A custom tool (10, 110, 200, 300, 302, 304, 500) for forming a dental restoration in a mouth of a patient, the custom tool (10, 110, 200, 300, 302, 304, 500) comprising: a facial mold body (12, 112, 212, 512) for a patient-specific, customized fit with the facial side of at least one tooth of the patient, wherein the facial mold body (12, 112, 212, 512) includes a restorative portion (16, 116, 216) and a first engagement portion (18a, 218a) extending away from the restorative portion (16, 116, 216); and a lingual mold body (14, 114, 214, 514) for a patient-specific, customized fit with the lingual side of the tooth of the patient, wherein the lingual mold body (14, 114, 214, 514) includes a restorative portion and a first engagement portion (19a, 219a) extending away from the restorative portion, wherein the first engagement portion (18a, 218a) of the facial mold body (12, 112, 212, 512) is adapted to interlock with the first engagement portion (19a, 219a) of the lingual mold body (14, 114, 214, 514), wherein the facial mold body (12, 112, 212, 512) and the lingual mold body (14, 114, 214, 514) are configured to combine with the tooth of the patient to form a mold cavity encompassing missing tooth structure of at least one tooth to be restored, characterized in that, to create a clamping force between the facial mold body (12, 112, 212, 512) and the lingual mold body (14, 114, 214, 514) when the first engagement portion (18a, 218a) of the facial mold body interlocks with the first engagement portion (19a, 219a) of the lingual mold body, either (i) the arch length of the facial mold body is shortened relative to the arch length of the lingual mold body, or (ii) a radius of curvature of the facial mold body is reduced relative to a radius of curvature of the lingual mold body. a facial mold body (12, 112, 212, 512) for a patient-specific, customized fit with the facial side of at least one tooth of the patient, wherein the facial mold body (12, 112, 212, 512) includes a restorative portion (16, 116, 216) and a first engagement portion (18a, 218a) extending away from the restorative portion (16, 116, 216); and a lingual mold body (14, 114, 214, 514) for a patient-specific, customized fit with the lingual side of the tooth of the patient, wherein the lingual mold body (14, 114, 214, 514) includes a restorative portion and a first engagement portion (19a, 219a) extending away from the restorative portion, wherein the first engagement portion (18a, 218a) of the facial mold body (12, 112, 212, 512) is adapted to interlock with the first engagement portion (19a, 219a) of the lingual mold body (14, 114, 214, 514), wherein the facial mold body (12, 112, 212, 512) and the lingual mold body (14, 114, 214, 514) are configured to combine with the tooth of the patient to form a mold cavity encompassing missing tooth structure of at least one tooth to be restored, characterized in that, to create a clamping force between the facial mold body (12, 112, 212, 512) and the lingual mold body (14, 114, 214, 514) when the first engagement portion (18a, 218a) of the facial mold body interlocks with the first engagement portion (19a, 219a) of the lingual mold body, either (i) the arch length of the facial mold body is shortened relative to the arch length of the lingual mold body, or (ii) a radius of curvature of the facial mold body is reduced relative to a radius of curvature of the lingual mold body.