How does bonding hold on a chipped front tooth without cutting a bevel?

What the drawing is measured from

1. The rebuild follows two principles from one textbook. The additive principle: in a direct restoration the etching and bonding are extended beyond the defect onto intact enamel, to blend and reinforce the restoration; its example is a small chipped edge restored without preparation: the tooth was etched, bonded and restored well beyond the fracture line under rubber dam. And natural guided stratification: a silicone index made from a wax-up or mock-up holds a palatal shell of enamel-like material, dentine-like increments are placed where the natural dentine was, and the last increment is the labial enamel. Magne and Belser 2022, Biomimetic Restorative Dentistry, volume 1, pages 319, 330 and 331.
2. A critical appraisal of clinical and laboratory publications: a bevel on the enamel margin was traditionally placed for retention and a gradual colour transition, but modern adhesives, composites and technique make adequate front-tooth composites possible without one, with a more conservative preparation, a smaller restored surface and more tooth kept when the restoration is redone. Baratieri and Ritter 2005, Journal of Esthetic and Restorative Dentistry. DOI
3. A 2024 German clinical guideline on direct composite restorations, agreed by strong consensus, recommends etching the enamel of every direct composite restoration with phosphoric acid, to improve the long-term quality of the enamel margin and prevent discoloration there. It finds both rubber dam and other isolation workable, with rubber dam possibly helping restorations last longer. These process recommendations are consensus-based. Sekundo et al. 2024, The Journal of Adhesive Dentistry, part 2. DOI
4. Acid on the enamel only, before a universal adhesive: in a randomised trial of 295 back-tooth fillings in 70 patients, fillings bonded this way showed significantly fewer defects at their edges after 24 months than those bonded with the adhesive alone. Barceleiro et al. 2023, Journal of Applied Oral Science. DOI
5. In fillings at the necks of teeth, a meta-analysis of 10 randomised trials found less staining and fewer adaptation defects at the edges when the enamel was etched selectively before a self-etch adhesive, and fewer fillings lost at three years. Szesz et al. 2016, Journal of Dentistry, systematic review and meta-analysis. DOI
6. Drawn as Dr. Khalid bonds a chipped edge: nothing is cut, not even a bevel; phosphoric acid goes on the enamel only, under rubber dam; then the adhesive over enamel and dentine, and a last layer that runs past the break onto intact enamel. The etched band and the adhesive are drawn wider than life so they can be seen; their widths are not measurements, and the length and thickness of the last layer are illustrative.
7. In a laboratory study on the ground enamel of 45 upper central incisors, phosphoric acid dissolved from about 3.5 micrometres of enamel (5 per cent acid for 15 seconds) to 27 micrometres (37 per cent acid for 60 seconds), so in life the etched band is far thinner than a drawing can show. Legler, Retief and Bradley 1990, American Journal of Orthodontics and Dentofacial Orthopedics. DOI
8. In 105 fillings at the necks of teeth followed for a year, the few edges that discoloured were put down to composite left on enamel that had not been etched; here the acid reaches past where the last layer ends. Burrow and Tyas 1999, American Journal of Dentistry. PubMed