Use of Porcelain Laminate Veneers for the Correction of Isolated Microdontia
Tony Aherne, MDS, DRD, RCS Ed
Although tooth size is prone to variation between the sexes and among different races, an individual's dentition generally has a symmetrical appearance. When significant size variations do exist, the entire dentition is rarely affected. The presence of unusually small teeth is termed microdontia, and the presence of larger than average teeth is termed macrodontia. Although heredity is the principal etiological factor in the size of developing teeth, genetic and environmental influences also contribute to a patient's appearance. While the deciduous dentition appears to be primarily affected by maternal intrauterine influences, the permanent teeth are generally subject to environmental factors.1 Isolated microdontia within an otherwise normal dentition is not uncommon. In these circumstances, the maxillary lateral incisor is frequently affected and typically presents as a peg-shaped crown overlying a root of normal length. The mesiodistal diameter is often reduced, and the proximal surfaces converge toward the incisal edge. In patients with a dramatically compromised single tooth or teeth, dental treatment is often requested in order to restore normal function and aesthetics.
A 19-year-old female patient who had recently completed orthodontic treatment presented with isolated microdontia in combination with postorthodontic spacing in which the maxillary lateral incisor and canine had a compromised form and shape (Figure 1). The contralateral congenitally absent lateral incisor was undergoing restoration with an osseointegrated implant. Although the maxillary left canine also exhibited inadequate form and shape, the remainder of the patient's dentition was well formed and demonstrated proper cuspal guidance. As is typical in cases of isolated microdontia, only the maxillary incisor and canines appeared smaller in relation to the remaining dentition. While the mesiodistal width of the canine would conventionally exceed that of the first premolar tooth, the opposite was true in this instance. The rationale for treatment of the microdontia was to correct the patient's aesthetic appearance and to eliminate the abnormal spacing between the maxillary dentition, which could potentially compromise function.
In patients with abnormally spaced dentition, the triangular sharp form of the papilla changes to a round, flat, or even a reverse form which results in a black space that lacks optimal aesthetics.2 The primary challenge was to re-create the correct shape and form of the lateral incisors and the canine so that a harmonious, aesthetic appearance could be established. An additional challenge was to restore the shape, contour, color, and health of the labial gingiva and the interdental papilla. A decision had to be made on how to best treat the patient's condition.
A rational diagnostic approach was formulated so that the patient would be able to visualize and approve the planned treatment objectives. Based on this criteria, a conservative treatment modality was selected that utilized 3/4 porcelain veneer restorations and minimal tooth preparation. In the initial stage of treatment, a freehand composite resin buildup was performed chairside and approved by the patient. The parameters for the buildup included the axis of facial symmetry, tooth axis, spacing, and form of the teeth, the appearance and function of the incisal edges, and the patient's smile line.3 An impression of the mock-up was subsequently transferred to the laboratory with the original study cases. A waxup of the desired tooth morphology was then performed.
At this phase, a definitive treatment plan that required the placement of 3/4 laminate veneer restorations on the lateral incisor, canine, and first premolar (despite the natural appearance of the first premolar) was formulated. It was decided that greater symmetry and harmony could be obtained if this tooth was included in the treatment plan. Although canine guidance was present, it was determined that this area could be improved by altering the shape of the palatal aspect and the tip of the canine tooth. The patient subsequently consented to the comprehensive treatment plan.
In the initial phase of the treatment, a computer-regulated anesthetic delivery system was utilized to administer the local anesthetic. Tooth preparation was performed utilizing a combination of burs and two striper burs. In order to allow the laboratory technician to establish a progressive emergence profile for the interdental zone of extension, extended interproximal preparations were required.3 A maximum lingual wrap was planned, and the margins were placed at lingual proximal line angles. This was performed in order to assist the laboratory technician with respect to form and emergence profile of the future restoration, and to improve the aesthetic definition of the porcelain restorations in the crucial incisal/occlusal zones. Incisal overlap was created in the lateral incisor and the canine in order to provide a design to the laminate veneer that closely resembled a 3/4 crown restoration.4
A chamfer margin was utilized on the cervical and interproximal regions (Figure 2), and a palatal butt margin was developed on the palatal aspect. Due to reduced height of the clinical crown restorations, an oblique path of insertion was performed to prevent tissue damage.3 The premolar preparation also involved the buccal cusp. During the clinical procedure, tissues were retracted with silk sutures and all preparation margins were performed in enamel. In order to avoid the creation of zones of stress concentration in the restorations, the prepared surface did not contain sharp angles.
Preparations were initially performed in two stages with the instrument inclined at two different angles in order to preserve the double convergence of the labiobuccal surface.5 An impression material was used during this process and forwarded to the laboratory to develop working models with die segments. Provisional restorations were fabricated utilizing a direct technique and composite resin. The die segments were duplicated with silicone duplicating material and poured in stone. The dies were relocated on a working model and the veneers were fabricated with porcelain in a segmental layering technique using the diagnostic waxup as a guide (Figure 3).
Once the patient had been anaesthetized, the provisional restorations were removed and the teeth were cleaned with pumice and rotary brushes. The veneer restorations were subsequently tried-in individually to assess fit. Once the individual fit was deemed satisfactory, the complete set was tried-in. Although the color of the try-in paste does not always achieve a precise match of the composite material (particularly following polymerization), try-in paste was used to assess the color of the restoration prior to final cementation. The veneer surfaces were subsequently re-etched with hydrofluoric acid, and a fine layer of silane coupling agent was placed over the internal surfaces (Figures 4 and 5).
Retraction cord was placed in the gingiva to allow access to all areas. The tooth was etched with 37% phosphoric acid and primed. All three restorations were placed together to ensure correct contact and location. Due to the thickness of the veneers, a dual-cured composite resin was utilized to bond the restorations in place. The location of the veneers on the preparations was facilitated by the oblique path of insertion. Following the removal of excess resin, the restorations were light cured from the buccal and palatal aspects using two lights simultaneously for 2 minutes. Once the restorations had been cured, the margins were cleaned using a fine metal strip and small white rubber polishers with diamond paste.
The definitive postoperative view of the patient demonstrated the elimination of the interdental spaces and a significant aesthetic enhancement. The higher chroma of the canine restoration exhibited a greater shade intensity.6,7 The presence of papilla and the absence of black triangles between the teeth also contribute to the improved aesthetic appearance of the patient (Figure 6).
In cases where isolated microdontia is present, 3/4 ceramic restorations can be an efficacious means of pursuing the restorative process. The ability of this porcelain material to replicate the natural form of the tooth, and the healthy reaction of the supporting gingival tissues assist in the creation of desired gingival contours and result in aesthetic success for this treatment modality.
- Neville BW, Damm DD, Allen CM, Bouquot JE. Oral and Maxillofacial Pathology. Philadelphia, PA: WB Saunders, 1995.
- Bichacho N. Papilla regeneration by noninvasive prosthodontic treatment: Segmental proximal restorations. Pract Periodont Aesthet Dent 1998;10(1):75-78.
- Belser UC, Magne P, Magne M. Ceramic laminate veneers: Continuous evolution of indications. J Esthet Dent 1997;9(4):197-207.
- el-Sherif M, Jacobi R. The ceramic reverse three-quarter crown for anterior teeth: Preparation design. J Prosthet Dent 1989;61(1):4-6.
- Touati B, Miara P, Nathanson D. Esthetic Dentistry & Ceramic Restorations. London, UK: Martin Dunitz, 1999.
- Touati B. Defining form and position. Pract Periodont Aesthet Dent 1998;10(7):800-807.
- Pietrobon N, Paul SJ. All-ceramic restorations: A challenge for anterior esthetics. J Esthet Dent 1997;9(4)179-186.