodontics, Nair Hospital Dental College, Mumbai, India 2Dental Surgeon and private practitioner, Mumbai, India Dates: Received: 01 April, 2017; Accepted: 19 June, 2017; Published: 20 June, 2017 *Corresponding author: Sachin Metkari, Assistant professor, Department of conservative dentistry & Endodontics, Nair Hospital Dental College, Mumbai, India, E-mail:


Introduction
Restoration of endodontically treated teeth has always been challenge in dentistry. Grossly carious crowns, severe fracture of teeth involving more than two-third of crown structure requires additional retention from root canal for crown restoration especially after root canal therapy. In such cases post and core treatment modality has been advised. If such cases became complicated with deep bite and minimum overjet then it will be very diffi cult to place a prosthetic crown.
Richmond crown can be placed in such situation as it does not require cemental interface between post-core and crown. This can also be advised in deep-bite cases involving minimum overjet with severely destructed tooth structure.
Richmond crown is a single-piece, post-retained crown with a porcelain facing designed to function as bridge retainer. Richmond crown is not a post and core system but it is customized castable post and crown system as both are single unit and casted together. It is easy to make cast metal restoration with aid of posts for long term retention [1].
Here, we have discussed two case reports one with fractured upper left central incisor involving Elli's type III fracture complicating severe deep bite and very minimum overjet.
Other case was having repeatedly dislodged crown in relation to upper left lateral incisor with minimum amount of tooth structure remaining. In both the cases crown was restored with Richmond crown treatment modality. We perceived successful follow-up for 2 years and 3 years respectively.

Case Report 1
25 years old male healthy patient reported with the chief complaint of fracture of upper left central incisor ( Figure 1). Patient was conscious, cooperative and well-oriented with time, space and environment. He met with an accident and fell down on fl oor with the face downward. He noticed that his upper anterior tooth was fractured and blood oozing from the tooth. He tried to stop bleeding with handkerchief and immediately rushed to local physician. Physician put gauze in between teeth to stop bleeding and administered painkiller injection followed he asked patient to visit dentist.

Intraoral examination and removal of fracture fragment
Clinical examination showed that he got fractured upper There was severe overbite and very less overjet in anterior segment of occlusion. Patient was not able to close his teeth in occlusion as fractured tooth was very tender. Prognosis for the reattachment of fractured fragment was very poor as tooth fracture line was below gingival margin. So it was decided that the fractured fragment of tooth should be removed, root canal therapy should be done and Richmond crown should be placed. Patient's written consent was obtained after explaining all advantage and drawback of treatment. Local anaesthesia (lignocaine with adrenaline, 1:100000, Makcur Laboratories, limited, Gandhinagar, India) was administered and fractured fragment was removed.

Endodontic therapy
After removal of fracture tooth fragment, bleeding was stopped and endodontic therapy was carried out. Cleaning and shaping was completed with X-smart protaper rotary endodontic system (Dentsply Maillefer, Japan) followed by no. 30 single cone obturation was done. Patient was recalled after two days. He was asymptomatic but he was very much concerned about esthetic of teeth hence he had diffi culty in socializing. So he demanded to restore his fractured tooth as early as possible.

Crown structure preparation
Seven days after successful root canal therapy of left maxillary lateral incisor remaining crown structure was prepared circumferentially for Richmond crown. Shoulder fi nish margin was prepared on buccal surface and chamfer on palatal surface with creating adequate ferrule.

Post and core preparation
Then after, post space was prepared with peeso reamer no.1 and no.2 (Nordin, stainless steel, Switzerland). Retraction cord (Ultradent product INC Rx South Jordan, Utah, 84095, USA) was used for isolation and retraction of marginal gingiva around the lateral incisor and indirect impression was made for customized post and core in relation with fractured lateral incisor. Impression of post space was done with light body addition silicone impression material (Take1 Advanced Kerr Corporation, 28200, wick road, Romulus, MI 48174, USA). 21 guage orthodontic wire (Pigeon Dental stainless steel, India) was adjusted in post space area and length was confi rmed on radiograph. Outer end of wire was made J-shaped. Light body was fl ooded in post space and immediately j-shaped adjusted orthodontic wire was inserted in post space. Full arch impression was made with j-shaped wire in position using light body and putty of addition silicone impression material (Care was taken not to disturb apical seal).

Fabrication of porcelain facing metal crown
Wax pattern (Inlay wax medium-green, GC, IWM. GRN, GC Japan) for Post and core was prepared on die with proper ferrule in core. Casting of post and core was made and fabrication was completed in base metal alloy. Placing the post and core in position impression was made for preparing porcelain facing metal crown (Figures 2,3).

Placement of crown
Final crown is placed in position and occlusion correction was made. High points were recorded and corrected. Final cementation was done with Type I glass ionomer cement (GC, Japan) (Figures 4,5).     (Figures 6-8).

Discussion
Restoration of endodontically treated teeth involved major aspect in restorative dentistry. Loss of too much tooth structure due to caries/fracture/developmental disorders always had challenge in restorative procedure. Remaining tooth structure is not enough to retain large prosthetic crown in such cases [2].
Post and core treatment has been successfully practiced since ages [3]. Alternative procedure needed to obtain remaining crown structure so as to manage arc of rotation under oblique forces (function) such as crown lengthening procedure or forceful orthodontic extrusion. Many causes of failure of post and core retained restorations have been identifi ed, including: recurrent caries, endodontic failure, periodontal disease, post dislodgement, cement failure, post-core separation, crowncore separation, loss of post retention, core fracture, loss of crown retention, post distortion, post fracture, tooth fracture, and root fracture. Also, corrosion of metallic posts also has been proposed as causes of fracture [4][5][6].
To overcome these problems Richmond crown can be advised in cases where there is deep bite, very less overjet and less occlusal clearance like in fi rst case.
The Richmond crown was introduced in 1878 and was incorporated as single piece post-retained crown with porcelain facing. Initially it was having a threaded tube in the canal with a screw retained crown, which was later modifi ed to eliminate the threaded tube and was redesigned as a 1-piece cast dowel and crown. Design include casting of post and crown coping as single unit over which ceramic is fi red and cemented onside canal and over prepared crown structure having same path of insertion. Ferrule collar is incorporated to increase mechanical resistance, retention apart from providing antirotational effect. Major technical drawback of this design is excessive cutting in making two different axis parallel which results in weakening of tooth and also this design increases stresses at post apex causing root fracture. Few indications for Richmond crown are grossly decayed or badly broken single tooth where remaining crown height is very less and in cases with steep incisal guidance [7] (deep bite and very less overjet).
As in fi rst case there was hardly any tooth structure remaining for preparation and there was deep overbite and very less overjet so it was ideal case for Richmond crown. Also less cervical tooth structure subjected to fl exion forces under function and this design provides more cervical stiffening than other post system and is needed to protect the crown margins and to resist leakage. As there was deep bite and very less overjet so there would be very inadequate clearance for post and core as also crown placement. Considering all the factors Richmond crown was advised for restoration of crown.   Second case was repeated failure of conventional crown.
There was less amount of remaining tooth structure and was very deep bite. Such tooth if given with post and core fi rst over which crown is cemented, needs adequate thickness which is a limitation here. To compensate this inadequacy if core is made thin then it is weak and also presents sharp margins and edges acting as stress points for overlying crown. Richmond crown is best possibility in both these conditions as less crown cutting is required to make two axis parallel in grossly decayed tooth and also it require less thickness for best esthetic results.
The advantages of this design are custom fi tting to the root confi guration, little or no stress at cervical margin, high strength, availability of considerable space for ceramic fi ring and incisal clearance, eliminate cement layer between core and crown so reduces chances of cement failure [8].
The operator should consider all pros and cons of all types of post and core systems as well as Richmond crown treatment modality and select a procedure that fulfi lls the needs of the case while maximizing retention and minimizing stress. Drawback of Richmond crown technique needs single path of insertion and withdrawal so more of tooth preparation is required. But in cases of loss of maximum tooth structure Richmond crown was defi nitely advised as there is no need for further tooth preparation. Although any number of post designs may be used in a clinical situation, success is dictated by the remaining tooth structure available after endodontic therapy. Conservation of the tooth should be always fi rst preference than extraction followed by crown and bridge/implant treatment modality. As later treatment need more invasive procedure with lot of time required. Still some traditional techniques are useful in some cases according to conditions as per need.