Occlusal Veneer-Retained Bridges: A Conservative Option for Replacing Posterior Teeth?

Introduction

Suppose a patient has lost a first molar, while the teeth adjacent to the edentulous space are sound. What options are available to replace the missing tooth?

An implant is one option, but it is not always feasible. Medical or anatomical limitations may be present, and some patients are unwilling to undergo surgery for financial or personal reasons.

Another option is a conventional three-unit bridge, which requires substantial preparation of two sound adjacent teeth to replace a single missing tooth.

Resin-bonded fixed partial dentures offer a more conservative alternative. However, these restorations also face problems such as debonding and fracture of the retainer or connector. These complications are particularly relevant posteriorly, where chewing forces are higher.

In a study published in 2026, researchers investigated a different design: using occlusal veneers as retainers for a posterior bridge.

The concept of covering the occlusal surface with a thin restoration was thus applied to a three-unit bridge.

What advantages might this design offer, and how much confidence can we place in its results?

Explanation

Design rationale

A successful resin-bonded bridge must address two issues simultaneously: providing sufficient bonding surface and adequate mechanical resistance.

In this design, the occlusal surfaces of the abutment teeth are covered instead of using inlay retainers or conventional wings. The retainer covers both the internal cusp inclines—the surfaces facing the central groove—and the external inclines.

On the side facing the edentulous space, this coverage extends onto the proximal surface of the tooth.

This provides a broad bonding surface, while the vertical components of the retainer may help resist displacement.

An important feature is that, unlike some inlay retainers, most of the bonding surface lies on enamel, which may support a durable bond.

Patient selection

The study included 40 bridges replacing first molars in 35 patients.

The abutment teeth were vital, periodontally healthy, and free of extensive caries. Clinical crown height was at least 4 mm, and tooth alignment was approximately normal.

Patients with bruxism, high caries risk, or unsuitable pulpal conditions were excluded.

The results therefore cannot be directly generalized to patients with extensive restorations, severely damaged abutment teeth, or high occlusal forces.

Abutment design and preparation

The researchers evaluated two preparation designs.

First design (D1)

The occlusal surfaces of both abutment teeth were reduced by approximately 1 mm while preserving their general anatomy.

The functional cusps were beveled, and a rounded shoulder approximately 1 mm wide was prepared around the occlusal perimeter.

Preparation also extended onto the proximal surfaces adjacent to the edentulous space, but remained within the buccal and lingual line angles.

Most of the buccal and lingual surfaces consequently remained untouched.

Second design (D2)

The second design was similar to D1, with two differences.

First, the proximal preparation extended beyond the lingual line angle to the midpoint of the lingual surface.

Second, an axial groove was added to the buccal portion of the proximal preparation on each abutment.

These changes aimed to increase bonding area, improve retainer resistance, and reinforce regions susceptible to fracture.

However, these potential benefits come at the cost of additional tooth reduction. It is therefore necessary to determine whether the extra preparation actually improves clinical performance.

Zirconia selection and bridge design

The researchers used two types of monolithic zirconia:

3Y-TZP offers greater strength and fracture toughness but is more opaque.

5Y-PSZ offers greater translucency but has weaker mechanical properties.

Combining the two zirconia types with the two preparation designs produced four groups of ten bridges.

The digital designs specified a minimum occlusal thickness of 0.8 mm and a connector cross-sectional area of 12 mm².

These dimensions matter because connectors and the junctions between retainer components are potential sites of stress concentration in posterior bridges.

Bonding: an important part of treatment success

The bond to the tooth plays a fundamental role in these bridges; mechanical retention alone cannot be relied upon.

In the study, the internal zirconia surface was sandblasted and treated with an MDP-containing primer. On the tooth side, enamel etching, an adhesive system, and a dual-cure resin cement were used.

The success of this treatment therefore depends on suitable isolation and a reliable bond on both the tooth and zirconia sides.

Clinical results

Patients were assessed at 1, 6, 12, and 18 months.

No debonding or secondary caries was reported during follow-up.

However, three mechanical complications occurred:

• Two complete fractures in the D1/5Y group at months 4 and 17, both at the junction between the horizontal and vertical retainer components.
• One crack in the D2/5Y group at the first-month assessment, on the internal incline of the premolar's buccal cusp.

In contrast, no fractures or cracks were reported among the 20 bridges made from 3Y zirconia.

The reported success rate was 100% for 3Y and 85% for 5Y. The survival rate for 5Y was 90%, because the cracked restoration remained in the mouth.

Despite this numerical difference, the between-group differences were not statistically significant. The study therefore cannot establish the definitive superiority of either material or preparation design.

Although 5Y received slightly higher esthetic scores, differences in patient and specialist satisfaction were also not significant.

What can the failures teach us?

An interesting feature of this study is that no restoration debonded, yet some fractured.

This shows that successful bonding does not necessarily mean mechanical success of the restoration.

The two complete fractures occurred at the junction of the horizontal and vertical retainer components, a region where stress may concentrate.

In one case, the restoration fractured while the patient was chewing a bone. In the other, wear facets on the cast raised the possibility of previously undetected bruxism.

The third crack may also have been associated with occlusal adjustment, because part of the cusp incline had been reduced to remove an interference during lateral movement.

Material selection, the design of connecting regions, and careful occlusal assessment therefore matter alongside bonding.

Conclusion

The study suggests that occlusal veneers used as retainers for posterior bridges can provide promising results, at least in the short term.

Several points must nevertheless be considered when interpreting the findings.

First, follow-up lasted only 18 months, and information on long-term durability remains insufficient.

Second, the sample was small. A lack of statistically significant differences does not establish equivalent performance of the materials or designs.

Third, although more conservative than a conventional bridge, this approach is not necessarily more conservative than every other resin-bonded design, because it requires preparation of the occlusal surfaces of both abutment teeth.

The technique also requires precise preparation and the ability to achieve suitable isolation for bonding.

The authors ultimately preferred D1 because it preserves more tooth structure and recommended 3Y-TZP for its superior mechanical properties.

My interpretation is that this paper introduces a new direction for conservative posterior bridge design rather than establishing a settled treatment method.

The central issue is balancing preservation of tooth structure, bonding area, and mechanical resistance of the restoration.

For now, it is therefore better regarded as a promising option for selected patients than as a general replacement for implants or conventional bridges.