Successful Management of Fractured Premolar with Veneerlay Following Morphology-driven Preparation Technique Principles

INTRODUCTION

Dental practice has shifted from a classic approach to a more conservative approach that favors minimally invasive techniques such as partial restorations. Recent studies show that less vigorous preparation of teeth is less traumatizing; the more we can prevent tooth structure loss, the less postoperative discomfort the patient will have. Minimally invasive techniques ensure biological and biomechanical requirements and also improve esthetic results. New cavity preparation called as morphology-driven preparation technique (MDPT) principles is based on morphological considerations in terms of geometry that include maximum profile line, the inclination of cuspal lines, and structure that includes dentin concavity and enamel convexity. The advantages of this new anatomic preparation design are (A) improved adhesion quality (optimized cutting of enamel prisms, and increased available enamel surface); (B) minimized dentin exposure; (C) maximum hard tissue preservation (the cavity that is been designed for cementation with composite resins, improvement of flow, and removal of excess material); and (D) optimized esthetic integration due to inclined plane design, which permits a better blending at the transition area between tooth and restoration.^1,2

Ceramics produce great esthetic restorations as they have a highly biocompatible nature and optimal mechanical properties. As the elastic modulus of lithium disilicate is similar to enamel, it prevents stress concentration at the bonded surfaces.

Overlay veneer or “veneerlay” is a bonded partial indirect restoration indicated on the cusped teeth, usually the maxillary premolars. It is indicated when the buccal cusp is discolored or disfigured and needs coverage. In such cases, instead of a full coverage restoration such as crown, a conservative approach with the veneerlay helps preserve tooth structure and prevent unnecessary tooth preparation. The term Veneerlay characterizes an esthetic ceramic bonded restoration of the posterior tooth, restoring both the occlusal and buccal surface. Although seemingly easy, tooth preparation for a veneerlay requires knowledge of adhesive principles and strict adherence to the clinical protocol. In this article, we present a case report illustrating ceramic veneerlay in premolar.

CASE DESCRIPTION

A 39-year-old female patient reported to the outpatient department of the Department of Conservative Dentistry and Endodontics, Sri Ramakrishna Dental College and Hospital with the complaint of a broken filling in relation to the upper right teeth region. The patient gave a history of oblique breakage of the tooth due to a blow on the left lower jaw 3 years ago, after which she got a tooth-colored restoration done by a local dentist. However, she stated that the restoration fell off within a few months, after which another similar restoration was placed. Now, it had been a few months since the previous restoration also fell off (Fig. 1) and she sought a permanent solution where the restoration did not require repeated replacements. The patient gave a non-contributory medical history.

On clinical examination, a shear fracture on the buccal cusp and buccal surface in relation to 14 was noticed (Figs 1 to 3). There was no evidence of previous restoration on the tooth suggesting an adhesive failure at the tooth restoration interface. The tooth responded normally to pulp sensibility tests and was not tender to percussion. The radiographs also revealed a satisfactory pulp–periodontal complex. Impressions of the upper and lower arches were made and diagnostic casts were fabricated. Considering that only the buccal portion of the tooth was involved, we decided to opt for veneerlay preparation to conserve tooth structure rather than extensive preparation followed by full-coverage crown. The treatment plan and alternative options were explained to the patient, including full-coverage crown. The patient was interested in conservative management of her tooth and opted for veneerlay.

At the second visit tooth preparation of 14 was done under local anesthesia. The principles of morphology-driven tooth preparation were followed while doing the preparation. A tapering carbide bur was used to reduce 0.5 mm of the occlusal surface following the cuspal contours. Next, the buccal surface was prepared using a veneer preparation – depth orientation bur to achieve depths of 0.3, 0.5, and 0.7 mm on the cervical third, middle third, and occlusal thirds of the buccal surface, respectively. The preparation ended palatally just 0.5 mm from the occluso-palatal plane and the buccal finish line was placed 0.5 mm supragingivally. A chamfer finish margin was given for the entire preparation. Finishing and polishing were done with polishing discs (Supersnap kit, Shofu Dental, India). Immediate dentin sealing (IDS) with a Universal Dentin bonding agent (Tetric N-Bond Universal – Ivoclar Vivadent) was done. The oxygen-inhibited layer, which could potentially affect the quality of rubber base impression material, was resolved by applying a layer of glycerin to block oxygen and additionally cured for 20 seconds (Figs 4 and 5). The final impression was made with polyvinyl siloxane (Elite HD+, Zhermack SpA, Italy) using the double-step impression technique (Figs 6 and 7). On the day of the trial, a few adjustments were made and sent to the laboratory for Glazing (Figs 8 and 9).

Prior to cementation, under rubber dam isolation, air abrasion was done on the IDS surface with Aluminum oxide followed by etching and bonding of enamel. Then veneerlay was cemented with self-cure, self-adhesive dual cure (RelyX, India) cement (Figs 10 and 11). The patient was given oral hygiene instructions and home care instructions for adequate care. Periodic review every three months was continued for 1 year, which showed the continued appearance of a definite margin according to Fédération Dentaire Internationale (FDI) criteria (Figs 12 and 13).

DISCUSSION

Recently, with rapid evolution in dental adhesive technology, less invasive approaches have been reported in contemporary restorative dentistry. The development of new restorative materials such as clay, inlay, and other indirect partial coverage restoration of teeth, retained by microretention through adhesives rather than macro-retention is increasingly accepted by dentists.³ In case of extensive tooth structure loss, onlays can achieve better re-establishment of tooth contours, resulting in protection of the weakened tooth concomitant with improved function in comparison to direct restorations or inlay. Conventional full crown preparation requires sacrificing a greater amount of residual sound tooth structure. As established by many laboratory studies and clinical trials the preservation of sound tooth structure is paramount for the longevity of restorations and teeth.

Partial coverage restorations in the posteriors fulfill esthetic requirements while adhering to bioeconomic principles resulting in biomechanical strengthening of the remaining tooth structure. Veneerlays are a practical restoration option rather than a full coverage crown in cases where only the buccal and occlusal surfaces are involved. This patient wanted a more conservative approach rather than an extensive approach. So, veneerlay was planned.

The occlusal surface is to be prepared similarly to that of an inlay, onlay, or overlay preparation. Bevels are strongly recommended and undercuts are to be avoided. Box walls should converge occlusal. The cavity depth can range from 1.5 to 2 mm; the isthmus should be no wider than 1/3 the intercuspal distance; a cervico-occlusal axial wall convergence should not be greater than 20°. The occlusal clearance recommended is at least 2 mm and all line angles should be rounded to avoid creating stress concentration in the crown. A cavity preparation on the occlusal surface can be included where indicated, with an occlusal divergence of 6–15°, and 90° cavosurface margins. The buccal surface preparation would be similar to a veneer preparation. The facial surface requires minimal tooth reduction of 0.6 mm with supragingival margins to ensure secure bonding.

We followed morphology-driven preparation technique as it would improve resistance by preserving dentin and enamel, adhesion by improving the quality of bonding substrate, and preserve marginal integrity and esthetics of the restoration. Immediate dentin sealing was performed before making the impressions. Immediate dentin sealing allows the dentin sealing and desensitization during the preparation and establishes a durable bond to enamel during cementation.⁴

A recent study demonstrated a higher degree of fracture resistance and a lower risk of catastrophic failures with lithium disilicate-reinforced ceramic as compared to composite restorations.⁵ Lithium disilicate (95 GPa) has a modulus of elasticity close to that of enamel (84.6 GPa), and also simulates the biomechanical behavior of a tooth. In a finite element model lithium disilicate occlusal onlays (0.6–1.4 mm) demonstrated higher load-bearing capacity when compared to zirconia onlays.⁶ Lithium disilicate was chosen as the material of choice for this case as standardized in literature.⁷

The luting agent is required to furnish an effective, durable bond between the restoration and the dental structure for the success of nonmetallic restorations.⁸ An adhesive dual-cure luting resin (3M™ RelyX™ Unicem 2 Automix) was used for cementation. It delivers high adhesion, helps resist discoloration, long-term stability, and minimal postoperative sensitivity.⁹ According to FDI criteria, follow-up after 1 year showed no distinct difference. The restoration was in perfect health. It represents a fully sufficient clinical situation, which does not need any further intervention.

CONCLUSION

Veneerlay represents a conservative restorative option for teeth requiring minimal coverage due to factors such as trauma, erosion, etc. Preparation of the tooth following MDPT principles allows for minimal tooth structure loss and a good long-term prognosis of the restoration after adhesive cementation.

ORCID

Nandhini Shanmugasundaram https://orcid.org/0009-0004-4990-3929

Subha Anirudhan https://orcid.org/0000-0002-1319-3097

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