Clinical assessment of direct composite veneer and indirect veneers using a minimally invasive preparation technique

Abstract

Aim:

The aim of this study was to compare and evaluate the clinical performance of direct composite veneers (DCVs), indirect composite veneers (ICVs), and ceramic veneers using a minimally invasive tooth preparation technique.

Materials and Methods:

A total of 90 veneers were placed on the anterior teeth: DCVs (n = 30), ICVs (n = 30), and ceramic laminate veneers (n = 30). Tooth preparations were standardized using magnification (×3 loupes) and depth-marking burs. DCVs were applied using a multilayered stratification technique and finished with a composite polishing kit. ICVs were CAD-CAM fabricated using Gradia HIPS, while ceramic veneers were milled from IPS e.max CAD HT blocks and layered with nanofluorapatite ceramic. All restorations were cemented using adhesive protocols tailored to each material. The restorations were assessed at baseline, 3 months, 6 months, and 1 year using the modified United States Public Health Service criteria.

Statistical Analysis:

Data were analyzed using SPSS 23.0 with a significance level of P < 0.05. Fisher’s exact test was used for comparing proportions, and Kaplan–Meier analysis assessed overall survival relative to observation time.

Results:

At 3, 6, and 12 months, marginal discoloration showed a statistically significant increase (total events: 8, 14, and 28; P < 0.001). No events were observed for caries or tooth fracture. Postoperative sensitivity occurred in three cases but was not statistically significant (P > 0.05). While fractured restorations showed no significant difference at 3 and 6 months, a significant increase was noted at 12 months (11 events; P = 0.02).

Conclusion:

Indirect composite and ceramic veneers showed superior performance over DCVs in minimizing marginal discoloration, postoperative sensitivity, and restoration fractures.

INTRODUCTION

As a minimally invasive esthetic option, laminate veneer restorations are recommended for teeth requiring morphological correction due to poor shape, inadequate volume or size, minor misalignment, bleaching-resistant discoloration, diastema, enamel defects, minor chipping, fractures, or deformities.[1,2,3] Veneers are contraindicated in cases of severe misalignment, extensive restorations, parafunctional habits, deep vertical overlap without horizontal overlap, or soft-tissue pathology.[4]

Material selection depends on factors such as socioeconomic status and treatment duration. Over time, improved materials with enhanced esthetics have been developed.[5] Currently, ceramics and composite resins are mostly used, with ceramics preferred due to superior color stability and fracture resistance. Indirect ceramic veneers have shown survival rates of up to 90% with 4–10 years follow-up,[6] whereas indirect composite veneers (ICVs) are more prone to fracture and discoloration.[7] Mazzetti et al. over a 10-year follow-up found that ceramic veneers had better success and survival than composites.[8] Korkut et al. reported a 90% survival rate for direct composite veneers (DCVs) used for diastema closure and recontouring over 4 years.[9]

Composite veneers can be applied through direct or indirect techniques. Direct veneers are cost-effective, single-visit options suitable for diastema closure and tooth recontouring. Indirect veneers, though more time-consuming, offer better wear resistance and easier handling.[10] Both are valid alternatives to ceramics. However, long-term success relies on marginal fit, shade match, and clinician skill – especially for freehand techniques.

The clinical success of veneers involves more than esthetics and durability; factors such as the risk of secondary caries, postoperative sensitivity, marginal discoloration, and potential fractures significantly influence long-term outcomes.[11]

Although numerous studies have focused individually on ceramic or composite veneers, very few have directly compared all three types – direct composite, indirect composite, and ceramic – using identical preparation protocols, adhesive strategies, and follow-up durations. Clinical decision-making for veneer selection often relies on subjective or material-specific evidence rather than head-to-head comparative data. Furthermore, with the rapid advancement in adhesive protocols and restorative materials, a re-evaluation of their clinical outcomes under contemporary minimally invasive techniques is warranted.

This study was designed to address this gap by comparing the clinical performance of the three veneer types using a controlled prospective model, standardized minimally invasive preparations, and evaluation using modified United States Public Health Service (USPHS) criteria over a 1-year period. The rationale lies in isolating the influence of material type on clinical success while eliminating confounding factors such as variable techniques, operator differences, and preparation designs.

Hence, this in vivo study was undertaken to evaluate and compare the clinical performance of direct and indirect veneers using a minimally invasive approach over a follow-up period of 12 months using modified USPHS criteria.

MATERIALS AND METHODS

The present study protocol was approved by the Institutional Ethical Committee (IEC GDCHA/CONS.3/2022) and was registered with CTRI (CTRI/2023/09/058161).

Sample size calculation was based on a previous study with a survival rate of 85.7% reported by Meijering et al.[12] using a 95% confidence interval and 5% allowable error. The total estimated sample size was 92.8, which was divided among three groups and rounded off to 30 participants per group, resulting in a total sample size of 90.

Inclusion criteria encompassed patients aged ≥18 years presenting with intrinsic discoloration due to tetracycline staining (Jordan and Boksman scores 3 and 4), fluorosis, and amelogenesis imperfecta (hypoplastic or hypomature type). Mild-to-moderate pitting defects observed in cases of fluorosis or amelogenesis imperfecta were managed conservatively. These defects were assessed for depth and location: shallow enamel pits were eliminated during minimal preparation. Moderate defects were masked or reshaped with mock-up-guided preparation. Severe pitting or cavitation into dentin led to exclusion to ensure optimal bonding. Other indications included fractured or worn teeth, abnormal morphology, mismatched shade, failed veneers or restorations, minor anterior malpositions not requiring extensive orthodontics, and midline diastema (1–2 mm).

Exclusion criteria included bruxism, Temporomandibular disorders (TMD), parafunctional habits, rampant caries, poor oral hygiene, severe malalignment, deep bite, and chronic smoking.

Patients who met the selection criteria were assigned to three groups: DCVs (n = 30), ICVs (n = 30), and ceramic laminate veneers (CLVs) (n = 30). All patients received thorough explanations and signed informed consent prior to treatment.

Pretreatment included comprehensive oral prophylaxis and standardized photography using a Canon 80D (APS-C sensor, 50 mm lens, 1/125 s, f/22, ISO 100, 1 m distance, ring flash at full output). Diagnostic impressions were made using addition silicone (President Putty, Coltene), and diagnostic casts were fabricated.

Shade selection was done on moist teeth with the distance of 25–35 cm (10”–14”) from the oral cavity, keeping the eye level of operator same as teeth using Vita Pan 3D-Master Shade Guide under natural daylight and was completed within 5 s. For DCV, the button try-in method was used.

All tooth preparations were done using magnifying loupes (×3). Diamond points (ISO 801 018, Diatech, Switzerland) were used to define the intended preparation depths, guided by the preestablished mock-up.

For DCV preparation, minimal preparations were done involving approximately 0.1–0.3 mm in the cervical area and 0.3–0.6 mm in the incisal area. Tapered round-ended diamond burs (ISO 856 018, Diatech) were used for these preparations. In cases where translucency was desired, a 1 mm incisal overlap was prepared. A cervical chamfer finish line was prepared, with all margins placed supragingivally.

A diagnostic wax-up was prepared on the cast to guide both ICV and CLV restorations. A silicon putty index was then fabricated from the wax model and transferred to the patient’s oral cavity using a cool-temp material. The transferred temporary restorations functioned as esthetic preevaluated temporary served the purpose to guide for minimal tooth preparation. Three-planar reduction was done on the labial surface, 0.3 mm gingivally, 0.5 mm midfacially, and 0.7 mm incisally. A cervical chamfer finish line was placed and extended interproximally to conceal margins within the contact area. All internal angles were rounded. For both the preparations, palatally, a butt joint was prepared by 2 mm incisal edge reduction.

Fabrication of direct composite veneers

Following rubber dam isolation, contour strips (Contour-Strip, Ivoclar Vivadent, Schaan, Liechtenstein) and wedges were placed to ensure a well-defined cervical contour. Enamel etching was performed using 37% phosphoric acid (N-Etch, Ivoclar Vivadent) for 15 s, followed by thorough rinsing and gentle air drying. A bonding agent (Tetric N-Bond, Ivoclar Vivadent) was then applied and light cured (DTE O-Light, Woodpecker, 2300 m/cm²) for 20 s.

Dentin-shade composite was applied cervically and cured, followed by a second layer of enamel shade extending incisally and then light cured. Thereafter, contouring and polishing were done with diamond burs (Diatech Composite Finishing and Polishing Kit) and stone burs (Prima Dental Illume FG Composite Finishing Kit). Discs and silicone rubber were used for final finishing and polishing (Super-Snap Rainbow Technique Kit).

Fabrication of indirect composite veneers

Veneers were fabricated using Gradia High Impact Performance Silica nanohybrid composite (Gradia HIPS) based on ceramic–polymer technology using the Computer Aided Design-Computer Aided Manufacturing (CAD-CAM) technique.

Cementation procedure

• (a) Surface treatment of veneers: Sandblasted with 50 μm alumina

• (b) Surface treatment of prepared tooth: All enamel surfaces were etched with 37% phosphoric acid (N-Etch etching gel) for 15 s, rinsed with water for 30 s, and dried. A thin layer of primer and adhesive was applied (Multilink Primer A and B, mixed in a 1:1 ratio), gently air-dried, and left for 30 s. Multilink Automix cement was mixed and applied to restorations and placed on the corresponding tooth under digital pressure. They were then precured cervically for 5 s, and excess cement removed using a scalpel blade number 11. Final curing (40 s each side) followed glycerin application to eliminate the oxygen inhibition layer. The restoration margins were polished using Astropol polishers (Astropol FP, Ivoclar Vivadent) along with interproximal strips, operated at a speed of 7500–10,000 rpm.

Fabrication of ceramic laminate veneers

Veneers were fabricated using IPS e.max CAD HT-A1-A2 blocks (Ivoclar Vivadent, Liechtenstein, Germany), subsequently layered with a nanofluorapatite ceramic, IPS e.max Ceram (Ivoclar Vivadent) for the final enhancements of the incisal edge. Finally, sintering and glazing were done.

Try-in

Restorations were assessed for fit and shade using try-in pastes, aligning with patient preferences.

Cementation procedure

• (a) Surface treatment of veneers: The intaglio surface was etched using 5% hydrofluoric acid (CeraEtch 5%, BM4, Florianopolis, Brazil) for 20 s and then rinsed with an air-water spray for 30 s. A thin layer of silane coupling agent (Monobond Plus, Ivoclar Vivadent, Liechtenstein, Germany) was applied for 1 min

• (b) Surface treatment of prepared tooth: It was done in a similar manner to that of ICV and bonded using Multilink resin cement (Ivoclar Vivadent, Liechtenstein, Germany).

Occlusion was checked during centric relation and protrusive movements of the mandible.

The restorations were evaluated at baseline, 3 months, 6 months, and 1 year using modified USPHS criteria:

• (a) Marginal discoloration (0 – no discoloration, 1 – slight staining, can be polished away, 2 – obvious staining, cannot be polished away, and 3 – gross staining)

• (b) Caries (0 – no evidence of caries continuous with the margin of restoration and 1 – caries evident continuous with the margin of restoration)

• (c) Postoperative sensitivity (0 – no symptoms, 1 – slight sensitivity, 2 – moderate sensitivity, and 3 – severe pain)

• (d) Fracture of restoration (0 – no fracture, 1 – minor crack line over restoration, 2 – minor chipping, i.e., ¼ of restoration, 3 – moderate chipping, i.e., ½ of restoration, 4 – severe chipping, i.e., ¾ of restoration, and 5 – debonding of restoration)

• (e) Fracture of tooth (0 – no fracture, 1 – minor crack line over tooth, 2 – minor chipping of tooth (¼ crown), 3 – moderate chipping of tooth (½ crown), 4 – crown fracture near cementoenamel junction, and 5 – crown root fracture).

Statistical analysis

Data were analyzed using the statistical package SPSS 23.0 (SPSS Inc., Chicago, IL, USA), and the level of significance was set at P < 0.05. The Fisher’s exact test was used to compare proportions, while Kaplan–Meier analysis was conducted to determine the overall survival rate over the observation period.

RESULTS

The results derived from the statistical analysis of the differences between the three veneer types such as DCV, ICV, and CLV across various criteria at 3, 6, and 12 months [Table 1] are as follows:

Table 1.

Summary of United States Public Health Service evaluations at different time intervals

Criterion	Score	At 3 months (n=30)			At 6 months (n=30)			At 12 months (n=30)
		Groups
		1	2	3	1	2	3	1	2	3
Marginal discoloration	0	22	30	30	19	27	30	7	25	30
	1	8	-	-	6	3	-	13	5	-
	2	-	-	-	5	-	-	10	-	-
	3	-	-	-	-	-	-	-	-	-
P		<0.001**			<0.001**			<0.001**
Caries	0	30	30	30	30	30	30	30	30	30
	1	-	-	-	-	-	-	-	-	-
P		-			-			-
Postoperative sensitivity	0	30	30	30	28	30	30	27	30	30
	1	-	-	-	2	-	-	2	-	-
	2	-	-	-	-	-	-	1	-	-
	3	-	-	-	-	-	-	-	-	-
P		-			0.33			0.10
Fracture of restoration	0	27	30	29	26	28	30	22	27	30
	1	-	-	-	-	-	-	-	-	-
	2	3	-	-	4	-	-	8	-	-
	3	-	-	-	-	1	-	-	1	-
	4	-	-	1	-	1	-	-	2	-
	5	-	-	-	-	-	-	-	-	-
P		0.10			0.19			0.02*
Fracture of teeth		30	30	30	30	30	30	30	30	30
	1	-	-	-		-	-	-	-	-
	2	-	-		-		-	-	-	-
	3	-	-	-	-	-	-	-	-	-
	4	-	-	-	-	-	-	-	-	-
		-	-	-	-	-	-	-	-	-
P		-			-			-

*P<0.05 (statistically significant), **P< 0.001 (highly significant)

Marginal discoloration: The total number of events which occurred for marginal discoloration was 8, 14, and 28 at 3, 6, and 12 months, respectively, which were statistically highly significant, P < 0.001.

No events were observed (n = 0) for caries and fracture of teeth.

For postoperative sensitivity, three events had occurred (2 at 6 months and 3 at 12 months), which was not statistically significant, P > 0.05.

For fractured restoration, no significant difference was observed at 3 and 6 months. However, at 12 months, a total of 11 events had occurred, showing statistically significant results, P = 0.02.

The Kaplan–Meier log-rank tests offer a comprehensive analysis of the three veneer types across various clinical criteria [Table 2]. The data showcase the excellent performance of CLV in preventing marginal discoloration, postoperative sensitivity, and fractures [Figure 1].

Table 2.

Kaplan–Meier log-rank tests showing number of events

Category	Groups	Total (n)	Number of events	Censored, n (%)
Marginal discoloration	Direct composite veneers	90	42	48 (53.3)
	Indirect composite veneers	90	8	82 (91.1)
	Ceramic veneers	90	0	90 (100.0)
	Overall	270	50	220 (81.5)
Caries	Direct composite veneers	90	0	90 (100.0)
	Indirect composite veneers	90	0	90 (100.0)
	Ceramic veneers	90	0	90 (100.0)
	Overall	270	0	270 (100.0)
Postoperative sensitivity	Direct composite veneers	90	5	85 (94.4)
	Indirect composite veneers	90	0	90 (100.0)
	Ceramic veneers	90	0	90 (100.0)
	Overall	270	5	265 (98.1)
Fracture of restoration	Direct composite veneers	90	15	75 (83.3)
	Indirect composite veneers	90	5	85 (94.4)
	Ceramic veneers	90	1	89 (98.9)
	Overall	270	21	249 (92.2)
Fracture of tooth	Direct composite veneers	90	0	90 (100.0)
	Indirect composite veneers	90	0	90 (100.0)
	Ceramic veneers	90	0	90 (100.0)
	Overall	270	0	270 (100.0)
Overall	Overall	1350	76	1274 (94.4)

Figure 1.

Kaplan–Meier curve showing (a) comparison of marginal discoloration, (b) Comparison of postoperative sensitivity, and (c) comparison of fracture of restoration

Figure 2.

(A) Shade matching procedure: (a) Vita 3D-Master shade guide, (b and c) shade matching carried out in natural daylight; (B) Direct composite veneers: (a) preoperative photograph, (b) tooth preparation, (c) etching of tooth surface with 37% phosphoric acid, (d) application of bonding agent, (e) immediate postoperative photograph after direct composite placement, (f) 3-month follow-up, (g) 6-month follow-up, (h) 1-year follow-up photograph; (C): Indirect composite veneers: (a) preoperative photograph, (b) wax mock-up, (c) temporaries transferred from mock-up, (d) tooth preparation, (e) preparation of veneer surface, (f) preparation of tooth surface, (g) immediate postoperative photograph after veneer cementation, (h) 3-month follow up, (i) 6 month follow up with chipping of restoration on 22, (j) 1 year follow up; (D) Ceramic laminate veneers: (a) preoperative photograph, (b) wax mock-up, (c) temporaries transferred from mock-up, (d) tooth preparation, (e) preparation of veneer surface, (f) preparation of tooth surface, (g) immediate postoperative photograph after veneer cementation, (h) 3-month follow-up, (i) 6-month follow-up, (j) 1-year follow-up

DISCUSSION

The selection of veneer material plays a pivotal role in determining the longevity, esthetics, and clinical performance of the restoration.[13] Among the available options, DCV offers affordable, minimally invasive, single-visit treatment with easy repairability but are limited by marginal discoloration, lower wear resistance, and polymerization shrinkage affecting longevity. ICV provides superior polymerization, wear resistance, and color stability over direct composites but requires laboratory fabrication, increasing cost and risk of debonding. Ceramic veneers, particularly those crafted from lithium disilicate, deliver unparalleled translucency, superior color stability, and exceptional long-term durability but come with a higher cost and demand meticulous bonding techniques for optimal retention.[14] Ultimately, the ideal choice hinges on balancing esthetic aspirations, functional demands, and patient-specific considerations to achieve a seamless and enduring smile transformation.[13]

The null hypothesis is rejected, as a statistically significant difference was observed in the survival of DCVs, ICVs, and ceramic veneers with respect to marginal discoloration and fracture-related outcomes. Evaluations were conducted during follow-up visits at 3, 6, and 12 months.

Marginal discoloration was the most frequently observed complication. By the end of 12 months, DCVs had 13 cases of slight staining (score 1), 10 cases of moderate staining (score 2), and 5 cases of severe discoloration, while ICVs had only 5 slight cases and 3 moderate, and CLVs showed no discoloration at all. This highly significant difference (P < 0.001) underscores the superior color stability of ceramics, likely due to their low surface porosity, high polishability, and absence of organic matrix, which limits extrinsic staining. The higher discoloration in DCVs can be attributed to the resin matrix’s hydrophilic nature and lower filler loading. Tetric N-Ceram, the composite used in DCVs, contains Bis-GMA – a viscous monomer prone to water absorption and subsequent pigment infiltration. On the other hand, Gradia HIPS used in ICVs contains Urethane Dimethacrylate (UDMA) and higher filler content, which results in a denser network less prone to staining.[15] The complete absence of discoloration in CLVs, likely due to the dense crystalline structure of lithium disilicate and a glazed surface, is consistent with previous studies showing that ceramic veneers outperform composites in long-term esthetics.[16,17]

Postoperative sensitivity was infrequent but exclusively occurred in the DCV group (three cases total), showing a trend toward significance. The sensitivity may stem from deeper polymerization shrinkage stress and less optimal sealing of dentinal tubules in the direct technique. In contrast, the indirect techniques – both composite and ceramic – allow for more controlled polymerization, improved marginal fit, and reduced chairside curing stress. In addition, indirect restorations undergo heat treatment or sintering, which enhances their stability and minimizes the risk of microleakage. The use of rubber dam isolation during bonding in all cases likely minimized this complication across all groups.[18,19]

At the 12-month follow-up, restoration fracture was most prevalent in the DCV group (11 events, 36.7%), while ICVs had three events and CLVs only one event, with statistically significant differences (P = 0.02). This aligns with known differences in flexural strength and fracture resistance of restorative materials. DCVs, due to their lower filler content and absence of laboratory-side curing, are more susceptible to chipping under occlusal stress. ICVs and CLVs, fabricated under controlled laboratory conditions, offer superior physical integrity. Notably, ceramic veneers showed the highest survival rates, consistent with prior studies reporting over 90% survival at 5–10 years.[20]

No cases of caries or tooth fractures were recorded across all groups throughout the study. This reflects meticulous case selection, conservative enamel-preserving preparation, and effective bonding strategies. Limiting the preparation to enamel enhances adhesion strength, reduces marginal leakage, and ultimately contributes to caries prevention.[18] The absence of tooth fractures also validates the strength preserving effect of the butt joint incisal preparation, which has been shown to offer superior resistance to functional loading compared to palatal chamfers or incisal overlaps.[21] This aligns with findings by Arora et al., who evaluated the fracture resistance of ceramic veneers with various preparation designs under different loading conditions and concluded that the butt joint design offers superior resistance to functional stresses.[22] Another study by da Costa et al. found that the butt joint design had minimal impact on tooth strength, whereas preparations involving palatal chamfers were associated with a greater reduction in fracture resistance.[23]

The results of this study reveal that ceramic veneers consistently demonstrated superior performance, emerging as the preferred option. Their exceptional ability to resist marginal discoloration, minimize postoperative sensitivity, and enhance fracture resistance underscores their long-term esthetic and functional advantages over composite alternatives. A longer-term clinical evaluation would provide a more comprehensive understanding of the differences in survival rates among direct composite, indirect composite, and CLVs.

While the study demonstrated clinically and statistically significant results, several limitations must be acknowledged. First, the 12-month follow-up period may not be sufficient to capture long-term outcomes such as secondary caries or late-stage restoration fractures. Second, operator-related variables, particularly in procedures such as composite layering or contouring, could introduce subjectivity despite efforts at standardization. Finally, the absence of evaluator blinding presents a potential for assessment bias, which may affect the objectivity of the clinical evaluations.

CONCLUSION

Within the limitations of this 12-month clinical evaluation, CLVs demonstrated the best overall performance with no cases of marginal discoloration, sensitivity, or fractures. ICVs performed better than DCVs, which despite being cost-effective and convenient, showed higher incidences of marginal discoloration and fractures. Notably, no cases of secondary caries or tooth fractures were observed across any group, reflecting the success of minimally invasive preparations and appropriate adhesive protocols. These findings highlight the importance of case-specific material selection and the need for extended follow-up studies to validate long-term clinical outcomes.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.